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Environmentally-Induced Failures of Electronic Grade Alloys and Coatings

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Corrosion".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 15221

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Prof. Dr. Balázs Illés

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Department of Electronics Technology, Budapest University of Technology and Economics, Budapest, Hungary
Interests: soldering; heat and mass transfer; reliability; metallurgy
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

Electronic-grade alloys are used in numerous electronic devices and systems, e.g., for interconnections, anodes, wires, surface coatings, fuel cells, batteries, solar cells, packaging, and lids. Electronic systems—like IoT devices, communications networks, autonomous cars, sensors, and actuators—are becoming more important in our everyday lives. Consequently, electronic-grade alloys should exhibit excellent mechanical, electrical, thermal, and reliability properties. This initiates the continuous development and preparation of new alloys via the use of novel techniques, like mechanical-, micro-, and composite-alloying, which belong to a rapidly evolving multidisciplinary research field combining metallurgy, chemistry, and physics.

In many fields, electronic devices need to operate in harsh environments, so not only the quality but the long-term reliability of the applied alloys is also critical. There is a strong need to investigate the environmentally induced failure mechanisms in these alloys, like corrosion, intermetallic formation, and microstructural changes, and their effects on alloy properties, which affect the life-time of electronic devices, and for examining the possible surface preservation methods of the applied material systems against the most frequent failure mechanisms like oxidation, dendrite, and whisker growth.

This Special Issue is dedicated to disseminating the recent advancements and latest results in this rapidly evolving interdisciplinary research field. We invite colleagues to contribute to this Special Issue in the aforementioned topics and keywords with full papers, short communications, and reviews. The Special Issue focuses on electronic-grade alloys, but other related topics are also welcome!

Dr. Balázs Illés
Guest Editor

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Keywords

Electronic-grade alloys
Coatings and surface preservation
Microstructure
Corrosion
Dendrites and whiskers
Alloy properties
Allotrope transition
Soldering and packaging
Fuel cells and batteries
Solar cells.

Published Papers (6 papers)

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Research

11 pages, 7816 KiB

Open AccessArticle

Investigation of the Mechanical Properties of Mn-Alloyed Tin-Silver-Copper Solder Solidified with Different Cooling Rates

by Tamás Hurtony, Oliver Krammer, Balázs Illés, Gábor Harsányi, David Bušek and Karel Dušek

Materials 2020, 13(22), 5251; https://doi.org/10.3390/ma13225251 - 20 Nov 2020

Cited by 3 | Viewed by 1852

Abstract

Manganese can be an optimal alloying addition in lead-free SAC (SnAgCu) solder alloys because of its low price and harmless nature. In this research, the mechanical properties of the novel SAC0307 (Sn/Ag0.3/Cu0.7) alloyed with 0.7 wt.% Mn (designated as SAC0307-Mn07) and those of the traditionally used SAC305 (Sn96.5/Ag3/Cu0.5) solder alloys were investigated by analyzing the shear force and Vickers hardness of reflowed solder balls. During the preparation of the reflowed solder balls, different cooling rates were used in the range from 2.7 K/s to 14.7 K/s. After measuring the shear force and the Vickers hardness, the structures of the fracture surfaces and the intermetallic layer were investigated by SEM (Scanning Electron Microscopy). The mechanical property measurements showed lower shear force for the SAC0307-Mn07 alloy (20–25 N) compared with the SAC305 alloy (27–35 N), independent of the cooling rate. However, the SAC0307-Mn07 alloy was softer; its Vickers hardness was between 12 and 13 HV, whereas the Vickers hardness of the SAC305 alloy was between 19 and 20 HV. In addition, structural analyses revealed rougher intermetallic compound layers in the case of the SAC0307-Mn07 alloy, which can inhibit the propagation of cracks at the solder–substrate interface. These two properties of SAC0307-Mn07 alloy, the softer nature and the rougher intermetallic layer, might result in better thermomechanical behavior of the solder joints during the lifetime of electronic devices. Full article

(This article belongs to the Special Issue Environmentally-Induced Failures of Electronic Grade Alloys and Coatings)

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14 pages, 5608 KiB

Open AccessFeature PaperArticle

Microstructure Influence of SACX0307-TiO₂ Composite Solder Joints on Thermal Properties of Power LED Assemblies

by Agata Skwarek, Przemysław Ptak, Krzysztof Górecki, Tamás Hurtony and Balázs Illés

Materials 2020, 13(7), 1563; https://doi.org/10.3390/ma13071563 - 28 Mar 2020

Cited by 27 | Viewed by 2615

Abstract

The effect of the microstructure of solder joints on the thermal properties of power LEDs is investigated. Solder joints were prepared with different solder pastes, namely 99Sn0.3Ag0.7Cu (as reference solder) and reinforced 99Sn0.3Ag0.7Cu–TiO₂ (composite solder). TiO₂ ceramic was used at 1 wt.% and with two different primary particle sizes, which were 20 nm (nano) and 200 nm (submicron). The thermal resistance, the electric thermal resistance, and the luminous efficiency of the power LED assemblies were measured. Furthermore, the microstructure of the different solder joints was analyzed on the basis of cross-sections using scanning electron and optical microscopy. It was found that the addition of submicron TiO₂ decreased the thermal and electric thermal resistances of the light sources by 20% and 16%, respectively, and it slightly increased the luminous efficiency. Microstructural evaluations showed that the TiO₂ particles were incorporated at the Sn grain boundaries and at the interface of the intermetallic layer and the solder bulk. This caused considerable refinement of the Sn grain structure. The precipitated TiO₂ particles at the bottom of the solder joint changed the thermodynamics of Cu₆Sn₅ formation and enhanced the spalling of intermetallic grain to solder bulk, which resulted in a general decrease in the thickness of the intermetallic layer. These phenomena improved the heat paths in the composite solder joints, and resulted in better thermal and electrical properties of power LED assemblies. However, the TiO₂ nanoparticles could also cause considerable local IMC (Intermetallic Compounds) growth, which could inhibit thermal and electrical improvements. Full article

(This article belongs to the Special Issue Environmentally-Induced Failures of Electronic Grade Alloys and Coatings)

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11 pages, 4537 KiB

Open AccessArticle

Effect of Recrystallization on β to α-Sn Allotropic Transition in 99.3Sn–0.7Cu wt. % Solder Alloy Inoculated with InSb

by Agata Skwarek, Balázs Illés, Tamás Hurtony, David Bušek and Karel Dušek

Materials 2020, 13(4), 968; https://doi.org/10.3390/ma13040968 - 21 Feb 2020

Cited by 2 | Viewed by 1859

Abstract

The effect of recrystallization of 99.3Sn–0.7Cu wt. % solder alloy on the allotropic transition of β to α-Sn (so-called tin pest phenomenon) was investigated. Bulk samples were prepared, and an InSb inoculator was mechanically applied to their surfaces to enhance the transition. Half of the samples were used as the reference material and the other half were annealed at 180 °C for 72 h, which caused the recrystallization of the alloy. The samples were stored at −10 and −20 °C. The β-Sn to α-Sn transition was monitored using electrical resistance measurements. The expansion and separation of the tin grains during the β-Sn to α-Sn transition process were studied using scanning electron microscopy. The recrystallization of the alloy suppressed the tin pest phenomenon considerably since it decreased the number of defects in the crystal structure where heterogeneous nucleation of β-Sn to α-Sn transition could occur. In the case of InSb inoculation, the spreading of the transition towards the bulk was as fast as the spreading parallel to the surface of the sample. Full article

(This article belongs to the Special Issue Environmentally-Induced Failures of Electronic Grade Alloys and Coatings)

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11 pages, 6896 KiB

Open AccessArticle

Preparation of Hydrogen Electrodes of Solid Oxide Cells by Infiltration: Effects of the Preparation Procedure on the Resulting Microstructure

by Bartosz Hołówko, Jakub Karczewski, Sebastian Molin and Piotr Jasiński

Materials 2020, 13(1), 131; https://doi.org/10.3390/ma13010131 - 27 Dec 2019

Cited by 6 | Viewed by 2497

Abstract

In this work, the infiltration technique was used to produce hydrogen electrodes for solid oxide cells. Different infiltration methodologies were tested in order to try to shorten the infiltration cycle time. The porous scaffolds used for infiltration were based on highly porous yttria-stabilized zirconia (YSZ) obtained by etching the reduced nickel from the Ni-YSZ cermet in HNO₃ acid. The support had a complex structure which included a ~130 µm porous functional layer with small pores and a ~320 µm thick supporting layer with large pores. Infiltrations have been carried out using aqueous nickel nitrate solutions. Various infiltration procedures were used, differing in temperature/time profiles. The results show that slow evaporation is crucial for obtaining a homogeneous material distribution leading to high-quality samples. A longer evaporation time promotes the proper distribution of nickel throughout the porous scaffold. The shortening of the heat treatment procedure leads to blockage of the pores and not-uniform nickel distribution. Full article

(This article belongs to the Special Issue Environmentally-Induced Failures of Electronic Grade Alloys and Coatings)

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11 pages, 4672 KiB

Open AccessArticle

Effect of Cu Substrate Roughness and Sn Layer Thickness on Whisker Development from Sn Thin-Films

by Balázs Illés, Tamás Hurtony, Olivér Krammer, Bálint Medgyes, Karel Dušek and David Bušek

Materials 2019, 12(21), 3609; https://doi.org/10.3390/ma12213609 - 03 Nov 2019

Cited by 13 | Viewed by 2629

Abstract

The effect of copper substrate roughness and tin layer thickness were investigated on whisker development in the case of Sn thin-films. Sn was vacuum-evaporated onto both unpolished and mechanically polished Cu substrates with 1 µm and 2 μm average layer thicknesses. The samples were stored in room conditions for 60 days. The considerable stress—developed by the rapid intermetallic layer formation—resulted in intensive whisker formation, even in some days after the layer deposition. The developed whiskers and the layer structure underneath them were investigated with both scanning electron microscopy and ion microscopy. The Sn thin-film deposited onto unpolished Cu substrate produced less but longer whiskers than that deposited onto polished Cu substrate. This phenomenon might be explained by the dependence of IML formation on the surface roughness of substrates. The formation of IML wedges is more likely on rougher Cu substrates than on polished ones. Furthermore, it was found that with the decrease of layer thickness, the development of nodule type whiskers increases due to the easier diffusion of other atoms into the whisker bodies. Full article

(This article belongs to the Special Issue Environmentally-Induced Failures of Electronic Grade Alloys and Coatings)

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15 pages, 5745 KiB

Open AccessArticle

Mechanism Understanding of the Role of Rare Earth Inclusions in the Initial Marine Corrosion Process of Microalloyed Steels

by Meng Tang, Kaiming Wu, Jing Liu, Lin Cheng, Xian Zhang and Yan Chen

Materials 2019, 12(20), 3359; https://doi.org/10.3390/ma12203359 - 15 Oct 2019

Cited by 22 | Viewed by 2457

Abstract

In this study, the corrosion behavior of rare earth (RE) microalloyed steels was first evaluated through potentiodynamic polarization tests and corrosion weight loss experiments, and then the corrosion morphologies were observed by scanning electron microscope (SEM). After immersion in a NaCl solution, the sulfides (or oxygen sulfides) dissolved preferentially, followed by corrosion at the boundary between the Fe matrix and oxides. Afterwards, the inclusions fell off as a whole, which promoted pitting nucleation. The first principle modeling demonstrated that the work functions of various kinds of inclusions descended in the following order: La₂Zr₂O₇ > LaAlO₃ > (La₂O₃ ≈ Fe ≈ La₂O₂S) > La₂S₃, which provided a theoretical explanation to the dissolution behaviors of inclusions. That is, inclusions containing sulfur tend to dissolve preferentially, whereas the oxides do not dissolve easily. Subsequently, the surface current distributions were detected by the scanning vibrating electrode technique (SVET), which provided more microscopic insight into the role of inclusions in the corrosion propagation. Results showed that the active sites of pitting nucleation accelerated the transverse propagation of corrosion. Finally, local corrosion spread to the whole surface as uniform corrosion. Full article

(This article belongs to the Special Issue Environmentally-Induced Failures of Electronic Grade Alloys and Coatings)

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