Edge Of Conductor Research Articles

Theory of the Slotted Coaxial Cable

The electromagnetic problem of the coaxial cable with a continuous slot along the outer conductor is solved taking into account the dielectric constant of tbe cable insulation. Cylindrical harmonics expansions for the inner and outer space are used. The basic difficulty is to express boundary conditions on a part of the period in Fourier series. It appears that the singularity of the fields at the edge of the outer conductor plays a key role in the uniqueness of the result. The propagation constants of the monofilar and coaxial modes are obtained with a good accuracy. It is shown that these modes have different transfer inductances.

Application of line-edge profile simulation to thin-film deposition processes

A computer simulation program based on a segment-motion model has been developed to investigate thin-film-deposition processes. This simulation program is used to study the physical phenomena in the thin-film-deposition process as well as the effects of different tooling configurations and operating conditions. The simulated results are compared with experimental results obtained from an electron-gun evaporator with planetary tooling and from a planarizing sputtered quartz system to verify the accuracy of the simulation and to illustrate imporant phenomena during the deposition process. The simulation program is also used in exploratory studies to find the optimum source angle for step coverage in a typical planetary evaporator. The step coverage is found to change only slightly for wafers at different locations on the planet, but can change significantly depending on the pattern orientation on the wafers if the wafer rotation is not independent of the planet rotation. A study of the sputtered quartz planarization process shows that the growth of different topological features can be accurately predicted from the change in deposition and etching rate as a function of the angle of incidence. In particular, the increased deposition near a conductor edge is attributed to the propagation of a growth front from the sidewall boundary conditions.

Application of Line-Edge Profile Simulation to Thin-Film Deposition Processes

A computer simulation program based on a segment-motion model has been developed to investigate thin-film-deposition processes. This simulation program is used to study the physical phenomena in the thin-film-deposition process as well as the effects of different tooling configurations and operating conditions. The simulated results are compared with experimental results obtained from an electron-gun evaporator with planetary tooling and from a planarizing sputtered quartz system to verify the accuracy of the simulation and to illustrate important phenomena during the deposition process. The simulation program is also used in exploratory studies to find the optimum source angle for step coverage in a typical planetary evaporator. The step coverage is found to change only slightly for wafers at different locations on the planet, but can change significantly depending on the pattern orientation on the wafers if the wafer rotation is not independent of the planet rotation. A study of the sputtered quartz planarization process shows that the growth of different topological features can be accurately predicted from the change in deposition and etching rate as a function of the angle of incidence. In particular, the increased deposition near a conductor edge is attributed to the propagation of a growth front from the sidewall boundary conditions.

Effect of Profile Angle and Strike Extent of the Vertical Sheet in One Loop Transient Induction Method (Modelling)

The effect of (a) profile angle b with respect to the strike, and (b) the limited strike extent of a vertical sheet conductor on the response of one loop transient induction method was studied by physical modelling. The results indicate that 95% of the maximum response can be obtained when b = 85°, while at least 40% of the maximum response can be obtained if the edge of the sheet conductor is covered by 0.5 L of the loop.

Effect of conductor crossings on propagation margins

The effects of conductor delineation technique on magnetic bubble propagation across the conductor edge are described. Propagation margins are obtained for bubble circulation around 18-μm diameter Permalloy discs which cross four edges of an Al-Cu feature. Specifically investigated are isotropic wet etching, anisottopic wet etching to achieve a uniform taper, ion beam milling, and metal lift-off to provide a planar structure. Margins are obtained at ± 40°C, with the most significant degradation observed at the lower temperature. Permalloy magnetic continuity in the crossings can be inferred from hysteresis loop measurements of a Permalloy sheet deposited over a grating pattern formed by the above processing techniques. Although the least anisotropic loops are invariably obtained with smoothly tapered Al-Cu edges under the Permalloy, propagation margins are not maximized with such structures, but rather favor a planar crossing. The results suggest that although patterned stress is still an important concern in functional operation, other geometric effects can be more significant. In particular, poor magnetic step coverage as inferred from loop measurements leads to spurious pole formation from the drive field, while even with adequate step coverage, static bias-field distortions can result because of the component of the field along the step.

Effect of conductor crossings on propagation margins

The effects of conductor delineation technique on magnetic bubble propagation across the conductor edge are described. Propagation margins are obtained for bubble circulation around 18 μm diameter permalloy discs which cross four edges of an Al-Cu feature. Specifically investigated are isotropic wet etching, anisotropic wet etching to achieve a uniform taper, ion beam milling, and metal lift-off to provide a planar structure. Margins are obtained at ±40°C, with the most significant degradation observed at the lower temperature. Permalloy magnetic continuity in the crossings can be inferred from hysteresis loop measurements of a permalloy sheet deposited over a grating pattern formed by the above processing techniques. Although the least anisotropic loops are invariably obtained with smoothly tapered Al-Cu edges under the permalloy, propagation margins are not maximized with such structures, but rather favor a planar crossing. The results suggest that although patterned stress is still an important concern in functional operation, other geometric effects can be more significant. In particular, poor magnetic step coverage as inferred from loop measurements leads to spurious pole formation from the drive field, while even with adequate step coverage, static bias field distortions can result because of the component of the field along the step.

A conductor crossing problem in magnetic bubble memories

Bubble propagation across a conductor depends, among other considerations, on the magnetostatic energy of the bubble-Permalloy interaction and strain due to patterned metallization layers. Previously neglected, another consideration—bias field distortion in the neighborhood of the crossing—is discussed here. Poles induced by the bias field on a Permalloy element shaped to conform to a conductor produce field components parallel and transverse to the nominal bias. In traversing an isolated crossing at right angles to the conductor length and at a fixed altitude within the magnetic garnet, one calculates for the distortion bias maxima near the conductor edges and a minimum at the center. To obtain a tractable solution for the bias field as a function of coordinates a two-dimensional model was chosen for the conductor crossing: an infinite half space of infinitely permeable Permalloy with a circular depression. At points infinitely removed from the depression which houses the conductor the complex field H=Hx+jHy=jH0; that is Hx vanishes and Hy assumes the value H0 of the nominal bias field. Near the conductor centered at x=0, however, Hx is generally not zero, Hy(0,y) <H0, and Hy(x,y) exhibits a minimum at x=0 for fixed y. Using this model to calculate the bias in the vicinity of a 4-μm wide, 0.5-μm thick conductor, one finds for the bias field, averaged over a 3-μm thick garnet film, extremal values of 0.952H0 and 1.007H0. For current materials with H0?150 Oe the local bias reduction is 7.5 Oe. Because bubbles reside at the edges of Permalloy features, the field perturbations encountered in practice will be smaller than predicted by this model. Were there no forces on a bubble other than those associated with the coordinate dependent bias, a domain situated between maxima would move to the bias minimum and be trapped there. As designers strive for greater information density, this aspect of the conductor crossing problem may assume greater importance because of difficulty in linear scaling of conductor dimensions and the use of materials with higher bias requirements.

High performance magnetic bubble replicate gate design

The design and characterization of a novel magnetic bubble replicate gate are described. The gate can replace a previously reported design for memory chips with 16μm basic circuit period and 2μm minimum features. The improvements consist primarily of the elimination of the need for a pole enhancing "tail" and for the presence of conductor edges near critical regions, both of which existed in the old replicate gate design. The benefits are greatly improved bubble propagate margins and replicate phase margins. The test results presented show that phase margin ranges as wide at 60° are available, and storage loop propagate margins of over 25 Oe are typical for rotating drive field amplitudes of 35 Oe to 45 Oe and frequencies up to 357 kHz. Data pertinent to margin ranges in other operating parameters are also presented, and the failure modes imposing the margins are discussed.

Statistical Analysis on the Electrical Failure Properties of the Form-Wound Epoxy Micaceous Insulation Systems for Rotating Machines

FROM the test results obtained with various epoxy micaceous insulation systems used for form-wound coils of high voltage rotating machines, electrical failure properties such as breakdown voltage and voltage endurance time were analyzed statistically using a Weibull distribution. It has been determined both theoretically and experimentally, that these properties are governed by the size of a cable-like construction combining the four corner parts of the form-wound coils: the radius of the inner conductor edge, the insulation thickness, and length. Further, the dependence of the electrical failure properties on electrical, thermal and environmental stress, and on operating loads was determined. Finally, as a result of comparison between the failure properties of the model bar and the actual machine coils, equations were developed for estimating the failure properties of actual machine coils from small model bar coils. Additionally, the relationship between sample numbers and parameters of the Weibull distribution was considered, using random number data obtained from a computer.

Edge-guided modes in ferrite microstrips with curved edges

A simplified model is proposed which explains spurious resonances in edgeguided (E.G.) wave devices in terms of leaky E.G. waves. These are unidirectional azimuthal surface waves guided by the edge of a curvilinear strip conductor under conditions of positive effective magnetic permeability.

Voltage Endurance Tests of Insulating Materials Under Corona Conditions

A systematic study shows how the failure times of insulating materials exposed to corona discharges are influenced by various factors, including conductor edge surface discharge conditions, test frequency, void depth, humidity, temperature, material thickness, and average electric stress. Accelerated higher frequency tests permit testing at low-voltage stresses used continuously in applications. These yield results equivalent to 60-cps (cycles per second) tests, in cycles to failure, if both tests are run at low humidity with limited dielectric heating.

Determination of the Capacitance, Inductance, and Characteristic Impedance of Rectangular Lines

This paper determines the capacitance, inductance, and characteristic impedance of rectangular lines by the method of conformal transformation. In practical applications, such lines may be used as transmission links of RF energy, as impedance-transforming sections, or as components in electron tubes. Formulas are given for the calculation of the parameters of rectangular lines having the following characteristics: 1) The inner conductor may have varying thickness compared with the depth of the outer conductor. 2) The axes of the conductors may coincide or may be displaced with respect to each other. 3) The edges of the inner conductor may be rounded to lessen the electrical stress occurring at sharp corners. Excellent agreement has been obtained between the calculated results and those found by use of the relaxation method, by direct measurement of models, and by electrolytic tank measurement.