smt patch and its main fault
1. SMD and its main 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. The placement machine is an essential equipment in the assembly line of SMT products, and is also a 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 SMC/SMD substrates are made of alumina ceramics, excessive stress will cause microcracks. If the assembly equipment cannot automatically judge the placement pressure, the SMC/SMD will be cracked and assembled into the product, which 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 welding 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 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. Figure 5.10 shows a schematic diagram of the working sequence of a common rotary head placement machine. The working sequence is as follows: A. Pick up chip components and move them; B. Positioning by the image recognition system; C. Compensation and placement; DX-Y The workbench moves; E. Output the printed board after placement.
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 failure before placement mainly occurs in the process A, and the failure after placement can be considered to be mainly in the process B~D.
