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In power device applications, weak adhesion between bonding wire and leadframe is a major cause of yield loss and field failure. The aim of this study is to determine the relationship between leadframe storage time and wirebond quality, and consequently establish the maximum duration by which leadframes can be stored under a given set of conditions (25+/-3 deg C and 55% RH). To accomplish this, a Design of Experiment using Multiple Range Analysis was done. Box and Whisker Plots were used to present the results of the comparative study of yield losses before and after implementation of the established leadframe storage life. This study basically consists of two experiments, the first of which characterizes the effect of increasing leadframe storage period on wirebond peel test (an alternative wirebond integrity assessment approach used by Philips) response using optimized wirebond parameters. The second experiment is similar to the first, except that the bonding parameters were not optimized. The study concluded that the storage life of leadframes is an important factor in attaining optimum wirebond quality. The maximum period that leadframes can be stored at a temperature of 25 +/- 3 deg C and a relative humidity (RH) of 55% without adversely affecting wirebond quality is 6 days.
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