Edge Plating vs Gold Finger in Flex PCB

In flex PCB design, edge plating and gold fingers are often confused because both involve exposed conductive edges or contact areas. However, they serve very different electrical, mechanical, and reliability purposes. Choosing the wrong option can lead to premature wear, poor connectivity, or assembly failures.

Their differences in manufacturing process, structural design, and application suitability directly impact performance, reliability, and long-term durability in flex PCB applications.

What Is Edge Plating in Flex PCB?

Edge plating (also called side plating) is a process where copper is plated along the edge or perimeter of a flex PCB, electrically connecting top and bottom copper layers.

Key characteristics

• Copper plated on PCB edges 

• Typically covered with surface finish (ENIG, immersion tin, etc.) 

• Not designed for repeated mechanical contact 

• Used mainly for electrical continuity and grounding

Common purposes

• Ground shielding around flex PCB edges 

• EMI containment 

• Mechanical reinforcement of the board edge 

• Creating a continuous ground path in rigid-flex transitions

What Are Gold Fingers in Flex PCB?

Gold fingers are exposed connector pads plated with hard gold (electroplated gold over nickel), designed for repeated insertion and removal into connectors.

Key characteristics

• Precisely defined contact pads 

• Hard gold plating with controlled thickness 

• Designed for friction and wear resistance 

• Strict dimensional and plating requirements

Common purposes

• Board-to-board or board-to-connector interfaces 

• High-reliability signal or power connections 

• Applications requiring multiple mating cycles

  

Edge Plating vs Gold Finger: Core Differences

Aspect	Edge Plating	Gold Finger
Primary function	Electrical continuity / grounding	Connector contact
Wear resistance	Low	High
Gold thickness	Thin (chemical gold)	Thick hard gold
Mechanical contact	Not intended	Designed for repeated mating
Cost	Lower	Higher
Design tolerance	Moderate	Strict

Manufacturing Differences That Matter

Plating process

• Edge plating requires special routing and masking to expose board edges during plating. 

• Gold fingers require selective hard gold electroplating, adding extra process steps and cost.

Flex-specific challenges

• Maintaining plating integrity during bending 

• Preventing copper cracks at plated edges 

• Controlling gold thickness on flexible substrates

From a manufacturing perspective, gold fingers demand tighter process control than edge plating, especially on thin polyimide-based flex PCBs.

Reliability Considerations in Flexible Applications

Edge plating limitations

• Not suitable for sliding or repeated contact 

• Risk of copper exposure or oxidation if used as a connector 

• Edge stress concentration during dynamic bending

Gold finger advantages

• Excellent wear resistance 

• Stable contact resistance 

• Proven reliability in high-cycle mating environments

If the flex PCB will experience insertion cycles, vibration, or movement at the contact area, gold fingers are the safer choice.

Application-Based Selection Guide

Choose edge plating when:

• The goal is grounding or EMI shielding 

• The edge is not part of a connector interface 

• Mechanical contact is minimal or nonexistent

• Typical uses:

• Shielded flex PCB designs 

• Ground continuity in rigid-flex boards

Choose gold fingers when:

• The PCB mates with a connector 

• Repeated insertion/removal is expected 

• Signal integrity and contact reliability are critical

• Typical uses:

• Display connectors 

• Wearable devices 

• Automotive and industrial modules

Design Tips for Flex PCB Engineers

• Avoid placing bend zones directly adjacent to gold fingers or edge-plated areas 

• Clearly define mating cycle requirements early in the design phase 

• Specify gold thickness and chamfer requirements for gold fingers 

• Consult your manufacturer to confirm flex-compatible plating limits

• Early design decisions greatly reduce cost and reliability risks in production.

Conclusion

Although edge plating and gold fingers may appear similar at first glance, they solve very different problems in flex PCB design. Edge plating focuses on electrical continuity and shielding, while gold fingers are engineered for durable mechanical connections.

Understanding these differences—and their manufacturing implications—helps engineers select the right solution, improve reliability, and avoid unnecessary redesigns.