Search results

The effects of varying reflow profiles on the tensile pull strength and structure of solder joints of components with tin plated and nickel‐palladium plated leads were studied. It was found that, in the case of tin plated leads, the structure and the tensile pull strength of the resultant solder joints were not significantly affected by varying the reflow conditions from Profile 1 (peak temperature range: 174°C to 195°C, reflow time 24 seconds) and Profile 2 (peak temperature range: 198°C to 218°C, reflow time 30 seconds). On the other hand, the mean pull strength of solder joints of nickel‐palladium plated lead was found to be significantly higher for joints reflowed with profile 2 than that of joints reflowed with Profile 1. Also, for both reflow profiles, the pull strengths of joints of nickel‐palladium plated leads were significantly higher than those of tin plated leads. This higher average pull strength may be due to the dissolution of palladium in the solder and/or the increased density of intermetallic precipitates in the solder fillet, and the increased intermetallic layer thickness at the lead/solder interface.

This paper aims to present an analytical approach for the determination of helical gear tooth geometry and introduces the necessary parameters. Tooth geometry including tooth chamfer, involute curve, root fillet, helix as well as tooth microgeometry can be obtained using the presented approach.

The presented analytical approach involves deriving the equivalent equations at the transverse plane rather than the normal plane. Moreover, numerical evaluation of microgeometry modifications is presented for tooth profile, tooth lead and flank twist.

An analytical approach is presented and equations are derived and explained in detail for helical gear tooth geometry calculation, including tooth microgeometry. Method 1, which was presented by Lopez and Wheway (1986) for obtaining the root fillet, is examined and it is proven that it does not work accurately for helical gears, but rather it works perfectly in the case of spur gears. Changing the normal plane parameters in Method 1 to the transverse plane ones does not give correct results. Two alternative methods, namely, Methods 2 and 3, are developed in the current research for the calculation of the tooth root fillet of helical gears. The presented methods and also the numerical evaluation presented for microgeometry modification are examined against the geometry obtained from Windows LDP software. The results show very good agreement, and it is feasible to apply the approach using the presented equations.

In the gear design process, it is important to model the correct gear tooth geometry and deliver all related dimensions and calculations accurately. However, the determination of helical gear tooth geometry has not been presented adequately by equations to facilitate gear modelling. The detailed helical gear tooth root has been enveloped using software tools that can simulate the cutter motion. Deriving those equations, presented in this article, provides gear design engineers and researchers with the possibility to model helical gears and perform design calculations in a structured, applicable and accurate method.

Rapid feedback on the effect of changes in materials or assembly process parameters on solder joint quality is essential in process optimisation for fine pitch surface mount solder assembly. This is particularly the case where the demands of high volume production do not allow lengthy experimentation to be carried out on the production line. The greater precision and care required in analysis of fine pitch solder joints places a further constraint on the speed at which the analysis can be carried out. The techniques of microstructural analysis, solder joint mechanical strength testing and short duration environmental stress testing must be used to meet a rapid turnaround quality and reliability analysis requirement and to maximise the amount of information obtained from each stage of the analysis. Three case studies are detailed which demonstrate the use of these techniques in a high volume production context to provide rapid feedback on joint quality. The case studies have been selected for presentation not only to demonstrate the analysis techniques but also because they address issues which are of current interest due to the increased usage of fine pitch packages in production and the constraints on the use of solvents for cleaning of circuit boards. The studies are:

This paper is the second of a series dealing with the blowholing problem on through‐hole plated printed circuit boards. In the previous paper the authors have considered the impact of the problem on the UK electronics assembly industry. Here they consider the nature of the gas causing blowholes and voids, its origin and the kinetics of its generation and evolution. When a printed circuit board with plated‐through‐holes is wave soldered, the thermal spike of the molten solder activates the evolution of gas, sometimes in relatively enormous quantities. The gas is seen bubbling from the surface of the molten solder in the joint. Upon freezing, the solder either traps the gas in a void enclosed within the fillet or, if the gas is escaping from the surface as freezing occurs, forms a blowhole.

This paper aims to investigate the characteristics of ultra-fine lead-free solder joints reinforced with TiO₂ nanoparticles in an electronic assembly.

This study focused on the microstructure and quality of solder joints. Various percentages of TiO₂ nanoparticles were mixed with a lead-free Sn-3.5Ag-0.7Cu solder paste. This new form of nano-reinforced lead-free solder paste was used to assemble a miniature package consisting of an ultra-fine capacitor on a printed circuit board by means of a reflow soldering process. The microstructure and the fillet height were investigated using a focused ion beam, a high-resolution transmission electron microscope system equipped with an energy dispersive X-ray spectrometer (EDS), and a field emission scanning electron microscope coupled with an EDS and X-ray diffraction machine.

The experimental results revealed that the intermetallic compound with the lowest thickness was produced by the nano-reinforced solder with a TiO₂ content of 0.05 Wt.%. Increasing the TiO₂ content to 0.15 Wt.% led to an improvement in the fillet height. The characteristics of the solder joint fulfilled the reliability requirements of the IPC standards.

This study provides engineers with a profound understanding of the characteristics of ultra-fine nano-reinforced solder joint packages in the microelectronics industry.

The findings are expected to provide proper guidelines and references with regard to the manufacture of miniaturized electronic packages. This study also explored the effects of TiO₂ on the microstructure and the fillet height of ultra-fine capacitors.

This paper deals with the thermal, chemical and metallurgical interactions between the printed circuit board and the solder wave. Special attention is devoted to the quality of the final solder fillet as a function of each variable. The individual zones inside of a solder wave is analysed. Their effect on the printed circuit and their components is explained. Guidelines for production parameters, i.e., solder temperature, conveyor speed, depths of immersion, impedance angle, hole‐to‐wire ratio, etc., are outlined. The wave solder operation cannot be isolated from fluxing and preheating; therefore, these two additional operations are also analysed. This will be limited, however, to those aspects directly related with wave dynamics. The paper concludes with a discussion of voids and entrapment in the solder fillet as they relate to the wave soldering process. A case history is used to outline the effect of voids on quality. Suggestions are made to avoid fillet imperfections such as blow holes, voids and incomplete fillets. Proper touch‐up procedures is also covered.

Peel adhesion of an epoxy filleting compound and Parylene C conformal coating to plasma treated, solder mask coated substrates and the apparent contact angle of water on the treated surfaces were evaluated. No significant improvement was achieved in the case of the epoxy filleting adhesive for most solder mask coatings studied. On the other hand, Parylene C peel adhesion significantly increased after substrates were treated with air plasma and reached the level of Silane coupling agent primed substrates. This was in contrast to the decrease in Parylene adhesion to argon plasma treated substrates in comparison with the non‐treated substrates. This was related to the oxygen functionalities created on the surfaces by the air plasma versus the ablative nature of the argon plasma. No clear correlation was found between peel strength and the water contact angle in the case of the epoxy adhesive, while for the Parylene conformal coating peel strength achieved its maximum value at the middle of the contact angle range which resulted from the pretreatments applied in this study. It is concluded that air plasma is a very efficient solder mask pretreatment for Parylene conformal coating that can replace Silane primer. Also, if a calibration curve is established for each solder mask‐adhesive and solder mask‐coating system, the apparent water contact angle can serve as a convenient quality control tool for printed circuit finishing processes.

Carp is a traditional aquaculture fish with decreasing relevance in European markets. Despite this, it is a protein source which could contribute to the worldwide protein supply. Traditional carp ponds are part of human cultural heritage with high relevance for biodiversity. But, market shares of carp are small compared to other seafood market, mainly due to low consumer demand. The aim of this research was to contribute to the discussion on how to increase demand for carp by testing the acceptance of selected preprocessed carp products.

A quantitative online survey was conducted in Germany and Poland with the aim of identifying consumers' attitudes towards carp and carp products. On this basis recommendations on how to best market carp products are developed.

Carp is perceived to be a fish eaten primarily at Christmas and New Year's Eve and to be difficult to prepare. The analyses reveal that a potential for novel carp products does exist in Germany and in Poland. The wider introduction of a bonecut filet to the market, a better availability of carp products, and the avoidance of off-flavors are important prerequisites for higher market relevance of carp.

In this research consumer preferences were elicited “theoretically” by showing pictures of carp products and asking them for their preferences. In this regard, the results presented here state a general consumer interest and a potential for new carp products. Further research, integrating product tastings might give additional information on the likely success of new types of carp products.

In order to let people know about the new products and at the same time to combat the sometimes existent bad image of carp, product tastings, also in combination with information regarding local origin and environmental/cultural impact, should be offered at the point of sale.

Carp is a highly sustainable fish and offers a valuable protein source for human consumption. But, in its common ways of market presentation it is not highly appreciated by consumers. This paper demonstrates options of overcoming this situation.

This paper aims to solve the lubrication failures in the turning arm bearing of RV reducer, give some help in perfecting the bearing structure design and provide theoretical basis for the reducer’s performance improvement.

The paper establishes a mixed lubrication analysis model to study performance parameters. According to the discretization of parameters and iteration of equations, numerical simulation and theoretical analysis are achieved in computational process.

Considering influences of contact load, real rough surface and realistic geometry of RV reducer turning arm roller bearing, the mixed lubrication analysis model is established to study the ratio of oil film thickness, pressure distribution and maximum von Mises stress in different speeds, temperatures and fillets. The results of mixed lubrication show that reasonable round corner modification, increase in temperature and speed, decrease of surface roughness and lubricant types can improve the lubrication performance.

The mixed lubrication analysis model is established to study the influences of contact load, real rough surface and realistic geometry of RV reducer turning arm roller bearing. Different speed, temperature, lubricant and fillet modification are also considered in the research to analyze oil film thickness, pressure distribution and maximum von Mises stress. These studies can optimize structural design of bearing and direct engineer operations.

The importance of the quality of the plated‐through‐hole copper barrel in double‐sided and multilayer PCBs is considered with regard to the problem of voids and blowholes in the solder fillet. The thickness of the copper, and its integrity and adherence to the drilled surface define its ability to withstand the pressure burst of gas from the outgassing laminate during the few seconds of the thermal spike induced by the molten solder prior to solidification. The ability of copper electroplate to bridge over areas devoid of electroless copper and produce a barrel free of pinholes is shown to be crucial to this problem. In addition, the use of a nickel layer is shown to enhance greatly the impermeability of the barrel to the evolving gases.