Hi Bob - your oven is a part of the issue equation. With a 5 zone oven you
are pushing a bunch of heat into the POP in contrast to a larger oven with
7-12 zones. You might be able to minimize the warp effects by going thru
the oven slower but make sure you also don't burn up the flux by the
extended temperature exposure. Using short ovens with minimum heat zones
can make profiling difficult.

Dave

On Mon, Jan 23, 2017 at 2:44 PM, Bob Wettermann <[log in to unmask]> wrote:

> We have a 5 zone oven.....and a BGA rework station (tried with some boards
> with the OMAP missing and all other parts populated) w/multi zone bottom
> heater.
>
> BWET
>
> On Mon, Jan 23, 2017 at 1:54 PM, David Hillman <david.hillman@
> rockwellcollins.com> wrote:
>
>> Hi Bob - in our testing, the package preformed better using a lead-free
>> temperature reflow profile - we had much less warpage and other associated
>> temperature impacts which we attributed to the package designers optimizing
>> their package construction characteristics for a lead-free reflow
>> temperature profile (its a lead-free part, so most frequent use would be in
>> a lead-free process). We were using a 12 zone oven so lots of room to
>> profile creation - how many zones in your oven?
>>
>> As for VP - I have never put a BGA in a VP process yet. It should work
>> provided the condensing VP fluid doesn't cause the BGA to physically move.
>>
>> Dave
>>
>> On Mon, Jan 23, 2017 at 1:48 PM, Bob Wettermann <[log in to unmask]>
>> wrote:
>>
>>> Hi Dave:
>>>
>>> This is SAC process.
>>>
>>> For rework we have tried to go "backwards" to Sn63 to reduce max temp.
>>> The results were better. Customer did not want to go throiugh the rel
>>> testing reqts of a bismuth-based alloy.
>>>
>>> Any thoughts on using a vapor phase reflow instead?
>>>
>>> BWET
>>>
>>> On Mon, Jan 23, 2017 at 1:29 PM, David Hillman <
>>> [log in to unmask]> wrote:
>>>
>>>> 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
>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Bob Wettermann
>>> BEST Inc
>>> [log in to unmask]
>>> Cell: 847-767-5745 <(847)%20767-5745>
>>>
>>
>>
>
>
> --
> Bob Wettermann
> BEST Inc
> [log in to unmask]
> Cell: 847-767-5745 <(847)%20767-5745>
>