Difference Between Immersion Gold and Gold Plating

Before talking about the difference between immersion gold and gold plating processes, let’s first know what they are.

What is gold plating and what is immersion gold?

Immersion gold, also called immersion nickel gold or chemical nickel gold, is a process in circuit board processing. It is the PAD required for welding and patching in the circuit diagram. Immersion gold prevents oxidation of the pad and facilitates welding.

Immersion gold forms a layer of coating through chemical oxidation-reduction reaction, which is generally thicker. It is one of the electroless nickel gold deposition methods that can achieve thicker gold layers.

Gold plating uses the principle of electrolysis, also known as electroplating. Most other metal surface treatments also use electroplating. The whole PCB is gold-plated, we generally refer to electroplated gold, electrolytic nickel-gold plate, electrolytic gold, electroplated gold, electroplated nickel-gold plate. There is a difference between soft gold and hard gold (usually gold fingers use hard gold).

The principle is to dissolve nickel and gold (commonly known as gold salt) in a chemical solution, immerse the circuit board in an electroplating bath and energize it, forming a nickel-gold plating layer on the surface of the copper foil of the circuit board.

Electroplated nickel gold has been widely used in electronic products due to its high hardness, wear resistance, and resistance to oxidation.

The difference between immersion gold and gold plating

1. Principle difference

Immersion gold uses chemical deposition method.

Gold plating uses the principle of electrolysis.

2. Appearance difference

Glod plating will have electroplated gold leads, but immersion gold will not. And if the requirements for gold thickness are not high, the method of immersion gold is used.

For example, the memory strip PCB uses a immersion gold method on its PAD surface.

The gold finger uses either immersion gold or gold plating.

3. Differences in production processes

Gold plating, like other electroplating, requires electricity and a rectifier. There are many types of processes, including those containing cyanide, non-cyanide systems, and non-cyanide systems including citric acid type, sulfite type, etc. All systems used in the PCB industry are non-cyanide systems.

Immersion gold does not require electricity. It deposits gold on the plate through a chemical reaction in the solution.

They each have their own advantages and disadvantages. In addition to being energized or not, gold plating can be made very thick, as long as the time is extended, and it is suitable for bonding boards. The probability of discarding gold plating potion is smaller than that of immersion gold potion. However, gold plating requires conduction across the entire board, and is not suitable for particularly thin lines. Immersion gold is generally very thin (less than 0.2 microns), and the purity of gold is low. The working fluid can only be discarded after it has been used to a certain extent.

4. The crystal structure formed by immersion gold is different from that of gold plating.

Soldering is easier than gold plating. It will not cause poor welding and cause customer complaints. The stress of gold plating is easier to control and is more conducive to the processing of bonded products.

In the skin effect, the signal is transmitted through the copper layer and does not affect the signal.

Compared with gold plating, the crystal structure of immersion gold is denser and less prone to oxidation.

As the traces become denser, the line width and spacing have reached 3-4mil. Gold plating can easily cause gold wire short circuits. There's only nickel and gold on the pads, so there's no chance of a gold wire shorting out.

5. Different flatness

The flatness of gold-plated PCB is not as good as that of immersed gold. For boards with higher requirements and better flatness, immersed gold is generally used. Immersed gold generally does not cause black pads after assembly