Re: [SI-LIST] : skin effect

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From: Muhammad S. Sagarwala (msagarwa@san-jose.tt.slb.com)
Date: Thu Aug 31 2000 - 10:42:09 PDT


Thanks a lot Ray,

Can I ask you a favour? It would be something you really don't want to do
this morning i.e. can you let me know
the equation which would let you figure out the skin depth at various
frequencies. I would really appreciate it.

I guess I had wrong numbers in mind when I was talking to my boss....

cheers,

Muhammad

-----Original Message-----
From: Ray Anderson <Raymond.Anderson@Eng.Sun.COM>
To: si-list@silab.eng.sun.com <si-list@silab.eng.sun.com>
Cc: msagarwa@san-jose.tt.slb.com <msagarwa@san-jose.tt.slb.com>
Date: Thursday, August 31, 2000 10:37 AM
Subject: Re: [SI-LIST] : skin effect

>Muhammad-
>
> I'll keep this very intuitive and non-mathematical because I don't
>feel like typing equations this morning.
>
>
>Consider that skin effect causes an effective increase in high-frequency
>resistance because the high-frequency current tends to flow mainly on the
>surface (or skin) of the conductor.
>
>
> At high frequencies the skin depth is very thin. For example at 1GHZ
>it is about .002 mm deep. Half ounce copper is about .7 mils thick (.18
mm).
>So the skin effect removes .002 mm of effective thickness from each side of
>the conductor .18mm - ( 2 x .002mm) = .176 mm . So doubling the copper
>thickness to 1 ounce material (1.4 mil or .36 mm) won't do you any good as
a
>means to reduce the skin loss as the current is still flowing predominantly
>in the outer .002 mm of the conductor no mater how thick the metal is.
>
>
> However, by making the conductor wider you can reduce the skin effect
>because you increase the surface area of the conductor which provides more
>parallel "squares" of material in the conductor which reduces the effective
>resistance.
>
>
>-Ray
>
>
>
>
>> Hello Si Gurus,
>>
>> I just had an interesting discussion with my boss on "skin effect on pcb
traces".
>> I was of the opinion that increasing the trace thickness from 1/2 oz. to
1oz. would help reduce the
>> skin effect but according to him skin effect does not reduce
significantly with the increase in
>trace thickness.
>> He was of the opinion ( and also had some data to back him up) that skin
effect is more dependent
>on the
>> width of the trace.
>>
>> I always thought that if one increases the overall perimeter of the pcb
trace - regardless of
>whether it is done by
>> increasing the width or increasing the thickness - the skin effect would
reduce. I would
>appreciate if somebody
>> could come up with a better explanation...
>>
>> Muhammad
>>
>> p.s.: when we talked about pcb traces we were talking about striplines in
particular...
>>
>>
>>
>>
>>
>> Muhammad S. Sagarwala
>> Design Engineer
>> Schlumberger SABER
>> Ph. (408) 586 7065
>> Fax (408) 586 4668
>>
>
>


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