How to design a microcontroller PCB in Altium?

 Here’s a practical, Altium-first workflow to design a microcontroller PCB (from “empty project” to “ready for fabrication”), with the checks that prevent 90% of first-rev pain.



1) Start with requirements (so the schematic is correct)

  • MCU part number + package (QFN/LQFP/BGA)

  • Power rails (1.8/3.3/5V), max current, ADC reference needs

  • Clocking (internal RC ok? need crystal?)

  • Programming/debug (SWD/JTAG/USB-UART/boot pins)

  • Interfaces (I²C/SPI/UART/CAN/USB), connector types

  • Environment (ESD, EMI, automotive? temperature?)

2) In Altium: create a clean project structure

  1. File → New → Project → PCB Project

  2. Add:

    • Schematic (.SchDoc)

    • PCB (.PcbDoc)

  3. Set units, grids, and templates early (keeps footprint placement sane).

3) Build or verify your libraries (critical)

You need:

  • Schematic symbol

  • Footprint

  • 3D model (optional but helpful)

  • Pin mapping correct (power pins, SWD, BOOT, NRST)

Best practice:

  • Prefer manufacturer/Altium verified libs when possible.

  • If you make your own footprint: verify pad sizes, pitch, courtyard, paste mask, and pin-1 marker against the datasheet.

4) Schematic design: microcontroller “minimum system” blocks

A) Power (must be done right)

  • Decoupling caps: typically 0.1 µF per VDD pin + 1–10 µF bulk near MCU.

  • Analog supply (VDDA/VREF): filter with ferrite bead or small resistor + cap (per datasheet).

  • Add power LED and test points (VIN, 3V3, GND, NRST, SWDIO, SWCLK).

B) Reset + boot straps

  • NRST: pull-up (commonly 10k) + optional RC (if recommended).

  • BOOT0/BOOT1 pins: pull-down/up per your boot strategy, add header/jumper if you’ll need recovery.

C) Clocking

  • If using a crystal: place load caps exactly as datasheet recommends; keep routing short/symmetric.

  • If internal oscillator is enough, skip crystal for cost and simplicity.

D) Programming / Debug

  • Add SWD header (2x5 1.27mm Cortex Debug or 1x4/1x6 custom):

    • SWDIO, SWCLK, NRST, GND, 3V3, (optional SWO)

  • If using USB: add ESD protection + correct impedance routing (see below).

E) I/O protection and connectors

  • Put ESD diodes at external connectors (USB, buttons, long cables).

  • Series resistors (22–47Ω) on fast edges (SPI SCK, USB FS signals, etc.) can help ringing/EMI.

5) Convert to PCB and define rules

  1. Design → Update PCB Document from schematic.

  2. Set:

    • Board shape

    • Layer stack (2-layer vs 4-layer)

    • Design Rules: trace width/clearance, via sizes, differential pairs (USB), solder mask rules.

If you can afford it: 4-layer makes MCU boards much easier (solid GND plane, cleaner EMI).

6) Placement (most important physical step)

  • Place MCU first.

  • Place decoupling capacitors:

    • as close as physically possible to each power pin

    • short trace to VDD pin, short via to GND plane

  • Keep crystal + caps very close and away from noisy switching nodes (buck SW node).

  • Put debug header at edge of board for easy access.

  • Put connectors where cables make mechanical sense.

7) Routing guidelines (quick but high-impact)

  • Ground: use an unbroken ground plane if possible. Don’t split GND unless you really know why.

  • Power: short/wide traces for VDD rails; avoid daisy-chaining sensitive analog supplies.

  • Clock/crystal: keep short, no vias if possible, guard with ground.

  • USB (if used):

    • route D+/D− as a differential pair

    • keep them length-matched and away from noisy power switching

    • follow your board stack’s impedance if you can; otherwise keep short and consistent

  • Add stitching vias around edges / near connectors (helps EMI).

8) ERC/DRC + sanity checks (do not skip)

  • Schematic ERC: unconnected power pins, wrong net labels, missing pull-ups.

  • PCB DRC: clearance, solder mask slivers, unrouted nets.

  • Check:

    • pin 1 orientation on footprint

    • decoupling caps actually connected to correct VDD pins

    • SWD header pinout matches your programmer

    • BOOT and reset resistors match your intended boot mode

9) Output manufacturing files

  • Gerbers / ODB++, NC Drill

  • BOM

  • Pick-and-place/CPL

  • Assembly drawings (optional but helpful)

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