I do not agree that using "etchback" will eliminate Post Separation (the new term for IPC-T-50E is "Internal layer separation" rather than post separation). The use of chemicals such as permangate or dry plasma etching to remove the resin adjacent to the internal layer connection will certainly remove epoxy smear. This is what "etchback" was designed to do. In my experience the use of smear removal which cleans the resin smear off the internal layer without overetching to make the internal layer protrude in to the hole is just as effective as etchback and is much easier to control. There are many opinions about the reliability of the PTH with etchback versus hole smear but I do not have data to support one position or the other. Internal layer separation is a result of leaving a deposit on the face of the internal layer which is subsequently metallized and plated and it is NOT epoy resin. The cause of innerlayer separation is associated with the chemistry used with hole metallization and will differ with each type chemistry (deposits from the metallization bath stabilizer and inadequate surface copper cleaning are examples) . I have seen internal layer separation with regular formaldehyde chemistry and with the direct plate process from Atototech. A lot of work has been done to look for the contaminate on the inner layer but the end result is that a metallurgical bond is not formed with the plated copper and the joint will fail under thermal stress from a solder float at 550 F for 10 sec. In my opinion the elimination of internal layer separation will occur with good control of the metallization process. It is definetly difficult to detect but I would suggest that all the Testing Labs associated with the IPC Post Separation Task Group can find the problem on purchased PWBs. I believe it is prudent to use them as a "referee" to verify hole quality on an ongoing basis. There are definitely different levels of severity of the poor internal layer connection and it can be seen in vertical crossections as a line with some good connection and some bad. These are the most difficult to detect by typical microsection in the horizontal direction. If you would like to learn more about this problem I would invite you to participate in the Post Separation TG. Foster Gray Chairman, IPC Post Separation Task Group PC Interconnects Austin, Tx e-mail: [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] * *************************************************************************** ----------------------- Headers -------------------------------- >From [log in to unmask] Fri Apr 11 15:27:11 1997 Return-Path: <[log in to unmask]> Received: from mrin10.mail.aol.com (mrin10.mail.aol.com [152.163.125.102]) by emin09.mail.aol.com (8.8.5/8.8.5/AOL-2.0.0) with ESMTP id PAA14427 for <[log in to unmask]>; Fri, 11 Apr 1997 15:27:10 -0400 (EDT) Received: from sol.corp.Harris.COM (sol.corp.harris.com [137.237.104.14]) by mrin10.mail.aol.com (8.8.5/8.6.12) with SMTP id OAA27948 for <[log in to unmask]>; Fri, 11 Apr 1997 14:17:09 -0400 (EDT) Received: from mailc.harris.com by sol.corp.Harris.COM (8.6.12/Kurts Special version 2.0) id OAA06505; Fri, 11 Apr 1997 14:16:43 -0400 Received: from ccMail by mailc.harris.com (IMA Internet Exchange 2.1 Enterprise) id 0002711F; Fri, 11 Apr 97 14:13:29 -0400 Mime-Version: 1.0 Date: Fri, 11 Apr 1997 14:07:02 -0400 Message-ID: <[log in to unmask]> From: [log in to unmask] (Administrator) Subject: Message not deliverable To: [log in to unmask] Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Content-Description: cc:Mail note part *************************************************************************** * 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] * ***************************************************************************