SMT assembly failure types and measurement and control methods A-958

1. Assembly failure
Assembly Fault (Assembly Fault) refers to faults caused by problems in the assembly process, such as solder bridge short circuit, virtual solder open circuit, wrong or missing components, and so on. In actual production, assembly failure, as the main source of failure of SMT products, is the core problem to be solved by SMT assembly quality control. Although in the assembly and production process of SMT products, various quality factors have an impact on the final result of the product, but on the premise that the quality factors of assembly design and assembly raw material quality, assembly equipment and testing equipment performance are basically guaranteed, The main link that affects the final result of assembly quality is the quality of the assembly process, and the main manifestation of poor assembly quality is assembly failure.
2. Types of assembly failure
The assembly process of SMT products is mainly composed of screen printing and application of solder paste or dispensing by glue dispenser, placement machine placement, reflow soldering furnace welding or curing, cleaning equipment cleaning, testing equipment online testing and other processes. Hidden dangers are almost distributed in every link of the assembly process. According to the above assembly process, the types of assembly failures can be divided into four categories: patch glue application failure, solder paste application failure, patch failure and soldering failure.
3. Measurement and control method of assembly failure
The assembly and production process of SMT products is a chain, so the common way of assembly quality management is: each link in the production process is checked separately, and the defective products are not sent to the next process. The specific implementation is to set up the corresponding testing equipment (or the corresponding testing function in the production equipment) after each process for testing, and to deal with the faults in the assembly process in time, as shown in Figure 5.5.
Schematic diagram of the composition of SMT production compensation line
Figure 5.5 Schematic diagram of typical SMT production compensation measurement line
The inspection methods of each process include manual visual inspection, automatic optical inspection (AOI), X-ray inspection, etc., assembly failure analysis and processing methods include various list methods, graphic methods, statistical methods, etc., and the quality control standards are based on the product quality level requirements According to the corresponding specifications.