In order to realy identify the true cause of your seepage issue, I
    would recommend you look at some resist side wall S.E.M.'s.
    This will help determine at the micro level what you have for
    resist at the foot where it is seeping from. Any negative resist
    foot on a 4/4 feature could result in lifting in the soap cleaner
    in pre clean as well as in pre clean to Solder plate. X sections
    of a copper/solder plated panel before resist strip would also
    help identify this. I would assume that you have already verified
    that you have done water break test on pre cleaned panels before
    resist lamination and all on that end is in spec. ie. Roll
    pressure, Roll temperature, exit temperature etc. As you know MLB
    lamination will follow the topo of the inner layers to some
    degree. Asking the laminator to apply resist with good contact
    can only go so far, you may try running a thicker film as a band
    aid just to find what will fix the problems and work backwards to
    eliminate it.  We resist laminate some pretty non uniform surfaces
    and have seen some of this ourself's in the past.

    [log in to unmask]






        On your multilayers, do you use <copper> foil lam or core <double
     sided> construction?  If you use core construction you may want to
     check into how well you remove/clean the outer oxided surfaces before
     electroless copper. Also check the copper surface before image.
     Tape test. If you get toooooo much e-less copper coming off then
     there's your adhesion problem.
     
     
     Groovy
______________________________ Reply Separator _________________________________

Subject: Disscussion on seepage /resist lifting problem in 4/4mil and
Author:  [log in to unmask] at SMTPLINK-HADCO
Date:    9/9/96 8:56 AM




    with respect to above mentioned problem i wud like to clarify that the
said defect is being noticed only in ML boards.The said problem is not
noticed to such an extent in DOUBLE SIDED RIGID boards for the same
complexity of the Product. Therefore we suspect strongly the ML lamination
process as a POTENTIAL CAUSE.Could any one throw some light on this

 

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