Correlation studies for component level ball impact shear test and board level drop test

This paper presents a comprehensive study of the resistance of solder joints to failure when subjected to strain rates that simulate the conditions of drop-impact on a portable electronic product. Two test methods are used in this study: the board level drop/shock test (BLDT) and the component level ball impact shear test (BIST). The performance of (i) 12 material combinations consisting of six solder alloys and two pad finishes; and (ii) 11 manufacturing variations covering three vendors, two finishes, three immersion gold thicknesses and three thermal aged conditions, were investigated using these two test methods, and analysis of correlations between the methods was performed. Quantitative correlation and sensitivity coefficients for the failure modes and the measured characteristic parameters – number of drops to failure for BLDT and peak load, total fracture energy, and energy-to-peak load for BIST – were evaluated. The lack of universal correlations between the two test methods has ruled out the use of BIST for evaluating solder joint materials, but BIST is recommended as a test method for quality assurance in view of the strong correlation between the measured parameters and the failure mode. The total fracture energy parameter is preferred over the peak load and energy-to-peak load due to its higher sensitivity and reduced susceptibility to measurement error.