---------------------------- 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