Thermal Degradation and Termination Behavior of Thick Film Resistors

Thermal stability was measured for Du Pont 1420 (10² ohims/square), Du Pont 1440 (10⁴ ohms/square), Cermalloy 540 (10⁴ ohms/square), and Cermalloy 550 (10⁵ ohms/square) thick film resistor materials. Samples were aged at 200, 300 and 400°c. In addition, effects of resistor-conductor termination area, laser trimming, and applied bias voltage on thermal stability were evaluated.

For 200 and 300°C exposure, the sheet resistivity increased for all materials. Maximum increase after 5000 hours exposure as +8%. For 400°C exposure, sheet resistivity decreased for all materials. Maximum decrease was -20% for 5000 hours exposure. The termination region had no significant effect on either asfired resistance or thermal degradation behavior. Laser trimming tended to stabilize resistors slightly and applied bias voltage had no significant effect.