The Price Curve between Accuracy Grades in One Product Family
Sensor accuracy price curves scale exponentially because higher tiers demand longer thermal chuck dwell times, lower silicon yields, and guard-banded calibration.
Thin Film Resistor
Deposition Method
Precision components created by sputtering a thin layer of resistive material onto a ceramic or silicon substrate provide high stability and low noise. A thin film resistor is characterized by a very uniform thickness of the metal film, which allows for extremely accurate resistance values. This construction is common in high performance analog circuits.
Temperature Coefficient
Selection of the specific alloy used for the film determines how much the resistance will change as the temperature fluctuates. A high quality thin film resistor often has a temperature coefficient of less than five parts per million per degree Celsius. This stability is essential for maintaining the gain accuracy of an amplifier over a wide operating range.
Laser Trimming
Final adjustment of the resistance value occurs by using a laser to remove small amounts of the film and increase the electrical path length. This process allows the manufacturer to hit a target resistance with a tolerance of 0.01 percent or better. Because the trimming happens after the film has been stabilized, the resulting component is much more reliable than a standard thick film part.
Long-term Performance
Resistance to moisture and chemical attack is improved by applying a protective passivation layer over the film. This ensures that the component maintains its precision over many decades of service in the field.