Hi Richard!

Done!

http://stevezeva.homestead.com/Soldermask_view.pdf

Steve


On Wed, Aug 6, 2014 at 1:40 PM, Stadem, Richard D. <
[log in to unmask]> wrote:

> I have taken the picture, blown it up, modified it to show the contrast a
> little better, and now it is easier to see where the soldermask makes
> contact almost at the beginning of the point where the crack starts on the
> left side. I am hoping Steve can post it. The rest of you will not see the
> attachment because Technet strips all attachments.
> During thermal cycling the masking is continually pushing against the
> solderball joint at the base near the edge of the pad. The pressure is both
> inward and upward. That is what causes the stress that leads to formation
> of the crack in the coarsened crystalline structure of the solder joint,
> and also what causes it to continue (the z-axis prying force upward). It is
> actually an extrusion process.
> At least that is what I think, based only on what I can see in the picture.
> dean
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna
> Sent: Wednesday, August 06, 2014 1:49 PM
> To: [log in to unmask]
> Subject: [TN] SJ fracture signature
>
> We see hundreds of cracked solder joints every year, but I can't say that
> I've ever seen one quite like this.  I have some suspicions, but I'll keep
> them to myself, as to not prejudice the crowd.
> EDS maps are forthcoming.
>
> This is a caught in-the-wild field failure of a 48-pin BGA Reballed to
> SnPb ENIG on board side Ni barrier on component side
>
> http://stevezeva.homestead.com/45268-1.JPG
>
> http://stevezeva.homestead.com/45268-2.JPG
>
> http://stevezeva.homestead.com/45268-8.JPG
>
> Thoughts?  And Thanks to Steve!
>
>
> Chris Mahanna
> President, Technical Manager
> Robisan Laboratory Inc.
>
>
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