Since the design spec only calls out max 1amp I'm more concerned on what the voltage is doing. The spacing is a huge issue in this current layout. Well below what IPC-2221a calls out. From talking with the engineer a few minutes ago the boards run up to 20 volts. At above 21 volts all the signals on the board become "crappy". At 200 volts the a white streak forms under the solder mask around the 50mil trace. Once they turn back to under 20 volts things return to normal.
So from what I can surmise the heat / trace is melting the pre-preg under the 50mil etch. Its not breaking the 50mil etch. The pre-preg is 8mil from what they had on the fab drawing. So would the 200 volts be looking for another path? Perhaps the GND plane under it since that would produce "crappy" signals?
Andrew W. Dalrymple, C.I.D.
DFM Design, A One Source Company
10810 Sanden Drive
Dallas, TX 75238
Phone: 214.575.5327
Fax: 214.575.5364
Mobile: 972.977.2561
www.onesource-group.com
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]]On Behalf Of
George Patrick
Sent: Tuesday, December 14, 2004 2:49 PM
To: [log in to unmask]
Subject: Re: [DC] High Voltage Rules
Are you worried about voltage or current? You didn't mention what clearance
you had between the 200V line and other lines, and you didn't specify
whether the smoke was from arcing or melting.
If it was arcing, for Cat II circuits (most common), UL calls for a minimum
clearance of ~1 mm at 200V, creepage clearance needs to be about 2.3 mm.
A 50 mil line should carry ~5.5 A with a 30° rise over ambient. (I have an
on-line calculator at http://www.pcb-designer.com/trace.html, or there is a
good stand-alone one at Doug Brooks site, http://www.ultracad.com)
--
George Patrick
Tektronix, Inc.
Central Engineering, PCB Design Group
P.O. Box 500, M/S 39-512
Beaverton, OR 97077-0001
Phone: 503-627-5272 Fax: 503-627-5587
http://www.tektronix.com http://www.pcb-designer.com
It's my opinion, not Tektronix'
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Dalrymple, Andrew
Sent: Tuesday, December 14, 2004 11:35
To: [log in to unmask]
Subject: [DC] High Voltage Rules
Good afternoon everyone.
I just had a customer send me a database finished by another design group
for review. They have assembled boards that keep smoking and want me to
find the issues. So upon looking at the design spec documents it has a
single 200 volt connection on it with 1amp current. I'm assuming this is
the cause of the smoke since the 200 volt net is routed using a 50mil trace
in 1 once copper. I have not worked with high voltage connections in 6-7
years anyone have some quick High Voltage calculations etc? Or at least a
good place to grab the information?
Cheers,
Andrew W. Dalrymple, C.I.D.
DFM Design, A One Source Company
10810 Alder Circle
Dallas, TX 75238
Phone: 214.575.5327
Fax: 214.575.5364
Mobile: 972.977.2561
www.onesource-group.com
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