Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2000-02-17
2002-08-20
Cuneo, Kamand (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S260000, C174S259000, C361S771000
Reexamination Certificate
active
06437251
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a technological field of a flexible printed wiring board, more particularly to a technology of producing a double-face flexible printed wiring board having a complicated shape.
DESCRIPTION OF THE RELATED ART
Flexible printed wiring boards each having a desired circuit pattern printed thereon have gained a wide application in the past and flexible printed wiring boards having various shapes corresponding to the shapes of various position at which the substrates are used have been required in recent years.
FIG.
4
(
a
) shows an arrangement when T-shaped flexible printed wiring boards
152
are cut out from a rectangular master sheet
150
. In this drawing, six flexible printed wiring boards
152
can be acquired.
However, when the flexible printed wiring boards
152
having special shapes are cut out, a large area of the master sheet
150
is discarded in vain.
In the conventional art, therefore, attempts have been made to take a flexible printed wiring board in a complicated shape apart into elemental pieces in simple shapes and then bond these pieces together to give a flexible printed wiring board.
FIG.
4
(
c
) shows an example where a flexible printed wiring board
155
having the same shape as that of the flexible printed wiring board
152
described above is formed by bonding two kinds of elemental pieces
153
and
154
together.
When the elemental pieces
153
and
154
having simple shapes are cut out from the master sheet
150
as shown in FIG.
4
(
b
), the master sheet
150
can be utilized effectively. In in the case of FIG.
4
(
b
), eight elemental pieces
153
and
154
can be acquired respectively. In this case, eight T-shaped flexible printed wiring boards
155
can be acquired by bonding the elemental pieces
153
and
154
to each other. Consequently, a greater number of T-shaped flexible printed wiring boards can be acquired than the case when the T-shaped flexible printed wiring boards
152
are directly cut out.
To bond plural elemental pieces to each other to thereby form a flexible printed wiring board, it is necessary to connect these elemental pieces mechanically and electrically to each other.
Reference numerals
120
and
130
in FIG.
3
(
a
) show the elemental pieces which include metal wirings
122
and
132
comprising patterned copper thin films are formed on each of the polyimide films
121
and
131
. To bond the elemental pieces to one another, the elemental pieces
120
and
130
are first arranged in such a manner that the metal wirings
122
and
132
face one another.
Solder coating films
123
and
133
are deposited by plating to each of the metal wirings
122
and
132
. The solder coating films
123
and
133
are brought into close contact with each other, are then pressed while being heated to melt the solder coating films
123
and
133
and are then cooled, providing a solder layer
104
. The solder layer
104
so formed gives a bond portion
112
at which the metal wirings
122
and
132
are firmly connected to each other.
Because these two elemental pieces
120
and
130
are firmly fixed through the bond portion
112
, one flexible printed wiring board
103
can be acquired (FIG.
3
(
b
)).
However, the pitch of the metal wirings
122
and
132
has become smaller and smaller because a large number of metal wirings on a flexible printed wiring board is required in recent years.
When the solder coating films
123
and
133
are molten while being pressed, the solder is likely to scatter because of the pressure. The scattering solder may exist sporadically inside the flexible printed wiring board
103
and in the extreme case, the outflow of the molten solder forms a bridge
116
between adjacent bond portions
112
and invites short-circuit of the adjacent portions
112
. As the pitch of the metal wirings
122
and
132
becomes smaller, the bridge
116
is more likely to develop. In consequence, the production yield of the flexible printed wiring board
103
using the elemental pieces
120
and
130
drops.
SUMMARY OF THE INVENTION
The present invention has been completed in order to solve the problems of the prior art described above, and is directed to provide a technology of producing specially-shaped double-face flexible printed wiring boards with a small pitch of metal wirings and a high production yield.
To accomplish the object described above, the present invention relates to a method of producing a flexible printed wiring board by laminating a plurality of elemental pieces each including a resin film, a metal wiring formed on said resin film and a low melting point metal coating film formed in at least a part of regions on the metal wiring, which method comprises the steps of arranging an adhesive resin that exhibits an adhesiveness upon heating between the metal wiring of one of the elemental pieces and the metal wiring of another elemental piece; pressing one elemental piece to another elemental piece while they are being heated; connecting the metal wiring of one elemental piece to the metal wiring of another elemental piece via the low melting point metal coating film that is so molten; and bonding one elemental piece and another elemental piece via the adhesive resin.
The present invention relates to a method of producing a flexible printed wiring board, wherein the adhesive resin is film-like.
The present invention relates to a method of producing a flexible printed wiring board wherein the low melting point metal coating film is formed on the surface of both of the metal wirings that are to be connected mutually.
The present invention relates to a method of producing a flexible printed wiring board, wherein either one or both of the surface of the metal wiring and the surface of the low melting point metal coating film are exposed on one of the surfaces of the flexible printed wiring board.
The present invention relates to a method of producing a flexible printed wiring board, wherein either one or both of the surface of the metal wiring and the surface of the low melting point metal coating film are exposed on both of the surfaces of the flexible printed wiring board.
The present invention relates to a flexible printed wiring board that comprises at least two elemental pieces each having a resin film, a metal wiring formed on said resin film and a low melting point metal coating film formed in at least a part of regions on the metal wiring, wherein the elemental pieces are bonded to one another via said adhesive resin, and the metal wirings of the elemental pieces are connected to one another via said low melting point metal coating film.
REFERENCES:
patent: 5714252 (1998-02-01), Hogerton et al.
patent: 6147870 (2000-11-01), Pommer
patent: 6246014 (2001-06-01), Pommer
patent: B2-2865241 (1998-12-01), None
patent: 01-102734 (2001-04-01), None
Anzai Yukio
Fukuda Mitsuhiro
Kurita Hideyuki
Shinohara Toshihiro
Watanabe Masanao
Cuneo Kamand
Oliff & Berridg,e PLC
Sony Chemicals Corp.
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