Immersion Tin has been primarily used as an alternative to a lead-based surface finish in Flexible PCB manufacturer’s factory. It is also used for its very flat and smooth finish making it ideal for fine geometries and fine pitch surface mount components.

Another reason to use immersion tin is sustainability. Elements that may be difficult to source on a consistent basis are used in other finishes, such as ENIG or HASL. Additionally, it uses less water and chemicals in the application process.

It is also easier to re-work.

As with all of the surface finishes we’ve compared so far, there are a number of advantages and disadvantages. Here are the advantages and disadvantages for Immersion Tin.

Advantages:

• Immersion Tin Finish allows excellent flatness (suitable for SMT), good for fine pitch / BGA / smaller components
• Immersion Tin has mid-range cost for lead-free finish
• Press fit suitable finish
• Retains good solderability after multiple thermal excursions
• Suitable for horizontal production line.
• Suitable for fine geometry processing, lead-free assembly.

Disadvantages:

• Sensitive to handling.
• Short shelf life, tin whiskering can occur after 6 months
• Aggressive to solder masks
• Not recommended to use with peelable masks
• Not a suitable choice for a contact switches.
• Special setting requires (soft probe landing) for electrical test