ASSEMBLIES CONTAINING COPPER PILLAR STRUCTURES PROCESSED USING ONE STEP CHIP ATTACH MATERIALS (OSCA) AND CONVENTIONAL MASS REFLOW PROCESSING

摘要

One step chip attach materials (OSCA) are dispensable polymeric materials for flip chip assembly, which are designed to flux metallic interconnections and subsequently turn into an underfill upon curing. OSCA materials enable a drastic simplification of the assembly process by combining the reflow, flux residue cleaning and capillary underfilling steps used in traditional die attach processing into a single step. The key challenge when designing OSCA materials for conventional mass reflow processing (OSCA-R) is the timing the sequence of curing, fluxing and soldering events during reflow processing. OSCA-R materials must also have a process-friendly rheological design that integrates seamlessly with standard dispensing equipment and enables high filler loading levels. This paper presents silicon die and substrate test vehicles with copper pillar interconnect structures assembled using OSCA-R materials for fluxing and underfilling that have been processed using conventional mass reflow techniques. Filler particle contributions to OSCA-R design and performance will also be discussed including; rheology, thermo-mechanical and thermal transport performance. Assembly of devices containing SnAg, SAC, will be discussed in conjunction with the reflow profile and process windows for OSCA-R materials.