I feel as though I�ve just walked in to a bar, where everyone I was supposed to meet has been drinking for 3 hours.
First, the volume of water displacement thing doesn�t make sense, as others have commented.
Second, I believe Dave Robbie wants measure the cleanliness of his board to be sure his cleaning process is in control prior to conformal coating his boards. So, he needs to know the cleanliness level is below �so & so�, before he coats the boards. The boards can be cleaner than �so & so�, but they cannot be dirtier.
As background, J-STD-001 wants boards to have a "cleanliness" level of < 1.56 micrograms / cm^2 (10.06 micrograms / inch^2) NaCl equivalence using ROSE [resistivity of solvent extract or as Eurolanders call it, Solvent Extract Conductivity (SEC).] testing. Historically, this 10.06 figure was for finished assemblies that were soldered with high solids rosin fluxes. So, it�s unclear that that number is appropriate for boards soldered with other fluxes.
So, Dave has some target [�so & so� micrograms / inch^2] that he needs to beat, but he still needs to calculate the surface area of his board, the �per inch^2� bit. * Naval Avionics Center Technical Report MRR-3-78 talked about this issue, if you can find a copy. Maybe try EMPF. * Old timers used LXWX3 as a "rule of thumb", but this was in the days when �men were men� and components were BIG. * Today, CSL [Contamination Studies Laboratory] uses LXWX2X1.1 * Even more conservative is LXWX2. If you make your �so & so� number with that, you�ve got a clean board. [The bonus here is, that none of those people in skirts (er, kilts) are going to ask you to explain how you came-up with a factor to compensate for component surface area. There is no factor.] * Contact Mike Konrad at Aqueous Technologies. He�s probably napping. He likes to talk about stuff like this. I�m sure he has a fresh point of view. * I don�t remember, and don�t have my copy handy, but as we�ve discussed before, here on SMTnet, "An In-Depth Look At Ionic Cleanliness Testing," RR0013, August 1993 is the seminal study on ROSE testing and maybe they discussed calculating surface area.
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