Gold Fingers are gold plated connectors on one edge of a printed circuit board.

A few of the qualities of the gold fingers include:

They must be hard in order to allow the circuit board to be inserted into a connector.
They should also be very smooth and flat to allow for easy insertion.
They are an excellent conductor which makes the connection much better.

How are PCBs with Gold Fingers used?

In a computer you have a number of different peripheral devices that need to be connected to the mother board.  Examples include:

Video and Graphics Card
Network Adaptor Card
Audio Adaptor Card
TV or Other Specialty Adaptor Card

In industrial applications you will see similar uses.   For example, in the “oil and well” industry there are many CPU devices and well locations.  Those CPU devices will be connected wirelessly to a network to transfer data.  The CPU will contain many open slots for connecting various devices and the well location.  Each of those devices requires a circuit board with gold finger connectors that will be inserted into the CPU.

Process and Specifications

An electrolytic process is used that includes hardeners and is plated over nickel.

Typically, the gold used is 98% pure, 24-carat gold.

The nickel is 150 to 200 micro inches thick.

The gold that is plated is 30 to 50 micro inches thick.

The gold is plated on the top and bottom of the board.

If the boards will be in an array, it is recommended that the fingers be placed at the outside edges of the array to allow for the gold plating process.