How to avoid high-speed transmission line effects in PCB Assembly?-1
1, suppress electromagnetic interference method
A good solution to PCB Assembly signal integrity board will improve the electromagnetic compatibility (EMC). Which is very important to ensure that PCB boards have a good grounding. The complex was designed with a signal level with a ground layer is very effective. In addition, the outermost layer of the PCB Assembly is to reduce the minimum density of the signal a good way of electromagnetic radiation, this method can be used "surface layer" "Build-up" system designed to do China PCB Assembly to achieve. Surface layer in the general process by adding a thin insulating layer PCB and for the pores through a combination of these layers to achieve, resistors and capacitors can be buried in the subsurface, the alignment unit area will nearly double the density, thus reduce PCB size. Reduce the PCB Assembly manufacturer area of the topology of the traces have a huge impact, which means reducing the current loop, reducing the length of the branch traces, and electromagnetic radiation similar to the current loop is proportional to the area; also features small size means that high-density lead pin package devices can be used, which in turn makes the connection length of the decline, thus reducing the current loop to improve the electromagnetic compatibility characteristics.
2, and strictly control the alignment of the key length of cable
If the design of high-speed jump edge, it must take into account the China PCB assembly, there is the problem of transmission line effects. Now widely used in very high speed integrated circuit chip clock frequency is the existence of such problems. Solve this problem there are some basic principles: If using CMOS or TTL circuits design, the operating frequency less than 10MHz, wiring length should not exceed 7 inches. 50MHz operating frequency in the wiring length should be not more than 1.5 inches. If the working frequency of 75MHz or more wiring length should be 1 inch. GaAs chip, the wiring for the maximum length of 0.3 inches. If you exceed this standard, there is transmission line problems.