PCB Fabrication

The difference between circuit board gold plating and immersion gold process

by:A-TECH      2021-04-01
The difference between gold plating and immersion gold process on circuit board 2020-06-18 16:37:00 The method of immersing gold on circuit board is chemical deposition, and a layer of plating is formed through chemical oxidation-reduction reaction method, which is generally thicker and chemically A method of depositing nickel-gold-gold layers that can achieve thicker gold layers. Gold plating uses the principle of electrolysis, also called electroplating. The surface treatment of other metals is mostly electroplating. In the actual product application, 90% of the gold plate is immersion gold plate, because the poor weldability of the gold plate is his fatal shortcoming, and it is also the direct reason that many companies abandon the gold plating process! The immersion gold process deposits a nickel-gold coating with stable color, good brightness, flat coating, and good solderability on the surface of the printed circuit. Basically, it can be divided into four stages: pre-treatment (degreasing, micro-etching, activation, post-dipping), immersion of nickel, immersion of gold, and post-treatment (washing waste gold with water, washing with DI water, and 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, it is generally used in key boards, gold finger boards, etc., and 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. Immersion gold is different from the crystal structure formed by gold plating. Immersion gold is much thicker for gold than gold plating. Immersion gold will be golden yellow and more yellow than gold plating (this is one of the ways to distinguish between gold plating and immersion gold. A), the gold-plated will be slightly whitish (nickel color). 2. Immersion gold and gold plating have different crystal structures. Immersion gold is easier to weld than gold plating 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 the immersion gold is softer than gold plating, so the immersion gold plate is not wear-resistant as the gold finger (the disadvantage of the immersion gold plate). 3. The immersion gold board only has nickel and gold on the pads, and the signal transmission in the skin effect is on the copper layer without affecting the signal. 4. Immersion gold has a denser crystal structure than gold plating, and it is not easy to produce oxidation. 5. As the precision requirements for circuit board processing are getting higher and higher, the line width and spacing have been below 0.1mm. Gold plating is prone to short circuit of gold wire. The immersion gold board only has nickel gold on the pad, so it is not easy to produce gold wire short circuit. 6. The immersion gold board only has nickel and gold on the pads, so the solder mask on the circuit and the copper layer are more firmly combined. The project will not affect the spacing during compensation. 7. For high-demand boards, the flatness requirements are better. Generally, immersion gold is used, and immersion gold generally does not show the phenomenon of black pads after assembly. Immersion gold plate has better flatness and service life than gold plate. Compared with gold-plated boards, PCBs using gold-plated boards mainly have the following characteristics: 1. Because the crystal structure formed by gold-plated and gold-plated is different, gold-plated gold will be yellower than gold-plated, and customers are more satisfied. 2. Because 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. 3. Because the immersion gold board only has nickel and gold on the pad, the signal transmission in the skin effect will not affect the signal on the copper layer. 4. Because immersion gold has a denser crystal structure than gold plating, it is not easy to produce oxidation. 5. Because the immersion gold board only has nickel and gold on the pad, it will not produce gold wire, which will cause the shortness and the bonding of the solder mask and the copper layer on the circuit to be stronger. 6. The project will not affect the distance during compensation. 7. Since the crystal structure formed by gold-immersion and gold-plating is different, the stress of the gold-immersion plate is easier to control. For products with bonding, it is more conducive to bonding processing. 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. 8. The flatness and stand-by life of the immersion gold board are as good as the gold-plated board. From this summary, most factories currently use the immersion gold process to produce gold plates. However, the immersion gold process is more expensive (higher gold content) than the gold plating process, so there are still manufacturers selling a large number of low-priced products that use the gold plating process (such as remote control boards, toy boards). Part of the content is picked from 'Personal Library'
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