Soldering Problems due to Residues of a Surfactant
Cleaning forms an integral part in almost all production processes. In particular, cleaning is necesary as preparation of parts before soldering. The success of a cleaning step is not only determined by the character of the contamination that needs to be removed. The choice of surfactant and the frequency of changing the cleaning bath or the tools have a considerable influence on the effect of the cleaning step. The quality of the final rinsing step is also often neglected. This step is, among others, decisive for the presence of surfactant residues on the surface which can lead to adhesion problems.
Example: Despite a thorough degreasing step and a subsequent plasma cleaning treatment, adhesion problems occurred on a nickel surface in the following soldering step. In order to identify the problem, the lateral distribution of detected components was investigated by ToF-SIMS. This analysis showed the presence of dodecylbenzenesulfonic acid (DBSA) on the surface of the cleaned metal. This chemical was identified as a component of the used cleaning agent and was not removed completely from the metal surface due to insufficient rinsing. A subsequent plasma cleaning step did not lead to a complete removal of the DBSA layer either causing the adhesive failure. Based on these analytical results, the final cleaning of the nickel plate could be improved and the failure rate during soldering could be reduced considerably.
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