An Introduction to the Types of Printed Circuit Boards
Because we live in a technology-driven time, you likely aren’t surprised to hear that you use dozens of circuit boards every day. But have you ever stopped to consider how many printed circuit boards you actually interact with? For example, how many PCBs do you rely on to get ready in the morning? Probably a lot more than you realize.
First, your alarm goes off, and you send signals through its circuit board every time you hit “Snooze.” Then, you wander into the bathroom to get ready. If you use an electronic razor or an electric toothbrush, you use additional circuit boards.
As you prepare breakfast, you activate multiple PCBs when you push buttons on the microwave, start your coffee machine, put a bagel into your toaster, or blend yourself a fruit smoothie. Do you watch the morning news while you eat? The PCB in your TV remote helped you find your favorite channel and adjust the volume.
Before you head out the door, you likely check your email and social media accounts. Whether you use your smartphone, your laptop, or your tablet to perform this task, the hidden PCBs inside the device processed your requests.
The scenario above demonstrates just how deeply PCBs have become integrated into modern life. The numerous applications for PCBs are possible in part because these integral parts can be made in various forms. Manufacturers choose what PCB type to use in a particular product based on its needs. Familiarize yourself with the major types of PCBs using the information below.
This type of printed circuit board contains just one layer of substrate, or base material. One side of the substrate is covered with a thin layer of metal, typically copper because it’s an excellent electrical conductor. Usually, a protective solder mask sits on top of the copper layer, and a final silkscreen coat may be applied to the top to mark parts of the board.
A single-sided PCB has electronic components and circuits on only one side. This type of board works best for simple electronics, and at-home hobbyists often design and construct this type of board first. Single-sided boards tend to cost less to mass-produce than other board types. But despite this low cost, they’re used infrequently because of their inherent design limitations.
Double-sided PCBs are much more common than single-sided boards. Both sides of the substrate have metal conductive layers, and parts are attached to both sides as well. Holes in the board allow circuits on one side to connect to circuits on the other side.
Double-sided circuit boards connect the circuits on each side using one of two methods: through-hole technology and surface mount technology. Through-hole technology involves feeding tiny wires, known as leads, through the holes and soldering each end to the appropriate component or circuit.
Unlike through-hole technology, surface mount technology does not use wires. Instead, many small leads get soldered directly onto the PCB. Surface mount technology allows more circuits to be made in a smaller space on a board, meaning the board can perform more functions, usually at a lower weight and at faster speeds than through-hole boards allow.
Multilayer PCBs expand on the technology used in double-sided boards. They have several layers of substrate boards, and insulating materials separate the individual layers. As with double-sided boards, components on multilayer boards can connect to each other through holes, or vias, in the board.
The multilayer design saves even more space than a double-sided design. Typical multilayer boards have 4, 6, 8, or 10 layers, but they can have more, depending on the demands of the product the board is intended for. Multilayer PCBs are found in equipment like computers, servers, medical machinery, and hand-held devices.
In addition to having various numbers of layers and sides, PCBs can also come in varying rigidities. Most consumers typically think of rigid PCBs when they picture a circuit board. Rigid PCBs use a solid, inflexible substrate material such as fiberglass that keeps the board from bending. A motherboard inside the tower of a desktop computer is a good example of a rigid PCB.
The substrate in a flex PCB is usually a flexible plastic. This underlying material allows the board to fit into shapes that rigid boards cannot and to bend or move during use without damaging the circuits on the board.
Although flex PCBs tend to cost more to design and produce than rigid PCBs, they come with a number of advantages. For example, they can replace heavy or bulky wiring in advanced equipment, like satellites, where weight and space matter. Flex PCBs can also come in single-sided, double-sided, or multilayer formats.
These boards combine technology from both rigid and flex circuit boards. A simple rigid-flex PCBs consists of a rigid circuit board that attaches to a flex circuit board. Rigid-flex boards can be more complex if design needs demand.
This blog only offers a limited view into the complex world of printed circuit boards. Manufacturers keep developing new PCB designs and technology that allow for the creation of advanced consumer electronics, medical and communication equipment, scientific systems, and other technologies. Contact a PCB manufacturer to learn more.