Multi-element module and production process thereof

Details Multi-element module and production process thereof Multi-element module and production process thereof

1998-12-28

2001-01-09

Gaffin, Jeffrey (Department: 2841)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C361S763000, C361S764000, C361S765000, C174S250000, C174S260000, C174S261000, C228S180210, C228S180220

Reexamination Certificate

active

06172878

ABSTRACT:

FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a multi-element module and a process for producing the multi-element module. The present invention also relates to an anisotropic conductive film-bonding apparatus for bonding an anisotropic conductive film having an anisotropic conductivity (i.e., a property of showing electroconductivity in a thickness direction and (electrically) insulating properties in a planar direction) to a substrate. The present invention further relates to an adhesive member for bonding two electrical elements or components to an adhesive member to each other while ensuring electrical connection between opposite electrodes provided to the two electrical components and a bonding method using the adhesive member.
There has been utilized solder or an anisotropic conductive adhesive (agent) as an adhesive member for bonding (different) two electrical components, thus ensuring electrical connection between electrodes of one of the electrical components and those of the other electrical component disposed to the (former) electrodes.
FIG. 1
is a schematic sectional view of an embodiment of a multi-element module includes a substrate
1
of, e.g., glass-epoxy or ceramics; a plurality of electrical elements including: a semiconductor device, such as an IC (integrated circuit) chip
2
, a passive element
3
(e.g., (electrical) resistor or capacitor) and electro-mechanical elements
4
and
5
(e.g., connectors); and solder
6
for bonding these electrical elements
2
,
3
,
4
and
5
to the substrate
1
disposed therebetween.
The substrate
1
is provided with electrodes
1
a
,
1
b
,
1
c
and
1
d
thereon, and the electrical elements
2
,
3
,
4
and
5
are provided with electrodes
2
a
,
3
a
,
4
a
and
5
a
, respectively, so that each of the electrodes (e.g.,
2
a
) is aligned with a corresponding electrodes (e.g.,
1
b
) of the substrate
1
in an opposed relationship when bonded to each other by the solder
6
.
On the other hand, as the adhesive member comprising an anisotropic conductive adhesive, there has been known an anisotropic conductive film comprising a resin and electroconductive particles dispersed in the resin.
The anisotropic conductive film has an anisotropic conductivity, i.e., a property of ensuring electrical connection between opposite electrodes of different electrical components (e.g., the substrate
1
and the electrical elements
2
-
5
) while retaining electrical insulation between adjacent electrodes for each electrical component (e.g., the substrate
1
), thus being utilized as the adhesive member in various fields.
For instance, there have been proposed multi-element modules using the anisotropic conductive film in, e.g., Japanese Patent Publication Nos. (JP-B) 59-2179 and 61-27902.
Such an anisotropic conductive film is also utilized for electrical connection of a driver IC to a glass substrate of a liquid crystal display panel according to a TAB (tape automated bonding) scheme using a tape carrier or a COG (chip on glass) scheme.
These conventional adhesive members (solder and (known) anisotropic conductive film) are, however, accompanied with the following difficulties.
In the case of using the solder,
(1) solder contains Pb and accordingly is required to be appropriately treated for its residue or waste so as to exclude adverse influences on environment, thus resulting in expensive treatment leading to an increase in production costs,
(2) solder is required to use flux in order to activate surfaces at respective bonding points and also is liable to cause (fine) particles thereof (so-called solder balls), thus requiring an additional washing (cleaning) step for removing these flux and solder balls to result in a complicated production process and increased production costs,
(3) it is necessary to coat solder with a resin (e.g., epoxy resin or silicone resin) in order to protect bonding points from moisture and dirt, thus requiring an additional step similarly as in the above (2),
(4) adjacent solder portions are bonded to each other when electrodes are disposed in a small pitch of at most 0.3 mm, thus failing to ensure electrical insulation (isolation) between adjacent electrodes, and
(5) defective products are liable to occur in a soldering step due to various causes, thus lowering a production yield.
In the case where the anisotropic conductive film described above is used instead of the solder
6
shown in
FIG. 1
for bonding the electrodes
2
a
-
5
a
having different thicknesses of the electrical elements
2
-
5
to the electrodes
1
a
-
1
d
of the substrate
1
, if the anisotropic conductive film used is too thin, bonding of the electrical element having a thicker electrode becomes insufficient, thus failing to ensure a reliability at the bonding portion.
On the other hand, if the anisotropic conductive film is too thick, an anisotropic conductivity (i.e., an electroconductive characteristic between opposite electrodes and an insulating characteristic between adjacent electrodes) thereof becomes insufficient, thus failing to ensure a desired (electrical) connection performance. Particularly, such a thicker anisotropic conductive film is not suitable for a connection structure requiring fine electrical connection. Accordingly, when driver ICs are electrically connected to a liquid crystal display device (panel) by using such an anisotropic conductive film, electrical elements other than the driver ICs (e.g., passive elements, such as resistor and capacitor and electromechanical elements, such as connectors) are not readily connected to the liquid crystal display device.
In a conventional bonding process of the anisotropic conductive film as described above, the anisotropic conductive film is first bonded to a substrate by using a heating and pressing means as shown in FIG.
7
.
Referring to
FIG. 7
, an anisotropic conductive film
72
is disposed on a substrate
71
and a heating tool
73
having a pressing function is disposed opposite to (immediately over) the anisotropic conductive film
72
.
For bonding operation, the heating (and pressing) tool
73
is moved downward to effect pressing and heating of the anisotropic conducive film
72
, thus bonding the anisotropic conductive film
72
to the surface of the substrate
71
.
Thereafter, by using the anisotropic conductive film
72
bonded to the substrate
71
surface, electrical elements (not shown) are bonded to the substrate
71
via the anisotropic conductive film
72
.
In the conventional bonding process of the anisotropic conductive film
72
to the substrate
71
as shown in
FIG. 7
, however, the bonding process has encountered the following problems.
(i) In recent years, anisotropic conductive films used in multi-element modules or liquid crystal displays tend to have larger width and length for providing a larger-sized module or panel, thus requiring a larger heating tool
73
. As a result, costs of equipment and production are correspondingly increased.
(ii) When a large-sized anisotropic conductive film
72
is contact-bonded by the heating tool
73
, it is difficult to cause the entire pressing surface of the heating tool
73
to uniformly contact the entire surface of the anisotropic conductive film
72
, thus being liable to leave air bubbles between the anisotropic conductive film
72
and the substrate
71
, at which an adhesiveness between the anisotropic conductive film
72
and the substrate
71
becomes worse.
Incidentally, referring again to
FIG. 1
, soldering of electrical elements
2
-
5
onto the substrate
1
has been performed by various methods.
One of the methods is the use of a mounter (element-mounting apparatus) in combination with a substrate
1
to which surface an adhesive agent
7
is applied in advance as shown in FIG.
14
. According to this method, electrical elements
2
-
5
mounted on the substrate
1
are bonded to the substrate by the adhesive agent
7
to effect bonding of the electrical elements
2
-
5
to the substrate
10
.
According to this method, however, the use of the adhesive agen

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