Any moisture entrapped in the PoP before reflow ?

MSL ?

GS

-----Messaggio originale-----
Da: TechNet [mailto:[log in to unmask]] Per conto di Bob Wettermann
Inviato: lunedì 23 gennaio 2017 19:58
A: [log in to unmask]
Oggetto: Re: [TN] Nitrogen Reflow and Warpage Issues on POPs

Thanks Joyce (and others).

We believe that there will be less thermal stress and hence less warping in vapor phase reflow.

If you were a betting person (so far I have gambled 25 cents in my life in Las Vegas but gamble every single day on our business) would you bet on vapor phase or nitrogen reflow?

Bob

On Mon, Jan 23, 2017 at 12:36 PM, Joyce Koo <[log in to unmask]> wrote:

> IMHO, nitrogen will allow you to lower the Tp 3-5 degree and change 
> reflow profile to shorter.  it does have an impact on the bridging, and warpage.
> the solder ball claps (reflow) of corner and center under nitrogen 
> showed little difference, but not in air... your HOP or bridge will 
> tell you the device might be tilt to one side or warped.  nitrogen 
> will help, but not cure all.  my 1.5 cents.
>             jk
> > Bob,
> > Did you see this? Lots of good process information.
> > http://www.ti.com/lit/an/swpa182c/swpa182c.pdf
> > Hope it helps.
> > dean
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Wettermann
> > Sent: Monday, January 23, 2017 11:29 AM
> > To: [log in to unmask]
> > Subject: [TN] Nitrogen Reflow and Warpage Issues on POPs
> >
> > 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
> >
>



--
Bob Wettermann
BEST Inc
[log in to unmask]
Cell: 847-767-5745


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