Foil interconnects

The plastic film with interconnection layers, denoted (2) in Fig. 16.1, can be made by a process similar to that used to manufacture flexible circuit boards. First, plastic films coated with copper foil are processed by a numerically controlled (NC) drilling machine to make via holes. Plating is then used to make interconnections between top and bottom sides though via holes. Finally, the copper layers are patterned by conventional photolithography and etching. Gold plating is occasionally employed to improve electronic interconnections. 

Fig. 13. Vh20, measured in aq. saturated or molten NaOH, at 1 atm.90 CO2 is excluded by argon purge. The molten electrolyte is prepared from heated, solid NaOH with steam injection. O2 anode is 0.6-cm2 Pt foil. IR and polarization losses are minimized by sandwiching 5 mm from each side of the anode, two interconnected Pt gauze (200 mesh, 50 cm2 = 5 cm x 5 cm x 2 sides) cathodes. Inset At 25 °C, 3 electrode values at 5 mV/s versus Ag/AgCl, with either 0.6-cm2 Pt or Ni foil, and again separated 5 mm from two 50-cm2 Pt gauze acting as counter electrodes.

Finally, it should be noted that metallic monoliths allow for some additional design freedom over ceramic monoliths. Numerous examples of this are found in the literature (Fig. 35) [28]. One example shows a metallic structure consisting of a macroscopic corrugated foil and a microscopic corrugated foil. The microscopic corrugation considerably increases the geometrical surface area of the structure. A further example shows a metallic monolith in which the channels interconnect to... 

On one side the development is based on thin film and micro-patterning technologies. Wafer level and foil processes used to produce high density interconnect electronic modules, and wafer level packaging was adapted to micro fuel cell development to achieve the required miniaturisation and cost reduction. By using reactive ion etching, high aspect ratio capillary structures of the anode and cathode side flow fields were achieved. 

As outlined above, the segmentation of MEA electrodes is a key process to implement the concept of integrated fabrication of micro fuel cells which consists of merely three foils. Figure 7-15 shows the electrical characterisation of the serial interconnected three cell demonstrator. Approximately 40 mA can be drained at 1.5 V. To illustrate the importance of MEA patterning a fuel cell has been assembled with three serial interconnected current collector structures according to Figure 7-9 but with a continuous piece of MEA. 

Interconnected cactus-like ZnFe204 structures growing vertically Nanotube arrays on a Ta foil... 

Laser-Opened Sealing Foil A Swiss company, SpinX, introduced a platform, intended for on-the-fly programming of the fluidic network. To this end the numerous (potential) vertical interconnects between two fluidic layers were blocked by a sandwiched sealing foil. The coordinated firing of a peripheral laser at the foil layers could, even during rotation, open the vertical vias and thus establish the fluid network. 

Carbon films of high conductivity with low activation energy that are very stable, chemically inert, and highly corrosion resistant have a wide range of applications, e.g., as standard resistors, electrode coatings, stripper foils for accelerators, interconnects in circuits, and corrosion-resistant coatings as listed below [191]. 

Specialist materials include buried capacitance laminate for wireless communication interconnects, servers and measuring instrument applications. This is a 0.002 inch thick glass reinforced material with double treated copper foil on both sides. The key features of this product are claimed to be improved electrical performance, excellent dielectric thickness accuracy and excellent electrical integrity. 

Whereas traditional PCB are flat or flexible, injection moulded three-dimensional versions, also known as moulded interconnect devices (MID) have been developed which combine a circnit board, enclosnre, connector and cable into one unit. Traditional techniques of installing the electronic circnitry on to the MID have included laser imaging, two-component moulding or hot foil stamping. 

Use of bipolar electrodes to form an ES stack is shown in Figure 5.9. The bipolar arrangement can effectively minimize the volume of the stack and circumvent the use of additional materials and external connections. In addition, the intimate surface level connection can help overcome macroscopic resistances generated from solder joints, long interconnects, and tabs that contact only part of the collector foil. The reduction in packing material (grid weight) for a module also improves cell performance. 

ADVANCED HIGH-DENSITY INTERCONNECTION (HDI) TECHNOLOGIES 23.9 Conventional lamination with pre >reg /foil or RCC Laser dril... 

Printed circuit board (PCB) structures and processes continue to be driven by device miniaturization, functional densification, and speed. The choice of components, actives and passives, and connectors are primary determinants of layer count and layer options, such as copper foil weights. Reductions in chip voltages are matched by an increase in current demand this in turn causes increases in the number and thickness of the plane layers. More device leads combined with decreasing pitch increases the number of vias and interconnecting layers, while miniaturization and weight reduction at the product level forces reduction in the physical package for the product. 

To facilitate the many choices of laminates and their associated properties, industry standards groups such as the IPC have defined minimum performance specifications and have issued several specifications to inform the selection process. Some of the most commonly used material specifications are those that deal with laminate,prepreg, and copper foil. IPC lOl, Specification for Base Materials for Rigid and Multilayer Printed Boards, and IPC-4652, Metal Foil for Printed Wiring Applications, are the primary specifications for clad laminates, prepregs, and foils. Another specification, IPC- 4104, Specification for High Density Interconnect (HDI) and Microvia Materials, deals with many of the new materials for HDI, such as epoxy-coated microfoils, as discussed in this chapter. 

Interconnection Separation. This is defined as the separation between the internal copper foil and the copper plating in the hole. It is also sometimes referred to as post separation. Any evidence of this imperfection in the microsection makes the associated PCBs nonconforming. This imperfection is a severe issue that will likely reduce the service life of the PCB (see Fig. 51.30). 

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