The water spec is common for what's also referred to as deionized water in industrial applications. We had a plant at pppl.gov that made thousands of gallons, since we used it to cool a number of? of high power devices like 8974 2.5 MW tube amplifier modules...
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While that NASA soldering spec dates from 2006, SN60/SN63 remains to this day in the NASA supply chain. Aerospace material suppliers still sell it. SAC305 (tin-silver-copper) is the current recommended replacement, at 4-5 times the cost.
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Chuck AI7SY