What Is Gold Plated Pcb Board

There are many surface treatment processes for PCB boards, such as anti-oxidation, tin spraying, lead-free spraying tin, immersion gold, immersion tin, immersion silver, hard gold plating, full board gold plating, gold finger, nickel palladium gold OSP and so on. So what is the pcb gold plating process?

Gold plating is also known as "hard gold". The processing cost of gold-plated PCB circuit boards is relatively high. Under normal circumstances, there are more and more applications of tin spraying. However, as the integration of IC is getting higher and higher, the more and denser the IC pins are. (For example: memory stick products), more and more boards are choosing gold plating process. PCB gold plating is mainly through electrolysis or other electroplating chemical methods to attach gold particles to the surface of the circuit board to form a thin layer of gold. Due to the strong adhesion of gold plating, the biggest advantage of the pcb gold plating process is its high hardness and strong wear resistance.

The difference between gold plating and immersion gold process:

Immersion gold adopts the method of chemical deposition. A layer of coating is formed by chemical redox reaction. Generally, the thickness is thicker.

Gold plating uses the principle of electrolysis, also known as electroplating. Most other metal surface treatments are also electroplated.

In actual product applications, 90% of gold plates are immersion gold plates, because the poor weldability of gold-plated plates is his fatal shortcoming, and it is also the direct reason why many companies give up the gold-plating process!

The immersion gold process deposits a nickel-gold coating with stable color, good brightness, smooth coating and good solderability on the surface of the printed circuit. Basically it can be divided into four stages: pre-treatment (oil removal, micro-etching, activation, post-dipping), nickel immersion, gold immersion, post-treatment (waste gold washing, DI washing, drying). The thickness of immersion gold is between 0.025-0.1um.

Gold is used in the surface treatment of circuit boards, because gold has strong conductivity, good oxidation resistance and long life, and is generally used in key boards, gold finger boards, etc. The most fundamental difference between gold-plated boards and immersion gold boards is that gold-plated is hard Gold (wear-resistant), immersion gold is soft gold (not wear-resistant).

1. The crystal structure formed by immersion gold and gold plating is different. The thickness of immersion gold is much thicker than that of gold plating. Immersion gold will be golden yellow, which is more yellow than gold plating (this is one of the methods to distinguish gold plating and immersion gold). 1), the gold-plated ones will be slightly whitish (the color of nickel).

2. The crystal structure formed by immersion gold and gold plating is different. Compared with gold plating, immersion gold is easier to weld and will not cause poor welding. The stress of the immersion gold plate is easier to control, and for products with bonding, it is more conducive to the processing of bonding. At the same time, it is precisely because immersion gold is softer than gold plating, so the gold finger of immersion gold plate is not wear-resistant (the disadvantage of immersion gold plate).

3. The immersion gold board only has nickel-gold on the pad. The transmission of the signal in the skin effect is in the copper layer and will not affect the signal.

4. Compared with gold plating, immersion gold has a denser crystal structure and is not easy to produce oxidation.

5. With the increasing requirements of circuit board processing accuracy, the line width and spacing have reached below 0.1mm. Gold plating is prone to short circuit of gold wire. The immersion gold plate only has nickel gold on the pad, so it is not easy to produce a short circuit of gold wire.

6. The immersion gold board only has nickel-gold on the pad, so the combination of the solder mask on the circuit and the copper layer is stronger. The project will not affect the spacing when compensating.

7. For boards with higher requirements, the flatness requirements are better, and immersion gold is generally used, and the black pad phenomenon after assembly is generally not caused by immersion gold. The flatness and service life of the immersion gold plate are better than that of the gold-plated plate.

6-layer PCB gold plating process:

Blue-coated glue: Only expose the surface of the board that needs to be plated with nickel-gold, and the conductive potential should be consistent with the direction of the board; Reel glue: Avoid using hot reel plates to prevent the adhesive tape from leaking glue; Upper plate → Pickling: Remove copper surface oxidation layer; water washing → grinding board: to further clean the copper surface and remove the defects of the copper surface; water washing → DI water washing → nickel plating → water washing → DI water washing → water washing → gold plating → recycling → two-stage water washing → board removal → blue glue tearing → board washing machine → Washing car