Seektronics

PCB engineers in doing PCB design, often encounter a variety of safety spacing problems, usually these spacing requirements are divided into two categories, one is the electrical safety spacing, the other is: non-electrical safety spacing. So, what are the spacing requirements for designing PCB circuit boards?   First, the electrical safety spacing   1 the spacing between the wires: the minimum line spacing, also line-to-line, line-to-pad spacing shall not be less than 4 MIL. from the production point of view, the greater the better, of course, when available. The general routine 10MIL is more common.   2 pad aperture and pad width: according to PCB manufacturers, pad aperture if the mechanical drilling method, the minimum shall not be less than 0.2mm; if the laser drilling method, the minimum shall not be less than 4mil. and aperture tolerance according to different plates slightly different, generally can be controlled within 0.05mm; pad width of the minimum shall not be less than 0.

  Protel 99 SE provides 32 signal layers, including the Top layer, Bottom layer and 30  M iddle layer.   Top signal layer: also known as the component layer, mainly used to place components, for multilayer boards can be used for wiring.   Mid Signal Layer: up to 30 layers, used to lay signal lines in multilayer boards.   The bottom signal layer : also known as the solder layer, mainly used for wiring and soldering, and sometimes can also be placed on the components.   Silkscreen layer: The silkscreen layer is mainly used for placing printed information, such as component outline and labeling, various comment characters, etc. Protel 99 SE provides two silkscreen layers, Top Overlay and Bottom Overlay. Generally, various annotation characters are placed on the top screen printing layer, and the bottom screen printing layer can be closed.   Top silkscreen layer: used to mark the projected outline of the component, the component's mark, nominal value or model number and various comment

  Electronic devices will generate a certain amount of heat when working, so that the internal temperature of the device rises rapidly, if the heat is not distributed in a timely manner, continued heating, the device will fail due to overheating, the reliability of electronic equipment performance will be reduced. Therefore, a good thermal treatment of PCB circuit boards is very important.         1.  PCB heat dissipation itself   PCB heat dissipation is a simple, practical, low-cost way to dissipate heat. The current PCB circuit board is mainly: copper/epoxy glass cloth substrate or phenolic resin glass cloth substrate, although these substrates have excellent electrical properties and processing performance, but poor heat dissipation can hardly be expected to conduct heat by the PCB itself resin. Therefore, it needs to be designed to dissipate heat from the surface of the component to the surrounding air.   So how to do it? The best way to improve the direct contact with the heat-gen

Why can't via hole be in pad? If I want Via in pad, how to do? Many newcomers to PCBs often have this problem when they first encounter it, because the board space is too small, dense devices lead to a small space, can not lead to fan holes, usually choose to punch the holes in the pads, which makes it much easier to connect their own lines, but often do not know what kind of problems will lead to the board? Can this be done? In order to make this issue clearly explained, it will be explained from the following two aspects: 1) Why can't via hole be in pad? 2) Under what circumstances can via holes be punched into pads? Why can't via hole be in pad In the early stage of PCB design, BGA pads are not allowed to have via holes. The main reason is that tin leakage leads to insufficient solder paste on the pads, which leads to virtual welding and unwelding of devices during device welding. Therefore, in general, holes are drilled on devices by leading out first and then drilling

  1. T ransformer drawings, PCB , schematic diagrams of the three transformer fly-by-wire bit number need to be one.   Reason: Safety certification requirements   This is a fault that many engineers will make when applying for safety certification submission.   2. The discharge resistor of X capacitor should be put in two sets.   Reason: UL62368, CCC certification requires to disconnect a group of resistors  and test the residual voltage of X capacitor   Many novices will make a mistake, and the only way to correct it is to change the PCB Layout  again, which will waste our time and the procurement of samples.   3. The PCB  aperture of transformer flyline shall take into account the maximum flyline diameter. If necessary, two groups of large and small PCB holes shall be reserved.   Reason: to avoid assembly  difficulties or furnace empty welding problems   Because safety application certification usually has a series, such as 24W application for a series, which contains 4.2V-36V volt