PCB News - The guiding ideology and basic wiring requirements of PCB layout

The guiding ideology and basic wiring requirements of PCB layout

When PCB layout, you can refer to these materials to introduce PCB layout and some common rules when drawing PCB, and draw a high-quality PCB. Of course, you can freely adapt it according to actual needs. This is a complete PCB Layout design rule. The layout of the components, the arrangement of the components, the wiring of the wires, the line width and spacing, as well as the pads, have been analyzed in detail. The following are the details:
1. Layout of components
The layout of the components of the PCB design rules includes: component layout requirements, component layout principles, component layout order, and layout methods of common components

2. Arrangement of components
The arrangement of the components on the PCB can be one of three arrangements: irregular, regular, and grid, or multiple at the same time.

3. Spacing and installation dimensions of components
It is about the spacing between the elements and the size of the installation in the PCB design, when the components are arranged

Four, printed wire wiring
Wiring refers to the placement of the direction and shape of the printed wires. It is the most critical step in PCB design, and it is the step with the largest workload.

5. Width and spacing of printed wires
The width and spacing of the printed wires, the minimum width of the general wires is 0.5-0.8mm, and the spacing is not less than 1mm

Six, the aperture and shape of the pad
Introduce the basic knowledge of PCB design, including the shape of the pad and the solder-like aperture

►Detailed parameters and basic rules
1. CLK (including DDR-CLK) basic wiring requirements:
1. The clk part cannot cross other lines, and there are no more than two Vias.
2. Do not cut across, and do not thread between the two pads of the part.
3. Do not cross the line on the front of the Crystal, and try not to cross the line on the back..
4. Differential Pair is routed in parallel with the minimum spacing. And on the same layer
5 The distance between clk and high-speed signal lines (1394, usb, etc.) should be greater than 50mil.
2. VGA: Basic wiring requirements:
1. RED, GREEN, and BLUE must be wound together, depending on the situation, including GND. R.G.B should not be cut across.
2 HSYNC and VSYNC must be wound together, including GND as appropriate.
3. LAN: basic wiring requirements
1. The same set of wires must be wound together.
2 Net: RX, TX: Differential pair must be wired
4.1394: Basic wiring requirements:
1. Differential pair winding, same layer, parallel, do not cut across.
2. The same set of wires must be wound together.
3 The distance between the high-speed signal line and the high-speed signal line is not less than 50mil
5. USB: Basic wiring requirements:
1 Differential pair winding, same layer, parallel, do not cut across.
2 The same group of wires must be wound together
6. CPU-NB (AGTL): Basic wiring requirements:
1. Wires on the same layer in the same group or on different layers in the same group, and the wires must be wound together in the same group
2. When winding, the same NET spacing is not less than four times the wire width
3. NET length should be added to the package length of CPU & NB.
4. STB N/P(+/-) Differential Pair winding
5 VIA type is VIA26
7. CPU-SB: Basic wiring requirements:
1. The same set of wires must be wound together.
2 pull up resistor, must be close to the CPU
8. NB-DDR: Basic wiring requirements:
1. Damping resistance and terminal resistance (exclusion) NET: MD & MA & DQS & DQM cannot be shared.
2.The wiring in the same group and the same layer is wound with four times the spacing.
9. NB-AGP: Basic wiring requirements:
1. Wires on the same layer in the same group or on different layers in the same group, and the windings must be wound together in the same group
2. When winding, the same NET spacing is not less than four times the wire width
3.STB +/- Differential Pair winding.
4 Try to follow guide lauout in the constraint area.
10. NB-SB: Basic wiring requirements:
1 Walk together, don't cross the cutting line.
2. When winding, the same NET spacing is not less than four times the wire width
11. IDE: Basic wiring requirements:
1.The same group and the same layer, the winding must be wound together in the same group.
2. When winding, the same NET spacing is not less than four times the wire width
12. PCI: Basic wiring requirements:
1 There are at most three lines between PAD and PAD
2 Resistors and capacitors should be placed as neatly as possible.
13. CNR: Basic wiring requirements:
1.Walk together.
14. POWER: Basic wiring requirements:
1 Generally use 30: 5 wiring, the line width is 40MIL or more, the time interval is not less than 10MIL, VIA is VIA40, (or 2 VIA24)
15. OTHER: Basic wiring requirements:
1. All IO lines cannot cross layers.
2. COM1, COM2, PRINT(LPT), GAME walk together in the same group.
3 COM1 and COM2 go through the capacitor first, and then pull the wire out.
16.Add test points:
1. The test aims at 100% and must be added to at least 98%.
2. The pin to pin spacing is preferably 75mil and the minimum is not less than 50mil.
3. The minimum pad of the test point is 27mil, try to use 35mil.
4. The distance between the single-sided test point and the outer frame of the part on the same layer is greater than 50MIL.
5. The CPU socket includes a ZERO lever, and no Top Side Test Point can be placed inside
6. The clk front-end does not need to add test points. The back-end can be replaced with test_via. (Require customer approval)
7. Do not affect the winding of Differential Pairs.
17. Modify DRC:
1.Complete the DRC check, the inner check, and the check of the PIN not connected.
2 All nets must not be short-circuited. There must be no extra line segments.
18. Cladding copper foil.:
For parts that need to be coated with copper foil, the net should be coated with copper foil correctly.
19. Place the text side:
1. The text surface is marked from left to right and top to bottom, and the direction is the same.
2. Part marking, the closer to the part, the better
3. Place the pins of the parts correctly and mark the polarity.
4. Whether the part symbol is marked.
CN, JP: pin mark (note the direction). Part polarity: ※Capacitor: + ※Crystal: G, D, S ※Diode: A, K5 Delete redundant line segments and labels.

The above is an introduction to the guiding ideology of PCB layout and basic wiring requirements. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology.