Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – With structure for mounting semiconductor chip to lead frame
Reexamination Certificate
1999-06-15
2001-08-28
Abraham, Fetsum (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
With structure for mounting semiconductor chip to lead frame
C257S684000, C257S700000, C257S731000, C257S781000, C257S783000
Reexamination Certificate
active
06281567
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a substrate for mounting a semiconductor chip wherein the semiconductor chip is bonded to a surface of the substrate via a resin. The present invention also relates to a semiconductor device using such a substrate.
2. Description of the Related Art
In the prior art, as shown in
FIGS. 2 and 3
, a semiconductor chip
20
is mounted onto a substrate body
10
made of a ceramic or a resin via a resin of an ACF
30
.
The ACF
30
is formed of thermosetting resin such as epoxy resin or thermoplastic resin such as polyethylene. If the ACF
30
is composed of thermosettable resin, the semiconductor chip
20
could be bonded onto a surface of the substrate body
10
via the thermosettable resin of the ACF
30
which is heated to be cured. On the other hand, if the ACF
30
is composed of thermoplastic resin, the semiconductor chip
20
could be bonded onto a surface of the substrate body
10
via the thermoplastic resin of the ACF
30
which is heated and then cooled to be hardened.
Together therewith, conductor bumps
22
such as Au bumps or others formed on a plurality of electrodes orderly arranged on a surface of the semiconductor chip
20
are electrically connected to a plurality of conductor pads
50
provided on a surface of the substrate body
10
at positions corresponding to the respective conductor bumps by the metallization or the etching of copper foil, via conductive particles (not shown) contained in the resin of the ACF
30
.
Thus, the semiconductor chip
20
is surface-mounted onto the substrate via the resin of the ACF
30
.
In this regard, ACF stands for “anisotropic conductive film” which contains conductive particles in the resin thereof. When the semiconductor chip is surface-mounted onto the substrate as described above, the conductive particles contained in the ACF resin are interposed between the conductor bump formed on the electrode of the semiconductor chip and the conductor pad formed on the surface of the substrate body. Thus, the electro-conductivity is imparted to a portion of the ACF interposed between the conductor bump on the semiconductor chip and the conductor pad on the substrate body, whereby the conductor bump of the semiconductor chip is electrically connected with the conductor pad on the surface of the substrate body via the conductive particles contained in that portion of the ACF.
The plurality of electrodes on the semiconductor chip
20
is arranged at a predetermined pitch on the surface of the semiconductor chip
20
on which integrated circuits are formed. Accordingly, the plurality of conductor pads
50
for electrically connecting the electrodes is formed on the surface of the substrate body
10
on which the semiconductor chip
20
is mounted at a predetermined pitch in correspondence to the arrangement of the electrodes.
As shown in
FIG. 3
, the above-mentioned conductor pad
50
is shaped to be widened strips extending in the lengthwise direction, so that the conductor bump
22
can be electrically connected to the corresponding conductor pad
50
in a reliable manner, even if a position of the conductor bump
22
is somewhat deviated from the aimed one in the lengthwise or widthwise direction of the conductor pads
50
for some reason, which conductor bumps are formed on the electrode of the semiconductor chip
20
to be electrically connected to the conductor pads
50
via the conductive particles contained in the resin of the ACF
30
.
For this purpose, the plurality of conductor pads
50
of widened strip-shape is arranged on the surface of the substrate body
10
on which the semiconductor chip
20
is to be mounted, so that a narrow gap
52
having a length corresponding to that of the conductor pad
50
is defined between every adjacent conductor pad
50
.
According to the above-mentioned substrate for mounting a semiconductor chip, however, voids are liable to generate anywhere in the resin of the ACF
30
when the semiconductor chip
20
is bonded to the surface of the substrate body
10
via the resin of the ACF
30
, which deteriorates the adhesion of the ACF resin and results in the stripping-off of the semiconductor chip
20
from the surface of the substrate body
10
on which the semiconductor chip is mounted via the resin of the ACF
30
. Thus, a favorable electrical connection is deteriorated between the conductor bumps
22
formed on the electrodes of the semiconductor chip
20
and the conductor pads
50
formed on the surface of the substrate body
10
connected to each other via the electro-conductive particles contained in the resin of the ACF
30
.
A cause of the above-mentioned voids generated anywhere in the resin of the ACF
30
is that gas generating from the resin of the ACF
30
during the heating thereof cannot smoothly pass through the narrow gap
52
, between the adjacent conductor pads
50
arranged on the surface of the substrate body
10
, in parallel to each other, and having a length equal to the longitudinal length of the conductor pad
50
, but a large proportion of the gas continues to dwell in the interior of the resin of the ACF
30
disposed inward of the conductor pad
50
and softened by heating.
Similarly, air left in a gap between complicatedly combined connection lines
12
and/or adhered on a stepped side surface thereof expands by the heating, which cannot smoothly pass through the narrow gap
52
, between the adjacent conductor pads
50
arranged on the surface of the substrate body
10
in parallel to each other, but a large proportion of the air continues to dwell in the interior of the resin of the ACF
30
disposed inward of the conductor pad
50
and softened by heating.
Particularly, if the ACF
30
is composed of a quick-curing resin, a heating time necessary for bonding the semiconductor chip
20
to the surface of the substrate body
10
via the resin of the ACF
30
is considerably short, for example, in a range from 20 to 60 seconds, whereby almost all the above-mentioned gas and/or air remains in the interior of the resin of the ACF
30
, resulting in the voids anywhere in the resin of the ACF
30
.
These are also true of a substrate wherein the conductor bumps
22
formed on the electrodes provided on the surface of the semiconductor chip
20
are electrically connected directly to the conductor pads
50
formed on the surface of the substrate body
10
whilst an underfill (not shown) composed of thermosettable resin or thermoplastic resin is filled in a gap between the semiconductor chip
20
and the substrate body
10
to bond the semiconductor chip
20
onto the surface of the substrate body
10
.
That is, in such a substrate, when the underfill composed of thermosettable resin or thermoplastic resin is heated, gas generated from the underfill or air left in the interior of the underfill and expanding during the heating could not smoothly pass through the long narrow gap
52
without resistance between every adjacent conductor pads
50
arranged on the surface of the substrate body
10
in parallel to each other, but a large proportion of the gas and/or air continue to dwell in the interior of the resin of the underfill disposed inward of the conductor pad
50
and softened by heating. This causes voids anywhere in the underfill resin, which results in the deterioration of adhesion of the underfill resin whereby the semiconductor chip
20
is easily stripped off from the surface of the substrate body
10
.
Accordingly, in the substrate wherein the semiconductor chip
20
is bonded to the surface of the substrate body
10
via the underfill resin, it has been impossible to maintain a favorable electrical connection between the conductor bump
22
formed on the electrode of the semiconductor chip
20
and the conductor pad
50
formed on the surface of the substrate body
10
.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above-mentioned problems in the prior art and to provide a substrate for mounting a semiconductor chip (hereinafter referred merel
Higashi Mitsutoshi
Murayama Kei
Abraham Fetsum
Shinko Electric Industries Co. Ltd.
Staas & Halsey , LLP
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