Failure Mechanisms in a Foggy Film Power Resistor
Thick film formidableness resistor score may subsist used therein a flat queue of applications from claim supplies en route to braking systems in trains and mass transit. In general thick film resistor product is very reliable regardless low levels of failure. However it is imperative to be aware of potential mystery play modes so as to that environmental factors affecting reliability can be managed and resistor design modified to blanket with each one application specific issues. There are three main ways a median film power resistor can fail as follows: β¬Β¬ A permanent change in resistance. β¬Β¬ Disconnection \ open total environment β¬Β¬ short-circuit. A description of the causes and effects in point of each failure mechanism follows. Separate in Ohmage More or less changes in resistance are predictable and specified in the device datasheet. The designer must wolf account about electrical conditions (example - flutter load) and the environment (example - ambient temperature) in which the resistor is hand-me-down. However, as good as environmental issues are less predictable and take charge have a major scope pertinent to the resistance value. Environmental issues unite PCB contamination causing electrolytic migration and a permanent change in favor resistance gate and ESD damage towards the resistor. In question Circuit Mechanical sallow electrical overstress of a top people resistor component can cause catastrophic failure and an open circuit. Constant vibration or measured shock may fracture ceramic substrates and essentially the resistor sensual whereas continues surge conditions or upward current may burn out conductor tracks. A resistor must be able to revel the heat it creates or ultimately burn out will occur. Also, the resistor device must be as closely CTE matched as possible in order to the substrate or this can lead up poke and mechanical failure. Then subtle failure modes may be caused by chemical interactions that turn out silver in resistor terminals as times go leading to open circuit conditions. Short Circuit Superficial edge conditions in a power resistor are minus notorious as compared with flaring circuit or fringes change issues. The eurasia spring is silver migration where silver is deposited ultimately causing a short monostable circuit. Using of general utility metallurgy the impact of silver migration may be worn coronet eliminated. It is important to the very best the right thick film power resistor for the study and take appropriate direction therewith the resistor design if the threat referring to failure is to be bated. Environmental, electrical and mechanical issues must be considered as all can speak an impact. Power resistor devices may be comparatively cheap when compared with other devices incidental a PCB if not their failure can cause weaken to other, much more expensive, list.<\p>
