Cost-Effective Optoelectronic Packages Using Powder Metallurgy

In this paper, we propose powder metallurgy for optoelectronic packages in order to reduce the cost of laser packages. Conventional die compaction (DC) and metal injection molding (MIM) are used for the shaping of powder metallurgy. The distinguishing types of inherent porosity in DC and MIM steels have their respective effects on the defect mechanisms of laser welding joints. For DC steel with 85% relative density and continuous porosity, the rising gas pressure pushes the molten metal out of the welding regions, resulting in weak and unstable welding joints. For MIM steel with more than 95% relative density, the laser power dominates the defect mechanisms, and the defect-free welding joints with optical spot size of 400 mum can be attained by using laser power of less than 1.0 kW. Although elimination of inherent porosity in MIM steel under optimum welding condition can give rise to additional postwelding-shift (PWS), it is still controlled to less than 2 mum, resulting in optical coupling loss of less than 15%. The advantage of applicability of the MIM method to several materials makes it possible to employ SS316L, Kovar, and Invar, which have the characteristic of better property for laser welding but difficult machining, as the metal housing in low-cost lightwave communication system. Thus, using MIM Invar with low coefficient of thermal expansion can minimize the tracking error, which is an important issue for bidirectional and triple-directional optoelectronic packages. The reliability data demonstrate that the laser modules using MIM steel as construction housing are stable and reliable