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Multilayer Subsurface Circuit Board Constructions

IP.com Disclosure Number: IPCOM000043946D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Mace, EW: AUTHOR

Abstract

The fabrication of subsurface circuit boards is reduced in cost through the introduction of multilayer construction. This technique represents a low-cost, easily produced design for such an electronic assembly. Subsurface circuit boards are usually prepared by injection-molding the desired circuit configuration using thermoplastic polysulfone. Circuit patterns are molded onto the surfaces of the circuit boards and polymer thick film pastes are then spread across the surface to fill the molded-in circuit lands. The pastes are dried and cured and the resulting circuit board may then be populated with discrete components, including polymer thick film resistors. The present technique provides multilayer circuit modules using two or more of the subsurface circuit boards fabricated through the method described above.

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Multilayer Subsurface Circuit Board Constructions

The fabrication of subsurface circuit boards is reduced in cost through the introduction of multilayer construction. This technique represents a low-cost, easily produced design for such an electronic assembly. Subsurface circuit boards are usually prepared by injection-molding the desired circuit configuration using thermoplastic polysulfone. Circuit patterns are molded onto the surfaces of the circuit boards and polymer thick film pastes are then spread across the surface to fill the molded-in circuit lands. The pastes are dried and cured and the resulting circuit board may then be populated with discrete components, including polymer thick film resistors. The present technique provides multilayer circuit modules using two or more of the subsurface circuit boards fabricated through the method described above. In the case of multilayer constructions, each mating surface of the circuit boards contains interlocking or press-fit pins and/or receptacles. These pins and receptacles are keyed to prevent misalignment during the assembly of the multilayer system. Vias, or layer-to-layer interconnections, can be molded into the polysulfone as conical holes with a thin area across the bottom of the hole (Fig. 1). The circuits are designed so that the via from one plane is aligned with the via from the plane to which it connects. Connection from plane to plane is accomplished by forcing a metallic pin into the conductive paste in the conical hole on one plane, and then through the thin film in the hole bottom. It then passes into or through the conductive paste in the hole with which it is aligned (see Fig. 2). Such a metallic pin may be hollow or tapered, or it may have a grooved or knurled surface. Knurled or grooved surfaces increa...