An investigation into the effects of pattern geometries on laser trimmed film resistors

This study investigates the influence of different trim patterns on the performance of laser trimmed film resistors. A variety of popular trim pattern geometries including the plunge and L-cut were modelled and tested and their effect on resistance value, temperature coefficient of resistance (TCR) and heat-affected-zone (HAZ) sensitivity was investigated. It is shown that variation in resistor dimensions and trim length in the trimming algorithm can increase the TCR of the resistors with results of 100-140 ppm/°C for the plunge cut and 100-130 ppm/°C for the L-cut. It is also found that the L-cut has lower sensitivity in the HAZ with a value of 11% in comparison with the plunge cut with a value of 12% for the same resistor dimensions.