Hi Craig - as a general industry rule, the acknowledged shelf life of a
component or printed board surface finish is one year. After that time
period, any solderability issues are your issues and not the fabricator
issues. Of course, some board fabricators may shorten that time period for
some types of finishes but as a general industry rule and per much of the
IPC JSTD 003 committee testing, a correctly processed surface finish would
be solderable after one year under standard (21C, 30-60% RH) storage
conditions. You can extend the one year time period a number of ways
including using MSL storage bags, nitrogen storage, etc and the IPC-1601
specification contains a wealth of information to assist on that topic.  I
have worked with some fabricators who know their surface finish processes
so well they can provide an ENIG finish that will be solderable after 2
years of storage. Bottom line - team with your board fabricator to
understand what is possible/necessary for your process. Hope this is
helpful.

Dave Hillman
Rockwell Collins
[log in to unmask]

On Thu, Aug 27, 2015 at 8:03 AM, Craig Sullivan <[log in to unmask]>
wrote:

> 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
>
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