SMT Assembly
SMT Assemblies
SMT Assembly (Surface-mount Technology) simply means that electronic components are assembled using automatic machines that place components on a PCB surface.
SMT & THT
Unlike Through-hole Technology (THT) processes, SMT components are placed directly on the PCB surface instead of being soldered. When it comes to electronic assembly, SMT is the most popular method in the industry.
Apply Solder Paste
Solder paste is SMT assembly first step. Solder paste is “printed” onto the boards using a silkscreen method. Depending on the PCB design, different stainless steel templates are used to “print” the paste on the board. Once solder paste is on the boards, a 2D solder paste inspection is performed to ensure the paste is applied evenly and correctly. Once the accuracy has been confirmed, boards are transferred to the SMT assembly line, where the components will be soldered.
Component Placement & Assembly
Electronic components that are ready to be assembled come on spools, then are loaded onto the SMT machine. During the loading process, intelligent software systems ensure that components are not changed or charged. The SMT assembly machine then automatically removes each component with a vacuum pipette from its spool, and places it on the board in the correct position using pre-programmed precise XY coordinates. Our machines are capable of assembling up to 25,000 components per hour.
Once the SMT assembly is complete, the boards are moved to reflow ovens for soldering, a process which sets the components on the board.
Component Soldering
To solder electronic components, we use two different methods, each has different advantages depending on the quantity that is being produced.
For mass production projects, the reflow soldering is used. The printed circuit board is placed in a nitrogen atmosphere that is gradually being inserted with hot air until the solder paste melts and the flux vaporizes, fusing the components to the PCB. After this stage, the boards cool down. As the tin in the solder paste hardens, the components are permanently bonded to the board and the SMT assembly process is complete.
For prototypes or highly sensitive components, Vapor Phase Soldering is used. In this process, the boards are heated until the paste specific melting point is reached. This lets you solder at lower temperatures or solder different SMT components at different temperatures depending on their individual characteristics.
AOI and Visual Audit
To ensure the assembled boards quality or to detect and correct an error, Automated Optical Inspections are performed for almost PCB assemblies.
Using multiple cameras, the AOI system automatically checks each board and compares one another appearance to the correct, pre-defined reference image. If there is any deviation, the machine operator will be informed about a potential problem, who then will be able to correct the error or to remove the board from the machine for further inspection. AOI visual verification ensures consistency and accuracy in the SMT assembly production process.