With finer lines and spaces, innerlayer cleanliness becomes more important. 
 We've observed some innerlayer cleanliness issues on product that showed up 
after burn in of the assembly.  All of the data I see being collected by 
board shops is for the final board cleanliness.  At these shops, innerlayer 
cleanliness is controlled by how good the DES line is working but all the 
SPC data for that line relates directly to how well you develop, etch, strip 
not how clean the final product is at the end of the line.   What are board 
shops and/or users of boards doing to ensure that they are getting product 
with good clean innerlayers?   

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