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SMT printer machine is one of the important equipments in SMT production line, and its working principle directly affects the SMT placement quality and production efficiency. Therefore, it is very necessary to understand the working principle of SMT printer machine.
SMT printer machine is mainly composed of mechanical part, electrical part and program control part. The mechanical part includes transmission system, substrate support and positioning system, printing system, etc.; the electrical part includes power supply, control circuit, sensors, etc.; the program control part includes computer control system, software and so on.
The working principle of the SMT Printer is as follows: During the printing process, the substrate support and positioning system fixes the substrate on the printing table, and the solder paste is transported to the stencil on the printing table through the dispenser. Under the instruction of the program control part, the transmission system moves the stencil to a suitable position, and then the printing system applies the solder paste evenly on the stencil through the squeegee to form the pattern of solder paste.
In the printing process, SMT printers also have some auxiliary functions, such as cleaning and drying. These functions can be realized by mechanical and electrical systems. For example, after the printing is completed, the SMT solder paste printing machine will spray compressed air to the surface of the stencil through the nozzle to blow away the excess solder paste on the stencil to ensure the clarity and precision of the solder paste pattern .
In addition, the printing accuracy and repeatability of SMT printers are also very important indicators. Printing accuracy refers to the degree of conformity of the formed solder paste pattern with the expected pattern, while repeat accuracy refers to the consistency of the formed solder paste pattern after multiple printings. In order to ensure these two indicators, SMT solder paste printers need to undergo strict manufacturing and testing .
The working principle of SMT printer is that the transport system will transport the PCB board fixed in the printing machine table, through the visual positioning system will stencil opening position and PCB pad position centering, the table rises. Then the left and right squeegees of the printing machine will leak the solder paste through the stencil holes and print it on the PCB pads, and finally the stencil and PCB will be automatically demolded and transported to the next process through the transmission system.
1, when the printing machine squeegee to a certain speed and angle of forward movement, the solder paste to produce a certain pressure, push to push the paste in front of the squeegee rolling, resulting in the injection of solder paste into the stencil holes in the pressure required;
2, the printing process squeegee speed, squeegee pressure, squeegee and the angle of the template there is a certain correlation between the squeegee, in order to ensure the quality of PCBA processing printing solder paste, you must correctly control these corresponding parameters;
3, the viscosity of the paste so that the paste in the scraper and stencil openings to produce shear, shear force makes the viscosity of the paste down, so as to smoothly injected into the stencil holes;
SMT printer is an important equipment in the SMT production line, its working principle and performance directly affects the SMT placement quality and production efficiency. Therefore, it is very necessary to understand the working principle and performance characteristics of SMT solder paste printing machine.
Operation flow of SMT printer
1、Preparation
Fixed stencil, debugging position assembly clean squeegee to add solder paste to the stencil into the check PCB board printing printing of the first 5PCS board full inspection, printing quality through the IPQC first inspection, notify the production line operators to start production .
2、Printing process
Operators need to check the printing effect every half hour to see if there is less tin, even tin, pull the tip, shift, leakage and other undesirable phenomena; every printing 5PCS, need to clean the stencil once, if there are pins on the PCB board is too dense components to increase the frequency of cleaning once every 3PCS cleaning; if you find that the printing of 3PCS consecutively bad, to notify the technician debugging; regularly check the solder paste whether the spillage of overflowing paste to collect. To collect the overflowed solder paste;
After the end of production, we should recycle solder paste, squeegee, stencil and other auxiliary materials and tools, and clean the fixtures and fittings, specifically according to the “Storage and Use of Solder Paste” and “Stencil Cleaning Operations Guidelines” operation.
