Hi Bob - I have done process compatibility testing with the TI OMAP BGA and
the use of a inert atmosphere has no impact on the warpage characteristics
of the package (been there, done that, have the Tshirt). Are you using a
tin/lead soldering process or a lead-free soldering process? POP technology
was "born" in the lead-free era and as such, that package isn't a fan of a
tin/lead soldering profile.

Dave Hillman
Rockwell Collins
[log in to unmask]

On Mon, Jan 23, 2017 at 11:29 AM, Bob Wettermann <[log in to unmask]> wrote:

> Dear Technetters:
>
>
>
> We have a Class 3 customer with very complex, high density placements
> (think cell phone for the military). This board is laden w/0201s, 0.4mm
> pitch BGAs, shields, mirrored BGAs and the TI Omap POP (0.4/0.5mm pitch).
>
>
> The problems in this board assembly for some time have been isolated to
> this OMAP part.  We have lots of shorts and opens (randomly-spaced) as
> confirmed by electrical testing, dye and pry and cross sectioning. The Omap
> has been shown to warp 5-7 mils depending on the reflow profile.( It is a
> no clean SAC305 process). We have profiled the reflow process by embedding
> TCs in the corners of the balls of the device (ball interface with the
> board where all of the problems are) , the die,  neighboring components
> etc. We dialed in the profile as low of a temp as possible.
>
>
> We are running several DOEs to come up with a placement/rework process.
>
> As part of the investigation the client is fixated on nitrogen reflow being
> part of the solution to these warped BGAs. Nitrogen reflow IMHO is the
> solution for joint aesthetics, wetting issues and enhanced reliability of
> the interconnection.
>
>
> ? Does anyone have experience with hot air reflow using nitrogen where its
> addition helped to mitigate warpage issues?
>
>
> Thanks!
>
>
> --
> Bob Wettermann
> BEST Inc
>