Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2001-12-04
2004-09-21
Cuneo, Kamand (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S261000, C361S792000, C029S847000, C029S879000, C029S882000
Reexamination Certificate
active
06794585
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of manufacturing a printed wiring board used in an electronic apparatus.
Referring to
FIGS. 1A through 1J
, description will be made of a method of manufacturing a printed wiring board as a related art.
Referring to
FIG. 1A
, preparation is made of a printed wiring board
1
having a plurality of interlayer connection holes. The printed wiring board
1
comprises an insulator substrate
1
a
, a copper plating layer
1
b
, and a copper foil
1
c
. 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 the interlayer connection hole of the printed wiring board
1
. The interlayer connection holes include a large-diameter through hole
2
having a diameter not smaller than the thickness of the printed wiring board
1
and a small-diameter through hole
3
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. A 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 a printing technique. A printing plate or pattern
50
is used to print a hole filling resin (for example, epoxy resin)
9
. 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
. Thus, the hole filling resin
9
is filled in the through holes
3
and
2
as filled resins
19
and
20
, respectively. After the through holes
3
and
2
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
2
and is left on a surface 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
2
. 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
2
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. As a result of polishing, the printed wiring board
1
as a whole is elongated. Since the copper plating layer
1
b
and the resin residue
100
different in hardness are simultaneously polished, it is difficult to improve the flatness of the printed wiring board
1
.
Referring to
FIG. 1F
, the protrusions are removed by polishing to produce flattened surfaces
130
and
120
of the hole filling resin
9
filled in the through holes
3
and
2
as the filled resins
19
and
20
, respectively. In this state, the through holes
3
and
2
may be referred to as filled through holes. Next, the printed wiring board
1
with the filled through holes is subjected to plating (
21
in
FIG. 1G
) in the following manner.
Referring to
FIG. 1G
, the printed wiring board
1
with the filled through holes is obtained through the above-mentioned steps and is subjected to plating
21
. By the plating
21
, the flattened surfaces
130
and
120
of the filled resins
19
and
20
on both sides of the printed wiring board
1
are provided with plating layers
22
. Thus, on each of the opposite surfaces of the printed wiring board
1
, the copper foil
1
c
, the copper plating layer (interlayer connection plating layer)
1
b
, and the plating layer
22
are formed to provide a thick layer. Next, a dry film (
23
in
FIG. 1H
) is adhered onto each surface of the printed wiring board
1
with the plating layer
22
formed thereon to determine a wiring pattern of the printed wiring board
1
.
Referring to
FIG. 1H
, the dry film
23
having a desired wiring pattern is adhered to the printed wiring board
1
plated in FIG.
1
G. Thus, the wiring pattern of the printed wiring board
1
is determined by the dry film
23
having the wiring pattern designed for the printed wiring board
1
. Next, etching (
24
in FIG.
1
I) is performed to remove a conductive layer
25
(comprising the plating layer
22
, the copper plating layer
1
b
, and the copper foil
1
c
) except an area where the dry film
23
is attached, as illustrated in FIG.
1
I.
Referring to
FIG. 1I
, the printed wiring board
1
with the dry film
23
attached thereto in
FIG. 1H
is subjected to the etching
24
. The conductive layer
25
comprises the plating layer
22
, the copper plating layer
1
b
, and the copper foil
1
c
. After the etching
24
, a part of the conductive layer
25
which is protected by the dry film
23
is left to form the wiring pattern (connection pad). Because the conductive layer
25
is thick, etching accuracy is degraded. Then, the dry film
23
remaining on the conductive layer
25
is removed as illustrated in FIG.
1
J.
Referring to
FIG. 1J
, the dry film
23
is removed from the printed wiring board
1
subjected to the etching
24
in
FIG. 1I
to provide the printed wiring board
1
with the through holes filled and the wiring pattern (connection pad) determined. In
FIG. 1J
, the connection pads are depicted by
34
.
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
as illustrated in
FIGS. 1A through 1J
.
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 connection pad
34
comprising the copper plating layer
22
can be formed on the filled resin
19
filled in the through hole
3
in such a manner that t
Abe Shigetoshi
Itagaki Takashi
Kato Tomoko
Matsumoto Kenji
Sato Yasuo
Alcala José H.
Collard & Roe P.C.
Cuneo Kamand
Japan Radio Co., LTD
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