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September 2008

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From:
Ioan Tempea <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ioan Tempea <[log in to unmask]>
Date:
Wed, 10 Sep 2008 09:18:18 -0400
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Bonjour Fabrice,

Problem number one with voids measuring is how you know when you have the real void size on the screen. On many machines the size of the voids depends on the energy you shoot at the board; the higher the energy, the bigger the void image.

So what is the optimal energy for seeing the real size of the voids? You might need to work this out with your machine manufacturer. The Glenbrook Jewel Box we have does not seem to be affected by that, the voids don't really change size when varying the energy.

Now that I raised a question instead of giving you an answer, I would like to be even more confusing: why do you want to complicate your life opening this voiding can of worms? It is a never-ending story and you are privileged, being part of an OEM, so you don't have to go through this hassle. Why privileged? Because you can define what you can accept in terms of voids, regardless the existing industry specifications. According to past threads on Technet nobody could bring an example of BGAs that failed because of voiding, so I would say that you should ESS boards with as big voids as you can get and see whether voiding can be an issue for your products.

Being in the CEM business I can tell you that voids measuring is prone to very subjective interpretations. If you can eliminate this concern, you will be happier.

Regards,

Ioan

-----Message d'origine-----
De : fabrice pires [mailto:[log in to unmask]] 
Envoyé : 10 septembre 2008 08:40
À : [log in to unmask]
Objet : Re: [TN] precise void size measurement

Alan,

I guess these ball bearings helped you to test image quality of tested 
equipment and calibrate the Xray equipment to define size of BGA balls 
and other things.

But do you thing metal balls can be used as precise calibration for 
measurement of voids inside BGA balls?
I mean voids are lack of material and balls are presence of material 
(metal).
In other way, does the equipment setups for correct observation of ball 
bearings is really the same for the voids observation and size measurement?

Thanks in advance for your input.
Fabrice

Alan Kreplick a écrit :
> Fabrice,
>
> When I was evaluating X-Ray equipment, I brought precision ball bearings 
> (I think they were .050").
>
> Each machine had some sort of measurement tool, but no matter the machine 
> or changing focus, tilting 50-75 degrees, etc., the .050" ball bearing was 
> my benchmark.
>
> To stop the ball bearing from rolling around on the table or assembly, I 
> glued it to a small piece of conductive composite material (left-over wave 
> solder fixture stock).
>
>
> Al Kreplick
> Sr. Manufacturing Engineer
> Circuit Card Assembly
> Air-toAir/Precision Strike/Land Combat
> Raytheon Integrated Defense Systems
> 978-470-9931office
> 978-245-1702 pager
> 978-470-4307 fax
> [log in to unmask]  
>
>
>
> fabrice pires <[log in to unmask]> 
> Sent by: TechNet <[log in to unmask]>
> 09/09/2008 11:01 AM
> Please respond to
> TechNet E-Mail Forum <[log in to unmask]>; Please respond to
> fabrice pires <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> [TN] precise void size measurement
>
>
>
>
>
>
> Hi Techneters,
>
> I would like your advices on the best way to calibrate XRay pictures in 
> aim to measure precisely voids inside BGA balls, after assembly.
> Everyone should agree on the fact slight setup variation on XR equipment 
> could change significantly the void size results.
>
> Do you have any trick to improve precision measures whatever the XR 
> equipment?
> Does the use of any reference/calibration on boards exists in that aim?
>
> Fabrice
>
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