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PCB Creepage Problem

Does any one have a chart/table or formula to calculate the necessary creepage distance for DC voltages on an FR-4 PCB?

I have been working on a new pcb, and 70 mil spacing was used for the AC lines... However, our layout person incorrectly set up his software to use this spacing everywhere except for copper pours (and the return plane is considered a copper pour!) All the routed traces on the board are correct, but there is one place on the ac lines where a through hole component only has a 15mil keep out. Now I know this is a problem, and there is a quick work around for it so that we can test the rest of the board.

However, on my ride home, I became concerned that his testpoints on the

300 VDC supply may only have 20mil keepouts on the ground plane(even though the software would not let him route a trace within 70 mils on the routing layers). The only documentation that I have about creepage distance is for AC lines, and came from one of the senior engineers at my company. He happens to be on vacation right now, and I spent a good part of the day looking on line trying to find some good information about creepage on pcb's. My search turned up very little information.

Can anyone help? I need to find out the creepage distance for 300VDC. Also, is creepage distance strickly related to potential difference? So would a ~170VDC have the same creepage breakdown as a 120VAC line?

Reply to
eric
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Reply to
eric

this site may help

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Reply to
TimPerry

component

creepage

The term 'creepage' is normally used in the context of regulatory standards relating to electric shock and fire hazards. The individual standards have equations and tables that are used to determine minimum dimensions. However, in portions of a product that are properly isolated from exposed conductive parts, it is usually up to the product designer to determine clearances for reliable operation. If the device is sealed and/or operated in a clean, dry environment, very small clearances may prove to be adequate. We often use 10V/mil (roughly

400V/mm) as a conservative value. Don't forget that ESD and other transients 'have the potential' to start an arc that is continued, at much lower voltage, by circuit potentials. Paul Mathews
Reply to
optoeng

The following may be of some help (just what I could find quickly).

Much of the work for creepage and clearance calculations were done for the CISPR series of standards, on which the IEC, ISO and other standards are usually based. You could spend some time looking out the appropriate CISPR documents or consult a standard appropriate to the product that you are manufacturing.

Reply to
Paul E. Bennett

Have you gotten your answer?

Reply to
jimto

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