Hi Keith
We build some similar stuff.  You have two options other than the hand trimming:

Run the DIP packages through a forming and trimming machine, to trim the leads to an acceptable length.  This is typically what we do, so we end up with enough lead that the CS-400 can crimp it but not too much for protrusion.

Alternatively - have a drawing note added to increase the allowable lead length to 90 thou or whatever is reasonable in the applications you have.  The drawing note overrules the IPC requirement, so you are in the clear.   



regards,

Graham Collins
Process Engineer, 
Northrop Grumman Canada Corporation
Halifax
(902) 873-2000 ext 6215

>>> [log in to unmask] 10/31/02 09:04AM >>>
We are having a vigorous discussion about how to deal with lead
protrusion on our thru hole boards.  We build mainly IPC class 3 boards,

and have two Contact Systems CS400-D thru hole insertion machines that
we use to populate these boards.  Discrete parts are not a problem, as
the leads are crimped to retain the parts in the boards for wave
soldering.  Our area of concern is DIP packages along with sockets, and
connectors.  When we insert DIPs we clinch two opposing corner pins,
connectors and sockets are retained with temporary solder mask (goop).
we are finding that the leads on these parts tend to exceed the max lead

protrusion permitted for class 3 boards when used in .06 nominal
thickness boards, but do not want to get into the quagmire of trimming
leads and inspecting or reflowing after trimming.  These boards will
meet the class 2 requirements, and there is no danger of violating the
minimum electrical spacing requirements when these boards are installed
in our systems.

Anyone else having this problem?  If so, how did you resolve it?  Your
support is greatly appreciated.


  Keith Calhoun
  Manufacturing Engineer
  Sierra Research, an Integrated Defence Technologies company
  485 Cayuga Road PO Box 222 Mail Stop 334
  Buffalo
  New York
  14225
  USA
                                         Fax: (716)631-7849
                                        Work: (716)631-6434
                                        <[log in to unmask]>

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