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Conceptronics oven reflow problems



Conceptronics oven reflow problems | 7 January, 2004

We currently have 2 HVA 102 conceptronic reflow ovens. I ran 2 profiles on the 2 seperate machines. One of the oven ran 7 degrees lower than the other oven. I checked all the fans and they seem to running fine. I get no warning on the monitors. I just need a little help trying to figure out the problem. Thanks for any input.

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Conceptronics oven reflow problems | 8 January, 2004

If I read this correctly you have two identical ovens that were setup the same ie zone temps, fan speeds etc... when you ran the same board through each of them one showed a lower board temp. Is this correct? Is the temp of the board 7 deg. lower throughout the entire profile? Here is a couple of thoughts.

1. Was the board the same temp at the start of each profile run? i assume the T/C locations did not change.

2. I have experienced this with other manufacturers ovens in the past. in fact i have yet to see two oven run exactly the same. The locations of the T/C in the oven might be in slighly different locations causing different readings, the actual heaters may be a little higher or lower to the conveyor in one oven, there may be a difference in the CFM of your venting in each oven, building airflow might be causing some deviation, etc...

3. If the oven setpoints and the actual readings from the oven T/Cs are the same or within allowable range (usually 5-10 deg.) there will be no warnings on the oven. keep in mind that they only read the heating element temps and not the board or the air within the zones.

4. The temp controllers may need calibration. If not then we have always adjusted the profile(s) for each oven.

Hope this was helpful Russ

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Conceptronics oven reflow problems | 8 January, 2004

James: The ovens can be calibrated to help get this a little closer. In the computer box are 3 cards (alike) attached to the motherboard. They are called IPS-7 cards. On these cards are 2 potentiometers to calibrate the T/Cs for the heat zones. There is a procedure in your HVC manual for calibrating the oven.

If you need any help with this, you can reach our service department at:

You can also reply to me and I'll make sure they know and someone will get back to you. Regards, Bill Morse

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Conceptronics oven reflow problems | 8 January, 2004

Unless your machine (internal) thermocouples are each calibrated and compensated no two machines will deliver eactly the same results.

Here are your challenges:

1. Data acquisition equipment A-D converter errors 2. PCB measurement thermocouple (t/c) error 3. Machine temperature A-D converter errors 4. Machine tempeature t/c errors

And thats just the measurement side of the equation. All of these have a tolerance. Wires typically are +/- 1.25% or 2.25 degrees (which ever is greater). Items 1-4 can stack-up for a total + or - tolerance which may explain why one machine is different than the other. Also, you did not mention if it was 7 degrees Celsius or Fahrenhiet.

Affects of anealing, insulation contamination, cold junction compensation, wire routing techniques, bond integredity, atachment techniques....these add up to an integrated error that typically is not accounted for. Remember profiling in Electronics is not absolute. There will always be a tolerance.

On the machine side of the equation you have issues like insulation (isolation), cross zonal heating uniformity, flow rates....these too can affect change in your result.

I had 4 furnaces once. two were build togeter (a and b) the others were built a year apart (c and d). All the furnaces were the same "model number"

a and b were within 2 degrees celsius of each other. c was 7 degrees hotter that a and b. d was 13 degrees hoter thatn a and b

I inquied with the manufacturer as to the differences. Different insulaiton material, different amounts of insulation, different blower manufacturer. Everything else was identical.

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