I would like to respond to your flatness concerns from a designer's point of view.... At the beginning of the year we designed a 6-layer, 8" diameter round PWB, all SMT one side. It suffered from bowing and twisting; we were concerned about solderability of components, reliability of those stressed out solder joints, etc., so in the next iteration of the design we added plating thieving within the board image area in all the open areas on the non-plane layers. It made a very noticeable difference, and was well worth cleaning up the hundreds of DRC errors I got when I first arrayed them into the design. EDA vendors, are you going to make this exercise easier (some CAM programs already will automatically add DRC-compliant plating thieving) ? Bill Bill Bromley Lead Designer Lucas Aerospace PSA MailStop D960 777 Lena Dr. Aurora OH 44202-8025 USA voice: 216-995-1000 ex 3092 email: [log in to unmask] > -----Original Message----- > From: Pat Bailey [SMTP:[log in to unmask]] > Sent: Monday, December 15, 1997 5:48 PM > To: [log in to unmask] > Subject: [TN] Board Flatness > > Hello, TechNetters, > > I was wondering what others are calling out for flatness requirements > on > double sided boards with surface mount components. IPC-A-600 calls > out > 1.5% but with a caveat that automated assembly and surface mount may > require more stringent requirements, and refers to IPC-D-275. The > most > stringent callout in D-275 for a 0.062" double sided board is 0.9%, > and > this is classed "reduced producibility". If we have, say, an 8.5"x11" > board with 0.9% bow or twist, I know we'll have difficulty running it > down > our lines. What are others calling out, and how have your fabricators > responded? Some of mine are balking at 0.7%, saying it can't be held > (would have to be sorted, possibly increasing cost) because of > variability > in the base material. I think 0.7% is met most of the time, but every > once > in a while... > > Thanks for any input. > > ***************************** > * Pat Bailey * > * Supplier Quality Engineer * > * Zytec Corporation * > * 1425 E. Bridge Street * > * Redwood Falls, MN 56283 * > * * > * phone 507 637-2966 x355 * > * fax 507 644-3720 * > * e-mail [log in to unmask] * > ***************************** > > ############################################################## > 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. > For the technical support contact Dmitriy Sklyar at [log in to unmask] or > 847-509-9700 ext.311 > ############################################################## ############################################################## 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. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################