Surface treatment processes in PCB manufacturing are critical to ensure solderability, corrosion resistance, electrical properties, and long-term reliability of the board. The following are some common PCB surface treatment processes and their performance and role:
Hot Air Solder Leveling (HASL, Hot Air Solder Leveling):
Performance: Forms a layer of tin-lead alloy on the PCB surface with good solderability and corrosion resistance. There are two kinds of processes: lead and lead-free.
Role: Protect the copper layer from oxidation, provide a good soldering surface, suitable for a variety of soldering processes.
Organic Solderability Preservatives (OSP, Organic Solderability Preservatives):
Performance: Forms a layer of organic protective film on the copper surface to prevent copper oxidation and provide good solderability.
Role: For short-term storage and use of PCB, environmental protection, suitable for lead-free soldering.
Electroless Nickel Immersion Gold (ENIG, Electroless Nickel Immersion Gold):
Performance: Wrapping a layer of nickel and gold on the copper surface, providing excellent solderability and corrosion resistance, high flatness.
Role: For high-density, fine-pitch PCB, long-term storage without oxidation, suitable for lead-free soldering.
Sinking Tin (Immersion Tin)
Performance: Deposits a layer of tin on the copper surface, with good solderability.
Role: For PCBs that need to be assembled quickly, but the storage time is limited and susceptible to environmental influences.
Immersion Silver
Performance: Deposited on the copper surface of a layer of silver, with good conductivity and solderability.
Role: Suitable for high-frequency and high-speed applications, but the silver layer will lose its luster under long-term exposure.
Electroless Nickel Palladium Immersion Gold (ENEPIG, Electroless Nickel Electroless Palladium Immersion Gold):
Properties: A palladium layer is added between nickel and gold to improve corrosion resistance and solderability, with a high degree of flatness.
Role: Suitable for high performance electronics, providing long term reliability.
Electroplating Hard Gold (EHG):
Performance: Electroplating a layer of higher hardness gold on the nickel layer, good wear resistance.
Role: Suitable for connectors that require multiple insertion and removal, improving wear resistance and reliability.
Laser Marking:
Performance: Using laser to engrave marks or patterns on the PCB surface with high precision.
Role: Suitable for high-precision, high-quality marking needs, no pollution.
Chemical tin-silver plating (ENEPIG, Electroless Nickel Electroless PALLADIUM Immersion Gold):
Properties: Forms a layer of nickel, palladium and gold on a copper surface, providing excellent corrosion resistance and solderability.
Role: Suitable for applications with high performance and reliability requirements, such as aerospace and military.
Carbon Ink / Peelable Blue Mask:
Performance: A carbon ink or peelable blue mask is applied to the PCB surface to protect the copper surface from oxidation.
Function: Suitable for PCBs that require temporary protection for subsequent processing and handling.
Choosing the right type of PCB finish is just as important as choosing a PCB manufacturer; using the wrong type of finish can lead to downstream problems during assembly or long-term reliability issues. Therefore, manufacturers need to choose the right surface treatment process for their specific needs in order to improve the reliability and stability of their PCBs. At the same time, attention needs to be paid to controlling process parameters and quality testing during the manufacturing process to ensure the quality of the surface treatment and the overall quality of the PCB.