What is a Printed Circuit Board?

Printed Circuit Board

A printed circuit board (PCB), also called a PCW or PWB, is the building block of most electronic devices. Whether it is a single layer used in your garage door opener or the six layers of a high-speed motherboard, these rigid and flat boards hold many other electronic components and connect them to one another.

The copper pathways on a PCB allow signals to flow and carry information between the components. Depending on the complexity of the circuit, the PCB can be made with two to a dozen or more conductive copper layers. The insulating layers separate the conductive layers and provide strength and structural integrity.

Printed circuit boards, like the ones in your electronics, are designed and manufactured using a variety of complex engineering processes. They are a key technology that allows us to work in a world where electronic devices saturate every aspect of our lives. From the silent alarm clocks that quietly monitor our sleep, to the phones that never stop streaming notifications, printing circuit boards have allowed our electronic devices to become ever more sophisticated and powerful.

PCBs are the foundation of all electronic devices, including cell phones, smart watches and automotive dashboards. They allow the electrical components in a device to “talk” to each other, transmitting data and controlling their function. They are also the means by which these devices can be built and assembled in a way that was impossible in the past.

What is a Printed Circuit Board?

A PCB has three main parts: a substrate that is the base for the board, a conductive surface and an insulator. The conductive surface has metal pads that the components are soldered to, allowing them to connect to the circuitry on the board. The insulator is typically a fiberglass or epoxy, while the substrate can be made from any number of materials, such as FR4, Rogers or polyimide.

The earliest printed circuit boards, invented in 1936 by Austrian engineer Paul Eisler as part of a radio set, used a wire-wrap technique to make connections. Modern Printed Circuit Boards are much more advanced, and can have multiple layers and include blind and buried vias that reduce signal loss and crossing delays.

Once the design for a PCB is completed, it is transferred to a computerized printer that prints the circuitry on the insulator substrate. The print head on a PCB printer works similarly to a desktop inkjet or laser printer, depositing layer by layer. The PCB can be either a rigid or flexible board, and can be a single-sided or double-sided.

A PCB that has been populated with electronic components is called a PCA, or a printed circuit board assembly (PCBA). The IPC, the International Panel for Circuit Boards, prefers the term backplane assemblies to avoid confusion with bare boards.

PCBs are used in nearly every industry, from small consumer electronic products to huge pieces of industrial equipment. They are a fundamental element of the IoT, enabling devices that weren’t electronic before to gain advanced features such as connectivity and speed.