Structural Change
Gradual reduction of internal elastic stress within a solid material under constant strain and high temperature describes a primary aging process in metal components. Thermal stress relaxation occurs in connectors and spring contacts when the atoms in the crystal lattice rearrange themselves to relieve the mechanical tension. It results in a permanent loss of the force originally designed to maintain a secure electrical connection.
This behavior is a major factor in the long-term reliability of power electronics and automotive systems.
Heat Mechanism
Energy from the environment allows dislocations in the metal to move more freely. The heat mechanism of thermal stress relaxation is driven by the fact that as temperature rises, the rate of atomic diffusion increases. Even if the part is not moving, the internal pressure that holds the contact together will slowly dissipate.
This process is non-reversible and continues until the internal stresses reach equilibrium with the thermal energy.
Reliability Bound
Mechanical failure occurs when the remaining force drops below the minimum required for low-resistance contact. The reliability bound of thermal stress relaxation is defined by the maximum operating temperature where the material can still hold ninety percent of its initial load over the product lifespan.
