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   TO:         I4235700 IBMMAIL   new address for ipc technet 25.6.96
               CROMONT  EXFR01    Christian Romont - Exacta France (SARL)

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

   DATE:       10 September 1997
   SUBJECT:    BGA and ENAu
   REFERENCE:  phosphorus content

    Does anyone have any data on the way in which the phosphorus
    content changes a) during the life of the nickel bath
                    b) as the thickness of the electroless nickel
    increases ie. is there a gradient in the Phosphorus content from
    the copper to the gold interfaces. and is this the reason why too
    little nickel causes solderability problems?

    The question is asked in conjunction with failures in intermetallic
    phases when BGAs soldered to ENAu are subjected to vibration and
    drop testing.

    Thankyou
    Dougal Stewart
    Viasystems, Selkirk