Method of producing self-supporting microstructures, thin flat parts or membranes, and utilization of microstructures produced by the method as resistance grids in a device for measuring weak gas flows

Abstract

Firstly, a supporting frame is produced, whose opening is spanned by an auxiliary layer flush on one side. Following the production of microstructures, flat parts or membranes on the common plane defined by the auxiliary layer and the supporting frame, the auxiliary layer is removed, preferably by etching. In a preferred application, the self-supporting microstructures produced in accordance with the method of the invention are used as electrically heatable resistance grids in a device for measuring weak gas flows.

I claim:  
     
         1 . A method of producing self-supporting microstructures, thin flat parts, or membranes, which comprises: 
 a) providing a supporting frame with at least one opening;    b) applying an adhesive film to the supporting frame such that the adhesive film spans the opening in the supporting frame flatly;    c) applying an auxiliary layer to an underside of the adhesive film and adjacent regions of the supporting frame such that the auxiliary layer spans the opening in the supporting frame on one side flush with the supporting frame;    d) removing the adhesive film;    e) constructing component elements selected from the group consisting of microstructures, flat parts, and membranes on the common plane comprising the auxiliary layer and the supporting frame; and    f) removing the auxiliary layer formed in step c).    
     
     
         2 . The method according to  claim 1 , which comprises, prior to applying the adhesive film to the supporting frame, laminating the adhesive film with a rear thereof onto an auxiliary carrier.  
     
     
         3 . The method according to  claim 1 , wherein the adhesive film is a photoresist film.  
     
     
         4 . The method according to  claim 3 , which comprises, subsequently to applying the photoresist film to the supporting frame, hardening the photoresist film with UV radiation.  
     
     
         5 . The method according to  claim 3 , which comprises, subsequently to applying the auxiliary layer, dissolving the photoresist film in a solvent selected from the group consisting of organic solvent and a weak hydroxide solution.  
     
     
         6 . The method according to  claim 1 , wherein the auxiliary layer is applied to the underside of the adhesive film and the adjacent regions of the supporting frame by means of chemical metal deposition and subsequent reinforcement by electroplating.  
     
     
         7 . The method according to  claim 1 , wherein the step of applying the auxiliary layer to the underside of the adhesive film and the adjacent regions of the supporting frame comprises vapor depositing metal in vacuum and subsequently reinforcing by electroplating.  
     
     
         8 . The method according to  claim 1 , wherein step e) comprises additively constructing microstructures by means of metal deposition by electroplating.  
     
     
         9 . The method according to  claim 8 , which comprises first applying a conductive layer to the common plane comprising the auxiliary layer and the supporting frame, and subsequently constructing the microstructures additively on the conductive layer by means of metal deposition by electroplating.  
     
     
         10 . The method according to  claim 1 , wherein step e) comprises subtractively producing the microstructures by structuring layers first applied to an entire area.  
     
     
         11 . The method according to  claim 1 , wherein step e) comprises constructing the microstructures in two planes by using a spacer layer, and removing the spacer layer in a region of the opening in the supporting frame.  
     
     
         12 . The method according to  claim 11 , wherein step of removing the spacer layer comprises etching the spacer layer.  
     
     
         13 . The method according to  claim 1 , wherein step f) comprises removing the auxiliary layer by etching.  
     
     
         14 . The method according to  claim 1 , wherein step c) comprises applying a membrane to the common plane comprising the auxiliary layer and the supporting frame, and, prior to removing the auxiliary layer in step f), producing circuit elements on the membrane.  
     
     
         15 . The method according to  claim 1 , which comprises producing circuit elements on the common plane comprising the auxiliary layer and the supporting frame, and subsequently applying a membrane embedding the circuit elements.  
     
     
         16 . In a device for measuring weak gas flows, an assembly of self-supporting microstructures produced in accordance with  claim 1  and configured as electrically heatable resistance grids in the device for measuring weak gas flows.  
     
     
         17 . The assembly according to  claim 16 , wherein said resistance grids are disposed to come in thermal contact with the gas flow through the device, and which further comprises a bridge circuit with said resistance grids connected therein, said bridge circuit having a first diagonal with a constant current source and a second diagonal with instruments configured to process measured values or display measured values.  
     
     
         18 . The assembly according to  claim 16 , wherein the device has a first chamber and a second chamber and a connecting tube therebetween, and said resistance grids are disposed in said connecting tube between said first chamber and said second chamber and are arranged at right angles to a flow direction at a distance from each other.  
     
     
         19 . The assembly according to  claim 18 , wherein said resistance grids are formed with a serpentine configuration.  
     
     
         20 . The assembly according to  claim 18 , which further comprises a frame-type spacer arranged between said resistance grids and defining a distance therebetween.  
     
     
         21 . The assembly according to  claim 16 , which comprises supporting frames of glass supporting said resistance grids.