No abstract

The authors propose solutions for constructing mechanical structures for electronic equipment in terms of plug-in units and subracks, allowing to increase the layout characteristics of electronic modules, sections and desktop devices and increase their functional capacity without changing the architecture of standard mechanical structures. The paper shows effectiveness of the developed solutions. There is a problem of restraining of mass redundancy of mechanical structures for electronic equipment in relation to the weight of the electronic components. On the other hand, the weight is an indicator of structural strength, providing of which is not less important problem. These problems can be solved in different ways, the main of which are the following: a) development of new mechanical structures for electronic equipment taking into account the development of the electronic components; b) improving layout characteristics of mechanical structures for electronic equipment without significant changes in their architecture. The aim of the study was to research mechanical structures of the first level (plug-in units and modules of the second level) of subracks to improve layout characteristics, and to develop methods for the use of connections for surface mounting and for the use of printed circuit boards of smaller dimensions without changing the architecture of the mechanical structures in order to improve layout characteristics. The research allowed the authors to develop the following solutions: 1. The design of plug-in units in which instead of one printed circuit board (PCB) may be two, three or more PCBs of smaller dimensions to compensate a decrease in PCB fill factor in time and to increase the functional capacity of electronic modules. 2. Construction of block designs with a bilateral arrangement of plug-in units and the organization of the electrical connections by way of backplanes with electrical connectors for surface mounting, which allows performing independent installation of plug-in units on both sides of the backplane and creates conditions for increasing the number of plug-in units. The proposed solutions do not lead to a change in the architecture of standard mechanical structures for electronic equipment or any performance degradation.

The authors present a method, an algorithm and a program, designed to determine the optimal size of printed circuit boards (PCB) of mechanical structures and different kinds of electronic equipment. The PCB filling factor is taken as an optimization criterion. The method allows one to quickly determine the dependence of the filling factor on the size of the PCB for various components.

The paper deals with the research and analysis of various quality indicators of the standard mechanical structures of two constructional systems in order to define and compare their characteristics, and to predict prospects for their use. To compare these two systems we have selected parameters which make it possible to make a quantitative assessment and can be calculated on the basis of the data from standards for such mechanical structures. Research has shown that, according to considered indicators, neither 19-inch system, nor the metric system has the absolute advantage. And only in the density ratio of contacts of output electrical connectors, the metric system has real advantages. Although, it shoul be noted, that certain measures are taken by the developers to improve the 19-inch constructional system. This may, to some extent, explain the fact that the 19-inch system is more widely used than the metric one, and continues to evolve and develop. For other indicators, which are more difficult to be assessed quantitatively, the metric system is more preferable, because it is more convenient in unit design consisting in establishment of interrelation between the coordinating sizes and basic, multiple and mounting steps. At the same time, the 19-inch system has no rival in technical readiness of the industry and in adaptation to the previous designs. The latter is the defining factor for choosing a constructional system by developers of electronic equipment. This, in turn, does not stimulate producers of mechanical structures to extend their production range in accordance with the standards of the metric system. On the basis of the analysis we can predict that in immediate future the 19-inch dimensional system will retain priority for the mechanical structures of electronic equipment. This project deals with the problem of determination of optimum sizes of printed circuit boards for standard mechanical structures for various electronic devices.