Posted by Mike_balbuena: Thu May 04, 2006 5:23 am    Post subject: Internal Void Monitoring Using X-ray

Does anyone does this in their back-end assembly area? What is the criteria and what equipment are you currently using? I remember generating the criteria for OSEP a while back( 1999) but I forgot already. I would appreciate any help and feedback. I was thinking for incorporating this again on our current process to preliminary monitor delam.

Thanks in Advance.
Mike

Posted by Jefriz: Tue May 09, 2006 7:26 pm    Post subject:

Mike,

We use that kind of inspection scheme in my previous company but it does not give much accurate result. You are going to look for 2 kinds of voids, DA region and the mold area. If you are using non-conductive epoxy, chances are you can't see the epoxy and the void using X-ray. Mold compound void is also hard to see using X-ray. I would recommend you use Through scan (T-scan). Then use C-scan for confirmation when you see a void/delamination to determine which layer have the anomaly.

Criteria for X-ray, you can try looking at MIL-STD-883F Method 2012.7. For package delamination (void), use J-STD-020C. This would give you defferent criteria on each area affected.

Added suggestion, if you see suspected delamination/void using T-scan/C-scan, don't just stop there, confirm it with cross section.

Jefriz

Posted by Mike_balbuena: Tue May 09, 2006 11:51 pm    Post subject:

Thanks, Jef. Appreciate that input.

Regards,
mike

Posted by newbie PE: Sun Jul 02, 2006 5:06 am    Post subject:

i remember my trainor's words when that question was raised while on training, he thinks there's no x-ray capability to detect voids yet, it has something to do with the material composition/ properties versus the capability of what x-ray waves can travel...

we usually use CSAM/ SAT for delam and void monitoring...

Posted by FARel Engr: Mon Jul 03, 2006 12:08 pm    Post subject:

Yup - the X-ray image formed by X-ray machines is based on the principle that the different densities of the different features of the package block x-rays at different levels. Denser/thicker features cast a heavier x-ray 'shadow' and appear darker on the image.

Plastic molding compound is not a dense material, and blocks x-rays minimally. This is the reason why plastic package cracks and voids are so difficult, if not impossible, to detect using x-rays - plastic molding compound offers very little x-ray contrast against open spaces.

X-ray, however, would be a good detector of cracks and voids in ceramic packages and eutectic die attach, since ceramic and gold are denser than plastic.