Solder-Joint Quantitative Crack Analysis—Ohmic Resistance Approach

This paper presents a novel technique in the area of solder-joint reliability testing, suggesting a new approach for efficient testing of new products. An analytical model was developed relating the solder-joint ohmic resistance and the joint crack´s length caused by temperature cycles. Based on the analytical model, a technique was developed allowing the measurement of a solder-joint´s crack length in a nondestructive, continuous way. Thus, prediction of the solder-joint´s end-of-life could be done at an early stage of the test, which substantially reduces the test time. This technique of resistance monitoring was validated with a commonly used test vehicle utilizing commercially off-the-shelf daisy-chain quad flat no-lead (QFN44) package. This method is not limited to lab tests, but rather is applicable also for prognostics and preventive maintenance in deployed products.