1. Size of SMT patch dispensing amount

According to work experience, the diameter of glue point shall be half of the product spacing. This will ensure that there is enough glue to bond the components and avoid excessive glue. The amount of dispensing depends on the length of time. In practice, the dispensing time should be selected according to the production situation (room temperature, glue viscosity, etc.).

2. SMT chip dispensing pressure

The dispensing equipment provides a certain pressure for the needle tube (glue gun) to ensure glue supply. The pressure determines the glue supply amount and the glue flow rate. Too much pressure is easy to cause glue overflow and too much glue; If the pressure is too small, intermittent dispensing and leakage will occur, resulting in product defects. The pressure shall be selected according to the glue property and working environment temperature. High ambient temperature will make the viscosity of glue smaller and the fluidity better. At this time, it is necessary to lower the pressure value, and vice versa.

3. Size of SMT patch dispensing tip

In practice, the inner diameter of the tip should be about 1/2 of the diameter of the dispensing point. During dispensing, the tip should be selected according to the size of the product. Different needles shall be selected for products with large difference in size, which can not only ensure the quality of glue point, but also improve the production efficiency.

4. Distance between needle and working face

Different dispensers use different needles, some of which have a certain degree of stop. The distance between the needle head and the working surface shall be calibrated before each work, that is, the Z-axis height calibration.

5. Viscosity of glue

The viscosity of glue directly affects the quality of dispensing. If the viscosity is large, the glue point will become smaller, even wiredrawing; If the viscosity is small, the glue point will become larger, and then the product may be infiltrated. During dispensing, select reasonable pressure and dispensing speed for glue with different viscosity.

6. Glue temperature

Generally, the epoxy resin glue should be stored in the refrigerator at 0~5 ℃, and taken out half an hour in advance when using, so that the glue temperature is consistent with the working environment. The use temperature of glue shall be 23 ℃~25 ℃; The ambient temperature has a great influence on the viscosity of the glue. When the temperature decreases, the viscosity increases, and the glue flow decreases accordingly, which makes it easier to draw wire. Under the same other conditions, the difference of ambient temperature by 5 ℃ will cause a 50% change in the amount of glue, so the ambient temperature should be controlled. At the same time, the temperature of the environment should also be guaranteed. If the temperature is too high, the glue spots will become dry, affecting the adhesion.

7. Curing temperature curve

For the curing of glue, the general manufacturer has given the temperature curve. In practice, higher temperature shall be used for curing as much as possible to make the glue have enough strength after curing.

8. Bubble

The glue must not have bubbles. A small bubble will cause many products without glue; Every time the rubber hose is replaced midway, the air at the connection shall be drained to prevent the occurrence of air strike.