Selection of Scraper Pressure and Speed for solder printing machine The pressure and speed of the scraper are two important technological parameters in stencil printing of solder printing machine.
Scraper speed: The selection principle is that the speed of the scraper is related to the viscosity of solder paste and the minimum pin spacing of SMD on PCB board. The speed of the scraper is lower when the solder paste is chosen with high viscosity, and vice versa. For the selection of scraper speed, the test printing should start at a lower pressure and increase slowly until a good solder paste is printed. The velocity ranges from 15 mm/s to 50 mm/s. The scraper speed should be reduced appropriately when printing fine spacing, generally 15-30 mm/s, to increase the stagnation time of solder paste at the window, thereby increasing the solder paste on PCB solder pad; the speed of printing wide spacing components is generally 30-50 mm/s. (> 0.5 mm pitch for wide spacing, and < 0.5 mm pitch for fine spacing) The allowable range of scraper speed of this machine is 0-120 mm/s.
Scraper pressure of solder printing machine: Pressure directly affects the printing effect. Pressure ensures that the edge of solder paste printed is clear, the surface is flat, and the thickness is suitable. The pressure is too small, the amount of solder paste is insufficient, resulting in virtual soldering; the pressure is too large, resulting in solder paste connection, will produce bridging. Therefore, the scraper pressure is generally set to 0.5-10 kg.
Demoulding speed and length of solder printing machine The demoulding speed refers to the speed at which the printed substrate is separated from the template. Before the solder paste and the template are separated completely, the separation speed is slower. When the printed substrate is separated completely, the substrate can decline rapidly. Slow separation is conducive to the formation of clear edges of solder paste, especially for fine spacing printing. Generally set to 3mm/s, too fast easy to damage the shape of solder paste. The machine is allowed to be set in the range of 0-20mm/s.
Separation time between PCB and template: That is, the time required for the printed substrate to leave the template at the stripping speed. It is easy to leave solder paste on the bottom of the template for too long time, which is not conducive to the standing of solder paste. It is generally controlled in about one second.
This machine uses the demoulding length to control this variable, which is generally set to 0.5-2 mm. The machine is allowed to be set in the range of 0-10 mm.
Formal production of solder printing machine:
After the above preparations are completed, the PCB board can be printed on trial. The operation method is as follows:
1. Click on the [Start Production] button in the main toolbar 2 and follow the instructions of the dialog box on the operation interface to complete the automatic printing of a PCB board.
2. If the test results do not meet the quality requirements, we should re-set the parameters or input the compensation value of printing errors; if the test results meet the quality requirements, we can formally start production.
3. Quality requirements for solder printing machine: Setting the thickness of solder paste between 0.1 mm and 0.3 mm and the area covered by solder paste over 75% can meet the quality requirements.
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