Have you ever been confused between immersion gold PCB and gold plating PCB? Wondering how to distinguish between them? Then, you are not alone. With numerous options available in the market related to surface finishes for the circuit board, you might get lost. Do not worry because this article will help you distinguish between Immersion Gold PCB and Gold Plating PCB.
So, by the end of this article, you will know precisely how to pick the right finish for your PCB.
So let’s get started.
Importance of PCB Surface Finish
As we all know, a PCB is a vital component in electronic devices, serving as a platform for connecting and supporting various electronic components. PCBs have a non-conductive substrate material, usually made of fiberglass, and conductive pathways that are etched or printed on it to form the circuit.
Surface finish is the coating over the exposed copper surfaces of a PCB that protects from oxidation and will allow for good soldering during the assembly process.
There are several types of surface finish: HASL (Hot Air Solder Leveling), ENIG (Electroless Nickel Immersion Gold), OSP (Organic Solderability Preservative), and Immersion Tin.
Some of the important key factors regarding the surface finish in PCBs are:
- Solderability: An essential function of a surface finish is to guarantee that an electronic component will logically solder to a printed circuit board. Satisfactory surface finishes offer a clean, level surface for soldering and help maintain sound, consistent electrical connections between components.
- Corrosion Resistance: Continuous operation of PCBs is affected due to several natural environmental conditions, either due to moisture or other forms of pollutants, thus causing corrosion of copper traces. Surface finishes act as a barrier, protecting the copper from oxidation and corrosion, therefore enhancing the long-term reliability of the PCB.
- Electrical Performance: The surface finish has an impact on the resistance to electrical performance, mainly in the aspects of signal integrity and impedance control. For this reason, some surface finishes, such as ENIG, have excellent electrical properties, which guarantee the homogeneous performance of the circuitry.
- Reliability: Another essential attribute of good surface finish is that it gives the PCB assembly a realization towards reliability. It will reduce the risk of failure in the soldered joint, good electrical connection consistently, and improve the lifespan of the electronic device.
The surface finish is a critical feature of the PCB manufacturing process, and it bears directly on solderability, corrosion resistance, and electrical performance to a large extent on the reliability of the devices.
Now let’s discuss what is the Immersion Gold PCB process in detail.
Immersion Gold (ENIG) PCB Process
ENIG is considered one of the most widely used surface finishes for its excellent solderability, planarity, and oxidation resistance in PCBs.
Here’s a step-by-step explanation of the ENIG process:
1.Chemical Cleaning
The surface of the PCB, which is copper, is cleaned of contaminations for better adhesion of the subsequent layers.
2.Nickel Deposition
The etched PCB is then sent through a solution in which, by the action of a chemical reaction, a skinny layer of nickel is deposited that fosters adhesion and holds back the diffusion of the copper.
3.Gold Immersion
In some instances, the PCB may be dunked in a gold solution after the nickel is deposited, after which the gold ions will chemically adhere to the nickel layer and form a skinny gold layer that is solderable and corrosion-resistant.
The gold deposition is followed by rinsing and drying steps in the series that are used to provide a uniform and reliable surface finish for electronic assemblies.
Gold Plating PCB Process
The process includes electroplating, where the gold is deposited as a layer on the copper surface of the PCB by applying an electric current.
Here’s a step-by-step explanation of the electroplating process for gold plating PCBs:
1.Cleaning and Preparation
The copper surface is cleaned very well to remove contaminants that may ensure proper adhesion during the gold plating.
2.Electroplating with Gold
The washed PCB is immersed in a solution with gold ions; when the electric current passes, these ions cling to the surface. Ideally, this technique can be used to achieve much thicker depositions of gold than other techniques, ensuring that better solder and corrosion resistance can be achieved.
Rinsing and drying processes remove any solution and moisture that remain on the circuit board after electroplating, thus forming the final finish of the PCB. Equally, it provides a surface finish of uniform and well-controlled thickness of the layer of gold, which is useful for many electronic applications.
Now you know the basics of both Immersion Gold PCB and Gold Plating PCB, it’s time to discuss their properties.
Properties of Immersion Gold vs. Gold Plating
Here’s a comparison of the key properties of Immersion Gold and Gold Plating:
|
Property
|
Immersion Gold
|
Gold Plating
|
|---|---|---|
|
Thickness
|
Thinner
|
Thicker
|
|
Flatness
|
More planar
|
Can have a rougher surface
|
|
Corrosion Resistance
|
Good resistance, slight edge due to nickel layer
|
Good resistance
|
This table provides a quick overview of the differences between Immersion Gold and Gold Plating in terms of thickness, flatness, corrosion resistance, and solderability.
Applications
The appropriate applications for both are:
Immersion Gold
- Fine-pitch Components: Great for fine-pitch components, immersion gold with excellent flatness on the substrate makes soldering equally essential to be done well, precisely, and reliably.
- High-Frequency Applications: The evenness of the surface of the immersion gold and low signal loss make it suitable for high-frequency applications, such as RF and microwave circuits.
- Good Corrosion Resistance: Immersion gold has good corrosion resistance, combined with the protection of the nickel layer, so it is suitable for harsh environments or those often exposed to moisture.
Gold Plating
- Thicker Gold Layers (Edge Connectors): Gold plating is the best choice for applications that require thicker gold layers, such as in edge connectors for electronic devices, where connection durability and longevity count.
- High Wear and Tear: Areas subject to frequent handling or mechanical stress, such as connectors or switches, benefit from the durability of gold plating, which withstands wear and tear over time.
- Excellent Solderability: Gold plating provides excellent solderability, making it the preferred choice for applications where reliable solder joints are crucial, such as in automotive electronics or aerospace applications.
Advantages and Disadvantages
Here’s the pros and cons of each surface finish:
Immersion Gold
Advantages
- Planar Surface: Provides flat and even top surfaces, ideal for fine-pitch components and ensuring fine soldering.
- Good Corrosion Resistance: assures good protection to the board against oxidation and corrosion, thus increasing the life of the PCB.
- Suitable for Fine-Pitch Components: Well-suited for applications requiring tight spacing between components due to its planar surface and precise solderability.
Disadvantages
- Thinner Gold Layer: The gold layer deposited in immersion gold is thinner compared to other methods, which may affect long-term durability.
- Additional Pre-soldering Steps: May require further surface preparation steps to achieve optimum solderability, thus adding some complexity to the manufacturing process.
Gold Plating
Advantages
- Thicker Gold Layer: Increases the thickness of the gold layer for better durability and a long life, especially in critical areas such as connectors.
- Superior Solderability: Provides good solderability, core to producing reliable and sufficiently strong solder joints that ensure robustness and performance of electronic applications.
- Better for High Wear Areas: It will resist high wear and tear, making it ideal for component use at places of high handling or mechanical stress.
Disadvantages
- Rougher Surface Finish: This higher gold content may likely contribute to a rougher appearance on the surface compared to immersion gold, which may degrade the performance of fine-pitch components.
- Not Ideal for Fine-Pitch Components: The rougher surface finish may, therefore, make this type of finish not the best option for applications that require fine-pitch components, typically with high soldering tolerances.
- More Expensive: Gold plating usually costs more than immersion gold, which holds a more significant amount of gold, raising the manufacturing cost.
Now you know everything about Immersion Gold PCB and Gold Plating PCB. But you must be wondering how you can choose the right one? Don’t worry as we are here to help you.
Choosing the Right Finish
Here are some tips to help you choose the most suitable finish for your project:
- Component Size and Pitch
For fine-pitch components or applications with close spacing between elements, it is preferred to use the planar surface and precise solderable surface of immersion gold.
Gold plating, in some cases with larger parts or wider pitch spacing, may be chosen for superior solderability and durability.
- Operating Environment
In very rough or chemically aggressive environments, which involve the impact of moisture, chemicals, or high temperatures, the use of immersion gold, bearing good corrosion resistance, may be better.
Gold plating may be adequate for use in a controlled environment with a low level of exposure to severe conditions; in this case, the gold coating would be thicker.
- Soldering Process
In cases of lead-free soldering or multi-reflow cycles, it is recommended to use a gold-plated surface because of its superior solderability and durability.
However if the soldering process is typical and does not facilitate excessive heating, the immersion gold might be sufficiently protective for fine-pitch components.
- Budget Constraints
Immersion gold can often be cheaper than gold plating if cost is a significant concern about other metal finishes. This is because immersion gold usually uses thinner layers of gold and more straightforward processing steps than gold plating.
Gold plating can be chosen among these alternatives in applications where performance and reliability are critical, and the cost is less of a factor.
Alternative Finishes
HASL (Hot Air Solder Leveling): Appropriate for applications where the budget is a concern, where the components are relatively large, and during standard soldering. Nevertheless, it is not very ideal for fine-pitch components because the surface is topographically uneven.
OSP (Organic Solder Preservative): Offers a thin organic layer for temporary protection before soldering. OSP is used in cost-effective applications with the most commonly used standard soldering processes but may lack the durability and corrosion resistance that immersion gold or gold plating has.
Final Words
So you have to understand the differences between Immersion Gold PCB and Gold Plating PCB since that would help you produce better boards in the PCB manufacturing process.
A flat surface finished with Immersion Gold is very good for having close tolerances for fine-pitch components, while Gold Plating offers thicker layers and is suitable for high-wear areas.
Consider factors like component size, operating environment, soldering process, and budget constraints when choosing the right finish.
Considering all these things, it gives you the edge to have perfect performance and reliability in the use of all your electronic devices.
