Hi Alasdair - so I would divide your question into two parts:

(1) Is the FOS appropriate for pcb surface finishes? The IPC-45XX
specifications contain the industry consensus/approved testing protocols so
if the FOS isn't listed in the specification, then its not a standard test
for that surface finish;

(2) Is the FOS appropriate for pcb surface finishes? To steal a phrase from
Doug "it depends"! Why are we proposing the use of FOS as a conditioning
test? Are we trying to understand how robust a specific plating process is
or in impact of changing a process step? Are we trying to understand how a
heavy sulfur environment exposure will impact a specific surface finish?
Need to understand the objective of using the test. Would I use the FOS as
an acceptance test? Most likely not as its a very harsh test and I should
already have a relationship with my board fabricator on what the
expectations of the surface finish should be as I relate it to my product
use environment.

Any conditioning test can be used on surface finishes, the critical element
is why are we proposing the use of a specific conditioning test. The FOS
test is useful if used in an appropriate manner but the FOS test is also a
harsh test with a significant acceleration aspect.

Dave

On Tue, Aug 14, 2018 at 8:34 AM, FTL Quality <[log in to unmask]
> wrote:

> Hello Dave,
>
> Thanks for the reply, is the FOS test appropriate for any common PCB
> plated finish?
>
> Thanks,
>
> ALsdair
>
> -----Original Message----- From: David Hillman
> Sent: Tuesday, August 14, 2018 1:29 PM
> To: [log in to unmask]
> Subject: Re: [TN] Flowers of Sulfur test
>
> Hello Alasdair - I would think that a FOS test on an immersion silver
> surface finish would not be an appropriate test as silver and sulfur do not
> like each other. The appropriate testing for printed circuit board surface
> finishes would be found in the IPC-45XX specification series.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> On Tue, Aug 14, 2018 at 7:25 AM, FTL Quality <
> [log in to unmask]
>
>> wrote:
>>
>
> We've been asked whether we use the flowers of sulfur test to check our
>> plating.
>>
>> Does anyone use this test for ENig, Pure Hard Gold, or Silver plating?
>>
>> I've got doubts as to whether completing this test would give any sort of
>> answer in any case as ENig is known to not withstand normal humidity
>> testing.
>>
>> Thanks,
>>
>> Alasdair
>>
>>