JP5785518B2 - Capacitor and its dielectric layer - Google Patents

Description

  The present invention relates to a decoupling capacitor using a Li ion conductive compound and a dielectric layer thereof.

  Conventionally, decoupling capacitors (also referred to as bypass capacitors) have been used in various electronic circuits and the like.

For example, in a high frequency circuit, a multilayer ceramic capacitor using BaTiO ₃ as a dielectric material is widely used. In general, a multilayer ceramic capacitor is obtained by alternately laminating green sheets containing BaTiO ₃ powder and conductive paste layers (electrode layers) containing metal powder such as Ni and firing them. Multilayer ceramic capacitors are widely used because they are nonpolar and excellent in frequency characteristics, but their capacitance is about 0.5 pF to 22 μF, and in recent years, a multilayer ceramic capacitor having a larger capacity has been demanded. Yes.

  In low frequency circuits, electrolytic capacitors such as aluminum electrolytic capacitors are often used. Although the electrolytic capacitor has a larger capacity (for example, 0.1 μF to 100,000 μF) than the multilayer ceramic capacitor, there is a problem that the electrolytic solution may leak to the outside and the frequency characteristics are poor.

In addition, an electric double layer capacitor is known as a capacitor having a very large capacity. As an example of an electric double layer capacitor using a solid electrolyte, Patent Document 1 includes a general formula Li _{1 + x} , M ¹ _x Ti _2-x (PO ₄ ) ₃ (where M ¹ is Al, Y, Ga, A material using at least one metal selected from the group consisting of In and La and using a Li ion conductive compound represented by 0 ≦ x ≦ 0.6) is disclosed.

  However, an electric double layer capacitor usually has extremely poor frequency characteristics, and is mostly used as a backup power source for personal computers, automobiles, etc., and cannot be used as a decoupling application.

JP 2008-130844 A

  The present invention has been made in view of the background art described above, and an object thereof is to provide a novel capacitor.

The object is to provide a general formula Li _{1 + x} M ¹ _x M ² _2-x (PO ₄ ) ₃ (where M ¹ is at least one metal selected from the group consisting of Al, Y, Ga, In and La, M ² is Ti, at least one metal selected G e or et al., 0 <include Li-ion conductive compound represented by a is) x ≦ 0.6, the film thickness is 10μm or less dielectric layers And a decoupling capacitor comprising an electrode layer facing each other through the dielectric layer.

The above object is also achieved by the general formula Li _{1 + x} M ¹ _x M ² _2-x (PO ₄ ) ₃ (where M ¹ is at least one metal selected from the group consisting of Al, Y, Ga, In and La). There, ^{M 2} is at least one metal Ti, selected G e or et al., 0 <include Li-ion conductive compound represented by a is) x ≦ 0.6, decoupling thickness is 10μm or less This is achieved by a dielectric layer for a ring capacitor.

  In the present invention, the film thickness is preferably 2 μm or less.

  According to the present invention, it is possible to obtain a decoupling capacitor having excellent frequency characteristics while using a Li ion conductive compound.

It is a figure which shows the frequency characteristic of the capacitor | condenser obtained in Example 1. FIG.

  Hereinafter, the present invention will be described in detail.

The present inventors initially examined the physical properties and characteristics of LiAlTi (PO ₄ ) ₃ , which is a Li ion conductive compound, as a solid electrolyte material for an electric double layer capacitor described in Patent Document 1. It was.

  The capacitor using the Li ion conductive compound does not depend on the thickness of the compound while operating in a low frequency region where the sweep speed is slow as reported in detail in Patent Document 1. It is operating as an electric double layer capacitor.

  However, while the inventors have studied the physical properties and characteristics of the Li ion conductive compound, the present inventors show that it behaves completely different from the conventional electric double layer capacitor depending on the applied frequency and its thickness. I found it.

  According to the study by the present inventors, capacitors using the Li ion conductive compound show a slight decreasing tendency when the film thickness of the compound is 10 μm or less in the low frequency band up to about several kHz. The capacitor capacity is almost independent of the film thickness. However, when the frequency band is higher than that (for example, about 10 kHz), the dependency of the capacitance on the film thickness appears.

  The present inventors pay attention to the fact that this dependency is such that the greater the film thickness, the worse the frequency characteristics on the high frequency side (= capacitance change increases), and the film thickness is controlled. Thus, the present inventors completed the present invention because they thought that a capacitor having good frequency characteristics and suitable for decoupling applications could be obtained while using the Li ion conductive compound.

  That is, the gist of the present invention is a decoupling capacitor in which a specific Li ion conductive compound is used as a dielectric and the thickness of the dielectric layer is 10 μm or less.

  In the present invention, the dielectric layer preferably has a film thickness of 2 μm or less because the frequency characteristics are further improved.

As the Li ion conductive compound used as the dielectric of the present invention, Li _{1 + x} M ¹ _x Ti _2-x (PO ₄ ) ₃ described in Patent Document 1 (where M ¹ is Al, Y, Ga, A Li ion conductive compound represented by a general formula of at least one metal selected from the group consisting of In and La (0 ≦ x ≦ 0.6) can be used.

However, in the above compounds, it has been confirmed that the effects of the present invention can be obtained even if a part or all of Ti is substituted with Ge . Therefore, the Li ion conductive compound of the present invention has the general formula Li _{1 + x} M ¹ _x M ² _2-x (PO ₄ ) ₃ (where M ¹ is at least one metal selected from the group consisting of Al, Y, Ga, In and La, and M ² is Ti, is at least one metal selected G e or al, it is shown as 0 <x ≦ 0.6).

By the present invention smell Te include metals M ^1, improved Li-ion conductivity, functions and effects such as the frequency characteristics of the high-frequency side is improved is obtained. A preferable range of x is 0.3 ≦ x ≦ 0.6.

  Furthermore, in the present invention, in the Li ion conductive compound, a part of Li may be substituted with a divalent metal such as Mg, Ca, Mn. When a part of Li is substituted with a divalent metal, the number of free sites of Li increases, and an improvement in high-frequency characteristics accompanying improvement in Li ion conductivity can be expected.

  In the present invention, the dielectric layer may be crystal glass (glass ceramic) in which the Li ion conductive compound described above is deposited by heat-treating Li-based glass.

  In the present invention, the dielectric layer can also be produced in substantially the same manner as the pellets and green sheets described in Patent Document 1, except that the film thickness after firing is 10 μm or less.

  For example, the Li ion conductive compound can be synthesized by mixing the raw materials of the Li ion conductive compound and then firing. Here, the raw material is not particularly limited, and may be appropriately selected from oxides, hydroxides, nitrates, carbonates, organic compounds, and the like containing a metal used for the target Li ion conductive compound. Under the present circumstances, the baking conditions of a raw material should just be set suitably according to the target Li ion conductive compound, for example, it bakes for 3 to 48 hours at the temperature of 200 to 1300 degreeC.

  In addition, in the present invention, the Li ion conductive compound may be a well-known spray pyrolysis method or a pyrolyzable raw material powder described in JP-A No. 2004-0667462 or JP-A No. 2004-083372. You may manufacture by the manufacturing method thermally decomposed in a phase. According to these production methods, fine and uniform product particles can be obtained, which is preferable. In addition, the raw material in this case, a heating condition, etc. can be suitably selected according to the target Li ion conductive compound.

  The obtained Li ion conductive compound is pulverized as necessary using a jet mill, a ball mill or the like, and then an organic binder and a solvent are added to prepare a slurry or paste. In this case, as organic binders that can be used, celluloses, butyral resins, acrylic resins, phenol resins, alkyd resins, rosin esters, etc., and solvents such as alcohols, ethers, esters, hydrocarbons, etc. An organic solvent, water, a mixed solvent thereof or the like can be used, but the present invention is not limited to these. Furthermore, you may add additives, such as a plasticizer, a viscosity modifier, and surfactant, as needed.

  A green sheet (unfired dielectric sheet) is produced by molding and drying using the slurry and paste thus obtained so that the film thickness after firing is 10 μm or less, preferably 2 μm or less. .

  Then, the dielectric material layer of this invention can be obtained by baking the said green sheet for 1 to 72 hours, for example at the temperature of 400 to 1300 degreeC.

  Subsequently, a capacitor structure can be obtained by forming a pair of electrode layers on both surfaces of the dielectric layer using a known printing method, thin film method, coating method, thermal spraying method, sputtering method, plating method, or the like. .

  As the conductive material used for forming the electrode layer, a metal material or an alloy material such as Au, Pt, Pd, Ag, Ni, or Cu can be used, and the electrode layer is used with a slurry or paste containing a powder material of these metals. Alternatively, the electrode layer may be formed using a resinate containing these metals.

  If the dielectric layer is thin and difficult to handle, slurry or paste may be applied or printed directly on the electrode.

  Further, the present invention may be a multilayer capacitor in which external electrodes are provided on a laminate in which dielectric layers and electrode layers are alternately laminated, similarly to the multilayer ceramic capacitor.

  That is, after forming a green sheet using the paste containing the Li ion conductive compound described above, and stacking a plurality of layers alternately with the internal electrode paste layer formed using the conductive paste to obtain an unfired laminate, By simultaneously firing this at a high temperature, and further applying and firing a terminal electrode paste on the end face where the internal electrode layer of the laminate is exposed to form a terminal electrode electrically connected to the internal electrode layer, can do. The laminated body may be manufactured by directly and alternately laminating dielectric paste and electrode paste without using a green sheet. In order to simplify the process, a terminal electrode paste may be applied to the end face of the unfired laminate and fired simultaneously with the laminate to form a terminal electrode.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
[Example 1]
As Li-ion conductive _compound, to prepare a _{Li 1.5 Al 0.5 Ti 1.5 (PO} ) 3.

  First, stoichiometric amounts of lithium nitrate, aluminum nitrate nonahydrate and titanium lactate (hydroxybis (lactato) titanium) were dissolved in water as raw materials to prepare an aqueous solution.

  This aqueous solution was spray pyrolyzed at 1000 ° C. in an oxygen-containing atmosphere, and the resulting product was recovered.

  A stoichiometric amount of ammonium dihydrogen phosphate was added to the recovered product, mixed uniformly, and then calcined at a temperature of 300 to 900 ° C. for 4 hours in an oxygen-containing atmosphere.

  Acetone is added to the obtained baked product, pulverized with a wet ball mill for 12 hours, and then uniformly mixed with a roll mill together with a butyral resin, mentanol and a polymer dispersant to prepare a slurry containing the above Li ion conductive compound. did.

  Using this slurry, an unfired dielectric layer was formed on a Pd electrode sheet so that the film thickness after firing was 75 μm, and then fired at 1000 ° C. for 2 hours in an oxygen-containing atmosphere.

  Thereafter, an Au electrode layer was formed on the surface of the obtained dielectric layer facing the Pd electrode layer by a sputtering method to produce a capacitor.

  Thereafter, in the same manner, capacitors having a fired dielectric layer thickness of 57 μm, 37 μm, 25 μm, 20 μm, 15 μm, 7 μm, 4 μm, 2 μm, and 1 μm were produced.

  For each capacitor, frequency characteristics were measured in the range of 20 Hz to 120 MHz with an AC amplitude voltage of 100 mV using an impedance measuring device “65120B” (manufactured by Wayne Kerr Electronics).

  The result is shown in FIG. In FIG. 1, the horizontal axis represents the film thickness of the dielectric (Li ion conductive compound), and the vertical axis represents the capacity retention ratio in the high frequency region based on the capacity at 1 kHz.

  As is apparent from FIG. 1, when the dielectric film thickness is 10 μm or less, the capacity can be maintained up to 10 kHz, and when the dielectric film thickness is 2 μm or less, the capacity can be maintained up to 1 MHz. .

Since the capacitance did not change even when a DC voltage was applied to each capacitor, it was confirmed that the capacitor of the present invention does not have a DC bias characteristic.
[Example 2]
Example 1 except that Li _1.3 Al _0.3 Ge _1.7 (PO) ₃ was used in place of Li _1.5 Al _0.5 Ti _1.5 (PO) ₃ as the Li ion conductive compound. As a result of the same experiment, the same frequency characteristics as in FIG. 1 were obtained.

Claims (4)

General formula Li _{1 + x} M ¹ _x M ² _2-x (PO ₄ ) ₃ (where M ¹ is at least one metal selected from the group consisting of Al, Y, Ga, In and La, and M ² is Ti is at least one metal selected G e or et al., 0 <include Li-ion conductive compound represented by a is) x ≦ 0.6, and the dielectric layer is a film thickness of 10μm or less,
A decoupling capacitor comprising an electrode layer facing through the dielectric layer.   The decoupling capacitor according to claim 1, wherein the film thickness is 2 μm or less. General formula Li _{1 + x} M ¹ _x M ² _2-x (PO ₄ ) ₃ (where M ¹ is at least one metal selected from the group consisting of Al, Y, Ga, In and La, and M ² is Ti is at least one metal selected G e or et includes 0 <x ≦ 0.6) Li-ion conductive compound represented by,
A dielectric layer used for a decoupling capacitor, wherein the film thickness is 10 μm or less. The dielectric layer according to claim 3 , wherein the film thickness is 2 μm or less.

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