Immersion Gold PCB and PCB Gold Plating Board
PCB surface finish has several processing technologies like bare board (without any surface treatment), rosin board, OSP (organic solder protective agent, slightly better than rosin), tin spray (lead tin, lead-free tin), immersion gold, gold plating, etc. In this article, differences between gold plating board and immersion board will be briefly introduced.
Immersion gold uses a chemical deposition method-- one of chemical nickel gold layer deposition methods that can achieve thicker gold layer-- to form a generally thicker coating by chemical redox reaction method. The principle of gold plating is electrolysis, also known as plating. In actual product applications, 90% golden board is immersion gold board, that’s because gold plating board has poor solderability.
Immersion gold has stable deposition color, good brightness, flat coating, and good solderability of nickel gold coating. Basic four stages can be divided into: pre-treatment (degreasing, micro-etching, activation, after the dip), nickel, immersion gold, post-processing (scrap gold washing, DI washing, drying). Immersion gold thickness is between 0.025-0.1um.
The fundamental differences between gold plating board and immersion gold board are as follows:
1.Gold thickness in immersion gold board is more than that in a gold plating board. Immersion gold board is more yellow than a gold-plating board, that’ because gold-plating board has the color of nickel.
2.Their crystal structures are different. Comparatively speaking, immersion gold is easier to be soldered with less poor solder issues. Immersion gold board is easier to control the stress, which is benefit for the bonding products.
3.Nickel is only used on immersion gold board’s pad, thus the signal transmission in the skin effect does not affect the signal at the copper layer.
4.The crystal structure of immersion gold is much denser than that in gold plating board, thus it is not easy to produce oxidation.
5.With the strict requirements for higher precision in PCB fabrication process, line width and spacing have below 0.1mm. Gold-plating board is easier to produce short circuit than immersion gold board.
6.Nickel is only used on immersion gold board’s pad, therefore solder resist on the circuit is solidly combined with the copper layer.
7.The flatness and service life of immersion gold board is better than the gold plating board.