Doug-
  You ask an interesting question. I don't believe there are any standards regarding the intensity of UV light for inspection of conformal coatings. 
   
  Before working for HumiSeal I worked for Polychrome, then one of the bigger manufacturers of presensitized printing plates. The photosensitive coatings on these plates are exposed with high intensity lamps in a vacuum frame. Sometimes it was necessary to calibrate the exposure units and we had a device we called a "puck". At least some exposure units use UV lamps. Some lamps loose illuminating strength over a period of time.
   
  There used to be a company in Chicago (UV Process Supply?) which sold everything related to UV curing including these "pucks". Spectronics and other manufacturers of UV lamps may know where to get UV intensity measurement instruments too. At HumiSeal we had a similar instrument to meassure the strength of our UV cure unit.
   
  The intensity of UV is proportional to the distance between the light source and the object being illuminated SQUARED  (or maybe even to a higher power?). You couldn't look at the light sources we were using at both employers.
   
  Now is a good time to mention that the glowing power of the fluorescent dye in conformal coatings sometimes declines with age. We suspected that this had to do with exposure to light. HumiSeals 1B31 & 1A33 contain a lot of fluorescent dye; it's easy to dissolve in the solvents in those coatings. It's not so easy to dissolve in some of the other coatings. So the glow strength will vary from coating to coating. I think it's dependent on coating thickness too.
   
  Don't discount that different operators will count different numbers of defects from the same screen. When I worked at Kodak (I got around) we saw this many times with microscopists.
   
  Don't get hung up on minute voids in conformal coatings. There are breaks in the coating that you can't see - the backs of flat leads, bends in flat wire (we called them "knees"). A different material should be used for absolute coverage.
   
  Edward Mines BEChE, MEChE 

       
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