The SIR test will check a board for its ability to survive heat and humidity by applying accelerated levels of both heat and humidity and measuring the insulation resistance of a special electrode pattern that is designed to be sensitive to surface effects. The test is carried out on a dedicated test coupon, but this is subjected to all the standard fabrication processes and quality controls, so that it is representative of the final board.
Survival of the SIR test will verify that there are no material incompatibilities and no processing residues with deleterious effects. The conditions and duration of test will be determined by the environment of the final application, the degree of certainty needed by the end-customer, and the acceleration factors which may be allowable. There will be more about this in Reliability and screening.
One might also include for test some samples which have also been subjected to the standard assembly processes. In this case, the SIR test would give assurance that there is no interaction between board quality and the post-fabrication processes, but only if there are no adverse effects due to such causes as flux residues. A positive conclusion for all samples would clear both finish and assembly processes, but failure restricted to the assembled coupons would demand further investigation.