Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


ENIG CONTAMINATION

Views: 7117


XPS

#59789

ENIG CONTAMINATION | 4 September, 2009

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

reply »

#60082

ENIG CONTAMINATION | 9 October, 2009

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

reply »

#60084

ENIG CONTAMINATION | 10 October, 2009

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.

reply »

#60157

ENIG CONTAMINATION | 22 October, 2009

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

reply »

#60168

ENIG CONTAMINATION | 23 October, 2009

--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

reply »

#60175

ENIG CONTAMINATION | 23 October, 2009

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.

reply »

#60286

ENIG CONTAMINATION | 3 November, 2009

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

reply »

#60287

ENIG CONTAMINATION | 3 November, 2009

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.

reply »

#60299

ENIG CONTAMINATION | 4 November, 2009

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.

reply »

#60303

ENIG CONTAMINATION | 4 November, 2009

what level did you have

reply »

#60304

ENIG CONTAMINATION | 4 November, 2009

It was 7 wt% according to the EDS spectrum at the EN layer near the ball-pad interface.

reply »

#60305

ENIG CONTAMINATION | 4 November, 2009

I thought it had to be > 10% Wt

reply »

#60309

ENIG CONTAMINATION | 4 November, 2009

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.

reply »

#60310

ENIG CONTAMINATION | 4 November, 2009

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

reply »

#60314

ENIG CONTAMINATION | 4 November, 2009

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

reply »

#60325

ENIG CONTAMINATION | 5 November, 2009

I see thanks for that

reply »

ii-feed SMT Intelligent Feeder

Heller Industries Mark 5获得了 2015年中国SMT远见奖 - 回焊炉领域