SMT, SMA and their assembly
1. SMT
Electronic circuit surface mount technology (SMT: Surface Mount Technology) is also known as surface mount or surface mount technology. It is a kind of surface assembly components without leads or short leads (SMC/SMD for short, often called chip components) placed on the surface of a printed circuit board (PCB: Printed Circuit Board) or the surface of other substrates. Circuit assembly technology in which reflow soldering or dip soldering is used for soldering and assembly. SMT consists of surface assembly components, circuit substrates, assembly design, assembly materials, assembly processes, assembly equipment, assembly quality testing, assembly system control and management and other technologies. It is a project involving microelectronics, precision machinery, automatic control, welding, Comprehensive engineering science and technology in various disciplines and disciplines, such as fine chemicals, materials, and testing.
2. SMA
PCB-level electronic circuit products assembled by SMT (SMT products for short) are also called surface mount assemblies (SMA: Surface Mount Assemblies) or printed circuit board assemblies (PCBA: Printed Circuit Board Assem ble) as shown in Figure 1.1 (a) A partial schematic diagram of the SMA with SMC/SMD assembled on one side of the PCB. Figure 1.1(b) shows the actual one-sided assembled SMA.
SMA schematic diagram of single-sided assembly of SMC/SMD
Figure 1.1 Schematic diagram of SMA with single-sided assembly of SMC/SMD
(A) A partial schematic diagram of SMA with PCB single-sided assembling SMC/SMD; (b) Single-sided assembling SMA in kind. 1-PCB; 2—metallized end; 3-component; 4—device; 5—short lead; 6—connector.
3. SMT assembly process and assembly system «
SMT has surface assembly methods such as single-sided assembly and double-sided assembly, and correspondingly have different process flow. Its main process technology includes solder paste coating (typically printing), adhesive coating (typically dispensing), patch (also called mounting), soldering, cleaning, testing, rework, etc. Its main assembly equipment includes soldering Paste screen printers, glue dispensers, placement machines, reflow soldering furnaces, wave soldering furnaces, cleaning equipment, testing equipment, rework equipment, etc. Generally, the main equipment such as screen printing machine, placement machine, and reflow soldering furnace forms an SMT production line), and then forms an SMT product (SMA) assembly production system together with other auxiliary equipment.
SMT product assembly production system is referred to as SMT assembly system for short. Due to the development of SMT and its products, there are also complete assembly of SMC/SMD on the PCB (known as full surface assembly), mixed assembly of surface assembly and plug-in assembly, and only assembly on one side of the PCB or on both sides. There are various product assembly forms such as all assembly, and the concept of SMT assembly system also has a broad sense corresponding to it. In actual production, a hybrid assembly production system including plug-in technology and equipment is often referred to as an SMT assembly system. Figure 1.4 is a schematic diagram of the basic composition of the SMT assembly system used in hybrid assembly.