U.S. patent application number 12/226237 was filed with the patent office on 2010-09-16 for laminate structure comprised of stainless steel foil, resin, and metal foil.
Invention is credited to Atsushi Mizuyama, Shuji Nagasaki, Jun Nakatsuka, Tsuyoshi Yamamoto.
Application Number | 20100233509 12/226237 |
Document ID | / |
Family ID | 38624646 |
Filed Date | 2010-09-16 |
United States Patent
Application |
20100233509 |
Kind Code |
A1 |
Yamamoto; Tsuyoshi ; et
al. |
September 16, 2010 |
Laminate Structure Comprised of Stainless Steel Foil, Resin, and
Metal Foil
Abstract
The present invention provides a laminate structure with little
warping comprised of a stainless steel foil, a resin, and a metal
foil, that is, a laminate structure comprised of a three-layer
structure of a stainless steel foil, a resin, and a metal foil
wherein the stainless steel foil is comprised of mixed phases of a
ferromagnetic phase and a nonferromagnetic phase and the ratio of
the ferromagnetic phase is 0.1 mass % to 4.0 mass %.
Inventors: |
Yamamoto; Tsuyoshi; (Tokyo,
JP) ; Nagasaki; Shuji; (Tokyo, JP) ; Mizuyama;
Atsushi; (Tokyo, JP) ; Nakatsuka; Jun; (Tokyo,
JP) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
38624646 |
Appl. No.: |
12/226237 |
Filed: |
April 14, 2006 |
PCT Filed: |
April 14, 2006 |
PCT NO: |
PCT/JP2006/308368 |
371 Date: |
October 10, 2008 |
Current U.S.
Class: |
428/685 |
Current CPC
Class: |
B32B 27/32 20130101;
B32B 2307/30 20130101; B32B 27/42 20130101; B32B 15/08 20130101;
B32B 27/08 20130101; B32B 27/38 20130101; B32B 27/34 20130101; B32B
2457/00 20130101; B32B 2307/308 20130101; B32B 2307/306 20130101;
B32B 27/281 20130101; Y10T 428/12979 20150115; C22C 9/06 20130101;
B32B 15/20 20130101; B32B 15/18 20130101; B32B 2307/714 20130101;
H05K 1/056 20130101; B32B 27/302 20130101; B32B 2457/08
20130101 |
Class at
Publication: |
428/685 |
International
Class: |
C25D 5/10 20060101
C25D005/10; C25D 5/04 20060101 C25D005/04 |
Claims
1. A laminate structure comprised of a three-layer structure of a
stainless steel foil, a resin, and a metal foil, said laminate
structure characterized in that the stainless steel foil is
comprised of mixed phases of a ferromagnetic phase and a
nonferromagnetic phase and the ratio of the ferromagnetic phase is,
by mass, 0.1% to 4.0%.
2. A laminate structure for a hard disk suspension comprised of a
three-layer structure of a stainless steel foil, a resin, and a
metal foil, said laminate structure characterized in that the
stainless steel foil is comprised of mixed phases of a
ferromagnetic phase and a nonferromagnetic phase, the ratio of the
ferromagnetic phase is, by mass, 0.1% to 4.0%, and the metal foil
is a copper foil or a copper alloy foil.
Description
TECHNICAL FIELD
[0001] The present invention can be utilized for a structure for
electronic equipment such as a memory device or circuit board. In
particular, it is suitable for a laminate structure for a
suspension for a hard disk drive where stable positioning precision
is required.
BACKGROUND ART
[0002] Composite materials, in particular laminate structures
comprised of a metal and resin, give a number of properties not
obtainable by single materials, so are being utilized in various
fields. Their fields of utilization are increasingly growing
including light and thin applications.
[0003] In these fields, to bring out magnetic, electrical, or
dielectric physical actions in devices with a good precision,
strict positioning precision is sought from the laminate structures
supporting the devices. For example, as structures utilizing
magnetic physical actions, the support parts for magnetic heads for
hard disks may be mentioned, as structures utilizing electrical
physical actions, flexible printed circuit boards may be mentioned,
and as structures utilizing dielectric physical actions, the
support parts for heads for ferroelectric memories, etc. may be
mentioned.
[0004] Laminate structures are utilized in various fields, but the
effect of warping can no longer be ignored due to the differences
in heat expansion and heat shrinkage in each material. In
particular, the effect becomes greater as the thicknesses are made
smaller.
[0005] The method used to suppress warping of laminate structures
has been, in the case of a thermoplastic resin, to raise the
temperature to soften the laminate structure and further apply
pressure to it by a press etc. to correct the warping, then to cool
the resin to raise the viscosity and improve the bonding strength.
On the other hand, in the case of a heat curable resin, the
practice has been to apply pressure to the laminate structure by a
press etc. to correct the warping and raise the temperature at that
time to cure the resin.
[0006] These measures are effective against warping in the state of
a high temperature of the resin, but when lowering the temperature
down to near room temperature, warping occurs due to heat
shrinkage. Even if eliminated, correction of the warping would
require long heating and pressing by a press. This would make the
productivity of the device drop remarkably.
[0007] The prior art relating to a laminate structure of a
suspension for a hard disk drive, for example, Japanese Patent
Publication (A) No. 2004-303358, alludes to the heat expansion
coefficient and bonding strength of a resin layer, while Japanese
Patent Publication (A) No. 2005-125588 alludes to the bonding
strength of a resin and etchability, but, as explained above, so
long as a process of heating in order to increase the bonding
strength is involved in the process of production of a laminate
structure, it is difficult to stably reduce the warping. The art
described in the present invention, that is, the optimization of
the ratio of the ferromagnetic phase inside the stainless steel
foil suppressing the warping of the laminate structure, is not
alluded to at all.
DISCLOSURE OF THE INVENTION
[0008] The present invention has as its object the provision of a
laminate structure comprised of a three-layer structure of a
stainless steel foil, a resin, and a metal foil and suppressed in
warping.
[0009] The gist of the present invention lies in a laminate
structure comprised of a three-layer structure of a stainless steel
foil, a resin, and a metal foil, the laminate structure
characterized in that the stainless steel foil is comprised of
mixed phases of a ferromagnetic phase and a nonferromagnetic phase
and the ratio of the ferromagnetic phase is, by mass, 0.1% to 4.0%.
More preferably, it is a laminate structure for a hard disk
suspension comprised of a three-layer structure of a stainless
steel foil, a resin, and a metal foil, the laminate structure
characterized in that the stainless steel foil is comprised of
mixed phases of a ferromagnetic phase and a nonferromagnetic phase,
the ratio of the ferromagnetic phase is, by mass, 0.1% to 4.0%, and
the metal foil is a copper foil or a copper alloy foil.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic view of a cross-section showing the
configuration of the laminate structure of the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0011] Below, the present invention will be explained more
specifically. FIG. 1 is a cross-sectional schematic view showing
the configuration of the laminate structure of the present
invention. As will be understood from FIG. 1, the laminate
structure 1 of the present invention forms a three-layer structure
comprised of a stainless steel foil 2, a metal foil 3, and, between
them for bonding the two foils, a thermoplastic resin or heat
curable resin or a composite of a thermoplastic resin and heat
curable resin 4.
[0012] The metal foil 3 is a foil of a metal and/or alloy of a
composition different from the stainless steel foil 2.
[0013] This laminate structure 1 is prepared by bonding the
stainless steel foil 2 and the metal foil 3 different from that by
joining them by a thermoplastic or heat curable resin 4, then
bonding the two by heat. The bonding temperature by this heat is
generally 100 to 400.degree. C., but the invention is not limited
to this. It is possible to suitably select this by the curing or
plasticizing temperature of the resin used.
[0014] In this regard, if laminating the stainless steel foil and
metal foil different in composition from it forming the present
invention by the interposition of a resin, warping occurs in the
laminate structure along with the difference in amounts of heat
shrinkage.
[0015] Stainless steel foil is comprised of a ferromagnetic phase
or a nonmagnetic phase or the two phases. The ferromagnetic phase
has a small amount of heat shrinkage. For example, if laminated
with copper or another metal, there is a tendency for warping at
the stainless steel side. On the other hand, the nonmagnetic phase
has a large amount of heat shrinkage. If laminated with copper or
another metal, there is a tendency for warping at the non-stainless
steel side.
[0016] Since the ferromagnetic phase of a stainless steel foil has
a small amount of heat shrinkage, while the nonmagnetic phase has a
large amount of heat shrinkage, it is possible to adjust the ratio
of these phases to control the warping at the time of making a
laminate structure. In the present invention, the ratio of the
ferromagnetic phase is made, by mass, 0.1% to 4.0%. If the ratio of
the ferromagnetic phase is less than, by mass, 0.1%, the effect of
suppressing warping is small and the structure warps at the side of
the stainless steel foil, while if over 4.0%, it easily warps at
the metal foil side. Note that the extent of the warping differs
depending on the type of the metal foil of the laminate structure,
but it is possible to suitably select the ratio within the above
range to suppress warping of the laminate structure.
[0017] The method of measurement of the ferromagnetic phase is not
particularly limited. A vibration sample magnetometer (VSM),
ferrite meter, etc. may be utilized.
[0018] Note that the stainless steel foil described in the present
invention means an austenitic stainless steel or two-phase
stainless steel. Stainless steel becomes a two-phase structure by
part of the nonmagnetic phase dielectrically transforming to the
magnetic phase in the processing of rolling to make it thinner. The
ratio of the ferromagnetic phase of the stainless steel foil can be
controlled by the reduction rate at the time of rolling, the
temperature of the stainless steel at the time of rolling, etc.
[0019] The "metal foil" described in the present invention is a
general name for a metal and an alloy different from the stainless
steel foil in ingredients and having a thickness of 100 .mu.m or
less. In particular, gold, silver, or copper has ductility and is
easy to work thinly and, further, is high in electrical
conductivity, can be etched to form circuits, further is superior
in heat conductivity as well, and is superior in heat radiating
action. Further, alloying enables the improvement of the mechanical
strength.
[0020] For copper alloys in the metal foils, as alloying elements,
typically Ni, Si, Mg, Be, etc. are used, but the invention is not
limited to these. From the viewpoint of maintaining physical
properties substantially the same as Cu alone etc. (other than
mechanical strength), it is believed that Cu is preferably 90 mass
% or more.
[0021] The resin described in the present invention includes both a
thermoplastic resin and a heat curable resin. The "thermoplastic
resin" indicates a thermoplastic polyimide, polystyrene,
polyethylene, polyamide, etc., but the invention is not limited to
these. In particular, in the case of a polyamide superior in heat
resistance, the amount of heat shrinkage between room temperature
and a high temperature is large and the effect of suppression of
warping described in the present invention is large.
[0022] The "heat curable resin" indicates a heat curable polyimide,
urea resin, melamine resin, phenol resin, epoxy resin, unsaturated
polyester, alkyd resin, urethane resin, ebonite resin, etc., but
the invention is not limited to these. The present invention
exhibits its effect by all resins requiring a heating step. The
resin may be a single layer or may be a plurality in a laminar
state. The selection and combination of the thermoplastic resin
layer and heat curable resin layer may be any selection and
combination. The thickness of the resin (in the case of multiple
layers, the total) is preferably 5 .mu.m to 100 .mu.m, for the
purpose of reducing the weight, more preferably 5 .mu.m to 25
.mu.m, but the invention is not limited to these values.
[0023] In the recently fast growing field of hard disk drives, the
increasingly higher densities are being accompanied with an
increasingly narrower distance between the magnetic head and
recording medium with each passing year. The distance of 100 nm
around 1995 is currently being made a closer 20 nm or less. On the
other hand, the suspensions for supporting magnetic heads are being
required to be reduced in weight due to the vibration resistance
characteristics. Stainless steel with such a required thickness of
100 .mu.m or less (generally, a thickness of 100 .mu.m or less is
called a "foil") is being used.
[0024] According to the present invention, it becomes possible to
eliminate the warping of a laminate structure comprised of a
stainless steel foil, a resin, and a metal foil and possible to
stably produce a laminate structure for a hard disk drive
suspension with little of the problems of positioning precision due
to warping caused by the difference in shrinkage even if thin.
Examples
[0025] Below, the present invention will be explained in detail
based on the examples.
Example 1
[0026] A stainless steel foil comprised of SUS304 foil with a
thickness of 20 .mu.m and a width of 400 mm and copper foil with a
thickness of 20 .mu.m were bonded by curing a thermoplastic
polyimide resin (curing temperature: 350.degree. C.) and the state
of warping was examined. For the warping, the laminate structure
was cut to 1 m length, then the top end was fixed and the structure
was hung downward. A maximum amount of warping of the laminate
structure from the vertical plane of 100 mm or less was judged to
be good. The thickness of the thermoplastic polyimide resin was
made 5 .mu.m, 25 .mu.m, and 100 .mu.m.
[0027] The stainless steel foils used for the samples good (low) in
terms of warping and samples not good in it were measured for
saturated magnetic flux density by a vibration sample magnetometer
(VSM), whereupon it could be confirmed that if a ferromagnetic
phase is present in the nonmagnetic phase in a certain range, a
good laminate shape is obtained.
[0028] A vibration sample magnetometer (VSM) is expensive, has to
be set in a clean environment, and is expensive in terms of
maintenance and inspection costs as well, so a ferrite meter able
to simply measure the ferromagnetic phase was used for measurement.
The results are shown in Table 1. For the measurement by the
ferrite meter, the stainless steel foil was stacked to 1.0 mm and
brought into contact with the magnetic sensor part for measurement.
The measurement temperature of the vibration sample magnetometer
(VSM) and ferrite meter was made room temperature (25.degree.
C.).
[0029] Note that the measured value of the saturated magnetic flux
density by a vibration sample magnetometer (VSM) is small in
dependency on the dimensions and shape of the sample, while the
measured value of the ratio of the ferromagnetic phase by a ferrite
meter has a shape dependency for the thickness of the sample from
the measurement principle. For this reason, the measurement by the
ferrite meter in the present invention was standardized to the
condition of a sample thickness of 1.0 mm obtained by stacking the
stainless steel foil to a sample thickness of 1.0 mm.
[0030] By making the sample thickness of the laminated foil
constant, the saturated magnetic flux density of the stainless
steel foil and the ferromagnetic phase ratio by measurement by the
ferrite meter have a constant correspondence as shown in for
example Table 1.
TABLE-US-00001 TABLE 1 Saturated magnetic flux Ferrite Resin
density Bs meter thickness Sample (G) (mass %) (.mu.m) Laminate
shape Sample 1 30 or less 0.1 or less 5 Warping at stainless
(0.095) steel side Sample 2 25 Warping at stainless steel side
Sample 3 100 Warping at stainless steel side Sample 4 370 0.5 5
Shaped well Sample 5 25 Shaped well Sample 6 100 Shaped well Sample
7 490 1.0 5 Shaped well Sample 8 25 Shaped well Sample 9 100 Shaped
well Sample 10 630 1.4 5 Shaped well Sample 11 25 Shaped well
Sample 12 100 Shaped well Sample 13 1320 4.0 5 Shaped well Sample
14 25 Shaped well Sample 15 100 Shaped well Sample 16 1850 6.0 5
Warping at copper side Sample 17 25 Warping at copper side Sample
18 100 Warping at copper side
Example 2
[0031] A stainless steel foil comprised of SUS304 foil with a
thickness of 100 .mu.m and a width of 650 mm (however, in the case
where the metal foil is Au or Ag, a width of 20 mm) and various
types of metal foil (thickness of 100 .mu.m and width of 650 mm,
however when the metal foil is Au or Ag, a width of 20 mm) were
bonded by curing an epoxy resin (resin thickness 18 .mu.m) and the
state of warping (curing temperature of 100.degree. C.) was
examined.
[0032] Note that the copper alloy Cu--Ni--Si--Mg used was one of a
range of composition of Ni: 2.2 to 4.2 mass %, Si: 0.025 to 1.2
mass %, and Mg: 0.05 to 0.3 mass %.
[0033] Further, the warping was examined in the same way as Example
1.
[0034] The stainless steel foil was annealed at 1050.degree. C.,
then rolled until 100 .mu.m. The ratio of the magnetic phase was
measured while changing the reduction rate at that time. In the
measurement, the stainless steel foil was stacked to a thickness of
1.0 mm and measured by a ferrite meter.
[0035] The ratio of the magnetic phase of the stainless steel foil
optimal for each type of metal foil is shown in Table 2. By
optimizing the ratio of the magnetic phase, a laminate structure
free of warping is obtained.
TABLE-US-00002 TABLE 2 Mass ratio (%) of magnetic phase in
stainless Type of steel foil metal foil 0.1% 0.5% 1.0% 2.0% 3.0%
4.0% 6.0% Au .DELTA. .DELTA. .DELTA. .largecircle. .largecircle.
.largecircle. Ag .largecircle. .largecircle. .largecircle. Cu
.DELTA. .largecircle. .largecircle. .largecircle. .largecircle. Al
.largecircle. Mg .largecircle. Sn .DELTA. .DELTA. .DELTA.
.largecircle. .largecircle. .largecircle. Cu--Ni--Si--Mg .DELTA.
.largecircle. .largecircle. .largecircle. .largecircle. Cu--Ni
.DELTA. .largecircle. .largecircle. .largecircle. .largecircle.
Cu--Si .DELTA. .largecircle. .largecircle. .largecircle.
.largecircle. Cu--Mg .DELTA. .largecircle. .largecircle.
.largecircle. .largecircle. Cu--Be .DELTA. .largecircle.
.largecircle. .largecircle. .largecircle. .DELTA. (Poor): Case of
warping at stainless steel side .largecircle. (Good): Shaped well
(Poor): Case of warping at metal side
Example 3
[0036] A stainless steel foil comprised of various types of
stainless steel foil with a thickness of 20 .mu.m and a width of
300 mm and a copper foil (thickness of 20 .mu.m and width of 300
mm) were joined by curing a thermoplastic polyimide resin (resin
thickness of 10 .mu.m) (curing temperature: 350.degree. C.) and the
state of warping was examined.
[0037] Note that the warping was examined in the same way as in
Example 1.
[0038] Each stainless steel foil was annealed at 1150.degree. C.,
then rolled to 20 .mu.m. The ratio of the magnetic phase was
measured while changing the reduction rate at that time. In the
measurement, the stainless steel foil was stacked to a thickness of
1.0 mm, then measured by a ferrite meter.
[0039] The ratio of the magnetic phase optimum for each stainless
steel foil is shown in Table 3. By optimizing the ratio of the
magnetic phase, a laminate structure free of warping is
obtained.
[0040] Here, the type of steel of the stainless steel foil is one
based on JIS G4304 and JIS G4305. Further, these steel types are
linked with the UNS, AISI, DIN, etc. of the ISO and related foreign
standards.
TABLE-US-00003 TABLE 3 Mass ratio (%) of magnetic phase in
stainless Type of steel foil stainless steel 0.1% 0.5% 1.0% 2.0%
3.0% 4.0% 6.0% SUS301 .DELTA. .largecircle. .largecircle.
.largecircle. .largecircle. SUS302 .DELTA. .largecircle.
.largecircle. .largecircle. .largecircle. SUS303 .DELTA.
.largecircle. .largecircle. .largecircle. .largecircle. SUS304
.DELTA. .largecircle. .largecircle. .largecircle. .largecircle.
SUS316 .largecircle. .largecircle. .largecircle. SUS316L
.largecircle. .largecircle. .largecircle. SUS317 .largecircle.
.largecircle. .largecircle. SUS321 .DELTA. .DELTA. .largecircle.
.largecircle. .largecircle. .largecircle. SUS347 .DELTA. .DELTA.
.largecircle. .largecircle. .largecircle. .largecircle. .DELTA.
(Poor): Case of warping at stainless steel side .largecircle.
(Good): Shaped well (Poor): Case of warping at copper side
INDUSTRIAL APPLICABILITY
[0041] According to the present invention, it becomes possible to
stabilize the warping of a laminate structure comprised of a
three-layer structure of a stainless steel foil, a resin, and a
metal foil at a low level. Specifically, the invention can be
utilized for a wide range of fields where strict positioning
precision is demanded such as the support of a magnetic head for a
hard disk, a flexible printed circuit board, a support of a head
for a ferroelectric memory, or the support of another electrical,
magnetic, or dielectric device. Inn particular, the invention can
become an effective means in suspension members for hard disk
drives where a thin structure and a high precision are
demanded.
* * * * *