1. The signal edge rate is getting faster and faster, and the on-chip and off-chip clock rates are getting higher and higher. The current clock frequency is no longer a few megabytes in the past, and clocks with hundreds of megabytes and gigabytes are becoming more and more common on single boards. Due to the rapid development of chip technology, the edge rate of the signal is getting faster and faster. At present, the rising edge of the signal is about 1ns, which will cause system and board level SI and EMC problems become more prominent;
2. The integration scale of the circuit is getting larger and larger, and the number of I/O is increasing, making the interconnection density of the single board continue to increase; as the function becomes more and more powerful, the integration level of the circuit is getting higher and higher. The level of chip processing technology is getting higher and higher. The DIP package in the past has almost disappeared on the current single board, and the small-pitch BGA and QFP have become the mainstream package of chips. This makes the density of PCB design increase accordingly.
3. The time for product development and market launch is constantly decreasing, so we must face the severe challenge of one-time design success; time is cost, and time is money. In the field of electronic products, where the upgrading and replacement is particularly fast, the profit opportunities will be much greater if the product is launched one day earlier.
4. Because PCB is the physical carrier of product realization. In high-speed circuits, the quality of PCB is related to the function and performance of the product. With the same device and connection, different PCB carriers have different results.
Therefore, the design process is slowly changing at present. In the past, the logic function design in the design often accounted for more than 80% of the hardware development and design, but this proportion has been declining. In the current hardware design, the logic function design only accounts for 50%, and the PCB design part also accounts for 50% of the time. Experts predict that in future designs, the logic function overhead of hardware will become smaller and smaller, while the overhead for developing design rules such as high-speed PCB design will reach 80% or even higher.
All these are just illustrates that PCB design will be the focus and difficulty in current and future design.
Generally, our PCB design mainly focuses on the following points:
1. Realization of function
2. Stable performance
3. Simpleness and easiness of processing
4. Beauty of the PCB board
The realization of the function is the first step of our PCB. In the past design, because the signal edge rate and clock frequency are relatively low, as long as the logical connection is correct, the physical connection will not affect the performance of use. But this view is not used in the current design. The correct connection of logic will not enable the correct realization of the function. The quality of the physical connection is also the main condition for the realization of the function.
The guarantee of performance depends on the design of the PCB. Everyone knows this point of view. With the same logic connection, the same device, different PCBs have different performance testing results. Good design not only has high stability, but also can pass various demanding tests. However, it is impossible to achieve such an effect with a non-ideal design. In some low-end products, many manufacturers use the same chipsets, and their logical connections are also similar. The only difference is the level of their respective PCB design levels. The difference of products is mainly reflected in the PCB design.
The simpleness and easiness level of PCB manufacturing processing is also an important indicator of the quality of PCB design. Good PCB design is convenient for processing, maintenance, testing, and manufacturing. The quality of PCB is not only related to the production efficiency of PCB processing manufacturers and SMT manufacturers, but also closely related to our testing and debugging convenience.
Beauty is also an element of PCB design. The overall beauty makes people feel comfortable when they see it. PCB is also a craft. A good PCB will make people stop and appreciate.
PCB design is a comprehensive discipline, the product of the coordination of quality, cost, time and other aspects. There is no best in PCB design, only better. In short, high-speed PCB design is a serious challenge confronted by the field of system design today. Whether it is design methods, design tools, or the composition of the design team, and the design ideas of engineers, they all need to be actively and seriously coped with.