Influence of defect size on popcorning [electronic packages]

Popcorning in electronic packages is driven by evaporated steam generated within defect during the solder reflow process. Generated steam is confined in a sealed defect volume creating a blister. Steam escapes when the blister is popped. The condition for popping is governed by the steam pressure and defect fracture resistance, the critical strain energy released rate. The quantity of steam generated within the defect is a function of the reflow condition as well as defect size. Analysis revealed that the steam pressure is inversely proportional to defect size at fixed reflow conditions. The resulting critical defect size is an exponential function of steam generation and critical strain energy released rate. Given a pre-existing defect, a small change in steam generation can pop the defect. Low steam generation and strong interfaces which are water resistant will enhance popcorn resistance