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ENIG CONTAMINATION
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Date:
September 04, 2009 01:49 PM
Author:
XPS
Subject: ENIG CONTAMINATION
Hi, in our company, we had performed a failure analysis on some PCB finishing ENIG faulty, cause detachement of heavy components. So we performed a SEM / EDX analysis on the nickel and we discover a 20 % of carbon instead of the standard 0.04% (on surface and into the nickel). So, now we have discovered that it is the cause of soldering problem, but we found very few study about that. So we need to know the cause of this contamination and its origin. And also we need to know if a serious study exist about it. Thanks
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=59789)
Date:
October 09, 2009 01:37 PM
Author:
tstrat
Subject: ENIG CONTAMINATION
We are seeing similar issues. We have a board that consistently has failures on a BGA part. After SEM/EDS it was shown that the fractures were occurring between the Ni-P and Ni-Sn intermetallic in the ENIG finish. The element map showed elevated concentrations of Carbon only in the ENIG layer. The lab noted that they had never seen this in the EN layer before. We have submitted a blank PCB of a different date code for analysis. I would be interested to know how your problem manifested itself and what type of solder/components/paste you were using. In our case, we had lower yield, but the primary issue was failure under mechanical stress (flex, shock, vibration). Thank you, TAS
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60082)
Date:
October 10, 2009 12:08 PM
Author:
davef
Subject: ENIG CONTAMINATION
George Milad [National accounts manager of technology, UIC/Uyemura International, gmilad at uyemura.com] is Chairman, IPC Plating Committee. He may be able to steer you towards a solution.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60084)
Date:
October 22, 2009 03:24 AM
Author:
Shinsei Technology
Subject: ENIG CONTAMINATION
Base on my PCB experience, the contamination issue might caused by PCB finishing or SMT process (like oven or printing). Before go further, maybe you can check few things. How many PCB affected per lot?? it might be caused by humidity (storage or packing). Remember, the lead time for ENIG only 6 monnths and need do baking before use if those boards was expired. Alex
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60157)
Date:
October 23, 2009 12:38 PM
Author:
kircchoffs
Subject: ENIG CONTAMINATION
--the lead time for ENIG only 6 monnths and need do baking before use if those boards was expired.
speaking of baking. what is the correct procedure? may i know the temps,time and profile? thanks
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60168)
Date:
October 23, 2009 05:40 PM
Author:
BLT Circuit Services Ltd
Subject: ENIG CONTAMINATION
So if you have Carbon showing on this would this not mean it is something Organic contaminating the pad.I have seen this before with solder resist depositing over the pad.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60175)
Date:
November 03, 2009 04:55 PM
Author:
tstrat
Subject: ENIG CONTAMINATION
If the contamination came from the SMT process I would have expected it to be present in the joint above the finish. It is isolated to the EN layer in the ENIG finish. We are doing more analysis to determine the number of boards with the contamination, but there are many board with failures in each of several different lots. The boards were only a few weeks old when assembled and were stored according to spec. Thanks,
tstrat
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60286)
Date:
November 03, 2009 05:52 PM
Author:
BLT Circuit Services Ltd
Subject: ENIG CONTAMINATION
Ask if they are seeing to much Phosphorous in the SEM or if they could determine if it is Phosphorous. Could be too much gold Brightener. Also this is not via in pad technology is it.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60287)
Date:
November 04, 2009 07:53 AM
Author:
tstrat
Subject: ENIG CONTAMINATION
The phosphorous concentration was not elevated w.r.t. levels needed for black pad syndrome. It is not via-in-pad. The component on the board that has been failing is just a standard BGA.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60299)
Date:
November 04, 2009 09:16 AM
Author:
BLT Circuit Services Ltd
Subject: ENIG CONTAMINATION
what level did you have
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60303)
Date:
November 04, 2009 09:47 AM
Author:
tstrat
Subject: ENIG CONTAMINATION
It was 7 wt% according to the EDS spectrum at the EN layer near the ball-pad interface.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60304)
Date:
November 04, 2009 10:01 AM
Author:
BLT Circuit Services Ltd
Subject: ENIG CONTAMINATION
I thought it had to be > 10% Wt
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60305)
Date:
November 04, 2009 11:00 AM
Author:
tstrat
Subject: ENIG CONTAMINATION
That is interesting, I have not seen that as a requirement before. From what I read if it is less than 7 wt% the corrosion resistance is pretty low, but if the value is too high it indicates that "black pad" is present from nickel corrosion. From what I could find the appropriate levels from the bath depend on the chemical supplier (typically between 8-14%). Do you have any more information on this?
Thanks.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60309)
Date:
November 04, 2009 11:25 AM
Author:
BLT Circuit Services Ltd
Subject: ENIG CONTAMINATION
No Sorry it was just from memory I will try to google it and see what I can find. I know it is bad to have too thin a Nickel layer and Phos layer. If you find anything can you let me know as well
Cheers
GREG
BLT
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60310)
Date:
November 04, 2009 01:15 PM
Author:
tstrat
Subject: ENIG CONTAMINATION
I asked our lab about this and received this response:
"Typically 7 - 9wt% phosphorus is used. Higher concentrations (10 - 12 wt% phosphorus) reportedly help prevent Ni-P corrosion during the IG processing step, but they are also reportedly more difficult to solder. Very high concentrations, ~ 28 wt% phosphorus, in a thin layer (~ 0.25 microns thick) at the EN/IG interface are a signature of 'black pad syndrome'. We did not see that problem on the boards you have sent us to date."
-tstrat
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60314)
Date:
November 05, 2009 04:17 AM
Author:
BLT Circuit Services Ltd
Subject: ENIG CONTAMINATION
I see thanks for that
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=60325)
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