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Flux not foaming

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#65063

Flux not foaming | 20 September, 2011

We've got a Novastar 12S wave solder machine and we've been using Kester 951 flux for years with no problems. We just got a new bottle of 951 and it does not foam correctly (thin foam with lots of large bubbles). After a lot of back and forth with Kester, they said there have been no reported problems and sent us another bottle (from a different batch). Same problem with this new bottle. We've tried a new stone and another air source, but same problem. I can't believe something in the machine just happened to fail at the same time we got a new bottle of 951, but Kester won't talk to us any more, they say it isn't their problem. We don't have any old bottles, so we can't try that. Does anyone have any ideas what our problem could be?

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#65064

Flux not foaming | 20 September, 2011

Check specific gravity: According to a quick web search, the specific gravity should be 0.813 ± 0.003. If you have records of the specific gravity, compare current reading to past readings.

Check pressure near stone: if you have records, compare to prior readings.

Vary pressure to see if you can control bubble size and head formation with pressure.

Is someone hand spraying boards with a flux prior to feeding them into the wave solder system? Consider if someone cleaned any wetted part of foam fluxer or feed lines prior to this occurrence. Could be cleaning chemistries from this cleaning were not thoroughly rinsed.

Consider if something is being introduced by the boards (or pallets that carry boards).

Consider if the onboard air compressor introduced oils or something else to the foam bath. If you switched air sources, what could have been introduced would still be there.

Check ability to produce foam head with preheaters off.

That's a quick list of idea's that I've shared with others before. If something else comes to mind, I'll post again.

Best of luck,

Shean Dalton www.fhpreps.com 512-971-2850

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#65065

Flux not foaming | 20 September, 2011

We don't have the equipment to check specific gravity, we just assume what's on the bottle is correct and we've never had a problem. The stone sits in an open chamber, so there really isn't any pressure to check. When we vary the air flow, the foam head rises or falls, but it doesn't make it more or less foamy. There is only a flow valve to manipulate. No hand spraying, boards go right in just like we have always done. No changes were made to the flux chamber, we follow our normal procedures and only had a problem when using a new bottle of 951. Just turning on the machine and starting the flux flow, the foam head is bad even before we feed anything in, so it can't be anything external (like boards or pallets). I'm not sure about the air compressor built-into the machine, there really isn't any way to test it, but it does make air, so we assume it's good. We also tried an external air compressor and got the same exact results, so this would seem to confirm it's not an air compressor problem. The Novastar process is just an air compressor pushing air into the stone, which sits in the flux bath beneath the trough, there are no preheaters, the only heater is after the flux bath, so it can't be affecting the foam formation. Since it's not foaming correctly as soon as we turn it on, it can't have anything to do with the rest of the machine or the circuit boards, it has to be either the air compressor, the stone, or the liquid, and we've eliminated all three (except for the liquid, which we really can't test and Kester denies they have a problem).

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#65066

Flux not foaming | 21 September, 2011

Russ,

Try to shake the 1 gallon jug and see if you can create foam on top of the liquid. If you don’t see any foam at all something is wrong with the flux.

Patrick

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#65067

Flux not foaming | 21 September, 2011

If I shake it hard, I get a thin foam which quickly goes away. Not sure what it should look like.

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#65068

Flux not foaming | 21 September, 2011

As long as you see foam it's probably not the flux. Try to increase the flux level in your fluxpot that should help reducing the bubble size.

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#65069

Flux not foaming | 21 September, 2011

The confusing thing is we are doing the same thing we've been doing for years, same flux levels, same procedures, etc. so you would expect the same results. The only difference is the new bottle of 951, but Kester insists there isn't a problem with it and I'm not sure how to verify that short of sending it to an outside lab, but I'm not sure what a lab could do. Does anyone know of another brand comparable to Kester 951 that would work in our machine? That's about the only thing left that I can think of to try.

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#65072

Flux not foaming | 21 September, 2011

Shenmao SM-816 is alcohol based no-clean liquid flux and can be used in the foam fluxer. http://db.tt/sHkmOOyf If you'd like more info, contact me offline.

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#65085

Flux not foaming | 23 September, 2011

Same happenend to me with another flux some years ago, to me its a reduced viscosity of the flux, what I did was to reduce the width of the slot on top, where the flux exits, reduced the distance from stone to pcb and filled the flux reservoir to the highest possible level...althought the best solution was to purchase an Aerograph (what artists use to paint large images or hobbists for small spray painting)and spray flux the boards, you save a lot of flux and increase the quality, its a cheap way around, the best is to purchase a professional spray fluxer. Hope this helps

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#65086

Flux not foaming | 23 September, 2011

Oswaldo,

Your reasoning is correct, but the strange part is that Russ didn’t have a problem for years using the same flux so you would assume his fluxer is designed for low solid fluxes.

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#65109

Flux not foaming | 26 September, 2011

I agree with Shean that contamianted air is your problem. Either water or oil got into the supply line and is mixing with the flux. You should have both a water and oil trap at the inlet of the machine and not back at the compressor.

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#65605

Flux not foaming | 7 December, 2011

OK, still haven't figured this out. New flux, new air pump, new tubing, new stone, but flux still not rising enough. Pump has correct voltage. We've eliminated everything, but we still cannot find the problem. What else could possible keep the flux from foaming enough?

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