COB on Flexible PCB

Flex Plus Tech team
Jul 31
3 min read

As technology trends move toward miniaturization and higher performance, COB on flexible PCB is becoming a critical solution for modern electronics. This technique allows bare chips to be mounted directly onto flexible substrates, enabling space-saving, lightweight, and high-speed designs.

At Flex Plus, we specialize in flex PCB manufacturing and offer COB services, enabling us to help customers bring advanced electronic designs to life quickly and efficiently.

What Is COB on Flexible PCB?

COB (Chip-on-Board) is a microelectronic packaging technique where bare semiconductor chips are mounted directly onto a circuit board—in this case, a flexible printed circuit. The chip is bonded directly to the copper pads on the flex PCB and connected via wire bonding, followed by encapsulation using epoxy or other protective materials.

Unlike traditional Surface Mount Technology (SMT), which relies on packaged components, COB eliminates the packaging layer, resulting in:

Significant space savings
Improved thermal and electrical performance
Faster signal transmission

When implemented on flexible PCBs, this technique provides a powerful solution for applications with stringent space, weight, and bendability requirements.

Why Choose COB on Flexible PCB?

Extreme Miniaturization

COB enables the mounting of ICs directly onto ultra-thin flexible substrates. This is critical for applications like medical sensors, smartwatches, hearing aids, and smart cards, where every millimeter counts.

Enhanced Heat Management

flex PCBs—especially polyimide-based ones—have excellent thermal stability. When combined with COB, the result is a more efficient heat dissipation system without the need for bulky heat sinks.

Superior Electrical Performance

Because there are no long leads or packaging materials, signal pathways are shorter and more direct. This reduces inductance and resistance, leading to higher-speed data transmission and lower power loss.

Improved Reliability

Fewer interconnects and solder joints mean fewer potential failure points. This is especially important in environments exposed to vibration, thermal cycling, or mechanical stress.

Flex Plus’s Capabilities

At Flex Plus, we offer complete, turnkey solutions—from flex PCB fabrication to COB process integration. Ensure higher quality and quicker turnaround.

Our Services Include:

Optimization of FPC Board Circuits for COB Compatibility

We work closely with customers to optimize pad layouts, routing, and materials for die attach and bonding.

Precision Die Bonding

High-speed placement of bare chips using adhesive or solder reflow, based on application needs.

Wire Bonding & Flip Chip

We support both gold and aluminum wire bonding, as well as flip-chip bonding for ultra-dense applications.

Encapsulation & Protection

Epoxy or silicone glob-top solutions provide environmental protection while maintaining flexibility.

Prototyping & Mass Production

Whether you need 10 samples or 100,000 units, we tailor our process to meet your volume, lead time, and budget.

Applications of COB on Flexible PCBs

Wearable Devices

Fitness trackers, AR glasses, and smart bands benefit greatly from COB on flex PCB, enabling lightweight and slim-profile designs.

Medical Electronics

Instruments like biosensors, portable ECG monitors, and implantable devices benefit from COB’s small form factor and reliable performance.

Automotive Modules

COB on flex PCB is widely used in automotive TPMS sensors, and dashboard electronics due to its vibration resistance and temperature stability.

Industrial Controls

In harsh environments where space is tight, such as robotic arms or sensor modules, this integration ensures durability and performance.

LED Lighting

COB flex PCBs allow high-brightness LEDs to be mounted directly to flexible substrates—perfect for architectural lighting, automotive, and displays.

Design Considerations for COB on flex PCB

For engineers considering this solution, some key factors must be accounted for:

Pad Design and Pitch: The copper pad layout must align precisely with the die’s bond pads.

Material Selection: Polyimide is preferred for its flexibility, heat resistance, and dimensional stability.

Moisture Sensitivity: Proper encapsulation is critical for reliability in humid or chemically harsh conditions.

Bending Radius: During design, consider the allowable bend radius to prevent damage to the chip or wires.

Our engineering team assists clients through each stage—from design validation to final testing.

Why Work with Flex Plus?

As a professional flex PCB manufacturer, we offer a streamlined process and one-stop support. Our clients benefit from:

Over 20 years of flex PCB fabrication experience
IPC Class 3 and ISO-certified manufacturing standards
Engineering support for custom and complex layouts
Competitive pricing and rapid delivery, even for small batches

Conclusion

Combining COB on flexible PCBs represents the generation of electronics manufacturing—smaller, faster, more efficient. At Flex Plus, we help businesses realize this potential by offering advanced, scalable solutions with unmatched reliability.

Whether you’re developing a new wearable device, upgrading your automotive lighting system, or creating medical sensors, our team is ready to support your innovation journey.