Authors: M. Roellig, R. Metasch, K. Meier
Affilation: Fraunhofer Institute for Non-Destructive Testing, Germany
Pages: 169 - 173
Keywords: solder fatigue, insitu force measurement
The paper presents a novel thermo-mechanical test method for in-situ force measurement on real solder joints during thermal cycling test. To generate more exact fatigue data for solder joints, a small mechanical machine has been designed. The loading frame works passive by its application in a usual temperature chamber. In the middle of the frame a FC/ CSP or BGA package can be clamped. Temperature changes inside the chamber leads to different thermal strain inside the copper and aluminium consisted frame. This thermal strain is used to induce shear forces at the solder joints. The applied force is directly measured using integrated force sensor elements. Due to plastic deformation inside the solder joints during the temperature cycles the solder-material-matrix continuously damages until micro cracks occur. This degradation behaviour is tracked by direct force measurement under thermal cycling loads. Based on the measurments the stress-strain behaviour of the solder joint is derived. Using this data the real plastic strain amplitude as well as the dissipated energy can be evaluated for each cycle for further use in fatige laws.