JP4770484B2 - Multilayer ceramic electronic components - Google Patents

Description

  The present invention relates to a multilayer ceramic electronic component, and more particularly to a highly reliable multilayer ceramic electronic component for temperature compensation.

As a conventional multilayer ceramic electronic component of this type, for example, there is a multilayer electronic component described in Patent Document 1 proposed by the present applicant. In this multilayer electronic component (for example, a multilayer ceramic capacitor), a dielectric ceramic layer and an internal electrode layer are formed by firing a raw multilayer body in which dielectric green sheet layers and internal electrode paste layers are alternately stacked. A laminate in which and are alternately laminated is obtained. A dielectric material mainly composed of forsterite and strontium titanate is used for the dielectric green sheet. This main component is a dielectric ceramic material represented by the general formula Mg _x SiO _{2 + x} + aSr _y TiO _{2 + y} , and x, y and a in the above general formula are 1.70 ≦ x ≦ 1.99 and 0, respectively. The relationship of .98 ≦ y ≦ 1.02 and 0.05 ≦ a ≦ 0.40 is satisfied.

  When the dielectric material described in Patent Document 1 is used, it can be fired at a lower temperature than the conventional forsterite, and can satisfy the predetermined temperature characteristic defined by the JIS standard. When designing electronic components, it is possible to obtain an excellent multilayer ceramic electronic component that can be multilayered without causing structural defects, reduce equivalent series resistance, and suppress variation in capacitance. .

WO 2005/058774

  However, although the multilayer ceramic electronic component of Patent Document 1 has excellent characteristics as described above, as a result of detailed examination of electrical characteristics such as temperature characteristics thereafter, the interface between the dielectric ceramic layer and the internal electrode layer There were slight structural defects in the vicinity, and the moisture resistance load characteristics were slightly deteriorated due to the influence of the structural defects.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a multilayer ceramic electronic component that can improve moisture resistance load characteristics and high temperature load characteristics to enhance electrical reliability.

The multilayer ceramic electronic component according to claim 1 of the present invention is a multilayer ceramic electronic component comprising a plurality of laminated dielectric ceramic layers and an internal electrode layer disposed between the dielectric ceramic layers. The main component of the dielectric ceramic layer is composed of a first main component composed of a forsterite crystal phase and a second main component composed of an oxide containing Ti, and the internal electrode layer includes the first main component. A ceramic having a component composition is present, and the second main component is substantially absent .

Further, the laminated ceramic electronic component according to claim 2 of the present invention is the invention according to claim 1, said first principal component in _{Mg x SiO 2 +} x (where, 1.70 ≦ x ≦ 1.99) And the second main component is at least one oxide selected from Sr _y TiO _{2 + y} , Ca _y TiO _{2 + y} , and TiO ₂ (provided that 0.98 ≦ y ≦ 1.02). It is.

According to a third aspect of the present invention, in the multilayer ceramic electronic component according to the second aspect , the first main component is Mg _x SiO _{2 + x} (where 1.70 ≦ x ≦ 1.99). And the second main component is Sr _y TiO _{2 + y} (where 0.98 ≦ y ≦ 1.02), and the molar ratio of the first main component to the second main component in the dielectric ceramic layer (first When (1-principal component / second-principal component) is represented by (1-a) / a, a satisfies the relationship of 0.05 ≦ a ≦ 0.29.

The multilayer ceramic electronic component according to claim 4 of the present invention is the multilayer ceramic electronic component according to any one of claims 1 to 3 , wherein the weight of the ceramic component and the metal component in the internal electrode layer is the same. The ratio (ceramic component / metal component) is 0.05 to 0.5.

That is, the dielectric ceramic layer forming the multilayer ceramic electronic component of the present invention is composed of a first main component composed of a forsterite crystal phase and an oxide containing Ti (hereinafter simply referred to as “Ti oxide”). And the second main component as a main component. The forsterite crystal phase has positive temperature characteristics and a low relative dielectric constant, and is excellent in high frequency characteristics. As the forsterite crystal phase, for example, one represented by Mg _x SiO _{2 + x} is preferable. In addition, since Ti oxide has negative temperature characteristics, by adding a predetermined amount to forsterite, a mixed crystal with the forsterite crystal phase is formed, so that the relative dielectric constant is low and the capacitance temperature is low. The characteristics are flattened, and a multilayer ceramic electronic component such as a low-capacity multilayer ceramic capacitor for temperature compensation used in a high-frequency module can be obtained. The Ti oxide, for example, strontium titanate _{(Sr y TiO 2 + y)} , calcium titanate _{(Ca y TiO 2 + y)} , an oxide of at least one selected from titanium dioxide (TiO ₂₎ is preferable.

Among these, Sr _y TiO _{2 + y} is preferable to other Ti oxides because it can simultaneously achieve a reduction in dielectric constant and an improvement in temperature characteristics of the dielectric ceramic layer. Sr _y TiO _{2 + y} has a large negative temperature characteristic gradient of −3000 for the relative dielectric constant (250 to 300), and a desired temperature characteristic can be obtained with a small addition amount, so that the relative dielectric constant can be kept low. it can. For this reason, when obtaining a desired capacitance as a multilayer ceramic electronic component, the number of laminated dielectric ceramic layers can be increased, and as a result, the equivalent series resistance can be lowered. Further, variation in capacitance can be suppressed.

Thus, _x in Mg _x SiO _{2 + x} preferably satisfies the relationship of 1.70 ≦ x ≦ 1.99. Conventional forsterite has a firing temperature as high as 1350 to 1400 ° C., but Mg _x SiO _{2 + x} has x in the above range, and further a Ti ceramic, preferably Sr _y TiO _{2 + y} , is added to the dielectric ceramic layer. The sinterability is greatly improved, and sintering is performed at a firing temperature of 1300 ° C. or lower to form a mixed crystal of forsterite crystal phase and Ti oxide crystal phase. When x is less than 1.7, the mixed crystal of the forsterite crystal phase and the Ti oxide crystal phase is not stable, and the temperature coefficient Tcc of the relative dielectric constant becomes positively large, and is required as a multilayer ceramic electronic component. The temperature characteristics may not be satisfied. Further, if x exceeds 1.99, the sintering temperature as the dielectric ceramic layer becomes high, and there is a possibility that sintering does not occur in a temperature range (for example, a temperature of 1300 ° C. or less) that does not adversely affect the internal electrode layer.

It is preferable that _{y of} Sr _y TiO _{2 + y} and Ca _y TiO _{2 + y} satisfy the relationship of 0.98 ≦ y ≦ 1.02. If y is less than 0.98 or exceeds 1.02, the temperature coefficient Tcc may be positively increased and the temperature characteristics of the JIS standard may not be satisfied.

Further, main component _(1-a) of the dielectric ceramic layers Mg x when expressed as _{SiO 2 + x + aSr y TiO} 2 + y, the molar ratio of the first and second principal components {1 major component / second principal component = A in (1-a) / a} preferably satisfies the relationship of 0.05 ≦ a ≦ 0.29. If a is less than 0.05, the temperature coefficient Tcc is positively large and does not satisfy the temperature characteristics of the JIS standard. Conversely, if a exceeds 0.29, the temperature coefficient Tcc becomes negatively large and does not satisfy the JIS standard, and the relative dielectric constant becomes as high as 26.

(1-a) In Mg _x SiO _{2 + x} + aSr _y TiO _{2 + y} , by satisfying 0.05 ≦ a ≦ 0.29, 1.70 ≦ x ≦ 1.99 and 0.98 ≦ y ≦ 1.02, The relative dielectric constant is about 8 to 22, and the temperature characteristics are JIS standard CG characteristics to SL characteristics (CG to CK, LG to LK, PG to PK, RG to RK, SH to SK, TH to TK, UH to UK and It is possible to obtain a multilayer ceramic electronic component that satisfies (SL characteristics) and can be fired at about 1300 ° C. or less.

In addition, a ceramic having a first main component (Mg _x SiO _{2 + x} ) is added to the internal electrode layer forming the multilayer ceramic electronic component. This internal electrode layer preferably does not substantially contain the second main component (Ti oxide). “Substantially free of Ti oxide” means that no Ti oxide is intentionally added, and means that a trace amount of impurities that are unavoidable is present in the raw material. By adding the first main component to the internal electrode layer, the moisture resistance load characteristics and high temperature load characteristics of the multilayer ceramic electronic components are improved. In the moisture resistance load test, the average life time is 200 hours or more, and in the high temperature load test, the average life time is increased. When the time is 250 hours or more, the electrical reliability as the multilayer ceramic electronic component is improved.

  When the internal electrode layer contains a ceramic containing both the first main component and the second main component (for example, a ceramic having the same composition as the dielectric ceramic layer), the high temperature load test does not reach 250 hours, but the moisture resistance load test Then, a multilayer ceramic electronic component having an average life time of 200 hours or more can be obtained. On the other hand, the internal electrode layer to which no ceramic is added has an average life time shortened to about 100 hours in the moisture resistance load test, and the electrical reliability as a multilayer ceramic electronic component is reduced as compared with the case where ceramic is present. To do.

According to the onset bright, humidity load characteristics average life of 200 hours or more, to provide a multilayer ceramic electronic component of the average life span of the high-temperature load characteristics can be enhanced electrical reliability is improved more than 250 hours it can.

  The present invention will be described below with reference to the embodiment shown in FIG. FIG. 1 is a cross-sectional view schematically showing one embodiment of the multilayer electronic component of the present invention.

  As shown in FIG. 1, for example, the multilayer ceramic capacitor 1 of the present embodiment includes a plurality of laminated dielectric ceramic layers 2 and a plurality of first and first dielectric ceramic layers 2 disposed between the dielectric ceramic layers 2. 2 includes a laminate 4 having internal electrode layers 3A and 3B. First and second external electrodes 5A and 5B are formed on both end faces of the laminate 4, respectively, and these external electrodes 5A and 5B are electrically connected to the internal electrode layers 3A and 3B, respectively.

  As shown in FIG. 1, the first internal electrode layer 3A extends from one end (left end in the figure) of the dielectric ceramic layer 2 to the vicinity of the other end (right end), and the second internal electrode layer 3B is a dielectric ceramic layer. 2 extends from the right end to the vicinity of the left end. The first and second internal electrode layers 3A and 3B are made of, for example, Pd, Ag, Cu, a Pd—Ag alloy, or the like.

  Further, as shown in FIG. 1, the first external electrode 5 </ b> A is electrically connected to the first internal electrode layer 3 </ b> A in the multilayer body 4, and the second external electrode 5 </ b> B is the second internal electrode layer in the multilayer body 4. It is electrically connected to 3B. The first and second external electrodes 5A and 5B are made of, for example, Ag or an Ag—Pd alloy. Furthermore, conventionally known first plating layers 6A and 6B and second plating layers 7A and 7B are sequentially applied to the surfaces of the first and second external electrodes 5A and 5B.

  Next, the present invention will be described based on specific examples. In this example, a plurality of types of dielectric ceramic materials shown in Table 1 and a plurality of types of internal electrode pastes shown in Table 3 were prepared by the following procedure, and then laminated using these dielectric ceramic materials and internal electrode pastes. A ceramic capacitor was produced. Next, electrical characteristics of these multilayer ceramic capacitors were evaluated, and the results are shown in Table 1. In Table 1, samples marked with * are outside the scope of the present invention.

(1) Preparation of dielectric ceramic material and ceramic slurry First, MgO and SiO ₂ are weighed as starting materials of the first main component so as to have the composition shown in Table 1, mixed and pulverized using a ball mill. The forsterite was pre-synthesized by calcining. In addition, SrCO ₃ and TiO ₂ or CaCO ₃ and TiO ₂ are weighed in advance as the starting material of the second main component so as to have the composition shown in Table 1, mixed and pulverized using a ball mill, and then calcined. Strontium titanate and calcium titanate were synthesized respectively. Further, titanium dioxide was prepared as the second main component. Then, forsterite and strontium titanate, calcium titanate or titanium dioxide were weighed, and a sintering aid comprising the composite oxide shown in Table 2 was added as necessary to these raw materials as necessary. Then, it mixed by the ball mill and the dielectric ceramic material which consists of a composition of sample No. 1-3 shown in Table 1 was prepared.

Even if BaO, ZrO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , MnO, CuO, ZnO, and rare earth oxide are included as impurities in the raw material, the electrical characteristics are not greatly affected.

(2) Preparation of internal electrode paste As shown in Table 3, after preparing Pd powder, Ag powder, Cu powder and ceramic powder, adding organic vehicle and organic solvent to each metal powder, mixing these, The ceramic powder was added in the ratio shown in Table 3 and mixed to prepare the internal electrode paste shown in samples a to j.

(3) Production of Multilayer Ceramic Capacitor Each of the dielectric ceramic materials of Sample Nos. 1 to 37 obtained in (1) was weighed, added with a polyvinyl butyral binder, and wet-mixed with a ball mill to prepare ceramic slurries, respectively. .

  Next, ceramic green sheets were produced from the ceramic slurries by the doctor blade method. Thereafter, the internal electrode pastes of samples a to j shown in Table 3 were printed on the ceramic green sheets, respectively, 10 layers were laminated so as to be a multilayer ceramic capacitor, and pressure-bonded to obtain a ceramic laminate. This ceramic laminate was cut into a predetermined chip size to obtain a raw ceramic laminate.

In the case of Pd internal electrode paste (samples a to e), the raw ceramic laminate was subjected to binder removal treatment at 350 ° C. in air, and then heated in air at a temperature rising rate of 50 ° C./min. And it baked at 1200 degreeC and obtained each ceramic sintered compact. In the case of an Ag internal electrode paste (samples i and j), the raw ceramic laminate was subjected to binder removal treatment at 350 ° C. in air, and then heated in air at a heating rate of 50 ° C./min. And it baked at 900 degreeC and obtained each ceramic sintered compact. In the case of the Cu internal electrode paste (samples g and h), the raw ceramic laminate was subjected to binder removal treatment at 350 ° C. in an N ₂ atmosphere, and then in an N ₂ / H ₂ / H ₂ O atmosphere. The temperature was raised at a rate of 50 ° C./min and fired at 900 ° C. to obtain each ceramic sintered body. And these ceramic sintered compacts were barrel-polished and the internal electrode layer was exposed from each end surface.

  About the ceramic sintered compact which has Pd and Ag internal electrode layers, Ag paste was apply | coated to each end surface, and after drying, Ag paste was baked in suitable temperature and atmosphere, and the external electrode was formed. Further, Cu paste was applied to the end face of the ceramic sintered body having the Cu internal electrode layer, and external electrodes were formed in the same manner. Furthermore, after forming the Ni plating layer on the external electrode of each ceramic sintered body by the barrel plating method, the Sn plating layer was further formed to obtain the multilayer ceramic capacitors of Sample Nos. 1 to 37 shown in Table 1, respectively. . The outer dimensions of these multilayer ceramic capacitors are 1.2 mm in width, 2.0 mm in length, and 1.2 mm in thickness, and the distance between the dielectric ceramic layers is about 5 μm. The total number of layers was 10 layers.

(4) Characteristic Evaluation of Multilayer Ceramic Capacitor Using Sample No. 1 to No. 37, the capacitance and Q value at 25 ° C., 1 MHz and 1 V were measured using an LCR meter (HP 4284A), and these measurements were made. The relative dielectric constant εr was calculated based on the value, electrode area, and element thickness, and the results are shown in Table 1. Further, the capacitance at each temperature was measured for each sample using a capacitance temperature characteristic measuring apparatus, and the temperature coefficient Tcc of the capacitance was calculated by the following formula, and the results are shown in Table 1. .
Tcc [ppm / ° C.] = {(C ₈₅ −C ₂₀ ) / C ₂₀ } × {1 / (85 ° C.−20 ° C.)}
× 10 ⁶
C ₂₀ : Capacitance at 20 ° C. C ₈₅ : Capacitance _at 85 ° C. The high temperature load test was performed under the conditions of a temperature of 150 ° C., an applied voltage of 100 V, and 72 samples. The average time when the insulation resistance value was less than ^109.0 Ω is shown in Table 1 as the high temperature load life.
The moisture resistance load test was performed under the conditions of a temperature of 120 ° C., a relative humidity of 90%, 2 atm, an applied voltage of 25 V, and 72 samples. The average time when the insulation resistance value was less than ^109.0 Ω is shown in Table 1 as the moisture resistant load life.

  According to the results shown in Table 1, among sample Nos. 1 to 37, the internal electrode paste (samples a to c and samples g and i) to which the first main component ceramic powder was added as shown in Table 3 was used. All of the samples had a high temperature load life of 250 hours or more and a moisture load resistance life of 200 hours or more. Also, among the samples Nos. 1 to 37, as shown in Table 3, all the samples using the internal electrode paste (samples f, h, j) to which the ceramic powder having the same composition as the dielectric ceramic layer was added were high in temperature. Although the load life was less than 250 hours, the moisture-proof load life was 200 hours or more.

  On the other hand, as shown in Table 3, the comparative sample No. 11 using the internal electrode paste (sample e) to which no ceramic powder was added had a moisture resistance load life as short as 150 hours. Also, as shown in Table 3, sample No. 10 using the internal electrode paste (sample d) to which 60% by weight of the first main component ceramic powder was added can measure the electrical characteristics as a multilayer ceramic capacitor. could not. In Sample No. 10, it is considered that the electrical characteristics could not be measured because the coverage of the internal electrode layer with Pd was lowered and the internal electrode layer could not be electrically connected to the external electrode.

Further, according to the results shown in Table 1, the main component of the dielectric ceramic layer is a first, second principal component _{(1-a) Mg x SiO} 2 + x + aSr y TiO 2 + y, 0.05 ≦ a ≦ 0. 29, 1.70 ≦ x ≦ 1.99, 0.98 ≦ y ≦ 1.02, sample Nos. 1 to 19 (excluding sample No. 11) and sample Nos. 24 to 37 are all 1200 Sintered as a dielectric ceramic layer at a temperature of ℃ or less, achieves low dielectric constant and improved temperature characteristics at the same time, has a relative dielectric constant of 8-22, and a temperature coefficient Tcc of capacitance to temperature is CG characteristics-SL A multilayer ceramic electronic component suitable for temperature compensation satisfying the temperature characteristics of JIS standards in a wide range of characteristics was obtained. Comparing sample No. 18 and sample No. 20 and 22, sample No. 18 containing SrTiO ₃ based crystal phase as the second main component is more than sample No. 20 and 22 containing CaTiO ₃ and TiO ₂ based crystal phase. The dielectric constant was lowered and the high temperature load characteristics were improved.

  In the above embodiment, the case where the multilayer ceramic capacitor is manufactured has been described. However, the present invention is not limited to the multilayer ceramic capacitor, and other multilayer electronic components such as an LC filter and a multilayer substrate can be similarly manufactured. In addition, the multilayer ceramic capacitor having an outer diameter of 1.2 mm in width, 2.0 mm in length, and 1.2 mm in thickness has been described. However, when designing a further miniaturized multilayer ceramic electronic component, the dielectric constant is low. Multiple layers can be formed without causing structural defects, equivalent series resistance can be reduced, and variation in capacitance can be suppressed. In addition, oxides, hydroxides, carbonates, and the like other than those used in the above examples can be used as starting materials for the dielectric ceramic material, and the dielectric ceramic material is sintered as shown in Table 2. Other than the auxiliary agent can also be used.

  The present invention can be suitably used for multilayer ceramic electronic components such as a low-capacity multilayer ceramic capacitor for temperature compensation used in a high-frequency module.

It is sectional drawing which shows typically one Embodiment of the laminated ceramic electronic component of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 2 Dielectric ceramic layer 3A, 3B 1st, 2nd internal electrode layer

Claims (4)

In a laminated ceramic electronic component comprising a plurality of laminated dielectric ceramic layers, and an internal electrode layer disposed between these dielectric ceramic layers,
The main component of the dielectric ceramic layer is composed of a first main component composed of a forsterite crystal phase and a second main component composed of an oxide containing Ti,
The multilayer ceramic electronic component, wherein the internal electrode layer includes a ceramic having the composition of the first main component and substantially does not include the second main component. The first main component is Mg _x SiO _{2 + x} (where 1.70 ≦ x ≦ 1.99),
Claim, characterized in that the second principal component is _{Sr y TiO 2 + y, Ca} y TiO 2 + y, TiO 2 ( where, 0.98 ≦ y ≦ 1.02) is at least one oxide of a chosen from 1 the multilayer ceramic electronic component according to. The first main component is Mg _x SiO _{2 + x} (where 1.70 ≦ x ≦ 1.99),
The second main component is Sr _y TiO _{2 + y} (where 0.98 ≦ y ≦ 1.02),
When the molar ratio of the first main component and the second main component (first main component / second main component) in the dielectric ceramic layer is represented by (1-a) / a,
The multilayer ceramic electronic component according to claim 2 , wherein a satisfies a relationship of 0.05 ≦ a ≦ 0.29. The weight ratio of the ceramic component and the metal component in the internal electrode layer (ceramic component / metal components), one of the claims 1 to 3, characterized in that from 0.05 to 0.5 1 The multilayer ceramic electronic component according to Item.

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