EMC design consideration of Industrial Fanless Embedded Computer

Whether it is a industrial Fanless Embedded computer/Vision Controller for Machine Vision or for business usage, the first consideration in EMC design is the EMI (electromagnetic interference) design of the board itself, so the electromagnetic radiation is greatly reduced in the design of the board, but due to the increase of the frequency of the processor, simply relying on the design of the board itself in EMI can not fully meet the requirements of EMC certification. Therefore, the EMC design of the vision industrial computer chassis has become more important.

EMC design of the vent
The best way to deal with electromagnetic radiation, both internally and externally, is to shield the electromagnetic radiator with a fully sealed metal box, and the thicker the metal layer for shielding, the better. In this way, electromagnetic shielding has the best effect both internally and externally. However, due to heat dissipation and external expansion equipment. No matter whether it is a commercial PC or an industrial computer, it cannot be strictly sealed. The important part of the chassis design to prevent electromagnetic leakage is the well-balanced design between heat dissipation and electromagnetic leakage. It must be fully cooled and designed with electromagnetic compatibility in mind. What is usually seen on commercial PCs is The heat dissipation aperture above is circular and porous. In fact, the design criteria for preventing electromagnetic leakage have many limitations on the size and shape of the heat dissipation aperture. Research experiments have shown that the square aperture has better electromagnetic leakage prevention than the circular aperture.

EMC design at the seam of the chassis
When the distance between two contact points on the chassis is greater than 0.25xλ (wavelength sign), harmful electromagnetic radiation can easily leak between the two points. Therefore, the design of the seam at the chassis is also an important indicator to examine the EMC design.
The environment of the Vision Controller is complex and variable. Some environments are highly vibrating. The EMI shrapnel design is easy to lose the elasticity of the shrapnel in a vibrating environment. The industrial control machine adopts the 1.2mm high-quality steel plate, which has excellent anti-deformation characteristics. Because the industrial control cabinet is mostly horizontal, the weight and steel characteristics of the top steel plate can ensure the close contact between the chassis walls. The excellent industrial computer chassis can also pass CE, FCC and other EMC certifications when EMI shrapnel is not used. If some environments are extremely electromagnetically rigorous, a more reliable metal conductive cloth will be used at the seams of the chassis.

Special design of the chassis surface
Vision Controller IPCs are sometimes used in highly corrosive environments such as sea salt, car exhaust from highways, and chemical plant gases. Therefore, the inner and outer surfaces of the chassis must be treated to resist corrosion.
Sometimes the computer will work in a vibrating environment. In some special cases, the vibration will cause some electrical components in the chassis to contact the internal surface of the chassis. Because the inner wall of the chassis is conductive, it is easy to cause a short circuit and burn the device.
The internal painting process of the industrial computer makes the inner wall of the chassis non-conductive, which can prevent such phenomena from happening. However, it is precisely because these non-conductive chassis inner walls have higher challenges for the EMC design of the industrial computer. Because the inner wall of the industrial computer is also painted, the surface of the chassis is not conductive and cannot be formed like a commercial PC. Therefore, it is only necessary to leave a contact surface with no paint at some positions to form an electrical conductor and form a surface on the entire chassis. The potential body and the processing technology are more complicated.