Thick film resistor failure is rarely because of a failure in the resistive component but is generally as a consequence of external environmental factors which include mechanical and electrical stresses and managing concerns. Failures may be either classed to be a degradation of overall performance or entire failure (commonly as an open as opposed to a short circuit).
6 widespread brings about of thick movie resistor failure are:
Thermal concerns
Mechanical pressure
Frequent overload
Surge
Environmental - metallic migration
ESD
MECHANICAL FAILURES
Aside from dealing with injury resulting in substrate cracks and chips most mechanical problems is attributable to either vibration or inappropriate mounting from the machine. Micro cracking in the resistor content because of vibration or compression / extension of your resistor on account of inappropriate mounting can cause alter from the resistance worth, harm to the resistive component or ingredient failure. In all conditions the chance of failure is amplified by existence of a number of of the stresses shown under.
ENVIRONMENTAL Aspects
Despite the fact that a thick movie resistor is often coated to safeguard it from moisture and aggressive chemical features environmental things for example moisture and contamination nonetheless call for very careful thought. The two could cause metallic migration in between the terminals in the resistor resulting in likely brief circuit or possibly a improve in resistance value.
THERMAL Concerns
Most mechanical failure modes of thick movie resistors are propagated by heat. It can be thus crucial to comprehend the heat dissipation Attributes on the resistor and substrate material. A lower electricity resistor dissipates heat by using conduction by its component leads or connections, while a significant electrical power resistor dissipates heat by means of radiation.
When present passes through a resistor it generates warmth and also the differential thermal expansions of the different materials Utilized in the resistor production course of action induces stresses from the resistor. Temperature Coefficient of Resistance (TCR) is the best identified parameter utilized to specify a thick film resistor security, and defines the resistive ingredient's sensitivity to temperature adjust. Electricity Coefficient of Resistance (PCR) quantifies the resistance change on account of self-heating when electricity is utilized and is particularly vital for resistors Utilized in ability purposes.
OVERLOAD Problems
A continuous above-load of a resistor machine degrades the insulation resistance and adjustments the resistor parameters after a while. Voltage strain can result in conduction from Commonly non-conductive supplies during the resistor movie bringing about deterioration and occasionally failure on account of very hot places. It truly is hence crucial that you observe the resistor greatest specified voltage.
SURGE Ailments
The crucial element ingredient in pinpointing the surge survivability of the thick movie resistor may be the mass of the resistor aspect, which is instantly proportional to its thickness multiplied by its floor space. The geometry of the resistor also impacts its surge withstand capability. A larger area region brings about the next film mass, and eventually an enhanced surge functionality. The improved surface area place will allow extra warmth dissipation which is important in power resistor purposes.
The final aspect contributing element to your resistor surge ability is how the component is resistor trimmed to establish the ultimate resistance benefit. The tactic used for trimming can generate weak spots that induce failure less than surge disorders.
ESD
Damage by way of ESD can be a latent defect which can be tricky to detect. The resistor may resistors be partly degraded by ESD but continue to complete its intended function. Having said that, the chances of premature or catastrophic failure in the resistor unit are enhanced, significantly Should the system is subjected to one or more of your stresses mentioned earlier mentioned.