The Effect of High Speed Laser Trimming on Accuracy and Stability of Thick Film Resistors

Abstract

Many recommendations have been made on the proper operating conditions for the laser trimming process. In general these recommendations have centered on accuracy, precision or throughput. In some instances, these have appeared to be mutually exclusive. If one wanted accuracy and precision, one had to sacrifice trimming speed and, therefore, throughput.It has been reported that 40% of the processing cost of a thick film resistor network is due to laser trimming. To continue to make these networks commercially attractive, the manufacturers of laser trimming systems have addressed themselves to the problem of providing suitable cuts at higher and higher trimming speeds.It is important for the user of such a system to understand the basics of the trimming process and to have an appreciation for the new factors which will affect the performance characteristics of laser trimmed thick film resistors. This paper summarizes the previous work as it relates to present technology. It then attempts to develop new guidelines for high speed laser trimming.