Study of interface reliability in QFN device under hygro-thermal environment

The interface crack caused by moisture absorption is a main reason for the failure of plastic packaging electronic devices. According to the failure of interface cracks in QFN plastic packaging devices caused by hygro-thermal environment, the paper combining with finite element method (FEM), carried on the research by moisture absorption experiment, lead-free reflow soldering experiment, high temperature tidal thermal experiment, and scanning electron microscope (SEM) experiment. The results of study show that: non-moisture absorption devices seldom produce cracks after the lead-free reflow soldering, and moisture absorption devices donpsilat produce any crack during absorbing moisture, but they easily produce cracks after lead-free reflow soldering; The cracks produced by the experiment mainly lay on the interface between die-attach material (DA) and the chip, and the cracks at the junction of chip, DA material and epoxy molding compound material (EMC) have the greatest damage; The position and the expansion direction of cracks are closely related to the characteristic and the interface intensity of the two connecting materials. These conclusions have important practical significance to the study and the evaluation criterion of crack.