Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2000-07-26
2002-09-17
Vo, Peter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S840000, C029S843000, C174S263000, C228S180100, C228S179100
Reexamination Certificate
active
06449836
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of Japanese Patent Applications No. 11-218014 filed on Jul. 30, 1999, No. 11-340601 filed on Nov. 30, 1999, No. 2000-161822 filed on May 31, 2000, and No. 2000-188278 filed on Jun. 22, 2000, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for interconnecting printed circuit boards and an interconnection structure.
2. Description of the Related Art
JP-A-9-8453 discloses an interconnection structure for printed circuit boards, using an anisotropic conductive resin material. Referring to
FIG. 18
, this structure has an anisotropic conductive thermoplastic resin
52
being placed between a conductive pattern surface of a first printed circuit board
50
and a conductive pattern surface of a second printed circuit board
51
, which is fused by applying pressure and ultrasonic waves. In this manner, a distance between lands
50
a
and
50
b
is reduced to establish an electric interconnection therebetween.
“Introductory High density Flexible Board (in Japanese)” (by Kenji Numakura, published by Nikkan Kogyo Co., Ltd.) discloses at page 100 a method for interconnecting a hard printed board and a flexible board. In accordance with this method of interconnection, as shown in
FIG. 19
, a land
60
a
of a conductive pattern on the hard printed board
60
is interconnected with a land
61
a
of a conductive pattern on the flexible board
61
by using a solder
62
. Furthermore, the flexible board
61
is adhered to the hard printed board
60
by using an adhesive
63
.
However, in the interconnection structure as shown in
FIG. 18
, an anisotropic conductive resin film must be mounted on the surface of the printed circuit boards
50
and
51
by printing or the like. This requires an additional process step to obtain the interconnection structure, and leads to an increase in the production cost.
Furthermore, the printed circuit boards
50
and
51
are interconnected with their surfaces being faced each other while incorporating the anisotropic conductive resin material
52
therebetween. Accordingly, the resulting product suffers poor reliability because voids tend to be generated in the connecting interface between the resin material
52
and each of the printed circuit boards
50
and
51
.
In the interconnection structure shown in
FIG. 19
, it is necessary to cover the edge portion of the flexible board
61
with a protective insulating film after interconnecting the flexible board
61
in order to assure the insulation reliability of the interconnected portion. Thus, in this case again, the production step is increased.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the aforementioned problems. Accordingly, an object of the present invention is to provide a method for interconnecting printed circuit boards and an interconnection structure, which is improved in the reliability of the interconnection and capable of reducing the production cost.
According to the present invention, a land of a first printed circuit board is overlapped with a land of a second printed circuit board to form an interconnection portion. The first printed circuit board has an insulating substrate made of a thermoplastic resin. Then, the interconnection portion is heated at a temperature approximately higher than a glass transition temperature of the thermoplastic resin while applying a pressure to the interconnection portion. Accordingly, the land of the first printed circuit board is electrically interconnected with the land of the second printed circuit board. Simultaneously, the interconnection portion is sealed with a part of the thermoplastic resin.
Thus, the interconnection portion is sealed with the resin constituting the substrate of the first printed circuit board without using an anisotropic conductive film or the like, resulting in reduced production cost. Since the thermoplastic resin is softened and deformed to seal the interconnection portion while expelling air, voids are less likely formed at the interconnection portion. As a result, the interconnection structure has high reliability.
REFERENCES:
patent: 4164071 (1979-08-01), Kruzick
patent: 4679122 (1987-07-01), Belke, Jr. et al.
patent: 4735847 (1988-04-01), Fujiwara et al.
patent: 5084961 (1992-02-01), Yoshikawa
patent: 5221417 (1993-06-01), Basavanhally
patent: 5669548 (1997-09-01), Miyake et al.
patent: 5799392 (1998-09-01), Mishiro
patent: 5935475 (1999-08-01), Scoles et al.
patent: 6143116 (2000-11-01), Hayashi et al.
patent: 6218030 (2001-04-01), Miyake et al.
patent: 6226862 (2001-05-01), Neuman
patent: 2002/0014518 (2002-02-01), Totani et al.
patent: 9-8453 (1997-01-01), None
patent: 9-320662 (1997-12-01), None
Numakura,Introductory High Density Flexible Board, Nikkan Kogyo Co., Ltd., 1998, pp. 99-103.
Hirano Kenzo
Iwama Hiroyasu
Kojima Katsuaki
Miyake Toshihiro
Nanami Tomoyuki
Denso Corporation
Law Offices of David G. Posz
Trinh Minh
Vo Peter
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