Phase Stability, Phase Transformations, and Reactive Phase Formation in Electronic Materials XXI: On-Demand Oral Presentations
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; Jaeho Lee, Hongik University; Zhi-Quan Liu, Shenzhen Institutes of Advanced Technology; A.S.Md Abdul Haseeb, Bangladesh University of Engineering and Technology (BUET); Vesa Vuorinen, Aalto University; Ligang Zhang, Central South University; Sehoon Yoo, KITECH; Yu-chen Liu, National Cheng Kung University; Ting-Li Yang, National Yang Ming Chiao Tung University

Monday 8:00 AM
March 14, 2022
Room: Electronic Materials
Location: On-Demand Room

Mesoscale Simulations Guiding Data-driven Design of Electronic Materials: Anil Kunwar1; Johan Hektor2; Upadesh Subedi3; Nele Moelans4; 1Silesian University of Technology; 2Malmö University; 3Tribhuvan University; 4KU Leuven
    The reliability of microelectronic devices has been a topic of special interest among the materials scientists and engineers, especially with the advent of Industry 4.0 era. With the ongoing miniaturization of solder joints , phenomena such as electromigration, thermomigration and rapid growth of intermetallics are challenging the functionality of the devices in a more pronounced manner. In order to mitigate these challenges, it is necessary to understand how the field gradients (driving forces) affect the interdiffusion mechanism and subsequently influence the evolution of phases and grains. Mesoscale phase-field simulation can describe the spatial-temporal evolution of microstructures . The data generated from phase field models can be utilized to construct physics-informed machine learning models, which can be further trained to predict several uncertain materials properties associated with electronic materials. Future outlook of such integrated methodology is towards the design of high-entropy solder alloys.

Data-driven Rational Design of Conductive Copper-based Alloys with High Performance: Jianxin Xie1; Huadong Fu1; 1University of Science and Technology Beijing
    To overcome the challenges of low efficiency and high cost of traditional trial and error alloy design method, this study proposes a data-driven rational alloy design strategy and three rational alloy design methods are developed taking high strength conductive copper-based alloys as an example. One is the rapid and accurate design method of the complex alloy composition oriented to required properties, which breaks through the problem of alloy composition design according to given properties with the realization of meet-demand alloy designs. The second method is put forward to realize the optimized alloy design with screening key features affecting alloy properties first, and then designing alloy composition according to the influence mechanism and degree of elements on properties. The third method is machine learning-assisted adaptive deformation-aging process design to solve the problem of large-amount and long-time experiments, which realizes the rapid design of alloy preparation processes.

Failure Analysis and Prediction of Solder Microbumps due to Side Wetting and Electromigration by 3D X-ray: Po-Ning Hsu1; Chih Chen1; Kai-Cheng Hsieh1; Tzu-Wen Lin1; Cheng-Che Wu1; Nien-Ti Tsou1; Yu-Chieh Lo1; Nan-Yo Chen2; Mia Wu3; Yong-Fen Hsieh3; K. N. Tu4; 1National Yang Ming Chiao Tung University; 2National Center for High-performance Computing, Taiwan; 3Materials Analysis Technology Inc.; 4UCLA/City University of Hong Kong
    The solder volume in a microbump continues to scale down. During reflow process or electromigration (EM) tests, solders may diffuse to the side walls of the under-bump-metallurgy (UBM) to form intermetallics, resulting in necking or voiding in the solder microbumps. In this presentation, non-destructive observation method through 3D X-ray was adopted to study voids formation and necking during reflow and EM. A daisy-chain test vehicle with the number of 400 solder microbumps was reflowed at 260 ℃ or under EM tests at 150 ℃. The structure of solder microbumps was Cu/Sn2.3Ag/Ni/Cu. With the non-destructive observation method, the evolution of EM failures can be analyzed when the resistance change was 0 %, 5 %, 10 %, and 20 %. Therefore, the process of void formation can be observed through different view angles of computed tomography (CT). Artificial intelligent deep learning was to employed to predict the reliability of the solder joints.

Phase Transformation Temperatures of Sn-based Solder Alloys: Sinn-wen Chen1; Jun-xiang Liu1; 1National Tsing Hua University
    Sn-based alloys, such as Sn-Ag-Cu, Sn-Ag-Bi, Sn-Ag-In, Sn-Cu-In, Sn-Ag-Bi-Cu and Sn-Ag-Cu-In are all important solder alloys. Although these alloys are of industrial application interests and have attracted relatively intensive investigations, it is surprising to find out that significant deviations exist regarding the liquidus temperatures obtained from Calphad-type calculation using available data bases and those determined experimentally using DSC (differential scanning calorimetry). For example, the liquidus temperature of Sn-7.0wt.%Ag-1.0wt.%Cu alloy determined by using DSC is 284.2℃, while those calculated using different data bases are 271.9, 276.2 and 287.5℃. Similar inconsistencies are observed in other Sn-based alloys. Better agreement between experimental determined and calculated results is observed regarding the invariant reaction temperatures. Sn-Ag-Cu, Sn-Ag-Bi, Sn-Ag-In, Sn-Cu-In, Sn-Ag-Bi-Cu and Sn-Ag-Cu-In alloys are prepared in this study. Their phase transformation temperatures are determined using DSC and Calphad calculation, focusing on the liquidus temperatures and the completely solidified temperatures, i.e. eutectic and solidus temperatures.

Electric Current-assisted Treatment for 7075 Aluminum Alloy to Withstand High-speed Impact: Shih-kang Lin1; Yu-chen Liu1; Yu-ching Chen1; Yu-ning Chiu1; 1National Cheng Kung University
    Aluminum alloy has kept increasing the interest in the application of automobile industry because of its high strength and light weighting properties. High-speed impact is one of the most crucial reliability tests for automobile industry. In this study, we introduced the electric current-assisted treatment for 7075 aluminum alloy to withstand high-speed impact. When the alloy was T6-heat treated, we found precipitation free zone (PFZ) in the microstructure and fracture occurred after the high-speed impact. Nevertheless, when the alloy was electric current-treated, fracture did not occur and PFZ was found vanished. We believed electric current changed the precipitation stability and therefore enhanced the ductility of 7075 aluminum alloy. The technique would be beneficial to automobile industry.

Electronic Material Properties Exploration Using Machine Learning: In Effective Charge, Hardness, and Dissipation Factor: Yu-chen Liu1; Shih-kang Lin1; 1National Cheng Kung University
    Machine learning (ML) methods have been aggressively pursued as a powerful tool to decipher and predict the complex physical properties of materials. In this talk, we will show how we employed the ML method to develop models for exploring properties of electronic materials. These properties included the effective charge in electromigration effect, the hardness of Sn-based solders, and dissipation factor of the low-temperature cofired ceramics. We used these models to design potential candidates for real applications. For instance, we designed solders with hardness as high as 40.7 and as low as 5.5 Hv and characterized their properties. The microstructure was complicated, but our ML model was able to capture the hardness of given alloys after only being informed by the composition. In general, ML is potentially a powerful tool for exploring material properties in complex systems by using solely the composition and the process information.

Solution-processed Perovskite Photoabsorbers with Mixed Cations for Improved Stability in Solar Cells: Mritunjaya Parashar1; Mohin Sharma1; Anupama Kaul1; Kishan Jayanand1; 1University of North Texas
    Perovskite solar cells (PSCs) have been the center of attention for third-generation photovoltaics ever since power conversion efficiencies (PCEs) of ~ 9.7% were reported in 2012. Since then, intense activity in perovskite research has resulted in a certified PCE of 25.5% in 2020 for single-junction PSCs. This feat can be partly ascribed to the development of various thin film deposition techniques to grow perovskite films, particularly using solution processing techniques. Following the pioneering work resulting from methylammonium lead triiodide (MAPbI3) PSCs, formamidinium lead triiodide (FAPbI3) has been investigated by various research groups as another promising candidate for the photoabsorber layer, largely due to its improved environmental stability compared to MAPbI3. In the present study, we have explored the phase transitions of solution-processed MAPbI3 and FAPbI3 perovskite films at various temperatures and provided a comparison on the stability of both these perovskite photoabsorbers in n-i-p or p-i-n device solar cell architecture.

Filp-chip Encapsulation with Hybrid Organic-inorganic Passivation of Perovskite Solar Cells: Tse-Lin Lai1; 1National Central University
     The oxide/nitride passivation and flip-chip package technology was developed for the perovskite solar cells. The heat resulted from the physical vapor deposition would decompose the active perovskite layer and degrade the efficiency of the perovskite solar cells down by more than 45%. Remarkably, with Si-nitride passivation processed by plasma-enhanced vapor deposition, the efficiency of the perovskite solar cell only decays about 9.1 %. It should be because that the plasma-enhanced vapor deposition causes much less external energy on the perovskite solar cell. Using the exponential efficiency-decay curves of the flip-chip packaged perovskite solar cells, the characteristic time of the reliability-tested solar cell can be calculated to be 145.8 hours, 390.7 hours, and 4864 hours for air ambient, glove chamber, and water ambient tests, respectively. We concluded that the concentration of O2(g) in the reliability test ambient is the root-cause for the efficiency degradation of the perovskite solar cells.

Cu Sintering Process Modified by Adding a Low Temperature Liquid Sintering Step: Bo Rong Huang1; 1National Central University
    Thick film technology is currently used to manufacture resistors, dielectric layers or conductive lines. In today's world, thick films are more widely used in high-power applications and passive components with thick film electrodes or substrates, such as low-level cofired ceramics (LTCC) and direct bonding copper (DBC). Therefore, there has a great significance for the industry to study the evolution of microstructure in the sintered thick film and to optimize the procedure of overall manufacturing. In this seminar, I will propose that adding low melting point ceramic powder in the mixed ceramic powder to optimize the process of copper thick film sintering, and how the evolution of the microstructure in the sintering process affects the electrical conductivity of the copper thick film, and finally show the conductivity and hardness of the copper thick film completed by sintering.

Bi Orientation-dependence and Mechanical Properties in a Sn-Bi-Ag Low-temperature Lead-free Solder: Chih-Han Yang1; Yu-chen Liu1; Yuki Hirata2; Hiroshi Nishikawa2; Shih-kang Lin1; 1National Cheng Kung University; 2Osaka University
    We designed low-temperature tin-bismuth-silver (Sn-Bi-Ag, SBA) solder by CALculation of PHAse Diagram (CALPHAD)-type thermodynamic calculations and performed corresponding key experiments. The goal is to suppress (Bi)-rich phase width growth, while keeping their low melting temperatures. This study shows that CALPHAD calculations make a good agreement with experimental results. In addition, we found Ag and Sn has some solubility in (Bi) phase. We furtherly used nanoindentation to investigate the orientation-dependence elastic modulus and hardness of (Bi) with different doping level. The elastic constant makes a good agreement with ab initio calculations. They show elastic and hardness anisotropy of (Bi) were alleviated by Ag and Sn addition. As for the tensile properties of the SBA solder in as-cast, high yield strength (YS), high ultimate tensile strength (UTS), and slightly better elongation than the conventional Sn-58Bi solder were obtained. After being thermally aged, higher strength and same elongation level of Sn-58Bi were observed.

Self-healing Kirkendall Voids at the Joint Interface between Sn and <111> Oriented and Nano-twinned Cu: Shiqi Zhou1; Yubo Zhang1; Yue Gao1; Li-Yin Gao1; Zhi-Quan Liu1; 1Shenzhen Institutes of Advanced Technology, CAS
    <111> oriented and nano-twinned Cu ((111)nt-Cu) has excellent mechanical strength, good ductility, and conductivity. Therefore, (111)nt-Cu is expected to be utilized as an under-bump-metallization (UBM), Cu pillar, and redistribution layer. By now, several studies on solder joints using (111)nt-Cu have been published. However, the understanding of this novel material is still lacking. In this study, the intermetallic compound (IMC) layer and kirkendall voids were investigated at both Sn/(111)nt-Cu and Sn/traditional-Cu interfaces under thermal aging conditions. Current results show severe kirkendall voids formed on the Cu3Sn/(111)nt-Cu interface after a short aging time. Then, around 93% of voids healed-up after aging time tripled. In addition, Cu3Sn layer thickness decreased gradually on Sn/(111)nt-Cu interface. By contrast, no kirkendall void was found at the Sn/traditional-Cu interface after these aging stages. Now, a prolonged aging test is conducted, and the final results can contribute to the understanding of joint reliability using (111)nt-Cu as the UBM.

Interfacial Reaction between In Coated Cu Sheet and ENIG Substrate: Hiroshi Nishikawa1; Jianhao Wang2; Kento Kariya3; Noriyuki Masago3; 1Osaka University; 2Nanjin University of Aeronautics and Astronautcs; 3Rohm Co., Ltd.
    The SiC power device provides the possibility to develop the next-generation power conversion circuit with high efficiency and high power density. To assemble the SiC device, the high temperature packaging technology such as die-attach process is required. Transient liquid phase (TLP) bonding is one of potential die-attach processes for the device. So we have proposed TLP bonding process without solvents using In coated Cu sheet. In this study, In coated Cu sheet was used for an insert material. The In coated Cu sheet was sandwiched between two electroless nickel immersion gold finished (ENIG-finished) Cu disks as a bonding sample. After bonding, cross-sectional views of the joints were obtained by scanning electronic microscope (SEM) and the microstructures of the joints were analyzed. As a result, it was found that the IMC phase was fully formed at the interface and successfully characterized.

Interfacial Reaction between Sn-rich Solder and FeCoNiCu High-entropy Alloy: Yu-An Shen1; Sheng-Wen Chen1; Hao-Zhe Chen1; 1Feng Chia University
    Sn-rich solders are commonly used for electrical interconnections in flip-chip and microbump solder joints for advanced electronic packaging. In the solder joints, the rapid growth of intermetallic compound (IMC) at the interfaces is a reliability issue during thermal aging and electromigration. To solve the issue, some studies focused on the interfacial reactions between the Sn-rich solders and metal pads with low diffusivities (Fe, Co, and Ni) in Sn. But the suppression of the interlayer growth is limited. On the other hand, the multi-elemental IMC formed at the interface between Sn-rich solders and high-entropy alloy possesses excellent thermal stability. However, the interfacial reaction between Sn-rich solder and FeCoNiCu high-entropy alloy(FCNC) is seldom studied. In this study, we will illustrate the wettability of Sn-rich solders on the FCNC substrate, and the crystal structure, elemental composition, and thermal stability of their interlayer.