PCBs Gold Fingers - Why It Matters ?

What is PCB Gold Finger?

PCB gold fingers refer to the metal contact points on a printed circuit board, typically located at the board's edge. They are commonly made of metallic materials such as gold or upgraded gold alloys . Since the surface of the pads is gold-plated and the conductive contacts are arranged like fingers, they are called "gold fingers".

Gold is extremely resistant to oxidation and has strong conductivity in comparison with other PCB surface finishes like HASL. Although it looks nice, gold plating is not merely for aesthetic purposes, it serves a practical function critical to the connector performance.

In the manufacturing process of PCB gold fingers, the selection of materials is crucial. Choosing the right materials while producing gold fingers on the PCB is really important . Gold fingers typically use top-notch materials like pure gold, gold alloy, or gold plating to make sure that electricity flows steadily and reliably. It's also important to pick materials that can resist corrosion and wear, so that the gold fingers last a long time.

There are two types of gold finishes available in the market.

Electroless Nickel Immersion Gold (ENIG):

It’s the most popular PCB surface finish used by Electronic Engineers, as it is economical and relatively feasible to solder than electroplate gold as shown below. JLCPCB offers a competitive price.

EING finish provides reliable electrical connection and better resistance from corrosion and oxidation while it also provides a relatively flat gold layer surface, which is conducive to soldering and assembly. But it’s much softer and cannot withstand the abrasive effects of repeated use.

Electroplated Hard gold :

The gold offered is hard, and the thickness can reach 3-50u. This is more suitable for gold finger PCBs that will be repeatedly plugged-in and removed.  It’s also suitable for PCB boards that require frequent mechanical friction. The cost of gold plating is extremely high, and it is only suitable for partial gold plating such as gold fingers.

Classification of Goldfingers:

1. Conventional gold fingers (flush fingers)Rectangular pads of the same length and width are neatly arranged at the edge of the board. Commonly used in physical objects such as network cards and graphics cards.

2. Long and short gold fingers (i.e. uneven gold fingers)Rectangular solder pads of varying lengths located on the edge of the board, commonly used in physical objects such as memories, USB flash drives, and card readers. ​

3. Segmented gold fingers (interrupted gold fingers)There are rectangular pads of different lengths located at the edge of the board, and the front section is disconnected.

Design Specifications    

In order to ensure the reliability of the gold finger , PCB Design engineers must follow some design rules when designing.Regardless of the purpose or size of the PCB itself, the following rules are always applicable in the design of gold fingers:
Gold-plated connectors should not be placed near PTH (plated-through holes).

• There is no solder mask or screen printing near the gold fingers, Solder masks and screen printing should be kept at a distance from the gold fingers.
• In order to bevel the PCB edge, the gold fingers should never face in the direction of the middle of the PCBs.
• Gold fingers need to be chamfered, generally 30°, 45°, 20°, etc.
• The gold finger is at least 1.0mm away from the PCB outline.Gold fingers should be placed outward from the center of the PCB

Commonly used gold finger chamfering parameters in JLCPCB

At jlcpcb you can find more design specifications about gold fingers.Failure to adhere to the aforementioned guidelines could result in the PCB being incompatible with the parent PCB. For example, the daughter board may not properly fit into the designated slot on the motherboard.

Applications of Gold Finger PCBs

In the digital age, printed circuit board (PCB) goldfingers have become integral components in a myriad of electronic devices that permeate our daily lives.

First of all, mobile phones have become an indispensable part of people's lives. From smartphones to traditional mobile phones, PCB gold fingers are used without exception. The SIM card slot and battery connector of mobile phones are usually connected using PCB gold fingers. These gold fingers not only provide a stable electrical connection, but can also withstand the wear and tear caused by frequent plugging and unplugging, ensuring the reliability and durability of the device.

Secondly, in the computer field, PCB gold fingers also play a vital role. The connection interfaces of memory slots, expansion card slots and other peripheral devices usually use PCB gold fingers. These gold fingers provide computers with high-speed data transmission and stable electrical connections, providing users with a smooth computing experience.
In addition, PCB gold fingers are also widely used in the automotive electronics field. Modern car dashboards, audio systems, navigation systems, etc. all need to be connected using PCB gold fingers. These gold fingers not only ensure stable communication between on-board electronic devices, but also resist vibration and temperature changes during vehicle driving.

In addition to the areas mentioned above, PCB gold fingers also play a role in many other daily devices. For example, in home entertainment systems, audio and video equipment are often connected using PCB gold fingers to bring users a high-quality audio-visual experience. In the office environment, peripheral devices such as printers and scanners are also inseparable from the support of PCB gold fingers.

Conclusion

In summary, PCB goldfingers are indispensable components in everyday life. They ensure stable connections and reliable communications across a diverse range of electronic devices, ultimately enhancing convenience and comfort in people's lives. As technology continues to advance, it is foreseeable that PCB goldfingers will play increasingly vital roles in various domains, promising to bring further convenience and innovation to our daily lives.