In the PCB production process, the surface treatment process is a very important step. It not only affects the appearance of the PCB, but is also directly related to the functionality, reliability and durability of the PCB. The surface treatment process can provide a protective layer to prevent copper corrosion, enhance soldering performance, and provide good electrical insulation properties. The following is an analysis of several common surface treatment processes in PCB production.
一.HASL (Hot Air Smoothing)
Hot air planarization (HASL) is a traditional PCB surface treatment technology that works by dipping the PCB into a molten tin/lead alloy and then using hot air to “planarize” the surface to create a uniform metallic coating. The HASL process is low-cost and suitable for a variety of PCB manufacturing, but may have problems with uneven pads and inconsistent metal coating thickness.
二.ENIG (chemical nickel gold)
Electroless nickel gold (ENIG) is a process that deposits a nickel and gold layer on the surface of a PCB. First, the copper surface is cleaned and activated, then a thin layer of nickel is deposited through a chemical replacement reaction, and finally a layer of gold is plated on top of the nickel layer. The ENIG process provides good contact resistance and wear resistance and is suitable for applications with high reliability requirements, but the cost is relatively high.
三、chemical gold
Chemical Gold deposits a thin layer of gold directly on the PCB surface. This process is often used in applications that do not require soldering, such as radio frequency (RF) and microwave circuits, because gold provides excellent conductivity and corrosion resistance. Chemical gold costs less than ENIG, but is not as wear-resistant as ENIG.
四、OSP (organic protective film)
Organic protective film (OSP) is a process that forms a thin organic film on the copper surface to prevent copper from oxidizing. OSP has a simple process and low cost, but the protection it provides is relatively weak and is suitable for short-term storage and use of PCBs.
五、Hard gold
Hard Gold is a process that deposits a thicker gold layer on the PCB surface through electroplating. Hard gold is more wear-resistant than chemical gold and is suitable for connectors that require frequent plugging and unplugging or PCBs used in harsh environments. Hard gold costs more than chemical gold but provides better long-term protection.
六、Immersion Silver
Immersion Silver is a process for depositing a silver layer on the surface of PCB. Silver has good conductivity and reflectivity, making it suitable for visible and infrared applications. The cost of the immersion silver process is moderate, but the silver layer is easily vulcanized and requires additional protection measures.
七、Immersion Tin
Immersion Tin is a process for depositing a tin layer on the surface of PCB. The tin layer provides good soldering properties and some corrosion resistance. The immersion tin process is cheaper, but the tin layer is easily oxidized and usually requires an additional protective layer.
八、Lead-Free HASL
Lead-Free HASL is a RoHS-compliant HASL process that uses lead-free tin/silver/copper alloy to replace the traditional tin/lead alloy. The lead-free HASL process provides similar performance to traditional HASL but meets environmental requirements.
There are various surface treatment processes in PCB production, and each process has its unique advantages and application scenarios. Choosing the appropriate surface treatment process requires considering the application environment, performance requirements, cost budget and environmental protection standards of the PCB. With the development of electronic technology, new surface treatment processes continue to emerge, providing PCB manufacturers with more choices to meet changing market demands.