Electricity: electrical systems and devices – Miscellaneous
Patent
1981-01-16
1983-01-11
Kucia, R. R.
Electricity: electrical systems and devices
Miscellaneous
174 685, 361385, 361382, 361415, H05K 114
Patent
active
043685030
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a hollow multilayer printed wiring board. By the term "hollow multilayer printed wiring board" used herein is meant a multilayer printed wiring board which comprises at least two insulating material substrates, on each of which a conductor pattern or patterns are formed, the conductor pattern or patterns being interconnected as may be required, and each of which substrate being spaced apart a predetermined distance from the adjacent substrate or substrates, the space being filled with an insulating gas or liquid.
2. Description of the Prior Art
The trend toward producing transistors, integrated circuits and other electronic devices and parts of small sizes in recent years has required a substantial increase in the wiring density of multilayer printed wiring boards by reducing the spaces between the parts. For this requirement substrates having an enhanced dimensional stability must be used. Furthermore, the signal conductor patterns must be arranged close to each other, which results in the following defects. First, electrical signals of a signal pattern are transferred to another neighboring signal pattern and interfere with the signals therein or produce noise, that is, the occurrence of so-called crosstalk phenomenon arises. Secondly, the parts, particularly where they are directly bonded to the substrate, cause a temperature rise in the surface of the substrate, thereby influencing the characteristics of the parts and the substrate, and occasionally damaging the parts.
Most conventional multilayer printed wiring boards are prepared by laminating substrates, having formed thereon conductor patterns, by interposing an adhesive layer comprised of glass fibers impregnated with a prepolymer of a thermosetting resin between the substrates. The adhesive layer used, however, must satisfy many requirements, such as good thermal resistance, low shrinkage upon curing and good moldability. With an increase in the packaging density, it becomes more and more difficult to manufacture the composite structure by using the adhesive layer of thermosetting resin-impregnated glass fibers.
SUMMARY OF THE INVENTION
It is, therefore, the main object of the present invention to provide multilayer printed wiring boards which exhibit good thermal resistance, as well as enhanced dimensional stability, and improved transmission and cooling characteristics, as compared with the prior art.
Other objects and advantages of the present invention will be apparent from the following description.
In one aspect of the present invention, there is provided a hollow multilayer printed wiring board which comprises a plurality of substrates superposed upon each other with a predetermined space therebetween filled with an insulating gas or liquid, with or without an interposed spacer or spacers. Each of these substrates has a signal conductor pattern formed on at least one surface thereof and a ground conductor pattern formed on at least one surface thereof. Each substrate has plated through holes in the ground conductor pattern, each of which holes is in line with another plated through hole of each of the neighboring substrates or of at least one of the neighboring substrates to form a continuous plated through hole or an interstitial through hole. A layer of a low melting point metal is formed at least on the upper and lower end surfaces of the plating layer defining each plated through hole. The low melting point metal layer serves as a through connection between two or more signal conductor patterns of the substrates and as an interlayer adhesion between the substrates. The superposed substrates, except for at least one surface substrate, are made of a thermally resistant organic synthetic resin sheet or an insulation-treated metal sheet.
In another aspect of the present invention, there are provided processes for manufacturing the above-mentioned hollow multilayer printed wiring board. A first process comprises the steps of:
preparing a plurality of substra
REFERENCES:
patent: 3365620 (1968-01-01), Butler
patent: 3568000 (1971-03-01), D'Aboville et al.
patent: 3616532 (1971-11-01), Beck
patent: 3648131 (1972-03-01), Stuby
patent: 3740678 (1973-06-01), Hill
patent: 3760091 (1973-09-01), Cannizzaro et al.
patent: 3780352 (1973-12-01), Redwanz
patent: 3875479 (1975-04-01), Jagger
patent: 3999105 (1976-12-01), Archey
Imura Takayoshi
Kurosawa Keiji
Mitsui Hisami
Miyabara Ayako
Miyagawa Kiyotaka
Fujitsu Limited
Kucia R. R.
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