[SI-LIST] Re: ESD strips on board edge
- From: "Curt McNamara" <CurtM@xxxxxxxxxxx>
- To: <weirsi@xxxxxxxxxx>, <davidjp@xxxxxxx>, <koh-yew.thoon@xxxxxx>, "SI-List" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 4 Aug 2005 10:41:28 -0500
I think the first place I saw ESD strips mentioned in print was Henry
Ott's
_Noise Reduction Techniques in Electronic Systems_ Here are a couple of
things
we do:
Cut the planes back from the board edge so the ESD strip is the first
piece
of metal that an ESD event could couple to.
Put ESD strips on top and bottom and tie them together with vias
regularly
(1cm or so).=20
Connect the ESD strip to the "RF Ground". This will be the largest piece
of=20
metal that energy could couple to. It may or may not be your circuit
ground!
If it *is* your circuit ground make this connection in a place where
energy cannot
travel across the plane and damage devices.
Curt
Curt McNamara. P.E.=20
Senior Electrical Engineer=20
Logic Product Development=20
411 Washington Ave. N Suite 101=20
Minneapolis, MN 55401=20
Tel 612-436-5178=20
Fax 612-672-0443=20
curtm@xxxxxxxxxxx=20
www.logicpd.com=20
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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of steve weir
Sent: Thursday, August 04, 2005 10:19 AM
To: davidjp@xxxxxxx; koh-yew.thoon@xxxxxx; SI-List
Subject: [SI-LIST] Re: ESD strips on board edge
Dr. Pommerenke, one additional note: It is important to maintain=20
dielectric sufficient separation between an ESD strip and any other PCB=20
features so that a secondary arc doesn't bypass the ferrite. Surface=20
contamination can be a problem.
Regards,
Steve.
At 10:01 AM 8/4/2005 -0500, Pommerenke, David wrote:
>Koh,
>
>In general, those strips are placed as landing area for sparks that hit
>the edge of the board. Sparks can hit the edge of the board in two-part
>plastic enclosures or during handling. However, during handling other=20
>parts can be hit to.
>
>If you are working with a two-piece plastic enclosure, then it might be
>a good idea to have an ESD strip on the board edge. The strip should be
>connected to your "ground". I suggest to avoid a direct connection, but
>to use a ferrite bead (e.g., 300 Ohm at 100MHz). The bead will survive=20
>the ESD current, but it reduces the current amplitude and increases the
>rise time. The fact that it will go into saturation is not that=20
>critical, tests have shown that it stays somewhat efficient in reducing
>the current peak amplitude and increasing the rise time. A resistor=20
>(e.g., 1000 Ohm) would be an alternative, but most resistors will be=20
>destroyed by the ESD current.
>
>Dr. David Pommerenke
>EMC laboratory
>University Missouri Rolla
>www.emclab.umr.edu
>
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx=20
>[mailto:si-list-bounce@xxxxxxxxxxxxx]
>On Behalf Of Thoon, Koh Yew
>Sent: Thursday, August 04, 2005 1:13 AM
>To: SI-List
>Subject: [SI-LIST] ESD strips on board edge
>
>=3D3D20
>Hi folks,=3D3D20
>
>I wonder if there's any good documents on implemenation of ESD strips=20
>for Board edge.
>
>Thanks
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