Apparatus for manufacturing components using electrophoretic deposition

Abstract

The invention is an apparatus, methods and systems for the production of coatings or small components having defined pre-set dimensions and properties by electrophoretic deposition (EPD) on electrically conducting or semi-conducting substrates. The invention provides efficient and precise mass manufacturing of components by EPD, such as anodes of electrolytic capacitors, by achieving high utilization of expensive raw materials and by consistently achieving tight dimensional tolerances of defined component shapes in repeated depositions. This includes production sequences of discrete components, batches of components, and production by semi-continuous operation.

1 . Apparatus for production of small components with defined pre-set dimensions and properties by electrophoretic deposition (EPD) on electrically conducting or semi-conducting substrates, said apparatus comprising: 
 a. an electrical circuit comprising a power supply;    b. an EPD cell containing a homogenous EPD suspension;    c. substrate fixtures for holding said substrates, for immersing said substrates in said EPD suspension, and for making electrical contact between said substrates and said electrical circuit;    d. counter electrodes; and    e. elements for shaping the component or providing tight dimensional tolerances.    
   
   
       2 . The apparatus of  claim 1  comprising components for monitoring the chemical and electrical properties of the EPD dispersion.  
   
   
       3 . The apparatus of  claim 1  comprising components for controlling the shape and strength of the electrical field in the EPD cell.  
   
   
       4 . The apparatus of  claim 1  comprising components for controlling the electrical current flowing through the external electrical circuit and the voltage across said circuit.  
   
   
       5 . The apparatus of  claim 1  wherein the substrate has a shape chosen from the group: 
 a. wire-shaped;    b. flat-shaped;    c. sieve-shaped; and    d. 3D shaped.    
   
   
       6 . The apparatus of  claim 1  wherein the substrate comprises of conductive and non-conductive areas.  
   
   
       7 . The apparatus of  claim 1  wherein the elements for shaping the component or providing tight dimensional tolerances comprise one of the following: 
 a. components for protecting selective areas on the conductive substrates from being exposed to the EPD dispersion, thereby sharply demarcating the part of said substrate upon which material is deposited by EPD and the part of said substrate that is clean of said deposit;    b. a structure in which part of said substrate is contained which sharply demarcates the part of said substrate upon which material is deposited by EPD from that part of said substrate that is clean of said deposit;    c. a physical barrier or masking structure placed near the end of said substrate undergoing electrophoretic deposition, thereby shaping or improving the dimensional tolerance of said end of the component made by EPD deposition on said substrate; and    d. multiple or secondary electrodes arranged around said components undergoing EPD, thus shaping the electric field around said component and thereby shaping the dimensions of said component.    
   
   
       8 . The apparatus of  claim 7 , wherein the substrate fixture covers a part of the substrate, thereby protecting selective areas on the conductive substrates from being exposed to the EPD dispersion.  
   
   
       9 . The apparatus of  claim 7 , wherein the structure in which part of the substrate is contained is a capillary or a tube.  
   
   
       10 . The apparatus of  claim 7 , wherein the structure in which part of the substrate is contained is a slit which is slightly wider and thicker than said substrate.  
   
   
       11 . The apparatus of  claim 7 , wherein the structure in which part of the substrate is contained is filled with clean solvent compatible with the dispersion fluid, thereby further reducing diffusion of particles into the gap between said substrate the walls of said structure.  
   
   
       12 . The apparatus of  claim 11 , wherein pressure is applied to the top end of the structure.  
   
   
       13 . The apparatus of  claim 12 , wherein the applied pressure creates a small amount of flow of clean solvent from the structure into the dispersion fluid, thereby further reducing diffusion of particles into the gap between the substrate and the walls of said structure.  
   
   
       14 . The apparatus of  claim 12 , wherein the structure is a capillary and the applied pressure is equal to the pressure exerted by the capillary force, thereby preventing capillary flow of dispersion fluid into the structure.  
   
   
       15 . The apparatus of  claim 12 , wherein the applied pressure is caused by a fluid reservoir at the upper end of the structure.  
   
   
       16 . The apparatus of  claim 11 , wherein the clean solvent is immiscible with the dispersion fluid, thereby creating a sharp barrier between the end of the structure and said dispersion fluid, thereby further reducing diffusion of particles into the gap between the substrate and the walls of said structure.  
   
   
       17 . The apparatus of  claim 1 , wherein the chemical and particle composition of the dispersion is maintained uniform throughout the deposition cell.  
   
   
       18 . The apparatus of  claim 1 , wherein structures in the EPD cell, which are necessary for structural support or other functions, are made of conductive material and charged to the potential of the counter electrode, thereby reducing deposition of dispersion particles on said structures.  
   
   
       19 . The apparatus of  claim 1 , wherein a uniform electric field is created within the deposition cell around the components undergoing electrophoretic deposition.  
   
   
       20 . The apparatus of  claim 1 , comprising a system for recycling the EPD dispersion, said system removing said dispersion from the EPD cell and causing it to flow to a recycling cell, wherein the properties of said dispersion are changed before returning it to said EPD cell.  
   
   
       21 . The apparatus of  claim 20 , wherein the dispersion is removed from and returned to the EPD cell in one of the following ways: 
 a. continuously; or    b. between deposition cycles.    
   
   
       22 . The apparatus of  claim 20 , wherein the properties of the dispersion that are changed before returning it to the EPD cell are chosen from the group comprised of: 
 a. particle concentration;    b. pH;    c. Z-potential; and    d. electrical conductivity.    
   
   
       23 . The apparatus of  claim 22 , wherein the concentration of the dispersion transferred to the recycling cell is corrected to its original concentration before returning it to the EPD cell.  
   
   
       24 . The apparatus of  claim 20 , wherein the recycling cell comprises ultrasonic agitation means to break down agglomerates to their original size distribution.  
   
   
       25 . The apparatus of  claim 20 , wherein the dispersion in the recycling cell is allowed to undergo sedimentation for a predetermined time in order to remove large agglomerates not compatible with the original particle size distribution.  
   
   
       26 . The apparatus of  claim 20 , wherein excessively fine particles that are not in compliance with the original particle size distribution are removed from the dispersion in the recycling cell.  
   
   
       27 . The apparatus of  claim 20 , wherein the chemistry of the dispersion fluid in the recycling cell is corrected by the addition of tiny amounts of chemical additives.  
   
   
       28 . The apparatus of  claim 1 , wherein the small components are formed by electrophoretic deposition in one of the following ways: 
 a. as discrete components; or    b. as batches.    
   
   
       29 . The apparatus of  claim 1 , wherein the small components are formed by electrophoretic deposition in a semi-continuous operation.  
   
   
       30 . The apparatus of  claim 29 , wherein the small components are formed on a substrate in the form of a continuous strip or ribbon.  
   
   
       31 . The apparatus of  claim 29 , wherein the small components are formed on substrates that are arranged on a carousel.  
   
   
       32 . The apparatus of  claim 1 , wherein the small components are selected from the group comprising: 
 a. porous anodes of electrolytic capacitors;    b. pitch bonding capillaries in microelectronics;    c. high temperature nozzles;    d. ferrules for connecting optical fibers;    e. high temperature engine components;    f. dental crowns; and    g. bearing parts.    
   
   
       33 . A method for controlling the use of the apparatus of  claim 1  for the preparation of a component by electrophoretic deposition, said method comprising making use of one of the following: 
 a. maintaining constant deposit mass from run to run in constant current operation by applying a new fVdt for each deposition run in accordance with the control model;    c. monitoring of the electrophoretic current under constant voltage operation in order to determine the endpoint for usage of the depleted dispersion; or    d. maintaining constant deposit mass from run to run by adjustment of the deposition time of sequential depositions.