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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

Skewed and popped components



Skewed and popped components | 23 September, 2003

If you have a board that you've run several times, now you run it and like before all settings are the same, but now you have 0603's randomly skewed or an inch or so away from their intended pad (as if popped up in the air), or an occasional 7343 cap skewed off pad, or a fine pitch SOIC skewed on its pad. If all conditions are the same as in the past (proper temp settings, oven is at greenlight, N2 is on, tunnel free of obstructions, etc...), could this be caused by moisture in the board resulting in outgassing? Or something else? This board has been thermally profiled.

Any thoughts would be certainly appreciated!

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Skewed and popped components | 24 September, 2003

Even when you run a board several times, the machine may not make the same travel path every time. This in itself does not create a problem, but the vacuum on the nozzles could be different, dependent on the configuration of components on the heads. Also the airflow kissing off the component may not be consistent. I did not yet see a component blown away by an inch, but loosing a component on the way to placement is a good possibility. Moisture in the air can certainly also make an impact. Electro-static charges may also change with the humidity, components are not properly rejected and are lifted from the pads after placement. If the board is flexing during placement, possible movements of the placed components are unpredictable.

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Skewed and popped components | 26 September, 2003

We have had some components that popped off in our IR oven. It was attributed to the solder paste. The humidity was above 60% the temp was about 70 degrees.

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