Enig refers to Electroless Nickel Immersion Gold, is a type of surface plating used for printed circuit boards. ENIG PCBs (also named ENIG PC boards or ENIG circuit board Construction) consists of an underlying layer of nickel with a thin layer of gold over the top. Enig Finish PCB provides various advantages such as high strenght, low contact resistance and etc, so it's widely used in many applications.
| Surface Finish | Content | Technological Capability |
| Hot Air Solder Leveling(Include:Lead-Free) | Min. panel size | 155*255mm |
| Max. panel size | 600*622mm | |
| Board thickness | 0.60 - 3.20mm | |
| Solder thickness | Standard: 1- 40um | |
| Advance: 5 - 40um | ||
| Minimum spacing form SMT pad | 0.2mm (with s/m brigde) | |
| 0.25mm (without s/m bridge) | ||
| Ground to ground or ground to track Spacing | 0.20mm | |
| OSP | Min. panel size | 75*75mm |
| Max. panel size | 610*610mm | |
| Board thickness | 0.40 - 3.20mm | |
| Coating thickness | 0.20 - 0.50um | |
| Immersion gold (According to IPC-4552-WAM1-2) | Board thickness | 0.20 - 3.2mm |
| Nickel thickness | 3.0-6.0μm | |
| Gold thickness | Min. 0.025um | |
| Immersion Ag (According to IPC-4553A) | Max panel size | 406*533mm |
| Board thickness | 0.20 - 3.2mm | |
| Immersion Ag thickness | 0.05 - 0.3um | |
| Immersion Tin (According to IPC-4554) | Max panel size | 406*533mm |
| Board thickness | 0.20 - 3.2mm | |
| Immersion Tin thickness | 0.75 - 1.2um |
Electroless nickel immersion gold is a two layer metallic coating of 2-8 μin Au over 120-240 μin Ni. The Nickel is the barrier to the copper and is the surface to which the components are actually soldered to. The gold protects the nickel during storage and also provides the low contact resistance required for the thin gold deposits. ENIG is now arguably the most used finish in the PCB industry due the growth and implementation of the RoHs regulation.
| Advantages | Disadvantages | |
| Enig PCBs | • Easy process mechanism • Flat surfaceh • Long Shelf Life • Good oxidation resistance • High temperature resistance • Good electric performance • Good for PTH (Plated Through Holes) • No Pb • Good thermal diffusion | • Expensive • Black Pad / Black Nickel • Signal Loss (RF) • Not Re-workable • Damage from ET • Complicated Process |
There are some differences between immersion gold and gold plating as follows:
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’s because gold-plating board has the color of nickel.
Compared with gold plate, immersion gold has a denser crystal structure and it is not easy to be oxidized.
The immersion gold board has only nickel gold on the pad, so the soldering on the line is more firmly combined with the copper layer. The project does not affect the spacing when making compensation.
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.
The flatness and service life of immersion gold board is better than the gold plating board.
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. At the same time, immersion gold has a poor anti - abrasion when doing gold finger as immersion gold is more flexible than plating gold.
Besides immersion gold and gold plating, there are more common surface finishes used in PCB manufacturing such as HASL / Lead Free HASL, Immersion Tin, immersion Silver, OSP / Entek and hard gold pcb surface finish.
If you aren't sure what you will need? Consult with a PCB fabricator prior to you making a selection. This will ensure that the combination of the surface finish and material will result in a high-yielding, cost-effective design that will perform as expected.
To achieve an ENIG finish on your PCB, there are several steps that you should follow:
Step 1: the surfaces and vias intended for the finish first have a nickel layer applied to the copper in an electroless process as a diffusion barrier.
Step 2: a thin gold finish is applied. The gold adheres to the nickel-plated areas through a molecular exchange, which will protect the nickel until the soldering process.
1. What is immersion gold PCB?
Electroless nickel immersion gold (ENIG or ENi/IAu), also known as immersion gold (Au), chemical Ni/Au or soft gold, is a metal plating process used in the manufacture of printed circuit boards (PCBs), to avoid oxidation and improve the solderability of copper contacts and plated through-holes.
2. What is immersion gold plating?
Direct Immersion Gold is a process in which gold is plated directly on copper as a surface finish for printed circuit board and package applications.
3. What is the difference between ENIG and immersion gold?
Immersion gold provides good plating around the holes in the circuit board. The gold plating is gold wire bondable, and can be soldered easily. ENIG surface finish is best for fine pitch products because the tracks or pads are square-edged and flat.
4. What is the difference between PCB immersion silver and gold?
Immersion gold has a layer of nickel under it, which provides it with physical strength. As there is no nickel layer under immersion silver, its physical strength is lower than that of immersion gold. Immersion silver requires more care for storage and handling than immersion tin does.
5. How thick is immersion gold?
ENIG plating thickness of each layer should be between 0.05 to 0.23 µm for the immersion gold layer and 2.5 to 5.0 µm for the electroless nickel. The thicker the immersion gold layer, the more likely it is to result in a black pad due to process complications.
6. What is the advantage of immersion plating?
Immersion plating alters metal surfaces to improve: Wear and corrosion resistance. Electrical resistance. Electrical conductivity..
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