Abstract

The demand for shifting from lead-containing to lead-free solder materials as well as the ongoing efforts for an improvement of the solder joint robustness for fine-pitch ball grid array packages requires ongoing testing of fresh solder alloys, changes in landing pad metallization and reflow processes. This testing includes mechanical and thermal stress tests and a detailed failure and material analysis. Besides the commonly used analysis methods like optical microscopy, scanning electron microscope (SEM) imaging of cross sections, fracture planes and energy dispersive X-ray compositional analyses, other techniques such as ion channeling contrast and transmission electron microscope (TEM) imaging can provide valuable information on intermetallic compounds (IMC) formation at solder joint interfaces. This paper discusses the advantages of SEM imaging of IMC morphology at the pad interface resulting from solder ball etching, focused ion beam imaging of solder ball cross sections with ion channeling contrast, and TEM analyses of failures.

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