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PCB Gold Finger Design and Processing Guide

2021-07-21

Gold Finger PCB is a special type of printed circuit board, commonly used in applications that require high reliability and wear resistance, such as computer motherboards, graphics cards and other electronic devices. This article will delve into the definition, surface treatment methods and design considerations of gold finger PCBs.

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Article Directory

Ⅰ. Definition of the Gold Finger

II. Surface finish methods for gold finger PCBs

III. Precautions for Gold Finger Design

IV. Precautions for Gold Finger Processing

Frequently asked questions and answers

1. Definition of the Gold Finger
Gold finger, also known as edge connector, is a device that inserts one end of a PCB into a connector slot. It uses the connector pins as the outlet for the external connection of the PCB to achieve conductivity between the solder pad or copper sheet and the corresponding position pins. In order to increase its conductivity, oxidation resistance and wear resistance, gold fingers are usually treated with nickel gold plating or ENIG. Due to its shape resembling a finger, it is named Gold Finger.
2. Surface finish methods for gold finger PCBs
The surface finish method of Gold Finger PCB is crucial for its performance and application areas. The following are two common ways:
1)Nickel Gold Plating
Nickel gold plating is a common surface finish method, and its thickness can reach 3-50 micro inches. It has excellent conductivity, oxidation resistance and wear resistance, so it is widely used on gold finger PCBs that require frequent insertion and removal or PCBs that require frequent mechanical friction. However, due to the high cost of gold, nickel gold plating is usually only used for the treatment of local areas such as gold fingers. The surface of this surface finish method is silver white, but its solderability is slightly poor.
2) ENIG
ENIG is another common surface finish method, with a thickness typically of 1 micro inch and up to 3 micro inches. ENIG has excellent conductivity, surface smoothness and solderability, making it widely used in high-precision PCBs with designs such as keyway, bound IC, BGA, etc. For gold finger PCBs that do not require high wear resistance, the whole panel ENIG process can also be chosen, which has a much lower cost. The surface of the finished ENIG is golden yellow.
3. Precautions for Gold Finger Design
When designing a gold finger PCB, there are some key points that need to be particularly noted:
1)Wear resistance of gold finger
For PCBs that require frequent insertion and removal, in order to increase the wear resistance of gold fingers, it is usually necessary to use hard gold electroplating.
2)Chamfering of gold finger
Gold fingers usually require chamfering, with a general chamfering angle of 45°. The presence of chamfers can reduce potential hazards, as shown in the figure.
3)Window opening for solder mask
The solder pad of the gold finger needs to be treated with window opening for the whole block of solder mask, without the need for steel mesh.
4)Distance between the solder mask and the gold finger
The distance between the solder pad and the gold finger needs to comply with the design specifications, usually requiring the solder pad to be at least 1mm away from the gold finger position, including via solder pads.
5)Surface finish of gold finger
The surface of the gold finger should not be covered with copper.
6)Copper cutting treatment
All layers of the inner layer of the gold finger require copper cutting treatment, usually with a copper cutting width of approximately 3mm. This can reduce the impedance difference between the gold finger and the impedance line, while also benefiting ESD.
The above are several aspects that need special attention when designing a gold finger PCB to ensure the reliability and performance of the gold finger.

4. Precautions for Gold Finger Processing
If you plan to use gold finger PCB, the following are some precautions to be taken during the processing of Rich Full Joy’s PCB:
1.The thickness range of the PCB that can be beveled is 1.2mm to 2.4mm. PCBs with thickness that are not within this range cannot be beveled.
2.The depth and angle of the beveled edge are usually between 20° and 45°. The distance between the gold finger and the edge of the PCB should be sufficient, generally recommended to be 0.6m to 1.5mm, to avoid damaging the gold finger.

Rich Full Joy specializes in processing gold finger PCBs to ensure high quality and reliability. Our process can meet different design requirements and provide excellent performance for your project.

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Gold finger PCBs play an important role in the modern electronic field, and their reliability and performance depend on surface finish methods and design details. By selecting appropriate processing methods and paying attention to key design considerations, it is possible to ensure excellent performance of Gold Finger PCBs in various applications. If you need high-quality gold finger PCB processing services, please consider Ruizhi Xinfeng, and we will be happy to provide you with support.

Q&A
1.What is a Gold Finger PCB?
Gold finger PCB is a special type of printed circuit board, commonly used in electronic applications that require high reliability and wear resistance, named after its shape resembling a finger.
2. What are the surface finish methods for gold finger PCB?
The common surface finish methods for gold finger PCBs include nickel gold electroplating and ENIG, which have different advantages and applicability.
3. How to increase the wear resistance of gold finger?
To increase the wear resistance of gold fingers, it is usually necessary to use hard gold electroplating to improve their surface hardness.
4. What precautions should be taken when designing a gold finger PCB?
When designing a gold finger PCB, it is important to pay attention to key issues such as chamfering, window opening for solder mask, distance between solder pads and gold fingers, and surface finish of gold fingers.
5. How to guarantee the quality of gold finger PCB?
We use advanced technology and strict quality control to ensure the provision of high-quality and reliable products.

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