U.S. patent application number 12/824709 was filed with the patent office on 2010-10-21 for wiring-connecting material and wiring-connected board production process using the same.
Invention is credited to Motohiro Arifuku, Tohru Fujinawa, Hoko Kanazawa, Satoyuki Nomura, Hiroshi Ono, Itsuo Watanabe, Masami Yusa.
Application Number | 20100265685 12/824709 |
Document ID | / |
Family ID | 26533677 |
Filed Date | 2010-10-21 |
United States Patent
Application |
20100265685 |
Kind Code |
A1 |
Fujinawa; Tohru ; et
al. |
October 21, 2010 |
WIRING-CONNECTING MATERIAL AND WIRING-CONNECTED BOARD PRODUCTION
PROCESS USING THE SAME
Abstract
The present invention provides a wiring-connecting material
comprising from 2 to 75 parts by weight of a polyurethane resin,
from 30 to 60 parts by weight of a radical-polymerizable substance
and from 0.1 to 30 parts by weight of a curing agent capable of
generating a free radical upon heating, and a process for producing
a wiring-connected board by using the wiring-connecting material.
The wiring-connecting material of the present invention may
preferably further contain a film-forming material and/or
conductive particles.
Inventors: |
Fujinawa; Tohru; (Ibaraki,
JP) ; Yusa; Masami; (Ibaraki, JP) ; Nomura;
Satoyuki; (Ibaraki, JP) ; Ono; Hiroshi;
(Ibaraki, JP) ; Watanabe; Itsuo; (Ibaraki, JP)
; Arifuku; Motohiro; (Ibaraki, JP) ; Kanazawa;
Hoko; (Ibaraki, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
26533677 |
Appl. No.: |
12/824709 |
Filed: |
June 28, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11485295 |
Jul 13, 2006 |
|
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|
12824709 |
|
|
|
|
10846507 |
May 17, 2004 |
7141645 |
|
|
11485295 |
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|
10069053 |
Jul 8, 2002 |
6762249 |
|
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PCT/JP00/05763 |
Aug 25, 2000 |
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|
10846507 |
|
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Current U.S.
Class: |
361/803 ;
29/829 |
Current CPC
Class: |
C08L 51/08 20130101;
C08G 18/672 20130101; H05K 3/323 20130101; Y10T 29/49124 20150115;
C08G 18/4277 20130101; C09J 4/06 20130101; C08G 18/672 20130101;
H01L 2924/14 20130101; H01L 2924/15788 20130101; C08F 283/006
20130101; H01L 2924/14 20130101; C08G 18/4854 20130101; C08L 51/08
20130101; H05K 2201/0154 20130101; C08G 18/8175 20130101; C08G
18/6607 20130101; C08G 18/4238 20130101; C08L 75/04 20130101; H01L
2924/0002 20130101; H01L 24/29 20130101; H01L 2924/0002 20130101;
C08F 290/067 20130101; C08G 18/8175 20130101; H01L 2924/15788
20130101; C08G 18/4018 20130101; C09J 4/06 20130101; C08L 51/08
20130101; H01L 2924/00 20130101; C08G 18/42 20130101; C08F 290/067
20130101; C08L 2666/02 20130101; C08G 18/42 20130101; H01L 2924/00
20130101; C08L 2666/02 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
361/803 ;
29/829 |
International
Class: |
H05K 1/14 20060101
H05K001/14; H05K 3/00 20060101 H05K003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 25, 1999 |
JP |
HEILL-238409 |
Mar 28, 2000 |
JP |
2000-92978 |
Claims
1. A wiring-connecting film provided between at least two wiring
members, each wiring member having a connecting terminal and so
disposed that the sides of the wiring members having the connecting
terminals face each other, the wiring-connecting film
interconnecting the wiring members so that the connecting terminals
of the wiring members are able to provide an electrical connection
between the wiring members by heating and applying a pressure, the
wiring-connecting film comprising: a radical polymerizable
substance; a curing agent generating a free radical upon heating;
at least one film-forming material; and a polyurethane resin
obtained by the reaction of a diol, having two hydroxyl groups in
the molecule, with a diisocyanate, having two isocyanate groups in
the molecule.
2. A wiring-connecting film according to claim 1, which further
comprises conductive particles.
3. A wiring-connecting film according to claim 1, wherein the at
least one film-forming material is selected from the group
consisting of phenoxy resin and polyimide resin
4. A process for producing a wiring-connected board, comprising:
interconnecting wiring members each having a connecting terminal,
said wiring members being so interconnected that their connecting
terminals are able to make an electrical connection between the
wiring members, said interconnecting comprising heating the
wiring-connecting film according to claim 1 while applying a
pressure thereto via the wiring members, the wiring-connecting film
being held between at least two wiring members so disposed that the
sides of the wiring members having the connecting terminals face
each other.
5. The process for producing a wiring-connected board according to
claim 4, wherein at least one of the connecting terminals has a
surface formed of at least one metal selected from the group
consisting of gold, silver and a platinum group metal.
Description
[0001] This application is a Divisional application of application
Ser. No. 11/485,295, filed Jul. 13, 2006, which is a Continuation
application of application Ser. No. 10/846,507, filed May 17, 2004
(now U.S. Pat. No. 7,141,645), which is a Continuation application
of application Ser. No. 10/069,053, filed Jul. 8, 2002 (now U.S.
Pat. No. 6,762,249), which is a National Stage application filed
under 35 USC 371 of International (PCT) Application No.
PCT/JP00/05763, filed Aug. 25, 2000. The contents of application
Ser. No. 10/069,053 are incorporated herein by reference in their
entirety.
TECHNICAL FIELD
[0002] This invention relates to a wiring-connecting material
making use of an adhesive composition and conductive particles, and
a process for producing a wiring-connected board.
BACKGROUND ART
[0003] Epoxy resin adhesives are widely used for various purposes
such as electric, electronic, construction, automobile and airplane
materials because they can provide a high bond strength and have
excellent resistance to water and resistance to heat. In
particular, one-pack type epoxy resin adhesives are usable with
ease because it is unnecessary to blend the chief material and the
curing agent, and are widely used in the form of film, paste or
powder. In such one-pack type epoxy resin adhesive, epoxy resins,
curing agents and modifiers can be combined in variety. Hence,
appropriate selection of their combination enables achievement of
any desired performance as disclosed in, e.g., Japanese Patent
Application Laid-open (KOKAI) No. Sho62-141083.
[0004] A filmlike adhesive disclosed in this Japanese Patent
Application Laid-open (KOKAI) No. Sho62-141083, however, can not
sufficiently be reactive at the time of curing because it uses a
catalytic curing agent which is inert at normal temperature, in
order to achieve both short-time curing properties (fast-curing
performance) and storage stability (storage properties) to attain a
good stability. Thus, though having a good operability, it must be
heated at about 140.degree. C. to about 180.degree. C. for a
connecting time of about 20 seconds, or must be heated at about
180.degree. C. to about 210.degree. C. for a connecting time of 10
seconds.
[0005] In recent years, however, in the field of precision
electronic instruments, circuits are being made highly dense, so
that connecting terminals have come to be formed in and at very
narrow width and pitch. Hence, this has caused come-off or peeling
and misregistration of wiring in some cases when terminals are
interconnected under connecting conditions adapted to such
conventional epoxy resin wiring-connecting materials. Also, it has
been sought to shorten connecting time so as to enable connection
within 10 seconds in order to improve production efficiency. To
satisfy these demands, it is sought to provide a low-temperature
fast-curable wiring-connecting material capable of curing at a low
temperature and yet in a short time.
DISCLOSURE OF THE INVENTION
[0006] An object of the present invention is to provide a
wiring-connecting material for electric and electronic use, having
better low-temperature fast-curing performance than any
conventional epoxy resin connecting materials and also having a pot
life, and a process for producing a wiring-connected board making
use of such a connecting material.
[0007] The present invention provides a wiring-connecting material
comprising from 2 to 75 parts by weight of a polyurethane resin,
from 30 to 60 parts by weight of a radical-polymerizable substance
and from 0.1 to 30 parts by weight of a curing agent generating a
free radical upon heating. The wiring-connecting material of the
present invention is especially preferable as a connecting material
which is interposed between connecting terminals facing each other
and with which the connecting terminals are electrically
interconnected in the pressure direction while pressing the
connecting terminals facing each other.
[0008] The wiring-connecting material of the present invention may
also preferably further comprise a film-forming material and/or
conductive particles. The film-forming material may preferably be
mixed in an amount of from 0 to 40 parts by weight, and a polyimide
resin is preferred.
[0009] As the polyurethane resin, a resin having a flow point of
from 40.degree. C. to 140.degree. C. as measured by the flow tester
method may preferably be used. As the curing agent, it is
preferable to use a curing agent having a weight retention at
25.degree. C. for 24 hours (i.e., the proportion of a difference in
mass before and after open-leaving at room temperature (25.degree.
C.) and normal pressure for 24 hours, with respect to the mass
before leaving) of not less than 20% by weight. As the
radical-polymerizable substance, urethane acrylate is
preferred.
[0010] The present invention also provides a wiring-connected board
production process comprising the step of interconnecting terminals
of wiring by the use of the wiring-connecting material of the
present invention. More specifically, the present invention
provides a process for producing a wiring-connected board,
comprising a connecting step of interconnecting wiring members each
having a connecting terminal, which members are so interconnected
that their connecting terminals are able to make conduction between
them;
[0011] the connecting step comprising the step of heating the
wiring-connecting material of the present invention while applying
a pressure thereto via the wiring members; the wiring-connecting
material being held between at least two wiring members so disposed
that their sides having the connecting terminals face to each
other. This production process of the present invention is
especially preferable when at least one surface of the connecting
terminal is formed of at least one metal selected from gold, silver
and a platinum group metal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIGS. 1(a) to 1(d) illustrate a wiring-connected board
production process carried out in Example 1.
[0013] FIG. 2 is a cross-sectional view showing connecting portions
of a flexible printed-circuit board used in Example 3.
[0014] FIG. 3 is a cross-sectional view showing connecting portions
on a wiring substrate of a liquid-crystal display panel, used in
Example 4.
BEST MODES FOR CARRYING O THE INVENTION
A. Curing Agent
[0015] The curing agent used in the present invention is a curing
agent capable of generating a free radical upon decomposition by
heating, such as a peroxide compound or an azo compound. The curing
agent may appropriately be selected in accordance with the intended
connecting temperature, connecting time, pot life and so forth. In
order to achieve a high reactivity and a long pot life, preferred
is an organic peroxide showing a 10-hour half-life at a temperature
of 40.degree. C. or above and a 1-minute half-life at a temperature
of 180.degree. C. or below, and more preferred is an organic
peroxide showing a 10-hour half-life at a temperature of 60.degree.
C. or above and a 1-minute half-life at a temperature of
170.degree. C. or below.
[0016] When the connecting time is made not longer than 10 seconds,
the curing agent may preferably be mixed in an amount of from 0.1
to 30 parts by weight, and more preferably from 1 to 20 parts by
weight, in order to attain a sufficient rate of reaction. If the
curing agent is mixed in an amount less than 0.1 part by weight,
any sufficient rate of reaction can not be attained to tend to make
it difficult to attain a good bond strength and a small connection
resistance. If it is mixed in an amount more than 30 parts by
weight, the wiring-connecting material tends to have low flow
properties, cause a high connection resistance and have a short pot
life.
[0017] The organic peroxide preferred as the curing agent used in
the present invention is exemplified by diacyl peroxides,
peroxydicarbonates, peroxyesters, peroxyketals, dialkyl peroxides,
hydroperoxides and silyl peroxides.
[0018] The diacyl peroxides may include isobutyl peroxide,
2,4-dichlorobenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide,
octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, succinic
peroxide, benzoyl peroxytoluene and benzoyl peroxide.
[0019] The peroxydicarbonates may include di-n-propyl
peroxydicarbonate, diisopropyl peroxydicarbonate,
bis(4-t-butylcyclohexyl)peroxydicarbonate, di-2-ethoxyethyl
peroxydicarbonate, di(2-ethylhexyl peroxy)dicarbonate,
dimethoxybutyl peroxydicarbonate, and di(3-methyl-3-methoxybutyl
peroxy)dicarbonate.
[0020] The peroxyesters may include cumyl peroxyneodecanoate,
1,1,3,3-tetramethylbutyl peroxyneodecanoate,
1-cyclohexyl-1-methylethyl peroxyneodecanoate, t-hexyl
peroxyneodecanoate, t-butyl peroxypivarate,
1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanonate,
2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane,
1-cyclohexyl-1-methylethyl peroxy-2-ethylhexanonate, t-hexyl
peroxy-2-ethylhexanonate, t-butyl peroxy-2-ethylhexanonate, t-butyl
peroxyisobutyrate, 1,1-bis(t-butylperoxy)cyclohexane, t-hexyl
peroxyisopropylmonocarbonate, t-butyl
peroxy-3,5,5-trimethylhexanonate, t-butyl peroxylaurate,
2,5-dimethyl-2,5-di(m-toluoylperoxy)hexane, t-butyl
peroxyisopropylmonocarbonate, t-butyl
peroxy-2-ethylhexylmonocarbonate, t-hexyl peroxybenzoate, and
t-butyl peroxyacetate.
[0021] The peroxyketals may include
1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane,
1,1-bis(t-hexylperoxy)cyclohexane,
1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,
1,1-(t-butylperoxy) cyclododecane, and
2,2-bis(t-butylperoxy)decane.
[0022] The dialkyl peroxides may include
.alpha.,.alpha.-bis(t-butylperoxy)diisopropylbenzene, dicumyl
peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and
t-butylcumyl peroxide.
[0023] The hydroperoxides may include diisopropylbenzene
hydroperoxide and cumene hydroperoxide.
[0024] The silyl peroxides may include t-butyltrimethylsilyl
peroxide, bis(t-butyl)dimethylsilyl peroxide, t-butyltrivinylsilyl
peroxide, bis(t-butyl)divinylsilyl peroxide,
tris(t-butyl)vinylsilyl peroxide, t-butyltriallylsilyl peroxide,
bis(t-butyl)diallylsilyl peroxide, and tris(t-butyl)allylsilyl
peroxide.
[0025] In the present invention, as the curing agent, any one of
these compounds may be used or any two or more compounds may be
used in combination. Also, any of these curing agents (free-radical
generators) may be used in combination with a decomposition
accelerator, an inhibitor and so forth.
[0026] In order to keep the connecting terminals of wiring members
from corroding, chloride ions and organic acids contained in the
curing agent may preferably be in a content not more than 5,000
ppm. Those generating less organic acid after heat decomposition
are more preferred. Also, on account of an improvement in the
stability of wiring-connecting materials produced, the curing agent
may preferably have a weight retention of not less than 20% by
weight after open-leaving at room temperature (25.degree. C.) and
normal pressure for 24 hours.
[0027] Any of these curing agents may also be coated with, e.g., a
polymeric material of polyurethane type or polyester type so as to
be made into microcapsules. Such a curing agent is preferred
because of a prolonged pot life.
B. Polyurethane Resin
[0028] As the polyurethane resin, a resin obtained by the reaction
of a diol, having two hydroxyl groups in the molecule, with a
diisocyanate, having two isocyanate groups in the molecule, is
preferred in the present invention because it has a good stress
relaxation at the time of curing and has a polarity to bring about
an improvement in adhesion.
[0029] As the diol, any of those which are linear compounds and
having hydroxyl groups at the terminals may be used. Stated
specifically, it may include polyethylene adipate, polydiethylene
adipate, polypropylene adipate, polybutylene adipate,
polyhexamethylene adipate, polyneopentyl adipate, polycaprolactone
polyol, poly(hexamethylene carbonate), silicone polyol, acrylic
polyol, poly(ethylene glycol), poly(propylene glycol) and
poly(tetramethylene glycol). Any of these compounds may be used
alone, or may be used in combination of two or more types.
[0030] The diisocyanate may include isophorone diisocyanate,
tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate,
naphthalene-1,5-diisocyanate, p-phenylene diisocyanate,
4,4'-methylenebiscyclohexyl diisocyanate, hexamethylene
diisocyanate, and cyclohexane diisocyanate. Any of these compounds
may be used alone, or may be used in combination of two or more
types.
[0031] The polyurethane resin used in the present invention may
preferably have a weight-average molecular weight of from 10,000 to
1,000,000. If it has a weight-average molecular weight less than
10,000, the wiring-connecting material tend to have a low cohesive
force to make it difficult to attain a sufficient bond strength. If
it has a weight-average molecular weight more than 1,000,000, the
wiring-connecting material tend to have poor mixing properties and
flow properties.
[0032] When the polyurethane resin is synthesized, in addition to
these dial and diisocyanate, a polyhydric alcohol, an amine or an
acid anhydride may further be mixed to allow them to react
appropriately. For example, an imide-group-containing polyurethane
obtained by reaction with an acid anhydride is preferred because it
can be improved in adhesion and heat resistance.
[0033] The polyurethane resin used in the present invention may be
a modified product. In particular, those modified with a
radical-polymerizable functional group are preferred because it can
be improved in heat resistance.
[0034] The polyurethane resin used in the present invention may
preferably have a flow point of from 40.degree. C. to 140.degree.
C., and more preferably from 50.degree. C. to 100.degree. C., as
measured by the flow tester method. The flow point measured by the
flow tester method is the temperature at which a cylinder begins to
move when temperature is raised at a rate of temperature rise of
2.degree. C./rain under application of a pressure of 3 MPa to make
a sample flow out of a die of 1 mm in diameter. The temperature is
measured with a flow tester. If the polyurethane resin has a flow
point lower than 40.degree. C. as measured by the flow tester
method, it may have inferior film-forming properties and adhesion.
If it has a flow point higher than 140.degree. C., it may have poor
flow properties to affect electrical connection adversely.
C. Film-Forming Material
[0035] The film-forming material used in the present invention may
include polyimide resins, polyvinyl formal resins, polystyrene
resins, polyvinyl butyral resins, polyester resins, acrylic resins,
polyamide resins, xylene resins and phenoxy resins. Any of these
may be used alone, or may be used in combination of two or more
types.
[0036] The film-forming material is a material providing mechanical
properties that enable films to be handled as films in an ordinary
condition, such that, when a liquid material is made into a solid
and its composition made up is formed into a self-supporting film,
the resultant film can be handled with ease and not be readily
broken or cracked or sticky.
[0037] As the film-forming material, polyimide resin is especially
suited for the present invention in view of resistance to heat.
Usable as the polyimide resin are, e.g., those obtained by
subjecting a polyamic acid synthesized by addition reaction of a
tetracarboxylic dianhydride with a diamine to heating and
condensation to effect imidization. The polyimide resin may
preferably have a weight-average molecular weight of from about
10,000 to about 150,000 in view of film-forming properties.
[0038] The acid dianhydride and diamine used when the polyamide
resin is synthesized may appropriately be selected taking account
of its solubility in solvents and compatibility with
radical-polymerizable materials. Also, they may each be used alone
as a single compound, or be used in combination of two or more
compounds. Incidentally, on account of an improvement in adhesion
and flexibility, at least one compound of the acid dianhydride and
the diamine may preferably have a siloxane skeleton.
[0039] The film-forming material used in the present invention may
be modified with a radical-polymerizable functional group.
D. Radical-Polymerizable Substance
[0040] The radical-polymerizable substance used in the present
invention is a substance having a functional group that polymerizes
by virtue of radicals, and may include acrylates, methacrylates and
maleimide compounds. Any of these may be used alone, or may be used
in combination of two or more types.
[0041] The radical-polymerizable substance may be used in the state
of either of a monomer and an oligomer, or may be used in
combination of a monomer and an oligomer.
[0042] As examples of the acrylates preferable in the present
invention, they may include methyl acrylate, ethyl acrylate,
isopropyl acrylate, isobutyl acrylate, ethylene glycol diacrylate,
diethylene glycol diacrylate, trimethylolpropane triacrylate,
tetramethylolmethane tetraacrylate,
2-hydroxy-1,3-diacryloxypropane,
2,2-bis[4-(acryloxymethoxy)phenyl]propane,
2,2-bis[4-(acryloxypolyethoxy)phenyl]propane, dicyclopentenyl
acrylate, tricyclodecanyl acrylate, tris(acryloyloxyethyl)
isocyanurate, isocyanuric acid ethylene oxide modified diacrylate,
and urethane acrylate. Methacrylates corresponding to these
acrylates may also be preferable in the present invention.
[0043] Radical-polymerizable substances having at least one of a
dicyclopentanyl group, a tricyclodecanyl group and a triazine ring
are preferred because the wiring-connecting material obtained can
be improved in resistance to heat.
[0044] As the radical-polymerizable substance used in the present
invention, urethane acrylates are particularly preferred because of
their superior adhesion. The urethane acrylates are those having at
least one urethane group in the molecule, and may include, e.g.,
reaction products of polyols such as poly(tetramethylene glycol)
with polyisocyanates and hydroxyl-group-containing acrylic
compounds.
[0045] On account of an improvement in bond strength on the
surfaces of inorganic matters such as metals, a
radical-polymerizable substance further having a phosphate
structure may also preferably be used in combination, in addition
to the radical-polymerizable substance described above.
[0046] Such a radical-polymerizable substance having a phosphate
structure, preferable in the present invention, may include
reaction products of phosphoric anhydride with 2-hydroxyethyl
acrylate or its corresponding methacrylate 2-hydroxyethyl
methacrylate. Stated specifically, mono(2-methacryloyloxyethyl)acid
phosphate and di(2-methacryloyloxyethyl)acid phosphate may be used.
Any of these compounds may be used alone, or may be used in
combination of two or more types.
[0047] As the maleimide compounds, those containing at least two
maleimide groups in the molecule are suited for the present
invention. Such maleimide compounds may include, e.g.,
1-methyl-2,4-bismaleimidebenzene, N,N'-m-phenylenebismaleimide,
N,N'-p-phenylenebismaleimide, N,N'-m-toluoylenebismaleimide,
N,N'-4,4-biphenylenebismaleimide,
N,N'-4,4-(3,3'-dimethylbiphenylene)bismaleimide,
N,N'-4,4-(3,3'-dimethyldiphenylmethane)bismaleimide,
N,N'-4,4-(3,3'-diethyldiphenylmethane)bismaleimide,
N,N'-4,4-diphenylmethanebismaleimide,
N,N'-4,4-diphenylpropanebismaleimide, N,N'-4,4-diphenylether
bismaleimide, N,N'-3,3'-diphenylsulfonebismaleimide,
2,2-bis[4-(4-maleimidophenoxy)phenyl]propane,
2,2-bis[3-s-butyl-3,4-(4-maleimidophenoxy)phenyl]propane,
1,1-bis[4-(4-maleimidophenoxy)phenyl]decane,
4,4'-cyclohexylidene-bis[1-(4-maleimidophenoxy)-2-cyclohexyl]benzene,
and 2,2-bis[4-(4-maleimidophenoxy)phenyl]hexafluoropropane.
[0048] In the present invention, in addition to these
radical-polymerizable substances, polymerization inhibitors such as
hydroquinones and methyl ether hydroquinones may optionally
appropriately be used.
E. Mixing Proportion
[0049] In the wiring-connecting material of the present invention,
the above respective ingredients may be contained in an amount of
from 2 to 75 parts by weight for the polyurethane resin, from 30 to
60 parts by weight for the radical-polymerizable substance, and
from 0.1 to 30 parts by weight for the curing agent capable of
generating a free radical upon heating. In the case when the
film-forming material is contained, it may be contained in an
amount of from 0 to 40 parts by weight. These ingredients may be
mixed in the amounts appropriately determined within the above
ranges.
[0050] If the polyurethane resin is in a content smaller than 2
parts by weight, the wiring-connecting material may have a poor
effect of stress relaxation at the time of heat loading to lower
bond strength. If it is in a content larger than 75 parts by
weight, there is a possibility of a low connection reliability.
[0051] If the radical-polymerizable substance is in a content
smaller than 30 parts by weight, the wiring-connecting material
tends to have a low mechanical strength after its curing. If it is
in a content larger than 60 parts by weight, the wiring-connecting
material may have a high tackiness before its curing, resulting in
poor handling properties.
[0052] If the curing agent capable of generating a free radical
upon heating is in a content smaller than 0.1 part by weight, no
sufficient rate of reaction can be attained as stated previously,
to tend to make it difficult to attain a good bond strength and a
small connection resistance. Also, if this curing agent is in a
content larger than 30 parts by weight, the wiring-connecting
material tends to have low flow properties, cause a high connection
resistance and have a short pot life.
[0053] If the film-forming material is in a content more than 40
parts by weight, the wiring-connecting material tends to have low
flow properties and cause a high connection resistance.
Incidentally, the film-forming material need not be contained as
long as other ingredients such as the polyurethane resin, the
radical-polymerizable substance and the curing agent capable of
generating a free radical upon heating enable sufficient film
formation.
F. Conductive Particles
[0054] The wiring-connecting material of the present invention can
interconnect the connecting terminals through their direct contact
even when it does not contain any conductive particles. Hence, it
need not particularly contain any conductive particles. However, on
account of achievement of stabler connection, it may preferably
contain conductive particles.
[0055] As the conductive particles, usable are particles of metals
such as Au, Ag, Ni, Cu and solder, carbon particles or the like. In
order to attain a sufficient pot life, the surface layers of
particles may preferably be formed of not a transition metal such
as Ni or Cu but a noble metal such as Au, Ag or a platinum group
metal, and particularly preferably be formed of Au.
[0056] Composite particles comprised of a transition metal such as
Ni the particle surfaces of which are covered with a noble metal
such as Au; and particles having a conductivity partly such as
composite particles comprised of anon-conductive, glass, ceramic,
plastic or the like the particle surfaces of which are covered with
conductive layers formed of the above metal and the surfaces thus
covered are further covered with outermost layers formed of a noble
metal may also be used in the present invention as the conductive
particles.
[0057] Coat layers of a noble metal in such composite particles may
be formed in a thickness of, but not particularly limited to, 100
.ANG. or larger in order to achieve a good resistance. When,
however, the layers of a noble metal are provided on the surfaces
of a transition metal such as Ni, noble-metal layer defects caused
when the conductive particles are mixed and dispersed, may cause
the action of oxidation-reduction to generate free radicals to make
the pot life short. Accordingly, the noble-metal layers may
preferably be in a thickness 300 .ANG. or larger. Also, if the
noble-metal layers have a thickness larger than 1 .mu.m, the effect
may become saturated, and hence a layer thickness not larger than 1
.mu.m is effective in view of cost and so forth.
[0058] Composite particles whose cores are formed of a plastic, or
heat-fused metal particles are preferred because they are highly
deformable upon application of heat and pressure, and deform with
ease by the heat and pressure applied at the time of connection to
enlarge the area of contact with connecting terminals, bringing
about an improvement in reliability.
[0059] In the case when the conductive particles are mixed in the
wiring-connecting material of the present invention, they may be
mixed in an amount of from 0.1 to 30% by volume based on the
adhesive component, which may appropriately be determined depending
on purposes. In order to prevent adjoining circuits from
short-circuiting due to any excess conductive particles, they may
preferably be mixed in an amount of from 0.1 to 10% by volume.
G. Additives
[0060] In addition to the ingredients A to F described above, the
wiring-connecting material of the present invention may further
contain a filler, a softener, an accelerator, an anti-aging agent,
a colorant, a flame retardant, a thixotropic agent, a coupling
agent and so forth.
[0061] The compounding of a filler is preferred because the
wiring-connecting material obtained can be improved in connection
reliability and so forth. The filler may preferably have a maximum
diameter that is smaller than the particle diameter of the
conductive particles, and it may be compounded in an amount of from
5 to 60% by volume. If it is in an amount more than 60% by volume,
the effect of improving reliability is saturated.
[0062] As the coupling agent, agents containing a vinyl group, an
acrylic group, an amino group, an epoxy group or an isocyanate
group are preferred in view of an improvement in adhesion.
H. Film Structure
[0063] The wiring-connecting material constituted as described
herein need not be in the form of a single layer in which all the
ingredients are present, and may be in the form of a stacked film
having two or more layers. For example, it may have a double-layer
structure consisting of a layer containing the curing agent capable
of generating a free radical upon heating and a layer containing
the conductive particles to separate these ingredients. This can
bring about not only the effect of enabling achievement of high
precision but also the effect of improving pot life.
I. Properties of Wiring-Connecting Material
[0064] The wiring-connecting material of the present invention
interconnects the connecting terminals facing to each other, by
bringing them into contact with the adhesive which melt-flows at
the time of connection, followed by curing to keep their
connection, and thus the flow properties of the adhesive is an
important factor. The wiring-connecting material of the present
invention may preferably have a value of flow properties (B)/(A) of
from 1.3 to 3.0, and more preferably from 1.5 to 2.5; the flow
properties (B)/(A) being expressed using area (A) at the initial
stage and area (B) after heating and pressing when, using glass
sheets of 0.7 mm thick and 15 mm.times.15 mm, a wiring-connecting
material of 35 .mu.m thick and 5 mm.times.5 mm is held between the
glass sheets and heated and pressured at 160.degree. C. and 2 MPa
for 10 seconds. As long as the value is 1.3 or more, the
wiring-connecting material has sufficient flow properties and can
achieve good connection. Also, as long as it is 3.0 or less, the
wiring-connecting material is less likely to cause air bubbles to
have a good reliability.
[0065] In addition, it is preferable for the wiring-connecting
material of the present invention that its temperature at which
exothermic reaction rises, Ta, is within the range of from
70.degree. C. to 110.degree. C., having a peak temperature (Tp) of
Ta+5 to 30.degree. C. and an end temperature (Te) of 160.degree. C.
or below, as measured with a differential scanning calorimeter
(DSC) at a rate of temperature rise of 10.degree. C./minute. Having
such properties, the wiring-connecting material can achieve both
low-temperature connecting performance and room-temperature storage
stability.
[0066] The wiring-connecting material of the present invention is
also advantageous for reducing internal stress of the resin after
connection and improving adhesive force, and also can achieve good
conduction characteristics. Accordingly, it may preferably have a
storage elastic modulus at 25.degree. C. after curing, of from 100
to 2,000 MPa, and more preferably from 300 to 1,500 MPa.
J. Production of Wiring-Connected Board
[0067] The wiring-connecting material of the present invention is
useful also as a filmlike adhesive for bonding IC chips to
chip-mounting substrates and for bonding electric circuits to each
other.
[0068] More specifically, the use of the wiring-connecting material
of the present invention enables production of a wiring-connected
board in the following way: A first wiring member having a first
connecting terminal and a second wiring member having a second
connecting terminal are heated and pressed while disposing face to
face the first connecting terminal and the second connecting
terminal and providing the wiring-connecting material (filmlike
adhesive) of the present invention between the first wiring member
and the second wiring member, resulting in an electrical connection
therewith.
[0069] The wiring member may include;
[0070] chips component parts such as semiconductor chips, resistor
chips and capacitor chips;
[0071] printed-wiring substrates on which chips have been mounted
and/or which have been resist-processed;
[0072] TCPs (tape carrier packages) which comprise a TAB
(tape-automated bonding) tape having chips mounted therewith and
have been resist-processed; and
[0073] liquid-crystal display panels.
[0074] It can be exemplified by;
[0075] an insulating substrate comprised of silicon, gallium
arsenide, glass, ceramics, a glass/thermosetting resin composite
material (such as a glass/epoxy composite material) or a plastic
material (such as a plastic film or a plastic sheet) of polyimide
or the like on which substrate a conductive metal foil is formed
via an adhesive to form a wiring which involves connecting
terminals;
[0076] an insulating substrate on which a conductive wiring has
been formed by plating or vacuum deposition; and
[0077] a substrate coated with a material such as a plating
catalyst and on which a conductive wiring has been formed.
[0078] As wiring members preferable for the connection carried out
by the production process of the present invention, they may
typically include TAB tapes, FPCs (flexible printed-circuit
boards), PWBs (printed-wiring boards), ITO (indium tin oxide), and
semiconductor chips having connecting pads.
[0079] Materials for the wiring member may be any of silicon or
gallium arsenide for semiconductor chips, glass, ceramics,
polyimide, a glass/thermosetting resin composite material (such as
a glass/epoxy composite material) and plastics, without any
particular limitations.
[0080] Where the surfaces of conductive connecting terminals coming
into contact with the wiring-connecting material are formed of a
transition metal such as copper or nickel, free radicals are
generated as a result of its action of oxidation-reduction. Hence,
radical polymerization may proceed when the wiring-connecting
material is applied to the first connecting terminal for
provisional adhesion and is left for a certain time, so that it may
become difficult for the connecting material to flow. This may
cause insufficient electrical connection at the time of final
connection to the second connecting terminal registered.
Accordingly, the surface of at least one of the connecting
terminals may preferably be constituted of at least one selected
from gold, silver, a platinum group metal and tin. A plurality of
metals may be used in combination, e.g., copper/nickel/gold, to
make up a multi-layer configuration.
[0081] In the wiring-connected board production process of the
present invention, it is also preferable for at least one of the
connecting terminals to be directly disposed on the surface of a
plastic substrate. Here, the plastic substrate may include films or
sheets of polyethylene terephthalate polyethylene naphthalate
resin, polyether sulfone resin, polycarbonate resin or polyimide
resin. It may preferably be comprised of polyimide resin.
[0082] Use of such a plastic substrate allows the wiring-connected
board to be thinner and lighter. In the production process of the
present invention, the use of the wiring-connecting material of the
present invention enables connection at a low temperature, and
hence a plastic having a relatively low glass transition
temperature or melting point can be used, making it possible to
obtain economically advantageous wiring-connected boards.
[0083] To make the wiring-connected board thin and light-weight, a
wiring member so made up that connecting terminals making use of no
adhesive are directly present on the plastic is preferred to those
in which the plastic serving as a connecting member and connecting
terminals formed of a conductive material are bonded with an
adhesive. A polyimide resin with metal foil is commercially
available which is obtained by a direct coating method where a
resin solution is directly applied onto a metal foil such as copper
foil in a uniform thickness without use of any adhesive. A wiring
member formed by patterning this metal foil is preferred in the
present invention. A member formed of a film extruded directly from
an extruder in that form and a metal foil which have been
thermocompression-bonded may also be used, and this metal foil may
be patterned. Such a member may also be used in the present
invention.
EXAMPLES
[0084] The present invention will be described below in greater
detail by giving Examples.
Example 1
(1) Synthesis of Polyurethane Resin
[0085] 450 parts by weight of polybutylene adipate diol having an
average molecular weight of 2,000, 450 parts by weight of
polyoxytetramethylene glycol having an average molecular weight of
2,000 and 100 parts by weight of 1,4-butylene glycol were mixed,
and then 4,000 parts by weight of methyl ethyl ketone was added.
These were uniformly mixed and thereafter 390 parts by weight of
diphenylmethane diisocyanate was added, where reaction was carried
out at 70.degree. C. to obtain a polyurethane resin A solution of
15 Pas (25.degree. C.) in a solid content of 20% by weight. This
polyurethane resin had a weight-average molecular weight of 350,000
and had a flow point of 80.degree. C. as measured by the flow
tester method.
(2) Preparation of Wiring-Connecting Material
[0086] In solid content weight ratio, 40 g of the polyurethane
resin A (as solid content) synthesized as described above, 39 g of
dimethyloltricyclodecane diacrylate, 1 g of phosphate type acrylate
(available from KYOEISHA cHEMICAL Co., Ltd.; trade name: P2M), 20 g
of phenoxy resin and 5 g of lauroyl peroxide (25 g as a methyl
ethyl ketone solution) were mixed, and 3% by volume of conductive
particles were further dispersed. The dispersion obtained was
applied on a one-side surface-treated PET (polyethylene
terephthalate) film of 80 .mu.m thick by means of a coater,
followed by hot-air drying at 70.degree. C. for 10 minutes to
obtain a wiring-connecting material having an adhesive layer of 35
.mu.m thick.
[0087] Here, as the radical-polymerizable substance,
dimethyloltricyclodecane diacrylate was used. As the film-forming
material, phenoxy resin (available from Union Carbide; trade name:
"PKHC"; weight-average molecular weight: 45,000) was used. As the
curing agent capable of generating a free radical upon heating, a
20% by weight methyl-ethyl ketone solution of lauroyl peroxide
[weight retention after open-leaving at room temperature
(25.degree. C.) and normal pressure for 24 hours: 97%) was used. As
the conductive particles, conductive particles having an average
particle diameter of 10 .mu.m were used which were produced by
providing nickel layers of 0.2 .mu.m thick on the surfaces of
particles whose cores were formed of polystyrene, and providing
gold layers of 0.04 .mu.m thick on the nickel layers.
(3) Connection of Wiring
[0088] As shown in FIG. 1 (c), using a polyimide film with copper
foil prepared in a triple-layer configuration by bonding copper
foil of 18 .mu.m thick to polyimide film 18 via an adhesive 17,
this copper foil was patterned in a line width of 100 .mu.m and a
pitch of 200 .mu.m and subjected to resist processing, and
thereafter Sn was plated onto the surface of a wiring and
connecting terminal 16 formed of the copper foil, then a chip (not
shown) was mounted, followed by encapsulation with a resin (not
shown) at 200.degree. C. to prepare a TCP (tape carrier package)
19.
[0089] As shown in FIG. 1 (a), using a laminated substrate 11
provided with copper foil of 35 .mu.m thick, the copper foil was
also patterned in a line width of 100 .mu.m and a pitch of 200
.mu.m to form a circuit 12 and subjected to resist processing, and
then gold was plated onto the copper foil surface to prepare a
printed-wiring board (PWB) 10.
[0090] Next, to the surface of the PWB 10, the first wiring member,
the bonding face of the wiring-connecting material 15, containing a
resin composition 13 and conductive particles 14, was previously
bonded, followed by heating and pressing at 70.degree. C. and 0.5
MPa for 5 seconds to effect provisional connection. Thereafter, the
PET film was peeled [FIG. 1 (b)], and the TCP 19, the second wiring
member, was placed thereon under registration [FIG. 1 (c)], where
pressure 20 was applied with heating to effect interconnection to
obtain a wiring-connected board 21 [FIG. 1 (d)].
Example 2
(1) Synthesis of Urethane Acrylate
[0091] 400 parts by weight of polycaprolactone diol having an
average molecular weight of 800, 131 parts by weight of
2-hydroxypropyl acrylate, 0.5 part by weight of dibutyltin
dilaurate as a catalyst and 1.0 part by weight of hydroquinone
monomethyl ether as a polymerization inhibitor were mixed while
heating them to 50.degree. C. with stirring. Then, 222 parts by
weight of isophorone diisocyanate was dropwise added, and further
the temperature was raised to 80.degree. C. with stirring to carry
out urethanation reaction. Making sure that the NCO conversion
reached 99% or more, the reaction temperature was dropped to obtain
urethane acrylate B.
(2) Synthesis of Polyimide Resin
[0092] An acid anhydride
2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (26.1 g)
was dissolved in 120 g of cyclohexanone to obtain an acid
dianhydride solution.
[0093] Diamines 2,2-bis[4-(4-aminophenoxy)phenyl]propane (14.4 g)
and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (3.8 g)
were also dissolved in 120 g of cyclohexanone to obtain a diamine
solution.
[0094] This diamine solution was dropwise added into a flask
holding the acid dianhydride solution while controlling the
temperature of the reaction system so as not to become higher than
50.degree. C. After its addition was completed, the reaction
mixture was further stirred for 10 hours. Next, a Dean-Stark trap
was attached to the system, 50 g of toluene was added and the
temperature was raised to 120.degree. C. and kept it for 8 hours to
effect imidization.
[0095] The solution obtained was cooled to room temperature, and
thereafter reprecipitated in methanol. The precipitate obtained was
dried to obtain a polyimide resin having a weight-average molecular
weight of 32,000. This was dissolved in tetrahydrofuran to form a
20% by weight polyimide solution C.
(3) Preparation of Wiring-Connecting Material and Production of
Wiring-Connected Board
[0096] A wiring-connecting material was prepared, and a
wiring-connected board was produced, in the same manner as in
Example 1 except that 40 g of the polyurethane resin (as solid
content) synthesized in Example 1 was used as the polyurethane
resin, 39 g of the urethane acrylate B synthesized in step (1) and
1 g of phosphate type acrylate were used in combination as the
radical-polymerizable substance and 20 g of the polyimide resin C
(as solid content) synthesized in step (2) was used as the
film-forming material.
Example 3
[0097] As shown in FIG. 2, using a polyimide film with copper foil
prepared in a double-layer configuration consisting of a polyimide
film 22 and copper foil of 18 .mu.m thick, this copper foil was
patterned in a line width of 100 .mu.m and a pitch of 200 .mu.m to
form a circuit and a connecting terminal 23 and subjected to resist
processing, and thereafter Au was plated onto the surface of the
connecting terminal 23 to prepare a flexible printed-circuit board
(FPC) 24. A wiring-connected board was obtained in the same manner
as in Example 2 except that the TCP 19 was replaced with this FPC
24.
Example 4
[0098] Using a wiring-connecting material of 15 .mu.m thick, a
wiring-connected board was obtained in the same manner as in
Example 3 except that the printed-wiring board (PWB) 10 was
replaced with a liquid-crystal display panel 27 comprising a glass
substrate 25 and a connecting terminal and wiring 26 provided on
the surface thereof using ITO.
Comparative Example 1
[0099] A wiring-connected board was obtained in the same manner as
in Example 1 except for using a wiring-connecting material prepared
by using a phenoxy resin (available from PKHC Union Carbide
Corporation; trade name: PKHC; weight-average molecular weight:
45,000), a bisphenol-A epoxy resin (available from Yuka Shell Epoxy
Kabushiki Kaisha; trade name: YL980) and an imidazole type
microcapsular curing agent (available from Asahi Chemical Industry
Co., Ltd.; trade name: 3941HP), setting the solid-content weight
ratio of phenoxy resin/bisphenol-A epoxy resin/imidazole type
microcapsular curing agent=40/20/40, and mixing conductive
particles therein in the same manner as in Example 1.
Comparative Example 2
[0100] A wiring-connecting material was prepared, and a
wiring-connected board was produced, in the same manner as in
Example 1 except that the polyurethane resin A was replaced with a
phenoxy resin (PKHC).
[0101] Using the wiring-connecting materials and wiring-connected
boards obtained in the foregoing Examples 1 to 4 and Comparative
Examples 1 and 2, the adhesion, connection resistance, storage
properties, insulating properties, polyurethane resin flow
properties, wiring-connecting material flow properties, modulus of
elasticity after curing, and DSC characteristics were measured or
evaluated. Results obtained are shown in Table 1. Here, the
measurement and evaluation were made in the following way.
[0102] (1) Measurement of Adhesive Force:
[0103] The wiring-member connected article (wiring-connected board)
obtained was separated in the direction of 90 degrees at a peel
rate of 50 mm/minute to measure adhesive force. The adhesive force
was measured immediately after the wiring-connected board was
produced (initial stage) and after it was kept in a
high-temperature high-humidity chamber of 85.degree. C. and 85% RH
for 500 hours.
[0104] (2) Measurement of Connection Resistance:
[0105] Using the wiring-connecting material obtained, a flexible
printed-circuit board (FPC) provided with 100 lines of copper
circuit plated with Sn, having a line width of 100 .mu.m, a pitch
of 200 .mu.m and a thickness of 18 .mu.m and a glass sheet on the
whole surface of which an ITO film was formed were connected over a
width of 2 mm by heating and pressing at 160.degree. C. and 3 MPa
for 10 seconds.
[0106] The value of resistance between adjoining circuit lines was
measured with a multi-meter at the initial stage and after keeping
in a high-temperature high-humidity chamber of 85.degree. C. and
85% RH for 500 hours. The resistance value was shown as an average
at 50 spots of resistance between the adjoining circuit lines.
[0107] (3) Evaluation of Storage Properties:
[0108] The wiring-connecting material obtained was kept in a
30.degree. C. thermostatic chamber for 30 days, and a circuit was
connected in the same manner as in the above (2) to evaluate
storage properties.
[0109] (4) Evaluation of Insulating Properties:
[0110] Using the wiring-connecting material obtained, a
printed-circuit board having a comb-shaped circuit provided
alternately with 250 lines of copper circuit wiring having a line
width of 100 .mu.m, a pitch of 200 .mu.m and a thickness of 35
.mu.m and a flexible printed-circuit board (FPC) provided with 500
lines of copper circuit wiring having a line width of 100 .mu.m, a
pitch of 200 .mu.m and a thickness of 18 .mu.m were connected over
a width of 2 mm by heating and pressing at 160.degree. C. and 3 MPa
for 10 seconds. A voltage of 100 V was applied to the comb-shaped
circuit of the resultant connected article, and the value of
insulation resistance after 500 hours of a 85.degree. C. and 85% RH
high-temperature high-humidity test was measured.
[0111] (5) Measurement of Flow Point of Polyurethane Resin:
[0112] The temperature at which a cylinder begins to move when
temperature is raised at a rate of 2.degree. C./min under
application of a pressure of 3 MPa to make a sample flow out of a
die of 1 mm in diameter was measured with a flow tester
(manufactured by Shimadzu Corporation; trade name: CFT-100
Model).
[0113] (6) Evaluation of Flow Properties of Wiring-Connecting
Material:
[0114] Using a wiring-connecting material of 35 .mu.m thick and 5
mm.times.5 mm, this was held between glass sheets of 0.7 mm thick
and 15 mm.times.15 mm, and heated and pressed at 160.degree. C. and
2 MPa for 10 seconds. The value of flow properties (B)/(A) was
determined using area (A) at the initial stage and area (B) after
heating and pressing, and regarded as an index of flow
properties.
[0115] (7) Modulus of Elasticity after Curing:
[0116] The wiring-connecting material was immersed in 160.degree.
C. Oil for 1 minute to effect curing. Storage elastic modulus of
the cured film was measured (rate of temperature rise: 5.degree.
C./minute; 10 Hz) with a dynamic viscoelastometer to measure
modulus of elasticity at 25.degree. C.
[0117] (8) Measurement of DSC Characteristics:
[0118] Using the wiring-connecting material obtained, the
temperature at which exothermic reaction rises, Ta, the peak
temperature (Tp) and the end temperature (Te) were determined when
measured with a differential scanning calorimeter (DSC;
manufactured by TA Instruments Japan Inc.; trade name: Model 910)
at a rate of 10.degree. C./minute.
TABLE-US-00001 TABLE 1 Comparative Comparative Items Example 1
Example 2 Example 3 Example 4 Example 1 Example 2 Adhesive Initial
stage 1000 1000 800 1000 100 200 force (gf/cm) 85.degree. C., 85%
RH, 800 900 600 900 peeled peeled 500 h Connection Initial stage
2.2 2.3 2.1 2.1 90.6 2.1 resistance (.OMEGA.) 85.degree. C., 85%
RH, 2.6 2.6 2.5 2.5 >500 2.6 500 h Storage properties 2.2 2.4
2.3 2.2 120 2.3 [connection resistance (.OMEGA.)] Insulation
Initial stage 1 .times. 10.sup.9< 1 .times. 10.sup.9< 1
.times. 10.sup.9< 1 .times. 10.sup.9< 1 .times. 10.sup.9<
1 .times. 10.sup.9< resistance (.OMEGA.) 85.degree. C., 85% RH,
1 .times. 10.sup.9< 1 .times. 10.sup.9< 1 .times.
10.sup.9< 1 .times. 10.sup.9< 1 .times. 10.sup.6 1 .times.
10.sup.9< 500 h Flow properties 1.9 1.9 1.9 1.9 2.4 1.8 Modulus
of elasticity 8001 600 600 600 1800 1400 (25.degree. C.) (MPa)
Exothermic Arising 89 92 92 92 98 86 reaction (DSC) temperature
(.degree. C.) (Ta) Peak 107 106 106 106 125 101 temperature (Tp)
End 148 150 150 150 160 142 temperature (Te)
[0119] In all Examples, the adhesive force was approximately from
7.85 to 9.81 N/cm (800 to 1,000 gf/cm) as initial values, and was
approximately from 5.88 to 8.83 N/cm (600 to 900 gf/cm) even after
the test for resistance to moisture, showing a good adhesive force
without any great decrease in bond strength. Comparative Example 1
showed insufficient curing reaction, and Comparative Example 2
showed a bond strength of about 1.96 N/cm (200 gf/cm) because the
polyurethane resin was not used, resulting in a low adhesive
force.
[0120] The wiring-connecting material obtained in Example 1 had a
low connection resistance at the initial stage and caused only a
little increase in resistance after the high-temperature
high-humidity test, showing a good connection reliability. The
wiring-connecting materials of Examples 2, 3 and 4 and Comparative
Example 2 also likewise achieved a good connection reliability. On
the other hand, in Comparative Example 1, the curing reaction was
so insufficient as to bring about a poor state of adhesion,
resulting in a high connection resistance.
[0121] In Examples 1 to 4, results of connection were obtainable
which were the same as those in a condition where the
wiring-connecting materials were not treated in a 30.degree. C.
thermostatic chamber for 30 days (i.e., at the initial stage). In
Examples 1 to 4, good insulating properties of
1.0.times.10.sup.9.OMEGA. was also obtainable, and any lowering of
insulating properties was observable.
[0122] With regard to the flow properties, both Example 1 and
Example 2 showed a value of 1.9. Also, the modulus of elasticity of
the wiring-connecting material of Example 1 at 25.degree. C. after
curing was measured, and it was 800 MPa.
[0123] The wiring-connecting material of Example 1 also showed a
curing reaction rise temperature of 89.degree. C., a peak
temperature of 107.degree. C. and an end temperature of 148.degree.
C. That of Example 2 showed a curing reaction rise temperature of
92.degree. C., a peak temperature of 106.degree. C. and an end
temperature of 150.degree. C. This proves that they are curable at
a lower temperature and, from the result of evaluation of storage
properties, they have superior storage properties.
[0124] Further, in the measurement of connection resistance, wiring
members were also prepared in one of which Sn was plated onto the
copper circuit and in the other of which it was not done. Using the
wiring-connecting material produced in Example 1, the wiring
members were provisionally connected to FPCs under the same
conditions as in Example 1 and were finally connected after they
were left for 24 hours, and then the connection resistance was
measured. As a result, it was 2.3.OMEGA. in the case where Sn was
plated, whereas it was 5.OMEGA. in the case where Sn was not plated
and the copper surface was uncovered.
INDUSTRIAL APPLICABILITY
[0125] As described above in detail, the present invention makes it
possible to provide a wiring-connecting material for electric and
electronic use, having better low-temperature fast-curing
performance than any conventional epoxy resin type materials, also
having a pot life, and less causative of circuit corrosion.
* * * * *