Printed circuit boards having embedded thick film capacitors

Abstract

A method of forming printed wiring boards having embedded thick-film capacitors includes covering capacitor layers with a protective coating prior to etching to prevent etching solutions from contacting with and damaging the capacitor layers and forming vias directly between the capacitor electrodes and the board circuitry.

1 . A method of making a capacitor comprising: 
 providing a metallic foil;    forming a dielectric over the metallic foil;    forming a first electrode over a portion of the dielectric;    forming a protective coating over a portion of the metallic foil,    including the entire dielectric; and    etching the metallic foil to form a second electrode.    
   
   
       2 . A capacitor comprising: 
 a first electrode formed from a metallic foil;    a dielectric adjacent to the first electrode;    a second electrode adjacent to the dielectric; and    a protective coating disposed over and contacting at least a part of the dielectric and at least part of the metallic foil.    
   
   
       3 . A printed circuit board, comprising: 
 at least one capacitor embedded in at least one layer of dielectric material, the capacitor comprising: 
 a first electrode formed from a metallic foil;  
 a dielectric adjacent to the first electrode; and  
 a second electrode adjacent to the dielectric; and  
   a protective coating disposed over and contacting the entire dielectric and comprising at least one of an organic encapsulant material and a fired glass.    
   
   
       4 . The printed circuit board of  claim 3 , wherein the at least one layer of dielectric material comprises a plurality of layers of dielectric material, the printed circuit board comprising: 
 one or more vias connecting to the capacitor.    
   
   
       5 . The printed circuit board of  claim 3 , wherein the dielectric is a two-layer dielectric.  
   
   
       7 . The printed circuit board of  claim 3 , wherein the protective coating contacts the first electrode.