OPTIMIZATION OF TEMPERATURE PROFILE OF THE THERMAL CYCLING TEST FOR PBGA SOLDER JOINT RELIABILITY
Author: Shi-Wei Ricky Lee Company: The Hong Kong University Date Published: 4/28/1997
Surface Mount International
Abstract: This paper presents a numerical parametric study to optimize the temperature profile of the thermal cycling test for solder joint reliability. The package under investigation is a 400-pin full-grid PBGA. The diagonal cross-section of PBGA with a printed circuit board (PCB) is modeled by plane-strain elements. Cyclic thermal loading is applied assuming the temperature in the whole assembly is uniform at every instant. A steady state creep constitutive model is adopted to model the response of solder material. The shear creep strain together with Coffin-Manson equation is used to estimate the life of solder joints. The stress-strain response and the thermal creep hysteresis loop of solder joint are presented. A series of parametric study is performed by changing the length of dwell time in the temperature profile. From the stress analysis, longer dwell time may increase the creep strain range and consequently reduce the thermal fatigue life cycles. However, it is found that the least cycles to failure do not correlate to the shortest life time. Therefore, the testing period of thermal cycling could be optimized by choosing an appropriate temperature profile. The result of this study will help the reliability engineers to determine the most efficient testing specification for solder joint reliability. Keywords: PBG& solder joint reliability, thermal cycling.