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Gold Plated PCB

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Printed circuit boards (PCBs) need protective coatings on the copper traces. Such coatings can protect PCBs from oxidation and corrosion. Thus, gold is often utilized as such a coating. It has high conductivity and corrosion resistance and can make reliable solder joints. Plating PCBs with gold is a standard practice in the PCB industry. This article covers everything about gold plating in PCBs and their types. It also compares gold-plated with Immersion Gold.

What is Gold Plating in PCB?

Gold Plating is the process of depositing layers of gold on the PCB surface. The coating helps the circuit board to resist corrosion. Besides, it also improves the electrical conductivity of PCB. 

Two methods carry out the gold plating.

  • Electroless Plating

Depositing a metal atom on the surface of a substrate forms a metal plating layer. Electroless plating in a water-based solution does not require an external power source. An external current is not required for this plating technique. The electroless plating layer has a consistent thickness.

  • Electroplating

This method involves placing a thick alloy or metal on the surface of the PCB. An external current is used for coating the metal in this method. During this process, the anode undergoes an oxidation reaction. This discharges the electrons and converts the metal atoms to cations.

gold plating pcb

Types of PCB Gold Plating

There are various gold-plated PCBs. Each gold-plated PCB has its characteristics and properties. Some common types of PCB gold surfaces include:

Electroless Nickel Immersion Gold (ENIG)

ENIG Gold Plating PCB

 

ENIG is a gold surface finish that is frequently utilized. First, the process deposits a thin layer of electroless nickel. Then, it is followed by immersion gold. The power supply devices are not used in the procedure. ENIG has a flat, smooth surface that is easily soldered. It has strong oxidation resistance and is suitable for fine-pitch components.

Consumer electronics and applications that require crucial flatness and solderability use ENIG.

Electroplated Gold

Gold is electroplated by adding a layer of gold to a PCB using electroplating. Electroplated gold provides excellent conductivity and corrosion resistance. It is frequently employed in high-reliability applications.

Electroplated gold is suitable for areas where durability and high conductivity are critical. This includes aerospace and military applications.

Types of Gold Plating PCB

Soft Gold

Soft gold is a gold alloy with a higher percentage of pure gold, which makes it softer and more flexible. Soft gold, like connectors, is appropriate for applications demanding repetitive insertions and removals.

It is used in connector applications where wear resistance and durability are essential.

Hard Gold

Hard gold is a gold alloy with a higher percentage of other metals like nickel or cobalt. This makes it harder and more wear-resistant. Where durability and wear resistance are crucial, people use it. Hard gold is often used in PCB areas requiring high reliability and longevity.

Flash Gold

Flash gold plating is the process of depositing a very thin layer of gold on the PCB surface for a brief period of time. It is a simple and inexpensive procedure. It improves mechanical properties while also reducing corrosion. When you only need a small amount of gold, it is useful.

Flash gold plating is often used in microelectronics. Cost is a significant factor.

Use of Gold Plating on PCB

The primary reason for using gold plating for PCBs is that it is more durable than immersion gold. Hard gold is perfect for sections that frequently come into contact with other electronic components. For example, gold plating is more typically utilized on the gold fingers that link a printed circuit board to another circuit board.

Because some gold fingers are entered and removed from another circuit board numerous times during the life of a PCB, they must be able to survive the abrasion caused by repetitive or incorrect insertion. Gold-plated gold fingers are less likely to be destroyed in this method than immersion gold fingers.

Gold plating may also be chosen due to its simplicity. If someone has no equipment to use gold immersion for their circuit board, they can use gold plating instead. Furthermore, if only a tiny region of a PCB needs to be plated, it is possible to brush that area with the gold plating solution rather than submerging the entire PCB.

One disadvantage of gold plating is that it is more expensive due to the thicker layer of gold. Of course, you won’t be able to solder the PCB if it’s too thick. However, the suitability of hard gold for touch and slide contacts may be worth the expense for many producers.

PCB Gold Plating Thickness

The thickness of gold plating significantly affects the performance, reliability, and cost of PCB. 

Electroless Nickel Immersion Gold (ENIG):

  • Thickness: Typically ranges from 1 to 5 microinches (25 to 127 micrometers).

Electroplated Gold:

  • Thickness: Commonly falls within the range of 10 to 50 microinches (0.25 to 1.27 micrometers). Thicker layers may be used in specific high-reliability applications.

Soft Gold (for connector contacts):

  • Thickness: Can range from 30 to 100 microinches (0.76 to 2.54 micrometers) or more.

Hard Gold (for gold fingers):

  • Thickness: Similar to soft gold, it can range from 30 to 100 microinches (0.76 to 2.54 micrometers) or more.

Flash Gold Plating:

  • Thickness: Typically in the range of 5 to 20 microinches (0.13 to 0.51 micrometers). This method provides a thin layer of gold.

Comparing Immersion Gold and Gold Plating PCB

Property/Aspect

Immersion Gold (ENIG)

Electroplated Gold

Application

Commonly used in consumer electronics, fine-pitch components

Often used in high-reliability applications, aerospace, military

Process

Electroless deposition of nickel followed by immersion in gold solution

Electroplating involves an electric current to deposit a layer of gold

Solderability

Good solderability, suitable for fine-pitch components

Excellent solderability, critical for high-reliability applications

Conductivity

Good conductivity, but lower than pure gold

Excellent conductivity due to the purity of the gold

Corrosion Resistance

Good corrosion resistance, suitable for standard environments

Excellent corrosion resistance, ideal for harsh environments

Thickness

Thinner gold layer compared to electroplated gold

Thickness can be controlled, offering flexibility for various applications

Durability

Moderate durability, suitable for standard applications

High durability, suitable for areas with high wear and repeated use

Cost

Generally more cost-effective compared to electroplated gold

Typically more expensive due to the electroplating process

Common Usage

Commonly used in general-purpose applications and consumer electronics

Commonly used in applications where durability and high reliability are critical

 

Factors to Consider While Selecting Gold-Plated PCB

Factors to Consider Gold Plating PCB

Before selecting the gold-plated PCB, some factors need to be adequately checked. Below are those factors to consider: 

  • Consider the material of the base (e.g., copper in PCBs) for good adhesion.
  • Ensure the surface is clean and conditioned for optimal adhesion.
  • Use chemicals to enhance the bond between the substrate and the gold layer.
  • Choose between electroless or electroplating based on cost, thickness needs, and substrate nature.
  • Control the composition of the gold plating solution for uniform and high-quality deposition.
  • Decide on the gold layer thickness based on application requirements.
  • Control the current density during electroplating for uniform deposition.
  • Maintain proper bath temperature and pH levels for consistent results.
  • Regularly monitor thickness, adhesion, and overall quality throughout the process.
  • Apply necessary treatments, like rinsing and drying, to ensure durability.

Standards

Industry standards ensure the quality, reliability, and consistency of gold-plated PCBs. Several standards organizations provide guidelines and specifications related to gold plating on PCBs. Some of the common standards include:

IPC-4552

  • This standard, published by IPC, provides specifications for the ENIG process. It includes the thickness of the gold layer, nickel layer, and other parameters.

IPC-6012

  • IPC-6012 sets the standards for the qualification and performance of rigid PCBs. It includes specifications for gold plating thickness, adhesion, and other relevant characteristics.

MIL-PRF-55110G

  • This military standard provides performance specifications for rigid insulation printed boards. Military and aerospace applications use it.

ISO 4521

  • ISO standards outline test methods for determining the properties of electrodeposited gold coatings. Besides, it also includes thickness measurement.

Conclusion

We can see that gold is such a precious metal and has its importance in the electronics industry. It is one of the commonly used surface finishes in PCBs. There are various types of gold-plated PCBs. The process of gold plating includes different other methods. The choice of gold leaf depends on multiple factors. The thickness of the plated layer affects the PCB’s overall working performance. With technological advances, there is a high demand for high-performance PCBs. This is likely to lead to more innovations and improvements in gold-plated technology. 

Take the next step in improving the dependability and durability of your PCBs. ElePCB offers gold-plated solutions that will set your electronics distinct. Contact us to discuss your project specifications and discover the ElePCB difference. ElePCB is where innovation meets excellence in electronics.

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