i was told by one of the Sr. engineer - chaps learn better with their own mistake... (if they survive with their mistake). - so my rule is maximum voice once, written down once and only if mission critical, additional raise issue with some aspirin dose prior to the meeting to reduce blood pressure ;-). On Mar 5, 2018, at 12:47 PM, Jack Olson wrote: > I hear ya, brother. and don't think I am arguing with the value of > doing > the work, > but (here I go anyway) > One of the major benefits of having the IPC in our industry is that > every > new circuit board designer that comes along, who doesn't know > whether to > put that note on his fabrication drawing or not, can learn from the > experience of others here. He doesn't have to repeat expensive > tests just > to verify what is already understood by the consensus of other > members that > have already contributed time and effort and resources to study the > issue. > (but I hear ya!) > > Jbro > > On Mon, Mar 5, 2018 at 10:51 AM, Dwight Mattix > <[log in to unmask]> > wrote: > >> Yeah, I blew past the thread to busy to contribute last week. >> >> All else being equal retaining non-functional pads tends to >> increase time >> to barrel wearout from circumferential cracking at/near the >> midline. One >> notion being that the pads make for a local lower resin content >> region >> around the via (less expansive dielectric acting on the copper >> column to >> wear it out). >> >> Non-func pads don't seem to have much bearing on the actual post >> interconnect reliability. Multiwire anyone? (speaking of >> dinosaurs). >> >> But back to the barrel wearout thing... All things are rarely >> equal. So >> if you actually build it and test it (due diligence? That's crazy >> talk. Who >> has time or money for that anymore?), I'd wager you'll get mixed >> results. >> A lot depends on factors like the fabricator's drilling and hole >> prep >> skill, the aspect ratio, material involved, copper weights of the >> included >> NF-pads etc. >> >> Leaving non-func pads in, increases the drilling challenge. That >> increases >> things that disrupt the hole and factor in to it's ultimate >> reliability. >> For example, a rougher hole wall is very likely to be part of the >> effect of >> leaving NF pads in. That introduces stress risers in the holewall >> topography that can accelerate copper wearout and crack propogation. >> >> So all of that say the original question, "It depends." :) >> >> Do your due diligence. If it really matters, build it and test it. >> Better >> yet, build it both ways and test it. Even better, build both ways >> at more >> than one fab and test it. You'll be illuminated and smarter at >> the end of >> the exercise than 99 of 100 veteran pwb tech people seen walking >> the floor >> with tacky polo shirts, broken down posture and done-lops last >> week at >> IPC/APEX. >> >> cheers, >> dw >> >> -----Original Message----- >> From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson >> Sent: Monday, March 5, 2018 7:49 AM >> To: [log in to unmask] >> Subject: Re: [TN] Non Functioning pads >> >> I must be behind-the-times on this one. >> Werner Englemaier used to talk about this all the time, and from >> my memory >> an analogy might be similar to comparing a simple rivet to a >> "rivet with >> ribs". If your goal is a robust product (which a lot of Class 3's >> are) then >> it seems like you would want the extra support. (I'm not making a >> statement, I'm repeating what I was taught). I'm pretty sure I've >> heard >> Gary Ferrari recommend keeping them in at least a half a dozen >> times in his >> seminars. Aren't the most common failures in boards related to vias? >> >> Maybe I have more learnin' to do on this one, but I'm surprised >> that NO >> ONE responded in favor of keeping the unconnected internal pads >> >> Well, since we are talking about vias, I was also advised to >> require 1mil >> hole wall plating, even though the standard is 0.8 (I think). But >> for the >> same reason, the stronger we can make our vias, the less "most >> common" >> failures we will have, right? (At Caterpillar, we want the most >> robust >> product we can get for the money) Am I sounding like an old >> dinosaur now? >> >> but really, is EVERYONE removing unconnected inner layer pads? >> Is "increasing the longevity of drill bits" the dominant theme now? >> >> onward thru the fog, >> Jack >> >> >> . >> On Tue, 27 Feb 2018 11:12:22 -0600, Larry <[log in to unmask]> >> wrote: >> >>> Is there any reason I cannot remove non functioning pads on the >>> inner >> layers for an Class 3 PCB? >>> >>> Many thanks, >>> >>> Larry >>