Electronic module including a low temperature co-fired ceramic (LTCC) substrate with a capacitive structure embedded therein and related methods
A method for making an electronic module includes forming a low temperature co-fired ceramic (LTCC) substrate with at least one capacitive structure embedded therein. Forming the LTCC substrate may include arranging first and second unsintered ceramic layers and the at least one capacitive structure therebetween. The at least one capacitive structure may include a pair of electrode layers, an inner dielectric layer between the pair of electrode layers, and at least one outer dielectric layer adjacent at least one of the electrode layers and opposite the inner dielectric layer. The at least one outer dielectric layer preferably has a dielectric constant less than a dielectric constant of the inner dielectric layer. The unsintered ceramic layers and the at least one capacitive structure may also be heated, and at least one electronic device may be mounted on the LTCC substrate and electrically connected to the at least one embedded capacitive structure.
1. An electronic module comprising:
a low temperature co-fired ceramic (LTCC) substrate;
at least one capacitive structure embedded in said LTCC substrate comprising a pair of electrode layers, an inner dielectric layer between said pair of electrode layers, and at least one outer dielectric layer adjacent at least one of said electrode layers and opposite said inner dielectric layer, said at least one outer dielectric layer having a dielectric constant less than a dielectric constant of said inner dielectric layer; and
at least one electronic device mounted on said LTCC substrate and electrically connected to said at least one embedded capacitive structure;
said at least one outer dielectric layer comprising respective at least one outer dielectric layers adjacent each of said electrode layers and opposite said inner dielectric layer, and each at least one outer dielectric layer comprising a first outer dielectric layer and a second outer dielectric layer between said first outer dielectric layer and a respective electrode layer;
said second outer dielectric layer having a greater dielectric constant than a dielectric constant of said first outer dielectric layer.
2. The electronic module of claim 1 wherein the dielectric constant of said first outer dielectric layer is in a range of about 7–10, and the dielectric constant of said second outer dielectric layer is in a range of about 11–17.
3. The electronic module of claim 1 wherein said inner dielectric layer has a dielectric constant of greater than about 2000.
4. The electronic module of claim 1 wherein said LTCC substrate further comprises at least one signal trace adjacent at least one of said outer dielectric layers.
5. The electronic module of claim 1 wherein said outer dielectric layers and said inner dielectric layer each comprises less than about 15% by weight of glass.
6. The electronic module of claim 1 wherein said outer dielectric layers comprise at least one of CaO, MgO, ZrO 2 , BaO, and SiO 2 .
7. The electronic module of claim 1 wherein said inner dielectric layer comprises BaTiO 3 .
8. The electronic module of claim 1 wherein said electrode layers comprise at least one of Ag, Au, and AgPd.
9. The electronic module of claim 1 wherein said inner dielectric layer has a thickness of less than about 3 mils.
10. The electronic module of claim 1 further comprising conductive vias for electrically connecting said at least one electronic device and said at least one embedded capacitive structure.
11. The electronic module of claim 1 wherein said at least one capacitive structure has a capacitive density of greater than about 1000 pF/mm 2 .