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Automatic dispenser should pay attention to the use of the matter

Release time:
2019/01/17
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Automatic dispenser may be used in the process of defects: the size of the tape is not qualified, the size of the needle, the distance between the needle and the PCB board, glue temperature, glue viscosity, drawing, glue dip pad, curing strength is not easy Out of pieces and so on. To solve these problems should be the overall study of automatic dispenser technical process parameters, so as to find a solution to the problem.

1. The size of the dispensing

According to work experience, the size of the dot diameter should be half of the pad spacing, patch after the dot diameter should be 1.5 times the diameter of the dot. So that you can ensure that there is sufficient glue to bond components and avoid excessive glue dip pad. The amount of dispensing is determined by the length of rotation of the screw pump. In practice, the rotation time of the pump should be selected according to the production conditions (room temperature, glue viscosity, etc.).

2. Dispensing pressure (back pressure)

The currently used dispenser uses a screw pump to supply a dispensing needle hose to take a pressure to ensure adequate glue supply to the screw pump. Back pressure pressure is too easy to cause plastic spill, glue too much; pressure is too small will appear dispensing intermittent phenomenon, leakage, resulting in defects. Should be based on the same quality of glue, the working environment temperature to select the pressure. High ambient temperature will make glue viscosity smaller, better mobility, then need to reduce the back pressure can guarantee the supply of glue, and vice versa.

3. Needle size

In the actual work, the size of the needle should be the diameter of the point of plastic point 1/2, dispensing process, according to the size of the pad on the PCB to choose dispensing needles: such as 0805 and 1206 pad size difference, You can choose the same needle, but for the difference between the pad will choose a different needle, so that both can guarantee the quality of plastic dot, but also can improve production efficiency.

4. The distance between the needle and the PCB

Different dispensers use different needles, some needles have a certain degree of stop (such as CAM / A LOT 5000). Every time you start the work should be needle and PCB distance calibration, that is, Z axis height calibration.

5. Glue temperature

General epoxy glue should be stored in the refrigerator 0 - 5℃, the use of 1/2 hours ahead of time to make the glue fully compatible with the working temperature. Glue the use of temperature should be 23℃ - 25℃; ambient temperature on the viscosity of a great impact on the glue, the temperature is too low will become smaller, there is drawing phenomenon. Ambient temperature difference of 5℃, will cause 50% of the amount of dispensing changes. So the ambient temperature should be controlled. While the temperature of the environment should also be given to ensure that the humidity of small plastic point easy to dry, affecting the cohesive force.

6. The viscosity of the glue

The viscosity of the glue directly affects the quality of the dispensing. Viscosity, the plastic point will become smaller, or even drawing; viscosity is small, plastic spots will become larger, and thus may damage the pad. Dispensing process, should deal with different viscosity of the glue, select a reasonable back pressure and dispensing speed.

Through the above description of the process debugging, the use of automatic dispensing machine can better help enterprises to improve production and improve efficiency.