simulated reflow... use what ever your process window.  measure flatness
before and after.  you need to establish what your tolerance you can
handle.  make sure you get sufficient sample size and sheet metal rolling
direction sort out (not cheap... but cheaper than you trouble shoot or
rework at MFG site... your design determine the cost.. if they skip qual,
you pay 10x at assembly line.  trade off using process window adjustment -
such as extend Tp, you might get other issues - some of the device may got
damaged = e.g. highend of chips may have limited temp you can be exposed
to).  good luck.
               jk
> I also suspect that it caused by stress release. The shield may have
> residual stress, when go through high temperature, metal yield strength go
> down and make shield deformation.
> Is there more information about the qualification process?
>
>
> Best regards
> Deng
> -----Original Message-----
> From: Yuan-chia Joyce Koo [mailto:[log in to unmask]]
> Sent: Wednesday, July 06, 2016 6:56 PM
> To: TechNet E-Mail Forum <[log in to unmask]>; Deng RongJun
> <[log in to unmask]>
> Subject: Re: [TN] Shielding cans deformation during reflow
>
> 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
>