Addressing Critical Assembly Challenges in 2.5D and 3D IC Assembly
Authors: Guilian Gao, Ph.D. Scott McGrath, Bong-Sub Lee, Ph.D, Cyprian Uzoh, Ph.D., Grant Villavicencio, Hala Shaba, Liang Frank Wang, Ph.D, Sitaram Arkalgud, Ph.D, and Eric Tosaya Company: Invensas Corporation Date Published: 1/31/2016
Abstract: After many years of research and development, 2.5D/3D IC technology has achieved the very significant milestone of manufacturing pioneer products in volume production in today’s market place. However, many challenges need to be overcome before the technology can ramp into true high volume production. On the assembly front, a variety of material and process-related issues, which have a major impact on assembly cost, yield and reliability, must be addressed. With densely integrated packages and stacked thin dies, warpage at various steps of assembly process can lead to die crack, weak or open interconnection, and delamination. Microbump die with copper post and solder cap lacks the flexibility of conventional BGA solder balls in warpage compensation. Solder reflow in a thermal compression bonder differs significantly from mass reflow in a convection belt oven. Such difference impacts flux choice, volume and thermal profile control. Ultra-low stand-off between dies creates new challenge for flux residue removal and underfill processing, adhesion and reliability. In this paper, we review various challenges encountered in assembly of the Invensas 2.5D TSV integration test vehicle and provide creative solutions to overcome the challenges.