Comparative Analysis of BGA Deformations and Strains Using Digital Image Correlation and Moiré Interferometry

The thermo-mechanical behavior of BGA solder joints under thermal cycling is characterized by using full field optical measurement techniques, namely Moiré Interferometry (MI) and Digital Image Correlation (DIC), and each technique’s advantages and disadvantages are discussed. Moiré Interferometry has been widely used in the electronics packaging for development and reliability assessment. Its high signal to noise ratio and in-situ measurement capabilities made the technique popular in the last two decades. Its application was further disseminated by the development of fringe shifting algorithms and fringe analysis software that made its virtual sensitivity as high as tens of nanometer per fringe order. However, the technique requires application of high frequency diffraction gratings and flatness of the inspected surface. Increases in computing capabilities, efficient algorithms, and affordable higher resolution CCD cameras have made Digital Image Correlation (DIC) a practical and quantitative deformation measurement technique. It does not require surface treatment in most of the applications, and this relaxed surface condition requirement appeals positively to the technical community. For these comparative analyses, a flip chip plastic ball grid array package (FC-PBGA) was cross sectioned to reveal a row of BGA solder interconnects and was subjected to a thermal cycle in an environmental chamber for in-situ measurement. The deformations and strains for the solder balls and the global deformations of the substrate and PCB have been compared for a ∆T of -80°C.