Spray valve

Abstract

The invention relates to an apparatus for coating a substrate ( 60 ), in particular a printed circuit board ( 61 ), with a device ( 16 ) for applying a coating material (material applying device) and a device ( 14 ) for supplying a gaseous medium (gas supplying device), the material applying device having an inner tubular element ( 16 ). The apparatus is distinguished by the fact that the gas supplying device has an outer tubular element ( 14 ) which is arranged coaxially in relation to the inner tubular element ( 16 ) and encloses the latter, so that a gas supply channel ( 19 ) is formed between the outer tubular element ( 14 ) and the inner tubular element ( 16 ), the supply channel ( 19 ) being designed in such a way that the gaseous medium flows out parallel to the coating material, in order to displace the coating material when it impinges on the substrate ( 60 ) and in this way distribute it over the surface area. Furthermore, the invention relates to a method for coating a substrate.

What is claimed is:  
     
         1 . An apparatus for coating a substrate, in particular a printed circuit board, with a device for applying a coating material (material applying device) and a device for supplying a gaseous medium (gas supplying device), the material applying device having an inner tubular element, wherein the gas supplying device has an outer tubular element which is arranged coaxially in relation to the inner tubular element and encloses the latter, so that a gas supply channel is formed between the outer tubular element and the inner tubular element, the supply channel being designed in such a way that the gaseous medium flows out parallel to the coating material, in order to displace the coating material when it impinges on the substrate and in this way distribute it over the surface area.  
     
     
         2 . The apparatus as claimed in  claim 1 , wherein the inner tubular element has an end portion of equal diameter, facing the substrate.  
     
     
         3 . The apparatus as claimed in  claim 1 , wherein the end portion of the outer tubular element has a diameter of approximately 4 mm.  
     
     
         4 . The apparatus as claimed in  claim 1 , wherein a heating device is provided for heating the gaseous medium, the heated medium heating the coating material in the inner tubular element on its way through the outer tubular element.  
     
     
         5 . The apparatus as claimed in  claim 1 , wherein the outer tubular element is assigned a flow element, in order to make the gas stream through the element laminar.  
     
     
         6 . The apparatus as claimed in  claim 1 , wherein the gas supplying device has an admixing unit, in order to admix a powdered material with the gaseous medium.  
     
     
         7 . The apparatus as claimed in  claim 1 , wherein the material applying device has a shut-off valve, the closing operation of which begins and ends the material flow in a way corresponding to an asymptotic curve.  
     
     
         8 . The apparatus as claimed in  claim 7 , wherein the shut-off valve is a ball valve in the form of a 3-way valve.  
     
     
         9 . The apparatus as claimed in  claim 7 , wherein the opening and closing speed of the shut-off valve can be controlled.  
     
     
         10 . The apparatus as claimed in  claim 8 , wherein the shut-off valve can be switched over for cleaning the inner tubular element.  
     
     
         11 . The apparatus as claimed in  claim 1 , wherein it is formed in such a way that it can be made to move in at least two directions (x axis, y axis).  
     
     
         12 . The apparatus as claimed in  claim 11 , wherein it is designed in such a way that it can be swiveled.  
     
     
         13 . A method for coating a substrate with a coating material with the steps of: 
 applying the coating material to the substrate in such a way that a bead is formed, and    subjecting the bead to a jet of a gaseous medium, with the result that the bead is displaced and distributed over the surface area.    
     
     
         14 . The method of  claim 13 , wherein said substrate is a printed circuit board, and the coating material is a protective coating.  
     
     
         15 . The method as claimed in  claim 13 , wherein the gaseous medium is guided coaxially in relation to the coating material.  
     
     
         16 . The method as claimed in  claim 13 , wherein the gaseous medium is an inert gas.  
     
     
         17 . The method as claimed in  claim 15 , wherein the gaseous medium is heated, it likewise heating the coating material on the way to the substrate.  
     
     
         18 . The method as claimed in  claim 13 , wherein the coating material is applied to the substrate in the form of drops.  
     
     
         19 . The method as claimed in  claim 13 , wherein a powdered additive is admixed with the gaseous medium.  
     
     
         20 . The method as claimed in  claim 13 , wherein low-viscosity and high-viscosity coating materials are used.  
     
     
         21 . The method as claimed in  claim 13 , wherein a casting resin (hotmelt adhesive) is used as coating material.