Guy, I can't disagree that a 3.5 aspect ratio hole is easy to drill, plate, clean and it is reliable. However, for an 0.062" board, this means an 18 mil finished hole size via, which then requires a 33 to 38 mil pad. It also requires a 48 mil anti-pad on the inner layers. We are talking some serious real estate here. This becomes a big problem when we use 6 mil line and space rules to route between 0.8mm pitch BGA's. With via pads and anti-pads this big, increasing the layer count won't always make a design routable. We can make the board thinner to allow smaller vias, but only when the board itself is physically small. What's your opinion (besides use microvias) when we need high routing density on an 0.062" thick board? Regards, Seth Goodman Goodman Associates, LLC Verona, WI USA > -----Original Message----- > From: TechNet [mailto:[log in to unmask]]On Behalf Of Guy Ramsey > Sent: Friday, September 27, 2002 4:54 PM > To: [log in to unmask] > Subject: Re: [TN] PCB design with mask over vias. > ----------- snip ------------- > Can they increase the via size? I am a firm believer in aspect > ratios less than 3.5. > > > > Guy Ramsey > Senior Lab Technician/Instructor > American Competitiveness Institute > E-Mail: [log in to unmask] > Ph: (610) 362-1200 x107 > Fax: (610) 362-1290 --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------