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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.



NO CLEAN FLUX RESIDUE | 26 January, 2000

I am using kester 958 no clean in an Electrovert Econopak 2 and having trouble with white residue, the solder pot has a foam fluxer and I have tried diferent setings on the air knife angle & pressure, the top board temp is aprox 200F.Any help would be apreciated.

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Re: NO CLEAN FLUX RESIDUE | 26 January, 2000

One thing I've found that will create that white residue is when moisture comes in contact with that flux.

1. Verify that you are not introducing any moisture with the compressed air supply at the foam fluxer.

2. Replace the flux and clean the flux tank. Try a different lot code of flux if you have it.

3. Trace back through your process & verify the flux is not getting contaminated.

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Steve Harshbarger


Re: NO CLEAN FLUX RESIDUE | 27 January, 2000


I have seen exactly what you are experiencing with the Kester 958 on other wave lines. No clean fluxes vary in how much flux residue is visually left behind. These no clean residues are typically not harmful to the PCB, but they are often cosmetically unattractive.

You might want to consider spray fluxing the 958 flux. With a foam fluxer, your process floods the bottom of the PCB with flux. When this flux dries it will leave a great deal of residue behind. When spray fluxing you have control to put 75% less flux on the PCB (just enough flux to get good solderability). 75% less flux means 75% less residue. This might get you to an acceptable level.

I have seen operations where 5 operators were cleaning the white flux residues off PCB's; the day after a sprayer fluxer was installed the cleaning procedure was no longer needed.

Good Luck,

Steve Harshbarger

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Chris McDonald


Re: NO CLEAN FLUX RESIDUE | 10 February, 2000

Instead of spending 15k on a spray fluxer spend a little bit on your foam tower. The narrower the foam head the less flux being applied. You might have to modify the foam tower but if works. I would switch fluxes though there are others out there that preform much better.

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