B. Wessling, M. Rischka and J. Posdorfer
The purpose of this paper is to introduce a new class of surface finishes as an alternative to current final surface finishes.
Abstract
Purpose
The purpose of this paper is to introduce a new class of surface finishes as an alternative to current final surface finishes.
Design/methodology/approach
This new finish utilises nanotechnology and is based on a new formulation of the “organic metal” (OM).
Findings
The final surface finish is an approximately 50 nm thin permanent layer, consisting of a complex between the OM and silver (Ag). Panels finished with OrmeSTAR™ Ultra show excellent solderability in spite of a low‐layer thickness and therefore offer significant advantages over existing surface finishes.
Originality/value
This new finish has proven to be a competitive alternative to current final finishes with excellent properties for soldering applications. The new nanotechnology can also significantly improve the environmental and economical consequences of solderable surface finishing.
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Keywords
The purpose of this paper is to synthesise polyaniline‐SiO2 (PANI‐SiO2) composites and investigate the anticorrosion properties of polyaniline‐SiO2‐containing coating on Mg‐Li…
Abstract
Purpose
The purpose of this paper is to synthesise polyaniline‐SiO2 (PANI‐SiO2) composites and investigate the anticorrosion properties of polyaniline‐SiO2‐containing coating on Mg‐Li alloy.
Design/methodology/approach
The PANI‐SiO2 composites were prepared by in situ chemical oxidative polymerisation in phosphoric acid medium. The PANI‐SiO2 composites were characterised by Fourier transform infrared, X‐ray diffraction and scanning electron microscopy techniques. The coating consisted of PANI‐SiO2 composites and epoxy resin was formed on Mg‐Li alloy. The anticorrosion properties were investigated by open circuit potentials (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation curves.
Findings
The results indicated that the PANI‐SiO2‐containing coating on Mg‐Li alloy demonstrated good anticorrosion properties in 3.0 wt% NaCl solution. It has been found that the OCP of PANI‐SiO2‐containing coating were able to maintain more noble potential values in comparison to pure epoxy coatings in 3.0 wt% NaCl solution. EIS analysis indicated that the resistance of PANI‐SiO2‐containing coating was more than 106 Ω cm2 in 3.0 wt% NaCl solution in immersion process. Furthermore, the corrosion current of PANI‐SiO2‐containing coating on Mg‐Li alloy showed a significant reduction.
Originality/value
Previous reports on PANI‐SiO2 composites were mostly focused on their conductivity and optical properties and there are few studies so far on their anticorrosion properties as protective coatings for Mg‐Li alloy.
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Ufana Riaz, S.M. Ashraf and Sharif Ahmad
The purpose of this paper is to report a comparative study of conducting polymer (CP) dispersed oil polyurethane coatings derived from a sustainable resource, i.e. polyaniline…
Abstract
Purpose
The purpose of this paper is to report a comparative study of conducting polymer (CP) dispersed oil polyurethane coatings derived from a sustainable resource, i.e. polyaniline (PANI)/coconut oil polyesteramide urethane (CPEAU) and poly(1‐naphthylamine) (PNA)/linseed oil polyurethane (LPUA) coatings.
Design/methodology/approach
The coatings were prepared chemically and were characterized for their physico‐chemical, physico‐mechanical, corrosion protective efficiency, and open circuit potential measurements. The morphological analysis of the corroded carbon steel (CS), coated uncorroded CS, and coated corroded CS specimens, was carried out by SEM analysis.
Findings
The study revealed that the presence of a CP enhanced the corrosion protective efficiency of the sustainable resource‐based organic coatings. The type of CP used also played a major role in defining the corrosion resistance behavior of the coating materials.
Originality/value
The comparative study of anticorrosive properties of CP with oil‐based polyurethane blends has been studied for the first time.
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Tongyan Pan and Qifeng Yu
This study aims to present the fabrication of the two-layer system, coating it on steel surface and evaluating the system’s anti-corrosion performance using the ASTM Standard…
Abstract
Purpose
This study aims to present the fabrication of the two-layer system, coating it on steel surface and evaluating the system’s anti-corrosion performance using the ASTM Standard Salt-Spray Test: B117 and the technique of Electrochemical Impedance Spectroscopy (EIS).
Design/methodology/approach
A synthesized electroactive polyaniline (PANi) was utilized in this study to make a PANi-based primer, with which a two-layer coating system was fabricated by overlaying the primer with a polyurethane top-coat.
Findings
In the Salt-Spray test, the two-layer PANi/polyurethane system exhibited higher corrosion resistance than the two-layer control epoxy/polyurethane system. In particular, the PANi/polyurethane system tended to mitigate the production of rust on substrate surface and demonstrated higher delamination resistance. The EIS analysis confirmed the high corrosion resistance and delamination resistance of the two-layer PANi/polyurethane system based on parameters obtained using the best-fit equivalent circuits.
Practical implications
The demonstrated anti-corrosion capacity of this new PANi/polyurethane system laid a solid base for industrial applications.
Originality/value
This novel coating system is expected to achieve improved corrosion protection for steels than the conventional zinc-rich three-layer coatings.
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As an alternative to hot air levelling, a fundamentally new surface finish chemistry and process for solderability preservation of printed circuit boards is described: a…
Abstract
As an alternative to hot air levelling, a fundamentally new surface finish chemistry and process for solderability preservation of printed circuit boards is described: a pretreatment of the copper followed by an optimized formulation of an immersion tin. The precise and reproducible surface finish formation offers reliable solderability, economic and technical advantages for all kinds of PCBs, even for those with the most modern miniaturized structures. The deposition chemistry and ageing properties of the new Organic Metal/tin surface is discussed, based on electrochemical, wet chemical and electron microscopy studies. The results culminate in an almost complete basic understanding of the tin chemistry and the surface finish performance.
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This paper describes the different thickness measurement techniques that enable reliable thickness assessments, and the determination of the recommended immersion tin thickness…
Abstract
Purpose
This paper describes the different thickness measurement techniques that enable reliable thickness assessments, and the determination of the recommended immersion tin thickness for lead‐free soldering.
Design/methodology/approach
Immersion tin layers were prepared with systematically varying layer thicknesses. The samples were annealed at different reflow profiles, used in assembly for tin/silver/copper (SAC‐alloy) soldering. The layers were characterized with X‐ray fluorescence, electrochemical stripping coulometry, and by examining the cross sections using a scanning electron microscope. The solderability of the samples was determined with a solder balance (Solderability Tester Menisco ST60) using a SAC‐alloy (melting point 217°C) with T(max) at ΔT=28°C and ΔT=43°C above melting.
Findings
If all pure tin is converted into the Sn/Cu IMC, so that no pure tin is left as solderable layer, the wetting behaviour will decrease dramatically. Especially for multiple soldering processes, two times reflow followed by wave soldering, it is essential to have a pure tin layer covering the Sn/Cu IMC before going to the final soldering process. The required amount of residual pure tin over the Sn/Cu IMC is detailed in several papers. It is stated that a minimum of 0.2 μm of pure tin over the Sn/Cu IMC is absolutely necessary to ensure reliable wetting and solder joint formation. With the current immersion tin thickness recommendation of 1 μm, based on the needs of lead containing solder pastes, a residual pure tin layer will not be evident or thick enough to ensure reliable assembly for multiple soldering with lead‐free temperature profiles.
Originality/value
Helps to enable reliable thickness assessments, and the determination of the recommended immersion tin thickness for lead‐free soldering.