components flying off board when reflowing in toaster oven

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components flying off board when reflowing in toaster oven

Post by t9corp » Mon Jul 30, 2007 9:50 am

We had a new problem come up when we recently tried some toaster oven reflow. About a dozen or so small components literally jumped off their pads and landed on the board. It was mostly 0805 capacitors and resistors. The popcorning started just before the boards would reflow, the solder paste would dry and it looked like the parts were hovering above the paste and then they would start popping off. We sqeegee the paste onto the boards and place all parts by hand. We have tried to follow the solder paste reflow guidelines, which is not 100% easy in a toaster oven but oh well. the first couple of boards didn't seem to do it but after about the 3rd board in a batch of ten the problems started. This was a brand new tub of AIM solder paste. Has anyone else had this problem. Our guess is either bad solder or bad reflow technique on our part. Did not have this problem with our first tub of AIM solder.
any ideas?

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Post by leon_heller » Mon Jul 30, 2007 11:59 am

The boards might have absorbed some moisture.

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Post by Philba » Mon Jul 30, 2007 1:59 pm

I'd bake the board before hand. However, the problem might be the components themselves. I know that I've gotten some that have humidity warnings. Check the datasheets. They will have a procedure that you will need to follow.

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