I am not familiar with the "HALT" terminology. Do you mean HAST testing? As for thermal fatigue, the most severe conditions are typically those cited for military and/or satellite applications. There are several temperature ranges that are used today; they are based upon the MIL-STD-883C document: -55-85�C; -55-125�C (most popular); and -65-150�C. The latter is sometimes used by the automobile manufacturers to represent under-the-hood enviroments. The high-end, non-military electronics will use 0-100�C as the temperature cycling limits (e.g., telecommunications). But remember, if the product uses an organic laminate, one does not want the high end temperature to exceed the glass transition temperture of that laminate; then, the test data on the solder joints become larglely meaningless due to softening of the laminate structure.
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