Printed circuit boards (PCBs) are the core of every electronic device we connect today. These PCBs. PCB basically interconnects electronic components by establishing a conductive path through copper solder pads and connecting wires. Therefore, the PCB assembly process has become one of the most interesting concepts in electronics. This article introduces the assembly process of different types of PCBs and provides insights into their functions.
Introduction to Traditional PCB Assembly Process
The basic PCB components (usually referred to as PCBA) are carried out in the following ways:
- Application of solder paste: Apply solder paste particles mixed with soldering flux onto the PCB substrate. Use templates of different sizes and shapes to ensure that the paste is only applied at specific locations.
- Component placement: With the help of an automatic pickup and release mechanism, the small electronic components of the circuit are manually or automatically placed on the solder paste board.
- Reflow: The solidification of solder paste is carried out during the reflow process. Pass the PCB board with installed components through a reflow soldering furnace with a temperature exceeding 500 ° After the solder paste melts, it is sent back to the conveyor and solidified by exposing it to the cooler.
- Inspection: This was conducted after reflow soldering. Perform checks to check the functionality of the component. This stage is important as it helps identify misplaced components, poor quality connections, and short circuits. Usually, misplacement occurs during the reflux process. PCB manufacturers use manual inspection, X-ray inspection, and automatic optical inspection at this stage.
- Insertion of through-hole parts: Many circuit boards require simultaneous insertion of through-hole and surface mount components. Therefore, it is completed in this step. Usually, through hole insertion is performed using wave soldering or manual soldering.
- Final inspection and cleaning: Finally, check the potential of the PCB board by testing it at different currents and voltages. Once the PCB board passes this stage of inspection, clean it with deionized water, as welding will leave some residue. After washing, dry it in compressed air and package it beautifully.
- This is the traditional PCB assembly process followed. As shown in the figure, most PCBs are assembled using through-hole technology (THT), surface mount technology (SMT), and hybrid assembly processes. These PCBA processes will be further discussed.
- Through-hole Technology Conference (THT): Introduction to the steps involved
The through-hole technology (THT) differs only in a few steps of PCBA. Let’s discuss the steps of THA for PCBA.
- Component placement: During this process, experienced engineers manually install the components. The installation process of manually picking and placing components requires maximum accuracy and speed to ensure component placement. Engineers should follow THT standards and regulations to achieve optimal functionality.
- Inspection and component calibration: The PCB board is matched with the designed transportation frame to ensure accurate placement of the components. If any improper allocation of components is found, correction will only be made at that time. It is relatively easy to calibrate before welding, so the position of the components has been corrected at this stage.
- Wave soldering: In THT, wave soldering is performed to solidify the solder paste and keep the component intact at its specific position. In wave soldering, the PCB board with components installed moves above the slowly moving liquid solder, which is heated at temperatures above 500 ° Then expose to the cooler to solidify the connection.
Surface Mount Technology Assembly (SMT): What are the different steps involved
The PCBA steps followed in SMT assembly are as follows:
- Application/printing of solder paste: Refer to the design template and apply the solder paste to the board through a solder paste printer. This ensures that the solder paste is printed in a satisfactory quantity at a specific location.
- Component placement: Component placement in SMT components is automatic. The circuit board is sent from the printer to the component installation rack, where the components are picked up and placed through an automatic mechanical pick-up and drop mechanism. Compared to manual processes, this technology saves time and also ensures the accuracy of specific component positions.
- Reflow soldering: After the component is installed, the PCB is placed in a furnace, and the solder paste is melted and deposited around the component. The PCB passes through the cooler to secure the component in that position.
Surface mount technology (SMT) has higher efficiency in complex PCB assembly processes.
Due to the increasing complexity of electronic equipment and PCB design, hybrid assembly types are also used in the industry. Although, as the name suggests, the hybrid PCB assembly process is a merger of THT and SMT.