PCBA plate making is very important, as is the process of gold plating and tin plating. Now let's talk about various processes.

Advantages and disadvantages of various coatings: First, we need to understand why nickel, silver, tin, tin, zinc and gold plating is required. We usually use tin plating and gold plating. Common: The coatings have a common advantage, which can prevent corrosion (improve oxidation resistance) and play a decorative role.

Here are the differences

1. Galvanizing: It is mainly used for corrosion prevention. It is characterized by low cost, convenient processing and good effect. Its disadvantage is that it is not suitable for friction parts, which will affect the welding performance. It is generally used by few people.

2.2. Nickel plating; It has good chemical stability in the atmosphere and alkaline solution after plating, and is not easy to change color. It is oxidized only when the temperature is above 600 ℃. It has high hardness and is easy to polish. Its disadvantage is porosity

3. Tin plating: It has high chemical stability, almost does not dissolve in dilute solution of sulfuric acid, nitric acid and hydrochloric acid, and has good weldability.

4. Chromium plating: separately plating decorative chromium and hard chromium. Decorative chromium is mainly used for beautification and corrosion prevention, but it is not wear-resistant. Hard chromium mainly improves the hardness, corrosion resistance and hardness of the workpiece

5. Gold plating and silver plating: mainly for decoration and anti-corrosion. The disadvantage is that the price is expensive. Why use gold plate

A. 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 solder pad, which brings difficulties to SMT mounting;

B. In addition, the shelf life of the tin spraying board is very short, and the gold-plated board just solves these problems: for the surface mounting process, especially for the 0603 and 0402 super small surface mount, because the flatness of the bonding pad is directly related to the quality of the solder paste printing process, and plays a decisive role in the subsequent reflow welding quality. Therefore, whole plate gold plating is often seen in high-density and subminiature surface pasting processes.

C. In the trial production stage, due to factors such as 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 PCB is many times longer than that of lead tin alloy, and the cost of gold plated PCB in the sample stage is almost the same as that of lead tin alloy.

3. Why to use gold deposit:

The gold plating process is divided into two types (the gold here is generally not pure gold but nickel gold). One is electroplating gold and the other is depositing gold (chemical method). As for the gold plating process, the effect of tin coating is greatly reduced, while the effect of tin coating is better; Unless the manufacturer requires Bangding, most manufacturers will choose the gold deposition process now!

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. The project 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 service life of the gold plated plate are as good as those of the gold plated plate.