IMPROVED BGA SHOCK AND BEND PERFORMANCE USING CORNER GLUE EPOXIES

摘要

The adoption of lead free solders has decreased the reliability of BGA packages subjected to shock and bend events. Also, as BGA packages grow in foot print and as pitches shrink, they are at increased risk of failure induced through handling. Capillary flow underfills can be used to significantly enhance the reliability performance of BGA packages. However, underfilling larger packages can take significant time. This can translate to slow assembly rates or multiple underfill machines operating in parallel to meet throughput requirements. We have explored the technique of using corner applied epoxies to enhance the performance of BGA packages. This technique is a very effective at increasing mechanical strength, and can be implemented using automated dispense machines or by manual dispense methods, therefore it can be implemented on larger packages without the beat rate concerns associated with capillary flow underfill. Critical factors to the success of this process include selecting the proper epoxy chemistry and using an appropriate amount of epoxy and the optimum pattern for the BGA package being protected. This paper will quantify the mechanical improvements seen when applying these epoxies to various BGA systems. The reliability of corner bonded and non-corner bonded devices in response to shock and bending will be reported as a function of the type of epoxy and dispense pattern used.