Improving the reliability of a plastic IC package in the reflow soldering process by DOE

Purpose - Optimisation of the package design in order to reduce stresses in a plastic small outline J-lead (SOJ) package and to thereby prevent fractures during the infrared soldering process. Design/methodology/approach - Finite element (FE) modelling was used, both with and without crack tip-modelling. A design of experiment (DOE) approach was used to reduce the number of FE models required. Findings - The optimum design values for minimization of thermal stress and the prevention of fracture were found to be different. The results allow the values of design variables such as the dimensions and material properties of the IC package. Practical implications - To reduce the stresses and thereby prevent fracture, the values of the Young's modulus and coefficient of thermal expansion of the epoxy moulding compound should be reduced. Originality/value - The work has used both stress analysis and fracture mechanics analysis along with DOE to identify the design values which simultaneously reduce the thermal stresses and prevent the fracture of the IC package.