U.S. patent number 3,765,936 [Application Number 05/174,198] was granted by the patent office on 1973-10-16 for electroless copper plate.
This patent grant is currently assigned to Shipley Company, Inc.. Invention is credited to Oleh B. Dutkewych, Michael Gulla, Charles R. Shipley, Jr., Lucia H. Shipley.
United States Patent |
3,765,936 |
Shipley, Jr. , et
al. |
October 16, 1973 |
ELECTROLESS COPPER PLATE
Abstract
An electroless copper deposit from a plating solution comprising
a source of cupric ions, hydroxyl radicals, formaldehyde or a
formaldehyde precursor, preferably paraformaldehyde, and a
complexing agent for copper which solution is characterized by the
addition of at least two members selected from the group consisting
of a formaldehyde addition agent, a solution soluble salt of a
Group VIII metal of the Periodic Chart of the Elements, and an
organic silicon compound. The copper plate deposited from the
preferred solution is alloyed with the Group VIII metal cation and
is distinguishable from prior art electroless copper deposits by
substantially improved bending or tensile properties and a
smoother, more highly reflecting surface appearance.
Inventors: |
Shipley, Jr.; Charles R.
(Newton, MA), Shipley; Lucia H. (Newton, MA), Gulla;
Michael (Newton, MA), Dutkewych; Oleh B. (Medfield,
MA) |
Assignee: |
Shipley Company, Inc. (Newton,
MA)
|
Family
ID: |
26869983 |
Appl.
No.: |
05/174,198 |
Filed: |
August 23, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
752250 |
Aug 13, 1968 |
3615735 |
|
|
|
Current U.S.
Class: |
174/256 |
Current CPC
Class: |
C23C
18/405 (20130101) |
Current International
Class: |
C23C
18/40 (20060101); C23C 18/31 (20060101); C23c
005/02 () |
Field of
Search: |
;106/1
;117/47A,130,13E,160,213,227,212 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hayes; Lorenzo B.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Pat. application
Ser. No. 752,250 filed Aug. 13, 1968 now U.S. Pat. No.
3,615,735.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electroless metal deposits of improved
appearance and bending or tensile properties.
2. Description of the Prior Art
Electroless copper deposition refers to the chemical plating of
copper over clean catalytically active surfaces by chemical
reduction in the absence of an external electric current. Such
processes and compositions useful therefor are known and are in
substantial commercial use. They are disclosed in a number of prior
art patents, for example, U.S. Pat. Nos. 2,938,805; 3,011,920;
3,310,430; and 3,383,224.
Known electroless copper deposition solutions generally comprise
four ingredients dissolved in water. They are (1) a source of
cupric ions, usually a copper salt, such as copper sulphate (2) a
reducing agent such as formaldehyde, or preferably, a formaldehyde
precursor such as paraformaldehyde, (3) hydroxide, generally an
alkali metal hydroxide and usually sodium hydroxide, sufficient to
provide the required alkaline solution in which said compositions
are effective, and (4) a complexing agent for copper sufficient to
prevent its precipitation in alkaline solution. A large number of
suitable complexing agents are known and described in the above
cited patents, and also in U. S. Pat. Nos. 2,874,072; 3,075,856;
3,119,709; 3,075,855 and 3,329,512 all incorporated herein by
reference. Known electroless plating solutions of the above type
usually provide a plate which, if mechanically dense and strong, is
somewhat brittle such that it can withstand only limited bending or
thermal stress without fracture. This is not a substantial
disadvantage where the electroless plate is of the order of
millionths of an inch in thickness and is over-plated with ductile
electrolytic copper. However, where the entire desired thickness,
typically 1 to 3 mils in an electrical application, is provided by
electroless plating, limited ductility is a serious limitation.
One means of improving the bending or tensile characteristics of an
electroless copper plate is described in U. S. Pat. No. 3,257,215
which discloses the addition of a cyanide or sulphur compound to a
copper plating solution. An additional means is described in U.S.
Pat. No. 3,310,430 which discloses the addition to a copper plating
solution of a water soluble compound of cyanide, vanadium,
molybdenum, niobium, tungsten, rhenium, arsenic, antimony, bismuth,
rare earth of the actinium series and rare earths of the lanthanum
series. Certain members of the above groups, especially the
vanadium compounds, provide significantly improved bending
characteristics. The reason for this is not fully understood but it
is stated in the patent that the agents poison the catalytic
surface so as to promote formation and release of hydrogen gas at
the catalytic surface, thereby inhibiting the inclusion of hydrogen
in the deposit as it forms. It has been found that where a
complexing agent or a bath formulation is used permitting rapid
deposition of copper with rapid evolution of hydrogen gas at the
surface, the improved ductility or bending characteristics are
frequently sacrificed or lost.
An alternative means for improving the tensile properties of an
electroless copper deposit while simultaneously improving
brightness and other appearance properties is described in U. S.
Pat. No. 3,475,186 incorporated herein by reference. Improved
properties are obtained by the addition of an organic silicon
compound to an electroless copper solution where silicon is
believed to be the active agent. A major advantage of this system
is that the rate of copper desposition does not substantially
affect tensile or bending properties. The manner in which silicon
compound improves tensile properties is not fully understood but is
believed to be due, at least in part, to a surface effect resulting
in deposition of a smoother deposit having fewer structural defects
as will be explained in greater detail below.
STATEMENT OF THE INVENTION
The subject invention is an improvement over that described in the
above noted patents and provides an electroless deposit of improved
bending or tensile properties. The copper deposit is from a
solution characterized by the addition of at least two members
selected from the group consisting of a formaldehyde addition
agent, a Group VIII metal salt of the Periodic Chart of the
Elements, and a solution soluble organic silicon compound. The
addition of either a formaldehyde addition agent or a Group VIII
metal salt provides some improvement in tensile properties.
Combination of the two provides an additive improvement in tensile
properties. Combination of the two with a silicon compound provides
a synergism that results in a substantial improvement in tensile
properties. In addition to the above noted improvement in tensile
properties, electroless copper deposits from the solutions of this
invention provide the advantages of excellent lay down properties,
excellent solderability and improved smoothness, brightness, and
over-all appearance.
Claims
We claim:
1. An article of manufacture comprising a catalytic substrate
plated with ductile copper produced by contacting said substrate
with an electroless copper plating solution comprising a source of
cupric ions, hydroxyl radicals, formaldehyde, sufficient complexing
agent to render said cupric ions soluble in alkaline solution and a
combination of at least two members of the group consisting of an
organic silicon compound, a formaldehyde addition agent and a Group
VIII metal salt of the Periodic Chart of the Elements, said organic
silicon compound being present in solution in an amount such that
the codeposited silicon varies between 1 and 500 parts per million
parts of the deposit, said Group VIII metal being present in
solution in an amount such that the codeposited Group VIII metal
varies between 0.1 and 5 percent by weight of the deposit and said
formaldehyde addition agent being present in an amount of from 0.01
moles per mole of formaldehyde to that amount that restricts
deposition from said solution.
2. The article of manufacture of claim 1 where said combination
comprises the organic silicon compound, the formaldehyde addition
agent and the solution soluble salt of the Group VIII metal of the
Periodic Chart of the Elements.
3. The article of manufacture of claim 1 where said combination
comprises the organic silicon compound and the solution soluble
salt of the Group VIII metal of the Periodic Chart of the
Elements.
4. The article of manufacture of claim 2 where the organic silicon
compound is selected from the group consisting of silanes and
polysiloxanes.
5. The article of manufacture of claim 2 where the Group VIII metal
salt is selected from the group of nickel, iron and platinum.
6. The article of manufacture of claim 1 in the form of a printed
circuit board having ductile copper conductors.
7. The printed circuit board of claim 6 having copper plated
through-holes.
Description
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A typical electroless copper solution in accordance with the
invention will have additives having the following concentration
ranges:
Preferred Copper salt 0.002 moles to saturation 0.02 to 0.12 moles
Formaldehyde 0.05 to 3.5 moles 0.1 to 1 moles Complexing minimum
necessary to about 1 to 3 times agent maintain copper in the moles
of cupric solution ion Free Hydroxide sufficient to provide 0.1 to
0.8 moles pH 10 or greater Silicon compound greater than 1 ppm 5 to
250 ppm Formaldehyde up to that amount that 0.01 to 1 times the
addition agent restricts deposition moles of formalde- hyde Group
VIII metal 5 to 2500 ppm 30 to 1000 ppm salt Water to 1 liter of
solution to 1 liter of solution
It should be understood that the above concentration ranges are
preferred, but not critical. Variations in the ranges are possible
without departing from the scope of the invention. In most cases,
additives may be added in an amount up to that amount that poisons
the solution.
In the above formulations, any water soluble copper salt heretofore
used for preparing electroless copper deposition solutions may be
used. For example, the halides, nitrate, acetate, sulfate and other
organic and inorganic acid salts of copper are generally suitable
as is known in the art. Copper sulphate is preferred.
Suitable complexing agents for the copper ions are well-known in
the art and include Rochelle salts, the sodium salts
(mono-,di-,tri-, and tetrasodium salts) of ethylene
diaminetetraacetic acid, nitrilotriacetic acid and its alkali metal
salts, triethanolamine, modified ethylene diaminetraacetic acids
such as N-hydroxyethylenediaminetriacetate, hydroxyalkyl
substituted dialkylene triamines such as pentahydroxypropyl
diethylenetriamine, sodium salicylate, and sodium tartrate. Other
complexing agents for copper ions are disclosed in U.S. Pat. Nos.
2,996,408; 3,075,855; 3,075,856; and 2,938,805.
The preferred class of complexing agents are those described in
U.S. Pat. No. 3,329,512 noted above. They include hydroxyalkyl
substituted tertiary amines, corresponding to one of the following
structures: ##SPC1##
where R is an alkyl group having from two to four carbon atoms, R'
is a lower alkylene radical and n is a positive integer. Examples
of these complexing agents include tetrahydroxpropyl ethylene
diamine, pentahydroxypropyl diethylene triamine,
trihydroxypropylamine (tripropanolamine), trihydroxpropyl
hydroxyethyl ethylene diamine, etc. As disclosed in said patent,
the aforesaid amines are preferably used in small amounts in
combination with other complexing agents and with certain polymers
dispersed in solution such as cellulose ethers, hydroxyethyl
starch, polyvinyl alcohol, polyvinylpyrrolidone, peptone, gelatin,
polyamides and polyacrylamides.
The rate of copper deposition is, to some extent, dependent upon
the selection of the complexing agent. Complexing agents such as
pentahydroxypropyl diethylene triamine provide a fast rate of
copper deposition, usually in excess of 1.0 mil per hour. Though
the copper solutions of this invention provide copper deposits from
solutions containing any of the known complexing agents for copper
ions, they are particularly well adapted for copper solutions
having complexing agents that provide a rapid rate of copper
deposition.
The silicon additive is one that is soluble in the copper solutions
and comprises the organic silicon compounds disclosed in the
above-noted U.S. Pat. No. 3,475,186. It should be noted that many
silicon compounds are not fully soluble in aqueous alkaline
solutions and many are considered insoluble. However, the silicon,
for purposes of the present invention, is required in solution in
parts per million and silicon compounds termed insoluble in aqueous
solution usually are soluble to the extent of a few parts per
million parts of solution and suitable for purposes of the present
invention. For those silicon compounds considered insoluble in
water, it is desirable to dissolve the compound in a solvent, such
as alcohol, and add the solution to the electroless copper solution
with agitation to form a dispersion or an emulsion. An excess of
the silicon compound will be required to provide the necessary
concentration of silicon compound in solution.
Exemplary of the silicon compounds within the scope of the
invention are the silanes, such as silane itself, disilane,
tetramethylsilane, trimethylethylsilane, tetraethylsilane,
tetraphenylsilane, dimethyldichlorosilane, etc., and low to
intermediate molecular weight polysiloxanes, such as silicone
fluids, gums, and resins substituted with methyl-, ethyl-, vinyl-,
phenyl-, chloro-, bromo-, methoxy-, hydroxy-, etc. Other suitable
organic silicon compounds are disclosed in the above noted U.S.
Pat. No. 3,475,186.
The polysiloxanes are the least soluble silicon compounds in basic
copper solutions, but are preferred because they provide the
greatest increase in ductility and also enhance appearance by
yielding a finer grained, more highly reflecting copper deposit. Of
the polysiloxanes, the silicone fluids are most preferred. The
solid polysiloxanes are preferably dissolved in a solvent such as
alcohol and added to the copper solution.
Silicon codeposits with the copper in minor quantity, typically in
amounts varying from as little as 1 part per million parts of the
deposit to about 500 parts per million parts. The amount of
codeposited silicon, though small, is believed to be significant in
providing the improved deposits of this invention.
The formaldehyde addition agent for purposes of this invention is
one that may be added to solution in amounts sufficient to undergo
reaction with formaldehyde to form a relatively unstable
formaldehyde adduct without poisoning the solution. Reactions of
this nature and formaldehyde addition agents are well-known in the
art and described in various publications, such as "Formaldehyde"
by J. Frederick Walker, Reinhold Publishing Company, Third Edition
1964, pages 219 to 221, included herein by reference. Preferred
formaldelyde addition agents are sulfites, bisulfites, and
phosphites of a metal cation that does not codeposit with copper
and preferably, an alkali metal cation. Preferred formaldehyde
addition agents are sodium sulfite, potassium bisulfite, and sodium
phosphite.
The formaldehyde addition agent and formaldehyde or preferably,
paraformaldehyde are reacted with each other to form the adduct
prior to addition to the remaining components of the copper
solution.
The Group VIII metal salts are preferably water soluble inorganic
salts of iron, cobalt, nickel, ruthenium, rhodium, palladium,
osmium, iridium, and platinum; salts of iron, nickel, and platinum
being most preferred and salts of palladium being least preferred
due to solution stability problems caused by palladium. Suitable
salts include phosphates, nitrates, halides, and acetates of the
above metals. Iron, nickel and platinum to a greater extent and the
remaining Group VIII metals to a lesser extent codeposit with
copper to form a copper alloy. The Group VIII metal codeposits in a
proportionally lesser amount relative to copper present in the
original electroless solution. Generally, the amount of the
codeposited Group VIII metal is no more than 5 percent by weight
and typically varies from about 0.1 to 3.0 percent by weight,
dependent upon the particular Group VIII metal involved.
A wetting agent may be added to solution in accordance with art
recognized procedure.
The baths may be used at widely varying temperatures, e.g., at
least room temperature and preferably up to about 140.degree.F. As
temperature is increased, it is customary to find an increase in
the rate of plating. Temperature is not highly critical, and within
the usual operating range, excellent, bright deposits of
electroless copper having excellent tensile properties are
obtained. Preferably, the bath is used without agitation.
In using the electroless copper solutions to plate metal, the
surface to be plated should be catalytically active and free of
grease and contaminating material. Where a non-metallic surface is
to be plated, the surface area to receive the deposit must first be
sensitized to render it catalytically active as by the well-known
treatment with an acidic aqueous solution of stannous chloride
followed by treatment with a dilute aqueous acidic solution of
palladium chloride. Alternatively, extremely good sensitization of
non-metallic surfaces is achieved by contact with an acidic
colloidal formulation formed by the admixture of stannous chloride
and a precious metal chloride, preferably palladium chloride, the
stannous chloride being present in stoichiometric excess based upon
the amount of precious metal chloride.
The invention will be better understood by reference to the
following examples where all parts were plated using the following
procedure:
a. Cut a phenolic substrate to a size of 2 .times. 2 inches.
b. Scrub part clean using an abrasive cleaner.
c. Rinse in cold water.
d. Immerse in a solution of a wetting agent identified as Shipley
conditioner 1159 at room temperature for 1 to 3 minutes.
e. Rinse in cold water.
f. Immerse in a colloidal stannic acid-palladium catalyst
(identified as Cuposit Catalyst 6F) maintained at room temperature
for 1 to 5 minutes.
g. Rinse in cold water.
h. Immerse in Cuposit Accelerator 19 or a mild perchloric acid
solution maintained at room temperature for 3 to 10 minutes.
i. Rinse in cold water
j. Immerse in electroless copper solution maintained at between
110.degree. and 130.degree.F for a period sufficient to provide a
deposit of desired thickness not to exceed 3 hours.
k. Dry parts and examine deposit for appearance and ductility.
Ductility is determined by peeling a copper deposit from the
substrate and bending it through 180.degree. in one direction,
creasing at the fold, then returning it to its original position
with pressing along the crease to flatten it. This cycle
constitutes one bend. The procedure is repeated until the sample
breaks at the crease. A sample unable to withstand at least
one-half bend is considered brittle.
EXAMPLES 1-20
CuSO.sub.4.sup.. 5H.sub.2 O 8.0 gm Paraformaldehyde 7.5 gm NaOH
(25% solution by wt.) 50.0 ml Tetrahydroxypropyl- ethylene diamine
12.0 gm Triisopropanolamine 2.0 gm Water to 1 liter of solution
The above formulation, with various additives, is used to deposit
electroless copper. Additive composition and deposit properties are
set forth in the following table.
Duc- Ex. Additives Additive Deposit Deposit tility No. concentra-
appear- thickness (Bends) tion ance in. X 10.sup.-.sup.3 1 control
- poor 0.50 brittle 2 NiSO.sub.4 300 ppm poor 0.37 brittle 3
Fe.sub.2 (SO.sub.4).sub.3 300 ppm poor 0.25 brittle 4 H.sub.2
PtCl.sub.6 150 ppm poor 0.10 brittle 5 OsO.sub.4 100 ppm fair 0.14
brittle 6 CoSO.sub.4 300 ppm poor 0.36 brittle 7 Na.sub.2 SO.sub.3
8 g/1 poor 0.46 brittle 8 NaHSO.sub.3 20 g/1 poor 0.43 brittle 9
Na.sub.2 HPO.sub.3.sup.. 5H.sub.2 O 20 g/1 fair 0.45 brittle 10
F-1-3514.sup. 1 200 ppm fair 0.34 1/2 11 methylvinyl- 250 ppm fair
0.87 1/2 silane 12 SF-1138.sup.(2) 200 ppm fair 0.46 1/2 13
F-1-3514.sup.(1) 200 ppm fair 0.41 1 NaHSO.sub.3 20 g/l 14
methylvinyl- silane 250 ppm fair 0.42 1 NaHSO.sub.3 20 g/l 15
F-1-3514.sup.(1) 200 ppm unstable H.sub.2 PtCl.sub.6 150 ppm 0.38 1
16 methylvinyl- silane 250 ppm good 0.22 1/2 H.sub.2 PtCl.sub.6 150
ppm 17 F-1-3514.sup.1 200 ppm good 0.18 3 H.sub.2 PtCl.sub.6 150
ppm NaHSO.sub.3 20 g/l 18 methylvinyl- silane 250 ppm good 0.39 5
H.sub.2 PtCl.sub.6 150 ppm NaHSO.sub.3 20 g/l 19 SF-1138.sup.2 200
ppm good 0.41 2 OsO.sub.4 100 ppm NaHSO.sub.3 20 g/l 20
SF-1138.sup.2 200 ppm good 0.35 3 NiSO.sub.4 300 ppm
NaHPO.sub.3.sup.. 5H.sub.2 O 20 g/l .sup.1 F-1-3514 A silicone
fluid believed to be a dimethylpoly-siloxane-ethylene glycol
copolymer available from the General Electric Co. .sup.2 SF-1138 A
silicone fluid believed to be a dimethylpoly-siloxane-polyalkylene
oxide copolymer available from the General Electric Company.
In the above examples, a deposit was considered poor if it was dark
in color and powdery in appearance. A fair deposit was one lighter
in color though powdery in appearance. A good deposit was one
having a fine grained metallic copper appearance.
The improvements in tensile properties using the preferred
electroless copper solutions of the present invention are readily
apparent by reference to the above examples. Examples 2 to 6
illustrate copper containing only a Group VIII metal salt. Examples
7 to 9 illustrate copper solutions containing only a formaldehyde
addition agent. No recordable improvement in properties is apparent
using either of these additives in the above copper solution.
Examples 10 to 12 illustrate the use of a silicon compound and show
some improvement in both appearance and tensile properties. The
combination of a silicon compound with either a Group VIII metal
salt or a formaldehyde addition agent (Examples 13 to 16) provides
a somewhat greater improvement. Combination of the silicon compound
with both a formaldehyde addition agent and a Group VIII metal salt
(Examples 17 to 20) provides substantial improvement in tensile
properties as evidenced by the ductility in all cases in excess of
2 bends and in some cases, as high as 5 bends.
EXAMPLES 21-28
CuSO.sub.4.sup.. 5H.sub.2 O 8.0 gm Paraformaldehyde 7.5 gm NaOH
(25% solution by weight) 50.0 ml pentahydroxy- propyldiethyl-
enetriamine 20.0 gm water to 1 liter of solution
The above formulation, with various additives, is used to deposit
electroless copper. Additive composition and deposit properties is
set forth in the following table:
Duc- EX. Additive Additive Deposit Deposit tibility No. Concentra-
Appear- Thickness Bends tion ance in. .times.10.sup.-.sup.3 21
control poor 0.30 brittle 22 SF-1138.sup.2 200 ppm good 0.34 1/2 23
NiSO.sub.4 300 ppm poor 0.46 1/2 24 NaHSO.sub.3 20 g/l fair 0.43
1/2 25 SF-1138.sup.2 200 ppm fair 0.15 1/2 NiSO.sub.4 300 ppm 26
SF-1138.sup. 2 200 ppm good 0.30 1/2 NaHSO.sub.3 20 g/l 27
NiSO.sub.4 300 ppm fair 0.41 1/2 NaHSO.sub.3 20 g/l 28
SF-1138.sup.2 200 ppm good 0.025 3 NaHSO.sub.3 20 g/l NiSO.sub.4
300 ppm
Example 28, using an electroless copper composition containing a
silicon compound, a formaldehyde addition agent and a Group VIII
metal salt provides a copper deposit having a significant
improvement in tensile properties. Formulations having one additive
only show some improvement.
EXAMPLE 29
a. CuSO.sub.4.sup.. 5H.sub.2 O8.0 gm b. Paraformaldehyde 7.5 gm c.
NaOH (25% solution by weight) 50.0 ml d. trihydroxypropylhydroxy-
ethyl ethylene diamine 20.0 gm e. SF-1138.sup.2 200 ppm f.
NiSO.sub.4 300 ppm g. NaHSO.sub.3 20 gm h. Water to 1 liter of
solution
Electroless copper deposited from the above solution was bright and
withstood 3 1/2 bends. Copper deposited from a control solution
free of additives e,f and g had a poor appearance and was
brittle.
EXAMPLE 30
a. CuSO.sub.4.sup.. 5H.sub.2 O8.0 gm b. Paraformaldehyde 7.5 gm c.
NaOH(25% solution by weight) 50.0 ml d. Tetrahydroxypropyl-
ethylene diamine 15.0 gm e. SF-1138.sup.2 200 ppm f. NiSO.sub.4 300
ppm g. NaHSO.sub.3 20 gm h. Water to 1 liter of solution
Copper deposited from the above solution was bright in color and
capable of withstanding in excess of five bends. Copper deposited
from a solution free of additive e,f and g was found to be
brittle.
EXAMPLES 31-38
CuSO.sub.4.sup.. 5H.sub.2 O 8.0 gm Paraformaldehyde 7.5 gm NaOH
(25% solution by weight) 50.0 ml Ethylenediaminetetraacetic acid
25.0 gm Tetrahydroxypropylethylene diamine 6.0 gm Water to 1 liter
of solution
The above formulation, with various additives was used to deposit
electroless copper. Additive composition and deposit properties are
set forth in the following table:
Duc- Ex. Additive Additive Deposit Deposit tility No. concentra-
appear- thickness (Bends) tion ance in. X10.sup..sup.-3 31 control
poor 0.35 brittle 32 SF-1138.sup.2 200 ppm fair 0.15 1 1/2 33
NiSO.sub.4 300 ppm poor 0.32 1 34 NaHSO.sub.3 20 g/l poor 0.33 1 35
SF-1138.sup.2 200 ppm fair 0.18 3 NiSO.sub.4 300 ppm 36
SF-1138.sup.2 200 ppm fair 0.24 1 37 NiSO.sub.4 300 ppm poor 0.27
brittle NaHSO.sub.3 20 g/l 38 SF-1138.sup.2 100 ppm fair 0.19 4 1/2
NiSO.sub.4 100 ppm NaHSO.sub.3 20 g/l
Each additive, alone or in combinations of two, increased ductility
substantially. However, the combination of the three additives
(Example 38) provided a substantially greater increase in
ductility.
EXAMPLE 39
a. CuSO.sub.4.sup.. 5H.sub.2 O8.0 gm b. Paraformaldehyde 7.5 gm c.
NaOH (25% solution by weight) 50.0 ml d. Sodium/potassium tar-
trate 25.0 gm e. Pentahydroxypropyl- diethylene 6.0 gm triamine f.
SF-1138.sup.2 200 ppm g. NiSO.sub.4 300 ppm h. NaHSO.sub.3 20 g/l
i. Water to 1 liter of solution
Copper deposited from the above solution was bright and withstood
in excess of five bends. Copper deposited from the same solution
free of additives f, g and h was found to be brittle.
EXAMPLES 40-47
CuSO.sub.4.sup.. 5H.sub.2 O 8.0 gm Paraformaldehyde 7.5 gm NaOH
(25% solution by weight) 50.0 ml Sodium/potassium tartrate 40.0 gm
Water to 1 liter of solution
The above formulation, containing various additives, was used to
deposit electroless copper. Additive composition and deposit
properties are set forth in the following table:
Duc- Ex. Additive Additive Deposit Deposit tibility No. Concentra-
Appear- thickness (Bends) tion ance in. X10.sup.-3 40 control fair
0.06 1/2 41 F-1-3514.sup.1 200 ppm fair 0.10 5 42 NiSO.sub.4 300
ppm fair 0.09 3 43 NaHSO.sub.3 20 g/l fair 0.09 1 44 F-1-3514.sup.1
200 ppm good 0.13 3 NiSO.sub.4 300 ppm 45 F-1-3514.sup.1 200 ppm
good 0.09 5 NaHSO.sub.3 20 g/l 46 NiSO.sub.4 300 ppm good 0.34 1
1/2 NaHSO.sub.3 20 g/l 47 F-1-3514.sup.2 200 ppm good 0.24 5
NiSO.sub.4 300 ppm NaHSO.sub.3 20 g/l
In the particular copper solution used, the addition of any
additive alone was effective. However, use of the silicon compound
in combination with the nickel sulfate and the sodium hyposulfite
produced a substantial improvement in ductility. In Example 47,
there was no indication of fracture of the copper deposit following
the fifth bend.
EXAMPLES 48-54
CuSO.sub.4.sup.. 5H.sub.2 O 8.0 gm Paraformaldehyde 7.5 gm NaOH
(25% solution by weight) 50.0 ml Tetrahydroxypropyl- ethylene
diamine 12.0 gm Triisopropanolamine 2.0 gm Water to 1 liter of
solution
The above formulation containing various additives was used to
deposit electroless copper. Additive compositions and deposit
properties are set forth in the following table:
Duc- Ex. Additive Additive Deposit tibility No. Concentra- appear-
(Bends) tion ance 48 control poor brittle 49 F-68.sup.(3) 350 ppm
fair 1/2 50 F-68.sup.(3) 350 ppm good 1/2 SF-1138.sup.2 200 ppm 51
F-68.sup.(3) 350 ppm good 5 SF-1138 200 ppm NaHSO.sub.3 20 g/l
NiSO.sub.4 300 ppm 52 F-68.sup.3 350 ppm good 5 SF-1138.sup.2 200
ppm NaHSO.sub.3 20 g/l H.sub.2 PtCl.sub.6 150 ppm 53 F-68.sup.3 350
ppm good 4 SF-1138.sup. 2 200 ppm NaHSO.sub.3 20 g/l CoSO.sub.4 300
ppm 54 F-68.sup.3 350 ppm good 3 SF-1138.sup. 2 200 ppm NaHSO.sub.3
20 g/l FE.sub.2 (SO.sub.4).sub.3 300 ppm .sup.3 F-68. A wetting
agent
EXAMPLE 55
CuSO.sub.4.sup.. 5H.sub.2 O 8.0 gm Formaldehyde 7.5 gm NaOH (25%
solution by weight) 50.0 ml Tetrahydroxypropyl- ethylene diamine
12.0 gm Triisopropanolamine 2.0 gm SF-1138.sup.2 200 ppm NiSO.sub.4
300 ppm H.sub.2 PtCl.sub.6 150 ppm NaHSO.sub.4 20 g/l Water to 1
liter of solution
The electroless copper deposited from the above formulation was
capable of withstanding in excess of five bends.
Deposits from representative examples were analyzed for the
codeposition of the Group VIII metal cation with results as set
forth in the following table:
Ex. No. Cu Conc. (%) Ni Conc. (%) Pt. Conc. (%) 17 97.85 1.83 47
98.65 0.170 51 99.35 0.056 55 97.07 0.036 2.48
From the above table, it can be seen that the Group VIII metal
codeposits with copper to form an alloy.
Copper solutions of this invention find utility for all purposes
for which electroless copper solutions have heretofore been used
including both decorative and industrial applications. They are
especially useful for the formation of printed circuit boards where
the deposits act as ductile conductors and as ductile connectors
plated onto the walls of through-holes. The formation of a printed
circuit board having conductive through-holes is illustrated in the
following example.
EXAMPLE 56
a. Sandblast one side of a phenolic substrate leaving the second
surface smooth.
b. Drill through-holes at desired locations.
c. Silk screen a reverse image of a printed circuit pattern onto
the roughened surface of the phenolic substrate using an epoxy
resin.
d. Immerse in a colloidal palladium sensitizing solution maintained
at room temperature for a period of five minutes.
e. Immerse in a stripping solution comprising 10 grams of copper
chloride, 100 grams of 37 percent hydrochloric acid and water to
one liter maintained at room temperature for 6 minutes.
f. Deposit electroless copper of Example 18 with copper deposition
taking place on the walls of the throughholes and on the roughened
surfaces in the image pattern. No copper deposition takes place on
the epoxy resist or on the smooth sides of the plastic
laminate.
It should be understood that various changes may be made in the
embodiments described above without departing from the spirit and
scope of the invention as defined by the following claims.
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