Step 1 — Choose the right EDA tool
The EDA tools I know that many people use are Altium Designer, Mentor PADS, and Cadence (OrCAD and Allegro). I have also used EAGLE, Protel, and Lichuang EDA. For beginners, I recommend Altium Designer. For those who may become professionals, I recommend Cadence.
A big part of learning PCB design is learning the EDA software. Once you know the software, the learning focus shifts to circuit design and manufacturing processes. Later you may learn protocols, firmware, high-speed signals, or EMC. Then the EDA tool is just a tool, not the main goal.
Step 2 — Finalize the circuit schematic
For example, a flashlight circuit schematic can look simple: two coin-cell holders, one switch, one current-limiting resistor, and one LED. This forms a very simple schematic.
For a more complex function, like a demo board for the SPI Ethernet chip KSZ8851SNL, the schematic may need dozens or hundreds of parts and hundreds of nets. How to draw such a schematic is a big topic. This article only gives an overview of the PCB design flow.
Step 3 — Draw footprints (component packages)
Before putting parts into the schematic, you draw each part’s footprint. After drawing footprints, you place the parts into the schematic one by one. The reason we make footprints first is that when the same part is used many times, we do not redraw it each time. We just reuse the saved footprint. This saves a lot of repeated work. If all footprints were shared, designers would skip this step.
In the flashlight example we used four types of parts. Each part has a symbol in the schematic. For each symbol we add pins and names. This finishes a part’s schematic symbol and links to its footprint. For common parts like resistors, capacitors, or inductors, most EDA tools provide example symbols and footprints. You can take them from the vendor library and save them in your own library.
For rare parts like special ICs or connectors, you often must draw the footprint by hand using the chip’s datasheet. For example, I worked with Yaskawa’s Mechatrolink protocol chip. The chip only comes from Yaskawa and they only provide a datasheet, not footprints for every EDA tool. I had to place its 100 pins one by one and assign names and numbers.
For large chips, like a ZYNQ XC7Z010-1CLG400I BGA with 400 pins, the job is big. You would need to place 400 pins, add numbers and names. For big vendor chips, manufacturers usually provide downloadable pinout files. For example, Xilinx provides Zynq-7000 pinout files you can import to create schematic symbols and footprints without typing 400 pins by hand:
https://www.xilinx.com/support/package-pinout-files/zynq7000-pkgs.html
For many common chips you can also find footprints online. See my answer about how to search and download chip schematics and PCB footprints.
Step 4 — Create the project, pages, and place parts
After making or importing footprints and symbols, create the project and pages. Place all parts in the PCB project.
Step 5 — Wire the schematic (connect parts)
Wire each pin according to the netlist. This builds the logical connections between parts.
Step 6 — Export / import netlist
The schematic lists every pin and their connections. After the schematic is done, start the PCB layout. For PADS and Cadence, the schematic and PCB tools may be separate. You must export the netlist from the schematic tool and import it into the PCB tool. Altium integrates schematic and PCB, so you can transfer the netlist with one click. Netlist formats are commonly shared, so many tools can export and import between each other. OrCAD and Allegro were once separate tools and later merged under Cadence.
Step 7 — Draw PCB footprints
Like schematic symbols, each part needs a PCB footprint. A PCB footprint is the set of pads, silkscreen, and the space the part occupies on the board. From the chip picture and its mechanical drawing you know how to draw the footprint. Pads are usually slightly larger than the pins. Soldermask openings are larger than the pads. The stencil layer matches the pad sizes. For through-hole parts you may also need a keep-out or negative layer for inner layers.
Silkscreen usually shows the part outline and pin-1 mark. For common footprints like SO14, you can copy from an existing library.
If a part is uncommon, use the datasheet to draw the footprint.
Step 8 — Set basic PCB parameters
After netlist import, set board basics: board thickness, layer count, and layer stack. These three are basic, but only layer count is typically shown in output files. Layer stack and board thickness are usually communicated in text to the fabricator. Stackup design matters: which layers carry signals, which are planes, and which combine plane and traces. For a 4-layer board, layers 2 and 3 are often GND and VCC, with top and bottom for routing. For a 6-layer board, you might put GND on 2 and 5 and VCC on 3 or 4. For 8+ layers the choices are flexible.
Step 9 — Draw board outline
Define the board shape and keep-out areas.
Step 10 — Place parts on the PCB
Place parts once footprints are ready. If one footprint is uncertain because you do not have the part yet, place other parts first and come back later.
Step 11 — Set vias, trace width, and spacing defaults
Set default via sizes, trace width, and spacing. These defaults apply during routing. For special nets or power nets, adjust temporarily.
Step 12 — Set advanced rules
If high-speed signals exist, set rules for routing constraints. Advanced rules include differential pair width/spacing, length match limits, necking of pads, and minimum clearances. For example, DDR3 signals require matched lengths: address, clock, and command lines need equal length; data lines and DQS need their own matching. Bad length control can break DDR timing and force lower speed. See these DDR resources for more detail:
- DDR working principle and DQS handling: www.elecfans.com/d/682335.html
- Differential clock, DQS & DQM: www.cnblogs.com/edadoc/p/6387049.html
Some rules may need routing first, then rule changes and rework to meet rules.
Step 13 — Route and draw polygon pours (shapes)
Routing connects schematic nets with copper traces. Most time in PCB design is spent routing. Auto-router tools exist, but for complex boards their results often need heavy cleanup. Some experts can set rules to use auto-routing well. For high-current nets you may use wide traces or copper pours. Use plane zones connected to pads as block networks.
Routing needs care: trace width, spacing, angles, and directions. I will cover routing tips later.
Step 14 — Adjust silkscreen
Adjust silkscreen size, position, and orientation so part numbers are clear for assembly and test. Manufacturers often print their logo or date code. Designers may leave their own notes.
Step 15 — Export drill files and Gerbers (plot files)
After placement, routing, and silkscreen, you can export manufacturing files. For Altium, some Chinese vendors accept project files directly. For PADS and Cadence you must export drill files and Gerbers. If non-round holes exist, also export milling files for cutters.
Step 16 — Provide fabrication parameters and process notes
Design files do not capture every parameter. You must send text instructions for parameters and requirements the files do not express. Check online board houses for the options to specify. I know some board houses: JLCPCB, HQPCB, JietaiPCB, Xunjiexing, Xingsen, Lichuang, etc. Below are screenshots of JLCPCB’s parameters — many parameters may not be visible here but are needed for complex boards. Online prototyping usually covers simpler needs.
Step 17 — Impedance and stackup adjustments
For high-speed signals, specify target characteristic impedance. When sending to the fab, design your stackup and calculate the line widths and spacing for the target impedance. Use your calculated values when routing. After routing, give the fab your stackup and impedance targets. The fab will check with their materials and processes and tell you if adjustments are needed and what the expected impedance error is. Then you can confirm if the target is feasible. If you do not calculate impedance first and just pick stackup and widths randomly, the fab may not be able to meet both impedance and crosstalk requirements.
Step 18 — PCBA (assembly and soldering)
After you finish the PCB files and the fab makes the boards, the next step is PCBA. For mass production, SMT lines are used. For small runs or prototypes, many parts (except BGA, large ground pads, or very small 0201 parts) can be hand-soldered. For small runs under 10 boards, manual soldering may be cheaper and faster than line assembly.
For assembly you must export and send:
- BOM (Bill of Materials),
- Pick-and-place file (part coordinates and orientation),
- Paste mask Gerber (from the pastemask layer).
Label all parts and send parts lists and references. Then wait for PCBA to finish.
Using PCB EDA software, you can design circuits and generate photoplot files on a computer fairly easily. But because PCBs are structurally complex, the real steps are still quite detailed. This article does not tell you which circuit does what. It only shows the PCB design process. It covers: footprint drawing, schematic drawing, PCB layout, and Gerber export. It gives the rough flow and some details. The aim is to help you understand the PCB design steps and match each design step with the actual manufacturing step.
Step 1 — Choose the right EDA tool
The EDA tools I know that many people use are Altium Designer, Mentor PADS, and Cadence (OrCAD and Allegro). I have also used EAGLE, Protel, and Lichuang EDA. For beginners, I recommend Altium Designer. For those who may become professionals, I recommend Cadence.
A big part of learning PCB design is learning the EDA software. Once you know the software, the learning focus shifts to circuit design and manufacturing processes. Later you may learn protocols, firmware, high-speed signals, or EMC. Then the EDA tool is just a tool, not the main goal.
Step 2 — Finalize the circuit schematic
For example, a flashlight circuit schematic can look simple: two coin-cell holders, one switch, one current-limiting resistor, and one LED. This forms a very simple schematic.
For a more complex function, like a demo board for the SPI Ethernet chip KSZ8851SNL, the schematic may need dozens or hundreds of parts and hundreds of nets. How to draw such a schematic is a big topic. This article only gives an overview of the PCB design flow.
Step 3 — Draw footprints (component packages)
Before putting parts into the schematic, you draw each part’s footprint. After drawing footprints, you place the parts into the schematic one by one. The reason we make footprints first is that when the same part is used many times, we do not redraw it each time. We just reuse the saved footprint. This saves a lot of repeated work. If all footprints were shared, designers would skip this step.
In the flashlight example we used four types of parts. Each part has a symbol in the schematic. For each symbol we add pins and names. This finishes a part’s schematic symbol and links to its footprint. For common parts like resistors, capacitors, or inductors, most EDA tools provide example symbols and footprints. You can take them from the vendor library and save them in your own library.
For rare parts like special ICs or connectors, you often must draw the footprint by hand using the chip’s datasheet. For example, I worked with Yaskawa’s Mechatrolink protocol chip. The chip only comes from Yaskawa and they only provide a datasheet, not footprints for every EDA tool. I had to place its 100 pins one by one and assign names and numbers.
For large chips, like a ZYNQ XC7Z010-1CLG400I BGA with 400 pins, the job is big. You would need to place 400 pins, add numbers and names. For big vendor chips, manufacturers usually provide downloadable pinout files. For example, Xilinx provides Zynq-7000 pinout files you can import to create schematic symbols and footprints without typing 400 pins by hand:
https://www.xilinx.com/support/package-pinout-files/zynq7000-pkgs.html
For many common chips you can also find footprints online. See my answer about how to search and download chip schematics and PCB footprints.
Step 4 — Create the project, pages, and place parts
After making or importing footprints and symbols, create the project and pages. Place all parts in the PCB project.
Step 5 — Wire the schematic (connect parts)
Wire each pin according to the netlist. This builds the logical connections between parts.
Step 6 — Export / import netlist
The schematic lists every pin and their connections. After the schematic is done, start the PCB layout. For PADS and Cadence, the schematic and PCB tools may be separate. You must export the netlist from the schematic tool and import it into the PCB tool. Altium integrates schematic and PCB, so you can transfer the netlist with one click. Netlist formats are commonly shared, so many tools can export and import between each other. OrCAD and Allegro were once separate tools and later merged under Cadence.
Step 7 — Draw PCB footprints
Like schematic symbols, each part needs a PCB footprint. A PCB footprint is the set of pads, silkscreen, and the space the part occupies on the board. From the chip picture and its mechanical drawing you know how to draw the footprint. Pads are usually slightly larger than the pins. Soldermask openings are larger than the pads. The stencil layer matches the pad sizes. For through-hole parts you may also need a keep-out or negative layer for inner layers.
Silkscreen usually shows the part outline and pin-1 mark. For common footprints like SO14, you can copy from an existing library.
If a part is uncommon, use the datasheet to draw the footprint.
Step 8 — Set basic PCB parameters
After netlist import, set board basics: board thickness, layer count, and layer stack. These three are basic, but only layer count is typically shown in output files. Layer stack and board thickness are usually communicated in text to the fabricator. Stackup design matters: which layers carry signals, which are planes, and which combine plane and traces. For a 4-layer board, layers 2 and 3 are often GND and VCC, with top and bottom for routing. For a 6-layer board, you might put GND on 2 and 5 and VCC on 3 or 4. For 8+ layers the choices are flexible.
Step 9 — Draw board outline
Define the board shape and keep-out areas.
Step 10 — Place parts on the PCB
Place parts once footprints are ready. If one footprint is uncertain because you do not have the part yet, place other parts first and come back later.
Step 11 — Set vias, trace width, and spacing defaults
Set default via sizes, trace width, and spacing. These defaults apply during routing. For special nets or power nets, adjust temporarily.
Step 12 — Set advanced rules
If high-speed signals exist, set rules for routing constraints. Advanced rules include differential pair width/spacing, length match limits, necking of pads, and minimum clearances. For example, DDR3 signals require matched lengths: address, clock, and command lines need equal length; data lines and DQS need their own matching. Bad length control can break DDR timing and force lower speed. See these DDR resources for more detail:
- DDR working principle and DQS handling: www.elecfans.com/d/682335.html
- Differential clock, DQS & DQM: www.cnblogs.com/edadoc/p/6387049.html
Some rules may need routing first, then rule changes and rework to meet rules.
Step 13 — Route and draw polygon pours (shapes)
Routing connects schematic nets with copper traces. Most time in PCB design is spent routing. Auto-router tools exist, but for complex boards their results often need heavy cleanup. Some experts can set rules to use auto-routing well. For high-current nets you may use wide traces or copper pours. Use plane zones connected to pads as block networks.
Routing needs care: trace width, spacing, angles, and directions. I will cover routing tips later.
Step 14 — Adjust silkscreen
Adjust silkscreen size, position, and orientation so part numbers are clear for assembly and test. Manufacturers often print their logo or date code. Designers may leave their own notes.
Step 15 — Export drill files and Gerbers (plot files)
After placement, routing, and silkscreen, you can export manufacturing files. For Altium, some Chinese vendors accept project files directly. For PADS and Cadence you must export drill files and Gerbers. If non-round holes exist, also export milling files for cutters.
Step 16 — Provide fabrication parameters and process notes
Design files do not capture every parameter. You must send text instructions for parameters and requirements that cannot be expressed in the design files. For the options that need to be specified, you can check the online ordering pages of Philifast (https://flj-pcb.com/).
Below are screenshots showing example parameters. For complex boards, additional parameters may be required beyond what is shown. Online PCB prototyping usually covers simpler requirements.
Step 17 — Impedance and stackup adjustments
For high-speed signals, specify target characteristic impedance. When sending to the fab, design your stackup and calculate the line widths and spacing for the target impedance. Use your calculated values when routing. After routing, give the fab your stackup and impedance targets. The fab will check with their materials and processes and tell you if adjustments are needed and what the expected impedance error is. Then you can confirm if the target is feasible. If you do not calculate impedance first and just pick stackup and widths randomly, the fab may not be able to meet both impedance and crosstalk requirements.
Step 18 — PCBA (assembly and soldering)
After you finish the PCB files and the fab makes the boards, the next step is PCBA. For mass production, SMT lines are used. For small runs or prototypes, many parts (except BGA, large ground pads, or very small 0201 parts) can be hand-soldered. For small runs under 10 boards, manual soldering may be cheaper and faster than line assembly.
For assembly you must export and send:
- BOM (Bill of Materials),
- Pick-and-place file (part coordinates and orientation),
- Paste mask Gerber (from the pastemask layer).
Label all parts and send parts lists and references. Then wait for PCBA to finish.
