A composition without contamination in the tin layer is required for a perfect soldering result. The tin coating of APL Hofstetter is dense compact, microcrystalline and has a very low amount of pores. Through suitable measures, APL Hofstetter keep the process-related shares of tin (IV+) compounds, copper and other decomposition products in the deposition tin coat as low as possible.

Repeated soldering is thereby possible with our immersion tin. A study by Fraunhofer ISIT (Institute for Silicon Technology), Itzehoe (No. 394956, October 09/2009 and No. 397142 11/2014) demonstrates a clear durability and resilience of the immersion tin layer. In this series of tests the pcbs actually stored for a specific period were fundamentally checked. The results emphasize our definition of a high-quality soldering surface.


Based on the physical features of chemical tin it’s regarded as a first choice in surfaces if the further application will be press fit technology. The ca. 1.0 µm thick tin layer serves as a “sliding surface” in this process technology. Contact corrosion can not occur between the press-fit pin and the immersion tin layer because the surface finish of the pin is the same material (tin).

Immersion tin refresh process

Trough the refresh process APL Hofstetter is able to transform pcbs with soldering problems to a solderable condition.

The not solderable tin layer does not have to be stripped from the pcb. The procedure of refresh with the tin-on-tin process occur a new tin layer on top of the old solderable tin coat. The increase of pure tin is about 0,1 – 0,25 µm depending on the intermetallic phase of the “unusable” tin layer.

In cooperation with Fraunhofer ISIT (Institute for Silicon Technology) APL Hofstetter is appropriate to prove the refresh process. Content of copper in the intermetal phase will be dissolved in the process of refresh tin plating. In return a new pure tin layer is deposited through this exchange reaction.

The refreshing process is often more cost-effective than a new manufacturing of pcb batches. That’s a possibility to save costs for your end customers. The storage of goods at APL Hofstetter lead to an “just-in-time” process in that way the pcbs will not be stored to long again. This will be a benefit for your customers because the goods are delivered to the assembly line in a “fresh” state.

If you need further information about our refresh process, do not hesitate to contact us.