On computer memory sticks and graphics cards, we can see a row of golden conductive touch plates, which are called “gold fingers”. In PCB design and production industry, Gold Finger, or Edge Connector, is used as the outlet of the board through the Connector Connector. Next, let’s understand the processing method and some details of the gold finger in PCB.

Goldfinger PCB surface treatment

1, electroplating nickel gold: thickness up to 3-50U “, because of its excellent conductivity, oxidation resistance and wear resistance, is widely used in the need to often plug and pull out of the goldfinger PCB or need to often carry out mechanical friction ON the PCB board, but because of the high cost of gold plating, only used in the local gold plating process such as goldfinger.

2, heavy metal, thickness of conventional 1 u “, up to 3 u “because of its superior electrical conductivity, smoothness and weldability, are widely used in such as buttons, binding IC, BGA design of high precision PCB, goldfinger PCB for wear-resisting performance requirements is not high, also can choose the whole plate zedoary process, and the process cost is electric gold process cost is much lower. The color of gold sink is golden yellow.

PCB gold finger details processing

1) In order to increase the wear resistance of gold fingers, gold fingers usually need to be plated with hard gold.

2) Gold finger needs chamfering, usually 45°, other angles such as 20°, 30°, etc. If there is no chamfering in the design, there is a problem; The 45° chamfering in PCB is shown below:

3) Golden finger needs to do the whole block blocking welding window opening process, PIN does not need to open the steel net;

4) The minimum distance between the tin-sink and silver-sink pads and the top of the finger is 14mil; It is recommended that the pad should be more than 1mm away from the finger, including the through-hole pad;

5) Do not lay copper on the surface of the finger;

6) All layers of the inner layer of gold finger need to be coppered, usually with a width of 3mm; Can do half finger coppers and whole finger coppers.

D: Is the “gold” of goldfinger gold?

First, let’s understand two concepts: soft gold and hard gold. Soft gold, usually of a softer texture. Hard gold, usually a compound of hard gold.

The main role of gold finger is to connect, so it must have good electrical conductivity, wear resistance, oxidation resistance, corrosion resistance.

Because pure gold (gold) is relatively soft, gold fingers generally do not use gold, but just a layer of “hard gold (gold compound)”, which can not only get good electrical conductivity of gold, but also can make it wear resistance, oxidation resistance.

So PCB has not used “soft gold”? The answer is of course used, such as the contact surface of some mobile phone keys, the aluminum wire On THE COB (Chip On Board). The use of soft gold is generally nickel gold precipitation in electroplating on the circuit board, its thickness control is more elastic.