Tom, Etchback exposes the cu circuit trace by "etching back" the dielectric inner layer mtl in a multilayer bd. De-smear only removes the surface layer of "smeared" mtl formed during the drilling of the hole through the pcb. Our experience (as an end user of pcbs) is that etchback is CRITICAL for long term reliability of higher count multilyr bds (6+). We specifiy it for ALL multilyrs. The etchback provides a positive interlock (2-3 point contact) of the cu trace and the plated cu in the pth. This is required to withstand differential expansion rates within the pth during T-cycle / shock. The higher the layer count and thermal excursion, the more important etchback becomes. The process is different depending on whether the dielectric is GF of GI. GI etchback is typically limited to plasma etch, although I believe there is a chemical (permangenate) process that will go beyond de-smear. GF etchback can be done chemically. The plasma process requires capital outlay by the PCB house ... so you must check to see if they are set up to do it if you want etchback. You can specify it by invoking the 55110 requirements for "positive etchback" on multilyr pcbs. Good luck! Vince Giardini Proj. Engin, Parker Hannifin Corp. ---------- From: INTERNET:[log in to unmask] Sent: Wednesday, March 26, 1997 2:30 PM To: INTERNET:[log in to unmask]; INTERNET:[log in to unmask] Subject: Etchback vs Smear Sender: [log in to unmask] Received: from simon.ipc.org ([168.113.24.64]) by arl-img-2.compuserve.com (8.6.10/5.950515) id OAA02417; Wed, 26 Mar 1997 14:06:07 -0500 Received: from ipc.org by simon.ipc.org via SMTP (940816.SGI.8.6.9/940406.SGI) id MAA28808; Wed, 26 Mar 1997 12:54:00 -0800 Resent-Date: Wed, 26 Mar 1997 12:54:00 -0800 Received: by ipc.org (Smail3.1.28.1 #2) id m0w9xOe-000BixC; Wed, 26 Mar 97 12:26 CST Resent-Sender: [log in to unmask] Old-Return-Path: <[log in to unmask]> Message-ID: <[log in to unmask]> Date: Wed, 26 Mar 1997 13:36:28 -0800 From: Thomas Kropski <[log in to unmask]> Reply-To: [log in to unmask] Organization: Sierra Technologies, Inc. X-Mailer: Mozilla 3.0 (Win16; U) MIME-Version: 1.0 To: [log in to unmask], [log in to unmask] Subject: Etchback vs Smear Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Resent-Message-ID: <"GNEmH1.0.EoB.xeMEp"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/2411 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask] When is etchback and/or smear removal applicable? What is the prefered method or required method and how should it be defined on the drawing for 55110 reqd board? Appreciate others knowledge, Thanks Tom *************************************************************************** * The mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text.* *************************************************************************** * If you are having a problem with the DesignerCouncil, please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * The mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text.* *************************************************************************** * If you are having a problem with the DesignerCouncil, please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************