[SI-LIST] Re: Dust and humidity impact on the signal
- From: "Tom Biggs" <tbiggs@xxxxxxxxxxxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Wed, 17 Jan 2007 11:59:33 -0800
'NEBS' testing is required of all telecom boxes intended for central
offices. One of these NEBS tests is a 'Hygroscopic Dust' test, where
boards are coated with hygroscopic (water absorbing) dust consisting of
sodium sulfide and then subjected to humidity until a certain insulation
resistance is reached.
This well controlled test could be used as a basis for a 'worse case'
for dust. I leave the dielectric measurements up to you.
-tom
=20
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Alan Hilton-Nickel
Sent: Wednesday, January 17, 2007 10:46 AM
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Dust and humidity impact on the signal
Considering that dust is something that randomly collects on a surface,
has little mass (as individual particles) and, unless
manipulated/compressed, is mostly comprised of air, I would expect it to
not change the Er at all. Might be an interesting experiment to measure
the Er of various kinds of dust, both natural and compacted (that'd be a
lot of dust). Problem is, there are a lot of different sources of dust.
Yes, sawdust and pet hair, but also shed human skin, soot, pollen, and
dirt, spider webs. Even dust due to dirt can have different compositions
from clay to decomposing leaves to worm casings.
What's the Er of worm poop?
Alan
(Who has clearly spent wayy too much time in his attic lately)
Loyer, Jeff wrote On 01/17/07 10:06,:
>It should be representative dust, with its corresponding Er. I don't=20
>think sawdust is a representative component, unless you've got your=20
>workshop in the kitchen (not that there's ANYTHING wrong with that,=20
>Scott, if you do - grin). =3D20
>
>I would propose dog or cat hair as a better material to spread over=20
>your board before TDR'ing it. If the study is taken to its extremes,=20
>the Er of various breeds could be determined, and characteristic=20
>impedance taken into account when visiting the pound.
>
>I hope the study finds a negligible effect due to dust - every home=20
>computer I've ever worked on has incredible amounts of dust. Maybe=20
>another reason to recommend stripline. :-)
>
>Cheers,
>Jeff Loyer
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx=20
>[mailto:si-list-bounce@xxxxxxxxxxxxx]
>On Behalf Of Scott McMorrow
>Sent: Wednesday, January 17, 2007 9:39 AM
>To: Fabrizio.Zanella@xxxxxxx
>Cc: Dorin.Oprea@xxxxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: Dust and humidity impact on the signal
>
>To follow up, accommodation of the impact of humidity on Er and =
loss=3D20
>tangent should be fairly easy, although I've not tried it.
>
>1) Dry out your target material in an autoclave
>2) Weigh it.
>3) Place the material in a humidity chamber
>4) Weigh it.
>5) Compute the percentage water by weight.
>6) Compute the average increase in Er and loss tangent by using =
the=3D20=20
>ratios of dielectric and absorbed water.
>
>Once you know these, it should be possible to create a lossy=20
>dielectric=3D20 model that is a pretty close match for 2D or 3D =
solvers.
>For extra=3D20 credit, actual material measurements could be made using =
>one of the many
>
>methods know for Er and TanD extraction, at multiple frequency=20
>points,=3D20 to create a more precise frequency dependent model. =20
>However, I think if
>
>you perform steps 1 to 6 above you'll be closer than you might=20
>imagine=3D20 (assuming that you know your original material properties
well.
>
>I wouldn't worry much about dust, except for microstrip. In that=20
>case,=3D20 I guess one could make some TDR measurements with and =
without=20
>dust and=3D20 see what happens. (It's not like it's hard to create some =
>good dust ...=3D20 just get yourself a good circular saw, create some=20
>fine dust, and=3D20 sprinkle it over the trace.
>
>
>Scott McMorrow
>Teraspeed Consulting Group LLC
>121 North River Drive
>Narragansett, RI 02882
>(401) 284-1827 Business
>(401) 284-1840 Fax
>
>http://www.teraspeed.com
>
>Teraspeed(r) is the registered service mark of Teraspeed Consulting=20
>Group LLC
>
>
>
>Fabrizio.Zanella@xxxxxxx wrote:
> =20
>
>>Dorin, there's a good paper from DesignCon 2004 which has information
>> =20
>>
>on
> =20
>
>>measurements on serial links including the effect of temperature and=20
>>humidity=3D3D2E 'The Impact of Environmental Conditions on Channel=20
>>Performance', by
>> =20
>>
>Greg
> =20
>
>>Sheets, Agere and John D'Ambrosia, Tyco=3D3D2E You can take the dk=20
>>information and apply it as a variable in a 3D simulator, and then use
>> =20
>>
>a
> =20
>
>>parametric sweep=3D3D2E
>>
>>I can send you this paper if you're interested=3D3D2E
>>
>>Regards,
>>
>>Fabrizio Zanella
>>
>>
>>-----Original Message-----
>>From: Dorin=3D3D2EOprea@alcatel-lucent=3D3D2Ecom
>>[mailto:Dorin=3D3D2EOprea@alcatel-lucent=3D3D2Ecom]
>>Sent: Wednesday, January 17, 2007 10:59 AM
>>To: si-list@freelists=3D3D2Eorg
>>Subject: [SI-LIST] Dust and humidity impact on the signal
>>
>>Hi,
>>
>>I try to simulate the dust and humidity impact on 10G differential=20
>>signal routed as micro strip on the board=3D3D2E I know that the dust=20
>>thickness and humidity can vary significantly, but I wonder what would
>>be a good approach, for start, to build the corresponding model in a
>> =20
>>
>3D
> =20
>
>>simulation tool (suggestions on dk, df)=3D3D2E
>>
>>Thanks,
>>Dorin
>>
>>
>>
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--
Alan Hilton-Nickel
Signal Integrity Engineer
Sun Microsystems Inc.
Netra Systems and Networking
Newark, CA
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