At present, high-speed PCB design is widely used in communication, computer, graphics and image processing and other fields. In these fields, engineers use different high-speed PCB design strategies, which involve over-design strategies of simulation and analysis.
In the field of telecommunications, the design is very complicated, and the transmission speed in data, voice and image transmission applications is far higher than 500Mbps. In the field of communications, people are seeking to launch higher-performance products faster, but the cost is not the first. They will use more boards, enough power layers and ground layers, and will use discrete components on any signal line that may have high-speed problems to achieve matching. They have SI (Signal Integrity) and EMC (Electromagnetic Compatibility) experts to simulate and analyze the board before wiring, and each design engineer follows the strict design regulations within the enterprise. Therefore, design engineers in the field of communication usually adopt this over-designed high-speed PCB design strategy.
Motherboard design in the field of home computers is the other extreme, with cost and effectiveness above all else. Designers always use the fastest, best and highest performance CPU chips, memory technology and graphics processing modules to form increasingly complex computers. However, home computer motherboards are usually 4-layer boards, and some high-speed PCB design techniques are difficult to apply to this field. Therefore, engineers in the home computer field usually use over-research methods to design high-speed PCB boards, and they should fully study the design details to solve those real high-speed circuit problems.
And the usual high-speed PCB design situation may be different. Manufacturers of key components in high-speed PCB (CPU, DSP, FPGA, industry-specific chips, etc.) will provide design data about the chips, which are usually given by referring to the design and design guide. However, there are two problems: firstly, there is a process for device manufacturers to understand and apply signal integrity, and system design engineers always want to use the latest high-performance chips at the first time, so the design guidelines given by device manufacturers may not be mature. Therefore, some device manufacturers will give several versions of design guidelines in different periods. Secondly, the design constraints given by device manufacturers are usually very harsh, and it may be very difficult for design engineers to meet all the design rules. However, in the absence of simulation analysis tools and the background of these constraint rules, meeting all the constraint conditions is the only high-speed PCB design method, and such a design strategy is usually called over-constraint.
It is mentioned that a backplane design uses surface mounted resistors to achieve terminal matching. More than 200 such matching resistors are used on the circuit board. Imagine if you want to design 10 prototype templates to ensure the best terminal matching effect by changing these 200 resistors, which will be a huge workload. However, in this design, no change of resistance value is due to the analysis results of SI software, which is really surprising.
Therefore, it is necessary to add the simulation and analysis of high-speed PCB design to the original design process, and make it an indispensable part of the complete product design and development.