Lead free ltcc tape composition

Abstract

The invention relates to the use of and method of forming Low Temperature Cofired Ceramic (LTCC) circuits for high frequency applications. Furthermore, the invention relates to the novel LTCC thick film compositions and the structure itself.

1 . A composite comprising (a) at least one low k thick film dielectric composition comprising, based on weight percent total inorganic composition:
 (1) 40-80 percent glass frit with a log viscosity range of 2-6 Poise;   (2) 20-60 percent ceramic oxide selected from the group consisting essentially of silica, silicates, and mixtures thereof, wherein said ceramic oxide has a dielectric constant in the range of 2 to 5 k; and   (b) at least one high k thick film dielectric tape having a dielectric constant in the range of 5 to 8.   
     
     
         2 . The composite of  claim 1 , the low k thick film dielectric composition further comprising: up to 5 weight percent inorganic oxides selected from the group consisting of copper oxide, silicon dioxide, aluminum oxides and mixed oxides. 
     
     
         3 . A method of using a low k thick film in the formation of a low temperature cofired ceramic structure for high frequency applications comprising the steps:
 providing two or more layers of a low k thick film dielectric tape, having dielectric constant in the range of 2 to 5 and comprising, based on solids:   (a) 40-80 weight percent glass composition; (b) 20-60 weight percent ceramic oxide; dispersed in a solution of (c) organic polymeric binder;   providing two or more layers of a high k thick film dielectric tape having a dielectric constant in the range of 5 to 8;   collating the layers of low k and high k thick film dielectric tapes wherein said dielectric tapes are not separated by a buffer layer;   laminating the layers of low k thick film and high k thick film to form an assembly; and   processing the assembly to form a low temperature cofired ceramic structure to obtain an x-y shrinkage from zero to 5%.   
     
     
         4 . The method of  claim 3  wherein said glass composition consists essentially of, based on mole percent, 50-56% B 2 O 3 , 0.5-5.5% P 2 O 5 , SiO 2  and mixtures thereof, 20-50% CaO, 2-15% Ln 2 O 3 where Ln is selected from the group consisting of rare earth elements and mixtures thereof;
 0-6% M I   2 O where M I  is selected from the group consisting of alkali elements; and 
 0-10% Al 2 O 3 , with the proviso that the composition is water millable. 
 
     
     
         5 . A thick film tape comprising the composition comprising, based on weight percent total inorganic composition:
 (1) 40-80 percent glass frit with a log viscosity range of 2-6 Poise;   (2) 20-60 percent ceramic oxide selected from the group consisting essentially of silica, silicates, and mixtures thereof, wherein said ceramic oxide has a dielectric constant in the range of 2 to 5 k;   
       said tape having a shrinkage of about 1% or less. 
     
     
         6 . A LTCC device comprising one or more tapes of  claim 5 , wherein the one or more tapes form a signal processing section. 
     
     
         7 . The LTCC device of  claim 6 , wherein the tape provides X-Y constraining. 
     
     
         8 . The LTCC device of  claim 6 , wherein the device further comprises a constraining tape. 
     
     
         9 . A method of using a low k thick film tape in the formation of a low temperature cofired ceramic structure for high frequency applications comprising the steps:
 (a) providing two or more layers of a low k thick film dielectric tape, wherein the tape comprises the composition of  claim 1  dispersed in a solution of organic polymeric binder;   (b) applying a conductor track on the two or more layers, and applying vias connecting the two or more layers, forming a functional layer;   (c) collating multiple functional layers;   (d) laminating the collated functional layers; and   (e) processing the assembly to form a low temperature cofired ceramic structure to obtain an x-y shrinkage from zero to 5%.   
     
     
         10 . The method of  claim 9 , wherein the LTCC device further comprises one or more high k thick films. 
     
     
         11 . The method of  claim 9  wherein, after the lamination of step (d), the two or more layers of a low k thick film dielectric tape form a single signal processing section. 
     
     
         12 . An LTCC device made by the method of  claim 9 . 
     
     
         13 . A beamformer, filter, antenna, or coupler comprising the LTCC device of  claim 12   
     
     
         14 . The beamformer of  claim 13 , wherein the beamformer is used in an application selected from the group consisting of: high frequency sensors, multi-mode radar modules, telecommunications components, telecommunications modules, and antennas. 
     
     
         15 . An electrically functioning circuit comprising one or more functional layers, wherein a functional layer comprises:
 (a) two or more layers of a low k thick film dielectric tape of  claim 5 ; and   (b) a conductor track portion, wherein the conductor track portion is on the two or more layers of low k thick film dielectric tape, wherein vias connect the two or more layers.   
     
     
         16 . The electrically functioning circuit of  claim 15 , wherein the circuit is a microwave module, package, or board. 
     
     
         17 . The electrically functioning circuit of  claim 15 , wherein the circuit further comprises a surface metallization. 
     
     
         18 . The electrically functioning circuit of  claim 15 , wherein the two or more tape layers form a signal processing section. 
     
     
         19 . The electrically functioning circuit of  claim 15 , wherein the tape provides X-Y constraining. 
     
     
         20 . The electrically functioning circuit of  claim 15 , wherein the circuit further comprises a constraining tape.