Softer Than Rubber, Thinner Than Foam

Unlike consumers themselves, many consumer products are getting thinner. And while losing bulk is good for products, it can cause other weighty issues, like gasketing.

A new breed of softer, thinner, conductive silicones may offer a solution for tomorrow's densely packed electronic products, which are running out of room for gasketing materials. The new nickel-graphite-filled conductive silicones from the Rogers Corp., known as the BISCO EC-2000 Series Silicones, are said to be made thin enough to meet tight space constraints and yet still be compressible.

Key to the new conductive silicones is a combination of features commonly considered incompatible. Like foams, they are soft. And like hard rubber gaskets, they can be made thin. Rogers engineers say that the EC-2000 material meets the softness criteria because its hardness ranges from 30 to 40 on the Shore A durometer scale. In contrast, hard rubber gaskets typically have a Shore A hardness of 55 to 75.

The engineers note the product offers standard thicknesses ranging from as little as 0.02 to 0.125 inch. As a result, they say, it meets the tight packaging constraints of next-generation cell phones.

"Portable electronics need a soft material to prevent breakage from a lot of closure force being applied to them. At the same time, they need something thin, because there isn't a lot of space left inside for gaskets," notes Susan Baushke, BISCO Silicones product manager. In some cases, the new material, compressed to 25%, requires about 50 psi closure pressures. In contrast, some conductive rubber materials require 200 psi.

The company contends that a commonly used approach known as fabric-over-foams can't be produced at such reduced thickness. "When your applications get really thin, fabric over foams can't compete," Baushke says. "Foams are made up of cells, and thickness is limited by their cell size. As a result, fabric-over-foams generally have a thickness of 0.031 inch or greater." Rogers Corp., www.rogerscorporation.com Enter 576