My memory as well...by design, single-layer pads were considered to be SMT components, as therefore use of a hole with such a pad was considered non-sequitur (illogical). Frankly, I don't think it's a bug, at least for the time in which single-layer pads were introduced to Protel, back when microvias were little more than a twinkle in the IC designers eyes.
Instead, the logical thing to do is place a multi-layer pad, define the desired hole size, and define all unused pad layers to a diameter of zero (0) for pad width. Since hole plating is executed only after the drill operation has been completed, any hole defined as a plated hole will be left unmasked and so will become plated. If plating of the hole is undesired, a note in your instructions should be sufficient to avoid plating. aj >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Abd ulRahman Lomax >Sent: Monday, October 24, 2005 12:16 PM >To: Protel EDA Discussion List >Subject: Re: [PEDA] Strange feature.. DRC misses an error condition. > >At 12:20 PM 10/21/2005, Brooks,Bill wrote: >>We had a part mis-defined with a PAD that was a 'toplayer' pad (not a >>'multilayer pad') that had a drill hole defined in it... not on >>purpose, but by accident. >> >>Now DRC did not pick up any shorts with planes or traces >running under >>this pad [...] Has anyone ever run across this before? > >I do recall there being error conditions with single-layer >pads with holes. It appears that the programmers designed >single-layer pads to not have holes, an easy mistake to make. >If you wanted to put a hole in a single-layer pad (for >example, for microvias-in-pad), you would place an extra pad, >multilayer, with the hole. Because the hole does exist on >other layers, it is an error to define the pad as being Top or >Bottom. But an easy one to make; it could be argued that the >programmers should have made it impossible to create this >condition, using an error dialog ("which do you want, a hole >or a single-layer pad with no hole"), and also a default >design rule that can't be turned off (there are a few of >these), to deal with imports containing this little beastie. > >Or, if you really do want a single-layer pad with a hole and >that's that, as long as the hole being in the center of the >pad is okay, then you would use a multilayer pad with a >padstack, and defined the pads on the other layers to be >small. I'd still recommend making them larger than the hole, >just because I get nervous about DRC's ability to correctly >measure clearances around such an animal. Whenever one strays >from common practice, there is a risk of running into a rare bug. > >In particular, holes are generally drilled 3 mils oversize or >so (diametric), and then plated back, so this reduces >clearance to hole metal by 1.5 mils as against the nominal >hole size, which is what Protel would know about. I've argued >in the past that DRC should factor for this, but I don't think >it ever has. (There would be a design rule specifying drill >oversize; it would be simple for this to be a default 1.5 mils >radial, and then this correction would always be applied to >holes for DRC purposes.) > >I'd think it possible to set up a design rule or rules to >detect any top/bottom layer pads with holes. It would take a >little experimenting, which I can't do right now.... Such a >rule could then become part of a standard design rule set. > > > > >____________________________________________________________ >You are subscribed to the PEDA discussion forum > >To Post messages: >mailto:[email protected] > >Unsubscribe and Other Options: >http://techservinc.com/mailman/listinfo/peda_techservinc.com > >Browse or Search Old Archives (2001-2004): >http://www.mail-archive.com/[email protected] > >Browse or Search Current Archives (2004-Current): >http://www.mail-archive.com/[email protected] > > This e-mail transmission and its attachments may contain information from Avtron Manufacturing, Inc. that is proprietary, privileged and/or confidential and is intended exclusively for the person(s) to whom it is addressed. Any use, copying, retention or disclosure by any person other than the intended recipient or the intended recipient's designees is strictly prohibited. If you have received this message in error, please notify the sender immediately by return e-mail and delete all copies. ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
