No abstract

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. A key challenge when designing filled OSCA materials for conventional mass reflow processing (OSCA-R) is to ensure that the materials have a process-friendly rheological design allowing seamless integration with jet dispensing equipment and allowing for accurate die placement. This paper presents research results and design concepts for OSCA-R materials focused on understanding the impact of filler loading, size, type and surface chemistry on rheology and the relationships with jet dispensing performance, die placement and reliability performance for test vehicles constructed with silicon and organic substrates.

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. A key challenge when designing OSCA materials for conventional mass reflow processing (identified as OSCA-R) is timing the cure kinetics with the fluxing and soldering sequences during reflow processing. OSCA-R materials must also have a process-friendly rheological design that integrates seamlessly with standard dispensing equipment and enables the filler loading levels required for customized thermal conductivities. The consideration of the interactions between the filler particles and the organic portion of OSCA materials is critical for first achieving fluxing and interconnection during reflow and second curing the material to develop target thermo mechanical properties for reliability such as Tg, TC, CTE modulus and adhesion after reflow. This paper presents research focused on understanding the impact of filler loading, size, type and surface chemistry on curing, fluxing and interconnection kinetics during reflow processing measured by thermal and rheological methods. Preliminary results indicate the presence of chemical interactions between the filler and organic formulations, as well as complex physical interactions which need to be considered in the design of OSCA-R materials for a device assembly using conventional mass reflow processing.