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   TO:         I4235700 IBMMAIL   new address for ipc technet 25.6.96

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

   DATE:       1 September 1997
   SUBJECT:    peel strength
   REFERENCE:  why?

    Does anyone have any data that supports the requirement for copper
    peel strengths?

    This is used by Oxide suppliers as a 'selling' point but does peel
    strength reflect the bond strength needed on inner layers in the Z
    axis during drilling and thermal stressing?

    Is peel strength only critical on outer layers in order that
    component stresses do not cause lifting of the copper from the
    laminate during soldering operations? Does anyone have any data on
    what is required, rather than what is achieved?

    Is peel strength merely that? - specified by someone because they
    invented this test and were able to find that 90% of products
    passed at this level - if you cannot find a failure then it's
    pointless doing the test !!!

    As lines and spaces get smaller, and low, very low profile and
    reverse treat copper foils become the preferred route to enable
    manufacture, will these specifications get changed in line with
    real needs (rather than what is achieved in 90% of tests)?

    Dougal Stewart
    Viasystems Selkirk
    Scotland