August, 2016
www.us-tech.com Product-Specific Drying and Curing Systems Continued from previous page
workpiece carrier. In order to respond flexibly to temperature
fluctuation, temperature and volumetric flow can be adjusted separately in each heat zone. Specially developed air ducts also ensure the uniform heat- ing of PCBs. The exhaust airflow rate can be indi- vidually regulated for each zone. This makes it possible to adapt the RVDS to the specific amount of lacquer applied to the PCBs and to the through- put requirements. Two conveyor variants with fixed or adjustable
conveyor widths are available for the vertical dryer. In the case of a fixed conveyor width, it is deter- mined by the width of the product. For the variable conveyor width, the recirculating workpiece carrier adjusts itself to the PCBs dimensions. This way, dif- ferent products with various widths can be fed to the drying system from several lacquering lines in mixed production.
Meander System Vertical dryers save floor space,
but they require adequate headroom in the manufacturing facility. Nat - urally occurring thermals are a fur- ther disadvantage of the vertical process chamber — heat rises. If tight tolerances are required for the repro- ducibility of the temperature-time pro- file, it might be advantageous to heat the products in a horizontal process chamber.
Rehm has developed a special
solution, the RDS 45000, which per- mits long product dwell times and provides an output rate of 3.5 pieces
convection modules, powered by EC fan technology, provide stable temperature profiles. According to the company, a fully-loaded magazine of 20 DCB power module panels can reproduce its target temperature
within a tolerance of ±7.5 K. By dividing the process chamber into seven
zones, and with the inclusion of airlock technology, the company has made it possible to implement a drying atmosphere with an oxygen content of less
than 5,000 ppm O2. In order to accommodate as many product variants as possible, the system was designed for magazine sizes up to 460 x 240 x 240 mm (18.11 x 9.45 x 9.45 in.).
Ultraviolet Dryer Shorter cycle times in the lacquering process
RDS UV dryer curing UV lacquers with a mercury medium-pressure lamp.
require shorter curing times. This can be accom- plished most effectively by using UV drying sys- tems. UV lacquers cure within a matter of seconds to allow for short processing times and increased production rates, and also have ecological and eco- nomic advantages. These traits are further supplemented by such qualitative aspects as increased glossiness,
Continued on page 67
Page 65
RVDS vertical drying system.
per minute in a horizontal setup. The products “meander” through the process chamber, which is equipped with 18 heat zones. The workpiece carrier conveyor can be loaded manu- ally or automatically.
Magazine Dryer No less frequently, products are
moved from one manufacturing step in magazines, which makes it effi- cient to subject the products to the time-consuming drying process while still in the magazine. This approach saves space and eliminates the need to unload and reload them. The company developed the
RDS magazine dryer in a project sponsored by the German federal Ministry of Education. The research was conducted under the working title “High-Temperature-Optimized Aluminum Bonding Technology for Offshore Applications — HotAl” and was completed earlier this year in collaboration with partners including Fraunhofer IZM, F&K Delvotec Bondtechnik, Heraeus Materials Tech nology, and Semikron Elek tron - ik. Among other requirements, it was necessary to dry power modules in conveyor magazines over a long peri- od of time in an inert atmosphere. Rehm’s RDS magazine dryer is
laid out for temperatures of up to 300°C (572°F) and can be used for cycle times ranging from three min- utes to 24 hours. High-performance
See at NEPCON South China, Booth 1G45
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