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.

As PCB designs grow more complex, partitioning and teamwork become part of the layout strategy.

Printed circuit board design grows in complexity with each passing year. Many protocols must be implemented. An ASIC (application-specific integrated circuit) or an FPGA (field-programmable gate array) may be the center of attention, but there will likely be a memory bus along with other architectures, such as ethernet or USB, to move data around. Interacting with the world around us requires some sort of sensor to read the room, while other circuits are used to feed this processed data back to the user.