Defect of the Month

Dr. Chris Hunt

Good design rules and assembly processes will result in high soldering yields.

Read more: LGA/QFN Solderability

Dr. Chris Hunt
When joints look perfect but nonetheless are failing, check the plating adhesion.

Read more: Solder Joint Separation
Chris Hunt
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.

Read more: Sulphur Corrosion on Solder Joints

Page 4 of 4