Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-04-20
2001-11-27
Gaffin, Jeffrey (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S760000, C361S762000, C361S764000, C361S773000, C361S783000, C361S795000, C257S700000, C257S723000, C257S737000, C257S778000, C174S262000, C174S264000, C428S209000, C428S304400, C428S321300, C428S901000
Reexamination Certificate
active
06324067
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a printed wiring board (PWB) for mounting a component including an electronic circuit, and an assembly of the same.
BACKGROUND OF THE INVENTION
As portable electronic equipment has become smaller and thinner, the mounting density of electronic components, such as semiconductor devices, resistors, capacitors, on PWBs has increased remarkably. Multilayer PWBs enable high-density mounting of such electronic components. A multilayer PWB, for example, is formed by laminating plural PWBs on which conductive circuit patterns are previously formed, and connecting the circuit patterns of the PWBs with each other by a via hole.
Published Unexamined Japanese Patent Application (Tokkai-Sho) No. 60-57999 discloses a multilayer wiring board, where the inner layer patterns of the laminated PWBs are partially exposed in step-wise, and a conductive pad is connected to the exposed conductive patterns. In a general multilayer wiring board, a conductive pad is provided only to the outer layer, therefore, many via holes are necessary to connect the exterior patterns and the inner layer patterns. On the other hand, the multilayer wiring board disclosed in this reference can reduce the number of the via holes by providing another conductive pad to the exposed portion of the inner layer. This reference, however, does not disclose how to connect the conductive pad provided to the exposed portion of the inner layer to the electronic component, or how to produce such a multilayer wiring board.
Published Examined Japanese Patent Application (Tokkoh-Hei) No. 5-41039 discloses a PWB, where a recess is provided by counterbore processing, and a semiconductor device is placed in the recess. The semiconductor device and the conductive pad of every layer are connected by a bonding wire, and sealed with resin. In this way, the semiconductor device is contained without substantially exceeding the thickness of the PWB. This method depends on connection by the bonding wires, and thus, this reference does not disclose application of the method to a surface mounting technology (SMT).
FIG. 16
is a cross-sectional view to show the PWB
31
to which a component
32
such as an integrated circuit is mounted by conventional surface mounting technology. Since a lead pin
32
a
of the component
32
is soldered to the conductive pad
33
on the PWB
31
, the component
32
is electrically connected and fixed to the PWB
31
.
FIG. 17
shows an example where a component
34
, such as a speaker, is mounted on the surface of the PWB
31
. The component
34
is fixed on the PWB
31
by an adhesive tape
35
, while the lead wire
34
a
from the component
34
is soldered to the conductive pad
33
on the PWB
31
.
In a PWB assembly using SMT, the mounting area is reduced due to the high density trend, however, the assembly has not decreased significantly in thickness. Especially, when a comparatively large component such as a package semiconductor (e.g. IC, LSI), a speaker, or a microphone is mounted, the component becomes much higher than the surface of the wiring board.
Therefore, an assembly using a conventional multilayer PWB does not meet the requirements for thin portable electronic equipment. If the assembly is thick, the portable electronic equipment cannot be thin, and the design of such electronic equipment will be limited. Reduction of the assembly's weight is another important aim.
SUMMARY OF THE INVENTION
This invention aims to provide a thin and light multilayer PWB and an assembly of the same in order to solve the above-identified problems of the conventional techniques.
A first PWB assembly of this invention comprises a PWB having an opening for receiving a component that includes an electronic circuit, and a component placed in the opening, which is substantially thinner than the PWB and is electrically connected to the PWB. As a result, a thin assembly can be provided. If a second component is mounted on the component which is received in the opening, or if the second component is mounted stretching over the first component and the PWB, other advantages can be obtained. For instance, the PWB area can be reduced. The other preferable embodiments according to this configuration will be explained below.
In a second PWB assembly of this invention, a component including an electronic circuit is placed in a recess formed in the PWB, and a connecting terminal provided to the bottom of the component is electrically connected to the conductive pad formed on the bottom of the recess by using a conductive adhesive layer. Examples of such an adhesive layer include a solder ball or a two-step protruded electrode and conductive adhesive. According to this configuration, a thin assembly can be provided, and a plurality of components can be mounted on the recess with a high density.
Such a recess for receiving a component can be formed by partially removing one or more layers of the plural conductive layers and insulating layers that comprise the multilayer PWB. More specifically, the process for producing such a PWB comprises the steps of:
a) preparing plural double-sided conductive layer boards manufactured by sandwiching an insulating layer between two conductive layers, and preparing at least one insulating layer board to be placed between the double-sided conductive layer boards;
b) forming holes in each board of step a) for electric connection between the conductive layers, and forming a hole that defines a recess for receiving a component in all but at least one board;
c) etching the conductive layers of the double-sided conductive layer boards of step b), so that a predetermined circuit pattern is left;
d) electrically connecting the conductive layers of the etched double-sided conductive layer boards of step c); and
e) laminating the double-sided conductive layer boards and at least one insulating layer board with holes aligned so as to form electric connection between the conductive layers and to form a recess for receiving the component, and heatpressing the laminate.
In a PWB assembly provided with a recess for component receiving, other embodiments can be used as the assembly having the opening, for instance, two components can be mounted one after another.
It is preferable that the insulating layer board be made of a compressible base material impregnated with resin, so that weight can be minimized. In addition, the electrical resistance is reduced and stabilized when the conductive layers are electrically connected to each other by filling the hole for electrical connection formed on the compressible porous material with conductive paste. The detail is explained below.
A third PWB assembly of this invention comprises a PWB having a recess, a vibration film provided to cover the recess, and a coiled conductive pattern placed opposing to the vibration film, so as to perform conversion between vibration of the vibration film and electric current flowing in the coiled conductive pattern. According to this configuration, it is possible to integrally form a speaker or a microphone with a PWB. In other words, the weight and cost can be reduced considerably compared to a case that the other component like a speaker or a microphone is mounted on the PWB. Various embodiments of this configuration will be mentioned in detail.
In another configuration, a PWB comprises a recess or an opening formed on the PWB in order to integrally form a speaker or a microphone with the PWB, a vibration film provided to cover the recess or the opening, a coiled conductive pattern provided to the vibration film, and a magnet placed opposing to the vibration film, so as to perform conversion between vibration of the vibration film and electric current flowing in the coiled conductive pattern.
REFERENCES:
patent: 3770529 (1973-11-01), Anderson
patent: 3852877 (1974-12-01), Ahn et al.
patent: 4080513 (1978-03-01), Cuneo et al.
patent: 4188513 (1980-02-01), Morrell et al.
patent: 4417413 (1983-11-01), Hoppe et al.
patent: 4663215 (1987-05-01), Dubuisson et al.
patent: 4677528 (1987-06-01),
Gaffin Jeffrey
Matsushita Electric - Industrial Co., Ltd.
Morrison & Foerster / LLP
Vigushin John B.
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