I'd clean it off the best you can, it says on their web page it is conductive on small traces pins and leads. I hate that damn tube they put it in, I covered my cpu in AS2 when I first got it.
Here are the specs listed at their web site.
Arctic Silver II features:
Made with 99.8% pure micronized silver.
78% to 82% silver content by weight.
Extended temperature limits: ? 40°C to >160°C
New formula insures minimal viscosity change from 0C to 150C
Thermal conductivity: 8.4 W/m°K to 8.8 W/m°K (Hot Wire Method Per MIL-C-47113)
Thermal Resistance: 0.0028°C-in²/Watt (0.001 inch layer)
2 to 7 degrees centigrade lower CPU core temperatures than other thermal compounds.
Negligible electrical conductivity.
Arctic Silver II was formulated to conduct heat, not electricity. It is only electrically conductive in a thin layer under extreme compression.
(While much safer than electrically conductive silver and copper greases, Arctic Silver II should be kept away from electrical traces, pins, and leads. The compound is slightly capacitive and could potentially cause problems if it bridged two close-proximity electrical paths.)
Arctic Silver II is now sold in 3 gram tubes. This is enough compound to cover at least 20 to 30 small CPU cores, or 7 to 12 large CPU cores, or 3 to 6 heat plates.
At a layer 0.003" thick, it will cover approximately 18 square inches.
Link To Artic Silver II