U.S. patent application number 13/396334 was filed with the patent office on 2012-06-14 for copper foil for printed circuit board and copper clad laminate for printed circuit board.
This patent application is currently assigned to JX Nippon Mining and Metals Corporation. Invention is credited to Kengo Kaminaga, Terumasa Moriyama.
Application Number | 20120148862 13/396334 |
Document ID | / |
Family ID | 41433982 |
Filed Date | 2012-06-14 |
United States Patent
Application |
20120148862 |
Kind Code |
A1 |
Moriyama; Terumasa ; et
al. |
June 14, 2012 |
Copper Foil for Printed Circuit Board and Copper Clad Laminate for
Printed Circuit Board
Abstract
A copper foil for a printed circuit board is provided. The
copper foil includes a layer including nickel, zinc, a compound of
nickel and that of zinc (hereinafter referred to as a "nickel zinc
layer") on a roughened surface of a copper foil and a chromate film
layer on the nickel zinc layer. The zinc add-on weight per unit
area of the nickel zinc layer is 180 .mu.g/dm.sup.2 or more and
3500 .mu.g/dm.sup.2 or less, and the nickel weight ratio in the
nickel zinc layer {nickel add-on weight/(nickel add-on weight+zinc
add-on weight)} is 0.38 or more and 0.7 or less. This surface
treatment technology of a copper foil is able to effectively
prevent the circuit corrosion phenomenon in cases of laminating a
copper foil on a resin base material and using a sulfuric acid
hydrogen peroxide etching solution to perform soft etching to the
circuit.
Inventors: |
Moriyama; Terumasa;
(Ibaraki, JP) ; Kaminaga; Kengo; (Ibaraki,
JP) |
Assignee: |
JX Nippon Mining and Metals
Corporation
Tokyo
JP
|
Family ID: |
41433982 |
Appl. No.: |
13/396334 |
Filed: |
February 14, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12738995 |
Apr 21, 2010 |
8142905 |
|
|
PCT/JP2009/059839 |
May 29, 2009 |
|
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13396334 |
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Current U.S.
Class: |
428/607 ;
428/612 |
Current CPC
Class: |
C23C 28/3455 20130101;
Y10T 428/12903 20150115; Y10T 428/12472 20150115; Y10T 428/12847
20150115; Y10T 428/27 20150115; C23C 28/345 20130101; H05K
2201/0239 20130101; Y10T 428/12438 20150115; Y10T 428/12944
20150115; C23C 28/321 20130101; C25D 3/562 20130101; Y10T 428/12792
20150115; Y10T 428/1266 20150115; Y10T 428/12618 20150115; Y10T
428/273 20150115; C23C 28/00 20130101; H05K 3/384 20130101; Y10T
428/12569 20150115; Y10T 428/1259 20150115; H05K 2201/0355
20130101; Y10T 428/263 20150115; Y10T 428/12583 20150115; C25D
3/565 20130101; H05K 2203/0723 20130101; C25D 7/0614 20130101 |
Class at
Publication: |
428/607 ;
428/612 |
International
Class: |
B32B 15/04 20060101
B32B015/04; H05K 3/38 20060101 H05K003/38 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 17, 2008 |
JP |
2008-157849 |
Claims
1. A copper foil for a printed circuit board comprising a
nickel-zinc layer including nickel, zinc, at least one of an oxide
and a hydroxide of nickel, and at least one of an oxide and a
hydroxide of zinc on a roughened surface of a copper foil, and a
chromate film layer on the nickel-zinc layer, wherein a zinc add-on
weight of the nickel-zinc layer per unit area of the copper foil is
180 .mu.g/dm.sup.2 or more and 3500 .mu.g/dm.sup.2 or less, and a
nickel weight ratio in the nickel-zinc layer {nickel add-on weight
per unit area/(nickel add-on weight per unit area+zinc add-on
weight per unit area)} is 0.38 or more and 0.7 or less.
2. The copper foil for a printed circuit board according to claim
1, wherein the {nickel add-on weight per unit area/(nickel add-on
weight per unit area+zinc add-on weight per unit area)} is 0.4 or
more and 0.55 or less.
3. The copper foil for a printed circuit board according to claim
2, wherein a chromium add-on weight of the chromate film layer per
unit area of the copper foil is 30 .mu.g/dm.sup.2 or more and 100
.mu.g/dm.sup.2 or less.
4. The copper foil for a printed circuit board according to claim
3, further comprising a silane coupling agent layer on the chromate
film layer.
5. The copper foil for a printed circuit board according to claim
4, wherein the copper foil is an electrolytic copper foil, and the
roughened surface is a rough face obtained during electrolytic
plating, a face obtained by additionally performing roughening
treatment to the rough face, or a face obtained by performing
roughening treatment on a gloss surface of an electrolytic copper
foil.
6. The copper foil for a printed circuit board according to claim
4, wherein the copper foil is a rolled copper foil and the
roughened surface is a face obtained by performing roughening
treatment to the rolled copper foil.
7. A copper clad laminate for a printed circuit board produced by
laminating the copper foil for a printed circuit board according to
claim 4, and a resin for a printed circuit board.
8. A copper foil for a printed circuit board according to claim 1,
wherein chromium add-on weight of the chromate film layer per unit
area of the copper foil is 30 .mu.g/dm.sup.2 or more and 100
.mu.g/dm.sup.2 or less.
9. A copper foil for a printed circuit board according to claim 1,
further comprising a silane coupling agent layer on the chromate
film layer.
10. A copper foil for a printed circuit board according to claim 1,
wherein the copper foil is an electrolytic copper foil, and the
roughened surface is a rough face obtained during electrolytic
plating, a face obtained by additionally performing roughening
treatment to the rough face, or a face obtained by performing
roughening treatment on a gloss surface of an electrolytic copper
foil.
11. A copper foil for a printed circuit board according to claim 1,
wherein the copper foil is a rolled copper foil and the roughened
surface is a face obtained by performing roughening treatment to
the rolled copper foil.
12. A copper clad laminate for a printed circuit board produced by
laminating the copper foil for a printed circuit board according to
claim 1, and a resin for a printed circuit board.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S.
application Ser. No. 12/738,995 which is the National Stage of
International Application No. PCT/JP2009/059839, filed May 29,
2009, which claims the benefit under 35 USC 119 of Japanese
Application No. 2008-157849, filed Jun. 17, 2008.
BACKGROUND
[0002] The present invention generally relates to a copper foil for
a printed circuit board and a copper clad laminate for a printed
circuit board having superior chemical resistivity and
adhesiveness, and in particular, relates to a copper foil for a
printed circuit board comprising a layer including nickel, zinc, a
compound of nickel and that of zinc (hereinafter referred to as a
"nickel zinc layer") at least on an adherend surface with a resin
of a copper foil, and a chromate film layer on the nickel zinc
layer, and also comprising a silane coupling agent layer as needed,
as well as to a copper clad laminate for a printed circuit board
produced by using the foregoing copper foil.
[0003] A semiconductor package substrate is one type of printed
circuit board, and is a printed circuit board that is used for
mounting a semiconductor IC chip and other semiconductor devices.
Since circuits that are formed on the semiconductor package
substrate are finer than those formed on a standard printed circuit
board, a resin base material that is different from a standard
printed circuit board is used for the substrate material.
[0004] A semiconductor package substrate is generally manufactured
according to the following processes. Foremost, a copper foil is
laminated and bonded to a base material such as synthetic resin
under high temperature and high pressure. This is referred to as a
copper clad laminate or simply as a laminate. Subsequently, in
order to form the intended conductive circuit on the laminate, a
pattern such as resin with anti-etching properties is used to print
a pattern that is equivalent to a circuit on the copper foil. The
unwanted part of the exposed copper foil is eliminated by way of
etching processing.
[0005] After the etching, the printed part is eliminated and a
conductive circuit is formed on the substrate. Prescribed devices
are ultimately soldered on the formed conductive circuit in order
to form various printed circuit boards for electronic devices. This
is ultimately bonded with a resist or buildup resin substrate.
[0006] Generally speaking, the quality demand of the copper foil
for a printed circuit board differs with the adherend surface to be
bonded with the resin base material (so-called roughened surface)
and the non-adherend surface (so-called gloss surface), and it is
necessary to simultaneously satisfy both demands.
[0007] Requirements of the gloss surface are as follows: (1)
favorable appearance and no oxidative discoloration during the
storage thereof, (2) favorable solder wettability, (3) no oxidative
discoloration during high-temperature heating, and (4) favorable
adhesion with the resist.
[0008] Meanwhile, main requirements of the roughened surface are as
follows: (1) no oxidative discoloration during the storage thereof,
(2) peel strength with the base material is sufficient even after
high-temperature heating, wet processing, soldering, chemical
treatment and the like, and (3) no so-called lamination
contamination that occurs in etching after the lamination with the
base material.
[0009] Moreover, pursuant to the finer circuit printed patterns in
recent years, the lower degree of roughness of the copper foil
surface is being demanded.
[0010] Further, with personal computers and electronic devices of
mobile communication and the like, the higher frequency of
electrical signals is progressing to accommodate faster speed and
greater capacity of communication, and printed circuit boards and
copper foils that are compatible with the foregoing demands are
being sought. When the frequency of electrical signals becomes 1
GHz or greater, the influence of the skin effect where the
currently flows only on the surface of the conductor becomes
prominent, and the influence of the increase in impedance caused by
changes in the current transmission path due to the irregularities
of the surface can no longer be ignored. From this point also, the
surface roughness of the copper foil is desirably low.
[0011] In order to meet the foregoing demands, numerous surface
treatment methods have been proposed for use in a copper foil for a
printed circuit board.
[0012] Although the surface treatment method differs with a rolled
copper foil and an electrolytic copper foil, an example of a
surface treatment method of an electrolytic copper foil is shown
below.
[0013] Foremost, in order to increase the bond strength (peel
strength) of the copper and the resin base material, generally
speaking, particles formed from copper and copper oxide are
provided on the copper foil surface (roughening treatment), and a
heat-resistant layer (barrier layer) formed of brass, zinc or the
like is formed to yield heat resistant properties.
[0014] Then, in order to prevent the surface oxidation and the like
during the transportation or storage, corrosion prevention
treatment such as chromate treatment based on immersion or
electrolytic zinc, electrolytic zinc chromate treatment or the like
is ultimately performed to obtain a product.
[0015] Among the above, in particular, the surface treatment method
of forming a heat-resistant layer is a major key in deciding the
surface properties of the copper foil. Thus, as the metal or alloy
forming the heat-resistant layer, numerous copper foils forming a
film layer of Zn, Cu--Ni alloy, Cu--Co alloy, Cu--Zn alloy and the
like have been put into practical use (for instance, refer to
Japanese Patent Application (Kokoku) Publication No.
S51-35711).
[0016] Among the above, a copper foil formed with a heat-resistant
layer formed from Cu--Zn alloy (brass) is broadly used industrially
since it yields superior characteristics such as no spots on the
resin layer when used as a printed circuit board formed from epoxy
resin or the like, and less deterioration in the peel strength of
the copper foil after the printed circuit board is retained at a
high temperature. Japanese Patent Application (Kokoku) Publication
No. S 54-6701 provides a detailed description regarding the method
of forming such a heat-resistant layer formed from brass.
[0017] In recent years, in the manufacturing processing of a
printed circuit board, in particular a package substrate, the
processing of roughening the copper foil gloss surface is being
performed based on soft etching using mixed solution of sulfuric
acid and hydrogen peroxide in order to improve the adhesion of the
resist or buildup resin substrate and the gloss surface of the
copper foil as the circuit side. Nevertheless, when the foregoing
soft etching using mixed solution of sulfuric acid and hydrogen
peroxide is performed to the copper foil circuit gloss surface of a
printed circuit board using a copper foil formed with a
heat-resistant layer formed from brass, the corrosion (circuit
corrosion) phenomenon of both ends (edges) of the previously formed
circuit pattern will occur, and there is a problem in that the peel
strength with the resin base material will deteriorate.
[0018] The circuit corrosion phenomenon is a phenomenon where the
adhesive boundary layer between the copper foil circuit and the
resin base material; that is, the circuit side surface where the
heat-resistant layer formed from brass is exposed will erode due to
mixed solution of sulfuric acid and hydrogen peroxide, whereby the
roughened surface side in the vicinity of the edge portion of the
circuit which should normally be a yellow color (caused by brass)
becomes red, and the peel strength of the copper foil of that
portion will deteriorate considerably. If this phenomenon occurs on
the entire surface of the circuit pattern, the circuit pattern will
peel from the base material and cause a major problem.
SUMMARY
[0019] Thus, an object of the present invention is to develop a
copper foil suitable for use in a semiconductor package substrate
capable of increasing, without deteriorating the other various
characteristics, the normal peel strength of the copper foil of a
printed circuit board that was produced by laminating a copper foil
and a resin base material, and the peel strength (hereinafter
referred to as the "heat-resistant peel strength") after the
printed circuit board was retained at a high temperature for a
given period of time, and to additionally reduce the foregoing
circuit corrosion phenomenon. In particular, an object of the
present invention is to establish surface treatment technology of a
copper foil capable of considerably improving the heat-resistant
peel strength by laminating a copper foil on a resin base material,
and effectively preventing the circuit corrosion phenomenon in
cases of using a sulfuric acid hydrogen peroxide etching solution
to perform soft etching to the circuit.
[0020] In order to achieve the foregoing object, as a result of
intense study regarding the conditions of performing surface
treatment to the copper foil, the present inventors discovered that
the corrosion resistivity (circuit corrosion resistivity) of the
roughened surface on the opposite side of the copper foil is
effective in improving the heat-resistant peel strength of the
copper foil and the resistivity of sulfuric acid and hydrogen
peroxide; that is, the resistivity during the soft etching of the
copper foil gloss surface using mixed solution of sulfuric acid and
hydrogen peroxide.
[0021] Based on the foregoing discovery, the present invention
provides a copper foil for a printed circuit board comprising a
layer including nickel, zinc, a compound of nickel and that of zinc
(hereinafter referred to as a "nickel zinc layer") on a roughened
surface of a copper foil, and a chromate film layer on the nickel
zinc layer, wherein the zinc add-on weight per unit area of the
nickel zinc layer is 180 .mu.g/dm.sup.2 or more and 3500
.mu.g/dm.sup.2 or less, and the nickel weight ratio in the nickel
zinc layer {nickel add-on weight/(nickel add-on weight+zinc add-on
weight)} is 0.38 or more and 0.7 or less, or alternatively, is 0.4
or more and 0.55 or less. The chromium add-on weight per unit area
of the copper foil of the chromate film layer can be 30
.mu.g/dm.sup.2 or more and 100 .mu.g/dm.sup.2 or less. Among all
zinc included in the nickel zinc layer, 45 to 90% of zinc existing
as zinc oxide or zinc hydroxide may be contained therein, and among
all nickel included the nickel zinc layer, 60 to 80% of nickel
existing as nickel oxide or nickel hydroxide may be contained
therein.
[0022] The copper foil may further comprise a silane coupling agent
layer on the chromate layer. In addition, the copper foil may be an
electrolytic copper foil, and the roughened surface may be a rough
face obtained during electrolytic plating, a face obtained by
additionally performing roughening treatment to the rough face, or
a face obtained by performing roughening treatment on a gloss
surface of an electrolytic copper foil. Alternatively, the copper
foil may be a rolled copper foil, and the roughened surface may be
a face obtained by performing roughening treatment to the rolled
copper foil.
[0023] The present invention also provides a copper clad laminate
for a printed circuit board produced by laminating the copper foil
discussed above and a resin for a printed circuit board.
[0024] As described above, the copper foil for a printed circuit
board of the present invention uses a nickel zinc layer in order to
prevent the deterioration in the peel strength of the copper foil
after retaining the printed circuit board at a high temperature,
and does not use a heat-resistant layer formed from brass, which
was conventionally considered to be indispensable. Consequently, it
is possible to dramatically improve the heat-resistant peel
strength of the copper foil. It is further possible to effectively
prevent the circuit corrosion phenomenon caused by chemicals, and
in particular new characteristics of being able to improve the
resistivity to sulfuric acid hydrogen peroxide. Thus, the present
invention is extremely useful as a copper foil for a printed
circuit board (in particular, a copper foil for a semiconductor
package substrate) and a copper clad laminate (in particular, a
copper clad laminate for a semiconductor package substrate)
produced by laminating a copper foil and a resin base material.
Needless to say, the present invention can also be used as a
general copper foil for a printed circuit board.
DETAILED DESCRIPTION
[0025] The present invention is now explained specifically and in
detail in order to facilitate the understanding thereof.
[0026] As the copper foil of the present invention, both an
electrolytic copper foil and a rolled copper foil can be used. In
the case of an electrolytic copper foil, the rough face obtained
during the electrolytic plating can be used. Moreover, roughening
treatment may be additionally performed to the foregoing rough
face. For example, in order to increase the peel strength of the
copper foil after its lamination with the resin base material, an
electrolytic copper foil subject to roughening treatment of
performing electrodeposition of copper in a "knobbed" shaped to the
degreased surface of the copper foil may be used as is.
[0027] Generally speaking, in a drum-shaped manufacturing apparatus
of an electrolytic copper foil, one side (drum side) is a gloss
surface and the other side is a rough face. With a rolled copper
foil, both sides will be a glossy rolled surface. In the present
invention, although the electrolytic copper foil has a rough face
and a gloss surface, the rough face can be used as is. The gloss
surface of the electrolytic copper foil is subject to roughening
treatment in order to increase the peel strength and made into a
roughened surface.
[0028] Roughening treatment is similarly performed to the rolled
copper foil. Well-known roughening treatment may be used in the
foregoing cases, and there is no particular limitation in the type
of roughening treatment that may be performed.
[0029] The roughened surface of the present invention refers to the
rough face that is obtained during the electrolytic plating of the
electrolytic copper foil, and the roughened surface of the
electrolytic copper foil or the rolled copper foil that was subject
to roughening treatment, and can be applied to either copper
foil.
[0030] Foremost, a brass film layer, which was conventionally
considered to be indispensable, is not provided to the copper foil
for a semiconductor package substrate. Conventionally, unless a
brass film layer was provided, it was considered that
characteristics would deteriorate; for instance, the peel strength
(heat-resistant peel strength) of the copper foil after the printed
circuit board was retained at a high temperature for a given period
of time would deteriorate. As a substitute method, the present
invention forms a nickel zinc layer in order to improve the
heat-resistant peel strength. Accordingly, a significant feature of
the present invention is that a brass film layer is not formed on
the copper foil, which was conventionally considered a technical
standard.
[0031] The nickel zinc layer is not a uniform nickel-zinc alloy,
and includes nickel and zinc which are in an oxidized or
hydroxidized state. For example, the nickel zinc layer can include
a surface oxide film or a surface hydroxide film.
[0032] As described above, the copper foil for a semiconductor
package substrate of the present invention is configured from a
nickel zinc layer formed on the roughened surface of the copper
foil to become the adherend surface with the resin, a chromate film
layer and, as needed, a silane coupling agent layer. As the copper
foil, the foregoing rolled copper foil or the electrolytic copper
foil can be used. As the chromate film layer, the electrolytic
chromate film layer or the immersion chromate film layer can be
used.
[0033] The present invention forms, as described above, a layer
including nickel, zinc, a compound of nickel and that of zinc
(hereinafter referred to a "nickel zinc layer") on a roughened
surface of a copper foil, and the zinc add-on weight per unit area
of the copper foil in the nickel zinc layer must be 180
.mu.g/dm.sup.2 or more and 3500 .mu.g/dm.sup.2 or less. If the zinc
add-on weight is less than 180 .mu.g/dm.sup.2, the deterioration of
the peel strength after the high-temperature heating will increase.
Moreover, if the zinc add-on weight exceeds 3500 .mu.g/dm.sup.2,
the corrosion of the circuit edge caused by the sulfuric acid
hydrogen peroxide etching solution will become prominent.
[0034] The {nickel add-on weight/(nickel add-on weight+zinc add-on
weight)} must be 0.38 or more and 0.7 or less. If it is less than
0.38, the circuit corrosion phenomenon cannot be effectively
prevented. Moreover, if it exceeds 0.7, the heat-resistant peel
strength will deteriorate.
[0035] The nickel zinc layer is normally formed under the following
conditions. Nevertheless, so long as the electroplating conditions
are able to achieve results where the zinc add-on weight per unit
area of the nickel zinc layer is 180 .mu.g/dm.sup.2 or more and
3500 .mu.g/dm.sup.2 or less, and the {nickel add-on weight/(nickel
add-on weight+zinc add-on weight)} is 0.38 or more and 0.7 or less,
there is no particular limitation in the electroplating conditions
and other electroplating conditions may also be used.
[0036] Plating Solution Composition: [0037] Ni: 10 g/L to 30 g/L
[0038] Zn: 1 g/L to 15 g/L [0039] sulfuric acid (H.sub.2SO.sub.4):
1 g/L to 12 g/L [0040] (each of the above is used as the basic
bath) [0041] Chloride ion: 1 g/L to 5 g/L is added as needed
[0042] Current density: 3 to 40 A/dm.sup.2
[0043] Next, as the chromate treatment, in order to produce this
chromate film layer, any chromate treatment among the electrolytic
chromate treatment, immersion chromate treatment and zinc chromate
treatment in which zinc is contained in the chromate bath may be
used.
[0044] Regardless of the chromate treatment method, if the chromium
add-on weight is less than 30 .mu.g/dm.sup.2, and the effect of
increasing the acid resistivity and heat resistivity is
insufficient. Thus, the chromium add-on weight is made to be 30
.mu.g/dm.sup.2 or more. Meanwhile, if the chromium add-on weight
exceeds 100 .mu.g/dm.sup.2, the effect of the chromate treatment
will become saturated and the chromium add-on weight will no longer
increase. In summary, it could be said that the chromium add-on
weight per unit area in the chromate treatment layer is desirably
30 to 100 .mu.g/dm.sup.2.
[0045] Examples of conditions for forming the chromate film layer
are shown below. However, as described above, the present invention
is not limited to the following conditions, and any well-known
chromate treatment may be used. Generally speaking, in the case of
the immersion chromate treatment, it is possible to achieve a
chromium add-on weight per unit area of 30 to 40 .mu.g/dm.sup.2.
Moreover, with the electrolytic chromate treatment, it is possible
to achieve a chromium add-on weight per unit area of 30 to 100
.mu.g/dm.sup.2. This corrosion prevention treatment is one factor
that affects the acid resistivity and heat resistivity of the
copper foil, and the chromate treatment is effective in improving
the acid resistivity and heat resistivity of the copper foil.
[0046] (a) Example of immersion chromate treatment: [0047]
CrO.sub.3 or K.sub.2Cr.sub.2O.sub.7: 1 to 12 g/L [0048]
Zn(OH).sub.2 or ZnSO.sub.4.7H.sub.2O: 0 to 10 g/L [0049]
Na.sub.2SO.sub.4: 0 to 20 g/L [0050] pH: 2.5 to 12.5 [0051]
Temperature: 20 to 60.degree. C. [0052] Time: 0.5 to 20 seconds
[0053] (b) Example of electrolytic chromate treatment [0054]
CrO.sub.3 or K.sub.2Cr.sub.2O.sub.7: 1 to 12 g/L [0055]
Zn(OH).sub.2 or ZnSO.sub.4.7H.sub.2O: 0 to 10 g/L [0056]
Na.sub.2SO.sub.4: 0 to 20 g/L [0057] pH: 2.5 to 12.5 [0058]
Temperature: 20 to 60.degree. C. [0059] Current density: 0.5 to 5
A/dm.sup.2 [0060] Time: 0.5 to 20 seconds
[0061] As the silane coupling agent to be used in the copper foil
for a printed circuit board of the present invention, it is
desirable to include at least one type among tetraalkoxysilane, and
alkoxysilane comprising a functional group having reactivity with
resin. Although the selection of this silane coupling agent is
arbitrary, selection in consideration with the adhesiveness with
resin is desirable.
[0062] In addition, the present invention provides a copper clad
laminate for a printed circuit board produced by laminating the
above referenced copper foil for a printed circuit board to a resin
base material for a printed circuit board.
[0063] Subsequently, the silane coupling agent treatment (drying
after application) was performed on the corrosion-resistant layer.
Conditions of the silane coupling agent treatment are as follows.
An aqueous solution including epoxy silane at 0.2% by volume and
TEOS (tetraethoxysilane) at 0.4% by volume was adjusted to pH 5,
thereafter applied and dried.
Test Method
[0064] The printed circuit board that was obtained by laminating
and bonding the copper foil that was produced as described above
with the following resin base material was used to perform various
tests, and the adhesion of the copper foil and the resin base
material was evaluated and the plating add-on weight of nickel and
zinc per unit area was measured. In addition, the abundance ratio
of the 0-valent metal state and bivalent oxidized state of nickel
and zinc contained in the nickel zinc layer was measured with XPS
(X-ray photoelectron spectroscopy).
[0065] The following two types of resin base material to be
laminated with the copper foil were used: FR-4 resin (glass cloth
base material epoxy resin); and BT resin (Bismaleimide-Triazine
Resin, Trademark name: GHPL-802 manufactured by Mitsubishi Gas
Chemical Co., Inc.). Incidentally, the BT resin is a material that
has high heat resistivity and is being used in a printed circuit
board for a semiconductor package.
Measurement of Normal Peel Strength and Heat-Resistant Peel
Strength Using FR-4 Substrate
[0066] Etching was performed to the copper foil formed on a
laminate produced by laminating the face formed with a nickel zinc
layer if the copper foil and the FR-4 resin base material, and a
copper foil circuit having a width of 10 mm was formed on the
laminate. The normal peel strength was measured by peeling this
circuit. Subsequently, the laminate formed with the foregoing
copper foil circuit having a width of 10 mm was heated in the
atmosphere at 180.degree. C. for 2 days. Then the peel strength
after the heating (hereinafter referred to as the "heat-resistant
peel strength") and relative deterioration rate (loss %) based on
the normal peel strength were measured. In terms of heat
resistivity, the FR-4 substrate is inferior to the BT substrate.
Thus, if favorable heat-resistant peel strength and a low
deterioration rate can be achieved when using the FR-4 substrate,
sufficient heat-resistant peel strength and deterioration rate can
also be achieve when using the BT substrate.
Measurement of Normal Peel Strength and Resistivity to Sulfuric
Acid and Hydrogen Peroxide Using BT Substrate
[0067] Etching was performed to the copper foil formed on a
laminate produced by laminating the face formed with a nickel zinc
layer if the copper foil and the BT resin base material, and a
copper foil circuit having a width of 0.4 mm was formed on the
laminate. The normal peel strength was measured by peeling this
circuit. Subsequently, the laminate formed with the foregoing
copper foil circuit having a width of 0.4 mm was used to perform
the test of the resistivity to sulfuric acid hydrogen peroxide.
[0068] In this test, the copper foil circuit on the laminate was
immersed in an etching solution including 100 to 400 g/L of
sulfuric acid 100 to 400 g/L and 10 to 60 g/L of hydrogen peroxide
to etch the copper foil circuit to have a thickness of 2 .mu.m, and
the relative deterioration rate (loss %) was thereafter measured
from the foregoing peel strength and the normal peel strength.
[0069] It could be said that the measurement of the peel strength
in the foregoing case was conducted under a harsh environment, and
the conditions when using the FR-4 substrate are more severe in
comparison to the evaluation of chemical resistivity that is
generally conducted. Accordingly, if favorable resistivity to
sulfuric acid and hydrogen peroxide can be achieved when using the
BT substrate, sufficient chemical resistivity (in particular, that
resistivity to sulfuric acid hydrogen peroxide) can also be
achieved with the FR-4 substrate.
Measurement of Plating Add-On Weight of Nickel and Zinc Per Unit
Area
[0070] A laminate was produced by laminating the face formed with a
nickel zinc layer of the copper foil with the FR-4 resin base
material so that the nickel zinc layer is exposed on the surface.
Subsequently, the nickel zinc layer that is exposed on the laminate
surface and the copper as its mother layer were dissolved in
hydrochloric acid or nitric acid, and the add-on weight of nickel
and zinc per unit area was measured by performing a chemical
analysis of the nickel and zinc concentration in the solution.
Analysis of Metal/Oxidized State of Zinc and Nickel
[0071] The abundance ratio of the 0-valent metal state and bivalent
oxidized state of nickel and zinc contained in the nickel zinc
layer was measured with XPS (X-ray photoelectron spectroscopy). The
measurement was conducted intermittently from the outermost layer
to the copper layer as the substrate of the nickel zinc layer while
etching the copper foil thickness based argon ion sputtering, and
the average abundance ratio of the nickel oxide and zinc oxide
(both including hydroxide) in the overall nickel zinc layer was
calculated by integrating the abundance ratio of nickel and zinc in
an oxidized state obtained in the respective depths with the depth
from the outermost surface.
[0072] AXIS-HS manufactured by KRATOS was used as the measuring
equipment, and the output of the argon ion sputtering was 52.5 W.
Under these conditions, the copper foil thickness is etched
approximately 20 .ANG. per minute. The sputtering time was 15 to
100 minutes.
EXAMPLES
[0073] The Examples and Comparative Examples of the present
invention are now explained. The results thereof are shown in the
respective tables below. These Examples are merely illustrative,
and the present invention shall in no way be limited thereby. In
other words, various modifications and other embodiments based on
the technical spirit claimed in the claims shall be included in the
present invention as a matter of course. The Comparative Examples
are indicated for comparison with the present invention.
Examples 1 to 7 & Comparative Examples 1 and 2
[0074] An electrolytic copper foil having a thickness of 12 .mu.m
was used, and a nickel zinc layer was formed on a roughened surface
(surface average roughness: 3.8 .mu.m) of the copper foil via
electroplating according to the following conditions. The plating
add-on weight of nickel and zinc per unit area and the nickel
weight ratio in the plating film are shown in Table 1.
[0075] Electroplating solution composition: [0076] Ni: 13 g/L
[0077] Zn: 5 g/L [0078] sulfuric acid (H.sub.2SO.sub.4): 8.5
g/L
[0079] Current density: 20 A/dm.sup.2
[0080] Plating time: 0.5 to 10 seconds
[0081] Chromate treatment was performed to form a
corrosion-resistant layer on the nickel zinc layer additionally.
The treatment conditions are shown below:
[0082] CrO.sub.3: 4.0 g/L
[0083] ZnSO.sub.4.7H.sub.2O: 2.0 g/L
[0084] Na.sub.2SO.sub.4: 15 g/L
[0085] pH: 4.2
[0086] Temperature: 45.degree. C.
[0087] Current density: 3.0 A/dm.sup.2
[0088] Time: 1.5 seconds.
TABLE-US-00001 TABLE 1 BT Substrate Properties After Sulfuric Acid
FR-4 Substrate Properties and Hydrogen Ni--Zn Plating Add-on Weight
Heat-Resistant Peroxide Solution Plating Ni Zn Normal Peel Strength
Normal Treatment Current Deposition Deposition Ni Peel Relative
Peel Relative Density Weight Weight Weight Strength Deterioration
Strength Deterioration (A/dm.sup.2) (.mu.g/dm.sup.2)
(.mu.g/dm.sup.2) Ratio (kN/m) (kN/m) Rate (%) (kN/m) (kN/m) Rate
(%) Example 1 20 128 194 0.40 1.57 1.49 5 1.20 1.08 10 Example 2 20
252 313 0.45 1.57 1.50 5 1.24 1.09 12 Example 3 20 476 581 0.45
1.53 1.45 5 1.04 0.93 11 Example 4 20 682 628 0.52 1.53 1.55 -1
1.04 0.93 11 Example 5 20 998 1292 0.44 1.59 1.52 5 1.21 1.07 12
Example 6 20 1599 2058 0.44 1.68 1.59 5 1.18 1.03 13 Example 7 20
1981 3381 0.38 1.64 1.65 -1 1.04 0.91 13 Comparative 20 124 159
0.44 1.51 0.69 54 1.01 0.96 5 Example 1 Comparative 20 2395 3909
0.38 1.67 1.67 0 1.10 0.93 16 Example 2
[0089] The plating add-on weight will change depending on the
plating time since the current density is constant (20 A/dm.sup.2).
The plating time of the treatment was within the range of 0.5 to 10
seconds. The zinc add-on weight per unit area was 194 to 3381
.mu.g/dm.sup.2 and the nickel weight ratio in the plating film was
37 to 52 wt %. All of these conditions fall within the scope of the
present invention.
[0090] With the FR-4 substrate, the normal peel strength was 1.53
to 1.68 kN/m, the heat-resistant peel strength was 1.45 to 1.65
kN/m, and the deterioration rate was within a range of 5% or less,
and all cases showed favorable normal peel strength and
heat-resistant peel strength. Meanwhile, with the BT substrate, the
normal peel strength was within the range of 1.04 to 1.24 kN/m. The
peel strength after treatment with mixed solution of sulfuric acid
and hydrogen peroxide was 0.91 to 1.09 kN/m, and the deterioration
rate was 10 to 13%, and showed favorable properties.
[0091] Nevertheless, with Comparative Example 1, the zinc add-on
weight per unit area was 159 .mu.g/dm.sup.2, and deviated from the
present invention. In Comparative Example 1, with the FR-4
substrate, the normal peel strength was 1.51 kN/m, the
heat-resistant peel strength was 0.69 kN/m, and the deterioration
rate was 54%, and the heat-resistant peel strength deteriorated
considerably.
[0092] Meanwhile, in Comparative Example 2, the zinc add-on amount
was 3909 .mu.g/dm.sup.2, and deviated from the present invention.
In Comparative Example 2, with the BT substrate (under a harsh
environment), the normal peel strength was 1.10 kN/m, the peel
strength after the treatment with mixed solution of sulfuric acid
and hydrogen peroxide was 0.93 kN/m, and the deterioration rate was
16%, and possesses necessary and sufficient properties.
Nevertheless, since the Ni add-on weight will increase, the Ni will
not be etched and remain during the formation of the copper foil
circuit, thereby causing a circuit fault. Thus, this is
inappropriate as the surface treatment of a copper foil for a
printed circuit board, and Comparative Example 2 deviates from the
present invention.
[0093] As described above, Examples 1 to 7 showed favorable peel
strength and heat-resistant peel strength with the FR-4 substrate,
and showed favorable chemical resistivity in resistivity test of
sulfuric acid and hydrogen peroxide with the BT substrate.
Accordingly, it is easy to understand that these Examples have less
deterioration in the peel strength after high-temperature heating,
and possess effective characteristics that are able to considerably
improve the circuit corrosion phenomenon.
[0094] In particular, it is possible to obtain surface treatment
technology of a copper foil capable of effectively preventing the
circuit corrosion phenomenon in cases of laminating a copper foil
on a resin base material and using a sulfuric acid hydrogen
peroxide etching solution to perform soft etching to the
circuit.
Examples 8 to 13
[0095] A nickel zinc layer was formed under the following
conditions by changing the current density: current density 3 to 40
A/dm.sup.2; and plating time: 0.5 to 10 seconds. The plating add-on
weight of nickel and zinc per unit area and the nickel weight ratio
in the plating film are shown in Table 2. The manufacturing
conditions other than the current density were the same as Examples
1 to 7. The type of substrate and the measurement of peel strength
were the same conditions as Examples 1 to 7. The results are
similarly shown in Table 2.
TABLE-US-00002 TABLE 2 BT Substrate Properties After Sulfuric Acid
FR-4 Substrate Properties and Hydrogen Ni--Zn Plating Add-on Weight
Heat-Resistant Peroxide Solution Plating Ni Zn Normal Peel Strength
Normal Treatment Current Deposition Deposition Ni Peel Relative
Peel Relative Density Weight Weight Weight Strength Deterioration
Strength Deterioration (A/dm.sup.2) (.mu.g/dm.sup.2)
(.mu.g/dm.sup.2) Ratio (kN/m) (kN/m) Rate (%) (kN/m) (kN/m) Rate
(%) Example 8 3 590 724 0.45 1.50 1.52 -2 0.92 0.88 4 Example 9 5
246 330 0.43 1.56 1.45 7 0.98 0.91 8 Example 10 10 372 411 0.48
1.50 1.45 4 1.03 0.94 8 Example 11 15 436 438 0.50 1.48 1.40 6 1.03
0.98 5 Example 12 25 641 588 0.52 1.48 1.50 -1 1.04 0.93 11 Example
13 40 359 367 0.49 1.51 1.47 2 0.98 0.96 3
[0096] With respect to the plating add-on weight, as shown in Table
2, the zinc add-on weight per unit area was 330 to 724
.mu.g/dm.sup.2, and the nickel weight ratio in the plating film was
43 to 52 wt %. All of these conditions fall within the scope of the
present invention.
[0097] Since the nickel zinc layer cannot be created if the current
density falls below 3 A/dm.sup.2, this would be inappropriate as
the plating condition of the nickel zinc layer of the present
invention. If the current density exceeds 40 A/dm.sup.2, since much
hydrogen will be generated in the cathode (copper foil) and the
current efficiency deteriorate enormously, this would be
inappropriate as the treatment condition of the nickel zinc layer.
Accordingly, the current density upon creating the nickel zinc
layer of the present invention is preferably 3 to 40
A/dm.sup.2.
[0098] With the FR-4 substrate, the normal peel strength was 1.48
to 1.56 kN/m, the heat-resistant peel strength was 1.40 to 1.52
kN/m, and the deterioration rate was within a range of 7% or less,
and all cases showed favorable normal peel strength and
heat-resistant peel strength.
[0099] Meanwhile, with the BT substrate, the normal peel strength
was 0.92 to 1.04 kN/m, the peel strength after treatment with mixed
solution of sulfuric acid and hydrogen peroxide was 0.88 to 0.98
kN/m, and the deterioration rate was 3 to 11%, and showed favorable
properties.
[0100] As described above, Examples 8 to 13 showed favorable peel
strength and heat-resistant peel strength with the FR-4 substrate,
and showed favorable chemical resistivity in resistivity test of
the sulfuric acid and hydrogen peroxide with the BT substrate.
Accordingly, it is easy to understand that these Examples have less
deterioration in the peel strength after high-temperature heating,
and possess effective characteristics that are able to considerably
improve the circuit corrosion phenomenon.
Examples 1, 7 & 14 and Comparative Examples 3 & 4
[0101] The range of the Ni weight ratio in the plating film is now
explained. As an example, Examples 1, 7 and 14 and Comparative
Examples 3 and 4 are shown in Table 3. In addition, the plating
add-on weight of nickel and zinc per unit area and the nickel
weight ratio in the plating film are shown in Table 3.
[0102] The manufacturing conditions other than the above were the
same as Examples 1 to 13. The type of substrate and the measurement
of peel strength were also the same as Examples 1 to 13. The
results are similarly shown in Table 3. The Ni weight ratio in the
plating film was 0.38 to 0.54.
[0103] With the FR-4 substrate, the normal peel strength was 1.54
to 1.64 kN/m, the heat-resistant peel strength was 1.42 to 1.65
kN/m, and the deterioration rate was within a range of 8% or less,
and all cases showed favorable normal peel strength and
heat-resistant peel strength.
TABLE-US-00003 TABLE 3 BT Substrate Properties After Sulfuric Acid
FR-4 Substrate Properties and Hydrogen Ni--Zn Plating Add-on Weight
Heat-Resistant Peroxide Solution Plating Ni Zn Normal Peel Strength
Normal Treatment Current Deposition Deposition Ni Peel Relative
Peel Relative Density Weight Weight Weight Strength Deterioration
Strength Deterioration (A/dm.sup.2) (.mu.g/dm.sup.2)
(.mu.g/dm.sup.2) Ratio (kN/m) (kN/m) Rate (%) (kN/m) (kN/m) Rate
(%) Example 7 20 1981 3381 0.38 1.64 1.65 -1 1.04 0.91 13 Example 1
20 128 194 0.40 1.57 1.49 5 1.20 1.08 10 Example 14 25 725 619 0.54
1.54 1.42 8 1.07 0.91 15 Comparative 20 120 206 0.37 1.39 0.97 30
1.12 0.91 19 Example 3 Comparative 40 745 233 0.75 1.50 1.02 32
1.01 0.92 9 Example 4
[0104] Meanwhile, with the BT substrate, the normal peel strength
was 1.04 to 1.20 kN/m, the peel strength after treatment with mixed
solution of sulfuric acid and hydrogen peroxide was 0.91 to 1.08
gN/m, and the deterioration rate was 13 to 15%, and showed
favorable properties.
[0105] Nevertheless, with Comparative Example 3, the Ni weight
ratio was 0.37, and deviated from the present invention. In
Comparative Example 3, with the FR-4 substrate, the normal peel
strength was 1.39 kN/m, the heat-resistant peel strength was 0.97
kN/m, and the deterioration rate was 30%, and the heat-resistant
peel strength deteriorated considerably.
[0106] Meanwhile, with Comparative Example 4, the Ni weight ratio
was 0.76, and deviated from the present invention. In Comparative
Example 4, with the FR-4 substrate, the normal peel strength was
1.50 kN/m, the heat-resistant peel strength was 1.02 kN/m, and the
deterioration rate was 32%, and, as with Comparative Example 3, the
heat-resistant peel strength deteriorated considerably.
[0107] Accordingly, the Ni weight ratio in the plating film is
preferably within a range of 0.38 to 0.70, and more preferably
within a range of 0.40 to 0.54.
Examples 15 to 19
[0108] The nickel zinc layer was formed upon changing the plating
bath composition under the following conditions. The plating add-on
weight of nickel and zinc per unit area and the nickel weight ratio
in the plating film are shown in Table 4. Here, the difference in
comparison to Examples 1 to 14 is that the component composition of
the plating bath was changed.
[0109] The component composition of the plating bath in Examples 15
to 19 is shown below.
[0110] Plating solution composition of Example 15: [0111] Ni: 10
g/L [0112] Zn: 1 g/L [0113] sulfuric acid (H.sub.2SO.sub.4): 8.5
g/L
[0114] Plating solution composition of Example 16: [0115] Ni: 20
g/L [0116] Zn: 8 g/L [0117] sulfuric acid (H.sub.2SO.sub.4): 1
g/L
[0118] Plating solution composition of Example 17: [0119] Ni: 25
g/L [0120] Zn: 12 g/L [0121] sulfuric acid (H.sub.2SO.sub.4): 12
g/L
[0122] Plating solution composition of Example 18: [0123] Ni: 30
g/L [0124] Zn: 15 g/L [0125] sulfuric acid (H.sub.2SO.sub.4): 8.5
g/L
[0126] Plating solution composition of Example 19: [0127] Ni: 10
g/L [0128] Zn: 1 g/L [0129] sulfuric acid (H.sub.2SO.sub.4): 6 g/L
[0130] chloride ion: 5 g/L
[0131] Current density: 20 to 25 A/dm.sup.2
[0132] Plating time: 1 to 8 seconds
[0133] The manufacturing conditions other than the above were the
same as Examples 1 to 7. The type of substrate and the measurement
of peel strength were also the same as Examples 1 to 7. The results
are similarly shown in Table 4.
TABLE-US-00004 TABLE 4 BT Substrate Properties After Sulfuric Acid
FR-4 Substrate Properties and Hydrogen Ni--Zn Plating Add-on Weight
Heat-Resistant Peroxide Solution Plating Ni Zn Normal Peel Strength
Normal Treatment Current Deposition Deposition Ni Peel Relative
Peel Relative Density Weight Weight Weight Strength Deterioration
Strength Deterioration (A/dm.sup.2) (.mu.g/dm.sup.2)
(.mu.g/dm.sup.2) Ratio (kN/m) (kN/m) Rate (%) (kN/m) (kN/m) Rate
(%) Example 15 25 318 320 0.50 1.57 1.50 5 1.09 0.91 17 Example 16
20 381 463 0.45 1.62 1.59 2 0.98 0.89 9 Example 17 20 668 817 0.45
1.52 1.56 -2 0.98 0.91 8 Example 18 20 637 807 0.44 1.59 1.57 2
1.09 0.97 11 Example 19 20 425 467 0.48 1.58 1.47 7 1.04 0.96 8
[0134] The zinc add-on weight per unit area was 320 to 817
.mu.g/dm.sup.2, and the nickel weight ratio in the plating film was
44 to 50 wt %. All of these conditions fall within the scope of the
present invention.
[0135] With the FR-4 substrate, the normal peel strength was 1.52
to 1.62 kN/m, the heat-resistant peel strength was 1.47 to 1.59
kN/m, and the deterioration rate was within a range of 7% or less,
and all cases showed favorable normal peel strength and
heat-resistant peel strength.
[0136] Meanwhile, with the BT substrate, the normal peel strength
was 0.98 to 1.09 kN/m, the peel strength after treatment with mixed
solution of sulfuric acid and hydrogen peroxide was 0.89 to 0.97
kN/m, and the deterioration rate was 8 to 17%, and showed favorable
properties.
[0137] As described above, Examples 15 to 19 showed favorable peel
strength and heat-resistant peel strength with the FR-4 substrate,
and showed favorable chemical resistivity in test of resistivity to
the sulfuric acid and hydrogen peroxide with the BT substrate.
Accordingly, it is easy to understand that these Examples have less
deterioration in the peel strength after high-temperature heating,
and possess effective characteristics that enable to considerably
improve the circuit corrosion phenomenon.
[0138] As described above, the plating bath conditions upon
producing the nickel zinc layer of the present invention are
preferably as follows: nickel concentration: 10 to 30 g/L, zinc
concentration: 1 to 15 g/L, sulfuric acid concentration: 1 to 12
g/L, and chloride ion: 0 to 5 g/L. If the concentration deviates
from the foregoing range and the concentration of nickel or zinc
becomes high, this would not be desirable as a plating bath
condition since it will interfere with the wastewater treatment.
Moreover, if the component concentration becomes low and deviates
from the foregoing range, in addition to the management of the
plating bath becoming difficult to factors such as changes in the
concentration caused by the plating, the current efficiency will
deteriorate enormously, and this is undesirable as a plating bath
condition.
Examples 20 to 22
[0139] Examples in cases where the method of chromate treatment is
changed are now explained. In these Examples, the nickel zinc layer
was formed under the same conditions as shown in Examples 1 to 7.
The same conditions for the current density and the plating time
(current density 20 A/dm.sup.2, plating time 1.8 seconds) were used
for comparison. The plating add-on weight of nickel and zinc per
unit area and the nickel weight ratio in the plating film are shown
in Table 5.
[0140] Here, the difference in comparison to Examples 1 to 7 is
that the conditions of the chromate treatment were changed. In
Examples 1 to 7, electrolytic zinc chromate treatment was
performed. The conditions of the chromate treatment in Examples 20
to 22 were as follows.
[0141] Chromate treatment of Example 20 (This is electrolytic
chromate treatment in which the chromate bath does not contain
zinc): [0142] CrO.sub.3: 6.0 g/L [0143] pH: 10.0 [0144]
temperature: 25.degree. C. [0145] current density: 2 A/dm.sup.2
[0146] time: 2 seconds
[0147] Chromate treatment of Example 21 (This is electrolytic zinc
chromate treatment): [0148] CrO.sub.3: 1.5 g/L [0149]
ZnSO.sub.4.7H.sub.2O: 1.0 g/L [0150] Na2SO.sub.4: 10 g/L [0151] pH:
4.5 [0152] temperature: 50.degree. C. [0153] current density: 1.5
A/dm.sup.2 [0154] time: 2 seconds
[0155] Chromate treatment of Example 22 (This is immersion zinc
chromate treatment): [0156] CrO.sub.3: 3.5 g/L [0157] ZnSO.sub.4
7H.sub.2O: 2.4 g/L [0158] Na.sub.2SO.sub.4: 15 g/L [0159] pH: 4.2
[0160] temperature: 40.degree. C. [0161] time: 10 seconds
[0162] The type of substrate and the measurement of peel strength
were also the same as Examples 1 to 7. The results are similarly
shown in Table 5.
TABLE-US-00005 TABLE 5 BT Substrate Properties After Sulfuric Acid
FR-4 Substrate Properties and Hydrogen Ni--Zn Plating Add-on Weight
Heat-Resistant Peroxide Solution Plating Ni Zn Normal Peel Strength
Normal Treatment Current Deposition Deposition Ni Peel Relative
Peel Relative Density Weight Weight Weight Strength Deterioration
Strength Deterioration (A/dm.sup.2) (.mu.g/dm.sup.2)
(.mu.g/dm.sup.2) Ratio (kN/m) (kN/m) Rate (%) (kN/m) (kN/m) Rate
(%) Example 20 20 329 434 0.43 1.51 1.47 3 1.03 0.94 8 Example 21
20 461 552 0.46 1.54 1.50 3 1.01 0.83 17 Example 22 20 312 347 0.47
1.48 1.43 3 1.08 0.98 9
[0163] As shown in Table 5, with Examples 20 to 22, the zinc add-on
amount was 347 to 552 .mu.g/d , and the Ni ratio was 43 to 47 wt %.
All of these conditions fall within the scope of the present
invention. With the FR-4 substrate, the normal peel strength was
1.48 to 1.54 kN/m, the heat-resistant peel strength was 1.43 to
1.50 kN/m, and the deterioration rate was within a range of 3% or
less, and all cases showed favorable peel strength.
[0164] Meanwhile, with the BT substrate, the normal peel strength
was 1.01 to 1.08 kN/m, the peel strength after treatment with mixed
solution of sulfuric acid and hydrogen peroxide was 0.83 to 0.98
kN/m, and the deterioration rate was 8 to 17%, and showed favorable
properties.
[0165] As described above, Examples 20 to 22 showed favorable peel
strength and heat resistivity with the FR-4 substrate, and showed
favorable chemical resistivity in resistivity test to the sulfuric
acid and hydrogen peroxide with the BT substrate.
[0166] Accordingly, it is easy to understand that these Examples
have less deterioration in the peel strength after high-temperature
heating, and possess effective characteristics that are able to
considerably improve the circuit corrosion phenomenon as a result
of selecting the substrate and selecting the etching solution.
[0167] As evident from Examples 20 to 22, since the heat
resistivity and chemical resistivity of the copper foil with the
nickel zinc layer of the present invention formed thereon will not
be affected by the type of chromate treatment, various types of
chromate treatment can be applied as the corrosion prevention
treatment.
[0168] As a result of the foregoing Examples and Comparative
Examples, it is possible to understand that, with the present
invention, hardly any corrosion due to the sulfuric acid hydrogen
peroxide solution will occur on the roughened surface, and the
deterioration in the peel strength after the high-temperature
heating is less. Thus, the present invention is able to
considerably improve the circuit corrosion phenomenon without
deteriorating the characteristics of a conventional heat-resistant
treatment layer formed from brass.
[0169] The chemical state of nickel and zinc contained in the
nickel zinc layer of the present invention is now explained.
[0170] With a standard alloy plating film, the metal elements
composing the film are alloyed, and only a small portion of the
metal elements existing on the outermost layer come in contact with
the atmosphere and become an oxidized state.
[0171] Nevertheless, according to the XPS measurement results, the
nickel zinc layer of the present invention does not contain nickel
zinc alloy itself, and has a structure where nickel and zinc in the
film is of a 0-valent state (metal) and bivalent oxidized state
(oxide and/or hydroxide) existing from the outermost surface layer
of the treated copper foil to the surface of the copper substrate.
For instance, in Example 14, among all nickel atoms in the film,
those taking a chemical state of oxide or hydroxide account for
55%, and, among all zinc atoms in the film, those taking a bivalent
chemical state account for 72%.
[0172] With the nickel zinc layer obtained by the surface treatment
of the present invention, it has been confirmed that, among all
zinc in the film, the ratio of those taking on a chemical state of
oxide or hydroxide is within a range of 45 to 90%, and, similarly,
among all nickel in the film, the ratio of those taking a chemical
state of oxide or hydroxide is within a range of 60 to 80%. As
shown in the Examples, it has been confirmed that the intended
characteristics and effects are yielded in the foregoing
conditions. The present invention covers all of the foregoing
conditions.
[0173] Although a case of applying the present invention to the
roughened surface of an electrolytic copper foil was described
above, it goes without saying that the present invention can also
be similarly applied to an electrolytic copper foil obtained by
performing roughening treatment to a gloss surface. In addition,
the same goes for applying the present invention to a rolled copper
foil that further was subject to roughening treatment. So as long
as a roughened surface of an electrolytic copper foil and a rolled
copper foil is used, although there will be some difference in the
absolute value of the normal peel strength due to the shape of the
roughening treatment and differences in the surface roughness, it
is possible to reduce the relative deterioration rate from the
normal peel of the heat-resistant peel strength and the peel
strength after the sulfuric acid hydrogen peroxide treatment.
[0174] The central objective of the copper foil for a printed
circuit board of the present invention is to select the optimal
conditions of the nickel zinc layer. Consequently, it will be
possible to dramatically improve the heat-resistant peel strength
of the copper foil, effectively prevent the circuit corrosion
phenomenon, and constantly and stably exhibit the effect in
resistivity to sulfuric acid and hydrogen peroxide.
[0175] Accordingly, it should be easy to understand that the
selection of the electrolytic copper foil and the rolled copper
foil or the selection of the roughened surface can be made
arbitrarily according to the intended purpose.
[0176] As described above, the copper foil for a printed circuit
board of the present invention uses a nickel zinc layer in order to
prevent the deterioration in the peel strength with resin after
high-temperature heating, and is thereby able to dramatically
improve the heat-resistant peel strength of the copper foil. In
addition, the circuit corrosion phenomenon can also be effectively
prevented, and the new characteristics of being able to constantly
and stably exhibit the effect in resistivity to sulfuric acid and
hydrogen peroxide are realized. While finer patterning and higher
frequency of the printed circuit are making progress in recent
years, the present invention is extremely useful as a copper foil
for a printed circuit board (in particular, a copper foil for a
semiconductor package substrate) and a copper clad laminate (in
particular, a copper clad laminate for a semiconductor package
substrate) produced by laminating a copper foil and a resin base
material.
* * * * *