Re:
">>...there
>> is a lot of subjectivity between the experts in defining what is
>> considered clean and not clean. IPC-5704 helps some with incoming board
>> cleanliness by setting up an industry standard that has been mutually
>> agreed upon within committee. However, no such standard exists for
>> assembly cleanliness..."
My 2 cents worth:
Table 6-4 of IPC-CH-65B July 2011 specifies contamination levels for circuit board assemblies per IPC-TM-650, 2.3.28, Ion Chromatography.