The current PCB circuit board primarily consists of the following components:

1. Circuit and pattern (Pattern): The circuit serves as a medium for conduction between components. In the design phase, a large copper area is often included to function as a grounding and power layer. The routing and layout are created simultaneously.

2. Dielectric layer (Dielectric): This layer is essential for maintaining insulation between the circuits and layers, commonly referred to as the substrate.

3. Holes (Through hole / via): Through holes allow connections between traces on multiple levels. Larger through holes are utilized for component insertion. Additionally, there are non-through holes (nPTH), which are typically employed for surface mount positioning and for securing screws during assembly.


4. **Solder Resistant / Solder Mask**: Not all copper surfaces require a tin coating; thus, non-tinned areas are printed with a layer of insulating material (typically epoxy resin) to protect the copper from tin corrosion. This helps prevent short circuits between non-tinned circuits. Depending on the process used, solder masks can be categorized into green oil, red oil, and blue oil.

5. **Silk Screen (Legend / Marking / Silk Screen)**: This component is not essential but serves a crucial purpose. Its primary function is to label the names and positions of each component on the circuit board, facilitating maintenance and identification post-assembly.

6. **Surface Finish**: Given that copper surfaces can oxidize easily in typical environments, those areas that require tinning must be protected to ensure good solderability. Protection methods include HASL, ENIG, Immersion Silver, Immersion Tin, and OSP. Each method has its unique advantages and disadvantages, collectively referred to as surface treatment.

### PCB Board Features

1. **High Density**: Over the decades, the high-density of printed circuit boards has evolved alongside advancements in integrated circuit integration and mounting technology.

2. **High Reliability**: Through rigorous inspections, testing, and aging assessments, PCBs can reliably function for extended periods, often up to 20 years.

3. **Designability**: PCB performance requirements (electrical, physical, chemical, mechanical, etc.) can be effectively achieved through design standardization, resulting in shorter development times and higher efficiency.

4. **Manufacturability**: With modern management practices, PCB production can be standardized, scaled, and automated, ensuring consistent product quality.

5. **Testability**: A comprehensive set of testing methods, standards, and various testing equipment has been established to evaluate the eligibility and lifespan of PCB products.

6. **Assemblability**: PCB products facilitate the standardized assembly of various components and enable automated, large-scale production. Additionally, PCBs can be integrated with various components to create larger assemblies and systems, ultimately leading to complete machines.

7. **Maintainability**: As PCB products and their associated components are designed for standardization and mass production, they are interchangeable. This allows for quick and flexible replacements in the event of system failures, enabling rapid restoration of functionality. Other benefits include miniaturization, weight reduction, and high-speed signal transmission.