Immersion Tin (White Tin) PCB Surface Finish
San Francisco Circuits

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January 13, 2025 - San Mateo, California - Immersion Tin, also known as White Tin, stands out as a RoHS-compliant (lead-free) PCB surface finish ideal for flat surface needs and fine pitch components.

San Francisco Circuits' application of Immersion Tin involves applying a thin layer of tin onto the copper layer of a PCB, offering exceptional flatness that supports small geometries and surface mount components. This finish is also one of the most cost-effective immersion coatings, making it a popular choice for budget-conscious designs.

Despite its affordability, Immersion Tin has some limitations, including a shorter shelf life (3-6 months) and susceptibility to tin whiskering, which may impact long-term reliability. Proper handling and timely assembly are crucial to maintaining its performance.

It's primarily used as a sustainable alternative to lead-based finishes, requiring fewer resources during its application. Its reworkability and flat surface make it an excellent choice for fine pitch components and BGA assemblies. However, it's not recommended for contact switches or applications requiring long shelf lives.

San Francisco Circuits provides comprehensive printed circuit fabrication and assembly solutions, including Immersion Tin finishes, to meet diverse industry needs. Whether for consumer electronics, telecommunications, or high-performance applications, we ensure top-quality and sustainable options tailored to your project.

Why Is It Used?

Immersion Tin has been primarily used as an alternative to a lead-based surface finish. 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 of Immersion Tin

• 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.

• 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 

While Immersion Silver offers several advantages, its sensitivity to contaminants and susceptibility to tarnishing make proper handling and storage critical. Choosing a qualified board house is essential to maintain quality and performance.

Read more about Immersion Tin PCB Surface Finish at San Francisco Circuits' website.

About San Francisco Circuits

San Francisco Circuits is a provider of PCB fabrication and assembly, has a dedicated team specializing in simple and complex PCB fabrication and assembly technologies. They can produce elaborate and high-quality PCBs in a number of custom and common layouts. From basic to intricate PCBs–their engineers will meet your PCB fabrication & assembly needs. The company provides a rare balance between technical expertise and competitive pricing. And they not only provide high-quality products but also high-quality customer service at the same time. San Francisco Circuits has been voted by National Television as the "world's greatest in PCBs" and has demonstrated experience as a power player in PCB fabrication and assembly.

If you are looking to discuss PCB projects of any size or scope, feel free to reach out to them via our website (see below).

Contact

Alex Danovich
San Francisco Circuits, Inc.
Phone: 1-800-732-5143

Web:  www.sfcircuits.com