Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Ken Daniels

#12891

Flux Residue in Oven Vents | 18 January, 1999

I have a severe problem with flux residue being drawn up the vent ducts of my reflow oven. This residue reaches a critical mass then begins to flow down the ducts and becomes very messy. I run a no-clean process and use IR oven. Has anyone else out there experienced and overcome this problem? Thanks for any help.

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marc p

#12892

Re: Flux Residue in Oven Vents | 18 January, 1999

| I have a severe problem with flux residue being drawn up the vent ducts of my reflow oven. This residue reaches a critical mass then begins to flow down the ducts and becomes very messy. I run a no-clean process and use IR oven. Has anyone else out there experienced and overcome this problem? Thanks for any help. |

Ken,

There are a few methods to deal with this issue. Not all of them are elegant but they are functional.

1)Install a flux collection box. There are a few out there but the only one that comes to mind is made by Impell Technologies. Their tel # is 770-939-6923.

This is basically a box with a series of filters that remove the flux from the exhaust. The filters are disposable and depending upon your production levels can last from 1 week to 3 months.

2)Install a trap in the exhaust line. In much the same way as a trap in the kitchen sink, a trap in the exhaust line will catch the flux before it drips back down into the oven. This configuration will also but some serious restriction on your exhaust system so the exhaust motor will likely have to be beefed up.

3)Install disposable exhaust tubing at the oven. Starting at the oven and running for 10-12 feet, utilize some inexpensive flex duct. When it gets "fluxed up", throw it out and put in a new piece of duct.

You probably have a feel right now as to how long before the duct starts to drip. You can take that information and incorporate it into your P.M. schedule.

4)Call your oven company and see if they have made any advances in this area. Several of the mfrs. are offering flux removal systems and some are field retrofittable. It couldn't hurt to ask.

Hope this helps,

Marc

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Dave F

#12893

Re: Flux Residue in Oven Vents/Wide Pipes 'er Narrow Pipes | 20 January, 1999

| I have a severe problem with flux residue being drawn up the vent ducts of my reflow oven. This residue reaches a critical mass then begins to flow down the ducts and becomes very messy. I run a no-clean process and use IR oven. Has anyone else out there experienced and overcome this problem? Thanks for any help. | While we're on the topic, why do some plants use vent piping that must be a foot in diameter and others use much narrower (6-8 inch) vent pipes for the same reflow machine? I looks as if those using the wide pipes have to put an adapter on their machine to match the output vent on the machine to the wider vent pipe.

TTYL

Dave F

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Todd Gilmore

#12894

Re: Flux Residue in Oven Vents | 21 January, 1999

Ken; my experience has been that eventually the flux builds up in the vents and then drips back down on the boards. For a simple oven with an air cooler the flux must go somewhere. Better in the ducts than in the oven. Just replace the ducts every year or so.

New Nitrogen ovens have methods to remove the flux. Call me if you have any questions

Todd Gilmore

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