Track 2 Session 11
10:30 to 11:30 a.m. Thursday June 19, 2008

LCC Solder Joint Reliability in Storage Environments and the Limitations of Modeling Mitigation Methods

With industrys move to Surface Mount components, Leadless Chip Carrier (LLC) castellation solder joints have become a reliability concern, specifically in a storage environment. This session describes a specific mitigation method and evaluates its effectiveness through accelerated thermal cycle testing. When a product sits in storage for 90% of its life before it is used, daily thermal cycling, however minimal, can reduce the reliability of the LCC solder joint if there is any Coefficient of Thermal Expansion (CTE) mismatch between the Printed Wiring Board (PWB) and the component package material. It is becoming increasingly more difficult to match the PWB and component CTEs because boards are becoming more densely populated with components, components are becoming more creatively packaged and pressure is being applied to reduce costs. Testing results contradicted the analysis that identified non-collapsible solder balls as the leading mitigation solution. Non-collapsible solder balls were concluded to be less reliable than standard castellation solder joints and therefore are an ineffective mitigation for solder joint cracking in storage environments.