Electronics manufacturing using surface-mount technology (SMT) simply means that electronic components are assembled with automated machines that place components on the surface of a board (printed circuit board, PCB). In contrast to conventional through-hole technology (THT) processes, SMT components are placed directly on the surface of a PCB instead of being soldered to a wire lead.When it comes to electronic assembly, SMT is the most frequently used process in the industry.Electronic assembly encompasses not only placing and soldering components to the PCB, but also the following production steps:
Applying soldering paste, which is made of tin particles and flux, to the PCB
Placing SMT components to the soldering paste on the PCB
Soldering the boards with a reflow process.
Applying Soldering Paste
Applying soldering paste is one of the first steps in the SMT assembly process. Soldering paste is “printed” on the boards using the silk-screen method. Depending on the design of the board, different stainless-steel stencils for “printing” the paste onto the board and various product-specific pastes are used.
Component Placement and Assembly
The electronic components to be assembled come in trays or reels, which are then loaded into the SMT machine. During the loading process, intelligent software systems ensure that components are not inadvertently switched or misloaded. The SMT assembly machine then automatically removes each component with a vacuum pipette from its tray or reel and places it on its correct position on the board using precise pre-programmed X-Y coordinates.
Component Soldering
To solder electronic components, we use two different methods, each of which has distinct advantages depending on the order quantity. For series production orders, the Reflow-soldering process is used. During this process, boards are put in a nitrogen atmosphere and are gradually warmed up with heated air until the soldering paste melts and the flux vaporizes, which fuses the components to the PCB. After this stage, the boards are cooled off. As the tin in the soldering paste hardens, the components become permanently affixed to the board and the SMT assembly process is completed.
AOI and Visual Check
Soldering is the second-to-last step of the SMT assembly process. In order to ensure the quality of the assembled boards, or to catch and correct a mistake, AOI visual inspections are performed for almost all series production orders.
