When fluid dispensing is well controlled, it results in a high-quality product, low assembly cost and a lean working environment. Increasing demands on quality and the ongoing miniaturization of products require high-quality fluid dispensing solutions.
In the electronics industry, commonly dispensed fluids include: adhesives (anaerobic, cyanoacrylates, epoxy and UV-Curable); conformal coatings; flux (liquefied and pasted); RTV silicone (room-temperature vulcanisation, curing without heat), solder mask and solder paste. We can offer you our in-house know-how to provide you with a complete dispensing solution, based on the material, viscosity and dispensed volume. Whatever materials you intend to dispense, whatever the size and accuracy of the application, there is an AMADA WELD TECH dispensing solution that meets your needs.
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Time/Pressure Dispensing (TPD) methods use a syringe and a pneumatic valve. The TPD Syringe method utilizes controlled and timed air pressure to producing a measured shot of air that forces fluid out of a syringe, through the dispensing needle, and onto the work surface. Due to its simplicity and low cost, this method is widely used in bench-top applications. To achieve more repeatable results, TPD valve methods incorporate a pneumatic valve to better control the volume of fluid being dispensed. For low to medium viscosity fluids, a Needle valve or a Diaphragm valve is recommended. An automated controller opens a piston/needle assembly or diaphragm, which in turn opens a path for the fluid to flow through. When the air signal stops, the piston returns to the original position and closes the valve. Time and pressure can be precisely controlled to dispense dots or continuous beads of fluid. Higher viscosity fluids often require a Spool Valve, where the piston drives down to open the fluid path. When the dispensing cycle is completed, the spring in the internal compression lifts the piston up and closes the valve. This creates a natural back-suction feature that prevents drips.
You can find more information on Single Component Time/Pressure Dispensing in our Knowledge Base.
A common weakness of time/pressure dispensing is its susceptibility to fluctuations in the dispensed fluid‘s viscosity. If the fluid becomes thicker or thinner, pressure must be adjusted accordingly to maintain repeatability. One way to avoid this problem is to use a Semi-Positive Displacement Method such as a Rotary or Auger pump. The auger pump uses a rotary feed screw (auger) that rotates inside a fluid chamber to push fluid from the auger inlet to the dispense tip. A better way to control repeatability of the dispense process is with a True Positive Displacement Method. As the name suggests, pushing down in a displacement chamber pumps an identical volume of fluid out of a matching dispensing chamber. Displacement pumps vary by the type of mechanical action used, such as the Auger Valve, Progressive Cavity Pump and Rod Displacement Valve.
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Jet Technology represents a paradigm shift in precision dispensing. In traditional contact methods, a needle touches down and physically applies the fluid. In non-contact dispensing, a jet hovers over and shoots fluid at the work surface without ever touching it. The difference is similar to a fountain pen compared with an inkjet printer.
Jetting is primarily a valve-based technology. In piezoelectric systems, a voltage is applied to a piezoceramic stack which then expands/contracts to operate the valve. In air-actuated systems such as TS9200D, air pressure operates the valve. However, instead of the large sliding valve stem in conventional needle valves, the TS9200D utilizes a very low-mass diaphragm, which requires less energy and speeds up the process. In jet dispensing, the fluid is separated from the applicator using droplet momentum and the result is a perfectly round dot. Jetting produces dots of extremely small size, low volume and high consistency. Furthermore, the positive shut-off of jet dispensing enables the execution of precise lines and sharp corners. Incorporating a multi-function process controller means that dispensing results can be perfected by fine-tuning the jet and fluid pressures, drop size, drop rate, and dispensing parameters such as refill and dwell time.
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