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February 1999

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Subject:
From:
Edward Brunker <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 17 Feb 1999 18:19:11 GMT
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text/plain (78 lines)
     I'm sorry to say this, but if it's not right at the design stage then
     it's too late!
     What were your pad lengths?


     If you have a lack of solder due to this extra pad where the track
     joins and the resist isn't covering it, then....
     there just isn't enough paste being put down.

     For fine pitch at this level you need really long strips of paste to
     achieve consistent solder fillets. You just have to bite the bullet
     and force your CAD people to give long pads.
     This really is fine pitch and there is no other way to provide that
     solder.
     Please, please fill us in on the specific dimensions of this device.
     Lead contact length, maximum outer dimensions, lead thickness etc...
     Regards
     Edward Brunker

     P.S. What stencil thickness and aperture width were you using?
     What grade powder are you using?
     (Did paste remain in the apertures causing lack of solder)?



______________________________ Reply Separator _________________________________
Subject: [TN] SMT assy issue
Author:  "TechNet E-Mail Forum." <[log in to unmask]>           Anne Ledger
<[log in to unmask]> at INTERNET
Date:    17/02/99 10:27


Good Morning Technetters,

Thanks for all the help on the board shop for the mil spec multilayer
board.  I have passed the info on to the powers that be.  Today I have a
different problem, pertaining to SMT assy and solder paste.

We have made a board that has 15 mil pitch, using 8 mil pads connected
to 8 mil tracks (some).  The problem is that the SMT is cleared on the
ends by 5 mils and the track width is pulling the paste from the pad and
causing the part not to adhere.  What can we do to block the paste from
traveling down the track at this point.  We have the boards made and
would prefer a good rework procedure instead of remaking the boards.

Thanks in advance for the assistance.

Anne Ledger
Mfg. Engineering Dept
EMDS, Inc.
[log in to unmask]

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