950 creepage experts- When applying Annex F, Fig. F.1 (narrow groove) and Fig. F.2 (wide groove), requirements to PWB's, does one have to abide by the minimum "value of X" only for grooves, or also for slots punched all the way through the PWB? It makes sense that if a groove is particularly narrow, a small accumulation of contamination would negate any creepage gained from having the groove.
However, what about a slot that goes completely through the board? Would contamination not collect in a slot as it would in a groove, and therefore the slot can be any width (therefore forcing the creepage measurement to be made around the edge of the slot)? We're thinking of an application between pins of an SMD multi-pin telco isolation transformer package: adjacent pins and their solder pads don't meet the required creepage, but if we punch slots through the PWB between pads, can we then measure our creepage around the edge of the slot? In this way we can create as much creepage as we need by simply lengthening the slot. We're thinking of punching a slot about 0.2-0.3mm wide between solder pads, of sufficient length to give us the required creepage. Any comments? Anyone know the history and rationale of this Annex F "X" requirement and can comment? Thanks, folks. Dirk __________________________________________________ Do You Yahoo!? Talk to your friends online with Yahoo! Messenger. http://im.yahoo.com --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
