Tombstone components issue after reflow?

There is no solution in above case, this is caused by the PCB design. There are no thermals on the pads connected to the copper poured area. So the other pad reflow first and lift the component.

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> Anyone who knows how to prevent such > flaw? > > Tombstones are those lifted components > from one sides. This results in costly and > time-consuming amounts of touch-up and re-work > after the assembly is completed. For the > customers, this extra work translates into > delayed delivery shipment, cost increases, and > considerable (but unnecessary) stress being > placed on the board's existing components.

This flaw could be due to inaccurate stencil design, among other factors. The assembly process can incur adverse effects when the stencil is not accurately designed. There can be such flaws as a number of tombstones and bridging when an incorrect stencil is run through the pick-and-place and reflow process.you share the screenshots of GTL with GTO and GBL with GBO for a further check?

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Any of the comments so far could be valid. To add my opinion, it looks like the pad size is too large. A smaller volume of solder will pull less than a larger volume. If you can't change the pad sizes, then the next thing to try is to get another stencil but modify the apertures so that only half the pad receives paste. I would print paste on the inner halves of the pad so that the part is set in the paste and let the outer halves unpasted.

This document might help: https://www.smtnet.com/library/files/upload/EFD-Tombstone-Troubleshooting.pdf

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Here is some food for thought. Try to answer these questions yourself and I am sure you will see huge improvement.

Reasons:

- Bad PCB design - Plating-uneven HASL cause more than OSP Au/Ni or Silver - Poor paste and print quality - uneven paste can cause it - Paste type - Type 4 is most resistant to Tombstone - Stencil - home plate apertures help reducing tombstone. Also decrease the volume of metal overall. - Incorrect placement of parts - parts should be centered to apertures. - Placement pressure - Paste composition and paste storage - Reflow profile

If you don't have control over design, next thing to do is print much less paste(homeplate apertures is better).

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Not enough solderpaste. Uneven solderpaste volume on pads. Bad quality of caps ( Metal ends), try new cap manufacturer, sound weird, huh!! but that happened to me. Good luck.

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The first reply from Tsvetan Usunov already answered your question - there are no thermals for one side of the chips.

You can try to reduce the phenomenon by using different solder pastes, tuning your soldering profile or even switching to different Mfr, BUT here it's obvious that the design is faulty. You will not be able to solve it for good without design's correction. Of course you can always glue the chips but that's a bit nonsense..

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