Interconnect Materials

Wire Interconnect Materials. Wire-bonding is accompHshed by bringing the two conductors to be joined into such intimate contact that the atoms of the materials interdiffuse (2). Wire is a fundamental element of interconnection, providing electrical connection between first-level (ie, the chip or die) and second-level (ie, the chip carrier, or the leadframe in a single-chip carrier) packages. 

The perovskite oxides used for SOFC cathodes can react with other fuel cell components especially with yttria-zirconia electrolyte and chromium-containing interconnect materials at high temperatures. However, the relative reactivity of the cathodes at a particular temperature and the formation of different phases in the fuel cell atmosphere... 

The interconnect material is in contact with both electrodes at elevated temperatures, so chemical compatibility with other fuel cell components is important. Although, direct reaction of lanthanum chromite based materials with other components is typically not a major problem [2], reaction between calcium-doped lanthanum chromite and YSZ has been observed [20-24], but can be minimized by application of an interlayer to prevent calcium migration [25], Strontium doping, rather than calcium doping, tends to improve the resistance to reaction [26], but reaction can occur with strontium doping, especially if SrCr04 forms on the interconnect [27],... 

Interconnects are formed into the desired shape using ceramic processing techniques. For example, bipolar plates with gas channels can be formed by tape casting a mixture of the ceramic powder with a solvent, such as trichloroethylene (TCE)-ethanol [90], Coating techniques, such as plasma spray [91] or laser ablation [92] can also be used to apply interconnect materials to the other fuel cell components. 

The difficulty and high cost of the fabrication of ceramic interconnect materials is their primary disadvantage and has led to recent emphasis on metallic interconnects, which will be discussed in the next section. 

Nevertheless, Ni(-Fe)-Cr base alloys may find application as interconnect materials through the use of innovative SOFC stack and seal designs and novel interconnect structures. For example, a cladding approach has been applied to fabricate a stable composite interconnect structure consisting of FCC Ni-Cr base alloy claddings on a BCC FSS substrate [134,135], The clad structure appeared to be stable over 1000 hours at 800°C in air and exhibited a linear CTE close to that of the FSS, but needs further long-term stability evaluation before its commercial use. 

Zhu WZ and Deevi SC. Development of interconnect materials for solid oxide fuel cells. Mater. Sci. Eng. A 2002 A348 227-243. 

Zhou X, Ma J, Deng F, Meng G, and Liu X. Preparation and properties of ceramic interconnecting materials, I.a07Ca0 Cr() n doped with GDC for IT-SOFCs. J. Power Sources 2006 162 279-285. 

Liu Z, Dong D, Huang Z, Lti Z, Sui Y, Wang X, Miao J, Shen ZX, and Su W. A novel interconnect material for SOFCs. Electrochem. Solid-State Lett. 2005 8 A250-A252. 

Sammes NM, Ratnaraj R, and Fee MG. The effect of sintering on the mechanical properties of SOFC ceramic interconnect materials. J. Mater. Sci. 1994 29 4319-4324. 

In planar SOFCs, individual cathode, anode, and electrolyte layers have been deposited by PS [109-111], as well as coatings on interconnect materials and full cells [108, 110, 112]. In addition to the interconnect layers themselves in tubular SOFCs, dense protective layers with good adhesion have also been deposited to protect planar SOFC interconnects from oxidation [110], and diffusion barriers to inhibit inter-diffusion between the interconnects and anodes have been produced by PS [113]. 

Wire bonding, 9 694-695 Wire coating extrusion, 19 548-549 Wire, extrusion of, 19 790 Wire insulation HDPE, 20 174-175 LLDPE, 20 208-209 Wire interconnect materials... 

Stability for use in optical interconnects. In the near future, optoelectronic integrated circuits and optoelectronic multichip modules will be produced. Materials with high thermal stability will thus become very important in providing compatibility with conventional 1C fabrication processes and in ensuring device reliability. Polyimides have excellent thermal stability so they are often used as electronic materials. Furuya et al. introduced polyimide as an optical interconnect material for the first time. Reuter et al. have applied polyimides to optical interconnects and have evaluated the fluorinated polyimides prepared from 6FDA and three diamines, ODA (3), 2,2-bis(3-aminophenyl) hexafluoropropane (3,3 -6F) (4), and 4,4 -6F (2), as optical waveguide materials. 

Chemical Vapor Deposition. Deposition of tungsten, molybdenum, and their silicides by chemical yapor deposition (CVD) is of relatively recent interest in the microelectronics industry. These materials arc useful for gates and interconnects in metal oxide semiconductors (MOS) devices. Aluminum, the widely used interconnect material, has a comparatively low melting point (600°C) and a markedly different coefficient of thermal expansion (compared to silicon), so that over a period of years researchers have been seeking an alternative for aluminum,... 

Interconnection materials are necessary to combine single cells to form multicell modules by connecting the anode material of one cell to the cathode material of the... 

Arrhenius plots of conductivity for the four components of the elementary cell are shown in Fig. 34. They indicate that electrolyte and interconnection materials are responsible of the main part of ohmic losses. Furthermore, both must be gas tight. Therefore, it is necessary to use them as thin and dense layers with a minimum of microcracks. It has to be said that in the literature not much attention has been paid to electrode overpotentials in evaluating polarization losses. These parameters greatly depend on composition, porosity and current density. Their study must be developed in parallel with the physical properties such as electrical conductivity, thermal expansion coefficient, density, atomic diffusion, etc. 

The second approach involves successive deposition of thick (typically 50 - 200 pm) layers of electrolyte, electrodes and interconnection materials on a... 

---