PROJECT DESCRIPTION
BACKGROUND
As a result of various cleaning and etching processes the electronic industry can have a harmful impact on the environment. These technical processes are necessary to obtain the required properties of the surfaces: no oxide layer on the surface, defined contact between the metal and the used solder etc. As a result of these preparations waste water from the electronic plants can contain a considerable amount of heavy metals. Vishay Semiconductor Austria produces about 200 million diodes a year at its plant in Vöcklabruck. These are used as fast rectifiers in a wide range of applications in monitors, switching circuits, fluorescent light tubes, PCs, TV sets and electronic components for cars. Production of the diodes involves the use of sintered molybdenum pins. In the past, these have had to be etched with nitric, sulphuric and hydrochloric acid before being used in the production process. The waste water generated was neutralised and then discharged into the river Vöckla with a molybdenum content of 18 mg/l. The Vöcklabruck plant was founded in 1965 by AEGTelefunken. Today it is owned by Vishay Intertechnology Inc., a worldwide operator with some 4 600 employees in the EU alone. Within this corporation the Vöcklabruck plant is of central importance for diode production. The ultra-modern semiconductor plant by the river Vöckla is one of the world's leading producers of high-quality diodes, with a turnover of around € 130 million a year. Investment in research and development, e.g. in clean production processes, enables the company to remain at the forefront of this technology. High quality and the specific properties of the products guarantee the competitive position of this location, as opposed to low salary countries in the Far East.
OBJECTIVES
The aim of the project was the total elimination of molybdenium emissions from the waste water by introducing an innovative change in the production process. It was intended to apply a totally new technology, already developed at laboratory scale, into the industrial process. A new coating process (presoldering) prior to the manufacturing of the pins replaced etching. For this purpose the different tests in the lab were adapted to technical scale and large scale production. The prototype was constructed and put into operation. The company's environmental statement declares that 'Everyone working with technologies stretching far into the future bears a particular responsibility for the environment'. Back in 1998, Vishay Semiconductor Austria obtained certification under the DIN ISO 14001 international standard on environmental management systems. This clean technology once again meets the goal of protecting the environment which the company has set for all its 480 staff.
RESULTS
The required properties of the coated surfaces were established, and possible deviations and acceptable tolerances were determined. The process was optimised at the laboratory scale. Defining the acceptable parameters in this way was an essential step in designing the production process and achieving the planned reduction in emissions. Test runs were conducted on equipment to select the process giving the best overall results. A prototype soldering furnace was acquired to ensure that the selected process met the requirements in terms of environmental performance, quality and cost. Checks and analyses have taken place in order to ensure product quality and environmental quality, and the old equipment has been taken out of service. The transfer of the process, which was developed and tested in the laboratory, to the industrial production process caused a significant reduction in the Mo load of the waste water. In absolute value the load of Mo was reduced from 18 mg/l down to 0.6 mg/l. The total Mo load per year was reduced from 540 kg down to 18 kg at full production capacity. The industrial quality standards were changed for this type of diode, and some difficulties and delays were encountered in adapting the new technology to meet the standards. However in the end it was proved that the industrial process was able to meet the more stringent requirements. The replacement of the polluting etching process with the cleaner pre-soldering process has been announced to Vishay’s customers and has been well received. Although the results is kept confidential by the company, the technology will probably be transfered to another of Vishay's sites in Hungary. The required properties of the coated surfaces were established, and possible deviations and acceptable tolerances were determined. The process was optimised at the laboratory scale. Defining the acceptable parameters in this way was an essential step in designing the production process and achieving the planned reduction in emissions. Test runs were conducted on equipment to select the process giving the best overall results. A prototype soldering furnace was acquired to ensure that the selected process met the requirements in terms of environmental performance, quality and cost. Checks and analyses have taken place in order to ensure product quality and environmental quality, and the old equipment has been taken out of service. The transfer of the process, which was developed and tested in the laboratory, to the industrial production process caused a significant reduction in the Mo load of the waste water. In absolute value the load of Mo was reduced from 18 mg/l down to 0.6 mg/l. The total Mo load per year was reduced from 540 kg down to 18 kg at full production capacity. The industrial quality standards were changed for this type of diode, and some difficulties and delays were encountered in adapting the new technology to meet the standards. However in the end it was proved that the industrial process was able to meet the more stringent requirements. The replacement of the polluting etching process with the cleaner pre-soldering process has been announced to Vishay’s customers and has been well received. Although the results is kept confidential by the company, the technology will probably be transfered to another of Vishay's sites in Hungary.
