U.S. patent application number 15/134701 was filed with the patent office on 2016-08-11 for adhesion promotion in printed circuit boards.
The applicant listed for this patent is Enthone, Inc.. Invention is credited to Joseph A. Abys, Theodore Antonellis, Abayomi I. Owei, Eric Walch.
Application Number | 20160234947 15/134701 |
Document ID | / |
Family ID | 49995143 |
Filed Date | 2016-08-11 |
United States Patent
Application |
20160234947 |
Kind Code |
A1 |
Owei; Abayomi I. ; et
al. |
August 11, 2016 |
Adhesion Promotion in Printed Circuit Boards
Abstract
Compositions and methods for enhancing adhesion between a copper
conducting layer and a dielectric material during manufacture of a
printed circuit board. Conditioning compositions contain a
functional organic compound and preferably a transition metal ion.
The functional organic compound, e.g., a purine derivative, is
capable of forming a self-assembled monolayer. Adhesion promoting
compositions contain an acid, preferably an inorganic acid, and an
oxidant. The latter compositions may also contain a corrosion
inhibitor and/or a transition metal ion selected from among Zn, Ni,
Co, Cu, Ag, Au, Pd or another Pt group metal. The corrosion
inhibitor may comprise a nitrogen-containing aromatic heterocyclic
compound.
Inventors: |
Owei; Abayomi I.; (Rancho
Cucamonga, CA) ; Abys; Joseph A.; (Guilford, CT)
; Antonellis; Theodore; (Bethany, CT) ; Walch;
Eric; (Langenfeld, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Enthone, Inc. |
West Haven |
CT |
US |
|
|
Family ID: |
49995143 |
Appl. No.: |
15/134701 |
Filed: |
April 21, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13558019 |
Jul 25, 2012 |
9338896 |
|
|
15134701 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 22/63 20130101;
C23G 1/20 20130101; B05D 5/10 20130101; H05K 3/383 20130101; H05K
3/385 20130101; C23C 22/78 20130101; B05D 3/10 20130101; C23C 22/52
20130101; C23F 1/18 20130101; C23C 22/73 20130101 |
International
Class: |
H05K 3/38 20060101
H05K003/38 |
Claims
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53. An aqueous alkaline composition as set forth in claim 117
wherein the aqueous alkaline composition is substantially free of
peroxide.
54. An aqueous alkaline composition as set forth in claim 117
wherein said aqueous alkaline composition is substantially free of
an oxidant.
55. An aqueous alkaline composition as set forth in claim 117
wherein said aqueous alkaline composition has an oxidation
potential not greater than about 1.02 volts or 0.8 volts or 0.2
volts or 0.1 volts.
56. An aqueous alkaline composition as set forth in claim 117
wherein said aqueous alkaline conditioning composition comprises an
alkaline component.
57. An aqueous alkaline composition as set forth in claim 56
wherein said alkaline component is selected from the group
consisting of an alkali metal hydroxide, an alkali metal carbonate,
or an alkalyamine.
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117. An aqueous alkaline composition comprising a functional
organic compound and a transition metal ion, said functional
organic compound being capable of forming a self-assembled
monolayer on a copper surface and being selected from the group
consisting of nitrogen-containing aromatic heterocyclic compounds,
arylamines, aralkylamines, fatty amines, sulfur-bearing aromatic
heterocyclic compounds, aryl thos, aralkyl thiols, and combinations
thereof, wherein the aqueous alkaline composition has a pH between
about 10 and about 15.
118. A composition as set forth in claim 117 wherein said
transition metal is selected from the group consisting of zinc,
nickel, cobalt, copper, silver, gold, palladium and other platinum
group metals.
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120. An aqueous alkaline composition as set forth in claim 117
having a pH between about 10 and about 14.
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122. An aqueous alkaline composition as set forth in claim 117
wherein said transition metal ion is selected from the group
consisting of Zn, Ni, Co, Ag, Au, Pd or other platinum group metal
ion.
123. An aqueous alkaline composition as set forth in claim 117
wherein said transition metal ion comprises a zinc cation or
zincate anion.
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125. An aqueous alkaline composition as set forth in claim 117
further comprising a surfactant.
126. An aqueous alkaline solution as set forth in claim 125
comprising both an anionic and a nonionic surfactant.
127. An aqueous alkaline solution as set forth in claim 117 further
comprising iodide ion.
128. An aqueous alkaline solution as set forth in claim 117 further
comprising an alkanolamine.
129. An aqueous alkaline solution as set forth in claim 117
comprising between about 0.1 and about 3 wt. % of the transition
metal ion and between about 0.05 and about 2.5 wt. % of the
functional organic compound.
130. An aqueous alkaline solution as set forth in claim 129
comprising between about 0.1 and about 3 wt % of a transition metal
ion selected from the group consisting of Zn, Ni, Co, Cu, Ag, Au,
Pd and other platinum group metals.
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132. An aqueous alkaline solution as set forth in claim 129
comprising between about 0.1 and about 3 wt. % zinc ion.
133. An aqueous alkaline solution as set forth in claim 117 further
comprising an anionic surfactant in a concentration between about
about 0.001 and about 0.03 wt. % and/or a glycol ether in a
concentration between about 0.5 and about 5 wt. %.
134. An aqueous alkaline solution as set forth in claim 117 further
comprising an alkanolamine in a concentration between about 0.5 and
about 5 wt. %.
135. An aqueous alkaline solution as set forth in claim 117
comprising purine or a purine derivative in a concentration between
about 0.05 and about 2.5 wt. %.
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137. An aqueous alkaline solution as set forth in claim 117 wherein
said functional organic compound capable of forming a self
assembled monolayer comprises both a ring ##STR00018## group and an
amine substituent on the ring.
138. An aqueous alkaline solution as set forth in claim 136 wherein
the substituted hydrocarbyl comprises a substituent selected from
the group consisting of amino, cyano, nitro, halo, hydroxy and
suithydryl.
139. An aqueous alkaline solution as set forth in claim 117 wherein
said nitrogen-containing aromatic heterocyclic compound comprises a
ring substituent selected from the group consisting of cyano,
nitro, halo, hydroxy and sulfhydryl.
140. An aqueous alkaline solution as set forth in claim 139 wherein
said nitrogen containing aromatic heterocyclic compound comprises a
compound selected from the group consisting of
mercaptobenzamidazoles, mercaptobenzothiazoles, and
mercaptobenzotriazoles.
141. An aqueous alkaline solution as set forth in claim 136 wherein
said conditioning composition comprises purine or a purine
derivative.
142. An aqueous alkaline solution as set forth in claim 141 wherein
said functional organic compound corresponds to the formula:
##STR00019## wherein each of R.sup.2, R.sup.6, and R.sup.8 is
independently selected from the group consisting of hydrogen,
hydrocarbyl, substituted hydrocarbyl, hydroxycarbonyl,
alkoxycarbonyl, alkoxy, alkenoxy, hydroxyl, hydroxyalkyl,
hydroxyalkenyl, sulfhydryl, halo, nitro, cyano and
NR.sup.9R.sup.10, R.sup.7 is selected from the group consisting of
hydrogen, hydrocarbyl, substituted hydrocarbyl, hydroxyl, or a
negative charge, and each of R.sup.9 and R.sup.10 is independently
selected from the group consisting of hydrogen, hydrocarbyl and
substituted hydrocarbyl.
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150. An aqueous alkaline solution as set forth in claim 142
comprising 6-benzylaminopurine.
151. An aqueous alkaline solution as set forth in claim 135 wherein
said purine derivative is substituted with a functional group
selected from the group consisting of substituted or unsubstituted
vinyl ether, substituted or unsubstituted amide, substituted or
unsubstituted amine, substituted or unsubstituted carboxylic acid,
substituted or unsubstituted carboxylate, substituted or
unsubstituted alcohol, substituted or unsubstituted silane or
alkoxysilane.
152. An aqueous alkaline solution as set forth in claim 117 wherein
said functional organic compound has the structure (Ia) or
structure (Ib): ##STR00020## wherein: A.sub.1, A.sub.2, A.sub.3,
A.sub.4, A.sub.5, A.sub.6, and A.sub.7 are carbon atoms or nitrogen
atoms and the sum of nitrogen atoms from A.sub.1, A.sub.2, A.sub.3,
A.sub.4, A.sub.5, A.sub.6, and A.sub.7 is 0, 1, 2, or 3; A.sub.11,
A.sub.27, A.sub.33, A.sub.44, A.sub.55, A.sub.66, and A.sub.77 are
selected from the group consisting of electron pair, hydrogen,
substituted or unsubstituted alkyl, substituted or unsubstituted
aryl, substituted or unsubstituted vinyl ether, substituted or
unsubstituted amide, substituted or unsubstituted amine,
substituted or unsubstituted carboxylic acid, substituted or
unsubstituted ester, substituted or unsubstituted alcohol, and
substituted and unsubstituted silane or alkoxysilane; and at least
one of A.sub.1I, A.sub.22, A.sub.33, A.sub.44, and A.sub.55 is
selected from the group consisting of substituted or unsubstituted
vinyl ether, substituted or unsubstituted amide, substituted or
unsubstituted amine, substituted or unsubstituted carboxylic acid,
substituted or unsubstituted ester, substituted or unsubstituted
alcohol, and substituted and unsubstituted silane or
alkoxysilane.
153. An aqueous alkaline solution as set forth in claim 152 wherein
the functional organic compound corresponds to structure (II),
structure (III), or structure (IV): ##STR00021## wherein A.sub.22,
A.sub.44, A.sub.55, A.sub.66, and A.sub.77 are as defined in
connection with structures (Ia) and (Ib).
154. An aqueous alkaline solution as set forth in claim 117 wherein
said functional organic compound has the structure (V):
##STR00022## wherein: A.sub.2, A.sub.3, A.sub.4 and A.sub.5 are
carbon atoms or nitrogen atoms and the sum of nitrogen atoms from
A.sub.2, A.sub.3, A.sub.4 and A.sub.5 is 0, 1 or 2; A.sub.22,
A.sub.33, A.sub.44, and A.sub.55 are selected from the group
consisting of hydrogen, substituted or unsubstituted alkyl,
substituted or unsubstituted aryl, substituted or unsubstituted
vinyl ether, substituted or unsubstituted amide, substituted or
unsubstituted amine, substituted or unsubstituted carboxylic acid,
substituted or unsubstituted ester, substituted or unsubstituted
alcohol, and substituted and unsubstituted silane or alkoxysilane;
and at least one of A.sub.22, A.sub.33, A.sub.44, and A.sub.55 is
selected from the group consisting of substituted or unsubstituted
vinyl ether, substituted or unsubstituted amide, substituted or
unsubstituted amine, substituted or unsubstituted carboxylic acid,
substituted or unsubstituted ester, substituted or unsubstituted
alcohol, and substituted and unsubstituted silane or
alkoxysilane.
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Description
FIELD OF THE INVENTION
[0001] This invention relates to improving adhesion of metal
surfaces, such as copper to an insulating layer, in the manufacture
of printed circuit boards.
BACKGROUND OF THE INVENTION
[0002] A multilayer circuit board (MLB) has, among other things, a
number of metal layers defining circuit patterns, and a number of
insulating layers there-between. The metal layers defining circuit
patterns today are typically formed from copper, and the insulating
layers are typically formed from a resinous fiber-impregnated
dielectric material. These respective layers can have a wide
variety of thickness. For example, they can be on the order of only
microns thick, or much thicker.
[0003] In manufacturing MLBs, it is desirable to enhance the
adhesion between the conducting and insulating layers to avoid
delamination in subsequent manufacturing operations or in service.
So called "black oxide" processes had been used for years which
created a strongly adherent copper oxide layer to which an
insulating layer would adhere better. Black oxide processes have,
for most of the industry, been replaced by processes such as
described in U.S. Pat. No. 5,800,859 involving formation of an
organometallic conversion coating (OMCC). These organometallic
conversion coating processes involve exposing the copper circuit
layer to an adhesion promotion solution, which contains various
components including an oxidizer, an inhibitor, and a mineral
acid.
[0004] One limitation on organometallic conversion coating
processes has been that the organometallic conversion coating must
be a uniform color, such as, for example, a dark brown or chocolate
color. The industry associates this color with a uniform coating
which has strong adhesion properties. A dark uniform color is
preferred because it provides color contrast with copper to aid in
inspection for defects. For example, it provides contrast for
inspection for the so-called "pink-ring" defect. Organometallic
conversion coating processes which produce significantly lighter
coatings are generally unacceptable, or at least undesirable for
most applications. For a lighter coating, "pink ring" defects are
substantially more difficult to detect.
SUMMARY OF THE INVENTION
[0005] Briefly, therefore, the application is directed to a method
for enhancing adhesion between a copper conducting layer and a
dielectric material during manufacture of a printed circuit board,
the method comprising contacting the copper conducting layer with a
conditioning composition, said conditioning composition comprising
a functional organic compound and a transition metal ion, said
functional organic compound being capable of forming a
self-assembled monolayer on a copper surface, and thereafter
contacting the copper conducting layer with an adhesion promoting
composition that comprises an oxidizing agent, an inorganic acid,
and a corrosion inhibitor.
[0006] In another aspect the invention is directed to a method for
enhancing adhesion between a copper conducting layer and a
dielectric material during manufacture of a printed circuit board,
the method comprising contacting the copper conducting layer with a
conditioning composition comprising an organic N-bearing compound
capable of forming a self-assembled monolayer on a copper surface,
and thereafter contacting the copper conducting layer with an
adhesion promoting composition that comprises an oxidizing agent,
an inorganic acid, a corrosion inhibitor and a transition metal ion
selected from the group consisting of zinc, nickel, cobalt, copper,
silver, gold, palladium and other platinum group metals, said
corrosion inhibitor comprising an aromatic heterocyclic compound
comprising nitrogen.
[0007] The invention is further directed to an aqueous alkaline
composition comprising a nitrogen-containing aromatic heterocyclic
compound and a transition metal ion, said heterocyclic compound
comprising a ring
##STR00001##
group or an amine substitutent on the ring wherein R7 is hydrogen,
hydrocarbyl, substituted hydrocarbyl, hydroxyl, or a negative
charge, said heterocyclic compound being capable of forming a
self-assembled monolayer on a copper surface.
[0008] The invention is also directed to an aqueous composition for
treating a copper surface to enhance adhesion to a dielectric, the
composition comprising between about 0.02 and about 2 wt. %
transition metal ion selected from the group consisting of zinc,
nickel, cobalt, copper, silver, gold, palladium and other platinum
group metal, between about 10 and about 50 wt. % sulfuric acid,
between about 1 and about 10 wt. % hydrogen peroxide, and a
corrosion inhibitor comprising a nitrogen-containing aromatic
heterocyclic compound.
[0009] In another aspect, the invention is directed to method for
enhancing adhesion between a copper conducting layer and a
dielectric material during manufacture of a printed circuit board.
The method comprises contacting the copper conducting layer with a
conditioning composition comprising a nitrogen-containing aromatic
heterocyclic compound that is capable of forming a self-assembled
monolayer on a copper surface. The nitrogen-containing aromatic
heterocyclic compound corresponds to the formula:
##STR00002##
wherein each of R.sup.2, R.sup.6, and R.sup.9 is independently
selected from the group consisting of hydrogen, hydrocarbyl,
substituted hydrocarbyl, hydroxycarbonyl, alkoxycarbonyl, alkoxy,
hydroxyl, sulfhydryl, halo, nitro, cyano and NR.sup.9R.sup.10,
R.sup.7 is selected from the group consisting of hydrogen,
hydrocarbyl, substituted hydrocarbyl, hydroxyl, or a negative
charge, and each of R.sup.9 and R.sup.10 is independently selected
from the group consisting of hydrogen, hydrocarbyl and substituted
hydrocarbyl. Thereafter the copper conducting layer is contacted
with an adhesion promoting composition that comprises an oxidizing
agent, an inorganic acid, a corrosion inhibitor, and a
surfactant.
[0010] The invention is still further directed to method for
preparing a copper conducting layer for adhesion to a dielectric
material during manufacture of a printed circuit board. The method
comprises contacting the copper conducting layer with a
conditioning composition comprising a nitrogen-containing aromatic
heterocyclic compound and an anionic surfactant. The
nitrogen-containing aromatic heterocyclic compound is capable of
forming a self-assembled monolayer on a copper surface and
comprises a ring
##STR00003##
group or an amine substitutent on the ring wherein R' is hydrogen,
hydrocarbyl, substituted hydrocarbyl, hydroxyl, or a negative
charge. Thereafter the copper conducting layer is contacted with an
adhesive promoting composition that comprises an acid and an
oxidant.
[0011] The invention is also directed to a method for preparing a
copper conducting layer for adhesion to a dielectric material
during manufacture of a printed circuit board. The method comprises
contacting the copper conducting layer with a conditioning
composition comprising a nitrogen-containing aromatic heterocyclic
compound, an alkali metal iodide and a glycol ether. The nitrogen
containing heterocyclic compound is capable of forming a
self-assembled monolayer on a copper surface, and comprises a
ring
##STR00004##
group or an amine substitutent on the ring wherein R' is hydrogen,
hydrocarbyl, substituted hydrocarbyl, hydroxyl, or a negative
charge.
[0012] Other aspects and features will be in part apparent and in
part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a series of bar graphs showing peel strength as a
function of copper loading for various laminates prepared at 15.5
bars after treatment with a conditioner and adhesion promoter of
the invention as described in Example 18, wherein each of the
conditioner and adhesion promoter compositions contained a
concentration of copper ion ranging from 0 to 10 g/l,
[0014] FIG. 2 is a series of bar graphs showing peel strength as a
function of copper loading for laminates prepared at 24.1 bars
after treatment with a conditioner and adhesion promoter of the
invention as further described in Example 18, wherein again each of
the conditioner and adhesion promoter compositions contained a
concentration of copper ion ranging from 0 to 10 g/l;
[0015] Each of FIGS. 3 to 6 is a series of bar graphs showing peel
strength as a function of copper loading for laminates prepared
after treatment with a conditioner and adhesion promoter at two
different laminating pressures (24.1 bars or 15.5 bars) and both
before and after reflow, as further described in Example 19,
wherein again each of the conditioner and adhesion promoter
compositions contained a concentration of copper ion ranging from 0
to 10 g/l;
[0016] Each of FIGS. 7 and 8 is a series of bar graphs showing peel
strength as a function of copper loading for laminates prepared at
15.5 bars and 24.1 bars, respectively, after treatment with a
conditioner and adhesion promoter as described in Example 20,
wherein each of the conditioner and adhesion promoting composition
had a copper ion content ranging from 0 to 10 g/l and the adhesion
promoting composition had not been doped with the conditioner;
[0017] Each of FIGS. 9 and 10 is a series of bar graphs showing
peel strength as a function of copper loading for laminates
prepared at 15.5 and 24.1 bars, respectively, after treatment with
a conditioner and adhesion promoter as described in Example 20,
wherein each of the conditioner and adhesion promoting composition
had a copper ion content ranging from 0 to 10 g/l and the adhesion
promoting composition had been doped with .about.1 g/l of
conditioner #2;
[0018] FIG. 11 is a series of bar graphs showing peel strength as a
function of conditioner #2 content in the adhesion promoting
composition for laminates prepared according to Example 21 wherein
each of the conditioner and adhesion promoting compositions had a
copper ion content of approximately 5 g/l;
[0019] FIG. 12 is a series of bar graphs showing peel strength as a
function of copper loading for laminates prepared according to
Example 22 wherein the copper ion concentration ranged from 0 to 50
g/l and no Conditioner #2 was added to the adhesion promoting
composition;
[0020] FIG. 13 is a series of bar graphs showing peel strength as a
function of copper loading for laminates prepared according to
Example 22 wherein the copper ion concentration ranged from 0 to 50
g/l and the adhesion promoting composition was doped with .about.1
g/l Conditioner #2;
[0021] FIG. 14 is a series of bar graphs showing peel strength as a
function of dwell time between application of the conditioner and
application of the adhesion promoting composition for laminates
prepared according to Example 23 wherein each conditioner and
adhesion promoter was doped with 40 g/l copper ions;
[0022] Each of FIGS. 15 and 16 is a series of bar graphs showing
peel strength as a function of conditioner #2 content in the
adhesion promoting composition for laminates prepared according to
Example 24 wherein each of the conditioner and adhesion promoting
compositions had a copper ion content of approximately 10 g/l.
DETAILED DESCRIPTION OF EMBODIMENT(S) OF THE INVENTION
[0023] The present invention is directed to compositions and
methods for enhancing adhesion between a copper conducting layer
and a non-conducting laminate. As a general proposition, the
development of an adhesive organometallic conversion coating on the
surface of the copper conducting layer occurs by contacting the
copper conducting layer with an adhesion promotion composition that
brings about the oxidation of copper on the surface of the
conducting layer into cuprous ions and cupric ions. Cuprous ions
(Cu.sup.+) which are formed by the oxidation reaction generally
dominate on the surface, and cupric ions (Cu.sup.2+) generally
dominate in solution. The cuprous ions on the surface bind with a
corrosion inhibitor in the adhesion promotion composition and form
a copper-inhibitor-complex as copper dissolves from the conducting
copper layer into the adhesion promoter chemistry at the same time.
This results in micro-roughened surface morphology of the
conducting copper layer. This micro-roughened copper surface
promotes adhesion with the subsequently applied insulating
layer.
[0024] In the process of the present invention, prior to contacting
the copper conducting layer with the adhesion promotion
composition, the copper conducting layer is preferably contacted
with a conditioning composition comprising a nitrogen-containing
heterocycle that is capable of forming a self-assembled monolayer
(SAM) on a copper surface. It has been discovered that the molecule
capable of forming a SAM may be incorporated into the alkaline
cleaner or it may be used in a separate pre-dip composition. The
self-assembled monolayer essentially consists of a densely packed
organic film formed of a monolayer of the nitrogen-containing
heterocycle molecule or other film-forming organic nitrogen or
sulfur compound chemisorbed to the copper surface. Without being
bound to a particular theory, it is believed that the self
assembled monolayer formed over the copper surface from the
conditioning solution functions to passivate the copper surface by
blocking access of oxygen contained in the adhesion promoting
composition. It thus modulates the effect of the subsequently
applied adhesion promotion solution by preventing excess copper
oxide formation that may otherwise result from the aggressive
effect of the peroxide component of the latter solution.
[0025] In addition to the nitrogen-containing heterocycle, the
conditioning composition preferably contains a transition metal
ion, typically in the form of a transition metal salt. Useful
transition metal ions include zinc, nickel, copper, cobalt, silver,
gold, palladium and other platinum group metals. Preferably, the
transition metal ion is selected from the group consisting of zinc,
nickel, cobalt, silver, gold, palladium and other platinum group
metals, more preferably zinc, nickel, cobalt or silver, still more
preferably zinc, nickel or cobalt. Zinc is preferred. Various salts
of the transition metal can be used, including sulfates, chlorides,
other halides, most prominently iodides, phosphates, phosphides,
carbonates, and various carboxylates, including, e.g., oxalates.
Oxides may also be used. It is believed that the presence of these
transition metal ions in the conditioning solution contributes to
the heat stability of the conversion coating produced in the
subsequent treatment with the adhesion promoting solution. In a
preferred embodiment of the invention, zinc is incorporated into
the conditioning solution in the form of an alkaline dispersion of
ZnO, a solution of alkali metal zincate, or a zinc ammonium halide
such as zinc ammonium chloride.
[0026] Preferably, the nitrogen-containing heterocycle is a purine
compound, for example, a compound that corresponds to the
formula:
##STR00005##
wherein each of R.sup.2, R.sup.6, and R.sup.8 is independently
selected from the group consisting of hydrogen, hydrocarbyl,
substituted hydrocarbyl, hydroxycarbonyl, alkoxycarbonyl, alkoxy,
hydroxyl, sulfhydryl, halo, nitro, cyano and NR.sup.9R.sup.10,
R.sup.7 is selected from the group consisting of hydrogen,
hydrocarbyl, substituted hydrocarbyl, hydroxyl, or a negative
charge, and each of R.sup.9 and R.sup.10 is independently selected
from the group consisting of hydrogen, hydrocarbyl and substituted
hydrocarbyl. Preferably, each of R.sup.9 and R.sup.10 is
independently selected from the group consisting of hydrogen,
alkyl, substituted alkyl, aralkyl and aryl.
[0027] In particularly preferred embodiments, R.sup.6 of Formula I
comprises NR.sup.9R.sup.10. Where the hydrocarbyl substituent is
substituted, the substituent on the hydrocarbyl is preferably
amino, cyano, nitro, halo, hydroxy or sulfhydryl. Most preferably,
R.sup.9 is hydrogen and R.sup.10 is benzyl, i.e., the compound
forming the self-assembling monolayer is most preferably an amino
substituted purine such as 6-benzylaminopurine:
##STR00006##
However, the compound of Formula I can also advantageously comprise
unsubstituted purine. In the preferably alkaline conditioner
solution, R.sup.7 is preferably hydrogen and said
nitrogen-containing aromatic heterocyclic compound is
deprotonatable in contact with a copper substrate. Thus, in the
solution, and especially in contact with a copper substrate,
R.sup.7 comprises hydroxyl or a negative charge.
[0028] The
##STR00007##
group in the purine ring enables an efficient interaction towards
the metal surface (copper). The presence of the ring
##STR00008##
group and/or other
##STR00009##
group (R.sub.7 being benzyl in the case of 6-benzylaminopurine)
substituent on the ring allows the formation of coordinate bonds at
the metal and purine compound interface.
[0029] Purine derivatives in the conditioning solution have been
found to contribute to bond strength between copper conductor and
resin after treatment of the conditioned surface with the adhesion
promoting composition and subsequent lamination. Purine derivatives
have further been found to contribute to the thermal stability of
the conversion coating produced by subsequent treatment with the
adhesion promoting solution.
[0030] Although purines and especially amine substituted purines
are especially preferred, other nitrogen heterocycles comprising a
ring
##STR00010##
group and/or an amino substituent on the ring can serve effectively
for formation of a self-assembled monolayer from the conditioning
solution onto the copper surface. Illustrative heterocycles that
function effectively for this purpose include benzotriazole:
##STR00011##
and various substituted benzotriazoles, as well as substituted and
unsubstituted triazoles, tetrazoles, benzimidazoles, etc. In
addition to amines, the heterocycle may comprise a functional ring
substituent such as thiol, vinyl ether, thiamide, amine, carboxylic
acid, ester, alcohol, silane, alkoxy silane. Exemplary compounds
useful in forming the self assembled monolayer include adenine,
2-mercaptobenzimidazole, mercaptobenzothiazole and
di(sulfhydrylmethyl) benzene.
[0031] In certain embodiments of the conditioning solution of the
invention, a variety of other functional organic compounds can be
present as the component which forms the self-assembling monolayer.
Especially in those embodiments wherein the conditioning solution
comprises a transition metal cation, the self-assembling monolayer
can be formed from: arylamines such as aniline, aniline
derivatives, toluidine and toluidine derivatives; aralkylamines
such as benzylamine, tolylamine and benzylamine and tolylamine
derivatives; various alkylamines, particularly fatty amines;
sulfur-bearing aromatic heterocyclic compounds such as thiophene,
thiophene derivatives, benzothiophene, benzothiophene derivatives,
benzothiazoles and benzothiazole derivatives; aryl thiols such as
thiophenol, thiophenol derivatives, tolyl thiol and tolyl thiol
derivatives; and other aralkyl thiols such as benzyl mercaptan and
di(sulfhydrylmethyl) benzene.
[0032] Among the nitrogen-bearing heterocycles, suitable components
from which the self-assembling monolayer can be formed include
multi-functional compounds having structure (Ia) or structure
(Ib):
##STR00012##
wherein:
[0033] A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.5, A.sub.6, and
A.sub.7 are carbon atoms or nitrogen atoms and the sum of nitrogen
atoms from A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.5, A.sub.6,
and A.sub.7 is 0, 1, 2, or 3;
[0034] A.sub.11, A.sub.22, A.sub.33, A.sub.44, A.sub.55, A.sub.66,
and A.sub.77 are selected from the group consisting of electron
pair, hydrogen, substituted or unsubstituted alkyl, substituted or
unsubstituted aryl, substituted or unsubstituted vinyl ether,
substituted or unsubstituted amide, substituted or unsubstituted
amine, substituted or unsubstituted carboxylic acid, substituted or
unsubstituted ester, substituted or unsubstituted alcohol, and
substituted and unsubstituted silane or alkoxysilane; and
[0035] at least one of A.sub.11, A.sub.22, A.sub.33, A.sub.44, and
A.sub.55 is selected from the group consisting of substituted or
unsubstituted vinyl ether, substituted or unsubstituted amide,
substituted or unsubstituted amine, substituted or unsubstituted
carboxylic acid, substituted or unsubstituted ester, substituted or
unsubstituted alcohol, and substituted and unsubstituted silane or
alkoxysilane.
[0036] Although an
##STR00013##
moiety of an aromatic heterocycle from which the self-assembling
monolayer is formed may comprise a substituted nitrogen, i.e.,
R.sup.7 may be hydrocarbyl, it is preferred that at least one
nitrogen atom of the film-forming aromatic heterocycle be bonded to
an acidic hydrogen atom, such that the compound may become
deprotonated and the resultant negatively charged aromatic
heterocyle is available to interact with copper(I) ions and
copper(II) ions in a manner which forms a copper(I) rich
organometallic adhesive film over the surface of the metal
substrate. In short, it is particularly preferred that an aromatic
N-bearing heterocycle which serves to form the monolayer
comprise
##STR00014##
in which R.sup.7 is hydrogen, and that the hydrogen be acidic,
e.g., wherein it exhibits a pK.sub.a of between about 5 and about
13, such as between about 3.5 and about 11, such as between about 4
and about 10. The ring may be fused to aromatic or cycloalkyl
groups, which may be homocyclic or heterocyclic.
[0037] Among the suitable multi-functional compounds of structures
I(a) and (b) are those having structure (II), structure (III), and
structure (IV):
##STR00015##
wherein A.sub.22, A.sub.44, A.sub.55, A.sub.66, and A.sub.77 are as
defined in connection with structures (Ia) and (Ib).
[0038] Other particular multi-functional compounds for forming the
self-assembling monoloayer include those having the structure
(V):
##STR00016##
wherein:
[0039] A.sub.2, A.sub.3, A.sub.4 and A.sub.5 are carbon atoms or
nitrogen atoms and the sum of nitrogen atoms from A.sub.2, A.sub.3,
A.sub.4 and A.sub.5 is 0, 1 or 2;
[0040] A.sub.22, A.sub.33, A.sub.44, and A.sub.55 are selected from
the group consisting of hydrogen, substituted or unsubstituted
alkyl, substituted or unsubstituted aryl, substituted or
unsubstituted vinyl ether, substituted or unsubstituted amide,
substituted or unsubstituted amine, substituted or unsubstituted
carboxylic acid, substituted or unsubstituted ester, substituted or
unsubstituted alcohol, and substituted and unsubstituted silane or
alkoxysilane; and
[0041] at least one of A.sub.22, A.sub.33, A.sub.44, and A.sub.55
is selected from the group consisting of substituted or
unsubstituted vinyl ether, substituted or unsubstituted amide,
substituted or unsubstituted amine, substituted or unsubstituted
carboxylic acid, substituted or unsubstituted ester, substituted or
unsubstituted alcohol, and substituted and unsubstituted silane or
alkoxysilane.
[0042] Various of the nitrogen-containing aromatic heterocyclic
compounds which form the self assembled monolayer may also comprise
one or more ring substituents selected from the group consisting of
cyano, nitro, halo, hydroxy and sulfhydryl. For example, the
monolayer film may be formed from heterocyclics such as
mercaptobenzamidazoles, mercaptobenzothiazoles, and
mercaptobenzotriazoles.
[0043] Where the corrosion inhibitor component of the adhesive
promoting solution also contains a component which may be
chemisorbed to the copper surface, such as benzotriazole or
benzotriazole 5-carboxylic acid, the process of the invention,
which combines treatment of the substrate with a conditioning
solution and subsequent treatment with an adhesion promoting
solution containing a heterocyclic corrosion inhibitor, is believed
to form a complex of the self assembled monolayer from the
conditioning solution, the corrosion inhibitor from the adhesion
promoting solution and copper which interact, in some or all
instances synergistically, to enhance binding of the copper
substrate to the dielectric in the laminating step of the
multi-layer circuit board manufacturing process.
[0044] In general, the process of the present invention is carried
out according to the following protocol: [0045] 1. Etch the surface
of the copper conducting layer with a micro-etchant composition.
[0046] 2. Rinse the surface of the copper conducting layer of the
etchant composition. [0047] 3. Clean the etched surface by
contacting the surface with an alkaline cleaner. The alkaline
cleaner may optionally comprise a molecule capable of forming a
self-assembled monolayer (SAM) on a copper surface. [0048] 4. Rinse
the surface of the copper conducting layer of the cleaning
composition. [0049] 5. Contact the cleaned and etched surfaces of
the copper conductive layer with a pre-dip composition comprising a
molecule capable of forming a self-assembled monolayer (SAM) on a
copper surface. If the alkaline cleaner comprises the molecule
capable of forming a self-assembled monolayer (SAM) on a copper
surface, this step is optional. [0050] 6. Rinse the surface of the
copper conducting layer of the pre-dip composition. [0051] 7.
Contact the cleaned, etched, and pre-treated surfaces of the copper
conducting layer with an adhesion promotion composition. [0052] 8.
Rinse the surfaces of the copper conducting layer of the adhesion
promotion composition to form an organometallic conversion coating
thereon. [0053] 9. Dry the surfaces of the copper, conducting
layer. [0054] 10. Inspect the organometallic conversion coating to
confirm the presence of a substantially uniform dark reddish brown
to chocolate brown color, free of any marked patchiness or
striations. The presence of the uniform brown color indicates the
presence of a conversion coating that enhances the adhesion of the
copper substrate to the dielectric in the subsequent laminating
step of the manufacturing process. [0055] 11. Adhere the surface of
the copper conducting layer having the organometallic conversion
coating thereon to a pre-preg laminate.
[0056] The process of the present invention is described in more
detail below.
Microetching
[0057] In some embodiments, the surface of the copper conducting
layer may have previously been provided with a tarnish-inhibiting
coating, e.g., by incorporating the tarnish inhibitor into a resist
stripping composition used in an immediately preceding step of etch
resist stripping. Tarnish inhibitors used in such strippers are,
for example, a triazole or other coating. Therefore, the conductive
copper surface is generally micro-etched, cleaned, and immersed in
a pre-dip composition prior to exposure to the adhesion promotion
composition.
[0058] The surfaces of copper conducting layer are exposed to an
etchant solution by immersion, spraying, cascading, or any other
industry appropriate method. The etchant solution may be, for
example, micro-etchant comprising about 12 to 20 wt. % Na
persulfate and 2 to 5 wt. % sulfuric acid with a minor fraction of
phenolsulfate, prepared for example by 40-60% dilution of a
concentrated available under the trademark Enthone.RTM. PC-7077
(from Enthone Inc.). In general, the copper conducting layer is
exposed to the etchant composition for durations between 10 to 120
seconds, such as between 20 to 60 seconds at solution temperatures
generally between of 20.degree. C. and 40.degree. C. Etching
micro-roughens the copper surface and removes excess copper oxide
and other oxide contaminants prior to the treatment according to
the invention with a conditioning solution followed by an adhesion
promoting solution.
[0059] The etched copper conducting layer is next rinsed of the
etchant composition, generally in warm water (tap water or
deionized) for between 10 and 120 seconds. Preferably, the rinse
water is deionized water to allow better process control. The rinse
water is preferably allowed to drain for 10 to 30 seconds in order
to avoid undue dilution of the subsequent process composition.
Cleaning
[0060] The etched surfaces of the copper conducting layer are next
cleaned by immersion, spraying, cascading, or any other industry
appropriate method cleaned of the layers in an alkaline cleaner.
Useful compositions include Enthone.RTM. PC-7086 and Enthone.RTM.
PC-7096 (10 to 15% concentrations, available from Enthone Inc.). PC
7086 comprises monethanolamine (78 wt. %), 1-methylbenzotriazole
(0.06 wt. %), KOH (10 wt. %), water (12 wt. %) and a quaternary
ammonium salt (0.02 wt. %), and PC 7096 comprises water (16 wt. %),
monethanolamine (72 wt. %), tetramethylammonium hydroxide 25% (3.2
wt. %) ethylenediamine (0.17 wt. %), ethoxylated quaternary
ammonium salts (0.032 wt. %), 1-methylbenzyltriazole (0.06 wt. %),
aqueous choline base (2.2 wt. %) and KOH (8 wt. %). In general, the
copper conducting layers are cleaned for a duration between 30 and
240 seconds, such as between 45 and 90 seconds at solution
temperatures generally between of 30.degree. C. and 50.degree. C.
In some embodiments of the invention, the cleaning composition
optionally further comprises a molecule capable of forming a self
assembled monolayer on a copper surface. Such molecules are further
described below in connection with the pre-dip composition.
Cleaning with an alkaline cleaner is effective to remove oily
residues, residual photo-resist and other organic and inorganic
contaminants present on the copper substrate as a result of prior
steps in the process of manufacturing the circuit boards. It also
neutralizes residual acid on the copper surface not fully removed
in the rinse step following the micro-etch.
[0061] The etched and cleaned copper conducting layer is next
rinsed of the alkaline cleaning composition, generally in warm
water (tap water or deionized) for between 10 and 120 seconds.
Preferably, the rinse water is deionized water to allow better
process control. The rinse water is preferably allowed to drain for
10 to 30 seconds in order to avoid undue dilution of the subsequent
process composition.
Pre-Treatment with Conditioner
[0062] The cleaned and etched surface of the copper conducting
layer is next contacted with a conditioner composition comprising a
molecule capable of forming a self assembled monolayer on a copper
surface. In general, the copper conducting layers are contacted
with the pre-dip composition for durations between 30 and 240
seconds, such as between 45 and 90 seconds at solution temperatures
generally between of 30.degree. C. and 50.degree. C.
[0063] In addition to the nitrogen-bearing heterocycle or other
functional organic compound that forms the self assembled
monolayer, the conditioning solution may usefully contain any, or
any combination, of other components such as, e.g., iodide ion,
e.g., in the form of KI, an ethanolamine such as MEA, an anionic
surfactant, diethylene glycol butyl ether, and/or zinc ions, e.g.,
in the form of a zinc compound such as zinc iodide or zinc ammonium
carbonate. Iodide and zinc ions in the conditioner help to enhance
bonding of the copper substrate to the dielectric in the laminating
step that follows application of the adhesion promoting solution.
Although synergism is not a requirement of the conditioning
compositions used in the methods herein described, it is understood
that the alkalinity of the conditioning composition can and often
does interact synergistically with the iodide ion optionally
contained therein to impart corrosion protection of the surface
after subsequent treatment with the adhesion promoting solution,
and to enhance bond strength between the conversion coating and the
resin after lamination.
[0064] In lieu of or in combination with zinc ions, the conditioner
may contain certain other transition metal ions including, e.g.,
nickel, cobalt, silver, gold, palladium, or other platinum group
metal. A further option is the presence of copper ions. Zinc or
other transition metal is incorporated into the conditioner
solution as a salt comprising a counteranion typically selected
from the group consisting of chlorides, iodides, phosphates,
carbonates, and various carboxylates, including, e.g., malates and
oxalates. Oxides may also be used. Thus, the conditioner
composition comprises zinc ion in the form of Zn.sup.2+,
Zn.sup.2+/ammonia complex, zinc oxide, ZnO.sub.2.sup.= or
combinations thereof. The composition further includes one or more
counteranions selected from the group consisting of chlorides,
iodides, bromides, phosphates, carbonates, hydroxides, and various
carboxylates, including, e.g., malates, oxalates; or in the case of
zincate, the counterion is a cation such as Na.sup.+, K.sup.+
and/or NH.sub.4.sup.+.
[0065] Preferably, the conditioner is alkaline, so that it can
function as the alkaline cleaner for the copper substrate, thereby
obviating the need for separate alkaline cleaning step. Alkalinity
also promotes solubility of zinc sources such as, e.g., zinc oxide
as well as oxides or hydroxides of other transition metals. More
preferably, the conditioner has a pH in the range between about 10
and about 15, still more preferably between about 10 and about 14,
most preferably about 13.5 to about 14. A pH in these ranges also
functions to maintain shelf life during storage and to extend
conditioner bath life during process operations. Alkalinity can
conveniently be imparted by the presence of an alkali metal
hydroxide such as NaOH or KOH. Potassium hydroxide is preferred
because of its favorable solubility and lesser susceptibility to
carbonation by absorption of CO.sub.2 from the environment.
[0066] A particularly preferred source of zinc ions, especially in
alkaline solution, is a zinc ammonium complex, or a combination of
zinc ammonium complex and alkaline zincate salt. A highly useful
commercial source of zinc is the formulation available under the
trade designation ZINPLEX 15 which contains zinc ammonium complex
(30-60 wt. %), ammonium carbonate (10-30 wt. %), ammonium hydroxide
(0.1 to 10 wt. % basis NH.sub.3) and minor to trace proportions of
zinc oxide in the form of zincate ions. In the preferred 10 to 14
pH range, the zinc is predominantly present as Zn.sup.2+ or a
Zn.sup.2+/ammonia complex, but at the upper end of the range some
zincate ion (ZnO.sub.2.sup.=) may also be present and is believed
to contribute to thermal stability of the conversion coating
subsequently applied from the adhesion promoting solution.
[0067] Zinc ion or other transition metal ion, and in particular
the combination of zinc ion and ammonia, are believed to promote
the formation of a more effective protective film comprising the
component that forms the self-assembled monolayer on the copper
substrate. The complexing capability of ammonia further contributes
to cleaning of the copper surface by contact with the
cleaner/conditioner. For example, contact with the alkaline
conditioner is effective to remove oxidation and oily residues such
as fingerprints from the copper surface and thereby enhance the
effectiveness of the subsequently applied adhesion promoting
composition.
[0068] For purposes of process control, the conditioner is
preferably substantially free of peroxide, more preferably
substantially free of other oxidants as well. For example, it is
generally preferred that the conditioner comprise a solution having
an oxidation potential not greater than about 0.8-1.02V, as
typically exhibited, e.g., by purine, guanine and adenine.
[0069] The preferred presence of iodide ion in the conditioner is
believed to promote the reduction of cupric ion to cuprous ion
which in turn promotes the formation of complex of cuprous ion with
the corrosion inhibitor component of the adhesion promoting
solution, e.g., benzotriazole, thereby forming a conversion coating
that enhances the bond strength between the copper substrate and
the resin in the laminate. Preferably, the concentration of iodide
ion in the conditioning solution is between about 0.001 and about
1.00 wt. %.
[0070] The conditioning solution also preferably contains an
alcohol, more preferably a glycol ether such as, e.g., diethylene
glycol butyl ether. Other alcohols described herein for
incorporation in the adhesion promoting solution can also
optionally be present in the conditioning solution. The alcohol,
and especially the preferred glycol ethers are understood to
function as dispersants, and further provide solvency and
stability. Preferably the conditioning solution contains the
alcohol component in a concentration between about 1.00 and about
20.00 wt. %.
[0071] The conditioning composition may further contain an
alkanolamine such as, e.g., methanolamine. Alkanolamines are
cleaning agents with good chelating properties. Preferably, an
alkanolamine is present in a concentration between about 1.00 and
about 20.00 wt. %.
[0072] It is further preferred that the conditioning solution
include one or more surfactants, preferably anionic to wet the
copper surface, reduce interfacial tension and enhance solubility
of the component that forms the self-assembling monolayer on the
substrate. Among the anionic surfactants, both aryl sulfonates and
sulfate ester salts are preferred. Exemplary anionic surfactants
which can be included in the conditioning solution are Na
2-ethylhexyl sulfate, sold under the trade designation Niaproof 08
and Na dodecylbenzenesulfonate, sold under the trade designation
Calsoft Las 99. Where present, non-ionic surfactants are preferably
present in the conditioning solution in a concentration between
about 0.0005 and about 1.00 wt. %.
[0073] Preferably, the conditioner comprises the combination of
between about 0.1 and about 3 wt. % transition metal selected from
the group consisting of Zn, Ni, Co, Cu, Ag, Au, Pd and other
platinum group metals, more preferably Zn, Ni, Co, Ag, Au, or Pd,
still more preferably Zn, Ni, or Co, most preferably Zn, and
between about 0.05 and about 2.5 wt. % of a nitrogen-containing
aromatic heterocycle comprising a ring .dbd.NR.sup.7 group. More
preferably, such solution further comprises between about 0.04 and
about 4 wt. % iodide ion, preferably in the form of KI.
[0074] Preferred embodiments of the conditioner generally also
contain an anionic surfactant in a concentration between about
0.001 and about 0.03 wt. % and/or a glycol ether in a concentration
between about 0.5 and about 5 wt. %. Preferred embodiments
generally also contain an alkanolamine such as monoethanolamine in
a concentration between about 0.5 and about 5 wt. %.
[0075] In each of these various embodiments, the nitrogen-bearing
aromatic heterocycle preferably comprises purine or a purine
derivatives in a concentration between about 0.05 and about 2.5 wt.
%.
[0076] The etched copper conducting layer is next rinsed of the
conditioner composition, generally in warm water (tap water or
deionized) for between 10 and 120 seconds. Preferably, the rinse
water is deionized water to allow better process control. The rinse
water is preferably allowed to drain for 10 to 30 seconds in order
to avoid undue dilution of the subsequent process composition.
Preferably prior to contact with the adhesion promotion
composition, the copper surface will be substantially dry or have
only minimal wetness.
Adhesion Promotion
[0077] The cleaned and etched surfaces of the copper conducting
layer are next contacted with an adhesion promotion composition.
Contact with the adhesion promotion composition may be by any
conventional means, for example by immersion in a bath of the
adhesion promotion composition or by spraying or any other means of
contact. Contact may be as part of a continuous process. As is well
understood in the art, immersion processes involve simply dipping
the substrate into a bath of the composition for the desired
period. Spray processes typically involve application using a
series of automated squeegee-type mechanisms. The method of
application is not critical to the invention. However, as discussed
above, the tolerance for copper loading can be greater for spray
processes than for dip processes because, for example, there is
more bath stagnation with dip processes.
[0078] The adhesion promotion composition may comprise an oxidizing
agent. Useful oxidizing agents include hydrogen peroxide and
persulfates, e.g., ammonium persulfate, potassium persulfate,
sodium persulfate, and the like. In general, hydrogen peroxide is
incorporated into the adhesion promotion composition of the
invention as an oxidizing agent to oxidize copper on the substrate.
The oxidizing agent, e.g., hydrogen peroxide, is present in the
adhesion promotion composition at a concentration of at least about
1 wt %. The concentration of oxidizing agent, e.g., hydrogen
peroxide, is typically no greater than about 20%, and in certain
preferred embodiments it is no greater than about 10%. One
preferred concentration of hydrogen peroxide is from about 0.5% by
weight of the adhesion promotion composition to about 4% by weight.
It has been found that when the concentration of hydrogen peroxide
in the adhesion promotion composition is too high the structure of
the roughened surface of the conducting layer forms a somewhat
dendritic structure which is more fragile than the desired
roughening effect, so that it forms a weaker bond than when lower
concentrations of hydrogen peroxide are used. Moreover, the
organometallic conversion coating becomes hazy if there is
over-etching by too much hydrogen peroxide. All percentages herein
are by weight unless indicated otherwise. Moreover, all
concentrations are normalized such that they refer to
concentrations of each element as if used in 100% concentrations.
For example, in one embodiment the H.sub.2O.sub.2 solution added to
the composition is 35% concentrated H.sub.2O.sub.2, rather than a
100% concentrated H.sub.2O.sub.2. However, the 20%, 10%, 4% etc.
numbers provided above are % of 100% H.sub.2O.sub.2 in the final
composition, not % of 35% H.sub.2O.sub.2 in the final
composition.
[0079] To enhance the stability of the composition, the composition
is preferably initially substantially free of copper and any other
transition metals which have a tendency to destabilize the
oxidizing agent. For example, copper ions are avoided in the
initial solution because they have a tendency to destabilize
hydrogen peroxide. This requirement pertains to the initial
composition in that the copper is avoided in the fresh composition
before its use to promote adhesion. Upon use, however, copper is
not excluded from the composition because, in fact, copper does
tend to accumulate in the solution during use.
[0080] Certain other transition metal ions have been found to
contribute to the thermal stability of the conversion coating
without destabilizing the peroxide. The transition metals
beneficially contained in the initial bath include nickel, cobalt,
silver, gold, palladium and other platinum group metals.
[0081] Other than nickel, cobalt, silver, gold, palladium, other
platinum group metals' (plus copper with which the composition
becomes loaded during use), the adhesion promoting composition is
"substantially" free of transition metals in that any trace amounts
in the composition are sufficiently low as to not significantly
contribute to degradation of the oxidizing agent; for example,
sufficiently low as to not increase the degradation rate by more
than about 10%.
[0082] The adhesion promotion composition comprises one or more
inorganic acids for the main purpose of solubilizing copper, and
maintaining other components of the composition in solution. A
variety of acids, such as mineral acids including phosphoric acid,
nitric acid, sulfuric acid, and mixtures thereof are workable. In
one preferred embodiment both HNO.sub.3 and H.sub.2SO.sub.4 are
employed. It has been discovered that in addition to solubilizing
the Cu, H.sub.2SO.sub.4 helps to moderate the etch rate, and
therefore help prevent over-etching of the substrate in isolated
areas. The HNO.sub.3 increases the etch rate; increases the
solubility of Cu; helps prevent premature sludge formation; and
works synergistically with H.sub.2O.sub.2, H.sub.2SO.sub.4, and the
corrosion inhibitor to darken the coating. The overall acid
concentration in the composition is generally at least 1%,
preferably at least 8%, and in certain preferred embodiments at
least 14% of the composition. The etch rate is slowed excessively
if the acid concentration is too high, with the exception of nitric
acid, and can yield an organometallic conversion coating which is
non-uniform and too light in color. For this reason, the acidity
level in previous compositions had been typically selected to be
about 20%. However, in the present invention it is possible to push
the acidity level up to about 25% and above, because with the other
additives described herein, the coating is not lightened as would
otherwise be expected with an acid level elevated to about 25%. The
overall acid level is typically maintained below about 50%. In one
preferred embodiment, therefore, there is between about 22% and
about 28% acid, including about 20% H.sub.2SO.sub.4 (50% grade) and
about 5% HNO.sub.3 (95% grade). In one preferred embodiment, the
inorganic acid constitutes at least about 30% of the composition.
Another preferred embodiment employs 28% H.sub.2SO.sub.4 (50%
grade) and 5% HNO.sub.3 (95% grade). HNO.sub.3 is employed in these
preferred embodiments because it has been discovered that it has a
unique ability to solubilize the inhibitor-Cu complex better than
do other mineral acids. It contributes to the etch rate, improves
the topography of the conversion coating and enhances copper
loading capacity of the adhesive promoting bath. While weight
fractions given above are percentages of the acids in the final
composition and are based on use of 100% concentrated acid, as
discussed above, the preferred forms of the acids actually added
are 50% concentrated H.sub.2SO.sub.4 and about 95% concentrated
HNO.sub.3.
[0083] Where a combination of nitric and sulfuric acids is
contained in the adhesion promoting solution, the total mineral
acid content is preferably at least about 20 wt. %. It is further
preferred that nitric acid be present in a concentration of at
least the difference between the total mineral acid content and 20
wt %.
[0084] Inasmuch as certain of the preferred compositions employ
HNO.sub.3, the overall composition is formulated to be compatible
therewith. In particular, thiourea-based complexing agents are
specifically avoided due to the explosive nature thereof when mixed
with HNO.sub.3.
[0085] In general, triazoles, tetrazoles, imidazoles and mixtures
thereof have been proposed as corrosion inhibitors in adhesion
promotion compositions. Useful corrosion inhibitors include
benzotriazole, triazole, benzimidazole, imidazole, Benzotriazole
(BTA) compounds are most preferred due to their effectiveness in
chelating Cu, their effectiveness to inhibit corrosion, and their
effectiveness to help darken the organometallic conversion coating
surface. The most preferred BTA compound currently is
1,2,3-benzotriazole, also known as aziamino-benzene or benzene
azimide, and has the formula C.sub.6H.sub.4NHN.sub.2. Purine and
the purine derivatives of Formula I can also be used, as may the
multi-functional compounds of Formulas I(a), I(b), III, IV and V.
Particularly desirable results are achieved with corrosion
inhibitor concentrations of at least 0.1%, more preferably more
than 0.5% by weight, and something more than 1% by weight.
Generally, the corrosion inhibitor will be present in the
composition in an amount no greater than 20%, preferably no greater
than 10%, and more preferably less than 5% by weight of the total
weight of the adhesion promotion composition. High concentrations,
such as more than 5% can be desirable as they can allow a reduction
in the processing time. In certain preferred embodiments, however,
the concentration is less than 5% or even less than 1%.
[0086] The invention also employs various additives to the adhesion
promoting composition, as discussed in more detail below, selected
from among monomeric and oligomeric alcohols, and polymeric,
oligomeric, and monomeric alcohol derivatives, including, but not
limited to alcohol sulfates, sulfonates, and ethoxylates.
[0087] Preferred embodiments of the invention may employ a
sulfonated anionic surfactant. It has been discovered that in
addition to surface wetting, this surfactant helps to stabilize the
H.sub.2O.sub.2. The most particularly preferred of such surfactants
is dodecylbenzene sulfonic acid (DDBSA). DDBSA is available from
Ashland Distribution Company of Santa Ana, Calif.; or from Pilot
Chemical Company of Santa Fe Springs, Calif. under the trade
designation Calsoft LAS 99. Other such surfactants include sodium
dodecylbenzene sulfonate available from Witco Corporation, Organic
Division, of New York, N.Y. under the trade designation Witconate
1850; the isopropyl amine salt of branched alkyl benzene sulfonate
available from Stepan Company of Northfield, Ill. under the trade
designation Polystep A-11; and TEA dodecylbenzene sulfonate
available from Norman, Fox & Company of Vernon, Calif. under
the trade designation Norfox T-60. The sulfonated anionic
surfactant is used in a quantity sufficient to achieve surface
wetting and H.sub.2O.sub.2 stabilization, which quantity can vary
depending on the overall composition of the adhesion promoter. One
currently preferred embodiment includes at least about 0.0001% of
sulfonated anionic surfactant. As a general proposition, the
sulfonated anionic surfactant concentration is at least about
0.005%, preferably at least about 0.1%; and is less than about 10%,
preferably less than about 5%, more preferably less than about 2%.
One specific example employs 0.002% of this surfactant,
particularly DDBSA.
[0088] A currently preferred embodiment of the invention also
incorporates a sulfated anionic surfactant. One preferred example
of this compound is sodium 2-ethylhexyl sulfate, also known as
2-ethylhexanol sulfate sodium salt, having the formula
C.sub.4H.sub.9CH(C.sub.2H.sub.5)CH.sub.2SO.sub.4Na. This is
available from Niacet Corporation of Niagara Falls, N.Y. under the
trade designation Niaproof 08, which contains 38.5 to 40.5% sodium
2-ethylhexyl sulfate and the balance water. Alternatives include
sodium tetradecyl sulfate available from Niacet under the trade
designation Niaproof 4, sodium lauryl sulfate available from Stepan
Company of Northfield, Ill. under the trade designation Polystep
B-5, and sodium n-decyl sulfate available from Henkel
Corporation/Emery Group, Cospha/CD of Ambler, and Pennsylvania
under the trade designation Sulfotex 110. The addition of a
sulfated anionic surfactant compound surprisingly permits the
acidity level to be raised, without the expected detrimental effect
of lightening the coating. Because the acidity level can be raised
in this manner, copper loading is increased. It also helps darken
the coating. This compound is present in this embodiment in a
concentration sufficient to increase copper loading without
substantial lightening of the coating. The typical concentration is
at least about 0.001%, and preferably at least about 0.1%. The
concentration of sulfated anionic surfactant is no greater than
about 10%, and preferably no greater than about 5%. One preferred
range is between about 0.05 and 2%. In one preferred embodiment the
sulfated anionic surfactant concentration is about 0.5%. In another
it is 0.15%.
[0089] In a currently preferred embodiment, the composition also
includes a nonionic surfactant. Anionic and nonionic surfactants
complement each other in the action of the adhesion promoter to
produce a conversion coating with the most favorable properties for
enhancing the adherence of resin to copper conductor. Anionic
surfactants are effective in removing oily/greasy residue on the
copper substrate and preventing their re-deposition. But anionic
surfactants also comprise a negatively charged head that can easily
be deactivated by water hardness (Ca.sup.2+ and Me.sub.2.sup.+
ions) that inhibits their cleaning efficiency. Builders can
optionally be used to sequester calcium and magnesium ions and
thereby preserve the effectiveness of anionic surfactants. But the
presence of nonionics assures that the oily residues are removed
even in hard water adhesion promoting formulations because, lacking
a negative charge, nonionics are unaffected by calcium or magnesium
ions.
[0090] In any event, the combination of an anionic and nonionic
surfactant in the adhesion promoting solution has been discovered
to provide the unexpected additional benefit of improving peel
strength. In one preferred embodiment this surfactant is one or
more ethoxylated nonylphenols, such as polyoxyethylene nonylphenol.
Polyoxyethylene nonylphenol is available from Dow Chemical Company
of Midland, Mich. under the trade designation Tergitol NP9.
Alternatives include an ethoxylated nonylphenol available from Dow
Chemical Company of Midland, Mich. under the trade designation
Tergitol NPB, nonylphenoxypolyethoxyethanol available from Union
Carbide Corporation of Danbury, Conn. under the trade designation
Triton N, and ethoxylated nonylphenol (or nonoxynol-2) available
from Rhone-Poulenc, Surfactant & Specialty Division of New
Jersey under the trade designation Igepal CO-210. The concentration
of this surfactant is selected to be sufficient to improve peel
strength. One currently preferred embodiment includes at least
about 0.0001% of an ethoxylated phenol derivative. As a general
proposition, the concentration is at least about 0.01%, preferably
at least about 0.2%; and is less than about 10%, preferably less
than about 5%. One preferred range is between about 0.0001% and
about 2%. One exemplary embodiment contains 0.02%.
[0091] It has been discovered that incorporating certain alcohols
into the adhesion promotion composition that solubilize the BTA
copper complex can enhance copper loading capacity of the adhesion
promotion composition. The alcohols may be monohydric or they may
be multihydric, e.g., dihydric (i.e., diols), trihydric (i.e.,
triols), tetrahydric, pentahydric, etc. The alcohols may be
primary, secondary, and/or tertiary alcohols.
[0092] Suitable aliphatic alcohols include monohydric alcohols such
as methanol, ethanol, n-propanol, isopropanol, n-butanol,
isobutanol, tert-butanol, pentanol, neopentanol, hexanol,
cyclohexanol, furfuryl alcohol, and tetrahydrofurfuryl alcohol, and
so forth. In general, due to elevated process conditions, alcohols
having higher boiling points, e.g., above about 110.degree. C. are
preferred over alcohols having lower boiling points.
[0093] Suitable aliphatic saturated alcohols include dihydric
alcohols, e.g., diols, such as ethylene glycol; propylene glycols
such as propane-1,2-diol and propane-1,3-diol; butylene glycols
such as butane-1,2-diol, butane-1,3-diol, butane-2,3-diol,
butane-1,4-diol, and 2-methylpropane-1,3-diol; pentylene glycols
such as pentane-1,5-diol, pentane-1,4-diol, pentane-1,3-diol,
2,2-dimethyle-1,3-propanediol, etc.; hexylene glycols such as
hexane-1,2-diol, hexane-1,4-diol, hexane-1,5-diol, hexane-1,6-diol,
2-methylpentane-2,4-diol, 1,2-cyclohexanediol, etc.; heptylene
glycols such as 2-methyl-2-propyl-propane-1,3-diol; octylene
glycols such as 2-ethyl-hexane-1,3-diol and
2,5-dimethylhexane-2,5-diol; nonanediols, decanediols,
dodecanediols, and so forth. Also suitable are certain derivatives
of diols, such as ethers, including methoxypropanols,
methoxybutanols, etc.
[0094] Suitable aliphatic saturated alcohols also include triols,
such as glycerol, butanetriol, pentanetriol, etc.
[0095] Oligomeric alcohols are those alcohols and alcohol
derivatives, e.g., ethers, that comprise multiple repeat units of
the general formula:
##STR00017##
wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6
may be hydrogen or a low molecular weight hydrocarbon having,
generally from 1 to about 6 carbon atoms, more generally from 1 to
about 3 carbon atoms, and even more generally from 1 to 2 carbon
atoms. In general, the number of repeat units in an oligomer is
low, such as between about 2 and about 12, more generally between
about 2 and about 6, more generally, 2, 3, or 4. Suitable
oligomeric alcohols include diethylene glycol, diethylene glycol
methyl ether, diethylene glycol dimethyl ether, triethylene glycol,
triethylene glycol monomethyl ether, triethylene glycol dimethyl
ether, dipropylene glycol,
[0096] Also suitable are unsaturated diols, such as butene diol,
hexene diol, and acetylenics such as butyne diol. An example of a
suitable trihydric alcohol is glycerol.
[0097] This additive is present in this embodiment at a
concentration sufficient to increase copper loading of the
composition. Typically, this concentration is at least about 0.01%,
and in certain embodiments is at least about 0.5%. The
concentration of this additive is no greater than about 20%, and in
certain embodiments no greater than about 10%.
[0098] Preferred alcohols include propylene glycol and/or
oligomeric polypropyleneglycol having a molecular weight generally
between about 300-4000 g/mol and about 4000 g/mol, preferably about
80 g/mol and about 76.09 g/mol. The propylene glycol and/or
oligomeric polypropyleneglycol may be added in a concentration
range between about 0.1 wt. % and about 5 wt. %, more suitably
between about 0.2 wt. % and about 1 wt. %, such as about 0.5 wt. %.
Incorporation of propylene glycol and/or oligomeric
polypropyleneglycol into the adhesion promotion composition has
been discovered to generally improve the peel strength of the
copper conducting layer with the pre-preg and to improve the
appearance of the organometallic conversion coating.
[0099] Another preferred alcohol that has proven to be especially
effective is the oligomer triethylene glycol (TEG). In particular,
compositions containing this oligomer have copper-loading capacity
of about 30 grams copper per liter solution up to about 35 and even
about 40 g/L in dip process applications. In spray process and
flooded immersion process applications, automated and conveyorized
applications, these compositions have copper-loading capacity of up
to about 45 g/L and even up to 50 g/L. This triethylene glycol is
an oligomer in that it is a molecule of intermediate relative
molecular mass with a structure comprising a small number of units
derived from molecules of lower relative molecular mass. This is in
contrast to a polymer, which has a high relative molecular mass.
This triethylene glycol is also oligomeric in that its properties
vary significantly with removal of one of its units; as opposed to
polymeric compounds, with which removal of one or a few units has a
relatively negligible effect on molecular properties. This
triethylene glycol has the molecular formula
C.sub.6H.sub.14O.sub.4, more specifically, HO(C.sub.2HO).sub.3H,
and a molecular weight of 150.17. Triethylene glycol is present in
this embodiment at a concentration of at least about 0.01%,
typically at least about 0.5%, and in one embodiment at least about
0.8%. The concentration of TEG is no greater than about 20%, and
preferably no greater than about 10%. In a currently preferred
embodiment the TEG concentration is about 1%. The TEG also has the
added benefit of helping to stabilize the H.sub.2O.sub.2.
[0100] The composition optionally also includes an additional
stabilizing agent for the H.sub.2O.sub.2. Suitable stabilizing
agents include, for example, dipicolinic acid, diglycolic and
thiodiglycolic acid, ethylene diamine tetra-acetic acid and its
derivatives, magnesium salt of an aminopolycarboxylic acid, sodium
silicate, phosphates, phosphonates, and sulfonates. When the
composition includes a stabilizing agent, preferably the
stabilizing agent is present in an amount of from 0.001% or even at
least 0.005% by weight of the adhesion promotion composition.
Generally there is no more than 1% by weight in the composition.
The currently preferred composition contains an additional
stabilizing agent, but relies primarily on the stabilizing function
of the TEG, as described above.
[0101] The composition further includes a source of halide ions.
This source is preferably HCl, and provides a chloride ion
concentration in the range of about 10 pp to 100 ppm, preferably
between about 20 ppm and about 100 ppm, even more preferably
between about 30 ppm and about 100 ppm. The units "ppm" in the
context of an aqueous composition are in terms of mass: volume, so
1 ppm is generally equivalent to 1 microgram per milliliter, or
about 1 mg per liter. In one embodiment, the chloride ion
concentration range is between about 60 and 65 ppm. In one
embodiment, the chloride ion concentration range is between about
65 and 75 ppm. In one embodiment, the chloride ion concentration
range is between about 75 and 85 ppm. In one embodiment, the
chloride ion concentration range is between about 85 and 95 ppm.
Preferred ranges are different for other embodiments depending on
the overall composition and application. This increased Cl.sup.-
level in comparison to previous formulations helps to increase the
ratio of cuprous copper to cupric copper, which has been discovered
to increase peel strength. The Cl.sup.- level tapers off and then
stabilizes during use of the composition. As such, an initial
Cl.sup.- ion concentration of between about 20 ppm and about 100
ppm is preferred in one embodiment in order to achieve Cl.sup.- ion
content in service of on the order of about 20 to 80 ppm.
[0102] The adhesion promotion composition is manufactured by mixing
the components in an aqueous solution, preferably using deionized
water. In accordance with standard safe practice, hydrogen peroxide
is added to the composition in a diluted form.
[0103] In one form the adhesion promotion composition is ready to
use and can be used directly for immersion or other exposure of the
substrate. In another form the invention is a concentrate that is
to be diluted to form the composition for immersion or other
exposure.
[0104] An exemplary ready-to-use composition includes the
following: [0105] 0.5 to 8 wt % H.sub.2O.sub.2 [0106] 16 to 25 wt %
H.sub.2SO.sub.4 [0107] 0.1 to 10 wt % HNO.sub.3 [0108] 0.1 to 2 wt
% 1,2,3-benzotriazole [0109] 0.01 to 5 wt % triethylene glycol
[0110] 0.05 to 2 wt % 2-ethyloxosulfonate (Niaproof 08) [0111]
0.0001 to 2 wt % dodecylbenzene sulfonic acid (DDBSA) [0112] 0.0001
to 2 wt % polyoxyethylene nonylphenol (Tergitol NP9) [0113] 40 to
70 wt % deionized water
[0114] When provided as a concentrate, the ranges described above
for the preferred proportions of the ingredients are essentially
doubled, because the product is diluted with, for example, 50%
water upon formulation of the composition for use. In one
embodiment, the concentrate has the following ingredients: [0115]
32-50 wt % H.sub.2SO.sub.4 [0116] 0.2 to 20 wt % HNO.sub.3 [0117]
0.2 to 4 wt % 1,2,3-benzotriazole [0118] 0.02 to 10 wt %
triethylene glycol [0119] 0.002 to 4 wt % 2-ethyloxosulfonate
(Niaproof 08) [0120] 0.0002 to 4 wt % dodecylbenzene sulfonic acid
(DDBSA) [0121] 0.0002 to 4 wt % polyoxyethylene nonylphenol
(Tergitol NP9)
[0122] The H.sub.2O.sub.2 is added later and is not included in the
concentrate formulation. This concentrate is then incorporated into
an overall solution in which, for example, about 43 wt % is this
concentrate, about 7 wt % is H.sub.2O.sub.2, and about 50 wt % is
water.
[0123] As mentioned above, various preferred embodiments of the
adhesion promoting composition also contain a transition metal ion
but it has been found important to be selective in choosing a
transition metal ion for the composition. A substantial class of
transition metal ions can adversely affect the stability of the
peroxide component of the composition and/or promote release of
excessive volumes of hazardous gases, e.g., H.sub.2, O.sub.2,
NO.sub.x and SO.sub.x. However, other transition metal ions can
contribute to the thermal stability of the conversion coating
produced in the adhesion promoting step of the process without
material adverse effect on the stability of the peroxide and
without generating excessive volumes of hazardous gases.
[0124] Preferred transition metal ions for inclusion in the
adhesion promoting solution include zinc, nickel, copper, cobalt,
silver, gold, palladium and other platinum group metals. The
transition metal ions are preferably incorporated into the adhesion
promoting composition in the form of their salts. Thus, the
preferred adhesion promoting solution contains zinc, nickel,
copper, cobalt, silver, gold, palladium or other platinum group
metals in the form of their cations plus a counteranion derived
from the salt that serves as the transition metal ion. More
preferably, the transition metal ion comprises Zn, Ni, Co, Ag, Au,
Pd or other platinum group metals, still more preferably Zn, Ni,
Co, or Ag, or Zn, Ni, or Co. Preferably, the transition metal is
introduced in the form of a sulfate, chloride, bromide, iodide,
phosphate, or any of various carboxylates, including, e.g., malates
and oxalates. Complex salts, such as, e.g., zinc ammonium halides,
can also be used. Preferably, the adhesion promoting solution
contains the transition metal ion in a concentration between about
0.02 wt. % and about 2 wt. %, a nitrogenous corrosion inhibitor in
a concentration between about 0.1 and about 5 wt. %, sulfuric acid
in a concentration between about 10 and about 50 wt. % and hydrogen
peroxide in a concentration between about 1 and about 10 wt. %.
More preferably, the composition contains one or more anionic
surfactants in a concentration between about 0.01 and 1 wt. %, and
an alcohol in a concentration between about 0.1 and 3 wt. %. Still
more preferably, the composition further comprises a one or more
nonionic surfactants in a concentration between about about 0.0005
and about 0.2 wt. %. In each of these various embodiments, it is
preferred that the composition further comprise nitric acid in a
concentration between about 0.5 and about 15 wt. %.
[0125] Most preferably, the transition metal ion component of the
adhesion promoting solution comprises zinc ion. A particularly
preferred source of zinc ion is ZnSO.sub.4.
[0126] In an especially preferred embodiment, the adhesion
promoting composition comprises: [0127] 20-35 wt. % sulfuric acid;
[0128] 2-8 wt. % nitric acid; [0129] 4-12 wt. % hydrogen peroxide;
[0130] 0.2 to 3 wt. % benzotriazole (Cobratec 99); [0131] 0.05 to
0.5 wt. % zinc sulfate; [0132] 0.2 to 2 wt. % triethylene glycol;
[0133] 0.02 to 0.5 wt. % Na 2-ethylhexyl sulfate sold under the
trade designation Niaproof 08; [0134] 0.0005 to 0.01 wt. % Na
dodecylbenzenesulfonate sold under the trade designation Calsoft
Las 99; [0135] 0.0005 to 0.01 wt. % polyoxyethylene nonylphenol
sold under the trade designation Tergitol NP9; and balance
deionized water, typically 45 to 70 wt. %.
[0136] Contact of the copper surface with the adhesion promotion
composition is typically at a temperature between about 20.degree.
C. and about 40.degree. C., though temperatures reasonably outside
this range are operable. The contact time is generally no less than
1 second, preferably no less than 5 seconds, and often at least 10
seconds, most preferably at least 30 seconds. The maximum contact
time may be up to 10 minutes, although preferably the contact time
is no greater than 5 minutes, most preferably no greater than 2
minutes. A contact time of about 1 minute or less than 1 minute is
standard. If the contact time of the adhesion promotion
composition' with the copper surface is too long, there is a risk
that the copper surface may be etched away due to dissolution
and/or that a deposit other than the micro-porous crystalline
deposit that forms the micro-roughened surface will be deposited
onto the surface of the conducting material.
[0137] The copper conducting layer having the organometallic
conversion coating thereon is next rinsed of the adhesion promotion
composition, generally in warm water (tap water or deionized) for
between 10 and 120 seconds. Preferably, the rinse water is
deionized water to allow better process control. The rinse water is
preferably allowed to drain for 10 to 30 seconds and the surface is
then dried.
[0138] After contact of the copper surface with the adhesion
promotion composition to form the micro-roughened surface,
generally a Pre-preg layer may be placed directly adjacent to the
copper surface and the Pre-preg layer adhered directly to the
copper surface in the adhesion step, forming a multi-layer PCB.
[0139] Appropriate substrate materials for a printed circuit board
include, for example, high-pressure laminates (i.e., layers of
fibrous materials bonded together under heat and pressure with a
thermosetting resin). In general, a laminate layer comprises an
electrical-grade paper bonded with phenolic or epoxy resin or a
continuous-filament glass cloth bonded with an epoxy-resin system.
Specific examples of laminate layers are: XXXPC which is an
electrical paper impregnated with phenolic resin; FR-2 which is
similar to XXXPC with a flame retardant property; FR-3 which is a
self-extinguishing laminate of electrical paper and epoxy resin;
G-10 which is a laminate of glass cloth sheets and epoxy resin;
FR-4 which is a self-extinguishing laminate similar to G-10; G-11
which is a glass cloth and epoxy mixture; FR-5 which is a
flame-resistant version of G-11. In one embodiment of the present
invention, the organic circuit board material is an FR-4 laminate
layer that is placed on top of, and in intimate contact with the
passive component pattern, and the two are laminated together.
[0140] Generally in the adhesion step heat and pressure are applied
to initiate the adhesion reaction. In the adhesion step, mechanical
bonding is due to penetration of the polymeric material of the
insulating layer into the micro-roughened surface provided in the
adhesion promotion step. Although it may be desirable to follow the
adhesion promotion step with a specially formulated rinse step, it
is often adequate to rinse just with water.
[0141] A pre-preg insulating layer is applied directly to the
micro-roughened surface, i.e., preferably without any intermediate
metal deposition onto the micro-roughened surface or the like,
although optionally with a post-treatment cupric oxide removal or
reduction operation to further enhance the bond strength as
disclosed in U.S. Pat. No. 6,294,220. Pressure is applied by
placing the layers that are to form the multi-layer laminate of the
PCB in a press. Where pressure is applied it is generally from 100
to 400 psi, preferably from 150 to 300 psi. The temperature of this
adhesion step will generally be at least about 100.degree. C.,
preferably between about 120.degree. C. and about 200.degree. C.
The adhesion step is generally carried out for any period from 5
minutes to 3 hours, most usually from 20 minutes to 1 hour, but is
for sufficient time and pressure and at a sufficiently high
temperature to ensure good adhesion between the first and second
layers. During this adhesion step, the polymeric material of the
insulating layers, generally an epoxy resin tends to flow ensuring
that the conductive pattern in the metal is substantially sealed
between insulating layers, so subsequent penetration of water and
air is avoided. Several layers may be placed together in the
adhesion step to effect lamination of several layers in a single
step to form the MLB.
[0142] Though the exemplary arrangement discussed at length herein
is a pre-preg layer adhered to a copper surface, the invention also
includes improving adhesion of other dielectric materials, whether
permanent or temporary, to copper. For example, the invention
improves adhesion between copper and a solder mask that is
dielectric. It similarly improves copper adhesion with inks,
polymeric photo-resists, and dry films. It also has application in
connection with photo-imageable dielectrics or other dielectrics
used in the context of high density interconnect and sequential
build up technologies.
[0143] Having described the invention in detail, it will be
apparent that modifications and variations are possible without
departing from the scope of the invention defined in the appended
claims.
EXAMPLES
[0144] The following non-limiting examples are provided to further
illustrate the present invention.
Example 1
Control Adhesion Promotion Process
[0145] Multiple adhesion promotion processes were carried out on
test copper coupons using commercially available microetchant,
cleaner, and adhesion promotion compositions. These processes,
designated A0S, were control processes and were carried out in
order to provide comparative data for peel strength, conversion
coating appearance, and number of solder dip cycles to
delamination.
[0146] The adhesion promotion processes were carried out on three
sets of 1'' (25.4 mm) by 2'' (50.8 mm) copper coupons according to
the following protocol: [0147] 1. Contact the surfaces of copper
coupons with micro-etchant Enthone.RTM. PC-7077 (40-60%
concentration, available from Enthone Inc.) by immersion or
spraying the coupons in or with the microetchant composition for 30
to 45 seconds at a solution temperature between of 27.degree.
C..+-.3.degree. C. PC-7077 is a conventional micro-etchant that
contains Na persulfate, Na phenolsulfate and sulfuric acid.
TABLE-US-00001 [0147] MAKE-UP 100 GALS. % BY PC 7077 NON-FLUORIDE
AMT IN. WT. MICROETCH LBS. GALS. (F = 1.89) SOFT WATER 606.507
72.68 55.48 SODIUM PERSULFATE 317.028 29.00 SODIUM PHENOLSULFONATE
4.373 0.40 POWDER SULFURIC ACID 50% 165.292 15.12 TOTAL 1093.200
100.00
[0148] 2. Rinse the coupons in warm water (tap water or deionized)
for 30 seconds. [0149] 3. Contact the etched surfaces of the copper
coupons with alkaline cleaner/Conditioner Enthone.RTM. PC 7096 10
to 15% concentration, available from Enthone Inc.) by immersion or
spraying the coupons in or with the alkaline cleaner composition
for 60-120 seconds at a solution temperature between of 43.degree.
C..+-.6.degree. C. [0150] 4. Rinse the coupons in warm water (tap
water or deionized) for 30 seconds. The water was allowed to drain
from the coupons for 10 to 20 seconds to avoid unnecessary dilution
of the adhesion promotion composition. [0151] 5. Contact the
cleaned and etched surfaces of the three copper coupons with
adhesion promotion composition AlphaPREP.RTM. PC-7030 (100%
concentration, available from Enthone Inc.) by immersion or
spraying the coupons in or with the adhesion promotion composition.
One set of coupons was contacted with AlphaPREP.RTM. PC-7030 for 45
seconds. One set of coupons was contacted with AlphaPREP.RTM.
PC-7030 for 1 minute. One set of coupons was contacted with
AlphaPREP.RTM. PC-7030 for 2 minutes. The solution temperature
between of 43.degree. C..+-.6.degree. C. The adhesion promotion
composition contained the following components and
concentrations:
TABLE-US-00002 [0151] Component Concentration H.sub.2O.sub.2 7.2
wt. % H.sub.2SO.sub.4 28.0 wt. % HNO.sub.3 5.0 wt. %
1,2,3-Benzotriazole 1.0 wt. % Triethylene glycol 0.9 wt. %
2-ethyoxosulfonate (Niaproof 08) 0.15 wt. % Dodecylbenzene Sulfonic
acid (DDBSA) 0.002 wt. % Polyoxyethylene Nonylphenol (Tergitol NP
9) 0.002 wt. % Chloride ion 65-75 ppm Water (Deionized) Balance
[0152] 6. Rinse the coupons in warm water (tap water or deionized)
for 30 seconds. [0153] 7. Air dry the coupons at ambient
temperature or up to about 35-40.degree. C., for between 30 seconds
to 5 minutes, as needed.
[0154] The copper coupons treated in this manner were inspected for
coating appearance and defects prior to lamination to a standard
FR4 pre-preg laminate such as Isola FR370HR (high Performance FR-4
material).
Example 2
Control Adhesion Promotion Process
[0155] Multiple adhesion promotion processes were carried out on
test copper coupons using commercially available microetchant,
cleaner, and adhesion promotion compositions. These processes,
designated A0, were control processes and were carried out in order
to provide comparative data for peel strength, conversion coating
appearance, and number of solder dip cycles to delamination. The A0
control processes were carried out in a similar manner to the A0S
control processes of Example 1, except that the chloride ion
concentration of the adhesion promotion composition was increased
to between about 85 and about 95 ppm.
[0156] The adhesion promotion processes were carried out on three
sets of 1'' (25.4 mm) by 2'' (50.8 mm) copper coupons according to
the following protocol: [0157] 1. Contact the surfaces of three
copper coupons with microetchant Enthone.RTM. PC-7077 (40-60%
concentration, available from Enthone Inc.) by immersion or
spraying the coupons in or with the microetchant composition for 30
to 45 seconds at a solution temperature between of 27.degree.
C..+-.3.degree. C. [0158] 2. Rinse the coupons in warm water (tap
water or deionized) for 30 seconds. [0159] 3. Contact the etched
surfaces of the three copper coupons with alkaline cleaner
Enthone.RTM. PC-7096 (10 to 15% concentration, available from
Enthone Inc.) by immersion or spraying the coupons in or with the
alkaline cleaner composition for 60 seconds at a solution
temperature between of 43.degree. C..+-.6.degree. C. [0160] 4.
Rinse the coupons in warm water (tap water or deionized) for 30
seconds. The water was allowed to drain from the coupons for 10 to
20 seconds to avoid unnecessary dilution of the adhesion promotion
composition. [0161] 5. Contact the cleaned and etched surfaces of
the three copper coupons with adhesion promotion composition
AlphaPREP.RTM. PC-7030 (100% concentration, available from Enthone
Inc.) by immersion or spraying the coupons in or with the adhesion
promotion composition. One set of coupons was contacted with
AlphaPREP.RTM. PC-7030 for 45 seconds. One set of coupons was
contacted with AlphaPREP.RTM. PC-7030 for 1 minute. One set of
coupons was contacted with AlphaPREP.RTM. PC-7030 for 2 minutes.
The solution temperature between of 43.degree. C..+-.6.degree. C.
The adhesion promotion composition contained the following
components and concentrations: PC 7030M (with MPG: Mono-Propylene
Glycol)
TABLE-US-00003 [0161] Component Concentration H.sub.2O.sub.2 7.2
wt. % H.sub.2SO.sub.4 28.0 wt. % HNO.sub.3 5.0 wt. %
1,2,3-Benzotriazole 1.0 wt. % Triethylene glycol 0.9 wt. %
Mono-propylene Glycol 0.5 wt. % 2-ethyoxosulfonate (Niaproof 08)
0.15 wt. % Dodecylbenzene Sulfonic acid (DDBSA) 0.002 wt. %
Polyoxyethylene Nonylphenol (Tergitol NP 9) 0.002 wt. % Methane
Sulfonic Acid (MSA) 70% 2.00 wt. % Chloride ion 85-95 ppm Water
(Deionized) Balance
PC 7030M-1 (without MPG: Mono-Propylene Glycol.
TABLE-US-00004 Component Concentration H.sub.2O.sub.2 7.2 wt. %
H.sub.2SO.sub.4 28.0 wt. % HNO.sub.3 5.0 wt. % 1,2,3-Benzotriazole
1.0 wt. % Triethylene glycol 0.9 wt. % 2-ethyoxosulfonate (Niaproof
08) 0.15 wt. % Dodecylbenzene Sulfonic acid (DDBSA) 0.002 wt. %
Polyoxyethylene Nonylphenol (Tergitol NP 9) 0.002 wt. % Methane
Sulfonic Acid (MSA) 70% 2.00 wt. % Chloride ion 85-95 ppm Water
(Deionized) Balance
[0162] Although not used in this Example, the following formulation
provides equivalent results.
TABLE-US-00005 [0162] Component Concentration H.sub.2O.sub.2 7.2
wt. % H.sub.2SO.sub.4 28.0 wt. % HNO.sub.3 5.0 wt. %
1,2,3-Benzotriazole 1.0 wt. % Triethylene glycol 0.9 wt. %
2-ethyoxosulfonate (Niaproof 08) 0.15 wt. % Dodecylbenzene Sulfonic
acid (DDBSA) 0.002 wt. % Polyoxyethylene Nonylphenol (Tergitol NP
9) 0.002 wt. % Methane Sulfonic Acid (MSA) 70% 0.00 wt. % Chloride
ion 85-95 ppm Water (Deionized) Balance
[0163] Monopropylene glycol is preferably included to inhibit
premature sludge formation in the adhesion promoting composition
bath. [0164] 6. Rinse the coupons in warm water (tap water or
deionized) for 30 seconds. [0165] 7. Air dry the coupons at ambient
temperature or up to about 35-40.degree. C., for between 30 seconds
to 5 minutes, as needed.
[0166] The copper coupons treated in this manner were inspected for
coating appearance and defects prior to lamination to a standard
phenolic filled, halogen-free and/or polyimide pre-preg laminate.
Useful phenolic filled dielectrics include those sold under the
trade designations Isola 370H, FR408HR, and Isola IS 410. Useful
halogen free, high glass transition temperature dielectrics include
DE 156 and DE 155, while useful polyimides include Isola P95 and
P96.
Example 3
Novel Conditioning Step Followed by Adhesion Promotion Process
[0167] Multiple adhesion promotion processes were carried out on
test copper coupons using commercially available microetchant,
cleaner, and adhesion promotion compositions. These processes,
designated A1, were control processes and were carried out in order
to provide comparative data for peel strength, conversion coating
appearance, and number of solder dip cycles to delamination. The A1
control processes were carried out in a similar manner to the A0
control processes of Example 2, except that the copper coupons were
contacted with a pre-dip composition prior to contact with the
adhesion promotion composition.
[0168] The adhesion promotion processes were carried out on three
sets of 1'' (25.4 mm) by 2'' (50.8 mm) copper coupons according to
the following protocol: [0169] 1. Contact the surfaces of three
copper coupons with microetchant Enthone.RTM. PC-7077 (40-60%
concentration, available from Enthone Inc.) by immersion or
spraying the coupons in or with the microetchant composition for 30
to 45 seconds at a solution temperature between of 27.degree.
C..+-.3.degree. C. [0170] 2. Rinse the coupons in warm water (tap
water or deionized) for 30 seconds. [0171] 3. Contact the etched
surfaces of the three copper coupons with a novel alkaline
cleaner/conditioner Enthone.RTM. (SAM8-R1--10 to 15% concentration)
by immersion or spraying the coupons in or with the alkaline
cleaner composition for 60 seconds at a solution temperature
between of 43.degree. C..+-.6.degree. C. SAM8R-1 has the following
composition:
TABLE-US-00006 [0171] TABLE 1 Formulation of Alkaline Cleaner
Conditioner (SAM8R-10 orXRD111901) as CONTROL Items # Raw Materials
% By wt Gm/L 1 Di Water 89.75 908 2 Dowano DB (Diethtylene Glycol
Butyl 1.86 19 Ether) 3 Caustic Potash 50% (Potassium Hydroxide 0.5
5.06 Liq.) 4 SAM #4 (6-Benzyl Amino Purine) 0.025 0.253 5 KI
(Potassium Iodide) 0.01 0.1 6 Niaproof 08 0.005 0.05 7 MEA
(Monoethanolamine) 1.5 15.2 8 Caustic Soda 50% Liq. (Sodium
Hydroxide 6.25 63.22 9 ZAC (Zinc Ammonium Carbonate Liq.) 0.1 1.01
SPG: 1.01-1.008 (8.430 lb/gal)
[0172] 4. Rinse the coupons in warm water (tap water or deionized)
for 30 seconds. [0173] 5. Contact the cleaned and etched surfaces
of the copper coupons with a pre-dip composition comprising sodium
bicarbonate (Na.sub.2CO.sub.3. H.sub.2O, 30 grams/Liter) for 60
seconds at a solution temperature between of 43.degree.
C..+-.6.degree. C. [0174] 6. Rinse the coupons in warm deionizied
water for 30 seconds. The water was allowed to drain from the
coupons for 10 to 20 seconds to avoid unnecessary dilution of the
adhesion promotion composition. [0175] 7. Contact the cleaned and
etched surfaces of the three copper coupons with adhesion promotion
composition AlphaPREP.RTM. PC-7030 (100% concentration, available
from Enthone Inc.) by immersion or spraying the coupons in or with
the adhesion promotion composition. One set of coupons was
contacted with AlphaPREP.RTM. PC-7030M-1 for 45 seconds. One set of
coupons was contacted with AlphaPREP.RTM. PC-7030 for 1 minute. One
set of coupons was contacted with AlphaPREP.RTM. PC-7030M for 2
minutes. The solution temperature between of 43.degree.
C..+-.6.degree. C. The adhesion promotion composition contained the
following components and concentrations:
TABLE-US-00007 [0175] Component Concentration H.sub.2O.sub.2 7.2
wt. % H.sub.2SO.sub.4 28.0 wt. % HNO.sub.3 5.0 wt. %
1,2,3-Benzotriazole 1.0 wt. % Triethylene glycol 0.9 wt. %
Mono-propylene Glycol 0.5 wt. % 2-ethyoxosulfonate (Niaproof 08)
0.15 wt. % Dodecylbenzene Sulfonic acid (DDBSA) 0.002 wt. %
Polyoxyethylene Nonylphenol (Tergitol NP 9) 0.002 wt. % Methane
Sulfonic Acid 70% 2.00 wt. % Chloride ion 85-95 ppm Water
(Deionized) Balance
[0176] 8. Rinse the coupons in warm water (tap water or deionized)
for 30 seconds. [0177] 9. Air dry the coupons at ambient
temperature or up to about 35-40.degree. C., for between 30 seconds
to 5 minutes, as needed.
[0178] The copper coupons treated in this manner were inspected for
coating appearance and defects prior to lamination to a standard
epoxy or novolac resin.
Example 4
Adhesion Promotion Process with 6-Benzylaminopurine Conditioning
Step
[0179] Multiple adhesion promotion processes were carried out on
test copper coupons. These processes, designated A3, were carried
out according to the method of the present invention. In these
processes, the copper coupons were pre-dipped in a composition
comprising a molecular capable of forming a self-assembled
monolayer on a copper surface. Additionally, the adhesion promotion
composition was further modified with polypropylene glycol.
[0180] The adhesion promotion processes were carried out on three
sets of 1'' (25.4 mm) by 2'' (50.8 mm) copper coupons according to
the following protocol: [0181] 1. Contact the surfaces of three
copper coupons with microetchant Enthone.RTM. PC-7077 (40-60%
concentration, available from Enthone Inc.) by immersion, spraying
or both, the coupons in or with the microetchant composition for 30
to 45 seconds at a solution temperature between of 27.degree.
C..+-.3.degree. C. [0182] 2. Rinse the coupons in warm water (tap
water or deionized) for 30 seconds. [0183] 3. Contact the etched
surface of the three copper coupons with alkaline cleaner
Enthone.RTM. PC-7096 (10 to 15% concentration, available from
Enthone Inc.) by immersing or spraying the coupons in or with the
alkaline cleaner composition for 60 seconds at a solution
temperature between of 43.degree. C..+-.6.degree. C. [0184] 4.
Rinse the coupons in warm water (tap water or deionized) for 30
seconds. [0185] 5. Contact the cleaned and etched surfaces of the
copper coupons with a pre-dip composition comprising 6-benzylamino
purine (5 grams/Liter, available from KingChem or Aldrich Chemicals
for 60 seconds at a solution temperature between of 43.degree.
C..+-.6.degree. C. [0186] 6. Rinse the coupons in warm deionizied
water for 30 seconds. The water was allowed to drain from the
coupons for 10 to 20 seconds to avoid unnecessary dilution of the
adhesion promotion composition. [0187] 7. Contact the cleaned and
etched surfaces of the three copper coupons with adhesion promotion
composition. AlphaPREP.RTM. PC-7030M (100% concentration, available
from Enthone Inc.) modified by adding polypropylene glycol or
propylene glycol (0.5 to 1.0 wt. %) by immersing or spraying the
coupons in or with the adhesion promotion composition. One set of
coupons was contacted with AlphaPREP.RTM. PC-7030 for 45 seconds.
One set of coupons was contacted with AlphaPREP.RTM. PC-7030 for 1
minute. One set of coupons was contacted with AlphaPREP.RTM.
PC-7030 for 2 minutes. The solution temperature between of
43.degree. C..+-.6.degree. C. The adhesion promotion composition
contained the following components and concentrations:
TABLE-US-00008 [0187] Component Concentration H.sub.2O.sub.2 7.2
wt. % H.sub.2SO.sub.4 28.0 wt. % HNO.sub.3 5.0 wt. %
1,2,3-Benzotriazole 1.0 wt. % Triethylene glycol 0.9 wt. %
Polypropylene glycol 0.5 to 1.0 wt. % 2-ethyoxosulfonate (Niaproof
08) 0.15 wt. % Dodecylbenzene Sulfonic acid (DDBSA) 0.002 wt. %
Polyoxyethylene Nonylphenol (Tergitol NP 9) 0.002 wt. % Methane
Sulfonic Acid (MSA) 70% 0.00 Chloride ion 85-95 ppm Water
(Deionized) Balance
[0188] 8. Rinse the coupons in warm water (tap water or deionized)
for 30 seconds. [0189] 9. Air dry the coupons at ambient
temperature or up to about 35-40.degree. C., for between 30 seconds
to 5 minutes, as needed.
[0190] The copper coupons treated in this manner were inspected for
coating appearance and defects prior to lamination to a standard
FR4 pre-preg laminate available under the trade designation Isola
FR4, Panasonic 155 plus, Nanya 170 or Nanya 175.
Example 5
Adhesion Promotion Process Using 6-Benzylaminopurine
Conditioner
[0191] Multiple adhesion promotion processes were carried out on
test copper coupons. These processes, designated 86, were carried
out according to the method of the present invention. In these
processes, the copper coupons were pre-dipped in a composition
comprising a molecular capable of forming a self-assembled
monolayer on a copper surface. Additionally, the adhesion promotion
composition was further modified with methane-sulfonic acid.
[0192] The adhesion promotion processes were carried out on three
sets of 1'' (25.4 mm) by 2'' (50.8 mm) copper coupons according to
the following protocol: [0193] 1. Contact the surfaces of three
copper coupons for 30 to 45 seconds with microetchant Enthone.RTM.
PC-7077 (40-60% concentration, available from Enthone Inc.) by
immersion, spraying or both, while maintaining the solution
temperature between of 27.degree. C..+-.3.degree. C. [0194] 2.
Rinse the coupons in warm water (tap water or deionized) for 30
seconds. [0195] 3. Contact the etched surface of the three copper
coupons with alkaline cleaner Enthone.RTM. SAME-R1 (10 to 15%
concentration, available from Enthone Inc.) by immersion, spraying
or both, the coupons in or with the alkaline cleaner/Conditioner
composition for 60 seconds at a solution temperature between of
43.degree. C..+-.6.degree. C. [0196] 4. Rinse the coupons in warm
water (tap water or deionized) for 30 seconds. [0197] 5. Contact
the cleaned and etched surfaces of the copper coupons with a
pre-dip composition comprising 6-benzylamino purine (5
grams/Liter), available from KingChem or Aldrich Chemical for 60
seconds at a solution temperature between of 43.degree.
C..+-.6.degree. C. [0198] 6. Rinse the coupons in warm deionizied
water for 30 seconds. The water was allowed to drain from the
coupons for 10 to 20 seconds to avoid unnecessary dilution of the
adhesion promotion composition. [0199] 7. Contact the cleaned and
etched surfaces of the three copper coupons with adhesion promotion
composition AlphaPREP.RTM. PC-7030 (100% concentration, available
from Enthone Inc.) modified by adding methanesulfonic acid (2 wt.
%), so that the solution contained nitric, sulfuric and
methanesulfonic acids, and immersing or sprayingthe coupons in or
with the adhesion promotion composition. One set of coupons was
contacted with AlphaPREP.RTM. PC-7030 for 45 seconds. One set of
coupons was contacted with AlphaPREP.RTM. PC-7030 for 1 minute. One
set of coupons was contacted with AlphaPREP.RTM. PC-7030 for 2
minutes. The solution temperature was 43.degree. C..+-.6.degree. C.
The adhesion promotion composition contained the following
components and concentrations:
TABLE-US-00009 [0199] Component Concentration H.sub.2O.sub.2 7.2
wt. % H.sub.2SO.sub.4 28.0 wt. % HNO.sub.3 5.0 wt. %
CH.sub.3SO.sub.4H 2.0 wt. % 1,2,3-Benzotriazole 1.0 wt. %
Triethylene glycol 0.9 wt. % 2-ethyoxosulfonate (Niaproof 08) 0.15
wt. % Dodecylbenzene Sulfonic acid (DDBSA) 0.002 wt. %
Polyoxyethylene Nonylphenol (Tergitol NP 9) 0.002 wt. % Chloride
ion 85-95 ppm Water (Deionized) Balance
[0200] 8. Rinse the coupons in warm water (tap water or deionized)
for 30 seconds. [0201] 9. Air dry the coupons at ambient
temperature or up to about 35-40.degree. C., for between 30 seconds
to 5 minutes, as needed.
[0202] The copper coupons treated in this manner were inspected for
coating appearance and defects prior to lamination to a standard
FR4 pre-preg laminate available under the trade designation Isola
370 FR, Isola FR408HR or Isola Is410.
Example 6
Adhesion Promotion Process
[0203] Multiple adhesion promotion processes were carried out on
test copper coupons. These processes, designated A7, were carried
out according to the method of the present invention. In these
processes, the copper coupons were pre-dipped in a composition
comprising a molecule capable of forming a self-assembled monolayer
on a copper surface. Additionally, the adhesion promotion
composition was further modified with methanesulfonic acid and
polypropylene glycol.
[0204] The adhesion promotion processes were carried out on three
sets of 1'' (25.4 mm) by 2'' (50.8 mm) copper coupons according to
the following protocol: [0205] 1. Contact the surfaces of three
copper coupons with microetchant Enthone.RTM. PC-7077 (40-60%
concentration, available from Enthone Inc.) by immersion, spraying
or both, the coupons in the microetchant composition for 30 to 45
seconds at a solution temperature between of 27.degree.
C..+-.3.degree. C. [0206] 2. Rinse the coupons in warm water (tap
water or deionized) for 30 seconds. [0207] 3. Contact the etched
surface of the three copper coupons with alkaline cleaner
Enthone.RTM. PC-7096 (10 to 15% concentration, available from
Enthone Inc.) by immersion, spraying or both, the coupons in or
with the alkaline cleaner composition for 60 seconds at a solution
temperature between of 43.degree. C..+-.6.degree. C. [0208] 4.
Rinse the coupons in warm water (tap water or deionized) for 30
seconds. [0209] 5. Contact the cleaned and etched surfaces of the
copper coupons with a pre-dip composition comprising 6-benzylamino
purine (5 grams/Liter, available from KingChem or Aldrich for 60
seconds at a solution temperature between of 43.degree.
C..+-.6.degree. C. [0210] 6. Rinse the coupons in warm deionizied
water for 30 seconds. The water was allowed to drain from the
coupons for 10 to 20 seconds to avoid unnecessary dilution of the
adhesion promotion composition. [0211] 7. Contact the cleaned and
etched surfaces of the three copper coupons with adhesion promotion
composition AlphaPREP.RTM. PC-7030 (100% concentration, available
from Enthone Inc.) modified by adding polypropylene glycol (0.5 to
1.0 wt. %) having an average molecular weight 76.1 g/mol, available
from KingChem or Aldrich Chemical, and by adding methanesulfonic
acid (2 wt. %), available from Huntsman Corporation thereby
producing a solution containing sulfuric, nitric and
methanesulfonic acids. The coupons were then immersed in and/or
sprayed with the adhesion promotion composition. One set of coupons
was contacted with AlphaPREP.RTM. PC-7030 for 45 seconds. One set
of coupons was contacted with AlphaPREP.RTM. PC-7030M for 1 minute.
One set of coupons was contacted with AlphaPREP.RTM. PC-7030 for 2
minutes. The solution temperature between of 43.degree.
C..+-.6.degree. C. The adhesion promotion composition contained the
following components and concentrations:
TABLE-US-00010 [0211] Component Concentration H.sub.2O.sub.2 7.2
wt. % H.sub.2SO.sub.4 28.0 wt. % HNO.sub.3 5.0 wt. %
CH.sub.3SO.sub.4H 2.0 wt. % 1,2,3-Benzotriazole 1.0 wt. %
Triethylene glycol 0.9 wt. % Polypropylene glycol 0.5 to 1.0 wt. %
2-ethyoxosulfonate (Niaproof 08) 0.15 wt. % Dodecylbenzene Sulfonic
acid (DDBSA) 0.002 wt. % Polyoxyethylene Nonylphenol (Tergitol NP
9) 0.002 wt. % Chloride ion 85-95 ppm Water (Deionized) Balance
[0212] 8. Rinse the coupons in warm water (tap water or deionized)
for 30 seconds. [0213] 9. Air dry the coupons at ambient
temperature or up to about 35-40.degree. C., for between 30 seconds
to 5 minutes, as needed.
[0214] The copper coupons treated in this manner were inspected for
coating appearance and defects prior to lamination to a standard
FR4 pre-preg laminate.
Example 7
Adhesion Promotion Process of the Invention
[0215] Multiple adhesion promotion processes were carried out on
test copper coupons. These processes, designated A8, were carried
out according to the method of the present invention. In these
processes, the copper coupons were cleaned in an alkaline cleaner
composition further comprising a molecular capable of forming a
self-assembled monolayer on a copper surface. Additionally, the
adhesion promotion composition was further modified with
methanesulfonic acid and polypropylene glycol.
[0216] The adhesion promotion processes were carried out on three
sets of 1'' (25.4 mm) by 2'' (50.8 mm) copper coupons according to
the following protocol: [0217] 1. Contact the surfaces of three
copper coupons with microetchant Enthone.RTM. PC-7077 (40-60%
concentration, available from Enthone Inc.) by spraying the coupons
in the microetchant composition for 30 to 45 seconds, or immersing
them with the solution, in either case at a solution temperature
between of 27.degree. C..+-.3.degree. C. [0218] 2. Rinse the
coupons in warm water (tap water or deionized) for 30 seconds.
[0219] 3. Contact the etched surface of the three copper coupons
with alkaline cleaner Enthone.RTM. SAM8-R1 (10 to 15%
concentration, available from Enthone Inc.) further comprising
6-benzylamino purine (5 grams/Liter) by immersing the coupons in
the alkaline cleaner composition for 60 seconds, or spraying them
with the composition, in either case at a solution temperature
between of 43.degree. C..+-.6.degree. C. [0220] 4. Rinse the
coupons in warm water (tap water or deionized) for 30 seconds. The
water was allowed to drain from the coupons for 10 to 20 seconds to
avoid unnecessary dilution of the adhesion promotion composition.
[0221] 5. Contact the cleaned and etched surfaces of the three
copper coupons with adhesion promotion composition AlphaPREP.RTM.
PC-7030 (100% concentration, available from Enthone Inc.) modified
by adding polypropylene glycol (0.5 wt. %) having a molecular
weight of 76.1 g/mol, and by adding methanesulfonic acid (2 wt. %)
so that the composition contained sulfuric, nitric and
methanesulfonic acid. Contact was by immersion or spraying or both.
One set of coupons was contacted with AlphaPREP.RTM. PC-7030M for
45 seconds. One set of coupons was contacted with AlphaPREP.RTM.
PC-7030 for 1 minute. One set of coupons was contacted with
AlphaPREP.RTM. PC-7030 for 2 minutes. The solution temperature was
43.degree. C..+-.6.degree. C. The adhesion promotion composition
contained the following components and concentrations:
TABLE-US-00011 [0221] Component Concentration H.sub.2O.sub.2 7.2
wt. % H.sub.2SO.sub.4 28.0 wt. % HNO.sub.3 5.0 wt. %
CH.sub.3SO.sub.4H 2.0 wt. % 1,2,3-Benzotriazole 1.0 wt. %
Triethylene glycol 0.9 wt. % Polypropylene glycol 0.5 wt. %
2-ethyoxosulfonate (Niaproof 08) 0.15 wt. % Dodecylbenzene Sulfonic
acid (DDBSA) 0.002 wt. % Polyoxyethylene Nonylphenol (Tergitol NP
9) 0.002 wt. % Chloride ion 85-95 ppm Water (Deionized) Balance
[0222] 6. Rinse the coupons in warm water (tap water or deionized)
for 30 seconds. [0223] 7. Air dry the coupons at ambient
temperature or up to about 35-40.degree. C., for between 30 seconds
to 5 minutes, as needed.
[0224] The copper coupons treated in this manner were inspected for
coating appearance and defects prior to lamination to a standard
FR4 pre-preg laminate.
Example 8-14
Adhesion Promotion Process
[0225] Multiple adhesion promotion processes were carried out on
test copper coupons that were designated B0S, B0, B1, B3, B6, B7,
and B8. Adhesion promotion processes B0S, B0, B1, B3, B6, B7, and
B8 were identical to process A0S, A0, A1, A3, A6, A7, and A8,
respectively, except that in each of B0S, B0, B1, B3, B6, B7, and
B8, the adhesion promotion compositions were formulated with 30 g/L
copper ions. in order to simulate a working adhesion promotion
process in which the adhesion promotion composition has accumulated
a substantial copper ion concentration.
Example 15
Lamination Process
[0226] The copper coupons treated as described in Examples 1
through 14 were laminated to a standard FR4 pre-preg laminate at
188.degree. C. of the type available under the trade designation
Isola 370HR, Isola IS410, Nanya 170, Nanya 175 or Panasonci R1551,
according to the following protocol: [0227] 1. One surface of the
copper coupon and one surface of the pre-preg were each coated by a
DuPont.TM. Tedlar.RTM. PVF Film. [0228] 2. The opposite, uncoated
sides of the copper coupon and pre-preg were placed in contact with
each other. [0229] 3. The Tedlar.RTM. coated sides were then
contacted with platens and compressed together in a hydraulic press
at about 765 kPa (about 111 PSI) for 5 minutes. [0230] 4. The
pressure was increased to 1436 kPa (about 208.33 PSI) for 10
minutes. [0231] 5. The pressure was increased to 1917 kPa (about
211 PSI) for 60 minutes. [0232] 6. The pressure was decreased to
1436 kPa (about 208.33 PSI) for 5 minutes.
[0233] The copper coupon coated pre-pregs were then subjected to
solder pot dip tests and peel strength tests.
[0234] The solder pot dip test is conducted by lowering a portion
of the copper laminated pre-preg into molten solder at a
temperature of 260.degree. C. for 10 second interval cycles. The
number of cycles until delamination is recorded.
[0235] Peel strength is determined with the Instron 4442 Instrument
(ASTM standard). The peel strength is run on five samples.
[0236] Additionally, the etch rate of copper in the adhesion
promotion composition was determined by measuring the copper ion
concentration in the adhesion promotion composition.
[0237] The empirical results are summarized in the following Tables
1 through 3:
TABLE-US-00012 TABLE 1 Empirical Data for Copper Coupons Treated in
Adhesion Promotion Composition for Two Minutes Copper Peel Solder
Dip Desig- weight Loss Etch Rate Total Etch Strength Appear-
(Cycles to nation (grams Cu.sup.2+) (.mu.m/min) (.mu.m) (N/M) ance
Delamination) A0S 0.083 1.79 3.58 301.9 3 16 B0S 0.077 1.67 3.33
942.15 4 15 A0 0.050 1.08 2.15 1165.6 3 17 B0 0.049 1.06 2.13
1092.8 4 16 A1 0.048 1.03 2.07 1040.2 3 17 B1 0.039 0.83 1.66
1075.2 4 17 A3 0.066 1.50 3.00 1372.9 5 23 B3 0.069 1.48 2.96
1339.7 5 24 A6 0.044 0.95 1.89 959.7 3 20 B6 0.042 0.90 1.80 991.2
4 22 A7 0.065 1.39 2.79 1162.8 4 29 B7 0.060 1.30 2.60 1126.0 5 28
A8 0.066 1.43 2.86 1204.8 4 31 B8 0.063 1.35 2.71 1210.1 5 30
TABLE-US-00013 TABLE 2 Empirical Data for Copper Coupons Treated in
Adhesion Promotion Composition for One Minute Copper Peel Solder
Dip Desig- weight Loss Etch Rate Total Etch Strength Appear-
(Cycles to nation (grams Cu.sup.2+) (.mu.m/min) (.mu.m) (N/M) ance
Delamination) A0S 0.040 1.7 1.7 795.1 2 12 B0S 0.032 1.39 1.39
872.1 3 13 A0 0.026 1.11 1.11 866.8 3 14 B0 0.026 1.13 1.13 882.6 3
16 A1 0.024 1.04 1.04 882.6 3 14 B1 0.022 0.96 0.96 889.6 3 15 A3
0.033 1.43 1.43 924.6 4 29 B3 0.033 1.43 1.43 900.1 4 30 A6 0.033
0.93 0.93 812.6 3 19 B6 0.022 0.93 0.93 826.6 3 18 A7 0.032 1.39
1.39 886.1 4 24 B7 0.034 1.47 1.47 849.3 4 25 A8 0.033 1.42 1.42
914.1 4 32 B8 0.034 1.47 1.47 882.6 4 33
TABLE-US-00014 TABLE 3 Empirical Data for Copper Coupons Treated in
Adhesion Promotion Composition for 45 Seconds Copper Peel Solder
Dip Desig- weight Loss Etch Rate Total Etch Strength Appear-
(Cycles to nation (grams Cu.sup.2+) (.mu.m/min) (.mu.m) (N/M) ance
Delamination) A0S 0.029 1.66 1.25 711.7 2 8 B0S 0.025 1.43 1.07
690.0 2 9 A0 0.019 1.1 0.82 791.5 2 10 B0 0.018 1.03 0.77 837.1 3
12 A1 0.018 1.04 0.78 749.5 3 9 B1 0.014 0.80 0.60 705.7 3 9 A3
0.025 1.44 1.08 866.8 5 20 B3 0.026 1.50 1.13 854.6 5 21 A6 0.016
0.03 0.02 698.7 3 9 B6 0.018 1.01 0.76 693.5 3 10 A7 0.025 1.44
1.08 819.5 4 26 B7 0.024 1.40 1.05 852.8 4 25 A8 0.024 1.37 1.03
872.1 4 30 B8 0.026 1.47 1.11 849.3 4 32
[0238] In the above tables, "Appearance" is a qualitative, eyeball
measurement of the appearance of the organometallic conversion
coating. A rating of 5 means that the coating was an excellent dark
brown color that the industry associates with a strongly adhesive
coating. A 4 rating means that the coating was good, uniform, and
dark reddish brown. A 3 rating means that the coating was fairly
uniform and still dark brown, but less so than a 4 or 5. Ratings of
1 or 2 mean that the coating was uneven; the dark reddish brown
color was spotty.
[0239] The results of the various adhesion promotion processes as
set out in Tables 1 through 3 indicate that the incorporation of
propylene glycol or polypropylene glycol in the adhesion promotion
composition in addition to a pre-dip in a composition comprising a
molecule capable of forming a self-assembled monolayer on a copper
surface improves the overall performance of the adhesion process.
Advantageous results achieved include an improvement in the
appearance of the organometallic conversion coating, an increase in
peel strength, and an increase in the number of solder dip cycles
prior to delamination. In some respects, the adhesion promotion
process was improved when compositions comprising a substantial
copper load were employed. It may therefore be concluded that an
adhesion promotion composition can be used for an extended duration
when copper coupons are pre-dipped in a composition comprising a
molecule capable of forming a self-assembled monolayer.
Example 16
Adhesion Promoting Process
[0240] Multiple adhesion promotion processes were carried out on
test copper coupons. These processes were carried out according to
the method of the present invention. In these processes, the copper
coupons were pre-dipped in a composition comprising a molecular
capable of forming a self-assembled monolayer on a copper surface.
Additionally, the adhesion promotion composition was further
modified with polypropylene glycol.
[0241] The adhesion promotion processes were carried out on three
sets of 1'' (25.4 mm) by 2'' (50.8 mm) copper coupons according to
the following protocol: [0242] 1. Contact the surfaces of three,
copper coupons with microetchant Enthone.RTM. PC-7077 (40-60%
concentration, available from Enthone Inc.) by immersion, spraying
or both, the coupons in the microetchant composition for 30 to 45
seconds at a solution temperature between of 27.degree.
C..+-.3.degree. C. [0243] 2. Rinse the coupons in warm water (tap
water or deionized) for 30 seconds. [0244] 3. Contact the etched
surface of the three copper coupons with alkaline cleaner
Enthone.RTM. PC-7096 (10 to 15% concentration, available from
Enthone Inc.) by immersing or spraying the coupons in the alkaline
cleaner composition for 60 seconds at a solution temperature
between of 43.degree. C..+-.6.degree. C. [0245] 4. Rinse the
coupons in warm water (tap water or deionized) for 30 seconds.
[0246] 5. Contact the cleaned and etched surfaces of the copper
coupons with a pre-dip composition having the following
composition:
TABLE-US-00015 [0246] % by Weight in Quantity/ Code Raw Material
Name Formulation Units 803313 WATER, DEIONIZED 92.808 0.942 803430
Potassium Hydroxide 45% Soln 0.552 0.0056 804371 SODIUM HYDROXIDE
PEARLS 3.113 0.0316 804763 NIAPROOF ANIONIC 08 0.005 0.05 809469
6-BENZYLAMINOPURINE 0.025 0.253 (BAP) 809470 ZINPLEX 15 0.121 1.23
805507 POTASSIUM IODIDE AR 0.010 0.1 803203 MONOETHANOLAMINE 1.498
0.0152 804329 BUTYL DIGLYCOL/BUTYL 1.872 0.019 CARBITOL 100.003
Specific Gravity 1.015
[0247] The cleaned and etched coupons were contacted with this
conditioning solution for 60 seconds at a solution temperature
between of 43.degree. C..+-.6.degree. C. [0248] 6. Rinse the
coupons in warm deionizied water for 30 seconds. The water was
allowed to drain from the coupons for 10 to 20 seconds to avoid
unnecessary dilution of the adhesion promotion composition.
[0249] Contact the cleaned and etched surfaces of the three copper
coupons with adhesion promotion composition having the composition
(specific gravity 1.13):
TABLE-US-00016 # OF RAW MAT'L RAW MAT'L Quantity RAWS CODE NAME WT
% in Gram 1 803313 DI WATER 55.59 628.17 2 803236 Calsoft Las 99
0.00 0.02 3 803382 Tergitol NP9 0.00 0.02 4 804763 Niaproof 08 0.15
1.70 5 803461 Nitric Acid 5.00 56.50 6 803679 Benzotriazole 1.00
11.30 cobratec 99 7 801051 Hydrogen 7.20 81.36 Peroxde(35%) 8
803257 Sulfuric 28.00 316.40 Acid(50%) 9 803046 Triethylene 0.90
10.17 Glycol 10 804699 Zinc Sulfate 0.16 1.79 Monohydrate
[0250] The solution temperature during contact of the adhesion
promoting solution with the coupons was between 43.degree.
C..+-.6.degree. C. In repetitive operations using this adhesion
promoting bath, the copper capacity reached >40 g/L. After
lamination in the manner described hereinabove, High Tg Phenolic
cured laminates achieved a peel strength of 690. N/m and survived
10.times.IR reflow without delamination. Panasonic 1551
halogen-free laminates achieved an initial peel strength of 835 N/m
which remained at 755 N/m after 10.times.IR reflow; Nanya NPG 170
halogen free laminates achieved an initial peel strength of 733 N/m
which increased to 784 N/m after 10.times.IR reflow. ISOLA 370
laminates achieved an initial peel strength of 835 to 890 N/m which
remained at 770 to 850 N/m after 10.times.IR reflow.
Example 17
Tests at Varying Copper Levels
[0251] In accordance with the method of the invention, multiple
adhesion promotion tests were carried out on copper coupons.
[0252] The coupons were micro-etched, rinsed, cleaned, rinsed again
in the manner described above, and then immersed for either 60 or
120 seconds at 43.+-.6.degree. C. in one of two different
conditioning solutions, either Conditioner #1 or Conditioner #2.
Conditioner #1 contained 6-benzylaminopurine and generally
corresponded to the formulation set out for the conditioner used in
Example 3, above. Conditioner #2 contained 6-benzylaminopurine and
Zinplex, and generally corresponded to the conditioner composition
used in Example 16. The coupons were thereafter rinsed, drained and
contacted with an adhesion promoting composition.
[0253] A control (Experiment #7) was run using the adhesion
promoting solution of Example 16 after conditioning only with a
standard alkaline cleaning solution.
[0254] After treatment with the adhesion promoting solution, the
coupons were laminated to a dielectric material generally in the
manner described above. In some instances, the lamination took
place after 10.times.IR-reflow, and in other cases lamination was
conducted before reflow.
[0255] After the lamination step, the laminated composites were
subjected to peel strength tests as described above. The peel
strength results for the coupons laminated before reflow are set
forth in Table 5 and the results for coupons laminated after reflow
are set forth in Table 6.
TABLE-US-00017 TABLE 5 As Laminated Before 10X Reflow--ISOLA 370HR
Peel Strength Experi- Adhesion Peel Peel Peel Peel Peel ment
Conditioner Promoter Sample #1 Sample #2 Sample #3 Sample #4 Sample
#5 1 #2, 1 min. 7030M-1, 879 813 809 760 781 Ex. 2 2 #2, 2 mins.
7030M-1, 802 809 795 848 802 Ex. 2 3 #1, 2 mins. 7030M-1, 823 799
750 715 697 Ex. 2 4 #2, 2 mins. 7030M-1, 953 900 893 851 840 Ex. 2
5 #1, 2 mins. 7030M-1, 816 805 732 750 736 Ex. 2 6 #2, 2 mins.
7030M-2, 135 217 228 252 214 Ex. 16 7 Std. standard 579 536 536 546
652 alkaline cleaner 8 #1 Standard 686.5 711 722 704 694 9 #2
standard 746 725 750 736 753
TABLE-US-00018 TABLE 6 After 10X IR-reflow--ISOLA 370HR Peel
Strength Experi- Adhesion Peel Peel Peel Peel Peel ment Conditioner
Promoter Sample #1 Sample #2 Sample #3 Sample #4 Sample #5 1 #2, 1
min. 7030M-1, 748 783 805 765 Ex. 2 2 #2, 2 mins. 7030M-1, 770 777
766 773 Ex. 2 3 #1, 2 mins. 7030M-1, 811 785 759 751 799 Ex. 2 4
#2, 2 mins. 7030M-1, 881 830 865 803 Ex. 2 5 #1, 2 mins. 7030M-1,
875 760 902 831 Ex. 2 6 #2, 2 mins. 7030M-2, 190 202 229 199 Ex. 16
7 Std. standard 525 550 509 519 alkaline cleaner 8 #1 Standard 533
568 582 609 9 #2 standard 560 530 601 628
[0256] Poor results were experienced with the adhesion promotion
formulation of Experiment #6, both in the case of lamination before
reflow and in the case of lamination after reflow, because of the
presence of polyglycol WL-5000 containing 0.1 wt. % butylated
hydroxytoluene in the adhesion promoting solution. The presence of
these components proved to have a sharply adverse effect on the
peel strength.
[0257] However, the remaining experiments using either (i)
Conditioner #1 (Experiments ##3, 5 and 8) or (ii) Conditioner #2
(Experiments ##1 to 5, 8 and 9) all gave results substantially
superior to the control (Experiment #7). A further increment in
peel strength was obtained in those experiments using both
conditioner #2 and an adhesion promoting solution of Example 16
containing Zn ions (Experiment #4).
Example 18
[0258] To simulate commercial operations in which the conditioning
and adhesion promoting solutions are subjected to contact with a
succession of different copper substrates in repetitive cycles of
conditioning, adhesion promoting, and laminating operations,
experimental runs were conducted in which the adhesion promoting
solution was spiked with copper. Copper was added in proportions
that reflect the actual accumulation of copper ions in the adhesion
promoting solutions during commercial operations in which each of
the two treating formulations is contacted with copper substrates
through repetitive cycles. In each run the conditioning step was
carried out using a conditioning solution having essentially the
composition of Conditioner #2. The conditions of treatment with
conditioner and adhesion promoting solution were as otherwise
described in Example 17.
[0259] In the test runs of this example, the adhesion promoting
solution was spiked with either 1, 5, or 10 g/l copper. The treated
coupons were then laminated to a dielectric material at either 15.5
or 24.1 bars and peel strength tests conducted on the resulting
laminated composites.
[0260] The average peel strengths for composites comprising the
three different dielectrics are depicted in FIG. 1 for laminates
prepared at 15.5 bar and in FIG. 2 for laminates prepared at 24.1
bar.
Example 19
[0261] Another series of tests were conducted substantially in the
manner described in Example 18.
[0262] Three different dielectric materials were used in the
experiments of this example, i.e., Isola 370R, 408 HR, and IS 410.
With each combination of conditioner and adhesion promoting
solution, separate lamination experiments were conducted at
laminating pressures of either 15.5 bars or 24.1 bars. Peel
strength tests were conducted both before and after reflow.
[0263] The average peel strengths for composites comprising the
three different dielectrics are depicted in FIG. 3 for laminates
prepared at 15.5 bar and tested before reflow, in FIG. 4 for
laminates prepared at 24.1 bar and tested before reflow, in FIG. 5
for laminates prepared at 15.5 bar and tested after reflow, and in
FIG. 6 for laminates prepared at 24.1 bar and tested after
reflow.
Example 20
[0264] Another series of tests were conducted in the manner
described in Example 19 except that, in one series of tests, the
adhesion promoting solution was doped with 1 g/l of Conditioner #2,
while in the other the adhesion promoting solution of Example 16
was used without adulteration.
[0265] The average peel strengths for composites comprising the
three different dielectric for laminates prepared at 15.5 bar and
24.1 bars, respectively, after treatment with an adhesion promoting
solution of Example 16 with no addition of conditioner #2 are
displayed in FIGS. 7 and 8 while the peel strengths for composites
prepared at 15.5 and 24.1 bars, respectively, after treatment with
an adhesion promoting solution that had been doped with .about.1
g/l of Conditioner #2 are depicted in FIGS. 9 and 10.
Example 21
[0266] Another series of tests were conducted generally in the
manner described in Example 17. Five different substrates were
used, including 370 HR, 408 HR, IS 410, Pan R-1556, and Nanya NPG
170 LT. The adhesion promoting solution was doped with copper ions
in a concentration of 5 g/l and with varying proportions of
conditioner #2, ranging from 0 to 10 g/l. Lamination was effected
at a pressure of 15.5 bars.
[0267] The average peel strengths obtained were as depicted in FIG.
11.
Example 22
[0268] Two additional series of tests were conducted substantially
in the manner described in Example 18, except that the adhesion
promoting solution was doped with a substantially broader and
higher range of concentrations of copper ions, i.e., 0, 1, 10, 40
and 50 g/l. Each run was conducted using Conditioner #2 followed by
the adhesion promoting solution of Example 16. The adhesion
promoting solution was not doped with any addition of
Conditioner.
[0269] The peel test results of the tests of this Example are
depicted as bar graphs in FIGS. 12 and 13.
Example 23
[0270] Additional tests were run generally in the manner described
in Example 18. Conditioner #2 was used, followed by the adhesion
promoting solution of Example 16. Both the conditioner and the
adhesion promoting solution were doped with copper ions in a
concentration of 40 g/l. The dwell time between application of the
conditioner and application of the adhesion promoting solution was
varied.
[0271] The peel test results of this Example are depicted in the
bar graphs of FIG. 14. "Hang time" refers to the time required to
remove the bulk of the water film adhering to the coupons after
treatment with the conditioner. "Cool Dry" refers to cool dry time
subsequent to removal of the water film.
Example 24
[0272] Additional experimental runs were conducted generally in the
manner described in Example 21 except that the copper ion
concentration in the adhesion promoting formulations was 10 g/l and
only dielectric substrates 370 HR, 408 HR and IS 410 were
tested.
[0273] Peel strength results are depicted in FIGS. 15 and 16.
[0274] In view of the above, it will be seen that the several
objects of the invention are achieved and other advantageous
results attained.
[0275] When introducing elements of the present invention or the
preferred embodiments(s) thereof, the articles "a", "an", "the" and
"said" are intended to mean that there are one or more of the
elements. The terms "comprising", "including" and "having" are
intended to be inclusive and mean that there may be additional
elements other than the listed elements.
[0276] As various changes could be made in the above compositions
and processes without departing from the scope of the invention, it
is intended that all matter contained in the above description and
shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
* * * * *