Mixed mode loading test and analysis on bonded joints

Abstract

Solder joints are a common sight in electronic packaging which serves as mechanical and

electrical interconnects in a package. Solder joints are prone to failure during a drop and

the fracture behaviour and failure modes can differ under various loading conditions. The

failure modes can vary from brittle intermetallic layer fracture to ductile bulk solder shear

failure or a combination of both depending on the conditions.

In this project, the solder joint is subjected to different type of tests under varying

parameters and loading conditions to investigate the effect of mode mixity and plastic

constraint on the failure mechanism. A CMM specimen is used to measure the outcome

by putting it under a universal tester machine and changing the strain rate, type of tests

and creating a crack within the solder joint.

Yield strength and work hardening were observed to increase substantially as strain rate

increases. Brittle failure is also noticed to be associated with higher strain rates and pure

tensile test, and vice versa. Pure tensile test is noted to produce intermetallic failure while

pure shear and mixed-mode tests results in bulk solder failure.

Based on the results collected and computed, the fracture failure behaviour and mode of

the solder joint are then recorded and discussed so as to establish, and improve the

mechanical properties of the solder joint.