DWELL TIME, MICROSTRUCTURAL DEPENDENCIES, AND THE INTERPRETATION OF THERMAL FATIGUE TEST DATA OF SnPb AND Pb-FREE SOLDERS
Authors: Richard Coyle1, et al. Company: Alcatel-Lucent, LSI, Corporation, Celestica Inc., Stokes Institute, University of Limerick, Sanmina-SCI, and Texas Instruments Date Published: 10/4/2009
Abstract: Accelerated temperature cycling (ATC) was used to compare the thermal fatigue performance of SnAgCu (SAC) Pb-free solders to SnPb eutectic solder. The temperature cycling was conducted on several ball grid array (BGA) test vehicles using a 0/100 ºC cycle and dwell times of 10, 30, or 60 minutes. The Pb-free solder alloys were either SAC405 or SAC305. Some of the samples were subjected to isothermal preconditioning to assess its impact on final fatigue life. The failure analysis and microstructural characterization was performed using optical metallography and scanning electron microscopy. The thermal fatigue of the SAC and SnPb solders is discussed in terms of the impact of the test parameters and test vehicles on the microstructural evolution and ultimately, on the measured reliability.