可压缩条件下超弹性电子封装材料中孔穴的增长问题

考虑了温度改变对高聚物材料体积变化的影响，将材料的不可压缩假定修正为可压缩假定。对具有neo-Hookea特征的高聚物电子封装材料在回流焊过程中由于湿热所引发的“爆米花”式的孔穴破裂现象进行了理论研究。利用有限变形的理论给出此类材料在计及体积改变效应下的孔穴增长和吸湿产生的蒸气压力与热应力之间的广义解析关系。该广义解析关系包含了不可压缩条件下的解析关系。分析结果表明：当温度改变引起的可压缩效应较大时，利用可压缩假定分析得到的极限载荷值与利用不可压缩假定分析得到的极限载荷值相比有所提高。但当温度改变引起的可压缩效应较小时，利用两种假定分析得到的极限载荷值相差不大。在温度变化范围不大的情况下，采用不可压缩的假定是合理的。

Growth Issue of Void of Hyperelastic Electronic Packaging Materials Under Compressible Condition

The assumption of materials' incompressibility was amended to compressibility when the effect of temperature change on the volume of polymer materials was taken under consideration. Theoretical research is conducted on the popcorn void crack phenomenon of polymer materials with neo-Hookea feature under the effect of hygro-thermal during reflow soldering. Using the theory of finite deformation, an general analytical solution relating the void growth to the vapor presser and thermal stress is obtained when the temperature change cause the material volume change. The general analytical solution will include the analytical solution of the material with incompressibility. The analysis results show that：Considering the effect of volume expansion of polymer materials, the critical load will be increased. If the expansion coefficient is smaller, the effect of volume expansion on the evolution of the void will be less. Using the incompressible hypothesis is reasonable when the temperature variation range is small.