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Future Dispensing and MID Technologies
New Scorpion dispensing machine.
By Adrian Kuhnis, Essemtec, Aesch, Switzerland
The number of applications for jet valves is growing rapidly, especially for LED manufacturing and production. Vermes Microdispensing GmbH — a subsidiary of the Essemtec Group — is involved with forming LEDs with filled media, a process that requires flexibility, accuracy and speed that currently can be achieved only by piezo jet valves.
Vermes offers two types of valves that provide different application forces to the media being dispensed. High-viscosity fluids require the direct application of the high force available from the piezo valves. These valves are typically considered to be open, while low viscosity fluids generally call for closed valves.
Selecting the right valve, the correct nozzle and the appropriate valve timing is a demanding task. The process engineer must know not only the required cycle time, but must also have a lot of information about the medium rheology and the application. Rheology includes such properties as viscosity, thread formation, temperature and fillers. The process engineer also must distinguish between shear thinning (no structure rebuilding at rest) and thixotropy (rebuilding of structure at rest).
The speed of a jet valve is limited because of the self-heating of the piezo. 500Hz is a high frequency for a piezo jet valve and 1000Hz can be achieved only for short periods of time. Reaching the required cycle time requires long-term experience. Vermes is currently developing a new technology that soon will go well beyond these limitations.
New Dispensing Machines
Jet valves can be installed on the new Scorpion dispensing machine and the new Paraquda pick-and-place machines from Essemtec. These machines have an innovative valve quick-change system. Because of their very high speed and accuracy, these machines are well prepared for future applications.
The Scorpion, a pure dispensing machine, is used for all types of dot, line and curve dispensing. Automatic calibration systems for height, viscosity and needle are included. A combined dispensing and placement machine such as the Paraquda is suggested for applications including paste adding, glue dot dispensing for some components or electronics prototyping.
LDS Technology for MID
LDS (Laser Direct Structuring), a technology developed by LPKF Laser & Electronics AG, is no longer used just for making prototypes. The technology is now used for making many new higher-volume products such as antennas for communications devices, as well as automotive and medical applications.
The concept of LDS is rather simple. A product is made from an LDS polymer or coated with an LDS paint. The laser then roughs (activates) the areas where copper will be built up in a subsequent chemical process. The roughness of the surface ensures excellent adhesion of copper and the work piece. Layout changes only require reprogramming the laser; no tooling costs are involved, and the process is very flexible.
New Design Rules
Many types of LDS polymers are available for different applications, including solderable high-temperature thermoplastics. It is even possible to create vias in LDS technology. Either the laser burns the required via itself, or it activates the surface inside the hole. However, layout designers must become familiar with a couple of new design rules:
LDS circuits should be rounded rather than angled so that the laser can activate them with continuous movement.
There is a 70° rule: a vertical surface (90°) cannot be activated by the laser. But if a surface is at an angle of 70°, then the laser can selectively activate it without having to turn the work piece.
3-D Placement And Dispensing
MID allows the application of circuits directly to housing parts, and as a result, MIDs are usually in 3-D. In 2011, Essemtec introduced Hydra, the first standard machine for the assembly of such products. It is a combination of a Paraquda pick-and-place with a 6-axis robot. Hydra dispenses glue and paste and it places components at almost any angle. Despite the complex process, the machine's operation is as simple as with a 2-D pick-and-place machine.
Hydra places all types of SMD components. In 3-D mode, the 4-nozzle pick-and-place head can place up to 2,500 components per hour. In 2-D mode the placement rate can reach up to 7,000 cph. The machine can be installed in a production line and, because of its flexibility, changeover between products can be done very quickly. Because of its design, Therefore, Hydra can assemble prototypes as well as significant production runs.
Contact: Essemtec USA, 816 N. Delsea Drive, #308, Glassboro, NJ 08028
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