Search results

1 – 10 of 171
To view the access options for this content please click here
Article
Publication date: 1 January 2007

O.O. Adejumo and J.O. Ojo

The results of trial experiments carried out with a computer simulation model of total reflection X‐ray fluorescence, TXRF system to determine optimum conditions for…

Abstract

The results of trial experiments carried out with a computer simulation model of total reflection X‐ray fluorescence, TXRF system to determine optimum conditions for detecting certain elements of interest under various analytical conditions in a given ten‐element standard sample is presented in this paper. Results of these trial experiments show that the detectability of elements improved with increasing applied voltages up to about 43kV (for a Molybdenum anode TXRF spectrometer) and atomic number of elements. Variation of geometry such as the glancing incidence angle of the excitation beam reflected slight increase in minimum detection limit, MDL values as the angle of incidence is reduced from an optimum value of 1.6mradian to 1.0mradian. The nature of the sample support was observed to affect the detectability of the elements as good detection limits were obtained if gold is used as sample holder..

Details

Multidiscipline Modeling in Materials and Structures, vol. 3 no. 1
Type: Research Article
ISSN: 1573-6105

Keywords

To view the access options for this content please click here
Article
Publication date: 1 March 2000

N.G. Paulter

A new time‐domain reflectometry measurement method is described that provides accurate measurements of the average high‐frequency (0.1GHz ‐ 10GHz) dielectric constant of…

Abstract

A new time‐domain reflectometry measurement method is described that provides accurate measurements of the average high‐frequency (0.1GHz ‐ 10GHz) dielectric constant of printed wiring board materials and is suitable for “factory floor” use. A parallel‐plate transmission line is used for the sample geometry. Only simple numerical processes are required to extract the characteristic impedance and dielectric constant of the sample from the acquired data. The long‐term measurement reproducibility and short‐term measurement repeatability of the method are described.

Details

Circuit World, vol. 26 no. 1
Type: Research Article
ISSN: 0305-6120

Keywords

To view the access options for this content please click here
Article
Publication date: 1 April 1989

K.M. Lin and F.H. Friend

With the increased use of surface‐mounted devices, both the component density and the board complexity are greatly increased on many circuit pack assemblies. Good…

Abstract

With the increased use of surface‐mounted devices, both the component density and the board complexity are greatly increased on many circuit pack assemblies. Good solderability for the components as well as for the printed circuit boards has become one of the most important elements in achieving the ultra‐high efficiency and quality required of an assembly soldering process in today's competitive environment. Solderability evaluation generally uses the ‘dip and look’ method that relies entirely on the individual inspectors' often inconsistent interpretations resulting from the examination of the specimen dip‐tested in a molten solder bath. This method is subjective, so the results can vary from person to person and from day to day. In addition, the sensitivity of such a method is inadequate in discerning the differences in solder wetting characteristics of very small device leads and terminations. Consequently, components with marginal or even bad solderability may pass through inspection and move onto the production line to cause many easily avoidable defects and their subsequent repairs. A sensitive and quantitative wetting balance method has been studied with the purpose of developing a better alternative to the ‘dip and look’ procedure. Special sample holders and test conditions have been developed for testing various types of components and printed circuit board coupons. Examples of solderability testings are provided to illustrate the capability of the instrument when proper testing procedures are followed. More effort is under way to simplify the test procedure, and to establish a practical solderability test standard for the wetting balance method.

Details

Circuit World, vol. 16 no. 1
Type: Research Article
ISSN: 0305-6120

To view the access options for this content please click here
Article
Publication date: 1 January 1986

J.A. Nelson and R. Zimmer

The ever‐increasing need for circuit boards places equally heavy demands on the control laboratory to prepare and examine sufficient polished cross‐sections for process…

Abstract

The ever‐increasing need for circuit boards places equally heavy demands on the control laboratory to prepare and examine sufficient polished cross‐sections for process analysis. High production facilities require large numbers of polished cross‐sections to meet the demands of industrial or military specifications. Manual sample preparation methods are totally inadequate to provide sufficient numbers of samples fast enough to prevent processing of material that is defective. Additional manual devices, technicians and expanded work areas are not capable of meeting the quantity or time demands imposed by high production. However, a system has been devised that addresses the shortcomings of manual sample preparation and provides an efficient, cost effective means of producing very large quantities of polished cross‐sections in a meaningful turn‐around time.

Details

Circuit World, vol. 12 no. 2
Type: Research Article
ISSN: 0305-6120

To view the access options for this content please click here
Article
Publication date: 13 April 2020

Christian Dejan Ielchici, Stefan Krenn and Stefan J. Eder

This paper aims on a methodology to overcome the fact that conventional service life testing of porous journal bearings (PJBs) requires long test times and is not economical.

Abstract

Purpose

This paper aims on a methodology to overcome the fact that conventional service life testing of porous journal bearings (PJBs) requires long test times and is not economical.

Design/methodology/approach

This paper sketches out a pathway to strongly accelerated life tests for PJBs enabled by high load and elevated temperature, which saves months or even years of testing. The testing time is not only reduced to a few weeks, but the results are also statistically secured via a multiple test rig construction of a custom-made tribometer.

Findings

An exemplary bearing-lubricant combination is tested in the mixed lubrication regime, where the coefficient of friction is monitored during the test.

Originality/value

A Weibull curve is fitted to the experimental results to show the survival probability of the combination over time.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0351/

Details

Industrial Lubrication and Tribology, vol. 72 no. 8
Type: Research Article
ISSN: 0036-8792

Keywords

To view the access options for this content please click here
Article
Publication date: 31 March 2020

Mohamed Amine Alaya, Viktória Megyeri, David Bušek, Gábor Harsányi and Attila Geczy

To improve productivity and reach better quality in assembling, measurements and proper process controlling are a necessary factor. This study aims to focus on the…

Abstract

Purpose

To improve productivity and reach better quality in assembling, measurements and proper process controlling are a necessary factor. This study aims to focus on the monitoring heat-level-based vapour phase reflow soldering (VPS), where – as it was found – different thermocouple constructions can affect the set parameters of the oven and resulting soldering profiles significantly.

Design/methodology/approach

The study experiments showed significant alteration of the heating profiles during the process of the reflowing using different construction of k-type thermocouples. In a heat-level-based VPS oven, polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA) gas and water-resistant, fibreglass, thin PFA and ultrathin PFA-covered thermocouples were tested with ±1 °C precision. The oven parameters were swept according to the heating power; the length of the introduced thermocouple cables was also taken into account. An FR4-based sample PCB was used for monitoring the temperature.

Findings

According to the results, due to the mass and volume of the thermocouples’ wires, different transients were observed on the resulting soldering profiles on the same sample PCB. The thermocouples with lower thermal mass result in faster profiles and significantly different heating factor values compared to the thermocouples that have larger thermal mass. Consequently, the length of the thermocouple wires put in the oven has also considerable effect on the heat transfer of the PCB inside the oven as well.

Originality/value

The paper shows that the thermocouple construction must be taken into account when setting up a required soldering profile, while the thermal mass of the wires might cause a significant difference in the prediction of the actual and expected soldering temperatures.

Details

Soldering & Surface Mount Technology, vol. 32 no. 4
Type: Research Article
ISSN: 0954-0911

Keywords

To view the access options for this content please click here
Article
Publication date: 16 January 2017

Divya Nath K. and Prabhu Ramanathan

The purpose of this paper is to analyze the moisture measurement techniques presently available, as accurate determination of the moisture content (MC) of grains or any…

Abstract

Purpose

The purpose of this paper is to analyze the moisture measurement techniques presently available, as accurate determination of the moisture content (MC) of grains or any food items at right time is very important for its processing, marketing and storing.

Design/methodology/approach

There are basically two types of MC measurement techniques – destructive method and non-destructive method. In the time-consuming destructive method, cleaning of the food items is done and shells of food items like peanuts are removed for which man power is required and so the technique becomes costly. A literature review of the existing non-destructive methods has been done, and the methodology of each approach is explained with the figure. The less time-consuming non-destructive technique used to measure MC require less man power, as grains or food items can be directly used without any process like cleaning or crushing so that the technique become economic.

Findings

Most of the techniques used magnetic or electric properties to measure the MC indirectly. The problem with existing non-destructive technique is that measurement of MC uses only few numbers or grams of grains or food items at a time.

Research limitations/implications

The farmers’ produce large quantity of grains. The small quantity of grains cannot be the representative sample for whole grains produced by the farmers. Most of the techniques use only small quantity of grains or food items at a time to measure the MC which is not accurate and representative of the produce. Also, the techniques are not simple and easily available. The cost of the techniques or arrangement to measure the MC is not reasonable.

Social implications

Most of the farmers in the developing countries are financially backward. To store the agricultural produce, MC of the commodities is a key factor influencing the quality of the storage. Measurement of the MC of the seeds is thus very important for the farmers.

Originality/value

This paper is a review of the previous research that happened in this area, and it would help the researcher to know the techniques already been used. To the knowledge of the authors, the review of the existing moisture measurement of seeds/agricultural commodities is available in the literature.

Details

Sensor Review, vol. 37 no. 1
Type: Research Article
ISSN: 0260-2288

Keywords

To view the access options for this content please click here
Article
Publication date: 1 January 1991

J.E. Moneyron, A. de Roy and J.P. Besse

The electrical properties related to the hydration of the hydrotalcite‐type lamellar compound Zn2Al(OH)6Cl.nH2O are such as to permit the realisation of a humidity sensor…

Abstract

The electrical properties related to the hydration of the hydrotalcite‐type lamellar compound Zn2Al(OH)6Cl.nH2O are such as to permit the realisation of a humidity sensor. The sensor is achieved by depositing thick film by the screen‐printing technique. First, the means of forming the material is optimised. Two types of sensor are then realised, one working with direct current, the other with alternating current. The performance of each device is studied by means of specified experiments. The authors create a new measurement cell for calibrating the alternating current sensor. Response time measurements are carried out, and results are interpreted and compared.

Details

Microelectronics International, vol. 8 no. 1
Type: Research Article
ISSN: 1356-5362

To view the access options for this content please click here
Article
Publication date: 6 February 2017

Attila Geczy, Daniel Nagy, Balazs Illes, Laszlo Fazekas, Oliver Krammer and David Busek

The paper aims to present an investigation of heating during vapour phase soldering (VPS) on inclined printed circuit board (PCB) substrates. The PCB is a horizontal…

Abstract

Purpose

The paper aims to present an investigation of heating during vapour phase soldering (VPS) on inclined printed circuit board (PCB) substrates. The PCB is a horizontal rectangular plate from the aspect of filmwise condensation with a given inclination setting.

Design/methodology/approach

The paper focuses on the measurement of temperature distribution on the PCBs with a novel setup immersed in the saturated vapour space. The measuring instrumentation is optimized to avoid and minimize vapour perturbing effects.

Findings

The inhomogeneity of the heating is presented according to the lateral dimensions of the PCB. The inclination improves temperature uniformity, improves heat transfer efficiency; however, a minor misalignment may affect the flow and result in uneven heating.

Practical implications

The results can be implemented for practical improvements in industrial ovens with the use of intended inclination. The improvements may consequently point to more efficient production and better joint quality.

Originality/value

The novel method can be used for deeper investigation of inclination during and can be complemented with numerical calculations. The results highlight the importance of precise PCB holding instrumentation in VPS ovens.

Details

Soldering & Surface Mount Technology, vol. 29 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

To view the access options for this content please click here
Article
Publication date: 30 September 2013

Mengqi Yuan, Timothy T Diller, David Bourell and Joseph Beaman

The purpose of this paper is to acquire thermal conductivities of both fresh and preheated polyamide 12 powder under various conditions to provide a basis for effective…

Abstract

Purpose

The purpose of this paper is to acquire thermal conductivities of both fresh and preheated polyamide 12 powder under various conditions to provide a basis for effective and accurate control during the laser sintering (LS) process.

Design/methodology/approach

A Hot Disk® TPS 500 thermal measurement system using a transient plane source (TPS) technology was employed for thermal conductivity measurements. Polyamide 12 powder was packed at different densities, and different carrier gases were used. Tests were also performed on fully dense laser sintered polyamide 12 to establish a baseline.

Findings

Polyamide 12 powder thermal conductivity varies with packing density and temperature, which is approximately one-third bulk form thermal conductivity. Inter-particle bonding is the primary factor influencing polyamide 12 thermal conductivity.

Research limitations/implications

Limited ranges of density were tested, and the carrier gas needed carefully control to prevent powder oxidation. Thermal properties obtained were not tested in the LS process.

Originality/value

This experimental result could be used to enhance thermal control during the LS process.

Details

Rapid Prototyping Journal, vol. 19 no. 6
Type: Research Article
ISSN: 1355-2546

Keywords

1 – 10 of 171