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Subject:
From:
Douglas Pauls <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Douglas Pauls <[log in to unmask]>
Date:
Thu, 21 Dec 2017 13:59:49 -0600
Content-Type:
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Could it be there was thin residual solder mask on those pads?  Enough to
interfere with a metallurgical bond forming?


Doug Pauls
Principal Materials and Process Engineer
Rockwell Collins

On Thu, Dec 21, 2017 at 1:56 PM, David Hillman <
[log in to unmask]> 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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