Gold Fingers: A Guide to Understanding Gold-Plated PCB Connectors
A prototype PCB's legend assists design engineers in determining the component designators, switch settings and test points of the PCB, which are very important for assembling, testing and servicing them. While there are three separate ways to print a prototype PCB's legend with respect to PCB assembly and production, there are more things that go into the legend. One of those things is gold plating. This article is a brief backgrounder to the gold plating PCB connector process, commonly call gold fingers.
What are gold fingers?
Gold fingers are the common name for gold-plated connectors that run on the edges of a PCB prototype. Since they are gold, long, and thin, they resemble fingers, hence, the name gold fingers.
What materials are used to manufacture gold fingers?
Gold fingers are manufactured from flash gold, which is one of the hardest golds around. The specifications to manufacture gold fingers must be precise. Their thickness must be in the range of 3Us to 50Us. Flash gold is used because its high level of harness ensures that it will have a long working life without a need for repair.
What do gold fingers do?
Used to electroplate the PCB's pads, gold fingers are edge connector contacts. Their function is to assist in protecting the prototype PCB from deterioration and failures. With the correct thickness and application, gold fingers can be used reliably for close to 1,000 cycles before repair is required.
How are gold fingers applied?
Gold fingers can be used for many different things. Their use would be based on the designer's purpose. Some common applications of gold fingers are:
Provide an interconnection point for transferring network data.
A place for attaching daughter boards or specialized adapters.
Connect external components to the prototype PCB.
Function as an audio adapter.
Do gold fingers have any unique design specifications?
Yes. This article previously cited that certain specifications depend on the gold finger’s use and application. Beyond that, there are a few design rules that should be adhered to no matter how they are applied, including:
Do not locate plated through holes near the gold fingers.
The gold fingers should not have solder mask or screen printing near them.
Always orient the gold fingers so they face opposite the center of the PCB.
If you would like to learn more about the design and application of gold fingers on PCBs, please call one of your design professional today.