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 >