Temperature humidity bias (THB) testing is performed to evaluate the reliability of non-hermetic packaged integrated circuit (IC) devices in humid environments. Temperature, humidity, and bias conditions are applied to accelerate the penetration of moisture through the external protective material (seal or encapsulate) or along the interface between the external protective material and the metallic conductors which pass through it.

The JESD22-A101 test standard for THB testing cites the use of bias of either one of two methods, continuous or cycled, whichever is more severe. This same standard requires that electrical testing be performed not later than 48 hours after the end of the test ramp-down. This time-to-test period can be extended to as much as 144 hours with the use of moisture-barrier bags. Silicon Cert Laboratories’ standard practice is to enclose all THB-tested samples in such bags.