JP2683144B2 - Dielectric paste - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dielectric paste used for a printed capacitor or the like in a thick film hybrid IC.

"Prior art" In recent years, for the purpose of high integration of electronic parts, electrodes or conductor circuits, capacitors, resistors, etc. are formed on a ceramic substrate such as alumina by a screen printing method.
Thick film hybrid by firing at a temperature of ~ 1000 ° C
ICs are being manufactured.

Capacitors, resistors, and the like are included in the elements of these thick film hybrid ICs, and of these, the capacitors occupy a large area in the IC. Among them, in a large capacity bypass capacitor, the size of the substrate is affected by the capacity per unit area. Therefore, in order to increase the degree of integration of electronic components, it is necessary to reduce the area of the substrate. Therefore, there is a demand for a small capacitor having a large capacity.

Therefore, it has been considered to use a ferroelectric powder in a dielectric paste for a capacitor and obtain a large-capacity capacitor by screen printing.

"Problems to be solved by the invention" However, Ba used as a conventional ferroelectric powder
Since firing of TiO ₃ -based, tungsten bronze-type or composite perovskite-type powder requires 1000 ° C or higher, it is necessary to use a highly heat-resistant capacitor electrode material, such as palladium or platinum. There was the inconvenience of having to use expensive materials.

For this reason, a dielectric paste mixed with glass frit has been developed for the purpose of measuring the decrease in the firing temperature of the ferroelectric powder.

Examples of such glass frit mixed dielectric paste include Pb (Mg _1/3 Nb _2/3 ) O ₃ and Pb (Ni _1/3 Nb _2/3 ) O ₃
Mixed with glass frit, BaTiO ₃ and Ba (ZrT
i) a mixture of the O ₃ and glass frit, ferroelectric and Z
A mixture of additives such as nO, Fe ₂ O ₃ , NiO, TiO ₂ , CuO and binder glass has been proposed.

However, since the dielectric constant of the glass frit is lower than that of the ferroelectric powder, there is a drawback that the mixing ratio is limited.

That is, if the mixing ratio of the glass frit is low, the firing temperature cannot be lowered. Conversely, if the mixing ratio of the glass frit is increased, the firing temperature can be lowered, but the content of the ferroelectric powder decreases. Therefore, the relative permittivity of the capacitor is reduced to about 1000 to 1800, and the capacitance per unit area of the capacitor is also reduced to about 200 to 400 pF.

There is a dielectric paste proposed in Japanese Patent Application No. 1-261476 which can solve the above problems.

This dielectric paste is Pb (Mg _1/3 Nb _2/3 ) O ₃ 0.60-0.
68 mol, Pb (Ni _1/3 Nb _2/3 ) O ₃ 0.04 to 0.16 mol, PbTiO ₃ 0.
With respect to the dielectric material of 22 to 0.30 mol, CuO 2.0 to 5.0 parts by weight, Bi ₂ O ₃ 0.3 to 1.0 parts by weight, Nd ₂ O ₃ 1.2 to 2.6 parts by weight and the composition obtained by firing is fired. It is a pulverized powder dispersed in a vehicle. This dielectric paste is intended to enable the production of printed capacitors with high relative permittivity and low dielectric loss by low temperature firing at 850 ° C.

However, the relative permittivity of a printed capacitor obtained by using this dielectric paste is still insufficient at about 3200 to 4100, and the rate of change in capacity with temperature change (hereinafter referred to as the rate of change in capacity) is large. The remaining.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a dielectric paste capable of producing a printed capacitor having a higher relative dielectric constant and a small capacitance change rate at a lower firing temperature. To do.

"Means for Solving the Problems" In the dielectric paste of the present invention, Pb (Mg _1/3 Nb _2/3 ) O ₃ 0.60 to 0.68 mol, Pb (Ni _1/3 Nb _2/3 ) O ₃ 0.04 to CuO2.0 to 5.0 parts by weight with respect to 100 parts by weight of the dielectric material in which 0.16 moles and 0.22 to 0.30 moles of PbTiO ₃ are added so as to be 1 mole in total.
Parts by weight, Bi ₂ O ₃ 0.3 to 1.0 parts by weight, Nd ₂ O ₃ 1.2 to 2.6 parts by weight are added, and PbO is further added to 100 parts by weight of the dielectric material.
The composition of 1.0 to 6.0 parts by weight was calcined and pulverized, and the obtained powder was dispersed in the vehicle to solve the problem.

Here, 0.60 to 0.68 mol of Pb (Mg _1/3 Nb _2/3 ) O ₃ and 0.04 to
0.16 mol of Pb (Ni _1/3 Nb _2/3 ) O ₃ and 0.22-0.30 mol of PbTi
It is for forming a dielectric layer on a dielectric material composed of O ₃ . The addition of CuO, Bi ₂ O ₃ , and Nd ₂ O _{3 in} the above parts by weight is for bonding the dielectric material onto the electrode and the substrate while allowing the dielectric material to be baked at a low temperature of 950 ° C or lower. Is. Furthermore, the addition of PbO in the above weight part is for further improving the relative permittivity of the dielectric layer and reducing the rate of change in capacitance with temperature.

The amount of Pb (Mg _1/3 Nb _2/3 ) O ₃ is less than 0.60 mol,
When the content of PbTiO ₃ is less than 0.22 mol, Pb (Ni _1/3 Nb
The compounding amount of _2/3 ) O ₃ becomes 0.18 mol or more, and the relative dielectric constant of the dielectric layer of the obtained printed capacitor decreases. Also
Pb (Mg _1/3 Nb _2/3) the amount of O ₃ exceeds 0.68 mol, PbTiO ₃
If the compounding amount exceeds 0.30 mol, the compounding amount of Pb (Ni _1/3 Nb _2/3 ) O ₃ will be 0.02 mol or less, and the sinterability of the dielectric material will decrease, which is not preferable.

If the amount of Pb (Ni _1/3 Nb _2/3 ) O ₃ blended is less than 0.04 mol, the sinterability of the dielectric material is reduced, and the electrical characteristics of the resulting printed capacitor are also deteriorated. Also Pb (Ni _1/3 Nb _2/3 ) O ₃
If the compounding amount is more than 0.16 mol, the relative dielectric constant of the dielectric layer of the obtained printed capacitor is lowered, which is not preferable.

If the additive amount of CuO is less than 2.0 parts by weight, Bi ₂ O ₃
If the compounding amount is less than 0.3 parts by weight, the sinterability of the dielectric material is reduced and the electrical characteristics of the obtained printed capacitor are deteriorated. On the other hand, if the content of CuO exceeds 5.0 parts by weight, the relative dielectric constant of the dielectric layer of the printed capacitor will decrease and the dielectric loss will increase, making it unpractical. Bi ₂ O
_If the compounding amount of ₃ exceeds 1.0 part by weight, the dielectric constant of the printed capacitor is lowered, the dielectric loss is increased, and the insulation resistance is lowered, which is not preferable.

If the blending amount of Nd ₂ O ₃ is less than 1.2 parts by weight, the capacity change rate due to the temperature of the printed capacitor cannot be sufficiently reduced, and if it exceeds 2.6 parts by weight, the relative dielectric constant is lowered, which is preferable. Absent.

If the compounding amount of PbO is less than 1.0 part by weight, the relative permittivity of the printed capacitor is not sufficiently improved, and the rate of change in capacity with temperature is not sufficiently reduced. Further, if the amount of PbO added exceeds 6.0 parts by weight, the insulation resistance of the printed capacitor is significantly deteriorated, which is not preferable.

In addition to the above components, Li ₂ CO ₃ may be added in an amount of 0.1 to 0.5 parts by weight with respect to 100 parts by weight of the dielectric material in order to improve the relative dielectric constant of the printed capacitor.

If the added amount of Li ₂ CO ₃ is less than 0.1 parts by weight, the effect of sufficiently improving the relative permittivity of the printed capacitor cannot be expected, and if it exceeds 0.5 parts by weight, the dielectric loss and the rate of change in capacity due to temperature increase. However, it is not preferable because it cannot be put to practical use.

The dielectric paste of the present invention is a dielectric raw material containing the above-mentioned additives, which is calcined and pulverized to obtain a dielectric calcined powder, and the resin is dissolved in a high-boiling organic solvent at a predetermined concentration in a vehicle. It is used dispersedly.

The vehicle contains at least one of an acrylic resin, ethyl cellulose, and nitrocellulose as a resin binder.
It is preferable to use at least one resin of at least one of butyl carbitol, butyl carbitol acetate, terpineol and the like as a high boiling organic solvent.

The mixing ratio of the residual binder to the high boiling point organic solvent is 5 to
30 wt% is preferred. Further, the mixing ratio of the mixture of the dielectric material and the additive in the vehicle is preferably 10 to 20% by weight.

Next, an example of the method for producing the dielectric paste of the present invention will be described.

First, dielectric materials such as lead oxide (PbO), magnesium oxide (MgO), niobium oxide (Nb ₂ O ₅ ), nickel oxide (Ni
O) and titanium oxide (TiO ₂ ) to Pb (Mg _1/3 Nb _2/3 ) O
₃ 0.60 to 0.68 mol, Pb (Ni _1/3 Nb _2/3 ) O ₃ 0.04 to 0.16 mol, and PbTiO ₃ 0.22 to 0.30 mol in such ratios. Next, CuO, Bi ₂ O ₃ , Nd ₂ O ₃ , Li ₂ CO ₃ and PbO as additives were added to CuO based on 100 parts by weight of the mixture of the dielectric material.
2.0 to 5.0 parts by weight, Bi ₂ O ₃ 0.3 to 1.0 parts by weight, Nd ₂ O ₃ 1.2 to 2.6
Parts by weight, Li ₂ CO ₃ 0.1 to 0.5 parts by weight, and PbO 1.0 to 6.0 parts by weight are added. Then, these are put into a mixing and pulverizing device such as a ball mill pot and mixed with zirconia balls or balls made of an alternative material thereof together with water or an organic solvent such as alcohol or acetone for 24 hours to sufficiently mix the above raw materials. Then, these are taken out from the ball mill pot, and water or an organic solvent is removed by filtering and drying. The sufficiently dried mixed powder is sieved with a 50-mesh sieve, put into an alumina crucible and calcined at 750 ° C. for 2 to 5 hours to obtain a calcined product of a dielectric material and an additive.

After the calcination, the calcinated product is put into a ball mill pot exactly as in the above step, and pulverized for 48 to 72 hours. After this pulverization, filtration and drying are performed to obtain a calcined dielectric powder.
Further, in order to remove water and organic solvent adsorbed on the calcined dielectric powder, vacuum drying is performed at 120 to 150 ° C.

The sufficiently calcined dielectric calcined powder is dispersed in the vehicle.

To disperse the dielectric calcined powder in the vehicle, use a mixer such as a mortar if the amount of the dielectric calcined powder and the vehicle is small, or a mixer such as a universal mixer or universal mixing stirrer if the amount is large. Roughen. Furthermore, after thoroughly kneading these with a three-roll mill to adjust the particle size of the dielectric calcined powder, a high-boiling organic solvent is added to maintain the viscosity required for printing, and the viscosity is adjusted. Obtain a dielectric paste.

Next, an example of a printed capacitor manufactured by using the dielectric paste of the present invention is shown in FIGS. 1 and 2.

This printed capacitor comprises a substrate 1, a lower electrode 2, a dielectric layer 3, and an upper electrode 4 which are sequentially laminated.
Such a printed capacitor can be manufactured by the following steps.

First, a conductive paste of silver or the like is printed on the substrate 1 of alumina or the like and baked at 850 ° C. for 10 minutes to form the lower electrode 2. Next, the dielectric paste of the present invention is printed and dried on the lower electrode 2 to form the dielectric layer 3, and the conductive paste is further printed and dried on the lower electrode 2 to form the upper electrode 4, and then at 850 ° C. for 10 minutes. Bake. From this, it is possible to manufacture a printed capacitor having a dielectric layer 3 with a thickness of about 30 to 60 μm.

[Operation] When the dielectric paste of the present invention is used, the printed capacitor can be fired at 850 ° C., which is a lower temperature than before, and the printed capacitor having a higher relative dielectric constant and a smaller capacitance change rate than before. Can be formed.

Example 1 Pb (Mg _1/3 Nb _2/3 ) O ₃ 0.64 mol, Pb (Ni _1/3 Nb _2/3 ) O ₃ 0.
10 mol, PbTiO ₃ 0.26 mol of lead oxide, magnesium oxide, niobium oxide, nickel oxide, titanium oxide were mixed to form a dielectric material mixture, to 100 parts by weight of this dielectric mixture. 3 parts by weight CuO, 0.5 parts by weight Bi ₂ O ₃ , 1.8 parts by weight Nd ₂ O ₃ and 1.0 to 6.0 parts by weight PbO were added. Next, acetone was added to this mixed powder as a dispersion medium, and the mixture was mixed for 24 hours in a pot mill charged with zirconia balls. Next, the acetone in this mixture was removed by filtration and drying to obtain a dried product, which was further sieved with a 50-mesh sieve.

Next, the dried product thus sieved was put into an alumina crucible and calcined at 750 ° C. for 2 to 5 hours. Further, water was added to this calcined product as a dispersion medium in the same manner as in the above step, and the mixture was crushed for 72 hours in a pot mill containing zirconia balls. Next, the water in this pulverized product was removed by filtration and drying, and then it was further sieved with a 50-mesh sieve to obtain a calcined dielectric powder.
Further, this dielectric calcined powder was vacuum dried at 120 to 150 ° C. to remove water adsorbed on the calcined product.

Next, the weight ratio of the above-mentioned dielectric calcined powder and vehicle was 10
After blending so as to be 0:17, mixing these in a mortar,
The mixture was thoroughly kneaded with a triple roll to obtain a dielectric paste.

The vehicle used was a butyl carbitol in which 24 wt% of a thermoplastic acrylic resin was dissolved.

A printed capacitor was manufactured on an alumina substrate by using the dielectric paste thus obtained. The printed capacitor was manufactured by the following procedure.

First, a silver-based conductive paste is screen-printed on an alumina substrate and baked at 850 ° C. for 10 minutes to form a lower electrode on the alumina substrate. Then, the above-mentioned dielectric paste is screen-printed on this, and after drying, the above-mentioned silver-based conductive paste is further screen-printed on this and dried, and at 850 ° C., 10
Bake for a minute. The thickness of the dielectric layer of the printed capacitor thus obtained was about 40 μm.

Next, the relative permittivity, dielectric loss, and insulation resistance of this printed capacitor at 25 ° C and the rate of change in capacitance between -25 and 85 ° C were measured. Table 1 shows the results. As a conventional example
The results of measuring the above electrical characteristics by manufacturing a printed capacitor using a dielectric paste prepared under the same conditions as above except that PbO was not added are also shown.

From the results in Table 1, Pb was added to the conventional dielectric paste.
It was confirmed that by adding 1.0 to 6.0 parts by weight of O, the relative permittivity of the formed printed capacitor was improved and the rate of change in capacity was reduced.

"Example 2" lead oxide, magnesium oxide, niobium oxide, nickel oxide, titanium oxide and _{CuO, Bi 2 O 3, Nd} 2 O 3, Li 2 CO 3, PbO
Were mixed so as to have the respective compositions shown in Table 2, and a dielectric paste was prepared in the same manner as in Example 1.

Using these dielectric pastes, a printed capacitor was formed on an alumina substrate in the same manner as in Example 1. The relative dielectric constant, dielectric loss, and insulation resistance of this printed capacitor at 25 ° C and between -25 ° C and 85 ° C. The capacity change rate was measured. The results are shown in Table 3.

From the results shown in Table ₃ , by adding 0.15 to 0.2 parts by weight of Li ₂ CO ₃ and 4 to 6 parts by weight of PbO to the conventional dielectric paste, the relative permittivity of the printed capacitor formed is improved. It was also confirmed that the rate of change in capacity with temperature was reduced.

"Effects of the Invention" As described above, the dielectric paste of the present invention can be fired at 850 ° C, which is a lower temperature than before, and has a higher relative dielectric constant than before and a small capacitance change rate. It can be formed.

Therefore, when the dielectric paste of the present invention is used, the capacity per unit area of the printed capacitor manufactured is 3 to 4 times that of the printed capacitor manufactured using the conventional dielectric paste. When designing printed circuit boards with the same capacity, the board area can be reduced to 1/3 to 1/4, and high integration is possible.

Moreover, since the dielectric paste of the present invention can be fired at 850 ° C., it is not necessary to use expensive palladium or platinum as an electrode material, and less expensive silver can be used.

Therefore, according to the dielectric paste of the present invention, it is possible to manufacture an element having a high degree of integration at low cost.

Further, the printed capacitor manufactured by using the dielectric paste of the present invention has a small substrate area and can be highly integrated, and thus is suitable as an electronic element of a handy type electric product which is greatly required to be downsized.

[Brief description of the drawings]

FIG. 1 is a plan view of a printed capacitor manufactured by using the dielectric paste of the present invention, and FIG. 2 is a sectional view taken along line I-I of the printed capacitor shown in FIG. 3 ... Dielectric layer.

Claims (1)

(57) [Claims] 1. Pb (Mg _1/3 Nb _2/3 ) O ₃ 0.60 to 0.68 mol Pb (Ni _1/3 Nb _2/3 ) O ₃ 0.04 to 0.16 mol and PbTiO ₃ 0.22 to 0.30 mol in total 1 Dielectric raw material 100 formulated to be molar
CuO 2.0 to 5.0 parts by weight Bi ₂ O ₃ 0.3 to 1.0 parts by weight Nd ₂ O ₃ 1.2 to 2.6 parts by weight with respect to 100 parts by weight of the above dielectric raw material 1.0 to 6.0 parts by weight A dielectric paste, characterized in that a powder obtained by firing and pulverizing a composition added in parts is dispersed in a vehicle.