What Are Printed Circuit Boards
The printed circuit boards (PCBs) that are the foundation of all electronics. They’re the key to enabling load balancers, power supplies, printers, elevators, phones, lights and virtually all electronic equipment to work properly.
How do circuit boards work contain electrically conductive pathways called “traces” that connect all the different electronic components to each other, allowing them to perform computing tasks. The PCB is one of the most important inventions that ushered in modern technology.
A PCB is a flat, rectangular piece of material made of a dielectric composite material that’s laminated to either fiberglass or a metal substrate. The traces are typically copper, but other metals can be used in special applications. Dielectrics are chosen to provide varying levels of insulation depending on the needs of the circuit board. The most common are polytetrafluoroethylene (Teflon), FR-4, FR-1, CEM-3, and CEM-5.
To create the conductive paths on a PCB, the bare laminate is covered with a photosensitive mask that’s imaged to expose only those areas of the circuit board that will become the conductive paths, known as traces. The exposed areas are then sensitized in a chemical bath to make them capable of bonding metal ions. The traces are then electroplated with copper. Several thicknesses are available, but 1 oz of copper per square foot is the most common.
In addition to the conductive traces, circuit boards also contain many other essential components such as resistors, capacitors, inductors, and diodes. Resistors apply a specific amount of resistance to the current, capacitors store electric charge, and inductors help block interference signals from interfering with the flow of electricity.
The advancing capabilities that these circuits enable are perhaps most evident in the computers and video games that we use today. We’ve gone from the pixelated Pong of the 1970s to the photorealistic battlefields that enable computer gamers to fight and race each other online. These technological advancements are only possible because of the incredibly complex and intricate circuit boards that drive them.
To ensure the quality of a PCB, manufacturers use visual inspection and automated optical inspection as well as JEDEC guidelines for component placement and soldering. Once the board is completed, it undergoes a number of tests to confirm that it works correctly:
The most crucial test is to verify that all conductive paths on a PCB have continuity and conductivity between adjacent layers. The manufacturer must also verify that all components are seated properly and that there’s adequate clearance between them for heat dissipation. Once these tests are complete, the final step is to check that the board satisfies its intended functions and that it’s free of defects such as shorts, open circuits and misplaced components. Finally, the board must pass inspection before it can be shipped to a customer. During shipping, the circuit board is protected by a plastic covering. This helps to prevent damage from rough handling or environmental contaminants.