The Way Of Assembly Line Of SMT Production System

The SMT production system formed by surface coating equipment, placement machines, welding machines, cleaning machines, testing equipment and other surface assembly equipment is customarily called SMT production line.

　　At present, the varieties and specifications of surface mount components are not complete, so some through-hole (THT) components are still needed in surface mount components (SMA). Therefore, in the so-called surface mount components, there are often both plug-in parts and mounting parts, and only a part of them are all SMC/SMD. The assembly of both plug-in parts and placement parts is called hybrid assembly, and the assembly of all SMC/SMD is called surface assembly.

　　According to different assembly objects, assembly processes and assembly methods, SMT production lines have multiple assembly methods.

　　The SMT production line of reflow soldering technology is generally used in the surface assembly of PCB single-sided assembly SMC/SMD, also known as single-line form. If the SMC/SMD is assembled on both sides of the PCB, a production line in the form of a tandem wire is required. When there are both plug-in parts and placement parts, sometimes it is necessary to add plug-in parts assembly lines and corresponding equipment on the basis of the original production line. When non-clean assembly is used, additional post-weld cleaning equipment is required. At present, some large enterprises have set up SMT product integrated assembly system equipped with feeding trolley, controlled and managed by computer, which is an advanced organizational form of SMT product automatic assembly and production.

　　The following is the general process of the SMT production line. The solder paste coating method, welding method and the presence or absence of the glue dispensing process are all different according to the different wiring methods.

1. Printing: Print solder paste or patch glue on the pads of the PCB to prepare for the welding of components. All equipments are solder paste printers, located at the forefront of the SMT production line.

2. Dispensing: it drips glue onto the fixed position of the PCB, and its main function is to fix the components to the PCB when wave soldering is used. The equipment used is a glue dispenser, which is located at the front end of the SMT production line or behind the inspection equipment.

3. Mounting: Accurately install the surface mount components on the fixed position of the PCB. The equipment used is a pick and place machine, located after the solder paste printer in the SMT line.

4. SMD adhesive curing: When using SMD glue, the SMD glue is cured, so that the surface mount components and the PCB are firmly bonded together. The equipment used is a curing oven, which is located behind the placement machine in the SMT production line.

5. Reflow soldering: Melt the solder paste to make the surface mount components and the PCB firmly bonded together. The equipment used is a reflow oven. Located behind the placement machine in the SMT production line.

6. Clear: remove the solder residues, such as flux, that are harmful to the human body or products on the assembled PCB. The equipment used is a cleaning agent, and the unknown may not be fixed, and it may be online or offline. This process is not provided when using no-clean soldering techniques.

7. Inspection: inspect the welding quality and assembly quality of the assembled SMA (surface mount components). The equipment used includes magnifying glass, microscope, in-line tester (ICT), first article tester, flying probe tester, automatic optical tester ( AOI), X-RAY tester, functional tester, etc. Unknown According to the needs of testing, it can be configured in a suitable place in the production line.

8. Repair: Repair the faulty SMA. The tools used are electric soldering iron, rework station, etc. Configured anywhere in the production line