Face Recognition System PCB: Design, Materials and Manufacturing

What the Board Has to Do

A face recognition terminal is a complete edge computing product. It captures an image from a camera, runs a neural network to detect and match a face, drives infrared illumination for operation in low light, stores templates securely, and communicates with an access control system over a network. All of that sits on a board that must fit behind a small display, run continuously, and do so without leaking the biometric data it holds. Each of those functions imposes its own requirement on the layout, and the difficulty is that they conflict: the high speed image interface wants short, impedance controlled traces, the AI processor wants a large thermal path, the camera wants a quiet power rail, and the security element wants isolation.

High Speed Interfaces

The camera connects through MIPI CSI, which is a high speed differential interface with a strict impedance target and tight length matching between the lanes. The processor connects to DDR memory with matched trace lengths and controlled impedance, and it usually talks to the outside world over USB, Ethernet or Wi-Fi. Each of these needs a continuous reference plane, and none of them should cross a plane split. The practical approach is to give the high speed nets their own region of the board, route them on inner layers with ground above and below, and keep the image interface as short as the mechanical design allows, because the camera position is fixed by the optics.

Thermal Design for the AI Processor

An AI processor running inference continuously produces significant heat in a small package, and the enclosure behind a display has little airflow. The board has to move that heat out, which usually means a thermal via array from the processor pad down to internal ground planes, generous copper area on those planes, and a mechanical path from the board to the enclosure or a small heatsink. Where the thermal load is severe, a metal core or a copper inlay under the processor becomes worthwhile. The thermal design has to be validated with an infrared measurement or a thermocouple on a prototype, because the processor will thermally throttle and the recognition speed will drop if the path is inadequate.

Power Architecture

The board carries several rails: a core rail for the processor, a memory rail, an analogue rail for the camera sensor and a higher voltage rail for the infrared LED driver. Sequencing matters, because most processors define a power-up order and will not start correctly if the rails come up in the wrong sequence. The camera sensor needs a low noise rail, so its regulator and its decoupling should be placed close to the sensor and away from switching nodes. The infrared illuminator draws high current pulses, so its driver loop must be short and its return path must not run through the analogue or camera area.

Security

Biometric data is sensitive, so the design usually includes a secure element or a trusted platform to store keys and templates, and the processor is configured for secure boot. On the board, that means the interface between the processor and the secure element should be short and, where the product requires it, protected against probing. Some designs add tamper detection mesh or switches so that the stored data is erased if the enclosure is opened. However it is implemented, the security architecture has to be decided before the layout, because retrofitting a secure element into a finished design is expensive.

Optical and Mechanical Considerations

The camera has to be aligned with the window and the lens holder, so the board position is set by the mechanical design, not the other way around. The infrared illuminator should be positioned so its light does not leak into the camera path, and its switching should be synchronised with the image capture to avoid washing out the frame. Electromagnetic compatibility matters here too: high current LED pulses near a sensitive image sensor can degrade the picture, so the illumination driver and its return path need to be kept away from the camera interface and the analogue supplies. Conformal coating or a gasket may be needed if the terminal is installed where moisture or dust can reach the board.

Materials and Manufacturing

A six to eight layer high-Tg stack-up is typical, with controlled impedance on the high speed layers and good thermal spreading through the internal planes. Where the AI processor has a dense ball grid array, HDI with microvias may be needed to escape the package, which raises the cost but also reduces the board area. Assembly is dominated by the fine pitch processor and the camera connector, and the process needs a controlled reflow profile because the image sensor is sensitive to temperature and moisture. Cleanliness matters as well, since residue near the sensor or the window affects image quality.

A face recognition terminal combines high speed design, thermal engineering and security on one board, so it should be planned with the fabricator from the start. Review how PCB manufacturing handles controlled impedance and HDI, apply the high speed and thermal rules in your PCB design and layout, and check the design and manufacturing considerations before release. A prototype PCB assembly run with camera bring-up and thermal measurement proves the design before volume.

FAQ

How many layers does a face recognition board need? Six to eight is typical, with HDI microvias when the AI processor package is dense.

Why is thermal design so important? Because the processor throttles when it overheats, which slows recognition and can cause dropped frames.

Does the camera need a separate power rail? Yes. The image sensor is sensitive to noise, so its analogue supply and decoupling should be isolated from the switching rails.

Is a secure element always required? Not always, but biometric data is sensitive, so secure storage and boot plus tamper protection should be considered from the beginning.

Conclusion

A face recognition system PCB has to serve a camera, an AI processor, an infrared illuminator and a secure element at the same time. Keep the image interface short and impedance controlled, build a real thermal path out of the processor, sequence the rails properly, isolate the analogue supplies and decide the security architecture before the layout. Planned that way in 2026, the board delivers fast, reliable recognition without throttling or compromising the data it holds.