I agree with Randy. I have used the dichromate etchant and had no trouble detecting post separation and copper cracking when it occurred. I have seen inexperienced operators who so overetched microsections with ammonium hydroxide peroxide microetch that the sections could not be reground to find the electroless copper interface to do an evaluation! Training of microsection personnel and constant monitoring is extremely important. The problem with the etching variability over time with ammonium hydroxide peroxide will show different results depending on where in that time period the etching is being done. I believe Randy's way of making etch when needed then discarding is the most reliable. I also recommend microsections be audited frequently in order to make insure the quality of the work of these inspectors. You can't spend too much time monitoring this area. NOTE: The shop I where I worked dropped dichromate in an attempt to get all chrome out of the shop. Regards, Dave Sullivan Rockwell Collins, Inc. [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: Microsection Etchants Author: [log in to unmask] at ccmgw1 Date: 3/31/97 1:23 PM I have noticed numerous posting on the best microsection etchant to use. There are merits and disadvantages in the etchants mentioned to date. I specifically would like to discuss the sodium dichromate and the ammonium hydroxide & hydrogen peroxide. The ammonium hydorxide & hydrogen peroxide is 1 of the more unstable copper etchants that does an excellent job of microetching. The most attractive attribute of this etchant is in the hands of a less skilled or naive person, the etchant will not overetch the surface to the severity of a chromate etchant. (Not say that only less skilled people use this etchant) I define 'instability' as variable etch quality over a short period of time (hours). At Merix, we make enough etchant to microetch the work at hand and discard the remainder. The soduim dichromate etchant is a stable etchant (last for months) that is more agressive than the ammonium hydroxide & hydrogen peroxide etchant. The aggressive nature of this etchant requires greater skill by the user to prevent the surface from being overetched which hides cracks and separations. I used the sodium dichromate etchant at my prior employer for 15 years and was able to detect separations and cracks. While I worked at this employer, we published papers on our ability to detect separations and our concerns that separation was being shipped. This leads me to believe the type of etchant is not so important as the user of the etchant. One of my favorite BC cartoons is a caption that "If you don't know what it does; don't screw with it". The skill and knowledge of the user is as impotant as the etchant itself. IPC-MS-810 lists the types of etchants that are recommended for etching of microsections. Whatever etchant is chosen for use, the key is to create the desired etch quality of the surface to make wise decisions on quality. The primary qualities are a faint definition of the electroless line, strike platre line (as applicable), and the copper grain boundaries. When these boundaries become wide and/or dark in appearance, sensitivity is lost for detecting separation and cracks. Lastly, the primary reason that the sodium dicromate etchant popularity declined is the the chrome content and EPA rulings on chrome. The issue over chrome was a key reason that the etchant was dropped from the test methods and military use. Happy microsectioning, Randy Reed Merix Corporation *************************************************************************** * 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) ; Mon, 31 Mar 97 13:22:58 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 AA297026174; Mon, 31 Mar 1997 13:22:54 -0600 Received: by stealth.cacd.rockwell.com; id NAA16739; Mon, 31 Mar 1997 13:20:54 -0600 Received: from unknown(168.113.24.64) by stealth.cacd.rockwell.com via smap (3.2) id xma016733; Mon, 31 Mar 97 13:20:31 -0600 Received: from ipc.org by simon.ipc.org via SMTP (940816.SGI.8.6.9/940406.SGI) id NAA14899; Mon, 31 Mar 1997 13:08:59 -0800 Resent-Date: Mon, 31 Mar 1997 13:08:59 -0800 Received: by ipc.org (Smail3.1.28.1 #2) id m0wBlmk-000BjiC; Mon, 31 Mar 97 12:26 CST Resent-Sender: [log in to unmask] Old-Return-Path: <[log in to unmask]> Date: Mon, 31 Mar 1997 10:33 -0800 From: "Reed, Randy" <[log in to unmask]> To: [log in to unmask] Subject: Microsection Etchants Message-Id: <[log in to unmask]> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Resent-Message-Id: <"qboLv1.0.iUK.D70Gp"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/11603 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] * ***************************************************************************