A novel thermo-mechanical test method of fatigue characterization of real solder joints

The paper presents a novel thermo-mechanical test method for in-situ force measurement on real solder joints during thermal cycling test. Due to plastic deformation in solder joints the solder-material-matrix is damaged and micro cracks occur. This degradation behaviour can be determined by direct force measurement under thermal cycling loads. After the overall characterization of the machine, first successful results were generated based on 400 mum solder balls on micro BGA-package stressed under -40degC and +125degC conditions. A force drop down to approx. 60% of initial force at the first cycles was measured. The measured forces kept in a steady state ranged over approx. 80% of lifetime until the material mechanically failed. The main tasks planned to be solved are the direct measurement of degradation of solder alloys for comparison purpose, the determination of solder material fatigue behaviour and derived material fatigue laws.