A STUDY TO CORRELATE SOLDER AGE WITH PHASE SIZE AND COMPOSITION ENRICHMENT

Abstract

This dissertation research aims to develop a forensic technique to identify and mitigate counterfeiting of microelectronics through correlation of phase size and composition enrichment of Sn-Pb solder with aging. Phase coarsening as a rate of time and temperature is measured, but the focus is on correlating this with phase enrichment, specifically how the percentage of Sn in the α-Pb phase changes with time and temperature. It is hypothesized that the two metrics will evolve differently with time as the system moves toward equilibrium thus giving a more difficult signature to counterfeit. Since Sn-Pb solder has been around for many years and older samples are readily available, this material has been selected for the basis of the research and several samples have been collected. To start, these samples are characterized using the Scanning Electron Microscope with Energy Dispersive Spectroscopy. Following the analysis on the time-aged samples, fresh samples are made and temperature-aged in an oven. Samples are thermally-aged for varying amounts of time and analyzed in the same way as the initial time-aged samples. All of these data points are used to create a method to estimate solder age. A secondary goal of this thesis project is to enable application of this method to lead-free solders, which are more complex. Other parameters, such as intermetallic compounds and their interactions are considered in additional systems to correlate age. Having developed this tampering and counterfeit mitigation technique, it can be used to determine if components have been added or replaced at a date after the initial manufacture.