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Article

Y.S. Lin, W.J. Lin and L.Y. Chiu

The purpose of this paper is to investigate the effects of H2 flow rate on improving the solder wettability of oxidized‐copper with liquid lead‐free solder…

Abstract

Purpose

The purpose of this paper is to investigate the effects of H2 flow rate on improving the solder wettability of oxidized‐copper with liquid lead‐free solder (96.5Sn‐3Ag‐0.5Cu) by Ar‐H2 plasmas. The aim was to improve the solder wettability of oxidized copper from 0 per cent wetting of copper oxidized in air at 260oC for 1 hour to 100 per cent wetting of oxidized‐copper modified by Ar‐H2 plasmas at certain H2 flow rates and to find correlations between the surface characteristics of copper and the solder wettability with liquid lead‐free solder.

Design/methodology/approach

To reduce the copper oxides on the surfaces of oxidized‐copper for improving solder wettability with liquid lead‐free solder, this study attempted to apply Ar‐H2 plasmas to ablate the copper oxides from the surfaces of oxidized‐copper by the physical bombardment of the Ar plasmas and to reduce the surfaces of oxidized‐copper by the chemical reaction of H2 plasmas with the surfaces of oxidized‐copper.

Findings

The solder wettability of oxidized‐copper was found to be highly dependent on the surface characteristics of the copper. The values of polar surface free energy and dispersive surface free energy on the surfaces of oxidized‐copper modified by Ar‐H2 plasmas were close to those values of solid lead‐free solder, which resulted in improved solder wettability with liquid lead‐free solder. Auger spectra indicated that the Ar‐H2 plasma modification was used to remove the copper oxides from the surfaces of oxidized‐copper.

Originality/value

The surface characterization of copper surfaces is typically determined by expensive surface analysis tool such as Auger Electron Spectroscopy (AES). This paper reports the results of a study of a promising technique called the sessile drop test method, for examining the surface free energies such as total surface free energy, polar surface free energy and dispersive surface free energy on the surfaces of copper to clarify how the solder wettability of oxidized‐copper with liquid lead‐free solder was enhanced by Ar‐H2 plasmas.

Details

Soldering & Surface Mount Technology, vol. 24 no. 3
Type: Research Article
ISSN: 0954-0911

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Article

C.C. Tu and M.E. Natishan

A study was performed to develop a different experimental methodology to assess wettabilities of solders on various printed wiring board (PWB) finishes, based on a…

Abstract

A study was performed to develop a different experimental methodology to assess wettabilities of solders on various printed wiring board (PWB) finishes, based on a modified spreading test in which solder pastes were heated following temperature reflow profiles representative of those used in surface mount technology (SMT) instead of using a fixed rate temperature ramp. Three solder alloys (Sn63‐Pb37, Sn96.5‐Ag3.5, and CASTINTM: Sn96.2‐Ag2.5‐Cu0.8‐Sb0.5), two fluxes (rosin, mildly activated, RMA, and no‐clean, NC), and seven PWB finishes (Pd, Au/Ni, Ni, Ag, Sn, and organic solderability preservatives: OSP), and bare copper were involved in the study. Better wettabilities were observed in the current study than the results reported in the literature for conventional tests on the same combination of solder alloy, flux, and substrate. The different results in measurement of wettabilities obtained in the current study were attributed to the more adequate heating process allowing flux activation, which reduced reoxidation of solder powders and substrates during the reflow process and thus improved wettabilities of solders. Compared to the results obtained from the popular wetting balance test, the current study demonstrated a more realistic simulation of, and approach to, assessing the wettability of solder for SMT.

Details

Soldering & Surface Mount Technology, vol. 12 no. 2
Type: Research Article
ISSN: 0954-0911

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Article

P.T. Vianco and A.C. Claghorn **

A study was performed which investigated the wettability of 63Sn‐37Pb and 96.5Sn‐3.5Ag solders oncopper and gold ‐nickel plated Kovar ™ using a rosin ‐based…

Abstract

A study was performed which investigated the wettability of 63Sn‐37Pb and 96.5Sn‐3.5Ag solders on copper and gold ‐nickel plated Kovar ™ using a rosin ‐based, mildly activated (RMA) flux, a water soluble organic acid flux (WS ),and a low residue (LR) flux. The quantitative metric was the contact angle, θc, measured by the meniscometer /wetting balance technique. The first part of the study (Part 1) examined wetting performance following continuous exposure to 25°C prior to testing. Then, a preheating step was introduced into the experimental procedure after flux application, but preceding the actual wettability test in order to simulate a factory reflow process; these results are presented in Part II of this study. Contact angles for the 63Sn‐37Pb solder (215°C) on copper were 22±2° with the RMA flux, 12±5° for the WS flux, and 31±6° for the LR flux. Increasing the 63Sn‐37Pb solder temperature to 245°C improved wettability with the RMA and LR fluxes, but no change was observed with the WS fulx. Theii 96.5Sn‐3.5Ag lead ‐free solder exhibited poorer wettability on copper compared with the 63Sn‐37Pb alloy, with contact angles of 41±2° (RMA), 63±15°(WS) and 39±4°(LR). For the gold ‐nickel plated Kovar™ substrates, the 63Sn‐37Pb solder at 215° had contact angles of 15±3°, 35±6° and 29±6° for the RMA, WS and LR fluxes, respectively. The values were reduced at the higher test temperature (245°). The 96.5Sn‐3.5Ag solder also exhibited good wetting performance on the gold ‐nickel plated Kovar™ specimens compared with copper. Analysis of the interfacial tension parameters, γSF‐γSLand γLF ,exemplified the importance of γLF as well as the condition of the surfaces (γSF ) on wettability performance. A so ‐called ‘combined analysis’ of the 63Sn‐37Pb and 96.5Sn‐3.5Ag wettability data on either copper or gold ‐ nickel plated Kovar™ substrates was used to predict the solder temperature dependence of wettability for the three fluxes and two base materials.

Details

Soldering & Surface Mount Technology, vol. 8 no. 3
Type: Research Article
ISSN: 0954-0911

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Article

Wayan Darmawan, Monica Br. Ginting, Asih Gayatri, Rumanintya L. Putri, Dumasari Lumongga and Aulia Hasanusi

The surface characteristics of wood such as surface roughness, surface free energy (SFE) and wettability are important properties influencing further manufacturing…

Abstract

Purpose

The surface characteristics of wood such as surface roughness, surface free energy (SFE) and wettability are important properties influencing further manufacturing processes such as gluing and coating. The purpose of this study is to determine the influence of surface roughness of ten tropical woods on their SFE, wettability and bonding quality for water-based acrylic and solvent-based alkyd varnishes.

Design/methodology/approach

The woods tested in this study were fast-growing teak, afrika, sungkai, mindi, merbau, durian, lamtoro, pulai, acacia and kempas. Wood surfaces were prepared in unsanded and sanded using an abrasive paper of 120 grits. SFE values were calculated based on the Rabel method. Wettability values were measured based on the contact angle between varnish liquids and wood surfaces using the sessile drop method, and the S/G model was used to evaluate the wettability of the varnishes on the woods surface. The bonding quality of the varnishes was measured using a cross-cut test based on the ASTM 3359-02 standard.

Findings

The results show that unsanded kempas wood had the roughest surface with a Ra value of 16.24 µm, whereas sanded lamtoro wood has the smoothest surface with a Ra value of 6.86 µm. The unsanded afrika wood had the highest SFE value of 53.61 mJ/m2, whereas sanded fast-growing teak had the lowest SFE value of 36.17 mJ/m2. Sanded merbau woods had the lowest K value of 0.022 for the water-based acrylic varnish, whereas unsanded afrika wood had the highest K value of 9.253 for the alkyd varnish. Afrika wood with the highest K values (highest wettability) for both acrylic and alkyd varnishes produced the highest bonding quality (grade 4-5). Compared to the water-based acrylic varnish, the solvent-based alkyd varnish was more wettable and generated better bonding quality.

Research limitations/implications

Improving the quality of fast-growing wood from plantation by painting could be considered to increase their use for higher value wood products.

Practical implications

Compared to water-based acrylic varnish, solvent-based alkyd varnish was more wettable and generated better bonding quality.

Originality/value

The originality of this research is to evaluate the values of surface free energy. SFE could be used to quantitatively determined the wettability of paints liquid in the surface of wood

Details

Pigment & Resin Technology, vol. 49 no. 6
Type: Research Article
ISSN: 0369-9420

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Article

Yunlong Jiao, Xiaojun Liu and Kun Liu

Dynamic spreading and wetting on the rough surfaces is complicated, which directly affects the fluxion and phrase transition properties of the fluid. This paper aims to…

Abstract

Purpose

Dynamic spreading and wetting on the rough surfaces is complicated, which directly affects the fluxion and phrase transition properties of the fluid. This paper aims to enhance our knowledge of the mechanism of micro-texture lubrication from interface wettability and provide some guidance for the practical manufacturing of the surfaces with special wettability and better lubrication characteristics.

Design/methodology/approach

The effect of surface topography on the wetting behavior of both smooth and rough hydrophilic surfaces was investigated using a combination of experimental and simulation approaches. Four types of patterns with different topographies were designed and fabricated through laser surface texturing. The samples were measured with a non-contact three-Dimensional (3D) optical profiler and were parameterized based on ISO 25178. Quantitative research on the relevancy between the topography characteristic and wettability was conducted with several 3D topography parameters.

Findings

Results show that for the surfaces with isotropic textures, topography with a small skewness (Ssk) and a large kurtosis (Sku) exhibits better wettability and spreading behavior. For the surfaces with anisotropic textures (smaller texture aspect ratio, Str), dominant textures (such as long groove, rectangle) play a significant guiding role in promoting spreading. In addition, the moving mechanism of the triple contact line and anisotropic spreading were also studied using a computational fluid dynamics simulation. The simulation results have a good adherence with the experimental results.

Originality/value

Most of the surface characterization methods at present remain at a level that is related to geometric description, and the topography parameters are limited to 2D roughness parameters. So in present study, the relevancy between wettability and 3D surface topography parameters is explored. The authors believe that the current work provides a new viewpoint to the relevancy between surface topography and wettability.

Details

Industrial Lubrication and Tribology, vol. 70 no. 6
Type: Research Article
ISSN: 0036-8792

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Article

Roman Koleňák and Michal Chachula

The purpose of this paper is to study Bi‐11Ag solder for higher application temperatures. The aim of the research work was to determine the soldering, thermal and…

Abstract

Purpose

The purpose of this paper is to study Bi‐11Ag solder for higher application temperatures. The aim of the research work was to determine the soldering, thermal and mechanical properties of Bi‐11Ag solder.

Design/methodology/approach

To determine the melting point interval of experimental Bi‐11Ag solder, DSC analysis was performed. The contact angles were studied on a copper, nickel and silver substrate by use of a sessile drop method. Wettability tests were realised at a temperature of 380°C in a shielding atmosphere (90% N2+10% H2). Based on experience achieved with wetting angle measurements, the specimens for measurement of shear strength of Cu, Ni and Ag/Bi‐11Ag joints were fabricated. EDX analysis was used for the study of the solder interaction with the surface of the three metallic substrates.

Findings

The best wettability at soldering in a shielding atmosphere was achieved with silver. The wetting angle at 30 min attained the value of 23°. The worst wettability was observed on copper, where at 30 min the wetting angle was 55°. Average shear strength varied from 31 to 45 MPa. The highest strength was obtained with the Cu substrate whereas the lowest was with the Ni substrate. The lowest strength achieved with the Ni substrate was caused by formation of brittle intermetallic phase NiBi3. Joint formation is realised by eutectic reaction at the contact of Bi with the surface of the copper substrate. Similar joint formation by eutectic reaction occurs also at Bi interaction with the surface of the Ag substrate. At Bi interaction with the nickel substrate a new intermetallic phase (NiBi3) is formed.

Originality/value

Wettability of Bi‐11Ag solder on Cu, Ag and Ni substrates was determined at application of a shielding atmosphere (90% N2+10% H2). Wettability was determined also at application of ZnCl2‐NH4Cl flux. The shear strength of Bi‐11Ag on different substrates was determined. The mechanism of joint formation was analysed.

Details

Soldering & Surface Mount Technology, vol. 25 no. 2
Type: Research Article
ISSN: 0954-0911

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Article

Yung-Sen Lin, Shiau-Min Lin, Jian-Yi Li and Min-Chih Liao

An investigation has been performed on the improved solder wettability of oxidized aluminum (Al) with lead-free solder (96.5Sn-3.5Ag) using Ar-H2 plasmas. The lead-free…

Abstract

Purpose

An investigation has been performed on the improved solder wettability of oxidized aluminum (Al) with lead-free solder (96.5Sn-3.5Ag) using Ar-H2 plasmas. The lead-free solder wettability was raised from 62.2 per cent wetting for Al oxidized in air at 250 C for 4 h to 98.4 per cent wetting of oxidized Al modified by Ar-H2 plasmas at a certain H2 flow rate. This study aims to gain insight on the surface characteristics of Al affecting the solder wettability with a liquid lead-free solder.

Design/methodology/approach

Ar-H2 plasmas at certain H2 flow rates are intended to reduce Al oxides on the surfaces of oxidized Al substrates both by physical bombardments via Ar plasmas and chemical reductions with H2 plasmas, while Al substrates are exposed in Ar-H2 plasmas to improve the solder wettability with a liquid lead-free solder.

Findings

Surface characteristics of oxidized Al substrates have been identified to play key roles for enhanced lead-free solder wettability using Ar-H2 plasmas. A decrease in polar surface free energy and an increase in dispersive surface free energy on the surfaces of oxidized Al substrates are exploited to advance the lead-free solder wettability. Decreased composition ratios of O to Al, detected by X-ray photoelectron spectroscopy (XPS) for oxidized Al substrates, are crucial for improved lead-free solder wettability.

Originality/value

XPS is typically used to analyze the surface compositions of Al oxides. To provide a rapid and non-expansive method to identify the surfaces of Al substrates prior to soldering to assure lead-free solder wettability, this study proposes a measurable skill, a so-called sessile drop test method, to investigate surface free energies such as total, polar and dispersive surface free energy on the surfaces of Al substrates, to illuminate how the lead-free solder wettability of oxidized Al is improved by Ar-H2 plasmas.

Details

Soldering & Surface Mount Technology, vol. 30 no. 1
Type: Research Article
ISSN: 0954-0911

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Article

Yu Tang, Shaoming Luo, Guoyuan Li, Zhou Yang and Chaojun Hou

The purpose of this paper is to investigate of the effects of Mn nanoparticle addition on the wettability, microstructure and microhardness of SAC0307-xMn(np) (SAC…

Abstract

Purpose

The purpose of this paper is to investigate of the effects of Mn nanoparticle addition on the wettability, microstructure and microhardness of SAC0307-xMn(np) (SAC: Sn–Ag–Cu; x = 0, 0.02, 0.05, 0.1 and 0.3 Wt.%) composite solders.

Design/methodology/approach

The SAC0307-xMn(np) composite solders were prepared by mechanically mixing different weight percentages of Mn nanopowders into the SAC0307 solder paste with rosin flux. In this study, the wettability of the solders was studied using contact angle and spread ratio methods. Afterward, the microstructure of the solders was investigated using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffractometry. Moreover, the microhardness of the solders was studied.

Findings

The wetting process of SAC0307-xMn(np) composite solders was found to experience four stages. Adding a small amount of Mn nanoparticles (x = 0.05 Wt.%) could improve the wettability compared to Mn-free solder. Beyond this level, the wettability deteriorated. The addition of Mn nanoparticles significantly refined the size and spacing of Ag3Sn grains in the solder matrix. When 0.1 Wt.% Mn nanoparticles was added, both the average size of the Ag3Sn grains and the spacing between the Ag3Sn grains decreased significantly and approached minimum values. Beyond this amount, the size and spacing between Ag3Sn grains increased slightly but remained smaller than those in the Mn-free solder matrix. The refined Ag3Sn grains increased the microhardness of the Mn-containing composite solders by 6-25 per cent, in good agreement with the prediction of the classic theory of dispersion strengthening.

Originality/value

The paper demonstrates that Mn nanoparticle addition could improve the SAC0307-xMn(np) solder wettability and reduce the grain size and spacing between Ag3Sn grains. The enhancement of the solder microhardness shows good correlation with the microstructure.

Details

Soldering & Surface Mount Technology, vol. 30 no. 3
Type: Research Article
ISSN: 0954-0911

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Article

K. Bukat, J. Sitek, M. Kościelski, Z. Moser, W. Gąsior and J. Pstruś

The purpose of this paper is to investigate the influence of Bi additions on the wetting properties of SnZn7Bi alloys (Bi=1 and 3 per cent by mass) on a copper substrate…

Abstract

Purpose

The purpose of this paper is to investigate the influence of Bi additions on the wetting properties of SnZn7Bi alloys (Bi=1 and 3 per cent by mass) on a copper substrate and printed circuit boards (PCBs) with lead‐free finishes (SnCu, immersion Sn, Ni/Au, organic solderability preservative) in the presence of fluxes. The practical implications of the results is the main purpose of these investigations.

Design/methodology/approach

A wetting balance method was used for wetting measurements at 230 and 250°C in nitrogen and air atmospheres in the presence of ORM0‐ or ROL0‐type fluxes. The PCBs were investigated ‘as received’ and after accelerated aging. The analysis of variance (ANOVA) analysis was performed in order to explain how the main factors of the experiments (the Bi content in the alloy (1 or 3 per cent), the test temperature and the test atmosphere) influenced the wetting ability of SnZn7Bi on Cu substrates.

Findings

As expected, a higher temperature and a higher Bi content in the alloy favoured the wetting of the copper substrate in the presence of the ORM0‐type flux in a nitrogen atmosphere. These results were confirmed by ANOVA analysis. Very good results were also obtained for the SnZn7Bi3 alloy's wettability on “tin coatings” on PCBs (SnCu and immersion Sn) both “as received” and after aging, in the presence of the ORM0‐type flux, for all the applied testing conditions (in both temperatures and N2 and air atmospheres). The less active flux (ROL0) caused a worsening of the alloy's wettability properties; however, the PCBs with SnCu and immersion Sn finishes maintained their wettability, even after aging, at very good and good levels, respectively.

Research limitations/implications

It is suggested that further studies are necessary for confirmation of the practical application, but they should be limited to the soldering of SnZnBi3 on PCBs with “tin coatings” and the quality of the solder joint performance.

Practical implications

The best SnZn7Bi3 wetting results on PCBs with “tin coatings” (SnCu and immersion Sn) at 230 and 250°C and in N2 and air atmospheres suggest the possibility of a practical usage of the tin‐zinc‐bismuth alloys for soldering in electronics using both the ORM0‐type flux and the even less active ROL0‐type flux, which are currently used in industrial lead‐free soldering processes.

Originality/value

The wetting balance method, combined with ANOVA was used as the quickest way to determine the wettability properties of SnZn7Bi on Cu substrates. Wettability measurements were also performed on the SnZn7 and SnZn7Bi alloys with different lead‐free finishes, in different experimental conditions.

Details

Soldering & Surface Mount Technology, vol. 22 no. 4
Type: Research Article
ISSN: 0954-0911

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Article

C. Melton

A quantitative dynamic solder wettability measurement was used to evaluate the effects of reflow processing on the wettability parameters associated with two non‐lead…

Abstract

A quantitative dynamic solder wettability measurement was used to evaluate the effects of reflow processing on the wettability parameters associated with two non‐lead bearing solders, 96.5% Sn/3.5% Ag and 58% Bi/42% Sn. An experimental design approach employing full factorial experiments was formulated to investigate the solder wetting dependence of the reflow parameters: atmosphere, peak reflow temperature, time above liquidus and metallisation. Solder wettability was determined with respect to the final degree of spread and the extent of solder wetting onto the lands of surface mount components. The solder alloy composition of 96.5% Sn/3.5% Ag was found to exhibit better wetting characteristics than the 58% Bi/42% Sn alloy. This wetting behaviour was enhanced under the reflow conditions of a nitrogen atmosphere and the use of a gold metallisation. The wetting of the conventional 63% Sn/37% Pb solder alloy was improved over the comparatively processed 58% Bi/42% Sn alloy. However, the 63% Sn/37% Pb solder alloy displayed a greater sensitivity to reflow atmosphere than the 96.5% Sn/3.5% Ag alloy, which generally exhibited better wetting characteristics than the Sn/Pb alloy.

Details

Soldering & Surface Mount Technology, vol. 6 no. 2
Type: Research Article
ISSN: 0954-0911

1 – 10 of 693