Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-08-08
2003-05-20
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S831000, C029S852000
Reexamination Certificate
active
06564451
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a hole filling method for a printed wiring board used in an electronic apparatus.
Referring to
FIGS. 1A through 1G
, description will be made of a related hole filling method for a printed wiring board using a printing technique.
Referring to
FIG. 1A
, preparation is made of a printed wiring board
1
to be subjected to a hole filling process. The printed wiring board
1
comprises an insulator substrate
1
a
and a copper plating layer
1
b
. The insulator substrate
1
a
has through holes formed therein as desired. Then, the insulator substrate
1
a
is subjected to copper plating to form the copper plating layer
1
b
on both surfaces of the insulator substrate
1
a
and inside surfaces of the through holes. The copper plating layer
1
b
formed on the inside surface of each through hole in the insulator substrate
1
a
has an inner surface defining an interlayer connection hole (simply referred to as an interlayer connection hole throughout the specification) of the printed wiring board
1
. The interlayer connection holes include a large-diameter through hole
3
having a diameter not smaller than the thickness of the printed wiring board
1
and a small-diameter through hole
4
having a diameter smaller than the thickness of the printed wiring board
1
.
The printed wiring board
1
prepared as mentioned above is an interlayer connection plating printed wiring board. The hole filling process is carried out for each single interlayer connection plating printed wiring board.
Referring to
FIG. 1B
, the printed wiring board
1
is placed on a printing table
40
in order to carry out the hole filling process using the printing technique. A printing plate or pattern
50
is used to print a hole filling resin (for example, epoxy resin)
9
at desired positions. A squeegee
70
serves to apply the hole filling resin
9
. After the printed wiring board
1
is placed on the printing table
40
, the printing pattern
50
is put on the printed wiring board
1
and the hole filling resin
9
is applied and spread on the printing pattern
50
covering the printed wiring board
1
by the use of the squeegee
70
.
Referring to
FIG. 1C
, the hole filling resin
9
is applied and spread on the printing pattern
50
by the squeegee
70
to be filled in the through holes
3
and
4
as filled resins
19
and
20
, respectively. After the through holes
3
and
4
are filled with the hole filling resin
9
, the printing pattern
50
is removed and the printed wiring board
1
is displaced from the printing table
40
.
Referring to
FIG. 1D
, the printing pattern
50
is removed from the printed wiring board
1
and the printed wiring board
1
is displaced from the printing table
40
. In this state, the hole filling resin
9
is cured. In
FIG. 1D
, a resin residue
100
is formed by a part of the hole filling resin
9
which has been present in an opening portion of the printing pattern
50
upon filling the hole filling resin
9
in the through holes
3
and
4
and is left on a resin insertion surface (upper surface in the figure) of the printed wiring board
1
or which leaks from the periphery of the opening portion of the printing pattern
50
. The resin residue
100
also includes a part of the hole filling resin
9
leaking from a gap between the printing pattern
50
and the printed wiring board
1
in the vicinity of open ends of the through holes
3
and
4
. The hole filling resin
9
is cured by heating or photocuring. At this time, both of the filled resins
19
and
20
filled in the through holes
3
and
4
and the resin residue
100
are cured together. As a result, protrusions are formed on the surface of the printed wiring board
1
. Such protrusions must be removed by polishing or the like.
Referring to
FIG. 1E
, the surface of the printed wiring board
1
is flattened and smoothed by the use of a polisher
110
. In order to remove the protrusions formed on the surface of the printed wiring board
1
due to presence of the resin residue
100
when the hole filling resin
9
is cured and to flatten and smooth the surface of the printed wiring board
1
, polishing is carried out by the use of the polisher
110
. At this time, the surface of the printed wiring board
1
is also shaved.
Referring to
FIG. 1F
, the protrusions are removed by polishing to produce flattened surfaces
120
and
130
of the hole filling resin
9
filled in the through holes
3
and
4
as the filled resins
19
and
20
, respectively. In this state, the through holes
3
and
4
may be referred to as filled through holes.
Referring to
FIG. 1G
, the printed wiring board
1
with the filled through holes is obtained through the above-mentioned steps. In the illustrated state, the through holes
3
and
4
are filled with the hole filling resin
9
as the filled resins
19
and
20
, respectively.
Next referring to
FIGS. 2 and 3
, description will be made of a merit achieved by filling the hole filling resin in the through holes formed in the printed wiring board
1
.
Referring to
FIG. 2
, a component
32
is mounted on the printed wiring board
1
in which the through holes are not filled. Referring to
FIG. 3
, the component
32
is mounted on the printed wiring board
1
in which the through holes are filled.
In
FIG. 2
, the hole filling resin
9
is not filled in the through hole
3
as the filled resin
19
. Therefore, a connection pad to connect the component
32
can not be formed on the through hole
3
. On the other hand, in
FIG. 3
, the through hole
3
is filled with the hole filling resin
9
as the filled resin
19
. Therefore, a pad
34
comprising a copper plating layer or the like can be formed on the filled resin
19
filled in the through hole
3
in such a manner that the pad
34
is connected to the copper plating layer
1
b
of the printed wiring board
1
. Then, the component
32
can be mounted on the pad
34
located on the through hole
3
.
As illustrated in
FIG. 3
, the pad
34
is formed on the through hole
3
buried with the filled resin
19
and the component
32
is directly connected to the pad
34
located on the through hole
3
. In this manner, the wiring distance is shortened and the inductance is reduced as compared with FIG.
2
. Thus, the impedance of the printed wiring board
1
is reduced.
However, in the related hole filling method described in conjunction with
FIG. 1
, the hole filling process must be carried out for each single printed wiring board
1
. Therefore, the productivity is inferior.
In addition, the resin filling step and the resin curing step must separately be carried out. Therefore, the productivity is inferior.
Furthermore, the hole filling process must be followed by polishing to improve the flatness of the surface of the printed wiring board. Therefore, the productivity is inferior.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a hole filling method for a printed wiring board, which is improved in productivity.
It is a specific object of this invention to provide a hole filling method for a printed wiring board, which is capable of simultaneously carrying out a hole filling process for two printed wiring boards.
It is another specific object of this invention to provide a hole filling method for a printed wiring board, which is capable of simultaneously carrying out a resin filling step and a resin curing step.
It is still another specific object of this invention to provide a hole filling method for a printed wiring board, which is capable of improving the flatness of the surface of the printed wiring board without requiring a polishing step after a hole filling process.
According to this invention, there is provided a hole filling method for a printed wiring board having an interlayer connection hole, comprising the steps of:
preparing first and second printed wiring boards each of which has the interlayer connection hole;
placing the first printed wiring board on a bottom plate;
placing on the first printed wiring board a first hole guide plate
Abe Shigetoshi
Itagaki Takashi
Kato Tomoko
Matsumoto Kenji
Sato Yasuo
Arbes Carl J.
Collard & Roe P.C.
Japan Radio Co. Ltd.
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