A Printed Circuit Board (PCB) is a fundamental component in nearly all electronic devices. Any device that incorporates electronic parts will have them mounted on a PCB, regardless of the board’s size. Beyond providing a platform for mounting components, the primary role of a PCB is to establish electrical connections between these components. As electronic devices evolve and become more complex, the demand for additional components and tighter circuit densities increases, causing PCBs to grow increasingly intricate. The most basic form of PCB, before components are added, is often referred to as a *Printed Wiring Board (PWB)*.
The core structure of a PCB consists of a base layer made from insulating materials, designed to be durable and resistant to bending or heat. The visible circuit pathways on the board are made from copper foil. Initially, the copper foil covers the entire surface of the board, but during manufacturing, parts of it are chemically etched away. What remains forms a network of tiny lines, called conductor patterns or traces. These traces serve as the electrical pathways that connect various components on the PCB, enabling them to work together in a functional circuit.
To secure components on a PCB, we solder their pins directly onto the copper traces. On a basic PCB (single-sided), components are placed on one side, and the wiring is on the other. To connect the components, we create holes through the board, allowing the component pins to pass through and be soldered on the opposite side. This results in the two sides of the PCB being referred to as the Component Side (where components are mounted) and the Solder Side (where soldering takes place).
In cases where a component might need to be removed or replaced after assembly, a socket is used during installation. Sockets are soldered onto the board, allowing the components to be easily inserted, removed, or replaced. A commonly used socket type is the ZIF (Zero Insertion Force) socket, often employed for CPUs. This socket design allows easy insertion and removal of the component, with a fixing mechanism to secure it once installed.
To connect two PCBs together, we typically use an edge connector, often called a “golden finger.” This connector features several exposed copper pads, which are part of the PCB’s wiring. The golden finger on one PCB is inserted into a corresponding slot on another PCB (often referred to as an expansion slot). This method is commonly used in computers to connect expansion cards such as display cards or sound cards to the motherboard.
The color green or brown visible on a PCB is the solder mask, which serves as an insulating layer. This protective coating helps maintain the integrity of the copper traces and prevents accidental soldering to the wrong locations. A silkscreen layer is often printed over the solder mask, displaying symbols or text (usually white) to indicate the correct positioning of components. This printed layer is known as the “legend” layer.
### Single-Sided PCBs
In the simplest type of PCB, components are placed on one side, and the wiring is on the other. Since all the traces are confined to one side, we call this a single-sided PCB. Single-sided boards impose significant design limitations, particularly when routing traces, as they cannot intersperse or overlap. Consequently, this type of board is primarily used for basic, early-stage circuit designs.
### Double-Sided PCBs
A double-sided PCB has copper traces on both sides, enabling more complex designs. To facilitate connections between the two sides, vias are used. A via is a small hole in the PCB that is either plated or filled with metal to connect traces from both sides of the board. Since a double-sided PCB provides twice the wiring area of a single-sided board and allows for more flexible trace routing, it is better suited for more advanced circuits that require higher density and complexity.
### Multilayer PCBs
To accommodate even more wiring, multilayer PCBs use multiple single- or double-sided boards stacked together, with insulating layers between them. These boards are pressed and bonded to form a single unit. The number of layers refers to the number of independent wiring planes, and this can range from a few to dozens. While most motherboards typically have 4 to 8 layers, it is possible to create boards with up to 100 layers. Such multilayer PCBs are often used in high-performance systems, such as large-scale supercomputers. However, with the advent of clusters of individual computers, these extremely multilayered boards are becoming less common. Although the internal layers of a multilayer PCB are hidden, careful inspection of a motherboard may reveal layer count indicators on the surface.
By using a combination of single-sided, double-sided, and multilayer designs, modern PCBs can support increasingly complex circuits, offering both efficiency and scalability in electronic systems.
The core structure of a PCB consists of a base layer made from insulating materials, designed to be durable and resistant to bending or heat. The visible circuit pathways on the board are made from copper foil. Initially, the copper foil covers the entire surface of the board, but during manufacturing, parts of it are chemically etched away. What remains forms a network of tiny lines, called conductor patterns or traces. These traces serve as the electrical pathways that connect various components on the PCB, enabling them to work together in a functional circuit.
To secure components on a PCB, we solder their pins directly onto the copper traces. On a basic PCB (single-sided), components are placed on one side, and the wiring is on the other. To connect the components, we create holes through the board, allowing the component pins to pass through and be soldered on the opposite side. This results in the two sides of the PCB being referred to as the Component Side (where components are mounted) and the Solder Side (where soldering takes place).
In cases where a component might need to be removed or replaced after assembly, a socket is used during installation. Sockets are soldered onto the board, allowing the components to be easily inserted, removed, or replaced. A commonly used socket type is the ZIF (Zero Insertion Force) socket, often employed for CPUs. This socket design allows easy insertion and removal of the component, with a fixing mechanism to secure it once installed.
To connect two PCBs together, we typically use an edge connector, often called a “golden finger.” This connector features several exposed copper pads, which are part of the PCB’s wiring. The golden finger on one PCB is inserted into a corresponding slot on another PCB (often referred to as an expansion slot). This method is commonly used in computers to connect expansion cards such as display cards or sound cards to the motherboard.
The color green or brown visible on a PCB is the solder mask, which serves as an insulating layer. This protective coating helps maintain the integrity of the copper traces and prevents accidental soldering to the wrong locations. A silkscreen layer is often printed over the solder mask, displaying symbols or text (usually white) to indicate the correct positioning of components. This printed layer is known as the “legend” layer.
### Single-Sided PCBs
In the simplest type of PCB, components are placed on one side, and the wiring is on the other. Since all the traces are confined to one side, we call this a single-sided PCB. Single-sided boards impose significant design limitations, particularly when routing traces, as they cannot intersperse or overlap. Consequently, this type of board is primarily used for basic, early-stage circuit designs.
### Double-Sided PCBs
A double-sided PCB has copper traces on both sides, enabling more complex designs. To facilitate connections between the two sides, vias are used. A via is a small hole in the PCB that is either plated or filled with metal to connect traces from both sides of the board. Since a double-sided PCB provides twice the wiring area of a single-sided board and allows for more flexible trace routing, it is better suited for more advanced circuits that require higher density and complexity.
### Multilayer PCBs
To accommodate even more wiring, multilayer PCBs use multiple single- or double-sided boards stacked together, with insulating layers between them. These boards are pressed and bonded to form a single unit. The number of layers refers to the number of independent wiring planes, and this can range from a few to dozens. While most motherboards typically have 4 to 8 layers, it is possible to create boards with up to 100 layers. Such multilayer PCBs are often used in high-performance systems, such as large-scale supercomputers. However, with the advent of clusters of individual computers, these extremely multilayered boards are becoming less common. Although the internal layers of a multilayer PCB are hidden, careful inspection of a motherboard may reveal layer count indicators on the surface.
By using a combination of single-sided, double-sided, and multilayer designs, modern PCBs can support increasingly complex circuits, offering both efficiency and scalability in electronic systems.
