By using two existing pieces of common printed wiring board manufacturing equipment, embedded resistor manufacturers can obtain laser trim results similar to the trimming obtained using a specialized probe card based laser trimmer. Existing electrical test equipment can be programmed to first measure the values of plated additive resistors manufactured on circuit board inner layers. Next, this value information is programmed into the software of a laser routinely used to drill microvias for circuit boards. A computer routine calculates the amount of the resistor that needs to be removed to adjust each resistor to the required design value. This trimming is then conducted on the actual inner layer. Advantages of this technology include eliminating the manufacture of probe cards for each new circuit design, and utilizing existing machines for this new technology task. While accuracy of trim with this "off line" machine may not be quite as precise as active trimming with probe cards, the accuracy is sufficient for many of the 5-10% resistor values needed for such design applications as digital signal termination. Plated additive resistors, with their uniform thickness across each resistor, are particularly easy for this technology combination to trim.
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