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Article
Publication date: 7 September 2015

Lilan Gao, Hong Gao and Xu Chen

This review paper aims to provide a better understanding of formulation and processing of anisotropic conductive adhesive film (ACF) material and to summarize the significant…

349

Abstract

Purpose

This review paper aims to provide a better understanding of formulation and processing of anisotropic conductive adhesive film (ACF) material and to summarize the significant research and development work for the mechanical properties of ACF material and joints, which helps to the development and application of ACF joints with better reliability in microelectronic packaging systems.

Design/methodology/approach

The ACF material was cured at high temperature of 190°C, and the cured ACF was tested by conducting the tensile experiments with uniaxial and cyclic loads. The ACF joint was obtained with process of pre-bonding and final bonding. The impact tests and shear tests of ACF joints were completed with different aging conditions such as high temperature, thermal cycling and hygrothermal aging.

Findings

The cured ACF exhibited unique time-, temperature- and loading rate-dependent behaviors and a strong memory of loading history. Prior stress cycling with higher mean stress or stress amplitude restrained the ratcheting strain in subsequent cycling with lower mean stress or stress amplitude. The impact strength and adhesive strength of ACF joints increased with increase of bonding temperature, but they decreased with increase of environment temperature. The adhesive strength and life of ACF joints decreased with hygrothermal aging, whereas increased firstly and then decreased with thermal cycling.

Originality/value

This study is to review the recent investigations on the mechanical properties of ACF material and joints in microelectronic packaging applications.

Details

Soldering & Surface Mount Technology, vol. 27 no. 4
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 October 2006

Laura Frisk and Kati Kokko

The purpose of this study is to investigate the effect of chip and substrate thickness on the thermal cycling reliability of flip chip joints assembled with anisotropic conductive…

320

Abstract

Purpose

The purpose of this study is to investigate the effect of chip and substrate thickness on the thermal cycling reliability of flip chip joints assembled with anisotropic conductive adhesives (ACA) on FR‐4 substrates.

Design/methodology/approach

Four test lots were assembled with two substrates and two test chips. The thicknesses of the substrates were 710 and 100 μm and the thicknesses of the chips were 480 and 80 μm. To study the effect of the bonding pressure each test lot contained four test series bonded with four different bonding pressures. The reliability of the test samples was studied using a temperature cycling test.

Findings

The reliability of the test lots varied widely during the test. The test lot with a thin substrate and thin chip demonstrated considerably better reliability than the other test lots. In addition, the test lots had different failure mechanisms. After the test delamination was found in every test lot except the one assembled with the thin chip and the thin substrate.

Originality/value

The work shows that the thermal cycling reliability of ACA flip chip joints can be markedly increased by using thinned chips or reducing the thickness of the substrate.

Details

Soldering & Surface Mount Technology, vol. 18 no. 4
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 March 2005

Sami T. Nurmi, Janne J. Sundelin, Eero O. Ristolainen and Toivo K. Lepistö

To study the behaviour of voids in PBGA solder joints and their influence on the lifetime of lead‐free solder joints.

816

Abstract

Purpose

To study the behaviour of voids in PBGA solder joints and their influence on the lifetime of lead‐free solder joints.

Design/methodology/approach

The behaviour of voids was studied using micro via and land pad PWBs, PBGA components, and by measuring voids in the solder joints. The lifetimes of solder joints were tested using accelerated temperature tests.

Findings

Number of factors affecting the solder joint lifetimes were found. The voids were discovered to have a significantly large influence on the solder joints.

Practical implications

The findings can be used to achieve better soldering results, methods, and designs.

Originality/value

In this paper, the effect and the behaviour of voids were studied profoundly. The findings can be valuable to researchers and process personnel.

Details

Soldering & Surface Mount Technology, vol. 17 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 December 2003

T. Alander, I. Suominen, P. Heino and E. Ristolainen

The solder joint reliability of FC components on organic substrates is questionable unless underfill is used to relieve the thermal strains. Besides the mechanical protection…

276

Abstract

The solder joint reliability of FC components on organic substrates is questionable unless underfill is used to relieve the thermal strains. Besides the mechanical protection, underfill provides the solder and I.C. surface with protection against the environment. Underfilling is however, time‐consuming and expensive. In an electrical sense, the underfill has no beneficial function and should, therefore, be considered as a ballast in an electronic assembly. However, to obtain a satisfactory level of reliability without underfill some novel methods are required. Wafer thinning is often performed to fit a die into a thin package, e.g. in smart cards. In this paper, the issue of thinning a package is studied utilizing 3D finite element method models. Various die and board thicknesses are evaluated with respect to their effect on the reliability of FC solder bumps. In addition, a novel idea to increase the joint reliability is studied.

Details

Soldering & Surface Mount Technology, vol. 15 no. 3
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 December 2005

Janne J. Sundelin, Sami T. Nurmi, Toivo K. Lepistö and Eero O. Ristolainen

To provide further knowledge of the effect of solder composition and PCB surface finish on the creep properties of lead‐free SnAgCu solder joints.

1041

Abstract

Purpose

To provide further knowledge of the effect of solder composition and PCB surface finish on the creep properties of lead‐free SnAgCu solder joints.

Design/methodology/approach

Single‐overlap shear specimens were prepared for the creep testing. The test matrix included three different SnAgCu pastes with hypoeutectic, eutectic, and hypereutectic compositions. An Sn63Pb37 solder paste was used as a reference. The PCB finishes used were NiAu, organic solderability preservative (OSP) and immersion tin. The creep tests were performed at 85 and 105°C using a dead‐weight system.

Findings

According to the results, the SnAgCu solder with eutectic or near‐eutectic composition is the safest choice when the creep behaviour of solder joints is considered. Of the three different PCB surface finishes, immersion tin is the most favourable choice for use with SnAgCu joints when creep is the predominant deformation mechanism in the joints. On the NiAu finish the creep properties of SnAgCu solder joints were significantly weaker in eutectic and hypereutectic SnAgCu joints than on Sn and OSP.

Originality/value

The results can be used to enhance the reliability of SnAgCu joints in demanding conditions, when special attention is paid to the choice of PCB surface finish and SnAgCu solder composition.

Details

Soldering & Surface Mount Technology, vol. 17 no. 4
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 April 2003

S.T. Nurmi, J.J. Sundelin, E.O. Ristolainen and T. Lepistö

Lead‐free soldering is becoming a common practice in the electronics industry because of the growing general opposition to lead‐containing solders. The reliability of lead‐free…

599

Abstract

Lead‐free soldering is becoming a common practice in the electronics industry because of the growing general opposition to lead‐containing solders. The reliability of lead‐free solders has been studied a lot recently, but knowledge of it is still incomplete and many issues related to them are under heavy debate. This paper presents results from a study of the formation of voids with regard to the number of reflow cycles in three different kinds of solder joints: first the ones prepared with lead‐free solder paste and lead‐free plastic ball grid array (PBGA) components, next the ones prepared with lead‐free solder paste and tin‐lead‐silver PBGA components, and last the ones prepared with tin‐lead solder paste and tin‐lead‐silver PBGA components.

Details

Soldering & Surface Mount Technology, vol. 15 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 April 1999

Aulis Tuominen, Eero Ristolainen and Ville Lehtinen

Owing to the incessant demand for reductions in the size of portable electronics, new dense packaging technologies are required. Reflow soldering is still mainly used for…

274

Abstract

Owing to the incessant demand for reductions in the size of portable electronics, new dense packaging technologies are required. Reflow soldering is still mainly used for component joining on the substrate. In tiny joints such as those in flip chip (FC) assemblies the flux effect is vitally important and needs to pass a narrower performance window than in ordinary surface mount technology (SMT). The determination of the suitability of a flux, as reported in this paper, is twofold; first, the flux must perform well in its intended purpose and second, the flux must not leave harmful residues causing leakage or electromigration. The first test used was the wetting balance test for all fluxes. Fluxes accepted on the basis of the wetting tests were then subjected to the surface insulation resistance test (SIR).

Details

Soldering & Surface Mount Technology, vol. 11 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 13 August 2019

Sung Yi and Robert Jones

This paper aims to present a machine learning framework for using big data analytics to predict the reliability of solder joints. The purpose of this study is to accurately…

699

Abstract

Purpose

This paper aims to present a machine learning framework for using big data analytics to predict the reliability of solder joints. The purpose of this study is to accurately predict the reliability of solder joints by using big data analytics.

Design/methodology/approach

A machine learning framework for using big data analytics is proposed to predict the reliability of solder joints accurately.

Findings

A machine learning framework for predicting the life of solder joints accurately has been developed in this study. To validate its accuracy and efficiency, it is applied to predict the long-term reliability of lead-free Sn96.5Ag3.0Cu0.5 (SAC305) for three commonly used surface finishes such OSP, ENIG and IAg. The obtained results show that the predicted failure based on the machine learning method is much more accurate than the Weibull method. In addition, solder ball/bump joint failure modes are identified based on various solder joint failures reported in the literature.

Originality/value

The ability to predict thermal fatigue life accurately is extremely valuable to the industry because it saves time and cost for product development and optimization.

Details

Soldering & Surface Mount Technology, vol. 32 no. 2
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 April 2003

Anne Seppälä, Kati Aalto and Eero Ristolainen

Flip chip assembly using anisotropic conductive adhesives offers an interesting alternative for making high‐density interconnections. The use of conventional organic printed…

359

Abstract

Flip chip assembly using anisotropic conductive adhesives offers an interesting alternative for making high‐density interconnections. The use of conventional organic printed circuit boards makes this technique even more attractive. However, a low‐cost adhesive flip chip bonding process will require a reduced bonding cycle time or the use of multi‐head joining equipment. Adhesive flip chip bonding is characterized by a long bonding cycle time due to the relatively long curing time of adhesives and the need for simultaneous application of pressure during the curing process. In soldered flip chip techniques, the bonding time per assembly is shorter, because all the chips on the substrate can be soldered in a reflow oven at the same time. In this study, the minimum pre‐curing time needed to make a reliable adhesive joint was determined using one commercial anisotropic conductive adhesive film used on FR‐4 substrates. The results are promising, since bonding time reduction from 40 s to 10 s does not reduce the joint reliability.

Details

Soldering & Surface Mount Technology, vol. 15 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 29 June 2010

Kati Kokko, Laura Frisk and Pekka Heino

The purpose of this paper is to study the effect of conformal coating on the thermal cycling reliability of anisotropically conductive adhesive film (ACF) joined flip chip…

315

Abstract

Purpose

The purpose of this paper is to study the effect of conformal coating on the thermal cycling reliability of anisotropically conductive adhesive film (ACF) joined flip chip components on FR‐4 and polyimide (PI) substrates.

Design/methodology/approach

Test chips were joined using flip chip technology and an anisotropically conductive adhesive. The conformal coating used was parylene C and it was applied using the vapour deposition polymerisation method. The reliability of ACF joined flip chip components on FR‐4 and PI substrates was evaluated using −40/+85°C thermal cycling testing. Test lots with and without parylene C coating were studied. Additionally, one test lot with initial moisture inside the coating layer and a PI substrate was subjected to the test. The reliability results were analyzed using Weibull analysis and failure analysis was performed to study the failure mechanisms using cross sectioning and optical and scanning electron microscopy.

Findings

The results show a clear difference between the FR‐4 and PI substrate materials. PI substrate material proved to be reliable enough to withstand the thermal cycling testing. Two different occurrences of the first failures are seen and analyzed with FR‐4 substrates. The conformal coating layer did not seem to impair the reliability. Parylene C coating proved to be a reliable choice to protect, and even improve, the thermal cycling reliability of flip chip devices.

Originality/value

Usually, conformal coatings are studied in humidity tests. However, it is also vital to know whether the conformal coatings affect the reliability in thermal cycling and there is a lack of reliability studies in this area. This paper gives reliability data for conformal coating users about the influence of thermal cycling.

Details

Soldering & Surface Mount Technology, vol. 22 no. 3
Type: Research Article
ISSN: 0954-0911

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