Electronic computer-aided design

If done as part of the electronic design automation (EDA) process using appropriate electronic computer-aided design (ECAD) software, the software wiU automatically assign copper directions to each component footprint, as weU as appropriate coordinates and dimensions. These may need adjustment based on considerations related to wave soldering, test points, RE, power and EMI/RFI issues, and board production limitations. Allowing the software to select 5-mil traces when the board production facility to be used can only reliably do 8-mil traces would be inappropriate. Likewise, the solder mask patterns must be governed by the production capabilities. 

One result of the computer-aided development of electric circuitry for printed circuit boards was that the software products had a two-dimensional development environment. Rectangular-shaped planar boards were the norm, so for decades this mode of representation was perfectly adequate. Expansions were allowed for the number of layers in a multilayer board construct, the placing of electronic components on both sides of the board, and the stacking of multiple flat boards. The differences in the complexity of the software tools for electronic computer-aided design (ECAD) can be explained by the difference in focus. The more layers in a printed circuit board (PCB) or the more specialized the applications (high-frequency circuits are a case in point), the larger are the quantities of data to be handled and the more specialized are the functions needed. 

Although adequate materials and devices are essential, successful manufacturing will require other capabilities as well. First, the process must have high yield, which implies low variability, and provide robust stability to environmental factors. To produce the envisioned products, there must be readily available electronic design tools that can adequately simulate both device and circuit performance. Although some of these computer-aided design tools are available from microelectronics technology, others must either be modified, because of the differences in the thin-hlm devices, or created anew because the devices have no equivalent (nanowires and nanotubes). 

The beauty of a molecular knot is naturally related to its representation and to the shape of the molecule itself [18] and, in all walks of chemistry, there are more and less beautiful representations of knotted structures. Few people envisage these beautiful molecules as the clouds of electron density and atomic nuclei that they are, but with computer-aided design it is likely that these attractive molecules will find renewed interest from those eager to attempt totally synthetic challenges in synthesis through template methods. One has simply to behold the remarkable and... 

Effects that cause non-uniformity in patterned electrodeposition of microscopic features are the subject of J. O. Dukovic s chapter. Mathematical models are used to identify process conditions which lead to flat profiled features of uniform height needed in electronic components. The emergence of computer-aided-design tools for electrochemical microfabrication is discussed. 

The fabrication of a lithographic mask involves the transformation of computer-aided designs of an IC into a physical layout to create a geometrical pattern of the mask. Coordinates of the IC layout are digitized and stored in appropriate electronic storage media such as tapes. The pattern is then transferred onto the surface of chrome-quartz plates or appropriate substrates, depending on the mask type. ... 

E. Munro, Computer-aided Design of Electron Lenses by the Finite Element Method, Image Processing and Computer Aided Design in Electron Optics, P. W. Hawkes (ed.). Academic Press, London, 1973. 

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