SMT PCB assembly process improvement inspection methods

The goal of quality management is not to put the defective printed circuit board on the production line back process, set up special testing equipment after the manufacturing station, and timely detect, find and correct the defects.The following diagram shows a typical surface assembly and testing process.

Solder paste printing - solder paste printing testing - SMT - SMT testing - reflow soldering - cleaning - online testing - installation of profiled parts - functional testing - finished products

1. Quality inspection of solder paste printing

70%~80% of the welding defects come from reflow welding technology in solder paste printing process.Which include poor solder paste quality, printing stencil manufacturing process not up to the requirements, improper printing process parameters and process environment conditions not up to requirements, which will lead to various SMT PCB assembly solder paste printing defects and welding defects

If the printing defects can be detected immediately after the solder paste printing, and the failure factors such as excessive and collapse of solder paste can be eliminated,which will be very beneficial to the improvement of the welding quality.Therefore, it is very necessary and important to set up inspection procedure after solder paste printing.The solder paste  printing quality inspection can be done by visual inspection with the aid of optical inspection equipment or special inspection equipment.It is usually equipped with automatic inspection machine to detect solder paste printing quality in high quality requirement smt pcb assembly line.

2.Mounting components quality inspection

The process of SMT quality inspection after components mounting is mainly about appearance inspection. Appearance inspection can detect missing assembly or position deviation of chip components and various electronic components placed on the printed circuit board after solder paste printing or dispensing.Appearance inspection can be carried out by manual visual inspection or automatic inspection device. The inspection procedure should be set after the placement machine and before welding.

3. Reflow welding inspection

The reflow welding inspection mainly includes the mounting position of SMT PCB assembly components, whether there are leaks or errors. The inspection method is based on the inspection standard, visual inspection or inspection with the help of a magnifying glass.

4.Plug-in detection dip components

The main content of the inspection is whether there are leakage parts, wrong parts and the insertion condition.Inspection method according to test criteria, visual inspection or inspection with the aid of a magnifying glass