Connector Reliability Research Articles

Acceleration of Service Life Testing by Using Weibull Distribution on Fiber Optical Connectors

The service life assessment of previous fatigue stress has a fundamental role in estimating the reliability of products like fiber optical connectors, and should replicate use in severe environments in telecommunications systems. However, the vibration prediction models used in the literature present limitations in vibration life prediction. In this paper, we propose using the insertion loss fatigue life and including it in the Weibull distribution to determine the Weibull parameters ƞ and β to evaluate fiber optic connector reliability R(t) under environmental and mechanical testing stress. We analyzed the failure data of a standard telecommunication fiber optical connector under a program of service life stress testing against that of a fiber optical connector under only mechanical vibration stress testing. The fiber connectors were monitored during the vibration testing to review the transient change of the optical signal. Their results showed that the reliability of the fiber connectors submitted to the service life program was Rt=0.694, while that of the fiber connectors submitted to mechanical vibration only was Rt=0.970. In addition, the analysis showed that the service life testing consumed 70.2% of the product’s lifetime. We present in Numerical Validation the steps to determine the acceleration factors of the vibration test developed.

Impact of modularity as a circular design strategy on materials use for smart mobile devices

ABSTRACT

Experimental estimation of seismic properties of new precast shear wall spatial structure model

Effective seismic properties are a basic requirement in precast shear wall applications. Therefore, this study focuses on the evaluation and improvement of precast shear wall seismic properties using the new pore-forming grouted connector with welded closure confinement steels (NPGCS) developed in previous research. The NPGCS connector reliability was verified and the seismic properties of the NPGCS spatial structure model were evaluated by carrying out a low cyclic reversed lateral loads experimental test on the NPGCS precast shear wall spatial structure model containing superposed connecting beams and precast shear walls, which were selected from a practical high-rise precast residential building. According to the testing results of the crack distribution and component failure modes, the superposed connecting beam properties were weak, and damaged early in the shear failure mode, while the precast shear walls cracked after the steel bars in the superposed connecting beams yielded. Furthermore, the failure mode indicated that the NPGCS connection applied in this spatial model is reliable, while two new weak sections were proven to exist at the connector ends. Together with the precast joint interface slip, the dowel shear action is demonstrated to be harmful to the joint interface properties. Additional seismic parameters, namely capacity, ductility, stiffness and energy consumption, were used to complete the evaluation of the seismic properties of the NPGCS spatial structure model. Overall, although the NPGCS spatial model ductility is low, the strengths are high, leading to continued effective energy consumption properties, which indicates favourable seismic properties of the NPGCS spatial structural model.

A Novel Model of Reliability Assessment for Circular Electrical Connectors

The reliability of circular electrical connectors was usually assessed according to standards like MIL-HDBK-217 (Reliability Prediction of Electronic Equipment). Given to their limitations and mislead results, a new assessment method needs to be presented. Some concerns on the physics of failure (PoF) modeling and reliability assessment of circular electrical connectors are addressed in this paper to overcome this defect. An original approach combining laboratory accelerated degradation testing (ADT) and PoF modeling is proposed for effectively assessing connector reliability. Random vibration and current stress are selected as acceleration factors that affect the contact life of electrical connectors. Then, an appropriate multiple-stresses ADT scheme is derived. The PoF model for electrical connectors under multiple stresses yielded the generalized Eyring relationship. According to the system reliability model for multiposition connectors, connectors' life follows Weibull distribution, which is derived from extreme-value distribution theory. Through ADT and data gained from tests, statistical analysis result yielded the estimated value of reliability character of MIL-C-38999 I series electrical connectors under the action of vibration and current stresses.

Study of minimum fretting for connectors used in automotive applications

For automotive applications, the mechanical behaviour of the contact area under vibration is one of the key factors for connector reliability. Such vibrations on the bulk contact device are typically in the range of 10–2,000 Hz and result in displacements of only a few microns at the contact interface. In the present study, a bench test has been developed to control motions down to 1 $$\upmu $$ m. The objective is to determine the minimum amplitude for fretting-corrosion degradation based on the evolution of contact resistance and to study the effects of the material, the contact force, the coating, for these low displacement amplitudes. To obtain the limit of the appearance of fretting, a sub-micrometer incrementing displacement amplitude methodology was applied on a high stiffness bench test including a double piezoelectric actuator. It was found that the fretting degradation starts to occur from 2 to 6 $$\upmu $$ m when the contact force is from 0.5 to 2.5 N with a tin-coated terminal. Moreover, pure copper, tin and nickel have similar amplitude fretting limits while noble metals confirm the absence of fretting up to 10 $$\upmu $$ m amplitude and for a large number of operations (10 $$^{6 }$$ cycles). Best fitting of the obtained minimum fretting amplitude data to the Mindlin equation is discussed and improved by a correction factor.

Enhancing connector reliability by using conducting polymer materials to minimise contact fretting

A typical luxury car has in excess of 400 electrical connectors with over 3000 individual terminals. Tin plated terminals are still widely used because of particular technical and commercial advantages, but this type of plating is susceptible to fretting corrosion leading to intermittent high contact resistance. This phenomenon is well known to be the main failure mechanism impairing electrical system reliability. Novel contact materials, such as conducting polymers, are investigated in this study as a possible replacement for tin plated terminals used in the automotive wiring harness. The design concept behind using a polymer contact is to minimise any fretting motion between two contacting components by the polymer flexing or bending. Fretting studies are conducted on the polymer–tin interface showing the improved mechanical and electrical behaviour of this novel interface. A mechanical model of the polymer interface is developed showing its behaviour under fretting conditions. To achieve a “zero fretting” condition, the elastic force opposing the fretting action of the deflected polymer must be lower than the frictional force at the contact.

Contact Area Analysis by FEM with Plating Layer for Electrical Contact

Electrical contacts are the most important parts of electrical circuits, and many reliability problems of the circuits are related to contact failure. The contact resistance is one of the important factors for assessing connector reliability, and thus the prediction of contact resistance is essential to designing electrical terminals. In this study, embossments, each I mm to 3 mm in radius, were brought into contact with flat planes to simulate the point of contact on a terminal, and the contact resistance was measured using a four-probe method under a load up to 40 N. Copper alloy samples, each plated with tin or silver and having an embossment of 1 mm to 3 mm in radius, were used and the visually clear indentations resulting from the embossment to plane contact were measured to determine their areas. Since the contact resistance is dependent on the contact area, an FEM analysis must be carried out to determine the contact areas correctly. In this paper, an elasto-plastic FEM analysis was performed taking the plating layers into account, and a method was established to make precise determination of the contact areas for different shapes of contacts and loads. The resultant contact areas were used to calculate the contact resistance, which showed a good agreement with experimental results. It was established that the load-resistance curves can be predicted on the basis of the shapes of the contacts as well as plating.

Experimental and Analytical Studies of the Connector Insertion Phase

Studies of connectors for electric and electronic automotive systems have been and still are being pursued. The electrical connector reliability mainly depends on the connector insertion force. This force is related to the contact force which is imposed by the connector design. A nonintrusive technique for contact force determination by deflection measurement of the contact spring during insertion phase using a laser device has been developed. The following insertion parameters during the insertion stroke can be measured: contact deflection which yields the contact force, insertion force, and contact resistance. Regarding the results for real connectors, an experimental sample of a connector based on a cylindrical pin crossed with a cylindrical spring is proposed in this paper. With this simple setup, an mathematical model was developed and permits analysis of the influence of each parameter (width, spring radius, etc). Based on analysis of the influence of the spring width and of the gap, this study offers the possibility of optimizing the design of such connectors for use in the automotive industry.

Design improvement using process capability data

Historical process capability data (PCD) is commonly used during product design. Such data can be stored in a formal database known as a process capability database (PCDB). PCD is primarily used during product design to allocate tolerances or forecast and manage manufacturing variation. However using a PCDB for these purposes alone does not exploit its full potential. This paper describes a method by which PCD can be applied to predict product performance variation early in the design process, thus saving time and reducing subsequent redesign costs. More specifically it describes the use of PCD during the initial design stage to predict how the product will operate, in terms of functional reliability, after it has been manufactured. An illustrative example based on the design of an electrical connector is provided. In this case connector beam normal force is a strong indicator of connector reliability and the example shows how the variation of this normal force can be predicted during initial connector design.

Influence of high-optical power light launched into optical fibers in MT connector

This paper describes the influence of a high-optical power light launched into optical fibers in an mechanically transferable (MT) connector. The features of the MT connector are the use of index matching material to suppress Fresnel reflection and the accommodation of several optical fibers to allow the connection of optical fiber ribbons. First, we experimentally investigated the relationship between connection loss, launched light power, temperature increase, and optical loss increase using an MT connector sample without contamination. Based on the results, we clarified the relationship between the allowed connection loss and the launched optical power in the optical fibers needed to maintain MT connector reliability. In addition, we examined the influence of the contamination of the connector endface and confirmed that it is necessary to clean the endface appropriately in an optical transmission system that uses high-optical power light to prevent any fatal damage to the MT connector.

Radio-frequency connector and interconnect reliability in spaceborne applications

In addition to quality electronic components and subsystems, highly reliable interconnects are imperative in high-reliability applications such as spacecraft and satellites. System designers must therefore address and resolve issues related to the proper design and assembly process for connectors and interconnects for passive and active components. We have developed guidelines for the design of a space-qualifiable connector system based on our experience with defective hybrid couplers and power dividers, as well as our understanding of the material properties of the connector dielectric. We also discuss testing and the qualification of vendors of connectors and interconnects necessary to ensure high-reliability radio frequency and microwave components. >

Analysis of set screw and side-lock connector reliability.

A retrospective review of complications with connectors and lead-to-header interfaces was performed following 649 pacing procedures between 1980 and 1990. There were 88 lead revisions (13.6%), 81 device replacements or modifications (12.5%), and 480 new implants (74%) using devices of five manufacturers. Two basic connector types were studied, one utilizing a set screw and the other using a side-lock compression fitting. The set screw makes electrical contact and mechanically secures the lead connector pin with a set screw insulated by a self-sealing grommet or an integral or separate set screw cover. The side-lock makes electrical contact with an automatic spring mechanism while the plastic lead terminal is secured in the connector block of the pacemaker by a Delrin side-lock compression fitting. Four hundred fifty-nine set screw connector devices were followed for up to 12 years with 14 complications (3.1%) whereas 82 side-lock connector devices were followed for up to 5 years with one complication (1.2%). The set screw and side-lock connectors were reliable over the period of follow-up. Although the complication rate appeared lower with the side-lock, follow-up was shorter and the number of implants smaller. With the leads used in this study, the side-lock proved to be a desirable feature due to simplicity, speed, safety, and ease of use. One limitation is the requirement for a precise IS-1 connector terminal diameter.

Time-wise increases in contact resistance due to surface roughness and corrosion

To understand failure and estimate connector reliability, a connector model was made in which two mated rough copper surfaces were subjected to ingression and corrosive attack by atmospheric oxygen. The rough surface segments the connector contact area into many small discrete areas (a-spots) through which currents flow. The initial a-spot contact radii a/sub e/ (formed as metal-to-metal bridges by mating surface heights on the two mating surfaces) was determined by the externally applied load, connector materials, geometry, and surface topography. Later, corrosive attack of the metallic surfaces cause the metallic contact radii to shrink and resistances to increase. Factors in the model that influence the corrosive process are environmental temperature, partial pressure of oxygen, and geometric factors associated with the contact. Resulting curves of contact resistance versus time are similar in trend and shape to experimentally measured curves. From time variations of contact resistance of the connector, methods for estimating the useful lifetime of electrical connectors are also given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A field study of connector reliability : Thomas A. Yager and Kimberly Nixon. IEEE Trans. Components Hybrids Mfg Technol.CHMT-7, 370 (1984)

A field study of connector reliability : Thomas A. Yager and Kimberly Nixon. IEEE Trans. Components Hybrids Mfg Technol.CHMT-7, 370 (1984)

A Field Study of Connector Reliability

The objectives of this investigation were 1) to survey field support personnel on the reliability and use of connectors in electronic test and computer equipment; 2) to characterize the types of defects found on gold-plated edge card connector fingers from a large sample of printed wire assemblies (PWA's), obtained randomly from customer sites; and 3) to characterize the chemistry of the most prevalent defects found on the edge card connector fingers. The field support survey provided information on proper selection, use, and care of connectors used in electronic equipment. The microscopic examination of PWA edge card connector fingers indicated that the presence of a film covering the gold surface was the predominant defect found. Other defects observed included wear scratches, dust, pore corrosion, and a build up of debris at the metal-to-metal contact area. Defects such as edge corrosion and creep were observed, but on only very few PWA's. Chemical analysis of the film on the connector fingers found it to be primarily organic.

Insulation displacement connector reliability : Electron. Prodn 26 (November/December 1983)

Insulation displacement connector reliability : Electron. Prodn 26 (November/December 1983)

The assessment of connector reliability : R. T. Lovelock. Microelectron. & Reliab.12, 475 (1973)

The assessment of connector reliability : R. T. Lovelock. Microelectron. & Reliab.12, 475 (1973)

The assesment of connector reliability : R. T. Lovelock. Radio & Electron. Engineer43, No. 8 (August 1973). p. 486

The assesment of connector reliability : R. T. Lovelock. Radio & Electron. Engineer43, No. 8 (August 1973). p. 486

The assessment of connector reliability

The simple “U” curve concept used to express the MTTF of components as a means of estimating the MTBF of equipment is based upon a number of simplifying assumptions which are often forgotten when applying the simple rules which result. While the simple rules adopted are sufficiently accurate to give a good working value for many components, they are unrealistic when applied to connectors. Those features in which a connector fails to approximate to the simple model normally adopted are considered, and their effects on connector reliability noted. The operating conditions of connectors are grouped and analysed. From these considerations practical suggestions are made for obtaining an approximation to a value of connector reliability which would serve as a model for the forecasting of equipment reliability.

The assessment of connector reliability

The simple ‘U’ curve concept used to express the mean time between failures (m.t.b.f.) of components as a means of estimating the m.t.b.f. of equipment is based upon a number of simplifying assumptions which are often forgotten when applying the simple rules which result.While the simple rules adopted are sufficiently accurate to give a good working value for many components, they are unrealistic when applied to connectors. Those features in which a connector fails to approximate to the simple model normally adopted are considered, and their effects on connector reliability noted. The operating conditions of connectors are grouped and analysed. From these considerations practical suggestions are made for obtaining an approximation to a value of connector reliability which would serve as a model for the forecasting of equipment reliability.