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From [log in to unmask] Mon May 19 10: |
21:54 1997 |
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Stella:
I have had similar experiences when we switched from an alcohol based flux
(RMA) to a water based flux (Kester HF1189A). While the HF1189A is not a
no-clean material but is a water soluble flux, I believe that you are
observing the same sizzling and popping of the the board in the solder wave
which generates solder balls due to the moisture in the flux hitting the
wave. Alcohol based fluxes dry much quicker allowing the flux to do what its
supposed to do.
What I found was that I needed to dry out the moisture in the flux without
overheating the flux. By turning up my air-knife after my foam fluxer I was
able to apply a thinner amount of flux to the board. I also lowered my
pre-heat settings and slowed down my conveyor to promote a slighly longer
drying period for the amount of pre-heat area that I have. (Note: I am
considering the purchase of additional pre-heat panels so that I can return,
at the very least, to my original conveyor speed.) This adjustment virtually
eliminated the solder ball condition that we were observing. Additional
adjustments to the solder wave temperature further improved the process to
the point that our quality was equal or better to that when we ran alcohol
based fluxes.
Bill Kasprzak
Moog Inc.
716-652-2000 ext 2507
email -- [log in to unmask]
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