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Tombstoning 0306's

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#36578

Tombstoning 0306's | 9 September, 2005

Hi all,

we are placing some of the 0306's (0603 size parts with the contacts down the long side of the part rather than on the ends). We are having quite a lot of tombstoning. The placement is dead on and the pad layout is per the mfg specs'.

Any ideas on how to increase yeald?

thanks

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???

#36579

Tombstoning 0306's | 9 September, 2005

sounds like the part is being picked up on its side....which means.......it could be....

1. pickup not taught correctly -- X-Y- or Z 2. head to camera calibration is needed 3. or least likely....feeder problems

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Rob

#36580

Tombstoning 0306's | 9 September, 2005

If the tombstoning is thermal (occuring during reflow) then try slightly reducing the stencil apertures so there is less the paste on the pads, reducing the forces acting on the component.

Also take a look at the cooldown profile & making it more gentle if you have the luxury of extra zones at the end of the oven.

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#36581

Tombstoning 0306's | 9 September, 2005

thanks for the feedback,

The part is not on its side, it is placed properly before the reflow.

We are starting the process of changing the stencil apps.

thanks

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#36582

Tombstoning 0306's | 9 September, 2005

Talk to your paste supplier. The reps for a couple of pastes have been very helpfull on various problems. And I've seen pastes advertised as being good for reducing tombstoning. And they see lots of customers and therefore see lots of problems and solutions. Adjusting the profile speed may help a little. It probably won't be practical but putting the boards in the oven at a 45 degree angle would help. Purposely placeing the components a little away from the direction of the oven would be another "don't let the manager see" option but would be extremely tricky to implement so that the components would shift the right amount.

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???

#36583

Tombstoning 0306's | 9 September, 2005

Try home-plated the stencil apertures, and make "V" shape home-plated outside edges of two pads instead of between two pads.

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#36585

Tombstoning 0306's | 9 September, 2005

thanks for the tip.

Could you clarify what you mean just a bit.

Thanks

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Mei

#36587

Tombstoning 0306's | 9 September, 2005

Nomorely the V-shape home-plated apertures look like two opening mouth facing each other. But this time just opposite way. And make 30% home-plated. Hope you can understand.

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RDR

#36589

Tombstoning 0306's | 9 September, 2005

What are the Mfg specs for pad layout? I had one that was wrong and we changed the center to center spacing to .032" and the width to .015" wider (.0075" on each side)than the solder terminations and everything was fine. As a general rule I never trust Mfg specs for pad layout being the optimum for all soldering anomalies. A lot of times I think they forget about wetting forces, printing ability, etc... I think they calculate solder volume and that is it if even that is performed or analyzed.

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Mika

#36601

Tombstoning 0306's | 11 September, 2005

If 0 or 180 degr. make v-shape openings to each other left & riht, if 90 or 270 degr. top/ bottom, on the stencil apertures; well, you understand... We use this and 87 % reduction of stencil apertures for 0603:s and 0402:s. 0.127 mm stencil thickness. We have no problem with tombstoning and solder abilitys. Sincerly,

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Mika

#36603

Tombstoning 0306's | 11 September, 2005

I mean we use 87 % of the original apertures. (You never know, sometimes it is better to overkill...:-) Sincerly,

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Slaine

#36626

Tombstoning 0306's | 13 September, 2005

hi Tombstoning can be relaited to the size of the pad, and ifits soldermask defined or non soldermask defined. it one of the pads is longer than the other or the track from the pad is not toataly masked, the solder will flow over it giving a larger surface tension on one side of the component than the other causing tombstoning/billboarding. could be that if youve checked everything else.

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