there are literature in the past regarding the mechanical stress  
distribution of LGA vs BGA... yes, increase solder paste will help  
somewhat, but you should minimize the smily or use the corner  
adhesive if necessary... check Cisco paper many years ago regarding  
the corner adhesive for large BGA (where you get your BGA from? if   
it is from large vendor, not repackaged stuff, you should ask for  
thermorie data (check thermoire google search, it may pop out many  
papers regarding size, BGA stand offs, and FEM),  and compare  to  
your own reflow profile and  see if you use it outside their  
recommended reflow profile... most likely, it is)..
best of luck.
jk
On May 16, 2018, at 5:12 PM, Frank Kimmey wrote:

> Can anyone point me in a good direction to learn more about  
> solderjoint elasticity with SAC305.
> We are seeing some issues with BGAs when they smile.
> Type 2 fractures and the vendor recommends increasing the solderpaste.
> This seems counter intuitive to me.
> If it was SnPb I would go back and hunt some of Werner's research.
> As it is Lead free I need some direction.
> Any help is appreciated,
> FNK
>
> Frank N Kimmey CID+
> Electrical Engineer/PCB Design
>
> Verifone
> 1400 W Stanford Ranch Road
> Rocklin, CA 95765
> T: 916-625-1818
> M: 916-833-9877
>
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