Phase Stability, Phase Transformations, and Reactive Phase Formation in Electronic Materials XX: Advanced Electronic Materials
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Alloy Phases Committee
Program Organizers: Hiroshi Nishikawa, Osaka University; Shih-kang Lin, National Cheng Kung University; Chao-Hong Wang, National Chung Cheng University; Chih-Ming Chen, National Chung Hsing University; Jaeho Lee, Hongik University; Zhi-Quan Liu, Shenzhen Institutes of Advanced Technology; Ming-Tzer Lin, National Chung Hsing University; Dajian Li, Karlsruhe Institute of Technology; Yu Zhong, Worcester Polytechnic Institute; 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
Thursday 8:30 AM
March 18, 2021
Room: RM 21
Location: TMS2021 Virtual
Session Chair: Vuorinen Vesa, Aalto University; Hiroshi Nishikawa, Osaka University
8:30 AM Keynote
Solid-Liquid Interdiffusion (SLID) Bonding; For Thermal Challenges in Microsystem Bonding: Knut Aasmundtveit1; Hoang-Vu Nguyen1; 1University of South-Eastern Norway
Solid-Liquid Interdiffusion (SLID) bonding for microelectronics and microsystems is based on a two- (or more) metal system, where a high-melting and a low-melting metal reacts to high-temperature stable intermetallics. By proper design of the initial metal layers, the final bond can then tolerate higher temperatures than the bonding temperature, and the final bondline may be in thermal equilibrium. SLID bonding is therefore an excellent choice for high-temperature applications, and can also provide fine-pitch bonding as well as very thin bondlines.The keynote will review the SLID work done at our university, which spans a number of SLID systems: Cu-Sn, where our focus was to optimize the process for industrial wafer-level bonding for vacuum encapsulation; Au-Sn, determining the intermetallic phases present and showing high reliability also when bonding dissimilar materials; Au-In-Bi, where very low bonding temperature gives temperature stability better than solder. Ni-Sn, Au-In and SLID related techniques will be covered.
9:10 AM Invited
Change in Electric Resistance of Conductive Pastes Including Ag Particles Coated with Various Higher Fatty Acids during Curing Process: Shinji Fukumoto1; Kazuhiro Makimoto1; Kengo Ohta1; Yoshihiro Kashiba1; Michiya Matsushima2; Kozo Fujimoto1; 1Osaka University; 2Osaka Universty
The electrical properties of the conductive pastes are determined by the contact state of the conductive phases in the paste, which is affected by various factors such as the ratio of binder resin, solvent and conductive particles, the type of organic film, and environmental changes. In the present study, the change in electric resistivity of conductive pastes including Ag particles coated with various higher fatty acids were measured in-situ during the curing process. The electric resistance of cured Ag-paste was also investigated under the bending load. The electric resistance of the paste began to decrease at lower temperatures when the molecular weight of the organic film covering the Ag particles was smaller. In addition, the electric resistance decreased even below the thermal decomposition temperature of the organic film, suggesting that the film at the interface between the Ag particles became thinner during the heating process.
9:40 AM
IMC-free Low-temperature TLP Cu-to-Cu Interconnection with Excellent Thermal Stability: Shih-kang Lin1; Yu-chen Liu1; Chih-han Yang1; Yu-Hsiang Hsieh1; Chien-wei Huang1; Chih-feng Lin1; 1National Cheng Kung University
Cu-to-Cu bonding is an essential process for advanced electronic packaging. The phase formation at the bonding interface crucially determines the reliability of the joint. Herein, we propose an approach for fabricating face-centered cubic solid-solution joints without formation of intermetallic compound by using a trace amount of Ga and Ni under-bump-metallurgy for the reactive diffusion bonding at 300°C. The Cu/Ni/Ga/Ni/Cu sandwich couple fully transformed into the Cu/fcc-(Ni,Cu,Ga)/Cu joint after bonding. A shear-strength of 43.5 MPa was achieved in the as-bonded joint due to the formation of grains across the bonding interface, while it does not degrade after prolonged post-annealing at 300°C for 200 h. Instead, an even stronger joint with a shear-strength of 48.2 MPa was obtained. We demonstrated the fabrication of IMC-free, low temperature, thermally stable Cu-to-Cu joints using transient molten Ga and Ni UBM, and the technology is potential for a large area bonding.
10:00 AM
Intermetallic Reactions and Interfacial Stability in Cu-Co-Sn System: Fahimeh Emadi1; Vesa Vuorinen1; Hongqun Dong1; Mervi Paulasto-Kröckel1; 1Aalto University
Wafer level Solid Liquid Interdiffusion (SLID) bonding is one of the most attractive novel methods for packaging of Micro (Opto) Electro Mechanical Systems (MEMS/MOEMS). Cobalt appears as a promising contact metallization for CuSn based SLID bonding metallurgy. When utilizing Co-Sn-Cu interconnections, several different intermetallic compounds (IMCs) like (Cu,Co)6Sn5, (Cu,Co)Sn, (Cu,Co)Sn3, and Cu3Sn are generated depending on the process parameters. Based on the IMC phase structure, the properties of the interconnections can vary significantly. For example, it was observed by C. Du et.al. that the weak (Cu,Co)Sn3/Co interface deteriorate the mechanical properties of the bond. In this work Cu-Sn electroplated Si chips were bonded to Co substrates. The interconnection microstructures and the changes in local equilibria were analysed as a function of bonding temperature and time. It was found out that the stability of the interconnection interfaces is drastically affected by the changes in local nominal composition of the bond.
10:20 AM
Synthesis and Characterization of Silver Tin Alloy Powders by High Energy Ball Milling: Wei-Chen Huang1; Chin-Hao Tsai1; C. Robert Kao1; 1National Taiwan University
Ag–10 wt% Sn alloy powders for die attachment of high-temperature power devices packaging are prepared by high energy ball milling of high-purity Ag and Sn powders in argon atmosphere. Stearic acid was added as process control agent in order to prevent agglomeration of the powders. Planetary ball-mill was performed in different speed for 1, 2 and 6 hr to determine the effect of milling speed and time. Characterization of the powders was carried out by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) to gain insight on the phase transformations and confirm the completion of alloying process. The morphology of the Ag–Sn powders was flake-like, with particle size within the micro size range.
10:40 AM
Interfacial Microstructure Evolution of Ag/ENIG and Ag/Cu Joint under Thermal Aging: Minsu Kim1; Sehoon Yoo1; Hiroshi Nishikawa2; 1Korea Institute of Industrial Technology; 2Osaka University
Nowadays, the electric-powered vehicles have been received attention to reduce carbon emission and air pollution. A power module is a key component in electronic vehicle, for the conversion and distribution of electrical energy. Ag sintering has been received attention its high electrical/thermal conductivity and superior mechanical properties for power module die attach. We adopted Ag nanoporous preform for the die attach material. Here we investigated thermally activated degradation of Ag nanoporous bonding joint with bare Cu and ENIG finished Cu substrates at elevated temperature in air condition. Thermal storage test was performed at 250 oC up to 1000 h in air condition. The microstructure evolution at the Ag/Cu and Ag/ENIG interfaces by the diffusion and oxidation was examined using EPMA and TEM.