A Guide To Printed Circuit Boards For Electronic Beginners
Posted On June 7, 2018
A printed circuit board (PCB) is a thin board that uses layers of fiberglass and copper to create a platform for an electrical circuit. The PCB is often designed for a specific circuit. The copper is etched to create electrical connections between different points on the circuit without crossing others. Those points often represent pins from microchips or the leads from various components, such as resistors, capacitors, and transistors.
You’ll find a PCB is just about any electronic device that you take apart. Only devices that use an incredibly small number of components don’t rely on these circuit boards. They are in remote controls, televisions, keyboards, and even many modern light bulbs.
Anyone with an interest in electronics, whether they are a hobbyist or a student, will need to learn about PCBs. In time, they will learn how to design them using computer-aided design software. Those designs may then be sent to a manufacturer who will produce a PCB based on the provided circuit schematic.
It’s also possible to purchase certain DIY electronic projects that come with pre-designed PCBs included. You then solder the necessary components onto the board according to the design and function of the circuit.
The DOT PCB
The simplest type of PCB and the one that hobbyists use most often is called a perfboard, or a DOT PCB. A perfboard is different from your standard PCB in many ways. They typically only have copper on one side of the board and that copper is never laminated over. The board is filled with holes in a grid design. Each hole has a small copper pad on the underside.
A person can quickly build a circuit using a perfboard by inserting the leads of components into the holes and then soldering them onto the copper pads beneath. In most cases, there are no traces or connections between any of the pads. Such connections must be made by the user with wires or other leads. Though, in some cases, there are specialty perfboards that contain unique connections between various copper pads.
A DOT PCB is a great tool for anyone who is learning electronics from Direct Components Inc – circuit board components, as well as anyone who wants to quickly build and test a circuit. There’s no need to design the circuit using a CAD program or to wait for a company to print the board. It’s considerably cheaper and faster than waiting for a standard PCB. However, you’ll never see a DOT PCB inside of an electronic device because they are all-around less efficient. They are simply a learning and prototyping tool.
The Standard PCB
A standard PCB like you would find inside of an electronic device is more complicated and more reliable than a DOT PCB. They contain many additional layers, features, and advantages that are not present on perfboards. Think of the DOT PCB as a rough draft circuit, but the with final product relying on a standard PCB.
The simplest of PCBs will contain at least four unique layers. Though it is possible for there to be duplicates of these layers. The layers are as follows, starting from the bottom:
The substrate is the is the primary material that the board is built from. The most commonly used substrate material is fiberglass. However, it’s possible for a manufacturer to use a number of different dielectric materials. Some substrates are designed with an epoxy resin that is reinforced with glass fibers woven into the resin. Perfboards, on the other hand, tend to be made with cheaper materials like phenolic paper.
A standard PCB substrate can be reinforced using woven materials like glass or non-woven materials. Many prefer woven boards because they are durable and affordable. However, woven boards are not ideal for frequency sensitive applications. Many boards designed for RF purposes will use non-woven reinforced boards or even boards that are not reinforced at all.
A very thin layer of copper foil is then applied to the top of the substrate. A combination of powerful adhesive and high temperatures is used to laminate the board with the copper foil. Many boards contain a layer of copper on both sides. Though, it is cheaper to only laminate a single side of the board, thus low-cost electronics often do not use double sided boards. It’s possible for a single board to contain many layers of copper on one side. A motherboard in a laptop, for example, may contain more than 15 layers of copper.
The copper is then etched to separate lines that connect one point to another. These lines are known as traces and the points that they connect correspond to the leads of various components. The board must be etched so that all of the components do not share a single electrical connection. Only the points connected by the traces share a connection.
A soldermask is then applied to the top of the copper. Soldermasks are most often green. When looking at the circuit’s soldermask you can usually see what areas of the board are copper, where the traces are, and all of the points where components need to be placed. The soldermask is meant to protect the copper traces from any sort of contact with other metal pieces or solder.
The soldermask should leave small areas exposed where the components will be soldered to the board. If the components use through hole technology, then the exposed areas may need to have a hole drilled so that the pins or leads can be inserted into the board. More modern surface mount components do not need holes.
The final layer of the PCB is the silkscreen. These are small, white decals that add useful information to the board. They can be used to label certain areas of the board with numbers, letters, or shapes. Silkscreens often make it easier to determine what a certain part of the board is used for if viewed after assembly.
As someone who is new to electronics, you may not find yourself designing and ordering professional PCBs just yet. However, it’s always a great idea to stock up on as many DOT PCBs as you might need. One final recommendation is to invest in a breadboard.
A breadboard is plastic circuit board with internal electrical connections. It’s used to create temporary circuits that require no soldering at all. Once completed, you can remove the circuit from the breadboard and rebuild the design on your DOT PCB.