Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2001-11-27
2003-10-07
Cuneo, Kamand (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S255000, C174S264000, C174S261000, C362S469000, C362S469000, C029S830000, C029S831000, C029S852000
Reexamination Certificate
active
06630630
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a multilayer printed wiring board for various kinds of electronic equipment and its manufacturing method.
BACKGROUND ART
In recent years, as a higher degree of functionality and components density is required of electronic equipment such as personal computers, mobile telephones, video cameras and the like, it has become necessary for the electronic components used in the electronic equipment, among which semi-conductor devices occupy a central position, to be smaller in size, larger in packing density, higher in speed and/or higher in I/O pin count.
As a result, it has become also necessary for multilayer printed wiring boards to be enhanced in the ability to accommodate wiring and in the surface mounting density of components. In addition, as the diameter for each respective land for soldering becomes smaller, it has become necessary for the reliability in adhesion between the board and the components mounted thereon to be enhanced. More specifically, it has been required of a printed wiring board to have the capability of meeting both requirements of a high density as exemplified by a ball grid array (referred to as BGA hereafter) of a 0.5 mm pitch and a small diameter land of 0.3 mm or less. For example, such a printed wiring board that shows excellent resistance to mechanical stresses such as an impact caused by a drop test and the like has been increasingly demanded.
In order to meet the foregoing requirements, such a prior art multilayer printed wiring board as described below is proposed. The prior art multilayer wiring board comprises an inner layer material and a photosensitive resin or a film-like insulating layer, formed on each respective surface of both sides of the inner layer material. The inner layer material includes a resin multilayer printed wiring board and the respective layers in the resin multilayer printed wiring board are connected to one another electrically by means of interstitial via holes (IVH). The photosensitive resin or insulating layer is formed on each respective surface of both sides of the inner layer material by coating or lamination. Non-through holes are formed in the inner layer material and the layers inside thereof are electrically connected with one another by means of a metal plating method.
Next, a description is given to a manufacturing method of the foregoing prior art multilayer printed wiring board.
FIG. 3
shows how the prior art multilayer printed wiring board is prepared. In
FIG. 3
, an insulating layer
12
formed of a photo-sensitive resin and the like is disposed on the outer most layer of the prior art multilayer printed wiring board
15
by means of coating or lamination. The prior art multilayer printed wiring board
15
comprises a conductive pattern
11
for outer layer, a resin insulating layer
12
, an inner layer material
13
, a non-through hole
12
a
and a surface via hole (SVH)
11
a.
The inner layer material
13
includes an insulating substrate
14
, a conductive pattern
14
a
for inner layer material, a copper foil
14
d
and a conductive paste
14
b
for inner layer material. The insulating substrate
14
is prepared from a prepreg
14
c.
The surface via hole
11
a
is formed by applying a metal plating to the non-through hole
12
a
formed in the resin insulating layer
12
. In preparing the surface via hole
11
a,
the non-through hole
12
a
is formed by the use of such a method as a light exposure-development method, a laser irradiation method or the like applied to the resin insulating layer
12
. The multilayer printed wiring board
15
has a conductive pattern inside and outside thereof, respectively. Now, a description is given to a manufacturing method of the multilayer printed wiring board structured as in above.
First, a hole making process is applied to a prepreg
14
c
in the step of FIG.
3
(
a
). A conductive paste
14
b
is filled in the hole formed as in above. Then, a copper foil is superimposed on the prepreg
14
c
and heat pressed, thereby having the copper foil attached by adhesion to the prepreg
14
c,
in which a conductive paste
14
b
is filled. Accordingly, a copper laminated board with a copper foil disposed by lamination on both sides of an insulating substrate
14
, respectively, is obtained. Thereafter, a conductive pattern
14
a
for inner layer material is formed by the use of such publicly known methods as a screen printing method, a photograph method and the like. Thus, the insulating substrate
14
with the conductive pattern
14
a
put in place on both sides thereof, respectively, is obtained.
In the step of FIG.
3
(
b
), a prepreg
14
c
is prepared by filling a conductive paste
14
b
in a hole. The prepreg
14
c
filled with the conductive paste
14
b
is superimposed, respectively, on both sides of an insulating substrate
14
with a conductive pattern
14
a
formed on both surfaces thereof, respectively. Further, a copper foil
14
d
is superimposed on the surface of the prepreg
14
c
filled with the conductive paste
14
b.
Then, those laminates are heated by a heat press and a pressing force is applied thereto.
In the step of FIG.
3
(
c
), the publicly known screen printing method, photographic method or the like is applied to the copper foil
14
d
put in place in the foregoing step of FIG.
3
(
b
), thereby allowing a conductive pattern
14
a
to be further formed, respectively, on both surfaces of an inner layer material
13
, which is consequently obtained as FIG.
3
(
c
) shows.
Next, in the step of FIG.
3
(
d
), a resin insulating layer
12
formed of a photosensitive type resin and the like is applied onto the inner layer material
13
so as to remain in a semi-hard state or the resin insulating layer
12
is laminated on the inner layer material
13
.
Then, in the step of FIG.
3
(
e
), a non-through hole
12
a
is formed at a predetermined position by the use of an exposure-development method, a laser irradiation method or the like.
In the step of FIG.
3
(
f
), a conductive pattern
11
is formed on the resin insulating layer
12
and a surface via hole
11
a
is formed in the non-through hole
12
a
by metal plating. The surface via hole
11
a
has the function of connecting electrically between an inner layer conductive pattern and an outer layer conductive pattern. As a result, a multilayer printed wiring board
15
is obtained.
Afterwards, an application of a solder resist is performed by the use of such publicly known methods as a photographic method and the like and then working on the outside shape and the like follow.
With the foregoing prior art multilayer printed wiring board, the inner layer material has an interstitial via hole (IVH) formed on each respective layer at an arbitrary position and further has a small non-through hole ranging from about 50 &mgr;m to 100 &mgr;m in diameter formed on the outer layer thereof. Accordingly, the prior art multilayer printed wiring board has shown the excellent ability to accommodate wiring and to perform high density surface mounting. However, on the other hand, the prior art multilayer printed wiring board has revealed a flaw of weak adhesion between the conductive pattern
14
a
for outer layer and the resin insulating layer
12
. In recent years, as a higher degree of ball grid array integration and a higher degree of components density are required, a land for soldering has become smaller and smaller in diameter and a requirement for enhanced adhesion between the conductive pattern
14
a
for outer layer and the insulating substrate
14
has been made.
More specifically, since a plated layer formed on a resin by metal plating shows weak adhesion therebetween, with the prior art multilayer printed wiring board
15
, in which a conductive pattern
11
is formed on a resin insulating layer
12
by metal plating, the adhesion between the conductive pattern
11
formed on the resin insulating layer
12
and the resin insulating layer
12
is weak. As a result, when components are mounted densely on the multilayer printed wiring board
15
with a
Maezawa Satoshi
Oishi Kazuya
Tachibana Masashi
Cuneo Kamand
Matsushita Electric - Industrial Co., Ltd.
Patel I B
RatnerPrestia
LandOfFree
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