Method for providing hermetic electrical feedthrough

Abstract

A method for fabricating the hermetic electrical feedthrough. The method comprises providing a ceramic sheet having an upper surface and a lower surface, forming at least one via hole in said ceramic sheet extending from said upper surface to said lower surface, inserting a conductive thickfilm paste into said via hole, laminating the ceramic sheet with paste filled via hole between an upper ceramic sheet and a lower ceramic sheet to form a laminated ceramic substrate, firing the laminated ceramic substrate to a temperature to sinter the laminated ceramic substrate and cause the paste filled via hole to form metalized via and cause the laminated ceramic substrate to form a hermetic seal around said metalized via, and removing the upper ceramic sheet and the lower ceramic sheet material from the fired laminated ceramic substrate to expose an upper and a lower surface of the metalized via.

1 . A method of fabricating a hermetic electrical feedthrough, the method comprising:
 providing a ceramic sheet having an upper surface and a lower surface;   forming at least one via hole in said ceramic sheet extending from said upper surface to said lower surface;   inserting a conductive thick film paste into said via hole;   laminating the ceramic sheet with paste filled via hole between an upper ceramic sheet and a lower ceramic sheet to form a laminated ceramic substrate;   firing the laminated ceramic substrate to a temperature to sinter the laminated ceramic substrate and cause the paste filled via hole to form a metalized via and cause the laminated ceramic substrate to form a hermetic seal around said metalized via; and   removing the upper ceramic sheet and the lower ceramic sheet material from the fired laminated ceramic substrate to expose an upper and a lower surface of the metalized via.   
   
   
       2 . The method of  claim 1 , wherein said ceramic sheet is formed of material comprised of at least 90% aluminum oxide. 
   
   
       3 . The method of  claim 1 , wherein said ceramic sheet is formed of material comprised of at least 92% aluminum oxide. 
   
   
       4 . The method of  claim 1 , wherein said ceramic sheet after said firing and material removal steps is less than or equal to 40 mils thick. 
   
   
       5 . The method of  claim 1 , wherein said ceramic sheet after said firing and material removal steps is less than 15 mils thick. 
   
   
       6 . The method of  claim 1 , wherein said paste comprises platinum. 
   
   
       7 . The method of  claim 1 , wherein the metalized via has a diameter of less than or equal to 20 mils. 
   
   
       8 . The method of  claim 1 , wherein the metalized via has a diameter of less than or equal to 10 mils. 
   
   
       9 . The method of  claim 1 , wherein the ceramic sheet is unfired. 
   
   
       10 . The method of  claim 1 , wherein forming at least one via hole in said ceramic sheet comprises punching the via hole using a punch tool, etching the via hole using a solvent etching, using laser ablation or drilling the via hole. 
   
   
       11 . The method of  claim 1 , wherein inserting a conductive thick film paste into said via hole comprises:
 disposing the ceramic sheet with the via hole between a stencil layer and a vacuum base, wherein the stencil layer includes at least one though hole that is aligned above the via hole;   roll the conductive thickfilm paste across the stencil layer; and   pull the conductive thickfilm paste into the via hole though the hole in the stencil layer with a vacuum created by the vacuum base.   
   
   
       12 . The method of  claim 1 , wherein laminating the ceramic sheet with paste filled via holes between the upper ceramic sheet and the lower ceramic sheet to form the laminated ceramic substrate comprises:
 placing the ceramic sheet with paste filled via holes together with the upper ceramic sheet and the lower ceramic sheet in a heatpress; and   applying heat and pressure by the heatpress until the laminated ceramic substrate is formed.   
   
   
       13 . The method of  claim 1 , wherein firing the laminated ceramic substrate comprises evaporation, binder burnout and sintering of the laminated ceramic substrate. 
   
   
       14 . The method of  claim 1 , wherein said ceramic material comprises aluminum oxide, zirconium oxide or mixture thereof. 
   
   
       15 . The method of  claim 1 , wherein said ceramic material comprises less than 99% aluminum oxide. 
   
   
       16 . The method of  claim 1 , wherein the fired laminated ceramic substrate has a thickness of less than 20 mils after removing the upper ceramic sheet and the lower ceramic sheet material. 
   
   
       17 . The method of  claim 1 , wherein the fired laminated ceramic substrate has a thickness of 15-20 mils after removing the upper ceramic sheet and the lower ceramic sheet material. 
   
   
       18 . The method of  claim 1 , wherein said conductive thickfilm paste comprises a material selected from the group consisting of platinum, titanium, gold, palladium, tantalum, and niobium. 
   
   
       19 . The method of  claim 1 , wherein said conductive thickfilm paste comprises noble metal, refractory metal or mixture thereof. 
   
   
       20 . A method of fabricating a hermetic electrical feedthrough, the method comprising:
 providing a plurality of ceramic sheets having an upper surface and a lower surface;   forming a plurality of via holes in each of the ceramic sheets extending from said upper surface to said lower surface of each ceramic sheet;   inserting a conductive thickfilm paste into the via holes of each ceramic sheet;   stacking the plurality of ceramic sheets on top of each other, wherein the via holes filled with conductive thickfilm paste of each ceramic sheet are substantially aligned with the via holes filled with conductive thickfilm paste of the other ceramic sheets;   sandwiching the stacked ceramic sheets between an upper ceramic sheet and a lower ceramic sheet;   laminating the stacked plurality of ceramic sheets with the lower ceramic sheet and the upper ceramic sheet to form a laminated ceramic substrate;   firing the laminated ceramic substrate to a temperature to sinter the laminated ceramic substrate and cause the paste filled via holes to form metalized vias and cause the laminated ceramic substrate to form a hermetic seal around the metalized vias; and   removing the upper ceramic sheet and the lower ceramic sheet material from the fired laminated ceramic substrate to expose an upper and a lower surface of the metalized vias.