Interesting idea. I've never seen anything like what you're describing. That 
"trace" it appears to dive beneath is actually a space between outer layer 
conductors. So it would have to be on top of outer metal, then dive beneath 
the area covered by dielectric, then re-emerge on top of the metal. Could you 
describe a production sequence that would create that? I've seen lots of bare 
die, but I really know little about the wafer fabrication. In the upper right 
of that central photo is clearly a piece of debris sitting on top of the die 
surface (it's out of focus, so I'm presuming it is above the plane of the die 
surface and not below.)

-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Thursday, October 08, 2015 1:32 PM
To: TechNet E-Mail Forum; Wayne Thayer
Subject: RE: [TN] Ropy grunge in IC

I respectfully disagree. If you look closely, it appears that some sections of 
the rope-like material are actually intertwined and run under the traces 
inside the die. It appears that the contaminant was there when the die was 
made. But on the other hand some of the same stuff is seen around the edges of 
the die as well. It is hard to tell.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Thursday, October 08, 2015 11:47 AM
To: [log in to unmask]
Subject: Re: [TN] Ropy grunge in IC

That LOOKS like just a poorly cleaned decapsulation job. The stuff you're 
asking about could either be from the overmold material or some deteriorating 
seals in the decapsulator. So my instinct is that it's a "red herring" in your 
failure analysis. This contaminant appears to be EXTREMELY thin, no more than
5 microns, because there doesn't seem to be a detectable difference in focus 
height between this and adjacent circuitry (unless the image is actually a 
composite of several different pictures at different focus heights).

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, October 08, 2015 12:31 PM
To: [log in to unmask]
Subject: Re: [TN] Ropy grunge in IC

Hi Julie,

Have your photo up, it's here:

http://stevezeva.homestead.com/3CK_2nd_decap_-_multiview.jpg

Steve

On Thu, Oct 8, 2015 at 10:21 AM, Julie Silk <[log in to unmask]> wrote:

> We had an intermittent failure on a part and after decap, there was a
> rope-like line that seemed to weave in and out of the circuitry.  I'm
> having Steve Gregory post a picture.  I'd like your thoughts on what
> is going on.  We're consulting with the supplier, but I'd like your input.
>

-- 


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