CN-1728 reworkable underfill encapsulant is designed to underfill package-on-package assemblies. Reportedly has a lower coefficient of thermal expansion, higher Tg, and better compatibility with flux residues. Is a fast-flowing capillary underfill with a viscosity of 900 cps; can be cured in as little as 1 min. at 150°C. Is suited for high-volume, high-speed inline processing. Rework is accomplished by use of temperatures between 170°C and 180°C to remove the underfill fillet. Then, the BGA is lifted from the board after heating it to reflow temperature. Underfill residue is easily scraped off.

Zymet Inc. www.zymet.com