S. Parupalli, Intel Corporation, Hillsboro, OR; K. Newman, Sun Microsystems, santa clara, CA; M. Ahmad, Cisco Systems, San Jose, CA

Summary: The transition to Pb-free materials has introduced many Printed Circuit Board (PCB) interconnect reliability challenges. New PCB laminate materials have been introduced to survive the higher Pb-free reflow temperatures. The increased stiffness of the most common Pb-free solder alloy, SnAgCu (SAC), relative to SnPb, coupled with reduced interconnect pitch and new laminate materials, have shifted the primary failure mode in mechanical bend and shock testing, from solder fractures to cratering underneath the PCB pads. Some standard characterization techniques (solder ball pull, solder ball shear, etc.) exist today for the assessment of solder ball mechanical fracture strength; however, it isn’t clear if these test methods would also provide characterization of PCB pad cratering susceptibility. This paper provides an overview of test methods being investigated by a PCB pad crater industry working group. This group was initiated during a break-out session in the 2006 Intel/IPC Pb-free symposium. The scope of this industry working group is two-fold: a) Standardization of PCB pad crater crack characterization and measurement methods b) Development of a quantitative quality metric for PCB pad cratering.