residual stress.  design and MFG  issues.  you should have co- 
planarity in dwg and spell out user condition before and after reflow  
simulation as part requirement.  and go through qualification process  
before hit production...  a vendor selection problem.
On Jul 6, 2016, at 2:39 AM, Deng RongJun wrote:

> Hello fellow Techies,
>
> I have got a problem with shielding cans deformation issue. There  
> are several kinds of shielding cans on board, we have found one  
> shielding have deformation after reflow, one side of shielding lift  
> and not solder on board.
> We also do a test, bake the individual shielding in oven with 230  
> degree, the shielding still have deformation and two corner have  
> lift. Take out the shielding from oven and temperature go down,  
> then shielding go back to good.
> Any one of you have experience on this case?
>
> Pictures:
> https://goo.gl/photos/xQLbFT1AEwTR2iV68
>
> Thank you very much.
>
> Best regards
> Deng