Is EMI/EMC still a big concern for a PC case?

Question

I've recently started looking into researching potential concerns when it comes to using a non-metal material for a custom PC case, specifically wood. I've seen people talk about heat, electrical grounding, and EMI.
I've found that the first two are not that big of a deal to worry too much about, but what I'm unsure of is the last one; EMI.

Some people have reported no detectable interference from their devices, while others have reported the opposite (one even said their power supply alone was at fault).

My knowledge on the topic is only second-hand from such reports (of which I'm not sure how much can still be applied to today, as technology improves over time), and it seems to me that some of the concern comes from the individual parts that a case with a full metal enclosure can simplify the solution for, though my question is: Should there still be concern for proper EMC shielding in a PC case, especially when one is using parts from well-known reputable brands for their computer?

Answer 1

First off PC's emit a large amount of EMI, even with the case properly grounded they can cause AM radio signals to be completely 'drowned out'. A PC has multiple clocks and DC DC converters with very large switching currents and emits radiation. If your a 'nice' person you'll use a properly grounded case that is made of metal or other shielding material.

If your selling PC's they should be FCC certified.

As far as building them yourself and as far the law is concerned is a grey area, technically a device sold in a residential area should have an FCC certification. But a computer you build yourself isn't sold as a complete unit and isn't subject to authorization by the FCC (which costs thousands of dollars). The FCC suggests that you use a well grounded case. If you did cause interference with someone else's radio bands, the FCC could order you to shut the device off or fix the problem.

A personal computer is a special type of digital device -- a computer that is marketed for use in the home. Computers that are marketed through retail outlets or through mail order catalogs, and advertised to the general public, are considered to be personal computers. In order to prevent the radio noise generated by the digital device from interfering with radio communications, digital devices must be designed to contain the noise. This is accomplished by: 1) designing the digital circuitry in a manner that minimizes radio noise emissions; 2) enclosing the circuitry in a well-grounded case that prevents radio noise from escaping; and, 3) including a well-filtered power supply that keeps the radio noise from leaking onto the electrical power lines.

Source: UNDERSTANDING THE FCC REGULATIONSFOR COMPUTERS AND OTHER DIGITAL DEVICES Page 2

What happens if a digital device causes interference?

Digital devices that comply with the FCC technical standards and have been certified and marketed in accordance with the FCC rules may not cause interference and must accept any interference that they receive. This means that the user of a personal computer may be required to shut the computer off if it is found to be causing interference to any authorized radio communications, such as police, fire, TV or radio,even if the computer has been certified and has an FCC ID tag on it to prove it. In the event that this happens, the user will be allowed to resume use of the computer only after the cause of the interference problem has been eliminated.

Source: UNDERSTANDING THE FCC REGULATIONSFOR COMPUTERS AND OTHER DIGITAL DEVICES Page 14

Answer 2

I built a wooden PC case when I was in college to house a Pentium III board.

The computer ran just fine, my analog TV reception was fine, my radio worked, and my neighbors never once mentioned that their TV or radio reception was unusually bad. No one from the FCC ever tracked me down and told me to turn it off.

The PC ran without problems for several years until I finally put it into storage when I got something better.

The case was made of mostly plywood. It had top, bottom, back, and left-side walls. But no right wall, and only half of the front wall. It was rather open so there was good ventilation. I made custom slide in rails from sheet metal to mount the disk drives.