There are several processes on the surface of the printed circuit board:naked pcb board (no surface treatment),OSP, Hot Air Leveling(lead tin, lead-free tin),Plating gold,Immersion gold etc. These are more visible.
The difference between the Immersion gold and Plating gold
Immersion gold is a method of chemical deposition. A chemical layer is formed by a chemical oxidation-reduction reaction. Generally, the thickness is relatively thick. It is a kind of chemical nickel-gold-gold layer deposition method, and can achieve a thick gold layer.
Gold plating uses the principle of electrolysis, also called electroplating. Most other metal surface treatments are also electroplated.
In the actual product application, 90% of the gold pcb board is the immersed gold pcb board,because the poor solderability of the plated circuit board is his fatal flaw, and it is also the direct cause of many companies to give up the gold plating process!
Immersion gold process deposited on the surface of the printed circuit boards with stable color, good brightness, smooth plating, and good solderability of nickel gold plating. Basically it can be divided into four stages: pre-treatment (oil removal, micro-etching, activation, post-dip), nickel precipitation, heavy gold, post-treatment (waste water washing, DI water washing, drying). Immersion gold thickness is between 0.025-0.1um.
Gold is applied to the surface treatment of printed circuit boards because of its high electrical conductivity, good oxidation resistance, and long lifespan. It is generally used as key boards, gold finger pcb boards, etc. The fundamental difference between gold-plated boards and gold-immersed boards is that gold plating is hard. Gold (abrasion resistant), gold is soft gold (not wear resistant).
1. The crystal structure formed by Immersion Gold and Gold Plating is different. Immersion Gold is much thicker than Gold Plating. Immersion Gold will be golden yellow and yellower than Gold Plating (this is the method of distinguishing between gold plating and heavy gold plating.) a) Gold plating will be slightly white (nickel color).
2. The crystal structure formed by immersion gold and gold plating is different. Immersion gold is easier to weld than gold plating and will not cause bad welding. The stress of the immerison gold board is easier to control, and it is more conducive to the bonding process for bonded products. At the same time, because gold is more gold-plated than gold, the gold-fingered gold finger is not wearable (shortcomings of the gold plate).
3. There are only nickel-gold on the pad in the gold-immersed pcb board.The signal transmission in the skin effect does not affect the signal in the copper layer.
4. Immersion gold is more dense than the gold plating crystal structure, not easy to produce oxidation.
5. With the increasing demand for printed circuit board processing accuracy, line width, spacing has reached 0.1mm below. Gold plating is prone to gold short circuit. The gold plate only has nickel and gold on the pad, so it is not easy to produce a gold short circuit.
6. The immersion gold only has nickel gold on the pad, so the solder resist on the line is more firmly bonded to the copper layer. The project will not affect the spacing when making compensation.
7. For the higher requirements of the pcb board, flatness requirements are better, the general use of immersion gold,immersion gold generally does not appear after the assembly of the black mat phenomenon. The flatness and service life of the gold plate are better than that of the gold plate.
So At present most factories use the immersion gold process to produce gold pcb board.However, the gold-immersed process is more expensive than the gold-plating process (more gold content), so there are still a large number of low-priced products using gold-plating processes (such as remote control panels, toy boards).