U.S. patent application number 14/422511 was filed with the patent office on 2015-07-30 for anisotropic conductive film and method of producing the same.
The applicant listed for this patent is DEXERIALS CORPORATION. Invention is credited to Seiichiro Shinohara.
Application Number | 20150214176 14/422511 |
Document ID | / |
Family ID | 50150047 |
Filed Date | 2015-07-30 |
United States Patent
Application |
20150214176 |
Kind Code |
A1 |
Shinohara; Seiichiro |
July 30, 2015 |
ANISOTROPIC CONDUCTIVE FILM AND METHOD OF PRODUCING THE SAME
Abstract
An anisotropic conductive film has a three-layer structure in
which a first connection layer is sandwiched between a second
connection layer and a third connection layer that each are formed
mainly of an insulating resin. The first connection layer has a
structure in which conductive particles are arranged in a single
layer in the plane direction of an insulating resin layer on a side
of the second connection layer, and the thickness of the insulating
resin layer in central regions between adjacent ones of the
conductive particles is smaller than that of the insulating resin
layer in regions in proximity to the conductive particles.
Inventors: |
Shinohara; Seiichiro;
(Kanuma-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DEXERIALS CORPORATION |
Tokyo |
|
JP |
|
|
Family ID: |
50150047 |
Appl. No.: |
14/422511 |
Filed: |
August 23, 2013 |
PCT Filed: |
August 23, 2013 |
PCT NO: |
PCT/JP2013/072571 |
371 Date: |
February 19, 2015 |
Current U.S.
Class: |
361/767 ;
156/308.2; 156/62.2; 428/161 |
Current CPC
Class: |
H01L 2224/27003
20130101; H01L 2224/29347 20130101; B32B 38/0008 20130101; B32B
2307/202 20130101; H01L 24/27 20130101; H01L 2224/29083 20130101;
H05K 1/0373 20130101; B32B 37/06 20130101; B32B 2305/30 20130101;
H01L 2224/29364 20130101; H01L 2224/2939 20130101; H01L 2924/15788
20130101; B32B 37/10 20130101; H01L 2224/29344 20130101; H01L
2924/181 20130101; B32B 37/025 20130101; B32B 2037/243 20130101;
H01L 2224/2929 20130101; H01L 2224/29344 20130101; H05K 2201/0215
20130101; H01L 2224/29082 20130101; H01L 2224/29339 20130101; H01L
2224/2939 20130101; H01L 2224/29355 20130101; H01L 2924/15788
20130101; H01L 2224/294 20130101; H01L 2924/12042 20130101; H01L
2224/29499 20130101; H01L 2224/83851 20130101; H01L 2924/181
20130101; H01L 2224/27005 20130101; H01L 2924/12042 20130101; H01L
2224/29339 20130101; H01L 2224/29357 20130101; H01L 24/83 20130101;
H01L 2924/00014 20130101; H01L 2224/29076 20130101; H01L 2924/00014
20130101; H01L 2924/00014 20130101; B32B 2457/00 20130101; C08G
59/68 20130101; C09J 4/00 20130101; Y10T 428/24521 20150115; B32B
37/24 20130101; H05K 3/323 20130101; H01L 2224/2919 20130101; H01L
2224/29357 20130101; H01L 2924/00 20130101; H01L 2924/00014
20130101; H01L 2924/00014 20130101; H01L 2924/00 20130101; H01L
2924/00014 20130101; H01L 2924/00014 20130101; H01L 2924/00
20130101; H01L 2924/00014 20130101; H01L 2224/29364 20130101; H01L
2924/00014 20130101; H01L 2224/29347 20130101; H01L 2224/294
20130101; H01L 2224/29355 20130101; H01L 24/29 20130101; H01L
2224/83851 20130101 |
International
Class: |
H01L 23/00 20060101
H01L023/00; B32B 38/00 20060101 B32B038/00; B32B 37/10 20060101
B32B037/10; B32B 37/06 20060101 B32B037/06; B32B 37/24 20060101
B32B037/24; B32B 37/00 20060101 B32B037/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 24, 2012 |
JP |
2012-184833 |
Claims
1. An anisotropic conductive film having a three-layer structure in
which a first connection layer is sandwiched between a second
connection layer and a third connection layer that each are formed
mainly of an insulating resin, wherein the first connection layer
has a structure in which conductive particles are arranged in a
single layer in a plane direction of an insulating resin layer on a
side of the second connection layer, and the insulating resin layer
has a thickness in central regions between adjacent ones of the
conductive particles which is smaller than a thickness of the
insulating resin layer in regions in proximity to the conductive
particles.
2. The anisotropic conductive film according to claim 1, wherein
the first connection layer is a thermal- or photo-radical
polymerizable resin layer containing an acrylate compound and a
thermal- or photo-radical polymerization initiator or a layer
obtained by subjecting the thermal- or photo-radical polymerizable
resin layer to thermal- or photo-radical polymerization; or a
thermal- or photo-cationic or anionic polymerizable resin layer
containing an epoxy compound and a thermal- or photo-cationic or
anionic polymerization initiator or a layer obtained by subjecting
the thermal- or photo-cationic or anionic polymerizable resin layer
to thermal- or photo-cationic or anionic polymerization.
3. The anisotropic conductive film according to claim 1, wherein
the conductive particles dig into the second connection layer.
4. The anisotropic conductive film according to claim 1, wherein a
degree of cure of the first connection layer in regions positioned
between the conductive particles and a surface of the first
connection layer that faces the third connection layer is lower
than a degree of cure of the first connection layer in regions
positioned between adjacent ones of the conductive particles.
5. The anisotropic conductive film according to claim 1, wherein
the first connection layer has a minimum melt viscosity higher than
that of the second connection layer and that of the third
connection layer.
6. The anisotropic conductive film according to claim 5, wherein
ratios of the minimum melt viscosity of the first connection layer
to the minimum melt viscosity of the second connection layer and to
the minimum melt viscosity of the third connection layer are each
1:4 to 400.
7. The anisotropic conductive film according to claim 1, wherein a
shortest distance in a horizontal direction between an end in a
thickness direction of the conductive particle and the second
connection layer is 0.5 to 1.5 times the diameter of the conductive
particles.
8. A method of producing the anisotropic conductive film according
to claim 1, the method comprising the following steps (A) to (D):
<Step (A)> the step of disposing conductive particles within
openings of a transfer die with the openings, and placing an
insulating resin layer formed on a release film so as to be opposed
to a surface of the transfer die with the openings; <Step
(B)> the step of applying pressure to the insulating resin layer
from a side of the release film to press an insulating resin into
the openings, to transfer the conductive particles to a surface of
the insulating resin layer, to form a first connection layer,
wherein the first connection layer has a structure in which the
conductive particles are arranged in a single layer in a plane
direction of the insulating resin layer, and the thickness of the
insulating resin layer in central regions between adjacent ones of
the conductive particles is smaller than that of the insulating
resin layer in regions in proximity to the conductive particles;
<Step (C)> the step of forming a second connection layer
formed mainly of an insulating resin on a surface of the first
connection layer on a side of the conductive particles; <Step
(D)> the step of forming a third connection layer formed mainly
of an insulating resin on a surface of the first connection layer
on a side opposite to the second connection layer.
9. A method of producing the anisotropic conductive film according
to claim 1, the method comprising the following steps (a) to (c):
<Step (a)> the step of disposing conductive particles within
openings of a transfer die with the openings, and placing an
insulating resin layer that has been bonded to a third connection
layer in advance so as to be opposed to a surface of the transfer
die with the openings; <Step (b)> the step of applying
pressure to the insulating resin layer from a side of a release
film to press an insulating resin into the openings, to transfer
the conductive particles to a surface of the insulating resin
layer, to form a first connection layer, wherein the first
connection layer has a structure in which the conductive particles
are arranged in a single layer in a plane direction of the
insulating resin layer, and the insulating resin layer has a
thickness in central regions between adjacent ones of the
conductive particles smaller than a thickness of the insulating
resin layer in regions in proximity to the conductive particles;
<Step (c)> the step of forming a second connection layer
formed mainly of an insulating resin on a surface of the first
connection layer on a side of the conductive particles.
10. The production method according to claim 8, further comprising
the step of irradiating the first connection layer with ultraviolet
rays through the conductive particle side, the step being performed
between the step (B) and the step (C).
11. The production method according to claim 9, further comprising
the step of irradiating the first connection layer with ultraviolet
rays through the conductive particle side, the step being performed
between the step (b) and the step (c).
12. A connection structure in which a first electronic component is
connected to a second electronic component by anisotropic
conductive connection using the anisotropic conductive film
according to claim 1.
13. A method of connecting a first electronic component to a second
electronic component by anisotropic conductive connection using the
anisotropic conductive film according to claim 1, the method
comprising: temporarily applying the anisotropic conductive film to
the second electronic component through the third connection layer
of the anisotropic conductive film; mounting the first electronic
component on the anisotropic conductive film temporarily applied;
and performing thermocompression bonding through the first
electronic component.
Description
TECHNICAL FIELD
[0001] The present invention relates to an anisotropic conductive
film and a method of producing the same.
BACKGROUND ART
[0002] An anisotropic conductive film has been widely used in
mounting of an electronic component such as an IC chip. In recent
years, an anisotropic conductive film in which conductive particles
for anisotropic conductive connection are arranged in a single
layer on an insulating adhesive layer has been proposed (Patent
Literature 1), in order to improve the connection reliability and
the insulating properties, improve the particle capturing
efficiency, and decrease the production cost in terms of
application to high-density mounting.
[0003] This anisotropic conductive film is produced as follows.
Conductive particles are first held in openings of a transfer die
with the openings, and an adhesive film with an adhesive layer for
transfer is pressed onto the conductive particles to primarily
transfer the conductive particles to the adhesive layer.
Subsequently, a polymer film that becomes a component of the
anisotropic conductive film is pressed on the conductive particles
attached to the adhesive layer, and heated and pressurized to
secondarily transfer the conductive particles to a surface of the
polymer film. An adhesive layer is formed on a surface of the
polymer film including the secondarily transferred conductive
particles on a side of the conductive particles so as to cover the
conductive particles, whereby this anisotropic conductive film is
produced.
CITATION LIST
Patent Literature
[0004] Patent Literature 1: Japanese Patent Application Laid-Open
No. 2010-33793
SUMMARY OF INVENTION
Technical Problem
[0005] The connection reliability, the insulating properties, and
the particle capturing efficiency of the anisotropic conductive
film of Patent Literature 1, which is produced using the transfer
die with openings, may be expected to be improved to some extent as
long as primary transfer and secondary transfer proceed smoothly.
However, generally, a film with relatively low adhesive force is
used as an adhesive film for primary transfer to facilitate
secondary transfer, and a contact area of the conductive particles
with the adhesive film is decreased. For this reason, during a
primary transfer process to a secondary transfer process, some
conductive particles are not primarily transferred. Further, some
conductive particles peel from the adhesive film after primary
transfer, and some conductive particles shift on the adhesive film.
Thus, the entire operation efficiency may be reduced.
[0006] On the other hand, when for a smooth primary transfer
operation at high speed, the adhesive force of the adhesive film is
increased to some extent, the conductive particles are stably held
on the adhesive film. However, this may cause the conductive
particles to be difficult to be secondarily transferred to the
polymer film. When the film property of the polymer film is
enhanced to avoid the above problem, another problem arises in
which the conduction resistance of the anisotropic conductive film
increases and the conduction reliability is also reduced. Even when
the anisotropic conductive film is tried to be actually produced
using the transfer die with openings as described above, primary
transfer and secondary transfer do not always proceed smoothly.
Therefore, the anisotropic conductive film has been still highly
required to achieve all favorable connection reliability, favorable
insulating properties, and favorable particle capturing
efficiency.
[0007] An object of the present invention is to solve the problems
in the conventional technology, and also to achieve favorable
connection reliability, favorable insulating properties, and
favorable particle capturing efficiency in an anisotropic
conductive film that is produced using a transfer die with openings
and has conductive particles arranged in a single layer.
Solution to Problem
[0008] The present inventor has found that the above object is
achieved when an anisotropic conductive film is produced using a
transfer die with openings by directly transferring conductive
particles from the transfer die to an insulating resin layer
constituting the anisotropic conductive film without primary
transfer to an adhesive film so that the conductive particles are
arranged in a single layer and the thickness of the insulating
resin layer at a center between adjacent ones of the conductive
particles is smaller than that of the insulating resin layer in
regions in proximity to the conductive particles, and placing
insulating resin layers that function as an adhesive layer on
respective faces of the insulating resin layer in which the
conductive particles are arranged in a single layer. Thus, the
present invention has been completed.
[0009] Accordingly, the present invention provides an anisotropic
conductive film having a three-layer structure in which a first
connection layer is sandwiched between a second connection layer
and a third connection layer that each are formed mainly of an
insulating resin, wherein
[0010] the first connection layer has a structure in which
conductive particles are arranged in a single layer in a plane
direction of an insulating resin layer on a side of the second
connection layer, and the thickness of the insulating resin layer
in central regions between adjacent ones of the conductive
particles is smaller than the thickness of the insulating resin
layer in regions in proximity to the conductive particles.
[0011] The present invention further provides a method of producing
the above anisotropic conductive film, the method including the
following steps (A) to (D).
<Step (A)>
[0012] The step of disposing conductive particles within openings
of a transfer die with the openings, and placing an insulating
resin layer formed on a release film so as to be opposed to a
surface of the transfer die with the openings.
<Step (B)>
[0013] The step of applying pressure to the insulating resin layer
from a side of the release film to press an insulating resin into
the openings, to transfer the conductive particles to a surface of
the insulating resin layer, to form a first connection layer,
wherein the first connection layer has a structure in which the
conductive particles are arranged in a single layer in a plane
direction of the insulating resin layer, and the thickness of the
insulating resin layer in central regions between adjacent ones of
the conductive particles is smaller than that of the insulating
resin layer in regions in proximity to the conductive
particles.
<Step (C)>
[0014] The step of forming a second connection layer formed mainly
of an insulating resin on a surface of the first connection layer
on a side of the conductive particles.
<Step (D)>
[0015] The step of forming a third connection layer formed mainly
of an insulating resin on a surface of the first connection layer
on a side opposite to the second connection layer.
[0016] The present invention provides another method of producing
the above anisotropic conductive film, the method including the
following steps (a) to (c).
<Step (a)>
[0017] The step of disposing conductive particles within openings
of a transfer die with the openings, and placing an insulating
resin layer that has been bonded to a third connection layer in
advance so as to be opposed to a surface of the transfer die with
the openings.
<Step (b)>
[0018] The step of applying pressure to the insulating resin layer
from a side of a release film to press an insulating resin into the
openings, to transfer the conductive particles to a surface of the
insulating resin layer, to form a first connection layer, wherein
the first connection layer has a structure in which the conductive
particles are arranged in a single layer in a plane direction of
the insulating resin layer, and the thickness of the insulating
resin layer in central regions between adjacent ones of the
conductive particles is smaller than that of the insulating resin
layer in regions in proximity to the conductive particles.
<Step (c)>
[0019] The step of forming a second connection layer formed mainly
of an insulating resin on a surface of the first connection layer
on a side of the conductive particles.
[0020] The present invention provides a connection structure in
which a first electronic component is connected to a second
electronic component by anisotropic conductive connection using the
above-described anisotropic conductive film.
[0021] Moreover, the present invention provides a method of
connecting a first electronic component to a second electronic
component by anisotropic conductive connection using the
above-described anisotropic conductive film, the method including:
temporarily applying the anisotropic conductive film to the second
electronic component through the third connection layer of the
anisotropic conductive film; mounting the first electronic
component on the anisotropic conductive film temporarily applied;
and performing thermocompression bonding through the first
electronic component.
Advantageous Effects of Invention
[0022] In the anisotropic conductive film of the present invention
that has a three-layer structure in which the first connection
layer is sandwiched between the second and third connection layers
that each are insulative, the first connection layer has a
structure in which the conductive particles are arranged in a
single layer in a plane direction of an insulating resin layer on a
side of the second connection layer, and a structure in which the
thickness of the insulating resin layer at a center between
adjacent ones of the conductive particles is smaller than that of
the insulating resin layer in regions in proximity to the
conductive particles. For this reason, the anisotropic conductive
film having the conductive particles arranged in a single layer is
allowed to achieve favorable connection reliability, favorable
insulating properties, and favorable particle capturing
efficiency.
BRIEF DESCRIPTION OF DRAWINGS
[0023] FIG. 1A is a cross-sectional view of an anisotropic
conductive film of the present invention.
[0024] FIG. 1B is a cross-sectional view of the anisotropic
conductive film of the present invention.
[0025] FIG. 1C is a cross-sectional view of the anisotropic
conductive film of the present invention.
[0026] FIG. 2A is a diagram illustrating step (A) of producing the
anisotropic conductive film of the present invention.
[0027] FIG. 2B is a diagram illustrating step (A) of producing the
anisotropic conductive film of the present invention.
[0028] FIG. 3A is a diagram illustrating step (B) of producing the
anisotropic conductive film of the present invention.
[0029] FIG. 3B is a diagram illustrating step (B) of producing the
anisotropic conductive film of the present invention.
[0030] FIG. 3C is a diagram illustrating a step (B) of producing
the anisotropic conductive film of the present invention.
[0031] FIG. 4 is a diagram illustrating step (C) of producing the
anisotropic conductive film of the present invention.
[0032] FIG. 5 is a diagram illustrating step (D) of producing the
anisotropic conductive film of the present invention.
[0033] FIG. 6A is a diagram illustrating step (a) of producing the
anisotropic conductive film of the present invention.
[0034] FIG. 6B is a diagram illustrating step (a) of producing the
anisotropic conductive film of the present invention.
[0035] FIG. 7A is a diagram illustrating step (b) of producing the
anisotropic conductive film of the present invention.
[0036] FIG. 7B is a diagram illustrating step (b) of producing the
anisotropic conductive film of the present invention.
[0037] FIG. 7C is a diagram illustrating step (b) of producing the
anisotropic conductive film of the present invention.
[0038] FIG. 8 is a diagram illustrating step (c) of producing the
anisotropic conductive film of the present invention.
DESCRIPTION OF EMBODIMENTS
[0039] Hereinafter, anisotropic conductive films of the present
invention will be described in detail.
<<Anisotropic Conductive Film>>
[0040] As shown in FIG. 1A, an anisotropic conductive film 100 of
the present invention has a three-layer structure in which a first
connection layer 1 is sandwiched between a second connection layer
2 and a third connection layer 3 that each are formed mainly of an
insulating resin. The first connection layer 1 has a structure in
which conductive particles 4 are arranged in a single layer in a
plane direction of an insulating resin layer 10 on a side of the
second connection layer 2. In this case, the conductive particles 4
may be close packed in the plane direction. It is preferable that
the conductive particles 4 be arranged regularly (for example, in a
square lattice) at constant intervals in the plane direction.
Further, the first connection layer 1 has a structure in which a
thickness t1 of the insulating resin layer in central regions
between adjacent ones of the conductive particles 4 is smaller than
a thickness t2 of the insulating resin layer in regions in
proximity to the conductive particles 4. When the insulating resin
layer thickness t1 is smaller than the insulating resin layer
thickness t2, the conductive particles 4 that do not exist between
terminals to be connected in anisotropic conductive connection are
not used, and therefore the conductive particles 4 can prevent
occurrence of short circuit. This is because the insulating resin
layer between the conductive particles 4 melts by heating and
pressurization during anisotropic conductive connection to cover
the conductive particles 4, forming a coating layer 1d, as shown in
FIG. 1B.
[0041] The central region between adjacent ones of the conductive
particles 4 herein means a region that falls within a range of
.+-.L/4 from a midpoint P of a distance L between the adjacent
conductive particles. The region in proximity to the conductive
particles means a position around a line segment that touches the
conductive particles 4 in a thickness direction of the first
connection layer 1.
[0042] It is preferable that the insulating resin layer thicknesses
t1 and t2 further satisfy the following relation. This is because
when the thickness t1 is much smaller than the thickness t2, the
conductive particles 4 are likely to flow, and the particle
capturing efficiency tends to decrease, and when the thickness t1
closely approximates to the thickness t2, the effects of the
present invention are unlikely to be obtained.
0.1.times.t2<t1<0.9.times.t2
[0043] When the absolute thickness of the insulating resin layer
thickness t1 is too small, the first connection layer 1 may be
unlikely to be formed. Therefore, it is preferably 0.5 .mu.m or
more. On the other hand, when the absolute thickness of the
insulating resin layer thickness t2 is too large, the insulating
resin layer 10 is unlikely to be removed from a connection region
during anisotropic conductive connection, and conduction failure
may occur. Therefore, it is preferably 6 .mu.m or less.
[0044] As shown in FIG. 1C, when the thickness of the resin layer
containing the conductive particles largely varies in the plane
direction and therefore, when the resin layer is divided, the
thickness of the insulating resin layer between the conductive
particles 4 may be substantially zero. The expression
"substantially zero" means a state where divided insulating resin
layers containing the conductive particle are each independent. In
this case, the relational expression described above cannot be
applied. Therefore, in order to achieve favorable connection
reliability, favorable insulating properties, and favorable
particle capturing efficiency, it is preferable that shortest
distances L.sup.1, L.sup.2, L.sup.3, L.sup.4 . . . between a
perpendicular line extending through the center of each conductive
particle 4 and a position where the insulating resin layer
thickness is the smallest be controlled. Specifically, when the
shortest distances L.sup.1, L.sup.2, L.sup.3, L.sup.4 . . . are
long, the amount of the resin in the first connection layer 1
relatively increases, and the productivity is improved. Therefore,
the fluidity of the conductive particles 4 can be suppressed. In
contrast, when the shortest distances L.sup.1, L.sup.2, L.sup.3,
L.sup.4 . . . are short, the amount of the resin in the first
connection layer 1 relatively decreases. Therefore, the distance
between the particles can be easily controlled. Accordingly, the
accuracy of position alignment of conductive particles can be
improved. The distances L.sup.1, L.sup.2, L.sup.3, L.sup.4, . . .
are preferably longer than 0.5 times and less than 1.5 times the
particle diameter of the conductive particles 4, and more
preferably within a range of 0.6 times to 1.2 times.
[0045] As shown in FIG. 1C, the conductive particles 4 may be
embedded in the first connection layer 1. The degree of embedding,
for example, shallow or deep depth, varies depending on the
viscosity of a material during formation of the first connection
layer 1, the shape or the size of openings of a transfer die for
arranging the conductive particles, and the like. In particular,
the degree of embedding can be controlled by a relation between the
bottom diameter and the opening diameter of the openings. For
example, it is preferable that the bottom diameter be 1.1 times or
more and less than 2 times the diameter of the conductive particles
and the opening diameter be 1.3 times or more and less than 3 times
the diameter of the conductive particles.
[0046] Within a range not impairing the effects of the present
invention, conductive particles 4' may be present in the second
connection layer 2 as shown by dotted lines in FIG. 1C.
<First Connection Layer>
[0047] As the insulating resin layer 10 constituting such a first
connection layer 1, a known insulating resin layer can be
appropriately used. For example, a thermal- or photo-radical
polymerizable resin layer containing an acrylate compound and a
thermal- or photo-radical polymerization initiator or a layer
obtained by subjecting the thermal- or photo-radical polymerizable
resin layer to thermal- or photo-radical polymerization; or a
thermal- or photo-cationic or anionic polymerizable resin layer
containing an epoxy compound and a thermal- or photo-cationic or
anionic polymerization initiator or a layer obtained by subjecting
the thermal- or photo-cationic or anionic polymerizable resin layer
to thermal- or photo-cationic or anionic polymerization can be
used.
[0048] In particular, as the insulating resin layer 10 constituting
the first connection layer 1, a thermal-radical polymerizable resin
layer containing an acrylate compound and a thermal-radical
polymerization initiator may be used. It is preferable that a
photo-radical polymerizable resin layer containing an acrylate
compound and a photo-radical polymerization initiator be used. In
this case, when the photo-radical polymerizable resin layer is
irradiated with ultraviolet rays to perform photo-radical
polymerization, the first connection layer 1 can be formed. When
the photo-radical polymerizable resin layer is irradiated with
ultraviolet rays from a side of the conductive particles before
formation of the second connection layer 2 to perform photo-radical
polymerization, the degree of cure of a region 1X between the
conductive particles 4 and a surface 3a of the third connection
layer 3 in the first connection layer 1, as shown in FIG. 1A, can
be made lower than that of a region 1Y between the adjacent ones of
the conductive particles. Therefore, the minimum melt viscosity in
the region 1X where the degree of cure in the first connection
layer is low can be made lower than that in the region 1Y where the
degree of cure in the first connection layer is high. During
anisotropic conductive connection, the position of the conductive
particles 4 can be prevented from shifting, the particle capturing
efficiency can be improved, the pressing property of the conductive
particles 4 can be improved, and the conduction resistance can be
decreased. Accordingly, favorable conduction reliability can be
achieved.
[0049] The degree of cure herein represents a value defined as a
decrease ratio of a functional group contributing to polymerization
(for example, vinyl group). Specifically, when the amount of vinyl
group after curing is 20% of that before curing, the degree of cure
is 80%. The amount of vinyl group can be measured by analysis of
characteristic absorption of vinyl group in infrared absorption
spectrum.
[0050] The degree of cure defined above in the region 1X is
preferably 40 to 80%, and the degree of cure in the region 1Y is
preferably 70 to 100%.
[0051] It is preferable that the minimum melt viscosity of the
first connection layer 1 that is measured by a rheometer be higher
than that of each of the second connection layer 2 and the third
connection layer 3. Specifically, when a value of [the minimum melt
viscosity (mPas) of the first connection layer 1]/[the minimum melt
viscosity (mPas) of the second connection layer 2 or the third
connection layer 3] is too low, the particle capturing efficiency
decreases, and the probability of occurrence of short circuit tends
to increase. When the value is too high, the conduction reliability
tends to be reduced. Therefore, the value is preferably 1 to 1,000,
and more preferably 4 to 400. As to the respective preferable
minimum melt viscosities, when the minimum melt viscosity of the
first connection layer 1 is too low, the particle capturing
efficiency tends to decrease, and when it is too high, the
conduction resistance tends to increase. Therefore, it is
preferably 100 to 100,000 mPas, and more preferably 500 to 50,000
mPas. When the minimum melt viscosity of the second or third
connection layer 2, 3 is too low, the resin tends to be squeezed
out during formation of a reel, and when it is too high, the
conduction resistance tends to increase. Therefore, it is
preferably 0.1 to 10,000 mPas, and more preferably 1 to 1,000
mPas.
<Acrylate Compound>
[0052] As the acrylate compound used in the insulating resin layer
10 constituting the first connection layer 1, a conventionally
known radically polymerizable acrylate can be used. For example, a
monofunctional (meth)acrylate (herein, (meth)acrylate includes
acrylate and methacrylate), or a polyfunctional (meth)acrylate such
as a bifunctional or more (meth)acrylate can be used. In the
present invention, it is preferable that a polyfunctional
(meth)acrylate be used for at least a portion of an acrylic monomer
to form a thermosetting adhesive.
[0053] Examples of the monofunctional (meth)acrylate may include
methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl
(meth)acrylate, -propyl (meth)acrylate, n-butyl (meth)acrylate,
i-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-methylbutyl
(meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate,
n-heptyl (meth)acrylate, 2-methylhexyl (meth)acrylate, 2-ethylhexyl
(meth)acrylate, 2-butylhexyl (meth)acrylate, isooctyl
(meth)acrylate, isopentyl (meth)acrylate, isononyl (meth)acrylate,
isodecyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl
(meth)acrylate, benzyl (meth)acrylate, phenoxy (meth)acrylate,
n-nonyl (meth)acrylate, n-decyl (meth)acrylate, lauryl
(meth)acrylate, hexadecyl (meth)acrylate, stearyl (meth)acrylate,
and morpholin-4-yl (meth)acrylate. Examples of the bifunctional
(meth)acrylate may include bisphenol F-EO-modified
di(meth)acrylate, bisphenol A-EO-modified di(meth)acrylate,
polypropylene glycol di(meth)acrylate, polyethylene glycol
(meth)acrylate, tricyclodecane dimethylol di(meth)acrylate, and
dicyclopentadiene (meth)acrylate. Examples of a trifunctional
(meth)acrylate may include trimethylolpropane tri(meth)acrylate,
trimethylolpropane PO-modified (meth)acrylate, and isocyanuric acid
EO-modified tri(meth)acrylate. Examples of a tetrafunctional or
more (meth)acrylate may include dipentaerythritol
penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate,
pentaerythritol tetra(meth)acrylate, and di-trimethylolpropane
tetraacrylate. In addition, a polyfunctional urethane
(meth)acrylate can also be used. Specific examples thereof may
include M1100, M1200, M1210, and M1600 (all available from TOAGOSEI
CO., LTD.), and AH-600 and AT-600 (all available from KYOEISHA
CHEMICAL CO., LTD.).
[0054] When the content of the acrylate compound in the insulating
resin layer 10 constituting the first connection layer 1 is too
small, a difference of minimum melt viscosity between the first
connection layer 1 and the second connection layer 2 is unlikely to
be produced. When it is too large, curing shrinkage increases, and
the workability tends to be reduced. Therefore, the content is
preferably 2 to 70% by mass, and more preferably 10 to 50% by
mass.
[0055] <Photo-Radical Polymerization Initiator>
[0056] A photo-radical polymerization initiator may be
appropriately selected from known photo-radical polymerization
initiators, and used. Examples thereof may include an
acetophenone-based photopolymerization initiator, a
benzylketal-based photopolymerization initiator, and a
phosphorus-based photopolymerization initiator. Specific examples
of the acetophenone-based photopolymerization initiator may include
2-hydroxy-2-cyclohexylacetophenone (IRGACURE 184, available from
BASF Japan Ltd.),
.alpha.-hydroxy-.alpha.,.alpha.'-dimethylacetophenone (DAROCUR
1173, available from BASF Japan Ltd.),
2,2-dimethoxy-2-phenylacetophenone (IRGACURE 651, available from
BASF Japan Ltd.), 4-(2-hydroxyethoxyl)phenyl (2-hydroxy-2-propyl)
ketone (DAROCUR 2959, available from BASF Japan Ltd.), and
2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl--
1-propan-1-one (IRGACURE 127, available from BASF Japan Ltd.).
Examples of the benzylketal-based photopolymerization initiator may
include benzophenone, fluorenone, dibenzosuberone,
4-aminobenzophenone, 4,4'-diaminobenzophenone,
4-hydroxybenzophenone, 4-chlorobenzophenone, and
4,4'-dichlorobenzophenone.
2-Benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1
(IRGACURE 369, available from BASF Japan Ltd.) can also be used.
Examples of the phosphorus-based photopolymerization initiator may
include bis(2,4,6-trimethylbenzoyl)-phenyl phosphine oxide
(IRGACURE 819, available from BASF Japan Ltd.) and
2,4,6-trimethylbenzoyl-diphenyl phosphine oxide (DAROCUR TPO,
available from BASF Japan Ltd.).
[0057] When the amount of the photoradical polymerization initiator
to be used is too small relative to 100 parts by mass of acrylate
compound, photo-radical polymerization is unlikely to proceed
sufficiently. When it is too large, a decrease in rigidity may be
caused. Therefore, it is preferably 0.1 to 25 parts by mass, and
more preferably 0.5 to 15 parts by mass.
<Thermal-Radical Polymerization Initiator>
[0058] Examples of the thermal-radical polymerization initiator may
include an organic peroxide and an azo compound. An organic
peroxide can be preferably used since nitrogen that becomes bubbles
is not generated.
[0059] Examples of the organic peroxide may include methyl ethyl
ketone peroxide, cyclohexanone peroxide, methyl cyclohexanone
peroxide, acetylacetone peroxide,
1,1-bis(tert-butylperoxy)-3,3,5-trimethyl cyclohexane,
1,1-bis(tert-butylperoxy)cyclohexane,
1,1-bis(tert-hexylperoxy)-3,3,5-trimethyl cyclohexane,
1,1-bis(tert-hexylperoxy)cyclohexane,
1,1-bis(tert-butylperoxy)cyclododecane, isobutyl peroxide, lauroyl
peroxide, succinic acid peroxide, 3,5,5-trimethyl hexnoyl peroxide,
benzoyl peroxide, octanoyl peroxide, stearoyl peroxide, diisopropyl
peroxydicarbonate, dinormal propyl peroxydicarbonate,
di-2-ethylhexyl peroxydicarbonate, di-2-ethoxyethyl
peroxydicarbonate, di-2-methoxybutyl peroxydicarbonate,
bis-(4-tert-butylcyclohexyl)peroxydicarbonate,
(.alpha.,.alpha.-bis-neodecanoylperoxy)diisopropylbenzene, cumyl
peroxyneodecanoate, octyl peroxyneodecanoate, hexyl
peroxyneodecanoate, tert-butyl peroxyneodecanoate, tert-hexyl
peroxypivalate, tert-butyl peroxypivalate,
2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane,
1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, tert-hexyl
peroxy-2-ethylhexanoate, tert-butyl peroxy-2-ethylhexanoate,
tert-butyl peroxy-3-methylpropionate, tert-butyl peroxylaurate,
tert-butyl peroxy-3,5,5-trimethyl hexanoate, tert-hexylperoxy
isopropyl monocarbonate, tert-butylperoxy isopropyl carbonate,
2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, tert-butyl peracetate,
tert-hexyl perbenzoate, and tert-butyl perbenzoate. An organic
peroxide to which a reductant is added may be used as a redox
polymerization initiator.
[0060] Examples of the azo compound may include
1,1-azobis(cyclohexane-1-carbonitrile),
2,2'-azobis(2-methyl-butyronitrile), 2,2'-azobisbutyronitrile,
2,2'-azobis(2,4-dimethyl-valeronitrile),
2,2'-azobis(2,4-dimethyl-4-methoxynitrile),
2,2'-azobis(2-amidino-propane) hydrochloride,
2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]hydrochloride,
2,2'-azobis[2-(2-imidazolin-2-yl)propane]hydrochloride,
2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane],
2,2'-azobis[2-methyl-N-(1,1-bis(2-hydroxymethyl)-2-hydroxyethyl)propionam-
ide], 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],
2,2'-azobis(2-methyl-propionamide)dihydrate,
4,4'-azobis(4-cyano-valeric acid),
2,2'-azobis(2-hydroxymethylpropiononitrile), dimethyl
2,2'-azobis(2-methylpropionate), and cyano-2-propyl
azoformaide.
[0061] When the amount of the thermal-radical polymerization
initiator to be used is too small, curing is difficult. When it is
too large, the product life is reduced. Therefore, the amount is
preferably 2 to 60 parts by mass, and more preferably 5 to 40 parts
by mass, relative to 100 parts by mass of the acrylate
compound.
<Epoxy Compound>
[0062] The insulating resin layer 10 constituting the first
connection layer 1 may include a thermal- or photo-cationic or
anionic polymerizable resin layer containing an epoxy compound and
a thermal- or photo-cationic or anionic polymerization initiator or
a layer obtained by subjecting the thermal- or photo-cationic or
anionic polymerizable resin layer to thermal- or photo-cationic or
anionic polymerization.
[0063] Preferred examples of the epoxy compound may include a
compound or a resin having two or more epoxy groups in its
molecule. These may be liquid or solid. Specific examples thereof
may include a glycidyl ether obtained by reacting epichlorohydrin
with a polyhydric phenol such as bisphenol A, bisphenol F,
bisphenol S, hexahydrobisphenol A, tetramethylbisphenol A,
diallylbisphenol A, hydroquinone, catechol, resorcin, cresol,
tetrabromobisphenol A, trihydroxybiphenyl, benzophenone,
bisresorcinol, bisphenol hexafluoroacetone, tetramethylbisphenol A,
tetramethylbisphenol F, tris(hydroxyphenyl)methane, bixylenol,
phenol novolak, and cresol novolak, and a polyglycidyl ether
obtained by reacting epichlorohydrin with an aliphatic polyhydric
alcohol such as glycerol, neopentyl glycol, ethylene glycol,
propylene glycol, butylene glycol, hexylene glycol, polyethylene
glycol, and polypropylene glycol; a glycidyl ether ester obtained
by reacting epichlorohydrin with a hydroxycarboxylic acid such as
p-oxybenzoic acid and .beta.-oxynaphthoic acid, and a polyglycidyl
ester obtained from polycarboxylic acid such as phthalic acid,
methylphthalic acid, isophthalic acid, terephthalic acid,
tetrahydrophthalic acid, hexahydrophthalic acid, endomethylene
tetrahydrophthalic acid, endomethylene hexahydrophthalic acid,
trimellitic acid, and polymerized fatty acid; a
glycidylaminoglycidyl ether obtained from aminophenol and
aminoalkylphenol; a glycidylaminoglycidyl ester obtained from
aminobenzoic acid; glycidylamine obtained from aniline, toluidine,
tribromoaniline, xylylenediamine, diaminocyclohexane,
bisaminomethylcyclohexane, 4,4'-diaminodiphenylmethane, and
4,4'-diaminodiphenyl sulfone; and a known epoxy resin such as
epoxidized polyolefin. An alicyclic epoxy compound such as
3,4-epoxycyclohexenylmethyl-3',4'-epoxycyclohexene carboxylate can
also be used.
<Thermal Cationic Polymerization Initiator>
[0064] As the thermal cationic polymerization initiator, a known
thermal cationic polymerization initiator for an epoxy compound can
be used. For example, the thermal cationic polymerization initiator
generates an acid in which a cationically polymerizable compound
may be cationically polymerized by heat. A known iodonium salt,
sulfonium salt, phosphonium salt, or ferrocene salt can be used. An
aromatic sulfonium salt that exhibits favorable latency with
respect to temperature can be preferably used. Preferred examples
of the thermal cationic polymerization initiator may include
diphenyliodonium hexafluoroantimonate, diphenyliodonium
hexafluorophosphate, diphenyliodonium hexafluoroborate,
triphenylsulfonium hexafluoroantimonate, triphenylsulfonium
hexafluorophosphate, and triphenylsulfonium hexafluoroborate.
Specific examples thereof may include SP-150, SP-170, CP-66, and
CP-77 available from ADEKA CORPORATION; CI-2855 and CI-2639
available from Nippon Soda Co., Ltd.; SAN-AID SI-60 and SI-80
available from SANSHIN CHEMICAL INDUSTRY CO., LTD.; and
CYRACURE-UVI-6990 and UVI-6974 available from Union Carbide
Corporation.
[0065] When the amount of the thermal cationic polymerization
initiator to be added is too small, thermal cationic polymerization
is unlikely to proceed sufficiently. When it is too large, a
decrease in rigidity may be caused. Therefore, the amount is
preferably 0.1 to 25 parts by mass, and more preferably 0.5 to 15
parts by mass, relative to 100 parts by mass of the epoxy
compound.
<Thermal Anionic Polymerization Initiator>
[0066] As the thermal anionic polymerization initiator, a known
thermal anionic polymerization initiator for an epoxy compound can
be used. For example, the thermal anionic polymerization initiator
generates a base in which an anionically polymerizable compound may
be anionically polymerized by heat. A known aliphatic amine
compound, aromatic amine compound, secondary or tertiary amine
compound, imidazole compound, polymercaptan compound, boron
trifluoride-amine complex, dicyandiamide, or organic acid hydrazide
can be used. An encapsulated imidazole compound that exhibits
favorable latency with respect to temperature can be preferably
used. Specific examples thereof may include NOVACURE HX3941HP
available from Asahi Kasei E-materials Corporation.
[0067] When the amount of the thermal anionic polymerization
initiator to be added is too small, curing tends to be difficult.
When it is too large, the product life tends to be reduced.
Therefore, the amount is preferably 2 to 60 parts by mass, and more
preferably 5 to 40 parts by mass, relative to 100 parts by mass of
the epoxy compound.
<Photo-Cationic Polymerization Initiator and Photo-Anionic
Polymerization Initiator>
[0068] As the photo-cationic polymerization initiator or the
photo-anionic polymerization initiator for the epoxy compound, a
known polymerization initiator can appropriately be used.
<Conductive Particles>
[0069] The conductive particles 4 constituting the first connection
layer 1 can be appropriately selected from particles used in a
conventionally known anisotropic conductive film, and used.
Examples thereof may include particles of metal such as nickel,
cobalt, silver, copper, gold, and palladium, and metal-coated resin
particles. Two or more kinds thereof may be used in
combination.
[0070] When the average particle diameter of the conductive
particles 4 is too small, the particles cannot correspond to
various heights of wirings, and conduction resistance tends to
increase. When it is too large, short circuit tends to occur.
Therefore, it is preferably 1 to 10 .mu.m, and more preferably 2 to
6 .mu.m. The average particle diameter can be measured by a general
particle size distribution measurement device.
[0071] When the amount of such conductive particles 4 in the first
connection layer 1 is too small, the particle capturing efficiency
decreases, and anisotropic conductive connection is difficult. When
it is too large, short circuit may be caused. Therefore, it is
preferably 50 to 40,000, and more preferably 200 to 20,000 per
square millimeter.
<Other Components in First Connection Layer>
[0072] In the first connection layer 1, if necessary, a
film-forming resin such as a phenoxy resin, an epoxy resin, an
unsaturated polyester resin, a saturated polyester resin, a
urethane resin, a butadiene resin, a polyimide resin, a polyamide
resin, and a polyolefin resin can be used in combination.
[0073] When the insulating resin layer 10 constituting the first
connection layer 1 is a layer obtained by photo-radical
polymerization of a photo-radical polymerizable resin layer
containing an acrylate compound and a photo-radical polymerization
initiator, it is preferable that the insulating resin layer 10
further contain an epoxy compound and a thermal cationic
polymerization initiator. In this case, it is preferable that the
second connection layer 2 and the third connection layer 3 be also
a thermal-cationic polymerizable resin layer containing the epoxy
compound and the thermal cationic polymerization initiator, as
described below. Thus, the interlayer peel strength can be
improved.
[0074] In the first connection layer 1, it is preferable that the
conductive particles 4 dig into the second connection layer 2
(i.e., the conductive particles 4 be exposed on the surface of the
first connection layer 1), as shown in FIG. 1A. When all the
conductive particles 4 are embedded in the first connection layer
1, the connection resistance may be reduced due to insufficient
exclusion of the insulating resin layer 10. When the degree of
digging is too small, the particle capturing efficiency tends to
decrease. When it is too large, the connection resistance tends to
increase. Therefore, it is preferably 10 to 90%, and more
preferably 20 to 80% of the average particle diameter of the
conductive particles 4.
[0075] The first connection layer 1 can be formed by disposing the
conductive particles 4 within the openings of the die with the
openings, placing the insulating resin layer 10 that forms the
first connection layer 1 formed on a release film so as to be
opposed to a surface of the die with the openings 21, and applying
pressure while heating if necessary, so that the insulating resin
does not enter into a corner of bottom of the openings.
<Second Connection Layer and Third Connection Layer>
[0076] The second connection layer 2 and the third connection layer
3 are both formed mainly of an insulating resin. The insulating
resin may be appropriately selected from known insulating resins,
and used. They can be formed from a material that is the same as
the material for the insulating resin layer 10 in the first
connection layer 1.
[0077] The second connection layer 2 is disposed on a side of the
conductive particles 4 in the first connection layer 1, and is
usually a layer disposed on a side of a terminal that requires high
accuracy of position alignment, such as a bump of an IC chip. On
the other hand, the third connection layer 3 is usually disposed on
a side of a terminal that does not require relatively high accuracy
of alignment, such as a solid electrode of a glass substrate.
[0078] When the thickness of the second connection layer 2 is too
small, the filled resin is insufficient, and therefore the
conduction failure may occur. When it is too large, the resin is
squeezed out during compression bonding, and a compression-bonding
device may be contaminated. Therefore, it is preferably 5 to 20
.mu.m, and more preferably 8 to 15 .mu.m. When the thickness of the
third connection layer 3 is too small, the third connection layer 3
may be insufficiently adhered to a second electronic component
during temporary application. When it is too large, the conduction
resistance tends to increase. Therefore, it is preferably 0.5 to 6
.mu.m, and more preferably 1 to 5 .mu.m.
<Method of Producing Anisotropic Conductive Film<<
[0079] Next, a method of producing the anisotropic conductive film
of the present invention will be described as one example. This
production method includes the following steps (A) to (D).
Hereinafter, each step will be described.
<Step (A)>
[0080] As shown in FIG. 2A, the conductive particles 4 are disposed
within openings 21 of a transfer die 20 with the openings 21, and
as shown in FIG. 2E, the insulating resin layer 10 formed on a
release film 22 is disposed so as to be opposed to a surface of the
transfer die 20 with the openings 21.
[0081] The transfer die 20 has openings that are formed, for
example, from an inorganic material such as various ceramics,
glass, and metal including stainless steel, or an organic material
such as various resins, by a known opening-forming method such as a
photolithography method. Such a transfer die 20 may have a shape of
a plate, a roller, or the like.
[0082] The openings 21 of the transfer die 20 house the conductive
particles 4 thereinside. The openings 21 may have a shape of
column, polygonal pillar such as square pillar, or pyramid such as
square pyramid.
[0083] It is preferable that the alignment of the openings 21 be
regular alignment such as a lattice pattern and a zigzag
pattern.
[0084] The diameter and the depth of the openings 21 of the
transfer die 20 can be measured by a laser microscope.
[0085] A method for housing the conductive particles 4 in the
openings 21 of the transfer die 20 is not particularly limited, and
a known procedure can be utilized. For example, a dried powder of
conductive particles or a dispersion liquid in which the powder is
dispersed in a solvent is sprayed or applied to an opening-forming
face of the transfer die 20, and the surface of the opening-forming
face may be wiped with a brush, a blade, or the like.
[0086] The ratio of the average particle diameter of the conductive
particles 4 to the depth of the openings 21 (the average particle
diameter of the conductive particles/the depth of the openings) is
preferably 0.4 to 3.0, and more preferably 0.5 to 1.5 in terms of
balance between improvement of transfer and conductive particle
retentivity.
[0087] The ratio of the average particle diameter of the conductive
particles 4 to the diameter of the openings 21 (the average
particle diameter of the conductive particles/the diameter of the
opening) is preferably 1.1 to 2.0, and more preferably 1.3 to 1.8
in terms of balance between easy housing of the conductive
particles, easy pressing of the insulating resin, and the like.
[0088] When the bottom diameter of the openings 21 is smaller than
the opening diameter of the openings 21, it is preferable that the
bottom diameter be 1.1 times or more and less than 2 times the
diameter of the conductive particles and the opening diameter be
1.3 times or more and less than 3 times the diameter of the
conductive particles.
<Step (B)>
[0089] As shown in FIG. 3A, pressure is applied to the insulating
resin layer 10 from a side of the release film 22 to press the
insulating resin into the openings 21, and the conductive particles
4 are transferred to a surface of the insulating resin layer 10 so
as to be embedded. Thus, the first connection layer 1 having a
structure in which the conductive particles 4 are arranged in a
single layer in the plane direction of the insulating resin layer
10, as shown in FIG. 3B, is formed. In the first connection layer
1, the thickness of the insulating resin layer in central regions
between adjacent ones of the conductive particles 4 is smaller than
the thickness of the insulating resin layer in regions in proximity
to the conductive particles. In this case, the thickness of the
insulating resin layer between the adjacent ones of the conductive
particles 4 may be substantially zero (see FIG. 1C). When it is
substantially zero, independence of each conductive particle after
connection is enhanced, and linkage of the conductive particles
during connection is easily prevented.
<Step (C)>
[0090] As shown in FIG. 4, the second connection layer 2 formed
mainly of an insulating resin is formed on a surface of the first
connection layer 1 on a side of the conductive particles 4. Thus, a
boundary between the first connection layer and the second
connection layer has an undulating shape, that is, a wave shape or
an irregular shape. When a layer in the film has an undulating
shape, as described above, a possibility of increasing a contact
area mainly with a bump during jointing can be increased.
Therefore, the adhesion strength can be expected to be
improved.
<Step (D)>
[0091] Subsequently, after the release film 22 is removed, the
third connection layer 3 formed mainly of an insulating resin is
formed on a surface of the first connection layer 1 on a side
opposite to the second connection layer 2. Thus, the anisotropic
conductive film 100 shown in FIG. 5 is obtained.
[0092] It is preferable that the first connection layer 1 be
irradiated with ultraviolet rays UV from the side of the conductive
particles 4 as shown in FIG. 3C between the steps (B) and (C).
Thus, the conductive particles 4 can be fixed on the first
connection layer 1. In addition, the degree of cure of the first
connection layer 1 below the conductive particles 4 can be made
relatively lower as compared with a periphery thereof, and the
pressing property of the conductive particles during anisotropic
conductive connection can be improved.
<<Method of Producing Anisotropic Conductive Film>>
[0093] An example of another method of producing the anisotropic
conductive film of the present invention will be described. This
method is an aspect in which the third connection layer 3 is used
instead of the release film 22 and includes the following steps (a)
to (c). Hereinafter, each step will be described.
<Step (a)>
[0094] As shown in FIG. 6A, the conductive particles 4 are disposed
within openings 21 of a transfer die 20 with the openings 21, and
as shown in FIG. 6B, and the insulating resin layer 10 that has
been bonded to the third connection layer 3 in advance is placed so
as to be opposed to a surface of the transfer die 20 with the
openings 21.
<Step (b)>
[0095] As shown in FIG. 7A, pressure is applied to the insulating
resin layer 10 from a side of the third connection layer 3 to press
the insulating resin into the openings 21, and the conductive
particles 4 are thereby transferred to a surface of the insulating
resin layer 10. Thus, the first connection layer 1 having a
structure in which the conductive particles 4 are arranged in a
single layer in the plane direction of the insulating resin layer
10, as shown in FIG. 7B, is formed. In the first connection layer
1, the thickness of the insulating resin layer in central regions
between adjacent ones of the conductive particles 4 is smaller than
the thickness of the insulating resin layer in regions in proximity
to the conductive particles. In this case, the thickness of the
insulating resin layer between the adjacent ones of the conductive
particles 4 may be substantially zero (see FIG. 1C). When it is
substantially zero, independence of each conductive particle after
connection is enhanced, and linkage of the conductive particles
during connection is easily prevented.
<Step (c)>
[0096] The second connection layer 2 formed mainly of an insulating
resin is formed on a surface of the first connection layer 1 on a
side of the conductive particles 4. Thus, the anisotropic
conductive film 100 shown in FIG. 8 is obtained.
[0097] It is preferable that the first connection layer 1 be
irradiated with ultraviolet rays UV from the side of the conductive
particles 4 as shown in FIG. 7C between the steps (b) and (c).
Thus, the conductive particles 4 can be fixed on the first
connection layer 1. In addition, the degree of cure of the first
connection layer 1 below the conductive particles 4 can be made
relatively lower as compared with a periphery thereof, and the
pressing property of the conductive particles during anisotropic
conductive connection can be improved.
[0098] In the anisotropic conductive film shown in FIG. 8, the
first connection layer 1 mainly includes the conductive particles
4. In this case, a region where each of the conductive particles is
encompassed by the first connection layer 1 has a convex shape on a
side of the second connection layer 2. Therefore, the width of the
region on the third connection layer 3 side is larger than that on
the second connection layer 2 side. The shortest distance p in a
horizontal direction between an end in the thickness direction of
the conductive particles 4 on a side of larger width (bottom end of
the particles) and the second connection layer 2 contributes to
stability of the conductive particles during connection.
Specifically, p acts as a base of a fixed portion. Therefore, the
convex shape of the resin in regions in proximity to the conductive
particles means that the particles encompassed by the resin remain
and are isolated. This is because a probability of relatively
suppressing the fluidity of the conductive particles in the plane
direction is increased by a skirt portion of the first connection
layer that encompasses the conductive particles during compression
of the conductive particles by pressing. This effect is
substantially the same even when the thickness of the first
connection layer in the central region between the conductive
particles is zero, as described above. This is because the fluidity
of the particles is suppressed by the shape of the resin in regions
in proximity to the particles, as described above, and whether the
end thereof is closed or slightly opened is not essentially
different. Therefore, an effect of preventing linkage between the
conductive particles can be expected to be expressed as
substantially the same result. Accordingly, p represents a
corresponding length to the skirt portion of the convex shape, that
is, a length that can be expected to have an operation effect. In
this case, the shortest distance p in the horizontal direction
between the end in the thickness direction of the conductive
particles and the second connection layer 2 is preferably 0.5 to
1.5 times, and more preferably 0.55 to 1.25 times the diameter of
the conductive particles.
<<Application of Anisotropic Conductive Film>>
[0099] The anisotropic conductive film obtained above can be
preferably applied to anisotropic conductive connection by heat or
light between a first electronic component such as an IC chip and
an IC module and a second electronic component such as a flexible
substrate and a glass substrate. The resultant connection structure
is also a part of the present invention. In this case, it is
preferable that the anisotropic conductive film be temporarily
applied to the second electronic component from the third
connection layer side, the first electronic component such as an IC
chip be mounted on the anisotropic conductive film temporarily
applied, and the anisotropic conductive film be subjected to
thermocompression-bonding from the first electronic component side
since the connection reliability is enhanced. Further, light curing
can also be used for connection.
EXAMPLES
[0100] Hereinafter, the present invention will be described
specifically by way of Examples.
Examples 1 to 10
[0101] An acrylate, a photo-radical polymerization initiator, and
the like were mixed in accordance with a composition described in
Table 1 or 2 to prepare a mixed liquid so that the solid content in
ethyl acetate or toluene was 50% by mass. This mixed liquid was
applied to a polyethylene terephthalate film (PET film) with a
thickness of 50 .mu.m so as to have a dried thickness of 5 .mu.m,
and dried in an oven at 80.degree. C. for 5 minutes, to form a
photoradically polymerizable insulating resin layer as a first
connection layer.
[0102] A stainless steel transfer die with columnar openings that
had a diameter of 5.5 .mu.m and a depth of 4.5 .mu.m and were
provided at longitudinal and horizontal pitches of 9 .mu.m was
prepared. Each opening housed each of conductive particles with an
average particle diameter of 4 .mu.m (Ni/Au plated resin particles,
AUL 704, available from SEKISUI CHEMICAL CO., LTD.). An insulating
resin layer for a first connection layer was placed so as to be
opposite to an opening-forming face of the transfer die. The
conductive particles were pressed into the insulating resin layer
by applying pressure under conditions of 60.degree. C. and 0.5 MPa
from a side of a release film. Thus, the insulating resin layer was
formed so that the thickness of the insulating resin layer in
central regions between adjacent ones of the conductive particles
was smaller than the thickness of the insulating resin layer in
regions in proximity to the conductive particles.
[0103] Subsequently, the photo-radical polymerizable insulating
resin layer was irradiated with ultraviolet rays with a wavelength
of 365 nm and an integrated light quantity of 4,000 mL/cm.sup.2
from the conductive particle side. Thus, the first connection
layer, on the surface of which the conductive particles were fixed,
was formed.
[0104] A thermosetting resin, a latent curing agent, and the like
were mixed in ethyl acetate or toluene to prepare a mixed liquid so
that the solid content was 50% by mass. This mixed liquid was
applied to a PET film with a thickness of 50 .mu.m so as to have a
dried thickness of 12 .mu.m, and dried in an oven at 80.degree. C.
for 5 minutes, to form a second connection layer. A third
connection layer with a dried thickness of 3 .mu.m was formed by
the same operation.
[0105] The second connection layer was laminated on the obtained
first connection layer under conditions of 60.degree. C. and 0.5
MPa so that the conductive particles were located inside, and the
third connection layer was similarly laminated on the opposite
surface to obtain an anisotropic conductive film.
[0106] In Examples 7 to 10, an anisotropic conductive film was
formed so that the thickness of the first connection layer between
the conductive particles was substantially zero. Specifically, an
anisotropic conductive film was formed in the same manner as in
Example 1 except that an insulating resin layer for a first
connection layer was placed so as to be opposed, and pressurized
from the release film side under conditions of 60.degree. C. and
0.5 MPa, followed by pressurization again under conditions of
60.degree. C. and 1.0 MPa.
Comparative Example 1
[0107] A photo-radical polymerizable insulating resin layer that
was a precursor layer of a first connection layer, similarly to
Example 1, was formed in accordance with a composition described in
Table 1.
[0108] A stainless steel transfer die with columnar openings that
had a diameter of 5.5 .mu.m and a depth of 4.5 .mu.m and were
provided at longitudinal and horizontal pitches of 9 .mu.m was
prepared. Each opening housed each of conductive particles with an
average particle diameter of 4 .mu.m (Ni/Au plated resin particles,
AUL 704, available from SEKISUI CHEMICAL CO., LTD.). An insulating
resin layer for a first connection layer was placed so as to be
opposed to an opening-forming face of the transfer die. The
conductive particles were transferred to a surface of the
insulating resin layer by applying pressure under relatively weak
conditions of 40.degree. C. and 0.1 MPa from the release film side.
This film having transferred conductive particles was taken out,
and the conductive particles were completely pressed into the
insulating resin layer so that the surface of the resin layer was
flat.
[0109] Subsequently, the photo-radical polymerizable insulating
resin layer in which the conductive particles were embedded was
irradiated with ultraviolet rays with a wavelength of 365 nm and an
integrated light quantity of 4,000 mL/cm.sup.2. Thus, a flat first
connection layer was formed.
[0110] A second connection layer with a thickness of 12 .mu.m and a
third connection layer with a thickness of 3 with that were formed
in the same manner as in Example 1 were laminated on the first
connection layer to form an anisotropic conductive film.
Comparative Example 2
[0111] From a mixture in which conductive particles that were the
same as in Example 1 were uniformly dispersed in a resin
composition for a first connection layer of Table 1 so that the
number was 20,000 per square millimeter, a conductive
particle-containing resin film with a thickness of 6 .mu.m was
formed. To this film, a second connection layer with a thickness of
12 .mu.m formed in the same manner as in Example 1 was bonded under
conditions of 60.degree. C. and 0.5 MPa, to form an anisotropic
conductive film having a two-layer structure.
<Evaluation>
[0112] A case where a uniform planar arrangement between the
conductive particles in the obtained anisotropic conductive films
is formed is evaluated as applicable (Yes), and another case is
evaluated as not applicable (No). A case where the thickness of the
insulating resin layer in regions in proximity to the conductive
particles is larger than that of the insulating resin layer in
central regions between the conductive particles (also including a
thickness of 0) is evaluated as an increase in the thickness of the
insulating resin layer in regions in proximity to the conductive
particles (Yes), and another case is evaluated as no increase (No).
The results are shown in Tables 1 and 2. The number of layers
constituting each of the anisotropic conductive films is also
shown.
[0113] An IC chip with a size of 0.5 mm.times.1.8 mm.times.20.0 mm
(bump size: 30 .mu.m.times.85 .mu.m, bump height: 15 .mu.m, bump
pitch: 50 .mu.m) was mounted on a glass circuit board (1737F) with
a size of 0.5 mm.times.50 mm.times.30 mm available from Corning
Incorporated using each of the obtained anisotropic conductive
films under conditions of 180.degree. C., 80 MPa, and 5 seconds to
obtain a connection structure sample. When the cross section of a
connection part of the connection structure sample was observed by
an electron microscope, the insulating resin layer around the
conductive particles was confirmed, as shown in FIG. 1A.
[0114] As described below, "minimum melt viscosity," "particle
capturing efficiency," "conduction reliability," and "insulating
properties" in the obtained connection structure sample were
evaluated on a test. The results are shown in Tables 1 and 2.
"Minimum Melt Viscosity"
[0115] The minimum melt viscosity of each of the first connection
layer and the second connection layer that constituted the
connection structure sample was measured by a rotational rheometer
(manufactured by TA Instruments) under conditions of a temperature
increasing rate of 10.degree. C./min, a constant measurement
pressure of 5 g, and a measurement plate diameter of 8 mm.
"Particle Capturing Efficiency"
[0116] The ratio of the "amount of particles actually captured on
bumps of the connection structure sample after heating and
pressurization (after actual mounting)" to the "theoretical amount
of particles existing on bumps of the connection structure sample
before heating and pressurization" was determined in accordance
with the following mathematical expression. In practical terms, the
ratio is desirably 50% or more.
Particle capturing efficiency (%)={[number of particles on bumps
after heating and pressurization]/[number of particles on bumps
before heating and pressurization]}.times.100
"Conduction Reliability"
[0117] The connection structure sample was left under an
environment of a high temperature of 85.degree. C. and a high
humidity of 85% RH. The conduction resistances at the initial stage
and after 500 hours were measured. In practical terms, the
resistance is desirably 10 or or less even after 500 hours.
"Insulating Properties"
[0118] The rate of occurrence of a short circuit in a comb-teeth
TEG pattern with a space of 7.5 .mu.m was determined. In practical
terms, the ratio is desirably 100 ppm or less.
TABLE-US-00001 TABLE 1 Example 1 2 3 4 Application of Uniform
Planar Arrangement of Conductive Particles Yes Yes Yes Yes Increase
in Thickness of Insulating Resin Layer in Regions in proximity to
Conductive Particles Yes Yes Yes Yes Number of Layers Constituting
Anisotropic Conductive Film 3 3 3 3 First Connection Phenoxy Resin
(Parts By Mass) YP-50 Nippon Steel & Sumikin 60 60 60 60 Layer
Chemical Co., Ltd. Acrylate (Parts By Mass) EB600 Daicel-Allnex
Ltd. 40 40 Photo-Radical IRGACURE 369 BASF Japan Ltd. 2 2
Polymerization Initiator (Parts By Mass) Epoxy Resin (Parts By
Mass) jER828 Mitsubishi Chemical 40 40 Corporation Thermal Cationic
SI-60L Sanshin Chemical 2 2 Polymerization Initiator Industry Co.,
Ltd. (Parts By Mass) Minimum Melt Viscosity of First Connection
Layer [mPa s] After UV Irradiation 20000 20000 20000 20000 for
Examples 1 and 2 Second Connection Phenoxy Resin (Parts By Mass)
YP-50 Nippon Steel & Sumikin 60 60 60 60 Layer Chemical Co.,
Ltd. Epoxy Resin (Parts By Mass) jER828 Mitsubishi Chemical 40 40
Corporation Thermal Cationic SI-60L Sanshin Chemical 2 2
Polymerization Initiator Industry Co., Ltd. (Parts By Mass)
Acrylate (Parts By Mass) EB600 Daicel-Allnex Ltd. 40 40 Organic
Peroxide (Parts By Mass) Perhexyl Z NOF Corporation 2 2 Minimum
Melt Viscosity of Second Connection Layer [mPa s] 500 500 500 500
Third Connection Phenoxy Resin (Parts By Mass) YP-50 Nippon Steel
& Sumikin 60 60 60 60 Layer Chemical Co., Ltd.. Epoxy Resin
(Parts By Mass) jER828 Mitsubishi Chemical 40 40 Corporation
Thermal Cationic SI-60L Sanshin Chemical 2 2 Polymerization
Initiator Industry Co., Ltd. (Parts By Mass) Acrylate (Parts By
Mass) EB606 Daicel-Allnex Ltd.. 40 40 Organic Peroxide (Parts By
Mass) Perhexyl Z NOF Corporation 2 2 Minimum Melt Viscosity of
Third Connection Layer [mPa s] 500 500 500 500 [Minimum Melt
Viscosity of First Connection Layer]/ 40 40 40 40 [Minimum Melt
Viscosity of Second or Third Connection Layer] Conduction
Resistance Value (.OMEGA.) Initial 0.2 0.2 0.2 0.2 85.degree. C.,
85% RH, 500 hr 5.0 6.0 8.0 7.6 Insulating Properties (Rate of
Occurrence of Short [ppm] 30 30 30 30 Circuit) Particle Capturing
Efficiency [%] 82.40 79.20 80.40 83.10 Example Comparative Example
5 6 1 2 Application of Uniform Planar Arrangement of Conductive
Particles Yes Yes Yes No Increase in Thickness of Insulating Resin
Layer in Regions in proximity to Conductive Particles Yes Yes No No
Number of Layers Constituting Anisotropic Conductive Film 3 3 3 2
First Connection Phenoxy Resin (Parts By Mass) YP-50 Nippon Steel
& Sumikin 80 40 60 60 Layer Chemical Co., Ltd. Acrylate (Parts
By Mass) EB600 Daicel-Allnex Ltd. 20 60 40 40 Photo-Radical
IRGACURE 369 BASF Japan Ltd. 2 2 2 2 Polymerization Initiator
(Parts By Mass) Epoxy Resin (Parts By Mass) jER828 Mitsubishi
Chemical Corporation Thermal Cationic SI-60L Sanshin Chemical
Polymerization Initiator Industry Co., Ltd. (Parts By Mass) Minimum
Melt Viscosity of First Connection Layer [mPa s] After UV
Irradiation 2000 100000 20000 20000 for Examples 1 and 2 Second
Connection Phenoxy Resin (Parts By Mass) YP-50 Nippon Steel &
Sumikin 60 80 60 60 Layer Chemical Co., Ltd. Epoxy Resin (Parts By
Mass) jER828 Mitsubishi Chemical 40 20 40 40 Corporation Thermal
Cationic SI-60L Sanshin Chemical 2 2 2 2 Polymerization Initiator
Industry Co., Ltd. (Parts By Mass) Acrylate (Parts By Mass) EB600
Daicel-Allnex Ltd. Organic Peroxide (Parts By Mass) Perhexyl Z NOF
Corporation Minimum Melt Viscosity of Second Connection Layer [mPa
s] 500 250 500 500 Third Connection Phenoxy Resin (Parts By Mass)
YP-50 Nippon Steel & Sumikin 60 60 60 Layer Chemical Co., Ltd..
Epoxy Resin (Parts By Mass) jER828 Mitsubishi Chemical 40 40 40
Corporation Thermal Catbnic SI-60L Sanshin Chemical 2 2 2
Polymerization Initiator Industry Co., Ltd. (Parts By Mass)
Acrylate (Parts By Mass) EB606 Daicel-Allnex Ltd.. Organic Peroxide
(Parts By Mass) Perhexyl Z NOF Corporation Minimum Melt Viscosity
of Third Connection Layer [mPa s] 500 250 500 -- [Minimum Melt
Viscosity of First Connection Layer]/ 4 400 40 40 [Minimum Melt
Viscosity of Second or Third Connection Layer] Conduction
Resistance Value (.OMEGA.) Initial 0.2 0.2 2.0 0.2 85.degree. C.,
85% RH, 500 hr 5.0 8.0 50.0 5.0 Insulating Properties (Rate of
Occurrence of Short [ppm] 100 10 30 3000 Circuit) Particle
Capturing Efficiency [%] 43.60 84.95 63.70 25
TABLE-US-00002 TABLE 2 Example 7 8 9 10 Application of Uniform
Planar Arrangement of Conductive Particles Yes Yes Yes Yes Increase
in Thickness of Insulating Resin Layer in Regions in proximity to
Conductive Particles Yes Yes Yes Yes Number of Layers Constituting
Anisotropic Conductive Film 3 3 3 3 First Connection Phenoxy Resin
(Parts By Mass) YP-50 Nippon Steel & Sumikin 60 60 60 60 Layer
Chemical Co., Ltd. Acrylate (Parts By Mass) EB600 Daicel-Allnex
Ltd. 40 40 Photo-Radical IRGACURE 369 BASF Japan Ltd. 2 2
Polymerization Initiator (Parts By Mass) Epoxy Resin (Parts By
Mass) jER828 Mitsubishi Chemical 40 40 Corporation Thermal Cationic
SI-60L Sanshin Chemical 2 2 Polymerization Initiator Industry Co.,
Ltd. (Parts By Mass) Minimum Melt Viscosity of First Connection
Layer [mPa s] 20000 20000 20000 20000 Second Connection Phenoxy
Resin (Parts By Mass) YP-50 Nippon Steel & Sumikin 60 60 60 60
Layer Chemical Co., Ltd. Epoxy Resin (Parts By Mass) jER828
Mitsubishi Chemical 40 40 Corporation Thermal Cationic SI-60L
Sanshin Chemical 2 2 Polymerization Initiator Industry Co., Ltd.
(Parts By Mass) Acrylate (Parts By Mass) EB600 Daicel-Allnex Ltd.
40 40 Organic Peroxide (Parts By Mass) Perhexyl Z NOF Corporation 2
2 Minimum Melt Viscosity of Second Connection Layer [mPa s] 500 500
500 500 Third Connection Phenoxy Resin (Parts By Mass) YP-50 Nippon
Steel & Sumikin 60 60 60 60 Layer Chemical Co., Ltd. Epoxy
Resin (Parts By Mass) jER828 Mitsubishi Chemical 40 40 Corporation
Thermal Cationic SI-60L Sanshin Chemical 2 2 Polymerization
Initiator Industry Co., Ltd. (Parts By Mass) Acrylate (Parts By
Mass) EB600 Daicel-Allnex Ltd. 40 40 Organic Peroxide (Parts By
Mass) Perhexyl Z NOF Corporation 2 2 Minimum Melt Viscosity of
Third Connection Layer [mPa s] 500 500 500 500 [Minimum Melt
Viscosity of First Connection Layer]/ 40 40 40 40 [Minimum Melt
Viscosity of Second or Third Connection Layer] Conduction
Resistance Value Initial 0.2 0.2 0.2 0.2 85.degree. C., 85% RH, 500
hr 5 5 8 8 Insulating Properties (Rate of Occurrence of Short [ppm]
30 30 30 30 Circuit) Particle Capturing Efficiency [%] 85 82 83
87
[0119] As seen from Table 1, the anisotropic conductive films of
Examples 1 to 6 exhibit preferable results in practical terms in
all evaluation items of particle capturing efficiency, conduction
reliability, and insulating properties. As seen from the results in
Examples 1 to 4, when the first, second, and third connection
layers are all the same curing system, the layers are reacted with
one another. Therefore the pressing property of the conductive
particles slightly decreases and the conduction resistance tends to
increase. Further, when the first connection layer is a cationic
polymerization system, the thermal resistance is improved as
compared with a radical polymerization system. Therefore the
pressing property of the conductive particles slightly decreases
and the conduction resistance tends to increase.
[0120] On the other hand, in the first connection layer of the
anisotropic conductive film of Comparative Example 1, the thickness
of the insulating resin layer in central regions between adjacent
ones of the conductive particles is not smaller than that of the
insulating resin layer in regions in proximity to the conductive
particles. Therefore, the conduction reliability is largely
reduced. In the anisotropic conductive film of Comparative Example
2 that has a conventional two-layer structure, the particle
capturing efficiency largely decreases, and the insulating
properties has a problem.
[0121] As seen from Table 2, the anisotropic conductive films of
Examples 7 to 10 have a thickness in central regions between the
conductive particles of zero. Therefore, the independence of the
conductive particles is enhanced, and the anisotropic conductive
films exhibit preferable results in practical terms in all
evaluation items of particle capturing efficiency, conduction
reliability, and insulating properties.
INDUSTRIAL APPLICABILITY
[0122] In the anisotropic conductive film of the present invention
that has a three-layer structure in which the first connection
layer is sandwiched between the second and third connection layers
that each are insulative, the first connection layer has a
structure in which conductive particles are arranged in a single
layer in a plane direction of an insulating resin layer on a side
of the second connection layer, and a structure in which the
thickness of the insulating resin layer at a center between
adjacent ones of the conductive particles is smaller than that of
the insulating resin layer in regions in proximity to the
conductive particles. For this reason, the anisotropic conductive
film having the conductive particles arranged in a single layer is
allowed to achieve favorable connection reliability, favorable
insulating properties, and favorable particle capturing efficiency.
Therefore, the anisotropic conductive film is useful in anisotropic
conductive connection of an electronic component such as an IC chip
to a circuit board.
REFERENCE SIGNS LIST
[0123] 1 first connection layer [0124] 1X region where the degree
of cure in the first connection layer is low [0125] 1Y region where
the degree of cure in the first connection layer is high [0126] 1d
coating layer [0127] 2 second connection layer [0128] 3 third
connection layer [0129] 3a surface of third connection layer [0130]
4 conductive particle [0131] 10 insulating resin layer [0132] 20
transfer die [0133] 21 opening [0134] 22 release film [0135] 100
anisotropic conductive film [0136] L distance between conductive
particles [0137] P midpoint of distance between conductive
particles [0138] t1, t2 insulating resin layer thickness
* * * * *