Tin Plating Corrosion resistance of the coating
Tin plating and its alloys are a kind of coating which has good weldability and has certain corrosion resistance, and is widely used in electronic components and printed circuit boards. Preparation of tin layer In addition to hot leaching, spraying and other physical methods, electroplating, dip plating and electroless plating and other methods for simple and easy to have been widely used in industry.
Dip is the workpiece immersed in the solution containing the metal salt, according to the principle of chemical replacement in the workpiece surface deposition of metal coating. This is different from the general principle of chemical plating, because the bath does not contain reducing agent. And contact with the plating is not the same, the contact is the workpiece immersed in the metal salt solution must be placed with a lively metal close connection, the active metal into the anode into the solution to release electrons, the higher the potential of metal ions in the solution after the electronic Deposited on the surface of the workpiece. Dip tin is only carried out on iron, copper, aluminum and their respective alloys.
The reduction agent for copper or nickel autocatalytic deposition can not be used to reduce tin. The simplest explanation is because the tin surface on the hydrogen overpotential high, and the above-mentioned reducing agent are hydrogen evolution reaction, it is impossible to tin ions reduced to tin element. To be chemically tinned, it is necessary to select another type of strong reducing agent without hydrogen, such as Ti3 +, V2 +, Cr2 + and so on, and only reported with T3 + / Ti4 +.
Tin plating type editor
Acid tin plating
1. tin is reduced by bivalent, electricity consumption;
2. Bath plating high conductivity, low bath voltage, high current efficiency;
3. Operation for temperature close to room temperature, free heating equipment;
4. Use the appropriate additives to obtain gloss coating;
5. Damage to the substrate less.
1. Operation and plating bath management to be careful to get a good coating.
2. The use of additives, or easy to produce branches or nodular coating.
3. Can not use insoluble anode.
4. Corrosive, plating to be made of rubber lining.
5. Divalent tin may oxidize to tetravalent tin and become a passive state.
Alkaline tin plating bath
1. Good uniformity;
2. can tolerate more impurities;
3. No additives can be gloss;
4. Available insoluble anode;
5. Wide operating range;
6. The formula is simple;
7. Pre-processing requirements are not high.