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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Solder balls defects

Views: 5008

#80791

Solder balls defects | 27 July, 2018

Hi, have some question: during solder paste printing I'm faced with problems on the edge of the PCB - solder balls on gold pads. During analisys we checked everything - change squeegee preasure, different cleaning cycles, squeegee speed - no effect. Maybe anybody faced with the same issue and can help to resolve it. Thank You.

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#80814

Solder balls defects | 1 August, 2018

Please check the solder paste height near PCB edges, Please check board clamping during solder paste printing. Please check tooling support boards must be fixed during the printing process.

try to set wiper cleaning frequency and fine tune for best results. please check below link for more information regarding solder balls defects and causes http://smtinsight.com/how-to-reduce-solder-ball-formation-in-reflow-soldering/

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#80821

Solder balls defects | 1 August, 2018

How close are your SMT pads to the gold fingers? Can you supply a photo?

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#80887

Solder balls defects | 14 August, 2018

Try something drastic just for testing - turn off cleaning! Then check again the result. Trust me, you can be surprised.

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#80891

Solder balls defects | 14 August, 2018

Every place I have ever worked has taped off the gold fingers. Maybe not the first run but within a few runs.

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#80894

Solder balls defects | 14 August, 2018

Vlad,

Reduce your aperture opening in the stencil, this will give the stencil a good seal around the specific area of concern. In a wave solder environment, solder balling top or bottom surfaces in a wave pallet is caused by excessive flux burning off too quickly or becoming trapped. Once the pallet/PCB hits the molten wave, a bunch of miniature explosions take place that creates solder balling. Maybe a combination stencil & profile??

My stencil Guru here at my Oregon facility can assist you if needed, reach out to me offline if needed...

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