SMTA International Conference Proceedings


Author: Ursula G. Marquez et al.
Company: Vitronics Soltec, Inc.
Date Published: 9/26/2004   Conference: SMTA International

Abstract: Selective soldering is a process for soldering thru-hole components on the bottom side of an assembly. In a selective soldering process a robot system is used to pick up the assembly and drag it over a single point select wave, or dip the assembly into multiple nozzles that are mounted on a product specific nozzle plate. In contrast, the soldering process utilizing traditional wave soldering equipment consists of transporting the entire assembly, by means of a conveyor system, over a liquid solder wave.

The implementation of lead-free alloys will affect the thermal load of components and board material due to higher process temperatures. Not all of the components can withstand the high temperatures that they may be exposed to during wave and reflow processes. For this reason selective soldering becomes interesting since in this process only the areas that come into contact with the lead-free solder will reach higher temperatures while other sections and components remain significantly below critical temperature levels.

This paper focuses on the effects of board surface finishes and selective soldering process parameters such as drag speed and solderpot temperatures, on the formation and strength of the solder joints. The analysis shows that the process development and material selection should be optimized per component type. This work was accomplished within the scope of the NEMI Lead Free Assembly and Rework Project.

Keywords: Lead Free, Selective Soldering, NEMI

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