BLACKPAD REVISITED

Since the implementation of lead-free soldering, solderability issues appear to have become more common. The higher soldering temperature releases volatiles creating solder voids. The higher temperature also increases board and component flexing. Surface mount components fall off boards and BGA (Ball Grid Array) balls crack cleanly at the intermetallic interface creating open circuits. Black pad is often found as the root cause of these issues. However, black pad is a catch-all expression used to describe a variety of problems. As common as it is, black pad is not always recognised. What does it look like? How can one differentiate black pad from other soldering defects? We present high resolution optical and SEM (Scanning Electron Microscopy) images of real-life soldering problems, demonstrating the difference between black pad issues, flexing issues and component issues, pointing at specific features identifying the syndrome.