Application of direct strain measurement to fatigue studies in surface solder joints

A direct method to measure the fatigue life of surface mount solder joints is proposed. This approach makes use of a quad flat pack (QFP) solder-printed circuit board (PCB) assembly as a shear specimen. After the assembly and thermal stress screening tests, the specimen is cut in half at the PCB. The displacement or strain variations between the split PCB's during mechanical strain cycling reflect the fatigue properties of the solder joints. This approach is useful to predict the fatigue life of a practical surface solder joint in electronic products and applicable to any leaded and leadless surface joints. The measurement of joint strain and chip stiffness can reveal fatigue status in the solder joint system, which is important to the understanding of its fatigue mechanism.<
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