The electronics manufacturing industry is gradually moving towards a lead-free environment. To switch from tin-lead soldering to lead-free soldering is by no means a simple process. As the industry migrates to a lead-free environment, there will be a period where lead-free materials will need to coexist with those containing lead on the same assembly. During this transition period, the use of tin-lead solder with lead-free parts and lead-free solder with components containing lead can hardly be avoided.; Solder voids are the holes and recesses that occur in the joints. Voiding has been a controversial topic for many years. Some say the presence of voids is expected to affect the mechanical properties of joint and reduce strength, ductility, creep, and fatigue life. Some believe that it may slow crack propagation by forcing a re-initiation of the crack. Therefore, it has the ability to stop a crack.; The primary objective of this research endeavor was to develop a robust assembly process for the mixed alloy assemblies such that the occurrence of voids is minimized. The impact of voiding on leaded assemblies is documented. However, its impact on lead-free assemblies, and more recently on mixed-alloy assemblies, has not been evaluated. This research entails a detailed study on the formation of voids for each of the abovementioned assembly types. Analytical models based on regression analysis and neural networks are developed to understand the relationship between the formation of voids and the various process parameters considered in this study.; Based on the results obtained through this research effort with respect to voids in solder joints, an optimal combination of various process parameters is prescribed in order to minimize voids in mixed-alloy assemblies. For mixed alloys, the optimal parameters are as follows: nickel gold surface finish, 4 mil thick stencil, soak profile type, time above liquidus of 30-60 seconds and 0.5 mm pitch components. For the tin-lead and lead-free assemblies, the same parameters are considered to be 'optimal', with the exception of surface finish. The most important finding of this research effort was that the mixed alloy assemblies can be built with minimal voids.
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