Senior PCB engineer's drawing board experience sharing

As an electronic engineer, many people start from the drawing board. Some people may feel that this work is boring and has no technical content. Some people have extracted some of their own ideas from the details and slowly found their way to the master. road.



"1, the filter capacitor should be as close as possible to the chip power supply, the oscillator is also, put the resistor at the front end of the oscillator
2, change the board size in the Design Board Shape
3, placing components, vias, pads, copper, text, etc. can be used shortcut keys P + L
4. After the painting is finished, it is necessary to stipulate the prohibition of the wiring layer, that is, the KeepOut-Layer layer, P+L wiring.
5, before the copper (place polygon pour) to modify the safety spacing design rules (clearance 16mil or so) Note that the general use of Hatched, and NET network connected to the ground GND, select pour all same net projects, but also remove dead copper (remove dead copper ) Supplement: Multi-layer copper should pay attention to the power layer and the ground layer, because the trace inside the FPGA is only 6mil, so when the copper is covered, the rule->clearance should be set to 6mil and then copper. When other layers are covered with copper, it is best. Rule->clearance get a little bigger than 16mil, then change the rules back, this time Track 8mil, Grid 24mil
6, pay attention to Track 12mil, Grid 24mil when the top and bottom copper
7, the ground wire and power cord are generally very thick 60-80mil, the normal minimum line width is 10mil, FPGA is generally 6mil
8. Use S+L for cable operation, use P+M wiring, “<” ">" to adjust the spacing, put the wire with P+L, especially when specifying a layer such as the forbidden wiring layer.
9, the keyboard plus or minus +, - number for switching between the layers, Page Up zoom, Page Down zoom 10, distance measurement R + M, unit mil and mm mm switch with Q button
11. When placing the device: X is symmetrical, Y is up and down symmetrical, SPACE is 90 degree flip, device view attribute is Tab key 12, when drawing package drawing, J+L is Jump to Location to a certain point 13. Fixed base point drawing package Origin Maker in Display in Preference PCB
14, paste the P+S in the queue when drawing the PCB package
15. When importing the PCB update, UPdate should be in the schematic diagram. The import schematic update should be UPdate in the PCB. If you do not change the schematic pin order, you can use the change sch pins in project->option->option. To do it, it is often used in interactive wiring, but need to pay attention: Sometimes only one device needs to be updated to find the network label and device to be updated. Do not update it. When processing, generally add solder mask (the surface is Green), silk screen (display device identification), board thickness is generally 1.5-2mm
17, draw PCB packaging drawings to be in TOP OverLayers (yellow)
18, between the analog power supply and the general power supply generally add an inductor (about 10mH) to eliminate the impact of the signal, plus two 0.1uf capacitor filter
19. The analog reference input terminal AREF of the MCU should be connected to the electrolytic capacitor filter, and it should be connected to the analog ground. A resistor should be added between the analog ground (AGND) and the general ground (GND), and a capacitor should be added between the positive and negative analog reference inputs. (0.1uf) filtering
20, automatic labeling with Tools--Annotate Schematics
21, when drawing the device schematic, make good use of the device arrangement rules to draw, such as the input pin on the left, the output on the right, the power on the top, the ground on the bottom
22, when drawing the principle library, you can use a part (part) to design a chip with a lot of pins.
23, low level can display a horizontal line on the letter head to indicate
24, first select multiple pads, press S plus component connection, plus Multiple traces, select the device, plus ~ key 25, when laying the PCB, you must first set the rules (very important), set in the rule Via, Clearance, etc.
26.Shift+S See all wiring on a single layer, Ctrl+right mouse+drag=zoom in or out, multi-layer routing is very useful.
27. When there are more repeating devices, use the alignment combination Align to select the components to be arranged, the shortcut key shift+ctrl+H, evenly arranged horizontally, shift+ctrl+V, evenly arranged vertically, shift+ctrl+T, shift +ctrl+B
28, put the component to the bottom: select the device, press L
29, when drawing PCB, when the device or via green is used, use the design->rule to set the rules, you can use the rules to check to see where the problem is.
30, group operation: select all the devices you want to operate, use Shift + left mouse button to double-click one of the devices for property settings
31, need to convert the schematic or PCB to pdf format: File->Smart PDF-> select the path and settings to get the schematic pdf format
32. The logos in all schematics in a project are all connected. If you want to use the master and subgraphs, select Design->Creat Sheet Symbol From Sheet or HDL.
Supplement: 1. Add the signal layer and select top layer and then add with Design->Layer Stack Manager.
2, fanout function: FPGA multi-pin can be Auto Route-> Fanout-> component and then select the device you want to fan out, check according to the situation
3. Decompose the PCB pin sequence and decompile it to the schematic. Use the Project->Project Option->options to remove the Changing Schematic Pins option, then Design->Update Schmetics in xx.ProPCB
4, interactive wiring: is to change the order of the pins need to pay attention to: a, first configure the switchable pins Tools->pin/Part Swapping->configure select the chip you want to exchange, such as FPGA, and then choose to exchange IO pins, can not select the clock and some configuration pins such as nCSO, nCE, ASDO, DATA0, etc., these can not be exchanged, Show Assign IO pin Only, and then they are selected and added to a group such as Type group. b. Pin Swap check this to allow the exchange of pins c, Tools->Pin/Part Swapping->Interactive Pin/Net swaping (shortcut TWI)
5, cloth multi-layer board Note: a, FPGA internal line width 6mil (this depends on the minimum spacing between the pins in the FPGA!), through hole size outer circle 20mil, inner circle 8mil, power class through hole outer circle 50 inner circle 20
b. Isometric line: For the clock synchronization, you need to wait for the long line. Check the PCB, view->Workspace Panels->PCB->PCB, and divide the network to be divided into groups to facilitate the observation of the line length (double-click All Net to add a group of networks) ), Tools->Interactive Lenth Tuning (shortcut TR), after selecting a line in the network, Tab can set up the network, and then find the longest line in the network for equal length wiring. Give enough space

c. Differential line: For the DVI class interface, you need to distribute the differential line. View->Workspace Panels->PCB->PCB and then select the Differential Pairs Editor. Create the difference line you want to cloth. You can also mark it in the schematic diagram first, then use Tools->Interactive Diff Pair Lenth Tuning (shortcut TI), select a line and press Tab to route the longest line you want to wire.

d, press S+N to select the whole network, which is beneficial to delete e, make the device fixed, double-click and select locked supplement 2: 1. What must be said, the final inspection of the board is very important, especially unrouted inspection, before board welding The power and ground check is also, don't make a big mistake. . .

2. Press L directly in the PCB to edit the display and hide of each layer.

3, try to cross the staggered wiring, reduce signal interference