What are the types of surface treatment processes for PCB circuit boards?

From the PCB processing board appearance, its appearance is mainly three colors of gold-silver-light red. If classified, gold is the most expensive, followed by silver, and the cheapest is light red.

From the appearance, it is easy to see whether the manufacturer has cut corners. Several parts of the circuit board are mainly pure copper, referred to as bare copper plate.

1. Bare copper plate has the advantages of low cost, smooth appearance, and good weldability without oxidation. However, attention should be paid not to be affected by acid and temperature. Copper is easy to oxidize in air after being put for a long time.

2. The gold on the sunken gold plate is gold, even if only a thin one is plated, the cost of this book already accounts for 10% of the cost of the entire circuit board. After sinking gold, it is not easy to oxidize, the storage time is longer, and the surface is relatively flat. It is suitable for welding some fine gap pins and some devices with relatively small solder joints, such as mobile phone boards. Its cost is relatively high and the welding strength is relatively high. Less.

3. The tin-sprayed circuit board is silver, it is sprayed with a layer of tin on the outside of the copper circuit, which can help welding, but there is no way to have the same long-term contact reliability as gold. If it is used for a long time, it is easy to oxidize and rust, resulting in poor contact. Commonly used in some small digital products on the circuit board, its price is cheap.

4. OSP process board is also called organic flux film in SMT factory. Because it is an organic matter, not a metal material, it is cheaper than the price of the tin spray process.

It has all the advantages of bare copper plate welding. Even the expired circuit board can be treated again, which is easily affected by acid and humidity. If the storage time is too long for more than three months, the surface treatment must be done again. OSP is an insulating layer, so the test point needs to be printed with solder paste to remove the original OSP layer before contacting the needle point for electrical test.