Manual visual inspection includes: manual inspection of solder paste printing, manual visual inspection of glue printing, manual visual inspection of solder joints, visual inspection of PCB surface quality and so on. Next, China PCBA processing factory SYS Technology will give you a brief introduction to the main purpose of manual visual inspection.
1. Solder paste printing
First, check whether the basic parameter settings of the solder paste printer are appropriate. The solder paste is printed on the PCB pad, whether the height of the solder paste is the same or presents a "trapezoid" shape, and the edges of the solder paste should not have rounded corners or collapse into a pile shape, but allow some peak shapes caused by pulling up a small amount of solder paste when the stencil is separated. If the solder paste is unevenly distributed, it is necessary to check whether the solder paste on the squeegee is insufficient or distributed uneven, also need to check the printing stencil and other basic parameters. Then check under the microscope whether the solder paste is bright after printing.
2. Placement of electronic devices
Before mount electronic components to the first PCB with solder paste applied, check whether the material racks are properly placed, whether the electronic components are correct, and whether the machine's picking position is appropriate. After completing placement of components to the first PCB, check in detail to see if each electronic component is properly placed and lightly pressed in the center of the solder paste instead of just being "placed" on top of the solder paste.
If you can see a slight depression of the solder paste in the microscope, it means it is placed properly. Are all the electronic devices on the bill of materials (BOM) the same as the electronic devices on the PCBA? All electronic devices that with positive and negative poles, such as diodes, tantalum electrolytic capacitors and ICs, are the orientation of them correct?