1, Needle transfer: first position the needle on the top of the plastic container, so that the needle is immersed in the glue; when the needle is lifted from the glue, due to the surface tension, the adhesive adheres to the needle; then the adhesive will be glued The needle of the agent is aligned with the pad pattern on the components of the PCB, and then the needle is slowly moved vertically downward.
In practical applications, the transfer of the needles is carried out in a momentary manner, and at the same time, multi-point dispensing is performed.
Needle transfer is widely used in the manual dispensing process, and automated needle transfer equipment can also be used. The success or failure depends on the viscosity of the adhesive and the warpage state of the PCB. The advantage of the needle transfer is that it can complete many yuan at a time. Dispensing of the device, equipment investment is small, but the dispensing is difficult to control, and the glue tank is hollow and easy to mix impurities.
2, Pressurized injection: also known as injection dispensing or dispenser dispensing, is the most common method of dispensing. First put the adhesive into the syringe, add compressed air from above or use a rotary mechanical pump Pressurize, forcing the glue to drain from the needle and drip to the required position on the PCB.
Air pressure, temperature and time are important parameters of dispensing. In addition to controlling the inlet pressure and dispensing time, the glue storage container often has a temperature control device to ensure the viscosity of the glue is stable. These parameters control the amount of glue. The size, state, pressure and time are adjusted reasonably, which can reduce the drawing phenomenon. The glue with high viscosity is easy to draw, and the viscosity is too low, which will lead to too much glue and even glue. In order to accurately adjust the dispensing volume and the accuracy of the dispensing position, a microcomputer control can also be used to automatically dispense the glue according to the program.
The characteristics of pressurized injection are adaptability, especially suitable for multi-variety products, easy to control, can easily change the amount of glue to meet the requirements of different sizes of components; and the adhesive is in a sealed state with stable performance.
3, Screen printing; screen printing method similar to ink printing, is a method suitable for flat glue. It has the advantages of fast, accurate, good repeatability, saving glue and improving the quality of dispensing. After completing the dispensing process, the components should be dispensed manually, semi-automatically or fully automatically according to the accuracy of the product, the amount of production and all the equipment and process conditions, and then the adhesive is cured to fix the components. Printed on the board.