Master PCB Design Build Real Circuit Boards

🔧 Introduction to PCBs

A Printed Circuit Board (PCB) is a flat board made of insulating material with conductive copper pathways etched or printed onto it. These copper pathways — called traces — connect electronic components together, replacing the need for messy point-to-point wiring.

PCBs are found in virtually every electronic device: your smartphone, laptop, TV, car dashboard, medical equipment, satellites, and even humble LED flashlights. They are the foundation of modern electronics manufacturing.

📜 A Brief History

Before PCBs, electronic circuits were built using point-to-point wiring — each component was connected with individual wires soldered directly. This was slow, error-prone, and unreliable.

• 1936 — Paul Eisler created the first PCB while working on a radio in England
• 1943 — The US military adopted PCB technology for proximity fuses in WWII
• 1950s — Through-hole technology became standard for manufacturing
• 1960s — Double-sided PCBs and plated through-holes revolutionized density
• 1980s — Surface Mount Technology (SMT) enabled much smaller components
• 2000s — HDI (High Density Interconnect) boards with micro-vias emerged
• Today — 20+ layer boards with 50µm features are routine in smartphones

🗂️ Types of PCBs

🔍 Anatomy of a PCB

A typical PCB consists of several key layers:

• Substrate (FR-4) — The fiberglass-reinforced epoxy base material that provides structural strength
• Copper Layers — Thin copper foil (typically 1oz = 35µm thick) where the circuit traces are etched
• Solder Mask — The green (or other color) coating that protects copper from oxidation and prevents solder bridges
• Silkscreen — White printed text showing component labels, reference designators, and logos
• Surface Finish — A protective coating on exposed pads (HASL, ENIG, OSP) to ensure solderability

🎥 Video: What is a PCB?

What is a PCB? — Printed Circuit Board Explained

Branch Education

🧱 Substrate Materials

The substrate is the base material of the PCB that provides mechanical support and electrical insulation between copper layers.

🥉 Copper Weight & Thickness

Copper thickness is specified in ounces per square foot (oz/ft²). This tells you how thick the copper foil is on each layer.

🟢 Solder Mask

The solder mask is a protective lacquer coating applied over the copper traces. It serves several crucial functions:

• Prevents oxidation of copper traces
• Prevents solder bridges between pads during assembly
• Provides electrical insulation between traces
• Protects against dust, moisture, and contamination

Available colors: Green (classic), Black, White, Red, Blue, Yellow, Purple, Matte Black, Matte Green.

✍️ Silkscreen

The silkscreen layer contains printed text and symbols for component identification. Best practices:

• Minimum text height: 0.8mm (1mm recommended)
• Minimum line width: 0.15mm
• Include reference designators (R1, C2, U3) next to components
• Add polarity marks for diodes, electrolytic caps, and ICs
• Include pin-1 indicators, test points, and board version numbers

✨ Surface Finish

🎥 Video: PCB Manufacturing Process

How PCBs are Made — Factory Tour

Strange Parts

📝 What is a Schematic?

A schematic is a symbolic diagram of an electronic circuit. Unlike a physical layout, a schematic shows the logical connections between components without representing their physical placement. It is the first step in any PCB design process.

Think of a schematic as the architectural blueprint — it defines what's connected to what. The PCB layout is the construction plan — it defines where everything physically goes.

🔣 Schematic Symbols

Standard schematic symbols you need to know:

🌐 Nets & Connections

In a schematic, connections are represented by wires (nets). When two wires cross, they are NOT connected unless there is a junction dot. Key concepts:

• Net — A named electrical connection (e.g., VCC, GND, SDA, SCK)
• Net Label — A text tag placed on a wire to name the connection without drawing a physical wire
• Power Flag — Tells the ERC that a net is intentionally powered
• No-Connect (X) — Marks unused pins so the ERC doesn't flag them as errors
• Junction Dot — Connects crossing wires; without it, wires just pass over each other

✅ Electrical Rules Check (ERC)

The ERC is an automated check that catches common schematic mistakes:

• Unconnected pins — Pins that should be connected but aren't
• Power conflicts — Two outputs driving the same net
• Missing power flags — Power nets without a defined source
• Short circuits — Direct connections between power and ground

⌨️ KiCad Schematic Shortcuts

🎥 Video: KiCad Schematic Tutorial

KiCad for Beginners — Step by Step Tutorial

DIY Hideout

📚 Library Structure

In KiCad, every component needs three things:

1. Schematic Symbol — The visual representation in the circuit diagram (e.g., a resistor zigzag)
2. PCB Footprint — The physical copper pattern on the board where the component is soldered
3. 3D Model (optional) — A STEP/WRL file for visual verification and mechanical clearance checks

KiCad comes with extensive built-in libraries, but for professional work you'll often need to create custom libraries or download from manufacturers.

🔍 Finding Components

Best sources for component data:

🏷️ Reference Designators

📋 Bill of Materials (BOM)

The BOM is a spreadsheet listing every component needed to build the board. A good BOM includes:

• Reference Designator — R1, C2, U3
• Value — 10kΩ, 100nF, LM7805
• Footprint — 0805, SOT-23, SOIC-8
• Manufacturer Part Number (MPN) — e.g., RC0805FR-0710KL
• Supplier & SKU — LCSC C17414, DigiKey 311-10KARCT-ND
• Quantity — How many of each part per board

🎥 Video: Creating Custom Libraries

KiCad Custom Libraries — Symbols & Footprints

DigiKey

👣 What is a Footprint?

A footprint (also called a land pattern) is the copper pad pattern on the PCB where a component is physically soldered. Every component in your schematic must be assigned a matching footprint.

🔌 Through-Hole (THT) Pads

Through-hole pads have a drilled hole that the component lead passes through and is soldered on the opposite side.

📏 SMD Pad Sizes

Surface Mount Device (SMD) pads sit flat on the board surface. Common passive component sizes:

🔥 Thermal Pads

Many power ICs and voltage regulators have a exposed thermal pad on the bottom. This pad must be connected to a large copper pour (usually ground) with multiple thermal vias to dissipate heat.

• Use a grid of 0.3mm vias spaced 1mm apart under the pad
• Connect to an inner ground plane for maximum heat spreading
• Apply solder paste at 50-80% of the pad area (too much causes the IC to float during reflow)

🎥 Video: SMD vs Through-Hole

How to Solder properly — Through-hole (THT) & Surface-mount (SMD)

GreatScott!

📐 Board Outline

The board outline (Edge.Cuts layer in KiCad) defines the physical boundary of your PCB. Best practices:

• Use round corners (radius ≥ 0.5mm) — sharp corners create stress concentrations
• Keep components at least 1mm from the board edge
• Standard board thickness: 1.6mm (most common), 0.8mm, 1.0mm also available
• Consider mounting holes — M3 (3.2mm drill) is standard
• For enclosures, check mechanical clearance with the 3D viewer

📊 Design Rule Setup

Before routing, configure your Design Rules based on your manufacturer's capabilities:

🎥 Video: KiCad PCB Layout Setup

KiCad 8 PCB Layout — Board Setup

DigiKey

🛤️ Routing Fundamentals

Routing is the process of drawing copper traces to connect component pads according to the netlist from your schematic. Key principles:

• Route signals first, then power, then ground (or use planes for power/ground)
• Use 45° angles — never 90° corners (they create impedance discontinuities and acid traps)
• Keep traces as short as possible — shorter traces = less resistance, less EMI
• Avoid running traces parallel for long distances — this causes crosstalk
• Use wider traces for power (25-50 mil) and normal width for signals (8-10 mil)

📏 Trace Width vs Current

The trace must be wide enough to carry the required current without excessive heating. The standard reference is IPC-2221:

🔀 Differential Pairs

Differential pairs are two traces that carry complementary signals (USB, Ethernet, HDMI). They must be routed with:

• Matched length — Both traces must be the same length (within 0.1mm)
• Consistent spacing — Fixed gap between the two traces
• Controlled impedance — Usually 90Ω differential (USB) or 100Ω (Ethernet)
• Symmetrical routing — Route both traces together, never split them

⌨️ KiCad Routing Shortcuts

🎥 Video: PCB Routing Techniques

How to Route a PCB Like a Pro

Phil's Lab

⚡ Ground Plane

A ground plane is a large copper pour connected to GND that covers most of a layer. It's arguably the single most important design technique in PCB design:

• Low impedance return path — Provides the shortest path for return currents
• EMI reduction — Acts as a shield against electromagnetic interference
• Thermal management — Spreads heat across the board
• Simplifies routing — No need to route individual GND traces

🔋 Power Distribution

Power traces need special attention because they carry the most current:

• Use wide traces (30-50 mil minimum) or dedicated power planes
• Place bulk capacitors (10-100µF electrolytic) near the power input
• Place decoupling capacitors (100nF ceramic) within 3mm of each IC's VCC pin
• Consider a star-point grounding topology for mixed-signal boards

🧊 Decoupling Best Practices

Every IC needs decoupling capacitors close to its power pins to filter high-frequency noise:

🔥 Thermal Management

Components that dissipate significant power need thermal design consideration:

• Use thermal vias under thermal pads — multiple 0.3mm vias in a grid pattern
• Connect to large copper pours on inner and outer layers for heat spreading
• Use thermal relief on pads connected to planes (flower pattern with spokes) for easier soldering
• Consider heatsinks or forced airflow for high-power designs

🎥 Video: Power Integrity

PCB Power Integrity & Decoupling

Phil's Lab

📚 Why Multi-Layer?

As designs grow in complexity, two layers aren't enough. Multi-layer boards provide:

• Dedicated power and ground planes — Improved power distribution and EMC
• More routing channels — Complex ICs with 100+ pins need the space
• Controlled impedance — Consistent trace impedance for high-speed signals
• Smaller board size — More routing layers = denser component placement

🏗️ 4-Layer Stackup

The most common multi-layer configuration. The standard 4-layer stackup is:

🕳️ Via Types

🎥 Video: Multi-Layer PCB Design

KiCad STM32 + USB + Buck Converter PCB Design

Phil's Lab

📏 Critical Design Rules

Design rules ensure your PCB can be manufactured reliably. The three most critical parameters:

1. Minimum Trace Width — The narrowest copper path allowed (typically 5-6 mil / 0.127-0.15mm)
2. Minimum Clearance — The smallest gap between copper features (typically 5-6 mil)
3. Minimum Drill Size — The smallest hole the fab can drill (typically 0.3mm mechanical, 0.1mm laser)

🔍 Common DRC Errors

✅ Running the DRC

In KiCad, run Inspect → Design Rules Check (or click the ladybug icon). The DRC will flag:

• Errors (red) — Must be fixed. Board won't work correctly.
• Warnings (yellow) — Should be reviewed. May or may not be problems.
• Exclusions — Items you've manually marked as acceptable.

🎥 Video: DRC Deep Dive

How To Do PCB Layout (Step by Step)

Robert Feranec

📡 What is EMC?

Electromagnetic Compatibility (EMC) is the ability of your circuit board to:

• Not emit excessive electromagnetic interference (EMI) to other devices
• Not be susceptible to external interference from other sources

Poor PCB layout is the #1 cause of EMC failures. Even a perfectly designed circuit can fail EMC testing if the PCB layout creates unintended antenna structures.

🔊 Crosstalk

Crosstalk occurs when a signal on one trace induces noise on an adjacent trace via capacitive or inductive coupling:

• Keep parallel runs short — Maximum 1-2 inches of parallel traces
• Increase spacing — The "3W rule": center-to-center spacing ≥ 3× trace width
• Use ground guards — Place grounded traces between sensitive signal pairs
• Route on different layers — Perpendicular crossing minimizes coupling

🔄 Return Path

Every signal has a return current that flows back to the source. This return current follows the path of least impedance — at high frequencies, that's directly underneath the signal trace on the ground plane.

📐 Impedance Control

High-speed signals require controlled impedance — the trace geometry must produce a specific impedance value:

🛡️ EMC Design Checklist

• ✅ Continuous ground plane with no splits or slots under signal traces
• ✅ Decoupling capacitors (100nF) on every IC power pin within 3mm
• ✅ Short, wide power traces or power planes
• ✅ 45° routing angles, no 90° corners
• ✅ Avoid routing under crystals or oscillators
• ✅ Keep high-speed signals away from board edges
• ✅ Use differential pairs for high-speed interfaces
• ✅ Place decoupling caps on the same layer as the IC
• ✅ Ground via stitching around board perimeter
• ✅ Separate analog and digital sections physically

🎥 Video: EMC for PCB Designers

Many EMC Tips to Help You Design Better PCB Boards

Robert Feranec

📁 What are Gerber Files?

Gerber files are the industry standard file format for PCB manufacturing. Each file represents one layer of your board:

📤 Exporting from KiCad

🏭 PCB Manufacturing Process

🛒 Popular PCB Fabs & Pricing

🎥 Video: Ordering from JLCPCB

How to Order PCBs from JLCPCB — Complete Tutorial

Delali

🔧 Hand Soldering Basics

For hobby and prototype boards, hand soldering is the most common method:

✅ Good vs Bad Solder Joints

🔥 SMD Soldering Techniques

• Drag Soldering — For fine-pitch ICs (QFP): tin one corner pad, align IC, solder remaining pins by dragging solder across all pins, wick excess with solder wick
• Hot Air Rework — Apply solder paste, place components, use hot air station (350-380°C) to reflow
• Solder Paste + Toaster Oven — DIY reflow: apply paste with stencil, place components, reflow in modified toaster oven with temperature control
• Hot Plate — Similar to toaster oven but using a ceramic hot plate (~220-250°C)

🏭 Professional Assembly (PCBA)

For production quantities, use a PCB Assembly (PCBA) service:

• Solder Paste Stencil — Laser-cut stainless steel stencil applies precise solder paste
• Pick and Place — Robotic machine places components at high speed (20,000+ CPH)
• Reflow Oven — Controlled temperature profile melts solder paste (preheat → soak → reflow → cool)
• AOI (Automated Optical Inspection) — Camera system checks for missing/misaligned components
• Wave Soldering — For through-hole components after SMD reflow

🎥 Video: SMD Soldering Masterclass

Beginner's Guide to Soldering Electronics

Branchus Creations

📏 Trace Width Calculator (IPC-2221)

🕳️ Via Current Calculator

📐 Microstrip Impedance Calculator

🔄 Unit Converter