just curious, does anyone see high voltage CAF (I mean >700-1000V)? thanks. jk abcd -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Hfjord Sent: Tuesday, September 26, 2006 3:27 PM To: [log in to unmask] Subject: Re: [TN] High-Voltage Board Spacings We are not allowed to have more than 500 Volts between surface traces and layers below . Over 500 Volts, FR-4 is not used because of the humidity risks, also high altitude phenomenons, like corona effects. For 1500 Volts we would typically use PTFE 1500 Volts means a high activation and the board is therefore much more susceptible to migration and other high voltage driven disasters. The dielectric withstanding is expressed in kV/mm, e.g. 40 kV/mm, and it makes people think kV rather than Volts. I represent HiRel and Mil manufacturing, I can imagine that the home electric equipment industry, and other commercials, have a less stringent desing rule here. Inge ----- Original Message ----- From: "Wayne Thayer" <[log in to unmask]> To: <[log in to unmask]> Sent: Monday, September 25, 2006 11:41 PM Subject: Re: [TN] High-Voltage Board Spacings > Your failure mode of deepest concern is most likely CAF (Conductive > Anodic Filament). The most common spot for this problem is via to > trace, and the seed is disturbances in the via side wall. CAF can also > grow along glass filaments within pre-preg from layer to layer. Failure > potentials are at less than 10% of the 750V/mil. Laminates are > available with very high CAF resistance if you need to push things. I > believe there are some BT based materials that are virtually immune, but > 1500V is a lot of potential! > > Wayne Thayer > >>>> [log in to unmask] 9/25/2006 5:06 pm >>> > Should I be using IPC Table 6.1 for conductor spacing for high voltage > in the z-axis of the pcb? > Or should I be using the approximately 750V/mil spec from the laminate > supplier and derate that number? > Board has +/- 1200V. > > Thank you. > > Kaye Clayo > Sr. P. C. Layout Designer > Keithley Instruments, Inc. > 440-498-2862 > > CONFIDENTIALITY NOTE: This message is intended only for the use of the > individual or entity to which it is addressed and may contain > information that is privileged, confidential, and exempt from disclosure > under applicable law. If the reader of this notice is not the intended > recipient, you are hereby notified that any dissemination, distribution > or copying of this communication is strictly prohibited. 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