Ga-
Thankyou for the clarifications.
I am now confused by the overhanging metal on the pcb the BGA is mounted to. Rather than ENIG, it appears to be electroplated gold, used as a final etch resist, and an extremely thick layer of it too: It looks at least 5 microns thick!!!
If the gold is indeed that thick, then you are likely experiencing severe gold embrittlement of the solder joint.
Perhaps you have a color visible light picture of this cross section at 400X for us to see.
Wayne
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tan Geok Ang
Sent: Thursday, January 15, 2009 8:05 PM
To: [log in to unmask]
Subject: Re: [TN] Possible cause on open
X1000
________________________________
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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