Case Study: Radial Cracks in a Rigid-Flex Assembly

摘要

Crane Aerospace & Electronics in Redmond, WA, develops, qualifies, and manufactures a variety ofimplantable devices for leading medical companies. An unusual phenomenon was discovered during aroutine visual inspection step on a recent development project. On the flexible portion of a rigid-flex PCBassembly, visible radial cracks were found on the annular rings of ENIG-plated thru-holes. The thru-holesremain unpopulated during Crane’s assembly process, and the defect was primarily seen on the top sideof the PCB. Additionally, the occurrences of these cracks vary in frequency and severity. This paperdescribes the testing and analysis Crane performed in order to determine the root cause of this defect.