Printed Circuit Boards (PCBs) are mechanical substrates used to hold and connect electronic components. Almost all modern consumer electronics and accessories use PCBs, including mobile phones, tablets, smartwatches, wireless chargers, and power supplies. These multi-material, multi-layered boards form the stable foundation of PCB assemblies (PCBAs) and are responsible for guiding electrical current between active and passive components.

　　The base layer of a PCB is typically composed of a robust, non-conductive material combination that provides insulation, waterproofing, and temperature stability. Common PCB materials include FR4, metal, and polyimide (PI). Cost savings, functional performance (e.g., thermal expansion), and environmental impact are all factors to consider when selecting PCB materials.

　　Etched onto the PCB base layer are pathways that transmit signals from point to point. These tiny features are called "traces," usually made of copper, a highly conductive material that allows electrons to move between components with minimal resistance.

　　 PCB Types

　　Different types of PCBs have different performance qualities, typically categorized by the flexibility of the substrate used. These substrates can be rigid, flexible, or a combination of both.

　　Beyond these three main types, PCBs can also be categorized by other standards, such as component placement (single-sided or double-sided PCBs), materials (metal core or ceramic PCBs), connection density, or number of layers (16-layer PCBs).

　　 PCB Application Industries

　　If it has a switch, it likely has a PCB. PCBs are used in virtually all electronic devices, with applications spanning various industries and device types.

　　High-Tech: Custom PCBs power innovation in the highly complex and rapidly evolving high-tech industry, including 5G infrastructure and high-speed data processing. These boards may utilize multiple layers and unique materials as the industry is at the forefront of device development.

　　Aerospace and Defense: Reliability is key in these applications, as the devices are often located remotely and may be subject to extreme environmental factors (e.g., temperature, vibration, or shock). Here, PCBs are used in sensors, power supplies, and navigation systems for satellites and aircraft.

　　Automotive: While PCBs can be found in the heads-up displays, airbags, advanced driver-assistance systems, etc., of all modern vehicles, they play an especially crucial role in electric vehicles, as they manage the operation of the electric motor and power delivery.

　　Energy: PCBs are critical for generating, collecting, and distributing electricity. Their reliability ensures the smooth operation of the energy sector while facilitating communication between the grid and controllers, energy storage, and system monitoring.

　　Industrial: Automated equipment used in industrial applications relies on PCBs to withstand harsh conditions, including high-voltage currents, mechanical vibrations, and extreme temperatures. They can be found in manufacturing rigs and presses, measurement equipment, and high-speed video capture.

　　 PCB Design Fundamentals

　　Early circuit board design relied on through-hole construction, later adopting surface mount technology (SMT). For decades, designs were hand-drawn, resulting in slow manufacturing speeds and high costs. The introduction of computers changed the entire design process, accelerating production while also improving consistency and functionality. Today's manufacturers use PCB design simulation software to model, analyze, and verify their designs at every step of development.

　　Challenges in PCB design include size constraints, thermal considerations, electromigration, mechanical integration, and power efficiency. These complexities require designers to collaborate with various specialists to ensure electrical, mechanical, and thermal engineering issues are addressed throughout the process.

　 　PCB Design Process:

　　Schematic Creation: Designers use electronic computer-aided design (ECAD) software to draw a 2D blueprint of the PCB. This determines the components of the PCB, the placement of the components, and how they are connected.

　　Material Selection: Based on the needs of the final assembly, designers select the materials to be used on the board. These choices can include FR-4, polyimide laminates, composite epoxy materials (CEM), liquid crystal polymers, etc.

　　Design Review: Before production, simulation software is used to test and verify the board's performance under various conditions. These tests ensure the component layout meets all requirements.

　 　How are PCBs Manufactured?

　　Once this process is complete, the board is ready for manufacturing. PCB manufacturing is a multi-stage process containing many key phases, but key steps include printing, etching, pressing, drilling, silkscreening, and masking.

　　First, the PCB schematic is printed onto a copper-clad substrate.

　　Then, excess copper is removed via an etching process, revealing the traces and pads of the circuit.

　　Next, materials are laminated together using high heat, and holes are drilled into the board to create mounting holes, through-hole pins, and vias.

　　Then a silkscreen layer is added, marking information such as polarity, connector names, and company logos on the surface.

　　Finally, a solder mask is applied to prevent oxidation and solder bridging.

　　 The Future of PCBs

　　As a mainstay of modern electronics, PCBs will continue to evolve as the devices and machines they power become smaller, more flexible, and more powerful. Miniaturization, as well as transparent and stretchable materials, will allow PCBs to complement electronic designs in a variety of interesting ways. With electrification driving innovation in automotive and aerospace, PCBs will play a significant role in defining how cleaner energy powers systems such as communication and navigation.