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Stencil Printing Experiment without AOI

#22922

Stencil Printing Experiment without AOI | 6 January, 2003

I made an experiment with our semi-auto stencil printer and used my naked eye to decide whether the alignment and deposition is pass or fail. I based the results in percentage and 100% is perfect result. Now here's the question:

Can anyone tell me what percentage of misalignment from the pad is pass and fail for a fine pitch device...I assumed that it must be 100% aligned. How about the percentage of volume deposition for both fine pitch and BGA? How many percent of deposition is required? Is 50% of solder paste deposit on a BGA a pass or fail? what about in fine pitch? is 80% deposit a pass or fail?

Thanks for your advice....

regards

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#22937

Stencil Printing Experiment without AOI | 8 January, 2003

It depends on your product requirements. We don't like to print off-pad, because: * Tough to control the amount of paste that squirts onto the board, because the aperture is not gasketed to the pad on the board. * Some paste that squirts between the pad and the board ends-up on the bottom of the stencil, increasing the mess and adding to the underwipe requirement.

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Hussman

#22952

Stencil Printing Experiment without AOI | 9 January, 2003

It depends on what the finished solder joint looks like after reflow. Use IPC to determine your solder joint acceptablity and check for solder shorts/solder misses to determine how far our of alignment you can go. Hope your not working with theta or you're gonna be there a long time.

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