This post starts off by speaking about the standard design of a thick film electrical power resistor products. We then protect the opportunity general performance limits this design can lead to and discuss the difficulties to contemplate when deciding upon a ability resistor for a distinct application.
The construction of a thick film resistor solution is a serial process. A substrate (normally Alumina) is printed with a resistor paste that comprises metal oxides and glass-centered fillers, which jointly with a solvent sorts a paste. The substrate and paste are then fired to burn off irregularities and solvents and to harden the substrate. The resistor element is then sealed to avert dampness and gasoline ingress.
While thick movie resistors are frequently the lowest priced parts on a PCB a failure can be just as catastrophic as the most expensive lively part. Picking out the ideal good quality for a thick film resistor commences by describing its use as follows:
– Describe the use and software.
– Explain The atmosphere for use. The crucial issues to think about are temperature, moisture, aggressive gases, mechanical stresses and EMC specifications.
– Extensive phrase reliability prerequisites.
– Specify the required high-quality conventional.
It may possibly be the electricity resistor gadget is only needed for a shopper software. In this case, the extended phrase effects on performance due to electrical stresses or environmental things these as temperature might be irrelevant.
Excellent requirements might not be an problem if the power resistor is for a very low-expense products with an expected quick lifespan. However, if the unit is for a armed service software environmental variables and excellent stages will be a critical worry.
In significant-dependability programs, the storage of factors, traceability and creation methods will be significant. Microcracking in the substrate due to inappropriate dealing with or trimming can cause failure. As can failure to seal the product correctly to prevent the ingress of humidity and gases (especially sulphur and chlorine).
Thick film electric power resistor devices are comparatively little, small value and high reliability in the majority of apps. But some awareness of the producing procedure and prospective failure modes is handy to guarantee proper element range. The clarity in the exact demands for the device will maximise the chances of prolonged expression part trustworthiness.
When an software-distinct resistor is the only answer, shut cooperation with a professional resistor company can generate the greatest success. Utilise the encounter of the provider engineering teams to ensure the power resistor unit is in shape for intent.