Hot tin plating / Hot air levelling (HAL unleaded)
Today, HAL is the most common procedure in the PCB industry. The PCB, wetted with flux, is dipped in liquid lead-tin resp. tin-copper (soldering tin) and finally blown with hot compressed air.
Chemical nickel-gold
In this procedure, a nickel layer is initially applied to the PCB in a chemical process. This prevents the copper diffusion into the gold layer that is applied chemically. The gold layer subsequently deposited is around 0,08 μm. Chemical nickel-gold has the advantage of absolute flatness and is principally used for PCBs with SMD insertion.
Galvanic nickel-gold
The PCB, coated with resist, is initially given a nickel layer, and only then does the actual gold plating take place. Gold thicknesses of between 0,7 and 2 μm are achieved. One application of this method are mechanically stressed contact areas for plugs or keyboards. |
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Silver
In this surface treatment, a layer of silver of 0,1 – 3,0 μm is chemically deposited on the copper surface. The surface is absolutely flat.
Chemical tin
In this procedure, a thin layer of tin, approx. 0,8 to 1,1 μm, is chemically applied, thus guaranteeing a very flat surface. Caution: PCBs with this surface are only partially suitable for multiple soldering and
have a limited storage life. Generally, a maximum storage time of 6 months is guaranteed.
Organic surfaces (unleaded) OSP
Organic passivation is an unleaded surface protection for PCBs. These surfaces are also available under various brand names. Normally, the soldering parameters in assembly have to be tailored. The thickness of the layer is approx. 0,2 – 0,5 μm. The surface remains flat. |
