Development of an optical inspection method for evaluating the surface condition of metal surfaces to be brazed

Project leader: Prof. Dr. Wolfgang Maus-Friedrichs, Dr. Lienhard Wegewitz Funding period: 01/2020 - 12/2022 Funding body: AiF / IGF Funding code: 21538 N

Researcher: N.N.

Development of an optical inspection method for the evaluation of the surface condition of metal surfaces to be brazed

For a close-meshed quality control in the soldering production there is a lack of fast and cost-effective measuring methods with sufficient reliability for the evaluation of the solderability of component surfaces. The aim of the project is to use spectroscopic ellipsometry to identify optical properties of metal surfaces that are at least suitable for making reliable statements ("IO" or "non-IO") about the surface condition of these metals with regard to their solderability. For this purpose, the surfaces of materials used in brazing technology (unalloyed and alloyed steels, copper) are modified in a defined manner (oxidized, contaminated with oils, etc.) and their optical behavior is measured by means of ellipsometry. At the same time, the adjusted surface conditions are analyzed in terms of material science and their wetting behavior during brazing is investigated. From this, a correlation between adjusted surface states, their soldering and wetting behavior and the optical properties of the surface will be obtained, which will allow to evaluate its solderability exclusively on the basis of the measured optical properties of the surface. The results should enable the realization of an automatic optical inspection method for component surfaces before (and possibly) after soldering, which could ideally be implemented by means of a very simply constructed ellipsometer suitable for harsh environmental conditions with a measuring range adapted to the material. Particularly with regard to SMEs involved in contract brazing production, for example, such a measuring method would represent a cost-effective and easy-to-use instrument for improving component quality and minimizing rejects in brazing production.