Using piezoelectric dispensing technology to improve photovoltaic flux application processes
12 December 2011
In tabbing and stringing processes in many industries, such as in electronics, automotive and solar production, the narrow solder-coated copper ribbon used to link the individual cells requires precise flux application to ensure a good connection and prevent discoloration.
Piezoelectric dispensing systems provide a way in production to apply flux at high speed with exceptional accuracy and without the mess, waste and safety hazards of flux baths and similar application methods.
Nordson EFD’s PICO piezoelectric jet dispensing systems incorporate two piezoelectric actuators composed of stacked ceramic coins that expand and contract in response to changes in voltage supplied from the valve driver.
When voltage is applied to the actuators, the rod and sealing ball are raised so the pressurised fluid can flow to the nozzle. When the voltage is changed, the rod and sealing ball descend rapidly to ‘jet’ the fluid out of the nozzle onto the substrate.
The extremely fast action of the piezoelectric actuators makes it possible to dispense fluid continuously at speeds of up to 150 cycles per second. Depending on the fluid, the system can produce consistent shots as small as 2 nanolitres, and the high resolution (0.01 milliseconds) of the valve controller makes it possible to adjust the size of the fluid deposit with exceptional precision.
Because the valve nozzle does not contact the substrate, piezoelectric jet dispensing systems are a good choice for applications where controlled amounts of fluid must be applied on surfaces that are not perfectly flat, such as thin photovoltaic wafers. They also eliminate the need for vertical Z-axis movement and precise height positioning, which can significantly increase production speeds on automated production lines.
PICO Piezoelectric dispense valves are powered by valve drivers that use an amplifier to generate the signal for the piezoelectric actuators. In addition, they contain a temperature controller for a heater integrated into the valve, to keep the fluid at optimal jetting viscosity.
EFD PICO valve controllers are used to set the fluid dispensing parameters for each valve. Graphical displays and user-friendly menus make it simple to create complex jetting processes on a PC, and then download them to the controller via an integrated SD card slot.
Piezoelectric dispensing systems provide a reliable, innovative way for photovoltaic and other manufacturers to improve process control and reduce costs through exceptional accuracy and faster production speeds.
EFD’s PICO piezoelectric jet dispensing systems are available through Nordson EFD’s worldwide network operating in over 30 countries.
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