One of the failed BGAs was certainly ENIG on BT. The other is a plastic
body NAND device not sure of the original finish on it.

On Thu, Dec 21, 2017 at 2:53 PM, George Wenger <[log in to unmask]>
wrote:

> Steve,
>
> It appears the pad you are trying to solder to is oxidized nickel or a
> Ni-Sn intermetallic.  Do you know what the original surface finish was on
> the BGA?  My guess it was ENIG and although I've always hated the name for
> this type of failure it does appear as if you have "Black Pad"
>
> George
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
> Sent: Thursday, December 21, 2017 2:40 PM
> To: [log in to unmask]
> Subject: [TN] BGA pad non-wetting
>
> 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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