JPH0343225B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a low-temperature sintered dielectric porcelain material having a high Q, and more particularly to a low-temperature sintered dielectric porcelain material suitable for producing a bulk sintered body of an LC composite chip element and a method for producing the same. . Conventionally, LC composite chip elements are constructed by combining separately manufactured chip inductors and chip capacitors, and are widely used as circuit elements having a resonant effect, such as trap circuits and filter circuits. The manufacturing method is to laminate dielectric layers and electrode layers, and to laminate magnetic layers and coil-forming conductors using sheet methods, printing methods, etc., and then sinter each laminate by firing each laminate at a predetermined temperature. It is common practice to use a chip capacitor and a sintered chip inductor and glue them one by one to form an LC composite chip element. As an alternative method, a method is also used in which LC composite chip devices are fired all at once to form an integrated device. In this case, crystallized glass is used as the capacitor material, but due to the large difference in coefficient of thermal expansion between the ferrite sintered body of the chip inductor and the crystallized glass sintered body, the joint surface may deteriorate after long-term use. Cracks and peeling may occur. In order to cope with this problem, it is currently necessary to interpose a strain relaxation layer made of glass or the like having a coefficient of thermal expansion between those of these two materials. Among the above methods, the method of gluing sintered chips has the drawback that the manufacturing process is complicated because the sintered chips are minute and mass production is not easy.
Furthermore, the method of forming the intermediate relaxation layer requires an extra layer, which complicates the manufacturing process, and also includes unnecessary parts that do not function in terms of circuitry. It is therefore an object of the present invention to provide a dielectric porcelain material that is suitable for bulk firing, does not require an intermediate relaxation layer, and exhibits excellent properties especially when sintered with ferrite magnetic material. The object of the present invention is to provide a low-temperature sintered dielectric porcelain material. The inventor of the present invention searched for a material that has no substantial difference in coefficient of thermal expansion with magnetic ferrite and has sufficient adhesive strength when fired together with the magnetic ferrite, and found that spinel-type ferrite We have discovered that a mixed sintered body of glass and other materials achieves the desired purpose. Furthermore, it was found that the material of the present invention has high electrical properties and can be sintered at a relatively low temperature. The present inventor invented low-temperature sintered ferrite as a magnetic material for chip inductors (Japanese patent application No. 56
Currently, crystallized glass is the only dielectric material exhibiting a high Q that can be used for LC resonant circuit elements with a similar sintering temperature, but as mentioned above, crystallized glass is Due to the large difference in coefficients, it was necessary to interpose an intermediate layer on the joint surface, but the dielectric ceramic material of the present invention is a dielectric material suitable for bulk sintering with the above magnetic ferrite without using an intermediate layer. It turned out to be a body material. The low-temperature sintered dielectric porcelain material of the present invention has the electrical properties necessary for a circuit element, and has the same sintering temperature and shrinkage rate as magnetic ferrite. It has a coefficient of thermal expansion of Therefore, an LC composite chip can be manufactured by sintering a preformed body with an integrated LC shape before firing, and the sintered bodies can be bonded one by one as described above, or an intermediate relaxation layer can be formed at the joint. There is no need to do this, mass production is easy, and the amount of material consumed is small because no intermediate layer is required, which has the advantage of reducing manufacturing costs. The present invention will be explained in detail below. Generally, spinel-type ferrite is used practically as a high-frequency magnetic material, and CuZn ferrite is one example thereof. This ferrite sinters at a lower temperature than other spinel-type ferrites because it contains Cu. It is also known that the Curie temperature of this type of ferrite changes depending on the content of non-magnetic Zu ferrite, and that it can be made non-magnetic at room temperature, a temperature range where various electrical devices are generally put into practical use. .
Furthermore, the dielectric constant ε of ferrite is generally 10 or more, making it a paraelectric material, and the coefficient of thermal expansion α of sintered ferrite is approximately 80 to 110×, regardless of the type of divalent ion.
It is in the range of 10 ^-7 /℃. From the above, non-magnetic
We investigated whether CuZn ferrite can be used as a dielectric suitable for simultaneous firing with magnetic ferrite. Figure 1 shows the results of a detailed investigation of the characteristics of nonmagnetic CuZn ferrite. The figure was fired at 1000℃
Composition of CuZn ferrite and ε, Q, d.sh (ε: relative dielectric constant, Q: Q of dielectric, d: sintered density g/cm ³ ,
sh: Shrinkage ratio (%)), Fe ₂ O ₃ 40~
Tc in the range of 50wt%, CuO0~20wt%, balance ZnO
= The part below -50℃, that is, becomes non-magnetic at temperatures above -50℃. However, as can be seen from this figure, although the sinterability is good and low temperature sintering is possible, the Q of CuZn ferrite is
was found to be extremely low, making it unsuitable as a dielectric material for LC composite chips. The Q of ferrite as a dielectric material seems to depend on its specific resistance, that is, the resistance of crystal grains and the resistance of crystal grain boundaries, so the inventors attempted to increase the resistance of CuZn ferrite by increasing these as much as possible. Ta. As a result, it was found that when a glass component was added to an oxide whose main component was non-magnetic CuZn ferrite (including Cu = 0 mol%) to introduce high-resistance grain boundaries, the Q value increased significantly.
This glass softens near the firing temperature.
Any glass with a specific resistance of 10 ⁹ Ω-cm or more is sufficient.
Boric acid glass, borosilicate glass, soda silicate glass, etc. can be used, as well as MgO, Al ₂ O ₃ ,
It may contain any component such as PbO, ZnO, or CaO. The non-magnetic CuZn ferrite, which is the main component, is the first
The Curie temperature in the lower right part of the range shown in the figure
Select from the composition excluding the part where Tc=-50℃ or higher. Fe ₂ O ₃ If the composition exceeds 50 mol%, it will be contained in the sintered body.
May generate Fe ²⁺ ions, Fe ²⁺ , Fe ³⁺
Even if glass is included due to electrical conduction of ions, Q will be significantly lowered, and if the amount of Fe ₂ O ₃ increases relative to the stoichiometric amount, the sintered body will deteriorate significantly, which is not preferable. In contrast, Fe ₂ O ₃ 50mol%
If it is below, the spinel solid solution deviates from the stoichiometry of spinel ferrite, and the spinel solid solution becomes an oxide mainly composed of two or more phases of spinel ferrite, but it has been found that there is no problem as a dielectric material. The CuZn ferrite specified above is 800~1000℃
It has good sintering properties when fired in the temperature range of 200 to 3000, making it an excellent material for LC composite chip devices. In the case of a mixed sintered body of oxide and glass where the firing temperature exceeds 1000℃, the sintering reaction of the oxide is slow and the sintered density is low, resulting in a large number of pores inside the sintered body, making it difficult to use as a dielectric material. has poor moisture resistance and is difficult to put into practical use. The amount of glass to be mixed is selected in the range of 1 to 50 wt% based on the total amount of the sintered body. Generally, the above-mentioned glass has a coefficient of thermal expansion of about 10 to 50 x 10 ^-7 /℃, which is 90 to 100 x 10 ^-7 /℃.
The coefficient of thermal expansion of the sintered body mixed with CuZn ferrite varies depending on the mixing ratio. The thermal expansion coefficient of low-temperature fired magnetic ferrite is approximately 90×
10 ^-7 /℃, so the thermal expansion coefficient α of the dielectric material to be combined with this is in the range of 70 to 110 × 10 ^-7 /℃,
In other words, the coefficient of thermal expansion of magnetic ferrite is ±20×
It is sufficient if it is within the range of 10 ^-7 /℃. This range is achieved with an amount of glass of about 50% or less. In the production of low-temperature fired ferrite powder,
By selecting appropriate conditions, the shrinkage ratio can be controlled within the range of 10 to 20% at a firing temperature of 800 to 900° C. without impairing the electrical and magnetic properties. Therefore LC
Non-magnetic CuZn has satisfactory electrical properties as a dielectric material when manufacturing composite chips by batch firing.
When combined with low-temperature-sintered magnetic ferrite, which has a shrinkage ratio of ±1% of a sintered body of a mixture of oxide and glass, which has ferrite as its main component, deformation due to the difference in shrinkage ratio between the magnetic part and the dielectric part will occur. , no curling occurs, and it is easy to manufacture LC composite chips that can be used for practical purposes. A chip inductor using low-temperature fired magnetic ferrite is a sintered body using Ag as the internal winding.
Its Q is about 50. The amount of attenuation required for trap circuits and filter circuits is generally -20 dB or more, and this amount of attenuation changes depending on the Q of the dielectric material used in combination. Figure 2 shows the attenuation of the LC resonant circuit when the Q of the combined dielectrics is changed.
The number 1 that follows the curve is μ = 108, Q = 50 (4MHz),
Sintered chip inductor with sh=12%, α=95×10 ^-7 /℃, number 2 is μ=153, Q=42, sh=17%, α
=89×10 ^-7 /℃ sintered chip inductor, number 3
is μ=125, Q=47, sh=15%, α=92×10 ^-7 /
℃ sintered chip inductors, all of which were fired at a firing temperature of 900℃. As can be seen from Figure 2, if the chip capacitor has a Q of 100 or more, it can be put to practical use, but the glass-mixed CuZn ferrite (including Cu = 0 mol%) of the present invention does not meet this requirement. fully satisfied. Next, examples of the present invention will be described. Example 1 Commercially available iron oxide, zinc oxide, and copper oxide powders were
Fe ₂ O ₃ 40.5 mol%, CuO 10.0 mol%, ZnO 49.5 mol
%, and 600 g of water was added to it, mixed in a ball mill for 2 hours, and dried after mixing. Next, this dry powder was calcined in air at 700°C for 2 hours. 0 to 100 wt % of ZnO-B ₂ O ₃ -SiO ₂ glass was added to the calcined powder, 480 g of water was added to 240 g of the mixture, pulverized in a ball mill for 100 hours, and dried after pulverization. A paste was prepared by weighing out 50 g of dry powder, 16 g of an 8% solution of ethyl cellulose (solvent: terpineol) as a binder, and 25 g of terpineol as a solvent, and stirring for 2 hours with a shaker. Chip capacitors are made by laminating this paste and Ag powder paste alternately by screen printing method, and after drying,
Cut the sintered body into chips with dimensions of 4.5 x 3.2 mm and heat at 850℃.
A chip capacitor was obtained by sintering in air at 900°C for 2 hours. The various properties were as shown in Table 1.

[Table] Curve 1 in Figure 3 is this example (calcined at 850℃)
This shows the relationship between the glass content of the dielectric and the coefficient of thermal expansion α.When the amount of glass exceeds about 50wt%, α becomes 70×10 ^-7 /℃ or less, and α of magnetic ferrite is approximately 90×10 ^{- 7} /℃, which is not desirable. Also, among the chip capacitors in this example, 4M
The Q of Hz is the line 1 in Figure 4 for those fired at 850℃.
As shown in , the one with 0% glass and Q=62 is
At 10wt%, Q=350. In addition, as shown by line 2, for those fired at 900°C, Q = 46 at 0%, but Q = 280 at 10wt%. Example 2 In Example 1, _{B2O3 - SiO2} was used as the glass.
Dielectrics were manufactured using the same method (firing temperatures of 850°C and 900°C) using 0 to 100% of As shown by curve 2 in FIG. 3, the glass content was about 50 wt% or less and the coefficient of thermal expansion α was about 70 to 95×10 ^-7 /°C. The characteristics are shown in the table below.

[Table] Example 3 In Example 1, B ₂ O ₃ (hydrate
Chip capacitors were manufactured using the same method (firing temperatures of 850° C. and 900° C.) using 0, 3.2 and 8.8 wt% of H ₃ BO ₃ ). Line 3 in FIG. 4 shows the product fired at 850°C, and line 4 shows the product fired at 900°C. obviously glass 1
% or more, Q is 100 or more, and 8.8% is 600 or more. The characteristics are shown in the table below.

[Table] Example 4 The same method as in Example 1 was used except that 48 mol% of Fe ₂ O ₃ and 52 mol% of ZnO were used as raw materials for non-magnetic ferrite without CuO, and 0 to 5 wt% of B ₂ O ₃ was used as glass. Manufactured chip capacitors. As shown in FIG. 5, Q was 200 or more when the glass was 1% or more. The characteristics are shown in the table below.

[Table] Example 5 NiCuZn obtained by firing in air at a firing temperature of 850°C
The characteristics of ferrite are μ=108, Q (4MHz)=
49, sh = 13.2%, α = 94 × 10 ^-7 /℃ Magnetic ferrite is laminated with Ag paste so that the conductor has 18 turns to form an internal coil.
A laminate with a thickness of 1200μ was formed, and four layers of the dielectric material of Example 1 were laminated alternately with Ag paste electrodes on top of the laminate to form a multilayer capacitor with a thickness of 900μ.
The chips were fired in air for 2 hours to obtain LC composite chips.
The frequency f characteristic of the attenuation amount is shown in FIG. this
The f _r of the LC circuit is 4.72MHz and the attenuation is -21.5dB,
Sufficient for practical use.

[Brief explanation of drawings]

Figure 1 shows the composition and characteristics of non-magnetic CuZn ferrite, and Figure 2 shows the chip capacitor with a Q of LC.
Graph showing the effect of composite chips on attenuation,
Figure 3 is a graph showing the relationship between the mixing ratio of glass mixed into the non-magnetic ferrite dielectric and the coefficient of thermal expansion.
Figures 4 and 5 show the mixing ratio of glass mixed into the non-magnetic ferrite dielectric and the Q of the chip capacitor.
FIG. 6 is a graph showing the attenuation characteristics of an LC composite chip constructed using the dielectric of the present invention.

Claims (1)

[Claims] 1. An oxide containing Zn-based ferrite as a main component (but not including Cu) with a composition of 40 to 50 mol% Fe ₂ O ₃ and the balance ZnO and a Curie temperature Tc = -50°C or less, and Fe ₂ O ₃ 40 to 50 mol%, CuO 20 mol% or less, and the balance ZnO, the Curie temperature Tc = -50
1 to 50 wt% to an oxide selected from oxides whose main component is CuZn-based ferrite with a composition below ℃.
A dielectric porcelain material made by mixing a glass composition. 2 An oxide whose main component is Zn-based ferrite (but does not contain Cu) with a composition in the range of 40 to 50 mol% Fe ₂ O ₃ and the balance ZnO and a Curie temperature Tc = -50°C or less, and Fe ₂ O ₃ 40 ~50 mol%, CuO below 20 mol% and balance ZnO, Curie temperature Tc = -50℃
Dielectric porcelain made by mixing 1 to 50 wt% of a glass composition to an oxide selected from oxides whose main component is CuZn-based ferrite having the following composition, and then firing at a temperature of 800 to 900°C. Method of manufacturing materials.