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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


0402 Cap tombstoning strange behaviour

Views: 4994

#63007

0402 Cap tombstoning strange behaviour | 28 October, 2010

Hi, previous topics found closed so I couldn't continue on them, but wanted to ask maybe something that we don't already know

paste shape and placement ok, reflow 12 zones profile looks ok (same since 2 yrs), component placement ok, one reference in 60 places do tombstone on selected ones (0402 capacitor) - strange thing we found, that components are mainly pulled in the GND direction (normally it should me cooler and let the Capa go - but not this time ;) ) we run our oven with nitrogen - we will switch it off for test but maybe there are other new solutions that we can work around???

reply »

#63008

0402 Cap tombstoning strange behaviour | 28 October, 2010

Try rotating your board 90 degrees when running it through your oven. Will probably solve the tombstoning issue on that cap but might cause tombstoning elsewhere.

reply »

#63010

0402 Cap tombstoning strange behaviour | 28 October, 2010

We saw this idea in older posts, but - we don't want tombstone elsewhere :) - rotating the boards before oven is complicated, so it could give more problems than the tombstoneing :) the issue is not 100%, it is 10 to 50 boards with component up per 350 boards passed (most of time it is one component per board that is up - but the places are all the time in the same areas)

reply »

#63014

0402 Cap tombstoning strange behaviour | 28 October, 2010

Dealing with these intermittent issues can be frustrating! Can you narrow down if the defects occur during a specific time in the run? i.e. beginning or end? Or, maybe after a pause in printing such as stopping the line for lunch?

Are there a lot of other 0402 packages on the board? Do you have paste inspection available on your printer?

There's a solution out there somewhere!

reply »

#63015

0402 Cap tombstoning strange behaviour | 28 October, 2010

If everything else is OK, capacitors quality could be the cause of this issue. Some caps could have been contaminated or the metal mass not even between two ends. Try different kind (manufacturer)of cap.

reply »

#63017

0402 Cap tombstoning strange behaviour | 29 October, 2010

I agree with DucHoang. If your board and reflow profile have not changed then I would suspect incoming parts. We've seen tombstones when a chip supplier had plating problems.

reply »

#63026

0402 Cap tombstoning strange behaviour | 31 October, 2010

#63056

0402 Cap tombstoning strange behaviour | 4 November, 2010

thanks for all the feedback... we also checked, just in case : - bake the components (no visible improvement) - bake the pcb (50% less tombstone components) - finally we changed LF paste to completely different manufacturer - and booom 0 (zero) tombstone... (in details, of 8h production, standard process 1h - 16 pcs 2h - 13 pcs baked pcbs introduced 3h - 7 pcs 4h - 4 pcs 5h - 8 pcs change of paste 6h - 0 pcs 7h - 0 pcs 8h - 0 pcs

so it seems that we have to work with our standard paste supplier to solve it out (permanent change of paste is not possible as for now) and we will take a look at the parts we are getting, as this issue is visible in such scale since only few weeks

reply »

#63208

0402 Cap tombstoning strange behaviour | 30 November, 2010

could be a printer or stencil issue. try to check your printing repeatability. Suggest to use SPI for a checking paste volume/height/area.A regular stencil cleaning may reduced your headache.

reply »

Used SMT machines