What are the benefits of using ENIG as surface finish?

PCB immersion gold process is a surface treatment technology that uses chemical deposition to create a thin layer of metal coating on the pads or other metallized areas of the circuit board. The following are the main advantages of the immersion gold process and its applicable situations:

Advantages of immersion gold process:

1. Good conductivity: Gold has good conductivity and can ensure reliable connection of the circuit board.

2. Anti-oxidation and corrosion resistance: The metal properties of gold are relatively stable, the crystal structure is relatively dense, and it is not easy to undergo oxidation reactions. It can effectively prevent oxidation and corrosion, protect the copper foil from environmental influences, and extend the service life of the circuit board.

3. It can be reflowed many times and has good solderability: The crystal structure formed by immersion gold is easier to weld than other surface treatments, and can provide stable welding effects. Even long-term storage will not affect the welding quality.

4. Contact reliability: In applications that require frequent plugging or contact, the gold layer can reduce contact resistance and improve the stability of electrical connections.

5. Flatness: The immersion gold process can usually provide better flatness and flatness, which is very beneficial for the installation of precision components. Chips like FPGAs are especially difficult to weld with pins.

6. Controllable thickness: The thickness of the immersion gold layer can be precisely controlled by process parameters to meet different application requirements.

7. Suitable for fine-pitch devices: For high-density PCB design, the board surface flatness and uniform thickness after immersion gold are suitable for fine pitch (high-density interconnect, HDI) and micro-via technology.

The immersion gold process has many advantages, so it is widely used in various scenarios:

1. Products with high reliability requirements: Military equipment, aerospace equipment, medical equipment and other products that require long-term stable operation have extremely high reliability requirements. The immersion gold process can provide them with excellent reliability and durability to meet the stringent requirements of the equipment during long-term use.
2. High-density assembly field: In the application scenarios of high-density assembly (HDI) boards and micro-via technology, the immersion gold process can play a key role. It can provide better flatness and smoothness, create good conditions for the assembly of tiny components, and help improve the accuracy and quality of the overall assembly.
3. Frequently plugged and unplugged connectors: Connectors such as the CPU socket on the server motherboard that need to be frequently plugged and unplugged are prone to contact wear during use. The immersion gold process can effectively reduce this wear and tear, significantly increase the service life of the connector, and ensure the stable operation of the equipment.
4. Precision measuring instruments: In precision measuring and testing equipment, it is crucial to ensure good contact performance. The immersion gold process can reduce signal loss, provide reliable protection for high-precision measurement of the instrument, and ensure the accuracy of the measurement results.
5. Application in harsh environments: When the equipment is in a harsh environment with high humidity, large temperature changes, or corrosive gases, the immersion gold process can provide additional protection. It can effectively resist the erosion of environmental factors on the equipment and extend the service life of the equipment in harsh environments.

Although the immersion gold process has many advantages, there are also some potential limitations:

• High cost: The immersion gold process requires the use of precious metals such as gold salts as raw materials. Special equipment is also required for manufacturing, the purchase cost of the equipment is high, and daily maintenance and maintenance require certain expenses. The immersion gold process includes multiple steps, and ensuring the quality and effect of the immersion gold will lead to an increase in production costs. Wastewater containing heavy metal ions will be generated in the immersion gold process, so special wastewater treatment equipment and processes are required to treat the wastewater to meet environmental emission standards.

• Limited soldering strength: immersion gold deposits a thin layer of gold on the copper surface through chemical replacement reaction to prevent copper oxidation, thereby improving the solderability and contact performance of the surface. Generally speaking, the gold layer is very thin. During the soldering process, if the soldering temperature and time are not properly controlled, the gold will quickly dissolve into the solder, causing the composition at the soldering interface to change, which may affect the soldering strength. And the soldering strength of the immersion gold process may not be sufficient to fix electronic devices stably for a long time.

• Risk of black pad or black nickel: In the immersion gold process, if there is a problem with the composition of the chemical nickel plating solution, the plating solution is contaminated by impurities, the gold layer is unevenly deposited or is too thin to completely cover the nickel layer, it may cause the generation of black pad and black nickel. Both phenomena will seriously affect the electrical performance and solderability of the product.