In our life, most of the electronic products, whether household appliances or some equipment machinery, which almost all contain PCB, PCB is one of the indispensable core functions, supporting the rapid development of social civilization. What is the difference between PCB and PCBA?PCB is the abbreviation of printed circuit board, and PCBA is the abbreviation of printed circuit board assembly, that is, the manufacture of PCB boards and related capacitors, resistors and other electronic components assembled to achieve the preset function of the PCB board, to ensure that it can work properly.The assembly of the PCB is also a precision work, and the process of assembling it will affect the performance and service life of the product, but also the whole product is also related to the performance and service life of the product. PCB assembly is also a precision work, its assembly process will affect the product performance and service life, but also related to the production cost of the entire product and delivery time. As a practitioner in the electronics industry, in-depth knowledge of PCB assembly will help our products to maintain an advantage in the market.

Definition of PCB Assembly

What is PCB assembly?PCB assembly is a series of processes to assemble electronic components into PCB boards.After assembly, the PCB boards form an effective circuit system to realize the function of product design. This process is not just a simple matter of attaching electronic components to the PCB, but also requires testing and other aspects to ensure that the board can be used properly. Assembly technologies are categorized into Surface Mount Technology (SMT) and Through Hole Technology (THT):
- Through-hole insertion technology (THT): Electronic components need to be inserted into the holes on the PCB board and then soldered, like some pressure-bearing components used.
- Surface Mount Technology (SMT): Through automated equipment, electronic components can be pasted on the PCB, generally applicable to small products.

PCB assembly application areas

PCB assembly technology has a wide range of application areas, from ordinary consumer electronics to high-end industrial equipment, in all kinds of electronic products have its figure, the common application areas are as follows:
- Life consumer electronics: cell phones, computers, smart watches, televisions, refrigerators, air conditioners, washing machines and so on.
- Automotive industrial electronics: intelligent seats, intelligent driving systems, electronic mirrors and so on.
- Medical equipment: respiratory machines, X-ray machines, ECG machines, ultrasound equipment, MRI equipment, blood glucose meters, pacemakers, etc.
- Industrial equipment: CNC machine tools, inverters, drones, industrial robots, programmable logic controllers, automatic conveyor systems, etc.

PCB assembly process

PCB assembly is a precise and complex work, involving multiple processes, each process will have an impact on the final product quality, so you need to control the precision operation of each step, generally speaking, PCB assembly is divided into the following steps:
- 1. solder paste printing: The role of the solder paste is in the subsequent operation process, after heating will melt, which contains the tin and flux, can be fixed components on the PCB, generally through screen printing technology, can be accurately printed on the pads of the PCB board.
- 2. Component placement: That is, according to the PCB design documents, the electronic components will be mounted on the PCB corresponding position, this step requires very precise instruments, like high-density circuit board precision requirements are higher, generally through the SMT placement machine to achieve.
- 3. Reflow Soldering: After the electronic components are mounted and fixed, the solder paste in the first step needs to be heated and melted, and then the components will be fixed and soldered to the pads, this process requires the use of reflow soldering furnace.
- 4. Inserted components welding (THT): In addition to the soldered components, there are some electronic components need to be inserted, manually or through the equipment, inserted, and then wave soldering machine to the electronic components to be soldered.
- 5. Detection and Repair: After the electronic components are welded to the circuit board, they also need to be detected, generally automatic optical inspection (AOI) and X-ray inspection, if the product is detected to have welding defects problems, it needs to be repaired or scrapped.
- 6. Functional testing: The final step is to comprehensively test the entire circuit board to ensure that all components work properly, the circuit board function to achieve all the design features.

PCB assembly equipment

PCB assembly relies on a variety of precision instruments and equipment, advanced equipment will greatly improve production efficiency and product quality, process, will generally use the following equipment:
- Screen printing machine: In the process of one “solder paste printing” will be used, the solder paste will be printed evenly to the PCB board pads.
- SMT mounter: in the “component placement” process will be encountered, can be high-speed electronic components automatically mounted to the PCB board, high precision requirements.
- Reflow Oven: Used to melt solder paste, need to realize specific temperature profile.
- AOI Inspection Equipment: This is optical inspection equipment that automatically detects whether the solder joints are in the correct position by means of a camera and a specific algorithm.
- X-ray Inspection Equipment: For blind areas that cannot be recognized by AOI equipment, soldering can be detected with X-rays.

PCB Assembly Tips

In the process of PCB assembly, mastering some practical methods and techniques can improve assembly efficiency and reduce product defects, the following 3 practical tips are prepared:
- Precision of Solder Paste Printing: Control the precision of screen printing machine, because if the solder paste is not uniform as well as the thickness is not suitable, it will affect the quality of soldering.
- Temperature profile control: Not all components have the same sensitivity to temperature, all need to reflow soldering, precise control of the temperature profile.
- Anti-static protection: During the assembly process, good anti-static measures can effectively reduce the damage of sensitive components.

PCB Assembly Common Problems

Although PCB assembly technology has been highly automated and sophisticated, the actual operation will still appear some common problems that need to be found and solved in a timely manner.
No matter how automated the PCB assembly technology has developed, some problems will inevitably occur during operation, and the following are 4 common problems in the PCB assembly process:
- Soldering defects: If there is a circuit to ask for failure, it may be a soldering problem, there is a cold soldering false soldering, usually caused by uneven solder paste or improper temperature.
- Component misalignment: This is caused by the positioning offset when the patch, you need to check the accuracy of the mounter as well as positioning, make timely adjustments.
- Short open circuit: Need to check whether the circuit connection in the PCB design file is correct, check the production process after checking.
- Component damage: Generally in the reflow soldering, the temperature is too sensitive to the components are susceptible to damage, or improper operation, electrostatic damage to the electronic components.

Cost components of PCB assembly

What are the costs involved in assembling a circuit board and electronic components into a circuit board that can fulfill a complete function? The following four costs are generally required:
- Material Costs: For purchasing materials such as PCB boards and electronic components.
- Processing costs: Processing costs for the entire process such as solder paste printing.
- Equipment depreciation: Assembly equipment will produce wear and tear after use, need depreciation costs.
- Labor Costs: Some processes require the use of labor, all need some labor costs.
If the circuit board line is more complex, more electronic components and high precision requirements, then the cost will rise accordingly, so in the product design, you need to be based on market demand for a reasonable design of the product features, balanced product performance and manufacturing costs.

A company that provides PCB assembly services

PCB assembly involves a lot of processes and precision instruments, which is a considerable investment, so most companies will outsource the manufacturing and assembly of PCBs to professional suppliers, we recommend three companies that provide PCB assembly services.
- Foxconn: Fortune 500 company, OEM for Apple and other technology companies, providing electronics manufacturing and assembly services.
- Zero One Solution Limited: A veteran PCB service provider with thirteen years of experience, providing one-stop solutions from PCB design to manufacturing and assembly, with offices around the world and serving global customers.
- Jabil Technology (Jabil): Also a provider of complete PCB solutions.
The above is all about PCB assembly, the electronics industry has great prospects for development, a variety of electronic products are emerging, the demand for PCB is also increasing, for practitioners in the field of electronics, mastering the assembly process of PCB will enhance our understanding of the product, so that we can compete in the market to gain more advantages.