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

About this list Date view Thread view Subject view Author view

From: George_Tang@Dell.com
Date: Thu Jul 27 2000 - 11:06:50 PDT


I am sorry for not being clear about this. The heat sink was not plated
plastic. It was plastic with metal particles (sand like) molded within the
plastic. The vendor said that the metal particles did not come in contact
with each other, so the particles were insulated. It was the capacitance
between the particles that caused the radiation.

George Tang

-----Original Message-----
From: Chris Padilla [mailto:cpad@cisco.com]
Sent: Thursday, July 27, 2000 6:35 AM
To: si-list@silab.eng.sun.com
Subject: RE: [SI-LIST] : Heat sink and radiated emissions

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,
>
>**** To unsubscribe from si-list or si-list-digest: send e-mail to
>majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
>si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
>si-list archives are accessible at http://www.qsl.net/wb6tpu
>****
>
>**** To unsubscribe from si-list or si-list-digest: send e-mail to
>majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
>si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
>si-list archives are accessible at http://www.qsl.net/wb6tpu
>****

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Wed Nov 22 2000 - 10:50:52 PST