|Ask the Experts|
November 25, 2019
Reflow Oven Calibration Schedule
Can you offer some guidelines regarding how often we should re-calibrate our reflow ovens?
|Expert Panel Responses|
Most manufacturing best practices say 1 year as a general guideline, but ultimately this needs to be determined by your own liability. If your oven is used for curing (or some other low precision requirement) for example, your liability may be quite low, and only require calibration every 18 months.
Now if you are making pacemakers, your liability goes up (and the level of precision as well), so you may want to calibrate more often (say every 6 months). You also need to take into account of variability of the oven your calibrating.
If you are consistently finding large offsets at calibration, the interval should be shortened. If your oven hasn't changed in 10 years, you may want to lengthen the interval to every 2 years. The real question to answer is "How long can I afford to make bad product, and how likely is that to happen?"
M.O.L.E. Line Product Manager
Electronic Controls Design, Inc. (ECD)
A good basic recommendation is to run a weekly profile, and to do control charting on the temperatures and timings to detect drift. This type of profile should not be done with a board, it should be done with a more thermally robust piece of tooling.
The objective is to track change, and any breakdown in the tooling, like delamination in the PWB used, will affect the results. Re-calibration should be done only when drift is detected that exceeds process limits defined by the process engineer.
The above will let you react to long-term drift, but if something changes suddenly within the week, you certainly need to know, or you potentially have a week worth of product at risk. The main failures that you need to account for are:
What does the reflow oven manufacturer recommend?
The oven manual or the oven manufacture is the best source for a recommendation on the calibration frequency.
However, many choose to calibrate their ovens annually, which is practical for most, and gives a reasonable record of historical calibration performance.
Senior Project Engineer
Electronic Controls Design Inc
First I would check the manufacturer's recommendation and have that on the internal PM schedule. Using a KIC or MOLE once a week or even once a day is a good practice to ensure that the oven works within the needed parameters.
I have detected variations in the temperature before due to motors malfunctions even though the reflow oven would not exhibit an alarm mode.
Engineering and Operations Management
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