JPS6033256A - Ceramic composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a porcelain composition, and particularly to a porcelain composition that can be sintered at a low temperature of 1000°C or less, has a high product of dielectric constant and specific resistance, and has high mechanical strength. .

Conventionally, barium titanate (B
It is well known that porcelain compositions containing aTi0a) as a main component have been widely put into practical use. However, those whose main component is barium titanate (BaTi01) have a sintering temperature of usually 1300 to 1400°C.

Therefore, when using this material in a multilayer capacitor, a material 9 that can withstand this sintering temperature must be used for the internal electrodes, such as expensive noble metals such as platinum and palladium, which has the disadvantage of high manufacturing costs. be. In order to manufacture multilayer capacitors at low cost, it is necessary to have a porcelain composition that can be sintered at as low a temperature as possible, especially at 1000° C. or lower, so that inexpensive metals mainly composed of silver, nickel, etc. can be used for the internal electrodes. ~ Incidentally, when fabricating a practical multilayer capacitor using a ceramic composition, many items must be evaluated as the electrical properties of the ceramic composition.

Generally, it is required that the dielectric constant be as large as possible, the dielectric loss as small as possible, the resistivity as large as possible, and the temperature change in the dielectric constant as small as possible.

However, for practical purposes, in multilayer capacitors, values such as the capacitance 9, the temperature change rate of the capacitance, the dielectric loss, etc. are required, rather than the dielectric constant. In multilayer capacitors,
Capacity is proportional to the dielectric constant of the porcelain composition, but is inversely proportional to its thickness, and proportional to the electrode area and the number of laminated layers, so it is not necessarily necessary that the dielectric constant of the porcelain composition be large in order to obtain a constant capacitance. It is not a factor. Furthermore, the temperature change rate of capacitance (temperature change rate of dielectric constant) has various permissible ranges depending on the application, and the temperature change rate of dielectric constant of ceramic composition also has an absolute value when manufacturing multilayer capacitors. Not a factor.

On the other hand, there is a regulation that the dielectric loss must be below a certain value depending on the application, and the maximum is 5.0% or below at room temperature.

Regarding specific resistance, for example, as stated in the EIAJ standard [Japan Electronics Industry Association's Multilayer Ceramic Capacitors for Electronic Equipment (Chip Type) RC-3698B], the insulation resistance of the multilayer capacitor should be 10,000 MΩ or more or the capacitance resistance. It is specified that the product is 500 μF-MΩ or more, whichever is smaller. In other words, it is any capacitance as long as the product of the permittivity and resistivity of the porcelain composition is not greater than the absolute value.

In particular, capacitors with large capacitances cannot be made to meet practical standards, so their uses are extremely limited and they have no practical meaning. This point will be explained in detail as follows. A multilayer capacitor has a structure in which single-layer capacitors are stacked, generally consisting of n layers of the same thickness and forming n+1 internal electrodes. In this case, if the capacitance of the single layer is CO9 and the insulation resistance is R8, then the capacitance C of the multilayer capacitor is n times C0, and the insulation resistance R is 1/1 of R8.
It becomes n. Here, if the permittivity of the ceramic composition is ε, the permittivity of vacuum is C0, the specific resistance of the ceramic composition is ρ, the thickness of the ceramic of the single layer capacitor is 62, and the area of the overlapping electrodes is 8, then the area of the overlapping electrodes is 8. C0 is (εo's)/d. is (ρa)/S. Therefore, the product CX R of the capacitance (C) and insulation resistance (6) of a multilayer capacitor consisting of n layers is [(ρ
d) / (,8)) X ((n layer. εS) / d
:]='oερ. In other words, the capacitance-resistance product (CXR) of a multilayer capacitor of any capacity is the product of ε and ρ of the ceramic composition. A constant value (ε. ερ) multiplied by
Standardized. Capacitance/resistance product CXR is 500μF・Ω
This means that ε, =8.855 x 10″4
4p/! Good, CX R+-8g tρ=8.855
X 10-”(F/C”) Xε×ρ≧500F
-Ω, yaw ztetl)=5.65
5X 10”Ω~ When ε=3000, ρ≧1.88
X 10”ΩΦ1.When ε=500, ρ≧1.13X1
0" Ω・α is required. Any large capacitance multilayer capacitor made of a ceramic composition with ρ greater than these values depending on the dielectric constant has a capacitance-resistance product of 500 μF・MΩ
satisfy. If ε is 3000 and ρ is 1.88 x 10”Ω α, which is 91 orders of magnitude lower than the required value, then ε, ερ = 50
μF-MΩ does not satisfy 500 μF-MΩ, and the standard value of insulation resistance is 10000 MΩ, that is, 101
In order to satisfy 6Ω or more, the capacitance C must be limited to 0.005 μF or less. The capacitance-resistance product ('CXR) of this multilayer capacitor is always 50μF・MΩ
Therefore, when R is 10000 MΩ, C is 0.005 μF. If c is larger than this, R is 1.
This is because 0.005 μF, which is smaller than 0000 MΩ, is the highest capacitance that satisfies the standard. Therefore, if the specific resistance of the ceramic composition is low, the practicality of the material, especially the small size and large capacity that is a feature of multilayer capacitors, cannot be taken advantage of, and it is completely meaningless. Therefore, it is extremely important in practice that the product of the dielectric constant and specific resistance of the ceramic composition has a certain value or more.

In addition, in the case of multilayer chip capacitors, when the chip capacitor is mounted on a board, due to the difference in thermal expansion coefficient between the board and the ceramic composition that makes up the chip capacitor,
Mechanical strain may be applied to the chip capacitor, causing cracks or damage to the chip capacitor. Furthermore, in the case of a dip capacitor coated with epoxy resin or the like, cracks may occur in the dip capacitor due to the stress of the coat resin. In either case, the lower the mechanical strength of the porcelain forming the capacitor, the more likely it is to crack and break, resulting in lower reliability.

Therefore, it is of practical importance to increase the mechanical strength of porcelain as much as possible.

By the way, Pb(Mg1/2W1/2)Os PbTiO
3 series porcelain compositions have already been developed by N.N. Krainik and A.I.Agranovskaya (N.N.Krain).
ikand A, 1. Agranovs'E';'a
(Fiziko Tverdog.

Te1a, Vo, 2. Nnl, pp70-72.
There was a proposal from Janvara (1960)).
Among the characteristics to be evaluated when manufacturing a multilayer capacitor, only the dielectric constant and its temperature characteristics were described, and their practicality was not clear. Also ( 5rxPb, -x 'r
io, ), (PbMg6.5Wo, 60x)B (where x = 0 to 0.10, a is o, 35 to 0.5
°b is 0.5 to 0.65, and a + b =
1) is disclosed in Japanese Patent Application Laid-Open No. 52-21662 as a monolift capacitor and its manufacturing method, and as a dielectric powder composition in Japanese Patent Application Laid-Open No. 52-2169.
It is disclosed in Publication No. 9. Here as well, it is stated that the composition has a dielectric constant of approximately 2000 to 5.0 cm and a dielectric loss of 0.5% to 5.0 cm as properties of the composition, but there is no mention of specific resistance or capacitance-resistance ratio, making it impractical. was not clear. Furthermore, Pb(Mg1/2W1/2)Ox
and PbTiO3, and Pb(Mg
1/2W1/2) On is 20.0 to 70.0 molti,
A high permittivity ceramic composition characterized by containing MgO'JiL in an amount of 30% or less of the calculated value in a composition having a PbTiO3 content of 3.0.0 to 80.0 molti is disclosed in JP-A-55-1989. It is disclosed as Publication No. 144609. However, in this patent, the dielectric constant is about 2300 to 71.
In addition to the description that the dielectric loss is 0.3 to 2.1 inches for 00, there is a description of the temperature characteristics of the dielectric constant, but there is no description of specific resistance or capacitance-resistance product. It's not clear. Next, the present inventors have already discovered that 910℃~9
Can be sintered at a temperature of 50℃, Fb (Mgl/2W1/2)
It is composed of two components of O8 and PbTiO3 system, which is (p b
(Mg1/2W1/2)Oa)x(PbTiOs)1-
A composition in which X, expressed as z, is in the range of 0.65<x≦1.0O is proposed. This composition has a product of dielectric constant and specific resistance as high as 5.65 x 10 m5 Ω·2 or more, and has excellent electrical properties with low dielectric loss. However, since all of the above compositions have low mechanical strength, their applications have been forced to be limited to a narrow range.

In view of the above points, the present invention can be sintered in a low temperature range of 900 to 1000°C, and has a product of dielectric constant and specific resistance of 5.65.
X 10”Ω・a (that is, the capacitance-resistance product is 500μF-
The purpose of this project is to provide a porcelain composition that has a high value of magnesium lead tungstate (Pb), has excellent electrical properties with minimal dielectric loss, and also has high mechanical strength. (Mgl/2Wl/2)03 and lead titanate < PbTi0a)
(Mg1/zW1/z)Os), (PbTi0s
) + -x, where X is 0.50≦X≦1.0
Manganese lead niobate (Pb(Mnl/2Nb1/2)03
) is added in an amount of 0.05 to 5 moJ% based on the main component.

The present invention will be explained in detail below using examples.

Lead oxide (PbO) with a purity of 99.91 or higher as a starting material
.

Magnesium oxide (MgO) + tungsten oxide (WO
s) to titanium oxide (Ti0z) to niobium oxide (Nb)
Using tOs ) p and manganese carbonate, weigh each to achieve the blending ratio shown in the table. Next, the weighed amounts of each material were wet mixed in a ball mill and heated at 750 to 800°.
The powder was pre-baked in C and ground in a ball mill, dried, mixed with an organic binder, sized and pressed to form four discs with a diameter of 16 mm and a thickness of about 2 m, A cylinder with a thickness of about 10 mm was produced. Next, 900-100 in the air
Sintering was carried out at a temperature of 0° C. for 1 hour.

Silver electrodes were baked on the top and bottom surfaces of four sintered disks at 600°C, and the frequency was set to I KHz using a digital LC1'L meter.

Voltage I Vr, m=s g The capacitance and dielectric loss were measured at a temperature of 20° C., and the dielectric constant was calculated. Next, I tested 50 with a super insulation resistance tester.
A voltage of V was applied for 1 minute, insulation resistance was measured at a temperature of 20° C., and specific resistance was calculated. In order to evaluate the mechanical properties by bending strength, a sintered cylinder with a thickness of 9.5 m and a width of 2111+
, 10 rectangular plates with a length of approximately 1311 m were cut out. The distance between the supporting points is 9s), and the breaking load Pm (K9) is calculated using the three-point method.
was measured, and the bending strength τ (l#/d) was determined according to the formula: τ,...3i"mA'(KP/cd)2wt". However, l
is the distance between the supporting points, t is the thickness of the sample, and W is the width of the sample.

Electrical characteristics are average values of four disk samples.

The bending strength was determined as the average value of 10 rectangular plate samples.

The main component of the porcelain thus obtained (Pb(Mgl/
2Wi/z)Os)x (PbTiOs)1-)c
The mixing ratio of S and the additive amount of subcomponents, bending strength, dielectric constant, dielectric loss, and capacitance-resistance product (indicated as εOερ in the table)
The relationship between is shown in the table.

As is clear from the results shown in the table, lead manganese niobate (P b (Mn 1/2Nb 1
/2) An excellent high dielectric constant porcelain composition which is highly reliable and highly practical, increasing both the flexural strength and the capacitance-resistance product by adding 01) and maintaining a low dielectric loss value. It can be seen that the following can be obtained. The porcelain composition of the present invention, which exhibits these excellent properties, has a low sintering temperature of 1000°C or less, which makes it possible to reduce the cost of the internal electrodes of multilayer capacitors, and also to save energy and furnace materials. Excellent effects also occur.

If the main component compounding ratio X is less than 0.5, the capacitance-resistance product will be smaller than the standard value and the dielectric loss will also exceed 5.0, which is not practical. Also, there is a subcomponent molecule c pb(Mnl/2N
J/2) If the amount of Os added is less than 0.05mo6%, the effect of improving the bending strength is small; If it exceeds %, the bending strength will be too small to be practical.

Claims (1)

[Claims] Magnesium lead tungstate (Pb (Mgl/2W
A binary composition consisting of lead titanate (PbTi03) and lead titanate (Pb(Mgl/2W1/2)08
), (PbTiOs), -. When represented as A porcelain composition characterized in that it contains 0.05 to 5 mo1%.