And a bit of hard won experience. Avoid "no-clean" flux, it will leak at high humidity. It is only to be used at less than 100 V.
Regards, --Paul -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, December 13, 2006 2:11 PM To: [email protected] Subject: Re: [PEDA] 500V power supply Oh, come on...Electrical leakage is leakage Brad. Creepage is a "cute" term meant to apply specifically to surface leakage, but it's all leakage, as in electrical current flowing unexpectedly through a dielectric medium. (call it over if you like, it's still "thru" to my physics eye.) That's one of the novel things that the IPC brings to the table. Redefinition of basic physics into terms that can suit the purposes of obsfucation...and of course profit by intellectual ownership of originally US-citizen-owned information. For instance, when I designed an instrument for KLM a couple years ago to (amongst other things) measure LEAKAGE from pin to pin on a connector, the mode of transport under consideration was not leakage across the air gap, but through the dielectric separating the contacts. It's my policy to leave the cute to the IPC, Altium's marketing Goo-Roos, and the cabal of "shhhhh...don't tell anyone its just water". And yes, DC or AC, the critical value is the peak value. All AC is DC if time passes slowly enough, and most DC is AC if you speed the clock a bit. Peak values Carlos. That means not only what you expect, but what might be. (Hence the engineering margins I spoke of earlier) Regards, aj >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Brad Velander >Sent: Wednesday, December 13, 2006 4:37 PM >To: Protel EDA Discussion List >Subject: Re: [PEDA] 500V power supply > > I don't believe I have seen anyone else point out that the spacing >requirements are typically specified for DC (RMS). >Any AC, pulses or spikes have to be suitably considered at their "peak" >values. That 'typically' bumps you up at least one voltage >rating/spacing category. > > I would say that you really need to read IPC-2221 section 6.3, as a >minimum. > > Besides that there is a lot of other information from safety >regulators like UL/CSA/EU/TUV, more specifically towards product safety >and power supply design. With the safety regulators it typically gets >even more complex because they start taking into account environmental >pollutants (humidity, dust or other particles which can compromise the >spacing) and applying pollutant/environment categories. Andrew mentions >"leakage" and leakage has two forms. Leakage is typically through air >or an air gap, "creepage" is across surfaces and is equally important >in most cases. > >Sincerely, >Brad Velander >Senior PCB Designer >Northern Airborne Technology >#14 - 1925 Kirschner Road, >Kelowna, BC, V1Y 4N7. >tel (250) 763-2232 ext. 225 >fax (250) 762-3374 > > >-----Original Message----- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] >Sent: Wednesday, December 13, 2006 1:15 PM >To: [email protected] >Subject: Re: [PEDA] 500V power supply > > >Exactly. Be careful that you don't think "ideally". Think instead >cautiously. Cautious is wider spacing. Do not go under, as you will not >necessarily see any immediate problem, even though there may very well >be a major problem. (leakage) > > > >____________________________________________________________ >You are subscribed to the PEDA discussion forum > >To Post messages: >mailto:[email protected] > >Unsubscribe and Other Options: >http://techservinc.com/mailman/listinfo/peda_techservinc.com > >Browse or Search Old Archives (2001-2004): >http://www.mail-archive.com/[email protected] > >Browse or Search Current Archives (2004-Current): >http://www.mail-archive.com/[email protected] > > This e-mail transmission and its attachments may contain information from Avtron Manufacturing, Inc. that is proprietary, privileged and/or confidential and is intended exclusively for the person(s) to whom it is addressed. Any use, copying, retention or disclosure by any person other than the intended recipient or the intended recipient's designees is strictly prohibited. If you have received this message in error, please notify the sender immediately by return e-mail and delete all copies. ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected] ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
