Abstract
ABSTRACTHigh temperature joints are required for packaging and assembling the emerging high temperature semiconductor devices. A technique of producing high temperature joints at relatively low process temperature is presented. The technique uses liquid-solid interdiffusion to formulate the joint and subsequent solid-state diffusion and interaction to convert the joint material into high temperature alloy. Processes have been developed using the indium-silver binary material system. Joint melting temperature higher than 700°C has been achieved while the process temperature stays below 210°C. In this development effort, the constituent element materials are deposited in multilayer structure in high vacuum to prevent oxidation. As a result, no flux is used and no scrubbing action is applied. The joints produced are examined with a scanning acoustic microscope (SAM) to evaluate the bonding quality. The joint cross-sections are studied using SEM and EDX to find the microstructure and composition. In conventional processes, the process temperature needs to exceed the alloy melting temperature in order to produce a joint. High stresses can develop due to thermal expansion mismatch among materials involved. In the present technique, the relatively low process temperature can significantly reduce the stresses. The multilayer bonding method also facilitates control of the alloy composition and the joint thickness.
Published Version
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