U.S. patent application number 11/664311 was filed with the patent office on 2009-01-08 for adhesive sheet and copper-clad laminate.
Invention is credited to Hisayasu Kaneshiro, Takashi Kikuchi.
Application Number | 20090011231 11/664311 |
Document ID | / |
Family ID | 36142609 |
Filed Date | 2009-01-08 |
United States Patent
Application |
20090011231 |
Kind Code |
A1 |
Kaneshiro; Hisayasu ; et
al. |
January 8, 2009 |
Adhesive Sheet and Copper-Clad Laminate
Abstract
Disclosed is an adhesive film having high dimensional stability
which can be suitably used for two layer FPCs. Specifically,
disclosed is an adhesive sheet composed of an insulting layer and
an adhesive layer arranged on one side or both sides of the
insulating layer. This adhesive sheet is characterized in that the
insulating layer has a ratio E'2/E'1 between the storage elasticity
modulus E'1 at 25.degree. C. and the storage elasticity modulus E'2
at 380.degree. C. of not more than 0.2 and a coefficient of thermal
expansion in the MD direction of 5-15 ppm at 100-200.degree. C. It
is further characterized in that the change in the coefficient of
thermal expansion of the adhesive sheet at 100-250.degree. C. after
heat treatment at 380.degree. C. for 30 second under tension of 20
kg/m is not more than 2.5 ppm in the tension direction and not more
than 10 ppm in the direction perpendicular to the tension
direction.
Inventors: |
Kaneshiro; Hisayasu; (Kyoto,
JP) ; Kikuchi; Takashi; (Shiga, JP) |
Correspondence
Address: |
KAGAN BINDER, PLLC
SUITE 200, MAPLE ISLAND BUILDING, 221 MAIN STREET NORTH
STILLWATER
MN
55082
US
|
Family ID: |
36142609 |
Appl. No.: |
11/664311 |
Filed: |
September 29, 2005 |
PCT Filed: |
September 29, 2005 |
PCT NO: |
PCT/JP05/18018 |
371 Date: |
March 29, 2007 |
Current U.S.
Class: |
428/355R ;
428/457 |
Current CPC
Class: |
H05K 2201/068 20130101;
H05K 1/0346 20130101; H05K 1/0393 20130101; Y10T 428/31678
20150401; C09J 7/25 20180101; H05K 2201/0154 20130101; H05K 3/386
20130101; Y10T 428/2852 20150115; C09J 2479/086 20130101 |
Class at
Publication: |
428/355.R ;
428/457 |
International
Class: |
B32B 15/04 20060101
B32B015/04; B32B 7/12 20060101 B32B007/12 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 5, 2004 |
JP |
2004-292949 |
Claims
1. An adhesive sheet comprising an insulating layer and an adhesive
layer on one or each side of the insulating layer, wherein the
insulating layer has a storage elasticity modulus ratio E'2/E'1 of
0.2 or less where E'1 is a storage elasticity modulus at 25.degree.
C. and E'2 is a storage elasticity modulus at 380.degree. C., the
insulating layer has a coefficient of thermal expansion in the MD
direction in a range of 5 to 15 ppm from 100.degree. C. to
200.degree. C., and a change in the coefficient of thermal
expansion of the adhesive sheet from 100.degree. C. to 250.degree.
C. is 2.5 ppm or less in a tension direction in which the tension
is applied, and a change in the coefficient of thermal expansion of
the adhesive sheet from 100.degree. C. to 250.degree. C. is 10 ppm
or less in a direction perpendicular to the tension direction,
where the change in the coefficient of thermal expansion is
calculated by Equation (1): Change in Coefficient of Thermal
Expansion=|(First Measured Value of Coefficient of Thermal
Expansion)-(Second Measured Value of Coefficient of Thermal
Expansion)| (1) where the measurements are carried out with the
adhesive sheet that has been heat-treated at a temperature of
380.degree. C. for 30 sec under tension of 20 kg/m.
2. The adhesive sheet as set forth in claim 1 wherein a peak top
temperature of tan .delta. in measuring dynamic viscoelasticity of
the insulating layer is in a range of 300 to 400.degree. C., and
tan .delta.>0.1.
3. The adhesive sheet as set forth in claim 1, wherein the
insulating layer is a polyimide layer.
4. The adhesive sheet as set forth in claim 3, wherein raw
materials of the polyimide layer include
2,2-bisaminophenoxyphenylpropane by 10 to 50 mol %,
p-phenylenediamine by 30 to 60 mol %, and an oxydianiline by 10 to
30 mol % with respect to a diamine component.
5. The adhesive sheet as set forth in claim 4, wherein the
oxydianiline is 3,4'-oxydianiline.
6. The adhesive sheet as set forth in claim 3 wherein the raw
materials of the polyimide layer includes pyromellitic dianhydride
by 60 to 95 mol %, and 3,3',4,4'-benzophenonetetracarboxylic
dianhydride and/or 3,3',4,4'-biphenyltetracarboxylic dianhydride by
5 to 40 mol % with respect to an acid dianhydride component.
7. The adhesive sheet as set forth in claim 1, wherein the adhesive
layer contains a polyimide-based adhesive.
8. The adhesive sheet as set forth in claim 1, wherein the adhesive
layer contains a straight-chained thermoplastic polyimide and/or a
3-dimensionally crosslinking polyimide.
9. The adhesive sheet as set forth in claim 1, wherein the adhesive
sheet is used after being laminated with a metal layer on one or
each adhesive layer by applying heat and pressure.
10. A two-layer copper-clad laminate prepared by laminating a metal
conductive foil on one or each side of adhesive sheet as set forth
in claim 1 by applying heat and pressure.
Description
TECHNICAL FIELD
[0001] The present invention relates to an adhesive film that is
preferably applicable to a two-layer FPC having a high dimensional
stability.
BACKGROUND ART
[0002] The recent trends toward lighter, smaller, and
higher-density electronic products have increased the demand for
various printing boards. In particular, the demand for flexible
laminates (also referred to as "flexible printing circuit boards
(FPCs)") has shown a notable increase. A flexible laminate is
constituted from an insulating film and a circuit formed from a
metal foil disposed on the film.
[0003] Typically, a flexible laminate is produced by bonding a
metal foil onto a surface of a substrate with an adhesive material
of various kinds under heating and pressure, the substrate being a
flexible film made from an insulating material of various kinds.
Polyimide films and the like are preferred as the insulating
flexible film, and thermosetting adhesives such as epoxy and
acrylic adhesives are typically used as the adhesive material.
Hereinafter, FPCs made using thermosetting adhesives are also
referred to as "three-layer FPCs".
[0004] Thermosetting adhesives are advantageous in that bonding at
relatively low temperatures is possible. However, requirements for
properties, such as heat resistance, flexibility, and electrical
reliability, are becoming more stringent, and it is possible that
three-layer FPCs using thermosetting adhesives will have difficulty
in meeting these stringent requirements. In order to overcome this
problem, FPCs (hereinafter also referred to as "two-layer FPCs")
using thermoplastic polyimide as the bonding layer or made by
directly forming a metal layer on the insulating film have been
proposed. The two-layer FPCs have properties superior to those of
the three-layer FPCs, and the demand for the two-layer FPCs is
expected to grow in the future.
[0005] The two-layer FPCs that have been suggested are classified
into three types, (1) PVD two-layer, (2) cast two-layer, (3)
laminate two-layer, which have various advantages and disadvantages
respectively. Among theses three types of two-layer FPCs, the
laminate two-layer FPC gains prominence over the others because of
its high productivity. The laminate two-layer FPC is produced by
laminating an electrically conductive metal foil on an adhesive
sheet on one or each side of which an polyimide-based adhesive
agent layer is formed. As an example of the PVD two-layer FPC,
Patent Citation 2 discloses a flexible copper-clad circuit board in
which a thermoplastic polyimide layer and a certain metal layer,
namely, a copper layer, are formed on a thermosetting polyimide
film. The metal layer is formed directly thereon by sputtering or
plating. These methods, however, cannot provide sufficient
adhesiveness between the thermoplastic polyimide layer and the
metal layer.
[0006] Moreover, the two-layer FPC is generally required to have
(i) a high soldering heat resistance to cope with lead-free
soldering, and (ii) a dimensional stability to cope with high
density packaging. The laminating step for the laminate two-layer
FPC should utilize high temperature and high pressure because the
adhesive is made of polyimide having high melting point. The high
temperature and the high pressure deteriorate the dimensional
change ratio after etching and after heat treatment. Various
attempts have been made to attain better dimensional stability. For
Example, Patent Citation 1 discloses a method in which a surface of
a polyimide film is mechanically roughed before the polyimide film
is laminated with an adhesive and a copper. Moreover, Patent
Citation 3 discloses a copper-clad laminate that is developed to
cope with high temperature at lamination. The copper-clad laminate
of Patent Citation 3 uses a multi-layer polyimide film integrally
comprising a substrate polyimide layer that is low in heat
expansion, and a thin-layer polyimide on both sides of the
substrate polyimide layer, each thin-layer polyimide having
particular structure and Tg. The art disclosed in Patent Citation 3
is characterized in its step of providing an adhesive agent layer,
and in the adhesive agent layer itself. Thus, the art disclosed in
Patent Citation 3 does not provide a fundamental improvement in
dimensional stability and its dimensional stability remained
insufficient.
[0007] Patent Citation 1: Japanese Unexamined Patent Application
Publication, Tokukaihei, No. 6-232553
[0008] Patent Citation 2: Japanese Unexamined Patent Application
Publication, Tokukai, No. 2002-280684
[0009] Patent Citation 3: Japanese Unexamined Patent Application
Publication, Tokukai, No. 2003-71982
DISCLOSURE OF INVENTION
Technical Problems
[0010] The present inventions is accomplished in view of the
aforementioned problems. An object of the present invention is to
provide an adhesive sheet suitable for use in FPC that is
obtainable by laminating a copper foil and the adhesive sheet.
Especially, an object of the present invention is to provide an
adhesive sheet suitable for use in a laminate two layer FCCL in
which an insulating layer and the adhesive layer are made of
polyimides, and a copper-clad laminate using the same. That is, the
present invention is:
[0011] (1) An adhesive sheet comprising an insulating layer and an
adhesive layer on one or each side of the insulating layer, wherein
the insulating layer has a storage elasticity modulus ratio E'2/E'1
of 0.2 or less where E'1 is a storage elasticity modulus at
25.degree. C. and E'2 is a storage elasticity modulus at
380.degree. C., the insulating layer has a coefficient of thermal
expansion in the MD direction in a range of 5 to 15 ppm from
100.degree. C. to 200.degree. C., and a change in the coefficient
of thermal expansion of the adhesive sheet from 100.degree. C. to
250.degree. C. is 2.5 ppm or less in a tension direction in which
the tension is applied, and a change in the coefficient of thermal
expansion of the adhesive sheet from 100.degree. C. to 250.degree.
C. is 10 ppm or less in a direction perpendicular to the tension
direction, where the change in the coefficient of thermal expansion
is calculated by Equation (1):
Change in Coefficient of Thermal Expansion=|(First Measured Value
of Coefficient of Thermal Expansion)-(Second Measured Value of
Coefficient of Thermal Expansion)| (1)
where the measurements are carried out with the adhesive sheet that
has been heat-treated at a temperature of 380.degree. C. for 30 sec
under tension of 20 kg/m.
[0012] (2) The laminate adhesive sheet as set forth in (1) wherein
a peak top temperature of tan .delta. in measuring dynamic
viscoelasticity of the insulating layer is in a range of 300 to
400.degree. C., and tan .delta.>0.1.
[0013] (3) The adhesive sheet as set forth in (1) or (2), wherein
the insulating layer is a polyimide layer.
[0014] (4) The adhesive sheet as set forth in (3), wherein raw
materials of the polyimide layer include
2,2-bisaminophenoxyphenylpropane by 10 to 50 mol %,
p-phenylenediamine by 30 to 60 mol %, and an oxydianiline by 10 to
30 mol % with respect to a diamine component.
[0015] (5) The adhesive sheet as set forth in (4), wherein the
oxydianiline is 3,4'-oxydianiline.
[0016] (6) The adhesive sheet as set forth in (3) to (5) wherein
the raw materials of the polyimide layer includes pyromellitic
dianhydride by 60 to 95 mol %, and
3,3',4,4'-benzophenonetetracarboxylic dianhydride and/or
3,3',4,4'-biphenyltetracarboxylic dianhydride by 5 to 40 mol % with
respect to an acid dianhydride component.
[0017] (7) The adhesive sheet as set forth in (1) to (6), wherein
the adhesive layer contains a polyimide-based adhesive.
[0018] (8) The adhesive sheet as set forth in (1) to (7), wherein
the adhesive layer contains a straight-chained thermoplastic
polyimide and/or a 3-dimensionally crosslinking polyimide.
[0019] (9) The adhesive sheet as set forth in (1) to (8), wherein
the adhesive sheet is used after being laminated with a metal layer
on one or each adhesive layer by applying heat and pressure.
[0020] (10) A two-layer copper-clad laminate prepared by laminating
a metal conductive foil on one or each side of adhesive sheet as
set forth in (1) to (9) by applying heat and pressure.
Technical Solution
[0021] As a result of diligent studies to attain the object, the
inventors of the present invention found that an adhesive sheet
having particular properties makes it possible to produce a CCL
(Copper-Clad Laminate) with a high dimensional stability. The
present invention is accomplished based on the finding.
EFFECT OF INVENTION
[0022] The present invention makes it possible to produce a CCL
with a high dimensional stability. More specifically, the high
dimensional stability thus attained makes it possible to cope with
finer wiring pattern and multi-layered structure required for
high-density packaging. Moreover, the present invention solves the
low adherability problem associated with the use of thermoplastic
polyimide as an adhesive. Thus, the present invention makes it
possible to cope with a higher reflow temperature required by
lead-free soldering.
BEST MODE FOR CARRYING OUT THE INVENTION
[0023] (Property of Adhesive Sheet of Present Invention)
[0024] An adhesive sheet of the present invention includes an
insulating layer and an adhesive layer on one or each side of the
insulating layer. By specifying the properties of the insulating
layer and adhesive sheet, it is possible to suppress a dimensional
change that occurs in a step of producing a CCL by applying heat
and pressure on the adhesive sheet and a metal foil. More
specifically, the inventors of the present invention considers that
(1) storage elasticity modulus of the insulating layer, (2)
coefficient of thermal expansion of the insulating layer, and (3)
coefficient of thermal expansion of the adhesive sheet are
important. As a result of diligent works, the inventors of the
present invention found that it is possible to produce a CCL
excellent in dimensional stability by appropriately designing the
adhesive sheet in these values (1) to (3).
[0025] To begin with, the storage elasticity modulus of the
insulating layer is specified in the present invention. It is
important that E'2/E'1 be 0.2 or less, where E'1 is a storage
elasticity modulus at 25.degree. C. and E'2 is a storage elasticity
modulus at 380.degree. C. The reasons why the storage elasticity
modulus at 25.degree. C. and storage elasticity modulus at
380.degree. C. are used as the indicators are as follows. Firstly,
the inventors of the present invention found that the adhesive
sheet needs a high elasticity around room temperatures in order to
reduces influences of tension that would occur in processing the
adhesive sheet. Secondly, the inventors of the present invention
found that the adhesive sheet needs a low elasticity modulus at a
processing temperature in order to alleviate distortion that would
occur in laminating the adhesive sheet. The ratio of the storage
elasticity modulus can be an indicator to show how much the resin
will be softened in heating, that is, in laminating. The resin
smaller in the ratio of the storage elasticity modulus is easier to
be softened. In the present invention, the ratio is preferably 0.2
or less, more preferably not less than 0.04 but not more than 0.2,
and especially not less than 0.06 but not more than 0.18. If the
ratio is above the range, the dimensional stability will be poor.
If the ratio is below the range, the dimensional stability will be
improved but it will become difficult to perform continuous film
formation. The storage elasticity modulus can be worked out from
dynamic viscoelasticity.
[0026] In the present invention, a coefficient of thermal expansion
in an MD direction (machine direction to transfer the sheet) is
also specified. The coefficient of thermal expansion in the MD
direction from 100.degree. C. to 200.degree. C. is in a range of 5
to 15 ppm in the present invention. If the insulating layer has a
coefficient of thermal expansion in the MD direction above the
range, the adhesive sheet cannot be designed to have an adhesive
agent layer with a sufficient thickness. This will make it
impossible to secure tight adhesion between the adhesive sheet and
a metal conductive foil. If the insulating layer has a coefficient
of thermal expansion in the MD direction below the range, the
dimensional stability in fully etching the CCL will be poor.
[0027] While the present invention designs the insulating layer
such that the storage elasticity modulus and the coefficient of
thermal expansion satisfy the ranges, the properties of the
insulating layer can be worked out from the CCL. That is, the
coefficient of thermal expansion of the insulating layer in the CCL
may be measured by I) measuring the coefficient of thermal
expansion of the insulating layer isolated from the CCL by etching
away the metal layer and adhesive agent layer, II) a coefficient of
thermal expansion of the insulating layer isolated from the CCL by
physically removing the adhesive agent layer completely by using a
knife or the like, or (III) the like method.
[0028] Furthermore, the coefficient of thermal expansion of the
adhesive sheet is specified in the present invention. The
coefficient of thermal expansion of the adhesive sheet is measured
after treating the adhesive sheet with a temperature of 380.degree.
C. for 30 seconds under tension of 20 kg/m. The tension of 20 kg/m
is applied in the measurement because the application of such a
tension simulates distortion that would occur in the adhesive sheet
in the step of processing. The heat of 380.degree. C. is applied
for 30 seconds in the measurement, because such heat application
certainly preserve the distortion in the adhesive sheet. Moreover,
specified is an absolute value of a difference between a first
measured value of the coefficient of thermal expansion and a second
measured value of the coefficient of thermal expansion, because the
absolute value indicates a degree of releasing accumulated
distortion.
Change in Coefficient of Thermal Expansion=|(First Measured Value
of Coefficient of Thermal Expansion)-(Second Measured Value of
Coefficient of Thermal Expansion)| (1)
The change in the coefficient of thermal expansion of the adhesive
sheet from 100.degree. C. to 250.degree. C. is measured according
to Equation 1. The change in the coefficient of thermal expansion
of the adhesive sheet from 100.degree. C. to 250.degree. C. is 2.5
ppm or less, preferably 2 ppm or less in the direction in which the
tension is applied (this direction is the MD direction in general).
Meanwhile, the change in the coefficient of thermal expansion of
the adhesive sheet from 100.degree. C. to 250.degree. C. is 10 ppm
or less, and preferably 8 ppm or less in a direction perpendicular
to the application of the tension (this direction is the TD
direction in general). If the change in the coefficient of thermal
expansion of the adhesive sheet was above the range, the
dimensional change in heating the CCL at 250.degree. C. after fully
etching the CCL would be extremely large.
[0029] There is no particular limitation in sheet size, heat
treatment method, etc. for the heat treatment of 380.degree. C. for
30 seconds under tension of 20 kg/m, provided that the tension is
kept being applied until the heat-treated sample is cooled down to
room temperatures. Moreover, in case where the adhesive agent layer
is made of a thermally reactive adhesive agent such as polyimide,
the heat treatment may be utilized as the step of reacting the
thermally reactive adhesive agent. Moreover, the change in the
coefficient of thermal expansion of the adhesive sheet of the
present invention may be measured by measuring a pre-lamination
adhesive sheet thus heat-treated, or measuring an adhesive sheet
thus heat-treated after completely removing an electrically
conductive layer from a post-lamination adhesive sheet.
[0030] A special care must be paid in case where a 3-dimensional
cross-linking type adhesive agent is used. To be measured in the
manner mentioned above, the reaction in the adhesive agent layer
must be completed or proceeded to such an extent that the adhesive
agent layer become practically usable. Thus, in this case it is
preferable to measure an adhesive sheet thus heat-treated after
completely removing an electrically conductive layer from a
post-lamination adhesive sheet
[0031] The property of the adhesive sheet can be confirmed by
testing a CCL from which the conductive layer is removed by, e.g.,
etching.
[0032] One preferable embodiment of the present invention is
described below. It is preferable that a peak top temperature of
tan .delta. in measuring dynamic viscoelasticity of the insulating
layer be in a range of 300 to 400.degree. C. It is especially
preferable that the peak top temperature of tan .delta. in
measuring dynamic viscoelasticity of the insulating layer be in a
range of 320 to 370.degree. C. It is preferable that tan
.delta.>0.1. If the peak top temperature of tan .delta. was
below the range, the insulating layer would have a glass transition
temperature of less than 250.degree. C. and accordingly become poor
in the heat resistance. If the peak top temperature of tan .delta.
was above the range, this would result in a large dimensional
change in heating. If tan .delta..ltoreq.0.1, the softening around
the process temperature would tend to be insufficient to alleviate
the distortion.
[0033] There has been no adhesive sheet satisfying all the
properties. The inventors of the present invention firstly found
such an adhesive sheet and confirmed its effect.
[0034] (Insulating Layer of Adhesive Sheet of Present
Invention)
[0035] The insulating layer of the present invention may be made of
any organic material having an excellent insulating property, such
as polyimide, polyamideimide, polyester, polyamide, liquid crystal
polymers, etc. Among them, polyimide and liquid crystal polymers
are preferable to use, considering heat resistance.
[0036] The polyimide to be used as the insulating layer of the
present invention is prepared from a polyamic acid as a precursor.
The polyamic acid may be produced by any methods known as methods
for producing polyamic acid. In general, an aromatic dianhydride
and an aromatic diamine in substantially equimolar amounts are
dissolved in an organic solvent thereby to prepare a solution in
which the polyamic acid is dissolved in the organic solvent. The
solution is stirred under controlled temperature condition until
polymerization of the acid dianhydride and the diamine is
completed. In this way, the polyamic acid is prepared. The polyamic
acid solution is obtained at a concentration generally in a range
of 5 to 35 wt %, and preferably in a range of 10 to 30 wt %. The
polyamic acid solution in this range has an appropriate molecular
weight and appropriate solution viscosity.
[0037] Various known processes and combinations of these processes
may be employed as the polymerization process. The key feature of
the polymerization process for producing polyamic acid is the order
of adding the monomers. The properties of the resulting polyimide
are adjusted by controlling the order of adding the monomers. Thus,
in the present invention, any process of adding monomers may be
employed for producing the polyamic acid. Representative examples
of the polymerization processes are as follows:
[0038] 1) After the aromatic diamine is dissolved in an organic
polar solvent, the aromatic tetra carboxylic dianhydride in an
amount substantially equimolar to the aromatic diamine is added
thereto and then the aromatic diamine and the aromatic tetra
carboxylic dianhydride are reacted for polymerization.
[0039] 2) The aromatic tetra carboxylic dianhydride and the
aromatic diamine compound (in an amount less in mole than the
aromatic tetra carboxylic dianhydride) are reacted with each other
in the organic polar solvent in order to obtain a solution of a
prepolymer in the organic polar solvent, the prepolymer having an
acid anhydride group on both ends. Next, to the solution of the
prepolymer, an aromatic diamine compound is added in an amount that
makes up the equimolar amount of aromatic diamine compound in an
overall process with respect to the aromatic tetra carboxylic
dianhydride. Then polymerization is carried out.
[0040] 3) The aromatic tetra carboxylic dianhydride and the
aromatic diamine compound (in an amount greater in mole than the
aromatic tetra carboxylic dianhydride component) are reacted with
each other in the organic polar solvent, thereby to obtain a
solution of a prepolymer in the organic polar solvent, the
prepolymer having an amino group on both ends. Next, to the
solution of the prepolymer, aromatic diamine compound is further
added and then an aromatic tetra carboxylic dianhydride is added in
an amount that makes up the equimolar amount of the aromatic tetra
carboxylic dianhydride in an overall process with respect to the
aromatic diamine compound. Then polymerization is carried out.
[0041] 4) After the aromatic tetra carboxylic dianhydride is
dissolved and/or dispersed in the organic polar solvent, the
aromatic diamine compound in an amount substantially equimolar to
the aromatic tetra carboxylic dianhydride is added thereto and then
the aromatic tetra carboxylic dianhydride and the aromatic diamine
compound are reacted for polymerization.
[0042] 5) The aromatic tetra carboxylic dianhydride and the
aromatic diamine in substantially equimolar amounts are dissolved
in the organic polar solvent and reacted for polymerization.
[0043] These methods may be employed solely or partially in
combination. The method for producing the polyimide film is
described, referring to a case where the insulating layer is used
as a polyimide film by way of example.
[0044] The polyimide film may be produced from these polyamic acid
solutions in any conventionally known methods, which encompass
thermal imidization method and chemical imidization method. Either
method may be employed to produced the film. However, the chemical
imidization method may be more easy to obtain a polyimide film
having the various properties that are preferable in the present
invention.
[0045] In the present invention, it is especially preferable that
the production process of the polyimide film include:
[0046] a) reacting an aromatic diamine and an aromatic
tetracarboxylic dianhydride in an organic solvent, so as to obtain
a polyamic acid solution;
[0047] b) flow-casting, on a support, a film formation dope
containing the polyamic acid solution;
[0048] c) heating the film formation dope on the support and
removing a gel film from the support; and
[0049] d) further heating the gel film so as to imidize residual
amic acid and dry the gel film.
[0050] In the above process, a curing agent containing a
dehydrating agent or an imidization catalyst. Typical examples of
the dehydrating agent include acid anhydrides such as acetic
anhydride. Typical examples of the imidization catalyst include
tertiary amines such as isoquinoline, .beta.-picoline, pyridine,
etc.
[0051] In the following, a preferable embodiment is described to
explain the production process of the polyimide film. In the
embodiment, the chemical imidization is explained for example. It
should be noted that the present invention is not limited to the
following arrangement descried by way of example, and the film
formation condition and heating condition may be varied as
appropriate according to the kinds of the polyamic acid, film
thickness, etc.
[0052] The dehydrating agent and imidization catalyst may be added
into the polyamic acid solution at a low temperature thereby to
prepare a film formation dope. Then, the film formation dope is
cast on a support such as a glass board, an aluminum foil, endless
stainless-steel belt, stainless-steel drum, or the like, thereby
forming a film thereof on the support. The film on the support is
heated in a temperature in arrange of 80.degree. C. to 200.degree.
C., preferably in a range of 100.degree. C. to 180.degree. C. in
order to activate the dehydrating agent and the imidization
catalyst. Thereby, the film is partially cured and/or dried. Then,
the film is removed from the support thereby obtaining a polyamic
acid film (hereinafter this film is referred to as a gel film).
[0053] The gel film is in an intermediate state in the curing of
the polyamic acid to the polyimide. The gel film is a
self-supportive film. A volatile content of the gel film is
expressed as formula (2):
(A-B).times.100/B (2)
where A is a weight of the gel film, and B is a weight of the gel
film after heated at 450.degree. C. for 20 min.
[0054] The volatile content of the gel film is in a range of 5 to
500 wt. %, preferably in a range of 5 to 200 wt. %, and more
preferably in a range of 5 to 150 wt. %. It is preferable to use a
film in these ranges. In a baking process, there is a risk of film
breakage, lack of uniformity in color tone of the film due to
unevenly drying the film, and property variation, etc.
[0055] The amount of the dehydrating agent is in a range of 0.5 to
5 mol, and preferably in a range of 1.0 to 4 mol per unit of amic
acid in the polyamic acid. Moreover, the amount of the imidization
catalyst is in arrange of 0.05 to 3 mol, and preferably in a range
of 0.2 to 2 mol per unit of amic acid in the polyamic acid.
[0056] The chemical imidization would be insufficient when the
amounts of the dehydrating agent and imidization catalyst are below
the ranges. The insufficient chemical imidization would results in
the film breakage during the baking or low mechanical strength. On
the other hand, the imidization would proceed too fast when the
amounts of the dehydrating agent and imidization catalyst are above
the ranges. The too-fast imidization would make it difficult to
cast the solution into the film-like shape.
[0057] The gel film held at its ends is dried. By being held at its
ends, the gel film can avoid the shrinkage due to the curing. The
drying removes water, residual solvent, residual converting agent,
and catalyst from the film, and completes the imidization of the
residual amic acid. Thereby, the polyimide film of the present
invention can be obtained.
[0058] The drying is preferably carried out at a temperature in a
range of 400 to 650.degree. C. for a time period in a range of 5 to
400 sec. Drying carried out at a temperature higher than the range
and/or for a time period longer than the range would possibly cause
thermal deterioration in the film. On the other hand, drying
carried out at a temperature lower than the range and/or for a time
period shorter than the range would possibly fail to attain the
desired effect.
[0059] Moreover, the heat treatment of the film may be carried out
with the film stretched at a lowest tension necessary for conveying
the film. This lowers an internal stress remained in the film. The
heat treatment may be carried out during the film production
process, or may be carried out in addition to the process. The
heating condition cannot be specified because the heating condition
varies depending on film property or apparatus to use. The internal
stress can be alleviated by heating at a temperature generally not
less than 200.degree. C. but not more than 500.degree. C.,
preferably not less than 250.degree. C. but not more than
500.degree. C., especially preferably not less than 300.degree. C.
but not more than 450.degree. C., for a time period in a range of 1
to 300 sec, preferably in a range of 2 to 250 sec, and especially
preferably in a range of 5 to 200 sec.
[0060] Moreover, the film may be stretched before or after the
fixing the gel film to the frame. For this stretching, the film has
a volatile content in a range of 100 to 500 wt. %, and preferably
in a range of 150 to 500 wt. %. Volatile content below the range
would make it difficult to extend the film. Volatile content above
the range causes the film to be poor in self-supporting property,
which makes it difficult the stretching operation.
[0061] The stretching operation may be carried out by using any
known method, encompassing a method using differential rollers are
used, a method widening a gap of a tenter, etc.
[0062] Moreover, in case where the polyimide-based adhesive agent
is used as the adhesive agent layer, the adhesive agent layer and
the insulating layer are formed concurrently by using die or the
like for a multi-layer concurrent extrusion.
[0063] Described below are monomers from which the polyimide film
usable as the insulating layer of the present invention is
produced. In the present invention, a diamine component preferably
include 2,2-bisaminophenoxyphenylpropane and/or p-phenylenediamine.
In general, the use of the p-phenylenediamine in a greater amount
tends to increase the elasticity modulus and storage elasticity
modulus and tan .delta. peak top temperature, while lowering the
coefficient of thermal expansion. Meanwhile, the use of
2,2-bisaminophenoxyphenylpropane in a greater amount lowers the
elasticity modulus and storage elasticity modulus while increasing
the coefficient of thermal expansion. The use of
2,2-bisaminophenoxyphenylpropane in a greater amount also decreases
water absorption and increases adherability. The use of an
oxydianiline in combination therewith tends to increase the
adherability further. Thus, it is preferable to use oxydianiline in
addition. In the case where the oxydianiline is also used, it is
preferable for easy balancing the coefficient of thermal expansion
that the diamine component contain 2,2-bisaminophenoxyphenylpropane
by 10 to 50 mol %, p-phenylenediamine by 30 to 60 mol %, and the
oxydianiline by 10 to 30 mol %.
[0064] Examples of oxydianiline encompass 4,4'-oxydianiline,
3,4'-oxydianiline, 3,3'-oxydianiline, 2,4'-oxydianiline, and so on.
Among these, 3,4'-oxydianiline is preferable, because the use of
3,4'-oxydianiline tends to make it easier to attain the object. The
use of the diamine component as described above by way of example
makes it easier to adjust the storage elasticity modulus ratio
E'2/E'1 and the coefficient of thermal expansion in the MD
direction from 100.degree. C. to 200.degree. C.
[0065] As an acid component, it is preferable to use pyromellitic
dianhydride and 3,3'4,4'-benzophenonetetracarboxylic dianhydride. A
preferable ratio to use them is such that pyromellitic dianhydride
is in a range of 60 to 95 mol %, and
3,3'4,4'-benzophenonetetracarboxylic dianhydride is in a range of 5
to 40 mol %. If the ratio was out of the range, the adhesion
strength would be lowered, or the coefficient of thermal expansion
would be too large. The use of the acid dianhydride component
described above by way of example makes it easier to adjust the
storage elasticity modulus ratio E'2/E'1 and the coefficient of
thermal expansion in the MD direction from 100.degree. C. to
200.degree. C.
[0066] Example 1 of Japanese Unexamined Patent Application
Publication, Tokukai, No. 2000-80178 describes a polyimide film
having the preferable composition of the present invention. Example
1 of Japanese Unexamined Patent Application Publication, Tokukai,
No. 2000-80178 is silent as to an adhesive film and its property. A
film was prepared according to Example 1 of Japanese Unexamined
Patent Application Publication, Tokukai, No. 2000-80178, and
properties of the adhesive film thus prepared were measured. This
proved that the properties of the adhesive film prepared according
to Example 1 of Japanese Unexamined Patent Application Publication,
Tokukai, No. 2000-80178 were out of the range of the present
invention.
[0067] Any solvents in which the polyimide precursor (hereinafter,
referred to as the polyamic acid) is soluble can be preferably used
as the solvent for the synthesis of the polyamic acid. Amide-based
solvents, such as N,N-dimethylformamide, N,N-dimethylacetoamide,
N-methyl-2-pyrorridone, may be used as the solvent. Especially,
N,N-dimethylformamide, and N,N-dimethylacetoamide are
preferable.
[0068] Moreover, the polyamic acid, which is the precursor of the
polyimide of the present invention, may be prepared by any
polymerization method such as these polymerization methods (1) to
(5) mentioned above by way of example. However, it is preferable to
prepare the polyamic acid by the following polymerization method,
in order to make it easier to control the storage elasticity
modulus ratio E'2/E'1 and the coefficient of thermal expansion in
the MD direction from 100.degree. C. to 200.degree. C. in the
polyimide film finally obtained. The preferable polymerization
method includes the steps of:
[0069] (A) reacting the aromatic dianhydride component and the
aromatic diamine component in an organic polar solvent in such a
manner that either the aromatic dianhydride component or the
aromatic diamine component is greater in molar amount than the
other, so as to obtain a flexible prepolymer having an amino group
or an acid dianhydride group on both ends.
[0070] (B) synthesizing a polyamic acid solution from the
prepolymer obtained in Step (A), an acid anhydride component, and a
diamine component in such an amount to make up substantially
equimolar amounts of the acid anhydride component, and the diamine
component, wherein the diamine component used in Step (A) and acid
anhydride component are selected such that an equimolar reaction of
the diamine component and acid anhydride component will produce a
thermoplastic polyimide, and the polyamic acid obtained in Step (B)
is a precursor of a non-thermoplastic polyimide.
[0071] To obtained the polyimide film, it is preferable to
flow-cast, on a support, a film formation dope solution containing
the polyamic acid solution, and then perform chemical and/or
thermal imidization for the film formation dope solution. As
described above, the block component derived from the thermoplastic
polyimide is prepared in Step (A). In the present invention, the
"block component derived from the thermoplastic polyimide" is such
a block component that a film made from a polymer prepared
therefrom will melt by heat application of a temperature in a range
of 250 to 500.degree. C., thereby losing its film shape. More
specifically, the diamine component and the acid anhydride
component are selected by checking whether a polyimide prepared
from an equimolar reaction of the diamine component and acid
anhydride component is melt at the temperature or lose its film
shape. Moreover, judging whether the polyimide is the
non-thermoplastic or not may be carried out by heating a film
thereof to a temperature approximately in a range of 450 to
500.degree. C. and checking whether or at the temperature it does
not melt to lose its film shape. If the film shape is maintained,
it would be judged that it is non-thermoplastic.
[0072] With the arrangement in which the size of the block
component derived from the thermoplastic polyimide is adjusted and
the polyamic acid obtained in Step (B) is non-thermoplastic, it
becomes easier to adjust the storage elasticity modulus ratio
E'2/E'1, the coefficient of thermal expansion in the MD direction,
the peak top temperature of tan .delta., and tan .delta..
Especially, by using, in combination, the diamine component and the
acid anhydride component mentioned above by way of example, it
becomes much easier to control the storage elasticity modulus ratio
E'2/E'1, the coefficient of thermal expansion coefficient in the MD
direction, the peak top temperature of tan .delta., and tan
.delta..
[0073] Depending on the kind of monomers to use, the kind of
polymerization method to adopt, and differences in film formation
conditions, and combinations thereof, the polyimide film of the
present invention will be varied in storage elasticity modulus
ratio E'2/E'1, the coefficient of thermal expansion in the MD
direction, the peak top temperature of tan .delta., and tan
.delta.. However, these property values can be easily measured.
Thus, a desired film may be designed through checking properties of
films prepared considering the above-described tendencies.
[0074] Moreover, a filler may be added in order to attain better
film properties such as slidability, heat conductivity, electric
conductivity, corona resistance, loop stiffness, etc. Any kind of
filler may be used. Preferable examples of the filler encompass
silica, titanium oxide, alumina, silicon nitride, boron nitride,
dibasic calcium phosphate, calcium phosphate, mica, and the
like.
[0075] The diameter of the filler particles may be determined based
on the film properties to be modified and the type of filler, and
is thus not particularly limited. The average particle diameter is
usually 0.05 to 100 .mu.m, preferably 0.1 to 75 .mu.m, more
preferably 0.1 to 50 .mu.m, and most preferably 0.1 to 25 .mu.m.
When the average diameter is below this range, the effect of
modification is not readily exhibited. At an average diameter
beyond this range, the surface quality and/or the mechanical
properties may be significantly degraded. The amount of the filler
to be added is determined based on the film properties to be
modified and the diameter of the filler particles and is thus not
particularly limited. The amount of the filler added is usually
0.01 to 100 parts by weight, preferably 0.01 to 90 parts by weight,
and more preferably 0.02 to 80 parts by weight per 100 parts by
weight of polyimide. At a filler content below this range, the
effect of the modification by the use of the filler may not be
sufficiently exhibited. At a filler content beyond this range, the
mechanical properties of the film may be significantly
degraded.
[0076] The filler may be added by any method. The examples of the
method include:
[0077] 1. Method of adding the filler to the polymerization
solution before or during the polymerization;
[0078] 2. Method of adding and kneading the filler into the
polymerization solution with a three-shaft roller after completion
of the polymerization; and
[0079] 3. Method including preparing a dispersion liquid containing
the filler in advance and adding the dispersion liquid into a
polyamic acid organic solvent solution.
[0080] Any method may be employed for the addition of the filler.
However, the method including preparing a dispersion liquid
containing the filler in advance and adding (especially right
before the film formation) the dispersion liquid into a polyamic
acid organic solvent solution is preferable because contamination
of the production line with the filler in this method is least
severe. In the preparation of the dispersion liquid, it is
preferable to use the same solvent as the polymerization solvent of
the polyamic acid. In order to sufficiently disperse the filler and
stabilize the dispersion state, a dispersant, a thickener, or the
like may be used in amounts that do not adversely affect the
properties of the film.
[0081] (Adhesive Layer of Adhesive Sheet of Present Invention)
[0082] Any kind of adhesive layer may be adopted in the present
invention. Considering the heat resistance, it is preferable to use
a polyimide-type adhesive agent, especially, a strain-chained
thermoplastic polyimide and/or a 3-dimensional crosslinking
polyimide. Especially, the use of the 3-dimensional crosslinking
polyimide significantly improves solder heat resistance. In case
where the straight-chained thermoplastic polyimide is used, the
adhesiveness and lamination processability can be improved by
controlling molecular weight by using an end terminator such as
phthalic acid compound, aniline-based compound, or the like. In
case where the 3-dimensional cross-linking polyimide is used, it is
preferable to use an end terminator having an acetylene group or
vinyl group. For example, ethynyl phthalic acid compound, phenyl
ethynyl phthalic acid compound, amino styrene, nasic acid compound,
chlorendic acid compound, maleic acid compound, or the like may be
used.
[0083] The polyamic acid used in the present invention, which is
the precursor of the thermoplastic polyimide, is not particularly
limited and any polyamic acid may be used in the present invention.
The polyamic acid solution may be produced with the raw materials,
the production conditions, etc. described above.
[0084] The properties can be adjusted by variously combining the
raw materials to be used. In general, a greater ratio of a diamine
having a rigid structure will increase the glass transition
temperature and/or increases storage elastic modulus at heating.
Accordingly, the adhesiveness and processability will be poor.
Thus, a greater ratio of the diamine having a rigid structure is
not preferable. The ratio of a diamine having a rigid structure is
preferably 40 mol % or less, more preferably 30 mol % or less, and
especially preferably 20 mol % or less. Moreover, an inorganic or
organic filler may be added if necessary. the filler may be added
in the same way as described above.
[0085] The adhesive layer may be prepared from the polyamic acid
solution in any method. For example, the adhesive layer may be
formed by flow-casting the polyamic acid solution on the polyimide
film and/or a metal foil, and then performing drying and
imidization. The adhesive layer may be formed by flow-casting the
polyamic acid solution on a PET film or the like, and transferring
the flow-cast on the polyimide film or metal foil. A thermoplastic
polyimide film may be formed and used as an adhesive film, thereby
providing the adhesive layer. The adhesive layer and the insulating
layer may be formed concurrently by concurrent multi-layer
extrusion etc. A polymer blend in which another resin is dissolved
in the polyamic acid solution may be used. The formation of the
adhesive layer is described below, discussing, by way of example,
the method in which the adhesive layer is formed by flow-casting
the polyamic acid solution on the polyimide film and/or a metal
foil, and then performing drying and imidization.
[0086] The flow-casting to apply the polyamic acid on the polyimide
film can be performed in any way, and performed by any conventional
method, such as using die coater, reverse coater, blade coater, or
the like. The thickness of the coating of the polyamic acid
solution is not particularly limited, and can be adjusted as
appropriate according to usage. However, too thick coating would
easily cause some problems such as low productivity due to a need
of a long curing time. Thus, it is preferable that the polyamic
acid solution is coated such that the thickness of the coating will
be 10 .mu.m or less after the imidization.
[0087] In general, the polyimide is produced by imidizing the
polyamic acid, which is the precursor thereof. The imidization is
carried out thermally and/or chemically. Examples of a dehydrating
agent for use in the chemical imidization encompass aliphatic
anhydrides, aromatic acid anhydrides, N,N'-dialkylcarbodiimides,
low alcohol halides, low aliphatic acid anhydride halides, aryl
phosphoric dihalides, thionyl halide, and mixtures of two or more
of them. For high availability and low cost, aliphatic acid
anhydrides such as aceticanhydride, propionic anhydride, lactic
anhydride, etc. and mixtures of two or more of them are preferable
among these dehydrating agents.
[0088] Moreover, examples of an imidization catalyst encompass
aliphatic tertiary amines, aromatic tertiary amines, heterocyclic
tertiary amines, etc. For high reactivity as a catalyst, it is
especially preferable to use a catalyst selected from among the
heterocyclic tertiary amines. Typical examples of such imidization
catalyst include tertiary amines such as quinoline, isoquinoline,
.beta.-picoline, pyridine, etc. Regardless of which method is
adopted, heating is necessary for the imidization and/or drying. A
higher heating temperature is preferable in terms of productivity
because it facilitates and speeds up the imidization. However, if
the heating temperature is too high, it would possibly cause
thermolysis of the thermoplastic polyimide.
[0089] A too low heating temperature makes it difficult to proceed
the imidization and prolongs the step of performing the
imidization. For the thermal imidization, the heating temperature
is preferably in a range of the glass transition temperature of the
thermoplastic polyimide to a temperature higher than the glass
transition temperature of the thermoplastic polyimide by
200.degree. C., more preferably in a range of a temperature higher
than the glass transition temperature of the thermoplastic
polyimide by 50.degree. C. to a temperature higher than the glass
transition temperature of the thermoplastic polyimide by
150.degree. C. Imidization period should be sufficient for
substantially completing the imidization and drying, and but cannot
be varied appropriately. In general, the imidization period is set
as appropriate within a range of 1 to 600 seconds.
[0090] Moreover, the flowability of the adhesive layer when the
adhesive layer is melted may be improved by intentionally keeping
imidization ratio low and/or by intentionally remaining the
solvent.
[0091] Tension to be applied during the imidization is preferably
in a range of 1 kg/m to 20 kg/m, and more preferably in a range of
5 kg/m to 15 kg/m. A tension below the range would lead to sagging
during transportation. Such sagging would be a problem in the film
winding. On the other hand, a tension above the range would be too
high not to be influential on the dimensional change even if the
metal foil is used.
[0092] The present invention specifies the coefficient of thermal
expansion of the adhesive film after heat-treated at 380.degree. C.
for 30 seconds under tension application of 20 kg/m. The adhesive
film is designed to be such that the change in the coefficient of
thermal expansion from 100.degree. C. to 250.degree. C., which is
calculated out in Equation (1) below, is 2.5 ppm or less in the
tension direction, and 10 ppm or less in the direction
perpendicular to the tension direction. To be such that the
adhesive film is designed to have (i) a polyimide film whose
storage elasticity modulus ratio E'2/E'1 is 0.2 or less, and whose
coefficient of thermal expansion in the MD direction from 100 to
200.degree. C. is in a range of 5 to 15 ppm, and (ii) the adhesive
layer controlled in composition and thickness. Equation (1) for
calculating out the change in the coefficient of thermal expansion
from 100.degree. C. to 250.degree. C. is as follows:
Change in Coefficient of Thermal Expansion=|(First Measured Value
of Coefficient of Thermal Expansion)-(Second Measured Value of
Coefficient of Thermal Expansion)| (1)
[0093] The value calculated out by Equation (1) can be worked out
by measuring the coefficient of thermal expansion. Adhesive films
are prepared and tested to work out the change in the coefficient
of thermal expansion, thereby determining final design of the
adhesive film whose change in the coefficient of thermal expansion
is 2.5 ppm or less in the tension direction and 10 ppm or less in
the direction perpendicular to the tension direction. The inventors
of the present invention are first to find out that the designing
the adhesive film considering the change in the coefficient of
thermal expansion can reduce the dimensional change in the
production process of the FCCL.
[0094] (Metal Layer)
[0095] There is no particular limitation as to the metal layer for
use in the present invention. To apply a flexible metal-clad
laminate according to the present invention in electronic apparatus
and electric apparatus, the metal foil may be, for example, copper,
copper alloy, stainless steel or alloy thereof, nickel or nickel
ally (including 42 alloy), or aluminum or aluminum alloy. The
present invention can preferably employ rolled copper foil or
electrolytic copper foil, which is widely used in general flexible
metal-clad laminate. Moreover, anti-corrosive layer, heat resistant
layer, or adhesive layer may be provided on a surface of the metal
foil.
[0096] In the present invention, the metal foil is not particularly
limited as to its thickness, provided that the metal foil with the
thickness can sufficiently function for the usage to which it is
applied. In generally, for example, the thickness of the metal foil
is preferably in a range of 1 to 35 .mu.m, more preferably in a
range of 2 to 25 .mu.m, and especially preferably in a range of 3
to 18 .mu.m. A thickness thinner than the range would easily cause
defective connection or low connection reliability in mounting on
various substrates in which an anisotropic electrically conductive
film or the like is used. A thickness thicker than the range would
make it difficult to form fine wiring. Moreover, it may be arranged
such that the lamination is carried out with the metal foil of a
thicker thickness and then the thickness of the metal foil is
thinned by a known method such as etching or the like.
[0097] (CCL Production)
[0098] The adhesive sheet of the present invention may be adhered
together with the metal foil, for example, by continuous process
using (i) a heat roll laminating apparatus having one pair or pairs
of metal rolls or (ii) double belt press (DBP). Of them, the use of
the heat roll laminating apparatus having one pair or pairs of
metal roll is preferable due to its simple apparatus structure and
low maintenance cost. The dimensional change easily occur in the
lamination with the metal foil performed by using the heat roll
laminating apparatus having one pair or pairs of metal roll. Thus,
the polyimide film and the adhesive film of the present invention
is significantly advantageous in such a lamination. The "heat roll
laminating apparatus having one pair or pairs of metal rolls" can
be any apparatus having metal rolls for heating and pressing a
material, and is not particularly limited as to its specific
apparatus arrangements.
[0099] Means for performing the thermal lamination is not
particularly limited as to its specific arrangements. It is
preferable to provide a protective material between the metal foil
and a pressuring surface in order to give a better outer appearance
to the laminate thus obtained. The protective material is not
limited to a particular material, provided that the protective
material can withstand against heating temperature of the thermal
lamination process. Heat resistant plastics such as
non-thermoplastic polyimide films and the like, and metal foils
such as copper foil, aluminum foil, SUS foil, and the like, and the
other material may be suitably employed as the protective material.
Among them, the non-thermoplastic polyimide film is more preferable
because it provides an excellent balance among the heat resistance,
reusability, and the other factors. Moreover, the non-thermoplastic
polyimide film is preferably 75 .mu.m or more in thickness, because
buffering and protection provided by a non-thermoplastic polyimide
film with too thin thickness will not be sufficient.
[0100] Moreover, the protective material is not limited to a single
layer and may have a multi-layer structure including two or more
layers having different properties.
[0101] The materials to be laminated may be heated in any way by
the thermal lamination means. For example, the thermal lamination
may adopt any heating means using conventionally known method that
can apply a predetermined temperature, such as heat circulation
method, hot air heating method, induction heating method, etc.
Similarly, the materials to be laminated may be pressured in any
way by the thermal lamination means. For example, the thermal
lamination may adopt any pressuring means using conventionally
known method that can apply a predetermined pressure, such as
hydraulic method, pneumatic method, gap-to-gap pressure method,
etc.
[0102] The heating temperature in the thermal lamination step, that
is, a lamination temperature is higher than the glass transition
temperature (Tg) of the adhesive layer preferably by 50.degree. C.
or more, and more preferably by 100.degree. C. or more. The
lamination temperature higher than the glass transition temperature
(Tg) of the adhesive layer preferably by 50.degree. C. or more can
attain good thermal lamination between the adhesive layer and the
metal foil. Moreover, The lamination temperature higher than the
glass transition temperature (Tg) of the adhesive layer preferably
by 100.degree. C. or more can increase lamination speed thereby
improving the productivity.
[0103] The lamination speed in the thermal lamination process is
preferably 0.5 m/min or higher, and more preferably 1.0 m/min or
higher. The lamination speed of 0.5 m/min or higher allows
sufficient thermal lamination while the lamination speed of 1.0
m/min or higher allows much better productivity.
[0104] The higher pressure (i.e., lamination pressure) in the
thermal lamination can allow the use of a lower lamination
temperature and a faster lamination speed. But too high lamination
pressure worsens the dimensional change of the laminate generally.
Moreover, too low lamination pressure results in a laminate in
which the metal foil is adhered with a low adhesion strength. Thus,
the lamination pressure is preferably in a range of 49 to 490N/cm
(5 to 50 kgf/cm) and more preferably in a range of 98 to 294N/cm
(10 to 30 kgf/cm). With the lamination pressure within these
ranges, the three conditions, namely, the lamination temperature,
the lamination speed, and the lamination pressure can be good and
the productivity can be further improved. As to tension to be
applied on the polyimide film during the lamination, the tension is
preferably in a range of 0.01 to 2 N/cm, more preferably 0.02 to
1.5N/cm, and especially preferably 0.05 to 1.0N/cm. Application of
a tension below the range will possibly make it difficult to attain
a CCL having a good outer appearance. Meanwhile, application of a
tension above the range tends to result in poor dimensional
stability.
[0105] To attain the flexible metal-clad laminate according to the
present invention, it is preferable to use a thermal lamination
apparatus by which the materials to be laminated are adhered by
pressure application while being continuously heated. Such a
thermal lamination apparatus may include, in an upstream of the
thermal lamination means, feeding means for feeding the materials
to be laminated, and may include, in a down stream of the thermal
lamination means, winding means for winding up the laminated
materials. By providing these means, the productivity of the
lamination apparatus is further improved. There is no particular
limitation as to specific arrangement of the feeding means and the
winding means. for example, a well-known roll-shaped winding
apparatus or the like, which can wind up the adhesive film, metal
foil, or the resultant laminate, may be adopted as the feeding
means or the winding means.
[0106] Furthermore, it is more preferable to provide winding means
for winding the protective material, or feeding means for feeding
the protective material. By providing the means for winding the
protective material and the means for feeding the protective
material, the protective material can be winded up after being
used, and provided to be refed. Thereby, the protective material
may be reused. Moreover, end-position detecting means and the
winding position correcting means may be provided in order to align
end sections of the protective material when the protective
material is wound. This makes it possible to wind the protective
material in a manner such that the end sections of the protective
material is precisely aligned. This makes it possible to increase
efficiency in reusing the protective material. There is no specific
limitation in arrangements of the means for winding up the
protective material, the means for feeding the protective material,
the end position detecting means, and the winding position
correcting means. Conventionally known various devices may be
employed as the means for winding up the protective material, the
means for feeding the protective material, the end position
detecting means, or the winding position correcting means.
[0107] In the CCL obtained by the present invention, a dimensional
changing ratio before and after the removal of the metal foil, and
a total value of a dimensional changing ratio before and after the
heat application of 250.degree. C. for 30 min after the removal of
the metal foil are very preferably within a range of -0.1 to +0.1
in both the MD direction and TD direction. The dimensional changing
ratio before and after the removal of the metal foil is expressed
by a ratio of a difference between predetermined dimensions of the
flexible metal-clad laminate before and after the etching step over
the predetermined dimension of the flexible metal-clad laminate
before the etching step. The dimensional changing ratio before and
after the heat application is expressed by a ratio of a difference
between predetermined dimensions of the flexible metal-clad
laminate before and after the heating step over the predetermined
dimension of the flexible metal-clad laminate before the heating
step.
[0108] The dimensional changing ratio of the range tends to result
in high defective fraction in mounting devices on the flexible
metal-clad laminate.
[0109] The measuring method for the dimensional changing ratios is
not particularly limited. Any conventionally known method that can
measure an increase and decrease in the dimension caused before and
after the etching or heating step.
[0110] It is necessary to measure the dimensional changing ratios
in both the MD direction and TD direction. In case the imidization
and the lamination are performed continuously, the tension is
applied differently in the MD direction and TD direction. Thus, the
heat expansion and heat shrinkage occur at different extents in the
MD direction and the TD direction. Thus, the dimensional changing
ratios are different in MD directions and the TD directions. For a
material with small dimensional changing ratios, it is necessary
that the dimensional changing ratios be small in both the MD
direction and the TD direction. In the present invention, a total
value of (1) the dimensional changing ratios before and after the
removal of the metal foil, and (2) the dimensional changing ratio
before the heat application of 250.degree. C. for 30 min is very
preferably in the range of -0.1 to +0.1 in both the MD direction
and TD direction.
[0111] Moreover, there is no particular limitation as to specific
arrangement of the etching step for measuring the dimensional
changing ratios. That is, the etching conditions would be varied
according to the kind of the metal foil, shape of pattern wiring to
be formed, etc. Thus, in the present invention, the etching for
measuring the dimensional changing ratios may be carried out under
any conventionally known condition. Similarly, the heating step is
not particularly limited, provided that the heating step applies a
heat of 250.degree. C. for 30 min.
EXAMPLE
[0112] The present invention will now be described in specifics by
way of examples. It is to be understood that the present invention
is not limited to these examples. Coefficients of thermal expansion
of insulating layers, changes in coefficient of thermal expansion
of adhesive sheets, and dynamic viscoelasticity of insulating
layers were evaluated as follows.
[0113] (Coefficient of Thermal Expansion of Insulating Layer)
[0114] The coefficient of thermal expansion from 100.degree. C. to
200.degree. C. was measured by using TMA 120C made by Seiko
Electronics Co. Ltd. A sample of 3 mm in width and 10 mm in length
was heated from 10.degree. C. to 400.degree. C. at a rate of
10.degree. C./min under 3 g load. Then, the sample was cooled down
to 10.degree. C. and then again heated at a rate of 10.degree.
C./min. Thermal expansion coefficients measured at 100.degree. C.
and 200.degree. C. were measured in the second heating, and then
averaged to work out the coefficient of thermal expansion from
100.degree. C. to 200.degree. C. The measurements were carried out
under nitrogen atmosphere.
[0115] (Change in Coefficient of Thermal Expansion)
[0116] An adhesive sheet was cut out in size of 10.times.35 cm such
that the MD direction was a longitudinal direction of the cut-out
film. One end of the film was held by a jig, and a weight of 2 kg
was hung from the other end thereby to apply a tension of 20 kg/m
in the MD direction. The jig was put in an oven preheated to
380.degree. C. and heat-treated for 30 seconds. After the heat
treatment, the jig was taken out of the oven and then cooled down
to a room temperature. After the weight was then removed, a piece
of approximately 10.times.15 cm was cut out from a center portion
of the film, and used as a measurement sample.
[0117] The change in the coefficient of thermal expansion from
100.degree. C. to 200.degree. C. was measured by using TMA 120C
made by Seiko Electronics Co. Ltd. A sample of 3 mm in width and 10
mm in length was heated from 10.degree. C. to 400.degree. C. at a
rate of 10.degree. C./min under 3 g load (first measurement). Then,
the sample was cooled down to 10 and then again heated to
400.degree. C. at a rate of 10.degree. C./min (second measurement).
Thermal expansion coefficients measured at 100.degree. C. and
250.degree. C. were measured to find coefficients of thermal
expansion in the first and second measurements. According to
Equation (1), the change in the coefficient of thermal expansion
was worked out.
Change in Coefficient of Thermal Expansion=|(First Measured Value
of Coefficient of Thermal Expansion)-(Second Measured Value of
Coefficient of Thermal Expansion)| (1)
[0118] (Dynamic Viscoelasticity)
[0119] A ratio between storage elastic modulus at 25.degree. C. and
380.degree. C., tan .delta., peak top temperature, and storage
elastic modulus ratio, were measured under the following conditions
by using DMS-600 made by Seiko Electronics Co. Ltd.
Temperature Profile: 0 to 400.degree. C. (3.degree. C./min) Shape
of Sample: 20 mm between holders, 9 mm in width.
Frequency: 5 Hz
Strain Amplitude: 10 .mu.m
Minimum Tension: 100
Tension Gain: 1.5
Initial Value of Force Amplitude: 100 mN
[0120] The storage elasticity modulus ratio was worked out from the
following Equation:
(Storage Elasticity Modulus Ratio)=(Storage Elasticity Modulus at
380.degree. C.)/(Storage Elasticity Modulus at 25.degree. C.)
Synthetic Example 1
Synthesis of Thermoplastic Polyimide Precursor
[0121] To a 2,000 mL glass flask, 780 g of N,N-dimethylformamide
(hereinafter, also referred to as DMF) and 115.6 g of
2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) were added. While
the resulting mixture was being stirred in a nitrogen atmosphere,
78.7 g of 3,3'4,4'-biphenyltetracarboxylic dianhydride (BPDA) was
gradually added to the mixture. Subsequently, 3.8 g of
ethylenebis(trimellitic acid monoester anhydride) (TMEG) was added,
and the resulting mixture was stirred in an ice bath for 30
minutes. A solution of 2.0 g of TMEG in 20 g of DMF was separately
prepared and gradually added to the reaction solution while
monitoring the viscosity under stirring. The addition and the
stirring were ceased when the viscosity reached 3,000 poise. A
polyamic acid solution thereby obtained.
Example 1
[0122] Into 468 kg of N,N-dimethylformamide (hereinafter, DMF)
cooled to 10.degree. C., 29.94 kg of
2,2-bis(4-aminophenoxyphenyl)propane (BAPP) and 9.75 kg of
3,4'-oxydianiline (3,4'-ODA) were dissolved. Then, 15.69 kg of
3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) was added
and dissolved therein. After that, 13.27 kg of pyromellitic
dianhydride (PMDA) was added. The mixture was stirred for 60 min,
thereby preparing a prepolymer.
[0123] In the solution thus obtained, 13.16 kg of
p-phenylenediamine (p-PDA) was dissolved. Then, 27.61 kg of PMDA
was added therein and dissolved by 1 hour stirring. A solution of
PMDA in DMF (weight ratio PMDA 1.59 kg/DMF 21.2 kg) was separately
prepared and added into the resultant solution. The addition was
ceased when the viscosity reached 3,000 poise. The solution was
stirred for 3 hours. Thereby, a polyamic acid solution was
obtained, which had a solid content of approximately 18.5 wt % and
a rotational viscosity of 3400 poise at 23.degree. C.
[0124] Into the polyamic acid solution, a chemical imidization
agent containing 20.71 kg of acetic anhydride, 3.14 kg of
isoquinoline, and 26.15 kg of DMF was added at a weight ratio of
50% with respect to the polyamic acid DMF solution and stirred
quickly by a mixer, and then extruded via a T die to be flow-cast
onto a stainless-steel endless belt running 15 mm below the die.
Here, acetic anhydride used as a dehydrating agent, was in such a
molar ratio that the acetic anhydride acting as the dehydrator was
2.5 and isoquinoline acting as a catalyst was 0.3 per one mole of
amic acid of the polyamic acid varnish. The resin film thus formed
was dried at 130.degree. C. for 100 second and peeled off from the
endless belt (volatile content 63 wt %). Then, the resin film was
held at a tenter pin and heated in a tenter furnace at 300.degree.
C. for 20 sec, 450.degree. C. for 20 sec, and 480.degree. C. for 20
sec for drying and imidization. Thereby, a polyimide film was
obtained. Properties of the film are shown on Table 1.
[0125] The polyamic acid solution obtained in Reference Example 1
was diluted with DMF to solid content of 10 wt %. Then, the
polyamic acid was applied on both sides of the polyimide film in
such a manner that thermoplastic polyimide layers (adhesive layers)
would be 2 .mu.m in thickness finally. Then, the laminate thus
prepared was heated at 140.degree. C. for 1 min. After that, the
laminate under 4 kg/m tension was passed through an infra-red
heater furnace of atmospheric temperature of 390.degree. C. for 20
sec for thermal imidization. Thereby an adhesive sheet was
obtained. An 18 .mu.m rolled copper foil (BHY-22B-T, produced by
Japan Energy Corporation) was laminated on each side of the
resulting adhesive film, and then a protective material (Apical
125NPI produced by Kaneka Corporation) was laminated on each copper
foil. The lamination was performed by thermal lamination under such
conditions such that the tension applied on the polyimide film was
2N/cm; the laminating temperature was 360.degree. C.; the
laminating pressure was 196N/cm (20 kgf/cm); and the laminating
speed was 1.5 m/min. Thereby, an FCCL was produced. Properties of
the FCCL are shown on Table 1.
Examples 2 to 4
[0126] Polyimide films and FCCLs were prepared with different
monomer ratios in the same manner as in Example 1. Properties of
the films and FCCLs are shown on Table 1.
Comparative Examples 1 to 4
[0127] FCCLs were prepared with commercially-available polyimide
films, namely Apical HP, Kapton EN, Apical NPI, Upilex S in the
same manner as in Example 1. Properties of the films and FCCLs are
shown on Table 1.
Comparative Example 5
[0128] A film was prepared according to Example 1 of Japanese
Unexamined Patent Application Publication, Tokukai, No. 2000-80178,
and FCCL was prepared in the same manner as in Comparative Examples
1 to 4. Properties of the film and FCCL are shown on Table 1.
TABLE-US-00001 TABLE 1 Com. Com. Com. Com. Com. Ex. 1 Ex. 2 Ex. 3
Ex. 4 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Polymer- BAPP 30 BAPP 30 BAPP
50 BAPP 30 Apical HP Kapton Upilex S Apical PDA 75 ization 3, 20 3,
20 BTDA 15 4, 20 (Kaneka EN (Ube NPI BAPP 25 Recipe 4'ODA 4'ODA
4'ODA Corp.) (Dupont- Industries (Kaneka BTDA 25 BTDA 20 BTDA 10
PMDA 30 BTDA 20 Toray Ltd.) Corp.) PMDA 75 PMDA 25 PMDA 35 PDA 50
PMDA 25 Col. Ltd.) Acetic 1 PDA 50 PDA 50 PMDA 55 PDA 50 anhydride
PMDA 55 PMDA 55 PMDA 55 Film 10 10 10 10 10 12.5 20 20 10 thickness
.mu.m CTE in MD 13 9 14 10 12 19 11 16 13 Direction ppm SEMR 0.10
0.15 0.07 0.15 0.06 0.04 0.23 0.33 0.25 tan .delta. 341.degree. C.
357.degree. C. 348.degree. C. 359.degree. C. 317.degree. C.
335.degree. C. 325.degree. C. >400.degree. C. >400.degree. C.
peak top tan .delta. 0.119 0.103 0.147 0.112 0.143 0.190 0.07 -- --
Adhesive 2 2 3 2 2 2 4 2.5 2 Thickness .mu.m Ex. 1 Ex. 2 Ex. 3 Ex.
4 Com. Ex. 1 Com. Ex. 2 Com. Ex. 3 Com. Ex. 4 Com. Ex. 5 CCTE MD
0.6 0.4 1.7 0.7 2.8 1.0 1.5 1.0 2.1 TD 5.8 4.8 7.9 5.1 17.1 5.6 6.8
3.1 7.1 DC MD 0.03 0.02 0.04 0.02 -0.04 -0.06 -0.08 -0.10 -0.11
(Etching) TD -0.02 0.03 -0.03 -0.03 0.09 -0.01 0.15 0.27 0.22 DC MD
-0.02 -0.03 -0.05 -0.02 -0.13 -0.07 -0.04 -0.05 -0.04 (250.degree.
C./ TD 0.01 0.02 0.05 0.02 0.13 -0.02 0.13 0.16 0.17 30 min) DC in
Total MD 0.01 -0.01 -0.01 0.00 -0.17 -0.13 -0.12 -0.15 -0.15 TD
-0.01 0.02 0.09 -0.01 0.22 -0.03 0.27 0.43 0.39
Abbreviations: Ex. stands for "Example". [0129] Com. Ex. stands for
"Comparative Example". [0130] CTE stands for "Coefficient of
Thermal Expansion". [0131] SEMR stands for "Storage Elasticity
Modulus Ratio" and the SEMR is between 50.degree. C. and
380.degree. C. [0132] CCTE stands for "Change in Coefficient of
Thermal Expansion". [0133] DC stands for "Dimensional Change".
INDUSTRIAL APPLICABILITY
[0134] The present invention makes it possible to produce a CCL
with a high dimensional stability. More specifically, the high
dimensional stability thus attained makes it possible to cope with
finer wiring pattern and multi-layered structure required for
high-density packaging. Moreover, the present invention solves the
low adherability problem associated with the use of thermoplastic
polyimide as an adhesive. Thus, the present invention makes it
possible to cope with a higher reflow temperature required by
lead-free soldering.
* * * * *