Evaluating Temperature Coefficient Wander in Thin Film Platinum Resistance Elements
Evaluating temperature coefficient wander in thin film platinum RTDs requires tracking substrate strain, glass passivation diffusion, and multi-point calibration.
Dielectric Passivation
Protective Isolation
Insulating layers are applied to semiconductor or thin-film sensor surfaces to shield them from chemical and electrical disruption. Through this technique, dielectric passivation coats the sensitive platinum tracks to prevent short circuits and oxidation. The material choice dictates how well the sensor withstands harsh process environments without loss of measurement resolution.
Choosing silicon dioxide or aluminum oxide provides the necessary thermal expansion match to avoid cracking during temperature sweeps.
Sensor Stability
Thin-film elements experience resistance changes when exposed to ambient moisture or active gases. Applying a dense oxide or nitride layer prevents these gases from reacting with the resistor track. This barrier keeps the nominal resistance stable over thousands of operating hours.
Contamination Prevention
Mobile ions from the surrounding package can migrate into the active sensor region under high-temperature conditions. This migration creates parasitic conduction paths that distort the calibration profile. Proper layer thickness prevents these ions from altering the electrical properties of the transducer.
Deposition Standard
High vacuum sputtering or chemical vapor deposition ensures uniform thickness and density across the substrate. The quality of the film is verified by measuring dielectric breakdown voltage and leakage currents at maximum rated temperatures. These test procedures confirm the integrity of the insulation under peak stress.