Surface-mounted components

The conventional method using screen printed solder pastes or isotropic conductive adhesives is drflicult to apply when the distance between adjacent connections is less than 0.5 mm. Thus, the main impetus for developing anisotropic conductive adhesives has been the fine pitch interconnection of electronic devices 

The development of anisotropic adhesives was initiated by the LCD industry but an extensive survey of the patent literature indicates other general trends [102]. The resins and fillers intended for use as anisotropic adhesives must satisfy new requirements compared to those previously defined for isotropic materials. In particular, the geometrical factors influence the formulation and the processing technique in relation to the final application LCD, surface mounting or flip chip bonding. 

Many alternatives exist and the choice between thermoplastic and thermosetting resins depends on the expected lifetime and maximum operating temperature. Styrene-butadiene block copolymers and acrylic resins can be used to produce low-end adhesives with an acceptable stability up to 100°C, whereas epoxy and silicone thermosets are preferred for their robustness at 150-200°C. In the most severe environments, poly(imide-siloxanes) and polyimides can sustain medium-term exposures to 250 and 300°C, respectively. Various conductive fillers are cited in the literature, including noble metals such as gold or silver, and low-cost metals such as copper, nickel, chromium, and soft solders. 

The surface-mount assembly of fine pitch integrated circuits is a potential market for anisotropic adhesive films [103,104]. The best conductive adhesives exhibit a volume resistivity of 2 to 5 X 10 cm with a contact resistance of 10 mfl, although AI Technology claims volume resistivities of 5 X 10 -5 X 10 n cm, similar to that of metallic solder joints. This allows a current carrying capabdity of 50-60 A mm compared to 20-30 A mm for typical 

The electrical properties and the reliability of connections made of an anisotropic adhesive loaded with both deformable conductive particles and non-deformable dielectric particles used as spacers have been reported [108]. The amount of deformation of the conductive particles is calculated from their diameter, 10 xm, relative to the diameter of the spacers, 4, 6, 8, and 10 p,m. Plotting the electrical resistance of the connection as a function of the number of particles, the authors show that the resistance decreases when the particle count expands from 5 to 60 

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Figure 4.34 Surface-mounted components such as valves, gauges and pressure regulators of the NeSSI consortium [23] (by courtesy of CPAC).

A selection of components surface-mounted to carrier plates is shown in Figure 4.34. The carrier plates support the internal fluidic pipes and can also be equipped with electrical heaters to permit trace heating of the fluid. The surface-mounted components of this system are compatible with the backbone concept introduced in the following. 

A process scheme (Figure 4.87) consists of standardized surface-mount components and can be arranged on the screen to a customized system. The software also delivers a summary considering necessary seals and pipe fittings which can be used for ordering directly (Figure 4.88). 

Figure 2. Multilayer circuit board with surface mounted components.

Generally, some improvement in Tg will be required, partly because this will help retain the mechanical properties over a wider temperature range, and partly because the soldering of surface mounting components often puts a large heat load on the entire board and not just on one surface. 

Connecting the modular surface-mount components (and optional auxiliary components) in Fig. 10.1 is the NeSSI -bus, which provides the electrical power and communication functions for controlling actuators and transmitting... 

Fig. 10.6 Cutaway view of the flow path for a single surface mount component (in this case a 2-port toggle valve) in the Swagelok MPC system.

Fig. 10.7 Cutaway view of a five-position Swagelok MPC assembly with a manifold layer assembled below Position 3. At this position, flow is diverted in two directions - up to the surface-mount component and down into the manifold layer.

Fig. 10.8 Examples of substrate and manifold channels, flow components, and surface mount components fortheSwagelok MPC NeSSI system.

CIRCORTech provides the parts needed to construct a pMS3 system, build to order complete systems, and a wide range of SP76 surface mount components for NeSSl systems. They also provide services for designing and installing their pMS3 systems according to customer specihcahons. 

C) the underside view showing the tubesets and mounting feet attached, and (D) with the surface mount components mounted. 

Fig. 10.14 Initial NeSSI offering from Parker-Hannifin the Integrated Conditioning System (PICS) could accommodate both IH" and V/f surface mount components based on the original draft ANSI/ASI SP76 specification.

The Parker-Hannifin PICS system was replaced by the Intraflow System as their main NeSSi commercial product line. Of course, their previous experience with the PICS system helped them to produce a second-generation NeSSi system with unique architecture and some interesting abilities. Also, the large number of 1% inch SP76 surface mount components they have developed work with the new system as well. The Parker-Hannifin web site describes the Intraflow System as ... 

Fig. 10.17 Picture showing how SP76 modular surface-mount components are attached to one of the commercially available substrates.

The modular nature of the surface-mount components makes it very easy to assemble or reconfigure a fluidic system to meet the requirements of a particular analyzer or sensor. Figure 10.19 shows three simple examples of surface-mount component systems being used to provide all, or part, of an analytical interface. 

Cormier, D. R. (1991), Neural Network Based Surface Mount Component Verification, Master s Thesis, State University of New York at Buffalo, Buffalo, NY. 

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