Circuit three-dimensional

This type of coil was prepared from copper cladded printed circuit board material by applying photolithographic techniques. The p.c. board material is available with difierent copper thicknesses and with either a stiff or a flexible carrier. The flexible material offers the opportunity to adapt the planar coil to a curved three dimensional test object. In our turbine blade application this is a major advantage. The thickness of the copper layer was chosen to be 17 pm The period of the coil was 100 pm The coils were patterned by wet etching, A major advantage of this approach is the parallel processing with narrow tolerances, resulting in many identical Eddy current probes. An example of such a probe is shown in fig. 10. 

Newer resins include polysulfone, polyethersulfone, polyetherimide, and polyetherketone. Some of these newer materials are high temperature thermoplastic, not thermoset, resins. They are being promoted for the design of injection-molded printed circuit boards in three-dimensional shapes for functional appHcations as an alternative to standard flat printed circuit boards. Only semiadditive or fully additive processing can be used with these devices. 

A new polymer type which emerged as important materials for circuit hoards are polycyanurates. The simplest monomer is the dicyanate ester of hisphenol A. When polymerized, it forms three-dimensional, densly cross-linked structures through three-way cyanuric acid (2,4,6-triazinetriol) ... 

Deep recesses, holes, and other difficult three-dimensional configurations can usually be coated with relative ease. For instance, integrated circuit via holes with an aspect ratio of 10 1 can be completely filled with CVD tungsten. 

Figure 11.16. Overview of 3D NW circuit integration, (a) Contact printing of NWs from growth substrate to prepatterned substrate, (b) Three-dimensional NW circuit is fabricated by the repetition of the contact printing, device fabrication, and separation layer deposition steps N times. [Reprinted with permission from Ref.75. Copyright 2007 American Chemical Society.] (See color insert.)...

Figure 11.17. Three-dimensional multifunctional circuits on plastics, (a) Schematics and circuit diagrams of inverter (top) and floating gate memory (bottom) elements.

Volume diffusion refers to the transport of atoms through the body of a solid. It is also called lattice or bulk diffusion. In amorphous or glassy solids and in cubic crystals, the speed of diffusion in all directions is the same and is said to be isotropic. In all other crystals, the rate of volume diffusion depends upon the direction taken and is anisotropic. Volume diffusion is usually much slower than short-circuit diffusion, which refers to diffusion along two- and three-dimensional imperfections in the material. 

The three-dimensional circuit elements are fabricated by a series of processes collectively known as lithography . The pattern is first generated in a polymeric film on a device wafer and this pattern is then transferred via etching, into the underlying thin film. The purpose of this book is to review the theory, materials, and processes that are used in the lithographic process. This book is intended to be a tutorial and not a comprehensive review. Each chapter contains many references to which the reader can refer for more detail on any specific aspect of microlithography. 

In atomic force microscopy (AFM), the sharp tip of a microscopic probe attached to a flexible cantilever is drawn across an uneven surface such as a membrane (Fig. 1). Electrostatic and van der Waals interactions between the tip and the sample produce a force that moves the probe up and down (in the z dimension) as it encounters hills and valleys in the sample. A laser beam reflected from the cantilever detects motions of as little as 1 A. In one type of atomic force microscope, the force on the probe is held constant (relative to a standard force, on the order of piconewtons) by a feedback circuit that causes the platform holding the sample to rise or fall to keep the force constant. A series of scans in the x and y dimensions (the plane of the membrane) yields a three-dimensional contour map of the surface with resolution near the atomic scale—0.1 nm in the vertical dimension, 0.5 to 1.0 nm in the lateral dimensions. The membrane rafts shown in Figure ll-20b were visualized by this technique. 

Photoresists. Three-dimensional relief images which can function as photoresists for circuit board fabrication were demonstrated using organotin activators (65). 

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