EM compatibility of single board computers and laptops

Question

Like a lot of people on this site, I own some single board computers (SBC) and microcontroller boards (UDOO, Raspberry Pi, Arduino, Atmel boards, etc.).

I wonder about the electromagnetic emissions of these products. Since they don't have a metallic enclosure (or any enclosure at all), they surely emit radiations. On the other hand, I think that they have CE compatibility and that it covers the level of tolerable emissions.

Now, I have a laptop with broken hinges and cracked plastic cover. I am currently building a new case in order to make an all-in-one desktop PC with it. Since I won't use the original shielding, I will have to provide some shielding myself (emi standards/best practices for PC cases) .

The question is: How do SBCs achieve EM compatibility without shielding? Is it because they use carefully crafted designs, or because they run on relatively lower power, or a combination of both?

Answer 1

It's all about the level of (well the quasi peak level of) radiated emissions. If you can design a card that doesn't exceed them without a shield then you don't need one. In high volume consumer electronic design your mission is pretty much never to use a shield (well maybe for an rf section).

Yes that means doing your design carefully and considering the impact of your decisions on your EMI. It also often means making use of a spread spectrum clock to take advantage of the way emissions are measured.

I would wager that some sbc boards you can buy have done the work to ensure they are compliant, and other cheaper knockoffs may just put the logo on and believe they'll never get caught...