Phase Stability, Phase Transformations, and Reactive Phase Formation in Electronic Materials XXII: Phase Stability of Electronic Materials
Sponsored by: TMS Functional Materials Division, TMS: Alloy Phases Committee
Program Organizers: Hiroshi Nishikawa, Osaka University; Shih-kang Lin, National Cheng Kung University; Chao-hong Wang, National Chung Chung University; Chih-Ming Chen, National Chung Hsing University; Jae-Ho Lee, Hongik University; Zhi-Quan Liu, Shenzhen Institutes of Advanced Technology; Ming-Tzer Lin, National Chung Hsing University; Yee-wen Yen, National Taiwan University of Science and Technology; A.S.Md Abdul Haseeb, Bangladesh University of Engineering and Technology (BUET); Ligang Zhang, Central South University; Sehoon Yoo, Korea Institute of Industrial Technology; Vesa Vuorinen, Aalto University; Yu-Chen Liu, National Cheng Kung University; Ting-Li Yang, National Yang Ming Chiao Tung University
Monday 2:00 PM
March 20, 2023
Room: Sapphire E
Location: Hilton
Session Chair: Yee-Wen Yen, National Taiwan University of Science and Technology; Yu-chen Liu, National Cheng Kung University
2:00 PM Invited
SAC-In,Bi(Sb) Solder Joints with Multiphase Microstructures and Their Mechanical Properties Guided by CALPHAD Design: Xiaojing Wang1; Shanshan Cai2; Yuhang Wang1; 1Jiangsu University of Science and Technology; 2Yunnan Tin Group (Holding) Co. Ltd
A CALPHAD-guided solder alloy design and corresponding experiments were performed to study the relationship between microstructures and mechanical properties of SAC based solder alloys with different alloying elements Sb, Bi, In additions. Alloys with different matrix phases were selected for experiment, including Beta Sn, Beta SnIn, Gama InSn based and duplex alloys. It is found that the duplex alloys with indium addition show supreme strength while keeping the plasticity without degeneration. Also with the strain rate increasing, the strength of indium doped duplex alloy increase with the elongation almost no change under tensile test. In contrast, elongations of alloys such as Sn58Bi, Sn40BiCu and Sn3Ag05Cu alloys decrease with increasing strain rate.
2:25 PM
Composition Design of Coherent Precipitate-strengthening Multi-principal Element Alloys by High-throughput CALPHAD-type Calculation: Shao-Yu Yen1; Hao-che Wang1; Hideyuki Murakami2; Shih-kang Lin1; 1National Cheng-Kung University; 2National Institute for Materials Science
For decades, multi-principal element alloys (MPEAs), also known as complex concentrated alloys (CCAs) and high entropy alloys (HEAs), has been attracting widely research due to their outstanding mechanical properties such as specific strength and tensile yield strength. Due to the numerous element combinations and multi-dimensional composition space for MPEAs, conventional exploration with trial-and–error experiments to study MPEAs is very costly and time-consuming. With the assistance of computational thermodynamics, the period of new alloy design can be significantly reduced. In this work, high-throughput CALPHAD-type calculation is performed with Pandat software and PanHEA database to search the alloy compositions can form ordered precipitate coherently embedding in disordered matrix. Compositions with γ/γ' in Al-Cu-Fe-Ni-Ti system as well as BCC/B2 in Al-Co-Cr-Mo-Ti system were selected as the prototypes for experiments, respectively. The results showed a good agreement with the calculations. A new calculation strategy for MPEAs design is proposed and demonstrated.
2:45 PM
Use of Molecular Dynamics Simulations to Examine Crystal Growth from the Melt in Pure Sn Systems: Andrea Papaleo1; Bruce White1; Stephen Whitelam2; Eric Cotts1; 1Binghamton University; 2Lawrence Berkeley National Laboratory
At length scales up to one hundred microns, atomic attachment kinetics have a strong influence on Sn crystal growth morphologies from the undercooled melt, and thus on the microstructure of Sn-based solder joints. Utilizing molecular dynamics to examine crystal growth from the melt in pure Sn systems, we determined that this process is best modeled using diffusion-limited growth (the Wilson Frenkel model). The anisotropy in growth from planar interfaces was characterized with values of kinetic growth coefficients for the [001], [100], and [110] directions. The roughness of the solid-liquid interfaces was characterized, and correlated with the measured growth coefficient values. These observations were compared with simulations of the growth of a Sn sphere in an undercooled melt.
3:05 PM
Ab Initio Exploration of Alloying Elements for Stabilizing η’ Nanoprecipitates in Al-Zn-Mg Alloys: Yu-ning Chiu1; Shao-yu Yen1; Chung-yi Yu2; Shih-kang Lin1; 1National Cheng Kung University; 2China Steel Corp, Aluminum Prod R&D Sect
The effect of interfacial segregation has been a key factor in determining the interfacial stability and morphological evolution of nanoprecipitates. In this work, the energetics and atomic local strain hydrostatic invariant (ALSHI) of different solute segregation on η’ nanoprecipitate in Al-Zn-Mg alloy were thoroughly investigated through density functional theory (DFT) calculations. Solutes with larger atomic radius were found to preferentially segregate into extensive sites, favoring the elimination of extensive strain, while smaller solutes segregated into compressive sites to eliminate compressive strain. This suggests that the ability to remove strain from the precipitates is the main driving force for solute segregation, which is highly correlated to the atomic radius of solute atoms. On this basis, a list of solute elements favorable for strain removal and improving interfacial stability of precipitates is proposed as alloying candidates for future optimized design of Al-Zn-Mg alloys.
3:25 PM Break
3:45 PM
Ag and Cu Whisker Formation: Sinn-wen Chen1; Pin- Shuo Huang1; Yohanes Hutabalian1; 1National Tsing Hua University
The Ag-Cu-Se-Te quaternary system is an important material system. Hair-like Ag and Cu whiskers are observed when Ag-Cu-Te and Ag-Cu-Se alloys are heat-treated. Their width is 10-100 μm and their length is as long as many centimeters. EDS, EPMA, XRD and EBSD are used to analyze their compositions, structures, and orientations. According to the compositions, there are three kinds of whiskers, Ag, Cu and Ag+Cu mixed. Compositional analysis results indicate the mutual solubilities of Ag and Cu are less than 1.5at.%. Grain boundaries are observed in the EBSD results of the whisker’s cross-section and plan-view. The results indicate these whiskers are not single crystals. Low-angle grain boundaries are observed in the orientation mapping and grain boundaries mapping. Stress is the driving force for whisker growth and is also the cause for formation of grains.
4:05 PM
3d-transition Metal-tin Compounds: Andreas Leineweber1; Stefan Martin1; 1Tu Bergakademie Freiberg
Late 3d-metals (e.g. Co, Ni, Cu) in contact with tin (e.g during soldering) create a characteristic sequence of phases involving peritectic reactions in the binary phase diagram. These phases are either the most Sn-rich stable phases of the corresponding binary equilibrium phase diagram, or they are even metastable, like NiSn4. The present contribution reviews results on crystal structure and microstructure analysis involving the corresponding phases. Common principles from the different systems in terms of crystal chemistry of the observed phases and their microstructures developing upon reactive phase formation are derived. Special features are discussed like the highly defective character of these phases, especially NiSn4 and CoSn3, if grown at low temperature, e.g. upon interaction of the metal with solid tin. Moreover, characteristic off-equilibrium order-disorder phenomena may occur, like upon cooling of Cu-rich η-Cu6Sn5 developing at elevated temperatures.
4:25 PM
Thermal and Mechanical Evaluation of Anisotropic Cu-Solder Composite Joint on High Temperature Storage: Hiroaki Tatsumi1; Hiroshi Nishikawa1; 1Osaka University
High power density operation of electronics devices, such as power modules, causes heat density increase. Therefore, a highly thermal-conductive and high-temperature reliable joint is demanded in electronics packaging. This study proposes a novel anisotropic Cu-solder composite joint by using a unidirectional porous Cu sheet and Sn-Ag-Cu (SAC) solder. During a simple reflow process at 260 °C, the anisotropic composite joint was successfully fabricated through the molten solder penetration into the porous-Cu pores. Steady-state thermal conductivity measurement showed that the equivalent thermal conductivity of this joint was approximately 2.5 times higher than that of the SAC-soldered joint. Finite element simulation revealed the unidirectional Cu structure contributed to thermal conductivity enhancement. High temperature storage (HTS) test at 200 °C for 1008 h demonstrated its stable joint strength: 48.8 (0 h) and 46.3 MPa(1008 h). These results have proven that this novel anisotropic composite joint is promising for high-temperature electronics applications.
4:45 PM
3D Electromagnetic Simulation and Experimental Measurements of Performance of Antenna at mm-wave Frequencies: Surface Finish Effect: Ying-Chih Chiang1; Pei-Chia Hsu1; Chun-Jou Yu1; Cheng-Hsien Chou2; Cheng-En Ho1; 1Yuan Ze University; 2Unitech Printed Circuit Board Corp.
Millimeter wave frequency band (76–81 GHz band) has received widespread attentions in the radar sensor applications as its high resolution, long range, and beam-steering radar characteristics. Under high-frequency transmission, the surface finish coatings would dominate the electrical properties of Cu circuits due to the so-called “skin effect’’. This study will deeply probe into the effect of surface coatings on performance of antenna at 76–81 GHz. We investigated different surface finishes over the Cu circuit of an antenna, including electroless nickel/immersion gold (ENIG), electroless nickel/electroless palladium/immersion gold (ENEPIG), ultrathin-Ni(P)-type ENEPIG, immersion tin, immersion gold, and immersion gold/electroless palladium/immersion gold (IGEPIG). A 3D electromagnetic simulation through ANSYS-HFSS software showed that the radiation efficiency significantly degrades with the Ni(P) thickness, suggesting that high permeability and low conductivity of Ni(P) is the root cause of the efficiency degradation. Further experimental and ANSYS-HFSS analyses will be presented in this study.
5:05 PM
Study of Interfacial Stability for Medium-temperature GeTe-based Thermoelectric Modules: Cheng-Hao Kung1; Albert T. Wu1; 1National Central University
GeTe has been considered as one of the potential medium-temperature thermoelectric materials because of its small band gap, excellent zT value and Pb-free. Assembly a thermoelectric module requires joining the GeTe with metallic electrodes, most probable to be Cu or Ni. Severe interaction would occur when the module is operated at temperatures higher than 200 oC. The instability of the interface would lead to failure of the joints. Furthermore, drastic atomic interdiffusion would lead to the formation of undesirable intermetallic compound. The formation of the compound that not only deteriorated the thermoelectric performance, it could drastically degrade the reliability of the modules. This study reports the morphological evolution along with materials characterization to discuss the kinetics of interfacial reaction. Selection of materials as a diffusion barrier to enhance the joint property is also discussed.