Quantitative analysis of Ag3Sn particle size in Sn3.5Ag solder alloy

Evaluation of the Ag₃Sn intermetallic compounds in the solder joints is a difficult issue; so a new image processing technique is developed to give quantitative, numerical results for the grain structure. During the cooling phase of the soldering method, different grain structures could be generated with different cooling rates. It is worth quantifying the difference. The developed image processing algorithm requires simple cross section images for input. During the preparation of the samples, they should be etched with OPS (Oxide Polishing Suspensions). After increasing the contrast, binarizing and filtering the image, the mathematical calculations regarding the grain structure could be performed. By using our algorithm, we found that the magnitude of Ag₃Sn grain size follows exponential distribution, so it can be characterized with the amplitude and the exponent of the fitted exponential curve. At last, these parameters were compared to commonly used quantitative parameters, like the mean intercept length or average area of Ag₃Sn particles.