SMTA International Conference Proceedings


Author: N. Pan et al.
Company: Hewlett-Packard Co.
Date Published: 9/25/2005   Conference: SMTA International

Abstract: Many studies have been published regarding the thermal cycle reliability of Sn-Ag-Cu (SAC) solder joints under accelerated test conditions. However, few quantitative models have been established for assessing the reliability of SAC solder joints under typical product service conditions. Specifically, validated models that take into account the cyclic temperature range, maximum temperature, and dwell time or cyclic frequency are not readily available.

In this study, accelerated thermal cycle (ATC) testing was performed using several thermal cycle profiles, in which the temperature range (.T), maximum temperature (Tmax), and dwell time (td) or cycle frequency (f) were systematically varied. These various cycle profiles were used to perform solder joint reliability tests for three different types of electronic packages: 2533-CBGAs, 60-CSPs, and 52-TSOPs. These Pb-free packages were assembled to the printed circuit board using Sn-Ag-Cu solder, producing entirely Pb-free joints.

Data from these experiments were analyzed using 2-parameter Weibull statistics, and the characteristic life from each set of experiments was determined. These data were used to evaluate the constants in the well-known Norris-Landzberg acceleration model. The differences between the constants for SAC solder from those for eutectic Sn-Pb solder are discussed.

Key words: SAC solder, reliability, acceleration model

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