The Study On The Effects Of Lead-free Solder On The Dynamic Reliability Of The Packaged Chip

Along with the arrival of information age, the electronic industry has obtained enormous development, which has been already one of the most attractive and potential industry, and which also brings along the development of electronic packaging industry, and is showing greater importance.At present, the research on the electronic packaging is mainly concentrated on the static problems, induced by heat or damp and is lacking systemic study on the dynamic breaking behavior of the solders. The welding-dot's breakage induced by impacting falling off, etc which then result in the breakage of parts has great proportion in three damage of electronic packaging chips (20%). Therefore, it is quite necessary to study the dynamic damage behavior of electronic packaging chips under high strain-rate. The experimental study on mechanical behavior of two kinds of lead-free solders under dynamic compression is carried out in this paper, and then derives the strain-rate dependent constitutive relations by fitting the experimental data and the primary exploration on the breaking properties of welding-dot of the lead-free and lead-based solders is made in the paper. The main contents are outlined as following:1. The stress-strain curves of the solders referred above under the various strain-rates of500s^-1～2000s^-1 are obtained through SHPB(split Hopkinson pressure bar) testing technique.2. Based on Cowper-Symonds model, the two viscous parameters c and p are obtained by fitting the experimental data. Thereby, we get the relationships between yield stress and strain-rate of the three solders.3. Using the available material Young's Modulus, static yield -stresses and by using finite element code LS-DYNA to get the material's tangent Modulus and Possion's ratio are obtained. Then, combining the material's static stress-strain relationships, the material's dynamic constitutive relationships which are strain-rate dependent are given.4. Using the derived basic mechanical performances and dynamic constitutive relationships of the solders. The dropping process of the simplified package module of BGA (ball grid array) is simulating through the FEM. The differences among the solders in the dropping are compared, and the solders' failure made under impacting load are analyzed and discussed. It can provide some references for the estimation of fatigue life and configuration optimization design of the solders.