A numerical study of the effect of die, die pad and die attach thicknesses on thin plastic packages

In this paper, the effects of thickness of the die (t_d), die-pad (t_p) and die attach (t_a) on delaminations in Thin Shrink Small Outline Plastic IC packages were studied. The effects of t_d and t_p on Crack I, II and III are individually investigated where Crack I lies in the pad-encapsulant interface, Crack II in the die-encapsulant interface and Crack III in the pad-die attach interface. A fracture mechanics approach was used to compute the strain energy release rate (ERR) at the crack tips. For the die attach thickness t_a, only its effect on Crack III was investigated. According to the literature, the Young´s Modulus E of the die attach has a great influence on delamination along the pad-die attach interface. Thus a full factorial analysis of die attach thickness (t_a) and Young´s Modulus E on Crack III crack tip energy release rate was also carried out. Among other things, it was found that increasing the thickness of the die increases the ERR of cracks at all three interfaces and increasing the thickness of die pad increases the ERR of Crack I and II. It was also found that a smaller Young´s Modulus and a greater thickness of the die attach is a good design against propagation of Crack III.