Exposed copper coupled with silver final finish is causing opens.

Figures 1 and 2 show two images of the same problem: one x-ray, the other optical. In both cases it’s the result of sulphur corrosion on the surface of copper and silver surfaces. Both surfaces remain exposed after a soldering operation, and in the presence of sulphur, it is possible to witness corrosion. In time it can result in an open connection, as the figures show. Figure 1, taken on a Dage x-ray system, shows different degrees of corrosion on the tracking just below the solder joint fillet. In failure investigations it’s important to see and record as much as possible without change or damage to the sample. On one joint there was an open connection on this QFP device.

From test coupons and burn-in chambers to ICT and flying probes, effective factory testing is essential for delivering reliable products and maintaining process control.

Factory testing comes in numerous flavors. The goal is to ship products that work in the field. Failures erode gross margins, which in turn affect the company’s market perception. Good customer relationships depend on the timely delivery of products that meet the requirements, which is the definition of quality. IPC-TM-650, Test Methods Manual covers the test procedures in detail.