Monitoring Fatigue Cracking in Interconnects in a Ball Grid Array by Measuring Electrical Resistance

Abstract

In displacement controlled mechanical fatigue of ball grid solder interconnect arrays, decrease in maximum load monitors total increase in crack area in an array while electrical resistance monitors only the area of large cracks that lead to electrical failure. Small cracks with good electrical contact between the crack surfaces have only minor effect on the resistance of the array. In this mechanical fatigue research of ball grid arrays, the fatigue damage was continually followed by simultaneously measuring maximum load and electrical resistance. Experimental details, results, and analysis of the results are given including a Paris relation fit to the data.