Evaluation of low temperature snap-cure die attach materials

Polymeric adhesive materials have been extensively used for die attachment in plastic IC package assembly for over two decades. They offer many advantages over gold-eutectic solder, soft solders, or silver-glass attach materials, due to lower temperature processing, lower stress on the chip, and lower cost. Recently, improved polymeric adhesive materials are entering the market. Snap-cure adhesives can reduce processing time and steps, which translates into cycle time reduction and cost savings. In addition, a lower temperature-cure material also provides compatibility with tin-lead solder pre-plated lead frames for assembly flow simplification, as well as for temperature sensitive devices. However, since these materials are relatively new, their effect on reliability of the encapsulated IC device is not well known, especially with respect to the volatile species evolved during cure and post-cure processing. The snap-cure adhesive chemistry differs from that of standard polymeric die attach materials. How that affects stress, thermal, and reliability behavior of the package requires study. This paper examines the differences in the material design of the snap-cure versus oven cure adhesives, and how that relates to assembly processability and package reliability. From the results, snap-cure die attach materials show comparable or superior performance to conventional polymeric die attach materials in these areas, which should aid their acceptance into the simplification of the plastic IC assembly flow