---------------------------- Forwarded with Changes --------------------------- From: Larry W. Barker Date: 1/16/96 7:55AM To: Bob H. Walker To: Larry W. Barker To: Duane B. Mahnke To: Andrew P Magee To: Len S. Calabrese Receipt Requested Subject: Re: Punching Problem ------------------------------------------------------------------------------- This interesting discussion concerns punching of polyimide flex circuit materials. Out of courtesy the circuit fabricator's name has been deleted. Andrew P. Magee - Applications Engineer Rogers Corp - Circuit Materials Unit Tel: (602) 917-5237 Fax: (602) 917-5256 E-Mail: [log in to unmask] ______________________________ Forward Header __________________________________ Subject: Re: Punching Problem Author: Larry W. Barker at Rogers-MCD Date: 1/16/96 7:55 AM Bob, It sounds to me that he has at least 2 problems. You said that the clearance is bad. I take it that means excessive. If there is too much clearance then you will get a ragged or rough cut because the punch winds up trying to tear the material rather than cut it. This is why putting the paper underneath helps. We normally ran with .0001 per side. The only thing I know to do other than get new punches and/or die plate (which is basically a new die) would be to replace the current punches with punches that are considerably softer than the die. What you do is peen the end of the punch so that it blossoms out then shear it into the die. This actually gives you a metal to metal, zero clearance die. The problem is that, obviously, it greatly reduces the life of the punch and may require a lot of maintenance due to wear. The second problem of the punches not cutting all the way through the Mylar sounds as if the punches aren't entering the die deep enough. The punches should enter about .010-.015. If you go much deeper you run the risk of creating a vacuum when the punch retracts and pulling slugs back up. Look at the die plate after some material has been punched and see how far down the slugs are pushed in the die plate. If they aren't being pushed down far enough normally you would grind the amount needed off the stop blocks so that the punches can enter farther. ______________________________ Reply Separator _________________________________ Subject: Punching Problem Author: Bob H. Walker at Rogers-MCD Date: 1/16/96 4:47 AM Larry, can you please advise on the following? ?????? uses hard tooled punches to punch Japanese materials with paper releases and orients the material Kapton up, so the punch cuts through the Kapton, then adhesive, then paper. Therefore, the stiffest (highest modulus) material gets punched last and supports the other materials being punched. The problem is he has a die made in ????????? and he thinks that the clearance is not very good. In using the die, the punch cuts through the Kapton and adhesive, and goes about 1/2 through the Mylar and never really cuts the slug out, so it ends up partially attached and comes off during the release removal step in lay-up. It is really lousy punching. He also believes that this is his problem and not the materials (so it appears not ALL problems get blamed on the material! - just kidding). He has tried using a stiff paper under the release during punching and you can image what a paper fiber mess he ends up with there, but it seems to help. He can not flip the coverfilm over as it is not a symmetric part. So Larry, any ideas of what to do? New dies are pretty expensive. Thanks for your help. Bob Walker