A no clean flux process for flip chip on board is characterized for ionic flux residue and board contamination using a new cleanliness testing system. The benchmarking procedure establishes a correlation of flux residue to thermal shock reliability. Speciation and quantitation of ionic printed wiring board (PWB) constituents permits segregation of incoming board contamination from that caused by the flux. A process window to minimize defects and maximize reliability performance is developed. Methods for performing similar characterization and benchmarking of processes are presented.
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