In a message dated 05/17/2000 12:10:55 PM Central Daylight Time, [log in to unmask] writes: << I believe I have searched through all the latest IPC specifications. I've not found any specific criteria that cover the Design and/or Finished board requirements related to external annular rings on Blind Vias, let alone the requirements when the design is via in pad for a .8mm BGA. I believe we are in new territory. Any information would be greatly appreciated. Dawn Patterson >> Hi Dawn! Did you look in the IPC-A-600F? I know this is the Acceptability of Printed Boards manual, but maybe by looking at what the minimum acceptable is, you can design your board so that it meets the minimums (and the the fab vendor is able to do). On page 54 when it talks about external annular rings for supported holes, the minimum required is .050mm (.002") for class 3. On page 55 for unsupported holes the minimum is .15mm (.00591") for class 3. On page 76 when it talks about internal annular rings the minimum is .025mm (.000984") for class 3 (of course that can only be measured by cross section. -Steve Gregory- ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################