Immersion Tin

The Immersion Tin surface finish describes a very thin layer of tin, applied over the copper layer of a PCB. This method is a Lead-Free PCB alternative that produces a consistently flat surface, which solders well and is cost-efficient. The tin layer’s appearance is usually mostly white, so the finish is sometimes referred to as White Tin, and is applied to the copper using an electroless chemical bath. This tin surface finish can protect the copper beneath from oxidation throughout the PCB’s intended shelf life.

The Immersion Tin surface finish has a relatively long shelf life, but does require careful handling during the PCB Assembly Process. Due to the potential for handling damage, Bittele strongly recommends our Complete PCB Assembly service for projects requiring the Immersion Tin finish; when PCB Fabrication and PCB Assembly take place under one roof, the potential for shipping & handling mishap is minimized.

One problematic aspect of this finish is the strong affinity of tin and copper for one another, allowing for the diffusion of one metal into the other. This process can cause the formation of “tin whiskers”, which are small strands of diffuse tin that can cause shorts and reduce the quality of solder joints, negatively impacting the shelf life and the performance of the PCB.

Pros

Lead-free
High Reliability
Flat Surface/Planar
Cost Effective
Can Substitute for Reflowed Solder
Top Choice for Press Fit Pin Insertion
Re-workable

Cons

Not Good for PTH
Process Uses Thiourea, a known Carcinogen
Not Good for Multiple Reflow/Assembly Processes
Tin Whiskers
Could Damage Solder Mask
Easy to Cause Handling Damage
Difficult to Measure Thickness

We at Bittele offer Immersion Tin as one of our PCB Options at a Standard Price, meaning no additional cost will be applied for selecting this finish. The table below lists our available surface finish options for your reference, along with some basic associated information for each finish.

If you still find yourself with any questions about Immersion Tin or any other surface finish, or to send along your PCB Design Files for an official quotation, please feel free to Contact Us at any time! Bittele is a Canadian PCB Assembly service provider, supplying top-quality PCB products and services to our clients worldwide, which includes helping you to determine which surface finish option is right for your project. To get in touch with one of our PCB experts today, you can send email to sales@7pcb.com, or call us toll-free at 1-888-812-1949.