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Anodizing to limit EMI/RFI Issues

 

I have built an aluminum enclosure (6061 t-6 sheet @ 0.0625) for some electronic components. Though the case is tightly sealed, I am still having some issues with EMI/RFI.

Rumor has it that anodizing the aluminum will provide a substantial barrier to EMI/RFI. Is this indeed the case?

Thanks ...

Keith Miracle
- Houston, Texas

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Keith,

I would be extremely surprised if you saw any improvement using anodized pieces for your enclosure. My experience has been that the anodized surface is an insulator as far as RFI/EMI is concerned. What you need is an absolutely bomb-proof ground. You might look into getting an RF gasket material to use between your enclosure and the chassis. (There are many suppliers of such material.) Any small crack or gap between your shield and the ground plane will allow certain levels of EMI/RFI to enter. Also be aware that any connectors or feedthroughs that you are using for signal to enter or leave your enclosure might be a problem. Most connectors have a rating for EMI/RFI on their spec sheet. You should have RF gasket material on the flange of your feedthroughs where they attach to the bulkhead. Using unshielded cable or a shielded cable with a bad ground connection also may be a cause of EMI/RFI problems. Corners that are sharp on your enclosure (rather than radiused) can lead to EMI problems if your ambient environment contains extremely high-power radar. If you are trying to meet a stringent specification for EMI/RFI because your instrument is going to be used in an environment with high power generators of RFI, you should probably seek the advice of an expert consultant in the field. Whole textbooks are written on this subject. If you are just having "pick-up" problems on equipment used in an office environment, you might try the RF gasket material and check your connectors for leakage.

Ronna Erickson
Radio Astronomy, University of Massachusetts - Amherst, Massachusetts