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   TO:         I4235700 IBMMAIL   new address for ipc technet 25.6.96

   FROM:       DSTEWART EX2       D.Stewart        - Product Development Manager.

   DATE:       23 March 1997
   SUBJECT:    EXCESSIVE CAKING OF DEBRIS (DRILL)

    A couple of issues to look at -
    1. what is the material you are drilling? as Tg goes higher,
    infeeds have to drop. We used to have issues like this with
    drilling BT epoxy, and I have heard of others have issues with
    multifunctional FR4 (Tg170).
    2. is the laminate fully cured?
    3. is your pressure foot insert too large? Many machine suppliers
    are now supplying smaller diameter inserts to allow good pressure
    onto the panel, and good extraction. The optimum insert diameter is
    7-8 mm.
    4. is your backing material sufficiently hard to break up chips,
    and are you drilling too deep into your backing?

    hope this helps

    Dougal Stewart
    Exacta Circuits
    Scotland

    The views etc.......

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