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A Random Trimming Approach for Obtaining High-Precision Embedded Resistors
MARYLAND UNIV COLLEGE PARK DEPT OF MECHANICAL ENGINEERING
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Embedded resistors are resistors fabricated inside of printed circuit boards used as an alternative to discrete resistor components that are mounted on the surface of the boards. However, it is difficult to fabricate embedded resistors to the required resistance value, so embedded resistors are often fabricated with a lower value and then trimmed to raise their resistance to the desired value. A study of embedded resistors containing random voids of varying size and density has been performed. A new trimming strategy in which the trims are made randomly rather than conventional L-shaped trims is proposed in this paper. Analysis results demonstrate that single-dive trimming combined with random trimming enables the manufacturing of embedded resistors with higher precision and producibility Cpk than can be obtained with conventional trimming patterns. The resistor trimming pattern impacts the distribution of heat in the resistor. Study results show that the highest temperature reached in randomly trimmed NiCr resistors is 7.5 lower than the highest temperature in single-dive trimmed resistors and 1.2 lower than the highest temperature in L-cut trimmed resistors.
APPROVED FOR PUBLIC RELEASE