In SMT solder paste printer printing PCB board, one of the processes is to use the squeegee to squeeze the solder paste, so as to transfer the solder paste from the stencil to the PCB board. Squeegee system is the most complex movement mechanism on the printing machine, including squeegee fixing mechanism, squeegee transfer control system and so on.
I. Functions performed by the squeegee system
Make the solder paste expand into a uniform layer over the whole stencil area, the squeegee presses the stencil to make contact between the stencil and the PCB.
The squeegee pushes the solder paste on the stencil to roll forward, and at the same time makes the solder paste fill the stencil opening.
When the template off the PCB, in the PCB corresponding to the template graphics at the appropriate thickness of the solder paste left.
II. Scraper has a metal scraper and rubber scraper, etc., respectively, for different applications.
It must have high friction resistance and solvent cleaning resistance, and its hardness is an important factor affecting the quality of solder paste printing. Sub knife made of rubber, when the squeegee head pressure is too large or the material is soft, easy to embed the metal template holes (especially large window holes), and the hole in the solder paste extrusion, resulting in the printing of the graphic depression, the printing effect is poor. For this reason, people use metal scraper instead of rubber knife. Metal vice knife mountain high hardness alloy made of very fatigue-resistant, wear-resistant, bend-resistant, and coated with a lubricating film on the knife edge. When the edge of the blade running on the template, the solder paste can be easily pushed into the window, eliminating the solder depression and high and low undulation phenomenon.
III. In recent years new closed scraper technology has emerged.
It offers the following advantages over the open squeegee described earlier.
1. Printing is still possible with a very small amount of solder paste.
2. It is favorable to solder paste and prevents oxidation of solder paste.
3. High effective utilization of solder paste.
4. Internal pressure increases the filling effect of solder paste and prevents the occurrence of printing defects.
5. Simpler process modulation and faster printing speed.
Features of NeoDen ND2 Automatic SMT Stencil Printer
1. Accurate Optical Positioning System
Four way light source is adjustable, light intensity is adjustable, light is uniform, and image acquisition is more perfect
2. High efficiency and high adaptability stencil cleaning system
Soft wear-resistant rubber wiping plate, cleaning methods of dry, wet and vacuum thorough cleaning, convenient disassembly
3. Intelligent squeegee system
Intelligent programmable setting, two independent direct motors driven squeegee, built- in precise pressure control system
4. Special PCB thickness adaptive system
The platform height is automatically calibrated according to PCB thickness setting, which is intelligent, fast, simple and reliable in structure.
5. Solder Paste Printing Quality Inspection
2D function can quickly detect the printing defects, the detection points can be increased arbitrarily
6. Printing Axis Servo Drive
Improve accuracy grade, provide good printing control platform, operational stability, extend the service life