Keyword: pcb copy board, pcb , PCB copy board process, pcb board
In the PCB copy board process if they can remember and practice the following principles some practical small pcb+board' target='_blank'>pcb board, must be much more effective. A printed wire width selection by pcb board: The minimum width of the printing wire and the flow of current through the conductor , the line width is too small , just printed wire resistance, a large line voltage drop will affect the circuit performance ; width is too wide, the wiring density is not high pcb board, board area increases, in addition to increasing costs, is not conducive to miniaturization pcb board. If the current load to 20A / square millimeter calculation, when copper clad thickness is 0.5MM , the ( usually so much ) then 1MM ( approximately 40MIL) linewidth of the current load of 1A, Thus , line width taking 1-2.54MM (40 - 100MIL) applications to meet the general requirements of the ground and the power supply device board , according to the power level , the line width can be increased , and in the low-power digital circuit , in order to improve the wiring density pcb board, the minimum width to take 0.254-1.27MM (10 - 15MIL) can be met. The same circuit board , power cord. Coarse ground than the signal line pcb board. 2 , line spacing: When the 1.5MM ( approximately 60MIL) , pcb board the line between the insulation resistance greater than 20M in Europe , the line between the maximum pressure up to 300V, when the line spacing of 1MM (40MIL) , the line between the maximum voltage of 200V, therefore , in the voltage ( line voltage is less than 200V) on the circuit board , the line spacing to take 1.0-1.5MM (40 - 60MIL) in low-voltage circuits , such as digital circuit system, without regard to the breakdown voltage , pcb board as long as the production process allows , it is small . 3 , the pad : For 1/8W resistor , the pads 28MIL wire diameter is sufficient pcb board, For of 1/2W , the diameter of 32MIL, lead hole is too large , the width of the pad is relatively reduced copper ring , resulting in decreased adhesion pads . Easy to fall off , the lead hole is too small , the component mounted broadcast difficulties . 4 , draw circuit Border: Border line and component pin pad shortest distance is not less than 2MM, pcb board ( general admission 5MM more reasonable ) or cutting difficult. 5 , component layout principles: A general principle : In the PCB design, if there are both digital circuits and analog circuits . And a high-current circuit layout must be separated so that each system to minimize coupling between circuits in the same type , according to the signal flow and function block, partition placed components. B: input signal processing unit pcb board, the output signal driving element should be close to the circuit board edge , the input and output signal lines as short as possible to reduce interference of input and output . C: component placement direction : elements only along the horizontal and vertical direction.
Shall not in plug-ins.pcb board D: element spacing: For medium density , small components , such as small power resistors , capacitors , diodes, and other discrete components and plug mutual spacing , welding craft, wave soldering , the component spacing can be taken 50-100MIL (1. 27 - 2. 54MM) manual can be bigger, such as taking 100MIL, iC chip , component spacing is generally 100 - 150MIL E: When a large potential difference between the elements , element spacing should be large enough to prevent the discharge phenomenon . F: clockwise circuit components as close to the microcontroller chip clock signal pin to reduce the length of the clock circuit connection . And the line below it is best not to go . G: In it into the IC chip decoupling capacitors close to the power ground pin fall pcb board. Otherwise, filtering effect will be worse. In digital circuits , digital circuits in order to ensure reliable operation of the system in each digital IC chips are placed between power and ground IC decoupling capacitors .
Decoupling capacitors generally use ceramic capacitors with a capacity of 0.01 ~ 0.1UF decoupling capacitance is generally chosen by the reciprocal of the system operating frequency F selection . In addition, the entrance to the circuit power supply and ground pcb board connection between the need to add a 10UF capacitor , and a 0.01UF ceramic capacitor pcb board.
