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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Edmund Loh

#9629

Tombstone | 14 September, 1999

Can anyone out there pls enlighten me on how to solve chip tombstone defects. I am running a board with a lot of 0603 chip. i had fine the profile and the alignment, but it still happen randomly on the board itself. Is there any other way to solve this problem, pls advice.

Rdgs...

reply »

Scott Davies

#9630

Re: Tombstone | 14 September, 1999

| Can anyone out there pls enlighten me on how to solve chip tombstone defects. | I am running a board with a lot of 0603 chip. i had fine the profile and the alignment, but it still happen randomly on the board itself. Is there any other way to solve this problem, pls advice. | | Rdgs... | Edmund,

There can be so many potential causes of tombstoning. But, fortunately, a little time and effort spent in the right places can usually sort these problems out.

You say that your profile and alignment appear to be OK. Well, remember that alignment has two elements to it; alignment of the solder paste to the solder pads when printing, and alignment of components to the pads when placing. Then, this throws up another load of variables, such as choosing appropriate stencil aperture reductions, stencil thickness, and fine tuning screen printing parameters to ensure the correct amount of paste gets printed (not too much, not too little). You may also want to investigate the size, shape and space between the pads which you are placing the components onto. And also check the components themselves to see if any contamination is present which may be affecting solderability. And, finally, check with your solder paste supplier to see if the paste you are using is appropriate for your application. Some manufacturers (like Multicore in the UK) are marketing pastes which, they claim, contain an anti-tombstoning alloy.

So, there are a few ideas to play with! Best of luck!

Regards Scott

reply »

Scott S. Snider

#9631

Re: Tombstone | 14 September, 1999

| Can anyone out there pls enlighten me on how to solve chip tombstone defects. | I am running a board with a lot of 0603 chip. i had fine the profile and the alignment, but it still happen randomly on the board itself. Is there any other way to solve this problem, pls advice. | | Rdgs... I think you started looking in the right places. Next verify that the pad design for the parts meets your specification (if you have control over this). Hopefully you specified something like the IPC standards. Also if you are using homeplate apertures look at the 0603's before reflow and make sure both ends are touching the paste. Depending on your stencil apertures and pad specification you can have everthing running with good Cpk but the parts are not touching paste on one side.

reply »

ii-feed SMD Intelligent Feeder

ii-feed SMD Intelligent Feeder