About PCB and PCBA

What are PCB and PCBA?

When you hold a smartphone or work on a computer, have you ever thought about the structural secrets behind these high-tech products? This guide will focus on two basic concepts of the electronics industry – PCB and PCBA, to help you clarify the essential differences between them and appreciate the microscopic beauty of the electronic world.
Printed Circuit Board (PCB) is known as the “skeleton” of electronic products. It is a basic platform that carries and connects electronic components. Through the preset copper circuit diagram, current can be accurately directed and transmitted between different electronic components. To put it figuratively, PCB is like a city’s transportation network, determining the direction and efficiency of the flow of information and energy.
Printed Circuit Board Assembly (PCBA), which is a finished product further processed on the basis of PCB. That is, the “assembled printed circuit board”. At this stage, PCB is no longer a simple circuit carrier, but undergoes a series of precision processes such as SMT (Surface Mount Technology) or THT (Through Hole Technology) to integrate various electronic components such as resistors, capacitors, and IC chips. It is precisely installed and welded on it to make it truly “alive” to form an electronic module with specific functions.

Analyze PCB and PCBA

1-1. What types of PCB are there?
1. Single-sided PCB: This is the most basic type of PCB. As the name suggests, it has only one side covered with copper and has some lines. It is used in simple electronic devices.

2. Double-sided panels: Double-sided panels and single-sided panels are connected to each other, increasing the circuit layout on the other side, doubling the wiring space, and effectively increasing the circuit density, which is widely evaluated in mid- to low-end electronic products.

3. Multilayer boards: When electronic equipment needs to handle more complex functions, double-sided boards alone can no longer meet the needs. At this time, multilayer boards emerge as the times require. It arises from multiple mutually insulated conductive layers and dielectric layers, which greatly increases circuit density and complexity. It is commonly found in high-end computer motherboards, communication equipment and other fields.

4. HDI (High-Density Interconnect) board: PCB with high-density interconnection technology, which has thinner wires, smaller apertures and denser wiring. It is especially suitable for mobile communication equipment and consumer products that pursue miniaturization and thinness. Class equipment electronic products.

5. FPC (Flexible Printed Circuit): Also known as flexible circuit board, its base material is a film material that can be bent and folded, which can adapt to various shapes of spatial layout. It is commonly used in folding screen mobile phones, wearable devices, etc. Flexible bending occasions.

6. Rigid-flex board: It combines the advantages of hard boards and soft boards. Some areas remain hard and do not deform, while other areas can bend freely. This hybrid structure is particularly suitable for complex electronic devices that require both strength and flexibility.

7. Three-dimensional PCB: This is one of the latest development trends of PCB technology. Three-dimensional wiring is realized through stacking technology, which greatly improves the integration and performance of electronic products.

1-2. The meaning and design of PCBA
Meaning: PCBA is an “assembled printed circuit board”, which contains various components such as resistors, capacitors, and IC chips. They are accurately installed and welded on the PCB to form a fully functional circuit system. ,
Design: Engineers first convert and determine the location and connection method of each PCB on the PCB based on the circuit schematic diagram with tight product functional requirements and the PCB wiring diagram. In addition, additional PCB materials, layers and processes are used, and advanced EDA design software is used for electrical performance simulation and optimization.

1-3. PCBA processing technology

In the PCBA industry, there are two core processing technologies, namely Surface Mount Technology (SMT) and Through-Hole Technology (THT).
SMT（Surface Mount Technology）
This technology allows components to be attached directly to the PCB surface without penetrating the circuit board. This process allows components to be small in size and closely spaced, significantly improving the wiring density and space utilization of the circuit board, and is very suitable for the needs of miniaturized and lightweight electronic products.
The main process steps of SMT in XHT company
1. Solder paste printing: Use screen printing technology to evenly apply solder paste with metal powder on the corresponding pad positions of the PCB to provide soldering materials for subsequent component placement.
2. Component placement: Using a high-precision SMT placement machine, the Surface Mount Device (SMD) is accurately adsorbed, aligned and placed on the solder paste-coated pad according to the preset program.
3. Reflow soldering: The mounted PCB passes through the reflow furnace. The temperature curve set in the furnace gradually melts the solder paste, tightly combining the components with the PCB pads, and forming a stable electrical connection after cooling.
THT（Through-Hole Technology ）
This technology requires components to be fixed through the pins passing through the guide holes of the PCB, and then electrically connected by soldering to the back of the board. Although THT is slightly inferior to SMT in terms of automation and component density, it has good mechanical strength and stability, and is especially suitable for situations where it can withstand greater impact, vibration or current load.
The main process steps of THT in XHT company
1. Component plug-in: Unlike SMT, electronic components (such as DIP, PGA, etc.) under the THT process have pins, and manual or automatic plug-in machines are required to insert the component pins into the reserved via holes of the PCB.
2. Wave soldering: Then, the PCB passes through the wave soldering machine, and the solder forms a continuous wave peak in the liquid state. When the PCB passes through the wave peak, the solder naturally fills the gap between the component pins and the PCB pad to achieve firm welding.
3. Manual repair welding: For some parts that are not suitable for wave soldering or difficult to automatically weld, experienced technicians are required to perform manual repair welding to ensure the quality of each solder joint.
In actual production, XHT Company will use a combination of SMT and THT processes for many complex electronic products to achieve the best balance between performance and cost. For example, the main body of the product uses SMT to achieve a high degree of integration and miniaturization design. At the same time, for specific functional modules or parts that require high reliability, the THT process is used to ensure sturdiness and durability. Such a mixed assembly strategy fully reflects the complementary advantages between SMT and THT to enhance customers’ market competitiveness.