Chemical tin
This surface is as planar as the surface of chemical gold but only specialized manufacturers are able to handle it. Its properties are similar to those of HAL. The shelf life of chemical tin depends on the temperature and on the packaging because of a faster oxidation process.
PROS:
- pads are planar
- suitable for fine pitch applications
- suitable for SMD
- best surface for press fit connectors
CONS:
- high priced version
- difficult manufacturing process (fingerprints on the surface corrupt the solderability)
- limited shelf life (approx. 6 months)
- multiple soldering is only possible to a limited extent (reflow soldering with nitrogen is recommended)
