Summary： Surface-mount technology (SMT) is a method for producing electronic circuits in which the components are mounted or placed directly onto the surface of printed circuit boards (PCBs).
Introduction:
Surface-mount technology (SMT) is a method for producing electronic circuits in which the components are mounted or placed directly onto the surface of printed circuit boards (PCBs). An electronic device so made is called a surface-mount device (SMD). In industry, it has largely replaced the through-hole technology construction method of fitting components with wire leads into holes in the circuit board. Both technologies can be used on the same board, with the through-hole technology used for components not suitable for surface mounting such as large transformers and heat-sinked power semiconductors. By employing SMT, the production process speeds up, but the risk of defects also increase due to component miniaturization and to the denser packing of boards. In those conditions, detection of failures has become critical for any SMT manufacturing process. An SMT component is usually smaller than its through-hole counterpart because it has either smaller leads or no leads at all. It may have short pins or leads of various styles, flat contacts, a matrix of solder balls (BGAs), or terminations on the body of the component.
Main Contents of SMT:
SMT is a very complex system engineering, whose basic composition includes surface assembly components, assembly substrate, assembly materials, assembly process, assembly design, detection technology, assembly and detection equipment, control and management and many other contents and technologies. See the figure below.
1. Assembly Components:
1) Design: Structural dimension, terminal form, welding resistance.
2) Manufacturing: The manufacturing technologies of various of components.
3) Packaging: Braided type, pipe type, tray, bulk, etc.
2. Substrates of PCB: Single side PCB, double layers PCB, aluminum substrate, copper substrate, ceramic substrate, etc.
3. Assembly Design: Electrical design, thermal insulation design, component layout design, substrate graphic layout design, etc.
4. Assembly Process:
1) Assembly Materials: Adhesive, solder, flux, cleaning agent, etc.
2) Assembly Technologies: Coating technology, paste technology, welding technology, cleaning technology, testing technology and so on.
3) Assembly Equipment: Coating equipment, bonding machine, welding machine, cleaning machine, testing equipment and so on.
4) Assembly system control and management: Assembly line or system composition, control and management, etc.
5. Detection Technologies:
1) Vision Inspection.
2) Automated Optical Inspection(AOI).
3) X-Ray Testing.
4) Ultrasonic detection.
5) ICT & FCT.
Basic Contents of SMT Process:
The basic content of SMT process technology can be divided into four parts: assembly material selection, assembly process design, assembly technology and application of assembly equipment, as shown in the following figure:
SMT Process:
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