Metal Oxide Film Resistor

The metal oxide film resistor is widely used these days being superior in performance to the carbon composition and carbon film resistors.

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As the name indicates, metal oxide film resistors axial leaded resistors that are made from a thin film of metal oxide that has been deposited into a ceramic rod.

The metal oxide film resistor was considered as the successor to the carbon film resistor as its performance was superior in most respects.

However as the metal film resistor was introduced, with a superior level of performance to that of the metal oxide film resistor, its use declined.

What is a metal oxide film resistor

As the name implies the metal oxide film resistor uses metal oxide as the resistive material within the resistor - the most common is tin oxide, although other oxides can be used.The metal oxide resistor is typically manufactured by taking a ceramic rod, which is heated then heated in a tin chloride vapour to deposit a thin layer of the metal. This is then oxidised to give the metal oxide film. Other metal oxides may use a different process.

One the metal oxide layer is established, the value is established by cutting a helix in the oxide using a laser. This makes the conductive path longer and narrower, considerably increasing he resistance.

Metal oxide film resistor performance

Typical performance figures for metal oxide film resistors are given below as a guide to the performance

Metal Oxide Film Resistor Performance Guide
Metal Oxide Film Resistor Parameter	Metal Oxide Film Resistor Performance
Typical tolerance availability	±1%, ±2%, ±5%, ±10%,
Value range	<1Ω - ~10MΩ
Load life (% change over 1000h)	2
Max noise (µV/V)	0.2
Temperature coefficient (ppm/°C)	~±300
Voltage coefficient (%/V)	0.0005
Max resistor temperature (°C)	300