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

(1)利用电子器件材料的力学数据研究电子器件所需的力学性能。结果表明，在循环加载等最恶劣的条件下，焊点（60sn - 40pb）仍能使用。(2) 60sn - 40pb焊料的应变速率效应和温度效应取决于应变速率和温度。在课题组组长提出的循环塑性本构模型的基础上，建立了粘塑性本构方程。验证了60Sn-40Pb焊料的粘塑性本构方程，该方程可以预测60Sn-40Pb焊料的应变速率效应和温度效应。(3)电子器件材料，特别是焊点，在循环载荷作用下容易发生疲劳失效。然后，利用塑性应变能密度的概念和提出的本构方程，建立了60Sn-40Pb疲劳失效预测方法。(4)详细观察了60Sn-40Pb焊料在不同温度下的力学性能，以清除相变引起的残余应力的影响。结果表明，在考虑运动应变时效的情况下，通过修正所提出的模型来预测60Sn-40Pb钎料相变效果的可能性。(5)利用提出的本构方程对电子器件进行了三维有限元优化分析。结果表明，本文提出的粘塑性本构方程可以预测实际电子器件的应力分布和变形。

(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.