SMTA International Conference Proceedings


Authors: Gunter Hagen, Klaus Wolter, and Armin Wagner
Company: Dresden University of Tech
Date Published: 9/22/2002   Conference: SMTA International

Abstract: Vacuum soldering has long been a common joining technique for various applications, mainly dealing with hard soldering (brazing) without flux, where vacuum is used as an atmosphere, which sufficiently prevents oxidation through low residual partial gas pressures and partially removes oxides.

The application in electronics manufacturing, where predominantly soft solders are used, is however rather restricted, whereat reasons for using vacuum in soldering electronics are the possibility for fluxless soldering and the potential to reduce or prevent trapped gas volumes within the solder joint (voids). The aim of current works at our laboratory is to evaluate the applicability of fluxless vacuum soldering for electronics packaging purposes.

This paper will discuss some aspects of fluxless soldering and give a short overview of existing approaches. Thermodynamical aspects of oxidation and oxide reduction in vacuum will be treated.

Experiments being described include the observation of wetting behaviour during fluxless solder reflow carried out within an ESEM, the application of vacuum soldering to fluxless solder ball attach, the extraction of voids from solder joints using a vacuum process, and the realization of larger area plane solder joints for joining ceramic substrates using solder foil.

Key words: vacuum, soldering, fluxless, voids.

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