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 effect ofjoint strength of PbSn and AuSn solders on thermal aging in laser packages has been studies experimentally and numerically. Samples were aged at 150°C for one, four, nine, sixteen, twenty-five, and thirty-six days. It was found that the joint strength decreased as the aging time increased. This joint strength decreased may be due to the brittle fractures associated with void formation increased in solder joints. A finite-element method (FEM) simulation of joint strength was in reasonable agreement with the experimental measurements. Introduction: Two eutectic solders of Pb(37)/Sn(63) (T, = 183°C) and Au(80)/Sn(20) (T, = 280°C) are often used in laser diode packaging to form the solder joints, as shown in Fig. 1 (a). The laser diode chip is bonded to the submount with AuSn solder to form laser-solder-submount assembly. Then the submount is bounded to a substrate with PbSn solder to form submount-soldersubstrate assembly. In order be used in system applications, the laser diode package is required for undergoing different reliability tests. One of the reliability tests is acceleration aging testing, which is used to predict the men time to failure of laser diode. In this work, we study the joint strength and intermetallic compound (IMC) growth of PbSn and AuSn solders under thermal aging at 150°C for different times. Experiment: To simplify the study of the solder joints in laser assembly, the laser-soldersubmount, and the submount-solder-Invar plate were substituted by the gold plated A1203 submount-solder-SS304, as shown in Fig. l(b). The dimension of SS304 (stainless steal 304) and
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