U.S. patent application number 15/626877 was filed with the patent office on 2018-10-18 for electrodeposited copper foil with low repulsive force.
This patent application is currently assigned to CHANG CHUN PETROCHEMICAL CO., LTD.. The applicant listed for this patent is CHANG CHUN PETROCHEMICAL CO., LTD.. Invention is credited to Kuei-Seng CHENG, Jian-Ming HUANG, Yao-Sheng LAI.
Application Number | 20180298509 15/626877 |
Document ID | / |
Family ID | 63556755 |
Filed Date | 2018-10-18 |
United States Patent
Application |
20180298509 |
Kind Code |
A1 |
LAI; Yao-Sheng ; et
al. |
October 18, 2018 |
ELECTRODEPOSITED COPPER FOIL WITH LOW REPULSIVE FORCE
Abstract
The present disclosure relates to a copper foil that exhibits
surprising low repulsive force characteristics; and to methods for
manufacturing such copper foils. Typically, the copper foil has (a)
a lightness L* value of the nodule untreated side, based on the
L*a*b color system, in the range of 75 to 90 and (b) a normal
tensile strength in the range of 40 kgf/mm.sup.2 to 55
kgf/mm.sup.2. The disclosure further relates to flexible printed
circuit boards and electronic devices using the above-mentioned
copper foils for forming conductive lines therein.
Inventors: |
LAI; Yao-Sheng; (Miaoli,
TW) ; CHENG; Kuei-Seng; (Miaoli, TW) ; HUANG;
Jian-Ming; (Miaoli, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CHANG CHUN PETROCHEMICAL CO., LTD. |
TAIPEI |
|
TW |
|
|
Assignee: |
CHANG CHUN PETROCHEMICAL CO.,
LTD.
TAIPEI
TW
|
Family ID: |
63556755 |
Appl. No.: |
15/626877 |
Filed: |
June 19, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15490608 |
Apr 18, 2017 |
|
|
|
15626877 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02E 60/10 20130101;
C25D 3/38 20130101; C25D 5/38 20130101; C25D 1/04 20130101; H01M
4/045 20130101; H01M 4/0469 20130101; C25D 5/48 20130101; H01M
4/0438 20130101; C25D 1/20 20130101 |
International
Class: |
C25D 1/04 20060101
C25D001/04; C25D 1/20 20060101 C25D001/20; C25D 3/38 20060101
C25D003/38 |
Claims
1. (canceled)
2. An electrodeposited copper foil comprising: (a) a lightness L*
value of a nodule untreated side, based on the L*a*b* color system,
in the range of 75 to 90; (b) a tensile strength in the range of 20
kgf/mm.sup.2 to 29 kgf/mm.sup.2, further comprising a low angle
grain boundary (LAGB) percentage, as measured via electron
backscatter diffraction (ESBD) of less than 7.0%.
3. An electrodeposited copper foil comprising: (a) a lightness L*
value of a nodule untreated side, based on the L*a*b* color system,
in the range of 75 to 90; (b) a tensile strength in the range of 20
kgf/mm.sup.2 to 29 kgf/mm.sup.2, further comprising a grain size in
the range of 4.5 .mu.m to 7.5 .mu.m.
4. An electrodeposited copper foil comprising: (a) lightness L*
value of a nodule untreated side, based on the L*a*b* color system,
in the range of 75 to 90; (b) a tensile strength in the range of 20
kgf/mm.sup.2 to 29 kgf/mm.sup.2, further comprising a degree of
curl, as measured by the lamination curl test, is in the range of
0.45 mm to 3 mm.
5.-6. (canceled)
7. The electrodeposited copper foil of claim 3, wherein the grain
size value is in the range of 7.0 .mu.m to 7.5 .mu.m and the degree
of curl, as measured by the lamination curl test, is in the range
of 0.45 mm to 1.5 mm.
8. The electrodeposited copper foil of claim 3, wherein the grain
size value is in the range of 5.0 .mu.m to 5.5 .mu.m and the degree
of curl, as measured by the lamination curl test, is in the range
of 1.5 mm to 2.5 mm.
9. The electrodeposited copper foil of claim 3, wherein the grain
size value is in the range of 4.5 .mu.m to 5.0 .mu.m and the degree
of curl, as measured by the lamination curl test, is in the range
of 2.5 mm to 3.0 mm.
10. The electrodeposited copper foil of claim 2, further comprising
an anti-tarnish layer.
11-17. (canceled)
18. A flexible printed circuit comprising an electrodeposited
copper foil according to claim 2.
19. An electronic component comprising a flexible printed circuit
board according to claim 18.
20. An electronic device comprising an electronic component
according to claim 18.
21. The electrodeposited copper foil of claim 2, further comprising
a repulsive force, as measured via lamination repulsive force
testing, of between 12 and 14 grams.
22. (canceled)
23. The electrodeposited copper foil of claim 2, further comprising
a nodule treated side opposite the nodule untreated side.
24. The electrodeposited copper foil of claim 23, further
comprising a passivation layer formed on the nodule treated side
and the nodule untreated side.
25. The electrodeposited copper foil of claim 10, wherein the
anti-tarnish layer is one selected from the group consisting of a
chromate, substituted triazole, or combinations thereof.
26. An electrodeposited copper foil comprising: (a) a lightness L*
value of a nodule untreated side, based on the L*a*b color system,
in the range of 80.5 to 90; and (b) a tensile strength in the range
of 20 kgf/mm.sup.2 to 36 kgf/mm.sup.2.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Non-Provisional
patent application Ser. No. 15/490,608, entitled "ELECTRODEPOSITED
COPPER FOIL WITH LOW REPULSIVE FORCE" and filed Apr. 18, 2017, the
contents of which are incorporated by reference in their entirety
as if fully set forth herein.
FIELD OF THE INVENTION
[0002] The present disclosure relates to an improved copper foil
that exhibits low repulsive force properties; to methods for
manufacturing the copper foil; and to use of the copper foil in
flexible printed circuits and electronic devices using the
same.
BACKGROUND
[0003] In general, rolled annealed copper foil has been used
extensively in the flexible printed circuits industry. The grain
structure and smooth surface is ideal for dynamic, flexible
circuitry applications. However, rolled copper typically includes a
horizontal grain structure, which can be more challenging for the
etching of tight conductor spaces. In contrast, electrodeposited
copper foil has a vertical grain structure that can be advantageous
for obtaining tight etched spacing and well-defined conductor
walls. The standard electrodeposited copper foil typically has a
relatively high profile or rough surface as compared to rolled
annealed copper foil, which can benefit bonding strength.
[0004] A typical device for manufacturing an electrodeposited
copper foil comprises a metal cathode drum and an insoluble metal
anode, the metal cathode drum being rotatable and having a mirror
polished surface. The insoluble metal anode is arranged at
approximately the lower half of the metal cathode drum and
surrounds the metal cathode drum. A copper foil is continuously
manufactured with the device by flowing a copper electrolytic
solution between the cathode drum and the anode, applying direct
current between these to allow copper to be electrodeposited on the
cathode drum, and detaching an electrodeposited copper foil from
the cathode drum when a predetermined thickness is obtained.
[0005] Copper foil manufactured in this manner is often used as a
conductive material for printed wiring boards, including flexible
printed circuits. Flexible printed circuits (FPC) refer to printed
circuits in which the electronic components for the FPC are mounted
or formed on a flexible substrate. As a result, the FPC can conform
to a desired shape, or to flex during its use. FPCs have been used
generally, for example, as wirings for bending portions of foldable
(clamshell type) cellular phones, movable portions of digital
cameras, printer heads, etc., and movable portions of equipment
relevant to disks such as HDDs (Hard Disk Drives), DVDs (Digital
Versatile Disks) and CDs (Compact Disks).
[0006] Therefore, at least where FPCs are involved, the flexibility
of the copper foil is important from both reliability and
manufacturing viewpoints. If the flexibility of the copper foil is
not large enough, the bent or deformed copper foil will act as a
spring and exert a restorative force against the flexible substrate
of the FPC. This is referred to as the repulsive force of the
copper foil. If the repulsive force is sufficiently high, the
copper foil could delaminate from the flexible substrate during
manufacturing or use. Further, when the FPC is connected to another
device, a high repulsive force exerted by the copper foil against
the flexible substrate could interfere proper bonding of the FPC to
another component. Worse, the FPC could debond from this other
component. Accordingly, solving the reliability problems and
manufacturing problems in FPCs due to the flexibility of the copper
foil are of particular interest in the copper foil industry.
SUMMARY
[0007] The present disclosure relates to an improved copper foil
that exhibits low repulsive force characteristics. As noted above,
copper foils with higher repulsive forces that are incorporated
into flexible printed circuits can cause manufacturing and
reliability problems. The improved copper foils of the present
disclosure exhibit lower repulsive forces that alleviate such
manufacturing and reliability problems.
[0008] More specifically, copper foils exhibiting the following
properties have lower repulsive forces: (a) a lightness L* value of
the nodule untreated side, based on the L*a*b color system, in the
range of 75 to 90; and (b) a normal tensile strength in the range
of 40 kgf/mm.sup.2 to 55 kgf/mm.sup.2. These copper foils may also
have a low angle grain boundary (LAGB) percentage, as measured via
electron backscatter diffraction (EBSD), of less than 7.0%, a grain
size in the range of 4.5 .mu.m to 7.5 .mu.m, and/or a degree of
curl, as measured by the lamination curl test, less than 3 mm.
[0009] Such copper foils can be useful in, for example, flexible
printed circuits, electronic components using such flexible printed
circuits, and electronic devices using such electronic
components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIGS. 1 and 2 are explanatory views illustrating the L*a*b*
colorimetric system;
[0011] FIG. 3 shows a typical device for manufacturing an
electrodeposited copper foil;
[0012] FIG. 4 shows a process for treating a surface of a bare
copper foil;
[0013] FIG. 5 is a method for measuring grain size;
[0014] FIGS. 6A, 6B, 6C, and 6D, illustrate a process for measuring
a repulsive force of a copper foil;
[0015] FIG. 7 illustrates a method for measuring a degree of curl;
and
[0016] FIG. 8 is a table of various tests and measurements;
[0017] FIG. 9 is a series of cross-section images for copper foils
manufactured with different amounts of chloride ion
concentrations.
DETAILED DESCRIPTION
[0018] The present invention is described with reference to the
attached figures, wherein like reference numerals are used
throughout the figures to designate similar or equivalent elements.
The figures are not drawn to scale and they are provided merely to
illustrate the instant invention. Several aspects of the invention
are described below with reference to example applications for
illustration. It should be understood that numerous specific
details, relationships, and methods are set forth to provide a full
understanding of the invention. One having ordinary skill in the
relevant art, however, will readily recognize that the invention
can be practiced without one or more of the specific details or
with other methods. In other instances, well-known structures or
operations are not shown in detail to avoid obscuring the
invention. The present invention is not limited by the illustrated
ordering of acts or events, as some acts may occur in different
orders and/or concurrently with other acts or events. Furthermore,
not all illustrated acts or events are required to implement a
methodology in accordance with the present invention.
[0019] The copper foil of the instant disclosure typically has:
[0020] (a) a lightness L* value of the nodule untreated side, based
on the L*a*b color system, in the range of 75 to 90; and
[0021] (b) a normal tensile strength in the range of 40
kgf/mm.sup.2 to 55 kgf/mm.sup.2.
[0022] In some cases, the copper foil has a low angle grain
boundary (LAGB), as measured by electron backscatter diffraction
(EBSD) after an anneal process is performed with the copper foil,
of less than 7% in the range of 3.5% to 7%, such as between 3.5,
4.0, 4.5, 5.0, 5.5, 6.0, or 6.5% and 7%; or between 3.5, 4.0, 4.5,
5.0, 5.5, 6.0% and 6.5%; or between 3.5% and 4.0%. The anneal
process is described below in greater detail.
[0023] As noted above, the copper foil has a specific color. The
color of an object generally relates to three factors: brightness
(lightness), hue (color shade), and chroma (clearness). For
accurately measuring and expressing these factors, a colorimetric
system to objectively express them as values is used. FIGS. 1 and 2
are explanatory views illustrating the L*a*b* colorimetric system.
The L*a*b* colorimetric system is a colorimetric system described
in JIS Z 8729, and assigns each color to a position in a spherical
color space as shown in FIG. 1. In this color space, the brightness
is represented by a position in the ordinate (z-axis) direction,
the hue is represented by a position in the circumferential
direction, and the chroma is represented by a distance from the
center axis.
[0024] The position on the ordinate (z-axis) representing
brightness is designated by L*, and the L* value changes from 0
corresponding to black to 100 corresponding to white. FIG. 2 is a
cross-sectional view of the spherical color space horizontally
taken along the plane of L*=50. As shown in FIG. 2, the positive
direction of the x-axis corresponds to a red direction, the
positive direction of the y-axis corresponds to a yellow direction,
the negative direction of the x-axis corresponds to a green
direction, the negative direction of the y-axis corresponds to a
blue direction, and the position on the x-axis is designated by a*
of which value changes from -60 to +60 and the position on the
y-axis is designated by b* of which value changes from -60 to +60.
The hue and chroma are represented by a* value and b* value,
respectively.
[0025] As noted above, the L* value can be in the range of 75 to
90. The L* values is measured using unannealed copper foil, which
is described below in greater detail. However, in some cases, the
copper foil has a lightness L* value in the range of 75 to 80, such
as between about 75.0, 75.5, 76.0, 76.5, and 77.0 to 77.5, 78.0,
78.5, 79.0, 79.5, and 80; or in the range of 80 to 85, such as
between about 80.0, 80.5, 81.0, 81.5, and 82.0 to 82.5, 83.0, 83.5,
84.0, 84.5, and 85; or in the range of 85 to 90, such as between
about 85.0, 85.5, 86.0, 86.5, and 87.0 to 87.5, 88.0, 88.5, 89.0,
89.5, and 90.
[0026] As noted above, the normal tensile strength of the copper
foil can be in the range of 40 kgf/mm.sup.2 to 55 kgf/mm.sup.2. As
used herein, the normal tensile strength refers to the tensile
strength of the copper foil, as measured prior to the anneal
process described below. However in some cases, the normal tensile
strength of the copper foil can be between about 40, 41, 42, 43,
44, 45, 46, 47, or 47.5 kgf/mm.sup.2 to about 48, 49, 50, 51, 52,
53, 54, or 55 kgf/mm.sup.2.
[0027] Tensile strength, as used herein, refers to the maximum
stress that a material can withstand while being stretched or
pulled before failing or breaking. Tensile strength is not the same
as compressive strength and the values can be quite different.
Elongation, tensile strength, and roughness are measured using
IPC-TM650.
[0028] The resulting copper foil is unique in that it does not curl
like traditional copper foils. As used herein, the resulting copper
foil refers to the copper foil following anneal processes and any
other post-manufacturing processes. A more detailed explanation of
the manufacture of the copper foils of the present disclosure is
provided below. As to the curl properties of the resulting copper
foil, the degree of curl, as measured by the lamination curl test,
can be less than 3 mm.
[0029] However, the degree of curl, as measured by the lamination
curl test, may be 2 mm or less, 1.5 mm or less, or 1 mm or less.
For example, in some cases, the degree of curl may be between about
2.5 mm and 3.0 mm, between about 1.5 mm and 2.5 mm, or between
about 0.5 mm and 1.5 mm. A more detailed discussion of the
lamination curl test is provided below.
[0030] The resulting copper foil, after being subjected to a
pressing with polyimide and heat treatment, also has a repulsive
force between about 12 and 14 grams, such as between about 12.0,
12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, and 12.9 grams to
about 13.0, 13.1, 13.2, 13.3, 13.4, 13.5, 13.6, 13.7, 13.8, 13.9,
and 14.0 grams, where the repulsive force is measured as described
below. In addition to the foregoing properties, the copper foil can
have a tensile strength in the range of 20 kgf/mm.sup.2 to 36
kgf/mm.sup.2 after the anneal process (heating at 200.degree. C.
for 1 hour) is performed, such as between about 20, 21, 22, 23, 24,
25, 26, 27, or 28 kgf/mm.sup.2 to about 29, 30, 31, 32, 33, 34, 35,
or 36 kgf/mm.sup.2. The heating at 200.degree. C. for 1 hour
simulates the heating of the copper foil during the pressing
process of the typical manufacturing process.
[0031] Further, the copper foil can have grain size between 4.5 and
7.5 .mu.m after the anneal process (heating at 200.degree. C. for 1
hour) is performed, such as between about 4.5, 4.6, 4.7, 4.8, 4.9,
5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, and 5.9 .mu.m to about
6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2,
7.3, 7.4, and 7.5 .mu.m.
[0032] Additionally, the copper foil can have a reduction in
tensile strength between 35% and 50% after the anneal process
(heating at 200.degree. C. for 1 hour), such as between about 34%,
35%, 36%, 37%, 38%, 39%, 40%, 41% to about 42%, 43%, 44%, 45%, 46%,
47%, 48%, 49%, and 50%.
[0033] The instant disclosure also relates to processes for
manufacturing the electrodeposited copper foil. This process for
manufacturing the electrodeposited copper foil is described below
with respect to FIG. 3.
[0034] The manufacturing process involves dissolving Copper wires
in a 50 wt % sulfuric acid aqueous solution to prepare a copper
sulfate electrolyte containing 320 g/l of copper sulfate
(CuSO4.5H2O) and 100 g/l of sulfuric acid. To per liter of the
copper sulfate electrolyte, chloride ion were added, so as to
provide chloride ion concentrations of 10 ppm to 20 ppm, such as 10
ppm, 15 ppm, or 20 ppm. The chloride ion may be applied by adding
hydrochloric acid or a water soluble chlorine-containing compound.
For example sodium chloride, potassium chloride, ammonium chloride,
and so on can be used as the water soluble. Subsequently, an
electrodeposited copper foil with thickness of 12 .mu.m was
prepared with a liquid temperature of 45.degree. C. and a current
density of 60 A/dm2.
[0035] In conventional practices, plating solutions for production
of the bare copper foil may contain a number of additives,
including accelerators, suppressors, and levelers. Accelerators,
alternatively termed brighteners, are additives which increase the
rate of the plating reaction. Accelerators are molecules which
adsorb on metal surfaces and increase the local current density at
a given applied voltage. Accelerators may contain pendant sulfur
atoms, which are understood to participate in the cupric ion
reduction reaction and thus strongly influence the nucleation and
surface growth of metal films. Accelerator additives are commonly
derivatives of mercaptopropanesulfonic acid (MPS),
dimercaptopropanesulfonic acid (DPS), or
bis(3-sulfopropyl)disulfide (SPS), although other compounds can be
used. Suppressors, alternatively termed carriers, are polymers that
tend to suppress current after they adsorb onto the metal surface.
Suppressors may be derived from animal gelatin, hydroxyethyl
cellulose (HEC), polyethylene glycol (PEG), polypropylene glycol
(PPG), polyethylene oxide, or their derivatives or co-polymers.
Levelers generally are cationic surfactants and dyes which suppress
current at locations where their mass transfer rate are most
rapid.
[0036] Normally, it is considered that organic additives have the
effect of inhibiting the growth of crystals, and are incorporated
into the grain boundaries. In this case, the greater the quantity
of organic additive incorporated into the crystal grain boundaries,
the smaller the grain size would be. To avoid the interference of
additives, except chloride ion, there is no organic or metallic
compounds were intentionally added into the copper sulfate
electrolyte.
[0037] A typical device 300 for manufacturing an electrodeposited
copper foil is illustrated in FIG. 3. As shown in FIG. 3, device
300 includes a metal cathode drum 302 and a dimensionally stable
anode (DSA) 304. The metal cathode drum 302 is rotatable and has a
mirror polished surface. The dimensionally stable anode (DSA) 304
is arranged with respect to the metal cathode drum 302 to surround
approximately a lower half of the metal cathode drum 302, as
illustrated in FIG. 3. A copper foil is continuously manufactured
with the device 300 by flowing a copper electrolytic solution
between the metal cathode drum 302 and the dimensionally stable
anode (DSA) 304 and applying an electrical current between these
two components, which allows copper ion from the copper
electrolytic solution to be electrodeposited on the metal cathode
drum 302. The initial electrodeposited ("bare") copper foil 306 is
then detached from the metal cathode drum 302 when a predetermined
thickness is obtained.
[0038] The bare copper foil 306 is so produced so that it has a
drum side 306A (the surface of the copper foil formed on the metal
cathode drum 302) and a deposited side 306B (the surface of the
copper foil in contact with the copper electrolytic solution
between the metal cathode drum 302 and the dimensionally stable
anode (DSA) 304) which is on the surface of the copper foil 306
opposite the drum side 306A.
[0039] Following the production of the bare copper foil, the bare
copper foil can be subjected to a post-electrodeposition surface
treatment process. These treatments can involve directing the bare
copper foil using a series of treatment vessels (with and without
electrodes) and/or ovens. An exemplary post-electrodeposition
surface treatment process 400 is described below with respect to
FIG. 4. A legend is provided in FIG. 4 to facilitate understanding
of the elements illustrated in FIG. 4
[0040] At the beginning of the process 400, the bare foil can be
directed, via a series of rollers, into an acid washing/cleaning
process (402). In the acid washing process, the inside of an acid
washing vessel can be filled with a copper electrolytic solution,
such as 130 g/L copper sulfate and 50 g/L sulfuric acid, and the
temperature of the electrolyte solution was maintained at
27.degree. C. The bare foil was soaked into the copper electrolytic
solution for 30 seconds to remove the oil, fat and oxide on the
surface and then the bare foil was washed with water (washing not
illustrated in FIG. 4).
[0041] The bare copper foil can then be roughened to form a copper
nodular layer (404). The copper nodular layer can be formed by
directing the bare copper foil into an electroplating bath and
electroplating additional copper onto the surface of the drum side
or deposited side of bare copper foil. For the formation of the
copper nodular layer, a copper sulfate and sulfuric acid solution
can be used for the electroplating. In one exemplary configuration,
the concentration of copper sulfate and sulfuric acid in the
solution were 70 g/L and 100 g/L, respectively, and the solution
temperature was maintained at. 25.degree. C. For the
electrodeposition itself, electrolysis was conducted for 10 seconds
at a current density of 10 A/dm.sup.2.
[0042] After the roughening, a cover plating process can be
conducted for preventing the exfoliation of the copper nodule layer
(406). The cover plating process can involve using a copper sulfate
and sulfuric acid solution for the electroplating. In one exemplary
configuration, the concentrations of copper sulfate and sulfuric
acid were 320 g/L and 100 g/L, respectively, and the temperature of
electrolyte solution was maintained at 40.degree. C. For the
plating, the current density of 15 A/dm.sup.2 was provided.
[0043] The cover plating process can then be followed by an
alloying process (408) in order to form a passivation layer for the
roughened copper foil. The passivation layer is formed on both
sides of the roughened copper foil. In one exemplary configuration,
zinc can be used as the passivation element and a plating process
can be used to simultaneously alloy both sides of the roughened
copper foil. To add zinc, a zinc sulfate solution can be used as
the electrolyte. Such a zinc sulfate solution can have a zinc
sulfate concentration at 100 g/L with a pH of 3.4 and the solution
temperature can be set at 50.degree. C. A current density of 4
A/dm.sup.2 can then be used for the alloying process. A washing
process with water can then be performed (not illustrated in FIG.
4).
[0044] Following the alloying process, an anti-tarnish process
(410) can be performed to provide rust-proofing. In the case of a
zinc-based passivation, a subsequent chromate passivation can be
performed. That is, a chromate layer can be electrolytically formed
on the zinc passivation layer. In one exemplary configuration, this
can be performed using a chromic acid solution with a concentration
of 5 g/L and a pH 11.5, while maintained at a temperature of
35.degree. C. The electrolysis can then be performed using a
current density of 10 A/dm.sup.2. Like the zinc passivation, the
electrolytic chromate passivation is also applied to both sides of
the copper foil.
[0045] Despite chromic anti-tarnish, an organic solution is also
suitable for rust-proofing. The organic anti-tarnish layer may
comprise at least one member selected from the group consisting of
triazoles, thiazoles, and imidazoles, or their derivatives, which
are selected for their ability to bond to copper. The triazole
group includes orthotriazole (1,2,3-triazole) and isomers thereof,
or derivatives thereof. Orthotriazole derivatives include
benzotriazole, tolyltriazole, carboxybenzotriazole, chlorine
substituted benzotriazole, aminotriazole and isomers thereof, or
derivatives such as alkali metal salts or amine salts and the like.
As the isomers of the aminotriazole, 3-amino-1,2,4-triazole,
2-amino-1,3,4-triazole, 4-amino-1,2,4-triazole and
1-amino-1,3,4-triazole can be used. Examples of derivatives of
aminotriazole include sodium salts or amine salts including, for
example, monoethanolamine salts, cyclohexylamine salts,
diisopropylamine salts, morpholine salts and the like.
[0046] Upon completion of the anti-tarnish treatment, the
passivated copper foil can be washed with water (not illustrated in
FIG. 4) and immediately, without drying the passivated copper foil
surfaces, a silane treatment (412) can be provided. In particular,
the passivated copper foil is treated such that adsorption of a
silane coupling agent is made only on the Zn/Cr passivated layer of
copper nodular layer in a silane coupling agent treatment vessel.
In one exemplary configuration, the silane treatment is performed
using a solution with a concentration of 0.25%
3-Aminopropyltriethoxysilane and spraying the solution against the
copper nodular side of the copper foil surface.
[0047] Further, the silane coupling agent layer may be formed using
epoxy silane, amino silane, methacryloxy silane, vinyl silane, a
silane coupling agent such as mercapto-type silane. It is to be
noted that such a silane coupling agent, may also be used as a
mixture of two or more. Among them, it is preferable that formed
using an amino-based silane coupling agent or an epoxy type silane
coupling agent.
[0048] The amino silane coupling agent referred to herein,
N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,
3-(N-styrylmethyl-2-aminoethylamino) propyl trimethoxy silane,
3-aminopropyltriethoxysilane, bis
(2-hydroxyethyl)-3-aminopropyltriethoxysilane,
aminopropyltrimethoxysilane, N-methyl-aminopropyltrimethoxysilane,
N-phenyl-aminopropyltrimethoxysilane,
N-(3-acryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane,
4-aminobutyl triethoxysilane, (aminoethyl aminomethyl) phenethyl
trimethoxy silane, N-(2-aminoethyl-3-aminopropyl) trimethoxysilane,
N-(2-aminoethyl-3-aminopropyl) tris (2-ethylhexoxy) silane,
6-(aminohexyl aminopropyl) trimethoxy silane, aminophenyl
trimethoxy silane, 3-(1-aminopropoxy)-3,3-dimethyl-1-propenyl
trimethoxy silane, 3-aminopropyl tris (methoxyethoxy) silane,
3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane,
.omega.-amino-undecyl trimethoxysilane silane,
3-(2-N-benzyl-aminoethyl aminopropyl) trimethoxy silane, bis
(2-hydroxyethyl)-3-aminopropyltriethoxysilane, (N,
N-diethyl-3-aminopropyl) trimethoxysilane, (N,
N-dimethyl-3-aminopropyl) trimethoxysilane,
N-methyl-aminopropyltrimethoxysilane,
N-phenyl-aminopropyltrimethoxysilane,
3-(N-styrylmethyl-2-aminoethylamino) propyl trimethoxysilane, it is
those selected from the group consisting of.
[0049] Finally, the copper foil can be dried and, optionally,
annealed (414) in an oven. The copper foil can then be cut and
wound, as needed for packing and shipping purposes.
[0050] It should be noted that the present disclosure contemplates
that the process and conditions specified above are solely for ease
of illustration and explanation. Further, any values stated above
are approximate. That is, the present disclosure contemplates that
any of the values specified above can vary form the state value.
For example, a particular value can vary by .+-.5%, .+-.10%,
.+-.15%, or even .+-.20% from the stated value.
Examples
[0051] The examples shown here are not intended to limit the
various embodiments. Rather they are presented solely for
illustrative purposes.
[0052] Manufacture
[0053] Various copper foils manufactured, including copper foils in
accordance with the present disclosure. Nine (9) copper foils were
manufactured in accordance with the present disclosure, as
described above. Six (6) copper foils were manufactured in
accordance with conventional copper foil manufacturing processes,
similar to that described above, but varied as indicated below.
[0054] For the conventional copper foil manufacturing process, the
initial copper plating process was performed using a plating
solution with 0 ppm to 5 ppm chloride ion concentration and using a
current density of 70 A/dm.sup.2 or a plating solution with 0 ppm
to 20 ppm chloride ion concentration and using a current density of
85 A/dm.sup.2. For the copper foils manufactured in accordance with
the present disclosure, the initial copper plating process was
performed using a plating solution with 10 ppm, 15 ppm, or 20 ppm
chloride ion concentration and using a current density of 60
A/dm.sup.2, 70 A/dm.sup.2 or 80 A/dm.sup.2.
[0055] The exact conditions for each copper foil manufactured are
shown below in Table 1, with "Example n" identifying a copper foil
manufactured in accordance with the present disclosure and "Comp.
Example n" identifying a copper foils were manufactured in
accordance with a conventional copper foil manufacturing
process.
TABLE-US-00001 TABLE 1 Copper Plating Process conditions [Cl.sup.-]
Current Density Sample ppm A/dm.sup.2 Example 1 10 60 Example 2 10
70 Example 3 10 80 Example 4 15 60 Example 5 15 70 Example 6 15 80
Example 7 20 60 Example 8 20 70 Example 9 20 80 Comp. example 1 0
70 Comp. example 2 5 70 Comp. example 3 10 85 Comp. example 4 20 85
Comp. example 5 0 85 Comp. example 6 5 85
[0056] Measurements
[0057] The following measurements were then performed for each of
the copper foils manufactured.
[0058] Normal Tensile Strength. Tensile strength was measured
according to IPC-TM-650.
[0059] The copper foils, subsequent to surface treatment but
without any annealing or pressing, were cut to obtain a test sample
in the size of 100 mm.times.12.7 mm (length.times.width). The test
sample was measured at room temperature (about 25.degree. C.) under
the conditions of a chuck distance of 50 mm and a crosshead speed
of 50 mm/min by using Model AG-I testing machine of Shimadzu
Corporation.
[0060] Tensile Strength After Annealing. The copper foils,
subsequent to surface treatment but without any annealing or
pressing, were cut to obtain a test sample in the size of 100
mm.times.12.7 mm (length.times.width). Then the test samples were
put in an oven, with no purging applied. The anneal condition was
set at 200.degree. C. for 1 hour. After annealing, the test sample
was measured at room temperature (about 25.degree. C.) under the
conditions of a chuck distance of 50 mm and a crosshead speed of 50
mm/min by using Model AG-I testing machine of Shimadzu Corporation.
Additionally, the reduction in tensile strength with respect to the
normal tensile strength was calculated.
[0061] Grain size after annealing. Grain size on annealed samples
of the copper foils (200.degree. C. anneal for 1 hour) was measured
using an Electron backscatter diffraction (EBSD) method. In
particular, the cross-section of an annealed copper foil sample was
analyzed using EBSD to obtain the surface area, i.e., boundaries,
of grains in the copper foil sample. Thereafter, this information
can be used to calculate maximum grain size values for the copper
foil sample. EBSD was conducted using Oxford Instruments NordlyNano
scanning electron microscope with a field emission gun operated at
15 kV to characterize grain boundaries and grain size. The EBSD
sample is tilted at approximately 70.degree. relative to normal
incidence of the electron beam. This configuration is schematically
illustrated in FIG. 5.
[0062] Low Angle Grain Boundary (LAGB). The EBSD data was also used
to identify a LAGB values for the above annealed samples of the
copper foils. In particular, the EBSD data was also used to
identify grain boundaries with angles between 2 degrees and 15
degrees. Thereafter, the LAGB values obtained represent the
percentage of such grain boundaries in the annealed samples.
[0063] Color L*. The color L*a*b* measurements were conducted on
unannealed samples of the copper foils based on the method of JIS Z
8722 (2000) using a spectrophotometer (Konica Minolta; CM2500c)
("Methods of color measurement--Reflecting and transmitting
objects"). The color measurements are based on nodule untreated
side because there are many nodules on nodule layer treated side,
which may affect the reflection.
[0064] Repulsive Force. The measurement of repulsive force involves
measuring repulsive force according to the lamination repulsive
force test. As used herein, the term "lamination repulsive force
test" refers to the process for laminated sample preparation and
subsequent measurement described below.
[0065] The laminated sample preparation involves obtaining first
and second sections of the copper foil, unannealed, each measuring
greater than 10 mm by 70 mm, such as 20 cm by 20 cm, and a section
of polyimide (KANEKA FRS-142#SW) of a thickness of about 25 .mu.m,
also measuring greater than 10 mm by 70 mm, such as 20 cm by 20 cm.
The sections of copper foil are substantially the same thickness,
i.e., less than a 10% difference between the thicknesses. The
thickness of the copper sections can be between about 9 .mu.m and
30 .mu.m, such as between about 12 .mu.m and 25 .mu.m, or between
about 12 .mu.m and 18 .mu.m. These sections are then arranged to
form a copper foil/polyimide/copper foil stack, as shown in FIG.
6A. The stack is then pressed together. The pressing process
consists of subjecting the materials to a pressure of 600 psi,
while adjusting the temperature from 150.degree. C. to 330.degree.
C. at a rate of 3.degree. C./min. It should be noted that the
pressing process has substantially the same effect on the copper
foil as the anneal process for the other measurements.
[0066] Thereafter, as shown in FIG. 6B, one of the copper foil
sections is fully etched off, using a solution of FeCl.sub.3, HCl,
and water, thus leaving only a stack of one layer of copper foil
and polyimide. The etching solution consisted of
FeCl.sub.3:HCl:H.sub.2O, in a ratio of 1:1:1 by weight. For the
etching process itself, the solution is sprayed onto one side of
the stack for 4 minutes, while the temperature is maintained at
25.degree. C. Thereafter, the resulting stack of materials is cut
into a 10 mm by 70 mm section. At this point the sample is ready
for measurement.
[0067] The measurement process first involves arranging the sample
in a loop or circle while both edges were adhered by double-sided
tape. The loop is then positioned on plate of a balance or scale
and the weight is zeroed. A cap is then positioned over the scale
to apply force to the circle, as shown in FIG. 6C. The cap is
pushed down until reaching the ground. At that moment, the space
between the bottom of the cap and the top of the plate is 10 mm, as
shown in FIG. 6D. For purposes of measurement, the scale and cap
should be configured so that noted that the bottom of the cap is
located on the area other than the measuring plate. In this way,
the weight of the cap is not included in the measurement. The
values shown by the scale or balance thus only include the
repulsive force demonstrated by the loop after being pushed.
Afterward, the value reported by the scale is recorded and used as
the repulsive force value.
[0068] Curl. Determining the degree of curl involves measuring curl
according to the lamination curl test. As used herein, the term
"lamination curl test" refers to the process for laminated sample
preparation and subsequent measurement described below.
[0069] The laminated sample preparation for the lamination curl
test involves preparing a sample in substantially the same way as
for repulsive force measurement. However, for the lamination curl
test, the sections of copper foil and polyimide are cut, prior to
pressing, are greater than 100 mm by 100 mm and, after pressing,
the resulting stack is cut into a 100 mm by 100 mm section prior to
etching of the copper foil. Thereafter, the stack is placed against
a solid plastic board with the copper foil facing upward. A sheet
of paper having a 10 cm by 10 cm cross drawn upon it was placed on
top of the copper foil. A knife is then used to slice through the
paper and the underlying stack along the lines of the 10 cm by 10
cm cross drawn upon the paper. A ruler was used to help stabilize
the knife during the cutting process and ensure that the cut was
straight. The paper was then lifted from the stack and the corners
of the copper foil resulting from the cuts were allowed to freely
curl upward. A ruler was used to measure the resulting curled
height of each of the four corners. The largest or maximum of the
four curled heights is then used as the measure of the degree of
curl for the sample.
[0070] FIG. 7 is a schematic showing a ruler 707 placed into the
opening created by a cross-shaped slit 703 in copper foil 758. The
ruler 707 is used to measure the maximum height of the curl at
corners 705. If the amount of curl is less than 3 mm, the copper
foil is said to be significantly resistant to curling. This
represents a low repulsive force. If the amount of curl is between
above 3 mm, the copper foil is said to be prone to curling. This
represents a high repulsive force.
[0071] The results of the various measurements and tests are
presented in Table 2, which is provided in FIG. 8. The data in
Table 2 shows that copper foils manufactured according to the
present disclosure exhibit an unexpected low repulsive force
compared to conventionally manufactured copper foils.
[0072] With respect to the grain size, the data in Table 1 and
Table 2 also shows that as the amount of chloride ions increased,
the normal tensile strength decreased and the grain size is
enlarged after annealing. The tendency of grain size after
annealing is also illustrated in FIG. 9. FIG. 9 shows a series of
cross-section Scanning Electron Microscope (SEM) images of copper
foil samples, after a 200.degree. C., 1 hour anneal process, as
described above, for chloride ion concentrations of 0 ppm, 2 ppm, 5
ppm, 10 ppm, 15 ppm, and 25 ppm. As can be observed from FIG. 9, as
the chloride ion concentration is increased, the grain size is also
increased during annealing. Thus increase in grain size also
translates into a lower repulsive force. For example, at 0 ppm, the
copper foil sample is found to have a repulsive force of 18 g.
However, at 20 ppm, the repulsive force is reduced to 12 g.
[0073] According to Table 1 and Table 2, increasing current density
resulted in higher LAGB and higher L*. If current density was too
high, the repulsive force might be too large therefore induced
large degree of curl.
[0074] Further, copper foils manufactured according to the present
disclosure will generally exhibit:
[0075] (a) a lightness L* value of the nodule untreated side, based
on the L*a*b color system, in the range of 75 to 90;
[0076] (b) a normal tensile strength in the range of 40
kgf/mm.sup.2 to 55 kgf/mm.sup.2.
[0077] (c) a low angle grain boundary (LAGB) percentage, as
measured via electron backscatter diffraction (EBSD), of less than
7.0%.
[0078] (d) a grain size in the range of 4.5 .mu.m to 7.5 .mu.m;
and
[0079] (e) a degree of curl less than 3 mm.
[0080] While various embodiments of the present invention have been
described above, it should be understood that they have been
presented by way of example only, and not limitation. Numerous
changes to the disclosed embodiments can be made in accordance with
the disclosure herein without departing from the spirit or scope of
the invention. Thus, the breadth and scope of the present invention
should not be limited by any of the above described embodiments.
Rather, the scope of the invention should be defined in accordance
with the following claims and their equivalents.
[0081] Although the invention has been illustrated and described
with respect to one or more implementations, equivalent alterations
and modifications will occur to others skilled in the art upon the
reading and understanding of this specification and the annexed
drawings. In addition, while a particular feature of the invention
may have been disclosed with respect to only one of several
implementations, such feature may be combined with one or more
other features of the other implementations as may be desired and
advantageous for any given or particular application.
[0082] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. Furthermore, to the extent
that the terms "including", "includes", "having", "has", "with", or
variants thereof are used in either the detailed description and/or
the claims, such terms are intended to be inclusive in a manner
similar to the term "comprising."
[0083] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
* * * * *