Introduction to traditional PCB Assembly process

The basic PCB component (commonly known as the PCBA) is performed in the following manner.

Application of solder paste: apply solder paste particles mixed with flux to the bottom plate of PCB. Use templates of different sizes and shapes to ensure that paste is only applied at specific locations.

L Component placement: manually or automatically place the small electronic components of the circuit on the solder paste plate by means of picking and unloading automatic mechanism.

L Reflow: the curing of solder paste is carried out during reflow. Pass PCB board with installed component through reflow furnace with temperature over 500°F. When the solder paste is melted, it is returned to the conveyor and solidified by exposing it to a cooler.

L Inspection: This is done after reflow welding. Perform checks to check the functionality of the component. This stage is important because it helps identify misplaced components, poor connections, and short circuits. Often, misplacement occurs during reflux. PCB manufacturers use manual inspection, X-ray inspection and automatic optical inspection at this stage.

Through-hole part insertion: Many circuit boards require both through-hole and surface-mount elements to be inserted. Therefore, you are done in this step. Generally, through-hole insertion is performed using wave soldering or manual welding.

L Final inspection and cleaning: Finally, check the PCB’s potential by testing it at different currents and voltages. Once the PCB passes this stage of inspection, clean it with deionized water, as the welding will leave some residue. After washing, it is dried under compressed air and packaged beautifully.

This follows the traditional PCB assembly process. As shown, most PCBS are assembled using through-hole technology (THT), surface-mount technology (SMT), and hybrid assembly processes. These PCBA processes will be discussed further.

Through Hole Technology Conference (THT) : An introduction to the steps involved

Through hole technology (THT) differs only in a few steps of PCBA. Let’s discuss THA for PCBA steps.

L Component placement: During this process, components are installed manually by experienced engineers. The installation process of manually picking up and placing components requires maximum precision and speed to ensure the placement of components. Engineers should follow THT standards and regulations to achieve optimal functionality.

L Inspection and calibration of components: PCB boards are matched to design transport frames to ensure accurate placement of components. If any misallocation of components is found, it is corrected only then. Calibration is easier prior to welding, so component positions are corrected at this stage.

Wave soldering: In THT, wave soldering is performed to solidify the paste and keep the assembly intact in its specific position. In wave soldering, the PCB with the component installed moves over a slow-moving liquid solder that is heated at temperatures above 500°F. It is then exposed to the cooler to solidify the connection.

Surface Mount Technology assembly (SMT) : What are the different steps involved

The PCBA steps to follow in SMT assembly are as follows:

Application/printing of solder paste: apply the solder paste to the plate through the solder paste printer, referring to the design template. This ensures that solder paste is printed in a satisfactory quantity at a given location.

L Component placement: Component placement in SMT components is automatic. The circuit board is sent from the printer to the assembly mount where the assembly is picked up and placed by an automatic mechanical pickup and drop mechanism. This technique saves time compared to a manual process, and also ensures accuracy in specific component locations.

L Reflow soldering: After assembly is installed, PCB is placed in furnace where solder paste is melted and deposited around assembly. The PCB passes through the cooler to hold the component in place.

Surface mount technology (SMT) is more efficient in complex PCB assembly processes.

Due to the increasing complexity of electronic equipment and PCB design, hybrid assembly types are also used in industry. Although, as the name implies, the hybrid PCB assembly process is a merger of THT and SMT.