Reliability Assessment of Preloaded Solder Joint Under Thermal Cycling

Abstract

The ever increasing power density in modern semiconductor devices requires heat dissipation solution such as heat sink to remove heat away from the device. A compressive loading is usually applied to reduce the interfacial thermal resistance between package and heat sink. In this paper, both experimental approaches and numerical modeling were employed to study the effect of compressive loading on the interconnect reliability under thermal cycling conditions. A special loading fixture which simulated the heat sink was designed to apply compressive loading to the package. The JEDEC standard thermal cycle tests were performed and the resistance of daisy chained circuits was in situ measured. The time to crack initiation and time to permanent failure were identified separately based on in situ resistance measurement results. Failure analysis has been performed to identify the failure modes of solder joint with and without the presence of compressive loading. A finite element based thermal-fatigue life prediction model for SAC305 solder joint under compressive loading was also developed to understand the thermal-fatigue crack behaviors of solder joint and successfully validated with the experimental results.

Thermal Management

“…At the start of the subsequent thermal cycle, the interface of the SAC305 solder joint is under compressive loading. The existence of a compressive preload has been previously shown to contribute to larger accumulation of plastic work per thermal cycle [12]. In this case, the compressive preload occurred at the cold temperature dwell and continued up to the glass transition temperature at which the acrylic material softens.…”

Experimental Validation of Fatigue Life of CCGA 624 Package with Initial Contact Pressure of Thermal Gap Pads under Random Vibration Excitation

“…Thus, a proper thermal management of high-heat-dissipating packages is important to prevent failure of spaceborne electronics used in a severe space thermal environment. In general, thermal gap pads act as essential hardware for heat sink implementation by enabling heat transfer path between the high-heatdissipating packages and a heat sink to avoid an excessive increase in temperature during their operation [8,9]. The heat transfer capability of the thermal pads can be enhanced by controlling the initial contact pressure level of the pads during the assembly process of heat sinks.…”