Raye,
Incomplete fill could easily cause chemistry entrapment.
This can be quite explosive (very small rapid expansions) during assembly.
Solid cause for reject.
Filling vias can improve overall reliability and allow via in pad if filled, planerized and cap plated, so if you can afford the added cost it can be worthwhile.
As always "it depends" (oops, owe Doug another Mountain Dew) on your end product requirements.
You should review with your design team and determine if filling is an actual requirement, then you can get a good plan for going forward.
All to often today, someone heard it was a good idea and we end up with it in our design requirements even if it is overkill.
Good luck,
FNK

Frank N Kimmey CID+
916-833-9877

Sent from my iPad

> On Dec 14, 2018, at 5:12 PM, Rivera, Raye <[log in to unmask]> wrote:
> 
> *** EXTERNAL EMAIL, think before you click. ***
> 
> Hello all,
> 
> I've recently had some PCBs rejected for incomplete via fill. This would be in 8 mil vias, aspect ratios between 9.5 and 10.3, to be filled and plated over.
> 
> I realized I have no idea why, or if, it is a good idea to fill vias.
> 
> Is anyone aware of PCB failures due to incomplete via fill?
> 
> And finally, is anyone else have trouble searching the Technet archives? I used to get good information that way, but now all my searches return zero results.
> 
> Best regards,
> Raye Rivera
> Quality Manager