Gold Plated Vs Immersion Gold: Applications & Methods

Inhaltsverzeichnis

Difference Between Gold Plated & Immersion Gold

Surface finishing plays a decisive role in printed circuit board performance. It ensures both the performance and life of a PCB. Among other finishing options, gold holds a distinctive position due to the following features:

  • Excellent conductivity which is crucial for Hochgeschwindigkeit applications
  • Gold delivers exceptional corrosion resistance which reduces electrical connection degradation

However, the application of pure gold seems impractical due to its high cost. Therefore, PCB manufacturing companies undertake two primary methods to leverage gold properties by addressing the abovementioned limitations.

What is gold plating in the PCB board?

In gold plating of PCB, PCB manufacturers apply a thin layer of gold onto the required area of the Leiterplatte. This process is called electroplating. Gold plating has two main advantages such as:

Advantages of Gold Plating:

  1. Gold’s physical properties such as ductility make it ideal to form any shape. This feature is quite useful in the assembly process for seamless Komponente attachment.
  2. Compared to immersion gold, in gold plating thicker layer is easy to deposit. It provides extra resistance.

Nachteilig:

  • Electroplating line setup and maintenance requires trained staff and particular equipment. The end product appears to be expensive compared to immersion gold.
  • Electroplating incorporates dangerous chemicals such as cyanide and gold salts. Strict procedures are required to minimize their environmental impact.

What is immersion gold in the circuit board?

Immersion gold is the application of a gold thin layer. It is also called Electroless Nickel Immersion Gold (ENIG). Unlike electroplating, it incorporates a chemical replacement process where gold ions displace surface atoms on the printed Leiterplatte. Later, it transforms into a thin gold layer. Immersion gold also comes with some advantages, such as:

Advantages of Immersion Gold

  1. Since it is a simple process and uses minimum material, immersion gold is quite an economical choice
  2. Immersion gold is more eco-friendly because it uses less hazardous chemicals.

Benachteiligungen

  • Immersion gold lacks malleability and ductility. This characteristic makes it more vulnerable during the Montageprozess where the chances of cracking are higher.
  • Since it contains a thinner layer which can lead to easy wear and tear. Similarly, its solderability is limited. We can say it is not suitable for applications which require swift electrical connections

Palladium Immersion Gold (PdIG):

Despite ENIG being a balanced surface finishing solution, Pdig is an improved version of immersion gold. This method places an additional layer between the gold topcoat and the base material. Its process is quite similar to ENIG; it goes through the following steps:

  • Vor-Behandlung
  • Electroless Palladium Plating
  • Gold immersion

PdIG is a good alternative to ENIG due to better resistance, improved signal strength, and enhanced adhesion.

Which is better: gold plating or immersion gold?

To understand this question, consider an example of a high-end graphic card. The complex design structure ensures smooth data transfer between the GPU and surrounding components. In this scenario, gold plating improved resistance ensures seamless matting cycles. Despite gold plating being expensive, it delivers high-end performance.

Key Differences between Gold Plating & Immersion Gold

difference between immersion gold and gold plated

Understanding the key differences will allow you to choose the most suitable finishing following project requirements. Let’s understand both by overviewing the following table:

Merkmal

Vergoldung

Immersion Gold (ENIG)

Prozess

Electroplating

Chemical Replacement

Kosten

More Expensive

Cost-Effective

Auswirkungen auf die Umwelt

Higher Impact

Lower Impact

Layer Thickness

Thicker (3-50 μin or more)

Thinner (3-5 μin)

Deposition Method

Electric current

Chemical reaction

Adhesion

Highly adherent

Good adhesion

Solder Joint Strength

Stronger

Slightly weaker

Whisker Formation

More prone

Less prone

 

What factors affect the layer quality?

Despite both gold plating and immersion gold providing different advantages achieving high-quality finishing requires several crucial factors:

Chemical Composition

The chemical composition of the gold plating plays a decisive role in determining the fine gold layer. Let’s have a closer look:

Concentration: 

The balance of the deposition rate is everything in gold plating. The concentration of gold ions directly impacts the deposition rate. An enhanced concentration leads to faster deposition. Similarly, it can also result in thicker and uneven layers. Subsequently, lower concentrations transform to slower deposition and thinner layers. Therefore, the balance is essential to obtain the optimal results.

pH: 

The solution’s pH level significantly impacts gold layer performance. For instance, a slightly acidic environment means lower pH shapes smooth and strong gold layers. Simultaneously, solutions with high acid quantity lead to rough surfaces, which can generate adhesion issues later.

Temperatur

As we have mentioned above the right balance of chemicals is important, similarly, balance in temperature is equally essential for a good-quality gold layer. Let’s find out why.

Temperature variations:

A minimal fluctuation rate in temperature can significantly impact both;

  1. The deposition rate
  2. Layer thickness.

Higher temperatures accelerate the overall deposition process. Conversely, it forms thicker layers with higher chances of cracking or other issues. Similarly, lower temperatures form thinner layers, which can impact the quality. 

Einheitlichkeit: 

You can see the entire process of finishing demands uniformity for a successful PCB surface finishing. Temperature changes can directly impact the thickness of the gold layer. It will lead to electrical performance issues, affecting your PCB company’s reputation.

Immersion Time

The thickness of the gold layer directly depends on the time a PCB is dipped in the gold solution.

Longer immersion time: 

Keeping a PCB in the gold solution will result in a thicker layer. For some PCB-Hersteller, it may seem an ideal state for better resistance. But always remember that thicker layers are vulnerable to quick cracking.

Note: A professional PCB-Hersteller will always optimize the immersion time.  A standard immersion time will give a decent thickness which is enough to resist wear and tear.

Applications of Gold Plating and Immersion Gold

application of gold plating
Choosing a suitable gold finishing method depends on understanding the project requirements. Below, we have discussed each case scenario.

Vergoldung

Connectors: 

Since gold plating provides excellent conductivity, it is an excellent choice for connectors that go through several mating cycles. A stable thickness of the layer can bear more plugging and unplugging without degradation. 

Edge Fingers: 

Fine gold plating can effectively cover the exposed areas of the PCB. It protects the delicate areas of a circuit board from wear and tear. The exposed edges of PCBs often require a robust finish.

Bear High Thermal Stress: 

High-power transistors, or voltage regulators, generate significant heat. If they are covered with a weaker layer of gold plating, the device performance can be affected on and off. Gold plating handles thermal stress smoothly, ensuring seamless performance in high-end applications.

Immersion Gold

Fine-Pitch Components: 

Modern printed circuit boards are made with complex designs meeting project requirements. Generally, they have tightly-paced connections. Immersion gold saves these parts from short circuits and any electrical hazards.

Ball Grid Arrays (BGAs): 

These compact packages feature several solder balls. Since immersion gold is a budget-friendly option, it is considered a suitable and cost-effective solution for the mass production of circuit boards using BGAs. 

Economical and Eco-Friendly: 

In some cases, customers need more economical and eco-friendly PCBs. Immersion gold is a relatively cheaper and more eco-friendly option compared to gold plating.

Alternative Gold Plating Methods

We have read some fundamental and advanced aspects of gold plating and immersion gold. But there are some alternatives also good for specific applications.

Brush Plating

Brush plating is a manual process where PCB manufacturers apply gold solution on a PCB using a brush. It is considered best for applying a gold layer over naked or weaker areas of the PCB board. Since it is a manual process, you need a skilled person. Yet, it can’t guarantee uniformity compared to electroplating.

Sputtering

It is called the vapor deposition (PVD) technique. Sputtering incorporates a high-energy beam to dislodge gold atoms from the targeted material. After dislodging the atoms, it condenses onto the PCB surface. Finally, it forms a thin gold layer. Sputtering offers numerous benefits as mentioned below:

Pure gold Layers: The PVD process reduces contamination which results in excellent pure gold layers.

Precise control: With sputtering, you can conveniently control the thickness of the gold layer.

Best for complex geometries: With this method, you can effectively coat complex features on printed circuit boards with high aspect ratios.

Note: Sputtering equipment is relatively more expensive compared to electroplating setups.

Fazit

Selecting the best gold finishing method depends on the PCB board requirement. Where gold plating delivers excellent performance, immersion gold is relatively a cheaper option.

So what is your choice? Making these critical decisions requires high-level professionalism and expertise. You can partner with FS Tech which provides a wide range of gold finishing options with quick turnaround time. Visit our website and get an instant online quote.

FAQs

Which method is more expensive in gold finishing?
Gold plating is generally more expensive due to the complex process and expensive material.

Which method is better for the environment?


Immersion gold incorporates low hazardous chemicals and produces less waste. So, it is a more environmentally friendly option.

Which gold finishing method is reliable?


Due to the thicker layer, gold plating typically provides excellent wear resistance.

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