PCBs 101

1 Anatomy of a PCB
- 1.1 PCB Layers
- 1.2 Key PCB Features
2 Types of PCB Components
3 Dissecting an Arduino
4 PCB Assembly
5 Specialized PCBs
- 5.1 Flex and Rigid-Flex PCBs
- 5.2 Metal Core PCBs
6 Additional Resources
- 6.1 PCB Design
- 6.2 PCB Manufacturing

Check out This Page for a Glossary of Electrical Terms!

Anatomy of a PCB

PCB stands for Printed Circuit Board, which is a bit of a misnomer, as the layers of modern PCBs are produced through subtractive processes. Only the silkscreen layers are ever printed - more on that in a second. The term “printed” has its origins in the first PCBs, which were produced by drawing “wires” with conductive ink on an insulating substrate.

PCB Layers

Although the Layer Count, of a board typically refers to the number of copper layers present,

copper layers - used to conduct electric currents. Confusingly, PCBs use ounces as units of thickness for copper layers. This is the thickness of copper achieved if you flatten out an ounce of copper over a square foot of area.
dielectric/prepreg layers - insulating layers which prevent shorts between the copper
solder mask layers - deposited on the top and bottom copper layers, this protects the copper from corrosion and environmental damage, and lends PCBs their color (typically green by default)
silkscreen layers (“silks”) - to call this a “layer” might seem odd, since this is just the text and decals printed on the top and bottom of the board, typically in white ink. Another anachronistic term, most PCB silkscreens are now produced with a direct printing or photoimaging process, rather than true screen printing.

Typical PCB cross-section. Source: Altium

Key PCB Features

Traces (or Tracks) - “wires” etched into the copper layers. Because the copper layers are a predetermined thickness, the width of copper traces is often increased for traces which carry more current. See Step 4 - Route Components for more details.
Vias - holes that go all or partway through a PCB, and which are plated in copper. These allow for signals to travel between copper layers.
Pads - If you’ve made it through the component creation guide, you’ll know that a pad is used to allow a component to be soldered onto the PCB. Pads may be surface mount (flat piece of copper) or through-hole (think an extra wide via).
Copper Pours - wide areas of copper that belong to a single net, so called because it looks like someone “poured” copper over part of the board. These are often used in areas of high current, or when many adjacent components share a common net.

If you’re interested in learning about how PCBs are manufactured, I highly recommend checking out this tour of the JLCPCB factory. Many of the boards on our car likely originated in that very factory!

Types of PCB Components

SMD/SMT/Surface Mount - Components which mount to a single side of a PCB

Through Hole - components which mount to one or more plated holes in a PCB. Most connectors we use are through hole.

Axial - Think the resistors you’d find in an electronics lab. Axial components have wire leads, and can be soldered into a board as a through hole component by bending the leads.

Dissecting an Arduino

Let’s take a look at a PCB that nearly every EE is familiar with - an Arduino!

YELLOW = RESET BUTTON

RED = CRYSTAL OSCILLATOR

PURPLE = INTEGRATED CIRCUIT

CYAN = DIODE

GREEN = CONNECTOR

ORANGE = CAPACITOR

BLUE = RESISTOR

YELLOW = SILKSCREEN

GREEN = TRACE/TRACK

BROWN = COPPER POUR

RED = SMD PAD

PURPLE = THROUGH HOLE PAD

BLUE = VIA

PCB Assembly

[TO BE CONTINUED]

Specialized PCBs

Flex and Rigid-Flex PCBs

Flex PCBs allow you to create electrical connections and solder components to a flexible substrate. This can be useful for compact electronics packaging, or niche applications like BMS thermistor and voltage taps.

Metal Core PCBs

For applications that demand good heat dissipation, aluminum and copper core PCBs are often a good solution. A common use case for this style of PCB is LED lighting fixtures.