Electrically conductive filled through holes

Abstract

The present invention provides a unique conductive composition for filling vias or through holes to make reliable vertical or Z-connects. The through holes may be plated or unplated prior to filling. A description for making high density electronic packaging using this feature is also disclosed.

We claim:  
     
         1 . A core-shell particle comprising: 
 a) a core having a predetermined melting point or decomposition point; and    b) a shell having a predetermined fusing temperature less than said melting point or decomposition point of said core, so that when said core-shell particle is heated above said fusing temperature, a non-porous solid is formed.    
     
     
         2 . The core-shell particle recited in  claim 1  wherein said particle is less than 20 microns in diameter and said shell is between about 0.2 and about 1 micron thick.  
     
     
         3 . The core-shell particle recited in  claim 1  wherein said core comprises a first metal and said shell comprises a second metal.  
     
     
         4 . The core-shell particle recited in  claim 3  wherein said first metal comprises copper and said second metal is selected from the group consisting of tin, indium, bismuth and antimony and alloys thereof.  
     
     
         5 . The core-shell particle recited in  claim 1  wherein said core comprises an organic composition.  
     
     
         6 . The core-shell particle recited in  claim 5  wherein said organic composition is selected from the group consisting of polyester and polystyrene.  
     
     
         7 . The core-shell particle recited in  claim 5  wherein the shell comprises two metal layers with the first metal selected from the group consisting of copper, nickel, palladium, platinum, silver and alloys thereof and the second metal selected from the group consisting of indium, tin, bismuth, antimony and alloys thereof.  
     
     
         8 . The core-shell particle recited in  claim 1  wherein said core comprises silica.  
     
     
         9 . The core-shell particle recited in  claim 8  wherein said silica comprises a solid particle.  
     
     
         10 . The core-shell particle recited in claimi  8  wherein said silica comprises a hollow particle.  
     
     
         11 . A mixture of a polymeric material and said core-shell particle defined in  claim 1  wherein said polymeric material is a thermosetting or thermoplastic substance having a predetermined curing temperature above said fusing temperature.  
     
     
         12 . A three phase composite conductive article comprising: 
 a) a first phase comprising a metal having a first, three dimensional lattice network defining a solid volume;    b) a second phase comprising particles embedded in and affixed to said first phase; and    c) a third phase comprising a polymeric material having a second, three dimensional lattice network, said second, three dimensional network interwoven within said first, three dimensional network and substantially filling said solid volume;    wherein the quantity of said second phase is sufficient to render said article conductive.    
     
     
         13 . The conductive article recited in  claim 12  wherein said second phase comprises a second metal, having a higher melting point than that of said first metal.  
     
     
         14 . The conductive article recited in  claim 12  wherein said second phase comprises an organic composition, having a higher melting point than that of said metal.  
     
     
         15 . A process of heating a mixture to form an electrically conductive, non-porous solid, comprising: 
 a) providing a core-shell particle comprising a core comprising a first metal having a predetermined melting point, and a shell surrounding said core comprising a second metal having a predetermined fusing temperature, said melting point being greater than said fusing temperature;    b) providing a polymeric thermosetting or thermoplastic substance having a predetermined curing temperature;    c) mixing said core-shell particle with said polymeric substance to create a substantially homogeneous mixture; and    d) heating said mixture to a temperature above said curing and said fusing temperatures to generate an electrically conductive, non-porous solid.    
     
     
         16 . A process of heating a mixture to form an electrically conductive, non-porous solid, comprising: 
 a) providing a core-shell particle comprising an organic core having a predetermined melting or decomposition point, and a metallic shell having a predetermined fusing temperature, said melting or decomposition point being greater than said fusing temperature;    b) providing a polymeric thermosetting or thermoplastic substance having a predetermined curing temperature;    c) mixing said core-shell particle with said polymeric substance to create a substantially homogeneous mixture; and    d) heating said mixture above said curing and said fusing temperatures to generate an electrically conductive, non-porous solid.    
     
     
         17 . A microelectronic package comprising: 
 a) a dielectric substrate having upper and lower lateral faces and at least one via being defined by a wall;    b) electronic circuitry and features affixed to at least one of said lateral surfaces; and    c) a composition comprising an interpenetrating network substantially filling said via, said network comprising a first matrix of cured thermosetting or thermoplastic material and a second matrix comprising an electrically conductive composition electrically connecting said via to said electronic circuitry.    
     
     
         18 . The microelectronic package recited in  claim 17  wherein said conductive composition comprises discrete metallic particles proximate each other, said particles being embedded in a layer of a metal.  
     
     
         19 . The microelectronic package recited in  claim 17  wherein said conductive composition comprises discrete organic particles proximate each other, said particles being embedded in a layer of a metal.  
     
     
         20 . The microelectronic package recited in  claim 17  wherein said second matrix is formed upon heating a core-shell particle above the fusing point thereof.  
     
     
         21 . The microelectronic package as recited in  claim 17  further comprising a conductive layer disposed between said interpenetrating network composition and said wall.  
     
     
         22 . A process of manufacturing a microelectronic package intermediary structure comprising the steps of: 
 a) providing a dielectric substrate having an upper and lower lateral surface;    b) forming at least one via within said dielectric substrate connecting said upper surface to said lower surface;    c) filling said via with a substantially uniform mixture of thermosetting or thermoplastic material having a predetermined curing temperature and core-shell particles having fusible shells; and    d) heating said filled via and said dielectric substrate to a temperature above said curing temperature in order to cure said material, to fuse said core-shell particles, and to form an electrically conductive via.    
     
     
         23 . The process of manufacturing a microelectronic package intermediary structure as recited in  claim 22  further comprising the step of: 
 e) after forming said via, step (b), flash plating or electroless plating a conductive layer to said upper and lower lateral surfaces and a via wall, forming a conductive layer having a thickness of at least 0.5 mil.  
 
     
     
         24 . The process of manufacturing a microelectronic package intermediary structure as recited in  claim 22  further comprising the steps of: 
 e) applying conductive layers to at least one of said lateral surfaces; and  
 f) circuitizing said conductive layer, whereby said circuitry is in electrical contact with said electrically conductive via.  
 
     
     
         25 . The process of manufacturing a microelectronic package intermediary structure as recited in  claim 22  further comprising the step of: 
 e) after heating said via and said substrate step (d), soldering an electrical component to a top surface of said filled via without the use of a pad.