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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Dry solder

Views: 734

#76860

Dry solder | 9 January, 2017

Hi,

We are doing pin in paste reflow process in one our product ( but paste printed on bottom side of the board and top side will be assembled through hole component)in which faced cold solder issue in THT capacitor location after reflow. The solder paste is melted and getting up to primary side of the PCB(at component side)but not soldering with component lead and PCB pad. The above said problem is occurs randomly like as one shift in a day or one day in a week. We tried with different analysis but issue not resolved and the analysis is below as, 1.Component lead tinning before manual assembly into the PCB. 2.Alternat component part used. 3.Stencil aperture opening increased to increase paste volume. We suspect the pin to hole ratio in respective component location and details is, component lead dia - 0.45mm and PCB hole dia - 0.7mm and the variants is 0.25mm.

So kindly help to provide the standard value of pin to hole ratio to check the above mentioned value. And also any one kindly provide the solution to arrest this issue.

Note: The PCB having solder pad at secondary side only, there is no pad on primary side.

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#76871

Dry solder | 11 January, 2017

Do you have some pictures of the condition that you are facing?

Your description of the issue sounds more like dewetting, rather than cold solder. A picture would help us better understand what you're facing.

Cheers, ..rob

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#76873

Dry solder | 11 January, 2017

First, why do you have paste on the opposite side of the component. I would recommend having it on the same side. Second, how thick is your stencil? Pin in paste requires thickness, to fill the whole barrel. Stencil should be really thick. Try to manually apply paste(if your stencil is 6mil think about 12mil aperture) on the component side, insert component and reflow.

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