JP3734098B2 - Evaluation method for multilayer ceramic capacitors - Google Patents

Description

[0001]
[Industrial application fields]
The present invention is a multilayer ceramic capacitor, more particularly, to a reliability of the determination method of a multilayer ceramic capacitor having internal electrodes made of nickel or a nickel alloy.
[0002]
[Prior art]
In recent years, with the development of electronics, the miniaturization of electronic devices has progressed rapidly, and as a result, the demand for electronic components has become increasingly severe, and the demand for smaller, larger capacity, lower prices, and higher reliability for multilayer ceramic capacitors has been increasing. The demands are getting more and more demanding.
[0003]
To meet these demands, various attempts have been made to develop dielectric ceramic materials for multilayer ceramic capacitors, manufacturing methods for multilayer ceramic capacitors in response thereto, thinning of ceramic dielectric layers, and adoption of inexpensive internal electrode materials. It has been.
[0004]
For example, a multilayer ceramic capacitor is generally formed by forming a dielectric material mainly composed of barium titanate (BaTiO ₃ ) into a sheet shape to form a ceramic green sheet, and applying an internal electrode material on the surface to form an internal electrode After the layers are formed, a plurality of green sheets are laminated and thermocompression bonded, the integrated laminate is chipped and fired at a temperature of 1250 to 1350 ° C. in a natural atmosphere, and then both ends of the obtained multilayer capacitor chip. It is manufactured by a method in which an external electrode conducting to the internal electrode is baked on the surface. In this case, since the internal electrode is fired in a high-temperature oxidizing atmosphere simultaneously with the dielectric ceramic, the internal electrode material has (a) a melting point higher than the firing temperature of the dielectric ceramic, and (b) high-temperature oxidizing property. It is necessary to satisfy the condition that it is not oxidized even in the atmosphere and does not react with the dielectric. Conventionally, noble metals such as platinum, palladium and silver-palladium alloys and alloys thereof have been used as internal electrode materials that satisfy these conditions. However, these have excellent characteristics but are expensive and are laminated ceramics. The ratio of the electrode material cost to the manufacturing cost of the capacitor has reached 30 to 70%, which is the largest cause for increasing the manufacturing cost. Therefore, as a means for reducing the cost of the multilayer ceramic capacitor, it is proposed to use an inexpensive base metal such as nickel, iron, cobalt, tungsten, manganese as the internal electrode material instead of the noble metal or its alloy, Correspondingly, a non-reducing dielectric ceramic that does not become a semiconductor when fired in a reducing atmosphere, for example, as described in Japanese Patent Publication No. 57-42588, barium sites (A) and titanium sites in a barium titanate solid solution. Non-reducing dielectric ceramics in which the ratio (A / B) of (B) is larger than the stoichiometric ratio have been developed, and multilayer ceramic capacitors using base metals as internal electrode materials have been put into practical use.
[0005]
On the other hand, as a method for reducing the size and capacity of a multilayer ceramic capacitor, it is a matter of course to employ a dielectric ceramic composition having a high dielectric constant. In addition to that, it has been proposed to make the dielectric ceramic thinner. Yes. However, in a multilayer ceramic capacitor with a thin dielectric layer, the electric field strength applied to the dielectric layer increases when a DC electric field is applied, and the tendency of the insulation resistance to deteriorate over time increases, and is incorporated into electronic devices. If such deterioration occurs in a laminated ceramic capacitor, the entire device may be seriously damaged. For this reason, the reliability of a multilayer ceramic capacitor is evaluated by a high-temperature load test in which a load is applied to the multilayer ceramic capacitor for a long time at a high temperature to determine the deterioration resistance of the insulation resistance over time. In this case, the determination of whether the insulation resistance of the multilayer ceramic capacitor is resistant to deterioration with time is usually performed by sampling inspection for each product lot. This is because if you try to measure the time until dielectric breakdown occurs in the high temperature load test, the high temperature load test will inevitably continue until the multilayer ceramic capacitor is destroyed, and the product after inspection becomes unusable. It is.
[0006]
[Problems to be solved by the invention]
However, a multilayer ceramic capacitor using a base metal as an internal electrode material is not a problem under normal use conditions compared to a multilayer ceramic capacitor using a precious metal fired in a natural atmosphere as an internal electrode material. There is a demand for the development of a more reliable multilayer ceramic capacitor that is less reliable when loaded.
[0007]
In addition, the high temperature load test has a problem that it takes a long time to measure, and since it is not 100% inspection, there is a possibility that a defective product is included in the product. In order to avoid this, if a high temperature load test is performed on all products and only the product that deteriorates at the initial stage is removed, the insulation resistance may deteriorate due to the high temperature load, and the life of good products may be shortened. is there.
[0008]
The present invention has been made in view of such a problem, and the insulation resistance does not deteriorate for a long time under a high temperature load, and a highly reliable and inexpensive multilayer ceramic capacitor is obtained. The main purpose is to make it possible to determine the deterioration resistance of the insulation resistance over time without causing any problems.
[0009]
[0010]
[Means for Solving the Problems]
The multilayer ceramic capacitor in the quality determination method of the present invention is composed of a plurality of dielectric ceramic layers laminated with an internal electrode interposed therebetween, and is electrically connected to the internal electrodes exposed alternately from both sides of the dielectric ceramic layer. a multilayer ceramic capacitor having an external electrode arranged in connection with a temperature of 100 to 150 ° C., applying a DC electric field 2. 0 ~5.0kV / Curie point shift before and after the capacity reduction test under the conditions of mm And the capacity change rate ratio is 0.1 or less.
[0011]
More particularly, the laminated ceramic capacitor, the Curie point by capacity reduction test by high-temperature load under conditions of temperature 100 to 150 ° C., applying a DC electric field 2. 0 ~5.0kV / mm is not shifted to the low temperature side When the properties or capacitance at room temperature (25 ° C.) before and after the capacity reduction test are C1, C2, and Curie points are T1, T2, the formula:
ΔT (° C.) = T2−T1, σ (%) = [(C2−C1) / C1] × 100
The property of 0 ≦ ΔT / σ ≦ 0.1 in the region where the Curie point shift amount ΔT and the capacity change rate σ defined by the equation satisfy the relationship of −12 <ΔT <0 and −60 <σ <−10 at the same time. Is provided in a multilayer ceramic capacitor.
[0012]
The properties of the multilayer ceramic capacitor can be imparted by baking an external electrode on the multilayer capacitor chip in the manufacturing process of the multilayer ceramic capacitor and then performing a heat treatment at a temperature in the range of 800 to 900 ° C. in a natural atmosphere. . That is , after forming a ceramic green sheet by forming a dielectric ceramic material and applying an internal electrode material on the surface to form an internal electrode layer, a plurality of green sheets are laminated and integrated into a chip. Baked in a non-oxidizing atmosphere such as a neutral or reducing atmosphere, and baked external electrodes electrically connected to the internal electrodes on both end faces of the obtained capacitor chip. The heat treatment is performed at a temperature within the range of 900 ° C.
[0013]
Any material can be used as the dielectric ceramic material, but it is advantageous to use a non-reducing dielectric ceramic from the viewpoint of obtaining an inexpensive multilayer ceramic capacitor. As this non-reducing dielectric ceramic, any known one can be used, including the barium titanate non-reducing dielectric ceramic described in Japanese Patent Publication No. 57-42588. In this case, an inexpensive base metal such as nickel, iron, cobalt, tungsten, or manganese can be used as the internal electrode material. Among these, nickel or a nickel alloy is preferably used.
[0014]
Then, according to the present invention can be laminated ceramic capacitor is determined more that reliable quality whether having said properties. Accordingly, the present invention is intended to provide even quality determination method of a multilayer ceramic capacitor, the method, the temperature 100 to 150 ° C., applying a DC electric field 2. 0~5. 0 kV / mm , application time 4 When the capacitance at room temperature (25 ° C.) before and after the capacity reduction test under the condition of 120 hours is C1, C2, and the Curie points are T1, T2, the formula : ΔT ( ° C. ) = T2-T1, σ ( % ) = [( C2-C1 ) / C1 ] × 100 The ratio ( ΔT / σ ) of the Curie point shift amount ( ΔT ) and the capacity change rate ( σ ) defined by −12 <ΔT <0 and −60 < sigma when satisfying 0 ≦ ΔT / σ ≦ 0. 1 in the range of <-10, and characterized by a good case [Delta] T is not a negative value. In this case, if the Curie point shift amount is positive, the ratio (ΔT / σ) of the Curie point shift amount (ΔT) and the capacity change rate (σ) is negative, that is, ≦ 0.1. If it does not shift to the low temperature side, it is not necessary to obtain the ratio (ΔT / σ) of the Curie point shift amount (ΔT) and the capacity change rate (σ) before and after the capacity decrease test, and the Curie point shift amount (ΔT) is negative. In this case, the ratio (ΔT / σ) may be obtained only. In the latter case, the multilayer ceramic capacitor only needs to have a property of 0 ≦ ΔT / σ ≦ 0.1 by the capacity reduction test.
[0015]
[Action]
The ratio of the temperature 100 to 150 ° C. in the multilayer ceramic capacitor, the applied DC electric field 2. 0 ~5.0kV / shift amount of the Curie point of before and after the capacity reduction test under the conditions of mm ([Delta] T) and capacitance change rate (sigma) ( When the property that ΔT / σ) is ΔT / σ ≦ 0.1, the insulation resistance is less deteriorated at a high temperature load, the life is extended, and the reliability is improved.
[0016]
Further, since the capacity drop is a phenomenon observed in a short time under a mild load condition as compared with the insulation resistance deterioration test, the test for causing the capacity drop in the multilayer ceramic capacitor, that is, the capacity drop test is performed at a temperature of 100 to 150. ℃, applied DC electric field of 2.0 to 5.0 kV / mm, which can be performed under milder conditions than the insulation resistance degradation test, and if this is applied to pass / fail judgment of multilayer ceramic capacitors, the product is not destroyed. The quality can be determined in a short time. Note that the capacity reduction test was performed under the above conditions when the temperature was less than 100 ° C. or the applied DC electric field was less than 2.0 kV / mm. It is not desirable because it is bad, and if the temperature exceeds 150 ° C. or the DC applied electric field exceeds 5.0 kV / mm, the load condition is too severe and the life of a good product may be reduced.
[0017]
【Example】
BaCO ₃ , CaCO ₃ , TiO ₂ , ZrO ₂ , MnO ₂ and SiO ₂ with a purity of 99.8% or more are prepared as raw materials, and these are [(Ba _0.9 Ca _0.1 ) O] _1.01 (Ti _0.8 Zr _0.2 ) O _2. Formulated to a ratio of +0.25 wt% MnO ₂ +0.2 wt% SiO ₂ , the resulting mixture was pulverized by wet mixing in a ball mill, dried, and then calcined in air at 1100 ° C. for 2 hours Subsequently, dry pulverization was performed to obtain a calcined powder having a particle size of 1 μm or less.
[0018]
An appropriate amount of a polyvinyl butyral binder and an ethanol organic solvent were added to the calcined powder and wet mixed by a ball mill to prepare a ceramic slurry. This ceramic slurry was formed into a sheet by a doctor blade method to obtain a rectangular green sheet having a thickness of about 23 μm. Next, nickel paste was screen-printed on these green sheets to form internal electrode patterns, and a plurality of layers were stacked and thermocompression bonded so that the electrode lead-out sides of the internal electrode patterns were alternated to obtain a laminate. .
[0019]
After this laminated body was made into chips, it was heated to 350 ° C. in a nitrogen atmosphere to burn and remove the binder, and the atmosphere was controlled so that the oxygen partial pressure was 10 ⁻¹¹ MPa and fired at 1250 ° C. for 2 hours. A multilayer capacitor chip was obtained. A silver paste containing palladium was applied to both end faces from which the internal electrodes of each chip were drawn, and baked at 600 ° C. in a nitrogen atmosphere to form external electrodes electrically connected to the internal electrodes. Thereafter, it was further heat-treated at 850 ° C. for 30 minutes in a natural atmosphere to obtain a multilayer ceramic capacitor.
[0020]
The obtained multilayer ceramic capacitor has outer dimensions of width: 1.6 mm, length: 3.2 mm, thickness: 1.2 mm, and the thickness of each dielectric ceramic layer between internal electrodes is 15 μm. Is 19 and the area of the counter electrode per layer is 2.1 mm. Its Curie point is about 0 ° C.
[0021]
For the multilayer ceramic capacitor according to the present invention and the comparative sample, the capacitance change rate dependency of the Curie point was measured by the following method. In addition, as a comparative sample, the sample in which the external electrode was formed in the above-described example, that is, the sample that was not heat-treated was used.
[0022]
For each sample, a high frequency voltage of 1 kHz and 1 Vrms was applied, and the temperature change of the capacitance was measured in the range of −50 ° C. to 150 ° C., and the capacitance (C1) and Curie point at room temperature (25 ° C.). (T1) was determined. Next, each sample is put into a thermostat, and the temperature is 100 to 150 ° C., the direct current applied electric field is 2.0 to 5.0 kV / mm, and the time is 4 to 120 hours. After conducting a capacity reduction test by applying a DC voltage of 3.5 kV / mm for 4 hours, the battery was taken out to room temperature and again subjected to the capacitance (C2) and Curie point (T2) at room temperature (25 ° C.) under the above method. ) And the capacity change rate (σ) and Curie point shift amount (ΔT) defined by the following equations were obtained.
σ = (C2−C1) / C1 × 100
ΔT = T2-T1
[0023]
The results of the obtained Curie point shift amount (ΔT) and the capacity change rate (σ) are shown in FIG. In the figure, the black squares indicate the results for the multilayer ceramic capacitor according to the example of the present invention, and the white circles indicate the results for the multilayer ceramic capacitor of the comparative example corresponding to the conventional example in which heat treatment is not performed after forming the external electrode. Corresponds to the ratio ΔT / σ = 0.1 of the Curie point shift amount (ΔT) and the capacity change rate (σ) before and after the capacity decrease test.
[0024]
As can be seen from FIG. 1, in the multilayer ceramic capacitor according to the example of the present invention, when the capacity reduction is caused by the capacity reduction test, the Curie point shift amount before and after the capacity reduction test (ΔT) and the capacity change rate ( The ratio (ΔT / σ) of σ) is higher than the one-dot chain line, that is, ΔT / σ ≦ 0.1. In the comparative example, the amount of shift of the Curie point before and after the capacity reduction test The ratio (ΔT / σ) of (ΔT) and the rate of change in capacity (σ) is lower than the one-dot chain line, showing a clear difference. More specifically, in the multilayer ceramic capacitor according to the present invention, the Curie point does not shift to a low temperature side when the capacitance change rate is less than −10%, and the capacitance change rate and the Curie point shift amount are respectively -12 <ΔT <0 and -60 <σ <−10, all satisfy the relationship of 0 ≦ ΔT / ΔC ≦ 0.1.
[0025]
Further, as is apparent from the results of FIG. 1, a capacity reduction rate of about 20% is sufficient for determining the quality of the multilayer ceramic capacitor, and the high temperature load required for this is the above load condition. 4 to 20 hours.
[0026]
Next, 10 samples each of the multilayer ceramic capacitor according to the present invention and the comparative example are used as samples, and a DC electric field of 5.0 kV / mm is applied to each sample at a temperature of 175 ° C. to accelerate the deterioration of insulation resistance. A life test was performed, and the insulation resistance was measured every predetermined time, and the change with time was obtained. As the life criterion, the time when the insulation resistance decreased by three digits from the initial value was regarded as the life, and the average life was obtained for the multilayer ceramic capacitor according to the present invention and the comparative example. The sample of the comparative example had an average life of 12.5 hours, whereas the sample of the present invention had an average life of 147 hours. From this, it can be seen that the multilayer ceramic capacitor according to the present invention has a significantly improved life compared to the comparative example.
[0027]
Furthermore, when the sample of the multilayer ceramic capacitor according to the present invention subjected to the capacity reduction test was heated at 150 to 200 ° C. for 20 to 40 minutes without applying a DC electric field, it decreased due to a high temperature load in the capacity reduction test. The capacitance recovered to the original state, and no decrease in insulation resistance was observed. Therefore, according to the present invention, even if all the multilayer ceramic capacitors are inspected, it is possible to make a good / bad determination of reliability in a short time without deteriorating the product, and only by performing a heat treatment after the inspection. , Can be restored to its original characteristics.
[0028]
【The invention's effect】
As is clear from the above description, the multilayer ceramic capacitor in the pass / fail judgment method of the present invention has a Curie point shift when a capacity reduction test is performed under a condition of a much higher temperature load than the conventional insulation resistance deterioration test. By giving the property that the ratio between the amount and the capacity change rate is ≦ 0.1, the insulation resistance does not deteriorate for a long time under a high-temperature load, and the multilayer ceramic capacitor is long-lived, highly reliable, and inexpensive . In the quality determination method of the present invention , the reliability quality can be determined in a short time without degrading the insulation resistance of the multilayer ceramic capacitor . For example, the capacitance decreases in the quality determination process. However, there are excellent effects such that the electrostatic capacity can be restored to the original state by a simple heat treatment.
[Brief description of the drawings]
FIG. 1 is a graph showing characteristics of multilayer ceramic capacitors according to the present invention and comparative examples.

Claims (1)

Laminate comprising a plurality of dielectric porcelain layers laminated with an internal electrode interposed therebetween, and an external electrode provided in electrical connection with the internal electrodes exposed alternately on both end faces from the dielectric porcelain layer A method for determining the quality of a ceramic capacitor,
In the multilayer ceramic capacitor, a temperature of 100 to 150 ° C., an applied DC electric field 2 . 0-5 . 0 kV / mm When the electrostatic capacity at room temperature (25 ° C.) before and after the capacity reduction test under the condition of application time of 4 to 120 hours is C1, C2, and Curie points are T1, T2, : ΔT ( ℃ ) = T2-T1, σ ( % ) = [( C2-C1 ) / C1 ] Curie point shift amount defined by × 100 ( ΔT ) And capacity change rate ( σ ) Ratio of ( ΔT / σ ) In the range of −12 <ΔT <0 and −60 <σ <−10, 0 ≦ ΔT / σ ≦ 0 . 1. A method for determining the quality of a multilayer ceramic capacitor, wherein 1 is satisfied, and ΔT is not a negative value.

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