Metal fusion bonding – Process – Using high frequency vibratory energy
Reexamination Certificate
1999-10-25
2002-06-25
Drodge, Joseph W. (Department: 1723)
Metal fusion bonding
Process
Using high frequency vibratory energy
C156S060000, C216S056000, C228S164000, C422S129000, C427S247000, C427S309000, C427S327000, C427S328000
Reexamination Certificate
active
06409072
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to chemical microreactors which can be used in the chemical industry amongst other things for synthesizing processes, to methods for their manufacture and to a preferred use of the microreactors.
There have been reports for a number of years in the literature relating to chemical micro reactors which have advantages in comparison with previous production systems for manufacturing chemical compounds. With the conversion of chemical methods into a large industrial production scale there is the basic problem that the dimensions of the production systems are larger by several orders of magnitude than the apparatus used on a laboratory scale for developing the processes. If for example a chemical synthesis is considered, then the relevant scale of size of the chemical species reacting with one another is determined by their molecular size, which generally is in the range of below one nanometer up to a few nanometers. For diffusion and heat transfer phenomena lengths of a few millimeters down to the micrometer range are relevant. Due to the production volumes required in large-scale industry, chemical reactors usually have dimensions which lie in the range between a few centimeters up to several meters. Therefore at least for homogeneous chemical reactions the experience gained on a laboratory scale with reaction volumes of a few liters up to about 100 liters relating to the process management, cannot be directly adopted on an industrial scale. Already with mixing liquids, a stirring mechanism is primarily necessary in order to increase the transport of materials in such a way that the distances between areas of differing concentration are reduced. The so-called scale-up problem also arises from the various dimensions of the reactor. A chemical reaction which has been optimised on the laboratory scale thereafter cannot immediately be transferred to the production system, but must be firstly transferred to a pilot system of dimensions between the laboratory and production scales (technical college scale), before it is finally used in industrial production. A problem is that each stage of this process development requires its own cycle of optimization, each of these cycles being additively involved in the development time required for introduction of the process. In heterogeneous catalysis on the other hand, the catalyst particles are often applied to porous carriers, whose pore size lies in the range of order of magnitude (millimeter to micrometer range) relevant for the transport of materials.
When the process control is not at its optimum and based purely on knowledge from the laboratory scale, for example the yield of the chemical synthesis can be too small, as excessively large proportions of undesired secondary products are formed due to secondary reactions which are preferably taking place.
In order to solve the above problems in transferring a process from the laboratory scale to the production scale, the concept of so-called microreactors was developed a few years ago. This involves a parallel arrangement of a plurality of reaction cells, whose dimensions extend from a few micrometers up to a few millimeters. These reaction cells are formed such that therein physical, chemical or electrochemical reactions can take place. In contrast to a conventional porous system (heterogeneous catalysis), the dimensions of the cells in a microreactor are defined, i.e. produced according to plan in accordance with a technical process. Even the arragement of the individual reaction cells in the ensemble of the reactor is likewise ordered, in particular periodically in one or two dimensions. The necessary feed (inlet) and return (outlet) structures for the fluids (liquids and gases), and sensors and actors, for example valves, cooling and heating members, which influence or monitor the flow of material and heat in the individual cells also belong to the reactors in the extended sense.
One individual reactor cell has a lateral extension which lies in an order of magnitude favourable for optimum transport of material and heat. As the volume flow through one individual reactor cell is extremely small, the entire reactor is enlarged (scale-out) by parallel multiplication of these elementary cells to the industrially necessary size. Due to the small dimensions, local differences of concentration and temperature in the fluid flows are reduced to a minimum. Thus, the processes may be much more accurately adjusted to the optimum reaction conditions, so that the conversion rates in a chemical reaction can be increased for an identical duration time of the reaction medium in the reactor. In addition, the purity and yield of the synthesized materials can be optimized by setting the approximately most favourable reaction conditions. In this way such chemical reactions can also be realized, which were not manageable in the previous way, such as intermediate products by trapping in a controlled manner.
There are a series of proposals for manufacturing the chemical microreactors.
On the one hand a microreactor can be produced for example by stacking a plurality of copper foils, in which grooves are machined by means of a diamond tool in order to form flow ducts. Such a microreactor which is used for partial oxidation of propene to form acrolein is described by D. Hönicke and G. Wiesmeier in the article “Heterogeneous Catalyzed Reactions in a Microreactor” in DECHEMA Monographs, Volume 132, Papers of the Workshop on Microsystem Technology, Mainz, 20 to 21, February 1995, pages 93 to 107. The individual reactor layers are connected together by diffusion bonding and subsequent electron beam welding. For carrying out the chemical reaction it was necessary for the copper inside the originating ducts to be converted into red copper oxide by partial oxidation.
For a precise and reproducible manufacture of the fine structures, a micro-positioning table suitable for such purposes is required. Basically the individual reaction cells are produced serially and thus in a time- and-cost-intensive way.
By means of the LIGA process (Lithographie, Galvano-Formung, Abformung=lithographie, electroforming, shaping), a plastic layer, usually polymethylmethacrylate (PMMA) is exposed by means of synchrotron radiation and is subsequently developed. The structure produced in this way is electrolytically filled up with a metal. Then the metal structure can be again duplicated in further process steps by means of a plastic replication. Such a method is described by W. Ehrfeld and H. Lehr in Radiat. Phys. Chem., Volume 45 (1995), pages 349 to 365, and W. Menz in Spektrum der Wissenschaft, February 1994, pages 92 to 99 and W. Menz in Automatisierungstechnische Praxis, Volume 37, (1995), pages 12 to 22. According to the details in the scientific paper in Spektrum der Wissenschaft loc. cit., individual components or subsystems, which are produced separately, are connected together by suitable jointing techniques.
A technique related to the LIGA process, which operates without the extremely expensive synchrotron radiation, is the so-called laser-LIGA method. In this case the plastic layer of PMMA is structured by a powerful UV laser and then electrolytically duplicated as in the LIGA process (W. Ehrfeld et al., “Potentials and Realization of Microreactors” in DECHEMA Monographs, Volume 132, pages 1 to 29).
W. Menz in Automatisierungstechnische Praxis, loc. cit. also proposes a modified method according to which a microelectronic circuit has been formed on a silicon substrate in a previously known way, firstly a protective layer, thereupon an entire-surface metallizing layer and thereon a plastic moulding compound are depoisited. Then, by means of a metal matrix which has been produced according to the LIGA process, the image of the fluid duct structures is impressed into the moulding compound. Thereafter the residual layers of the moulding compound covering the metal layer in the recesses formed are removed by plasma etching, and metal is deposited electrochemically in the recesses.
Breuer Norbert
Meyer Heinrich
Atotech Deutschland GmbH
Drodge Joseph W.
Paul & Paul
LandOfFree
Chemical microreactors and method for producing same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Chemical microreactors and method for producing same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Chemical microreactors and method for producing same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2976164