1)HASL，hot air solder leveling
HASL also known as hot air solder leveling, it is in the molten tin-coated surface of the PCB and use heated air leveling (blown flat) process, to form a layer of copper oxide can be both anti provide good solderability of the coating layer. HASL solder and copper usually formed with copper-tin metal compound has a thickness of about 1 ~ 2mil.
2)OSP
Skim -> micro etch -> Pickling -> water cleaning -> organic coating -> cleaning, process control relative to other treatment processes more easily.
3)Electroless Nickel / Immersion Gold (also known as chemical gold)
Clean off the pickling -> micro-etch -> grep -> activate -> Electroless Nickel -> chemical leaching of gold; their process of six chemical tank, involving nearly a hundred kinds of chemicals, the process is relatively complicated.
4)Immersion Silver
Immersion Silver is a displacement reaction, it is almost sub-micron silver coating. Sometimes silver leaching process can also contain organic compounds, mainly to prevent migration of silver silver corrosion and eliminate the problem, this is very difficult to measure out a thin layer of organic matter, analysis showed less than 1% by weight of the organism.
5)Immersion Tin
Due to the current all tin-based solder is, the tin layer with any type of solder to match, from this point of view, immersion tin process is very promising. But previous PCB via solder dipping process easy after whisker, welding and tin migration over soldering shall bring reliability problems, thus limiting the immersion tin process of adoption. After immersion tin solution, the organic additive, the granular structure of the tin layer structure to overcome the previous problem, but also has good thermal stability and weldability.
Sophie Deng
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Wonderful PCB Limited
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