The Ultimate PCB Glossary: A-Z Terminology for UK Electronics Manufacturing

Whether you are an electronics engineer, a procurement specialist, or a hobbyist designing your first circuit board, the world of PCBs (Printed Circuit Boards) comes with its own language. It is a language full of acronyms and specific jargon that can be baffling if you aren’t speaking it every day.

At PCB Company, we believe that clear communication stops errors before they happen. If you know exactly what “Impedance Control” or “Tented Vias” mean when you place an order, the final fabrication will be smoother, faster, and more cost-effective.

Here is our breakdown of the essential PCB terminology you need to know, written with the UK market in mind.

A

Annular Ring

This is the copper ring that surrounds a hole on a PCB. Think of it as the target bullseye. When a drill hits the centre to make a via or a component hole, the annular ring is the copper pad left around it. If the drill is slightly off-centre, you still need enough copper remaining to make a reliable electrical connection. A “broken” annular ring is a common manufacturing defect we watch out for.

ART Work (Phototool)

In the “old days,” this literally referred to the film or transparency used to transfer the circuit image onto the copper. Today, while most of the process is digital (Gerber files), the term is still used to describe the data packages used for imaging the inner and outer layers of the board.

Assembly (PCBA)

This is the process of soldering electronic components onto the bare board. The board itself is the PCB; once it has resistors, chips, and capacitors attached, it becomes a PCBA (Printed Circuit Board Assembly).

B

BOM (Bill of Materials)

Your shopping list. This is a document that lists every single component needed to build the board. For a smooth assembly process here in the UK, your BOM must include the manufacturer’s part number, the quantity, and the reference designator (e.g., R1, C3). Incomplete BOMs are the number one cause of assembly delays.

Breakaway Tabs

These are small tabs used to connect smaller PCBs together in a larger array or panel. They allow the boards to be processed as one unit during manufacturing and then snapped apart (depanelled) later without damaging the actual circuit.

Buried Via

A via that connects two or more inner layers but does not go all the way through to the outer surface of the board. You can’t see it from the outside. These are essential for high-density designs where surface space is at a premium.

C

Controlled Impedance

This is critical for high-speed signals (like USB, HDMI, or Ethernet). It refers to the precise matching of the trace width and thickness, and the distance to the reference plane, to ensure the electrical signal travels without distortion. If you are designing for high frequency, you need to specify this, or your signal might “reflect” and fail.

Copper Weight

You will often see boards described as 1oz, 2oz, or half-ounce copper. This refers to the thickness of the copper foil. One ounce means one ounce of copper spread evenly over one square foot of board. Heavier copper (e.g., 2oz or 4oz) is used for high-current applications like power supplies because it carries more load without overheating.

Core

The central part of a double-sided or multi-layer board. It is a rigid piece of dielectric material (usually FR4) with copper foil on both sides.

D

DFM (Design for Manufacturability)

This isn’t a physical part of the board, but a process. It is the analysis of your design to ensure it can actually be manufactured reliably. At PCB Company, we run DFM checks to spot issues like traces too close together or drill holes that are too small before we start cutting metal. It saves you money and headaches.

Dielectric

The insulating material between the copper layers. FR4 is the most common dielectric, but there are specialised materials for high-frequency or high-temperature applications. The “Dk” value of a dielectric tells you how well it stores electrical energy.

Double-Sided Board

A PCB with tracks on both the top and bottom layers, but no internal copper layers. This is the most common type of board for general electronics.

Drill File

Often called an “Excellon file,” this tells the CNC machines exactly where to drill holes and what size drill bits to use.

E

ESD (Electrostatic Discharge)

The sudden flow of electricity between two electrically charged objects. Think of the shock you get touching a door handle in winter. In PCB terms, ESD can fry sensitive components. Proper design includes ESD protection diodes to safeguard the board.

Etch

The chemical process used to remove unwanted copper from the board. We cover the copper we want to keep with a protective resist and wash away the rest using an etchant solution.

F

Fiducial Mark

A small, round copper mark (usually bare copper or plated with gold) placed on the surface of the board. It acts as a reference point for vision systems in pick-and-place machines. It ensures the machine knows exactly where the components need to go.

FR4

This is the industry standard material for PCBs. It stands for “Flame Retardant 4.” It is a composite of woven fibreglass cloth with an epoxy resin binder that is flame resistant. If you just ask for a standard PCB, you are getting FR4.

G

Gerber File

The universal language of PCB fabrication. It is a file format (usually RS-274X) used to describe the PCB images: copper layers, solder mask, silkscreen, and drill data. If you send us a Gerber, we can build your board.

Ground Plane

A large continuous area of copper connected to the ground potential. It is usually found on one of the inner layers or the bottom side of the board. It helps reduce noise and provides a stable reference voltage for the circuit.

H

HASL (Hot Air Solder Levelling)

The most common surface finish for PCBs. After the board is etched and drilled, it is dipped into molten solder, and then hot air knives blow off the excess, leaving a flat, shiny surface. It’s durable and cost-effective, though not ideal for very fine-pitch components.

HDI (High Density Interconnect)

Boards with finer lines and spaces, smaller vias, and higher connection pad density than standard boards. You see these in modern smartphones and laptops where space is incredibly tight.

Hole Breakout

This is a defect where a drill hole cuts into the edge of a pad rather than sitting comfortably in the middle of the annular ring. It breaks the electrical connection and renders the board useless.

I

Impedance

The resistance to the flow of alternating current (AC). In PCB design, matching impedance is vital for signal integrity. Mismatched impedance causes signal reflection, leading to data errors.

IPC Standards

The IPC (Association Connecting Electronics Industries) sets the global standards for PCB design and manufacturing. In the UK, we generally work to IPC Class 2 (standard consumer electronics) or IPC Class 3 (high-reliability aerospace/military).

L

Laminate

The base material of the PCB. It is made by layers of material (like fibreglass and resin) bonded together under heat and pressure.

Land Pattern

The arrangement of pads on a PCB that a specific component will sit on. You might hear this called a “footprint.”

Lead-Free

RoHS (Restriction of Hazardous Substances) legislation in the UK and EU requires that electronics sold in Europe be lead-free. This changes the soldering process slightly, as lead-free solder has a higher melting point than traditional tin-lead solder.

M

Microvia

A very small via, usually less than 150 microns in diameter. These are used in HDI boards and are typically laser-drilled rather than mechanically drilled.

Mounting Hole

A hole used to screw the PCB into an enclosure or chassis. These are often non-plated (NPTH) to avoid shorting against a metal screw, though they can be plated for grounding.

Multi-Layer Board

A PCB that has more than two conductive layers. This includes 4, 6, 8, or even 12+ layers. The layers are sandwiched together, allowing for incredibly complex routing in a compact footprint.

N

NPTH (Non-Plated Through Hole)

A hole that goes through the board but has no copper plating inside. These are typically used for mechanical mounting or tooling holes.

O

OSP (Organic Solderability Preservative)

A surface finish that is flat and cheap. It uses a chemical compound to protect the copper from oxidising until it is ready to be soldered. It’s great for lead-free soldering but has a shorter shelf life than ENIG or HASL.

Overhang

This generally refers to the amount of resist or plating that extends beyond the edge of a feature. In routing, it can refer to the slight overcut made by a router bit.

P

Pad

The exposed metal area on the PCB surface where a component lead is soldered.

Panel

A large piece of material containing multiple identical PCBs. Manufacturers print several boards on a single panel to increase efficiency. Once assembly is complete, the boards are cut out of the panel.

Paste Mask

This is the stencil used to apply solder paste onto the pads before placing components. It is usually the opposite of the solder mask; it opens up only where the solder needs to go.

PCB (Printed Circuit Board)

The foundation of electronic devices. It mechanically supports and electrically connects electronic components using conductive pathways, tracks, or signal traces etched from copper sheets laminated onto a non-conductive substrate.

Pick and Place

The assembly process where a machine picks up components and places them onto the PCB. It is fast, accurate, and essential for volume production.

Plated Through Hole (PTH)

A hole that goes from the top of the board to the bottom and is plated with copper. This allows electrical connections to be made between the top and bottom layers or to connect a component lead through the board.

Polyimide

A high-performance material used for flexible circuits. It can withstand much higher temperatures than standard FR4 and is very durable.

Pth

Sometimes used as an abbreviation for “Plated Through Hole,” but also used to mean “Pin Through Hole” technology (traditional components with legs that go through the board), as opposed to SMT (Surface Mount Technology).

R

Reflow

The process of heating the board (in a reflow oven) to melt the solder paste, thereby permanently attaching the components to the pads.

Resist

A material that is used to protect specific areas of the copper during the etching process. “Photoresist” is sensitive to light and is used to transfer the circuit pattern.

Rigid-Flex

A hybrid construction that combines rigid boards with flexible circuits. It is often used in military and aerospace applications or in modern folding phones.

RoHS (Restriction of Hazardous Substances)

A crucial directive in the UK and EU that restricts the use of specific hazardous materials (like lead, mercury, and cadmium) in the manufacture of electronic equipment.

S

Silkscreen

The white (usually) printing on the top of the board. It shows component designators (R1, C1, etc.), logos, and warning symbols. It is essentially the labelling system for the board.

Solder Mask

The protective layer (usually green) that covers most of the copper traces. It prevents solder from bridging between traces and protects the copper from oxidising. It is the “skin” of the PCB.

Solder Paste

A sticky mixture of tiny solder spheres suspended in flux. It is printed onto the pads to hold components in place before reflow soldering.

SMT (Surface Mount Technology)

The method of assembling electronics where components are mounted directly onto the surface of the PCB. This is the standard for modern manufacturing, allowing for much smaller components than “through-hole” methods.

Surface Finish

The coating applied to the bare copper pads to prevent oxidation and ensure solderability. Common types include HASL, ENIG, OSP, and Immersion Tin.

T

Tented Via

A via that is covered by the solder mask. This prevents solder from wicking away from a pad into the via hole during soldering, and it also protects the via from corrosion.

Trace (Track)

The copper pathways that carry electrical signals between components. You will hear engineers talk about “trace width” or “trace spacing” when discussing how much current a board can handle.

Turnkey

A service offered by PCB Company where we handle the entire process: sourcing the components, fabricating the bare board, assembling it, and testing it. You just give us the design, and we give you the finished product.

V

Via

A small hole in a PCB that is used to connect two or more layers electrically. Think of it as an elevator for electricity; it lets a signal travel from the top floor down to the basement without taking the stairs.

W

Warp and Twist

Mechanical distortions of the board. Warp is a bend along the length, while twist is a deformation along the diagonal. Excessive warping can cause problems during assembly, especially with fine-pitch components.

Wicking

When solder travels up a component lead or via hole, leaving the joint with insufficient solder. It is often caused by excessive heat or poor plating.

Still confused?

If you have come across a term that isn’t on this list, or if you need advice on which specification is right for your project, get in touch with our engineering team. We don’t just manufacture boards; we help you design them right the first time.