Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor
Reexamination Certificate
2000-10-16
2004-11-02
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
C438S025000, C438S026000, C438S051000, C438S055000, C438S064000, C257S123000, C257S678000, C257S686000, C257S688000, C439S055000, C439S068000, C439S069000, C439S070000, C439S072000, C439S943000
Reexamination Certificate
active
06812060
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the field of flexible wiring boards, particularly to the technique of laminating flexible wiring board pieces into a flexible wiring board of multilayer structure.
Recently, multilayer flexible wiring boards are widely used in the field of electronic apparatus. A method for forming a multilayer flexible wiring board involves laminating a plurality of flexible wiring board pieces.
An example of process for laminating two flexible wiring board pieces is explained with reference to the attached drawings as follows. Referring to
FIG. 8
, the reference
110
represents a flexible wiring board piece used for lamination. This flexible wiring board piece
110
has a base film
117
on which a metal wiring
115
is formed by patterning a copper foil. A resin film
112
is provided on metal wiring
115
.
This resin film
112
is thermoplastic, i.e. it is not adhesive at normal temperatures but softens to develop adhesiveness upon heating.
Resin film
112
has a plurality of openings
120
in which a plurality of bumps
121
are provided.
The bottom of each bump
121
is connected to metal wiring
115
while the top projects from the surface of resin film
112
.
The reference
130
in
FIG. 9
represents a flexible wiring board piece to be laminated to said flexible wiring board piece
110
. This flexible wiring board piece
130
has a base film
132
on which a metal wiring
135
is formed by patterning a copper foil, similarly to said flexible wiring board piece
110
.
A non-thermoplastic cover film
138
is provided on metal wiring
135
and said cover film
138
has openings
139
at the locations corresponding to bumps
121
of said flexible wiring board piece
110
so that the surface of metal wiring
135
is exposed at the bottom of each opening.
For laminating these two flexible wiring board pieces
110
,
130
, one flexible wiring board piece
130
is mounted on a table
142
with openings
139
upward and opposed to the other flexible wiring board piece
110
with bumps
121
downward (FIG.
10
(
a
)).
Then, the top of bump
121
is contacted with the surface of metal wiring
135
at the bottom of opening
139
, and an ultrasonic resonator
145
is pressed against base film
117
of one flexible wiring board piece
110
(FIG.
10
(
b
)).
Ultrasonic resonator
145
is connected to an ultrasonic wave generator not shown, which is activated to transmit ultrasonic wave to ultrasonic resonator
145
pressed against flexible wiring board pieces
110
,
130
so that ultrasonic resonator
145
applies ultrasonic wave to flexible wiring board pieces
110
,
130
. Thus, bumps
121
are connected to metal wiring
135
in contact with said bumps
121
by this ultrasonic vibration.
Then, these flexible wiring board pieces
110
,
130
are heated under pressure so that resin film
112
softens to develop adhesiveness, whereby flexible wiring board pieces
110
,
130
are connected via resin film
112
into a multilayer flexible wiring board
150
(FIG.
10
(
c
)).
Thus, the use of ultrasonic resonator
145
eliminates the use of solder to electrically connect flexible wiring board pieces
110
,
130
by a single ultrasonic application while pressing a plurality of bumps
121
against metal wiring
135
.
However, such bumps
121
are formed by a complex copper plating process.
With such an ultrasonic resonator
145
pressed against the whole flexible wiring board pieces
110
,
130
to apply ultrasonic wave, connection failure may occur if the heights of bumps
121
are not uniformity. For example, the reference
151
in FIG.
10
(
c
) represents such a connection failure, in which a lower bump
122
is not connected to metal wiring
135
because of lack of contact with metal wiring
135
during ultrasonic application in contrast with a higher bump
121
connected to the surface of metal wiring
115
.
Bumps
121
should have a uniformity of height within ±3 &mgr;m or less to efficiently connect flexible wiring board pieces
110
,
130
, but this is difficult when bumps
121
are formed by electroplating as described above.
Moreover, bumps
121
should fill openings
120
and project from the surface of resin film
112
by growing copper to a thickness of 40 &mgr;m or more, but it takes one hour or more to attain such a thickness by electroplating, resulting in increase of production costs.
An object of the present invention is to obtain a multilayer flexible wiring board from flexible boards at low cost with high yield to overcome the disadvantages of the prior art described above.
SUMMARY OF THE INVENTION
In order to attain the above object, the present invention provides a process for manufacturing a multilayer flexible wiring board by laminating flexible wiring board pieces having a base film including a resin film and a metal wiring provided on said base film, said process comprising applying ultrasonic wave to said metal wirings of said flexible wiring board pieces to be laminated in close contact with each other at their surfaces to bond said metal wirings.
The present invention also provides a process for manufacturing a multilayer flexible wiring board by bonding metal wirings of at least two flexible wiring board pieces having a base film including a resin film and a metal wiring provided on said base film, said process comprising contacting the tip of ultrasonic resonator with the exposed opposite side of a portion to be bonded of said metal wirings of at least one flexible wiring board piece in two flexible wiring board pieces to be bonded, and applying iltrasonic wave to said ultrasonic resonator to bond said two metal wirings to be bonded.
In the process for manufacturing a multilayer flexible wiring board of the present invention, ultrasonic wave is applied to said metal wirings in close contact with each other at their surfaces while a thermoplastic resin layer developing adhesiveness upon heating is placed between said metal wirings.
In the process for manufacturing a multilayer flexible wiring board of the present invention, said metal wirings are ultrasonically bonded and then heated to laminate said flexible wiring board pieces by the adhesion of said thermoplastic resin.
In the process for manufacturing a multilayer flexible wiring board of the present invention, a metal coating selected from a metal coating based on gold, a metal coating based on silver, a metal coating based on nickel, a copper-nickel alloy coating, a coating based on aluminium, a coating based on titanium and a solder coating is preliminarily formed on at least one of the surfaces of the parts of said metal wirings to be ultrasonically bonded before said metal wirings are ultrasonically bonded.
In the process for manufacturing a multilayer flexible wiring board of the present invention, ultrasonic wave is individually applied to the parts of said metal wirings to be bonded.
The present invention also provides a multilayer flexible wiring board formed by laminating at least two flexible wiring board pieces having a base film and a metal wiring provided on said base film, wherein at least one flexible wiring board piece has a cover film including a resin film on said metal wiring and a first opening is provided on said cover film, and said metal wiring exists at the bottom of said first opening so that said metal wirings of said flexible wiring board pieces are bonded to each other by applying ultrasonic wave while the part of said metal wiring located at the bottom of said first opening is in close contact with said metal wiring of the other flexible wiring board piece.
In the multilayer flexible wiring board of the present invention, said cover film has insulating properties to prevent said connected metal wirings from contacting with each other except for the part located at said first opening.
In the multilayer flexible wiring board of the present invention, said cover film has a thermoplastic resin layer developing adhesiveness upon heating at least on its surface.
In the multilayer flexible wiring board of the present invention, s
Hishinuma Hiroyuki
Kurita Hideyuki
Lee, Jr. Granvill D.
Oliff & Berridg,e PLC
Smith Matthew
Sony Chemicals Corporation
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