steve, you are dealing with the cleanliness GURU.  The GURU as below.
> Steve
>
> Just a few thoughts before the gurus speak. If you do an extraction
> conductivity test, as you suggest, what will you be measuring after
> soldering? The residues from your no-clean flux, not the cleanliness of
> your assembly. Are these important? Possibly, but...
>
> What may be important (depending mainly on your board manufacturer) is
> whether the boards are clean before fluxing/soldering/reflow. IMHO, this
> is the most important thing to test.
>
> Personally, for a 'no-clean' process I would not test for ionic
> contamination after soldering. Instead, I would rely on a reputable
> well-chosen flux and let it go at that. This does not mean you can use
> out-dated or contaminated flux/paste or that your housekeeping leaves to
> be desired.  You will still need good, ordinary, practices.
>
> FWIW
>
> Brian
>
> On 23/06/2017 14:50, Steve wrote:
>> I realize that this is an old and continuing subject of debate in the
>> industry, but I am interested in the current updated consensus on the
>> topic. Specifically, what kind of PCBA cleanliness level should be
>> reasonably expected to achieve?
>>
>> Of course the answer is always "it depends," because that is the
>> reality. And the actual acceptance or control level needs to be set
>> according to product requirements. But what I am after is slightly
>> different: What level of cleanliness would you expect to be readily
>> achieved by a good quality manufacturing process under normal
>> circumstances?
>>
>> Some general parameters to narrow down the question:
>>
>> - Measurement technique bulk solvent (ROSE per IPC TM-650 2.2.25)
>> - Pretty normal PCBA design - 0403 components, some through hole,
>> nothing really unusual
>> - Pretty normal process, RoHS, no-clean.
>> - Class 2 PCBA, but high impedance low current battery powered
>> application
>> - High production volume (>1 million units annually)
>>
>> I am not aware of anything that has replaced the 1.56/cm^2 "standard."
>> but this has been around forever, it seems. Common sense tells me that
>> even if a formal standard has not changed general performance might have
>> improved, on account of smaller components, tighter board spacing and
>> general technological improvements.
>>
>> What has been your actual experience in this regard?
>>
>> Thanks in advance,
>> Steve
>>
>
>