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Edge Connector PCB: What are the Best Gold Plating Methods?

The mobile-activated and computerized world of today, signals are usually sent between many devices. To be able to enact each command, there must be communication between at least two circuit boards. This cannot be possible without using gold fingers. This is because gold fingers serve as a connecting contact between the motherboards and their components such as sound cards or graphics.

The technology that is useful in the transmission of these commands and signals has become a great achievement from the electronics produced earlier, which are made of different separate modules, which became difficult in bringing some communication with them.

When there are gold fingers, then a circuit board’s processes are read immediately with the help of the major processing board.

Furthermore, the processes linked with advanced technology have a link between all the corners of the private and public sectors. Also, in the manufacturing world, signals are usually sent in-between different machines and devices to enact some processes, majority of which won’t be conducted by humans.

At food-packaging plants and auto-assembly factories, computer-prompted machinery fulfills many commands, majority of which make use of circuit boards having different sizes.

Gold fingers make the industrial processes of today possible. So what are pcb gold fingers and what is their significance to the computer technology’s inner workings.

What are PCB Gold Fingers?

gold finger
gold finger

These are gold-plated columns, which are usually seen around the edges of PCBs. The major purpose of the secondary PCB is to serve as a computer’s motherboard. Furthermore, pcb gold fingers help in other devices, which communicate through digital signals like smartwatches and consumer smartphones. Gold is useful in these PCB connecting points due to the superior conductivity of the alloy.

Three types of gold can be applied to the plating process of the PCB gold finger:

Electroplated Hard Gold Plating

The gold here is hard or solid and thick. Therefore, this is ideal for any abrasive effects due to the constant usage of the PCB.

Flash Gold

When we mean flash gold, we mean rapid gold plating. This is a pre-process when dealing with hard gold plating. It makes use of large current as well as a solution with higher gold content that forms a thinner and dense gold plating later on the nickel layer. This facilitates subsequent electroplating of gold-cobalt alloy or gold nickel.

There are people that believe that it is possible to make gold plated PCB while the price is less expensive and the time for PCB manufacturing is shorter. This makes it possible to sell these flash Gold printed circuit boards in the market.

Due to the fact that flash gold does not have the electroplating gold process, the cost is very cheap compared to that of hard gold plating. However, it has a very thin gold layer, which cannot cover the nickel layer underneath the gold effectively. Therefore it becomes very easy to cause the issue of oxidation after the storage of the circuit board for long, which could affect the solderability further.

Electroless Nickel Immersion Gold Plating

This is also called ENIG and this gold is easier and more cost-effective to solder compared to electroplated gold. However, it is thin and soft and makes ENIG not good for any abrasive effect as a result of the circuit board removal and insertion.

Gold fingers ensure that circuit boards can communicate.  For a specific command to become enacted, there are signals which have to pass between the different contacts.

Immediately you enter a command, this signal will have to pass in-between at least one circuit board before reading it.  This process involved in pcb gold fingers plating deals with many meticulous steps. This makes sure that each of the circuit boards rolls off the line of production properly to conduct error-free signals.

Furthermore, the standards necessary for the plating helps in ensuring a good fit between gold fingers present on each of the circuit boards with the slots on the specific motherboard.

To make sure that these slots and fingers fit the hand-in-glove, the printed circuit board has to pass through some defect tests and inspections. If the circuit board’s gold plating doesn’t work with the surface adequately, then the results won’t be sufficient for any commercial release.

To ensure that PCB gold fingers come together, the process of plating has to be completed in about three steps where the board’s surrounding details are first completed. When it is time to plate the fingers, apply nickel over this copper.

Ways to Choose the Best Gold Plating Method

Solderability or Adhesion

With non-precious elements present in hard gold plating, soldering of the ENIG plating or soft gold plating becomes more difficult. Furthermore, for joints that are very sensitive like thermostatic bonding, wire bonding, etc, you should only consider ENIG/soft gold plating.

Wear Resistance or Contact Force Absorption

Hard gold plating offers better wear resistance and hardness. For applications requiring repeated on-off switching or sliding wear, it is necessary to specify hard gold plating.

Contact Resistance

Soft gold plating features lower contact resistance in contrast to hard gold plating. Most especially for any high temperature application, as a result of the quick formation of oxides as well as other compounds, any hard gold plating will lead to an increase in contact resistance.


ENIG plating or soft gold plating will more likely be scratched. In general, it is advised to make use of hard gold plating in any application requiring beautiful gold contacts like visible interconnect applications.

Biocompatibility or Corrosion Resistance

ENIG plating or soft gold plating boasts high purity. Furthermore, it is superior with respect to corrosion resistance, while other hard gold plating components reducing the coating’s corrosion resistance at high temperatures are easily oxidized. Therefore, for any medical application, it is advisable to use ENIG plating or soft gold plating.

Usefulness of Gold Plating

Gold plating serves as a connecting contact that is found in-between the adjoining PCBs. Apart from its conductivity, the major aim of the gold plating is to serve as a protection for the connecting edges. As a result of the wear and tear that could result from many uses.

As a result of the hard gold’s strength at its thickness, the pcb gold fingers ensure that PCBs are connected, reconnected, and disconnected up to about a thousand different times in the corresponding slot.

Gold fingers serve multipurpose functions. When there is a specific computer setup, you will discover some peripherals, which connect with computers as a result of the PCB gold fingers. Below are some of the usefulness of gold fingers:

Interconnection Points

Whenever there is a connection between a secondary PCB and the motherboard, this is achieved via one of some female slots like AGP, ISA, and PCI slot. Via these slots, the gold plating conducts signals in-between an internal card or a peripheral device and the computer.

External Connections

The connection of outer peripherals, which has been added to the computer station to the motherboard, is only possible by using PCB gold fingers. Devices like monitors, printers, scanners, subwoofers, and speakers all plugged into some slots found behind the tower. So also, these slots attach to the printed circuit boards (PCBs) connecting the motherboard.

Special Adapters

With PCB gold fingers, it becomes possible to add many performance enhancements to the personal computer. Furthermore, through secondary printed circuit boards which slot perpendicularly in the motherboard, computers will be able to deliver hi-fidelity sound and better graphics. Because the cards are seldom reattached and unattached, generally, the gold fingers outlast the card.

To ensure that a specific device functions, the card has to connect to a specific power source. This is all possible due to the motherboard’s corresponding slots and fingers. With gold plating, power is provided for the module PCBs. This helps to function and offer modern-day functionalities to the users or stationary and remote computing devices.

What is PCB Gold Finger Beveling?

On a circuit board, the process of PCB hard gold plating is useful after applying the solder mask and just before the surface finish. Let us consider the hard gold plating process.

Nickel Plating: First of all, the plating of about 3 to 6 microns is done first to the fingers’ connector edges.

Beveling: The beveling of the connector edges is done at specific angles. This ensures easier and a better insertion on the corresponding slots. Normally, beveling is done at angles between 30 and 45 degrees.

Gold Plating: The plating of about one to two micros of solid gold is done over the nickel. Usually, this gold is enhanced using cobalt to ensure boosted surface resistance.

Some fingers of hard gold plating will be shorter or longer than the others. Take for instance, circuit boards may feature longer fingers present at one of the ends. By this, the PCB can be easily inserted into a specific slot, as ends having longer fingers will easily snap in place.

What are the Major Restrictions when Plating?

There are some restrictions when plating. The major restrictions include:

  • The inner layers along the edge of the PCB must be copper-free. This prevents exposure of copper when beveling.
  • The plated pads must not exceed a length of 40 millimeters
  • Pads, SMD, and plated holes mustn’t be placed within 1.0 mm of the hard gold plating fingers
  • There must be a distance of about of about 0.5 mm

Deviation from all the standard requirements for the spacing around the hard gold fingers present on a PCB cannot happen. This could cause a dysfunctional or physically weak card.


We hope we have been able to cover what edge connector pcbs are. If there is any aspect where you need some explanation, please reach out to us here.




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