Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor
Reexamination Certificate
1999-08-26
2002-10-08
Everhart, Caridad (Department: 2825)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
C438S118000, C438S119000, C438S120000
Reexamination Certificate
active
06461890
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor chip, and more particularly, it relates to the structure of a semiconductor chip suitable for a chip-on-board system and methods of fabricating and mounting the same.
For example, a semiconductor chip such as an IC chip provided with a plurality of terminals on its major surface is mounted on a printed wiring board or a lead frame in the so-called chip-on-board system. In order to cope with the chip-on-board mount system, an anisotropic conductive film, for example, is stuck on the major surface of the semiconductor chip.
2. Description of the Prior Art
FIG. 1
illustrates a semiconductor chip
10
which is mounted on a circuit board
20
in the chip-on-board system. A plurality of first bumps
11
for connection are protrusively formed on a major surface of the semiconductor chip
10
. On the other hand, a plurality of second bumps
21
are protrusively formed on a surface of the circuit board
20
, to be opposed to the first bumps
11
of the semiconductor chip
10
respectively. The chip-on-board system is adapted to oppose the major surface of the semiconductor chip
10
to the circuit board
20
through an anisotropic conductive film
30
and bring these members into pressure contact with each other under heat, thereby electrically connecting and bonding the opposed first and second bumps
11
and
21
with each other while keeping insulation in the remaining regions. Throughout the specification, the term “bump” must be understood as indicating an electrode, a terminal pad or a conductor pad formed in a slightly protruding manner.
The anisotropic conductive film
30
includes an adhesive resin film
31
and conductive grains
32
dispersed in this resin film
31
. The conductive grains
32
are prepared from metal balls, for example. The metal balls may be replaced with resin balls having nickel-plated surfaces or those further having gold plating on such nickel-plated surfaces, for example.
When prescribed pressure is so applied under heat that the semiconductor chip
10
and the circuit board
20
approach to each other through the anisotropic conductive film
30
interposed therebetween, portions of the anisotropic conductive film
30
located between the first bumps
11
of the semiconductor chip
10
and the second bumps
21
of the circuit board
20
are softened and crushed. Consequently, the first and second bumps
11
and
21
are electrically connected with each other through the conductive grains
32
.
In the remaining uncrushed regions of the anisotropic conductive film
30
not located between the first and second bumps
11
and
21
, the conductive grains
32
are still dispersed. Thus, these regions keep insulation. Further, the semiconductor chip
10
and the circuit board
20
are bonded with each other due to the adhesive strength of the anisotropic conductive film
30
.
In the aforementioned mount method, electrical conduction can be attained only in necessary portions, and the semiconductor chip
10
can be mounted on the circuit board
20
by simply applying pressure so that the semiconductor chip
10
and the circuit board
20
approach to each other through the anisotropic conductive film
30
interposed therebetween. This method is remarkably simple as compared with a method of mounting the semiconductor chip
10
on the circuit board
20
or the like by the so-called chip bonding and wire bonding.
However, the method of connecting the bumps
11
and
21
through the anisotropic conductive film
30
shown in
FIG. 1
is merely adapted to press the semiconductor chip
10
and the circuit board
20
through the anisotropic conductive film
30
interposed therebetween with application of heat. Therefore, this method is insufficient. in stability of electrical connection. Namely, the conductive grains
32
contained in the anisotropic conductive film
30
may not properly come into contact with the bumps
11
and
21
unless the heating temperature and the pressure-contact force are properly managed. When the semiconductor chip
10
is to be mounted on a printed circuit board based on glass epoxy resin or the like, the board may be distorted or warped, leading to loose connection between the bumps
11
and
21
.
In the conventional mount method shown in
FIG. 1
, the anisotropic conductive film
30
having a size corresponding to that of the semiconductor chip
10
is previously prepared, to be interposed between the semiconductor chip
10
and the circuit board
20
. The prepared anisotropic conductive film
30
is first placed on a prescribed position of the circuit board
20
, so that the semiconductor chip
10
is placed on this anisotropic conductive film
30
. Alternatively, the anisotropic conductive film
30
formed in a prescribed size is previously stuck on the major surface of the semiconductor chip
10
, so that the semiconductor chip
10
having the anisotropic conductive film
30
is placed on a prescribed position of the circuit board
20
.
In either case, a single anisotropic conductive film
30
must be prepared for a single semiconductor chip
10
, in order to mount the semiconductor chip
10
on the circuit board
20
in the chip-on-board system. Therefore, the anisotropic conductive film
30
must be prepared in the size corresponding to that of the semiconductor chip
10
, and such anisotropic conductive films
30
must be prepared in a number responsive to that of semiconductor chips
10
to be mounted, leading to reduction of workability and increase in cost. Further, the anisotropic conductive films
30
formed in the prescribed size must be placed one by one on the circuit boards
20
or stuck one by one to the surfaces of the semiconductor chips
10
. Thus, the number of working steps is increased and the workability is deteriorated.
In general, each semiconductor chip
10
is packaged with resin, to be prevented from penetration of moisture or air from the exterior. If an unpackaged semiconductor chip
10
is mounted on the circuit board
20
or the like in the chip-on-board system, an electronic circuit formed on the semiconductor chip.
10
cannot be completely blocked and shielded against the exterior in the mounted state. Therefore, moisture or air disadvantageously penetrates into the electronic circuit of the semiconductor chip
10
, to inhibit the semiconductor chip
10
from exhibiting its original characteristics.
SUMMARY OF THE INVENTION
An object of the present invention is to further ensure electrical connection between butted terminals.
Another object of the present invention is to improve workability in case of mounting a semiconductor chip on a circuit board or the like in the chip-on-board system.
Still another object of the present invention is to effectively prevent penetration of moisture or air from the exterior in a semiconductor chip having an anisotropic conductive film stuck on its major surface.
A connection structure between terminals according to an aspect of the present invention comprises a first member having a first terminal on its surface, a second member having a second terminal opposed to the first terminal on its surface, and an anisotropic conductive film arranged between the first and second members. The anisotropic conductive film includes an adhesive resin film and conductive grains dispersed in this resin film. The first and second terminals are electrically connected with each other through the conductive grains. The. conductive grains are alloy-bonded with at least either one of the first and second terminals. Typically, the first member is a semiconductor chip, and the second member is a circuit board or a lead frame.
No alloy bonding is attained by merely heating/pressing the anisotropic conductive film. Namely, the alloy bonding can be implemented by properly selecting metals forming the terminals and the conductive grains contained in the anisotropic conductive film and supplying ultrasonic vibration between the terminals to be electrically connected with each other. The alloy
Arent Fox Kintner Plotkin & Kahn
Everhart Caridad
Rohm & Co., Ltd.
Yevsikov V.
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