Section: Design -- Components

Northfield, Minn. - Sheldahl Inc. and Mentor Graphics Corp. (Wilsonville, Ore.) have teamed to move Sheldahl's high-density flexible-circuit-board technology into the marketplace. Mentor, which developed software under an Arpa grant, will provide design services for engineers who want to implement Sheldahl's NovaClad technology.

The materials are said to provide far higher densities and smaller via holes than competing board and multichip-module (MCM) technologies. Trace widths are as small as 25 microns, providing six times more density than the alternatives.

Though it has densities that match those of ceramic and thin-film substrates, Sheldahl's technology has pricing similar to that of laminate boards. It eliminates eight processing steps, making it possible to cut costs by 10 to 40 percent.

"Mentor and Sheldahl will call on key OEMs and multichip module makers," said Ellen McCoy, business manager at Sheldahl Electronic Materials. "Sheldahl will then support those companies and conversion sites, which are people now doing rigid boards who want to use our technology. We want to sell materials, and Mentor wants to sell design services and kits. We work with Mentor so it's easier for other companies to get into the business," she said.

The companies got together through a consortium established by Arpa, the Advanced Research Projects Agency, last year (see Sept. 26, 1994, page 42). In that consortium, one of three in which Sheldahl is involved, Mentor developed software for Sheldahl's new circuit board material.

"The way the ARPA consortium works, the members have developed a design kit that works with Mentor Graphics design systems," said Russell F. Henke, vice president and general manager at Mentor's Professional Services Division.

In production

The Sheldahl NovaClad material is starting to move into production in Longmont, Colo., where a new facility is ramping up.

"We do three things at Longmont," McCoy said. "We make NovaClad, which puts copper on a polyimide film that is 1 and 2 mils thick. We also make ViaGrid, which uses NovaClad, but has holes in it that are metallized. We also make chip carriers and multichip modules using NovaClad and ViaGrid."

The ViaGrid approach is expected to be the most popular of the three routes at the beginning of the technology's life cycle because it's easiest to use.

Holes in the ViaGrid substrates come in 1-, 3- and 5-mil sizes. Those sizes are smaller than the vias on most circuit boards now being produced. That makes it easier for designers to put several traces in a small area, since the holes don't take up much of the available board space. The material is also very thin, with copper thicknesses of 5 to 15 microns.

Though ViaGrid is designed to move from concept into production in a short time, using the grid layout requires special tools. Designers can't route traces using conventional tools, since these tools aren't designed to work with a grid that is laid out in a set pattern.

"The only way to take advantage of the new ViaGrid technology is to use it in conjunction with our software and engineering station," Henke said.

~~~~~~~~

By Terry Costlow