RESEARCH ON THERMO-MICRO-MECHANICS OF COMOPSITE MATERIALS FOR ELECTRONIC DEVICE

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(1) Mechanical properties required for electronic devices were investigated by the mechanical data of materials for electronic devices. As a result, it was found that solder joint (60 Sn - 40 Pb) is used nder most severe condition such as cyclic loading.(2) Strain rate effect and temperature effect of 60 Sn - 40 Pb solder depends on both strain rate and temperature. Moreover, a cnstitutive equation for viscoplasticity was constructed based on the constitutive model for cyclic plasticity previously proopsed by the head of investigator. The constitutive equation for viscoplasticity was verified to predict both the strain rate effect and temperature effect of 60Sn-40Pb solder.(3) Materials for electronic devices, especially solder joints, odccur fatigue failure caused by cyclic loading. Then, a method to predict fatigue failure of 60Sn-40Pb was constructed using the concept of the plastic strain energy density and the proposed constitutive equation.(4) Mechanical properties of 60Sn-40Pb solder at several temperature were observed in detail to clear the effect of residual stress induced by phase transformation. As a result, the possibility ot predict the effect of phase transformation of 60Sn-40Pb solder by modifying the proposed model considering the kinematic strain aging.(5) Three dimension finite element analysis was conducted for optimization of electronic devises using the proposed constitutive equation. As a result, it was found out that both stress distribution an deformation of the actual electronic devices was predicted using the proposed constitutive equation for viscoplasticity.