Just had to go look it up again to make sure...
(You guys always get me curious about the facts...)
The slash sheet says... MIN. electric strength is 30KV/mm (30,000 volts per mm)
That's 762 volts per mil. Minimum.
I don't know where this 300V/mil thing is coming from... Hmmm...
William Brooks, CID+
Senior MTS (Contract)
2747 Loker Ave West
Carlsbad, CA 92010-6603
760-930-7212
Fax: 760.918.8332
Mobile: 760.216.0170
E-mail: [log in to unmask]
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Brooks, William
Sent: Monday, March 10, 2014 3:16 PM
To: [log in to unmask]
Subject: Re: [DC] FW: [DC] IPC-2221B Electrical Spacing
-----Original Message-----
From: Anne Marie Mulvihill [mailto:[log in to unmask]]
Sent: Monday, March 10, 2014 2:08 PM
To: DesignerCouncil; Brooks, William
Subject: RE: [DC] FW: [DC] IPC-2221B Electrical Spacing
Bill, no idea what is making things kerflooey from IPC to its own server. But it happens.
Would you please re-post the text for me?
Thanks so much!
From: Marc Carter, IPC Director of Technology Transfer
Sent: Monday, March 10, 2014 3:01 PM
To: Anne Marie Mulvihill
Subject: RE: [DC] IPC-2221B Electrical Spacing
Yes, the raw material in perfect, undisturbed, pristine state, in a laboratory, has a theoretical maximum isolation of 300v per mil.
No drilling. No irregular “tooth” on the back of the copper. No lamination effects, no chemical immersion, no nothing that would disturb it’s perfect, theoretical maximum.
Class 3 is predicated on GUARANTEED stability and long-term reliability as the goal. As such it will be VERY conservative. One POSSIBLE alternative would be to build to Class 3 with the exception of the isolation, and test it under various environmental stressors for whatever the customer and this builder agreed is sufficient time to develop any latent defects.
Another POSSIBLE alternative is that it’s possible that 500 v isolation is not required between EVERY layer of the board. Symmetry is great, but if you HAVE to build an assymetric stack up, and you can deal with the degradation in warp and twist that may bring, then that’s an avenue. I’ve done it. Don’t care to, but sometimes, ya gotta.
If you want it to meet the implications of Class 3, then you kinda have to build it to Class 3 (production allowances, exposures, chemistry, etc.) and all.
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