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

Abstract

Thermal gap pads are widely used for effective heat transfer from high-heat-dissipating components to a heat sink. The initial contact pressure of thermal pads is an important parameter for enhancing the heat transfer capability of thermal design during the assembly process of the heat sink. However, this causes stress on the solder joint of the component as a result of the pad’s inherent resistance to deformation. In this study, we investigated the effect of thermal pad on the fatigue life of the solder joint of CCGA 624 package for space usage. A random vibration fatigue test for several specimen assembly sets with various pressurization levels of thermal gap pads was performed, and their fatigue lives were compared with that of the package without the initial pressure of thermal gap pads.

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“…However, this causes stress on the solder joint of the component because of the pad's inherent resistance to deformation. In a previous study, we verified that PCB specimens with various compression ratios of thermal pads of 0%, 10% and 50% exposed to launch random vibration loads exhibited increased fatigue lives on the solder joint, owing to the inherent damping and restriction on the dynamic displacement of the PCB [10].…”

“…To reduce the total mass of unit and guarantee the structural safety on the solder joint of electrical, electronic, and electromechanical (EEE) parts of an HSDRU, the heat sink is designed, such that it functions as a mechanical stiffener to restrict the out-of-plane dynamic displacement of the PCB. Thermal gap pads for effective heat transfer from heat-dissipating components to the heat sink was constructively applied to the design, based on the results of a previous study [10]. The initial contact pressure of thermal pads is an important parameter for enhancing the heat transfer capability.…”

“…Table 9 and Figure 15 presents the first Eigen-frequency and the change of Q factor calculated via the half power method according to the rise in the vibration level. In the previous study [10], fatigue life tests and analyses of FPGA (CCGA624 package) according to the thermal pad compression ratios from 0% to 50% were conducted in a random vibration environment of 20 grms by adopting a CCGA624 daisy-chain, which has the same mechanical structure and electrical form/fit [15]. Figures 16 and 17 present the test setup and the results of time histories for daisy-chain resistances for each specimen.…”