Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-03-17
2003-03-11
Gray, Linda (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S261000, C156S273500, C156S298000, C156S299000, C156S305000, C156S306600, C156S306900, C228S180220, C427S096400, C427S097100, C029S832000, C029S852000
Reexamination Certificate
active
06531022
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a mounting method of semiconductor element for mounting a flip chip type semiconductor element on a circuit board of semiconductor element at high reliability and high density.
BACKGROUND ART
Conventional mounting methods of semiconductor element are described below by referring to the drawings.
(Prior Art 1)
FIG. 16
is a sectional view of mounting a semiconductor element on a circuit board in prior art 1.
In
FIG. 16
, reference numeral
1
is a semiconductor element, an electrode
2
is formed on the semiconductor element
1
, and a protruding bump (metal ball bump)
15
made of gold, copper, aluminum, solder or the like is formed on the electrode
2
by wire bonding method.
Reference numeral
4
is a circuit board made of an insulating substrate, and a copper foil
5
to be used as wiring is formed on this circuit board
4
, and a copper-plated external electrode terminal
6
is formed on the circuit board
4
. To conduct within the circuit board, a hole
8
formed in the circuit board
4
is filled with conductive paste
7
.
Reference numeral
22
is a conductive paste (conductive adhesive) having conductive powder of silver, gold, nickel, carbon or the like dispersed uniformly on phenol or epoxy resin. The external electrode terminal
6
of the circuit board
4
and the electrode
2
of the semiconductor element
1
are electrically connected with each other through the protruding bump
15
. The space between the circuit board
4
and semiconductor element
1
is filled with epoxy resin
20
.
A mounting method of thus constituted semiconductor device is described below.
The conductive paste
22
is transferred on the protruding bump
15
formed on each electrode
2
of the semiconductor element
1
by transfer method, it is mounted so that the protruding bump
15
may coincide with the external electrode terminal
6
of the circuit board
4
to be mounted, and then it is heated to cure the conductive paste
22
. In this way, the electrode
2
of the semiconductor element
1
and the external electrode terminal
6
of the circuit board
4
are electrically connected. After the connection, the space between the semiconductor element
1
and circuit board
4
is filled with the epoxy resin
20
, and by making use of the shrinking force of its curing, continuous contact of the conductive powder of the conductive paste
22
is obtained, so that electrical and mechanical reliability is assured.
(Prior Art 2)
FIG. 17
is a sectional view of mounting a semiconductor element on a circuit board in prior art 2. Same parts as in the constitution in
FIG. 16
are identified with same reference numerals and their explanation is omitted.
In
FIG. 17
, reference numeral
23
is a metal bump formed on an electrode
2
by electric plating method, and the metal bump
23
is, for example, plated with copper and further plated with gold
24
. Reference numeral
25
is an external electrode terminal, and
16
is a passivation film for protecting the active surface of the semiconductor element
1
.
A mounting method of thus constituted semiconductor device is described below.
The conductive paste
22
is transferred on the metal bump
23
formed on each electrode
2
of the semiconductor element
1
by transfer method, it is mounted so that the metal bump
23
may coincide with the external electrode terminal
25
of the circuit board
4
to be mounted, and then it is heated to cure the conductive paste
22
. In this way, the electrode
2
of the semiconductor element
1
and the external electrode terminal
25
of the circuit board
4
are electrically connected. After the connection, the space between the semiconductor element
1
and circuit board
4
is filled with the epoxy resin
20
, and by making use of the shrinking force of its curing, continuous contact of the conductive powder of the conductive paste
22
is obtained, so that electrical and mechanical reliability is assured.
(Prior Art 3)
FIG. 18
is a sectional view of mounting a semiconductor element on a circuit board in prior art 3. Same parts as in the constitution in FIG.
16
and
FIG. 17
are identified with same reference numerals and their explanation is omitted.
In
FIG. 18
, reference numeral
3
is a protruding bump (protruding electrode) formed on an electrode
2
by plating method, and
26
is an insulating adhesive film, and conductive particles
27
of nickel, solder, carbon, or the like are uniformly dispersed in the insulating adhesive film
26
.
A mounting method of thus constituted semiconductor device is described below.
The insulating adhesive film
26
is positioned between the semiconductor element
1
and external electrode terminal
25
of the circuit board
4
, and heated and pressurized simultaneously. As a result, the adhesive film
26
is melted to flow into the space in the electrode
25
, the conductive particles
27
are fixed and held by the protruding pump
3
and external electrode terminal
25
, so that the protruding bump
3
and external electrode terminal
25
conduct. In the space, on the other hand, the conductive particles
27
remain dispersed in the adhesive, and the insulation is maintained. The adhesive film
26
is cured when cooled, and the semiconductor element
1
and circuit board
4
are fixed, and the connection reliability is assured.
In the mounting method of semiconductor element in prior art 1 (or prior art 2), however, as shown in
FIG. 19
, when transferring the conductive paste film
28
on the protruding bump
15
by transfer method and joining the bump
15
to the external electrode
6
of the circuit board
4
, it is hard to control the amount of the conductive paste
22
to be transferred, and if the amount of the paste
22
is slightly excessive, a short circuit
30
may be formed in the electrode
2
by the conductive paste
22
. Or if the circuit board
4
is slightly warped, the electrode
2
of the semiconductor element
1
and the external electrode terminal
6
of the circuit board
4
do not contact with each other through the conductive paste
22
, and it is electrically open between the electrode
2
and external electrode terminal
6
.
Further, as shown in
FIG. 20
, when filling the space between the semiconductor element
1
and circuit board
4
with epoxy resin
20
, the epoxy resin
20
contained in a syringe
31
is injected from the periphery of the semiconductor element
1
, and it takes more than 10 minutes to inject, and it was a bottleneck for shortening the cycle time of production line of semiconductor element
1
.
In the mounting method of semiconductor element in prior art
3
, since conduction is achieved by fixing and holding the conductive particles
27
between the electrode
2
of the semiconductor element
1
and electrode
25
of the circuit board
4
, if the circuit board
4
is slightly warped or curved A as shown in
FIG. 21
, the conductive particles
27
remain dispersed in the adhesive
26
, and the protruding bump
3
of the semiconductor element
1
and the electrode
25
of the circuit board
4
do not contact with each other, and hence it is electrically open between the protruding bump
3
and electrode
25
. In the mounting method of prior art 3, incidentally, it is applied to a glass substrate which is hardly warped or curved, and is not applied to resin substrate.
It is hence an object of the invention to present a mounting method of semiconductor element free from occurrence of defects such as short circuit or open state between electrodes, capable of mounting at high electric reliability, curtailing the time substantially in the sealing process, and shortening the cycle time of semiconductor production line.
DISCLOSURE OF THE INVENTION
To achieve the above object, the mounting method of semiconductor element of the invention comprises a step of forming a hole in a position of a circuit board for connecting a circuit of the circuit board and an electrode of a semiconductor element, a step of filling the hole with a conductive paste for forming an external electrode termi
Gray Linda
Matsushita Electric - Industrial Co., Ltd.
RatnerPrestia
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