U.S. patent application number 11/585881 was filed with the patent office on 2007-02-22 for copper foil for high frequency circuit, method of production and apparatus for production of same, and high frequency circuit using copper foil.
This patent application is currently assigned to Furukawa Circuit Foil Co., Ltd.. Invention is credited to Kazuhiro Hoshino, Akira Matsuda, Takami Moteki, Kensaku Shinozaki, Yuuji Suzuki.
Application Number | 20070042212 11/585881 |
Document ID | / |
Family ID | 32652962 |
Filed Date | 2007-02-22 |
United States Patent
Application |
20070042212 |
Kind Code |
A1 |
Moteki; Takami ; et
al. |
February 22, 2007 |
Copper foil for high frequency circuit, method of production and
apparatus for production of same, and high frequency circuit using
copper foil
Abstract
A copper foil reducing transmission loss at a high frequency and
excellent in bond strength with a resin substrate, including at
least a granular layer and a columnar layer in its thickness
direction, the columnar layer being formed on at least one surface
of the granular layer forming the copper foil or the granular layer
being formed on at least one surface of the columnar layer forming
the copper foil, the relation of the thickness A of the granular
layer and the thickness B of the columnar layer in the copper foil
being preferably A/(A+B)=40 to 99%, a method of production and
apparatus for production for the same, and a high frequency circuit
using the same.
Inventors: |
Moteki; Takami; (Tochigi,
JP) ; Suzuki; Yuuji; (Tochigi, JP) ; Hoshino;
Kazuhiro; (Tochigi, JP) ; Shinozaki; Kensaku;
(Tochigi, JP) ; Matsuda; Akira; (Tochigi,
JP) |
Correspondence
Address: |
ARENT FOX PLLC
1050 CONNECTICUT AVENUE, N.W.
SUITE 400
WASHINGTON
DC
20036
US
|
Assignee: |
Furukawa Circuit Foil Co.,
Ltd.
|
Family ID: |
32652962 |
Appl. No.: |
11/585881 |
Filed: |
October 25, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10768704 |
Feb 2, 2004 |
|
|
|
11585881 |
Oct 25, 2006 |
|
|
|
Current U.S.
Class: |
428/606 ;
204/291 |
Current CPC
Class: |
Y10T 428/1291 20150115;
Y10T 428/12438 20150115; Y10S 428/935 20130101; C25D 1/04 20130101;
H05K 1/0237 20130101; Y10T 428/12431 20150115; H05K 2201/0355
20130101; Y10T 428/12569 20150115; C25D 7/0614 20130101; H05K 1/09
20130101 |
Class at
Publication: |
428/606 ;
204/291 |
International
Class: |
B21C 37/00 20060101
B21C037/00; C25B 11/04 20060101 C25B011/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 4, 2003 |
JP |
2003-026629 |
Claims
1. A method of production of a copper foil for a high frequency
circuit comprising immersing and rotating a foil-making drum in an
electrolytic tank to form a columnar layer on the surface of said
foil-making drum, then plating a granular layer on at least one
surface of the same.
2. A high frequency circuit fabricated using a copper foil produced
by a method of production as set forth in claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a copper foil reducing
conductor loss in high frequency applications and superior in bond
strength with a substrate, more particularly a copper foil superior
for use in a high frequency circuit, for example, relates to a
copper foil optimal for a high frequency circuit including an
antenna of an IC card; a method of production and apparatus for
production for the copper foil; and a high frequency circuit using
that copper foil.
[0003] 2. Description of the Related Art
[0004] As the resin of a substrate of a printed circuit board
handling a high frequency signal, a polyimide resin, modified
polyimide resin, fluororesin, polystyrene, polyethylene,
polyphenylene sulfide, polyphenyloxide, polytetrafluoroethylene,
etc. is used. For the conductor circuits, normally copper foil is
used since its conductivity is high and it is resistant to
stain.
[0005] A printed circuit board for a high frequency circuit has to
be reduced in transmission loss in order to maintain and secure the
quality of signal. If viewing the transmission loss from the
perspective of the copper foil forming the base of the conductor
circuits, the increase in transmission loss due to conductor loss
and the drop in bond strength with the resin accompanying the
reduction in dielectric constant and reduction in dielectric
dissipation factor of the substrate in order to keep down the
dielectric loss (drop in bond strength of copper foil and circuit
board) become problems.
[0006] Among these, the conductor loss is directly related to the
copper foil. If the signal becomes high in frequency, the loss is
increased due to the increase in the skin resistance. At a high
frequency, the skin effect (where passage of an alternating current
through the conductor results in a change in the magnetic flux and
therefore the occurrence of an inverse electromotive force at the
center of the conductor and a consequent difficulty in flow in
current) means that the current will flow at the surface portion of
the conductor. Therefore, the effective sectional area through
which the current flows decreases and the resistance rises.
[0007] The relationship between the frequency and depth of flow of
current (skin depth) in a copper foil is calculated as being about
20 .mu.m at 10 MHz, about 3 .mu.m at 0.5 GHz, about 2 .mu.m at 1
GHz, and about 0.6 .mu.m at 10 GHz. There is a large effect due to
the drop in dielectric constant accompanying slight roughness of
the surface or content of impurities.
[0008] Therefore, the profile of the copper foil at the surface has
a great effect on the transmission loss. A very rough copper foil
has a longer signal propagation distance, resulting in problems of
signal attenuation or delay. That is, the smoother the surface, the
smaller the conductor loss.
[0009] The dielectric loss is determined by the dielectric constant
and dielectric dissipation factor of the substrate resin. If a
pulse signal is run through a circuit, a change will occur in the
electric field surrounding the circuit. When the period (frequency)
of change of the electric field approaches the relaxation time of
polarization of the resin, a delay will be caused in the electric
displacement. At this time, molecular friction will occur inside
the resin and heat will be generated. This heat will result in
dielectric loss. Therefore, the resin for a high frequency
substrate preferably is resistant to polarization due to change in
the electrical field, that is, is a resin reduced in or free of
substituent groups with a large polarity. On the other hand,
however, substituent groups with a large polarity contribute
greatly to the chemical bonding of the resin and copper foil. A
resin reduced in substituent groups with a large polarity so as to
reduce the dielectric constant and dielectric dissipation factor
becomes poor in bondability with copper foil resulting in a sharp
drop in the peel strength of the circuit. The generally used FR-4
material gives a high peel strength due to cohesion destruction (in
the resin), but with low dielectric dissipation factor substrates,
interfacial destruction (interface of copper foil and resin) occurs
and a high peel strength cannot be obtained. With such a low peel
strength, there is a possibility of circuit peeling or mounted
parts dropping off at the outermost layer in the process of
production of a printed circuit board.
[0010] The problem of the peel strength can be circumvented by use
of a copper foil with a large roughness, but in high frequency
applications, as explained above, the transmission loss would
become greater, so use would become difficult. That is, a good peel
strength and transmission loss are properties difficult to secure
at the same time.
[0011] In recent high performance electronic equipment, however,
due to the demands for smaller size and higher processing speeds,
the materials used for the circuit interconnects are required to be
made thinner to assist reduction of pitch and weight and to be made
lower in impedance with respect to high frequency current. One
example is an IC card.
[0012] An IC card is a card with a built-in IC chip and enables
more sophisticated judgments and more complicated processing. The
storage capacity is about 100 times larger than that of a magnetic
card. Further, since information can be both read and written,
security is higher. The method of transmission of information of
such an IC card includes not only the direct contact type for
exchange of data by physical contact with a contact point, but also
the noncontact type enabling exchange of data over a spatial
distance of as much as several meters using electromagnetic waves
etc.
[0013] Direct contact type IC cards utilizing the above features
are expected to find use in an extremely broad range of fields such
as ID cards, train/bus tickets, commuter passes, electronic money,
highway passes, health insurance cards, residence cards, medical
cards, logistics control cards, etc.
[0014] Further, noncontact type IC cards are divided into four
types according to the communications distance such as the close
coupled type (communication distance up to 2 mm), proximity type
(10 cm), vicinity type (70 cm), and microwave (several meters). The
communication frequencies are 4.91 MHz for the close coupled type,
13.56 MHz for the proximity type and vicinity type, and 2.45 and
5.8 GHZ for the microwave type--thereby extending from the MHz to
the GHz region.
[0015] A noncontact IC card is basically constructed from an
insulation sheet, antenna, and IC chip. The IC chip incorporates a
ferroelectric memory, a nonvolatile memory, ROM, RAM, modem
circuit, power supply circuit, enciphering circuit, control
circuit, etc. As the antenna member, there are for example a coated
copper coil, silver paste, aluminum foil, copper foil, etc. These
are selected for use according to the number of turns, application,
production cost, etc. When the number of turns is small and a high
conductivity is required, rolled copper foil or electrodeposited
copper foil is often used as the antenna material.
[0016] However, while the high strength, high conductivity copper
alloys in use now as lead frame materials have a higher material
strength compared with pure copper foil, they are becoming
insufficient for coping with the demands of recent years for higher
speed signal transmission, smaller size, and greater reliability.
Use of copper alloys improved in properties compared with
conventional copper alloys is being proposed to deal with the
demands for fine pitches and lighter weight (for example, see
Japanese Unexamined Patent Publication (Kokai) No. 2002-167633),
but none of these has satisfied the requirements of an antenna
material of sufficient bond strength with a resin and reduced
transmission loss in the high frequency region.
SUMMARY OF THE INVENTION
[0017] An object of the present invention is to provide a copper
foil reducing transmission loss at a high frequency when used as a
material for a high frequency circuit and excellent in bond
strength with a resin substrate, a method of production and
apparatus for production for the same, and a high frequency circuit
using the same.
[0018] The inventors engaged in intensive research to achieve the
above object and as result developed a copper foil having a small
transmission loss in the high frequency region and having a high
bonding strength with a resin substrate and a method of production
and apparatus for production for the same.
[0019] According to a first aspect of the present invention, there
is provided a copper foil for a high frequency circuit comprising
at least one granular layer and columnar layer in a thickness
direction.
[0020] According to a second aspect of the present invention, there
is provided a copper foil for a high frequency circuit comprising a
granular layer forming the copper foil and a columnar layer formed
on at least one surface of the same.
[0021] According to a third aspect of the present invention, there
is provided a copper foil for a high frequency circuit comprising a
columnar layer forming the copper foil and a granular layer formed
on at least one surface of the same.
[0022] Preferably the relation between a thickness A of the
granular layer forming the copper foil and the thickness B of the
columnar layer is A/(A+B)=40 to 99%.
[0023] Preferably at least one surface is roughened.
[0024] More preferably, at least one surface is subjected to at
least one of plating by nickel, zinc, chrome, alloys of the same,
chromate treatment, organic stainproof treatment, and silane
coupling agent treatment.
[0025] According to a fourth aspect of the present invention, there
is provided a method of production of a copper foil for a high
frequency circuit comprising immersing and rotating a foil-making
drum in an electroforming cell to form a granular layer on the
surface of the foil-making drum, then plating a columnar layer on
at least one surface of the same.
[0026] According to a fifth aspect of the present invention, there
is provided a method of production of a copper foil for a high
frequency circuit comprising immersing and rotating a foil-making
drum in an electroforming cell to form a columnar layer on the
surface of the foil-making drum, then plating a granular layer on
at least one surface of the same.
[0027] According to a sixth aspect of the present invention, there
is provided an apparatus for production for a copper deposited
layer for a high frequency circuit working a method of production
as set forth above comprising immersing and rotating a foil-making
drum in an electroforming cell for making a granular layer and
columnar layer and continuously electrodepositing a granular layer
and columnar layer on the foil-making drum.
[0028] According to a seventh aspect of the present invention,
there is provided a high frequency circuit fabricated using a
copper foil as set forth above, a copper foil produced by a method
of production as set forth above, or a copper foil produced by an
apparatus for production as set forth above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] These and other objects and features of the present
invention will become clearer from the following description of the
preferred embodiments given with reference to the attached
drawings, wherein:
[0030] FIG. 1 is an explanatory view showing the structure of an
electroforming cell showing a first embodiment of the present
invention;
[0031] FIG. 2 is an explanatory view showing an electroforming cell
showing a second embodiment of the present invention;
[0032] FIG. 3 is an explanatory view showing an electroforming cell
showing a third embodiment of the present invention;
[0033] FIG. 4 is an explanatory view showing an apparatus for a
surface treatment performed continuously after an electroforming
cell showing a fourth embodiment of the present invention; and
[0034] FIG. 5 is an explanatory view showing an apparatus for a
surface treatment performed continuously after an electroforming
cell showing a fifth embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] Preferred embodiments of the present invention will be
described in detail below while referring to the attached
figures.
[0036] On the surface of a copper foil, generally, if the columnar
layer becomes thicker, the surface roughness increases. On the
other hand, in the case of a granular layer, the surface tends to
be smoothed. Therefore, with only these single layers, it is
difficult to control the surface roughness and the actual surface
area ratio.
[0037] If the copper foil is run through with current at a high
frequency, the resistance increases sharply due to the skin effect.
This invites an increase in the impedance and makes normal signal
transfer impossible in some cases. This phenomenon was analyzed and
as a result it was learned that if using a conventional rolled
copper alloy material, since the conductivity is lower than with
pure copper etc., the influence of the skin effect is large and the
possible range of use is extremely narrow.
[0038] Further, even when the surface is rough, the above trouble
occurs. It was learned that, as an indicator of surface roughness,
both Rz and Ra and the ratio of the apparent surface area with the
actual surface area are effective.
[0039] That is, Rz should be not more than 5.0 .mu.m, while Ra
should be not more than 0.5 .mu.m. On the other hand, if the
surface is too smooth, the bond strength with a resin will fall, so
Rz should be at least 1 .mu.m and Ra at least 0.2 .mu.m.
[0040] Rz, Ra, and the ratio between the apparent surface area and
actual surface area may be measured under the following conditions
using for example a Keyence superdeep shape measurement microscope
Model VK8500: TABLE-US-00001 Measurement conditions Lens
magnification: 2000.times. Run mode: Color superdeep Sensitivity
Monochrome: Gamma 3 Color Gamma 1 Pitch: 0.05 .mu.m
[0041] In the present invention, the above roughness or actual
surface area ratio of a copper foil can be obtained by use of at
least one granular layer and columnar layer in the thickness
direction of the copper foil. The ratio between the thickness A of
the granular layer and the thickness B of the columnar layer, that
is, A/(A+B), is preferably 40 to 99%, particularly preferably 50 to
99%, according to research findings.
[0042] The granular layer and the columnar layer can be fabricated
separately simply by changing the electrolytic baths for the
plating, but it is also possible to use the same electrolytic bath
and change the current density to form the two layers.
[0043] Further, from the standpoint of the high frequency
characteristics, it is not preferable to perform on the surface a
roughening treatment, a stainproof treatment, etc., but when
further bondability with a resin etc. or corrosion resistance is
required, it is sometimes preferable to apply such treatment even
at the partial sacrifice of the high frequency characteristics.
[0044] A roughening layer applied in a roughening treatment means a
layer obtained by an apparatus as shown for example in the later
mentioned FIG. 4 by causing electrodeposition of fine particles of
copper or copper and cobalt, nickel, iron, and chrome or mixtures
of these with oxides of vanadium, molybdenum, tungsten, and other
elements and smoothly plating over these with copper to prevent
particles from falling off. Normally, an amount of deposition of at
least 0.01 mg/dm.sup.2 is sufficient for improving the bonding
strength with the substrate resin.
[0045] Further, it is also possible to apply a stainproof treatment
or silane coupling agent treatment over this. As stainproof
treatment, in general nickel plating, zinc plating, chrome plating,
or plating of alloys of the same, chromate treatment, or organic
treatment by benzotriazole etc. is effective. The silane coupling
agent treatment is suitably performed depending on the material of
the substrate used such as the vinyl type or epoxy type.
[0046] FIG. 1 shows an embodiment of an apparatus for producing the
copper foil for a high frequency circuit of the present invention.
In the figure, reference numeral 1 represents a titanium
electrolytic drum forming the cathode. This drum 1 rotates at a
constant speed about a shaft 2. Reference numeral 3 is a power feed
unit for passing current through the electrolytic drum 1 serving as
the cathode. Reference numeral 4 is a first plating tank. The
plating tank 4 is filled with an electrolytic solution A1 causing
deposition of the electrodeposited foil serving as the granular
layer on the surface of the electrolytic drum 1. Reference numeral
5 is an electrode serving as the anode provided in the plating tank
4. Reference numeral 6 is a second plating tank. The plating tank 6
is filled with an electrolytic solution A2 for causing deposition
of the electrolytic layer serving as the columnar layer on the
granular layer formed on the surface of the electrolytic drum 1.
Reference numeral 7 is an electrode serving as an anode provided at
the plating tank 6.
[0047] As illustrated, the electrolytic drum 1 is made to turn so
as to successively pass through the first plating tank 4 and the
second plating tank 6 in that order. The copper foil 10 deposited
on the drum 1 is peeled off from the drum 1 when emerging from the
second plating tank 6, whereby the final product is obtained. In
this way, by rotating the electrolytic drum 1, it is possible to
continuously produce a copper foil comprised of a granular layer on
which a columnar layer is formed.
[0048] Further, by switching the order of the electrolytic
solutions A1 and A2, it is possible to form a copper foil comprised
of a columnar layer on which a granular layer is formed.
[0049] FIG. 2 shows a second embodiment of the present invention.
Parts common with FIG. 1 are assigned the same reference numerals.
FIG. 2 shows an apparatus for production of a copper foil which
uses a common plating solution and changes the current density of
the anode to cause deposition of a granular layer and a columnar
layer. The electrolytic drum 1, immediately upon immersion in the
plating solution A, has an electrolytic deposit formed on it by a
current density giving a granular layer by a first anode electrode
5, then has an electrolytic deposit formed on it by a current
density giving a columnar layer by a second electrode 7. After
emerging from the plating solution, the copper foil 10 produced is
peeled off from the electrolytic drum 1, whereby the final product
is obtained.
[0050] Further, by reversing the order of the current densities of
the anode from the above, it is possible to produce a copper foil
comprised of a columnar layer on which a granular layer is
formed.
[0051] FIG. 3 shows a third embodiment of the present invention.
Parts common with FIG. 1 and FIG. 2 are assigned the same reference
numerals. FIG. 3 shows an electrolytic drum 1 rotated in a first
plating tank 4 to form a granular layer (or columnar layer) on the
drum 1, peeling off the copper foil 30 formed on the drum 1 from
the drum 1 when leaving the first plating tank 4, then dipping it
in the electrolytic tank 31. The electrolytic tank 31 is comprised
of electrodes 32 and 35 serving as anodes and a power feed unit 33
using the copper foil 30 as a cathode. The electrolytic tank 31 is
filled with a plating solution B.
[0052] Note that only one of the electrodes 32 and 35 is run
through with current when causing the plating layer to deposit on
one surface of the copper foil. Both of the electrodes are run
through with current when causing the plating layer to deposit on
both surfaces of the copper foil. In this way, a copper. foil
comprised of a granular layer and columnar layer is produced.
[0053] That is, to produce the copper foil in FIG. 3, the
electrolytic drum 1 is rotated to continuously produce a copper
foil 30 compared of the granular layer (or columnar layer), then
the copper foil 30 is introduced into the electrolytic tank 31 to
form a columnar layer (or granular layer) on one or both
surfaces.
[0054] FIG. 4 shows a fourth embodiment of the present invention.
Parts common with FIG. 2 are assigned the same reference numerals.
FIG. 4 shows the post-treatment process of the copper foil produced
by the apparatus of FIG. 2. Reference numeral 41 is a plating tank
comprised of an electrode 42 serving as the anode and a power feed
unit 43 having the copper foil 40 as a cathode. The plating
solution B filled in the plating tank 41 is made the formulation
required for surface treatment of the copper foil. For example a
copper, nickel, zinc, chromium, or other plating solution is
filled.
[0055] Note that reference numeral 45 indicates an electrode
serving as an anode. The electrodes 42 and 45 are selectively used
to enable either one of the surfaces of the copper foil or both of
the surfaces to be roughened or otherwise treated.
[0056] Using the apparatus shown in FIG. 4, the copper foil 10
peeled off from the electrolytic drum 1 is continuously guided into
the plating tank 41 and roughened at its surface at the plating
tank 41.
[0057] FIG. 5 shows a fifth embodiment of the present invention.
Parts common with FIG. 1 and FIG. 4 are assigned the same reference
numerals. FIG. 5 shows the post-treatment process of the copper
foil produced by the apparatus of FIG. 1. The copper foil 10 peeled
off from the electrolytic drum 1 is continuously guided into the
plating tank 41 and roughened at its surface at the plating tank
41.
[0058] Note that FIG. 4 to FIG. 5 show processes for in-line
post-treatment of the copper foils peeled off from the electrolytic
drum 1, but it is also possible to once wind the copper foil peeled
off from the electrolytic drum 1 on a bobbin etc. and then apply
roughening treatment to it as required.
EXAMPLES
[0059] Next, the present invention will be explained in detail in
accordance with examples with reference to the drawings. These
examples are given for the purpose of generally explaining the
present invention and do not have any limitative meaning at
all.
1. Plating and Surface Treatment Conditions in Examples
[0060] (1) Granular Layer Plating Conditions TABLE-US-00002 Plating
bath Cu: 90 g/liter H.sub.2SO.sub.4: 110 g/liter Sodium
3-mercapto-1-propanosulfonate: 1 ppm Hydroxyethylcellulose: 5 ppm
Low molecular weight glue 5 ppm (molecular weight about 3000):
Chloride ion: 30 ppm Current density: 50 A/dm.sup.2
[0061] (2) Columnar layer Plating Conditions TABLE-US-00003 Plating
bath Cu: 80 g/liter H.sub.2SO.sub.4: 100 g/liter Cl: 50 ppm Current
density: 30 A/dm.sup.2
(3) Roughening Treatment Conditions
[0062] First treatment is performed and then second treatment is
performed. These treatments are performed two times. TABLE-US-00004
First treatment Plating bath Cu: 20 g/liter H.sub.2SO.sub.4: 100
g/liter Bath temperature: 25.degree. C. Current density: 30
A/dm.sup.2 Second treatment Plating bath Cu: 60 g/liter
H.sub.2SO.sub.4: 100 g/liter Bath temperature: 60.degree. C.
Current density: 15 A/dm.sup.2
[0063] (4) Ni Plating Treatment TABLE-US-00005 Plating bath
NiSO.sub.4.7H.sub.2O: 300 g/liter NiCl.sub.2.6H.sub.2O: 60 g/liter
H.sub.3BO.sub.3: 40 g/liter Current density: 4 A/dm.sup.2
[0064] (5) Zinc Plating Treatment TABLE-US-00006 Plating bath ZnO:
8 g/liter NaOH: 90 g/liter Current density: 0.7 A/dm.sup.2
[0065] (6) Chromate Treatment TABLE-US-00007 Plating bath
K.sub.2Cr.sub.2O.sub.7: 5 g/liter Current density: 0.1
A/dm.sup.2
(7) Silane Coupling Agent Treatment
[0066] Coating by 0.2% solution of 3-aminopropyltriethoxysilane
(8) Benzotriazole Treatment
[0067] Dipping in 10% aqueous solution of Chiolight C-71AT made by
Chiyoda Chemical for 5 seconds
2. Measurement of Peel Strength and High Frequency Transmission
Loss
(1) Measurement of Peel Strength
[0068] The peel strength was measured at ordinary temperature.
(2) Measurement of High Frequency Transmission Loss
[0069] The high frequency transmission loss was measured by
laminating the copper foils on resin substrates, then forming
patterns of interconnect lengths of 1,000 mm and line widths of
0.16 mm, then measuring the transmission loss at 85.degree. C. and
5 GHz by a Network Analyzer (Agilent Technologies Co., 8753ET).
Example 1
[0070] Using a titanium electrolytic drum polished smoothly by
#2000 buff as a cathode, a 28 .mu.m copper foil was prepared by
granular layer plating. The copper foil was peeled off from the
titanium electrolytic drum, then a 2 .mu.m columnar layer was
plated on its shiny side, that is, granular surface which had been
in contact with titanium electrolytic drum (granular layer: about
93%). This was then further nickel plated, zinc plated, chromate
treated, then treated by a silane coupling agent.
Example 2
[0071] In the same way as in Example 1, a 26 .mu.m copper foil was
prepared by granular layer plating, peeled off from the titanium
electrolytic drum, plated on its shiny side with a 4 .mu.m columnar
layer (granular layer: about 87%), then further nickel plated, zinc
plated, chromate treated, then treated by a silane coupling
agent.
Example 3
[0072] In the same way as in Example 1, a 24 .mu.m copper foil was
prepared by granular layer plating, peeled off from the titanium
electrolytic drum, plated on its shiny side with a 6 .mu.m columnar
layer (granular layer: about 80%), then further nickel plated, zinc
plated, chromate treated, then treated by a silane coupling
agent.
Example 4
[0073] In the same way as in Example 1, a 22 .mu.m copper foil was
prepared by granular layer plating, peeled off from the titanium
electrolytic drum, plated on its shiny side with an 8 .mu.m
columnar layer (granular layer: about 73%), then further nickel
plated, zinc plated, chromate treated, then treated by a silane
coupling agent.
Example 5
[0074] In the same way as in Example 1, a 26 .mu.m copper foil was
prepared by granular layer plating, peeled off from the titanium
electrolytic drum, plated on its shiny side with a 4 .mu.m columnar
layer (granular layer: about 87%), then roughening treated by 0.4
g/dm.sup.2, further nickel plated, zinc plated, chromate treated,
then treated by a silane coupling agent.
Example 6
[0075] In the same way as in Example 1, a 26 .mu.m copper foil was
prepared by granular layer plating, peeled off from the titanium
electrolytic drum, plated on its shiny side with a 4 .mu.m columnar
layer (granular layer: about 87%), then roughening treated by 0.4
g/dm.sup.2, further nickel plated, zinc plated, chromate treated,
then treated by benzotriazole and treated by a silane coupling
agent simultaneously.
Example 7
[0076] In the same way as in Example 1, a 22 .mu.m copper foil was
prepared by granular layer plating, peeled off from the titanium
electrolytic drum, plated on its both surfaces with a 4 .mu.m
columnar layer (granular layer: about 73%), then roughening treated
by 0.4 g/dm.sup.2 on the shiny side at the time of foil production,
further zinc plated, chromate treated, then treated by a silane
coupling agent.
Example 8
[0077] In the same way as in Example 1, an 8 .mu.m copper foil was
prepared by granular layer plating, plated on its matte side, that
is, side opposite to shiny side with a 22 .mu.m columnar layer
(granular layer: about 27%), then roughening treated by 0.4
g/dm.sup.2, then chromate treated.
Example 9
[0078] Using a titanium electrolytic drum polished smoothly by
#2000 buff as a cathode, a 22 .mu.m copper foil was prepared by
columnar layer plating, then was plated on its matte side with a 8
.mu.m granular layer (granular layer: about 27%), then nickel
plated, zinc plated, chromate treated, then treated by a silane
coupling agent.
Comparative Example 1
[0079] Using a titanium electrolytic drum polished smoothly by
#2000 buff as a cathode, a 30 .mu.m copper foil was prepared by
granular layer plating. Its shiny side was then nickel plated, zinc
plated, chromate treated, then treated by a silane coupling
agent.
Comparative Example 2
[0080] In the same way as in Comparative Example 1, a 30 .mu.m
copper foil was prepared, roughening treated by 0.4 g/dm.sup.2 on
its shiny side, then nickel plated, zinc plated, chromate treated,
then treated by a silane coupling agent.
Comparative Example 3
[0081] In the same way as in Comparative Example 1, a 30 .mu.m foil
was prepared, roughening treated by 0.4 g/dm.sup.2 on its shiny
side, then nickel plated, zinc plated, chromate treated, then
treated by benzotriazole and treated by a silane coupling agent
simultaneously.
Comparative Example 4
[0082] In the same way as in Comparative Example 1, a 30 .mu.m
copper foil was prepared, roughening treated by 0.4 g/dm.sup.2 on
its shiny side, then zinc plated, chromate treated, then treated by
a silane coupling agent.
Comparative Example 5
[0083] In the same way as in Comparative Example 1, a 30 .mu.m foil
was prepared, roughening treated by 0.4 g/dm.sup.2 on its shiny
side, then chromate treated.
Comparative Example 6
[0084] Using a titanium electrolytic drum polished smoothly by
#2000 buff as a cathode, a 30 .mu.m copper foil was prepared by
columnar layer plating. Its shiny side was then nickel plated, zinc
plated chromate treated, then treated by a silane coupling
agent.
[0085] The surface shapes of the copper foils before treatment (the
Rz's, the surface area ratios), the peel strengths and the
transmission losses were measured for Examples 1 to 9 and
Comparative Examples 1 to 6. The results are shown in Table 1. Note
that the transmission losses are shown as ratios with the
transmission losses of the comparative examples.
[0086] In the table 1, Examples 1 to 4 are compared with
Comparative Example 1 (the same treatment), Example 5 is compared
with Comparative Example 2 (the same treatment), Example 6 is
compared with Comparative Example 3 (the same treatment), Example 7
is compared with Comparative Example 4 (the same treatment),
Example 8 is compared with Comparative Example 5 (the same
treatment), Example 9 is compared with Comparative Example 6 (the
same treatment), and Comparative Example 6 is compared with
Comparative Example 1 (the same treatment). TABLE-US-00008 TABLE 1
Peel Strength and Transmission Loss of Copper Foil (1) Surface
shape Columnar before treatment layer Surface Copper Silane
(Granular area ratio roughened Nickel Zinc Chromate Benzo- coupling
Peel layer as Rz (actual/ layer layer layer layer triazole agent
strength Transmission Foil for Ex. 9) (.mu.m) apparent)
(g/dm.sup.2) (mg/dm.sup.2) (mg/dm.sup.2) (mg/dm.sup.2) layer layer
(kN/m) loss ratio Ex. 1 Granular 2 .mu.m on 1.77 1.39 None 0.1 0.1
0.05 None Yes 1.10 1.010 layer shiny side Ex. 2 Granular 4 .mu.m on
1.88 1.46 None 0.1 0.1 0.05 None Yes 1.19 1.018 layer shiny side
Ex. 3 Granular 6 .mu.m on 2.13 1.56 None 0.1 0.1 0.05 None Yes 1.27
1.027 layer shiny side Ex. 4 Granular 8 .mu.m on 2.74 1.78 None 0.1
0.1 0.05 None Yes 1.36 1.042 layer shiny side Ex. 5 Granular 4
.mu.m on 1.93 1.46 0.4 0.1 0.1 0.05 None Yes 1.69 1.012 layer shiny
side Ex. 6 Granular 4 .mu.m on 1.91 1.46 0.4 0.1 0.1 0.05 Yes Yes
1.64 1.010 layer shiny side Ex. 7 Granular 4 .mu.m each on 1.83
1.44 0.4 None 0.1 0.05 None Yes 1.66 1.031 layer both surface Ex. 8
Granular 22 .mu.m on 4.56 2.45 0.4 None None 0.05 None None 1.96
1.081 layer matte side Ex. 9 Columnar 8 .mu.m on 2.97 1.69 None 0.1
0.1 0.05 None Yes 1.30 1.032 layer matte side Comp. Granular None
1.61 1.33 None 0.1 0.1 0.05 None Yes 0.97 1.000 Ex. 1 layer Comp.
Granular None 1.61 1.33 0.4 0.1 0.1 0.05 None Yes 1.48 1.000 Ex. 2
layer Comp. Granular None 1.61 1.33 0.4 0.1 0.1 0.05 Yes Yes 1.46
1.000 Ex. 3 layer Comp. Granular None 1.61 1.33 0.4 None 0.1 0.05
None Yes 1.46 1.000 Ex. 4 layer Comp. Granular None 1.61 1.33 0.4
None None 0.05 None None 1.37 1.000 Ex. 5 layer Comp. Columnar None
3.41 1.72 None 0.1 0.1 0.05 None Yes 1.35 1.051 Ex. 6 layer
[0087] Comparing the examples and comparative examples by Table 1,
Examples 1 to 4 were examples of plating the shiny sides of the
copper foils of the granular layers with columnar layers, then
nickel plating them, zince plating them, chromate treating them,
then treating them with silane coupling agents. Compared with
Comparative Example 1 with similar treatment, the thicker the
columnar layers, then greater the Rz's and surface area ratios
(actual/apparent) and the higher the peel strengths as well.
[0088] Further, comparing Example 4 with Comparative Example 6
(copper foil comprised of columnar layer), while the peel strength
was about the same, the transmission loss ratio became smaller.
[0089] In Example 5, the shiny side of the copper foil of a
granular layer of 26 .mu.m was plated with a columnar layer to 4
.mu.m and roughening treated by 0.4 g/dm.sup.2, then nickel plated,
zinc plated, chromate treated, and treated by a silane coupling
agent. Compared with Comparative Example 2 with similar treatment,
the peel strength rose.
[0090] In Example 6, the shiny side of the copper foil of a
granular layer of 26 .mu.m was plated with a columnar layer to 4
.mu.m and roughening treated by 0.4 g/dm.sup.2, then nickel plated,
zinc plated, chromate treated, and treated by benzotriazole and
treated by a silane coupling agent simultaneously. Compared with
Comparative Example 3 with similar treatment, the peel strength
rose.
[0091] In Example 7, the both surfaces of the copper foil of a
granular layer of 22 .mu.m were plated with columnar layers to 4
.mu.m, then one side was roughening treated by 0.4 g/dm.sup.2, then
zinc plated, chromate treated, and treated by a silane coupling
agent. Compared with Comparative Example 4 with similar treatment,
the peel strength rose.
[0092] In Example 8, the matte side of the copper foil of a
granular layer of 8 .mu.m was plated with a columnar layer to 22
.mu.m and roughening treated by 0.4 g/dm.sup.2, then chromate
treated. Compared with Comparative Example 5 with similar
treatment, the peel strength rose.
[0093] In Example 9, the matte side of the copper foil of a
columnar layer of 22 .mu.m was plated with a granular layer to 8
.mu.m, then nickel plated, zinc plated, chromate treated, and
treated by a silane coupling agent. Compared with Comparative
Example 6 with similar treatment, the transmission loss ratio
became smaller.
[0094] Comparative Examples 6, a 30 .mu.m copper foil was prepared
by columnar layer plating. Its shiny side was then nickel plated,
zinc plated, chromate treated, and treated by a silane coupling
agent, but due to the difference in Rz, Comparative Example 6 has a
larger transmission loss ratio compared with Comparative Example
1.
Comparative Example 7
[0095] In the same way as in Comparative Example 1, a 30 .mu.m
copper foil was prepared, roughening treated by 0.1 g/dm.sup.2 on
its shiny side, then nickel plated, zinc plated, chromate treated,
then treated by a silane coupling agent.
Comparative Example 8
[0096] In the same way as in Comparative Example 1, a 30 .mu.m
copper foil was prepared, roughening treated by 0.2 g/dm.sup.2 on
its shiny side, then nickel plated, zinc plated, chromate treated,
then treated by a silane coupling agent.
Comparative Example 9
[0097] In the same way as in Comparative Example 1, a 30 .mu.m
copper foil was prepared, roughening treated by 0.3 g/dm.sup.2 on
its shiny side, then nickel plated, zinc plated, chromate treated,
then treated by a silane coupling agent.
Comparative Example 10
[0098] In the same way as in Comparative Example 1, a 30 .mu.m
copper foil was prepared, roughening treated by 0.4 g/dm.sup.2 on
its shiny side, then nickel plated, zinc plated, chromate treated,
then treated by a silane coupling agent.
Comparative Example 11
[0099] In the same way as in Comparative Example 1, a 30 .mu.m
copper foil was prepared, roughening treated by 0.6 g/dm.sup.2 on
its shiny side, then nickel plated, zinc plated, chromate treated,
then treated by a silane coupling agent.
Comparative Example 12
[0100] In the same way as in Comparative Example 1, a 30 .mu.m
copper foil was prepared, roughening treated by 0.6 g/dm.sup.2 on
its shiny side, then nickel plated, zinc plated, chromate treated,
then treated by benzotriazole and treated by a silane coupling
agent simultaneously.
Comparative Example 13
[0101] In the same way as in Comparative Example 1, a 30 .mu.m
copper foil was prepared, roughening treated by 0.6 g/dm.sup.2 on
its shiny side, then zinc plated, chromate treated, then treated by
a silane coupling agent.
Comparative Example 14
[0102] In the same way as in Comparative Example 1, a 30 .mu.m
copper foil was prepared, roughening treated by 0.8 g/dm.sup.2 on
its shiny side, then chromate treated.
[0103] The surface shapes of the copper foils before treatment (the
Rz's, the surface area ratios), the peel strengths and the
transmission losses were measured for Examples 1 to 8 and
Comparative Examples 7 to 14. The results are shown in Table 2.
Note that the transmission losses are shown as ratios with the
transmission losses of the comparative examples.
[0104] In the table 2, for comparison of the high frequency
characteristics, as comparative foils, ones with the same surface
deposits and roughened to give about the same peel strengths were
used, that is, Example 1 is compared with Comparative Example 7,
Example 2 is compared with Comparative Example 8, Example 3 is
compared with Comparative Example 9, Example 4 is compared with
Comparative Example 10, Example 5 is compared with Comparative
Example 11, Example 6 is compared with Comparative Example 12,
Example 7 is compared with Comparative Example 13, and Example 8 is
compared with Comparative Example 14. TABLE-US-00009 TABLE 2 Peel
Strength and Transmission Loss of Copper Foil (2) Surface shape
before treatment Surface Copper Silane area ratio roughened Nickel
Zinc Chromate Benzo- coupling Peel Columnar Rz (actual/ layer layer
layer layer triazole agent strength Transmission Foil layer (.mu.m)
apparent) (g/dm.sup.2) (mg/dm.sup.2) (mg/dm.sup.2) (mg/dm.sup.2)
layer layer (kN/m) loss ratio Ex. 1 Granular 2 .mu.m on 1.77 1.39
None 0.1 0.1 0.05 None Yes 1.10 0.974 layer shiny side Ex. 2
Granular 4 .mu.m on 1.88 1.46 None 0.1 0.1 0.05 None Yes 1.19 0.921
layer shiny side Ex. 3 Granular 6 .mu.m on 2.13 1.56 None 0.1 0.1
0.05 None Yes 1.27 0.892 layer shiny side Ex. 4 Granular 8 .mu.m on
2.74 1.78 None 0.1 0.1 0.05 None Yes 1.36 0.802 layer shiny side
Ex. 5 Granular 4 .mu.m on 1.93 1.46 0.4 0.1 0.1 0.05 None Yes 1.69
0.893 layer shiny side Ex. 6 Granular 4 .mu.m on 1.91 1.46 0.4 0.1
0.1 0.05 Yes Yes 1.64 0.902 layer shiny side Ex. 7 Granular 4 .mu.m
each on 1.83 1.44 0.4 None 0.1 0.05 None Yes 1.66 0.943 layer both
surface Ex. 8 Granular 22 .mu.m on 4.56 2.45 0.4 None None 0.05
None None 1.96 0.863 layer matte side Comp. Granular None 1.61 1.33
0.1 0.1 0.1 0.05 None Yes 1.09 1.000 Ex. 7 layer Comp. Granular
None 1.61 1.33 0.2 0.1 0.1 0.05 None Yes 1.21 1.000 Ex. 8 layer
Comp. Granular None 1.61 1.33 0.3 0.1 0.1 0.05 None Yes 1.26 1.000
Ex. 9 layer Comp. Granular None 1.61 1.33 0.4 0.1 0.1 0.05 None Yes
1.38 1.000 Ex. 10 layer Comp. Granular None 1.61 1.33 0.6 0.1 0.1
0.05 None Yes 1.68 1.000 Ex. 11 layer Comp. Granular None 1.61 1.33
0.6 0.1 0.1 0.05 Yes Yes 1.67 1.000 Ex. 12 layer Comp. Granular
None 1.61 1.33 0.6 None 0.1 0.05 None Yes 1.64 1.000 Ex. 13 layer
Comp. Granular None 1.61 1.33 0.8 None None 0.05 None Yes 1.96
1.000 Ex. 14 layer
[0105] As clear from Table 2, comparing Example 1 and Comparative
Example 7, Example 2 and Comparative Example 8, Example 3 and
Comparative Example 9, and Example 4 and Comparative Example 10,
Examples 1 to 4 were examples of plating the shiny sides of the
copper foils of the granular layers with columnar layers, then
nickel plating them, zinc plating them, chromate treating them,
then treating them with silane coupling agents. Compared with
Comparative Examples 7 to 10 roughening treatment instead of being
plated with columnar layers, the transmission loss ratio became
smaller.
[0106] Further, there was a tendency shown for the transmission
loss ratio to become smaller the higher the peel strength.
[0107] In Example 5, the shiny side of the copper foil of a
granular layer of 26 .mu.m was plated with a columnar layer to 4
.mu.m and roughening treated by 0.4 g/dm.sup.2, then nickel plated,
zinc plated, chromate treated, and treated by a silane coupling
agent. Compared with Comparative Example 11 roughening treated by
0.6 g/dm.sup.2 without being plated with a columnar layer, the
transmission loss ratio became smaller.
[0108] In Example 6, the shiny side of the copper foil of a
granular layer of 26 .mu.m was plated with a columnar layer to 4
.mu.m and roughening treated by 0.4 g/dm.sup.2, then nickel plated,
zinc plated, chromate treated, and treated by benzotriazole and
treated by a silane coupling agent simultaneously. Compared with
Comparative Example 12 roughening treated by 0.6 g/dm.sup.2 without
being plated with a columnar layer, the transmission loss ratio
became smaller.
[0109] In Example 7, the both surfaces of the copper foil of a
granular layer of 22 .mu.m were plated with columnar layers to 4
.mu.m, then one side was roughening treated by 0.4 g/dm.sup.2, then
zinc plated, chromate treated, and treated by a silane coupling
agent. Compared with Comparative Example 13 roughening treated by
0.6 g/dm.sup.2 without being plated with a columnar layer, the
transmission loss ratio became smaller.
[0110] In Example 8, the matte side of the copper foil of a
granular layer of 8 .mu.m was plated with a columnar layer to 22
.mu.m and roughening treated by 0.4 g/dm.sup.2, then chromate
treated. Compared with Comparative Example 14, the transmission
loss ratio became smaller.
[0111] Summarizing the effects of the invention, by making a copper
foil double layer structure as explained above, it is possible to
improve the peel strength without reducing the high frequency
characteristics and therefore possible to provide a copper foil
suitable for a fine pattern printed circuit board (in particular
for high frequency use), a method of production and a production
apparatus for the same, and a high frequency circuit using such a
copper foil.
[0112] Note that the copper foil of the present invention can also
be used to good effect for COF and PDP applications, that is, its
applications are not particularly limited.
[0113] While the invention has been described with reference to
specific embodiments chosen for purpose of illustration, it should
be apparent that numerous modifications could be made thereto by
those skilled in the art without departing from the basic concept
and scope of the invention.
* * * * *