The Influence of Flux on the Reliability of Solder-Sealed Hermetic Packages for Active Implantable Medical Devices

Abstract

This paper discusses the influence of fluxing materials on the properties of lead-free solder seals on screenprinted metal thick films. Pull tests revealed a strong impact on the layer adhesion if an aggressive flux is used. A milder flux was able to improve the pull test results slightly. Investigations on the hermeticity demonstrated the difficulty of hermetic packaging with SnAg solder. None of the fluxes under test allowed the manufacturing of hermetic packages in the desired range of 10 -9 mbar l s -1 or lower. Consequently we came to the decision to use lead containing SnPb solder compounds until further investigations on the processing of lead-free materials are performed.