Definition
Thermal fatigue is the progressive cracking of solder joints and interconnects caused by repeated heating and cooling cycles rather than a single overstress event. Each power-up and power-down expands and contracts the materials in an assembly. Because a solder joint, the component body, and the board laminate all expand at different rates (a coefficient-of-thermal-expansion, or CTE, mismatch), the joint is forced to absorb cyclic shear strain. Over many cycles this initiates and propagates cracks until the joint fails.
How engineers model it
Solder-joint fatigue life is commonly described with Coffin-Manson-type relations, in which life correlates inversely with the strain amplitude experienced each cycle. Larger temperature swings, larger components (longer distance over which CTE mismatch accumulates), and stiffer joints all shorten predicted life. Cracks usually nucleate at the joint-to-pad interface where shear strain concentrates, then grow until resistance rises and the connection becomes intermittent or open.
Why mining hardware is exposed
Hashboards experience large, repeated temperature excursions as they cycle between idle and full load, and the chips dissipate substantial heat. That makes thermal fatigue a leading long-term failure mode for ASIC and connector joints. Practical countermeasures include avoiding unnecessary power cycling, keeping operating temperatures moderate and stable, and ensuring good airflow so individual joints do not see extreme local swings.
Related wear-out mechanisms are covered in our entries on solder joint fatigue and electromigration.
Trace intermittent faults with the diode & voltage reference.
In Simple Terms
Thermal fatigue is the progressive cracking of solder joints and interconnects caused by repeated heating and cooling cycles rather than a single overstress event. Each…