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EMI and plastic PC cases

I

iddqd

Member
There are a lot of PC cases now on the market with plastic side covers or just completely made out of plastic. I remember EMI used to be the justification for a steel case. There used to be steel covers for open 5.25" and 3.5" slots. So are the components now are less sensitive? Is steel still important?

I am posting it here since there is nothing more technical then a physics question.


Thanks.
 
steel is not the only item which blocks "emi".

those plastic ones have a steel frame with a thin sheet of metal on the inside which block em radiation. those steel covers still exist, to comply with FCC standards.

it's not really a physics question.

steel is just cheap, that's all. but now, plastic is cheaper.
 


<< There are a lot of PC cases now on the market with plastic side covers or just completely made out of plastic. I remember EMI used to be the justification for a steel case. There used to be steel covers for open 5.25" and 3.5" slots. So are the components now are less sensitive? Is steel still important?

I am posting it here since there is nothing more technical then a physics question.


Thanks. >>



The shield is there to prevent emission of interference, not for protecting from outside EMI. In the United States, shielding enclosure is mandated for computer thats in use.
 
As far as raw materials go, steel is still much cheaper than plastic and half as much as aluminum, but total cost for plastic can be less once manufacturing costs are added. I suspect that many computers wouldn't pass the FCC class B test if housed in a plastic case.
 
These plastic cases have to have some kind of embedded conductive layer, or simply a metallic coating on the inside. But a standard PC's weak spot on EMI are the slot brackets, drive bays and outgoing cables.

regards, Peter
 
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