[SI-LIST] Re: Heatsink acting as EMI shield.
- From: "hansm" <hans.mellberg@xxxxxxxxxxxx>
- To: <zhang_kun@xxxxxxxxxx>, <trilok.budathoki@xxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 15 Jul 2004 16:53:01 -0700
Its not just a matter of clean ground, its also a matter of antenna theory.
If one end is properly grounded and the die is conviniently located 1/4
lamda (or any other non-zero exitable distance) from the grounded end, no
matter what you do, you will have a properly driven plate antenna! Unless
the heatsink/EMIshield(!) is circumpherentially grounded around the die, it
will most likely be an antenna whether a poor one or an efficient one.
Dr. Bertram Chan and I have pattented a couple of noise emission reduction
techniques exactly on this topic utilizing improved grounding techniques.
Hans Mellberg
Engineering Manager
BACL, a TCB and an EU CAB
230 Commercial Street
Sunnyvale CA 94085 USA
408-732-9162 x38
408-732-9164 fax
----- Original Message -----
From: "Zhangkun" <zhang_kun@xxxxxxxxxx>
To: <trilok.budathoki@xxxxxx>; <si-list@xxxxxxxxxxxxx>
Sent: Thursday, July 15, 2004 12:33 AM
Subject: [SI-LIST] Re: Heatsink acting as EMI shield.
> Dear Trilok
>
> Even if the heatsink is connected to the ground, it also could act as one
antenna of EMI because the ground is not clean enough. The primary method is
to lower the power ground noise at the location of the heatsink by means of
local decoupling.
>
> Hope this will help.
>
> Best Regards
>
> Zhangkun
> 2004.7.15
> ----- Original Message -----
> From: "Budathoki, Trilok (GE Consumer & Industrial)"
<trilok.budathoki@xxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Sent: Thursday, July 15, 2004 3:13 PM
> Subject: [SI-LIST] Heatsink acting as EMI shield.
>
>
> > Hello Everyone
> >
> > I was read an articles that mentions the PGA & BGA packages have an
efficient heatsink on the top of the package, which not only serves to
dissipate the heat, but also acts as an EMI shield.
> > Does it mean EMI is achieved as one end of heatsink is connected to Gnd.
> > If the Heatsink is left floating. How can it act as EMI shield. Can
anyone explain.
> > Thanks
> > Trilok Budathoki
> > GE - India Business Center
> > *: 91-40-27881731
> > * : trilok.budathoki@xxxxxx
> >
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