Connections resistance

It is not practical to determine the contact resistance in power connectors. The resistance of the connection of a specified length of conductor on each side of the connector is measured and is called the overall resistance or the connection resistance. One industry specification (32) defines the included lengths and requites the stabiUty of the connection resistance to be within 5% of its average value throughout the heat-cycle test. 

It is useful to think in terms of a resistance formulation for this problem because all the connecting resistances between the nodes in Fig. 3-6 are equal that is,... 

The impedance of the series connected resistance and bounded CPE element (BCPE), shown in Figure 4.10a, is calculated by adding their impedances ... 

Heat generation occurs as current flows due to electrolyte resistance and electrical connection resistance. Therefore, a heat exchanger is required to overcome overheating the electrolyte, avoid cathode deterioration and oxidation of anodes. Thus, a temperature rage of 30 C [Pg.195]

Equation (83) is the mathematical formulation of the well known rule that the true effective conductivity of MHM is higher and lower than those estimated from adiabatic and isothermal sectioning respectively [8]. The physical meaning of the rdevant assumptions (Eqs. (74) and (78) respectively), may be assessed from consideration of the tt circuit of two randomly connected resistances (Fig. 3a). The upper bound of the effective resistance (Le., Eq. (74)) would then correspond to elimination of all transversal connections (Fig. 3b) since the finite resistances are replaced by infinite ones (circuit breakers). In its turn, the lower bound (i.e, Eq. (78)) would be obtained assuming zero resistance for all transversal connections (Fig. 3c). 

Electrochemical impedance spectroscopy is useful in the evaluation of coatings, the elucidation of transport phenomena in electrochemical systems, and the determination of corrosion mechanisms and rates. Bode and Nyquist plots are the most common data output formats, and an example of each for a simple parallel-connected resistance-capacitance circuit are shown in Figs. 31.3, and 31.4, respectively. The Bode plot format shows the... 

When a spherical particle meets a metallic pad, there are three separate contributions to the resistance the intrinsic conductive resistance of each particle, the constriction resistance at the contacts, and the tunneling resistance at the contacts (Hohn 1979 Ruschau et al. 1992). Therefore, the connection resistance through the conductive particles, Rc, is expressed by... 

Among the contributions to the connection resistance described above, the intrinsic resistance of an individual conductive particle can be estimated with respect to its deformation. Since the metal-coated conductive particles are deformed plastically during the bonding process of an ACA, the numerical model for the calculation of the connection resistance should consider the plastic deformation of the conductive particles. Yim and Paik (1998) derived the connection resistance of an ACA joint from Holm s electrical contact theory, and the derived model described the connection resistance of the ACA in terms of the sample geometry, particle size, applied pressure, and the intrinsic properties of the conductive particles. However, this... 

Using this derivation, the connection resistance of the ACA interconnect can be easily calculated by the simple investigation of the physical shape of the connected pathway. This derivation is based solely on the physical contact of the two unmelted metals, so it could be applied to the other two types of adhesives, i.e., ICAs and NCAs. In the case of ICAs, the shape of the current flowing path is more complex, which means that the contact resistance might also be more complex than that in the ACA case. However, the resistance components of an ICA interconnect are completely identical to those of an ACA interconnect, so the derivation and calculation of the components are also easy to perform. In the case of an NCA, there are no conductive fillers and, therefore, Rqk and Ri can be excluded from the derivation. This means that the connection resistance for an NCA joint consists only of Rf, so that the resistance should also be lower than that of an ACA joint. 

A flip-chip technology developed by Toshiba Corporation utilized an ACF to attach bare umbumped chips (with A1 pads) onto a polychlorinated biphenyl (PCB) with bumps formed from a silver paste screen printed on the PCB [32]. After curing, Ag bumps were formed (70 pm diameter, 20 pm height), which were subsequently overplated with Ni/Au. It was determined that an ACF with a low CTE (28 ppm/°C), low water absorption rate (1.3%), and utiUzing a Au-plated plastic ball worked best. It was also found that Ni/Au-plated Ag paste-formed bumps exhibited a lower initial connection resistance and a lower connection resistance increase as compared to Ag paste-formed bumps that were not overplated with Ni/Au. The initial connection resistance for Ni/Au-plated Ag paste bumps and nonplated bumps was 22 and 48 pll, respectively, with a respective increase of 294 and 717 pO after 1000 hr of accelerated thermal cycling (ATC) testing. 

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