Building up Structures

Engineered nanoparticles can be prepared in two ways top-down by breaking apart conventional bulk substances, or bottom-up by building up structures from the molecular scale. There also is a growing trend to combine the top-down and bottom-up approaches to produce more sophisticated nanoparticle systems (Horn and Rieger, 2001). 

Build up structures from randomly seeded atoms and randomly selected torsions... 

While die above reactions will provide carboxylic acid products, each has problems associated with it. The cleavage of olefins to carboxylic acids [reaction (7.1)] can be carried out using potassium permanganate or by ozonolysis at low temperature followed by oxidative workup with hydrogen peroxide. Neither of diese mediods is very useful since only symmetric olefins provide a single carboxylic acid product. Unsymmetrical olefins give a mixture of two acids which must be separated. Furthermore the most useful synthetic processes are those which build up structures, whereas these reactions are degradative in nature. 

The great advantage of this method is that it can be used to build up structures of much larger molecules quickly and without having to imagine that the molecule is made up from isolated atoms. So it is easy to work out the structure of ethene (ethylene) the simplest alkene. Ethene is a planar molecule with bond angles dose to 120°. Our approach will be to hybridize all the orbitals needed for the C-H framework and see what is left over. In this case we need three bonds from each carbon atom (one to make a C-C bond and two to make C-H bonds). 

The wealth of natural examples provides immense inspiration for the molecular design of novel peptide-based materials that can be potentially applied as devices, sensors, and biomaterials for medical applications. In addition to hierarchical self-assembly, nature uses other mechanisms, for example, enzyme-mediated covalent cross-linking, to build up structural proteins and higher-ordered structures. In the following sections we will focus on manmade peptide-based materials that belong to the three classes listed below. They will be split with respect to the underlying design concept into materials formed by ... 

Tackifiers. Pine tar, coumarone-indene resins, zylol-formaldehyde, and other resins are used to increase the tack of rubber compounds. Tack, here, means stickiness of the un-cmed rubber stock to itself, rather than to other things, such as metal surfaces. Tack has also been called autoadhesion. It is extremely important for building up structures such as tires. Natural rubber inherently has good natural tack, but most synthetic rubbers do not. 

Blodgett technique. The enhanced materials stability may make functional siloxane-based systems suitable for device integration and operation. It is noteworthy that standard isocyanate/hydrolysis polymerization chemistry can be used as well to build-up structurally regular multilayers. 

Printed wiring boards (PWBs) with microvia hole structures are called different names, such as HDI, SBU (sequential build-up), and BUM (build-up multilayer). However, HDI covers a broader range of high-density wiring boards such as extremely high-layer-count multilayer boards (MLBs) without microvia holes. MLBs with microvia holes are not necessarily built sequentially, nor do they necessarily have build-up structures.These definitions are not appropriate for the discussions in this chapter, and therefore we shall address MLBs with microvia holes simply as microvia hole boards (all microvia hole boards are essentially multilayer boards). 

Type I to Type VI constructions currently describe all known HDI build-up structures, but as the technology evolves, new ones are hkely to be created. The notation used is as follows ... 

IBSS-AAPIO System, The Interpenetrating Polymer Network Build-Up Structure System (IBSS) is a new photodielectric. This photo-imageable dielectric (PID) is a proprietary photodielectric developed by Ibiden of Japan. It complements Ibiden s older epoxy type of photo-redistribution layer technology, IP-10. 

FIGURE 23.4 The Sony DCR-PC7 digital camcorder utilized the SLC process for the 2+4+2 build-up structure and 0.5 mm CSPs to achieve over 600 connections (pins) per sq. in. 

MSF. Shinko of Japan developed the MSF HDI technology. It utilizes laser-drilled RCC materials and vias filled with a conductive paste. After testing, these are laminated into the parallel build-up structure. Figure 23.24 shows the typical manufacturing sequence for this HDI technology. 

Fig. 103. Change in Registry File to the mode for building up structures...

In addition there are a number of abbreviations, 51 at present, which make it easier to build up structures. These shortcuts can be displayed online by... 

Build-up technology, such as SLC , has achieved up to three board build up layers per side of laminate core as shown in Figure 4A. One method, the interpenetrating polymer network build-up structure system (or IBSS) technology, developed by Ibiden Corporation, achieves fine lines (2-mil lines and spaces) and photo via holes with 4-mil diameters. One of the important aspects of micro-via formation is the ability to register the via fully within the capture pad. The process tolerances of each formation method requires the via pad to be larger than the via by... 

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