How SMT prints solder paste on PCB

How SMT prints solder paste on PCB
Everyone knows that everyday electronic products have a PCB in..., which is densely covered with various electronic components. How are these electronic components installed on the PCB?
The editor below will show you how the SMT front-end equipment solder paste printer prints solder paste to the circuit board for better installation and soldering of electronic components.
Everyone is familiar with PCB. There are many pads on the PCB. In the process of smt wafer processing, in order to make the solder paste cover a specific pad, it is necessary to make a workpiece corresponding to the pad position. The steel plate is installed on the solder paste printer to ensure that the steel plate mesh and the pad on the PCB are in the same position. After positioning, the scraper on the solder paste printer moves back and forth on the mold, and the solder paste penetrates the grid on the steel plate, covering the print of solder paste on the specific PCB pad.
Circuit board

Further reading:
What type of solder paste is SMT chip processing, and basic understanding of storage and use environment
SMT Solder Paste Printer Classification
1. Full automatic solder paste printing machine: the general mass/mainstream SMT production line is a full-automatic printing machine production line. As long as the relevant parameters of the printing machine are set, the machine can automatically feed plates and position steel plates, print solder paste, output plates, and automatically transfer them to the next workstation through the conveyor belt.
2. Semi automatic solder paste printing machine: Semi automatic solder paste printing process mostly occurs in the trial production stage or a small number of diversified product lines. Plate loading, unloading and plate alignment are usually manually operated, while only solder paste printing is automatically operated. You must be a master of this kind of equipment, otherwise it is easy to produce bad circuit boards. On the one hand, this type of semi-automatic printing machine does not want to occupy the entire SMT automatic production line, while semi-automatic solder paste printing machine is relatively cheap.
3. Handmade solder paste printing machine: This is usually in areas with low product prices and low labor costs. There is basically no manual printer in mainland China. All operations are manual. Only steel plate, scraper and solder paste can be completed.
Criteria for Solder Paste Printing Quality
1. Solder paste printing position
2. Solder paste printing quantity
The above two types are the standards for testing the printing quality of solder paste printers. If the solder paste is not printed well, it will often lead to less tin, more tin and tin sticking on the PCB. The occurrence of these types usually leads to solder short circuit and empty soldering problems.
Factors Affecting Solder Paste Printing Quality
1. Scraper type: For solder paste printing, select the appropriate scraper according to the characteristics of unused solder paste or red glue. At present, most mainstream scrapers are made of stainless steel.
2. Scraper angle: The angle of the scraper to scrape the solder paste is generally between 45-60 degrees.
3. Scraper pressure: The scraper pressure affects the amount of solder paste. The greater the pressure of the scraper, the less solder paste. Due to the high voltage, the gap between the steel plate and the circuit board is compressed.
4. Scraper speed: The scraper speed affects the shape and quantity of solder paste printing, and also directly affects the quality of solder. Generally, the scraper speed is set between 20-80mm/s. In principle, the scraper speed must match the solder paste. The higher the viscosity, the better the fluidity of the solder paste, and the faster the scraper should be, otherwise it is easy to seep out.
5. Stripping speed of steel plate: too fast peeling speed is easy to cause solder paste drawing or sharpening
Whether to use the vacuum seat: the vacuum seat can help the circuit board to be fixed in the fixed position smoothly, and strengthen the tightness of the steel plate and PCB circuit board.
6. Whether the circuit board is deformed: The deformed circuit board will lead to uneven solder paste printing, which will lead to short circuit in most cases.
7. Steel plate opening: steel plate opening directly affects solder paste printing quality
8. Cleaning of steel plate: whether the steel plate is clean is related to the quality of solder paste printing, especially the steel plate and PCB circuit board, to prevent the residual solder paste on the steel plate from reaching the position where there should be no solder paste on the PCB Normally, SMT chip factory enters the factory after producing several circuit boards and cleans the bottom of the steel plate with test paper Some printers are designed with an automatic wipe function It is also necessary to specify the frequency of cleaning the steel plate with solvent The purpose is to remove the residual solder paste at the steel plate opening, especially those small ones Throw PCB pad to ensure that solder paste printing is not blocked