Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Patent
1993-01-29
1995-05-09
Picard, Leo P.
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
174255, 174266, H05K 100
Patent
active
054142245
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the manufacture of printed circuit boards and has specific reference to multilayer PCB's and methods of their manufacture.
PRIOR ART
Known in the art is a double-sided PCB on a metal base with mounting holes and holes for interconnections (U.S. Pat. No. 3,296,099). The metal base with holes drilled or punched in advance is given a coat of insulation and a coat of insulation is applied to the inside of the holes. The insulation serves as the substrate for a first and a second layer of conducting pattern. The mounting holes and those for the interconnections are metal plated and are used as conductors between the elements of the first and second layers of conducting patterns, if conditions warrant this.
Another multilayer PCB on a metal base is made by employing the through-hole plating method for establishing the interconnections between the elements of the layers of conducting patterns (U.S. Pat. No. 4,496,793). The metal base with a plurality of large diameter openings is given an insulating coat on both sides. Disposed at one side of the insulation is a double-sided PCB, and at the opposite side of the insulation there is imposed an outward layer of conducting pattern. The other outward layer of conducting pattern is applied to the double-sided PCB, being separated therefrom by an insulation. All the layers of conducting patterns, i.e. two inward and two outward, are interconnected by the through-plated holes made in the existing openings.
An alternative method of interconnecting the layers of conducting patterns relies on connecting posts as this is the case in another multilayer PCB (EPV; A; 0247,572,A2) the technical concept whereof can be regarded as a kind of the forerunner of the disclosed invention.
The known PCB comprises: conducting pattern, whereby the first layer has metal tracks and its side facing the other layer is roughened. The other (second) layer of conducting pattern has tracks in a conducting polymer paste; conducting patterns; as interconnections between the first and second layers of conducting patterns.
Characterized by a more or less satisfactory interconnections between the electric and radio components, the known PCB is not free from shortcomings, such as; and the etching of foil; application of the PCB.
The PCB referred to hereinabove in U.S. Pat. No. 3,269,099 is adapted to accommodate any electric or radio component at its surface. However, the packing density is low due to the reasons as follows. Firstly, bell-shaped recesses are formed around the holes in the course of applying the coat of insulation so that the connecting pads must be increased in size in order to reach the flat surface of the insulation with their outer edges. Secondly, the design features of the known board make it impossible to built up a multilayer assembly. Thirdly, the holes indispensable in providing the interconnections between the layers not only occupy much space by themselves but encroach upon extra space due to their bell-mounted ends. These factors have an adverse effect on the packing density.
The multilayer PCB on a metal base (U.S. Pat. No. 4,496,793) is of a design conductive to good packaging density of electric and radio components, the multilayer configuration and the planeness of the outer surface being the main beneficial factors. However, the packing density is impaired to some extent by the interconnecting through-plated holes, and the plurality of the holes in the metal base reduce the heat-dissipating ability of the base.
Known in the art is a method of manufacturing printed circuit boards (U.S. Pat. No. 4,651,417) which avoids electroless processing, except electroplating. Pursuant to this method, holes for interconnecting the layers of conducting patterns at a later stage are drilled in a base made from a thermoplastic material. The base is put in a press to form therein a network of grooves about 0.05 mm deep of the same configuration as that of a layer of conducting pattern. The base is given a 2-micron coat of copper, using
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Adasko Vladimir I.
Emelyanov Alexandr L.
Emelyanov Viktor L.
Piliposian Pogos M.
Rogozhin Jury F.
Figlin Cheryl R.
Filial Vsesojuznogo Nauchno Issledovatelskogo Instituta
Picard Leo P.
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