Popcorn failure in Hyperelastic-plastic electronic packages under thermal load and moisture was studied.Elastic constitutive relation was described by Neo-Hookean strain energy function and plastic constitutive relation was described by the Tresca yield condition.Using the theory of finite deformation

the analytical relation were obtained between void growth and the sum of the vapor pressure induced by moisture and thermal stress induced by heat mismatch.Numerical analysis show that the regularity of the unstable void growth changes when the elastic-plastic behavior of materials is considered.The critical stress of the unstable void growth in elastic-plastic analysis is much lower than the result of pure elastic analysis.