Two-sided boards aren't so thick - they don't need to be beyond rigidity requirements - and don't have the high internal level of resin that MLB's do, so the unsupported length of plated barrel is relatively short, and resin recession doesn't occur so much, if at all. I agree with the observation that the right angled corners between barrel and pad are a focus for stress fractures, but if there is differential movement between pad and barrel to cause this fatigue, how much worse or how much more quickly would it occur if, say, only top and bottom layer pads were connected to the barrel? (Rhet.) Fewer points across which to disperse the load. Peter Duncan Warren_Crow@I -O.COM To: [log in to unmask] Sent by: cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST TechNet Aero/ST Group) <[log in to unmask] Subject: Re: [TN] Remove unused "dead" pads on ORG> internal layers 01/16/02 12:49 AM Please respond to "TechNet E-Mail Forum."; Please respond to Warren_Crow Actually the cracked vias I have witnessed in the inter barrell tend to start at the intersection of the copper planes. A corner or stress riser starts the crack during thermal shock tests. Don't understand how the extra non- connected pads could help barrell, if so then there is no hope for a 2 sided board. "Hinners Hans M Civ WRALC/LUGE" <[log in to unmask]> on 01/15/2002 07:40:50 AM Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to "Hinners Hans M Civ WRALC/LUGE" <[log in to unmask]> To: [log in to unmask] cc: (bcc: Warren Crow/US/I-O INC) Subject: Re: [TN] Remove unused "dead" pads on internal layers 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. Thanks, Pat This e-mail may contain SEL confidential information. The opinions expressed are not necessarily those of SEL. Any unauthorized disclosure, distribution or other use is prohibited. If you received this e-mail in error, please notify the sender, permanently delete it, and destroy any printout. 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