Low cost flip chip processing and reliability of fast-flow, snap-cure underfills

Abstract

Flip chip technology is finding increasing applications in the electronics manufacturing and packaging industries and is projected to grow at a 30-40% rate into the next decade. Development of new material systems will enable this growth provided they reduce manufacturing time and enhance reliability. Among these new materials are fast-flow, snap-cure underfills. These underfills can significantly decrease manufacturing costs by eliminating excessive underfill flow times and lengthy dedicated cure cycles. This is especially true in double sided board assembly where snap-cure underfills can be cured during the soak stage of a typical second side reflow cycle while the reflow spike forms the second side interconnects and also provides additional curing. This work presents a study of fast-flow, snap-cure underfill materials and includes data on the reliability in air to air thermal cycling (-55/spl deg/C to 125/spl deg/C) and JEDEC Level 3 Moisture Sensitivity Preconditioning prior to thermal cycling of FCOB test vehicles. Samples cured using a second reflow pass are compared to baseline samples snap-cured in a standard batch oven at the underfill manufacturers' recommended cure schedule. The goal of this work is to determine the performance of fast-flow, snap-cure underfills in the context of low cost flip chip processing using second side reflow for underfill cure. The approach evaluates commercial fast-flow, snap-cure underfills with respect to JEDEC Level 3 Moisture Sensitivity Testing and air to air thermal cycling both with and without the preconditioning.