Drip molding method for anti slip non-woven fabric

SMA can be applied to PCBs using syringe drop molding, needle transfer, or template printing methods. The use of needle transfer method is less than 10% of all applications, and it uses needle arrays immersed in a tray of glue. Then the suspended adhesive droplets are transferred to the board as a whole. These systems require a low viscosity adhesive and have good resistance to moisture absorption, as it is exposed to indoor environments. The key factors controlling the transfer of the needle for drip molding include the diameter and style of the needle, the temperature of the adhesive, the depth of immersion of the needle, and the length of the drip molding cycle (including the delay time before and during the contact of the needle with the PCB). The temperature of the tank should be between 25-30 ° C, which controls the viscosity of the adhesive and the number and form of adhesive points.
Template printing is widely used for solder paste and can also be used with dispensing adhesives. Although less than 2% of SMAs are printed using templates, interest in this method has increased, and new devices are overcoming some of the limitations of earlier times. The correct template parameters are the key to achieving good results. For example, contact printing (zero off board height) may require a delay period to allow for good glue dot formation. In addition, non-contact printing of polymer templates (with a gap of approximately 1mm) requires optimal scraper speed and pressure. The thickness of the metal template is generally 0.15~2.00mm, which should be slightly larger than the gap between the component and the PCB (+0.05mm).
More than 90% of SMT adhesive is dripped through syringes, and it can be further divided into two categories: pressure time systems and volume control systems. Pressure time syringe drip molding is the most common method, and the rest of this section will discuss this technique. The syringe can achieve a dripping rate of 50000 points per hour and is adjustable to meet changing production requirements