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This study aims to investigate the effects of ball–material ratio on the properties of mixed powders and Cu-Bi self-lubricating alloy materials.

Cu-Bi mixed powder was ball milled at different ball–material ratios, and the preparation of Cu-Bi alloy materials was achieved through powder metallurgy technology. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were conducted to study the microstructure and phase composition of the mixed powder. The apparent density and flow characteristics of mixed powders were investigated using a Hall flowmeter. Tests on the crushing strength, impact toughness and tribological properties of self-lubricating alloy materials were conducted using a universal electronic testing machine, 300 J pendulum impact testing machine and M200 ring-block tribometer, respectively.

With the increase in ball–material ratio, the spherical copper matrix particles in the mixed powder became lamellar, the mechanical properties of the material gradually reduced, the friction coefficient of the material first decreased and then stabilized and the wear rate decreased initially and then increased. The increase in the ball–material ratio resulted in the fine network distribution of the Bi phase in the copper alloy matrix, which benefitted its enrichment on the worn surface for the formation a lubricating film and improvement of the material’s tribological performance. However, a large ball–material ratio can excessively weaken the mechanical properties of the material and reduce its wear resistance.

The effects of ball–material ratio on Cu-Bi mixed powder and material properties were clarified. This work provides a reference for the mechanical alloying process and its engineering applications.

Component positioning is an important part of aircraft assembly, aiming at the problem that it is difficult to accurately fall into the corresponding ball socket for the ball head connected with aircraft component. This study aims to propose a ball head adaptive positioning method based on impedance control.

First, a target impedance model for ball head positioning is constructed, and a reference positioning trajectory is generated online based on the contact force between the ball head and the ball socket. Second, the target impedance parameters were optimized based on the artificial fish swarm algorithm. Third, to improve the robustness of the impedance controller in unknown environments, a controller is designed based on model reference adaptive control (MRAC) theory and an adaptive impedance control model is built in the Simulink environment. Finally, a series of ball head positioning experiments are carried out.

During the positioning of the ball head, the contact force between the ball head and the ball socket is maintained at a low level. After the positioning, the horizontal contact force between the ball head and the socket is less than 2 N. When the position of the contact environment has the same change during ball head positioning, the contact force between the ball head and the ball socket under standard impedance control will increase to 44 N, while the contact force of the ball head and the ball socket under adaptive impedance control will only increase to 19 N.

In this paper, impedance control is used to decouple the force-position relationship of the ball head during positioning, which makes the entire process of ball head positioning complete under low stress conditions. At the same time, by constructing an adaptive impedance controller based on MRAC, the robustness of the positioning system under changes in the contact environment position is greatly improved.

The purpose of this paper is to analyze the force and basic rating life of angular contact ball bearings of RV reducer under the actual operating condition.

Force analysis of angular contact ball bearing under the actual operating condition, calculate the axial, radial load and internal load distribution, calculate the basic rating life of angular contact ball bearing under variable load conditions.

The external load has a great influence on the radial load of angular contact ball bearing, further affecting the basic rating life of angular contact ball bearing, which is a great influence on the overall life of RV reducer under the condition of high frequency and heavy load.

This paper provides important ideas for the design and manufacture of RV reducer in theory and experiment technology.

The alignment precision of existing methods is limited by the precision of detecting element and worker’s experience, which the parallelism between ball screw and guide way is not guaranteed effectively. Thus, this paper aims to propose a method of detecting ball screw’s alignment error (BSAE) via monitoring the average vibration magnitude induced by rotational frequency of ball screw (VMRFBS).

In this study, the ball screw is simplified as a freely supported beam. A mathematical model of the effect of BSAE on the contact angle of the ball and screw is established. The change of contact angle has effect on the deformation and contact stiffness according to the Hertz contact theory. To improve the accuracy of the experimental results, the VMRFBS are analyzed by using average method, and the average values of the VMRFBS at different BSAEs are calculated by using the least squares method.

The experimental results show that the average VMRFBS increases with the increasing of BSAE under the BSAE from 0 to 0.2 mm, while the other conditions are unchanged.

This method provides an approach to monitor the BSAE and improve the alignment accuracy of machine tools and automation equipment, which has a certain guide for improving the alignment accuracy of ball screw.

A ball is the main instrument in most outdoor games, and be it football, baseball, cricket, tennis or golf, the common aim is controlled flight in the air. Superficial considerations of the mechanics of a ball in free flight may suggest that the ball describes a simple arc with trajectory in one vertical plane. This rarely happens; it climbs, plunges, swerves laterally and even stalls. It seems to possess a will of its own which defeats most players of all games, yet when exploited by a master of any one of them is a thrill to watch, e.g. an in‐swinging corner‐kick landing in the net, a straight driven golf ball boring into the wind, a cricket ball bowled with late swerve, a tennis ball topping the net and diving to the court, to list but a few. For these things to happen some complex force must act on the ball. This force, since it can come only from the air, is an aerodynamic force. Many learned papers have been written on rotating cylinders and spheres but few of them can be understood by an intelligent layman. It is the purpose of this article to explain in a simple way how this force comes about.

An evaluation of the feasibility of copper ball‐wedge bonding on Au, Cu thick film and aluminium metallisations was carried out. This evaluation is not merely a check for feasibility, but will also give more insight into the problems concerning copper ball‐wedge bonding. This article does not pretend to represent profound research on copper ball bonding, but will give qualitative insight. Copper ball bonding, without using cover gas, is possible, but the bond quality decreases. Extrusion and penetration of the ball bond in the substrates are caused by the hardness of the copper. This can only be avoided when the hardness of the substrate is matched to the hardness of the copper ball/wire. Bonding mechanisms are similar for bonding on thick film to those for bonding on metallisations. Matching hardness of the substrate to the ball/wire seems to be a necessity for proper ball‐wedge bonding.

The purpose of this paper is to develop a cost effective ball grid array (BGA) workcell for solder ball attachment.

This paper presents the construction of a low‐cost high‐efficiency automatic ball attachment workcell. In fact, it is an economical means of simultaneous placement of all solder balls on BGA substrates containing multiple BGA units as well as singulated substrates. Common industry problems such as the effect of static charges, the solder ball oxidation, the missing ball, the extra ball, the ball alignment, the deformed ball and, etc. will be addressed and critical issues affecting yield will also be discussed in this paper.

BGA is a popular integrated circuit packaging that is often applied in laptop computers and other handheld electronic devices for the provision of a high‐connection count in a relatively small area. However, the cost of a market available BGA solder ball attachment workcell is very expensive and the flexibility in fitting various customized process is usually low.

The developed workcell cost is about half of the market available machines with similar specifications; the yield achieved is within three sigma confidence interval with competitive output rate. The maintenance and troubleshooting are easy since the machine was developed by the in‐house engineering team.

This paper aims to provide thermal elastohydrodynamic lubrication (TEHL) contact model to study all balls’ lubrication performance of the ball screw when the multidirectional load is applied.

A new TEHL contact model combining the multidirectional load and the roughness surface texture is established to describe fatigue life of the ball screw. Meanwhile, the authors use the Reynolds equation to study the lubrication performance of the ball screw.

When the multidirectional load is applied, contact load, slide-roll ratio and entrainment velocity of all balls have a periodic shape. The TEHL performance values at the ball-screw contact points including contact stress, shear stress, minimum film thickness and temperature rise are higher than that at the ball-nut contact points. The TEHL performance values increase with the increase of root mean square (RMS) except for the film thickness. In addition, the radial load of the ball screw has a significant effect on the fatigue life.

The results of the studies demonstrate the new TEHL contact model that provides the instructive significance to analyze the fatigue life of the ball screw under the multidirectional load.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2020-0097/

Presents the results of a study of the effects of solder ball pad metallurgy, intermetallic compound (IMC) thickness and thermal cycling on the shear strengths of PBGA package solder balls. The study of the microstructures of solder balls revealed that only a very thin layer of intermetallic compound existed between solder balls and Ni or Ni alloy barrier layers immediately after ball placement and reflow. The protective Au layer was dissolved completely and a needle like AuSn₄ intermetallic compound was then formed and dispersed evenly in the solder balls. The overall thickness of the IMC layers was thicker than 15μm after storage at 150°C for 1,000 hours. During the shear tests failure occurred at the interface of the two IMC layers. The fracture surfaces of solder balls with electrolytic Ni and thick Au layers were smooth and brittle fracture was observed. The ball shear strength decreased dramatically with the formation of IMC layers. For the solder balls with electroless Ni and thin Au layers, only a single IMC layer was formed at the interface and its thickness was only 2.5 μm after storage at 150°C for 1,000 hours.

A new alloy for lead‐free solder balls is introduced combining the advantages of a smooth surface after production and a uniform reflectivity after the ball attach process. This property significantly simplifies the inspection process during ball grid array (BGA) processing. By adding small amounts of Indium and Lanthanum to the ternary eutectic SnAgCu‐alloy a pentary, virtually eutectic composition with a melting point of 214°C is realised. It is shown that the processability in terms of reflow behaviour and the shear strength of BGA spheres made of this alloy is comparable to or better than that of ternary SnAgCu‐balls.