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September 1999

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Subject:
From:
"Stephen R. Gregory" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 1 Sep 1999 17:14:02 EDT
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In a message dated 09/01/1999 3:29:57 PM Central Daylight Time, [log in to unmask]
writes:

<< Bonjour Everybody,

 I am actually facing a problem when I am performing BGA repairs on boards.
The problem is the following:

     a.. The solder mask surounding the BGA pads is removed while we are
removing the solder residues after parts was taken off it's location. The way
we are preparing the site is the following: We are depositing paste soldering
flux over the area to rework and then with the use of a soldering iron and a
desoldering braid we remove the solder. We are trying not to scratch the
board with the desoldering braid and keep the iron tip temperature at the
minimum workable temperature. After the completion of that cycle we are
cleaning gently the board to remove excess of burnt flux. Is there any other
known good method about how to prepare the BGA site before installing a BGA
at the same site again ? (Note: the one using Bismuth alloy is not aceptable
for us...)
 I am waiting anxiously for an answer so please contact me about this topic.
Thanks !

 Best Regards

 Mario Dion >>

Hi Mario!

How much solder is being left on the pads after you remove the BGA? Are the
balls being left on the pads? I imagine that there's going to be some...

You aren't dragging the wick across the pads are you? As you've found out,
the mask won't take that. Need to use a nice fine weave of wick too, if it's
too coarse, it'll be really rough on the mask as well.

If there isn't a whole lot of solder on the pads, I'd just leave them alone
and use a hot air tool to re-level everything out. But whenever you do use
wick, don't drag it across the pads...

-Steve Gregory-

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