PCBA for non-contact infrared thermometer

What is the gold finger in PCB?

March 27 , 2021

The gold finger of PCB is mainly used for computer hardware such as: (between the memory stick and the memory slot and the graphics card slot, etc.). All signals are transmitted through the golden fingers in the PCB. This type of design requires high wear resistance and conductivity on the surface of the pad. Its arrangement is similar to a finger, so it is called "golden finger". The function of the golden finger: through the contact and conduction between the golden finger and the spring piece in the card slot, the PCB and the motherboard can be interconnected and it is convenient to disassemble and replace.

Gold plating: The gold is attached to the PCB board by electroplating, so it is called electro-gold. Because of its strong adhesion, it is also called hard gold. Its thickness can usually reach 5-30u". Gold has excellent conductivity and can It is guaranteed to be conductive while not oxidizing. At the same time, because gold is wear-resistant and frequently plugged and unplugged, it also has very good conductivity. Gold plating is generally widely used in PCB memory sticks, etc., but the cost of gold plating is higher, and it is generally more suitable for gold fingers.

Immersion gold: through a chemical reaction, the gold is bonded to the PCB pad, because the adhesion is weak, it is also called soft gold. Its conventional thickness is 1u", up to 3u". It has excellent electrical conductivity, flatness and solderability. Immersion gold is generally widely used in solder joints of electronic components.

Since the crystal structure formed by immersion gold and gold plating is different, immersion gold is easier to weld than gold plating and will not cause welding defects. At the same time, it is also because immersion gold is softer than gold plating. Therefore, gold finger PCBs generally choose gold plating, hard gold has better wear resistance, and can ensure that the quality is not affected by plugging and unplugging. However, the hard gold processing technology is relatively complicated, and the high gold thickness requires more gold salt, which will directly cause the cost to be too high. If the PCB does not need to be plugged and unplugged frequently, it is recommended to make ENIG, which can not only effectively save costs, but also make the components easier to solder.

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