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Determinative locating and riveting distortions are highly coupled at assembly locale. Recent methods only take every tested or assumed locating errors at the mating surface into the process planning for the assemblies in a simple form. However, the growth of part number makes it nearly infeasible to take every locating error at every mating surface into the dimensional precision calculation. This paper aims to provide a solid riveting process planning for the reduction of practical locating-related distortions.

Large-scale metrology firstly measures the determinative coordinates for the locating-deviated key points. Iterative finite element (FE) analyses then calculate the riveting-related key point distortions from every rivet upsetting directions (UDs) and assembly sequence. These key points on the actual assembly contour and relative FE nodes yield two virtual planes. Virtual plane manipulation adds the riveting distortions into the locating-deviated coordinates. Finally, optimal algorithm integrates the iterative FE analyses with virtual plane manipulation.

Case studies validate that the virtual plane manipulation coincides with the test well, and the proposed method has good compensation of practical locating distortion.

The optimized rivet UDs may be set in a chaotic distribution, which may complicate the abundant riveting operations and the assembly appearance. Therefore, the use of automatic riveting systems can overcome the operational complexity, and the industrial design of rivet UD distribution will improve the assembly appearance.

The optimized UDs and assembly sequence are for assembly workers or automatic riveting systems.

The proposed method is the first to reduce the determinative locating distortion by a novel and efficient solid riveting process planning in detail, and the solid riveting process designed is conservative and accurate for practice.

The purpose of this paper is to improve the accuracy and signal-to-noise ratio (SN) of a crop nitrogen sensor.

The accuracy and wide adaptability of two spectral calibration methods for a crop nitrogen sensor based on standard reflectivity gray plates and standard detector, respectively, were compared.

The calibration method based on standard detector could significantly improve the measurement accuracy and the SN of this crop nitrogen sensor. When compared with the method based on standard gray plates, the measurement accuracy and the SN of the crop nitrogen sensor calibrated based on the standard detector method improved by 50 and 10 per cent, respectively.

This research analysed the calibration problems faced by the crop nitrogen sensor (type CGMD302) based on standard gray plates, and proposed a sensor calibration method based on a standard detector. Finally, the results of the two calibration methods were compared in terms of measurement accuracy and the SN of the crop nitrogen sensor.

Gives an in depth view of the strategies pursued by the world’s leading chief executive officers in an attempt to provide guidance to new chief executives of today. Considers the marketing strategies employed, together with the organizational structures used and looks at the universal concepts that can be applied to any product. Uses anecdotal evidence to formulate a number of theories which can be used to compare your company with the best in the world. Presents initial survival strategies and then looks at ways companies can broaden their boundaries through manipulation and choice. Covers a huge variety of case studies and examples together with a substantial question and answer section.

Man has been seeking an ideal existence for a very long time. In this existence, justice, love, and peace are no longer words, but actual experiences. How ever, with the American preemptive invasion and occupation of Afghanistan and Iraq and the subsequent prisoner abuse, such an existence seems to be farther and farther away from reality. The purpose of this work is to stop this dangerous trend by promoting justice, love, and peace through a change of the paradigm that is inconsistent with justice, love, and peace. The strong paradigm that created the strong nation like the U.S. and the strong man like George W. Bush have been the culprit, rather than the contributor, of the above three universal ideals. Thus, rather than justice, love, and peace, the strong paradigm resulted in in justice, hatred, and violence. In order to remove these three and related evils, what the world needs in the beginning of the third millenium is the weak paradigm. Through the acceptance of the latter paradigm, the golden mean or middle paradigm can be formulated, which is a synergy of the weak and the strong paradigm. In order to understand properly the meaning of these paradigms, however, some digression appears necessary.

This study aims to study the mechanical, photoelectric, and thermal reliability of SAC307 solder joints with Ni-decorated MWCNTs for flip-chip light-emitting diode (LED) package component during aging. By adding nanoparticles (Ni-multi-walled carbon nanotubes [MWCNTs]) to the solder paste, the shear strength and fatigue resistance of the brazed joint can be improved. However, the aging properties of Ni-modified MWCNTs composite solder joints have not been deeply studied. In this research, the mechanical, photoelectric and thermal reliability of SAC307 packaged flip-chip LEDs with Ni-MWCNTs added during aging were studied.

Compared with SAC solder alloys, the effects of different contents (0, 0.05, 0.1 and 0.2 Wt.%) of Ni-MWCNTs on the photoelectric and thermal properties of composite solder joints were examined. To study the aging characteristics of composite solder joints, the solder joints were aged at 85°C/85% relative humidity.

The addition of an appropriate amount of reinforcing agent Ni-MWCNTs reduces the density of the composite solder to 96% of the theoretical value of the SAC solder alloy. In addition, the microhardness increases and the wetting angle decreases. Two different phase compositions were observed in the solder joints with Ni-MWCNTs reinforcement: Cu₃Sn and (Cu, Ni)₆Sn₅. The solder joints of SAC307-0.1Ni-MWCNTs exhibit the highest luminous flux and luminous efficiency of flip-chip LED filaments, the lowest steady-state voltage and junction temperature. And with the extension of the aging time, its aging stability is the best. In short, when the addition amount of Ni-MWCNTs is 0.1 Wt.%, the solder joints exhibit the best wettability and the thinnest intermetallic compound layer. And the shear strength of the tested solder joints is the best, and the void ratio is the lowest. At this time, the enhancement effect of Ni-MWCNTs on the composite solder has been best demonstrated.

The content range of enhancer Ni-MWCNTs needs to be further reduced.

The authors have improved the performance of Ni-modified MWCNTs composite solder joints.

Composite solder with high performance has great practical application significance for improving the reliability and life of the whole device.

This paper aims to systematically study the effects of reflow temperature and SAC0307 (SAC) content on the micromorphology and mechanical properties of Sn58Bi-xSAC0307 composite solder joints to meet the requirements of high integration and low-temperature packaging of devices and provide references for the application of composite solder joints.

Sn58Bi and SAC0307 solder paste was mechanically mixed in different proportions to prepare Sn58Bi-xSAC0307/ENIG solder joints. The thermal properties, microstructure and mechanical properties of the composite solder joints were studied.

As SAC content in the solder increases, the balling temperature of SnBi-SAC solder gradually increases. The addition of SAC alloy reduces the grain size of large Bi-rich phase, and there are small-sized dispersed Bi and Ag3Sn particles in the bulk solder. The intermetallic compounds composition of the SnBi-xSAC/ENIG solder joint changes from Ni3Sn4 to (Ni, Cu)3Sn4 and (Cu, Ni)6Sn5 with SAC increasing. As the soldering temperature increases, the strength of all solder joints shows a rising trend. Among them, the shear strength of SnBi-20SAC solder joints at a reflow temperature of 150°C is approximately 37 MPa. As the reflow temperature increases to 250°C, the shear strength of solder joints increases to approximately 67 MPa.

This study provides a reference for the optimization of low-temperature solder composition and soldering process under different package designs.

Summarizes the literature on mentoring and its effects, pointing out that little research has been done on international mentoring despite globalization. Considers how mentoring could be used to help accountants make international assignments into successful learning experiences and to cope with the culture shock they often report. Discusses the possible role of the mentor before, during and after the assignment, highlighting the critical factors during the process; and compares horizontal and vertical approaches. Urges accounting firms to use mentoring to improve international performance and as a basis for organizational learning in a global environment.

The purpose of this study is to address two kinds of printed circuit board (PCB) failures with electrolytic Ni/Au as the surface finish. One was the weak bondability of gold wires to Ni/Au pads and the other was “dull gold” and weak solder wettability, which both caused great loss for the PCB manufacturer.

The failure samples were studied and analyzed in terms of macro- and micro-morphology of the surface finish, its element composition and thickness by various characterization techniques, such as three-dimensional stereo microscope, scanning electron microscope, energy dispersive spectroscopy and X-ray fluorescence spectrum.

Then the causes of the two failures were both found to be the inadequate thickness of gold deposit and other surface finish defects, but these causes played different roles in either failure or the mechanisms differ. Finally, their failure mechanisms were discussed and corresponding countermeasures were put forward for prevention.

This study not only addresses a practical failure problem but also provides some clues to a better and further understanding of the effect of PCB process and management on its quality and reliability in manufacturing practice.

It sheds light on how the thickness and quality of surface finish affects its wire bonding and soldering performances.

The purpose of this paper is to improve the seal performance by proper design of the cavity shape of the damping holes, especially the rotordynamics characteristics of the hole-pattern damped seal (HPDS).

A new damping seal structure that comprises a circle-shaped cavity and two directional leaf-shaped cavities with a dovetail-shaped diversion groove is proposed. The comparative study on the sealing characteristics of dovetail-shape, leaf-shape and classical circular HPDSs was carried out using ANSYS CFX.

The dovetail-shaped HPDS significantly outperformed two other damping seal designs in leakage and rotordynamic performance. At a rotating speed of 7,500 rpm, it showed a 25% reduction in leakage, a 23% increase in average effective damping and a 119% increase in average effective stiffness. The cross-coupled stiffness K_xy shifted from positive to negative, reducing circumferential flow. The dovetail's inclined leaf-shaped grooves create a double vortex that slows jet velocity in the seal clearance and alters spiral flow direction, resulting in a uniform pressure distribution and enhanced rotor stability at low frequencies.

This study proposes a novel HPDS with dovetail-shaped diversion grooves. The seal can realize the simultaneous improvement of rotordynamics and leakage characteristics compared to the current seal structure.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2024-0127/