Search results

21 – 30 of over 1000
Content available
Article
Publication date: 1 December 2004

42

Abstract

Details

Circuit World, vol. 30 no. 4
Type: Research Article
ISSN: 0305-6120

Keywords

Article
Publication date: 1 March 1986

AT a manufacturing stage or to ensure the continued airworthiness of an aircraft's components, non‐destructive testing (NDT) occupies an important place in any inspection

Abstract

AT a manufacturing stage or to ensure the continued airworthiness of an aircraft's components, non‐destructive testing (NDT) occupies an important place in any inspection programme. By means of the methods employed, parts can be inspected and returned to service with confidence in their ability to fulfil a role in a system or structure. Also of significance is the early detection by NDT methods of potential defects so that preventative measures can be immediately implemented. This is particularly important where engine components are concerned in which high stress levels are part of the normal operating environment together with creep and fatigue in several forms.

Details

Aircraft Engineering and Aerospace Technology, vol. 58 no. 3
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 14 February 2018

Alexander Hanss and Gordon Elger

For soldering, flux is essential because it enables the wetting of the molten solder. Fluxless soldering, i.e. residue-free soldering with the aid of gaseous activators, has been…

Abstract

Purpose

For soldering, flux is essential because it enables the wetting of the molten solder. Fluxless soldering, i.e. residue-free soldering with the aid of gaseous activators, has been known for many years, but is only well established in the field of opto- and microwave electronics where the solder is applied as preform. In high-volume SMD applications where solder paste is printed, this technology is rarely used until now. The reducing effect of a gaseous activator like formic acid vapor on certain solder alloys is known in practice. However, the corresponding reactions which occur under soldering conditions in nitrogen atmosphere have so far not been systematically investigated for different solder alloys. This study aims to analyze the different chemical reaction channels which occur on the surface of different solders, i.e. catalytical dissociation of formic acid on the pure or oxidized metal surface and the formation and evaporation of metal formates. Based on this analysis, a residue-free solder process under formic acid is developed for solder paste applications.

Design/methodology/approach

In this paper, different solder alloys (SnAgCu, SnPb, BiSn, In) were analyzed with thermal gravimetric analysis (TGA) under formic acid flow. Details on mass change depending on the soldering temperature are presented. Activation temperatures are estimated and correlated to the soldering processes. Based on the analysis, fluxless solder pastes and suitable soldering processes are developed and presented. Major paste properties such as printability are compared to a commercial flux solder paste. High-power flip chip LEDs which can be assembled directly on a printed circuit board are used to demonstrate the fluxless soldering. Likewise, the soldering results of standard paste and fluxless paste systems after a reflow process are evaluated and compared.

Findings

The experimental results show that TGA is an efficient way to gain deeper understanding of the redox processes which occur under formic acid activation, i.e. the formation of metal formates and their evaporation and dissociation. It is possible to solder residue-free not only with preforms but also with a fluxless solder paste. The resulting solder joints have the same quality as those for standard solder paste in terms of voids detected by X-ray and mechanical shear strength.

Originality/value

In the fluxless soldering process, the reduction of oxide layers, and therefore the wetting of the solder spheres, is enabled by gaseous formic acid. After the soldering process, no cleaning process is necessary because no corrosive residues are left on the circuit boards and components. Therefore, soldering using solder paste without aggressive chemical ingredients has a high market potential. Expensive preforms could be replaced by paste dispensing or paste printing.

Details

Soldering & Surface Mount Technology, vol. 30 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 23 November 2021

Xiuqian Wu, Dehong Ye, Hanmin Zhang, Li Song and Liping Guo

This paper aims to investigate the root causes of and implement the improvements for the inter layer dielectric (ILD) crack for LQFP C90FG (CMOS90 Floating Gate) wafer technology…

Abstract

Purpose

This paper aims to investigate the root causes of and implement the improvements for the inter layer dielectric (ILD) crack for LQFP C90FG (CMOS90 Floating Gate) wafer technology devices in copper wire bonding process.

Design/methodology/approach

Failure analysis was conducted including cratering, scanning electron microscopy inspection and focus ion beam cross-section analysis, which showed ILD crack. Root cause investigation of ILD crack rate sudden jumping was carried out with cause-and-effect analysis, which revealed the root cause is shallower lead frame down-set. ILD crack mechanism deep-dive on ILD crack due to shallower lead frame down-set, which revealed the mechanism is lead frame flag floating on heat insert. Further investigation and energy dispersive X-ray analysis found the Cu particles on heat insert is another factor that can result in lead frame flag floating.

Findings

Lead frame flag floating on heat insert caused by shallower lead frame down-set or foreign matter on heat insert is a critical factor of ILD crack that has never been revealed before. Weak wafer structure strength caused by thinner wafer passivation1 thickness and sharp corner at Metal Trench (compared with the benchmarking fab) are other factors that can impact ILD crack.

Originality/value

For ILD crack improvement in copper wire bonding, besides the obvious factors such as wafer structure and wire bonding parameters, also should take other factors into consideration including lead frame flag floating on heat insert and heat insert maintenance.

Details

Microelectronics International, vol. 39 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

Content available
Article
Publication date: 20 September 2011

256

Abstract

Details

Soldering & Surface Mount Technology, vol. 23 no. 4
Type: Research Article
ISSN: 0954-0911

Article
Publication date: 1 April 2004

Joe Smetana, Rob Horsley, John Lau, Ken Snowdon, Dongkai Shangguan, Jerry Gleason, Irv Memis, Dave Love, Walter Dauksher and Bob Sullivan

The High Density Packaging Users Group conducted a substantial study of the solder joint reliability of high‐density packages using lead‐free solder. The design, material, and…

Abstract

The High Density Packaging Users Group conducted a substantial study of the solder joint reliability of high‐density packages using lead‐free solder. The design, material, and assembly process aspects of the project are addressed in this paper. The components studied include many surface mount technology package types, various lead, and printed circuit board finishes and paste‐in‐hole assembly.

Details

Soldering & Surface Mount Technology, vol. 16 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

Content available
Article
Publication date: 8 February 2008

47

Abstract

Details

Soldering & Surface Mount Technology, vol. 20 no. 1
Type: Research Article
ISSN: 0954-0911

Article
Publication date: 2 May 2017

Hanmin Zhang, Ming Hu, Zhijie Wang, Qingchun He and Denghong Ye

The purpose of this paper is to attempt to study the failure mechanism of BGA (ball grid array) Cu wire bond ball lift and specifically focused on substrate outgassing’s impact on…

Abstract

Purpose

The purpose of this paper is to attempt to study the failure mechanism of BGA (ball grid array) Cu wire bond ball lift and specifically focused on substrate outgassing’s impact on Cu wire bonding quality and reliability.

Design/methodology/approach

The Galvanic corrosion theory has been widely adopted in explaining the failure mechanism of Cu ball bond lift issue during reliability test or field application in the presence of moisture. In this study, ion chromatography was performed on BGA substrate halogen analysis. EDX (energy-dispersive X-ray spectroscopy) was also used to detect the contaminant’s element at the bottom surface of a window clamp. Further FTIR (Fourier transform infrared spectroscopy) analysis verified that the contamination is from substrate outgassing during wire bonding. A new window clamp design proved effective in reducing the negative impact from substrate outgassing during wire bonding.

Findings

The solder mask in a fresh substrate contains a chlorine element. The chlorine can be detected in the BGA substrate outgassing during wire bonding by FTIR and EDX analyses, which have a negative impact on the Cu wire bonding. The window clamp with a larger opening can reduce the negative impact of the Cu wire bonding from the BGA substrate outgassing.

Research limitations/implications

Because of the limitation of time and resources, bonding pad surface contamination from substrate outgassing and its correlation with Cu bonding ball lift failure after reliability test will be studied in depth later.

Originality/value

The BGA substrate outgassing has negative impacts on Cu wire bondability. A window clamp with a larger opening can reduce the negative impact from substrate outgassing.

Details

Microelectronics International, vol. 34 no. 2
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 24 May 2013

Gilad Sharon, Rachel Oberc and Donald Barker

The development of micro‐electro‐mechanical systems (MEMS) for use in military and consumer electronics necessitates an analysis of MEMS component reliability. The understanding…

Abstract

Purpose

The development of micro‐electro‐mechanical systems (MEMS) for use in military and consumer electronics necessitates an analysis of MEMS component reliability. The understanding of the reliability characteristics of SCSi within MEMS structures should be improved to advance MEMS applications. Reliability assessments of MEMS technology may be used to conduct virtual qualification of these devices more efficiently. The purpose of this paper is to create a simple, inexpensive test methodology to use the dynamic fracture strength of a MEMS device to predict its reliability, and to verify this method through experimentation.

Design/methodology/approach

The dynamic fracture strength of single crystal silicon (SCSi) was used to model MEMS devices subjected to high shock loading. Experimentation with SCSi MEMS structures was performed following the proposed test methodology. A probabilistic distribution for bending of Deep Reactive Ion Etching (DRIE) processed SCSi around the <110> directions was generated as a tool for assessing product reliability.

Findings

Post shock test inspections revealed that failures occurred along {111} planes. Additional experiments provided preliminary estimates of the fracture strength for bending of DRIE processed SCSi around the <100> directions in excess of 1.1 GPa.

Originality/value

This paper proposes a test methodology for an efficient method to assess the reliability of processed SCSi based on dynamic fracture strength.

Details

International Journal of Structural Integrity, vol. 4 no. 2
Type: Research Article
ISSN: 1757-9864

Keywords

Content available

Abstract

Details

Soldering & Surface Mount Technology, vol. 24 no. 1
Type: Research Article
ISSN: 0954-0911

21 – 30 of over 1000