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Article
Publication date: 27 July 2012

Sung Yi and Tatiana M. Lam

The purpose of this paper is to provide a design and material selection guideline for a plastic ball grid array (PBGA) package in order to improve its reliability and…

Abstract

Purpose

The purpose of this paper is to provide a design and material selection guideline for a plastic ball grid array (PBGA) package in order to improve its reliability and manufacturing ability after post mold cure.

Design/methodology/approach

Numerical experiments based on a three‐dimensional (3‐D) viscoelastic finite element method have been conducted to evaluate governing damage mechanisms after post mold cure (PMC) for PBGA packages. The parametric studies for the PBGA package with various molding compounds have been performed. A wide range of the modulus (1MPa∼15GPa) and the coefficient of thermal expansion (CTE) (10ppm∼300ppm) are evaluated to see feasibility of a new class of material set in the molding compound. Effects of thermo‐mechanical properties of selected molding compound on the warpage and residual stress of the PBGA are analyzed.

Findings

The present study shows that the material properties such as modulus and CTE of molding compounds play an important role in warpages and reliability of PBGA packages. After post mold cure, compressive normal stress σxx is observed in the silicon die, while tensile stress occurs in the rest of the PBGA package. The maximum normal stress σxx is observed at the center of the silicon die and decreases near the edge of the package. As the coefficient of thermal expansion of the silicon die is substantially less than that of the molding compound or substrate, the molding compound and the substrate are trying to shrink more when temperature decreases and in turn compressing the silicon chip. The molding compound with low modulus produces low stresses in the Si die and the die attach. Moreover, for the low modulus case, the CTE of molding compound does not affect the warpage of the PBGA package and the stresses in the silicon die or the die attach. However, for the high modulus case, the warpage and stresses are increased significantly by increasing the CTE of molding compound.

Research limitations/implications

It is suggested that adhesion strengths of die attaches should be studied in future studies, since those affect the delamination between dies and substrates.

Practical implications

The findings can be used as general design guidelines for a PBGA package.

Originality/value

The results presented in the paper will be very useful to designers of PBGAs.

Details

Microelectronics International, vol. 29 no. 3
Type: Research Article
ISSN: 1356-5362

Keywords

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Article
Publication date: 12 March 2018

Donghua Zhao, Weizhong Guo, Baibing Zhang and Feng Gao

The purpose of this paper is to review available technologies, analyse their features, propose a new approach of 3D sand mould printing based on line forming, introduce…

Abstract

Purpose

The purpose of this paper is to review available technologies, analyse their features, propose a new approach of 3D sand mould printing based on line forming, introduce the manufacturing principle and show advantages of this approach, especially for larger parts with large Z steps in the build, such as 2 mm stepwise.

Design/methodology/approach

This paper introduces 3D sand mould printing, compares and analyses technological process and existing fabrication approaches among available technologies first. Then, a new approach of 3D sand mould printing is proposed to improve build speed. In addition, the proposed system will be analysed or benchmarked against existing systems.

Findings

A new approach based on line forming of sand mould printing is put forward by reviewing and analysing available technologies, to improve build speed from the aspect of basic moulding movement instead of optimization of moulding methods and process parameters. The theoretical calculation and analysis shows that build speed can be improved greatly, and it is more suitable for the manufacture of large-scale casting’s sand mould when considering dimensional accuracy and printing error, as well as uniformity of each layer.

Research limitations/implications

The specific implement scheme of line forming and nozzle’s specific structure of this new approach need further study.

Practical implications

Much higher build speed of 3D sand mould printing with new approach brings evident implication for moulds companies and manufacturing industry, having a far-reaching influence on the development of national economy.

Originality/value

This paper reviews available technologies and presents a new approach of 3D sand mould printing for the first time. Analysis of the new approach shows that this new method of sand mould printing can boost build speed greatly. So, its application prospect is great.

Details

Rapid Prototyping Journal, vol. 24 no. 2
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 1 August 1998

Jaroslav Mackerle

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder…

Abstract

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder metallurgy and composite material processing are briefly discussed. The range of applications of finite elements on these subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE researchers/users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for 1994‐1996, where 1,370 references are listed. This bibliography is an updating of the paper written by Brannberg and Mackerle which has been published in Engineering Computations, Vol. 11 No. 5, 1994, pp. 413‐55.

Details

Engineering Computations, vol. 15 no. 5
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 18 January 2008

Aditya Kelkar and Bahattin Koc

The objective of this paper is to develop geometric algorithms and planning strategies to enable the development of a novel hybrid manufacturing process, which combines…

Abstract

Purpose

The objective of this paper is to develop geometric algorithms and planning strategies to enable the development of a novel hybrid manufacturing process, which combines rapidly re‐configurable mold tooling and multi‐axis machining.

Design/methodology/approach

The presented hybrid process combines advantages of both reconfigurable molding and machining processes. The mold's re‐configurability is based on the concept of using an array of discrete pins. By positioning the pins, the reconfigurable molding process allows forming the mold cavity directly from the object's 3D design model, without any human intervention. After a segment of the part is molded using the reconfigurable molding process, a multi‐axis machining operation is used to create accurate parts with better surface finish. Geometric algorithms are developed to decompose the design model into segments based on the part's moldability and machinability. The decomposed features are used for planning the reconfigurable molding and the multi‐axis machining operations.

Findings

Computer implementation and illustrative examples are also presented in this paper. The results showed that the developed algorithms enable the proposed hybrid re‐configurable molding and multi‐axis machining process. The developed decomposition and planning algorithms are used for planning the reconfigurable molding and the multi‐axis machining operations. Owing to the decomposition strategy, more geometrically complex parts can be fabricated using the developed hybrid process.

Originality/value

This paper presents geometric analysis and planning to enable the development of a novel hybrid manufacturing process, which combines rapidly re‐configurable mold tooling and multi‐axis machining. It is expected that the proposed hybrid manufacturing process can produce highly customized parts with better surface finish, and part accuracy, with shorter build times, and reduced setup and tooling costs.

Details

Rapid Prototyping Journal, vol. 14 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 29 May 2009

Nagahanumaiah and B. Ravi

The purpose of this paper is to present the results of an investigation into the effect of injection molding process parameters on the performance of direct metal laser…

Abstract

Purpose

The purpose of this paper is to present the results of an investigation into the effect of injection molding process parameters on the performance of direct metal laser sintered (DMLS) mold in producing quality Zytel nylon 66 plastic parts with consistency in part shrinkage and shot/part weight.

Design/methodology/approach

The injection mold for an industrial component (hub gear) was fabricated in EOS M‐250 machine using bronze‐based material. The effect of four injection molding parameters (injection pressure, melt temperature, speed, and injection time) on part shrinkage and weight were studied experimentally using L9 orthogonal array. The weight of the part just after ejecting from the cavity, and the average shrinkage measured after cooling, were used in grey relational analysis technique to assess the effect of each molding parameter. Further, surface properties such as surface finish, wear, scratch and corrosion resistance tests were conducted on DMLS mold material samples, in order to evaluate its use in rapid manufacturing applications.

Findings

The study found that injection speed and melt temperature have significant influence on part weight and shrinkage. The optimized molding process variables were slightly more in the case of DMLS molds as compared with the parameters suggested in the plastic datasheet. Scanning electro microscope (SEM) analysis of the mold surface after producing 5,000 glass filled Nylon 66 (Zytel) moldings did not indicate any surface degradation, confirming the use of DMLS mold in rapid manufacturing of few thousands of moldings.

Research limitations/implications

The grey relational analysis does not compute the effect of any two or more variables together unlike ANNOVA. Second, this study alone is not enough to estimate life of DMLS mold, although 5,000 glass filled nylon 66 moldings are successfully produced without any damage on mold surface.

Practical implications

This investigation demonstrates a generic approach of using grey relational analysis to quantify the effect of different molding process variables on selected quality parameters. This method can be easily extended for new processes and materials. The preliminary tests on surface finish, scratch, wear and corrosion resistance performed on DMLS mold samples have highlighted the need for improving surface properties to enhance their life. The authors are currently working on hard coating of DMLS molds as one of the solutions.

Originality/value

Use of grey relational analysis is new to the problem of injection molding process optimization. Moreover, effect of injection molding parameters on part weight and shrinkage in DMLS mold has not been studied previously. This study helps while considering DMLS molds for manufacturing few thousands of parts.

Details

Rapid Prototyping Journal, vol. 15 no. 3
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 10 May 2013

Xiong Liang, Bing Li, Xiaoyu Wu, Hongyan Shi, Kun Zeng and Yatao Wang

The purpose of this paper is to present a method for ultrasonically molding polymer powder in a micro plastic part mold. In the method, a printed circuit board (PCB) in…

Abstract

Purpose

The purpose of this paper is to present a method for ultrasonically molding polymer powder in a micro plastic part mold. In the method, a printed circuit board (PCB) in which micro‐hole arrays are drilled is used as a micro cavity insert. With the utilization of ultrasonic vibration, the polymer powder, which is prefilled and compacted in a micro cavity, mutually generates great sliding friction heat so as to be rapidly plasticized and molded.

Design/methodology/approach

Micro carbide drill bits of which the diameters are 100.0 μm, 150.0 μm and 200.0 μm, respectively, are used for drilling the PCB to form a micro‐hole array insert. Next, two kinds of various ultra‐high molecule weight polyethylene (UHMW‐PE) powder with various grain diameters are directly filled into a charging barrel and a mold cavity with the micro‐hole array insert. Proper process parameters are set on ultrasonic plasticizing and molding equipment so that a molding test can be performed. The melt of UHMW‐PE can be rapidly filled into the cavity. Finally, micro‐column array plastic parts are successfully prepared.

Findings

The micro‐hole array PCB is a mold insert which is quite applicable for the ultrasonic molding of the powder in the mold. When a molding material is the coarse UHMW‐PE powder with the grain diameter of about 350 μm, the diameter replication rates of the micro‐column array plastic parts become good in order with the increased micro‐hole diameter of the PCB. When the fine UHMW‐PE powder with the grain diameter of about 80 μm is adopted, the diameter replication rates of the micro‐column array plastic parts become good in order with the decreased micro‐hole diameter of the PCB.

Originality/value

In this paper, the micro‐column array plastic parts with good replicability are successfully prepared by a technique for ultrasonically plasticizing and molding in the cavity. The technique can be applied to the fields of medical treatment, communication, optics, chemistry and so on, such as biological micro needle arrays, micro biological chips, optical memories, and micro chemical reaction chips.

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Article
Publication date: 1 March 2001

Rajitha Aluru, Michael Keefe and Suresh Advani

Injection molding is a very mature technology, but the growth of layer‐build, additive, manufacturing technologies (rapid prototypying) has the potential of expanding…

Abstract

Injection molding is a very mature technology, but the growth of layer‐build, additive, manufacturing technologies (rapid prototypying) has the potential of expanding injection molding into areas not commercially feasible with traditional molds and molding techniques. This integration of injection molding with rapid prototyping has undergone many demonstrations of potential. What is missing is the fundamental understanding of how the modifications to the mold material and mold manufacturing process impact both the mold design and the injection molding process. This work expanded on an approach to utilize current numerical simulation programs and created a tool for optimizing the creation and use of non‐metal molds for injection molding. Verification and validation work is presented. The model was exercised by studying the effect of varying the thermal conductivity on final‐part distortions. This work clearly showed that one could not obtain reasonable results by simply changing a few input parameters in the current simulations. Although the approach did produce more realistic results, more work will be required for a tool capable of accurate, quantitative predictions.

Details

Rapid Prototyping Journal, vol. 7 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 1 April 2005

C. Carl Pegels and Craig Watrous

The purpose of this paper is to describe a study of the successful application of the theory of constraints (TOC) to a manufacturing plant operations problem. The TOC…

Abstract

Purpose

The purpose of this paper is to describe a study of the successful application of the theory of constraints (TOC) to a manufacturing plant operations problem. The TOC application required the identification of a bottleneck constraint in the manufacturing process which limited through‐put and thus negatively affected plant productivity and efficiency.

Design/methodology/approach

The methodology used was a detailed case study of the bottleneck in the manufacturing process. The bottleneck in this case was the mold‐changing operations, consisting of a plastic injection process for heavy‐duty truck‐lighting systems components.

Findings

It was found that to eliminate the bottleneck four separate solution approaches were applied to the problem, and these four solutions collectively eliminated the bottleneck constraint.

Research limitations/implications

The limitation of this approach is that the application of the TOC method is highly specific to the particular operation.

Originality/value

On completion of the study the mold‐changing process improvements resulted in increased through‐put and concomitant improvements in productivity and efficiency in the heavy‐duty truck‐lighting systems plant.

Details

Journal of Manufacturing Technology Management, vol. 16 no. 3
Type: Research Article
ISSN: 1741-038X

Keywords

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Article
Publication date: 1 September 1999

Christopher Collins

Only continuously monitoring cavity pressure allows the detailed recording of the injection molding process in the injection, compression and holding pressure phases. It…

Abstract

Only continuously monitoring cavity pressure allows the detailed recording of the injection molding process in the injection, compression and holding pressure phases. It alone correlates with all significant molding features such as weight, morphology, degree of forming, burr formation, shrink marks and cavities as well as shrinkage and deformation. The cavity pressure not only optimizes the timing of the switching point from the compression to the holding pressure phase, but also serves directly as a criterion for the switching. Molding weights and countless other quality characteristics thereby vary considerably less than with switching based on hydraulic pressure, screw travel or time. Quartz sensors have proved particularly successful for direct and indirect measurement of pressure. Advocates the use of cavity pressure sensors for monitoring and control of the injection molding process and describes commercial products that are available.

Details

Assembly Automation, vol. 19 no. 3
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 7 August 2017

Long Wu, Kit-Lun Yick, Joanne Yip and Sun-Pui Ng

One of the crucial steps in the molded bra production is the process of developing the mold head. The purpose of this paper is to determine the final cups style and size…

Abstract

Purpose

One of the crucial steps in the molded bra production is the process of developing the mold head. The purpose of this paper is to determine the final cups style and size. Compared with traditional development process of the mold head, less time-consuming and a more quantitative method is needed for the design and modification of the mold head.

Design/methodology/approach

A three-dimensional (3D) numerical model for the simulation of large compressive deformation was built in this paper to research the foam bra cup molding process. Since the head cones have more representative than the mold heads, the male and female head cones were used in the simulation. All of the solid shapes are modeled by using 3D Solid 164 elements as well as an automatic surface-to-surface contact between head cones.

Findings

Simulation of the foam cup molding process is conducted by inputting different properties of the foam material and stress-strain curves under different molding temperatures.

Research limitations/implications

In order to simulate the laminated foam moulding process, heat transfer through a layered textile assembly can be studied by using the thermo-mechanical coupled FE model.

Practical implications

According to the different foam performance parameters under different temperatures along with different head cone shapes, distribution and variation in the stress field can be obtained as well as the ultimate capacity of foam materials.

Social implications

A computer-aided parametric design system for the mold heads provides an effective solution to improving the development process of mold heads.

Originality/value

The distribution and variation in the stress fields can be analyzed through simulation, providing a reference for the mold head design.

Details

International Journal of Clothing Science and Technology, vol. 29 no. 4
Type: Research Article
ISSN: 0955-6222

Keywords

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