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Solder Paste Mis-print

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#76399

Solder Paste Mis-print | 29 September, 2016

Is it ok to re-print the mis-print PCB? Personally I am oppose to re-print the mis-print board. For two reasons. 1. You will end up adding solder paste on the bottom side of the stencil. 2. You may smear solder paste in some area. But I would like to get help from the experts. Thank you for your time.

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Tom

#76401

Solder Paste Mis-print | 30 September, 2016

We sometimes have a misprint and we would never re-print on a board with paste on it already because it will surely get paste all over the bottom of your stencil and could smear between traces. If we do mispront we have to clean the paste off the board first but you can never get it all off and you can have many more solder balls form after reflow with misprint boards.

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#76406

Solder Paste Mis-print | 3 October, 2016

We successfully re-print mis-prints all of the time. We have SPI machines at every printer that let us know if it is OK or not.

Sometimes dealing with the solder defect is better than cleaning the mis-print. It is very difficult not to wedge solder spheres in between the solder mask and pads during the clean off process.

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#76407

Solder Paste Mis-print | 3 October, 2016

Good printers can do it without problem. Make sure you check after that(SPI is the best).

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#76416

Solder Paste Mis-print | 4 October, 2016

We have a "Blundell Stencil Cleaner" screen washer here, and if boards are badly printed, we put them in the wash, then dry them off thoroughly and reprint them. There are small, insignificant signs of tiny solder spheres afterwards, but nowhere near enough to be an issue.

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Tom

#76434

Solder Paste Mis-print | 8 October, 2016

Well I stand corrected; we tried re-printing mis-prints on Friday with our auto printer and indeed it worked out very well. I did let the paste dry up a bit on the mis-printed board while a few others went through to try and prevent smearing as it re-aligned with the stencil.

We had a semi-auto printer before we were able to move up to an automatic mpm (old up500) but the vision alignment works well enough to reprint apparently.

We've decided that re-printing is far better than cleaning- not only is it faster but we get better results after reflow with fewer errant spheres.

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