The two main concerns driving aircraft manufacturers are increasing fuel efficiency and conforming to anti-pollution regulations. To increase fuel efficiency, electronics are being moved close to their function in order to decrease the weight of the aircraft by reducing cabling. To comply with anti-pollution regulations, electric engines are being used to move the aircraft on the ground.
However, these changes have also created new performance requirements for electronic components, including resistors. In this article, we will discuss different resistor types for aeronautics applications – from strap resistors to high-precision chip resistors and resistor networks – and their required parameters, including high-temperature capabilities for stringent operating conditions, long-term stability, low TCR, and tight tolerances.
In terms of performance, these systems required components with operating temperature ranges from –55°C to +175°C, but this quickly needed to be expanded to +200°C. Drifts in performance were acceptable, as long as the parts would come back to their original values at +155°C.
Components with good long-term stability were also required, as the measurements had to remain stable for the life of the aircraft. The expected drift after several thousand hours of life could not exceed a given percent. Finally, the components had to exhibit good behavior during acceleration, vibration, and harsh environments. SMD products were shown to be the best under such conditions.
The control of all the others parameters – namely Ta, Pd, and Rthspa – are addressed by the customer’s assembly designers. Designers must take the PCB material, the thickness and layout of the copper tracks, the cooling system, and the interaction between surrounding components into consideration. Their designs are becoming more and more computer aided, which is the only way to face the increasingly stringent requirements of new electronic equipment in terms of miniaturization, power dissipation density, temperature exposure, reliability, etc.
A poor thermal management might induce melting or reduced reliability of the solder joints; reduce PCB performance; and lower chip resistor performance due to high reversible or irreversible drifts. Hence, thermal management and TCR is so important.
Microhm Electronics Limited, Precision Resistor, MVR low TCR series meet with most of the spec and requirement of Aero industries and is widely adopted in the industry.
