JPH0722065B2 - Thick film capacitor and manufacturing method thereof - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thick film capacitor used in an electronic circuit for high-density mounting of IC, LSI and the like, and a manufacturing method thereof.

2. Description of the Related Art In recent years, as miniaturization and multi-functionalization of various electronic devices have been progressing year by year, high-density mounting technology for circuit components has played an important role. In particular, due to the development of active elements such as IC and LSI, the transition of passive elements such as resistors and capacitors to chips and thick films, and the multilayering of wiring boards, the mounting of circuit parts is becoming more dense. Tend to be Above all, the conductor wiring, the resistor, and the capacitor are formed into a thick film on the surface of the ceramic insulating substrate such as alumina, and the IC
A so-called thick film hybrid that carries chip products such as
ICs have penetrated deeply due to their high reliability, high packaging density, and easy manufacturing process.

An example of the conventional thick film capacitor described above will be described below with reference to the drawings.

FIG. 5 is a perspective view of a conventional thick film capacitor, and FIG. 6 is a view showing a fine structure of a cross section of the conventional thick film capacitor. In both figures, 40 is a lower electrode layer, 50 is a thick film capacitor layer, 41 is an upper electrode layer, 30 is a ceramic insulating substrate,
51 indicates a dielectric particle and 52 indicates a glass phase. The conventional thick film capacitor is obtained by the following method. On the insulating substrate 30 made of ceramic such as alumina, Ag-Pd, Au-P
The lower electrode layer 40 is screen-printed using a thick film paste of d, Au-Pd or the like, dried, and then baked in air at a temperature of 750 to 950 ° C for 5 to 20 minutes. Next, a dielectric paste is screen-printed on the lower electrode layer 40 and dried to form a dielectric phase 50. Further, an upper electrode layer 41 is printed on the upper part of the dielectric phase 50 by using a noble metal thick film paste such as Ag-Pd in the same manner as the lower electrode layer 40, and after drying, in an air at a temperature of 750 to 900 ° C. Bake for ~ 20 minutes to make thick film capacitors.

The inorganic component of the dielectric paste is barium titanate (BaTiO ₃ ) with a perovskite structure (A ²⁺ B ⁴⁺ O ₃ ) as a dielectric.
These substitution types are mainly used, and they are composed of lead silicate-based bismuth silicate-based low softening point glass used for the purpose of having both mechanical strength and moisture resistance. The reason why BaTiO ₃ is used as the dielectric is that BaTiO ₃ itself has a large permittivity and a large-capacity thick film capacitor can be easily obtained, and the glass phase 52 is densely packed with these dielectric particles 51 to be strong. A material that works as a so-called inorganic binder for binding and that does not easily react with the dielectric particles 51 is suitable. Such thick film capacitors are
A unit capacity of 200 to 200,000 (pF / cm ² ) is practically used and is widely used for various thick film Hic.

(For example, "Thick film IC technology", published by Industrial Research Society, edited by Japan Microelectronics Association) Problems to be solved by the invention However, the conventional thick film capacitors described above have excellent characteristics, In fact, it uses a noble metal as an electrode material and has a big drawback that it is very expensive. That is, in the case of a capacitor element, the capacitance is large when a large-capacity capacitor proportional to the counter electrode area is required, and multiple expensive precious metal materials are required. For this reason,
In some cases, the cost of the electrode material in the material cost may be close to 50%.

In order to solve such a problem, it is conceivable to use a base metal material such as copper (Cu), which is orders of magnitude less expensive than a noble metal material, as an electrode material. However, since the base metal material is generally easily oxidized, in an oxidizing atmosphere such as air which is a conventional atmosphere, it becomes a base metal oxide and reacts with the dielectric to impair the dielectric properties, and also to cause insulation. Loses its performance as an electrode. Therefore, when an inexpensive base metal material is used as an electrode of a thick film capacitor, the thick film capacitor must be formed in a neutral or reducing so-called non-oxidizing atmosphere. However, conventional thick film capacitor materials are composed of oxides that are easily reduced in a non-oxidizing atmosphere, and the dielectric particles become BaTiO ₃ + xH ₂ → BaTiO _3-x + xH ₂ O and become semiconductor due to oxygen defects. , The specific resistance decreases and the dielectric characteristics are lost. In addition, PbO and Bi ₂ O _{3 which} are glass components are reduced at a relatively low temperature to become Pb and Bi metals, and the function as glass is completely lost.

PbO + H ₂ → Pb + H ₂ O or PbO + Ni → Pb + NiO As described above, the conventional thick film capacitors could not be formed at all in the non-oxidizing atmosphere due to the properties of the materials used. Therefore, in reality, it has been difficult to realize a low-cost thick film material using an inexpensive base metal material.

The present invention provides a thick film capacitor that uses an inexpensive base metal material as an electrode material, can be fired in a non-oxidizing atmosphere, and has excellent dielectric properties, and a method for manufacturing the same.

Means for Solving the Problems In order to solve the above problems, a thick film capacitor of the present invention and a method for manufacturing the same are provided with a perovskite-type dielectric ceramic crude product in which charge compensation is performed using a base metal as an electrode, and a non-reducing glass. It is a thick film capacitor composed of a dielectric thick film layer composed of components, and is fired at a temperature of 750 ° C to 1050 ° C in a non-oxidizing atmosphere.

Effect According to the present invention, the charge-compensated perovskite-type dielectric material has a dielectric property in which electrical neutralization is maintained by valence control even if oxygen defects are generated by firing in a non-oxidizing atmosphere. On the other hand, on the other hand, non-reducing glass components such as borosilicate glass based on borosilicate do not metallize even under high temperature in non-oxidizing atmosphere and sufficiently flow to form a binder glass. work. Therefore, an inexpensive thick film capacitor using a base metal material as an electrode can be realized.

Example A thick film capacitor according to an example of the present invention will be described below with reference to the drawings.

Example 1 First, barium carbonate (BaCo
₃ ), calcium carbonate (CaCO ₃ ), strontium carbonate (SrCO ₃ ), magnesium oxide (MgO), titanium oxide (Ti
O ₂ ), zirconium oxide (ZrO ₂ ), tin oxide (SnO ₂ ),
Manganese oxide (MnO), nickel oxide (NiO), cobalt oxide (CoO), chromium oxide (Cr ₂ O ₃ ), gallium oxide (Ga
Several powders of ₂ O ₃ ) and iron oxide (Fe ₂ O ₃ ) were weighed so as to have the composition shown in Table 1, wet-mixed for 20 hours, pulverized and dried. 5% by weight of water in which 5% of polyvinyl alcohol (PVA) was used as a binder was added to and mixed with the dielectric coarsely-mixed powder, and the mixture was granulated and mold-molded at a pressure of 750 kg / cm ² . These dielectric crude moldings,
After firing at 1250 to 1380 ° C for 2 hours in the air to sinter, coarsely pulverize this sintered body, and then wet pulverize it with a zirconia ball so that the particle size becomes 3 μm or less, and then the crude dielectric material is obtained. It was powdered.

Next, a non-reducing glass having the composition shown in Table 2 was prepared, and added to a solid component obtained by adding 5 to 30% by weight to the above-mentioned dielectric rough product, even if it was heated in a non-oxidizing atmosphere. Beagle in which an acrylic binder was dissolved in 20% by weight of terpinenol was added as an organic binder that is easily volatilized by decomposition, and well kneaded with a roll to obtain a capacitor paste. At this time, the amount of beagle with respect to the solid component was about 30% by weight considering the printability of the paste and the viscosity of the paste.

On the other hand, aluminum oxide (AI ₂ O ₃ ) is used as the insulating substrate 30.
A so-called alumina substrate with a content of 96% by weight is prepared, and a base metal electrode paste containing glass frit of several% by weight for the purpose of increasing adhesion to a base metal powder made of copper, cobalt, nickel or an alloy of these on one side. To 300
Printing with a mesh screen and drying at 120 ° C. for 10 minutes formed the lower electrode layer 10.

Further, printing of the above-mentioned capacitor paste on a screen of 250 mesh and drying at 120 ° C. for 10 minutes were repeated twice to form a dielectric layer 20 so that a part thereof remained on the lower electrode layer 10. . Further, a base metal electrode paste was formed on this under the same condition so as to face the lower electrode layer 10 to form an upper electrode layer.

These printed substrates and high peak temperatures of 750 to 1
With a temperature profile held at 050 ° C for 10-30 minutes,
A thick film capacitor was obtained by firing through an electric furnace in a non-oxidizing atmosphere. The firing temperature at this time is limited by the melting point of the electrode material used, and the firing atmosphere is limited by the thermodynamic properties of the electrode material.

Table 3 shows the melting points of Cu, Ni and Co and the calculated standard free energy (ΔG °) of oxide formation at 1000 ° C. Based on these points, the amounts of nitrogen (N ₂ ), hydrogen (H ₂ ) and water vapor (H ₂ O) were adjusted to obtain a non-oxidizing atmosphere suitable for each electrode material.

In this way, some typical thick film capacitors with combinations of different dielectric materials, non-reducing glass, firing temperature, firing atmosphere, and electrode materials were measured at the basic capacitor characteristics of 20 ℃. Table 4 shows capacitance (Co), dielectric loss (tan δ), and insulation resistance (IR) per unit area at a frequency of 1 KHz. At this time, the thickness of the capacitor dielectric layer after firing is about 50 μm, and the area of the counter electrode is 25 μm.
mm ² and IR was measured by measuring the resistance value between electrodes after applying DC 50 V for 1 minute at 20 ° C. and calculating based on the measured value and the dimension.

Based on the sample numbers 18 and 20 of Example 1 in Table 4 above, the relationship between the added amount of the glass component and the dielectric loss (tan δ) to the dielectric rough product is shown in the figure, and the curve a in FIG. And b respectively. When the firing temperature is low (a), when the glass component is small, the flow of the glass is small and the dielectric layer is insufficiently sintered and porous so that tan δ becomes large. When it contains a glass component, the dielectric layer becomes over-sintered and tan δ increases. As described above, the preferable addition amount of the glass component varies depending on the firing temperature,
It is in the range of 5 to 30% by weight.

FIG. 7 shows the relationship between the firing temperature and the capacitor characteristics for the composition of sample No. 7 in the examples. By firing at a temperature lower than 750 ° C., not only the dielectric layer is not densified but also the base metal electrode layers 10 and 11 are insufficiently sintered, so that a capacitor having satisfactory capacitor characteristics cannot be obtained. On the other hand, 11
If the temperature is higher than 00 ° C, the viscosity of the glass will decrease and diffuse more than necessary in the electrode layer, the film shape of the dielectric layer will be deformed, or the dielectric component will change depending on the composition of the glass component. As it dissolves in glass and causes compositional shift, it becomes impossible to maintain excellent capacitor characteristics.

The non-oxidizing atmosphere during firing depends on ΔG ° of the electrode material used, and has little influence on the dielectric properties as long as it is under an oxygen partial pressure within a range where the electrode is not oxidized. However, since the charge compensation component is added to the perovskite-type dielectric (eg, BaTiO ₃ -d) that has oxygen defects due to the reduction action in an excessive amount, the charge control component controls the atom to attain electrical neutrality. Thus, there is an optimum charge compensation amount that balances with the non-oxidizing degree (oxidizing concentration) of the firing atmosphere when the firing temperature is constant.

Regarding the electrode material, as shown by sample numbers 11 to 13 in Table 4, copper, cobalt, nickel or alloys thereof are essentially the same. Generally, the wetting of metal and oxide at high temperature is small, but the oxides react easily with each other. For this reason, when a large amount of the surface of the electrode material is oxidized, it reacts with the glass component and the dielectric coarse product, and sometimes diffuses deeply into the dielectric film, significantly lowering the insulation resistance and the dielectric constant. Oxidation of this electrode metal occurs by oxygen gas in the atmosphere during firing (for example, Ni + 1 / 2O ₂ → Ni
O), and can also occur due to reducing oxides in the glass component. (For example, 2Cu + PbO → Cu ₂ O + Pb) (Example 2) FIG. 4 is a sectional view of a thick film capacitor showing a second example of the present invention. In the figure, 10 is a lower electrode layer, 11 is an upper electrode layer, 20 is a dielectric layer, 30 is an insulating substrate, and above is the first
The configuration is similar to that shown in the figure. The difference from the configuration of FIG. 1 is that the insulating layer 35 and the conductor wiring layer 15 form a circuit pattern in which they are simultaneously formed on an insulating substrate.

As the material of the insulating layer 35, a material having a composition containing 50% by weight of AI ₂ O ₃ in borosilicate glass was used in the example because of the reactivity with the dielectric layer 20 and the relationship of the sintering temperature. The conductor wiring layer 15 is preferably made of the same base metal (Co, Ni, Cu) as the electrode layers 10 and 11.

By configuring as described above, a thick film capacitor having a high density wiring becomes possible.

As described above, according to the present invention, a perovskite-type dielectric magnetic crude product in which charge compensation is performed using a base metal as an electrode, and a dielectric thick film layer composed of a non-reducing glass component are used in a non-oxidizing atmosphere of 750 to 1
By firing at a temperature of 050 ° C, it is possible to provide a thick film capacitor that is inexpensive and has excellent performance.

[Brief description of drawings]

FIG. 1 is a perspective view of a thick film capacitor according to an embodiment of the present invention, and FIGS. 2 and 3 are graphs showing the relationship between the glass concentration and firing temperature of the thick film capacitor obtained in the embodiment and dielectric properties. FIG. 4 is a sectional view of another example of the thick film capacitor of the present invention, FIG. 5 is a perspective view of a conventional thick film capacitor, and FIG.
The figures each show a model view of a cross section of a conventional thick film capacitor. 10 ... Lower electrode layer, 11 ... Upper electrode layer, 15 ... Conductor wiring layer, 20 ... Dielectric layer, 30 ... Insulating substrate, 35 ... Insulating layer, 40 ... Lower electrode layer, 41 ... … Upper electrode layer, 50 …… Dielectric layer, 51 …… Dielectric particles, 52 …… Glass phase.

Claims (4)

[Claims] 1. A perovskite-type dielectric rough product which is charge-compensated with an opposing conductor layer made of a base metal as an electrode on an insulating substrate, and 5 to 30% of the base metal with respect to the dielectric rough product. A thick film capacitor comprising a dielectric film made of non-reducing glass. 2. The thick film according to claim 1, wherein the base metal is copper, cobalt, nickel or an alloy thereof, and the non-reducing glass component is borosilicate glass. Capacitors. 3. A perovskite-type dielectric ceramic crude product is titanate (MeTiO ₃ ), zirconate (MeZrO ₃ ), or a solid solution thereof, and Me is one of barium, strontium, calcium, and magnesium. The thick film capacitor according to claim 1, wherein the thick film capacitor is one or more of the above. 4. A step of forming an electrode layer made of copper, cobalt, nickel, or an alloy thereof on an insulating substrate, a perovskite-type dielectric coarse material having a charge compensation, and a non-reducing agent which is not reduced by the electrode. A step of forming a dielectric film made of glass on the electrode layer, a step of forming the electrode layer and the dielectric layer by laminating, 750 to 1050 ° C.
A method of manufacturing a thick film capacitor, which comprises a step of firing in a non-oxidizing atmosphere at a temperature of.