Inspection of the contaminants at failed connector contacts

2006

Journal of The Electrochemical Society, 2006

Corrosion of electronic components can produce a wide range of failure signatures, from intermittent electrical faults to complete functional breakdown. This paper presents an investigation on the exposure of a simple connector-coating system. The system consists of a copper contact coated with a nickel layer underneath a gold finish layer. The system was characterized using the following techniques: optical microscopy, atomic force microscopy ͑AFM͒, scanning electron microscopy ͑SEM͒, energy dispersive X-ray spectroscopy ͑EDAX͒, secondary ion mass spectroscopy ͑SIMS͒ and focused ion beam ͑FIB͒. After initial characterization, the connector was exposed to 2, 4, 7, 15, and 30 days in an aggressive environment consisting of 90% relative humidity, 40°C, and 4 ppm H 2 S. Digital images of the corrosion products that developed on the contacts after exposure clearly demonstrated localized corrosion by-products present on the connector surface. SEM, EDAX, and SIMS analysis of the corrosion sites demonstrated the presence of copper sulfide and nickel sulfur corrosion product, which suggest a two-step mechanism: first, the Ni layer is attacked by the aggressive environment at the sites where the gold layer is not available, followed by the diffusion of copper through the nickel layer. FIB cross-sectional analysis revealed that surface defects in the gold layer resulted in sites for corrosion initiation and subsequent development of a thick copper sulfide layer of approximately 5 m. It is concluded that this copper connector coating system does not prevent the formation of insulating corrosion products on the surface of the connector in a very aggressive environment.

2021

International audienceReliability of connectors is still a major concern for end users in many applications. One way to improve it is to optimize the surface coatings deposited on base substrates. Although gold remains the most widely used contact plating material, many alternative coatings have been developed in the past or recent years. Among these alternatives are silver final coatings and gold flash over palladium-nickel plated alloy. The properties of these two platings have been mainly investigated in symmetrical configurations where male and female contacts have similar deposits. In this work, asymmetrical configurations - where platings on male and female contacts are dissimilar - are studied. Wear behaviour was investigated with friction and fretting tests. The aim was to characterize the role of the various layers on the wear performances of contacts. Contact resistance behaviours were measured and correlated to the wear tracks investigated with various techniques such as ...

The European Physical Journal Applied Physics, 2010

Due to ongoing miniaturization in electronics, connector contact designs have to follow the same trends. The prediction of the mechanical and electrical performance of low force connector contacts becomes increasingly important. This paper shows a new approach to model the elastic plastic contact of two multi-layered nonconforming rough bodies subjected to pressure and shear traction. Three main considerations will be presented. 1. To investigate the influence of the surface topography on contact performance, measured three dimensional digitized surfaces are not always available. Hence a numerical description of a 'real' rough surface is of great importance. It can be shown that an engineering surface can be modeled by five scale independent parameters: RMS roughness, x/y correlation length, kurtosis and skew. 2. Based on Papkovich Neuber Potentials and both multi grid and conjugate gradient methods, a numerical algorithm has been developed to calculate the stresses and deformations in a contact system with up to three different layers per contact partner. The plastic deformation of the individual contact points (a-spots) can be interpolated using different material hardening behaviors. 3. If the a-spot distribution is known, the constriction resistance of the true contact area can be calculated. The voltage drop inside the contacting bodies is interpolated by solving the Laplace equation iteratively. The different electrical properties of the contact layers as well as the interaction of the individual a-spots, is also taken into account. The simulation algorithms are validated using a Au/Ni/CuSn6 contact system. The results show excellent agreement between measured and simulated contact resistance results over a normal force range from 1 gram up to 250 grams. The algorithms are implemented with an 'easy to use' windows interface "First Contact". The software also incorporates a material database that when used together with a surface modeler, allows for the fast calculation and 3d visualization of all mechanical and electrical contact characteristics..

IEEE Transactions on Components and Packaging Technologies, 2000

Components, Hybrids, and …, 1983

Absrruct-The interaction of organic vapors, evolving from connec-tor housings, printed wiring boards (PWB's), and wire insulations, etc., with the connector contact materials may cause the formation of surface films and a contact resistance (CR) increase. In this study, the results ...

2005

The paper presents a review of research data published during last 40-year period in the field of electrical contact lubrication. The paper examines the role of lubrication in corrosion protection as a barrier between contact surfaces and atmospheric pollutants. For effective long-term corrosion protection, it is important to properly choose and thoroughly qualify a lubrication product for a specific contact material and a specific combination of environmental variables. Another use of lubricants is to protect contacts from mechanical wear and/or friction, and from degradation due to fretting. Conversely, use of inappropriate lubricants may induce a significant risk by producing degradation, collecting participate matter, and developing a high electrical resistance of the contact surfaces. It is very important to carefully choose the lubricants to maintain a stable contact resistance and preserve the physical integrity of the contact surface. This paper also analyzes the effect of chemical composition and consistency (fluids, greases, solid lubricants) on the durability of lubricants in regards to various types of contact material, design and load.

Electrical Contacts - 2006. Proceedings of the 52nd IEEE Holm Conference on Electrical Contacts, 2006

Electrical contacts are used in a large number of industrial applications, this includes all sorts of modern transportation: airplanes, trains and automobiles. Mechanical assemblies are subjected to vibrations and micro-displacements between mating surfaces are observed leading to fretting wear. Mechanical degradation can additionally be accelerated by a corrosive factor caused by variable humidity, temperature and corrosive gas attack. Fretting-corrosion leads to an increase of contact resistance or intermittent contact resistance faults as corrosion products change the nature of the interface primary through a range of film formation processes. In this work the impact of a corrosion product film formed on copper and gold surfaces on the electrical contact fretting behavior is shown. It has been observed that modification of the interface by the formation of the surface layer can surprisingly lead to increase of the electrical contact durability.

Computer Methods and Experimental Measurements for Surface Effects and Contact Mechanics VIII, 2007

Electrical contacts are an essential part of electrical circuits and many reliability problems are related to their failure. The present work uses numerical simulation in view of a better analysis of the electromechanical phenomena, in the case of multilayer electrical contacts. We study a ball/plane contact made of bulk CuZn alloy, protected by a thin Sn surface layer. A coupled finite element analysis is performed in order to calculate the contact resistance of the device: an elasto-plastic model is used to determine the geometry of the contact area, then an electrical model gives the resulting constriction resistance. Results of the simulation are compared to experimental data. The respective contributions of the mechanical and electrical phenomena are analysed.

Wear, 2010

In this paper the transition from mild wear to severe wear of lubricated, concentrated contacts is dealt with. It is suggested that this transition is thermally induced. The transition from a mild wear to severe adhesive wear occurs when more then 10% of the surface transcends a predefined, critical temperature. A method for determining this critical temperature is presented. Using a BIM based numerical model including the local implementation of Archard's wear law, for the contact pressure and temperature the transition diagram for a model system is calculated and validated by experiments. The transition predicted by numerical calculations is in very good agreement with the experimental determined transition.