PCB Technical - PCB Immersion Gold and Gold Plated Board

The role of the two processes

Immersed gold board and gold-plated board are commonly used processes in the production of circuit boards today. With the increasing integration of ICs, the more IC pins become denser. The vertical spray tin process is difficult to flatten the thin pads, which brings difficulty to the placement of SMT; in addition, the shelf life of the spray tin plate is very short. The gold-plated plate just solves these problems. For the surface mount process, especially for 0603 and 0402 ultra-small surface mounts, because the flatness of the PCB pad is directly related to the quality of the solder paste printing process, it has a decisive influence on the quality of the subsequent reflow soldering, so the whole board is gold-plated It is common in high-density and ultra-small surface mount processes.

In the trial production stage, due to factors such as component procurement, it is often not that the board is soldered as soon as it comes, but often it takes a few weeks or even to use it. The shelf life of the gold-plated board is many times longer than that of the tin board. . So everyone is happy to adopt it. Besides, the cost of gold-plated PCB in the sample stage is almost the same as that of lead-tin alloy board.

What is gilding: the whole plate is gilded

generally refers to [electroplating gold] [electroplating nickel gold plate], [electrolytic gold], [electric gold], [electric nickel gold plate], there is a distinction between soft gold and hard gold (usually used as a gold finger). The principle is to dissolve nickel and gold (commonly known as gold salt) in chemical water, immerse the circuit board in the electroplating cylinder and pass current to form a nickel-gold plating layer on the copper foil surface of the circuit board. The characteristics of high hardness, wear resistance, and resistance to oxidation are widely used in electronic product names.

What is heavy gold

A layer of plating layer is formed by the method of chemical oxidation-reduction reaction, which is generally thicker, which is a kind of chemical nickel-gold layer deposition method, which can reach a thicker gold layer, usually called immersion gold.

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Difference between Immersion Gold Plate and Gold Plated Plate

1. Immersion gold is different from the crystal structure formed by gold plating. Immersion gold is much thicker than gold plating. Immersion gold will be golden yellow and yellower than gold plating. Customers are more satisfied.

2. The crystal structure formed by immersion gold and gold plating is different. Immersion gold is easier to weld than gold plating, and will not cause poor welding and cause customer complaints. 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 the immersion gold is softer than the gilding, so the immersion gold plate is not wear-resistant as the gold finger.

3. The immersion gold board only has nickel and gold on the pads. In the skin effect,the signal transmission is on the copper layer and will not affect the signal.

4. Immersion gold has a denser crystal structure than gold plating, and it is not easy to produce oxidation.

5. As the wiring becomes denser, the line width and spacing have reached 3-4MIL.Gold plating is prone to short circuit of gold wire.The immersion gold board only has nickel gold on the pad, so it will not produce gold wire short circuit.

6. The immersion gold board has only pads. There is nickel gold on the board,so the PCB solder mask on the circuit and the copper layer are more firmly bonded.The project will not affect the spacing during compensation.

7. It is generally used for relatively high-demand boards. The flatness is better. Immersion gold is generally used.Immersion gold generally does not appear as a black pad after assembly. The flatness and stand-by life of the immersion gold board are as good as the gold-plated board.