Editor's note: Appearance can be deceiving

Inspection tells us what something looks like, regardless of how it works. When functionally equivalent products look sufficiently different, convincing an inspection system to pass both presents a challenge.

One proposed solution involved the use of design-for-inspection guidelines, limiting parts choices so inspection systems would not get confused. Such guidelines proved about as popular as design-for-testability guidelines had in generations past.

New advances in technology may complicate matters further. Technology Review reports that researchers in Japan have begun creating semiconductor devices out of silicon carbide, which can withstand extremes in environmental conditions much better than ordinary silicon can. Until now, its very imperviousness has precluded its use in electronics. SiC crystals were formed by condensing supersaturated vapor, but the technique always introduced numerous flaws. The Japanese researchers discovered they could build the wafers in several stages, drastically reducing the number of defects.

Although the process will not likely provide SiC semiconductors for commodity products anytime soon, the resiliency of the circuits will encourage their use in military, space, and other high-reliability applications. Such parts will undoubtedly work logically the way today's counterparts do, but they will just as certainly look very different. Once again, inspection techniques will have to remain flexible to avoid becoming obsolete.

Contact Steve Scheiber at sscheiber@aol.com .