Inspection? What's inspection?

Steve Scheiber, Technical Editor -- Test & Measurement World, 8/1/2005

Putting out this test report requires drawing the boundaries within which to work. Where does testing stop and inspection begin?

Identifying automated optical or x-ray techniques as inspection does not require much of a stretch. Ditto classifying functional or system test or "hot mock-up" as test. But some techniques fall into a gray area.

Infrared analysis looks for hot spots on a printed circuit board. Most commonly used to detect shorts on a board (very) briefly under power, subtler versions can examine a board in normal operation, comparing its thermal signature to that of a good board. In that sense, the technique resembles functional test more than inspection. Nevertheless, because it tests by "looking" at the board—even a board in operation—I classify it as inspection.

Some moving-probe testers include cameras for more accurate x-y positioning. Those cameras can also perform rudimentary inspection—especially presence/absence inspection. Because these systems' primary function is test, however, I lump them in with the testers.

The ultimate goal of all the techniques is the same—to ensure that a circuit works—so making such divisions may seem pointless. But finding an optimum engineering solution generally means breaking large problems into manageable pieces. Establishing these distinctions, however arbitrary, helps to focus our attention on optimizing each process step.

Contact Steve Scheiber at sscheiber@aol.com.