PASSIVE RESISTIVE COMPONENT SURFACE ABLATION TRIMMING TECHNIQUE USING Q-SWITCHED, SOLID-STATE ULTRAVIOLET WAVELENGTH LASER

摘要

A method of laser trimming a passive resistive component changes its resistance value while leaving substantially unchanged coverage of the substrate area the component occupies to maintain its power dissipation capacity or preserve its high frequency response characteristics. In a preferred embodiment, the output of a 266 nm or 355 nm, Q-switched YAG laser or a 349 nm, Q-switched YLF laser is controlled so that no single output pulse completely removes thick-film resistor material depthwise at any given location. The laser output is moved in a line scan or raster scan fashion across an area of the resistor material to ablate a portion of its surface area to a depth that is less than the height of the resistor material. Varying the laser fluence, scan speed, bite size, repetition rate, and pitch makes possible the control of the amount of material, and particularly the depth of material, removed by the laser. The laser output is scanned across the exposed surface of the resistor until its resistance value reaches a desired value. Partly removing the resistor material allows resistance tuning with no damage to the substrate. Leaving substantially unchanged the substrate area that the resistor covers maintains its power dissipation capacity and preserves its frequency response characteristics.