RE: [SI-LIST] : Heat sink and radiated emissions

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From: Chris Padilla (cpad@cisco.com)
Date: Thu Jul 27 2000 - 06:34:47 PDT


I had such a problem with one heat sink that floating worked a lot better
than trying to improve the poor grounding. I actually ended up putting
plastic stand-offs on it to curb my 1 GHz emission problem!

The skin effect is your reason behind metallized plastic radiating as
well as an all metal one--especially at high frequencies like 1.5 GHz.

----->Chris

At 08:54 PM, George_Tang@Dell.com wrote:
>I have seen EMI problems caused by aluminum heat sinks when they are not
>grounded. But the problem can become much worse if they are incorrectly
>grounded. Identify the current loops and keep them small. I have tried
>plastic heat sinks molded with metal particles to give better heat
>conduction. Above 1.5 GHz, the plastic heat sink radiated as well as its
>metal counter part. Ceramic heat sinks might work well for you depending on
>your applications.
>
>Regards,
>
>George Tang
>
>
>-----Original Message-----
>From: Wayne Gibson [mailto:wayne.gibson@alcatel.com]
>Sent: Tuesday, July 25, 2000 1:18 PM
>To: si-list@silab.eng.sun.com
>Subject: [SI-LIST] : Heat sink and radiated emissions
>
>
>Hello,
>
>I have an EMC oriented question. Currently, investigating the use of
>aluminum, ceramic and enhanced plastic heat sinks for possible use on a
>TBPA package. Does anyone have information regarding different heat
>sink material with respect to radiated emission levels? As well as heat
>dissipation for different material.
>
>Thank you,
>
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