Virtual Imaging Of Interconnect Stress Test Coupon Failures
Authors: M. Anthony, D. Blake, R. Hu, and D. Ramjattan Company: Research In Motion, Ltd. Date Published: 5/4/2011
ICSR (Soldering and Reliability)
Abstract: This paper reports on the use and limitations of thermal imaging and 3D X-ray techniques to determine the locations and types of failures in coupons used in Interconnect Stress Testing. A voltage is periodically applied to the PCB coupons containing microvias and buried vias to cycle them to approximately 190°C for 1000 cycles, or until they experience a 10% increase in resistance. This resistance increase is due to the microvias and buried vias experiencing stresses that create knee cracks, possible pad separations, or other failure modes. The slope of the graph of the resistance increase over time gives some indication of the type of failure, but it is impossible to verify or locate these without viewing the internal structure of the IST coupon. The use of 3D X-ray tomography and thermal imaging is investigated here as techniques to map the internal structure of the coupon, in order to locate and identify failure sites.
Key words: IST, failure mode analysis, thermal imaging, 3D X-ray