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The purpose of this paper is to verify the influence of superplasticizer and air entrainment admixtures (AEs) in the electrical resistivity of concrete.

Ten different types of concrete have been studied. Three levels of superplasticizer and air AEs have been used (0.20, 0.35 and 0.50 per cent). Concrete samples were cast and the electrical resistivity was monitored at the ages of 28, 63 and 91 days. Compressive strength and density tests have also been executed.

The superplasticizer admixture presented an optimal level of 0.35 per cent that significantly increased the electrical resistivity. The air AEs at the same dosage caused a considerable decrease in the electrical resistivity. The concrete with air AEs showed highest resistivity/MPa ratio.

The results should be carefully extrapolated for other materials and admixtures.

The usage of chemicals admixture in concrete is extremely common nowadays. However, only a few authors have studied the impact of such materials on the concrete’s electrical resistivity. Since many other researchers have already correlated electrical resistivity with other concrete’s properties, such as strength, setting time and corrosion probability, it is important to better understand how superplasticizers and air-entraining agents, for instance, impact the resistivity.

The vast majority of studies only tested the resistivity of cement paste or mortar and usually for short period of time (up to 28 days), which seems not to be adequate since the cement reaction continues after that period. This paper fills this gap and studied the impact of admixture on concrete and for a period of 91 days.

The trend towards high speed digital processing has stimulated the need for new substrate materials with superior electrical properties for multilayer printed wiring board (PWB) applications. Two important electrical substrate parameters are dielectric constant and dissipation factor. This study examines the effect of combining different resin and fibre systems for altering or possibly improving electrical performance. Resin systems studied include FR‐4, cyanate ester and polytetrafluoroethylene. Materials used for reinforcement include E‐glass, S‐glass and polytetrafluoroethylene based fibres. Results of the electrical and thermal characterisation work on the test vehicles built based on the mixed resin and fibre systems are reported.

In this work, commercial silver metal contacts welded on top of silver plated brass or brass substrates have been exposed to air rich in NaCl. Scanning electron microscopy and energy dispersive analysis of the exposed contact surfaces were performed to identify the corrosion by‐products on top of the silver contacts, suspending wafers, and welding materials. Surface corrosion products were mainly found to consist of small spherules of Cu‐Zn or Ag‐Cu compounds which cover the surface of the contact proper with low adhesion properties. They mainly originate from the underplating wafer or welding materials. Electrical characterization of the contacting materials was based on dc temperature overheat tests, current switching cycle tests, and energy storage during ac current excitation. The experimental results display that the operating environment is indeed a very significant parameter determining the overall performance of the electrical contacts. New design rules as well as material selection properties may have to be systematically considered to allow for electrochemical induced degradation in saline operating environments.

The present study aims to investigate the corrosion and electrical properties of the chromate conversion coatings on aluminium alloy Type 6061 in electrically bonded interfaces.

Tests were carried out to obtain the optimum conditions for chromate bath composition and immersion time for standard requirement provisions such as corrosion resistance in the salt‐spray test, electrical resistance and coating quality. The applied coatings were tested electrochemically in seawater and distilled water. The protection mechanism was evaluated from Tafel and cyclic polarisation curves in the said environments.

The evaluations showed that the passive film layer contained chromate with alumina formed on the substrate. The good performance of the conversion coating in terms of its corrosion and electrical conductivity was probably due to the characteristics of this protective film.

The paper presents findings on the corrosion of chromate conversion films on aluminium in electrically bonded interfaces.

The purpose of this study is to form fabrication and electrical characteristics of passive device embedded substrate that is embedded chip bead inductor and chip capacitor inside substrate for the application of radio frequency (RF) modules.

Passive device embedded substrate was fabricated using embedding process that consists of lamination process, laser drilling at the electrode Cu pads of passive components, electro-less Cu plating formation process such as photolithography, electrolytic Cu plating and etching. Impedance and capacitance characteristics of the fabricated passive device embedded substrate were evaluated.

By checking what embedded components are placed in the appropriate place using failure analysis via connection performance between copper plane and embedded components was verified. For measuring electrical characteristics of the fabricated passive device embedded substrate, the evaluation was done using test methods like continuity test for checking interconnections which are not connected to any embedded components and in-circuit test for checking interconnections which are connected to any embedded component. From in-circuit testing for embedding passive components with series and parallel circuits, the authors verified how to test passive device embedded substrate by using capacitance and impedance measurement with the comparison of measured results between good samples and bad samples.

Ultra miniaturized and low-profile mobile products are driving the need for embedded passive component integration technologies using a novel manufacturing-compatible organic substrate and interconnect technologies. Fabrication and test methods for passive device embedded substrate described in this paper are expected to lead to be developed to make quality measurable for the application of RF modules.

The use of Taguchi experimental design techniques to examine the effects of package type, solder paste type and solder reflow technique on the quality of fine pitch surface mount IC package solder joints is described. In particular, the effect of the use of ceramic or plastic packages, copper or Alloy 42 leadframes, silver loaded or non‐silver loaded solder paste and infra‐red, laser or hot‐bar reflow on solder joint metallurgical structure, electrical resistance and mechanical strength is evaluated. In addition to these solder joint parameters, an associated visual inspection was used to find the best process parameters to minimise solder balling, bridging etc. and a correlation between paste contacts at placement and solder bridges after reflow was also conducted. The experiment used an L9 array to find the optimum parameters from three factors, each at three levels. An extension to the basic Taguchi array was included in the form of an outer (noise) factor to include the effect of climatic stress on the solder joints under investigation. Response tables separate out the contribution of each factor level to the mechanical strength and electrical resistance of the assemblies. By comparing the response tables before and after climatic testing it is possible to estimate the effect of each factor level on the long‐term quality of the solder joints. It is shown how Taguchi experimental design techniques can be used to minimise the number of experiments required to predict optimum solder assembly process parameters. The accuracy of the prediction is shown by the results of a confirmation run which yielded mechanical strengths very close to those predicted, both before and after highly accelerated stress testing of the solder assemblies.

IN Figure 1 is shown an example of a purely electrical dynamometer, which uses two electrical carcases in tandem; its range of power and speed being suitable for dealing with medium‐sized aero‐engines and the more powerful automobile and lorry engines. Its speed range is from 500 to 3000 r.p.m. and its maximum continuous absorption 240 b.h.p. The two carcases are yoked together by steel members, and the two shafts are also coupled together by a flexible coupling. Both carcases are mounted on anti‐friction trunnion bearings, so as to permit the utilisation of the principle of torque reaction for the measurement of load. An interesting feature is that by a simple arrangement of levers the steelyard which measures the load caters for forces in either sense, so that it indicates torques arising either from the absorption of the engine power output, or from the use of electrical power to motor the engine.

THE present rapid progress in the development of internal‐combustion engines necessitates rapid and accurate testing methods, and it has been the aim of the electrical industry to produce braking equipment with which the power output can be conveniently and exactly measured. These devices are termed “Electric Dynamometers” and consist of an electric generator, the frame of which is not rigidly secured but so supported as to be able to be swung slightly about the axis of the rotor. This arrangement is no different in principle from the well‐known Prony brake, since the brake‐drum and blocks of the latter are merely replaced by the rotor and swinging frame respectively of the electric machines.

This study examines solvent extract conductivity (SEC) testing, e.g., Ionograph or Omega Meter testing, which measures ionic cleanliness of printed wiring boards (PWBs). SEC has been a quality control (QC) monitor to assure product electrical reliability. Typical SEC measurements occur after wave soldered products have been solvent‐cleaned. This study concerns SEC testing on new wave soldering processes that involve no solvent cleaning, i.e., inert gas soldering with ‘no clean’ fluxes. Results show ionic residues from ‘no clean’ fluxes may have other characteristics that make QC testing for ionic cleanliness inappropriate. However, SEC may be appropriate as a process control monitor after soldering with these fluxes. An Ionograph measured SEC response for the following chemicals: NaCl, NaF, NaBr, KCl, MgCl2, CaCl2, HCl, succinic acid, malic acid, glutaric acid, adipic acid and ethylene glycol. The list includes inorganic salts, strong electrolytes, which may arise from manufacturing or PWB materials. The list also includes weak organic acids (WOAs) common to ‘no clean’ fluxes. One non‐ionic hygroscopic chemical, ethylene glycol, was studied. Ionograph response was measured via (i) direct injection of aqueous solutions and (ii) immersion of PWBs with individual chemicals as surface deposits. All ionisable compounds, including all WOAs, produced substantial SEC response. Surface conductivity was measured at 35°C/90% relative humidity (RH) with controlled amounts of the above chemicals deposited on clean PWB test circuits. Surface loadings corresponded to the molar‐ionic equivalent of 2.0 ?g/cm2 NaCl. In addition, NaCl, adipic acid and polyethylene glycol (PEG 400) were examined as a function of concentration. Several ionisable chemicals including all WOAs produced no measurable effect, i.e., surface conductivities were indistinguishable on clean and deposited specimens. Surface conductivity increased for ionic contaminants with critical RH below ∼80% and for the non‐ionic hygroscopic glycol. SEC measurements and surface conductivities were compared. The latter is more directly related to electrical reliability. Although all ionic compounds including the WOAs showed a SEC response, not all enhanced surface conductivity. Achievement of critical RH appears to be the important factor. Adipic acid required the presence of hygroscopic glycol to enhance surface conductivity. Therefore, SEC can be a misleading QC test for electrical reliability when WOA flux residues are present.

The purpose of the work is to investigate the feasibility of using anisotropically conductive adhesives to join surface‐mount devices as solder replacement. The results from a literature and market survey are reported. Based on industrial demands, two anisotropically conductive adhesives were chosen for the experimental work. During the experimental work, the conductive adhesive joints were produced at various curing conditions. The joints were characterised by shear testing and electrical resistance measurement after ageing at 20, 70 and 120°C to 1000 hours. Optical and scanning electron microscopy were used to characterise the adhesive joints. In addition to this, temperature cycling tests, humidity test and pull tensile tests were used to qualify the adhesive joint reliability and quality. From the results of the present work, it can be concluded that the anisotropically conductive adhesive A joints are stable in the 85°C/85% RH environment and therefore have better corrosion resistance than adhesive B joints. Neither of the adhesives can pass temperature cycling from −55 to 125°C for 1000 cycles according to military standard 883C.