Layout and type selection of printed circuit boards used in SMT processing

1 The main factors to be considered in mechanical design:
1)Selecting the best printed circuit board to make the best panel size;
2)Panel mounting hole, bracket, splint, clip, shielding box and radiator location;
3)suitable for heavy components of the fixed device;
4)Suitable aperture for component installation;
5)Assembly of the circuit board in the transport process to have compression and seismic resistance;
6)Circuit board assembly (vertical mounting / horizontal mounting);
7)Cooling mode;
Printed circuit board not only provides mechanical support,is also connected to the components installed on it.Therefore, for the designer of the printed circuit board,It is necessary to understand the entire panel designers physical size (frame size), the position of mounting holes, height restrictions and related details.

2 The choice of single or double sided board must meet the most effective cost utilization.
According to the experience, the double sided printed boards with plated through holes cost 5 -10 times as much as a single panel.Similarly, the cost of assembly components is an important aspect to consider.The cost of assembling a single printed circuit board component (manual) is about 25% -50%.While ,the assembly of a double-sided printed circuit board with PTH components, the cost is 15% -30%.
Double plate:Double sided board can be used or can not use PTH,because of the high price of PTH board.PTH will be used when the complexity and density of the circuit is required.In the layout design, the number of wires must be kept at least,to ensure easy access to the required materials.In the PTH board, plated through holes are used only for electrical connections but not for the installation of components.The number of holes should be kept to a minimum for economic and reliability considerations.To select a single panel or double-sided board, it is important to take into account the surface area of the component (C).The ratio of the surface area (C) of the component to the total area (S) of the printed circuit board is an appropriate constant proportion,which is useful for the installation of components.