Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-04-26
2001-08-21
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S277000, C029S740000
Reexamination Certificate
active
06277222
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic component connecting method, and more particularly, to an electronic component connecting method suitable for use in mounting a chip-type electronic component, such as an IC chip, on a wiring board.
2. Description of the Related Art
FIGS. 2A
to
2
F show a conventional electronic component connecting method disclosed in Japanese Unexamined Patent Publication No. 5-190599. This connecting method results in the state shown in
FIG. 2F
, in which an IC chip
1
serving as a first electronic component is mounted on a wiring board
2
serving as a second electronic component.
First, as shown in
FIG. 2A
, an IC wafer
3
is prepared as a mother component which is later cut (
FIG. 2C
) to form a plurality of the IC chips
1
. On one main surface
4
of the IC wafer
3
, connecting electrodes
5
are formed at predetermined positions in regions corresponding to the IC chips
1
.
Three connecting electrodes
5
are shown in FIG.
2
A. On the right-side connecting electrode
5
, a projecting electrode
6
is formed to serve as a bump electrode.
FIG. 2A
sequentially illustrates the process of forming this projecting electrode
6
in connection with the left-side connecting electrode
5
, the center connecting electrode
5
, and the right-side connecting electrode
5
.
The projecting electrode
6
is basically formed by ball bonding. First, as illustrated in connection with the left-side connecting electrode
5
in
FIG. 2A
, a ball
9
is formed at the leading end of a gold wire
8
that passes through a capillary
7
. Next, the ball
9
is placed on the connecting electrode
5
, as illustrated in connection with the center connecting electrode
5
, and is pressed against the connecting electrode
5
by the capillary
7
. Then, the gold wire
8
is cut off the ball
9
, as illustrated in connection with the right-side connecting electrode
5
in FIG.
2
A. In this way, the projecting electrode
6
is given a two-stage structure by the ball
9
and a part of the gold wire
8
.
By repeating the above-described steps, projecting electrodes
6
that serve as bump electrodes are formed on all the connecting electrodes
5
on the main surface
4
of the IC wafer
3
, as shown in FIG.
2
B.
Subsequently, as shown in
FIG. 2C
, the IC wafer
3
is cut into a plurality of IC chips
1
by, for example, dicing.
Then, a conductive adhesive
10
is applied on the projecting electrodes
6
formed on the connecting electrodes
5
of the IC chip
1
by, for example, dipping, as shown in FIG.
2
D.
Also shown in
FIG. 2D
is the preparation of the wiring board
2
. On one main surface
11
of the wiring board
2
, connecting electrodes
12
are formed corresponding to the connecting electrodes
5
on the IC chip
1
.
Next, the IC chip
1
is pressed against the wiring board
2
, as shown in
FIG. 2E
, while the main surface
4
of the IC chip
1
and the main surface
11
of the wiring board
2
are opposed to each other, as shown in FIG.
2
D. In this case, since the conductive adhesive
10
is not hardened, it deforms to follow the surfaces of the connecting electrodes
12
on the wiring board
2
, and is brought into close contact with the projecting electrodes
6
and the connecting electrodes
12
. Furthermore, since the projecting electrodes
6
have a two-stage structure, spaces are formed between the projecting electrodes
6
and the connecting electrodes
12
so as to receive the conductive adhesive
10
. For this reason, the conductive adhesive
10
does not generally spread out in a horizontal direction.
Subsequently, the conductive adhesive
10
is hardened while the IC chip
1
and the wiring board
2
are aligned with each other, as shown in FIG.
2
E.
Next, as shown in
FIG. 2F
, a filling material
13
is applied and hardened between the IC chip
1
and the wiring board
2
. The filling material
13
serves to reinforce the connected portion between the IC chip
1
and the wiring board
2
, to relax thermal stress, and to improve moisture resistance of the IC chip
1
, and is filled in a clearance between the IC chip
1
and the wiring board
2
.
In this way, according to the conventional electronic component connecting method shown in
FIGS. 2A
to
2
F, since the projecting electrodes
6
have a two-stage structure, spaces are formed between the projecting electrodes
6
and the connecting electrodes
12
so as to receive the conductive adhesive
10
, as described above. Therefore, even when the IC chip
1
is pressed against the wiring board
2
, the conductive adhesive
10
is prevented from being horizontally spread out. This makes it possible to reduce the pitch between a plurality of connecting electrodes
5
and the pitch between a plurality of connecting electrodes
12
, to reduce the size of the IC chip
1
, and to improve packaging density.
The electronic component connecting method shown in
FIGS. 2A
to
2
F has, however, the following problems which must be solved.
First, a plurality of steps shown in
FIG. 2A
must be performed to form a projecting electrode
6
having a two-stage structure, and be repeated for each of the connecting electrodes
5
. Therefore, much time is taken to form projecting electrodes
6
on all the connecting electrodes
5
, and the length of time is proportional to the number of the connecting electrodes
5
. In particular, the time to process becomes longer as the arrangement density of the connecting electrodes
5
increases. This results in an increase in cost.
In the above-described ball bonding for forming the projecting electrodes
6
, metal-to-metal solid phase bonding is performed by applying load and ultrasonic energy, and this may cause damage to the IC wafer
3
, and further, to the IC chip
1
.
In order to reduce such damage, an active area, where elements such as a capacitor and a transistor are arranged, must not be placed directly below the connecting electrodes
5
. This countermeasure, however, produces another problem in that the size of the IC chip
1
is increased to form the connecting electrodes
5
outside the active area.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an electronic component connecting method that can solve the above problems.
The present invention is aimed at a method of electrically connecting a first electronic component having a first connecting electrode, and a second electronic component having a second connecting electrode via the first and second connecting electrodes, and includes the following steps to solve the above-described technical problems.
According to an aspect of the present invention, the electronic component connecting method includes the steps of forming a projecting electrode serving as a bump electrode by applying and hardening a thermosetting conductive adhesive on a first connecting electrode; applying a conductive adhesive for connection on at least one of the projecting electrode and a second connecting electrode; aligning (positioning) the first electronic component and the second electronic component before hardening the conductive adhesive for connection so that the end of the projecting electrode and the second connecting electrode are in contact with each other; and hardening the conductive adhesive for connection while the first electronic component and the second electronic component are aligned (positioned) with each other.
Preferably, the projecting electrode is tapered and projects in the shape of a cone, such as a circular cone or a pyramid.
According to another aspect of the present invention, the electronic component connecting method includes the steps of forming a tapered projecting electrode serving as a bump electrode by applying and hardening a thermosetting conductive adhesive on the first connecting electrode by printing; applying a conductive adhesive for connection on at least one of the projecting electrode and the second connecting electrode; aligning the first electronic component and the second electronic co
Morimoto Ryoichi
Nitta Koichi
Ball Michael W.
Haran John T.
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen
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