If PCB electroplating is subdivided, it can be divided into many electroplating types. Let's introduce which electroplating types are divided into:
1： The whole PCB is gold-plated.
Generally, it refers to [electroplated gold], [electroplated nickel gold plate], [electrolytic gold], [electroplated gold], [electroplated nickel gold plate], and there is a distinction between soft gold and hard gold (generally used as gold finger). Its principle is to dissolve nickel and gold (commonly known as gold salt) in chemical solution, immerse the circuit board in an electroplating tank and apply current to generate a nickel gold coating on the copper foil surface of the circuit board. Electroplated nickel gold is widely used in electronic products due to its high hardness, wear resistance and resistance to oxidation.
2： PCB gold deposit:
The method of chemical oxidation-reduction reaction is used to generate a layer of coating, which is generally thicker. It is one of the methods of chemical nickel gold gold deposition. It can reach a thicker gold layer, usually called gold deposition.
3： PCB gold plate
With the increasing integration of IC, the IC pins become more and more dense. The vertical tin spraying process is difficult to smooth the thin bonding pads, which makes it difficult to mount SMT; In addition, the shelf life of tin spraying plate is very short. The gold-plated board just solves these problems: 1. For the surface mounting process of PCB, especially for 0603 and 0402 super small surface mount, because the pad flatness is directly related to the quality of solder paste printing process and plays a decisive role in the subsequent reflow welding quality, the whole board gold-plated is often seen in high-density and super small surface mount processes. 2. In the trial production stage, due to factors such as PCB component procurement, it is often not that the boards are welded immediately when they arrive, but that they are often used after several weeks or even months. The shelf life of gold plated boards is many times longer than that of lead tin alloys, so everyone is willing to use them. In addition, the cost of gold plated PCB in the sampling stage is almost the same as that of lead tin alloy plate.
However, with the increasingly dense wiring, the line width and spacing have reached 3-4 4MIL. Therefore, the problem of gold wire short circuit arises:
With the increasing frequency of the signal, the effect of signal transmission in multiple coatings due to skin effect on the signal quality is more obvious:
Skin effect refers to: high-frequency alternating current, the current will tend to concentrate on the surface of the wire flow.
According to the calculation, the skin depth is related to the frequency:
Other disadvantages of the gilded plate are listed in the difference table between the gilded plate and the gilded plate.
4： PCB gold plate
In order to solve the above problems of gold plated boards, PCB with gold plated boards mainly has the following characteristics:
1. Because the crystal structure formed by gold deposition and gold plating is different, the gold deposition will be golden yellow, which is more yellow than gold plating, and the customer is more satisfied.
2. Because the crystal structure formed by gold deposition is different from that formed by gold plating, gold deposition is easier to weld than gold plating, which will not cause poor welding and cause customer complaints.
3. Since only the pad of the gold plated plate has nickel gold, the signal transmission in the skin effect will not affect the signal in the copper layer.
4. Because the crystal structure of gold deposit is more compact than that of gold plating, it is not easy to produce oxidation.
5. Since only the bonding pad of the gold plate has nickel gold, it will not produce gold wire to cause slight shortness.
6. Since only the pad of the gold plated plate has nickel gold, the bonding between the solder mask and the copper layer on the circuit is stronger.
7. PCB engineering will not affect the spacing when making compensation.
8. Because the crystal structure formed by gold deposition and gold plating is different, the stress of the gold plate is easier to control, which is more conducive to the processing of bonding products. At the same time, because the gold is softer than the gold plating, the gold finger made of the gold plating plate is not wear-resistant.
9. The flatness and standby life of PCB gold plated plate are as good as those of PCB gold plated plate