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Subject:
From:
David Hillman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, David Hillman <[log in to unmask]>
Date:
Fri, 22 Dec 2017 07:47:30 -0600
Content-Type:
text/plain
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text/plain (85 lines)
Hi team! Great discussion! I'll add one comment since Guy confirmed its
ENIG. When you remove the BGA , you can get a very flat dull surface that
can be either the nickel plating (which stacks up on the oxidized nickel
surface root cause that folks have detailed) or the NiSn intermetallic
layer (which folks have also added good root cause details). Regardless of
why the pads are not soldering, its going to be very difficult to
reactivate all of those surfaces in such a manner that you have confidence
that making sound acceptable solder joint is going to happen. The use of a
highly active, acid type flux might be a path to success but then you have
cleaning issues to address.  Pretty rough situation to be in.

Dave

On Thu, Dec 21, 2017 at 3:44 PM, Guy Ramsey <[log in to unmask]> wrote:

> ENIG
>
> On Thu, Dec 21, 2017 at 2:56 PM, David Hillman <david.hillman@
> rockwellcollins.com> wrote:
>
>> Hi Steve - do you know what original board finish was used? ENIG? ImAg?
>> ImSn?
>>
>> Dave Hillman
>> Rockwell Collins
>> [log in to unmask]
>>
>> On Thu, Dec 21, 2017 at 1:39 PM, Steve Gregory <[log in to unmask]>
>> wrote:
>>
>> > Hi all,
>> >
>> > I've been asked to post this to the Technet by a dear friend:
>> >
>> > *We installed this little processor. At test we identified opens on the
>> > device. When we removed it we saw a number of pads that were matte gray
>> > with no evidence of solder adhered to the pad. *
>> > *We attempted to bump the pads with solder, they did not wet easily. In
>> > some cases we had to scrape through the matte finish to a shiny metal.
>> > But, we did get all the pads to appear wetted.*
>> >
>> > *We cleaned the site well and then fluxed the bumps with a tacky flux
>> ROLO
>> > designed for POP, placed the BGA and reflowed it on a rework station.*
>> >
>> > *The assembly failed test with similar result, opens under the
>> processor.*
>> >
>> > *The attached photo shows that the bump process only appeared to wet the
>> > pads. The condition returned when we removed the BGA  second time.*
>> >
>> > * http://stevezeva.homestead.com/2017-12-21_11.21.17.jpg
>> > <http://stevezeva.homestead.com/2017-12-21_11.21.17.jpg>*
>> >
>> > *Have you seen this before? Is there any recovery? This assembly is
>> worth
>> > about $45K. *
>> >
>> > Thanks,
>> >
>> > Steve
>> >
>> > --
>> > Steve Gregory
>> > Kimco Design and Manufacturing
>> > Process Engineer
>> > (208) 322-0500 Ext. -3133
>> >
>> > --
>> >
>> >
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