Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-03-02
2003-09-30
Tugbang, A. Dexter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S837000, C029S841000, C029S846000, C228S180210, C264S272110
Reexamination Certificate
active
06625880
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for producing a printed wiring board having electronic components, such as LSI (large-scale integrated circuit), enclosed therein.
2. Description of Related Art
Heretofore, a printed wiring board unit, arranged in a casing forming an electronic equipment, has a pre-set wiring pattern formed on its one or both sides, and electronic components, such as LSIs, mounted on a land to form a number of variable electrical circuits. In a certain printed wiring board, used in a miniaturized multi-functional electronic equipment, plural substrates, each carrying a wiring pattern, are layered together, and electronic components are mounted on both sides of the layered structure.
Meanwhile, in a certain printed wiring board, plural substrates are layered together, and electronic components are embedded in the interior, in order to mount a larger number of electronic components on the substrate. The printed wiring board, having electrical components embedded therein, are formed as shown for example in
FIGS. 1
to
4
. That is, a first wiring pattern
52
is formed on one surface of a first substrate
51
, as shown in FIG.
1
. On the other surface of the first substrate
51
is formed an electrically conductive layer
53
, formed by a copper foil, in order to form a fourth wiring pattern. A via-hole
60
is formed in the first substrate
51
for establishing electrical connection between the first wiring pattern
52
and the fourth wiring pattern as later explained. The via-hole
60
is plated with copper as at
60
a
. On one surface of the first substrate
51
, carrying the first wiring pattern
52
, there is provided a spacer
54
for achieving insulation from a second substrate
55
layered on the first substrate
51
. On at least one surface of the second substrate
55
is formed a second wiring pattern
56
.
The first substrate
51
, on which is formed the first wiring pattern
52
, and the second substrate
55
, on which is formed the second wiring pattern
56
, are formed separately from each other. The second substrate
55
is stacked on the spacer
54
and bonded thereto by hot pressing. A via-hole
65
then is formed for electrically connecting the electrically conductive layer
53
of the first substrate
51
and the second wiring pattern
56
of the second substrate
55
and the inside of the via-hole is plated wan copper at
66
.
For exposing an area on the first substrate
51
on which to mount an electronic component
57
to outside, an opening
58
is formed by a router
59
in the second substrate
55
and in the spacer
54
. Specifically, the router
59
is run along an approximately rectangular path to cut the outer rim of the opening
58
, and subsequently the router is run along a staggered path in the interior of the rectangle to form the opening
58
extending through the thicknesses of the substrate
55
and the spacer
54
. So, a component mounting portion
61
of the electronic component
57
, placed on one surface of the first substrate
51
, is exposed to outside via the opening
58
formed in both the substrate
55
and in the spacer
54
. On this component mounting portion
61
, exposed to outside via the opening
58
, the electronic component
57
, such as LSI, is mounted and soldered in position. The opening, in which the electronic component
57
has been mounted as described above, a synthetic resin mass
67
is charged by potting.
On the second substrate
55
, a third substrate
62
is formed by RCC (resin coated copper foil) molding, as shown in FIG.
4
. Specifically, the third substrate
62
is formed on the second substrate
55
by press fitting a resin-coated copper foil under vacuum heating. An electrically conductive layer of a copper foil, formed on the third substrate
62
, is etched to form a third wiring pattern
63
. An electrically conductive layer, provided on the opposite surface of the first substrate
51
, is also etched to form a fourth wiring pattern
64
. A via-hole
68
then is formed in the third substrate
62
in order to provide for electrical connection between the third wiring pattern
63
provided on the third substrate
62
and the second wiring pattern
56
provided on the second substrate
55
. The printed wiring board, prepared as described above, then is checked electrically whether or not the wiring pattern is short-circuited. This electrical check is conducted because the fourth wiring pattern
64
is not formed in the previous step, with the electrical circuit of the printed wiring board being in a short-circuited state.
In the method for producing the printed wiring board, as described above, the opening
58
is formed by the router
59
for mounting the electrical component
57
on the component mounting portion
61
of the first substrate after layering the spacer
54
and the second substrate
55
on the first substrate
51
. However, a drill of the router
59
has a tolerance in the vertical direction on the order of ±30 &mgr;m, so that, if the drill intruding depth is too shallow, the first wiring pattern
52
is not exposed, whereas, if the drill intruding depth is too deep, the first wiring pattern
52
also is cut. So, a thin copper foil cannot be used as the first wiring pattern
52
so that a thin pattern is difficult to form. In addition, the component mounting portion
61
cannot be worked to high planarity.
In the above-described process, the electrical component
57
is mounted on the component mounting portion
61
of the first substrate
51
, the third substrate
62
is mounted on the second substrate
55
and finally the printed wiring board is checked electrically. So, if this electrical check has revealed that the printed wiring board is short-circuiting, not only the first to third substrates
51
,
55
,
62
, but also the electrical component
57
are wasted.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a manufacturing method for a printed wiring board whereby a printed wiring board having electronic components enclosed therein can be manufactured easily and efficiently.
According to the present invention, there is provided a method for producing a printed wiring board including the steps of forming a wiring pattern on one surface of a first substrate and forming a component mounting portion for mounting an electronic component thereon, forming an insulating spacer having a first opening formed in registration with the component mounting portion of the first substrate, forming a second substrate, stacking the spacer on the one surface of the first substrate, with the first opening in registration with the component mounting portion, stacking the second substrate on the spacer, pressing together the first substrate, spacer and the second substrate, thus stacked, for bonding the first and second substrates together, boring a second opening in the second substrate, after bonding the first substrate, spacer and the second substrate together, in registration with the first opening, so that the second opening is in continuation to the first opening, for exposing the component mounting portion of the first substrate to outside, mounting an electronic component on the component mounting portion of the first substrate which makes up the bottom of a spacing delimited by the first and second openings, continuing to each other, and filling resin in the spacing, having the electronic component mounted therein, and providing a third substrate on the second substrate to stop the spacing after charing resin in the spacing.
Since the spacing is provided by the spacer provided with the first opening, the second opening may be formed by a router in the second substrate without damaging the component mounting portion of the first substrate.
By forming the spacer by the core material, the first prepreg provided between the core material and the first substrate and the second prepreg provided between the core material
26
and the second substrate, the resin component, such as epoxy res
Komatsu Nobuo
Nabemoto Yoshie
Kananen, Esq. Ronald P.
Nguyen Donghai
Rader & Fishman & Grauer, PLLC
Tugbang A. Dexter
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