TANSTAAFL - There Ain't No Such Thing As A Free Lunch http://www.apc.net/ia/scrmaim.htm http://www.magicpub.com/netprimer/acronyms.html#T
Cheers! Drew ----- Original Message ----- From: "Dennis Saputelli" <[EMAIL PROTECTED]> To: "Protel EDA Forum" <[EMAIL PROTECTED]> Sent: Saturday, June 08, 2002 2:51 PM Subject: Re: [PEDA] unused QFP pins > this is being driven (and may possibly be worth the trouble) because > the customer really really (did i say really?) wants a single side board > they saw someone else who did it single sided (not skipping pads but > accomplished a single side board in a comparable application - although > it was a different circuit and they had a lot less leads) > > they will settle for a double sided if it is silver through hole > phenolic or CEM > > someday they may bond out the chip for us with less leads > > BTW, i think i am pretty good at IMHO AFAIK etc. etc. > but what the fk is TANSTAAFL ? > i must have missed that one in BBS school > > Dennis Saputelli > > Abd ulRahman Lomax wrote: > > > > At 06:13 PM 6/7/2002 -0700, Dennis Saputelli wrote: > > >i've got a 144 pin PQFP 0.5mm pitch > > >there are only a small number of connected pins, maybe a dozen or so > > >excluding power > > > > > >i am thinking about deleting a lot of unused pads to possibly open up > > >top side routes and reduce inspection and bridging concerns > > > > > >am i crazy? > > > > Dennis, yes, you are crazy :-), but that doesn't answer the question.... > > Even crazy people sometimes have good ideas.... > > > > >do you think the leads will short thru the solder mask to traces below? > > > > Mr. Selfridge gave a good answer, I think. But maybe the idea does not have > > to be completely tossed. > > > > >is this good practice even if i don't run traces there, i.e. will it > > >solder and align properly with missing pads? > > > > As an experiment, you might try this: > > > > Determine a set of pads that you want to solder, make it symnetrical so > > that the part will be firmly held. Maybe most pads would be soldered, or at > > least more than half. Do leave solder mask openings so that the extra leads > > are not stressed, but the openings might be reduced a bit. This *might* > > allow you to run a thin trace between the pads, but I wouldn't be on it. If > > it will not be enough to allow 1-thrus, I'd leave the mask openings the > > same as for the pads to be soldered. > > > > The only advantage of this, in the latter case, would be less possibility > > of bridging, but I don't know how much of a factor that is, anyway, my > > knowledge of current assembly criteria is somewhat in need of renewal.... > > > > In short, however, the whole affair is probably not worth the trouble, but > > ultimately that is an engineering question which I am sure you are > > qualified to answer.... with a little help from your friends. > > > > -- > ___________________________________________________________________________ > www.integratedcontrolsinc.com Integrated Controls, Inc. > tel: 415-647-0480 2851 21st Street > fax: 415-647-3003 San Francisco, CA 94110 > * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/[email protected] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
