Thick Film Trimming
So-called thick films are coatings of different conductivities, which are achieved by applying/printing resistor pastes to an isolating substrate followed by curing at about 850°C. When designing the circuit (paste application) or the components, the shape can be freely selected to a large extent.
However, depending on the quality of the pastes and the printing process, components with batch-dependent resistivity may occur during production. By subsequent laser trimming of these devices, the resistance can be precisely tuned to the required value either by measuring it directly (passive trimming) or by measuring some output signal of the circuit (active trimming).