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Techniques for Edge Connector PCBs

Jarnistech > Goldfinger PCB > Techniques for Edge Connector PCBs
Edge Connector PCB

In today’s mobile-activated and computerized world, the communication between devices is facilitated by the exchange of signals. Gold fingers play a crucial role in enabling this communication by serving as connecting contacts between circuit boards and components such as sound cards or graphics.

The advancement in technology has revolutionized the transmission of commands and signals, marking a significant improvement from the earlier electronics that comprised separate modules, making communication challenging.

Gold fingers play a vital role in allowing immediate reading of a circuit board’s processes by the main processing board. This seamless connectivity is instrumental in ensuring the efficient functioning of electronic devices.

Moreover, the integration of advanced technology has interconnected various sectors, bridging the gap between private and public domains. In manufacturing industries, signals are transmitted between machines and devices to execute processes, many of which are automated and do not require human intervention.

In settings like food-packaging plants and auto-assembly factories, computer-controlled machinery executes commands using circuit boards of different sizes. Gold fingers play a pivotal role in enabling these industrial processes, making modern operations feasible.

In essence, PCB gold fingers are essential components that facilitate the inner workings of computer technology by establishing crucial connections between circuit boards and components, thereby enabling seamless communication and operation of electronic devices.

What are PCB Gold Fingers?

PCB gold fingers, also known as edge connectors, are gold-plated contacts on the edge of a printed circuit board (PCB). These contacts are typically used to establish a connection between the PCB and external devices or components, such as expansion cards, memory modules, or connectors. The gold plating on the PCB gold fingers serves several important purposes:

1.Electrical conductivity:

Gold is an excellent conductor of electricity, making it ideal for transmitting signals between the PCB and external components without loss of signal quality.

2.Corrosion resistance:

Gold is highly resistant to corrosion, ensuring the longevity and reliability of the connection over time.

3.Wear resistance:

The durable nature of gold plating ensures that the contacts maintain their integrity even with repeated insertions and removals of external components.


Gold plating provides a surface that is easily solderable, allowing for a secure and reliable connection between the PCB gold fingers and external components.

Gold Plating Techniques for Edge Connectors

Gold plating is a critical process in the manufacturing of edge connector PCBs, as it enhances the electrical performance, durability, and solderability of the connectors. The choice of gold plating method depends on various factors, including the operating environment, signal integrity requirements, assembly processes, and budgetary considerations.

Electroless Nickel Immersion Gold (ENIG)

●Process: Electroless nickel plating followed by immersion gold plating.

●Properties: Excellent solderability, corrosion resistance, and wear resistance.

●Applications: High-reliability applications, such as aerospace, military, and medical devices.

Hard Gold Plating

●Process: Electrolytic deposition of pure gold over a nickel underlayer.

●Properties: High hardness, wear resistance, and low contact resistance.

●Applications: Connectors subjected to high wear and tear, such as in industrial and automotive applications.

Flash Gold Plating

●Process: Thin layer of gold electroplated over a nickel or copper underlayer

●Properties: Good solderability and corrosion resistance at a lower cost than other gold plating methods.

●Applications: General-purpose applications where cost and solderability are primary concerns.

Comparison of Gold Plating Methods

FeatureENIGHard GoldFlash Gold
Corrosion ResistanceExcellentExcellentGood
Wear ResistanceGoodExcellentFair
Contact ResistanceModerateLowModerate
Lead TimeModerateLongShort

Advantages of ENIG:

●Excellent solderability and corrosion resistance.
●Good wear resistance.
●Lower cost than hard gold plating.

Advantages of Hard Gold Plating:

●High hardness and wear resistance.
●Low contact resistance.
●Excellent corrosion resistance.

Advantages of Flash Gold Plating:

●Good solderability and corrosion resistance.
●Lower cost than ENIG and hard gold plating.
●Short lead time.


●ENIG is preferred for reflow soldering, while hard gold is more suitable for press-fit applications.

●Hard gold plating provides lower contact resistance for high-speed signals.

●Flash gold plating is a good option for cost-sensitive applications where solderability is a priority.

Ultimately, the choice of gold plating method depends on the specific requirements of the application, including the operating environment, signal integrity needs, assembly processes, and budgetary constraints.

Factors to Consider When Selecting Gold Plating Method

Factors to Consider When Selecting Gold Plating Method for Edge Connectors:

1. Operating Environment:

●Harsh environments (e.g., high temperature, humidity, corrosive chemicals) require gold plating with high corrosion resistance, such as ENIG or hard gold.

●Less demanding environments may allow for flash gold plating.

2. Signal Integrity Requirements:

●High-speed signals require gold plating with low contact resistance, such as hard gold.

●Lower-speed signals can tolerate higher contact resistance, making ENIG or flash gold plating suitable options.

3. Assembly Processes:

●Reflow soldering is compatible with ENIG plating.

●Press-fit applications typically require hard gold plating for better wear resistance.

4. Budgetary Considerations:

●Flash gold plating is the most cost-effective option.

●ENIG and hard gold plating are more expensive but offer better performance.

5. Other Factors:

●Solderability: ENIG and flash gold plating provide good solderability. Hard gold plating may require additional surface preparation for optimal solderability.

●Wear Resistance: Hard gold plating offers the highest wear resistance, followed by ENIG and flash gold plating.

●Contact Resistance: Hard gold plating has the lowest contact resistance, followed by ENIG and flash gold plating.

●Lead Time: Flash gold plating typically has a shorter lead time than ENIG or hard gold plating.

General Guidelines:

●For high-reliability applications in harsh environments, ENIG or hard gold plating is recommended.

●For high-speed signals, hard gold plating is preferred.

●For cost-sensitive applications, flash gold plating may be a suitable option.

●For applications with specific assembly requirements, consider the compatibility of the gold plating method with the intended soldering or press-fit processes.

By carefully evaluating these factors, manufacturers can select the optimal gold plating method for their edge connector PCBs, ensuring reliable performance and long-term durability.

Usefulness of Gold Plating in Edge Connectors for PCBs

Gold plating is a critical component in edge connectors for printed circuit boards (PCBs), serving both as an electrical contact and a protective layer for the connecting edges. Its durability and resistance to wear and tear ensure reliable connections, even after repeated insertions and removals.

Key Functions of PCB Gold Fingers:

Interconnection Points:

Gold plating enables signal transmission between internal cards or peripheral devices and the computer through female slots such as AGP, ISA, and PCI slots on the motherboard.

External Connections:

External peripherals such as monitors, printers, and speakers connect to the motherboard via PCB gold fingers, which provide a secure and reliable interface.

Special Adapters:

PCB gold fingers allow for the addition of performance enhancements to computers through secondary PCBs that slot into the motherboard. These cards provide features such as high-fidelity sound and enhanced graphics.

Power Supply:

Gold plating ensures a stable power connection for module PCBs, enabling them to function properly and provide advanced functionalities to both stationary and remote computing devices.

Benefits of Gold Plating:

●High Conductivity: Ensures reliable signal transmission.
●Durability: Withstands wear and tear from frequent insertions and removals.
●Corrosion Resistance: Protects the connecting edges from environmental factors.
●Low Contact Resistance: Minimizes signal loss and ensures efficient data transfer.

Key Limitations in the Plating Process

When it comes to plating PCB gold fingers, there are several important restrictions that must be adhered to in order to ensure the integrity and functionality of the circuit board. These restrictions include:

1. The inner layers near the edge of the PCB must be free of copper to avoid exposure when beveling the edges.

2. The length of plated pads on the PCB gold fingers should not exceed 40 millimeters.

3. Pads, surface-mount devices (SMD), and plated holes should not be positioned within 1.0 mm of the hard gold plating on the fingers.

4. A minimum distance of approximately 0.5 mm should be maintained around the hard gold fingers to prevent any interference or short circuits.

5. Any deviation from the standard spacing requirements around the hard gold fingers can lead to a dysfunctional or physically weak circuit board.

Adhering to these restrictions is essential to ensure the proper functioning and reliability of the PCB gold fingers, as any violation of these guidelines could result in performance issues or structural weaknesses in the circuit board.

Best Practices for Edge Connector PCB Gold Plating

●Surface Preparation: Proper cleaning and activation of the connector surface is essential for good adhesion.

●Plating Thickness Control: Adhere to specified plating thickness requirements to ensure optimal performance.

●Post-Treatment Processes: Annealing or heat treatment can improve the properties of the gold plating.

By carefully selecting the appropriate gold plating technique and adhering to best practices, manufacturers can achieve high-quality edge connector PCBs that meet the specific requirements of their applications.


Gold plating is a critical process in the manufacturing of edge connector PCBs, as it enhances their electrical performance, durability, and solderability. The choice of gold plating method depends on various factors, including the operating environment, signal integrity requirements, assembly processes, and budgetary considerations.

This article has provided a comprehensive overview of the different gold plating techniques available for edge connectors, including electroless nickel immersion gold (ENIG), hard gold plating, and flash gold plating. We have compared their properties, applications, and advantages to help manufacturers make informed decisions.

By carefully considering the factors outlined in this article and selecting the appropriate gold plating method, manufacturers can achieve high-quality edge connector PCBs that meet the specific requirements of their applications. This will ensure reliable performance, long-term durability, and optimal signal integrity for their electronic devices.

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