The Journey of Printed Circuit Board (PCB) Finishes: From Tin-Lead to Gold
As technology rapidly advances, so does the printed circuit boards (PCBs) and how they are finished. A PCB finish is a thin layer applied to the copper substrate of a PCB to protect it from oxidation and to ensure a stable connection. PCB finishes have evolved over the years, from tin-lead to gold to the newer options such as Immersion Tin (ISn) and Electroless Nickel Immersion Gold (ENIG). This blog post explores the journey of PCB finishes, highlighting the benefits and drawbacks of each option.
The use of Tin-Lead finishes was the predominant option for many years. However, this process had environmental implications, and the advent of RoHS compliance led to the decline of this process due to its negative impact on the environment. The Tin-Lead finish has been replaced entirely by Lead-Free alternatives. Although Tin-Lead remains an excellent option for the aerospace and military industries, it is slowly becoming a dying finish.
Gold remains one of the most popular finishes in the PCB market due to its durability and conductivity. Even though the cost of adding gold to your board is more expensive than other options, it remains the standard for applications that warrant a high level of consistent performance. One of the most significant benefits of the Gold finish is its corrosion resistance, making it an excellent option for boards that will be used in harsh environments.
Immersion Tin (ISn) Finish:
Immersion Tin is a RoHS compliant option that is cost-effective and available for high-volume production. It is an excellent finish option that allows for good solderability, making it a perfect fit for surface mount assembly. However, it is not suitable for long storage periods, and if the soldering process is not completed relatively quickly, the PCB runs the risk of oxidation.
Electroless Nickel Immersion Gold (ENIG) Finish:
Electroless Nickel Immersion Gold, popularly known as ENIG, is a combination of two finishes. It was created to address the challenges of the preceding finishes. ENIG provides excellent oxidation protection, and the copper material withstands several soldering cycles without the risk of being exposed to oxidation. The Nickel layer provides an excellent barrier for corrosion, while the Gold layer ensures the durability and longevity of the PCB. They are also RoHS compliant.
PCB finishes have come a long way, and the journey keeps getting more innovative. Finishes like HASL, OSP, and Silver have emerged as viable options that fill specific niches. Choosing the right PCB finish will differ per application, as some finishes will offer more advantages for your specific design compared to others. In conclusion, it is imperative to do adequate research before selecting a PCB finish to ensure that you choose the correct finish that will maximize your board’s performance and longevity.