Method of making a laminated structure

Details Method of making a laminated structure Method of making a laminated structure

2002-01-24

2004-10-12

Copenheaver, Blaine (Department: 1733)

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

C156S306900, C438S108000, C438S119000, C438S613000

Reexamination Certificate

active

06802930

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a laminated structure. More particularly, this invention relates to a laminated structure provided with pairs of corresponding bumps or conjunction portions which are electrically connected to each other by particles embedded.
2. Description of Prior Art
ACF (Anisotropic Conductive Film) is a conductive film composed of epoxy resin and a plurality of metal particles and is often used as interlayer clamped between two corresponding bumps or electrodes of a substrate and LSI (Large Scale Integrated Circuit), COG (Chip On Glass), FPC (Flexible Printed Circuit), PCB (Printed Circuit Board), TAB (Tape Automatic Bonding) or TCP (Tape Carrier Package) so as to form a laminated structure for use in LCD panels.
However, two adjacent bumps or electrodes of the substrate can easily short-circuit or suffer low conductivity when the laminated structure is bent, causing the particles in the ACF that are located between two electrodes, to crowd together.
Further, the manufacturing process of ACF is complicated, and the tolerance of the height difference among the bumps of LSI/FPC/PCB/TCP cannot always be precisely controlled. If the design aims to increase the amount of conductive particles captured by the bumps or electrodes, the size of the bumps or electrodes formed on the LSI/FPC/PCB/TCP cannot be too small to contact the conductive particles within the predetermined area. If the design aims to increase the conductivity between two corresponding bumps or electrodes by increasing the number of particles in the ACF, the effective space (Fine Pitch Design) between any two of the adjacent bumps or electrodes cannot be so narrow as to cause a short circuit.
FIGS. 1A
,
1
B and
1
C are three plan views sequentially depicting the steps for forming a laminated structure
1
according to a prior art. The substrate
11
,
12
are two conductive plates of LSI/COG/FPC/PCB/TAB/TCP.
As shown in
FIG. 1A
, the laminated structure
1
is composed of two substrates
11
(
12
), a plurality of conductive particles
13
and an epoxy
14
. The substrate
11
has a surface
110
with a plurality of spaced bumps A
1
~A
3
, and the substrate
12
has a surface
120
with a plurality of spaced bumps (B
1
~B
3
) corresponding to bumps A
1
~A
3
. The so-called Anisotropic Conductive Film (ACF) is made of epoxy
14
mixed with the particles
13
, and the ACF is used as an intermediate to bond the substrates
11
and the substrates
12
together and electrically connect the substrates
11
to the substrates
12
. The bumps A
1
~A
3
of the substrate
11
are respectively provided with end surfaces A
01
, A
02
and A
03
, and the bumps B
1
~B
3
of the substrate
12
are respectively provided with end surfaces B
01
, B
02
and B
03
. A height difference t
1
exists between the bump B
1
and the bump B
2
, and another height difference t
2
exists between bump B
2
and bump B
3
.
FIG. 1B
shows the substrate
11
and the substrate
12
being brought toward each other by the application of a clamping force F.
FIG. 1C
shows the first substrate
21
and the second substrate
22
being combined together by the epoxy
14
and electrically connected to each other via the particles
13
.
In
FIG. 1B
, a force F is applied on the two substrates
11
,
12
to form the laminated structure
1
. The epoxy
14
is gradually deformed and thinned by the approaching substrates
11
and
12
, and then the particles
13
stored in the epoxy
14
are irregularly dispersed during the clamping process. Then, the bump A
1
and the bump B
1
, the bump A
2
and the bump B
2
, the bump A
3
and the bump B
3
respectively clamp the particles
13
stored in the epoxy
14
as shown in FIG.
1
C.
However, with the height differences t
1
and t
2
between bump B
2
and bump B
1
, B
2
, the number of the particles
13
clamped between each two corresponding bumps is quite different, i.e. the particles
13
are not easily captured by the any two corresponding bumps. Moreover, a short circuit may occur between any two of the bumps of the substrate
11
or
12
between which the number of the particles
13
is dense.
U.S. Pat. No. 5,065,505 disclosed by Hiroshi Matsubara et al, Sharp Kabushiki Kaisha, mentions that the conductive particles are adhered to the electrodes of the glass board by means of the uncured photocuring adhesive. However, height differences existing among the electrodes cannot be effectively compensated while the circuit board is connected to the electrodes of the glass board.
SUMMARY OF THE INVENTION
The primary object of this invention is to provide a laminated structure, comprising a first substrate, a second substrate, an intermediate and a plurality of particles. The first substrate has a first conjunction portion and a second conjunction portion, and the second substrate has a third conjunction portion and a fourth conjunction portion which are provided with a first hardness. The intermediate is disposed between the first substrate and the second substrate. The particles with a second hardness larger than the first hardness are coated on the third conjunction portion for contacting the first conjunction portion and coated on the fourth conjunction portion for contacting the second conjunction portion. A height difference with reference to the base surface of the second substrate exists between the end surface of the third conjunction portion and the end surface of the fourth conjunction portion.
A height difference is exists between the fourth conjunction portion and the third conjunction portion and the height of the fourth conjunction portion is presupposed lower than that of the third conjunction portion. The height difference can be compensated by the particles embedded in the fourth conjunction portion when a clamping force is applied, and therefore the junction between the third conjunction portion and the first conjunction portion can be uniformly bridged by the particles located therebetween.


REFERENCES:
patent: 5065505 (1991-11-01), Matsubara et al.
patent: 5965064 (1999-10-01), Yamada et al.
patent: 6137162 (2000-10-01), Park et al.
Flip Chip Technologies, by John Lau(editor), McGraw Hill, 1995, p. 326-331.

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