The influence of thermal aging on joint strength and fracture surface of Pb/Sn and Au/Sn solders in laser diode packages

Abstract

The joint strength and fracture surface of Pb/Sn and Au/Sn solders in laserdiode packages after thermal-aging testing were studied experimentally. Specimens were aged at 150°C for up to 49 days. The joint strength decreased as aging time increased. The microstructure and fracture surface of the Pb/Sn and Au/Sn solder joints showed that the joint strength decrease was caused by both the enlargement of the initial voids and an increase in the number of voids as aging time increased. The formation of Kirkendall voids with intermetallic-compound (IMC) growth of the Pn/Sn solder as aging time increased was also a possible mechanism for the joint-strength reduction. Finite-element method (FEM) simulations were performed on the joint-strength estimation of Pb/Sn and Au/Sn solders in thermal-aging tests. The coupled thermal-elasticity-plasticity model was used to simulate distributions of the thermal and residual stresses, creep deformation, and joint-strength variations in the solder joints under various thermal-aging tests. Simulation results were in good agreement with the experimental measurements that the solder-joint strength decreased as aging time increased. The result suggests that the FEM is an effective method for analyzing and predicting the solder-joint strength in laserdiode packages.

The joint strength and microstructure of fluxless Au/Sn solders in InP-based laser diode packages

“…3, the distributions of thermal stresses, residual stresses, creep deformation, and the joint strength in the solder joints were obtained. In this study, the FEM model of the InP-solder-Si submount with an initial void was used in order to correlate the experimental observation results, as shown in Fig.…”

“…The coupled thermal-elasticityplasticity model was employed to simulate the solidification and the thermal-aging processes. 3 An eight-node cube element model with the temperature-dependent material properties was used in this work. 15 Figure 8 shows a cross-sectional finiteelement method (FEM) model of the InP-solder-Si submount with an initial void.…”

“…Because it exhibits higher yield strength and less creep effect of the eutectic tin-based solder of Au/Sn, the hard solder Au/Sn is often used in the packaging of a laser diode. [1][2][3] In order for it to be used in system applications, the laser-diode package must undergo different reliability tests. The acceleration aging and temperature-cycling tests are commonly used in the electronics industry to characterize the thermal-fatigue failure and to predict the reliability of solder joints in microelectronics packaging technology.…”

“…Previously, to simplify the solder joints in the laser-diode assembly, the laser-diode packages were substituted by the gold-plated Al 2 O 3 -solder-SUS304 substrate assembly. [2][3] However, the behavior of solder-joint strength and microstructure may be different between the real laser diodes and the substituted materials.…”

Thermodynamic Properties of Liquid Ag-Au-Sn Alloys

“…Many investigations have been done on binary Ag-Sn and Au-Sn systems. [2][3][4][5][6][7] Eutectic 80Au-20Sn (wt.%) solders are widely used for high-temperature applications for optoelectronics such as laser diodes and photodiodes because of their good creeping properties and high tensile strength. They are also used in flip-chip technology.…”