Measles in Advanced Technology

摘要

Continuous measling, or unidirectional crazing, was observed in a multi-layer polyimide printed wiring board following assembly operations. Damage to the PWB preferentially followed the warp direction of the glass fiber reinforcement and extended beyond the region of localized heating. Further investigation revealed that glass fiber pullout in cross-sectional mounts is an indicator of laminate material that is prone to measling or crazing. Testing showed that boards with fiber pullout were significantly more likely to show damage in base material in subsequent process, especially when a drying bake was not recently performed. Damage to these PWBs consisted of cracks not between bundles of glass-fiber reinforcement, but within individual bundles. These cracks may produce reliability risks in PWB.