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Preparation of printed circuit boards

In Electronic Infomation Category: P | on February 01,2012

(1) Select plate
CCL selection will directly affect electrical performance and MT8994BC datasheet and service life. In the design of printed circuit boards, should be based on the products electrical and MT8994BC price and mechanical properties and MT8994BC suppliers and the use of the environment use different CCL. Mainly based on: whether the heating circuit components (such as high power components) and the circuits operating frequency; structural requirements of printed circuit board in place in the electrical mode (vertical or horizontal) and the board whether the quality of the heavier devices; is working in the humid, high temperature environment. Design must also consider the cost performance, if all the indicators are the finest selection of plates, while ignoring the different sheet in the price difference, it is likely to cause no significant increase in product quality and cost is a significant increase in the case . The pocket transistor radio, for example, due to the circuit board inside the machine itself is small, the line width is printed too, good use of the environment, the whole low price, so should be the main consideration in the selection of the price factor, the paper substrate can be selected phenolic not necessary to use high-performance epoxy glass cloth board. Another example, in micro-computers and other high-end electronic equipment, due to the high density component assembly,
printed narrow lines, board size, the circuit board in the machine manufacturing costs only account for a small percentage of the cost Therefore, the design selection, should be the technical performance of CCL as the major factors considered, not one-sided demands and low cost.

(2) PCB thickness to determine
in the choice of PCB thickness, PCB size and mainly based on the weight of the selected components and conditions of use and other factors identified. If the PCB board size is too large or heavy components (such as large-capacity electrolytic capacitor or high-power devices, etc.) should be increased plate thickness or reinforcement measures taken on board, or board prone to warping. Table 4-1 lists the nominal thickness of the laminate. In addition, when the boards external connection through socket, socket slot must pay attention to the gap is generally 1.5 mm, if the PCB is inserted does not go too thick, too thin, can easily cause poor contact.

(3) determine the shape of
PCB PCB shape and internal structure of the machine usually determines the size of spatial location. Appearance should be as simple as possible, usually rectangular, to avoid the use of shaped board. Rectangular, can greatly simplify the amount of plate forming the edge. In the tape recorders, television sets and other high-volume products, in different parts of the machine often requires a few different sizes on the printed circuit board. In order to reduce the circuit board production costs, increase the proportion of automatic assembly welding, usually two or three smaller, PCB fight with the main circuit board to form a large rectangle, made into a full-board, to be assembled, welded After the hole and then along the process or process tank break apart.

(4) determine the size
PCB PCB determine the size to take into account the machines internal structure and the number of components on the PCB, size and installation arrangement, the board the arrangement of components to be retained between certain intervals, especially in high-pressure circuit, pay attention to the discretion retained enough space, consider the components in the area occupied, we should pay attention to heat sink the size of the components to be installed, in determining the printed board, the net area, the outward expansion should be a 5 ~ lOmm (unilateral), to facilitate printed circuit board installed in the machine fixed. If the PCB of the larger, heavier components or vibration environments, should be used borders, strengthen the tendons or multi-point support and other forms of reinforcement. When the machine a number of blocks within the PCB, especially when these PCB and socket fixed by rail, they should make the size of each plate tidy, which is conducive to their fixation and processing.

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