Low CTE reworkable underfill boosts thermal cycle performance

ZYMET X2825 Silica-filled, reworkable board-level underfill encapsulant provides coefficient of thermal expansion (CTE) of 26 ppm/C. Product enhances drop and shock test reliability and provides improved thermal cycle performance. Addition of silica filler to an otherwise reworkable underfill ordinarily damages reworkability. Product is easily reworked, despite the presence of filler. Rework is accomplished by use of elevated temperature, 170C to 180C, to remove the underfill fillet. The BGA is lifted from the board after heating it to above reflow temperature and the underfill residue is easily scraped off.

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