The difference between immersed gold plate and gold plated plate
1. The difference between immersed gold plate and gold plated plate
2. Why use gold-plated plates
As ICs become more and more integrated, the more pins there are, the denser they become. The vertical tin spraying process is difficult to blow the thin pads flat, which brings difficulties to SMT placement; In addition, the shelf life of the tin spraying plate is very short. The gold plate solves these problems: 1. For the surface mount process, especially for 0603 and 0402 ultra-small surface mounts, because the flatness of the pads is directly related to the quality of the solder paste printing process, and plays a decisive role in the subsequent reflow soldering quality, so the whole plate gold plating is common in high-density and ultra-small surface mounting processes. 2. In the trial production stage, affected by factors such as component procurement, the board is often not welded as soon as it comes, but often has to wait for several weeks or even months before use, and the shelf life of the gold-plated plate is better than that of lead and tin
Gold is many times longer, so everyone is happy to use it. Besides, the cost of gold-plated PCB in the sample stage is almost the same as that of lead-tin alloy plates.
However, as the wiring becomes denser, the line width and spacing have reached 3-4MIL. Therefore, it brings the problem of short circuit of gold wire:
As the frequency of the signal increases, the effect of the signal transmission in multiple coatings due to the skin effect becomes more obvious on the signal quality:
The skin effect refers to the high-frequency alternating current, and the current tends to flow on the surface of the wire.
According to calculations, the depth of skin tone is related to frequency:
Other disadvantages of gold-plated plates are listed in the table of differences between immersion plates and gold-plated plates.
3. Why use immersion plates
In order to solve the above problems of gold plated plates, the PCB using immersion plates mainly has the following characteristics:
1. Because the crystal structure formed by immersion gold and gold plating is different, immersion gold will be golden yellow than gold plating, 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 plate 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. Because immersion gold has a denser crystal structure than gold plating, it is not easy to oxidize.
5. Because the immersion plate only has nickel gold on the pad, it will not produce gold wire and cause slight shortness.
6. Because the immersion plate only has nickel gold on the pad, the combination of the solder mask and the copper layer on the line is stronger.
7. The project will not affect the spacing when compensating.
8. Because the crystal structure formed by immersion gold and gold plating is different, the stress of the immersion plate is easier to control, which is more conducive to the processing of bonding for products with bonding. At the same time, it is precisely because the immersion gold is softer than the gold plating, so the gold plate is not wear-resistant.
9. The flatness and standby life of the immersed gold plate are as good as those of the gold plate. Concentrate:
1. What is gold plating: the whole plate is gilded. Generally refers to [electroplated gold], [electroplated nickel gold plate], [electrolytic gold], [electric gold], [electric nickel gold plate], there is a distinction between soft gold and hard gold (generally used as gold fingers). Its principle is to dissolve nickel and gold (commonly known as gold salt) in chemical water, immerse the circuit board in the electroplating cylinder and apply current to generate a nickel-gold plating on the copper foil surface of the circuit board. 2. What is immersion gold: A layer of plating is generated by the method of chemical redox reaction, which is generally thicker and is a kind of chemical nickel gold layer deposition method, which can achieve a thicker gold layer, usually called immersion gold.
