Bill, Positive etchback or etchback, as you know, is where the resin in the hole is removed (commonly by plasma etch) thus exposing the top and bottom of the pad. This exposed surface will be plated and you end up with a 3 point connection, the top, front and bottom of the pad. If we were talking lumber this is the equivelant of a tongue and groove joint. No etchbadk is when you drill a hole and don't remove any resin. Panels are run through a desmear cycle that removes any resin that might have 'smeared' on the surface of the pad. (This is really hard to explain without pictures). Now when the hole is plated the plating will only attach to one surface; the front of the pad. Another wodworking term. This would be the equivalent of a butt joint. So imagine looking at a cross sectional view of a hole with no etchback - The resin and copper are in the same plane. When the panel is run down the electroless line one of the chemistries is micro-etch. The micro etch is desiged to remove copper. You can imagine (I hope) that when a panel with no etchback (butt joint) goes through the micro-etch the copper some of the pad will be removed. So the copper pad will be recessed slightly - below the plane of the resin. (No woodworking term) This is negative etchback. Having said all of this and re-reading I decided to find some pictures on the web. (I just did a Google Search - I know Delson is a lab but I am not associated in any manner. ) There are pictures of both Positive and Negative etchback. http://www.delsen.com/gallery.html Hope this helps. pete Click on this link and there is a picture titled Negative Etchback. >From: Bill Dworak <[log in to unmask]> >Reply-To: TechNet E-Mail Forum <[log in to unmask]>, Bill Dworak ><[log in to unmask]> >To: [log in to unmask] >Subject: [TN] I have a question >Date: Thu, 16 Dec 2004 15:36:08 -0800 > >Hi everybody I have a question that I hope is not a stupid one that I was >just asked it is about the etch back process. >What does a positive etch back mean? And what does a Flush etch back mean >and what is the typical spec on these? >I know what etch back means but not up on the two of these??? Please >forgive me I am just a sales guy. > Thank you in advance. > > Bill Dworak > >--------------------------------------------------- >Technet Mail List provided as a service by IPC using LISTSERV 1.8e >To unsubscribe, send a message to [log in to unmask] with following text in >the BODY (NOT the subject field): SIGNOFF Technet >To temporarily halt or (re-start) delivery of Technet send e-mail to >[log in to unmask]: SET Technet NOMAIL or (MAIL) >To receive ONE mailing per day of all the posts: send e-mail to >[log in to unmask]: SET Technet Digest >Search the archives of previous posts at: http://listserv.ipc.org/archives >Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 >for additional information, or contact Keach Sasamori at [log in to unmask] or >847-615-7100 ext.2815 >----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------