Differences in resistance between FeCrAl and Kama alloy

Under high-current conditions, the resistance of an alloy shunt resistor is not constant but is governed by two coupled pathways—electrical and thermal. Joule heating raises the temperature of the resistor body, which simultaneously induces a change in resistivity and a geometric dimensional change due to thermal expansion. As these two effects superimpose in the same direction, their combined impact manifests as the "current coefficient."

Under simultaneous temperature cycling and damp heat, thermal expansion mismatch, interfacial dielectric changes, and electrochemical migration become strongly coupled, yielding failure modes and damage accumulation paths that differ fundamentally from those under single-stress testing.

Laser trimming, with its advantages of non-contact operation, high resolution, and automation, has become the mainstream trimming method for thin-film and alloy foil resistors. However, it simultaneously introduces localized thermal effects and residual stress into the resistor body.

Heat treatment is the key process that transforms "chemical composition" into a "stable microstructure": it determines grain size, precipitate state, and residual stress level—the three dominant variables governing TCR and long-term drift.