1. Hot air leveling (tin spraying)
Hot air leveling (also known as hot air solder leveling (commonly known as tin spraying), it is the process of coating molten tin (lead) solder on the surface of PCB and heating compressed air leveling (blowing), so that it forms a coating layer that is not only anti-copper oxidation, but also provides good weldability.Thermally fluidized solder and copper form an intercalated copper-tin compound at the junction.PCB should be immersed in molten solder during hot air conditioning.Blow-flat liquid solder before the solder solidifies;The wind knife minimizes and prevents weld bridging in the curved month of the solder on the copper surface.
2. Organic weldability protectant (OSP)
OSP is a process for surface treatment of printed circuit board (PCB) copper foil in accordance with RoHS instructions.OSP is the abbreviation of Organic Solderability Preservatives.In a nutshell, OSP is a chemical process to grow a layer of organic skin on a clean bare copper surface.
This film has anti-oxidation, heat shock and moisture resistance to protect copper surface from rust (oxidation or vulcanization, etc.) in normal environment.However, at subsequent welding temperatures, the protective film must be easily removed by the flux, so that the exposed clean copper surface can be immediately combined with the molten solder to form a solid solder spot in a very short time.
3. All plates are plated with nickel gold
Nickel-gold plating is to coat the surface conductor of PCB with a layer of nickel and then a layer of gold. The main purpose of nickel plating is to prevent the diffusion between gold and copper.There are two types of electroplated nickel gold: soft gold (pure gold, with an unshiny surface) and hard gold (smooth and hard, wear-resistant, and containing other elements such as cobalt, with a shiny surface).Soft gold is mainly used for chip packaging with gold wire.Hard gold is mainly used for electrical interconnections in non-welds.
The deposit is a thick nickel gold alloy with good electrical properties on the copper surface, which can protect the PCB for a long time.It also has environmental tolerance that other surface treatment processes do not.Gold also prevents copper from dissolving, which would be beneficial for lead-free assembly.
5, sink a tin
Since all current solders are based on tin, the tin layer can match any type of solder.The process of settling tin can form a flat copper-tin intergeneric compound, which makes it as weldable as hot air leveling without the flatness problem of hot air leveling.The solder plate cannot be stored for too long and must be assembled according to the order of the solder plate.
6, heavy silver
The silver precipitation process is between organic coating and chemical nickel plating/gold precipitation.Even when exposed to heat, moisture and pollution, silver remains well weldable, but it loses its luster.Sunken silver does not have the physical strength of electroless nickel/sunken gold because there is no nickel below the silver layer.
7. Chemical nickel palladium
Chemical nickel palladium is a layer of palladium between nickel and gold, which can prevent corrosion caused by replacement reaction and make full preparation for alloy deposit.Gold covers palladium tightly, providing a good interface.
8. Hard gold electroplating
In order to improve the wear resistance of the product, increase the number of insertion and extraction and electroplating hard gold.
As the requirements of users become higher and higher, the environmental requirements become more and more strict, and the surface treatment process becomes more and more. It seems that the surface treatment process with more development prospect and more versatility should be chosen.It is impossible to predict exactly where PCB surface treatment will go in the future.Either way, meeting user requirements and protecting the environment must be done first!