PCB Surface Finishing ENIG vs Gold plating vs HASL

The difference between ENIG and Gold plating on PCB circuit board?

• The ENIG and the Gold plating are commonly used in PCB circuit boards. The Gold plating has been widely applied in electronic products due to the advantages of high hardness, wear resistance and no oxidation.ENIG is generated by chemical redox reaction and create a layer of gold coating. It can be thick gold layer.
• The gold thickness of ENIG is much thicker than Gold plating, The crystal structure formed by the two are different,Gold will be golden yellow than Gold plating.
• Because of the different crystal structure formed by ENIG and Gold plating, ENIG is easier to weld than Gold plating, and it will not cause welding defect.It is also because ENIG is more soft than Gold plating, so gold finger PCBs are generally plated with hard gold.
• The ENIG only has nickel gold on the pad, the signal transmission in copper area does not affect in the skin effect.
• The crystal structure of ENIG is more compact than Gold plating, and it is not easy to produce oxidation.
• As the wiring becomes more and more dense, the line width and spacing have reached 3-4mil, Gold plating can easily lead to the short circuit of gold wire,The ENIG only has nickel gold on the pad, so it will not produce a short circuit of gold wire.
• The ENIG has nickel gold only on the pad, so the soldermask on the line is more firm with the copper layer. CAM editing will not affect the spacing when it is compensated.
• The ENIG is used in advanced board, the flatness is better, and the black mat phenomenon after the assembly will not appear.

The above is the difference between the ENIG and the gold-plating. Now the gold price is high. In order to save costs, many manufacturers are reluctant to produce gold plating boards, and only do the ENIG.

Why do not “HASL” in general?

As the integration of IC gets higher and higher, the more IC feet are more denser. However, it is difficult for the vertical tin spraying process to make the slender pad smooth, which makes it difficult for the SMT to mount.In addition HASL inactive shelf life is a short life. And gold plates just solve these problems.

• For the surface mount technology, especially for the 0603 and 0402 super miniature sheets, because the flatness of the pad is directly related to the quality of the solder paste printing process, which plays a decisive role in the quality of the reflow soldering. Therefore, the whole plate gold plating is often seen in the high density and super small surface bonding process.
• At the trial stage, affected by factors such as the component purchasing tend not to immediately board welding, but often have to wait a few weeks or even months before use.Engineer prefer to use gold PCB as gold plate shelf life is many times longer than HASL,besides the gold cost is not much difference compared with HASL in PCB prototype.