In metal film resistor, the desired resistance value can be achieved by either trimming the thickness of metal layer or by cutting the metal film in a helical manner along its length. This is generally done by using the lasers. Once the desired resistance value is obtained, the cutting of metal is stopped. Resistance of metal film resistor depends on the thickness of metal film layer and width of helical metal film cut.
The resistance of the metal film resistor is inversely proportional to the thickness of the metal film layer. The metal film resistors with very thin film layer allow only a small amount of electric current. The resistance of the metal film resistor is inversely proportional to the width of helical metal film cut. The helical metal film cut with large width provide less resistance to the electric current because the free electrons have to travel only a small distance through the resistive path. Hence, the possibility of collision of free electrons with the atoms is less. Therefore, only a small number of free electrons collide with the atoms and the remaining large number of free electrons moves freely from one place to another place.
Metal film resistors are applied to wide range of occasions, like high frequency applications, benefit from the feature of low cost, less noise ,wide operating range, long-term stability, low tolerance, low temperature co-efficient of resistance and very small in size.
