Well Steve I agree with you. We should not have any snap off but snap off should be used to setup the GSP. You ask how? I'm glad you asked. Use of a feeler gauge or some other known thickness material and raise the table until resistance is felt. Remove gauge and raise the table by X amount. X amount is the thickness of the gauge used. Possible defects if a snap off is used with a stencil;solder paste peaks,bad solder paste definition and inconsistent printing. ______________________________ Reply Separator _________________________________ Subject: Solder Paste Printing "Snap-off"....... Author: [log in to unmask] at ~INTERNET Date: 4/25/95 4:03 PM Received: by ccmail Received: from netcomsv by pragma.com (UUPC/extended 1.11) with UUCP; Tue, 25 Apr 1995 16:03:07 PDT Received: from gagme.wwa.com by netcomsv.netcom.com with SMTP (8.6.12/SMI-4.1) id PAA20598; Tue, 25 Apr 1995 15:07:54 -0700 Resent-Date: Tue, 25 Apr 1995 15:07:54 -0700 Received: from ipc by gagme.wwa.com with uucp (Smail3.1.28.1 #8) id m0s3sqy-000FHhC; Tue, 25 Apr 95 17:13 CDT Received: by ipchq.com (Smail3.1.28.1 #2) id m0s3sB9-0000GmC; Tue, 25 Apr 95 16:29 CDT Old-Return-Path: <gagme!pragma.pragma.com!sgregory> From: [log in to unmask] X-ccAdmin: postmaster@netcomsv Date: Tue, 25 Apr 95 13:45:10 Encoding: 2536 Text Message-Id: <[log in to unmask]> To: [log in to unmask] Subject: Solder Paste Printing "Snap-off"....... Resent-Message-ID: <"fAT0H3.0.qX8.IdMdl"@ipc> Resent-From: [log in to unmask] X-ccAdmin: postmaster@netcomsv X-Mailing-List: <[log in to unmask]> archive/latest/429 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask] Good day! First I would like to express my thanks for the inputs I have received in response to several of my requests in the past. They have all been very helpful in resolving the issues that I needed help on, or when I needed "another voice" to echo my position on certain issues. I think we all get busy and sometimes neglect to acknowledge the efforts of others. So now that I've finished "kissing-up"...<GRIN ;^D> I'm wondering if I could solicit for some more opinions....It has to do with stencil set-up. We're refining and detailing our ISO 3rd-level procedure for the Screen Printer. A few of us seem to be at "loggerheads" on the issue of stencil "Snap-off"..... * One side says that when dealing with "fine pitch", using snap-off is the best way to ensure that you'll get enough paste through the stencil and on to the PCB..... * The other side feels that snap-off is a hold-over from the days of printing solder paste through a screen, and also used to "band-aid" a problem with the design and/or the workmanship of the stencil...that as long as the apertures are designed within the guidelines for aspect ratio of 1.5-2 times the thickness, sidewall quality is good, and the correct mesh paste is being used, there should be no reason at all for "snap-off"..... We want to write the kind of 3rd-level procedures that spell out possible problems that could be encountered during production, so that operators will "raise the flag" when they run across situations that may have an affect on the yield of the process, rather than trying to "make something work" when it isn't right to begin with..... Thanks in advance!! .---. .----------- * / \ __ / ------ * / / \(..)/ ----- * Steve Gregory ////// ' \/ ` ---- * [log in to unmask] */*/ * // : : --- * Pragmatech Incorporated * /` '-- * 101 Nicholson Lane *//..\\ San Jose, California 95134 ----VVV--VVV---- Phone: (408) 943-1151 ----'//||\\`---- Fax : (408) 943-1461 //-/ \-\\