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Reflow CFM Too High (FPM above 4000!! target=1433)

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#50790

Reflow CFM Too High (FPM above 4000!! target=1433) | 22 June, 2007

Our Heller oven is functioning well. However, we see defects from the oven, such as shifted coil inductor components, and missing chip components from time to time. When we re-scan the board at the AOI, the defect was not present at that stage,hence confirming that the defect occured at the oven. Upon measuring the oven exhaust, all the ovens showed a wind velocity exceeding 4000 fpm. We also notice that the exhaust coil is bending inwards due to the excessive exhaust speed. Will this excessive exhaust preassure cause components to fly off the board?

Puvendran Sangaran Flextronics Shah Alam

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#50800

Reflow CFM Too High (FPM above 4000!! target=1433) | 22 June, 2007

Are you sure your units are correct? Is this in the exhaust duct or actually in the reflow area? 4000 FPM = 67 FPS or 45 MPH (73 km/H). I have no doubt such a wind would blow larger parts off the board. If this is only in the exhaust ducting, then you'd have to compute the ratio of areas to figure out what the air velocity was in the reflow part of the oven.

Jon

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#50823

Reflow CFM Too High (FPM above 4000!! target=1433) | 25 June, 2007

This is ducting air speed. Please advise on how to obtain reflow air speed. Our measurement tool is a Dwyer No. 460 Air Meter (max. 4000 FPM, accuracy of 10 FPM).We are using 8 inch ducting.

Thank you for you help thus far.

Puvendran

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#50826

Reflow CFM Too High (FPM above 4000!! target=1433) | 25 June, 2007

I don't know much about Hellers other than the 1500 models which don't have blower speed adjustments (except for cooling), but with that much air flow I'd be worried about over working your heater elements.

Have you checked in zone setups to see how much power they're requiring to hold the set points? Anything over 70% in reflow (according to the manual) is the result of too much exhaust flow.

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#50841

Reflow CFM Too High (FPM above 4000!! target=1433) | 25 June, 2007

If you calculate CFM using the numbers you have provided you are pulling 1396CFM out of the oven. I am not sure what Hellers spec is but I know a Speedline OmniExcel Air machine should be set at 300CFM. I do know for a fact that to much exhaust can shift components or blow them off. I would check with Heller and lower the exhaust. Be careful when changing the exhaust though.........if you have set recipes based off profiles ran with the exhaust this high. They will more than likely need changed if the exhaust flow is lowered too much.Watch you TAL Times!

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#50843

Reflow CFM Too High (FPM above 4000!! target=1433) | 25 June, 2007

Our Hellers exhaust has a range from 500 to 600 CFM, depending on model. I am aware that the profile will need adjustment due after reducing the exhaust air velocity, but i'm not getting a reply from Heller for power consumption specification. I will contact my local vendor today. Will keep you updated. Thank you for all your advice thus far.

Puvendran

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reflow oven profiler

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