Signal Transmission Requirement: Why USB 2.0?

1. Digital Signal Transmission

   Output signals of modern uncooled infrared thermal imaging sensors (detectors) are fully digital. As a mature and universal digital data transmission protocol, USB 2.0 is ideal for carrying image data streams generated by detectors.
2. Sufficient Bandwidth

   For mainstream infrared detectors with VGA resolution (640×480) or lower, their data rates fall well within the 480 Mbps bandwidth of USB 2.0, with ample bandwidth headroom reserved.
3. Integrated Power Supply & Control

   Besides data transfer, the USB port supplies +5V power to directly feed the detector or front-end circuits. Meanwhile, the USB protocol enables straightforward control operations including detector initialization and parameter tuning.

Physical Form Factor Requirement: Why FPC?

1. Ultra-Compact Size

   Thermal imaging modules are integrated into compact devices such as phone accessories, handheld temperature detectors, security cameras and UAVs, where internal space is extremely limited. Flexible Printed Circuit (FPC) boasts ultra-thin thickness (less than 0.2 mm), an unmatched advantage over rigid PCBs and ordinary cables.
2. Flexibility for Movable & Rotatable Structures

   Many devices require rotational movement or separation between the thermal imaging module and main board.

• Example 1: The screen and lens detection unit of handheld thermal imagers often need relative rotation.
• Example 2: Plug-in mobile thermal imaging attachments (e.g. FLIR ONE) rely on a flexible bridge to connect the phone port and remote lens module.
  The outstanding bending resistance of FPC is critical to realize such structural designs.

1. High Integration & Reliability
   Essential resistors, capacitors, ESD protection components and even miniature chips can be directly mounted onto FPC to form a complete signal transmission board. This reduces connection points and boosts overall equipment reliability.

Typical Application Scenarios & Device Forms

External Thermal Imaging Cameras for Smartphones

Miniature Security & Industrial Temperature Measurement Cameras

Internal Wiring of Handheld Thermal Imagers

Summary of Technical Advantages

1. High Integration: Combines data, power and control signals into one single line to simplify circuit design.
2. Maximized Space Savings: Lays a solid foundation for miniaturized, slim device development.
3. Enhanced Reliability: Eliminates failure risks introduced by multiple discrete connectors and wiring harnesses; FPC connections feature stable, fixed assembly.
4. Mass Production Friendly Modular Structure: Detector modules and main boards can be tested separately before quick assembly via FPC, compatible with automated production lines.

Key Considerations

1. Cable Length Limitation: The transmission distance of USB 2.0 signals over FPC is restricted (typically under 1 meter), which fully meets the needs of internal device interconnection.
2. Electromagnetic Interference (EMI): Shielding design is required for high-speed digital signals transmitted on flexible cables; premium-grade FPC is equipped with ground and shielding layers.
3. Connector Durability: Repeated bending stress concentrates at the joint between FPC and connectors, so proper connector model selection and locking structure design are essential.

Conclusion