Electronic – EMC testing of unenclosed PCB assembly

ceemcfcc

What is the most common practice in performing EMC tests for PCB assemblies that will be sold without a housing? In my case it is an FPGA development board. Is it possible to design excessive switching hardware in a way that it passes CE and FCC testing without a metal housing? Or do you usually define a designated case of application with a housing?

Best Answer

You can make single board products with fast electronics pass CE/FCC in plastic or no housing.

It is easier if you:

  • keep all cables attached in one end only
  • use fewer cables
  • specify a specific simple application for the FCC/CE test
  • don't have things that stick off the board (display, large connectors etc.)
  • make a very low impedance power distribution network (PDN)
  • have good filtering on the interfaces off the board

It is very difficult if you have multiple boards (plug-in, stacked, cable connected etc.). Actually I would specify a Faraday cage type box if you have multiple boards.

If you absolutely must include a display - try to get one with LVDS interface.

If you have a radio as part of your design, some of this becomes a bit more complex.

I suspect many go fairly light on the CE/FCC thing and self-certify with limited time spent on measurements. It is highly unlikely anyone will ever sue you for an eval board that is out of FCC/CE spec and most of these boards runs in fairly limited volumes.

Also: I have seen some outfits in China offer to do very cheap CE/FCC marking for you. You get the paperwork - they get some money. Win-win. :-)