Martin Birkett

Laser Trimming of CuAlMo Thin-Film Resistors:Effect of Laser Processing Parameters

This paper reports the effect of varying laser trimming process parameters on the electrical performance of a novel CuAlMo thin-film resistor material. The films were prepared on Al2O3 substrates by direct-current (DC) magnetron sputtering, before being laser trimmed to target resistance value. The effect of varying key laser parameters of power, Q-rate, and bite size on the resistor stability and tolerance accuracy were systematically investigated. By reducing laser power and bite size and balancing this with Q-rate setting, significant improvements in resistor stability and resistor tolerance accuracies of less than ±0.5% were achieved.

Laser Trim Pattern Optimization for CuAlMo Thin-Film Resistors

The influence of varying laser trim patterns on the electrical performance of a novel CuAlMo thin-film resistor material is investigated. The benefits and limitations of various trim geometries are considered before two patterns, the “L” cut and serpentine cut, are selected to laser-trim resistor samples to target values of 1-10 Ω, using previously optimized laser conditions. The effect of increasing trim gain and varying trim pattern on the stability and standard deviation of the films is then systematically investigated. A two-stage trimming process is used to reduce resistance drift to <;0.1% following storage for 168 h at 125°C in air, which also allows much tighter resistance tolerances of <;±0.1% to be achieved.

Thin film resistive materials: past, present and future

This paper explores the key developments in thin film resistive materials for use in the fabrication of discrete precision resistors. Firstly an introduction to the preparation of thin films and their fundamental properties is given with respect to well established systems such as NiCr, TaN and CrSiO. The effect of doping these systems in both solid and gaseous forms to further refine their structural and electrical properties is then discussed before the performance of more recent materials systems such as CuAlMo and MmAgCuN are reviewed. In addition to performance of the materials themselves, the effect of varying processing parameters such as deposition pressure and temperature and subsequent annealing environment, as well as laser trimming energy and geometry are also studied. It is shown how these parameters can be systematically controlled to produce films of the required properties for varying applications such as high precision, long term stability and high power pulse performance.

A new trimming approach for shunt resistors used in metering applications

A growing number of smart energy meters and electric charging stations have sparked a demand for a high precision, low value shunt resistors to measure the flow of electrical current. This paper investigates the possibility of trimming 100 micro ohms Manganin shunt resistors with tolerance of 5 percent to improve their accuracy and performance for use in smart energy meters. In theory, reducing the standard 5 percent tolerance of the shunt resistors can be achieved by removing controlled amounts of the resistive material. In this experiment, theoretical analysis is carried out to determine the maximum amount of resistive material that can be removed from Manganin shunt resistor to reduce its standard tolerance of 5 percent. Two alternative designs are then used to trim the material from the Manganin strip using machining techniques. Implications of the experimental results to the flow of electrical current and temperature rise in the shunt resistors are discussed. Results from the initial trimming trials show that the standard tolerance of 5 percent can be reduced to less than 1 percent.

Effect of Abrasive Machining on the Electrical Properties Cu86Mn12Ni2 Alloy Shunts

This paper studies the effect of abrasive trimming on the electrical properties of Cu86Mn12Ni2 Manganin alloy shunt resistors. A precision abrasive trimming system for fine tuning the resistance tolerance of high current Manganin shunt resistors is proposed. The system is shown to be capable of reducing the resistance tolerance of 100 μΩ shunts from their standard value of ±5% to <±1% by removing controlled amounts of Manganin material using a square cut trim geometry. The temperature coefficient of resistance (TCR), high current, and high temperature performance of the trimmed shunts was compared to that of untrimmed parts to determine if trimming had any detrimental effect on these key electrical performance parameters of the device. It was shown that the TCR value was reduced following trimming with typical results of +106 ppm/°C and +93 ppm/°C for untrimmed and trimmed parts respectively. When subjected to a high current of 200 A the trimmed parts showed a slight increase in temperature rise to 203 °C, as compared to 194 °C for the untrimmed parts, but both had significant temporary increases in resistance of up to 1.3 μΩ. The results for resistance change following high temperature storage at 200 °C for 168 h were also significant for both untrimmed and trimmed parts with shifts of 1.85% and 2.29% respectively and these results were related to surface oxidation of the Manganin alloy which was accelerated for the freshly exposed surfaces of the trimmed part.

Effects of varying laser trimming geometries on thin film resistors

Purpose This paper aims to study the effects of varying laser trim patterns on several performance parameters of thin film resistors such as the temperature coefficient of resistance (TCR) and target resistance value. Design/methodology/approach The benefits and limitations of basic trim patterns are taken into consideration, and the plunge cut, double plunge cut and the curved L-cut were selected to be modelled and tested experimentally. A computer simulation of the laser trim patterns has been developed for the modelling process of the resistors. The influence of the trim length and resistor dimensions on the TCR performance and resistance value of the resistors is investigated. Findings It is found that variation in trim length, within the range of 5 to 15 mm, can give significant increases in the TCR of the thin films. Thus, for the plunge cut, TCR can reach up to 11.51 ppm/oC, for the double plunge cut up to 14.34 ppm/oC and for the curved L-cut up to 5.11 ppm/oC. Originality/value Research on the effects of various laser trimming geometries on the TCR and target resistance accuracy is limited, especially for patterns such as the curved L-cut, which is investigated in this paper.

Electrical resistivity of CuAlMo thin films grown at room temperature by dc magnetron sputtering

We report on the thickness dependence of electrical resistivity of CuAlMo films grown by dc magnetron sputtering on glass substrates at room temperature. The electrical resistance of the films was monitored in situ during their growth in the thickness range 10–1000 nm. By theoretically modelling the evolution of resistivity during growth we were able to gain an insight into the dominant electrical conduction mechanisms with increasing film thickness. For thicknesses in the range 10–25 nm the electrical resistivity is found to be a function of the film surface roughness and is well described by Namba’s model. For thicknesses of 25–40 nm the experimental data was most accurately fitted using the Mayadas and Shatkes model which accounts for grain boundary scattering of the conduction electrons. Beyond 40 nm, the thickness of the film was found to be the controlling factor and the Fuchs–Sonheimer (FS) model was used to fit the experimental data, with diffuse scattering of the conduction electrons at the two film surfaces. By combining the Fuchs and Namba(FN) models a suitable correlation between theoretical and experimental resistivity can be achieved across the full CuAlMo film thickness range of 10–1000 nm. The irreversibility of resistance for films of thickness >200 nm, which demonstrated bulk conductivity, was measured to be less than 0.03% following subjection to temperature cycles of−55 and+125 °Cand the temperature co-efficient of resistance was less than±15 ppm °C−1.

An investigation into the effects of pattern geometries on laser trimmed film resistors

This study investigates the influence of different trim patterns on the performance of laser trimmed film resistors. A variety of popular trim pattern geometries including the plunge and L-cut were modelled and tested and their effect on resistance value, temperature coefficient of resistance (TCR) and heat-affected-zone (HAZ) sensitivity was investigated. It is shown that variation in resistor dimensions and trim length in the trimming algorithm can increase the TCR of the resistors with results of 100-140 ppm/°C for the plunge cut and 100-130 ppm/°C for the L-cut. It is also found that the L-cut has lower sensitivity in the HAZ with a value of 11% in comparison with the plunge cut with a value of 12% for the same resistor dimensions.

Efficient nondominated sorting with genetic algorithm for solving multi-objective job shop scheduling problems

In this paper a combination of Genetic Algorithm (GA) and a modified version of a very recent and computationally efficient approach to non-dominated sort called Efficient Non-dominated Sorting (ENS) has been introduced to solve the Multi-Objective Job Shop Scheduling Problem (MO-JSSP). Genetic algorithm was used to lead the search towards the Pareto optimality whilst an Efficient Non-dominated Sorting using a Sequential Strategy (ENS-SS) has been employed to determine the front to which each solution belongs, but instead of starting with the first front, the proposed algorithm starts the comparison with the last created front so far, and this is termed as a Backward Pass Sequential Strategy (BPSS). Efficient Non-dominated Sorting using the Backward Pass Sequential Strategy (ENS-BPSS) can reduce the number of comparisons needed for N solutions with M objectives when there are fronts and there exists only one solution in each front to O(M(N -1)). Computational results validate the effectiveness of the proposed algorithm.

Genetic Algorithms for Solving Bicriteria Dynamic Job Shop Scheduling Problems with Alternative Routes

Solving scheduling problems with a single criterion is considered unsatisfactory for real-world applications. Therefore, more attention has been given to multiple objective scheduling problems. In this paper, we use a genetic algorithms to solve job shop scheduling problems with alternative routes and dynamic job arrival in order to simultaneously minimize the maximum lateness and makespan. Firstly, genetic algorithms have been applied to find a set of optimum feasible solutions for the makespan criterion. Individuals or solutions with values less than or equal to the value of maximum lateness with minimum makespan are then used to form the initial population in genetic algorithms for the second criterion in order to minimize the maximum lateness. A method of finding non-dominated solutions is then proposed, and weighted-sum is used to find the most desirable solution based on the weight of each criteria. Finally the model is tested using different instances, with the obtained results demonstrating the effectiveness of the proposed method to solve bicriteria dynamic job shop scheduling problems with alternative routes.