if you are dealing with co-planarity sensitive device, you should  
have internal calibration (part of FPGA to allow you correct the  
tilt, z-level, etc. in relation to the reference).  depend upon  
sensitivity and requirement of the design, if you do not want spend  
the time and money to correct it using software or build-in feature,  
you have to find your own way of engineering know how - equipment,  
process dependent.
good luck.
         jk
On Feb 26, 2015, at 11:23 AM, Amol Kane wrote:

> Schlumberger-Private
> ________________________________
> Dear Technetters,
> What are people using to inspect co-planarity of gull wing devices  
> (fine pitch QFPs and SOICs) prior and post soldering? I am  
> especially interested in techniques that can detect small  
> differences in z axis causing the lead to just "sit" on solder  
> after assembly and cause premature failure or intermittent  
> operation. I was looking on line and found some inspection mirrors  
> for pre-soldering inspection but not a whole lot else. I would be  
> grateful if you can share your experiences regarding what other  
> techniques work.
>
> On a related topic; what is the general feeling about correcting  
> coplanarity issues by using reworking templates to push the leads  
> back to their intended position. I do not like it as it may damage  
> the seal around the lead and the body depending on the extent of  
> rework. Can you point me to any studies done on this topic that  
> highlight the failure modes resulting from this practice?
>
> Thanks,
> Amol
>
>
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