On mode II fracture toughness of sintered silver based on end-notch flexure (ENF) test considering various sintering parameters

Shearing fracture toughness of sintered silver (Ag) is an important parameter to reflect its shearing resistance. In this paper, mode Ⅱ fracture toughness of sintered Ag is investigated based on end-notched flexure (ENF) test. Various sintering conditions are adopted to study the effect of sintering parameters on mode Ⅱ fracture toughness of sintered Ag. The results show that the fracture toughness of sintered Ag increases rapidly with the increase of sintering temperature and holding time. Three shearing crack types are confirmed, i.e., interface delamination, tunneling cracking and cohesive cracking, and the cracking type varies from "interface delamination" or "tunneling cracking" to "cohesive cracking" with the increase of sintering temperature and holding time. An empirical equation is proposed to predict the mode II fracture toughness of sintered Ag. Through statistics investigation on microstructure evolution, it is found that the shearing fracture toughness heightens with enlargement of the Ag particle size, increase of the particle shape form factor, and decrease of the porosity. This study provides an alternative method to rigorously evaluate the shearing fracture toughness of die-attach materials in electronics packaging.