1. Hot air leveling (tin spraying)
Hot air leveling, also known as hot air soldering material leveling (commonly known as tin spraying), is a process of coating the surface of PCB with molten tin (lead) soldering material and heating compressed air leveling, so that it forms a layer of coating that is not only anti-copper oxidation, but also good weldability.
The solder and copper formed copper - tin intermetallic compounds at the junction of hot air.
PCB shall be immersed in the molten solder during the hot air cleaning.
The air knife blows out the liquid solder before the solder solidifies.
The air knife minimizes the crescent shape of the solder on the copper surface and prevents the solder bridge from joining.
2. Organic solderability protector (OSP)
OSP is a process of surface treatment of printed circuit board (PCB) copper foil in accordance with RoHS instructions.
OSP is the abbreviation of Organic Solderability Preservatives. It is translated into Organic Solderability Preservatives, also known as Preflux.
In short, the OSP is a chemical coating of organic skin on a clean bare copper surface.
This layer of film has anti-oxidation, heat shock and moisture resistance, so as to protect the copper surface from rust (oxidation or vulcanization, etc.) in normal environment.
However, in the following welding high temperature, the protective film must be easily removed by the flux quickly, so that the exposed clean copper surface can be immediately combined with the melted tin to become a solid soldering point in a very short time.
3. The whole plate is plated with nickel gold
Nickel plating on the PCB surface conductors is first coated with a layer of nickel followed by a layer of gold plating nickel plating mainly to prevent the diffusion of gold and copper.
There are two types of electroplated nickel gold these days: soft gold (pure gold, which does not appear bright) and hard gold (which is smooth and hard, wear-resistant, contains cobalt and other elements, and has a shiny surface).
Soft gold is mainly used in chip packaging for gold line;
Hard gold is mainly used for electrical interconnection in non-welded places.
The deposit is a thick, electrically conductive nickel-gold alloy coated on the copper surface, which can protect the PCB for a long time.
It also has environmental tolerance that other surface treatments do not.
It also prevents copper from dissolving, which would be beneficial for lead-free assembly.
5.sink a tin
Since all solders are currently based on tin, the tin layer can match any type of solder.
The soldering process can form a flat copper-tin intergeneric compound, which makes it as weldable as hot air leveling without the headache of hot air leveling.
The sinking tin plate shall not be stored for too long and must be assembled according to the sequence of sinking tin.
6. Heavy silver
The silver precipitation process is between organic coating and electroless nickel/gold plating.
Even when exposed to heat, moisture and pollution, silver retains good weldability but loses its luster.
Silver does not have the good physical strength of electroless nickel/gold plating because there is no nickel underneath the silver layer.
7.Chemical nickel palladium
Compared with sinking gold, chemical nickel palladium has an extra layer of palladium between nickel and gold. Palladium can prevent corrosion caused by displacement reaction and make full preparation for sinking gold.
Gold is tightly covered with palladium, providing a good contact surface.
8. Hard gold plating
In order to improve wear resistance of products, increase the number of plug and pull and plating hard gold.