Seektronics

  Description of the phenomenon.   A plastic enclosure product with an I/O cable was found to exceed the radiation emission limit when conducting the radiation emission test specified in the EMC standard, specifically at 160 MHz. the cause of its radiation exceedance needs to be analyzed and appropriate countermeasures are given.     Reason Analysis   This product has only one PCB, which has a crystal with a frequency of 16MHz. It can be seen that the 160MHz radiation should be related to the crystal (Note: it does not mean that the radiation exceeds the standard is caused by the direct radiation of the crystal, may be multiplier generated). Figure 1 shows the product's local PCB layout, from Figure 1, it is clear that the 16MHz crystal is arranged right at the edge of the PCB.   Figure 1 The product's local PCB layout of the actual diagram   In signal lines or high-speed devices and the laboratory between the reference grounding plate, there is an electric field distribution o

Now whenever you open the SoC original PCB Layout Guide, will mention the high-speed signal alignment of the corner angle problem, will say that high-speed signals do not take a right angle alignment, to a 45-degree angle alignment, and will say to take the arc will be better than 45-degree corners.     People began to struggle with the corner angle of the PCB alignment, that is, the last decade or two. In the early 1990s, Intel, the dominant player in the PC industry, led the customization of PCI bus technology.   (At that time, the old wu thanked Intel for releasing the PCI interface, it is with the PCI bus interface bandwidth enhancement, including the later AGP bus interface, to give birth to graphics cards like 3DFX VOODOO Voodoo, the old wu at that time also experienced the first Tomb Raider Lara Croft style, and the cool Need for Speed 2, the classic Thor's Hammer, etc. In retrospect, it is the market demand for 3D games and other multimedia applications, to promote the deve

  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

  A good circuit board, in addition to achieving the principle function of the circuit, but also considers EMI, EMC, ESD (electrostatic discharge), signal integrity and other electrical characteristics, but also to consider the mechanical structure, the heat dissipation of large power consumption chips, on this basis and then consider the aesthetic issues of the board, just like the art of carving, deliberate on every detail of it.   Common PCB layout constraints principles   In the layout of PCB components often have the following considerations.   (1) Does the PCB board shape match the whole machine?   (2) Is the spacing between components reasonable? Are there any horizontal or height conflicts?   (3) whether the PCB needs to be put together? Is the process edge reserved? Are the mounting holes reserved? How to arrange the positioning holes?   (4) How to place the power module and heat dissipation?   (5) Is it convenient to replace the components that need to be replaced frequently?