Introduction

When it comes to Printed Circuit Boards (PCBs), the surface finish plays a crucial role in their overall functionality, reliability, and longevity. PCBs with the right surface finish provide protection against oxidation, wear & tear, and environmental factors. Surface finishes also determine the ease of soldering and other assembly processes.

In this blog post, we will compare two popular surface finish options for PCBs - Surface Mount Technology (SMT) Solder Mask Over Bare Copper (SMOBC) and Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG). We'll provide an unbiased comparison with relevant facts, figures, and references.

SMT Solder Mask Over Bare Copper (SMOBC)

SMOBC is a surface finish option where a solder mask is applied over a bare copper surface. It is one of the most cost-effective and widely used surface finishes in the industry due to its simplicity and durability.

Pros:

• Cost-effective
• Excellent solderability
• Provides good protection against oxidation

Cons:

• Limited shelf-life due to the tendency to oxidize
• Prone to wear & tear with repeated assembly and disassembly
• Thickness of the copper layer can vary depending on the etching process

Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG)

ENEPIG is a surface finish option that involves electroless nickel plating, followed by electroless palladium plating and immersion gold plating. This surface finish is well-suited for complex PCB designs with fine-pitch components and high-density interconnects.

Pros:

• Provides excellent corrosion resistance
• RoHS-compliant
• Suitable for a wide range of applications, including high-frequency circuits, PCBs used in harsh environments, and medical implants
• Provides a uniform surface finish, ensuring consistent performance across the board

Cons:

• Expensive compared to other surface finishes
• Slower manufacturing process due to multiple plating steps

Comparison

Conclusion

Both SMOBC and ENEPIG are excellent surface finish options for PCBs, but they differ in terms of their properties, manufacturing processes, and costs. The choice of surface finish depends on the specific requirements of the PCB, such as its application, operating environment, and budget.

We hope this comparison helps you make an informed decision about which surface finish to choose for your next PCB project. For more information, please refer to the references below.

References

1. "Surface Finish Selection for SMT and BGA Assemblies," IPC Association Connecting Electronics Industries, July 2005.
2. "Printed Circuit Board Finish Types," Altium, accessed January 2022.
3. "Surface Finishes for Printed Circuit Boards," Tech-Etch, accessed January 2022.
4. "ENEPIG: The Surface Finish Solution for High-Reliability Applications," Advanced Assembly, accessed January 2022.