THERMAL CYCLING RELIABILITY ASSESSMENT FOR 4 ARRAY RESISTOR OF MEMORY MODULE

摘要

The thermal cycling failure mechanism of the 4-array resistor was investigated by simulation tool and daisy chain board test. Furthermore, the effects about the factors that can affect the TC reliability of the 4-array resistor were investigated by various analyses. Solder joint crack mechanism initiates a crack from the bottom solder and propagates it in the solder fillet direction, but the crack propagation can change direction according to the shape. Also TC reliability is expected to increase with the increase of the bottom solder height. The effects of the number of board layers, pad design, fillet shape, solder composition, PCB metal finish on the reliability of the resistor were studied. Furthermore, the reliability improvement due to the decrease in the stiffness caused by the reduction in the number of board layers was confirmed. Lastly, the convex type fillet shape, determined by the increases of the toe side pad and solder volume, was found to be a key design parameter that can improve reliability.