Steps Involved in SMT Assembly
SMT assembly uses state-of-the-art automated equipment to set and solder surface mount components on PCBs. The process allows for much higher assembly density, enabling electronic devices to be smaller, lighter and more energy efficient. SMT assembly is used by OEMs (Original Equipment Manufacturers) and EMS (Electronics Manufacturing Services) companies to create high quality products at a faster pace than traditional THT assembly.
The first step of the smt assembly process is to prepare the component kits for the production line. Kits are assembled using a number of different materials to include all the required component parts, and they are then loaded into cartridges for use by the pick-and-place machines in the production line. Once the components are ready, the machine will read the BOM and start to place the components on the PCB. The pick-and-place machines are programmed to correctly match the component parts with their corresponding locations on the circuit board, and they also have the ability to check for proper placement via a visual inspection process known as AOI (Automated Optical Inspection).
Once the component placement is complete, the entire PCB is then passed through a reflow soldering machine (or oven) where the solder paste melts and bonds the components and the PCB together. The reflow soldering process is crucial for the quality of the final product, as it ensures that all the connections between the components and the PCB are securely made.
After the reflow soldering is complete, the assembled PCBs will undergo extensive inspection and testing to ensure the quality of the finished product. This can include automated optical inspection (AOI), X-ray inspection, performance testing and more depending on the client’s specifications.
What Are the Steps Involved in SMT Assembly?
Unlike through-hole components, SMDs cannot be mechanically secured in place before being soldered, and they are therefore usually placed on the PCB using a precision robotic arm with fine tip tweezers. This method is also much faster than a manual hand-insertion process, which can take a lot longer and can be quite error-prone due to the small size of SMDs and their narrow lead spacing.
Assembled PCBs will then pass through a final cleaning process to remove any residue from the reflow soldering process, as well as any non-washable components that were not placed in the washable part placement stage of the SMT line. Once the board is cleaned, it will be transported to the insertion stage of the line, where through-hole parts will be inserted into the appropriate locations on the printed circuit boards.
For this stage, the insertion equipment will usually use a liquid flux solution to clean the leads of each through-hole component before inserting them into their proper positions on the PCB. This process can be automated with special SMT insertion robots or manually by skilled operators. Depending on the client’s specification, additional processes like selective soldering or conformal coating may be performed to further enhance the durability and reliability of the final product. Once the insertion is complete, the final product will be inspected and tested once again.