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August 2015

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From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Thu, 27 Aug 2015 19:46:56 +0000
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text/plain (1 lines)
That is not something I have seen before. The discoloration can be seen right through the soldermask, so it is not something in your process. I would show these to the fabricator and ask for full credit for any CCAs that may have been built up, plus full credit for any unused PWBs, and then I would find a better fabricator. If they refuse to settle then you should call your friends at Rabinovitch, Rabinovitch, and Rabinovitch.

-----Original Message-----
From: Craig Sullivan [mailto:[log in to unmask]] 
Sent: Thursday, August 27, 2015 2:27 PM
To: 'TechNet E-Mail Forum'; Stadem, Richard D.; 'David Hillman'; 'Steve Gregory'
Subject: RE: [TN] ENIG coating durability

Attached are pics. Sent to Steve Gregory for posting, directly to Dean and David.

Pic 0 is where a trim pot lifted right off, 1 minute ago. It appears to be a layer of Ni left on the pad.
Pic 1 is a circuit where a trim pot fell off at the slightest touch. Again, looks like a layer of Nickel left on the pad. It's gray in color compared to the gold PTH.
Pic 2 is what I am seeing on PTHs after we reflow these things.

It only appears after the reflow. I have not seen it before.
Also, I have seen no discernible difference in plating colors. 

Craig Sullivan
Manufacturing Engineer / IT Administrator
Phone:  (607) 266-0480 x115
Fax:  (607) 266-0482
Email: [log in to unmask]
Web:  www.mplinc.com

MPL, Inc.
41 Dutch Mill Road  |  Ithaca  |  NY  |  14850 P Please consider the environment before printing this e-mail.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, August 27, 2015 3:06 PM
To: [log in to unmask]
Subject: Re: [TN] ENIG coating durability

Sorry about the lack of continuity in my emails. But the reason I asked about the orange pads is because through the years I have noticed that sometimes if the immersion gold layer is too thin, say from 1 to 3 uinches, the nickel layer can begin to oxidize underneath as Dave described, and if the boards are older, the nickel can oxidize so badly that it does not even provide a barrier to the copper underneath the nickel. What happens then is that the copper can reach the gold, and it reacts right up on the surface and it shows up as orange pads interspersed amongst the gold pads I can see (at 20X magnification).
I have seen this (myself) like 3 or 4 times in the past 15 years, and I have found that it is a sure indicator of either nickel skips in the plating, or the ability of the nickel to completely oxidize and allow the copper through (thin nickel), or insufficient gold, all of which can lead to the oxidized pads and solderability issues in older ENIG PWBs. If you can see any evidence of this on PWBs not yet soldered, it is evidence of absence of either nickel or gold, or both. No fabricator can dispute it. Evidence of absence is not absence of evidence.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, August 27, 2015 1:27 PM
To: [log in to unmask]
Subject: Re: [TN] ENIG coating durability

No problem. Send pictures of the pad surface after the parts were removed also, if you can. That can be very revealing.
One more question. On the bare PWBs not yet processed, are there pads that are a little bit more "orange" than gold in appearance?

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Craig Sullivan
Sent: Thursday, August 27, 2015 1:14 PM
To: [log in to unmask]
Subject: Re: [TN] ENIG coating durability

Sections and SEM are forthcoming. 
I agree with both of you. 

Richard: Apologies for my terminology. Yes... we assembled bare PCBs into CCAs and the problems appeared at this process.

Craig Sullivan
Manufacturing Engineer / IT Administrator
Phone:  (607) 266-0480 x115
Fax:  (607) 266-0482
Email: [log in to unmask]
Web:  www.mplinc.com

MPL, Inc.
41 Dutch Mill Road  |  Ithaca  |  NY  |  14850 P Please consider the environment before printing this e-mail.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Thursday, August 27, 2015 2:06 PM
To: [log in to unmask]
Subject: Re: [TN] ENIG coating durability

Hi Richard - good info. The issue Craig described could also just be oxidation of the nickel thus making solderability near zero and then the parts just "fall off".

Dave

On Thu, Aug 27, 2015 at 9:50 AM, Stadem, Richard D. < [log in to unmask]> wrote:

> I seldom see issues with ENIG-finished PWBs even after 5 years or 
> longer, provided the ENIG finish was properly applied in the first 
> place and the boards were stored properly during that time. ENIG, when 
> done properly, is a very, very durable finish. The 4-5 uinches of gold 
> will protect the underlying nickel very well, and that is what you 
> actually solder to, not the gold.
> However, when problems such as those you are describing show up after 
> soldering, it is a very strong indicator of Black Pad. If the ENIG is 
> not plated properly and the immersion gold is not applied just right, 
> after soldering the components you can send perfectly robust CCAs into 
> the field, and in a few months the components can begin literally 
> falling off the board. It sounds like what you are seeing is Black Pad.
> Just google up ENIG and Black Pad and you will see examples of the 
> cratering and appearance of the pads, and compare them with the 
> pictures of your own.
> Just about every time, the pictures are very similar.
> Quite often, much older ENIG PWBs from one vendor solder much better 
> than those of another vendor that were fabricated and plated two weeks 
> ago. This is due to the plating process controls (or lack thereof) at 
> the fabricator, not the age of the plated PWB itself.
> Your email is a little bit confusing; when you state " PCBs just over 
> a year old are showing signs of oxidation after processing, components 
> can be flicked off with ease." Printed circuit boards (PCBs) are bare 
> boards with no components assembled, whereas PCBs with components 
> assembled are known as CCAs (Circuit Card Assemblies).
> If you mean that after the PCB is processed to solder components, and 
> immediately after that the parts fall off, yes, that is a sign of one 
> type of Black Pad, but it can also show up months later on assemblies 
> that were perfectly robust immediately after soldering.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Craig Sullivan
> Sent: Thursday, August 27, 2015 8:03 AM
> To: [log in to unmask]
> Subject: [TN] ENIG coating durability
>
> J-STD-003 and IPC-4552 basically state the ENIG should meet category 3
> (>6 months storage).
>
> My question is, what is the storage threshold for ENIG after the 6 months?
> 1 year, 2 years?
>
> What length of time should we conceivably expect to be able to store 
> an ENIG board before seeing issues?
>
>
>
> Scenario: PCBs just over a year old are showing signs of oxidation 
> after processing, components can be flicked off with ease. The Cu and 
> Ni (if any
> left) on a PTH look horrendous after processing. Here's a kicker, 
> these boards are date code 3414, but date code 3514 appears to be ok 
> and solders fine, and date code 3114 shows a very low and random case 
> of the oxidation/solderability issue.
>
>
>
> All PCBs stored in the same environment/manner
>
>
>
> Craig Sullivan
>
> Manufacturing Engineer / IT Administrator
>
> Phone:  (607) 266-0480 x115
>
> Fax:  (607) 266-0482
>
> Email:  <mailto:[log in to unmask]> [log in to unmask]
>
> Web:   <http://www.mplinc.com/> www.mplinc.com
>
>
>
> MPL, Inc.
>
> 41 Dutch Mill Road  |  Ithaca  |  NY  |  14850
>
> P Please consider the environment before printing this e-mail.
>
>
>
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