Hi Joseph,

Of course my experience with punching boards is somewhat limited to the work
I did back in the 1980's for a high volume manufacturer of power supplies,
ACDC Electronics, now known as Astec Power supplies... We used CEM1 for the
material and changing the location of any features once you went into
production was limited to traces only, no cutouts or holes could move
because they would affect the tooling. Blanking dies where not cheap and we
were experimenting back then with a process called 'punch and return' which
was supposed to keep the board in its assembly panel while assembling it and
then allow the assembly line to pop it out after assembly since it had
already been punched all around it's perimeter...

I'm sure there are others who have had more experience with punched boards
than I have but I do remember that the blanking company was definitely not
interested in punching FR4 because of the die wear.  Die wear might explain
the cracks he's seeing in the board edges due to poor shearing... but I'm
sure a qualified ME or board inspector with a microscope would be able to
diagnose the problem more accurately...

Best regards,

Bill Brooks - KG6VVP
PCB Design Engineer , C.I.D.+, C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
e-mail:[log in to unmask]
http://www.dtwc.com
http://pcbwizards.com


-----Original Message-----
From: Johnson, Joseph [mailto:[log in to unmask]]
Sent: Thursday, February 17, 2005 10:45 AM
To: [log in to unmask]
Subject: Re: [TN] Cracking FR4

 Bill,

        I can tell you for a fact that 90% of all boards for your car are
CEM1 and they are punched.  I worked at a manufacturer in Detroit for a
couple of years.  We were actually the company that made the DRL's (Daylight
Running Lamps) for Ford, GM and Chrysler. (It's the same module, at least it
was in the 90's)  Anyway, we made 25K of those a month.   The board was a
CEM1 material that was punched.  From what I understood.....   The punch
with this material virtually never wore out.

        The trick is to make a change to the design after the punch and die
were made and not move any holes.....  You could re-use the holes for
something else but you could not move one.

        Joe J.

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