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From the viewpoint of degree of cure, the purpose of this paper is to find how to improve the reliability of flip‐chip packaging modules based on an anisotropically conductive adhesive film (ACF) interconnection process.

The work begins by revealing the correlation of adhesive strength and contact resistance of flip‐chip joint interfaces with the degree of cure of the ACF. The effect of different degrees of curing on the electrical and mechanical properties of some typical ACF‐interconnected joints is studied, and the optimum degree of cure is suggested to achieve highly reliable ACF joints, where the performance variations of the adhesion strength and contact resistance are considered simultaneously. First, the degradation data of the contact resistance of some ACF assemblies, bonded with several degrees of cure, is collected during a standard high‐hydrothermal fatigue test. The resistance distribution is verified using a two‐parameter Weibull model and the distribution parameters are estimated, respectively. After that, a reliability analysis method based on the degradation data of contact resistance is achieved, instead of the traditional failure time analysis, and the reliability index, as well as the mean‐time‐to‐degradation of the ACF joints, as a function of the degree of cure, is deduced, through which the optimum degree of cure value and recommend range are suggested.

Numerical analysis and calculations are performed based on the experiments. Results show that the optimum degree of cure to achieve highly reliable joints is 83 per cent, and the recommend range is from 82 to 85 per cent for the ACF tested (considering a 95 per cent confidence interval).

The paper provides important support for optimizing the curing process for various ACF‐based packaging applications, such as chip‐on‐glass packaging of liquid crystal displays and flip‐chip bonding of radio frequency identification, etc.

This paper aims to investigate the fire performance of composite beams when considering the hogging moment resistance of the fin-plate beam-to-girder joints including the effect of continuity of reinforcements.

Experiments on composite beams with fin-plate joints protected only at the beam ends are conducted. The test parameter is the specification of reinforcement, which affects the rotational restraint of the beam ends. In addition, a simple method for predicting the failure time of the beam using an evaluation model based on the bending moment resistance of the beam considering the hogging moment resistance of the fin-plate joint and the reinforcement is also presented.

The test results indicate that the failure time of the beam is extended by the hogging moment resistance of the joints. This is particularly noticeable when using a reinforcing bar with a large plastic deformation capability. The predicted failure times based on the evaluation method corresponded well with the test results.

Recent studies have proposed large deformation analysis methods using FEM that can be used for fire-resistant design of beams including joints, but these cannot always be applicable in practice due to the cost and its complexity. Our method can consider the hogging moment resistance of the joint and the temperature distribution in the axial direction using a simple method without requirement of FEM.

The aim of this paper is to implement direct teaching of industrial manipulators using current sensors. The traditional way to implement teaching is either to use a teaching pedant, which is time consuming, or use force sensors, which increases system cost. To overcome these disadvantages, a novel method is explored in the paper by using current sensors installed at joints as torque observers.

The method uses current sensors installed at each joint of a manipulator as torque observers and estimates external forces from differences between joint-driven torque computed based on the values of current sensors and commanded values of motor-driven torque. The joint-driven torque is computed by cancelling out both pre-calibrated gravity and friction resistance (compensation). Also, to make the method robust, the paper presents a strategy to detect unexpected slowly drifts and zero external forces and stop the robot in those situations.

Experimental results demonstrated that compensating the joint torques using both pre-calibrated gravity and friction resistance has performance comparable to a force sensor installed on the end effector of a manipulator. It is possible to implement satisfying direct teaching without using force sensors on 7 degree of freedom manipulators with large mass and friction resistance.

The main contribution of the paper is that the authors cancel out both pre-calibrated gravity and friction resistance to improve the direct teaching using only current sensors; they develop methods to avoid unsafe situations like slow drifts. The method will benefit industrial manipulators, especially those with large mass and friction resistance, to realize flexible and reliable direct teaching.

The purpose of this study is to put forward a high-strength bolt end-plate connection of prefabricated concrete beam-column joint and carry out the pseudo-static test.

ABAQUS finite element software is used to study the fire resistance performance of high-strength bolt end-plate prefabricated joint. This mainly considers the influence of axial compression ratio, screw preload, end-plate thickness and steel hoop thickness.

The results show that the thickness of end-plate and steel hoop has a certain effect on the fire resistance. The change of screw preload has little effect on the fire resistance limit. Compared with the cast-in-place concrete beam-column joint, the deformation trend of column-beam end of the fabricated joint is basically the same as that of cast-in-place joint.

To study the mechanical performance of this kind of joint more comprehensively, the finite element software is used to study the prefabricated concrete beam-column joint with end-plates, and the effects of axial compression ratio, screw preload, end-plate thickness and steel hoop thickness on the fire resistance of joints are mainly considered.

The purpose of this paper is to clarify the method of using RF impedance changes as an early indicator of degradation of solder joint. It proposes the mode of crack propagation in solder joint and outlines why RF impedance analysis can be capable of detecting small cracks. The study aims to show the potential of RF impedance analysis as a prognostic tool that can provide advanced warning of impending failures of solder joint.

In this paper, the mode of crack propagation in solder joint was studied to show why RF impedance analysis could be capable of detecting small cracks. A real simple impedance‐controlled test vehicle was developed to allow RF impedance and DC resistance measurements to monitor solder joint degradation. The influence of crack length on RF impedance was evaluated by high frequency structure simulator (HFSS) simulation for the first time.

The paper demonstrates that RF resistance can respond to an open state of a solder joint as well as DC resistance. Furthermore, RF impedance can monitor partial degradation of solder joints, while the DC resistance cannot do it. In addition, time‐domain reflection coefficient is found to be more useful than RF impedance in detecting solder joint degradation. The HFSS simulation results show that even very slight physical degradation of solder joints can be detected using RF impedance analysis.

In this paper, HFSS simulation is used for the first time to evaluate the influence of crack length on RF impedance.

The purpose of this paper is to discuss a new method to measure the fatigue of single solder joints in shear, and hence calculate the joint strain energy density in each fatigue cycle.

There has been a step change in the requirement to characterise solder joint reliability with the number of new alloys introduced as a result of the recent RoHS legislation. Experimental testing for every configuration is expensive and time consuming, and hence modelling has become more attractive. The accuracy of modelling predictions is limited by the accuracy of the materials data. The data for these new alloys must reflect the miniaturisation of electronics and that solder joints are loaded in shear, two aspects not well reflected in the existing SnPb data. The approach here has been to develop an instrument interconnect properties test machine, where the strain and stress can be measured directly for small solder volumes and in shear. A four‐point measurement system for resistance monitoring has also been evaluated and found to correlate well with load decreases recorded during fatigue testing of solders, and hence provide a method to calculate the crack area.

The experiments have recorded the stress strain behaviour during isothermal fatigue. The developing crack area has been measured using an electrical resistance technique and has been used to correct the stress values. Using the corrected stress the strain energy data can be calculated.

The work has been limited to a single alloy and a single joint configuration, with time these will be broadened and the experimental fatigue parameters extended.

These measurements will provide a route for calibrating the finite element models. A databank of material properties could be built up for alloys used in a range of configurations. This would help support and widen the use of modelling to predict fatigue life.

There is an increasing awareness of the importance of measuring microelectronic solder joint fatigue properties. There are a number of approaches being pursued, but the work at NPL is important in allowing the experiment to be controlled by either stress, strain or temperature, and with the added ability to measure crack area. This uniquely enables the measurement directly of the strain energy density during a fatigue experiment.

The high specific strength makes magnesium alloys have a wide range of applications in aerospace, military, automotive, marine and construction industries. However, its poor corrosion resistance and weldability have limited its development and application. Friction stir welding (FSW) can effectively avoid the defects of fusion welding. However, the microstructure, mechanical properties and corrosion behavior of FSW joints in magnesium alloys vary among different regions. The purpose of this paper is to review the corrosion of magnesium alloy FSW joints, and to summarize the protection technology of welded joints.

The corrosion of magnesium alloy FSW joints includes electrochemical corrosion and stress corrosion. This paper summarizes corrosion protection techniques for magnesium alloys FSW joints, focusing on composition, microstructure changes and surface treatment methods.

Currently, this research is mainly focused on enhancing the corrosion resistance of magnesium alloy FSW joints by changing compositions, structural modifications and surface coating technologies. Refinement of the grains can be achieved by adjusting welding process parameters, which in turn minimizes the effects of the second phase on the alloy’s corrosion resistance.

This paper presents a comprehensive review on the corrosion and protection of magnesium alloys FSW joints, covering the latest research advancements and practical applications. It aims to equip researchers with a better insight into the field and inspire new studies on this topic.

Duplex stainless steel is composed of equal amounts of austenite and ferrite, which has excellent corrosion resistance and strength. However, after the metal was welded, the ratio of austenite and ferrite in the joint is unbalanced, and secondary phase precipitates are produced, which is also an important cause of pitting corrosion in the joint.

This paper aims to study the mechanical and corrosion behavior of welded joints, by adjusting the welding parameters of laser hybrid welding, dual heat sources are used to weld 2205 duplex stainless steel. The two-phase content of different parts of the welded joint is measured to study the influence of the ratio of the two-phase on the mechanical and corrosion properties of the joint.

The ratio of austenite and ferrite in different welded joints has an obvious difference, and from top to bottom, the austenite content decreased gradually, and the ferrite content increased gradually. The harmful phases are precipitated in the middle and lower part of the joint. The strength of welded joints is slightly lower than that of base metal. At the same time, the fracture analysis shows that some ferrite phases are affected by the precipitate in the grain and produce quasi-cleavage fracture. The corrosion results show that the corrosion resistance of the welded joints is lower than that of the base metal, and the concentration of chloride ions affects the corrosion resistance.

In this paper, the authors use the influence of different welding processes on the two-phase ratio of the joint to further study the influence of the microstructure on the corrosion resistance and mechanical properties of the weld.

The resistance, capacitance and inductance of anisotropic conductive film (ACF) connections determine their high frequency electrical characteristics. The presence of capacitance and inductance in the ACF joint contributes to time delays and cross‐talk noise as well as simultaneous switching noise within the circuit. The purpose of this paper is to establish an experimental method for estimating the capacitance and inductance of a typical ACF connection. This can help to provide a more detailed understanding of the high frequency performance of ACF assemblies.

Experiments on the transient response of an ACF joint were performed using a digital oscilloscope capable of achieving the required ns resolution. An equivalent circuit model is proposed in order to quantify the capacitance (C) and inductance (L) of a typical ACF connection and this model is fitted to the experimental data. The full model consisted of two resistors, an inductor, and a capacitor.

The capacitance and inductance of a typical ACF connection were estimated from the measured transient response using Kirchhoff's voltage law. The method for estimation of R, L, and C from the transient response is discussed, as are the RLC effects on the high frequency electrical characteristics of the ACF connection.

There was decay time deviation between the calculation and the experiment. It may have resulted from the skin effect in the high frequency response and the adhesive surrounding joint as well. The main reason may be the capacitance zctric lost. Further research work will be done to determine more accurately the dielectric losses in anisotropic conductive adhesive (ACA) joint.

This paper presents a new method to characterise the high frequency properties of ACA interconnections and will be of use to engineers evaluating the performance of ACF materials in high frequency applications.

This paper aims to perform thermal and mechanical characterization for silver-based sintered thermal joints. Layer quality affects thermal and mechanical performance, and it is important to achieve information about how materials and process parameters influence them.

Thermal investigation of the thermal joints analysis method was focused on determination of thermal resistance, where temperature measurements were performed using infrared camera. They were performed in two modes: steady-state analysis and dynamic analysis. Mechanical analysis based on measurements of mechanical shear force. Additional characterizations based on X-ray image analysis (image thresholding), optical microscope of polished cross-section and scanning electron microscope image analysis were proposed.

Sample surface modification affects thermal resistance. Silver metallization exhibits the lowest thermal resistance and the highest mechanical strength compared to the pure Si surface. The type of dynamic analysis affects the results of the thermal resistance.

Investigation of the layer quality influence on mechanical and thermal performance provided information about different joint types.