How to Connect Two PCB Boards: PCB Interconnection Methods & Design Guide

Connecting two printed circuit boards (PCBs) is a common requirement in modern electronic product design.

As electronic systems become smaller and more complex, engineers often need to connect multiple PCBs to achieve:

• Modular product designs
• Better space utilization
• Easier assembly and maintenance
• Improved electrical performance

However, there is no single best method for connecting two PCBs.

The correct solution depends on:

• Mechanical structure
• Available space
• Signal requirements
• Operating environment
• Production volume
• Reliability expectations
• Cost target

This guide explains the most common PCB connection methods and how to choose the right solution for different applications.

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1. Common Methods How to Connect Two PCB Boards

There are several ways to connect two PCBs, from simple wire connections to advanced rigid-flex PCB structures.

The most common PCB interconnection methods include:

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2. FPC (Flexible Printed Circuit) Connection

FPC is one of the most popular methods for connecting two PCBs when space is limited or the boards are positioned at different angles.

A flexible PCB cable provides electrical connection while allowing bending and movement.

Common applications:

• Mobile devices
• Displays
• Wearable electronics
• Automotive electronics
• Compact consumer products

Advantages of FPC:

✔ Flexible and space-saving
✔ Lightweight structure
✔ Supports complex mechanical designs
✔ Reduces wiring complexity

Limitations:

• Higher material cost than wires
• Requires careful bending radius control
• Not suitable for excessive mechanical stress

Also you can refer to our FPC (Flexible PCB)

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3. Board-to-Board (B2B) Connector Connection

Board-to-board connectors create a direct connection between two PCBs through pins and sockets.

They are widely used in modular electronic systems.

Common types include:

• Pin header connectors
• Socket connectors
• Mezzanine connectors
• Stacked connectors

Applications:

• Industrial controllers
• Communication equipment
• Embedded systems
• Test equipment

Advantages:

✔ Easy assembly and replacement
✔ Suitable for modular designs
✔ Good electrical performance
✔ No additional wiring required

Limitations:

• Requires accurate mechanical alignment
• Connector height may increase product thickness
• Cost increases for high-performance connectors

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4. Wire-to-Board Connection

Wire connections are a simple and flexible method for connecting two PCBs.

The wires can be connected through:

• Solder joints
• Terminals
• Pin headers
• Wire harnesses

This method is common when two boards are physically separated.

Applications:

• Industrial equipment
• Power electronics
• Control cabinets
• Large mechanical systems

Advantages:

✔ Low cost
✔ Flexible positioning
✔ Easy modification during prototype stage

Limitations:

• More manual assembly work
• Potential wiring mistakes
• Less compact compared with FPC

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5. Direct PCB-to-PCB Soldering

For permanent connections, two PCBs can be connected directly through soldering.

Common methods include:

• Solder bridges
• Castellated holes
• Edge soldering
• Pin soldering

This method is often used when:

• The boards will not be separated
• Maximum mechanical stability is required
• Production cost needs to be minimized

Advantages:

✔ Low cost
✔ Strong mechanical connection
✔ No additional connector required

Limitations:

• Difficult to repair
• Not suitable for modular products
• Requires manufacturing process control

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6. Ribbon Cable Connection

Ribbon cables are flat cables containing multiple parallel conductors.

They are commonly used when many signal lines need to be transferred between two PCBs.

Applications:

• Computer systems
• Industrial machines
• Control panels
• Instrumentation equipment

Advantages:

✔ Supports many signals
✔ Organized wiring structure
✔ Easy assembly

Limitations:

• Larger than FPC solutions
• Limited flexibility
• Not ideal for compact products

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7. Rigid-Flex PCB: Integrated PCB Connection Solution

For advanced electronic products, connecting multiple PCBs with external connectors may not be the best solution.

A rigid-flex PCB combines:

• Rigid PCB sections
• Flexible PCB sections

into one integrated circuit board.

Instead of connecting two separate boards, the flexible section becomes the permanent electrical bridge.

Applications:

• Medical electronics
• Aerospace systems
• Automotive electronics
• High-end industrial equipment

Advantages:

✔ Eliminates connectors
✔ Reduces assembly complexity
✔ Improves reliability
✔ Saves product space

Limitations:

• Higher manufacturing cost
• Requires specialized PCB manufacturing capability

Also you can refer to our Rigid-Flex PCB

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8. How to Choose the Right PCB Connection Method?

The best connection method depends on several engineering factors.

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8.1 Available Space

For compact products:

Recommended:

• FPC
• Rigid-flex PCB
• Small board-to-board connectors

Large systems may use:

• Wires
• Ribbon cables

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8.2 Signal Integrity Requirements

High-speed signals require careful consideration.

Important factors include:

• Impedance control
• Signal loss
• Crosstalk
• EMI performance

For high-speed applications:

• Controlled impedance FPC
• High-quality connectors
• Rigid-flex PCB

are usually preferred.

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8.3 Mechanical Stress and Reliability

Applications exposed to:

• Vibration
• Temperature cycling
• Mechanical movement

require stronger connection methods.

Recommended:

• Rigid-flex PCB
• Secure connectors
• Proper strain relief

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8.4 Assembly and Maintenance Requirements

If products require frequent repair:

Choose:

• Board-to-board connectors
• Cable connections

For permanent products:

Choose:

• Direct soldering
• Rigid-flex PCB

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8.5 Cost Considerations

The lowest-cost solution is not always the most economical.

A cheaper connection method may increase:

• Assembly labor
• Failure rate
• Maintenance cost

Engineers should consider the total product lifecycle cost.

About PCB manufacturing process, you can know here

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PCB Connection Method Comparison

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Conclusion

Connecting two PCB boards requires balancing electrical performance, mechanical design, manufacturing cost, and long-term reliability.

For simple applications, wires or connectors may be sufficient.

For compact and high-reliability products, FPC and rigid-flex PCB solutions provide better performance and design flexibility.

The best PCB connection method is not always the most advanced one. It is the solution that matches the product requirements, manufacturing capability, and reliability expectations.

Choosing the correct PCB interconnection method at the design stage can reduce manufacturing problems and improve product performance.

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Frequently Asked Questions (FAQ)

1. What is the best way to connect two PCB boards?

The best method depends on the application. FPC is suitable for compact products, connectors are suitable for modular designs, and rigid-flex PCB is ideal for high-reliability applications.

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2. Can two PCBs be connected without connectors?

Yes. Two PCBs can be connected using wires, direct soldering, FPC, or rigid-flex PCB technology.

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3. What is the difference between FPC and ribbon cable?

FPC is a flexible printed circuit manufactured with copper traces, while ribbon cable uses multiple parallel wires. FPC usually provides better space efficiency and reliability.

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4. Is rigid-flex PCB better than using connectors?

For high-reliability products, rigid-flex PCB can reduce connection points and improve reliability. However, connectors may still be better when easy maintenance is required.

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5. How do you connect two PCBs for high-speed signals?

High-speed designs usually require controlled impedance solutions such as high-quality connectors, FPC with impedance control, or rigid-flex PCB structures.