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Effect of Dust Contamination on Electrical Contact Failure
Abstract
Dust contamination is a major cause of current disruption in electric contacts. It is fast becoming the greatest influence on their reliability. However, due to its complexity, the effect of dust is difficult to simulate in the laboratory; and effective ways to reduce the failure caused by the fine dust particles on contacts still present a difficult and unsolved research problem. Based on the inspection of failed electric contacts, and also on the study of the characteristics of dust particles, this paper describes the composition of the materials in dust, and also the mechanical, electrical, and chemical characteristics of the particles. The conditions required for the dust to cause contact failure are discussed: in particular the effect of micro motion at the contact interface; the selective deposition of dust particles; the adhesion between particles; the chemical and electrostatic attachment of particles to the contact surface; and the creation of high resistance due to particle accumulation.
... An factors including corrosion [1], mechanical vibration [2], thermal effects [3] and contamination [4]. Dust particle contamination at the contact interfaces can cause electrical contact failures [4][5][6][7]. ...
... An factors including corrosion [1], mechanical vibration [2], thermal effects [3] and contamination [4]. Dust particle contamination at the contact interfaces can cause electrical contact failures [4][5][6][7]. There are several early works published by Williamson et al [5], Mano [6] and Reagor et al [7]. ...
... It was found that about 80% by weight of the materials were inorganic compounds, including quartz, various feldspars (albite, anorthoclase), micas (muscovite, biotite), gypsum, calcite, etc [8], roughly 20% of the dust contained approximately 20 kinds of organic materials, mainly alkanes and two ortho-benzendicarboxylic acid esters [9]. Analysis of failed connector contacts showed that not only hard materials, such as silicon compounds, but also soft materials such as gypsum, mica and organic materials, may cause contact problems [4]. Thus, it is importance to study the contact model of particle contaminated electrical contacts and the effect of particle contamination on contact failure for device reliability. ...
The presence of third body contamination can hinder the effectiveness of electrical contacts. Examples of such contaminations are dust particles, wear debris and so on. These particles can penetrate the contact regions and affect the contact mechanics. Once the particles engage in contact, they reduce the conductive real area of contact i.e. contact conduction. This work presents a third body contact model for the contact of two rough surface contaminated with particles. Particles are assumed to be in different sizes defined by a distribution function. A statistical approach has been adopted to model the contact of surface asperities and particles. The model is used to study the effect of sand particle contamination on the conduction of gold surfaces in cellphone connectors. The overall effect of particles is an increase in the contact force at a constant surface separation, which translates into a decrease in the conductive area of contact at a constant contact force.
... The contamination from particulate debris has been addressed by Williamson [101] and others [102,103] in their effect on static or closing contacts. Zhang et al. [104] made study of dust in Beijing, China and found three key elements: (1) inorganic compounds (abrasive), (2) organic compounds (film forming) and (3) water soluble salts (corrosion agents, see also Chapter 4.). The particle(s) can moderate the contact performance during wipe or slide. ...
... The clusters are usually nonconductive because of the insulating nature of the fluid that surrounds the particles. Particles can be drawn to a contact member because of electrostatic charges and caused to align with electrostatic fields, influencing both wear and electrical isolation of circuits [104]. ...
One important application for electrical contacts is the transfer of electrical signals and power between two members that are in relative motion to each other. This transfer is allowed through sliding electrical contacts. This chapter will discuss the theory of operation of sliding electrical contacts and the important performance parameters for their successful operation in common instrumentation and control applications. By far the most common of these applications are slip ring assemblies that transmit signals, data, and power across rotary platforms, and it is these rotary devices that will be the most common examples in this discussion.
The study of sliding electrical contacts has traditionally been divided into two areas of
study: power capacity and signal quality. The study of power contacts is typically focused
on an understanding of the impact on the sliding contact from power loading and the
effect power (both current and voltage) have on the power rating and contact reliability.
On the other hand, the study of sliding electrical contacts used for signal transfer is
focused on the ability of the electrical contact to function within a signal transmission line
with minimal impact on signal quality.
... Both thermal and dust loads result in an enormous maintenance effort for tunnel equipment (Ehrbar, 2017;Sturm et al., 2022). Thermal stress accelerates the aging process of electronic components (Hertl et al., 2009;Frivaldsky et al., 2017), and electrically conductive particles can cause malfunctions and damage to sensitive components (Zhang, 2007). In order to protect sensitive components (e.g. ...
When it comes into operation in 2026, the Koralmtunnel in Austria will be the world́s seventh longest railway tunnel. The installation of the power supply, telecommunications and electro-mechanical services is currently ongoing. Parts of these systems have to be protected from temperature and humidity variations and from the high dust loads which are characteristic of the tunnel atmosphere. In particular, cooling systems are required to counteract the significant amounts of heat released by some installations. Information on a large number of parameters (e.g. tunnel air temperatures) is required in the design process. However, such information is only partly available in the design stage. Hence, a prediction of tunnel air temperatures has to be made. Additionally, since hardly any information about the tunnel climate in long railway tunnels is available and in-situ measurements are not possible, as thermal conditions differ significantly between the construction/equipping phase and the operation phase, a novel methodology for the prediction of the tunnel climate had to be developed. This article presents a description of a new method comprising four main investigative steps and of its application to the Koralmtunnel as a selected case study. While steps 1 and 2 provide information about the actual cooling requirement and tunnel air temperatures for a period of 50 years, steps three and four of the investigation aim at the technical and economic optimization of cooling systems.
... Both stresses result in an enormous maintenance effort for the tunnel equipment [17] [20]. While thermal stress accelerates the aging process of electronic components [10] [7], electrically conductive particles can cause malfunctions and damage to sensitive components [22]. ...
The operation of long railway tunnels requires numerous technical installations. Parts of these installations react sensitively on thermal loads and dust loads and require protection from the tunnel atmosphere. In the case of modern twin-tube single track tunnels such components are often placed in utility rooms which are situated in cross-passages. In order to meet the temperature requirements of the utility rooms, cross-passage cooling systems have to be installed. Designing these cooling systems requires extensive investigations on the tunnel climate. This represents a big challenge, as information about the tunnel climate in long railway tunnels is rare. For this reason, a method to support the design process of cross-passage cooling systems had to be developed. The application of this method on a certain tunnel provided the required information for a data based system design of the cooling systems in the Koralmtunnel (AT). This includes both, details about the technical feasibility of ventilation and air conditioning systems as well as economic considerations.
... Metal ions preferentially form electrodeposits at high-energy sites on the cathode, which eventually bridge the two electrodes aer continuous accumulation. [6][7][8][9] Previous work has shown that the inuencing factors involved in ECM and electronic equipment corrosion include ionic pollutants, temperature, humidity, electric eld strength, liquid lm thickness, etc. [10][11][12] According to the ndings, various microorganisms exist in the atmosphere, once they adhere to the surface of the device, their continued growth and metabolism created an acidic environment that could cause corrosion. [13][14][15] It has also been demonstrated that microorganisms bridged the circuit and formed ion channels, which promoted the ECM process and aggravated the short-circuit failure. ...
In the electrochemical migration behavior (ECM) of printed circuit boards containing mold under a static magnetic field (SMF), the role of the field perpendicular to the electrodes is discussed; the B field inhibits the growth and metabolism of mold, while controlling electrochemical diffusion and nucleation. The field indirectly affects the function of mold as a transmission bridge between two electrodes. In this work, the water drop test was used to simulate the adhesion and growth of mold on the circuit board in a humid and hot environment; confocal laser scanning microscopy, scanning electron microscopy, energy dispersive spectroscopy, Raman spectra, and a scanning Kelvin probe were used to analyze the mechanism of static magnetic field and mold on the electrochemical migration.
... The dust enters the electronics with the airflow and deposits on the PCB and components by the static electricity and the gravity. The compositions of dust particles collected from indoor of Beijing are about 70% inorganics, which is divided into the soluble and insoluble parts [3]. On one hand, the insoluble particles not only block the heat dissipation from the surface of PCB but also change the local electric field distribution of PCB due to its dielectric properties [4]. ...
Under the air pollution environment, the dust enters the electronic products and deposits on the printed circuit boards (PCB) during the service life. Soluble salts in the airborne dust can reduce the critical humidity and increase the ion concentrations on condensed water film on PCB, which has been proven to aggravate the insulation failure of the high-density PCB caused by electrochemical migration (ECM). It is practical application significance for how to establish a life model to evaluate the ECM of PCB under the interaction of soluble salt with temperature, relative humidity, and electric field strength. In this article, through the temperature humidity bias acceleration experiment, the ECM failure of PCB under the contamination of the different concentrations of NaCl solution is simulated, and the ECM characteristics and failure mechanism are studied through the change of surface insulation resistance (SIR) and the morphology and element compositions of migration products. The time to the insulation failure of PCB under different conditions are obtained by the analysis of SIR curves. Based on the data-driven method, the life modeling of ECM failure of PCB under soluble salt contamination is studied by multivariate non-linear regression and machine learning methods, such as support vector regression, gradient boost regression tree, and random forest regression. It is proved that it is valid to use machine learning to establish the ECM failure life model of PCB in complex environments with limited life data.
... This arrangement is designed to work in a specific area. The conventional water spraying method as a measure of dust control wets the material before the dust is generated (Zhang 2007). The electrostatic precipitator technology consists of grounded collecting plates that ionize the air. ...
Dust suppression system plays a significant role in mining and allied industries. It has become an integral part of the environmental management system. Dust emission from mining and mineral processing industries poses environmental and health problems to workers and surrounding people. Dust creates a reliability issue in machinery and ventilation systems, causing infrastructural damage and the industry’s financial losses. This paper deals with a smart dry fog dust suppression system which has been developed for effectively controlling dust emission from mining and mineral processing activities. The system has been implemented in an iron ore crushing and screening plant in India, and its efficacy has been evaluated for controlling dust emission. The installed dry fog system reduced dust concentration to 0.10–0.17 mg m⁻³ from the prevailing dust concentration of 0.62–1.73 mg m⁻³ in work zone areas, which was much below the permissible limit below 1 mg m⁻³ where silica content in the dust was less than 5%. Percentage of free silica in the work zone dust reduced to traces from 3.61 to 4.80%. Similarly, PM10 and PM2.5 concentrations in the ambient air were decreased to 90–99 μg m⁻³ and 49–58 μg m⁻³ from 185 to 250 μg m⁻³ and 148–200 μg m⁻³, respectively. Further, concentrations of PM10 and PM2.5 were drastically reduced by 51.35–60.4% and 69.69–71.0%, respectively. The reduced dust concentrations in the ambient air were within the prescribed limit of PM10 (100 μg m⁻³) and PM2.5 (60 μg m⁻³). The system significantly reduces dust and free silica concentration in the work zone areas below the permissible limit. The system controls dust emission with an increase in production as it has been found that the number of nozzles is directly correlated with a reduction in dust. Furthermore, the system does not change the raw material’s mass as water added to dust is less than 0.01% of the raw material. The system is designed to give the best results within the closed environment of the plant. The system helps in eco-friendly and clean mining. The system reduces the breakdown and maintenance cost of mining equipment, thereby decreasing overall operating costs. Further, the system minimizes mine workers’ health problems, like silicosis and severe other occupation diseases. The system is automatic, cost-effective, energy efficient, and easy to maintain. Further, the system is capable of handling dust problems in the closed environment of crushing and screening plants. These properties make the system techno-economically feasible for installation in mineral processing plants.
Graphic abstract
... Studies have been performed to investigate and control the effects of dust particulate deposition on artworks, as reported in [4]. The semiconductor industry is also well known to be susceptible to particulate contamination [5] [6]. When there is a need to reduce the impact of particle deposition on critical materials and surfaces, operations are typically conducted in cleanrooms. ...
In this work we present a method for the direct determination of contaminant fallout rates on material surfaces from exposure to dust. Naturally occurring radionuclides K-40, Th-232, U-238 and stable Pb were investigated. Until now, background contributions from dust particulate have largely been estimated from fallout models and assumed dust composition. Our method utilizes a variety of low background collection media for exposure in locations of interest, followed by surface leaching and leachate analysis using inductively coupled plasma mass spectrometry (ICP-MS). The method was validated and applied in selected locations at Pacific Northwest National Laboratory (PNNL) and the SNOLAB underground facility.
... Effective ways to reduce the failure caused by the fine dust particles on contacts still present a difficult and unsolved research problem. The conditions required for the dust to cause contact failure are discussed: in particular the effect of micro motion at the contact interface; the selective deposition of dust particles; the adhesion between particles; the chemical and electrostatic attachment of particles to the contact surface; and the creation of high resistance due to particle accumulation [7] . ...
... This reduced reliability of coaxial connectors which are the elementary components, may then exacerbate the reliability of the whole communication system. Previous studies [3] show that electric contact failure is one of the main reasons resulting in Bit Error Rate (BER) of communications, computer networks and control systems in China. Therefore, it is theoretically and practically important to make effective life time predictions of electrical contact failure in the fields of connector design and engineering applications. ...
The high concentration of dust particles in the environment is one of the main causes resulting for electrical contact failure of coaxial connectors. Therefore, it is important to carry out proper methods to predict life time of coaxial connectors. In the life time investigation of coaxial connectors, a model is designed and analyzed. Then conclusions are drawn based on a novel accelerated life test. In this paper, a life time prediction method is proposed based on an 1µm-diameter particle environment for the first time, and at the same time a kind of experiment operating equipment is designed to control the concentration of particles for accelerated testing. The result shows an exponential change in contact resistance of coaxial connectors under 1µm-diameter particle environment. We then establish Inverse Power Law-Weibull model for life time prediction in electrical contact failure and obtain the contact reliability and characteristic life. Keywords-coaxial connectors; lifetime prediction; inverse power law-weibull model; contact resistance I. INTRODUCTION
Bu çalışmada ısı enerjisi etkisiyle busbar sisteminde bulunan malzemelerin uzamasının yatay hat sistemi üzerinde oluşturduğu mekanik gerilmeleri dengelemek için kullanılan yatay dilatasyon modülünün elektriksel ve konstrüksiyon olarak iyileştirilmesi ele alınmıştır. Dilatasyon modülleri busbar sistemlerinin mekanik gerilmelerini almak için içerisinde esneme kabiliyeti bulunan malzemeler bulundurur. Esneme kabiliyeti olan bu malzemeler aynı zamanda kesintisiz olarak elektrik akımını da iletmelidir. Günümüzde kullanılan dilatasyon modüllerinden farkı esnekliği sağlayan modülün içerisindeki elektrik iletimi sağlayan bölümde ilave malzeme kullanılmadan yapılmasıdır.
With the miniaturization of printed circuit board (PCB), the distance between the circuit traces or assembled component terminals is becoming smaller and smaller. Under the certain temperature, relative humidity, and bias voltage (THB), it is easier for the insulation performance between circuits to degrade due to electrochemical migration (ECM). The airborne dust deposited on the PCB during a long-term service may change the failure mechanism and time to failure (TTF) of ECM between circuits. In this paper, the mechanism and the characteristics of the combined effects of quartz particles in airborne dust, the temperature, the relative humidity and the bias voltage on the ECM failure of immersion silver finished PCB were studied by THB experiments. Then, the influencing significance of four factors on TTF of ECM were studied by the orthogonal test and range analysis. The results show that the silver cations migrate firstly but the exposed copper substrate on the positive electrode become the main migrated substance finally. The TTF of ECM changes non-monotonously with the increase of particle coverage density due to the bidirectional function of the insoluble particles, which can increase water condensation on PCB by the capillary action, but can extend the migration path of metal cations by physical barriers. The turning point is about the coverage density of
/cm 2. The insoluble particles with high coverage density can significantly shorten the TTF of ECM on the PCB than that with low coverage density under the same THB conditions.
Voltage drift over time in charge amplifiers is a problem not fully solved yet for DC measurements and continues to be a challenge for the scientific community. In this study we analyse the factors that cause this unwanted effect and propose a new method to compensate it. An automatic electronic circuit compensates the drift effect in two stages: first, a closed-loop proportional-integral control is used to bring the output voltage of the charge amplifier to zero and hold it while no measurement is being taken; and second, the voltage drift is compensated with an open-loop control when measurement is being taken. The proposed method allows us to compensate the voltage drift whatever its magnitude. Simulation and experimental results show that the drift effect in the output voltage of the charge amplifier is attenuated up to 99%.
This chapter broadly describes the type of contamination found in the electronic devices today and originating from the components, materials, manufacturing, and the assembling processes. The severity of residues is discussed in terms of their interaction with moisture under varying temperature and humidity conditions and their assistance in formation of the conductive water film on the electronic surfaces. The science behind the common flux-related corrosion reliability problems in electronics is thoroughly explained and backed by the most recent findings in this area. Moreover, the harmful effect of a variety of atmospheric contaminants originating from the user environment is described together with the related electronic issues found in the field.
As a major component of Electrical Wiring Interconnection Systems (EWIS), aircraft electrical connectors are used for the transmission of electrical signals and electrical connection between electrical equipment. It is kown that electrical contact failure is the primary failure mode of connectors. Contact resistance often presents transient characteristic that is difficult to reflect the degradation comprehensively. The electrical contact failure mechanism of connectors is studied in this paper. In order to evaluate and quantify the electrical contact failure state, a high frequency contact impedance model is established to represent the relationship between micro-physical characteristics and electrical parameters. Further, the influence of surface roughness and corrosion degree on the high frequency contact impedance model is investigated by finite element simulation and accelerated degradation experiment. The trends of contact impedance at high frequency is compared with that of contact resistance at DC condition under the circumstances of different degradation degree. Finally, the variation law of contact impedance at high frequency is revealed, which can provide the theoretical basis for performance degradation assessment, service life prediction and reliability evaluation for electrical connectors.
In this work we present a method for the direct determination of contaminant fallout rates on material surfaces from exposure to dust. Naturally occurring radionuclides ⁴⁰K, ²³²Th, ²³⁸U and stable Pb were investigated. Until now, background contributions from dust particulate have largely been estimated from fallout models and assumed dust composition. Our method utilizes a variety of low background collection media for exposure in locations of interest, followed by surface leaching and leachate analysis using inductively coupled plasma mass spectrometry (ICP-MS). The method was validated and applied in selected locations at Pacific Northwest National Laboratory (PNNL) and the SNOLAB underground facility. A comparison between data obtained from direct ICP-MS measurements and those estimated from current model-based predictors is also performed. Discrepancies of one order of magnitude or higher are observed between estimated and directly measured accumulation rates.
An electrical connector undergoes varying types of environmental and operating load conditions depending on the nature of the application. When the electrical connector is switched on, the current flows through the contact spring, contact interface, and connector pins. Resistive joule heating at the contact interface can result in the following failure mechanisms: creep, welding of joints, silver migration, tin whisker formation, fretting, and corrosion. Humidity can cause corrosion of the contact material, silver migration, and fretting corrosion of contact material. These topics are discussed in detail in the chapter. Selection and applications of electrical connectors for a build‐up of spacecraft should be carefully conducted to avoid catastrophic failures. Case studies for the external tank feed‐through connector failure had been conducted by NASA engineers.
With the miniaturization of the electronic devices, the spacing among the circuit traces on printed circuit boards (PCB) keeps reducing, which increases the risk of insulation failure based on electrochemical migration (ECM), especially for immersion silver (ImAg) plated PCB. Meanwhile, due to the severe air pollution in developing countries, airborne dust can deposit on the PCBs in electronic devices. The soluble salts in the dust can decrease critical humidity and increase the ion concentration in the moisture condensed on the PCB surfaces, so that the failure mechanism based on ECM may be changed and the time to failure (TTF) can be shorten. In this paper, the effect of the soluble salt with various concentrations on the ECM failure on PCB was investigated. The life model of ECM was built up based on the electrochemical reactions on electrodes. Then the ECM of PCB under sodium chloride (NaCl) solution with various concentrations was simulated on Y-pattern PCB by water drop (WD) test method. The failure characteristics of ECM during various stages of migration and under various concentrations of salt solution were analyzed by the morphology and element compositions of dendrite products, as well as real time monitoring of surface insulation resistance (SIR). The TTF of ECM was extracted to fit the life model. Finally, the mechanism and performance of ECM of PCB under salt solution was analyzed. And the application of the life model of the ECM failure of PCB contaminated by soluble salts was discussed.
The development and testing of a module that removes dust from air based on cyclone technology and its coupling to a chemical detector are described. This development was performed in a laboratory facility that is capable of simulating a harsh environment in which the target material can be mixed with dust at controlled climatic conditions. The size-dependent removal efficiency of the module was tested at different operational conditions. For dust particles of 5 µm and higher, removal efficiency is about 100%. The efficiency for smaller particles is lower, and the overall efficiency is 97%. No significant adverse effect on the detector (flame photometric detector) performance at low to moderate target material concentrations (100 µg/m³), even at high dust concentration, is observed. The cyclone operation does not require the use of consumable and its maintenance is minimal. Power consumption is 15W, which is acceptable for a fixed site or car transportable system and can be further reduced for the handheld version.
Surface charge on materials is important due to its wide range of consequences and applications in many industries (e.g., semiconductor). One important parameter needed for the design of devices and selection of materials is the polarity of charge of solid surfaces after the surfaces are charged by contact electrification. Currently, it is only known that one surface charges positively while the other surface charges negatively after contact (i.e., in accordance to the law of conservation of charge). This manuscript describes a previously unreported anomalous charging behavior of a general class of materials: the inorganic materials. Both contacting inorganic materials charged either both positively (e.g., mica and NaCl), or both negatively (e.g., quartz and CaF2). A close monitoring of the charge in real time showed that charge was conserved immediately after contact; however, an active interaction of the separated surfaces and the surrounding atmosphere unexpectedly changed the polarity of one surface rapidly (e.g., 1 s), thus resulting in both positively or both negatively charged surfaces. This anomalous charging behavior fundamentally changes our understanding of the design of devices related to contact electrification of inorganic materials and the triboelectric series (i.e., an ordered list of materials routinely used for designing devices).
The effects of oxide etch on the surface morphology of metals for industrial application is a common cause of electrical contacts failure, and it has becomes a more severe problem with the miniaturization of modern electronic devices. This study investigated the effects of electrical contact resistance on the contactor under three different atmospheres (oxygen, air, and nitrogen) based on 99.9% copper/pogo pins contacts through fretting experiments. The results showed the minimum and stable electrical contact resistance value when shrouded in the nitrogen environment and with high friction coefficient. The rich oxygen environment promotes the formation of cuprous oxide, thereby the electrical contact resistance increases. Scanning electron microscope microscopy and electron probe microanalysis were used to analyze the morphology and distribution of elements of the wear area, respectively. The surface product between contacts was investigated by x-ray photoelectron spectroscopy analysis to explain the different electrical contact properties of the three tested samples during fretting.
Abstract— This article presents an analysis of hot-spots
effects onevr the performances of a photovoltaic system in use. IV
and P-V characteristics are analyzed considering different
cases of degradation for the photovoltaic module (few hot-spots,
large number of hot-spots and highly damaged module).
Simualtions and experimental data are presented and analyzed
considering the energetical performances.
Electrical connectors play a critical role in wireless communication systems by serving as the infrastructure for exchanging information between the circuit modules. Unexpected connector failures can alter the signal that is being transmitted and lead to faults as well as bit errors. In this work, a fault detection and location method for connectors in wireless receiver front-end circuits was presented by simulation results. For connectors suffering from different levels of pollution, their impedance modulus varies continuously. In previous works, the parameters of the connectors or faulty components were usually assumed to be a certain specific value during fault diagnosis. In this current study, the impedance model of faulty connector and the range of the connector's impedance parameters are considered in order to better match the real system. First, the fault modes were determined. The parameters of the connectors were then sampled to generate training and testing samples. Finally, based on the samples, a MMSE (Minimum Mean Square Error) algorithm and a neural network algorithm are adopted to classify the fault modes. Both algorithms can diagnose the faulty connectors in a wireless receiver front-end circuit. If trained and tested by data obtained from actual wireless receiver circuits, this method can be applied to diagnose the faulty connectors in an actual circuit. In addition, this fault diagnosis method of connectors is completely automated and can also be applied to other types of circuits.
Serious environmental pollution degraded the reliability of gold-plated connectors in many-handed terminals. It was found that gold-plated contacts disassembled from failed mobile phones were tarnished and worn out. The main compositions of the contaminants on the failed contacts were dust particles, organic compounds, and worn contact materials with their oxide. The micromotion between contacts abrasively wore the contacts with the dust particles and organic compounds. Contact resistance on the tarnished contacts increased with the thickness of contaminants on the contacts. The combined effects of dust particles, organic compounds, and micromotion on the electrical behaviors of the gold-plated contacts were simulated and studied by adapting a fretting simulation system. The hard particles caused seriously abrasive wear of gold plating and quickly formed fretting corrosion to shorten the contact life. Tiny content of organic compounds supplied certain adhesion function of dust particles, which made it easy for the dust particles to insert the contact interfaces. The contaminants and wear debris with their oxide formed complexly tarnished morphology under micromotion conditions, which finally caused contact failure.
Particle contamination may cause serious electric contact failure. However a series of dust simulation tests could hardly reproduce the real contact problem of intermittent high resistance, i.e. very few contact failure has been found during the tests. This paper is based on testing and analyzing many practical failed connector contacts in mobile phones. The special features of the failed contacts that are due to particle contamination are then summarized. The mechanism of connector contact high resistance failure is that during micro movement, contaminated particles are accumulated and inserted at the interface instead of being pushed away. Therefore important criteria should be met: micro movement with irregular directions, variable moving lengths to wear out surface materials, stirring up particles of dust and corrosion products caused by the water soluble salts in the dust, trapping the dust particles and thus embed the particles into the contact surface, presence of some organics acting as adhesives to adhere particles together to prevent them from spreading away during micro movements. Materials within dust particles such as quartz, feldspar, mica, calcite and carbon etc. may also contribute to the contact failure. After several simulation tests it is verified that contact failure can occur only if the testing conditions and parameters include the above discussed phenomena. The testing and theoretical result have greatly convinced that further research is necessary in order to create and develop a workable simulation dust testing system for connectors.
Communication connectors are often exposed to atmospheric environments and could easily be subjected to contaminants. The existence of faulty connectors will alter the signal that is being transmitted and lead to faults as well as bit errors in communication systems. In the present work, fault detection of connectors in radio frequency circuit systems was studied and analyzed using a wavelet transform approach. Experiments were conducted to observe the signal changes introduced by contaminated connectors. Because real signals are often mixed with some noise, a wavelet de-noising method is also applied. Both experimental and simulation results show that the occurrence of faults could be determined by the wavelet transform method. By analyzing changes of the frequency and amplitude, the locations of faulty connectors could also be determined in circuit systems.
As semiconductor industry strives to keep pace with the rapidly shrinking feature size and ever-smaller chip size, surface sensitivity has increased gradually especially on micro-chips. Stronger emphasis must be placed on chip contamination to achieve higher reliability. Phase shifter chip employed in this paper was contaminated on the surface. By combining scanning electron microscopy and X-Ray spectroscopy, microstructure and micro-area composition of contaminants were thoroughly analyzed. The results revealed that the pollutants were mainly salt and organic compound. In order to further determine the salt source, comparative simulated trial on clean wafer was also conducted. It confirmed that the contamination was caused by human body fluid due to the participation of human in the processing of chips. On the basis of that, the corresponding improvement measures have been proposed to greatly suppress the similar contamination.
Some organic compounds were proven to exist on the failed electrical contacts on the printed circuit boards in mobile phones. They mixed with both the dust particles and wear debris to cause contact failure under fretting conditions. The bonding function of organic compounds to particles and the influencing factors were analyzed theoretically. As one of the organic compounds found on the contaminated electrical contacts in failed mobile phones, the sodium lactate was chosen as the testing sample of the organics. The effects of sodium lactate on the contacts covered by the typical dust particles (quart, mica) were studied by using a vibration and a fretting simulation respectively. The critical content of sodium lactate to make the particles enter the contact interfaces under fretting was presented. The simulation results suggest that low content of organic compounds can degrade the contact reliability under dust contamination.
The reliability of mobile communication devices is affected by many factors, such as structure design, mechanical and electrical characteristic of devices, electromagnetic disturbance, electrical contact, dynamic environmental, temperature changes, , environmental pollution, etc. Studies show that 14% failure of the electronic products is caused by dust and salt mist. Dust particles ingress electronic device, and contaminate the internal components. This results in electric contact failure and reduced reliability of contact components. It is a very important consideration in electronic product design to protect internal components from operational impairment that due to ingress of dust particles and reduce the impact of dust on the communication device. This paper studies the ability of mobile communication device structure design to resist dust particles ingress and penetration the internal areas. It gives the dust distribution in the mobile phone by experiments and finite element analysis (FEA) using a mobile phone as the representation of the mobile communication device; it provides guidance for structure design and improves reliability of portable electronic products in the future.
Dust particle is an electric contact failure causative factor that must be taken into account. In previous research, (1,2) the effect of dust particles on electric contacts was indicated and simplified model was established for the hazardous size range of hard dust particles entering into the contact interface. The electrical contact behaviors of several typical dusts with different compositions were also studied (3). As a continuation, the specific characters of dust particle which could cause contact failure are investigated in this paper. The mechanics model of dust particles on contact surface under static and dynamic conditions is built. The mechanics analysis of dust particle on contact interface is performed. Through the sliding experiments of two kinds of dust particles with different bonding strength, failure mechanism and the influence factors on contacts related to dust particles is analyzed and discussed.
Dust particles can cause serious failure of electrical contacts. Based on the previous analysis of dust and contaminated particles on the failed contacts of connectors, we identified several hard and soft materials (quartz, feldspar, calcite, mica, gypsum) commonly found in fine dust particles that could be harmful. Among them, calcite was one of the most in the fine particles. We studied the failure phenomena of electrical contacts covered by calcite particles under both static and dynamic conditions by simulation experiments. The failure mechanism of electrical contacts related to the calcite particles and the influencing factors was also investigated. Keywords-calcite; electrical conatcts; failure
Dust may cause corrosion in humid environment. Investigation of water solution of dust collected from Beijing and Shanghai showed that SO4-2 and Cl-1 were the major negative ions and Na+1, K+1, Ca+2 dominated the positive ions. Obvious corrosion was formed on the coupon surface when such solution was dropped on. Artificial particles including NaCl, Na2SO4 and CaSO4 are selected to simulate dust corrosion in laboratory. Solution of NaCl particles can cause serious corrosion on copper and gold plated coupon. However, the corrosion formed by Na2SO4 and CaSO4 solution is too slight to be observed. The result is mainly affected by characteristics of negative ions in salt solution, as well as relative humidity and temperature. The characteristic factors include penetration, adsorption, solubility, and acidity of ions. An effective method to reproduce corrosion found on failed contacts in laboratory setup would be spraying NaCl solution with limited concentration on SiO2 particles spread on coupon surface, thus producing SiO2 particles surrounded with NaCl. It is shown that NaCl with 2.5% concentration would be the effective method from repeated experiments. It takes tenths or even hundreds of fretting cycles to push SiO2 particles surrounded with corrosion product away. The number decreases to only several cycles for the particles without surrounded by corrosion products. It can be deduced that trapping effect of corrosion product on SiO2 particles is not neglected, and particle corrosion should be included in laboratory simulation of dust particles.
Carbon paste is commonly used in printed circuit boards as conductive pads and jumpers, or printed resistors etc. Recently, its application as conductive pads is expanding due to material cost competitiveness comparing with gold and other coating materials. This paper introduces the characteristics of carbon paste during micro motion. The micro motion test is carried out on a fretting test apparatus. Scanning Electron Microscope (SEM) and X-ray Energy Dispersive Spectroscopy (EDS), as well as 3-dimensional morphology analyzer are used in analysis of tested samples. It is found that the increase of contact resistance for carbon pastes during micro motion is a regular phenomenon and mainly caused by the accumulation of carbon particles and successive formation of carbon flakes on the surface, its mechanism is discussed. This research is helpful in understanding the tribology performance of carbon paste as conductive pads. resistance of carbon paste on test boards is increased during micro motion test. In order to find the reason why resistance keeps increasing, we investigated and analyzed the surface of carbon paste with the use of a Scanning Electron Microscope (SEM), an X-ray Energy Dispersive Spectroscopy (EDS), as well as a 3-dimensional morphology analyzer. This paper describes a possible mechanism involved in increase of contact resistance and attempts to give an explanation for the process.
Dust is a causative factor in connector's failure. To evaluate dust influence on the reliability of electric/electronic devices and connectors, dust tests are required for both ingression and contact behavior. Dust influence involves two typical stages: deposition and redistribution. Many factors such as air flowing, particle size, connector structure, electromagnetic characteristic of electronic devices, electric charge of dusts and dynamic environments may affect the results. Normally, vibration including bouncing is used to simulate dust ingression in the test. However, the results are not quite consistent with real situation. In this paper, for improving dust test method, the study of some influencing factors in the ingress of dust into electronic devices is performed. Dynamic models of finite element method were established for the evaluation of these influences. Based on analysis, an improved test method is presented.
In digital communication systems, the deleterious effects of contacts at coaxial connector is one of the major causes of declining quality of communication. This paper describes the effects of contact degradation caused by contamination of a coaxial connector on transmitted signal integrity and error code rate. Transmission of high frequency current through degraded coaxial connectors is simulated and analyzed based on finite element method (FEM). An improved contact impedance model is introduced and its influence on high speed signal transmission is investigated. The impedance of degraded coaxial connectors is presented. The phenomena of contact failure which lead to error codes in signal transmission are confirmed in the experiments.
Dust particles can cause serious failure of electrical contacts. Designing and building a proper test system to simulate exposure to dust particles is an urgent need. To choose the appropriate materials to act as artificial dust particles is one of the major processes. Based on the previous analysis of dust collected indoors from west of Beijing and contaminated particles on the failed contacts of connectors, we identified several materials commonly found in fine dust particles (less than 50μm) that could be harmful. These materials include quartz, calcite, mica, gypsum, fibers, and sodium lactate. We studied these materials under both static and dynamic conditions. The failure mechanisms of contacts related to these particles were investigated.
Because the electronic products are sealed up incompletely, it is easy to be influenced by the environment to cause the electrical failure. Through the micro-examination of interior of the failed mobile phones, it was discovered that the fiber was one of the main pollutants. The distributed characteristic and the size scope of fibers in the failed mobile phones were analyzed. By using simulation experiments of static and dynamic contact conditions, the failure mechanisms of electrical contacts covered by fibers were studied.
An investigation has been made of the manner in which two solids touch when one of the contacting surfaces is contaminated with dust. The behaviour is discussed in terms of the probability that intimate contact will be established between the solids in any particular closing operation. It is shown that this probability is related in a simple manner to the number and size of the contaminating particles, to the load between the solids, and to the nature of the contacting surfaces. The manner in which a dust particle can become trapped between the approaching bodies and thus prevent direct contact occurring is considered and a simple physical model of the processes is proposed. For this model, the dependence of the nature of the contact on the number and size of the contaminating particles is derived. The experimental behaviour is in good agreement with that predicted. The theoretical discussion indicates that the effectiveness of the contamination in preventing direct contact should fall off rapidly if the surface roughness is increased until the height of the irregularities is comparable with that of the particles. The effect has been verified experimentally. It has also been demonstrated that there is a sharp change in the probability of the occurrence of intimate contact if the area of contact between the solids is made comparable with the cross-sectional area of the particles. The practical significance of these observations is discussed. The various possible methods of increasing the probability that direct contact will occur are considered, and general relations are given by means of which the behaviour of two contacting solids under any given concentration of dust may be predicted.
In the spring of 1963, a well-known research institute made a market survey to assess how many scanning electron microscopes might be sold in the United States. They predicted that three to five might be sold in the first year a commercial SEM was available, and that ten instruments would saturate the marketplace. In 1964, the Cambridge Instruments Stereoscan was introduced into the United States and, in the following decade, over 1200 scanning electron microscopes were sold in the U. S. alone, representing an investment conservatively estimated at 100,000 each. Why were the market surveyers wrongil Perhaps because they asked the wrong persons, such as electron microscopists who were using the highly developed transmission electron microscopes of the day, with resolutions from 5-10 A. These scientists could see little application for a microscope that was useful for looking at surfaces with a resolution of only (then) about 200 A. Since that time, many scientists have learned to appreciate that information content in an image may be of more importance than resolution per se. The SEM, with its large depth of field and easily that often require little or no sample prepara interpreted images of samples tion for viewing, is capable of providing significant information about rough samples at magnifications ranging from 50 X to 100,000 X. This range overlaps considerably with the light microscope at the low end, and with the electron microscope at the high end.
Nowadays electronic devices and systems are widely used in various dynamic environments. However, they cause electrical contact instability that can easily be ignored. This phenomenon is considered as contact failure caused by a dynamic influence. In this paper, the investigation of contact failure caused by dynamic influences and analysis method for such contact failure are discussed. The results show that a dynamic influence could not be well covered in the experimental testing for a new product.
Large number of electronic connectors are widely used in various electronic and telecommunication systems. No matter whether it is optical telecommunications or mobile phone systems, connectors are important links for electronics. Unfortunately connector contacts are exposed in air, they are different from any other electronic components, the contacts are greatly influenced by the environment where they operate. In China, dust and corrosion products are the main contaminants to cause contact failure. Evidently the failed contacts seriously deteriorate the reliability of electronic and telecommunication systems. This paper summarizes the recent achievements obtained by our Lab on the effect of dust and corrosion products to the connector contact failure. Since dust contamination is a very complex problem which is not only popular in China, but also happened in many countries. Continuous studies will be very useful to improve the contact reliability of connectors, setting up new and effective testing methods and standards, building up experimental and computer simulation systems.
Adhesion of particles and the attaching of particles on contact surfaces are two of the major problems for the simulation test on contact failure caused by dust particles. Based on the inspection of electric contact failure of mobile phone used in China, it is found that the adhesion of particles are mainly caused by organic materials such as sodium lactate and other chemicals from the sweat. Particles tightly attach on contact surface can be caused by various factors; corrosion products trap the dust particles could be one of the important reasons. This paper identifies the sodium lactate and other materials found at failed contacts of mobile phones and describes its contribution to the failure. With the support of experimental result it also evidentially describe the trapping effect of the corrosion products. This paper could be of use to improve the simulation dust test for mobile phone used in China.
On inspection of failed connector's contacts, various wear tracks of micro motion are found. The tracks appear as straight line, curve and twisting. The effect of micro motion not only produces wear debris of contact metals and their oxidation products but also grabbles and accumulates contaminants which cause high and fluctuated contact resistance. Analysis on the cause of micro motion that related to external vibration and shocks are carried out. Supporting experimental results are also discussed.
On inspection of failed connector's contacts, various wear tracks of micro motion are found. The tracks appear as straight line, curve and twisting. The effect of micro motion not only produces wear debris of contact metals and their oxidation products, but also grabbles and accumulates contaminants which cause high and fluctuated contact resistance. Analysis on the cause of micro motion that related to external vibration and shocks are carried out. Supporting experimental results are also discussed.
Inspection on 95 failed connector contacts of 23 mobile phones shows that the contaminants at the contact areas are formed by various sizes of particles. They are adhered together. It seems that smaller ones accumulate the larger ones. The composition of contaminants is very complex, which include dust particles containing mainly silicates (quartz, mica, feldspar) and calcium compounds (gypsum, calcite and lime), wear debris of surface materials, corrosion products (sulfates, chlorides and oxides of copper and nickel) and high concentration of organics. Organic materials seem to act as adhesives at different temperatures. Contaminants causing failure usually located at or near the wear tracks. The most important function of micromotion is to move the separated contaminants and accumulate them together at the contact; they also produce wear debris, and destroy the surface metal layer as well. High contact resistance happened in several small regions at the contaminant that provide high enough thickness. Failure could be happened within very short time period (3-4 months) depends on the high resistance region is formed. Conventional ways of corrosion gas test, sand or artificial dust test, shock and vibration test can hardly simulate the failure of contact occurred in China.
As it is known, dust contamination may cause serious contact failure. Deposition of dust and adhesion of particles are affected by the electric charges carried by the dust particles. In an external electric field, the deposition of particles is greatly enhanced. By using the Milliken method, the electric charges carried by particles are measured. It is found that particles of different materials may carry different electric charges. Therefore, dust particles are not equally deposited when in the presence of an electric field. Inspection on some failed contact surfaces shows that gypsum, organic materials, mica and titanium oxide etc. that are present in less amounts in the dust but contribute more to the contact failure. They seem to be "selectively" deposited on the surface and caused contact problem. Soft materials such as gypsum can be deformed and squeezed at the contacts and provide SO42- ions in the water film to cause corrosion at the local region. Organic material may act as adhesives to stick with other particles. Thus, various sizes of particles can grow during the operation. Silicon compounds are in the majority of dust, even mica is hard to be distinguished and some of them possess less charge, however they are still commonly found at the failed contacts. Particles may attach water-soluble salts that carry less electric charges, but they frequently appeared in hand set telecommunication, and cause serious corrosion.
Serious contamination formed on contact surface is one of the main reasons for electric contacts failure. Investigation shows that more than 60% of the corrosion products contain elements of dust, such as Si, Al, Mg, Na, Ca etc. Analysis for water solution of dust demonstrates that water-soluble salts are contained in the dust. Such solution forms electrolyte and makes metal corrosion. To illustrate the effect of dust on corrosion in real environment, elements of positive ions of dust, besides elements of corrosion products of Cu or Ni, have to be identified in the contaminants. Dust corrosion may cause connector contact failure within 2 months of operation. Long-term exposure in air shows that contact failure may be caused by both dust and gas corrosion. There seems to be no definite value of critical relative humidity (R.H.) for dust to corrode metal since corrosion can be found even R.H. value is as low as 10%. However, corrosion is increase rapidly with humidity. Corrosion can be greatly reduced by strictly controlling the humidity.
Dust contamination on electric contacts appears to be very serious in China. The adhesion of dust on contact surfaces is due to the static electric charges carried by the particles. Measurement of the charges is of importance for laboratory simulation. The Millikan testing method was used for the measurement, with 183 sets of data collected and used for fitting the curves. The final result shows that electric charges increase with the effective radius of the particle. Particles with a radius in the range between 0.5 and 2.5 μm may carry electric charges between 1.3×10-18 C and 1.1×10-16 C.
Due to its simple structure, easy installation and low cost,
bolt-type power connector, the parallel groove clamp is widely used in
overhead power transmission and distribution lines. However, due to high
and fluctuating current loads and harsh environments in China, there are
many problems in application of this kind of connector. After analysis
of failed connectors collected from Chinese overhead power lines, the
main failure causes were found (Luo et al., 1999). For further
understanding and simulation in the lab, electrical current tests for
parallel groove clamps were conducted and finite element analysis was
used to simulate the failure process. Some useful results are summarized
and described in this paper. (1) Bolt tension force linearly increases
with temperature rise. The force increase rate is up to 43.98 N/°C.
Thus, oxidation on contact surfaces is accelerated and contact
resistance increases accordingly. (2) Vibration model FEM analysis shows
that there are many kinds of vibration modes for parallel groove clamps,
including clamp shaking, rocking and swinging and relative motion
between upper and lower covers. The scope of mode frequency is close to
vibration of overhead power lines induced by wind, which may cause
two-thirds of failed samples with obvious fretting wear morphology at
contact interfaces. (3) Imbalance of contact resistance among clamps and
connected wires may cause electric current to pass through the bolts,
increasing temperature rise and accelerating bolt stress relaxation. (4)
Contact force, film resistance and fretting at the contact interfaces
are the key points of connector failure
The environmental effects on several contact platings including
gold, silver, nickel and tin were studied after investigating the
morphology, composition and fretting behavior of natural corroded
products, which were formed in Shanghai, China after long-term indoor
air exposure. Corrosion formed on all of the testing coupons are found
as discrete islands rather than continuous layers as predicted. Not only
the protrusive core product but also one or more dark rings centrically
surrounding the core are seen on gold plated coupons. Micro-observation
on the ring shows that it is formed by accumulated and discrete islands
similar to that of the core. The height of corroded products on the ring
is much lower than that of the core. The composition of corroded product
on the ring is similar to that of the core. Fretting across the dark
ring also causes high contact resistance. Preliminary investigation
shows that this may cause sudden and rapid high impedance and error
codes in telecommunication systems
It is found that one of the most important reasons causing high
error code rates in digital communication systems is the contact failure
of coaxial connectors installed in the systems. Preliminary
investigation into the failed connectors collected in-situ has revealed
that the contact failure of coaxial connectors may be caused by many
factors, such as corroded products or dust particles on the contact
surfaces, and the change of normal contact force caused by relaxation of
the spring elements, etc. It is interesting to learn how the contact
failure causes high and erratic contact impedance and results in error
codes in digital communication systems which are still unknown. The
effects of tarnish materials on the contact impedance and also the
influence of the contact failure on digital signal transmission are
studied theoretically and experimentally. Some of the results and
tentative conclusions are presented in this paper
A comprehensive analysis of the organic compounds of the airborne
dust collected in Beijing University of Post and Telecommunications has
been carried out by combined application of four analytic methods
including infrared spectroscopy, gas chromatography-mass spectrometry
(GC/MS), high performance liquid chromatography-mass spectrometry
(LC/MS) and thermogravimetric analysis. The aim is to gain a better
understanding of the main organic constituents in the dust and seek an
efficient method for analysis of the organic compounds. The results show
that weight percentage of the organic compounds and “black”
carbon is about 20% of the dust. The main constituents of the organic
compounds are a series of alkanes (C7-C40+) and
two ortho-benzendicarboxylic acid esters. These materials probably are
from the chimney of the central heating station and exhaust gas of
vehicles. Evidences show that the organics in dust may also contribute
to electrical contact failures of connectors and cannot be ignored
The inorganic compounds in the airborne dust collected indoors at
Beijing University of Post and Telecommunications has been analyzed by
jointly using X-ray powder diffraction (XRPD), electron probe
microanalysis (EPMA) and transmission electron microscopy (TEM). The
results showed that the dust was composed of up to 24 compounds,
including quartz, feldspar, mica and calcite etc.. The distilled water
separation method effectively enabled size separation of airborne
particles. In analysis of airborne particles, combined application of
three methods, i.e., XRPD, EPMA and TEM, can provide comprehensive and
reliable results. In the studies of dust contamination on electrical
contacts, soft dust particles may contribute to the electrical contact
failures; their effects can not be ignored
Sliding electric contact experiments show that, in dusty
environments, liquid lubricants appear to perform better than wax
lubricants. Experimental and theoretical analysis indicates that high
permittivity of the lubricants plays an important role in attracting
dust. The mixture of dust particles and wax could be very harmful to the
contact, especially under low normal force. Dust particles floated on
the surface of liquid droplets appear to have high mobility, which
reduces the dust problem. Electric current flowing through the contacts
possibly melts the wax and decreases contact resistance. On the
contrary, electric current weakens the mobility and floating ability of
dust on the liquid surface, which leads to an increase in resistance.
Simply reducing the contact size can cause the embedding of dust into
wear tracks in low normal force applications
The porosity of electric contacts caused by dust contamination during gold plating was much more serious than that caused by simply a roughness of the substrate. Nevertheless, experimental results showed that even when plating on a dusty substrate, porosity was still closely related to the substrate roughness. Dust contamination on rougher substrates produced larger numbers of pores. Pores caused during gold plating were inspected by both scanning electron microscopy and X-ray energy spectrometry. Silicon and aluminium, as well as other elements of dust particles found in the pores, showed the existence of dust contamination on the substrate. Various chemical and ultrasonic cleaning methods were tested in an attempt to improve the plating quality and to reduce pore formation at the contacts. It was found that ultrasonic cleaning in acetone for more than 20 minutes is necessary for reducing porosity and increasing the sliding duration
Dust deposition is influenced by many factors such as orientation
of the coupon, electric static field, and permittivity of the lubricant
which covers the coupon surface. Morphology of the surface is found to
be an important factor which effects the dust size and density
distribution curve: the rougher the surface, the larger the particles
that are deposited. This phenomena is explained theoretically by means
of the balance among various forces, including electric attracting force
and mass gravity force of the dust particle. Experimental results showed
that electric contact failure is closely related to the particle size
and the morphology of the contact surface. Theoretical analysis
indicates that there is a hazardous size range of the dust particles,
within which dust particles are difficult to be moved away from the
contact and thus cause the contact failure
The deposition of natural and artificial materials onto electrical contact surfaces within telecommunication equipment has resulted in many equipment failures. Dealing with these contaminants is a continuing problem that requires the use of a variety of analytical techniques and imagination in order to find solutions. A number of problems that have occurred in the field are discussed in terms of 1) the nature of the problem, 2) analytical methods required, 3) identification of contaminating material and source, and 4) recommendations on equipment restoration. Chemical contamination of electrical contacts can result in the deposition of insulating films that produce electrical opens, as in the case of si!icone o!l degradation on arcing contacts or in the case of dust accumulation on Surfaces. These insulating films can also produce intermittent electrical problems. Alternatively, contaminants can result in electrical leakage as in the cases of water damage, silver migration, and ozone attack of hard rubber insulators. The sources of these chemicals can be a manufacturing procedure, the operating environment, or even outgassing from other parts within the equipment. Some of the areas reviewed include equipment damage from dust contamination, gases and vapors, floods, rain, and water leaks, fires, and contamination arising during manufacture.
Dust seriously influences the reliability of electric contacts. Evidence shows that failure of electric equipment is closely relaterl to this problem. Scanning electron microscope (SEM) photos investigating the morphology and size distribution of the dust particles are shown. The composition of the particles was examined by X-ray energy spectroscopy (XES). Electric contact experiments show that the contact resistance was not only affected by the geometry of the surface but also strongly dependent on the normal force and electric current effect which causes nonlinear and irreversible contact resistance. Theoretical explanation for these phenomena is given by means of the plastic deformation which is due to the load or the joule heating that causes dust particle embedding into the surface. Increasing load or electric current is not an acceptable solution. Future work for dust research is also briefly discussed.
Sliding electric contact experiments show that in dusty
environments, liquid lubricants appear to perform better than wax
lubricants. Experimental and theoretical analysis indicates that high
permittivity of the lubricants plays an important role in attracting
dust. The mixture of dust particles and wax could be very harmful to the
contact, especially under low normal force. Dust particles floating on
the surface of liquid droplets appear to have high mobility, which
reduces the dust problem. Electric current flowing through the contacts
possibly melts the wax and decreases contact resistance. On the
contrary, electric current weakens the mobility and floatability of dust
on the liquid surface, leading to an increase in resistance. Simply
reducing the contact size may cause the embedding of dust into wear
track in low-normal-force applications
Characteristics of dust deposition and the effect of dust on electric contacts
- J G Zhang
Water soluble salts in dust and their effects on electric contact surfaces
- J W Wan
- J C Gao
- X Y Lin
- J G Zhang
Electrical contacts, principles and applications. Chapter 2 Introduction to contact tarnishing and corrosion
- P Slade
Tidal corrosion and concentric rings on gold plated contacts
- J G Zhang
- X Y Lin
- Y L Zhou
- J B P Williamson
Reliability of contact components (Japanese)
- K Mano
Development of a new connector dust test
- L White
FEM analysis on stationary contact
- D Wang
Economic effects on air pollution on electrical contacts
- R C Robbins
Preliminary investigation on error code ratio of high speed digital circuitry by electric contact failure
- B S Sun
- Y L Zhou
- X Y Lin
- J G Zhang
Water soluble salts in dust and their effects on electric contact surfaces
- wan
Tidal corrosion and concentric rings on gold plated contacts
- zhang