First, the amount of plastic volume
　　According to the working experience all along, the diameter of the glue point should be half of the distance between the solder pads. The diameter of the glue point after the glue should be 1.5 times of the glue point diameter. This ensures that there is enough glue to bond the components and avoid excessive glue dip pad. The amount of glue by the length of the spiral pump to determine the length of rotation, in practice, should be based on production conditions (room temperature, glue viscosity, etc.) to choose the pump rotation time.
　　Second, dispensing pressure (back pressure)
　　The currently used dispensing machine uses a screw pump supply dispensing needle hose to take a pressure to ensure adequate glue supply screw pump. Too large backpressure pressure can cause glue overflow, too much glue volume. When the pressure is too low, intermittent dispensing phenomenon may occur, resulting in defects. Should be based on the same quality glue, the working environment temperature to choose the pressure. Ambient temperature will make the glue viscosity becomes smaller, better fluidity, then need to reduce the back pressure to ensure the supply of glue, and vice versa.
　　Third, the size of the needle
　　In practice, the inner diameter of the dispensing needle should be 1/2 of the dispensing point diameter. During the dispensing process, the dispensing needle should be selected according to the size of the pads on the PCB. For example, if the pad sizes of 0805 and 1206 are different from each other Large, you can choose the same needle, but for the difference between the pad should choose a different needle, this will not only ensure the quality of glue points, but also can improve production efficiency.
　　Fourth, the distance between the needle and the PCB board
　　Different dispensers use different needles, some have a certain degree of stop (eg CAM / A LOT 5000). Each job should be done at the beginning of the needle and PCB distance calibration, that is, Z-axis height calibration.
　　Five, glue temperature
　　General epoxy glue should be stored at 0 - 5 ℃ refrigerator, use should be taken out 1/2 hour in advance, so that the glue fully consistent with the working temperature. The use of glue temperature should be 23 ℃ - 25 ℃; ambient temperature has a great impact on the viscosity of the glue, the temperature is too low, the glue point becomes smaller, there drawing phenomenon. Ambient temperature difference of 5 ℃, will result in 50% dispensing volume changes. Therefore, the ambient temperature should be controlled. At the same time the temperature of the environment should also be given to ensure that the humidity is easy to dry plastic points, affecting the adhesion.
　　Sixth, the viscosity of glue
　　The viscosity of the glue directly affects the quality of the glue. Viscosity, then the glue point will be smaller, or even drawing; viscosity is small, glue point will become larger, which may infiltrate the pad. Dispensing process, dealing with different viscosity of glue, select a reasonable back pressure and dispensing speed.