Szu-Chun Wang

Post-weld-shift in dual-in-line laser package

The post-weld-shift (PWS) effect in laser welding for a dual-in-line package (DIP) with fiber pigtail to semiconductor laser connection has been studied experimentally and numerically. Experimental results show that the PWS of an optical component welded by a dual-beam laser system deforms and the welded component rotates counterclockwise as the difference of the energies between two laser beams increases. This indicates that the PWS in laser packaging can be minimized by properly controlling the laser beam-to-beam energy balance. A thermal-plasticity coupled finite-element model (FEM) has been also carried out on the analysis of the effect of PWS in laser packaging. Numerical results show that a PWS in the DIP may be introduced from an unbalanced distribution of residual stresses introduced from the solidification shrinkage. A satisfactory agreement between the experimental results and FEM calculations suggests that the FEM may provide an effective method for predicting the PWS in laser welding technique for optoelectronic packaging.

Fiber alignment shift formation mechanisms of fiber-solder-ferrule joints in laser module packaging

The fiber alignment shifts of fiber-solder-ferrule (FSF) joints in laser module packaging under temperature cycle testing using PbSn and AuSn solders are studied experimentally and numerically. The measured results showed that the fiber shifts of FSP joints with the hard AuSn solder exhibited shifts two times less than that with the soft PbSn solder. This suggests that the hard solder may be more suitable for FSF assembly than the soft solder. The results also showed that fiber shifts increased as the temperature cycle number and the initial fiber eccentric offset increased. The experimental measurements of fiber shifts were in good agreement with the numerical calculations of the finite-element method analysis. The major fiber shift formation mechanisms of FSF joints in temperature cycling may come from the localized plastic solder yielding introduced by the local thermal stress variation, the redistribution of the residual stresses, and the stress relaxation of the creep deformation within the solder. Furthermore, the stress relaxation of creep deformation in solder with either 21% (PbSn solder) or 5% (AuSn solder) may have significant influence on the fiber shifts. This study has provided an optimum approach for reduction of the fiber alignment shift of FSF joints in laser module packaging under temperature cycle testing, which is to solder the fiber near to the center of the ferrule and to select the AuSn hard solder.

Effect of Au thickness on laser beam penetration in semiconductor laser packages

Comprehensive measurements of the dependence of the weld width, penetration depth, and joint strength on the Au coating thickness in laser welding techniques for semiconductor laser packages are presented. The results obtained from the Invar-Invar joints show that the welded joints with thick Au coating exhibit narrower weld width, shallower penetration, and hence less joint strength than those the package joints with thin Au coating. A finite-element method (FEM) has been carried out on the effect of Au thickness on laser beam penetration in Invar-Invar joints. This method has been employed successfully to predict the laser beam penetration in laser welded Au-coated materials that the weld width and the penetration depth are reduced as the Au coating thickness increases. The likely cause for the reduction is the increased thermal conduction of thicker Au in the welded region. In addition to Au coating, the effect of Ni coating on laser beam penetration is also presented. Detailed knowledge of the effect of Au coating thickness on laser beam penetration is important for the practical design and fabrication of reliable optoelectronic packaging having laser welded Au-coated materials.

Crack formation mechanism in laser-welded Au-coated Invar materials for semiconductor laser packaging

Crack formation mechanism in laser-welded Au-coated Invar materials for semiconductor laser packaging is investigated experimentally and numerically. Experimental results obtained from metallography, scanning electron microscope (SEM), SEM mapping, and energy dispersive spectrometer (EDS) line profile show that high concentration of Au composition accumulate near the crack region. The cause of Au accumulation may come from the segregation of Au along the track region. A finite-element method (FEM) is performed on the calculation of thermal stresses during spot-welding for Au-coated Invar materials. Numerical results show that the high tensile stresses of the Au segregation layer generated by rapid solidification shrinkage is the possible cause for crack formation. Both experimental and numerical results suggest that the crack formation mechanism in laser-welded Au-coated optoelectronic materials is directly related to the combined effects of the Au segregation and high tensile stresses induced by the strain shrinkage during the final stage of solidification.

Post-weld-shift in semiconductor laser packaging

Post-weld-shift (PWS) in laser welding technique for a package (DIP) with fiber pigtail to laser connection has been studied experimentally and numerically modelled. Experimental results show that the PWS of optical component welded by a dual-beam laser welding system shifts more to the counterclockwise as the energy difference of the laser beam increases. This indicates that the PWS in laser packaging can be minimized by properly controlling the laser beam energy delivery. A finite-element method (FEM) has been carried out to analyse the effect of laser beam energy variation on PWS in laser packaging. A satisfactory agreement between the experimental results and FEM calculations suggests that the FEM provides one of the effective methods for predicting the PWS in laser welding technique for optoelectronic packaging.Post-weld-shift (PWS) in laser welding technique for a package (DIP) with fiber pigtail to laser connection has been studied experimentally and numerically modelled. Experimental results show that the PWS of optical component welded by a dual-beam laser welding system shifts more to the counterclockwise as the energy difference of the laser beam increases. This indicates that the PWS in laser packaging can be minimized by properly controlling the laser beam energy delivery. A finite-element method (FEM) has been carried out to analyse the effect of laser beam energy variation on PWS in laser packaging. A satisfactory agreement between the experimental results and FEM calculations suggests that the FEM provides one of the effective methods for predicting the PWS in laser welding technique for optoelectronic packaging.

Thermally induced shifts in an optical fiber soldered into a ferrule

The thermally induced fiber shifts under a temperature cycling test of an optical fiber soldered into a ferrule packaging was measured experimentally. Up to a 0.18 /spl mu/m of the fiber shift was found in temperature cycling from -40 to +85/spl deg/C. This fiber displacement may arise from both the relief of the residual stresses and the intermetallic compound growth within the solder during the temperature cycling test. A finite-element method (FEM) analysis was also performed on the calculation of the up-bound fiber shift. Results showed that up to a 0.27 /spl mu/m of the fiber shift was predicted. This indicates that the FEM is an effective method for predicting the up-bound fiber shifts in temperature cycling test for laser module reliability study.

Effect of Au thickness on laser beam penetration in Invar-to-Invar packages

Comprehensive measurements of the dependence of the laser beam penetration on the Au coating thickness in laser welding techniques for semiconductor laser packages are presented. The results obtained from the Invar-Invar joints Show that the welded joints with thick Au coating exhibit narrower weld width, shallower penetration, and hence less joint strength than those the package joints with thin Au coating. A finite-element-method (FEM) is done of the effect of laser beam penetration On the Au thickness in the Invar-Invar joints. This method has been employed successfully to predict the laser beam penetration in laser welded Au-coated materials that the weld width and the penetration depth are found to be reduced as the Au coating thickness increases. The likely cause for the reduction is due to the increased thermal conduction of thicker Au in the welded region. Detailed knowledge of the effect of Au coating thickness on laser beam penetration is important for practical design and fabrication of reliable optoelectronic packaging having laser welded Au-coated materials.

Finite-element analysis of fiber shifts in fiber-solder-ferrule joints using AuSn solder

The thermally induced fiber alignment shifts of fiber- solder-ferrule (FSF) joints in laser module packaging under temperature cycling tests have been studied numerically by a elastic-plastic finite-element method (FEM). The FSF joints were assembled using both the Pb(37)/Sn(63) and Au(80)/Sn(20) solders. Comparison between the calculated results shows that the Au/Sn solder in the FSF joint exhibits three times less fiber than Pb/Sn solder. This is due to the higher Youngs modulus, yield strength, and melting temperature of AuSn hard solder than PbSn soft solder. This suggests that the hard solder of Au/Sn is more suitable for use in FSF assembly than soft solder Pb/Sn for laser module packaging to reduce thermally induced fiber alignment shift. Numerical calculations show that the major cause of fiber shift in FSF joints may come from the plastic solder yielding introduced by the thermal stress variation and the redistribution of the residual stresses during temperature cycling.

Fiber alignment shift in temperature cycling test

A finite-element method (FEM) analysis has been carried out on the fiber alignment shift in an optical fiber soldered into a ferule. Results show that the maximum fiber alignment shifts are strongly depend on the geometry of fiber offset from the center of the ferrule.Up to 0.24 and 0.27 micrometers of the maximum fiber alignment shifts were predicted in temperature cycling from -40 to +85 degrees C and -40 to +100 degrees C, respectively. Detailed knowledge of predicting the maximum fiber alignment shift in temperature cycling test is important for practical design and fabrication of high yield optoelectronic packaging.

Finite-element analysis of solder joint strength in laser diode packaging

The effect of PbSn solder joint strength on temperature tests in laser diode packaging has been studied experimentally and numerically. It was found that the solder joint strength increased as temperature cycle number increased. A finite-element method (FEM) analysis is performed on the calculation of joint strength of PbSn solder in temperature cycling tests for laser diode packaging. Numerical calculations were in good agreement with the experimental measurements that the solder joint strength increased as the temperature cycle increased. This is may be due to the redistribution of the residual stresses within the solder during the temperature cycling tests, and hence reducing the residual stresses and increasing the solder joint strength as the temperature cycle number increased. The result suggests that the FEM is an effective method for predicting the solder joint strength in laser diode packages.