What Are PCB Gold Fingers?

PCB Gold Fingers are the narrow, long, thin, and columned connections on the edge of a printed circuit board and whose purpose is to enable the board to connect with others. They act as the connector points onto which the other board's connectors make contact.

The fingers are also used to connect external components to the board. In other cases, these boards offer a connection point for transferring network data. They also operate as audio adapters. This is, for instance, employed in designing smartphones and smart watches.

As their name goes, they resemble fingers. They are made of flash gold, which is the hardest gold form. They vary from 3 to 50 microns in thickness.

PCB Gold Fingers are made to resist wear and tear, as boards are connected and disconnected from each other regularly. This explains the use of Cobalt and Nickel in a mixture with gold in manufacturing the fingers. Otherwise, gold renders them highly corrosion resistant. Gold is third after copper and silver in terms of strength of corrosion resistance and electrical conductivity. This article will explain how to make gold fingers for PCB.

Tips for Designing PCB Gold Fingers

PCB Gold Fingers are made according to the intended use and application. Therefore, different boards have different specifications. However, some tips apply when designing all the fingers.

- Never locate solder masks or screen printing near the gold fingers.

- They should be aligned to face opposite the center of the printed circuit board.

- You should also avoid locating plated-through holes near the fingers.

- When designing PCB Gold Fingers, it is advisable to use the most ideal type of electroplated hard gold which is more resistant to wear and tear when the terminals come into contact with other connectors.

Although electroless Nickel Immersion Gold can be used and is more cost-effective than the EH hard gold, it is less resistant to abrasion.

- The design process must ensure perfect fitting between different fingers, for the different boards that are to be interconnected. This is achieved by following the required standards in the plating of gold fingers.

- Inspections ensure that the fingers and slots will fit properly. Each PCB must therefore pass through this inspection process. Inspection is done using a magnifying glass. Defects testing is also required to ensure gold plating is done and functions as required.

Those that do not or perhaps have fingers that do not properly adhere to the PCB surfaces are singled out and taken for correction. Adhesion tests ensure that this is so.

- The plating process is done in a series of steps to ensure the fingers come together. First, the board details are completed, nickel is then applied over the copper when it's time to attach the fingers, and then the surface finish is applied.

- Gold Fingers should also be designed and produced in adherence to the specific guidelines, standards, and regulations that govern them. This includes the use of gold and at least 10% of cobalt. Tape testing of contact edges must also be done. This test is done to ensure the fingers adhere to the board nicely.

What is PCB Gold Finger Beveling?

Beveling minimizes a square edge to achieve a sloping side. Edge connectors beveling, in Gold Fingers, is achieved after solder mask and before applying the surface finish.

Beveling is one of the three processes involved in gold finger plating. In this case, connector edges are beveled at angles of 30 to 45 degrees to ease insertion on corresponding slots. The purpose of beveling is to make sure the connectors achieve insertions quickly. It is commonly done based on the specifications of the client.

Beveling is necessary for circuit boards with longer gold fingers. It helps to fit them together as a single piece. Beveling can also help where edge connectors are needed at specific measurements. During the leveling process, the fingers must be made to snap together into place easily. Otherwise, the edge connector parts may fail to fit together.

The Specifications of PCB Gold Fingers You Should Know

There are many design specifications that you should follow when designing PCB Gold Fingers. First, you are to avoid using copper on the PCB layers towards the PCB edges. This prevents exposure during the beveling process.

We already said that you should maintain a 1 mm distance between the gold fingers and the plated-through-holes (PTH). You must also keep a minimum distance of 0.5 mm between the fingers and the circuit board outline.

Failure to adhering to the above spacing requirements may cause the board to be weak and one that easily malfunctions. There also should be no solder masking or screen printing near the fingers. The fingers are also to be placed facing outwards from the center of the PCB.

During the production of Gold Fingers, some standards must be followed. These standards include:

Chemical composition

The gold plating should have 5 to 10% cobalt in composition. This helps to achieve maximum rigidity along the PCB Gold Finger edges.

Thickness of the fingers

It is required to be 2 to 50 microinches. However, they are standardized into different thicknesses including 0.031 inches, 0.062 inches, 0.093 inches, and 0.125 inches.

Visual tests

These tests are done using a magnifying glass to ensure that the finger contact edges are smooth, clean, and free from excess plating.

Tape test

This should be done to ensure the plating adheres properly with other contacts. The test involves fastening a strip of tape over the content edge and then removed. The tape is then inspected for plating traces. Plating is not passed on for continuous injection and ejection if there is any gold visible on the tape.

In some boards, PCB Gold Fingers have varying lengths. A good example is fingers on memory cards. In this case, the device connected through the long fingers has to be powered first to those devices on the shorter finger connectors. When designing these fingers, you should avoid any confusion because wrongly connecting powered devices to the wrong connectors may lead to shorting.

For water-resistant and rugged electronics, it is advisable to use segmented gold fingers. These fingers vary in length. Some of them are also disjointed within the same fingers.

Applications of PCB Gold Fingers

For those looking for information on how to make gold fingers PCB, using PCB Gold Finger plating helps to prevent oxidation. This is achieved by gold plating. Gold plating also ensures high conductivity and durability of the fingers. This is despite having uneven surfaces. The fingers are also extremely expensive.

In case designers want to ease soldering when making PCB Gold Fingers, immersion gold is used instead of gold plating. It also does not affect the signal. The immersion gold is also hard to get oxidized although is less durable.

The basic application of Gold Fingers is to serve as a connector contact between two printed boards. The gold will prevent the edges from wear and tear when the board is being used regularly. For commercial and technical applications of Gold Fingers, please see the following.

The fingers are used to make special adapters, in which case they allow easier inclusion or adding of several enhancements to a PC. Fingers also act as interconnection points, for instance where female slots such as ISA, AGP, or PCI must connect to the secondary PCB. Gold Fingers serve to conduct signals between the computer, a peripheral device, or even an internal card.

Gold fingers also serve as external connections providing contacts between the board and other machinery and equipment, for instance. This is evident in computerized industrial applications.

Conclusion

Gold Fingers are mainly used as connector points for boards with each other. This facilitates the transfer of data and information. They can be used in industrial and commercial settings, for instance, where manufacturing processes are computerized. Other applications include making adapters in computers where several peripherals must connect to the motherboard.

This article is for those looking for information on how to make gold fingers PCB. These fingers are specially designed based on the application and need for the board contacting. For instance, they are hardened by using flash gold to minimize wear and tear that results in connecting two or more boards. They are further hardened using cobalt and nickel.

Plating is done in steps and inspection and testing must be done to ensure the fingers meet special application requirements. The design specifications must be followed to design fingers that do not wear out easily and that allow boards to snap into each other. For instance, there are thickness and chemical composition specifications to be followed when designing and manufacturing these Gold Fingers.

In addition, although Nickel Immersion Gold can be used for plating to save on costs, it is less resistant to abrasion. Using this type of gold for plating means the durability of the fingers is at stake. Otherwise, electroplated flash gold is used to reduce any wear and tear on the terminals.

Depending on the application of the board, all the Gold fingers can be equal or some can be shorter than others on the same board.