Technical requirements and precautions for component installation
Published time: 2019-08-16
There are various types of electronic components, different shapes, and various lead wires. Therefore, the mounting method of printed circuit boards is different, and must be determined according to the characteristics of the product structure, assembly density, product usage methods and requirements.
Technical requirements for component installation:
1) The direction of the marking of the component shall be in accordance with the requirements specified in the drawings, and the marking on the component can be seen after installation. If the orientation is not indicated on the assembly drawing, the markings should be easily identifiable outward and read from left to right and bottom to top.
2) The polarity of the components must not be misplaced, and the corresponding casing should be placed before installation.
3) The installation height should meet the specified requirements, and components of the same specification should be installed at the same height as much as possible.
4) The installation sequence is generally low and then high, first light and then heavy, first easy and then difficult, first general components and special components.
5) The distribution of components on the printed circuit board should be as uniform as possible, uniform and uniform, and arranged neatly and beautifully. Oblique rows, solid intersections, and overlapping arrangements are not allowed.
6) The components and leads of the components must not touch each other. To ensure a safety clearance of about 1mm, if it is unavoidable, the insulating sleeve should be sleeved.
7) The lead diameter of the component and the hole diameter of the printed circuit board pad should have a reasonable gap of 0.2-0.4mm.
8) The installation of MOS integrated circuits should be carried out on an equipotential table to avoid electrostatic damage to the device. The heating components are not allowed to be mounted on the board. The installation of larger components should be done by binding and fixing.
Component installation precautions:
1) Insert the components, the direction of the bend of the pins should be the same as the direction of the copper foil.
2) When installing the diode, besides paying attention to the polarity, pay attention to the outer casing, especially the glass casing is fragile. When the lead is bent, it is easy to burst. When installing, the lead can be re-installed for 1-2 turns for high current. Diodes, some use the lead body as a heat sink, so the length of the lead must be determined according to the requirements of the diode specifications, and it is not appropriate to put the lead on the insulating sleeve.
3) In order to distinguish the positive and negative ends of the electrode of the transistor and the electrolytic capacitor, a color-bearing sleeve is generally added during the installation to distinguish it.
4) High-power triodes are generally not suitable for mounting on printed circuit boards due to their high heat generation.
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