Analysis of Solder Joint with Copper Pad UBM in Electronic Packages - a Fracture Mechanics Approach
Keywords:
Solder joints, Linear Elastic Fracture Mechanics, Stress Intensity FactorAbstract
Solder joints in flip chip packages are soft and hence often prone to failure. The aim of this work is to estimate the fatigue life of solder joints. Initially the package is subjected to thermal cycling range of -40°C to 125°C. Results from analysis reveal that the edge solder is prone to large thermo-mechanical stresses/strains and hence is badly affected. The edge solder joint with the intermetallic compounds and the under bump metallization is modeled and subjected to fracture analysis using LEFM approach (crack assumed at solder-IMC interface). Two materials are taken for analysis. Sn-3.5Ag solder is highly reliable than Pb-5Sn material. Also the effect of IMC thickness on the fatigue life of the solder is studied. It is preferable to allow thin IMC formation during soldering process for longer solder life.
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References
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