Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With contact or lead
Reexamination Certificate
1999-03-24
2001-07-24
Clark, Sheila V. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With contact or lead
C257S783000, C257S778000, C257S787000
Reexamination Certificate
active
06265770
ABSTRACT:
INDUSTRIAL FIELD OF THE INVENTION
The present invention relates to a mounting structure of a semiconductor chip, wherein a semiconductor chip is mounted onto a substrate using an adhesive material such as an anisotropic conductive film (ACF), and, more particularly, to a mounting structure of a semiconductor chip, wherein a plurality of bumps of a semiconductor chip and a plurality of lands on a substrate are joined together in such a manner as to allow electrical conduction therebetween. The present invention also relates to a liquid crystal device employing the mounting structure of a semiconductor chip and electronic equipment using the liquid crystal device.
DESCRIPTION OF THE RELATED ART
Currently, liquid crystal devices are widely used in electronic equipment, such as portable telephones or portable information terminals. In order to display visible information consisting of, for example, characters, numerals, or patterns, liquid crystal devices are frequently used in electronic equipment.
In general, such a liquid crystal device comprises liquid crystal filled between a pair of light-transmissive substrates, and the orientation of the liquid crystal is controlled as a result of controlling the voltage applied to the liquid crystal, in order to modulate the light incident upon the liquid crystal. In order to control the voltage applied to the liquid crystal, the liquid crystal device requires an integrated circuit (IC) for driving the liquid crystal, that is a semiconductor chip, with the IC being connected to the aforementioned light-transmissive substrates either directly or indirectly through a substrate.
The connecting of the liquid crystal driving IC to the light-transmissive substrates of the liquid crystal device through a substrate is considered, for example, in the following way, as illustrated in
FIG. 9. A
mounting structure
58
is formed by connecting the liquid crystal driving IC
51
on the substrate
52
using the ACF
53
, and the substrate
52
in the mounting structure
58
is connected to the light-transmissive substrate
57
a of the liquid crystal device
56
using connecting members such as FPC (Flexible Printed Circuit)
54
. The liquid crystal device
56
comprises the light-transmissive substrate
57
a
and a light-transmissive substrate
57
b
with liquid crystal
59
filled therebetween.
However, in general, as shown in
FIG. 10
, in the conventional mounting structure
58
of a semiconductor chip, area A for mounting thereon the liquid crystal driving IC
51
of the substrate
52
is formed on the same flat surface as the other areas of the substrate
52
. Therefore, when there is too much ACF
53
, a large residual stress is produced in the ACF
53
during press-bonding, resulting in the problem that joining failure occurs with the passage of time.
In
FIG. 10
, reference numeral
62
denotes an input wiring with respect to the IC
51
, and reference numeral
63
denotes an output wiring from the IC
51
. Although many wires are actually formed, only some of the wires are shown in full in
FIG. 10
, while the rest, which are not shown in full, are shown by chain lines.
Japanese Unexamined Utility Model Publication No. 3-39876 discloses a technique of forming transfixion holes in an area to which chip parts, which are different from the semiconductor chip, are mounted. However, the transfixion holes discussed in this document are formed for the purpose of making it easier to allow the chip mounting portion to be depressed, and not for the purpose of preventing generation of residual stress in the adhesive. Therefore, according to the conventional document, the following technical requirements are not satisfied: the formation of transfixion holes in an area surrounded by a plurality of lands disposed on the substrate side in correspondence with the bumps of the semiconductor chip, and the formation of transfixion holes in such a manner that they are spread out over the area.
In view of the above-described problem, it is an object of the present invention to make it possible to achieve more reliable connection between electrode terminals, in a mounting structure which mounts a semiconductor chip such as a liquid crystal driving IC onto a substrate using an adhesive such as ACF.
SUMMARY OF THE INVENTION
(1) To this end, according to the present invention, there is provided a mounting structure of a semiconductor chip comprising a semiconductor chip with a plurality of bumps, and a substrate with a plurality of lands; wherein the semiconductor chip and the substrate are connected together with an adhesive so as to allow electrical conduction between the bumps and the lands. In the mounting structure of a semiconductor chip, a plurality of transfixion holes are formed in an area of the substrate surrounded by the plurality of lands such that the transfixion holes are spread out over the area.
According to the mounting structure of a semiconductor chip, pressing the semiconductor chip against the substrate with an adhesive therebetween, causes the semiconductor chip to be affixed to the substrate. In this case, when there is too much adhesive between the semiconductor chip and the substrate, the excess adhesive enters the transfixion holes, so that residual stress is not produced in the adhesive. As a result, it is possible to eliminate the problem that joining failure at the joint portion occurs with the passage of time.
The mounting structure of a semiconductor chip of the present invention can be formed by, for example, the COB (chip on board) method or the COF (chip on FPC) method. A mounting structure formed by the COB method comprises a semiconductor chip mounted onto a relatively hard and thick substrate, such as an epoxy substrate. A mounting structure formed by the COF method comprises a semiconductor chip mounted onto a flexible and relatively thin board, such as a flexible printed circuit (FPC) substrate.
(2) It is desirable that the ratio R, in percent, of the area of the transfixion holes to the area of the liquid crystal driving IC (that is, the semiconductor chip) be
0%<
R
≦18%
By setting R within this range, the excess adhesive can reliably escape to the transfixion holes during press-bonding.
(3) It is more desirable that the ratio R, in percent, of the area of the transfixion holes
9
to the area of the semiconductor chip be
2%<
R≦
10%
By setting R within this range, the excess adhesive can reliably escape to the transfixion holes during press-bonding, so that the substrate can provide a larger area for forming wiring patterns thereon.
(4) Regarding the above-described mounting structure of a semiconductor chip, it is desirable to form the through holes, to be formed in the substrate, within an area surrounded by the lands such that they are provided closer to the lands than to the center portion of the area. This allows all of the excess adhesive, removed by the bumps and the lands, to reliably escape to the transfixion holes.
(5) The substrate used in the present invention may be formed with one with a single wiring layer or one with a plurality of wiring layers that are electrically connected to each other through a plurality of electrically conductive through holes. When a substrate with a plurality of electrically conductive through holes is used, these electrically conductive through holes can be used as transfixion holes for allowing escape of excess adhesive.
At present, the electrically conductive through holes to be formed in the substrate are often formed outwardly of the IC chip mounting area. When the wiring patterns are to be formed close together within a small area of the substrate, it is very effective to dispose the electrically conductive through holes within the IC chip mounting area. In this case, it is very effective to use the electrically conductive through holes as transfixion holes for allowing escape of excess adhesive.
(6) The liquid crystal device of the present invention comprises liquid crystal sandwiched between a pair of light-transmissive substrates, wherein the orientation of the l
Clark Sheila V.
Harness & Dickey & Pierce P.L.C.
Seiko Epson Corporation
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