Electronic Design

New Printed Circuits Closing A Gap In Design

Printed circuitry, criticized as recently as a year ago as lagging in the big push forward by the electronics industry, is posting some impressive advances for designers. Among recent developments are integrally damped boards, highly resistant to vibration; circuitry printed on anodized aluminum; eyelets, formed by an electroplating method, that offer the advantages of both eyelets and plated-through holes; resistance-fused eyelets that minimize cold-working effects; and circuits printed on flexible, heat-resistant Teflon.

Graphik Circuits Div., Cinch Manufacturing Co., City of Industry, Calif., has announced development of electroformed eyelets made by electroplating that give the advantages of continuity of conductor from surface to surface while maintaining a constant thickness of metal wall in the hole. In the technique, only the hole and the land immediately around it are plated. It permits the metal in the hole to be thicker than that in the conductors, assuring reliable connections.

A copper-clad board is printed or silk-screened, then etched to remove excess copper. After drilling, it is sensitized by copper reduction and selectively masked with a plating resist that leaves holes and their lands exposed. These are then plated. The final two steps are removing the resist and dissolving the sensitized film in an oxidizing solution, which leaves the board with a copper-printed circuit and copper-plated holes, with a continuity of copper from conductors to holes. (Electronic Design, April 12, 1961, p. 4)

As vacuum tubes were replaced with transistor circuits, punched metal chassis gave way to printed-circuit boards. Many specialized techniques were developed—rugged metal-core boards, Teflon-based boards, flexible circuits, etc.—but it was the technique described here that was the bread-and-butter method for producing the interconnection platforms for semiconductor devices.

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