Lecture
Pure or surface mounting is now very rare. Boards with planar components contain wires or connectors in the leading housings, and modules assembled mainly from the lead elements contain microcircuits in planar packages. The desire to manufacture electronic modules from one planar components requires the restructuring of production and the introduction of not only new equipment, but also completely new standards for monitoring compliance with technology requirements. The transition of production from lead-to-surface mounting is possible only through the release of modules assembled using a mixed-mounting technology.
Surface mounting imposes new requirements for the development of printed circuit boards, which complicates the development. The lack of surface mounting of the holes that have taken place in the terminal mounting now results in a huge number of vias from one side of the board to the other. Output mounting is promoted as a technology that reduces the cost of drilling holes for the findings. And at the same time there is a need for drilling vias. If earlier in the development of the board, the transition from one side to the other was due to the hole for the component output, now it is necessary to introduce a transition hole when designing the board. Tracing the board is more difficult, for such work requires an experienced developer.
The use of a balanced mixed installation allows you to use the best components from the output and planar and develop a good charge that gives the best electrical properties of the module.
With manual installation, the soldering area contains a lot of flux residues. Applying flux to the entire board during wave soldering results in a large amount of solid and liquid residues. To eliminate flux residues is washed. The remaining flux may affect the parameters of the electronic module. Often, washing is carried out manually, using an alcohol-gasoline mixture, but now there are more effective means. For washing use special flushing fluids. Washing off provides not only a decent appearance of the modules, but also ensures good contact of the board with a waterproof coating.
At the end of the cleaning, the module is checked for operability, after which the board with the parts is covered with several layers of waterproof varnish. Each layer is dried with hot air. Varnishing prevents exposure to moisture, improves the thermal mode of the components of the module and increases the vibration strength.
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Design and engineering of electronic equipment
Terms: Design and engineering of electronic equipment