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Article
Publication date: 19 September 2008

K. Bukat, J. Sitek, R. Kisiel, Z. Moser, W. Gasior, M. Kościelski and J. Pstruś

The purpose of this paper is a comparable evaluation of the influence of a particular element (Bi and Sb) added to Sn‐Ag‐Cu and Sn‐Zn alloys on their surface and…

Abstract

Purpose

The purpose of this paper is a comparable evaluation of the influence of a particular element (Bi and Sb) added to Sn‐Ag‐Cu and Sn‐Zn alloys on their surface and interfacial tensions, as well as the wetting properties on the Cu substrate expressed by the wetting angle.

Design/methodology/approach

The authors applied the L8 orthogonal Taguchi array to carry out the experiments and discussed the results using analysis of variance (ANOVA).

Findings

It was expected, on the base of previous studies, the decrease of the surface and interfacial tensions and thus improving wettability after the Bi and Sb addition to Sn‐Ag‐Cu and Sn‐Zn alloys. Unfortunately, the obtained results on the quinary Sn‐Ag‐Cu‐Bi‐Sb alloys and the quaternary Sn‐Zn‐Bi‐Sb alloys do not confirm these trends. The performed analyses suggest that the compositions of the quinary Sn‐Ag‐Cu‐Bi‐Sb alloys, as well as the quaternary Sn‐Zn‐Bi‐Sb alloys, do not have optimal compositions for practical application. The Cu, Bi and Sb elements in the case of the Sn‐Ag‐Cu‐Bi‐Sb alloys and the Zn, Bi and Sb elements in the case of the Sn‐Zn‐Bi‐Sb alloys show mutual interaction and, in consequence, there is no correlation between the tendency of the surface and interfacial tensions changes and the wettings of the Cu substrate.

Research limitations/implications

It is suggested that further studies are necessary for the purpose of the practical application, but they should be limited mainly to the Sn‐Ag‐Cu‐Bi and the Sn‐Zn‐Bi alloys with the optimal compositions.

Practical implications

The performed analysis suggests that none of the investigated compositions of the quinary Sn‐Ag‐Cu‐Bi‐Sb alloys, as well as the quaternary Sn‐Zn‐Bi‐Sb alloys, have the optimal compositions for practical application.

Originality/value

The quickest way to determine which element of the alloy composition influences the surface tension and the wetting properties, and how, is to apply orthogonal analysis. After choosing the orthogonal array, the experiments were performed and analysis of variance (ANOVA) was used to perform the quantifiable analysis of the measured and calculated results of surface and interfacial tensions, as well as the wetting properties on the Cu substrate.

Details

Soldering & Surface Mount Technology, vol. 20 no. 4
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 13 April 2010

Liang Zhang, Song-bai Xue, Li-li Gao, Yan Chen, Sheng-lin Yu, Zhong Sheng and Guang Zeng

The purpose of this paper is to investigate the effects of minor addition of the rare earth (RE) element cerium, Ce, on the microstructures and creep properties of Sn-Ag-Cu

Abstract

Purpose

The purpose of this paper is to investigate the effects of minor addition of the rare earth (RE) element cerium, Ce, on the microstructures and creep properties of Sn-Ag-Cu solder alloys.

Design/methodology/approach

The pure Sn, Sn-Cu alloy, Sn-Ag alloy and Cu-Ce alloy were used as raw materials. Sn-Ag-Cu alloys with different contents of RE Ce were chosen to compare with Sn-Ag-Cu. The raw materials of Sn, Sn-Cu alloy, Sn-Ag alloy, Cu-Ce alloy were melted in a ceramic crucible, and were melted at 550°C ± 1°C for 40 minutes. To homogenize the solder alloy, mechanical stirring was performed every ten minutes using a glass rod. During the melting, KC1 + LiCI (1.3:1), were used over the surface of liquid solder to prevent oxidation. The melted solder was chill cast into a rod.

Findings

It is found that the microstructure exhibits smaller grains and the Ag3Sn/Cu6Sn5 intermetallic compound (IMC) phases are modified in matrix with the addition of Ce. In particular, the addition of 0.03 wt.% Ce to the Sn-Ag-Cu solder can refine the microstructures and decrease the thickness of the IMC layers of Sn-Ag-Cu solder alloys. Meanwhile, thermodynamic analysis showed that these phenomena could be attributed to the reduction of the driving force for Cu-Sn IMC formation due to the addition of Ce. Results calculated using the thermodynamic method are close to the above experimental data. Thus, the optimum content of Ce in Sn-Ag-Cu solder alloys should be about 0.030 percent. Additionally, the effect of Ce on the creep rupture life of Sn-Ag-Cu soldered joints was studied. It was found that the creep rupture life may be increased up to 7.5 times more than that of the original Sn-Ag-Cu alloy, when Ce accounts for 0.030 percent.

Originality/value

This paper usefully investigates the effects of the RE cerium (Ce), on the microstructures and creep properties of Sn-Ag-Cu solder alloys, optimizing the quantity of Ce in the Sn-Ag-Cu solder alloy through a thermodynamic method and by creep-rupture life testing.

Details

Soldering & Surface Mount Technology, vol. 22 no. 2
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 6 June 2016

Xiangxia Kong, F. Sun, Miaosen Yang and Yang Liu

This paper aims to investigate the creep properties of the bulks of low-Ag Cu/Sn-Ag-Cu-Bi-Ni/Cu micro solder joints from 298 to 358 K. The creep constitutive modelling was…

Abstract

Purpose

This paper aims to investigate the creep properties of the bulks of low-Ag Cu/Sn-Ag-Cu-Bi-Ni/Cu micro solder joints from 298 to 358 K. The creep constitutive modelling was developed. Meanwhile, the creep mechanism of the bulks of Cu/Sn-Ag-Cu-Bi-Ni/Cu micro solder joints was discussed.

Design/methodology/approach

The creep properties of the bulks of low-Ag Cu/Sn-Ag-Cu-Bi-Ni/Cu micro solder joints from 298 to 358 K were investigated using the nanoindentation method.

Findings

The results of the experiments showed that the indentation depth and area increased with increasing temperatures. At the test temperature of 298-358 K, the creep strain rate of the bulks of the micro solder joints increases with the rising of the tested temperature. The values of creep stress exponent and activation energy calculated for the bulks of Cu/Sn-Ag-Cu-Bi-Ni/Cu micro solder joints were reasonably close to the published data. At the tested temperatures, dislocation climb took place and the dislocation climb motion was controlled by the dislocation pipe mechanism, and the second-phase particles enhancement mechanism played a very important role.

Originality/value

This study provides the creep properties of low-Ag Cu/Sn-Ag-Cu-Bi-Ni/Cu solder joints at different temperatures. The creep constitutive modelling has been developed for low-Ag Cu/Sn-Ag-Cu-Bi-Ni/Cu solder joints.

Details

Soldering & Surface Mount Technology, vol. 28 no. 3
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 September 2005

Meng‐Kuang Huang, Chiapyng Lee, Pei‐Lin Wu and Shyh‐Rong Tzan

The effects of thermal fatigue and printed circuit board (PCB) surface finish on the pull strength, failure modes and reliability of chip scale package (CSP) solder joints…

Abstract

Purpose

The effects of thermal fatigue and printed circuit board (PCB) surface finish on the pull strength, failure modes and reliability of chip scale package (CSP) solder joints were investigated.

Design/methodology/approach

Mechanical pull test, metallographic examination and electrical measurement were used. Tin lead (Sn‐Pb) and lead free (Sn‐Ag‐Cu) alloys were used with Au/Ni and organic solderability preservative (OSP) surface finishes.

Findings

The experimental results showed that the pull strength of the Sn‐Ag‐Cu/(Au/Ni) solder joint did not change noticeably with an increasing number of thermal cycles. However, the pull strength of the Sn‐Pb/(Au/Ni) solder joints drastically degraded and that of the Sn‐Ag‐Cu/OSP and Sn‐Pb/OSP solder joints slightly decreased during thermal cycling. For both Sn‐Ag‐Cu and Sn‐Pb alloys, the solder joint fracture of as‐soldered samples was the main failure mode when an Au/Ni surface finish was used. For the Sn‐Ag‐Cu/(Au/Ni) and Sn‐Ag‐Cu/OSP solder joints, the proportion of component trace tearing considerably decreased, whereas that of PCB trace tearing considerably increased, during thermal cycling. The Weibull lifetimes of the solder joints were increasingly longer in the order of Sn‐Pb/(Au/Ni), Sn‐Pb/OSP, Sn‐Ag‐Cu/OSP, and Sn‐Ag‐Cu/(Au/Ni).

Research limitations/implications

This was not an exhaustive study and all of the findings are for lead free and tin lead CSP solder joints, which perhaps limits the usefulness of the results elsewhere.

Practical implications

A very useful source of information and impartial advice for engineers planning to conduct a switch from tin lead to lead free technology in their production lines.

Originality/value

This paper fulfils an identified information/resources need and offers practical help to an engineer starting out on an engineering development.

Details

Soldering & Surface Mount Technology, vol. 17 no. 3
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 8 February 2011

Liang Zhang, Song‐bai Xue, Li‐li Gao, Zhong Sheng, Wei Dai, Feng Ji, Huan Ye, Yan Chen and Sheng‐lin Yu

The purpose of this paper is to explore the formation and growth mechanism of bulk Cu6Sn5 intermetallic compounds, selecting Sn‐Ag‐Cu‐Ce solders as specimens.

Abstract

Purpose

The purpose of this paper is to explore the formation and growth mechanism of bulk Cu6Sn5 intermetallic compounds, selecting Sn‐Ag‐Cu‐Ce solders as specimens.

Design/methodology/approach

In order to further enhance the properties of SnAgCu solder, trace amount of rare earth Ce was selected as alloying addition into the alloy; in previous investigations, the enhancements include better wettability, physical properties, creep strength and tensile strength. In this paper, the microstructure of Sn‐Ag‐Cu‐Ce soldered joints and its interfacial intermetallic compounds were investigated. Moreover, different morphologies of Cu6Sn5 IMCs were enumerated and described, and Ostwald ripening theory was employed to interpret the formation mechanism of bulk Cu6Sn5 IMCs.

Findings

In addition, based on finite element simulation, it is found that the von Mises stress concentrate around the bulk Cu6Sn5 IMCs inside the Sn‐Ag‐Cu‐Ce soldered joints after three thermal cycling loading (−55‐125°C). From the stress distribution, the failure site was predicted to fracture near the bulk Cu6Sn5 IMCs interface. This coincides with the experimental findings significantly.

Originality/value

The results presented in this paper may provide a theory guide for developing novel lead‐free solders as well as reliability investigation of lead‐free soldered joints.

Details

Soldering & Surface Mount Technology, vol. 23 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 17 August 2021

Bin Zhou, Jin Ma, Hongyan Zhou, Xiaoliang Shi and Ahmed Mohamed Mahmoud Ibrahim

This paper aims to investigate the friction noise properties of M50 matrix curved microporous channel composites filled with solid lubricant Sn-Ag-Cu (MS).

Abstract

Purpose

This paper aims to investigate the friction noise properties of M50 matrix curved microporous channel composites filled with solid lubricant Sn-Ag-Cu (MS).

Design/methodology/approach

Pure M50 (MA) and MS are prepared by selective laser melting and vacuum-pressure infiltration technology. The tribological and friction noise properties of MA and MS are tested through dry sliding friction and then the influential mechanism of surface wear sate on friction noise is investigated by analyzing the variation law of noise signals and the worn surface characteristics of MS.

Findings

Experimental results show that the friction noise sound pressure level of MS is only 75.6 dB, and it mainly consists of low-frequency noise. The Sn-Ag-Cu improves the surface wear state, which reduces self-excited vibration of the interface caused by fluctuation of friction force, leading to the decrease of friction noise.

Originality/value

This investigation is meaningful to improve the tribological property and suppress the friction noise of M50 bearing steel.

Details

Industrial Lubrication and Tribology, vol. 73 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 1 December 2005

Junling Chang, Dirk Janz, W. Kempe and Xiaoming Xie

To investigate the degradation of lead free solder heat‐sink attachment by thermal shock. Samples with high voiding percentages were selected for the investigation in…

Abstract

Purpose

To investigate the degradation of lead free solder heat‐sink attachment by thermal shock. Samples with high voiding percentages were selected for the investigation in order to get information on the significance of voids on the reliability of Sn‐Ag‐Cu heat‐sink attachment.

Design/methodology/approach

Through the use of X‐ray, C‐mode scanning acoustic microscopy, dye penetration, cross section and scanning electron microscopy/energy‐dispersive X‐ray tests, the degradation of Sn‐Ag‐Cu heat‐sink attachment during thermal shock cycling was evaluated.

Findings

The results showed that the Sn‐Ag‐Cu heat‐sink attachment where the area of voiding was 33‐48 per cent survived 3,000 thermal shock cycles, although degraded. The main degradation mechanism for the solder attachment was not solder fatigue but interface delamination due to Kirkendall voids at the Cu/Cu3Sn interface. It was found that the large voids in the Sn‐Ag‐Cu heat‐sink attachment were not significantly affecting the solder joint lifetime. Big differences of intermetallic compound growth behaviour and Kirkendall voids at device/solder and solder/Cu pad interfaces are found and the reasons for this are discussed.

Originality/value

This work has clarified the general perception that large voids affect the thermo‐mechanical lifetime of solder joint substantially and also provides further understanding of the Sn‐Ag‐Cu heat‐sink attachment degradation mechanism.

Details

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

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Article
Publication date: 1 April 2004

B. Salam, C. Virseda, H. Da, N.N. Ekere and R. Durairaj

A study of the Sn‐Ag‐Cu lead‐free solder reflow profile has been conducted. The purpose of the work was to determine the Sn‐Ag‐Cu reflow profile that produced solder bumps…

Abstract

A study of the Sn‐Ag‐Cu lead‐free solder reflow profile has been conducted. The purpose of the work was to determine the Sn‐Ag‐Cu reflow profile that produced solder bumps with a thin intermetallic compound (IMC) layer and fine microstructure. Two types of reflow profiles were studied. The results of the experiment indicated that the most significant factor in achieving a joint with a thin IMC layer and fine microstructure was the peak temperature. The results suggest that the peak temperature for the Sn‐Ag‐Cu lead‐free solder should be 230°C. The recommended time above liquidus is 40 s for the RSS reflow profile and 50‐70 s for the RTS reflow profile.

Details

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

Keywords

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Article
Publication date: 8 February 2011

Z. Moser, P. Fima, K. Bukat, J. Sitek, J. Pstruś, W. Gąsior, M. Kościelski and T. Gancarz

The purpose of this paper is to investigate the influence of In additions on the wetting properties of the Sn2.86Ag0.40Cu (in wt%) eutectic‐based alloys, on a copper…

Abstract

Purpose

The purpose of this paper is to investigate the influence of In additions on the wetting properties of the Sn2.86Ag0.40Cu (in wt%) eutectic‐based alloys, on a copper substrate, in the presence of a flux. The main goal was to find correlations between the results of the wetting balance (WB) and the sessile drop (SD) method, in relation to the contact angles.

Design/methodology/approach

The WB method was applied for the wetting measurements, at 250°C, in an air atmosphere and in the presence of a flux. The SD measurements were conducted at the same temperature, in the presence of the same flux, but in an Ar atmosphere, while the maximum bubble pressure (MBP) and dilatometric measurements were conducted in an Ar+H2 atmosphere. The density data from the dilatometric method were used for the determination of the surface tension by means of MBP, and the WB method was used to determine the surface and interfacial tension. Next, the surface tension data from these two methods were compared. The WB data were used to calculate the contact angles and the obtained indirect data were compared with the results of the direct SD measurements of the contact angle.

Findings

A higher In content in the alloy resulted in a lower contact angle on the copper, and the WB results agreed well with the results of the SD experiments. It was confirmed that, in liquid In‐Sn and the alloys containing In and Sn (Ag‐In‐Sn, Sn‐Ag‐Cu‐In, Sn‐Zn‐In), the improvement of the wettability was indicated only by the increase of the contact angle with the increasing In content.

Research limitations/implications

Further studies are necessary for the confirmation of practical application, but they should be directed to the soldering of high indium alloys on printed circuit boards, with different finishes and qualities of the solder joint performance.

Practical implications

Taking into account the contact angle data from the WB and SD methods, the best results of the SAC‐In alloy on copper were obtained for the alloy of the highest In content. It was found that the contact angles from SD after 4 s were higher (non‐equilibrium conditions) than the values calculated from WB after 3 s. In contrast, the contact angles from SD after 10 min (equilibrium conditions) were lower than those from WB after 3 s. The comparison suggests that the contact angles from WB are situated within the data from SD, showing the same lowering tendency with the increasing content of In, and they may be well accepted for practical purposes. On the other hand, the sample of the solder in the SD method, after a prolonged time – in order to get the equilibrium contact angle – may be used to study the interfacial phenomena with the Cu substrate. The differential thermal analysis results indicate that the melting temperature decreases with increasing tin concentration. Taking into account the results of this study and the available literature data, alloys containing 8‐10 wt% of In can be recommended for practical application.

Originality/value

The WB and SD methods were used for the contact angle determination of a wide range of solder compositions, in the same temperature and flux conditions. Also, the surface tensions for these alloys were determined with the use of two independent methods: the MBP and the WB methods. The results obtained made it possible to draw conclusions regarding the correlation between the output of different methods and the conditions in which a comparison of the results can be made. It is supposed that these observations apply to many other alloy systems.

Details

Soldering & Surface Mount Technology, vol. 23 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 25 September 2007

Sunil Gopakumar, Peter Borgesen and K. Srihari

The objective of this research is to address issues that relate to the assembly of Sn/Ag/Cu bumped flip chips.

Abstract

Purpose

The objective of this research is to address issues that relate to the assembly of Sn/Ag/Cu bumped flip chips.

Design/methodology/approach

Flip chips bumped with Sn/Ag/Cu bumps were assembled onto different lead‐free surface finishes at lead‐free soldering temperatures. Sensitivity to fluxes, reflow profiles, pad finishes and pad designs were all investigated and the potential consequences for assembly yields were calculated numerically.

Findings

Soldering defects, such as incomplete wetting and collapse and poor self‐centring were observed in the assemblies. Defect levels were sensitive to contact pad metallurgy and flux type, but not to flux level and reflow profile within the ranges considered. Owing to a particularly robust substrate‐pad design, defects observed in this work were limited to incomplete wetting and collapse, as well as poor self‐centering.

Research limitations/implications

The scope of this work is limited to the lead‐free fluxes available at the time of research. A switch to lead‐free solder alloys in flip chip assemblies raises concerns with respect to the compatibilities of materials and the quality of soldering that is achievable. While this may be less of an issue in the case of larger area array components, such as ball grid arrays and chip scale packages, it is more of a concern for applications that use flip chips due to the smaller size of the solder spheres. Assembly yields tend to become more sensitive to the reduced collapse of the joints. More work is essential to investigate the potential benefits of more active lead‐free fluxes, both no‐clean tacky and liquid fluxes, in reducing or eliminating soldering defects.

Originality/value

The paper offers insights into assembly issues with Sn/Ag/Cu bumped flip chips.

Details

Soldering & Surface Mount Technology, vol. 19 no. 4
Type: Research Article
ISSN: 0954-0911

Keywords

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