Multilayer PCB Design for Electronic Products
The signal line is placed on the electrical (ground) layer
In multilayer PCB design laying tracks, as in the signal layer is no cloth finish line there aren't many left, add layer will cause production waste, will also increase a certain workload and cost accordingly, in order to solve this contradiction, can consider laying lines in the electrical(ground) layer. In priority should consider to use power supply layer, followed in ground layer. Because it is best to maintain the integrity of ground layer.
Processing of connecting pins in large-area conductors
For large area of grounding (electricity) layer, common used components pins connect with it, the processing of the connection pins needs to be considered comprehensively, in terms of electrical performance, the welding pads of component pins and copper surface full connected is good, but for the component welding assembly there are some bad hidden dangers such as: (1) welding needs a high power heater,(2) easy to cause virtual solder joint.Therefore, considering both the electrical properties and process needs, it is necessary to make cross-shaped welding pad, called heat shield, commonly known as thermal, so that the possibility of producing virtual solder joints can be greatly reduced due to excessive heat dissipation of section.The electrical (ground) pin of the multilayer pcb is treated the same.
The role of network system in PCB design laying lines
In many CAD systems, laying lines is determined on the basis of network system. The grid too close, although path increased, but the step is too small, figure the amount of data is too large, it will certainly has higher request to the storage space of the equipment, as well as computer object class has greatly influence the speed of electronic products. And some of the path is invalid, for example, it is occupied by welding pad of component pin, or by the mounting hole and the fixing hole, etc. The grid is too thin and the path is too few, which has a great impact on the distribution rate. Therefore, it is necessary to have a grid system with reasonable density to support the lining.
The distance between the legs of standard components is 0.1 inches (2.54mm), so the basis of grid system is generally 0.1 inches (2.54mm) or less than the integer multiples of 0.1 inches, such as 0.05inches, 0.025inches, 0.02 inches and so on.