Maximize total copper on all layers - this will minimize your etching load (cost). Use solid copper borders with 0.125" vacuum channels. Use 16ga. (0.060" thk.) separator plates, preferably hardened 420SS. Ensure adequate resin volume to fill the non-functional space and account for this reduced volume in the overall thickness prediction. Depending on your chemistry, you can probably expect 6-8 mils of line width reduction (i.e., blow the .024" track up to .030"-.032"). Can your photoresist withstand the required etchant exposure time? Keeping pH on the low end might buy you a little extra time. If this is a high-volume program, do a mfg.cost reality check per pound of etched copper. (Cupric chloride, incidentally, etches the same for roughly half the cost depending, of course on a myriad of other factors). Good luck. J.Felts PC World, Toronto ______________________________ Reply Separator _________________________________ Subject: FAB: 3 layer board with 4 oz copper Author: [log in to unmask] at INET Date: 2/27/97 2:46 PM I have 2 issues that I'd like to get some advise on. 1) Does anybody have advise on etching 4 oz copper? The traces are .024" and we etch with ammoniacal etchant. 2) Is there any advise on laminating a 3 layer board with 4 oz base copper on all layers? .062" finish thickness and the layup is at our discretion. *************************************************************************** * 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] * *************************************************************************** *************************************************************************** * 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] * ***************************************************************************