Fault Isolation for Board-Level Solder Joint Failure Using Time-Domain Reflectometry

Failure analysis (FA) is an important step after a board level reliability test, which can help to clarify the weak point in product and proceed further improvement. Hence, in order to accurately locate the failures in daisy-chained solder joints after temperature cycling test, a non-destructive electrical failure analysis (EFA) technique, Time-Domain Reflectometry (TDR), is proposed. By measuring the time of reflected voltage and monitoring the variation of reflected voltage, the failures can be predicted. In addition, this technique can shorten the entire process of solder joint analysis. In this study, the distance of failure signal is calculated by reflected time and velocity to compare with actual layout drawing and estimate the fault location. After that, the physical failure analysis (PF A) validations were performed to the estimated fault locations, and the corresponding solder joint cracks were observed.