Minor alloying addition of Ag improves the hydrogen storage capacity and reduces the dehydrogenation temperature of the amorphous Mg65Cu25Y10 alloy. Hydrogen storage capacity is increased from ...2.1 wt% to 3.2 wt% when substituting Mg by only 1 at% of Ag. After hydrogenation, the amorphous Mg-Cu-Y(-Ag) alloys decompose into two types of sites for hydrogen occupations: i.e. a new amorphous Mg-Cu(-Ag) hydride clusters and YH3 nanocrystals. This study shows a simple method to tailor hydrogen storage properties of amorphous Mg65Cu25Y10 alloy.
This study shows a simple method to tailor hydrogen storage properties of amorphous Mg65Cu25Y10 alloy via minor alloying addition. Display omitted
•Hydrogen storage property of amorphous alloy is efficiently tuned via minor alloying.•Addition of 1 at.% Ag increases hydrogen storage capacity.•Addition of 1 at.% Ag reduces dehydrogenation temperature.
•The effects of Cr, Ca and Pd on the Sn–0.7Cu–based solders were investigated.•High temperature Sn–0.7Cu–based solder for automotive was developed.•Refined CrSn2 IMC is newly considered as a strategy ...to enhance solder properties.•The addition of Pd, Cr and Ca increased wetting properties.•The addition of Pd, Cr and Ca increased both the UTS and elongation.
The exemption clause for Pb-containing automobile parts in the RoHS (Restriction of Hazardous Substances) legislation will expire in a few years. Therefore, there is an urgent need to develop new Pb-free solder alloys that are suitable for automobiles. To improve the properties of the Pb-free solders used in automobiles that are consistently exposed to high temperatures and vibrations, we investigated the effects of minor alloying additions of chromium, calcium and palladium and examined the various properties of the resulting Sn–0.7Cu solders. We then investigated the new intermetallic compounds observed after the addition of chromium. In addition, we conducted thermal analysis to confirm the stability of the alloys at temperatures of approximately 230°C. The wettability and interfacial reactions between the solder alloys and the Cu under bump metallurgy are discussed. Furthermore, to evaluate the mechanical properties of the developed solder alloys, tensile tests were conducted. We confirmed that our minor alloying strategy enhances the strength and hardness of solder alloys without decreasing their melting temperatures.
Due to the RoHS and WEEE legislations for restricting the use of six hazardous materials in the manufacture of various types of electronic and electrical equipment, developing novel Pb-free solders ...becomes a real challenge for many industrials in recent years. In addition, mechanical properties of the lead-free alloys are very important factors in the design and reliability evaluation of the soldered joints. This paper reports the findings of an investigation into the tensile properties of a new lead-free solder alloy which contains Ni, Bi and Sb additives (SAC387-3Bi-1.5Sb-0.15Ni). The fabrication procedure of the bulk samples is described in this study, as well as the mechanical testing of the obtained specimens. The tensile tests are conducted at temperatures between room temperature and 125 °C and under strain rates between 2.0 × 10−5 and 2.0 × 10−2 s−1. The results show that both temperature and strain rate may have great effects on the mechanical behavior of the solder alloy. The strength was found to decrease with increasing test temperature and decreasing strain rate. It is noted that the mechanical properties of SAC387-3Bi-1.5Sb-0.15Ni solder alloy are strongly dependent on temperature and significantly sensitive to strain rate. Compared with the reference material without additives, additions of Sb, Ni and Bi elements result globally in an increase in strength of the solder alloy. Also, the stress-strain curves from tensile tests are used to identify nine Anand material parameters by using non-linear least square fitting. The identified parameters prove to be in good agreement with those found in literature on other usual solder alloys. Based on the Anand model, a FEM analysis of a multilayered IGBT packaging module under cyclic thermal loading is presented to predict the fatigue life of the solder joints. In addition, SEM and EPMA microanalyses of both as-cast bulk and fracture specimens are carried out to assess effects of testing conditions on microstructure changes in the SAC387-3Bi-1.5Sb-0.15Ni solder material. The improved strength is found to result from the solid solution hardening effect of Sb and Bi in the Sn matrix, together with the formation of (Cu,Ni)6Sn5 and Ag3(Sn,Sb) intermetallic compounds (IMCs).
Display omitted
•Solder properties are highly dependent on temperature and strain rate.•Solder strength is improved with addition of alloying elements Sb, Ni and Bi.•Solid solution is formed in Sn with Sb and Bi and new IMCs are formed with Ni.•FEM analysis shows improved response of the solder joint in IGBT power module.•Microstructure of fracture surfaces are analyzed by SEM and EPMA techniques.
De nos jours, une des stratégies pour améliorer les propriétés des brasures sans plomb est d'introduire en petites quantités certains éléments d'alliage. Dans notre étude, deux nouveaux types de ...brasures, dénommés Innolot et SAC-Bi et dont l'utilisation dans diverses applications électroniques augmente, sont caractérisées. En particulier, l'effet des éléments Ni, Sb et Bi sur les propriétés mécaniques est analysé. L'étude vise également à évaluer l'influence des facteurs de sollicitation, du vieillissement en température sur la réponse des matériaux et leurs évolutions microstructurales. A cet effet, une machine permettant de réaliser des essais de micro-traction sur éprouvettes miniatures a été conçue et fabriquée. Les sollicitations qu'elle permet d'appliquer sont multiples (traction, cisaillement et cyclage) et des conditions en température et en vitesse de déformation peuvent être imposées lors de l'essai. La fabrication des éprouvettes nécessaires aux essais a également été entreprise dans cette étude afin d'avoir un matériau similaire à celui issu du process industriel et de disposer d'une géométrie adaptée au type de caractérisation souhaitée (éprouvettes massives, à simple recouvrement, etc.).Après ces étapes préparatoires, des tests ont été réalisés sous sollicitations de traction, cisaillement, fluage et fatigue en faisant varier les conditions d'essais. Le premier objectif a été l'identification du comportement des brasures, y compris en prenant en compte l'effet du vieillissement. Ces données ont permis ensuite de réaliser des simulations thermo-mécaniques sur les matériaux utilisés sous forme de joints de brasure dans un module de puissance sous cyclage thermique. Les analyses de microstructure (SEM/EDS et EPMA) faites par la suite ont montré le rôle des éléments d'alliage (Ni, Sb et Bi) sur les performances mécaniques des brasures en termes de résistance, limite élastique et rigidité. Le rôle des facteurs d'essai, comme la température, la vitesse de sollicitation et la durée de vieillissement, a également été mis en évidence au niveau des propriétés obtenues et des changements dans la microstructure. Il a été établi que l'élément Sb permet de favoriser le durcissement par écrouissage des brasures, tandis que l'ajout des éléments Ni et Bi permettent un raffinement de la microstructure. Les essais ont aussi permis d'identifier les 9 paramètres de la loi d'Anand par une procédure numérique s'appuyant sur les données de traction et de cisaillement, permettant ainsi de réaliser des simulations par éléments finis. Ces dernières suggèrent un meilleur comportement à la fatigue pour la brasure Innolot qui bénéficie est effets favorables des additifs.
Nowadays, one of the strategies to improve the reliability of lead-free solder joints is to add minor alloying elements to solders. In this study, new lead-free solders, namely InnoLot and SAC387-Bi, which have begun to come into use in the electronic packaging, were considered to study the effect of Ni, Sb and Bi, as well as that of the testing conditions and isothermal aging, on the mechanical properties and microstructure evolution. A new micro-tensile machine are designed and fabricated, which can do tensile, compressive and cyclic tests with variation of speeds and temperatures, for testing miniature joint and bulk specimens. Additionally, the procedure to fabricate appropriate lap-shear joint and bulk specimens are described in this research. The tests, including shear, tensile, creep and fatigue tests, were conducted by micro-tensile and Instron machine at different test conditions. The first study is to characterize, experimentally, the mechanical behaviors and life time of solder joints submitted to isothermal aging and mechanical tests. The second goal of the project is to perform thermo-mechanical simulations of IGBT under thermal cycling. The experimental results indicate that, with addition of Ni, Sb and Bi in to SAC solder, the stress levels (UTS, yield stress) are improved. Moreover, testing conditions, such as temperature, strain rate, amplitude, aging time, may have substantial effects on the mechanical behavior and the microstructure features of the solder alloys. The enhanced strength and life time of the solders is attribute to the solid hardening effects of Sb in the Sn matrix and the refinement of the microstructure with the addition of Ni and Bi. The nine Anand material parameters are identified by using the data from shear and tensile tests. And then, the obtained values were utilized to analyze the stress-strain response of an IGBT under thermal cycling. The results of simulations represent that the response to thermal cycling of the new solders is better than the reference solder, suggesting that additions of minor elements can enhance the fatigue life of the solder joints. Finally, the SEM/EDS and EPMA analysis of as-cast, as-reflowed as well as fractured specimens were done to observe the effects of these above factors on the microstructure of the solder alloys.
