**Is a PCB board different from an integrated circuit? What is the difference?**
**Composition of a PCB Board by the Manufacturer**
A typical circuit board is primarily composed of the following elements:
1. **Circuit and Pattern (Pattern):** The circuit serves as a means for electrical conduction between components. During the design process, a large copper area is often included as a grounding and power layer. The routing and patterning are done simultaneously.
2. **Dielectric Layer (Dielectric):** This layer ensures insulation between the circuits and layers, commonly referred to as the substrate.
3. **Holes (Through Hole / Via):** Through holes connect circuits between different layers. Larger holes are used for component lead insertion. Additionally, there are non-through holes (nPTH), typically used for surface mount component positioning or for fixing screws during assembly.
4. **Solder Resist / Solder Mask:** Not all copper areas require soldering. To prevent unwanted solder flow, a layer of material (usually epoxy resin) is applied to protect the non-soldered copper areas, thus avoiding short circuits. Solder masks come in various colors, including green, red, and blue, depending on the process used.
5. **Silkscreen (Legend / Marking / Silkscreen):** Although not essential, the silkscreen layer is used to label the names and placement of components on the board. This is helpful for maintenance and identification after assembly.
6. **Surface Finish:** To prevent oxidation, which can impair solderability, copper surfaces are typically protected with a surface finish. Common protection methods include HASL, ENIG, Immersion Silver, Immersion Tin, and OSP. Each method has its advantages and disadvantages, and they are collectively referred to as surface treatments.
**PCB Board Features**
1. **High Density**: For decades, the high-density of printed circuit boards has evolved alongside advancements in integrated circuit integration and mounting technology.
2. **High Reliability**: Through a series of inspections, testing, and aging tests, PCBs are designed to function reliably for extended periods (typically around 20 years).
3. **Design Flexibility**: PCB design can be achieved efficiently and with high precision to meet electrical, physical, chemical, and mechanical performance requirements. This is made possible through design standardization and modular approaches.
4. **Manufacturability**: With modern management techniques, PCBs can be standardized, scaled (quantified), and automated, ensuring consistency in product quality.
5. **Testability**: A comprehensive array of testing methods, standards, and instruments have been established to assess the eligibility and service life of PCB products.
6. **Assemblability**: PCB products are designed not only for standardized component assembly but also for automated, large-scale production. Additionally, PCBs can be integrated with various components to form larger systems or even complete machines.
7. **Maintainability**: Due to the standardized design and mass production of PCB products and their components, repairs and replacements can be made quickly, allowing the system to be restored efficiently. Furthermore, the design allows for system miniaturization, weight reduction, and high-speed signal transmission.
**Integrated Circuit Characteristics**
Integrated circuits (ICs) offer several advantages, including small size, light weight, fewer lead wires and soldering points, long lifespan, high reliability, and excellent performance. Additionally, ICs are cost-effective and ideal for mass production. These benefits make ICs widely used in both industrial and civilian applications such as tape recorders, televisions, and computers, as well as in military, communication, and remote control systems. By using ICs, the assembly density of electronic devices can increase tens or even thousands of times compared to traditional transistors, significantly extending the operational lifespan of the equipment.
**Application Examples of Integrated Circuits**
1. **555 Touch Timer Switch**
The integrated circuit IC1 is a 555 timer configured as a monostable circuit. In normal operation, with no induced voltage on the P terminal of the touch pad, the capacitor C1 discharges through pin 7 of the 555. As a result, the output at pin 3 remains low, and the relay KS is deactivated, keeping the light off.
To turn on the light, the user touches the metal plate P, causing a voltage signal induced by the human body to trigger the 555 timer via C2. This changes the output at pin 3 from low to high, activating the relay KS and turning the light on. At the same time, pin 7 of the 555 disconnects internally, and the power supply begins to charge C1 through R1, initiating the timing process.
When the voltage on capacitor C1 reaches 2/3 of the supply voltage, pin 7 of the 555 discharges C1, causing the output at pin 3 to switch from high to low, deactivating the relay and turning the light off. The timing ends.
The timing duration is determined by R1 and C1: T1 = 1.1 * R1 * C1. With the component values shown, the timing duration is approximately 4 minutes. D1 can be either 1N4148 or 1N4001.
2. **Single-to-Dual Power Supply Circuit in PCB Design**
In the circuit shown, the 555 timer is configured as an astable multivibrator, with pin 3 producing a 20 kHz square wave with a 1:1 duty cycle. When pin 3 is high, C4 charges, and when pin 3 is low, C3 charges. Due to the presence of diodes VD1 and VD2, C3 and C4 only charge and do not discharge in the circuit, and the maximum charging value is equal to EC. By connecting the B terminal to ground, a dual power supply of +/-EC is generated between points A and C. The output current of this circuit exceeds 50mA.
**Difference Between PCB and Integrated Circuits**
An integrated circuit (IC) generally refers to a chip, such as the north bridge chip on a motherboard or the internal components of a CPU, which is also referred to as an “integrated block.” A printed circuit board (PCB), on the other hand, is the physical circuit board that we typically see, which includes printed connections for soldering components.
The IC, or integrated circuit, is mounted and soldered onto the PCB, which serves as its carrier. A PCB is a printed circuit board that appears in almost every electronic device. Whenever an electronic device contains components, those components are usually mounted on PCBs of various sizes. Besides holding components in place, the primary function of the PCB is to provide electrical connections between the various components.
In simple terms, an integrated circuit integrates a complete circuit into a single chip. Once an IC is damaged internally, the entire chip is compromised. In contrast, a PCB can be repaired by replacing individual components if they fail.
The above outlines the key characteristics and distinctions between PCB boards and integrated circuits in PCB layout design.
