Nowadays, the factors considered in pcb design are more and more complicated, such as clock, crosstalk, impedance, inspection, manufacturing and processing technology, which often urges the design staff to repeatedly carry out a lot of reasonable layout, certification, maintenance and other work. On-line editor of main parameter bundle can compile this main parameter into formula calculation, and help PCB designers solve this main parameter which sometimes even will continue to be opposite to each other as soon as possible in the process of design and processing.
In recent years, the regulations on the rational layout and wiring of pcb have become more and more complicated, and the total number of triodes in integrated circuit chips has to continue to increase at the rate predicted by Moore’s Law, which further promotes the rapid speed of components and the reduction of the gain value of each single pulse edge. In addition, the number of pins is also increasing-often 500 ~ 2,000 pins. All these problems are related to the relative density, clock and crosstalk when designing pcb.
Two years ago, the vast majority of pcbs had only a few “critical” connection points (net), which generally meant that they suffered from some constraints in terms of impedance, length and gap, etc. Generally, PCB designers first made manual wiring for this kind of wiring, and then used mobile phone software to make large-scale automatic wiring for all power circuits. Nowadays, there are often 5,000 or even a large number of connection points on pcb, and more than 50% of them belong to critical connection points. Because of the pressure of time to market, it is impossible to choose manual wiring at this time. In addition, not only the total number of critical connection points has increased, but also the linear combination of each connection point has been improved.
This linear combination is mainly caused by the increasing complexity of the correlation of main parameters and their design regulations. For example, the distance between two wires will be a culvert related to the working voltage of the connection point and the raw materials of pcb. The reduction of the gain value of large digital IC will do harm to the design of both high clock rate and low clock rate, because the single pulse will make the creation and maintenance time shorter. In addition, the interconnection timing, as a key part of the high-speed power supply circuit design, is also critical to the low-speed design.
If the circuit board is designed to be bigger, some of the above problems will be easier to deal with, but today’s development trend is just the opposite. Because of the requirements of interconnection time and high-density packaging, the circuit board has been continuously reduced, and then the high-density power supply circuit design appears. In addition, the practical design standard must be followed. By reducing the gain value and adding this practical design standard, the problem of crosstalk noise becomes more and more prominent, while the ball grid array and other high-density packages themselves will aggravate the problems of crosstalk, power switch noise and ground wire bounce.
Limitation of the existence of fixed tube bundle
The traditional way to deal with this problem is to convert the electrical equipment and processing technology regulations into fixed main parameters of the tube bundle by working experience, default values, numerical tables or calculation methods. For example, PCB technical engineers may first define a rated impedance when designing the power supply circuit, then “estimate” a graphic limit of the rated impedance that can achieve the required impedance according to the final processing technology, or use the calculation report or arithmetic program flow to detect the influence, and then calculate the linear combination of long and short.
In this way, it is generally necessary to design a complete set of work experience data information as the basic and specific guiding standards for pcb designers, so that this data information can be used when designing with the full-automatic and rational layout and wiring tools. The difficulty of this method depends on the fact that the work experience data information is only a general standard. In most cases, they are all appropriate, but in some cases, they fail or cause incorrect results.
People discuss the deviation caused by this kind of method with the above example of definite impedance. The factors related to impedance include the electrolytic medium characteristics of circuit board materials, the aspect ratio of copper foil, the distance between each layer and the ground/power supply layer, and the graphic boundary. Because the first three main parameters are generally decided by the production process, designers generally rely on the graphic boundary to manipulate impedance. Because the distance between each route layer and the ground or power layer is different, it is obviously incorrect to use the same work experience data information for each layer. In addition, the production process or circuit board characteristics selected in the whole process of development and design will change anytime and anywhere, so the problems will continue to be more complicated.
In most cases, this kind of problem will be exposed in the sample making process. Generally, after finding the problem, it will be dealt with according to repairing the pcb circuit board or redesigning the wood board. The cost of doing that is relatively high, and the repair will often continue to produce additional problems and further adjustments must be made. In the end, the damage to revenue caused by the delay in time to market is far higher than the adjustment cost. Basically, all manufacturers of electronic devices have encountered that kind of problem. In the end, it all comes down to the fact that the traditional pcb design mobile phone software can’t keep up with the specific situation of the current regulations on the characteristics of electrical equipment. Here, it is not as simple as the working experience data information of mechanical equipment design.
Solution: Parametric tube bundle
At present, the distributors who design mobile phone software try to deal with this problem by improving the main parameters in the linear combination. The best part of this method depends on the index value of mechanical equipment that can fully describe the characteristics of various internal electrical equipment in detail. If it is added to pcb design, the design mobile phone software can use this information content to operate the full-automatic rational layout and wiring special tools.
When the production process is changed afterwards, there is no need to design again. PCB designers can change the linear combination automatically only by simply upgrading the main parameters of processing characteristics. PCB design staff can then operate DRC (Design Standards Inspection) to find out whether the new technology and new process also violate other PCB design standards, and find out which aspect of the design should be changed to correct all the inaccuracies.
