Reliability of Leadfree Solders in High Temperature Vibration in Automotive Environments

Abstract

Applications in down hole drilling, automotive industry and avionics industry require exposure of electronics to sustained high temperatures electronics combined with vibration loads. Electronics component in automotive under hood application can be located at engine and at transmission, can subjected to combined mechanical vibrations and thermal loads. In these conditions, maximum temperature can exceed 200 °C and vibration G-Level up to 10g. Combined effect of elevated temperature and vibration can cause faster failure in electronics components. Most of the previous research of solder joints is focused on either single stress of vibration or thermal cycling. Very few researchers have studied the solder joint reliability under simultaneously high temperature and vibration. Previously the literature on reliability of lead-free alloys under combined high temperature and vibration is sparse. This study presents reliability for SAC105 and SAC305 alloy compositions at elevated test temperature and vibration. Pristine and aged test board with lead-free SAC daisy chain CABGA packages have been subjected to harmonic vibration at their 1st natural frequency at three test temperatures (25°C, 55°C and 155°C) and vibration with amplitude of 5g, 10g and 14g. Test boards were exposed to isothermal aging conditions at 150°C for 60 days. Resistance data were measured at each test conditions using high speed data acquisition. Material properties of the printed circuit board at elevated temperatures have been measured using tensile tests. High speed camera is also used to capture the vibration event during testing. The experimental system characteristics such as mode shapes and natural frequencies and displacement amplitudes for each test condition compared with global-local FE models. Hysteresis loop and plastic work density of critical solder joint extracted using FEA based global and local method. S-N curves were obtained for test vehicle. Failure mode analysis has been done for test board. Anand Viscoplasticity material data from the prior studies by the authors have been used to capture the high-strain rate temperature dependent aging behavior of the solder joints. A comparison between simulation and experimental results is conducted. A new model has been proposed to predict the high frequency fatigue life under simultaneous temperature-vibration.