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
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