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Failure of an electronic package generally initiates from the interface corners, due to the stress and strain singular behaviors near the corners. Since the solder materials are viscous elastic and even maybe viscous plastic, the singular behavior near the solder joint corner is thereby time-dependent, and is quite different from that of an elastic one. It is necessary to clarify such a singular behavior for the strength and life evaluation of an electronic package. This paper firstly has deduced the approximated viscous elastic singular fields theoretically based on the principle of correspondence and the Laplace transformation techniques, and secondly has investigated the viscous plastic singular behavior of an elastic-plastic interface corner by the analogue method; finally the numerical analysis of an electronic package has been carried out to show the details of the singular behaviors.

In this paper, a proportional method for evaluating an intensity of singular stress field (ISSF) at an interface corner in a butt joint (BJ) with an adhesive spew is proposed. Square-shaped inclusion models under bi-axial tensile stress and under shear stress are used as reference models. The ISSFs for the BJ are calculated by superposing those for the reference models. The reference and BJ models are analyzed by FEM under the same mesh division and the same material combination, and the stresses applied to the reference models are determined by the FEM stresses at the interface corner. The validity of the present method is examined by applying to the BJ composed of the steel and the epoxy resin. The asymptotic solution obtained by the method is in agreement with the FEM stress distributions. Then, the ISSFs for the BJ are calculated by changing adhesive spew similarly. It is shown that the ISSF normalized by the adhesive thickness is constant independent of the thickness.

Failure of an electronic package generally initiates from the interface corners, due to the stress and strain singular behaviors near the corners. Since the solder materials are viscous elastic and even maybe viscous plastic, the singular behavior near the solder joint corner is thereby time-dependent, and is quite different from that of an elastic one. It is necessary to clarify such a singular behavior for the strength and life evaluation of an electronic package. This paper firstly has deduced the approximated viscous elastic singular fields theoretically based on the principle of correspondence and the Laplace transformation techniques, and secondly has investigated the viscous plastic singular behavior of an elastic-plastic interface corner by the analogue method; finally the numerical analysis of an electronic package has been carried out to show the details of the singular behaviors.