With the continuous improvement of the living environment for human beings, the environmental problems involved in PCB production are particularly prominent. The topics related to lead and bromine are the most popular. Lead-free and halogen-free will affect the development of PCB in many aspects. Although the changes in the surface treatment process of the PCB are not large at present, it seems to be a relatively long-term issue, but it should be noted that the long-term slow changes will lead to huge changes. With increasing environmental protection, the PCB surface treatment process will surely change dramatically in the future. The most basic purpose of surface treatment is to ensure good solderability or electrical properties. Since natural copper tends to exist in the form of oxides in the air, it is unlikely that it will remain as copper for a long period of time, and therefore other treatments of copper are required. Although in the subsequent assembly, strong fluxes can be used to remove most of the copper oxides, the strong fluxes themselves are not easy to remove, so the industry generally does not use strong fluxes. There are many PCB surface treatment processes. The common ones are hot air leveling, organic coating, electroless nickel/immersion gold, immersion silver, and immersion tin. These are introduced one by one. 1, hot air leveling (spraying) Hot air leveling, also known as hot-air solder leveling (commonly known as spray tin), is the process of applying a molten tin (lead) solder on the surface of a PCB and heating (or blowing) the compressed air to form a layer that resists copper oxidation. It also provides a good solderability coating. When the hot air is leveled, the solder and copper form a copper-tin intermetallic compound at the junction. When the PCB is hot-air levelled, it sinks into the molten solder; the air knife blows the liquid solder before the solder solidifies; the air knife minimizes the meniscus of the solder on the copper surface and prevents solder bridging. 2. Organic Solderability Protection Agent (OSP) The OSP is a process that complies with the RoHS directive for surface treatment of printed circuit board (PCB) copper foils. OSP is the abbreviation of Organic Solderability Preservatives. Chinese translation is organic solder mask, also known as copper protector. English is also known as Preflux. Simply put, OSP is to chemically grow a layer of organic film on the surface of clean bare copper. This layer of film has anti-oxidation, thermal shock resistance, moisture resistance, to protect the copper surface in the normal environment no longer continue rust (oxidation or vulcanization, etc.); but in the subsequent welding temperature, this protective film must be very It is easily removed by the flux quickly, so that the exposed clean copper surface can be immediately combined with the molten solder in a very short time to become a solid solder joint. 3, full plate nickel-plated gold Nickel-plated gold is plated with a layer of nickel on the surface of the PCB and then plated with gold. Nickel plating is mainly used to prevent the diffusion between gold and copper. There are two types of electroplated nickel gold: gold-plated (pure gold, gold surface does not look bright) and gold plated (surface smooth and hard, wear-resistant, containing cobalt and other elements, the gold surface looks brighter). Soft gold is mainly used for gold wire in chip packaging; hard gold is mainly used in non-welded electrical interconnections. 4, Shen Jin Immersion gold is a thick layer of nickel-gold alloy coated on the copper surface, which can protect the PCB in the long-term; in addition it also has the endurance to the environment that other surface treatment processes do not have. In addition, Immersion Gold can also prevent the dissolution of copper, which will benefit lead-free assembly. 5. Shen Tin Since all current solders are based on tin, the tin layer can match any type of solder. Immersion tin process can form a flat copper-tin intermetallic compound, this feature makes it possible to have the same good solderability as hot air leveling without the headache flatness problem of hot air leveling; it can not be stored for too long. The assembly must be carried out according to the order of sinking tin. 6, Shen Yin The silver immersion process is between organic coating and electroless nickel/immersion gold. The process is simple and fast. Even if exposed to heat, humidity and pollution, silver can maintain good solderability but it will lose its luster. . Shen Yin does not have the good physical strength of electroless nickel/immersion gold because there is no nickel below the silver layer. 7, chemical nickel palladium gold The chemical nickel-palladium-gold has a layer of palladium between nickel and gold compared with the gold-immersed gold. Palladium can prevent the phenomenon of corrosion caused by the substitution reaction and make full preparation for the heavy gold. Gold is tightly covered on the palladium, providing a good contact surface. 8, plating hard gold In order to improve the wear resistance of the product, the number of plugs and pulls is increased and the hard gold plating is performed. As users demand more and more, environmental requirements become more and more stringent, and surface treatment processes become more and more. In the end, it is necessary to select a surface treatment process that has promising development and more versatility. At present, it seems a bit dazzling and confusing. . Where will the PCB surface treatment process go in the future, and now it cannot be accurately predicted. Regardless, satisfying user requirements and protecting the environment must be done first! Solar Controller,Solar Charging Controller,Solar Water Heater Controller,Automatic Switch Solar Controller GuangZhou HanFong New Energy Technology Co. , Ltd. , https://www.gzinverter.com