Gary Thompson wrote: > > Sorry for the slightly off-topic post... > > Anyone know if there is an IPC standard governing the composition of > thermal reliefs on plane layers for thru-hole components? The rigid board design spec (IPC-2222) has most of a page on "how to". IMHO anyone doing physical design of genuine product is really in need of this spec, or its variants (for flex, PCMCIA, MCM, etc). The gist of the standard comes down to total web widths don't exceed 60% of ideal land dia per layer, and is again limited to a total of 4mm at 1oz Cu (maintain this ratio for other copper weights). If you need to violate this to meet current carrying needs it must be noted, they say to do so on the fab drawing but I personally belive it is more pertinent on the assembly drawing. HTH, -- Jeff Seeger Applied CAD Knowledge Inc Chief Technical Officer Tyngsboro, MA 01879 jseeger "at" appliedcad "dot" com 978 649 9800 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu