Rod,

I can't answer your first question.
For the second question, please contact Sherman Sum of
Richey Electronics in Burnaby (420-0313).  I currently use
Chemtronics Twillwipes, p/n: C900.  It does wonderful job of
cleaning stencils and leave no wiper shreds, but I don't know if
roller wiper version for automatic cleaning is availabe from
Chemtronics.

Give my regard to Sum.
Matthew Park
NII-Norsat International Inc.
Surrey, BC.

>>> Rod Lafond <[log in to unmask]> January 11,
1999  10:58 am >>>
Actually I have two questions.
1)  Does anyone have data showing the effect on solder joint
reliability of
a twice re-flowed BGA?   A client is considering a board design
with BGAs on
both sides and is concerned about the reliability of the solder
joints on  a
BGA placed on the first side because it would be exposed to two
reflow
cycles. Has anyone done this and followed up with any long term
studies?
Would a second application of flux be useful ?
2)  This one is more straight-forward.  Where can I buy a
'tack-roller' for
cleaning solder paste from the bottom side of stencils?   Even
the best
'lint free' wipers tend to shear and leave tiny shreds on the
stencil.
Thanks in advance, Rod Lafond
                                  Manufacturing Engineering
                                  Aimtronics, Delta B.C.

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