Name: 6 Layers Golden Finger PCB manufacturer
Brand: PCB Printed Circuit Board and PCBA manufacturing
Rating: 5 (1 reviews)

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Data Sheet

Gold fingers, also known as edge connectors, refer to a row of gold-plated conductive contact arrays widely distributed on computer memory modules, graphics cards and other plug-in PCBs. They serve as the electrical interface for external interconnection and signal transmission, and are key structural components for board-to-board connection and pluggable replacement. This document specifies the surface treatment processes, key design details, material selection principles and manufacturing methods of PCB gold fingers for engineering reference and process implementation.

1 PCB Surface Treatment for Gold Finger Applications

1.1 Electroplated Nickel Hard Gold

Electroplated nickel-gold system can achieve gold thickness ranging from 3–50 μm, featuring excellent electrical conductivity, oxidation resistance and mechanical wear resistance. It is commonly used in PCBs requiring frequent plugging and unplugging or periodic mechanical friction. Due to relatively high material and process costs, this process is generally limited to local selective gold plating on gold finger contacts.

1.2 Electroless Nickel Immersion Gold (ENIG)

Immersion gold typically provides a gold layer of approximately 1 μm, with a maximum thickness of up to 3 μm. Benefiting from high surface flatness, stable conductivity and excellent solderability, it is widely applied in high-precision PCBs with key bonding areas, IC bonding positions and BGA layouts. For applications with low wear resistance requirements, full-board immersion gold can be adopted, with significantly lower overall cost compared to electroplated hard gold. The finished surface presents a uniform golden appearance.

2 Key Design & Processing Details of Gold Fingers

To improve wear resistance and service life, gold fingers are generally required to use electroplated hard gold alloy.
Chamfering must be applied at the front end of gold fingers, mostly at a standard 45° angle; 20°, 30° and other angles can also be customized according to assembly requirements. Lack of chamfer design will lead to insertion difficulties and potential contact damage.
Solder mask opening shall be implemented in the entire gold finger area, and no stencil opening is required on the PIN contacts.
The minimum clearance between the tip of gold fingers and tin/silver solder pads shall be no less than 14 mil. In actual design, it is recommended that all pads (including via pads) maintain a distance greater than 1 mm from the gold finger area.
Copper routing or copper pouring is prohibited on the surface of gold finger contacts.
Inner-layer copper removal shall be implemented on all internal signal layers, with a typical copper-free width of 3 mm. Copper can be removed in half-finger or full-finger configuration according to structural requirements.

3 Classification of Soft Gold & Hard Gold and Application Differentiation

Gold coatings for PCB contacts are divided into soft gold and hard gold. Soft gold is relatively low in hardness and close to pure gold texture; hard gold is a gold-based alloy with enhanced mechanical hardness.

As the core function of gold fingers is electrical interconnection, they must maintain stable conductivity, wear resistance, oxidation resistance and corrosion resistance under service conditions. Since pure gold has low mechanical strength and poor wear resistance, gold fingers generally do not use pure soft gold, but adopt a hard gold alloy electroplating system to achieve balanced electrical and mechanical performance.

Soft gold is still applied in specific scenarios, such as mobile phone keypad interfaces, COB aluminum wire bonding areas and other low-wear contact positions. Soft gold is usually deposited via electroless nickel-gold process, with more flexible thickness control to meet different bonding and contact requirements.

4 Application Rationale of Gold Finger Structure

Gold finger and slot matching structures are widely used in pluggable PCBA modules that require interconnection with the mainboard while supporting convenient replacement, similar to the plug-and-socket mechanism.

Gold possesses high electrical conductivity and strong chemical inertness, effectively resisting oxidation and corrosion even under long-term exposure. This ensures stable electrical contact performance after repeated insertion and extraction, which is critical for memory, expansion cards and other plug-in components.

5 Selection of Gold Finger Process Specifications Based on Application Scenarios

In conventional high-wear scenarios, gold fingers are typically plated with hard gold at a thickness of 5–30 μm to support up to 20,000 insertion-extraction cycles, and the gold layer is generally required to be thicker than 5 μm. However, the hard gold electroplating process is complex and consumes large amounts of gold salt, resulting in relatively high manufacturing costs.

For many PCB products that do not require frequent plugging, thick hard gold is unnecessary. Instead, immersion gold (soft gold system) with a thickness of 1–3 μm can be used to effectively reduce PCB manufacturing costs while meeting functional requirements.

6 Standard Manufacturing Process of Gold-Plated Fingers

Standard gold fingers adopt an electroplating process. To ensure uniform electroplating, conductive conducting wires are arranged at the bottom of gold fingers to provide electrical path. The process sequence is as follows:

Deposit a nickel barrier layer on the base copper surface;
Electroplate gold to the specified thickness on the nickel layer;
Prior to gold plating, all non-gold-plated pads are covered with high-temperature resistant tape;
After gold plating completion, the protective tape is removed;
The gold finger area is then taped again, and other pads undergo subsequent surface treatment such as hot air solder leveling (HASL), OSP, immersion gold, etc.;
After finishing all surface treatments, the protective tape on gold fingers is removed;
During board profiling, the front end of gold fingers is beveled to form a chamfer structure for smooth slot insertion.

Model: 6 Layer Golden Finger PCB

Material: FR4

Layer: 6 Layers

Color: Green/White

Finished Thickness: 1.6mm

Copper Thickness: 1OZ

Surface Treatment: Immersion Gold+Gold Finger

Trace/Space: 4mil/4mil

Special Process: Gold Finger (0.1um)

6 Layers Golden Finger PCB manufacturer

Description

Data Sheet