1, the impact of temperature on viscosity
Temperature is the most critical factor affecting the adhesiveness of the patch. According to test data from Shanghai Changxiang Industrial Experimental Center, the temperature has increased by 7°C and the viscosity has decreased by 40%. In production, when the viscosity decreases, it means that the amount of patch glue that comes out of the needle tube increases, and the height of the glue on the PCB decreases, so the ambient temperature of the glue should be constant, generally maintained at around 25°C. Make sure the best spot shape.
2. Influence of pressure on viscosity
In the pressure dispensing process, an increase in pressure means that the speed of the glue passing through the outlet of the syringe increases, that is, the shear rate increases. Usually, the pressure of the dispenser is controlled at 5 bar (1 bar) during production. Within 1 kPa), it is generally set at a median value of 3.0-3.5 bar, and the high pressure will increase the shear rate D, causing the hair of the needle tube to become hot and causing the adhesive properties of the patch to deteriorate.
3, the impact of viscosity on time
The key to the time effect is the storage time of the patch glue. Assuming that the patch glue exceeds the shelf life, the viscosity will increase. This is an indirect effect of time on the viscosity of the adhesive. However, in the injection dispensing process, it can affect the amount of glue, the time will increase, and the amount of rubber will increase.
It can be seen that the main factors affecting the change of the adhesive viscosity of the patch are temperature and pressure. It is suggested that our customers should pay special attention to the changes of these two factors in actual production.
January 09, 2019
