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January 2009

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Subject:
From:
Phillip Bavaro <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Phillip Bavaro <[log in to unmask]>
Date:
Fri, 16 Jan 2009 14:43:40 -0800
Content-Type:
text/plain
Parts/Attachments:
text/plain (236 lines)
Ok, I am confused.......

This is a 1.0 mm pitch BGA with a 0.5 mm solderball mounted onto a 0.4 mil pad.
I agree that the apparent curl is just the solder filling in the mask to 
pad gap but how do you make a BGA pad with a flanged top lip edge?
It reminds me of an upside down Top Hat!
And why is there what looks to be 6x as much copper under the part of the 
pad without the lip.
At that pitch, there could be a thru hole via in it, but I don't see the 
barrel or even a via wall.
I hope my confusion is due to the lack of cold weather outside this 
week.   (+) 27 C right now.

Phil

  At 09:47 AM 1/16/2009 -0600, Stadem, Richard D. wrote:
>I expanded the images and I am sending them back to Steve for
>re-posting. I can see a lot of flower-petal patterns, a lot of rod and
>cone structures just above the IMC. It appears as if there are very
>heavy gold intermetallics along the top of the IMC, and the gold
>nucleated back towards the IMC from the solder ball. The IMC layer is
>very thin.
>The solder between the edge of the soldermask and the edge of the pad
>causes the pad edge to look like they curled at the edges, but I think
>you can see that it is just the crack curling downwards inside of the
>solder. Full reflow obviously took place because the solder melted down
>the sides of the pads and filled the space between the soldermask and
>the curled edges of the pad. In the image taken near the center of the
>pad, it is obvious the crack propogated through the solder in some
>areas.
>The crack along the entire length of the pad and down the sides
>indicates severe stresses due to either the vibration forces or the CTE
>from the temperature cycling, or both. The crack probably formed due to
>the brittle nature of the IMF, what with having the worst possible
>combination of ENIG, lead-free solder, and lateral stresses. There are
>some voids with flux debris above the whole thing that tend to confuse
>the issues going on.
>Steve, I am sending my expanded image to you for posting separately.
>Thanks.
>Richard
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Igoshev, Vladimir
>Sent: Thursday, January 15, 2009 8:42 PM
>To: [log in to unmask]
>Subject: Re: [TN] Possible cause on open
>
>Thank you for sending me the image. Honestly, I don't quite understand
>what I see. The finish doesn't look like ENIG and the cavity above
>something that DOES NOT look like a typical intermetallic shouldn't be
>there, not to mention a "hair-like" something (crack?????) above the
>cavity.
>
>It looks like a proper joint had never been formed. Can you ask the lab
>to slightly etch the section?
>
>Regards,
>
>Vladimir
>
>________________________________
>
>From: Tan Geok Ang
>To: Igoshev, Vladimir; [log in to unmask]
>Sent: Thu Jan 15 20:09:33 2009
>Subject: RE: [TN] Possible cause on open
>
>
>About 1.05um
>
>
>
>________________________________
>
>From: Igoshev, Vladimir [mailto:[log in to unmask]]
>Sent: Friday, 16 January 2009 9:01 AM
>To: Tan Geok Ang; [log in to unmask]
>Subject: Re: [TN] Possible cause on open
>
>
>
>The info I'm asking about is at the bottom of the images you sent to
>Steve. You should be able to read from the originals what it says (how
>many microns)
>
>Regards,
>
>Vladimir
>
>----- Original Message -----
>From: Tan Geok Ang <[log in to unmask]>
>To: TechNet E-Mail Forum <[log in to unmask]>; Igoshev, Vladimir
>Sent: Thu Jan 15 19:53:13 2009
>Subject: RE: [TN] Possible cause on open
>
>The service lab has not come out much information at this time. Will
>input you once I have the information. Thank you.
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Igoshev, Vladimir
>Sent: Thursday, 15 January 2009 10:50 PM
>To: [log in to unmask]
>Subject: Re: [TN] Possible cause on open
>
>It looks like there could be something fishy in the intermetallic layer.
>GA, can you tell me please what is the reading on the micron bars?
>
>Regards,
>
>Vladimir
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
>Sent: Thursday, January 15, 2009 8:05 AM
>To: [log in to unmask]
>Subject: Re: [TN] Possible cause on open
>
>Mornin' Everbody!
>
>Well, here in Tulsa, we're just like a lot of other people in the
>country this morning, trying to stay warm. Right now we're sitting at
>-10 C. with a wind chill of -15 C. It's supposed to be colder
>tomorrow...
>
>GA, I have your pictures posted now. They're at:
>
>http://stevezeva.homestead.com/files/Fracture1.jpg
>
>http://stevezeva.homestead.com/files/Fracture2.jpg
>
>Hopefully someone can give you some ideas...
>
>Steve
>
>
>________________________________
>
>From: Tan Geok Ang [mailto:[log in to unmask]]
>Sent: Wednesday, January 14, 2009 7:27 PM
>To: [log in to unmask]; Steve Gregory
>Subject: Possible cause on open
>
>
>
>Hi Steve,
>
>             Please help to download these pictures TechNet, thanks.
>
>
>
>
>
>
>
>Hi All experts,
>
>             Testing (combine test of 16G at 85 oC) was performed on
>evaluation boards with under-filled BGAs. Open issue (cracks) was
>detected only at some corners of the BGA (35x35mm with 1156 balls) after
>the test. Lead-free process and PCB with ENIG surface finish. Peak
>temperature is 248 oC with a 65 sec above 217 oC.
>
>FYI, the service lab has not come out a report.
>
>             What are the possible causes? (CET mismatches, Lead-free
>alloy related, material, processes)
>
>
>
>             Thank you in advance.
>
>
>
>Regards
>
>GA Tan
>
>
>
>
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