PCB hardboard lamination design tips
PCB according to the material can be divided into "PCB hard board" and "PCB software" two types, PCB hard board refers to the non-bendable circuit board, the application field is very wide, from large to aviation and military, small to household appliances are inseparable from its figure, PCB hard board minimum layer single panel, the highest layer of the bottom sixty layers of high precision board, this time mainly to explain the PCB hard board design skills and methods!
Design PCB hard board laminate is based on the circuit schematic to achieve the functions required by the circuit designer, PCB hard board design mainly refers to the layout design, the need to consider the layout of external connections, the optimal layout of internal electronic components, the optimal layout of metal connections and through holes, electromagnetic protection, thermal dissipation and various other factors. Excellent layout design can save production costs, achieve good circuit performance and thermal performance, simple layout design can be achieved manually, complex layout design needs to be achieved with the help of computer-aided design (CAD).
In the process of designing PCB rigid board, controllable impedance board and line characteristic impedance is one of the most important and common problems, first understand the definition of transmission line: transmission line consists of two conductors with a certain length, a conductor used to send signals, the other used to receive signals (remember that "loop" instead of "ground" concept, in a multilayer board, each line is a component of the transmission line, the adjacent reference plane can be used as a second line or loop, a line to become a "good performance" transmission line is the key to make its characteristic impedance in the entire line The key to a line becoming a "good performance" transmission line is to keep its characteristic impedance constant throughout the line.
The key to a circuit board becoming a "controlled impedance board" is to make all lines meet a specified value of characteristic impedance, usually between 25 ohms and 70 ohms, and in a multilayer board, the key to a good transmission line is to keep its characteristic impedance constant throughout the line. The easiest way to understand characteristic impedance is to look at what the signal encounters in transmission.
When moving along a transmission line with the same cross-section, which is similar to the microwave transmission shown in Figure 1, assume that a 1 volt voltage step wave is added to this transmission line, such as a 1 volt battery connected to the front of the transmission line (which is located between the transmitting line and the loop), once connected, this voltage wave signal travels along the line at the speed of light, which is typically about 6 inches per nanosecond, and this signal is indeed The voltage difference between the transmitting line and the loop, which can be measured from any point of the transmitting line and the adjacent point of the loop, is a schematic representation of the transmission of this voltage signal.