SMT Process Specification

- Aug 05, 2020-

1. Template: first, according to the designed PCB processing template. General templates are divided into chemical etching (also known as etching) copper template or stainless steel template (low price, suitable for small batch, test and chip pin spacing > 0.65mm); laser cutting stainless steel template (high precision, high price, suitable for large batch, automatic production line, and 0.3mm chip pin spacing 0.5mm).

2. Missed printing: its function is to use a scraper to leak the solder paste onto the pad of PCB to prepare for the installation of components. The equipment used is screen printing machine (automatic, semi-automatic screen printing machine) or manual silk printing table, scraper (stainless steel or rubber), located at the forefront of SMT production line.

3. Mounting: its function is to accurately install surface mount components to the fixed position of PCB. The equipment used is SMT Machine (automatic, semi-automatic or manual), vacuum suction pen or special tweezers, which is located behind the screen printing machine in SMT production line.

4. Reflow soldering: its function is to melt the solder paste, so that the surface mount components and PCB are firmly welded together to achieve the electrical performance required by the design, and it is completely controlled according to the international standard curve. The equipment used is reflow oven (automatic infrared / hot air reflow oven - Heller reflow oven motor in stocks with reasonable price), which is located behind the SMT production line.

5. Cleaning: its function is to remove the materials that affect the electrical properties or welding residues harmful to human body, such as flux, on the mounted PCB. If no cleaning solder is used, it is generally unnecessary to clean. The equipment used for cleaning is ultrasonic cleaning machine and special cleaning solution. The position can not be fixed, it can be on-line or off-line.

6. Detection: its function is to test the assembly quality and welding quality of the PCB. The equipment used includes magnifying glass, microscope, on-line tester (ICT), flying needle tester, automatic optical detector (AOI), X-ray detection system, function tester, etc. According to the needs of detection, the location is arranged in the appropriate place of the production line.

7. Rework: it is used to repair the PCB with fault detected. The tools used are soldering iron, repair workstation, etc. At the same time, reflow welding machine can also be used for setting, which can be repaired without damage. Configuration in any position in the production line.