Well, I'm impressed and I see why you USA board fabs stay in business ! Even the best automatic printers with optical registration would find it hard to achieve 0.001" positional tolerance - the heat from the lamps exposing the artwork will make the artwork shift by more than this..... So, if this is what you specify, you will have to pay the price, which is either scrap or rework at the fab house, which they should add onto your board price, or is absorbed by the fabricator, who then goes out of business trying to achieve the physically near impossible. After that you will go to the far east for your supply where they will ignore your requirement (sorry, not understand) and you are back to having ganged openings or reduced pad width. I have only come across one soldermask capable of achieving a soldermask dam of less than 0.004", as normally the undercut will remove the dam if the artwork is less than 0.006". To achieve dams on a 20 mil pitch device (which is actually 19.685 mil), use a 10 mil pad, and just state that you require solder dams. Why don't you allow ganged openings - what part of your assembly process can't you control? Is it solderpasting, position of paste screen, volume of paste, or positioning of components? Dougal Stewart email: [log in to unmask] phone: +44 1896 822204 mob: +44 7984 629667 ----- Original Message ----- From: "Greg Scott" <[log in to unmask]> To: <[log in to unmask]> Sent: Friday, June 21, 2002 11:19 PM Subject: Re: [TN] Registration of soldermask > Loan, > > What we do is design with 2mil per side opening with a solder mask note: > No finished solder mask over pad edge. Annular ring of exposed board material around pad edge to > be .001 min, .003 max. > Maintain a solder mask bridge of .004 min. wide between fine pitch solder pads. > > Also the pad can not be wider then .012 with this approach. Do not allow for ganged soldermask > relief. We had all > rework problems with that approach. > Have not had problems since this note. > > Greg Scott > Cray Inc. > Seattle, WA. > > "Tempea, Ioan" wrote: > > > Hi technos, > > > > what would be a reasonable requirement for the registration of the solder > > mask on boards with 20 mils fine pitch having solder mask dams. We asked for > > 0.002" and it almost comes over the edges of the pads. > > > > Is 0.001" doable, with no impact on the price? > > > > Thanks, > > Ioan > > > > -------------------------------------------------------------------------- ------- > > Technet Mail List provided as a free service by IPC using LISTSERV 1.8d > > 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL > > 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 > > -------------------------------------------------------------------------- ------- > > -------------------------------------------------------------------------- ------- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8d > 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL > 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 > -------------------------------------------------------------------------- ------- > --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------