Thick film resistor failure is rarely due to a failure with the resistive factor but is usually as a consequence of external environmental things such as mechanical and electrical stresses and dealing with concerns. Failures might be both classed for a degradation of efficiency or finish failure (commonly being an open up rather then a short circuit).
Six prevalent results in of thick film resistor failure are:
Environmental - metallic migration
In addition to handling problems leading to substrate cracks and chips most mechanical injury is caused by possibly vibration or inappropriate mounting of your machine. Micro cracking of the resistor product caused by vibration or compression / extension on the resistor due to inappropriate mounting can lead to modify in the resistance worth, harm to the resistive aspect or component failure. In all conditions the risk of failure is greater by presence of a number of of the stresses detailed below.
While a thick film resistor is commonly coated to shield it from humidity and aggressive chemical aspects environmental components including humidity and contamination nevertheless have to have thorough consideration. Each can result in steel migration between the terminals from the resistor leading to potential limited circuit or possibly a modify in resistance price.
Most mechanical failure modes of thick movie resistors are propagated by warmth. It can be consequently essential to know the warmth dissipation Homes of the resistor and substrate substance. A reduced electric power resistor dissipates heat by using conduction through its component leads or connections, although a significant power resistor dissipates heat as a result of radiation.
When latest passes through a resistor it generates warmth along with the differential thermal expansions of the various product used in the resistor manufacturing method induces stresses while in the resistor. Temperature Coefficient of Resistance (TCR) is the best acknowledged parameter accustomed to specify a thick movie resistor stability, and defines the resistive aspect's sensitivity to temperature adjust. Energy Coefficient of Resistance (PCR) quantifies the resistance transform resulting from self-heating when energy is utilized and is especially vital for resistors Utilized in power purposes.
A continuous about-load of the resistor product degrades the insulation resistance and variations the resistor parameters over time. Voltage stress might cause conduction from normally non-conductive products inside the resistor film bringing about deterioration and infrequently failure because of very hot places. It can be consequently essential to notice the resistor maximum specified voltage.
The key ingredient in figuring out the surge survivability of a thick movie electronic components resistor is definitely the mass of the resistor ingredient, which happens to be specifically proportional to its thickness multiplied by its area location. The geometry of a resistor also affects its surge endure functionality. A bigger floor region ends in a higher movie mass, and in the end an improved surge efficiency. The greater surface area space enables extra heat dissipation which is essential in electrical power resistor programs.
The ultimate element contributing variable to a resistor surge capacity is how the part is resistor trimmed to determine the ultimate resistance price. The method used for trimming can develop weak places that trigger failure under surge conditions.
Destruction by way of ESD is actually a latent defect which might be difficult to detect. The resistor can be partly degraded by ESD but proceed to complete its intended functionality. Nevertheless, the probability of premature or catastrophic failure of your resistor machine are enhanced, significantly If your product is subjected to a number of with the stresses listed over.
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