Methinks it's an Old Husband's tale, unless your pcb vendor in question produces uncured boards. If the unused pads are free to move about, so is everything else (though perhaps a little less freely if they're anchored to other features). I can understand the argument when it comes to drilling holes. The extra copper might well hasten the degradation of a drill's sharpness, and blunt drills cause copper smear which could connect one layer to another layer when you don't want it to. "If the pads ain't there to start with, there ain't nought to smear." BUT I think that's penny-pinching by the fab houses and not in the best interest of boards, particularly class 3 boards, where the extra support offered by the unused pads is valuable. If nice sharp drills are used, at the right speed and feed, you should get nice clean holes, no? Rgds Peter "Roger M. Stoops" <rstoops@SPECTRAPRECISI To: [log in to unmask] ONDAY.COM> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Sent by: TechNet Aero/ST Group) <[log in to unmask]> Subject: Re: [TN] Remove unused "dead" pads on internal layers 01/17/02 03:10 AM Please respond to "TechNet E-Mail Forum."; Please respond to rstoops I have been following this thread with interest. When I asked a pcb vendor about having non-functional pads in the inner layers, they said it was not a good idea, that the unattached pads/lands would move around, or "float," and cause potential mfg problems, such as shorts to other copper. Question: Is there any truth to this statement, or is this just an old husband's tale? TIA, Roger M. Stoops, C.I.D., PCB Designer [log in to unmask] Trimble Engineering and Construction Division 5475 Kellenburger Rd. Dayton, OH 45424-1099 USA Ph: +01 937.233.8921 or +01 937.233.4574 ext 288 Fax: +01 937.233.7511 "<Peter George To: [log in to unmask] Duncan>" cc: Sent by: Subject: Re: [TN] Remove unused "dead" pads on internal layers TechNet <[log in to unmask] ORG> 01/15/02 09:09 PM Please respond to "TechNet E-Mail Forum."; Please respond to peter.duncan Hi, Actually these "unused" pads are replicates of the hole "rules" created for the surface layers. Most routing packages, or routers, seem to do this by default for each layer to save manual replication where traces, etc are to be connected. (At least PADS, Alegro and Mentor do). On the grounds that it's always easier to destroy than to build, it's easier to delete pad data than to create it, so it's put in by default as there's a good chance it will be needed. I still say you should consider hole barrel strength/support issues before just deleting them - e.g. they can constrain the "resin recession" and hole wall pull-away that have been recent threads on this forum. Think of the "unused" pads as 'wall ties' holding the copper at frequent intervals to the hole wall. Copper bulging or pull-away in the event of recession or whatever is reduced. Peter Duncan Hinners Hans M Civ WRALC/LUGE To: [log in to unmask] <Hans.Hinners@ROBI cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST NS.AF.MIL> Aero/ST Group) Sent by: TechNet Subject: Re: [TN] Remove unused "dead" pads on <[log in to unmask]> internal layers 01/15/02 09:40 PM Please respond to "TechNet E-Mail Forum."; Please respond to Hinners Hans M Civ WRALC/LUGE Hi Patrick, As others have said, I don't think the class of board matters for "unused" pads. It all depends on what your procurement documentation states, are you building to drawing or is there a clause that says process improvements that do not affect functionality are permissible. "Are they really unused pads?" They may be electrically nonfunctioning but they are there for a reason - better lamination quality (avoiding low pressure areas or excessive prepreg flow), better hole wall quality, better plating quality (esp. for any isolated traces), reduced loading of your etch solution or better thermal loading during assembly. Hans Integrity First - Service Before Self - Excellence in All We Do ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Hans M. Hinners Electronics Engineer Warner Robins - Air Logistics Center (WR-ALC/LUGE) 226 Cochran Street Robins AFB GA 31098-1622 mailto:[log in to unmask] Com: (478) 926 - 5224 Fax: (478) 926 - 4911 DSN Prefix: 468 -----Original Message----- From: Patrick Lam [mailto:[log in to unmask]] Sent: Friday, January 11, 2002 5:12 PM To: [log in to unmask] Subject: [TN] Remove unused "dead" pads on internal layers Hi TechNetters, For class 3 boards, is it acceptable to have unused pads removed on interanal layers. 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