Low loss glass-ceramic materials, method of making same and electronic packages including same

Abstract

A glass-ceramic is provided having a thermal expansion coefficient in a range of 3-6 ppm/° C., a dielectric constant that is less than 5 and a Quality factor Q of at least 400. The glass-ceramic consists essentially of SiO 2 in a range of 45-58 wt %, Al 2 O 3 in a range of 10-18 wt % and MgO in a range of 10-25 wt %. A method of making the glass-ceramic is also provided. Further, an electronic package is also provided, including a base member and a glass-ceramic substrate bonded to the base member.

1 . A method of making a glass-ceramic substrate having a thermal expansion coefficient in a range of 3-6 ppm/° C., a dielectric constant of less than 5 and a Quality factor (Q) of at least 400 for use in high frequency electrical applications, said method comprising the steps of:
 providing a glass-ceramic powder having an average particle size in a range of 1-20 μm and consisting essentially of SiO 2  in a range of 45-58 wt %, Al 2 O 3  in a range of 10-18 wt % and MgO in a range of 10-25 wt %;   combining said glass-ceramic powder with processing additives to form a mixture;   forming a green body from said mixture;   sintering said green body at a temperature in a range of 900-1150° C. for up to 6 hours to form a sintered glass-ceramic body; and   cooling said sintered glass-ceramic body to form said glass-ceramic substrate.   
     
     
         2 . The method of  claim 1 , wherein said green body comprises a green sheet. 
     
     
         3 . The method of  claim 2 , further comprising the steps of providing a plurality of said green sheets and laminating said plurality of green sheets under heat and pressure to form a laminated green multi-layer structure. 
     
     
         4 . The method of  claim 1 , wherein said sintering step is performed at a temperature of about 900° C. for 10 minutes. 
     
     
         5 . The method of  claim 1 , wherein said sintering step is performed at a temperature of about 1000° C. for 1 hour. 
     
     
         6 . The method of  claim 1 , wherein said sintering step is performed at a temperature of about 1100° C. for 3 hours. 
     
     
         7 . The method of  claim 1 , further comprising the steps of:
 providing an additive consisting of a particulate material selected from the group consisting of a thermal expansion coefficient increasing additive, a thermal expansion coefficient reducing additive, and a sintering aid, said additive having a particle size in a range of 1-20 μm; and   adding said additive to said glass-ceramic powder in said combining step.   
     
     
         8 . The method of  claim 7 , wherein said thermal expansion coefficient increasing additive comprises 1-15 wt % crystalline silica. 
     
     
         9 . The method of  claim 7 , wherein said additive comprises 4-12 wt % of a borosilicate glass. 
     
     
         10 . The method of  claim 7 , wherein said thermal expansion coefficient increasing additive comprises 1-15 wt % of a material having a composition consisting essentially of 50-55 wt % SiO 2 , 12-18 wt % Al 2 O 3 , 10-18 wt % MgO and 4-16 wt % ZnO and having a primary crystal phase consisting of crystalline silica.