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Help TQFP welding problem

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Help TQFP welding problem | 16 April, 2021

We are currently producing a project that brings a TQFP64. But some boards do not solder the component well with its ideal fillet, some are well soldered when they come out of the reflow oven, but some are not. Can the pins be sulphated? How can we check and make sure they are sulfated?

I mount the curve we currently use for alpha om5300 type 4 paste


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Help TQFP welding problem | 16 April, 2021

I'm concerned by the solder spheres in the via on the first picture.

Are these boards mis prints that got washed and printed again? To me it almost looks like someone washed the board, but left a lot of solder paste on it. The lack of flux prevents the solder balls from flowing cleaning onto the pads

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Help TQFP welding problem | 20 April, 2021

I agree with DWL's comments. Also, your profile is really really inconsistent. How did you attach the probes to the board? You have a 25c delta in your peak temps. Unless that is from a probe lifting, that is really bad. What type of oven are you using?

Another thought on the solder balls could be just using way too much paste? The fillets honestly look fine to me, the solder balls and excess paste combined with the bad profile is my concern.

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Help TQFP welding problem | 27 April, 2021

Solder balls, can be excess paste by opening ST. Do you see the curve still working pasty with lead with alloy "63Sn / 37Pb alloy" has defects?

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