One of the key concepts that all the tech-geeks often talk about is the printed circuit board or PCB; if this term is new to you and you want to know some other common terms regarding PCB, then you’ve come to the right place.
This tutorial is about what makes up a PCB and some of the terms used in the PCB world.
Shall we begin?
Before digging in the term, let me give you a short background.
Before the invention of PCB, circuits were constructed via a laborious process of point-to-point wiring, which led to frequent failures at wire junctions and short circuits when wire insulation age and crack.
A significant advance started with the development of wire wrapping, where a small wire is wrapped around a post at each point, creating a gas-tight connection which is durable and easily changeable.
As electronics moved from vacuum and relays to silicon and integrated circuits, both the size and cost of electronic components decreased. Electronics started reaching to consumer goods, and the pressure to reduce the size and manufacturing costs drove manufacturers to look for better yet economical solutions.
This is how PCB appeared on the tech. surface.
What is PCB?
A printed circuit board (PCB) electrically connects and mechanically supports electronic or electrical components using conductive tracks, pads and others etched from one or more layers of copper laminated onto and/or between sheet layers of a non-conductive substrate.
Components are soldered onto the PCB to both electrically and mechanically connect and fasten them.
Printed circuit boards are used in all yet the simplest electronic products, such as passive switch boxes.
PCBs require additional efforts to lay out the circuit, but manufacturing and assembly can be automated; only specialized can explain to you the real efforts. Thanks to best PCB assemblers and PCBA manufacturers like RayPCB by RAYMING, for making our lives more compact yet convenient by electronic manufacturing and assembling PCBs.
In non-techie terms, PCB is an acronym for a printed circuit board that has lines and pads to connect various points together, allowing signals and power to be routed among physical devices; thanks to solder for being a strong mechanical adhesive.
It is used to mechanically support and electrically connect electronic components with conductive tracks, pathways, or signal traces etched from copper sheets laminated onto a non-conductive substrate.
I don’t want you to get bored, but most of you might be interested to know how PCB made of, so allow me to give an overview; I promise I will be as concise and precise as I could.
What PCB consists of?
PCB is like a layer cake or lasagna- with other alternating layers of different materials laminated together with heat and adhesive.
Let's start with all the basic components;
- FR4 – The solid base material, usually fiberglass, gives the PCB its rigidity and thickness; they are flexibly built on a flexible high-temp. plastic (Kapton or the equivalent). Cheaper PCBs and perf boards are made of other materials – epoxies or phenolics – which lack the durability of FR4 but are less expensive. These substrates are often found in low-end consumer electronics.
- Copper – The next layer is a copper foil, laminated to the board with heat and adhesive; in double-sided PCBs, you will find copper to both sides of the substrate. In some economical electronic gadgets, the PCB have copper on only one side. The copper thickness can vary in weight, the majority of PCBs have 1 ounce of copper per square foot while others – those handle high power – use 2 or 3-ounce copper.
- Soldermask – The layer on top of the copper foil is the solder mask; this is where PCB gets green (or any color). It is overlaid onto the copper to insulate its traces from accidental contact with another solder, metal, or conductive bits. This layer helps in soldering to the correct places and prevent solder jumpers; the silver rings and SMD pads exposed to be soldered to.
- Silkscreen – The white silkscreen layer is on top of the solder mask. The silkscreen adds numbers, letters, and symbols to the PCB for easier assembly and for humans to better understand the board. You often find silkscreen labels to indicate what the function of each pin or LED performs.
Originally, electronic components had wire leads, and a PCB had holes drilled for each wire representing each component. The component leads were then inserted in the holes and soldered to the copper PCB traces. This method of assembly is known as through-hole construction.
However, the wires and holes seemed inefficient since drilling holes was expensive and used to consumes drill bits, protruding wires were cut off and discarded.
From the 1980s, small surface-mount parts have been using instead of through-hole components; this has led to smaller boards and lower production costs but invited some additional difficulty in servicing faulty boards.
In the 1990s, multilayer surface boards became more frequent; size was further minimized and flexible yet rigid PCBs started incorporating in different devices.
Then comes in HDI technology for a denser design on the PCB with smaller components, using blind/buried vias or a combination of micro-vias. The applications for HDI technology are computer and mobile phone components as well as military communication equipment and medical equipment.
Recent advances in 3D printing, utilizing to print items layer by layer with a liquid ink that contains electronic functionalities.
This is how a revolutionary PCB evolved.
Types of PCB
PCBs can be;
- Single-sided (one copper layer)
- Double-sided (two copper layers on both sides)
- Multi-layer (outer and inner layers of copper).
Multi-layer PCBs are for much higher component density because circuit traces on the inner layers would otherwise eat up the surface space between components.
The rising popularity of multilayer PCBs with more than two, and four, copper planes was concurrent with the surface mount technology.
Is that enough to understand what is PCB?
I hope I have cleared all your queries and confusions regarding PSB!
Anyways, to end this, let me clear your equip your mind with some related jargons – so that you won’t feel isolated when you’re with your techie or engineering fellows.
Now that you've got what is PCB structure, let's define some terms that you hear when dealing with PCBs:
- Annular ring – Copper ring around a plated-through hole in a PCB.
- DRC – Design rule check; software to make sure the design does not contain errors – traces that incorrectly touch, traces too skinny, or too small drill holes.
- Drill hit – Places on a design where a hole to be drilled, or actually were drilled on the board.
- Finger – Metal pads along the edge of a board, used for a connection between two circuit boards.
- Via – A hole on a board used to pass a signal between layers, it is where components and connectors are attached for easy soldering.
- Mouse bites – An alternative to v-score for separating boards from panels.
- V-score – A partial cut on a board, allowing the board to be snapped along a line.
- Pad – Portion of exposed metal on a board to a soldered component.
- Panel – A larger circuit board with many smaller boards; automated circuit board handling equipment has trouble with smaller boards, but gathering several boards speeds up the process significantly.
- Paste stencil – A thin, metal (or plastic) stencil lies over the board, allowing solder paste to be deposited during assembly.
- Plane – A continuous copper block on a circuit board, defined by borders not by a path. Also called a “pour”.