What is SMT mount assembly?

Surface Mount Technology (SMT) is a method of electronic component assembly in which components are mounted directly onto the surface of a printed circuit board (PCB). SMT mount assembly is the process of assembling electronic components using this technology.

In SMT mount assembly, electronic components are typically much smaller than the through-hole components used in older assembly methods. SMT components are mounted on the surface of the PCB using solder paste and reflow soldering. Solder paste is a mixture of tiny balls of solder and flux that is applied to the pads of the PCB. The components are then placed onto the solder paste and heated until the solder melts, creating a permanent bond between the component and the PCB.

SMT mount assembly has several advantages over older assembly methods. It allows for higher component density, which means that more components can be packed into a smaller space. It also allows for automated assembly, which can increase efficiency and reduce costs. Additionally, SMT mount assembly can result in more reliable connections between components and the PCB, as there are no holes that can become clogged or damaged.

What equipment is used in SMT assembly？
Pick-and-Place Machine: This machine is used to pick up components from reels or trays and place them precisely onto the PCB. It uses a vacuum nozzle to pick up the component and then places it using a precision actuator.

Reflow Oven: Once the components are placed on the PCB, the board is passed through a reflow oven to melt the solder paste and create a permanent electrical and mechanical connection between the components and the PCB.

Screen Printer: This machine is used to apply solder paste to the PCB before components are placed. It uses a stencil to deposit the paste onto the PCB in a precise pattern.

Inspection Equipment: Various types of inspection equipment are used to check the quality of the assembled PCBs. This includes automated optical inspection (AOI) systems, X-ray machines, and manual visual inspection.

Soldering Equipment: In addition to the reflow oven, various other soldering equipment may be used in SMT assembly, including soldering irons, hot air rework stations, and wave soldering machines.

PCB Cleaning Equipment: Once the PCB has been assembled, it may need to be cleaned to remove any residue or flux. This is typically done using a cleaning machine that sprays a cleaning agent onto the PCB and then rinses it with water.

What is the difference between SMT assembly and THT assembly?

Components for THT assemblies have longer leads than SMT assemblies;THT assemblies require drilling holes in the bare circuit board, whereas SMT assemblies do not, as SMCs or SMDs are mounted directly on the PCB; Wave soldering is mainly used for THT
assembly, whereas reflow soldering is mainly used for SMT assembly; SMT placement assembly can be automated, whereas THT placement assembly depends only on manual operation; components for THT assembly are heavy, high and bulky, whereas SMC helps to reduce more space.

In which product areas are SMT components used?
Currently, SMT components are used in advanced electronics, especially in computer-based and telecommunication products. In addition, SMT components are used in various areas, including medical, automotive, telecommunications, industrial control, military, aerospace, etc.

Is it necessary to clean the PCB after SMT assembly?
PCBs after SMT assembly must be cleaned before leaving the workshop, as the surface of the assembled PCB may be covered with dust, after reflow brilliant residues, such as solder, all of which can reduce the reliability of the product to some extent. It is therefore essential to clean the assembled PCB.

Why is the type of soldering used during SMT assembly?
Reflow soldering is used in SMT assembly to permanently fix components on the PCB and is carried out in a reflow oven containing temperature zones. In the reflow reflow soldering process, the solder paste is first melted at high temperatures in the first and second stages. As the temperature decreases, the solder paste hardens so that the components are are fixed to the corresponding pads on the PCB.