smt assembly common faults
SMC/SMD placement is a key process in the assembly and production of SMT products. Automatic placement is the main method of SMC/SMD placement. Placement machines are essential equipment in the assembly line of SMT products, as well as key equipment of SMT. It is the main factor that determines the degree of automation, assembly accuracy and production efficiency of SMT product assembly. When the SMC/SMD is assembled by the placement machine, the most important factor affecting the assembly quality is the placement pressure, that is, the mechanical impact stress. Because most of the SMC/SMD substrates are made of alumina ceramics, excessive stress will cause microcracks. If the assembly equipment cannot automatically judge the placement pressure, causing SMC/SMD micro-cracks and assembled into the product, it will directly affect the reliability of the product. At the same time, the position accuracy of SMC/SMD placement should be within the specified range, otherwise solder quality problems will occur, which is another important factor.
The automatic high-speed placement machine can be divided into rotating head and fixed head from the working mode. These two working methods have their commonalities in terms of the principles and methods of completing placement. The following only takes the rotating head high-speed placement machine as an example to introduce the causes and troubleshooting methods of placement failures. The work sequence is as follows: A. Pick up the chip components and move; B. Positioning by the image recognition system; C. Compensate and mount; D. X-Y worktable movement; E. Output the printed board that has been mounted.
Considering the placement machine as the center, the undesirable phenomena can be divided into two categories: ① failures before placement; ② failures found after placement. The faults before placement mainly occur in the A process, and the faults after the placement can be considered to be mainly in the B~D process.