The surface of the circuit board has several processes: Bare PCB (surface without any treatment), Rosin board, OSP (organic solder preservative, slightly better than rosin), HASL (a tin, lead free tin), gold plating, ENIG(Electroless Nickel/Immersion Gold), which is more common. We briefly introduce the difference between gold plating and ENIG.
ENIG is a method of chemical deposition, and a layer of coating is formed by chemical oxidation-reduction reaction. The thickness of the deposit is thicker, which is one of the chemical nickel, gold and gold layer deposition methods, which can reach a thicker gold layer.
Gold plating uses the principle of electrolysis, also known as electroplating. Most other metal surface treatments are plated.
In the actual product applications, 90% of the gold boards are the ENIG, because the poor weldability of the gold-plating is his fatal flaw, but also a direct cause of many companies to abandon the gold-plating process.
ENIG of printed circuit surface is stable color, good brightness, good coating and good weldability. Basically can be divided into four stages: pretreatment (degreasing, micro corrosion, activation, after immersion), immerse nickel, immerse gold, end treatment (waste gold washing, DI washing, drying). The thickness of ENIG is between 0.025-0.1um.
Gold used in circuit board surface treatment, because the conductivity of gold is strong, good oxidation resistance, long life, general applications such as key board, finger board, etc. The fundamental difference between gold plating and ENIG is gold plating is hard gold (hard wearing), ENIG is soft gold (not hard wearing).
So most factories now use ENIG process to produce gold PCB. But the ENIG process is more expensive than the gold plating process (higher gold content), so there are still a large number of low-priced products using gold plating process (such as remote control board, toy board).
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