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1 – 10 of 52
Article
Publication date: 1 January 1992

J. Lau, G. Dody, W. Chen, M. McShane, D. Rice, S. Erasmus and W. Adamjee

The reliability of 0·5 mm pitch, 208‐pin FQFP solder joints has been studied by experimental temperature cycling and 3‐D nonlinear finite element analysis. Temperature cycling…

Abstract

The reliability of 0·5 mm pitch, 208‐pin FQFP solder joints has been studied by experimental temperature cycling and 3‐D nonlinear finite element analysis. Temperature cycling results have been presented as a Weibull distribution. Thermal fatigue life of the solder joints has been estimated based on the calculated plastic strain and isothermal fatigue data on solders. A correlation between the experimental and analytical results has also been made.

Details

Circuit World, vol. 18 no. 2
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 March 1995

S.V. Vasan, P.T. Truong and G. Dody

This paper discusses chip removal and replacement processes of flip chip assemblies (FCAs) on printed wiring boards (PWBs). The original chip connection is achieved via mass…

Abstract

This paper discusses chip removal and replacement processes of flip chip assemblies (FCAs) on printed wiring boards (PWBs). The original chip connection is achieved via mass reflow as in a surface mount assembly process. The FCA interconnection is one involving a surrogate solder bump on a chip and a lower melt solder on the PWB pads that fuses with the bump during reflow. The chip removal process thus entails melting the lower melt solder locally using hot gas. The following considerations will be discussed in the paper: chip size, chip removal methodology, local vs mass reflow for replacement attachment, solder height, the impact of multiple reflows on the solder joint integrity of assemblies. The use of the flip chip rework machine to remove ball grid arrays (BGAs) and quad flatpacks (QFPs) will be briefly addressed.

Details

Circuit World, vol. 21 no. 3
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 4 January 2021

Mazrina Mazlan, Muhammad Rizwan, Ahmad Danial Azzahari, Vidhya Selvanathan, Faridah Sonsudin and Nurshafiza Shahabudin

The purpose of this study is to modify guar gum (GG) into guar gum acetate (GGA) and phthaloyl guar gum (PHGG) by transesterification and phthaloylation, respectively.

Abstract

Purpose

The purpose of this study is to modify guar gum (GG) into guar gum acetate (GGA) and phthaloyl guar gum (PHGG) by transesterification and phthaloylation, respectively.

Design/methodology/approach

GG has been modified into GGA through transesterification reaction between GG and vinyl acetate and PHGG through esterification reaction with phthalic anhydride. The modified GG was characterized by solubility test, Fourier-transform infra-red (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, X-ray diffractometry (XRD) and thermogravimetric analysis. Swelling properties of GGA and PHGG hydrogels in water were evaluated.

Findings

These two types of modified GG have better solubility such as in dimethyl sulfoxide and N,N-dimethylformamide but no true organosolubility was achieved. The modifications were confirmed through FTIR with new absorption peaks at 1,733 cm−1 for GGA and 1,709 cm−1 for PHGG coupled with observed substitution peaks at 1.80 to 2.20 ppm and 7.40 to 7.90 ppm, respectively, from 1H NMR spectroscopies. XRD revealed both GGA and PHGG are less crystalline than native GG. GGA was found to be more thermally stable than native GG, whereas PHGG was slightly less thermally stable than native GG. The swelling property in distilled water for native GG, PHGG and GGA was 918.43 ± 46.62%, 537.04 ± 2.87% and 393.04 ± 13.42%, respectively.

Research limitations/implications

The GGA and PHGG hydrogels are expected to be useful for biomedical fields such as tissue engineering and drug-delivery.

Originality/value

Modifications of native GG into GGA using vinyl acetate and PHGG using phthalic anhydride are novel.

Details

Pigment & Resin Technology, vol. 50 no. 6
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 1 April 1992

J. Lau, R. Govila, C. Larner, Y.‐H. Pao, S. Erasmus, S. Dolot, M. Jalilian and M. Lancaster

Solvent‐clean and no‐clean mass reflow processes of 0.4 mm pitch, 28 mm body size, 256‐pin fine pitch quad flat packs (QFPs) are presented. Emphasis is placed on fine pitch…

Abstract

Solvent‐clean and no‐clean mass reflow processes of 0.4 mm pitch, 28 mm body size, 256‐pin fine pitch quad flat packs (QFPs) are presented. Emphasis is placed on fine pitch parameters such as printed circuit board (PCB) design, solder paste selection, stencil design, printing technology, component placement, mass reflow, cleaning and inspection. Furthermore, cross‐sections of component/PCB assemblies from both processes have been thoroughly studied using scanning electron microscopy (SEM).

Details

Circuit World, vol. 19 no. 1
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 25 February 2014

Dawid J. D'Melo, Anagha S. Sabnis, Mohan A. Shenoy and Mukesh S. Kathalewar

The purpose of this paper is to evaluate the efficiency of acrylated guar gum (AGG) as an additive in alkyd resin for improved mechanical properties and to optimize the results of…

Abstract

Purpose

The purpose of this paper is to evaluate the efficiency of acrylated guar gum (AGG) as an additive in alkyd resin for improved mechanical properties and to optimize the results of such an addition.

Design/methodology/approach

For studying the effect of AGG on coating properties, guar gum was modified to various degrees of esterification and various compositions of alkyd systems were made by incorporating different concentrations of AGG. The mechanical and solvent absorption of the unmodified and modified alkyd systems were characterized.

Findings

The incorporation of AGG into alkyd coating showed significant improvement of mechanical properties over the unmodified one. The modification caused an additional crosslink site through its unsaturation which led to increased crosslink density without phase separation of additive from the alkyd system which was confirmed by SEM scans.

Research limitations/implications

The reactive additive, AGG used in the present study was synthesised using acryloyl chloride. Besides, it could also be synthesised from methacryloyl chloride and the effect of methyl substitution on water and solvent absorption could be studied.

Practical implications

The method developed provided a simple and practical solution to improving the mechanical properties of alkyd coatings.

Originality/value

The method for enhancing mechanical properties of cured alkyd system was novel and could find numerous applications in surface coatings.

Details

Pigment & Resin Technology, vol. 43 no. 2
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 1 December 2000

T.A. Nguty, N.N. Ekere, J.D. Philpott and G.D. Jones

High‐density packaging devices have unique characteristics which make their assembly, test and repair very difficult. The only realistic method of rework is to replace the…

Abstract

High‐density packaging devices have unique characteristics which make their assembly, test and repair very difficult. The only realistic method of rework is to replace the defective component with a new or re‐balled component. Although a wide range of rework techniques is available, degradation in assembly reliability may accompany the process. The formation of brittle secondary intermetallic compounds following CSP rework can adversely affect the mechanical properties of the joint, particularly when they make up a significant proportion of its thickness. Reports on the effects of different CSP rework techniques on intermetallic layer formation. Two PCB pad‐cleaning methods and three flux/paste deposition methods are investigated. The reworked joints are analysed using optical microscopy to determine the extent of intermetallic growth. Their quality is also assessed using shear strength testing prior to, and after, thermal ageing at 1008C to accelerate the growth of intermetallic compounds and evolution of the solder grain structure.

Details

Soldering & Surface Mount Technology, vol. 12 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 April 1993

J. Lau, S. Golwalkar, P. Boysan, R. Surratt, R. Forhringer and S. Erasmus

The reliability of 0.5 mm pitch, 32‐pin thin small outline package (TSOP) solder joints has been studied by experimental temperature cycling and a cost‐effective 3‐D non‐linear…

Abstract

The reliability of 0.5 mm pitch, 32‐pin thin small outline package (TSOP) solder joints has been studied by experimental temperature cycling and a cost‐effective 3‐D non‐linear finite element analysis. Temperature cycling results have been presented as a Weibull distribution, and an acceleration factor has been established for predicting the failure rate at operating conditions. Thermal fatigue life of the corner solder joints has been estimated based on the calculated plastic strain, Coffin‐Manson law and isothermal fatigue data on solders. A correlation between the experimental and analytical results has also been made. Furthermore, failure analysis of the solder joints has been performed using scanning electron microscopy (SEM) and an optical method. Finally, a quantitative comparison between the Type‐I and Type‐II TSOP solder joints has been presented.

Details

Circuit World, vol. 20 no. 1
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 January 1994

J. Lau, Y.‐H. Pao, C. Larner, R. Govila, S. Twerefour, D. Gilbert, S. Erasmus and S. Dolot

The reliability of 0.4 mm pitch, 28 mm body size, 256‐pin plastic quad flat pack (QFP) no‐clean and water‐clean solder joints has been studied by temperature cycling and…

Abstract

The reliability of 0.4 mm pitch, 28 mm body size, 256‐pin plastic quad flat pack (QFP) no‐clean and water‐clean solder joints has been studied by temperature cycling and analytical analysis. The temperature cycling test was run non‐stop for more than 6 months, and the results have been presented as a Weibull distribution. A unique temperature cycling profile has been developed based on the calculated lead stiffness, elastic and creep strains in the solder joint, and solder data. Also, the thermal fatigue life of the solder joints has been estimated and correlated with experimental results. Furthermore, a failure analysis of the solder joints has been performed using scanning electron microscopy (SEM). Finally, a quantitative comparison between the no‐clean and water‐clean QFP solder joints has been presented.

Details

Soldering & Surface Mount Technology, vol. 6 no. 1
Type: Research Article
ISSN: 0954-0911

Article
Publication date: 1 March 1992

J. Glazer, P.A. Kramer and J.W. Morris

The effect of gold (Au) on the reliability of 0.65 mm pitch surface mount solder joints between plastic quad flat packs and Cu‐Ni‐Au FR‐4 printed circuit boards was investigated…

Abstract

The effect of gold (Au) on the reliability of 0.65 mm pitch surface mount solder joints between plastic quad flat packs and Cu‐Ni‐Au FR‐4 printed circuit boards was investigated. Cu‐Ni‐Au is a desirable printed circuit board finish for multi‐chip modules or printed circuit boards that would otherwise require a selective Au finish, for example for edge connectors or wire bondable parts. However, Au is known to embrittle solder when it is present in sufficiently high concentrations, creating a concern that solder joint fatigue life in service will also be adversely affected. This paper reports the results of mechanical shock, mechanical vibration and thermal cycling testing of fine pitch solder joints containing varying amounts of Au. Tests were performed on as‐soldered joints and on joints that had been heat‐treated to evolve the microstructure towards equilibrium. The tests were designed to accelerate in‐service conditions in a typical industrial environment. Under these conditions, the Au concentrations tested did not promote solder joint failures. Microstructural characterisation of the distribution and morphology of the Au‐, Ni‐ and Cu‐Sn intermetallics in the joint before and after accelerated testing was also performed. On the basis of these observations it is recommended that the Au concentration in solder joints between plastic quad flat packs and Cu‐Ni‐Au FR‐4 printed circuit boards not exceed 3.0 wt.%.

Details

Circuit World, vol. 18 no. 4
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 January 1994

J. Liu

This paper describes the influence of soldering parameters on solder joint quality and reliability of 0.65 mm pitch QFP technology. Soldering process parameters such as soldering…

Abstract

This paper describes the influence of soldering parameters on solder joint quality and reliability of 0.65 mm pitch QFP technology. Soldering process parameters such as soldering temperature, conveyor speed and board size have systematically been varied using factorial experimental analysis. Solder joint quality has been characterised in terms of solder ball formation, open joints and porosity behaviour. Equipment used includes microfocus X‐ray non‐destructive testing apparatus, optical and scanning electron microscope. The reliability of solder joints has been investigated by temperature cycling from −55 to + 125°C for 1000 cycles. The time per cycle was approximately 1 hour. The results from the present work show that pad layout on the printed circuit board (PCB) and the quality of pretinning during PCB production have a considerable influence on the solder joint yield. No failures have been observed during temperature cycling. This indicates that 0.65 mm (25 mil) pitch QFP components have very high reliability in respect of temperature cycling and are extremely compliant for absorbing the thermal stress developed during temperature cycling.

Details

Soldering & Surface Mount Technology, vol. 6 no. 1
Type: Research Article
ISSN: 0954-0911

1 – 10 of 52