There will be defects in the process of use: the size of unqualified distribution points, the size of pins, the distance between pins and PCB, bad glue temperature, glue viscosity, wire drawing, glue immersion pad, curing strength, easy to reduce debris. In order to solve these problems, we need to study the technical parameters as a whole to find the solution.
According to the work experience, the diameter of the solder joint should be half of the distance between the pads, and the diameter of the glue point after the patch should be 1.5 times of the diameter of the glue point. This will ensure that there is enough glue to bond the components and avoid too much glue to dye the pad. It is determined by the rotation time of the screw pump. In actual operation, the rotation time of the pump should be selected according to the production conditions (room temperature, glue viscosity, etc.).
2. Dispensing pressure (back pressure)
At present, screw pump is used in dispensing machine to pressurize dispensing needle hose to ensure that screw pump has enough glue supply. If the back pressure is too large, it is easy to cause rubber overflow and too much rubber; if the pressure is too small, it will cause intermittent phenomenon of dispensing, air leakage and defects. The pressure should be selected according to the same quality of glue and the temperature of working environment. Higher ambient temperature will make the viscosity of glue smaller and the fluidity better. At this time, it is necessary to reduce the back pressure to ensure the supply of glue, and vice versa.
3. Needle size
In practice, the diameter of the needle should be assigned to 1/2 of the glue point diameter. During the dispensing process, the size of the needle should be distributed according to the PCB plate. If the size of the pads in 0805 and 1206 is similar, you can choose the same needle, but different pins will be selected for different pads to ensure the quality of the gel point and improve the production efficiency.
4. Distance between pin and PCB
不同的分配器使用不同的针，有些针有一定的停止度(如CAM/A LOT 5000)。每项工作开始时，都要校准针与PCB的距离，即校准z轴高度。
Different dispensers use different needles, some of which have a certain stopping degree (such as cam / a lot 5000). At the beginning of each work, calibrate the distance between the needle and PCB, that is, calibrate the z-axis height.
5. Water temperature
Generally, the epoxy resin glue should be stored in the refrigerator at 0-5 ℃, and taken out 1 / 2 hour in advance when using, so that the glue solution is completely consistent with the working temperature. The temperature of glue is 23 ℃ - 25 ℃; the ambient temperature has a great influence on the viscosity of glue. The difference of ambient temperature at 5 ℃ will result in 50% change of dosage. Therefore, the ambient temperature should be controlled. At the same time, the temperature of the environment should also be given to ensure that the adhesion point with low humidity is easy to dry and affect the adhesion.
6. Viscosity of glue
The viscosity of glue directly affects the quality of glue. When the viscosity is large, the glue point will become smaller, or even wire drawing will occur; when the viscosity is small, the glue point will become larger, and then it may penetrate into the pad. In the process of gluing, the reasonable back pressure and gluing speed should be selected according to the viscosity of glue.
7. Curing temperature curve
For glue curing, temperature curves are given by general manufacturers. In practice, high temperature curing should be used as far as possible to make the cured glue have enough strength.
The above is a detailed introduction of the two-component gluing machine to the precautions for the full-automatic gluing machine. To learn more, please click the official website http://www.jncsjx.com