Non-destructive Evaluation and Life Monitoring of Solder Joints in Area Array Packaging

Determining the lifetime of solder joints on area array packaging through non-destructive evaluation subjected to thermomechanical loads is crucial for reliability testing of electronic devices. Circuit board assemblies (CBA) are expose to cyclic changes in temperature. The rate of change, exposure time and thermal excursion limits are dependent upon product application and usage known as 'Mission Life'. The purpose of this study is to evaluate the application of an acoustic micro-imaging (AMI) inspection technique, in monitoring solder joints through lifetime performance. Test boards with various area array packages, different surface finish configurations and substrate thickness were subjected to an accelerated thermal cycling test (ATC). The test profile used was -40°C to +85°C with 30 minutes dwell. AMI scanning was performed every 4 cycles over a total period of 220 cycles, in order to obtain enough adequate failure data at high stress to accurately project (extrapolate) what the cumulative distribution function (CDF) at use will be. The cracks on the solder joints was determined by using statistical analysis to observe the behavior of the joints at the region of interest (ROI) with increase in thermal cycling. The differences in the plot patterns also confirms the variations of frequency intensity levels for different thermal cycles.