Influence of temperature, humidity, and defect location on delamination inplastic IC packages

The modified J-integral and the stress intensity factor based on linear ela stic fracture mechanics can be applied to predict the growth of interfacial delamination in integrated circuit (IC) packages. One of the key parameter s required is the interfacial fracture toughness. This paper describes the measurement of the interfacial fracture toughness as a function of temperat ure and relative humidity using a three-point bending test. The interfacial fracture toughness was found to decrease with temperature and relative hum idity, It is proposed that delaminations propagate from very small voids or defects present at the interface, The effect of the location of these inte rfacial defects or cracks on delamination was studied. The IC package evalu ated in this paper was an 80-pin quad flat package with a 0.2 mm defect or crack at the edge or at the center of the interface. It was found that as t he temperature of the package was increased, the stress intensity factor of the edge crack was higher than that of the center crack, However, whether the edge crack will propagate first as temperature is increased depends on the ratio of mode II interface toughness to that of the made I interface to ughness.. For the package under investigation, it was established that when this ratio is less than 2.69 the edge crack would propagate first, otherwi se the center crack would, For small defects, it mas found that the water v apor pressure developed at the interface did not have a significant effect on the value of the crack-tip stress intensity factor.