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   TO:         I4235700 IBMMAIL   new address for ipc technet 25.6.96

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

   DATE:       13 September 1996
   SUBJECT:    COMPENSATION MACHINE

    Re - compensation machine

    X-ray optimisers, as they are known, are available from a number of
    companies:
    Multiline (OPL)
    Pluritec
    etc.
    Some of them work by looking at a target on all layers at the same
    time, then making a best fit, compensating to centralise the datum,
    and then drilling or punching tooling holes on a fixed pitch,
    whilst others look at targets on each individual layer, and
    compensate to get best fit.
           The advantage of the latter system is the feedback it gives
    on a layer by layer basis of the material shift, in order that
    compensations can be made to improve NEXT time round. The former
    system also feeds back information on shift, but is limited to the
    best fit data.

    Dougal Stewart
    Product development manager
    Exacta Circuits
    Scotland

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