The layout ofcomponents shall be designed according to the requirements of SMT chipprocessing and production equipment and process. Different processes, such asreflow soldering and wave soldering, have different layout of components.During double-sided reflow welding, there are different requirements for thelayout of side A and side B.

The basicrequirements of SMT process for the layout design of components are that thedistribution of components on the printed circuit board should be as uniform aspossible, the heat capacity of high-quality components during reflow solderingis large, and excessive concentration is easy to cause low local temperatureand lead to false soldering; At the same time, the uniform layout is alsoconducive to the balance of center of gravity. In the vibration impact test, itis not easy to damage the components, metallization holes and pads.

Layout directionof components in reflow soldering process: the layout direction of componentsshall consider the direction of printed circuit board entering reflow solderingfurnace. In order to make the welding ends on both sides of the two end chip componentsand the pins on both sides of the SMD components heated synchronously, andreduce the welding defects such as monument, displacement and separation of thewelding end from the pad due to the failure of synchronous heating of thewelding ends on both sides of the components.

In order toprevent short circuit between layers caused by touching printed wires duringPCB processing, the conductive pattern at the edge of inner layer and outerlayer shall be more than 1.25mm away from the edge of PCB. Installation spacingof components: the minimum installation spacing of components must meet therequirements of manufacturability, testability and maintainability of SMT patchprocessing.