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Article
Publication date: 9 February 2010

J. Mittal and K.L. Lin

The purpose of this paper is to visualise the activities of three solders; Sn‐37Pb, Sn‐9Zn and Sn‐3.5Ag on Cu substrates during reflow near their melting points and to…

Abstract

Purpose

The purpose of this paper is to visualise the activities of three solders; Sn‐37Pb, Sn‐9Zn and Sn‐3.5Ag on Cu substrates during reflow near their melting points and to relate them with reflow reactions between solder and substrate.

Design/methodology/approach

Melting activities of three solders near their melting points on copper substrates are visualised in an infrared reflow furnace.

Findings

Solder balls demonstrate different ways of melting and reflowing behaviours in dissimilar times and temperature intervals. Melting of Sn‐9Zn solder balls is initiated simultaneously at the surface and joint between solder balls. This is followed by the melting at the joint between solder balls and the Cu substrate. During melting, solder balls are first merged into each other and then reflow on the substrate from top to bottom. Opposite to Sn‐9Zn, Sn‐3.5Ag solder balls start to melt at the surface and the joint between the solder and substrate, simultaneously. Balls are first reflowed from top to bottom and, in the process, liquid solder is merged. Unlike Sn‐9Zn and Sn‐3.5 Ag, melting of Sn‐37Pb solder balls is initially commenced at the surface only. This is followed by simultaneous melting at both joints. Variation in melting activities of these solders is found to be closely related to the coalescence mechanism of solder balls and the reflow reactions between the solders and the Cu substrate.

Originality/value

The elementary melting activities of different solders on Cu substrates is related with their reflow behaviours. This provides better understanding of solder behaviour and selection of good lead‐free solder for applications in the electronic industry.

Details

Soldering & Surface Mount Technology, vol. 22 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 March 1987

Y. Fukuoka, E. Matsumoto and M. Ishizuka

This paper describes one of the new package cooling technology concepts using low melting point alloys in order to perform high density packaging. Two kinds of cooling…

Abstract

This paper describes one of the new package cooling technology concepts using low melting point alloys in order to perform high density packaging. Two kinds of cooling alloy materials, Bi/Sn/In and Bi/Pb/Sn/ln, whose melting points were less than 80°C and whose costs were low, were selected. The experimental substrate sample was fabricated by greensheet technology on which a tungsten metallised resistor heater was formed. Two kovar weld rings were brazed together to the top side and back side surfaces of the substrate individually. One kovar metal shell was laser welded to the top side weld ring in order to protect many devices. Another kovar metal shell, with a hole in the centre, was laser welded to the back side weld ring. The low melting point alloy was melted and poured into the back side kovar shell through the hole in a liquid state. After it was cooled and changed into a solid state, the hole was sealed hermetically with a small kovar metal cap by a laser beam. The authors performed a thermal experiment and confirmed that the substrate back surface temperature was fixed at the cooling alloy material's melting point for several minutes by thermal absorption while the low melting point alloy phase changed from its original solid state into a liquid state. This new package cooling technology is extremely useful for a high power motor drive circuit package which consists of many high power transistor chips and other analogue IC chips, and whose motor drive operation is performed intermittently for several minutes with some interval times.

Details

Microelectronics International, vol. 4 no. 3
Type: Research Article
ISSN: 1356-5362

Article
Publication date: 10 April 2009

C.D. Zou, Y.L. Gao, B. Yang, Q.J. Zhai, C. Andersson and J. Liu

The purpose of this paper is to study the melting temperature of the nanoparticles of the new developed Sn‐0.4Co‐0.7Cu (wt%) lead‐free solder alloy.

Abstract

Purpose

The purpose of this paper is to study the melting temperature of the nanoparticles of the new developed Sn‐0.4Co‐0.7Cu (wt%) lead‐free solder alloy.

Design/methodology/approach

Nanoparticles of Sn‐0.4Co‐0.7Cu lead‐free solder alloy were prepared by the self‐developed consumable‐electrode direct current arc technique, where ultrasonic vibration was applied during the manufacturing of the particles. X‐ray diffraction and field emission scanning electron microscope were employed to analyze the crystal structure and morphology of the nanopartiles, respectively. Differential scanning calorimetry was used to investigate the melting temperature of both the bulk alloy and as‐prepared nanoparticles.

Findings

The melting temperature of the nanoparticles was approximately 5°C lower compared to that of the bulk alloy.

Originality/value

As a novel developed lead‐free solder alloy, the Sn‐0.4Co‐0.7Cu (wt%) alloy provides a cost advantage compared to the extensively used Sn‐Ag‐Cu system. Some limitations still exist, however, mainly due to its relatively higher melting temperature compared to that of eutectic Sn‐37Pb solder. In view of this situation, the attempt to lower its melting temperature has recently attracted more attention based on the knowledge that the melting temperature for pure metals is reduced when the particle size is decreased down to a few tens of nanometers.

Details

Soldering & Surface Mount Technology, vol. 21 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 20 June 2019

Huijin Xu, Yan Wang and Xingchao Han

Phase change energy storage is an important solution for overcoming human energy crisis. This study aims to present an evaluation for the thermal performances of a phase…

Abstract

Purpose

Phase change energy storage is an important solution for overcoming human energy crisis. This study aims to present an evaluation for the thermal performances of a phase change material (PCM) and a PCM–metal foam composite. Effects of pore size, pore density, thermal conductivity of solid structure and mushy region on the thermal storage process are examined.

Design/methodology/approach

In this paper, temperature, flow field and solid–liquid interface of a PCM with or without porous media were theoretically assessed. The influences of basic parameters on the melting process were analyzed. A PCM thermal storage device with a metal foam composite is designed and a thermodynamic analysis for it is conducted. The optimal PCM temperature and the optimal HTF temperature in the metal foam-enhanced thermal storage device are derived.

Findings

The results show that the solid–liquid interface of pure PCM is a line area and that of the mixture PCM is a mushy area. The natural convection in the melting liquid is intensive for a PCM without porous medium. The porous medium weakens the natural convection and makes the temperature field, flow field and solid–liquid interface distribution more homogeneous. The metal foam can greatly improve the heat storage rate of a PCM.

Originality/value

Thermal storage rate of a PCM is compared with that of a PCM–metal foam composite. A thermal analysis is performed on the multi-layered parallel-plate thermal storage device with a PCM embedded in a highly conductive porous medium, and an optimal melting temperature is obtained with the exergy optimization. The heat transfer enhancement with metal foams proved to be necessary for the thermal storage application.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 16 October 2018

Ya Qian, Wentao Yan and Feng Lin

This paper aims to study the effect of processing parameters and the fundamental mechanism of surface morphologies during electron beam selective melting.

Abstract

Purpose

This paper aims to study the effect of processing parameters and the fundamental mechanism of surface morphologies during electron beam selective melting.

Design/methodology/approach

From the powder-scale level, first, the discrete element method is used to obtain the powder bed distribution that is comparable with the practical condition; then, the finite volume method is used to simulate the particle melting and flowing process. A physically reliable energy distribution of the electron beam is applied and the volume of fluid method is coupled to capture the free boundary flow. Twelve sets of parameters grouped into three categories are examined, focusing on the effect of scan speed, input powder and energy density.

Findings

According to the results, both melting pool width and depth have a positive relation with the energy density, whereas the melting pool length is insensitive to the scan velocity change. The balling effect is attributed to either an insufficient energy input or the flow instability; the hump effect originates from the mismatch between electron beam moving and the fluid flow. The scan speed is a key parameter closely related to melting pool size and surface morphologies.

Originality/value

Through a number of case studies, this paper gives a comprehensive insight of the parameter effects and mechanisms of different surface morphologies, which helps to better control the manufacturing quality of electron beam selective melting.

Details

Rapid Prototyping Journal, vol. 24 no. 9
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 2 August 2011

Evren Yasa, Jan Deckers and Jean‐Pierre Kruth

Selective laser melting (SLM) is a powder metallurgical (PM) additive manufacturing process whereby a three‐dimensional part is built in a layer‐wise manner. During the…

5789

Abstract

Purpose

Selective laser melting (SLM) is a powder metallurgical (PM) additive manufacturing process whereby a three‐dimensional part is built in a layer‐wise manner. During the process, a high intensity laser beam selectively scans a powder bed according to the computer‐aided design data of the part to be produced and the powder metal particles are completely molten. The process is capable of producing near full density (∼98‐99 per cent relative density) and functional metallic parts with a high geometrical freedom. However, insufficient surface quality of produced parts is one of the important limitations of the process. The purpose of this study is to apply laser re‐melting using a continuous wave laser during SLM production of 316L stainless steel and Ti6Al4V parts to overcome this limitation.

Design/methodology/approach

After each layer is fully molten, the same slice data are used to re‐expose the layer for laser re‐melting. In this manner, laser re‐melting does not only improve the surface quality on the top surfaces, but also has the potential to change the microstructure and to improve the obtained density. The influence of laser re‐melting on the surface quality, density and microstructure is studied varying the operating parameters for re‐melting such as scan speed, laser power and scan spacing.

Findings

It is concluded that laser re‐melting is a promising method to enhance the density and surface quality of SLM parts at a cost of longer production times. Laser re‐melting improves the density to almost 100 per cent whereas 90 per cent enhancement is achieved in the surface quality of SLM parts after laser re‐melting. The microhardness is improved in the laser re‐molten zone if sufficiently high‐energy densities are provided, probably due to a fine‐cell size encountered in the microstructure.

Originality/value

There has been extensive research in the field of laser surface modification techniques, e.g. laser polishing, laser hardening and laser surface melting, applied to bulk materials produced by conventional manufacturing processes. However, those studies only relate to laser enhancement of surface or sub‐surface properties of parts produced using bulk material. They do not aim at enhancement of core material properties, nor surface enhancement of (rough) surfaces produced in a PM way by SLM. This study is carried out to cover the gap and analyze the advantages of laser re‐melting in the field of additive manufacturing.

Details

Rapid Prototyping Journal, vol. 17 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 1 May 2000

Bruno Binet and Marcel Lacroix

A numerical study is conducted for natural convection dominated melting inside discretely heated rectangular enclosures. This study finds applications in the design and…

Abstract

A numerical study is conducted for natural convection dominated melting inside discretely heated rectangular enclosures. This study finds applications in the design and operation of thermal energy storage units and the cooling of electric equipment. Results show the benefits of discrete heating over uniform heating for optimizing the melting process. For enclosures of high aspect ratios (A ∼> 4), configurations leading to well controlled heat source temperatures and long melting times are obtained. For cavities of low aspect ratios (A ∼< 4), it is found that the source span η is the most influential parameter. For η ∼ < 0.45, the melting times are shorter and the heat source temperatures remain equal and moderate during the entire melting process. A map for determining the cavity size and the source distribution that optimizes the melting process is presented.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 10 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 2 January 2018

Barry Haworth, John R. Tyrer and Zhou Zhou

There is a requirement to match selective laser melting (SLM) technologies to a wider range of polymeric materials, as the existing market for SLM powders is dominated by…

Abstract

Purpose

There is a requirement to match selective laser melting (SLM) technologies to a wider range of polymeric materials, as the existing market for SLM powders is dominated by polyamide PA12. Drivers include the tailoring of physical properties to individual applications or cost reduction. Polypropylene (PP) currently has limited use in SLM; so, this paper aims to explore the potential use of PP materials of varying molecular weight (Mw).

Design/methodology/approach

PP polymers of differing Mw were characterised using a range of analytical techniques, including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), rotational rheometry and real-time hot-stage (optical) microscopy.

Findings

The techniques are sufficiently sensitive to distinguish Mw effects, notably in terms of material viscosity. The stable sintering region for SLM has been defined clearly. Some success was achieved in melting parts using all grades of PP, including higher Mw grades, which potentially offer improved mechanical performance.

Research limitations/implications

The range of techniques (DSC, oxidative induction time and TGA) form an effective analytical package with which to consider new polymeric materials for SLM.

Practical implications

High-Mw PP polymers, in tape or powder form, have potential use in SLM processes, providing scope to enhance part properties in future.

Originality/value

This is believed to be the first in-depth study noting the influence of PP Mw on important physical performance in a proprietary SLM process, using holographic beam manipulation.

Details

Rapid Prototyping Journal, vol. 24 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 8 May 2018

Mahantesh M. Nandeppanavar

This paper aims to investigate laminar boundary layer flow and heat transfer from a warm laminar Casson liquid to a melting sheet moving parallel to a melting stream. The…

Abstract

Purpose

This paper aims to investigate laminar boundary layer flow and heat transfer from a warm laminar Casson liquid to a melting sheet moving parallel to a melting stream. The governing equations, i.e. continuity, momentum and heat transfer, are coupled non-linear partial differential equations. These equations are reduced to non-linear ordinary differential equations by means of similarity transformations, converted into first-order differential equations, and are solved numerically using the Runge–Kutta–Felhberg method with an efficient shooting technique. The velocity and temperature profiles are plotted for various values of the governing parameters, such as the moving parameter, Prandlt number, melting parameter and Casson parameter. It is found that the problem admits multiple solutions. The results of this study are validated by comparing them with the earlier published studies’ results. Thus, a good agreement is obtained.

Design/methodology/approach

This study carries out numerical solution of melting heat transfer analysis.

Findings

The findings of this study show the analysis of flow and melting heat transfer characteristics.

Research limitations/implications

In this study, analysis of dual solution is carried out.

Originality/value

In this paper, the melting heat transfer analysis on Blasius flow of a Casson fluid is taken into consideration. To the best of the author’s knowledge, no investigations have been reported on this topic.

Article
Publication date: 28 June 2019

Amin Samimi Behbahan, Aminreza Noghrehabadi, C.P. Wong, Ioan Pop and Morteza Behbahani-Nejad

The purpose of this paper is to study thermal performance of metal foam/phase change materials composite under the influence of the enclosure aspect ratios (ratio of…

Abstract

Purpose

The purpose of this paper is to study thermal performance of metal foam/phase change materials composite under the influence of the enclosure aspect ratios (ratio of enclosure height: length). In this study, a compound metal foam/phase change material (PCM), which has been proved to be one of the most promising approaches for thermal conductivity promotion on PCMs, was used.

Design/methodology/approach

The PCM is considered initially at its melting temperature. The enclosure for all the cases has a constant volume with various aspect ratios. The left side of the enclosure is suddenly exposed to a thermal source having a constant heat flux, while the other three surfaces are kept thermally insulated. A two-dimensional numerical model considering the non-equilibrium thermal factor, non-Darcy effect and local natural convection was proposed. The coupling between velocity and pressure is solved using the SIMPLEC, and the Rhie and Chow interpolation is used to avoid the checker-board solutions for the pressure.

Findings

The effects of foam porosity and aspect ratio of the enclosure on the PCM’s melting time were investigated. The results indicated that enclosure aspect ratio plays a fundamental role in phase change of copper foam/PCM composites. For higher porosities, enclosures with bigger aspect ratios proved to led to optimal melting time. Besides, the best enclosure aspect ratio and foam porosity for a fixed-volume enclosure to have the shortest melting time are 2.1 and 91.66 per cent, respectively. However, for a specific amount of PCM inside a variable volume enclosure, the optimal melting time was for foam with ε = 95 per cent. The achieved results prove the great importance of selection of aspect ratio to benefit both conduction and convection heat transfer simultaneously.

Originality/value

The area of energy storage systems is original.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 9
Type: Research Article
ISSN: 0961-5539

Keywords

1 – 10 of over 10000