Surface Insulation Resistance (SIR) testing is a tool used not only for characterization testing of production processes such as solder masks, soldering flux, and conformal coatings, but also for examining the electrochemical reactions at each stage of the electronic assembly production process. This handbook covers the terminology, theories, test procedures and test vehicles of SIR testing, including temperature-humidity (TH) and temperature-humidity-bias (THB). Discussions on failure modes and troubleshooting are also included. Revision A provides significant expansion on the discussion of available industry test vehicles for SIR as well as test chamber setup.