Dual composition ceramic substrate for microelectronic applications

Abstract

Ceramic substrates ( 1 ) for microelectronic modules are formed in multiple layers ( 7 & 9 ) fused into a unitary one-piece assembly. The layers contain the same ceramic material but in different purity so that one outer layer ( 9 ) is optimal in composition for bonding to a thick film conductor ( 11 ) and the other outer layer ( 7 ) is optimal in composition for bonding to a thin film conductor ( 13 ). In a dual composition substrate embodiment one layer is formed of a 96% alumina composition and the second layer is formed of a 99.6% alumina composition.

1 - 8 . (canceled)  
     
     
         10 . The method of manufacturing a dielectric ceramic substrate for a microelectronic module, comprising the steps of: 
 forming a first layer of a first composition of ceramic material and binder;    forming a second layer of a second composition of said ceramic material and binder over said first layer;    heating said first and second layers to fuse said ceramic material and binder of said first layer and of said second layer and to fuse said first and second layers together to form a one-piece unitary assembly; and    cooling said one-piece unitary assembly.    
     
     
         11 . The method of manufacturing a dielectric ceramic substrate for a microelectronic module as defined in  claim 10 , wherein said step of forming a first layer of a first composition of ceramic material and binder includes the steps of: 
 preparing a first slurry of ceramic material and binder in said first composition, skiving said first slurry onto a carrier tape and drying said first slurry to form a first green tape on said carrier tape; and    wherein said step of forming a second layer of a second composition of said ceramic material and binder over said first layer, includes the steps of:    preparing a second slurry of said ceramic material and binder in said second composition, skiving said second slurry onto said first green tape and drying said second slurry to form a composite green tape on said carrier tape.    
     
     
         12 . The method of manufacturing a dielectric ceramic substrate for a microelectronic module as defined in  claim 11 , further including the step of removing said composite green tape from said carrier film following said step of drying said second slurry.  
     
     
         13 . The method of manufacturing a dielectric ceramic substrate for a microelectronic module as defined in  claim 12 , wherein one of said first and second compositions of ceramic and binder comprises 96% alumina and the remainder binder and wherein the other of said first and second compositions comprises 99.6% alumina and the remainder binder.  
     
     
         14 . The method of manufacturing a dielectric ceramic substrate for a microelectronic module as defined in  claim 13 , further comprising the step of grinding and lapping said one piece unitary assembly.  
     
     
         15 . The method of manufacturing a dielectric ceramic substrate for a microelectronic module as defined in  claim 10 , further comprising the step of grinding and lapping said one piece unitary assembly.  
     
     
         16 . The method of manufacturing a dielectric ceramic substrate for a microelectronic module as defined in  claim 13 , further comprising the steps of forming a thick film conductor on said one of said first and second layers and forming a thin film conductor on said other one of said first and second layers.