Each cycle of the pump displaces a column of material, rather than a single sphere. In operation, the unit cycles at frequencies that create a “stream” of material that can deliver increased flow rates (greater than 70 µl/sec). The displacement piston, driven by a linear motor/encoder assembly, is carbide, so it is extremely wear resistant. The design of the pump unit allows for easy removal and cleaning of the fluidic module that contains all wetted parts. Only three o-rings need to be replaced, so downtime and cost of ownership are minimal. This technology will enable increased dispense rates especially, with underfill applications.
For processes currently using non-contact dispensing, the primary throughput benefits come from two areas. First, Z travel of the dispense head is virtually eliminated as material is released from a nozzle 2 to 3 mm above the PCB surface. Needles, on the other hand, are typically 0.25 mm above the surface and require Z motion to snap off the material from the tip and to clear any obstructions in moving to the next location. The second area where productivity gains are made is in reducing the number of height senses needed to perform the dispense operation. Needle height above the substrate is critical in order to maintain a reliable process. For underfill, height sensing might be performed once for each component, be it a Flip-Chip, CSP or BGA. Dispense height is less critical for streaming, since the technology is much more forgiving and only needs a single reference height measurement, further reducing cycle time.
EPP Europe 439
