SMT patch is the most popular patch technology in the industry. SMT is called the surface assembly technology. Its principle is to install the components assembled on the surface of the PCB plate on the surface of the non pin or short lead surface, and then weld and assemble by flow welding or immersion welding. The advantages of SMT process are high density, strong reliability and strong anti vibration ability. The method of patch makes welding spot defect rate low, high frequency characteristic, easy to realize automation and improve production efficiency.
At present, almost all electronic components on printed circuit boards of electronic products have patch elements, all of which are mounted on the printed circuit board by SMT mounter.
SMT electronic components are increasingly integrated, microminiaturized, and how many micro electronic components can be fitted to the circuit board accurately and quickly through the SMT patch machine. The important reason for this is that the visual system of the SMT patch machine is similar to the patch machine with eyes. In the process of high speed pickup and mounting components of the SMT patch machine, it can detect whether the component can work according to the configuration of the program.
As we all know, the development of domestic LED patch machine is fast, many LED patch machine manufacturers can even compare with many imported patch machine brands, but there is a big gap in the SMT piece, of which the precision and speed are quite restricted. The homemade SMT placement machine is basically invisible to the electronic components on the market without visual system. Today, let's talk about some knowledge of vision system.
SMT placement machine is prone to mismatch when attaching components. Visual inspection error of components is one of the main reasons leading to misplacement. What factors cause the visual inspection error of components?
1, the influence of the foreign object on the lens, the glass lens above the aperture, the effect is to prevent dust into the aperture and influence the intensity of the light source, but if there are dust, components and other foreign objects on the glass lens, the intensity of the light source is affected. If the intensity of the light source is low, the gray value is low. This leads to bad recognition, so the placement machine should pay attention to the cleaning of lenses and lenses.
2, the impact of the reflective plate, the reflective plate plays a role in the backlight. When there is dust on the reflector, the intensity of the light source will be reduced and the gray value will be reduced, which causes the bad recognition and the loss of the components. So, the reflective plate is the part that needs to be periodically polished when the patch machine is maintained.
3, the influence of the light circle light source, the light source intensity will gradually decrease after a period of use, because the intensity of the light source is proportional to the gray value of the solid-state camera conversion, and the larger the gray value is, the closer the digital image is with the observed view, so with the decrease of the intensity of the light source, the gray value is also reduced accordingly. But the gray value of the machine will not decrease with the intensity of the light source. Only the regular correction detection is only proportional to the intensity of the light source. When the intensity of the light source is weakened to the unrecognized element, the bulb needs to be replaced.
4. The parameters of the component library are not set properly. This is usually caused by the disshape of the element's shape when the material is changed. It is necessary to recheck the parameters of the identification parameters and check the items including the shape and size of the components. The solution is to let the visual system "learn" the configuration of the component, and the system will automatically produce a comprehensive description of the CAD, which is efficient and effective. Size consistency is not good, may be appropriate to increase the allowable error.
5, sound absorption of the mouth, when the backlight recognition, if the suction mouth shape is larger than the device contour, the image will have the outline of the suction nozzle, the recognition system will take the outline of the suction nozzle as part of the element, thereby affecting the element recognition. In view of this phenomenon, we can handle it based on specific reasons.
A, if the outer diameter of the suction nozzle is larger than the size of the device, replace the nozzle with smaller outer diameter.
The position deviation of B and suction nozzle causes the shape of the suction nozzle to extend to the device profile and adjust the material level deviation. The high performance SMT patch machine has the function of automatically correcting the position of the element. By continuously measuring the location of a component, the average error is calculated and the correction value is automatically produced. The corrected value is stored in the Feeder (B) Offest. The zero value of the material position can solve the problem.