Search results

The benefits of Nitraclean I nitrogen inerted reflow soldering are well documented. However, there has been some debate as to the maximum oxygen level that can be tolerated by different types of paste if those benefits are to be realised. It is demonstrated that, for all paste types, solder balls decrease and the spread factor increases with increasing oxygen level, but that it has little effect on either joint strength or microstructure. It is concluded that for RMApastes a maximum oxygen level of 1000 ppm is required and that for low residue pastes the level needs to be reduced to 200 ppm for optimum results.

The purpose of this paper is to shed light on the body of logistics customer service (LCS) research published in leading logistics journals from 1990 to 2017. Specifically, the paper presents a call to arms for logistics and supply chain researchers to address new and emerging issues impacting customer service in the age of omnichannel and e-commerce retailing.

The authors reviewed academic journals to identify articles focusing on LCS from 1990 through 2017. The authors noted trends in academic research activity/focus and supplemented the findings by examining more recent trends covered in trade publication articles.

The authors observed a large amount of LCS research in the early 1990s and 2000s, but noticed a substantial decline in coverage within academic journals since the late 2000s while industry continues to give customer service issues even greater attention. The difference between the level of coverage within academic journals and the increased importance firms place on customer service represents a critical gap and opportunity for scholars. This research represents a “call to arms” to address this gap. With particular emphasis on observed customer impatience and escalating requests, within omni- and e-commerce channels of distribution, we suggest greater theoretical insights into customer service strategies and their role in successfully navigating today’s changing logistics service environment are needed.

The review serves as a call for more attention to customer service issues within leading logistics journals. Suggestions for research into new and emerging topics are offered.

For reflow soldering in today's changing component and soldering technology, requirements with respect to profiling seem to be difficult to determine and even harder to meet. State‐of‐the‐art reflow trackers can be of help here, but, without some knowledge of the fundamentals in profiling, it will be easy to misunderstand measurements. The use of nitrogen as a protective gas for reflow soldering can be advantageous for fine pitch technology, bare copper boards and low residue solder pastes. However, because reflow solder defects are related to more than just the use of nitrogen, one may find different benefits for the use of nitrogen, depending on how the investigations are carried out. Wetting under nitrogen is certainly better and more reproducible, while the near absence of oxygen is beneficial to oxidation‐related problems. For high numbers of solder joints per board, it is not easy to achieve an acceptable first pass yield. Only with low, controlled defect levels found within a robust reproducible process is it possible to achieve this. Using forced convection together with nitrogen for reflow soldering is becoming the preferred method.

Several effects of the atmosphere in the soldering oven on both the soldering process itself and the soldering results are discussed. Experiments have been undertaken to compare the results of soldering in air and in nitrogen containing 10,100 and 1000 ppm oxygen, in which, e.g., discolouration, wettability, solderability after reflow, solder bridging and solder‐ball formation were investigated. Unmounted FR‐4 testboards with both an RMA solder paste of known high quality and a low‐residue paste were used. Mounted test boards were used to analyse the self‐alignment of components and to compare the levels of soldering defects obtained in air and in nitrogen. The test results show that a nitrogen atmosphere containing 1000 ppm of oxygen or less is sufficiently pure to realise improved soldering conditions for most types of components. For the low‐residue paste tested, 1000 ppm is too high, but 100 ppm is sufficiently low. All effects on the soldering process will depend on the amount of oxygen in the gas. To produce an oven atmosphere of nitrogen with a very low amount of O2 (e.g., <100 ppm) is rather expensive, if this oven is to work under production conditions. Will the extra cost of investment and gas consumption be worthwhile in view of a better production yield and higher product quality? The authors explain why they do not believe this to be the case.

Date: 20 October 1993 Venue: The Regency Hotel, Shirley, Solihull, West Midlands Introduction This conference will provide a forum for discussions on recent advances in high technology joining process such as soldering, brazing, diffusion and adhesive bonding. Papers cover a wide range of scientific and technical developments and latest advances in production techniques, particularly those which may involve environmental considerations, and highlight the technological advances being made in the move towards the 21st century.

This paper aims to study the influence of reflow atmosphere and placement accuracy on the solderability of 01005 capacitor/SAC305 solder joints.

The 01005 capacitors were mounted on OSP-coated pads, and the samples were fabricated in four different atmospheres, i.e. 200 ppm O₂/N₂, 1,000 ppm O₂/N₂, 3,000 ppm O₂/N₂ and air. After the reflow process, visual inspection and X-ray detection were carried out to examine the solder joint shapes and possible defects. Some of the samples fabricated in different conditions were cross-sectioned and the solder joint microstructures were analyzed. On the other hand, besides placing the components on their normal pad positions, a 50 per cent offset of the x-axis (long axis) or y-axis (short axis) was introduced into the chip mounter programs to evaluate the 01005 capacitor’s assembly sensitivity to placement accuracy. The process-induced defects were investigated.

Experimental results indicated that an N₂-based protective atmosphere was necessary for 01005 type assembly, as it could obviously improve the 01005 solder joint quality, compared with the air condition. The protective atmosphere had little effect on the appearance, quality and microstructure of solder joints when the oxygen concentration was below 3,000 ppm. But a very low oxygen concentration could increase the risk of tombstoning defects for the assembly process. The N₂-based protective atmosphere containing 1,000-2000 ppm O₂ was acceptable and appropriate for the assembly of tiny components.

The results of this work provide a set of reflow process parameters and recommendations for 01005 size component assembly in manufacturing.

DURING the past twelve years there have been six investigations of the spectral transmission of light through fog, mist, or liaze carried out in the United States. The conditions of the tests have been varied. Three of the researches were made with fog chambers; three with natural fogs. One was made with a path of only 1·9 m. (6·2 ft.); the longest path was 1,200 m. (3,900 ft.). One of the fogs was so light that a 1,000,000 candle‐power airway beacon could be seen 13 km. (8 miles); the densest would permit such a beacon to be seen only 0·03 km. (0·02 mile). One investigator scarcely covered the entire visible spectrum. Two included the infra‐red as far as 3·0 microns and 2·5 microns respectively, and the latter of these extended his work as far as 0·324 micron in the ultra‐violet. It is not surprising that curves based on data taken under such diverse conditions should show little resemblance to one another.

The evidence‐based Incredible Years Teacher Classroom Management (TCM) Programme was developed to meet demands from teachers for strategies to manage disruptive behaviours in the classroom (Webster‐Stratton, 1999). This article describes the programme and reports on its first use in the UK. In the first study 23 teachers attended the five‐day classroom management programme, 20 completed the final satisfaction questionnaire and 21 participated in a semi‐structured follow‐up interview. Teachers who implemented the training in their classrooms reported satisfaction with the programme and believed that the strategies taught were effective and improved pupils' conduct. In the second study, blind observation of teacher classroom behaviour was undertaken in 21 classes: 10 teachers had received the TCM training and 11 had not. Teachers who received TCM training gave clearer instructions to children and allowed more time for compliance before repeating instructions. The children in their classes were more compliant than children in the classes of untrained teachers. The implications of these findings are discussed.

The aim of this article is to summarise the available evidence from systematic reviews about the effectiveness of interventions to prevent or treat child physical abuse and neglect. A computerised search was undertaken of major electronic databases up to December 2005 using key search terms. Only systematic reviews were included in which the primary studies evaluated the effectiveness of targeted or indicated interventions for child physical abuse or neglect. A total of 31 systematic reviews were identified and 15 met all the inclusion criteria. They covered a range of interventions/services, including home visiting, parenting programmes, multi‐component interventions, intensive family preservation services, family‐focused casework and multi‐systemic family therapy. There was limited evidence of the effectiveness of services in improving objective measures of abuse and neglect, due in part to methodological issues involved in their measurement, but good evidence of modest benefits in improving a range of outcomes that are associated with physical abuse and neglect, including parental and family functioning and child development. The results also showed some interventions (eg. media‐based and perinatal coaching) to be ineffective with high‐risk families. The evidence provided by these reviews has clear implications for children's services in the UK and other western developed countries.

This study examined the effectiveness of the Triple P‐Positive Parenting Program in a government child health service delivery context with Chinese parents in Hong Kong. Specifically, the study sought to identify pre‐intervention variables that might predict programme outcomes such as level of clinical improvement and programme completion. Participants were 661 parents of pre‐school and primary aged children participating in a group version of the Triple P‐Positive Parenting Program. There were significant decreases in disruptive child behaviours, levels of parenting stress, general stress and anxiety and an increase in parenting sense of competence. Greater change in reports of child behaviour problems was related to lower levels of family income, new immigrant family status, and higher pre‐intervention levels of parenting stress. The present study provides a profile of parents who are most likely to benefit from parent training programmes.