I agree with Dougal. I've tried this before and it gets out of hand very rapidly. There is too much variation in the incoming laminate (no reflection on our laminate supply brethren) to run SPC on permanganate weight loss. Plus, if you have an automatic line, getting down line to pull off the coupon is something the operator will want to do reluctantly at best. My suggestion of things to control on a permanganate bath are: 1. Permanganate concentration 2. Caustic concentration 3. Manganate levels 4. Total solids 5. Temperature I assume you are using electrolytic permanganate regeneration. If you aren't, then I do not believe you will be able to control this process as it degenerates too rapidly, which may be (I guess) why you would want to control by weight loss. Follow Dougal's suggestion. It is the only way to achieve control of this process. Regards, Dave Sullivan Rockwell Collins, Inc. [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: DESMEAR FOLLOW-UP Author: [log in to unmask] at ccmgw1 Date: 3/7/97 6:57 AM Edward Szpruch wrote: We intend to upgrade our follow - up in desmear process and implement SPC . We intend to perform weight-loss measurements on uncladed laminates . What are the most common figures for FR-4 and modified resins such as FR-405 ? Edward, we used to run SPC on weight loss at desmear, but you have to be very careful, because you will find that every time you change the batch or supplier of laminate used for your weight loss panels, the SPC goes into an out of control situation, and the line starts running above or below the previous average. This is because of the variation in surface resin on the laminate, and it is this surface resin that is attacked by the permanganate. The other issue is that you cannot re-use the coupon, as the surface resin is removed and so the permanganate is now trying to remove resin from between the glass bundles. The real key is to use the weight loss panel as a measure during a DOE to establish the critical factors in the process (incl.sweller) and then run SPC on those parameters, not the product attributes. Dougal Stewart Exacta Circuits Scotland *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** Received: from by ccmgw1.cacd.rockwell.com (SMTPLINK V2.11) ; Fri, 07 Mar 97 06:57:21 cst Return-Path: <[log in to unmask]> Received: from stealth.cacd.rockwell.com (stealth) by mailserv with ESMTP (1.40.112.8/16.2) id AA165939442; Fri, 7 Mar 1997 06:57:22 -0600 Received: by stealth.cacd.rockwell.com; id GAA10360; Fri, 7 Mar 1997 06:55:35 -0600 Received: from unknown(168.113.24.64) by stealth.cacd.rockwell.com via smap (V3.1.1) id xma010354; Fri, 7 Mar 97 06:55:05 -0600 Received: from ipc.org by simon.ipc.org via SMTP (940816.SGI.8.6.9/940406.SGI) id GAA08037; Fri, 7 Mar 1997 06:45:19 -0800 Resent-Date: Fri, 7 Mar 1997 06:45:19 -0800 Received: by ipc.org (Smail3.1.28.1 #2) id m0w2ygE-000BC5C; Fri, 7 Mar 97 06:23 CST Resent-Sender: [log in to unmask] Old-Return-Path: <[log in to unmask]> From: [log in to unmask] Message-Id: <[log in to unmask]> Date: Fri, 07 Mar 1997 07:32:44 EST To: [log in to unmask] Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: DESMEAR FOLLOW-UP Resent-Message-Id: <"z83Ez.0.YZK.rY08p"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/10921 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************