Hi Bob-
What diagnostic tools have you used to conclude this is a warpage problem and not some other problem, such as flux distribution, solder deposition, substrate overall flatness, etc.?
I'm worried you could have our TechNet brain trust barking up the wrong tree!
I put down a few of those parts around 4 years ago, and I recall it being a bit of process development, but I was able to make it happen without a large furnace (we had a 5 zone, but I can't even remember whether I ended up doing it on a rework machine or even a set of hot plates! I do recall that getting the fluxing right was one of the issues.
Wayne
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Monday, January 23, 2017 1:02 PM
To: [log in to unmask]
Subject: Re: [TN] Nitrogen Reflow and Warpage Issues on POPs
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>
>
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