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Electrical Design



Description Link
Art of Electronics, 3rd Edition, Paul Horowitz and Winfield Hill
Microcontrollers Intro (Jay Carlson)
ROHM EE Knowledge Base
Thermal Intuition (Texas Instruments, 2020)
Custom Silicon with Google

Circuit Design

Description Link
Linear Circuit Design Handbook (Analog Devices, 2008)

PCB Design

Description Link
MFG Design Limits (Candor Industries)


Description Link
Comparing Bus Solutions (Texas Instruments, 2017)


Description Link
Canada Electrical Code


Description Link
Wire Gauge Chart (Powerstream)

Key Knowledge

Topic Keywords
basic resistor, capacitor, inductor, impedance
x ground shift, parasitics (leakage, distortion), reliability, whiskering, corrosion (ECM, CAF)
reliability corrosion, ionic contamination, dendritic growth, intermetallics, dielectric breakdown, charge trapping
thermal expansion, cycling, real-time distribution, operating range, circuit-longevity (based on temp average/volatility), flammability
electromagnetics (EMI, EMC)
mechanical form trade-offs (weight, 3D size), part protection, SMT/THT shock-resist, ingress protection, transient voltage suppression, moisture sensitivity, conformal-coat/encapsulation
signal integrity impedance matching/continuity, capacitive coupling, skin effect loss, trace length loss, dielectric loss, dissipation loss
power integrity decoupling capacitor (against inductive delay), inductive bounce/ringing/kickback, snubber
PCB fabrication layers, surface finish, impedance control, vias (landless, blind, buried, tented, filled, plated-over), soldermask-defined pads
PCB assembly reflow conduction paths, flux activation, first-side mass limit of two-sided assembly
MCU workflow IDE, IPE, debugger, production programmer
quality assurance optical inspection, QVL/PPAP, MFG revision errata
extra FIT, cascading-events, silkscreen, connector mechanisms, universal footprints/pinouts, standard interfaces, one-firmware multiple-configurations
debug single-wire-debug (SWD), JTAG
regulatory compliance RoHS, REACH, WEEE, CE (EU), UL Listed/Recognized, FCC, TUV, Flammability (ex. UL94V-0), EMC, RED (EU)

Qualified Vendor List (QVL), Qualified Parts List (QPL)


Main Design Program


Free, open-source, cross-platform, sponsored by CERN

Normal Workflow:

  1. Prepare schematic symbols and layout footprints
  2. Design schematic (abstract circuit design)
  3. Import schematic into layout (each symbol should be mapped to a footprint)
  4. Design layout (physical board design, all layers)

Export Workflow for PCB Fabrication

  1. Export layer files (outline/copper/soldermask/silkscreen, gerber format) and drill file (absolute, mm, excellon format).
  2. Specify, as necessary, the layer stack-up (table) and any impedance control on which traces (table/graphic)
  3. Specify extra info:
Specification Notes
board material
finished copper thickness per layer (ex. 2oz)
finish plating (ex. ENIG)
finished board thickness (ex. 1.6mm)
fabrication class (ex. IPC2)
soldermask color green (RCMD)
silkscreen color white (RCMD)
depanelization (ex. individually routed boards; one-up)
electrical testing yes (RCMD)
board dimensional tolerance (ex. +0mm, -0.2mm) (if important)
tented vias (if any in design)
soldermask-defined pads (if any in design)

Export Workflow for PCB Assembly:



Function Name Notes
Oscilloscope Siglent SDS2104X Plus (2020) 100-350MHz, 8-bit ADC, 2GSa/s, 4-channel
DC Power Supply Siglent SPS5083X (2021) 80V, 45A, 1080W, 1mV/1mA

Design Targets


Scope Specification
measurement standard metric
DC voltages 48V, 24V, 12V, 5V, 3.3V


Scope Specification
nominal size 1608 metric or bigger (smaller can be acceptable)
composition RoHS (RoHS3, EU Directive 2015/863, without exemptions), halogen-free (IEC 61249-2-21), red-phosphorous-free, antimony-free, REACH (EU Regulation 1907/2006, without candidate substances)
operating temperature -40C to 125C
reliability qualification automotive (AEC-Q Grade 1)
quality assurance features wettable flanks (for optical inspection; MOI/AOI)
moisture sensitivity (for assembly) MSL 1 (low priority target)
lifetime 10+ years
tin finish (if applicable) matte-tin (reduced whiskering)


  • glow-wire connectors (thermal ignition safety)
  • soft-termination MLCC (anti-crack)
  • aluminum-polymer bulk capacitors (long-life)


Scope Specification
impedance control for high-frequency, precision-analog
material performance high thermal stability (ex. low-CTE, cycling tolerance, high electromechanical stability, high thermal conductivity (ex. 0.7W/mK is a good non-ceramic benchmark), good impedance-properties (ex. low relative-permittivity, low dissipation-factor)
surface finish ENIG
soldermask color green (optical ergonomics)
silkscreen color white
fabrication class IPC2, IPC3
flame resistance UL94-V0
mounting M3 screws
corners rounded (5mm+ radius)
Footprints pad rounded-corner (0.05mm), BGA pads soldermask-defined, thermal reliefs for THT and high-maintenance SMT
PCB Assorted Trace-to-Via Teardrop, 0.15mm thruhole dia tolerance
PCB Silkscreen reference-designator for each part-footprint (ideal), remove designators when space is limited (use fab drawing for assembly), complete perimeter outline per footprint (incomplete outline for space; dotted/dashed outline for flux-scatter, ex. high-rel BGA assembly), functional label for every external pin
PCB Silkscreen Text Size 1.2/0.6 mm height (normal/minimum), 0.2/0.15 mm line width (normal/minimum)
PCB Spacing (min) 0.2mm board-edge to silkscreen-edge, 0.5mm board-edge to hole-edge
Via Size (drill dia, ring dia) landless (0.2mm, 0.2mm), compact (0.25mm, 0.35mm), thermal (0.3mm, 0.5mm)
External Conductor Clearance (IPC-2221, min) 0.1mm (30V class B3), 1.5mm (100V class B3), 3.2mm (170V class B3)
Internal Conductor Clearance (IPC-2221, min) 0.05mm (30V), 0.1mm (100V), 0.2mm (300V)
quality assurance electrical testing

PCB Silkscreen, Common Elements:

Meaning Example Required
Company Name Guidebolt Always If Possible
Part ID BC2023R4 Always If Possible
Component Designator R1 Always If Possible
Component Value 1K Optional
Batch Date/ID 202305C1 Optional
MFG Origin Made in Canada with Imported Parts Optional

PCB Assembly

Scope Specification
solder lead-free solder (SAC305) containing low-activity no-halogen flux (category L0, no-clean, IPA-washable)
conformal coating especially for condensing/high-altitude environments and compact high-voltage
underfill for best shock and thermal cycling (especially for BGA, WLCSP)


  • Lightning Resistance
  • ESD Resistance
  • Overvoltage Protection (OVP)
  • Overcurrent Protection (OCP)
  • Reverse Polarity Protection (RPP)
  • Electromagnetic Compatibility (EMC)

PCB Parts and Circuits


Resistor Standard: R1608M (SMT), AEC-Q200, 100V, Thin Film, Inorganic Passivation, -55C to 175C

MLC Capacitor Standard: AEC-Q200, 100V, Soft Termination, X7S/X8L

10A Diode: Diodes Inc, SBR10M100P5Q-13 (100V, 2uA leak-max 25C, 0.88V drop-max, 18ns switch, 245pF junction, -55 to 175C, 4x6.5/26mm2) (recommended)

Controller Area Network (CAN)

Standards: CAN, CAN-FD, CAN-SiC (CiA 601-4), CAN-XL, CANOpen

CAN-FD Transceiver: (testing) (target spec: CAN-FD-SiC, AECQ-G1, 8Mbps, -58 to 58V bus fault tolerance, exposed pad, ESD tolerance, UVLO, standby, VIO, hot-swap, thermal shutdown, 3x3mm)


RS485 Transceiver: Maxim Integrated, MAX14775EATA+ (-40 to 125C, 20Mbps, -65 to 65V fault tolerance, hot-swap, thermal shutdown, 3 to 5.5V input, SCP, reliable output state) (3x3x0.75mm, TDFN8, exposed pad, side pads) (Datasheet)

We wanted 100Mbps (ex. Maxim Integrated, MAX22501E) but we highly value 60V+ fault protection (given our 48VDC power standard) and our current node MCU frequencies are too low anyway (future goal, 1GHz+ low-power compact MCUs).

Single Pair Ethernet (SPE)

(SPE: IEEE 802.3)

SPE Summary, Microchip Webpage

100BASE-T1, TI, SZZY009, 2018 (PDF)

OPEN Alliance

  • video-audio bridge
  • time-sensitive networking (TSN)


ISA: Complex, Reduced (General), Reduced (Graphics)

AMD, Intel, Nvidia

RISC-V International



  • 8 Core, 16 Thread, 3+ GHz Base, iGPU
  • Cache: L1-I 32KBx8, L1-D 32KBx8, L2 512KBx8, L3 16MBx1
  • 64GB DDR5 RAM Support
  • <30W TDP

General Memory

Commercial SATA 2.5FF SSD: SAMSUNG, 870 EVO, 4TB (0 to 70C, 2400TBW) (Datasheet)

Industrial M.2 NVMe SSD: (testing) (target spec: PCIe 3.0, NVMe 1.4, -40C to 85C, 2280FF, SLC, vibration/shock/altitude)


  • integrated development environment (IDE) (develop MCU firmware)
  • integrated programming environment (IPE) (upload MCU firmware) (advanced mode, production mode)

  • AECQ-G1 (-40 to 125C)

  • <100uA/MHz
  • ECC Dual-Bank Flash
  • Ethernet MAC

SWD over USB-C:

  • SWDIO (A2, B2) (digital signal, continuously unique, debug data)
  • SWDCLK (A3, B3) (digital signal, single frequency clock, debug data rate)
  • RST (A10, B10) (digital signal, simple momentary, debug start sequencing)
  • VTG (A11, B11) (analog signal, constant, debug I/O voltage setting)

Embedded Memory

Ferroelectric RAM (non-volatile): 4Mbit (AEC-Q100), 50MHz max, 10+ trillion writes/reads (4mA max at 50MHz), 120ns write cycle

Resistive RAM (non-volatile): 12Mbit, 10MHz max, 1 million writes (1.5mA typical), unlimited reads (0.15mA typical at 5MHz)

NRAM (carbon nanotubes):


Thermal Jumpers: Vishay, THJP (170W/m-K, -65C to 150C) (preferred: 1608M/3216M, tin-plated nickel termination) (Datasheet)

XY Thermal Pads: (testing) (1800 W/m-K, -40C to 120C)

Z Thermal Pads: (testing) (28 W/m-K, -55C to 400C)


USB-C 24-pin Connector: Wurth Electronik, 632723300011 (SMT/THT standard-mount, -40C to 105C, 6.2mm insertion length, 1.9mm pin length)


USB2 SPEC-DL WEBPAGE, 2021-07-01

USB4 SPEC-DL WEBPAGE, 2021-06-09


USB Type-C REV2.1 SPEC-DL WEBPAGE, 2021-05-25



General-Purpose Wire-to-Wire: Molex, CP-4.5 Series (600V/10A max, 16-20/22-26AWG, -40C to 120C, polarized/color-mating, locking, genderless terminals, halogen-free)

High-Current Detachable: Wurth Electronik, THT External-Thread, 74651173 (M3, 50A, -55C to 150C, tin-plated brass)

Medium-Current Permanent Wire-to-Board: Molex, Solder-Right (1.95mm low-profile, 28AWG to 14AWG crimp, dual THT mounting, 1.6mm thick PCB compatible, -40C to 105C) (40N pullout-min for 16AWG)

Low-Current Permanent Wire-to-Board: Molex, Board-In 2.5mm Series, Right-Angle Models (3A/125V max, -40 to 125C, 0.22 to 0.35mm2 wire, halogen-free)


48V-Power Time-Delay Fuse: Schurter, UMT-H Series (C-UL-US/TUV/CQC, AECQ, -55 to 125C, 125VAC/72VDC, 5.3x16mm, 500A breaking) (Datasheet)

Class-J Time-Delay Fuse: Mersen, AJT Series (UL/CSA, 200kA-AC/100kA-DC interrupt, open fuse indication, dual-element) (aka 4TAR9 at Grainger Canada) (Datasheet)

Fuse Reducer: Mersen J636 (UL/CSA, 600V, adapts 30A fuse to 60A fuseholders)


(Wifi: IEEE 802.11)

Wifi Alliance

Wifi Antenna: 2.4/5/6GHz, <1.5 VSWR, 80%+ efficiency, omnidirectional, -30 to 85C, SMA-M

  • 2400 to 2485 MHz
  • 5150 to 5850 MHz
  • 5925 to 7125 MHz

RF Bulkhead: SMA-F to SMA-F, 18GHz max, <1.22 VSWR, <2mohm, -65 to 165C, 50 ohm impedance

  • stainless steel body
  • beryllium copper contact
  • gold finish (body+contact)
  • PTFE insulation
  • silicone seal

RF Cable: SMA-M to SMA-M, 8GHz max, <1.5 VSWR, gold finish, 50 ohm impedance

Infrastructure Parts and Circuits

20A 125V Duplex Outlet: Schneider Electric, Square D, X Series, SQR42204WH (tamper-resistant, matte white, outdoor, heavy-duty)

NEMA 15-50 Straight Plug: Hubbell, HBL8451C

NEMA 15-50 Receptacle: Hubbell, HBL8450A (requires 63mm-hole 2-gang wallplate, deep 2-gang box)

63mm-hole 2-gang Wallplate: Hubbell, SS701 (stainless steel)

Deep 2-gang 3/4-Hub Box: Thomas and Betts, 2IHD5-2 (requires 3/4-hub closure x2, 3/4-hub fitting)

3/4-hub closure: Thomas and Betts, PLG-2-RD (zinc) (can also be sourced from 3/4-hub box included-accessories)

1/2-hub AC90 fitting: Thomas and Betts, CI71 (zinc alloy)

3/4-hub AC90 fitting: Thomas and Betts, CI72 (zinc alloy)

Thomas and Betts, Iberville, Commercial Grade Fittings: PDF

PCB Assembly


Capillary Underfill Dispensing Method (web article, GPD Global)

As summarized in Test-to-Fail Methodology for Accurate Reliability and Lifetime Evaluation of eGaN Devices in Solar Applications (PDF article, EPC), underfill significantly improves the failure rate to zero (88 devices, 1800 ramp-dwell cycles of -40C to 125C).

Henkel Loctite Board-Level Underfill Solutions (PDF)


Thermal Asymptote: When current flows through a trace, its temperature approaches infinity; when a soldering tip touches a pad, its temperature approaches the tip temperature.

Footprints are spaced to support part-holding with tweezers (0.8mm tip-thickness).

Same-net pads can be closer together. Different-net pads should be further apart.

Other Resources

(less common use)

Description Link
MIL-STD-202: Electrical Part Testing WEB-PDF
AEC Qualification WEB-PDF