PW Circuits Provides PCB Surface Finish Options for Diverse Assembly and Interconnection Requirements

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PW Circuits, a provider of PCB fabrication, assembly, design support, and surface finish solutions for a range of electronic application, provides a range of PCB surface finish options designed to protect copper traces from corrosion, improve solderability, and support different assembly and interconnection requirements across printed circuit board applications.

PCB surface finishes play a critical role in determining solderability, corrosion resistance, RoHS compliance, and compatibility with manufacturing processes. PW Circuits outlines multiple finish technologies, ranging from standard and RoHS-compliant finishes to advanced solutions for wire bonding and high-frequency applications.

Standard PCB Surface Finishes

PW Circuits offers several commonly used PCB finishes, including Hot Air Solder Leveling (HASL), lead-free HASL (LF-HASL), immersion silver, and Electroless Nickel Immersion Gold (ENIG). Lead-free HASL is a RoHS-compliant alternative to traditional leaded HASL and is applied by solder dipping followed by removal of excess solder using air knives. Immersion silver deposits silver onto exposed copper surfaces and is compatible with surface mount, BGA, and through-hole components. ENIG uses a nickel layer followed by a thin gold coating to provide wear resistance, solderability, and deposition uniformity. The gold layer protects the nickel surface from oxidation while maintaining compatibility with multiple assembly technologies.

Surface Finish Characteristics

PW Circuits compares PCB finishes across characteristics including planarity, solderability, wire-bonding capability, and suitability as contact surfaces. HASL and LF-HASL provide good solderability but are not suitable for aluminum or gold wire bonding. Immersion silver and ENIG support aluminum wire bonding, while ENEPIG and soft gold support both aluminum and gold wire bonding applications. ENIG, ENEPIG, hard gold, and soft gold can also serve as contact surfaces.

Special Requirement PCB Finishes

The company also provides specialized finishes for applications with unique performance requirements. Leaded HASL remains available where RoHS exemptions permit its use. Hard gold, produced through an electrolytic plating process, is commonly used for edge connectors and may also be plated across entire PCBs. Electrolytic pure soft gold consists of 99.99% pure gold and is typically used for wire-bonding applications.

Organic Solderability Preservatives (OSP) create an anti-oxidation layer on exposed copper surfaces through an organo-metallic coating while maintaining RoHS compliance.

Advanced PCB Finish Technologies

PW Circuits offers advanced finishes including Immersion Silver/Immersion Gold (ISIG) and Electroless Nickel/Palladium/Gold (ENEPIG). ISIG is a nickel-free finish that uses a two-step process involving silver followed by gold deposition. The finish supports aluminum and gold wire bonding, fine-line circuitry, flexible PCBs, and high-frequency signal transmission, although it has a shorter shelf life than some alternatives.

ENEPIG consists of electroless nickel, electroless palladium, and immersion gold layers. The multilayer finish is designed to prevent copper oxidation while supporting soldering and wire-bonding applications. The palladium layer also prevents nickel corrosion during processing.

By offering a broad portfolio of standard, specialized, and advanced surface finishes, PW Circuits supports PCB designs with varying requirements for solderability, interconnection reliability, wire bonding, and environmental compliance.

Click here to learn more about the PW Circuits' PCB surface finishes.