MULTI-LAYER CERAMIC CAPACITOR AND MANUFACTURING METHOD OF MULTI-LAYER CERAMIC CAPACITOR

• US 20090073635A1
• Filed: 08/08/2008
• Published: 03/19/2009
• Est. Priority Date: 08/09/2007
• Status: Active Grant

• Current Assignee: Taiyo Yuden Company Limited (Taiyo Yuden Co)
• Original Assignee: Taiyo Yuden Company Limited (Taiyo Yuden Co)
• Inventors: Taniguchi, Katsuya
• Granted Patent: US 8,064,190 B2
• Time in Patent Office: Days
• US Class Current: 361/321.400
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3265 Mn2O3
• CPC Class Codes: C04B 2235/3418 Silicon oxide, silicic acids or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint
• CPC Class Codes: C04B 2235/5445 submicron sized, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/6025 Tape casting, e.g. with a doctor blade
• CPC Class Codes: C04B 2235/6562 Heating rate
• CPC Class Codes: C04B 2235/6565 Cooling rate
• CPC Class Codes: C04B 2235/6582 Hydrogen containing atmosphere
• CPC Class Codes: C04B 2235/663 Oxidative annealing
• CPC Class Codes: C04B 2235/79 Non-stoichiometric products, e.g. perovskites (ABO3) with an A/B-ratio other than 1
• CPC Class Codes: C04B 2235/85 Intergranular or grain boundary phases
• CPC Class Codes: C04B 35/4682 based on BaTiO3 perovskite phase
• CPC Class Codes: C04B 35/638 Removal thereof
• CPC Class Codes: H01G 4/1227 based on alkaline earth titanates
• CPC Class Codes: H01G 4/30 Stacked capacitors H01G4/33 takes precedence

Abstract

A small, large-capacitance multi-layer ceramic capacitor suppressed for remarkable lowering of permittivity, having a capacitor main body formed of ceramic dielectric layers comprising barium titanate as a main component and an Si oxide at a ratio of 0.5 to 10 mol being converted as SiO₂ based on 100 mol of barium titanate and internal electrode layers, and a pair of external electrodes which are formed at the end faces of the capacitor main body and connected electrically with the internal electrode layers, in which the ceramic dielectric layer has crystal grains, crystal grain boundaries each present between the crystal grains and a grain boundary triple point, and B/A is 0.5 or less assuming the amount (mol) of an Si oxide being converted as SiO₂ contained based on 100 mol of barium titanate as A and the volumic rate (vol %) of the Si oxide present at the crystal grain boundary and the grain boundary triple point of the ceramic dielectric layer as B, whereby remarkable lowering of a permittivity due to precipitation of an Si oxide to the crystal grain boundary and the grain boundary triple point is suppressed.

Claims

1. A multi-layer ceramic capacitor having a substantially hexahedral capacitor main body wherein:

the ceramic dielectric layers comprise barium titanate;

the internal electrode layers are laminated alternately; and

the internal electrode layers are formed such that they are exposed at the ends thereof alternately to end faces opposed to each other, and a pair of external electrodes formed at the end faces where the ends of the internal electrode layers of the capacitor main body are exposed and connected electrically with the internal electrode layers;

wherein the ceramic dielectric layer contains an Si oxide being converted as SiO₂ at a ratio of from 0.5 to 10 mol based on 100 mol of barium titanate, wherein;

the ceramic dielectric layer has crystal grains, crystal grain boundaries present between the crystal grains and grain boundary triple points; and

B/A is 0.5 or less, wherein the amount (mol) of an Si oxide being converted as SiO₂ contained based on 100 mol of barium titanate is A and wherein the volumic ratio (vol %) of the Si oxide present at the crystal grain boundary and the grain boundary triple point of the ceramic dielectric layer as B.

2. The multi-layer ceramic capacitor of claim 1, wherein said ceramic capacitor has one or more additional components selected from the group consisting of Mg oxide, Mn oxide and R oxide.

3. The multi-layer ceramic capacitor of claim 2, wherein the Mg oxide is being converted as MgO at a ratio of from 0.1 to 2 mol based on 100 mol of barium titanate.

4. The multi-layer ceramic capacitor of claim 2, wherein the Mn oxide is being converted as Mn₂O₃ at a ratio of from 0.05 to 1 mol based on 100 mol of barium titanate.

5. The multi-layer ceramic capacitor of claim 2, wherein the R oxide is being converted as RO at a ratio of from 0.1 to 4 mol based on 100 mol of barium titanate

6. The multi-layer ceramic capacitor of claim 5, wherein R is at least one compound selected from the group consisting of Sc, Er, Tm, Yb, Lu, Y, Dy, Ho, Tb, Gd, and Eu.

7. The multi-layer ceramic capacitor of claim 1, wherein the internal electrode layers comprises a compound selected from the group consisting of Ni, Ni alloy, Cu, and Cu alloy.

8. The multi-layer ceramic capacitor of claim 1, wherein the crystal grain has an average size of 0.3 μ

m or less.

9. A method of manufacturing a multi-layer ceramic capacitor comprising;

weighing a barium titanate powder, an Si oxide corresponding to 0.5 to 10 mol being converted as SiO₂ based on 100 mol of barium titanate and an extraneous component and then mixing them;

adding and mixing a binder and a solvent to the obtained mixture to prepare a slurry;

sheeting the obtained slurry;

printing an internal electrode material on the surface of the obtained sheet to form an internal electrode pattern;

laminating obtained sheets and then dividing them into a plurality of laminate chips;

applying a debinding processing to the obtained laminate chips;

firing the obtained laminate chips by elevating temperature in a reducing atmosphere, holding the same at a predetermined temperature and then reducing the temperature;

applying a re-oxidation heat processing to the obtained sintered body chip in a nitrogen gas atmosphere;

forming external electrodes to a pair of end faces of the obtained sintered body chip opposed to each other, wherein;

the rate of temperature reduction in the step of firing the laminate chip is 100°

C./hr or lower.

10. A multi-layer ceramic capacitor having a substantially hexahedral capacitor main body made by the steps of;

weighing a barium titanate powder, an Si oxide corresponding to 0.5 to 10 mol being converted as SiO₂ based on 100 mol of barium titanate and an extraneous component and then mixing them;

adding and mixing a binder and a solvent to the obtained mixture to prepare a slurry;

sheeting the obtained slurry;

printing an internal electrode material on the surface of the obtained sheet to form an internal electrode pattern;

laminating obtained sheets and then dividing them into a plurality of laminate chips;

applying a debinding processing to the obtained laminate chips;

firing the obtained laminate chips by elevating temperature in a reducing atmosphere, holding the same at a predetermined temperature and then reducing the temperature;

applying a re-oxidation heat processing to the obtained sintered body chip in a nitrogen gas atmosphere;

forming external electrodes to a pair of end faces of the obtained sintered body chip opposed to each other, wherein;

the rate of temperature reduction in the step of firing the laminate chip is 100°

C./hr or lower.

11. A method of making a capacitor comprising:

forming ceramic sheets comprising metal oxide and a sintering aid;

laminating the ceramic sheets with electrode material therebetween;

sintering the laminated sheets at an elevated temperature; and

reducing the temperature from said elevated temperature at a rate of 100 degrees C. per hour or less.

12. The method of claim 11, wherein the metal oxide comprises barium titanate.

13. The method of claim 12, wherein the silicon oxide is present in an amount of 0.5 to 10 mol being converted as SiO₂ based on 100 mol of barium titanate.

14. A capacitor made by the method of:

forming ceramic sheets comprising metal oxide and a silicon oxide sintering aid;

laminating the sheets with electrode material therebetween;

sintering the laminated sheets at an elevated temperature;

reducing the temperature from said elevated temperature at a selected rate such that the ratio B/A becomes less than or equal to 0.5, wherein A is the number of moles of silicon oxide being converted to silicon dioxide per 100 moles of barium titanate, and wherein B is the volumic ratio (vol %) of the Si oxide present at the crystal grain boundary and the grain boundary triple point of the ceramic sheet.

15. The method of claim 14, wherein the metal oxide comprises barium titanate.

16. The method of claim 15, wherein the silicon oxide is present in an amount of 0.5 to 10 mol being converted as SiO₂ based on 100 mol of barium titanate.