Influence of trimming of resistive thick films on nonlinearity of their current vs. voltage characteristics

An investigation of the changes of nonlinearity of thick resistive films, trimmed by laser and by grinding, has been carried out. Laser trimming has been realized by an Ar laser, mechanical trimming by grinding of the layer by a milling machine using a diamond miller. The simplest method of trimming has been used - the resistors have been trimmed by realization of a groove, approximately in the middle of their length, perpendicularly to the axes of the resistors. The length of the trimming groove has been from 10% to 80% of the width of the resistor. All measured values of nonlinearity after trimming have been recalculated for starting values of the resistors. Nonlinearity has been examined for constant current density at the narrowest cross section of the resistive layer. It has been found that changes of nonlinearity caused by trimming depend on the ratio of the width and the length of the resistors. The changes have been very similar for resistors trimmed by the laser and for resistors trimmed mechanically.