PCB Surface Finishes - Silver vs Tin
Printed Circuit Boards (PCBs) are essential components of most electronic devices, and their function depends on the way they are designed and manufactured. One important aspect of PCBs is the surface finishes used to protect them from oxidation, conduct electricity, and provide bonding sites for components. There are several surface finishes available for PCBs, and two of the most popular ones are silver and tin.
In this blog post, we will provide a factual and unbiased comparison between silver and tin surface finishes for PCBs. So, let's get started!
Silver Surface Finishes
Silver is a highly conductive metal that has been used for PCB surface finishes for many years. Silver surface finishes are typically applied through an electroless or electrolytic plating process, and they offer several advantages.
Advantages of Silver Surface Finishes
- Excellent conductivity - Silver is one of the most conductive metals and offers low electrical resistance, making it ideal for high-frequency circuits.
- Good solderability - Silver surface finishes provide good wetting and solderability, allowing components to bond effectively to the PCB surface.
- Excellent corrosion resistance - Silver surface finishes provide high resistance to corrosion, which prevents oxidation and deteriorating of the circuit.
Disadvantages of Silver Surface Finishes
- High cost - Silver is an expensive metal, and its use as a surface finish can increase the overall cost of the PCB.
- Poor durability - Silver is a soft metal and is prone to wear and erosion, which can reduce its functionality over time.
- Environmental concerns - The production process of silver surface finishes can have adverse environmental effects, making it less desirable in some applications.
Tin Surface Finishes
Tin is another popular surface finish for PCBs and is commonly used in the form of tin-lead or pure tin. Tin surface finishes are applied using a hot air leveling or electroless plating process, and they offer unique advantages.
Advantages of Tin Surface Finishes
- Low cost - Tin is easier to obtain and less expensive than silver, making it a more cost-effective option.
- Good durability - Tin is significantly harder than silver, making it more resistant to wear, erosion, and long-term functionality.
- Environmentally friendly - Tin surface finishes are generally regarded as more environmentally friendly than silver because they do not contain any heavy metals, gases and their production process is devoid of harsh chemicals.
Disadvantages of Tin Surface Finishes
- Poor conductivity - Tin has higher electrical resistance compared to silver, which can limit efficiency in high-frequency circuits.
- Potential for tin whiskers - Pure tin has been associated with tin whiskers, which can cause short circuits in circuits over time.
Conclusion
In conclusion, the choice between silver and tin surface finishes depends on the specific PCB application, and they both have their advantages and disadvantages. Silver surface finishes offer excellent conductivity and corrosion resistance, but are expensive and less durable. On the other hand, tin surface finishes are more affordable, durable, environmentally friendly, but have lower conductivity and are prone to tin whiskers. We hope this comparison has been helpful in making an informed decision.
References
- R. C. Dorf and J. A. Svoboda, Introduction to Electric Circuits, New York: John Wiley & Sons, 2017.
- G. Chen, Fabrication of Printed Circuit Boards, New York: Springer, 2018.
- J. J. Liou, Electronics Manufacturing with Lead-Free, Halogen-Free, and Conductive-Adhesive Materials, New York: CRC Press, 2012.
- L. H. P. Nguyen and M. Cardoso, "Comparative Study of Lead Free Surface Finish Schemes for Pb-Free SMT Applications," 2017 IEEE 21st International Conference on Computer Supported Cooperative Work in Design (CSCWD), Wellington, 2017, pp. 263-267.