JPH05124855A - Ceramic substrate and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Structure] 92 to 94% by weight of Al ₂ O ₃ having an average particle diameter of 0.8 to 1.8 μm, and SiO ₂ and Ca which are sintering aids.
O and MgO are contained in a total of 6 to 8% by weight, and the composition ratio of these sintering aids is SiO ₂ 50 to 80% by weight, CaO 0.
~ 12 wt%, MgO 10-40 wt% ceramic raw material is molded into a predetermined shape, the maximum firing temperature of 1550 ℃ or less, high-speed firing with a firing time of 6 hours from the start of temperature rise to the end of temperature fall Then, the ceramic substrate is manufactured. [Effect] It can be manufactured at low cost, and Al ₂ O ₃ 9
It is possible to obtain a ceramic substrate having excellent electrical characteristics and thick film adhesion strength comparable to those of about 6% and without abnormal grain growth, and it can be suitably used as a ceramic substrate for electronic parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic substrate for electronic parts, which is used for a thick film, a resistor and a DBC substrate, and a method for manufacturing the same.

[0002]

_2. Description of the Related Art Conventionally, an alumina ceramic substrate containing Al ₂ O ₃ as a main component has been used (see, for example, Japanese Patent Publication No. 2-17506). In this ceramic substrate manufacturing method, first, Al ₂ O ₃ 96% by weight, which is the main component,
4% by weight of SiO ₂ , CaO, Mg as a sintering aid
The weight ratio of O is SiO ₂ : CaO: MgO = 7.
A ceramic raw material is prepared by adding and mixing so as to be 0: 5: 25, and the ceramic raw material is mixed in an organic solvent, and then a green sheen of a predetermined thickness is formed by a doctor blade method.
After being molded into a mold and punched into a predetermined shape with a mold, firing is performed in an oxidizing atmosphere at 1550 to 1650 ° C., and the obtained sintered body is subjected to surface treatment such as vibration barrel, blast and buff. Was there.

[0003]

However, the conventional ceramic substrate requires firing at a high temperature of 1550 to 1650 ° C. during the manufacturing process, and requires a firing time of about 24 hours, which is high in cost. Met. So A
It has been considered to perform low temperature firing by reducing the content of 1 ₂ O ₃ , but a satisfactory circuit board has been obtained in terms of electrical characteristics, thick film adhesion strength with a thick film paste, and the like. There wasn't.

[0004]

Therefore, according to the present invention, 92 to 94% by weight of Al ₂ O ₃ having an average particle size of 0.8 to 2.5 μm and SiO ₂ , CaO and MgO which are sintering aids are used. 6 to 8 wt% in total, and the composition ratio of these sintering aids to each other is SiO ₂ 50 to 80 wt%, CaO 0 to 12 wt%,
A ceramic raw material having a MgO content in the range of 10 to 40 wt% is molded into a predetermined shape and subjected to high-speed firing at a maximum firing temperature of 1550 ° C. or lower with a firing time of 6 hours from the start of temperature increase to the end of temperature decrease. A substrate is manufactured.

According to the present invention, the average particle size is 0.8 to
An Al ₂ O ₃ raw material having a small particle diameter of 2.5 μm, preferably 0.8 to 1.8 μm is used, and the content thereof is 92 to 94.
Since it is reduced to the weight%, low temperature and high speed firing are possible, and the cost can be reduced. If the average particle size of the Al ₂ O ₃ raw material is smaller than 0.8 μm, molding is difficult,
On the other hand, if it is larger than 2.5 μm, firing at 1550 ° C. or lower becomes difficult. Further, if the Al ₂ O ₃ content is more than 94% by weight, low-temperature firing becomes difficult, while if it is less than 92% by weight, the electrical characteristics deteriorate.

Further, according to the present invention, the Al ₂ O ₃ content of 92
Even if the content is up to 94% by weight, a sintering aid such as SiO ₂ , C
By setting the composition ratio of aO and MgO within the above range, the Al ₂ O ₃ content has about the same electrical characteristics as 96 wt% and the thick film adhesion strength with the copper paste is 3 k.
It has been found that an excellent thick film adhesion strength of g / mm ² or more can be provided. The ceramic substrate of the present invention may contain 0.1% by weight or less of impurities with respect to the whole, in addition to Al ₂ O ₃ , SiO ₂ , CaO, and MgO.

The high-speed firing of the present invention can be easily carried out by using, for example, a roller hearth kiln, and the maximum firing temperature is 1550 ° C. or lower, preferably 150.
At 0 ° C or less, the firing time from the start of temperature increase to the end of temperature decrease is 6
It is set to not more than an hour, preferably not more than 2 hours. Since such high speed firing is performed, the obtained ceramic substrate has no abnormal grain growth with a grain size of 10 μm or more, an average crystal grain size of 1 to 5 μm, and an apparent specific gravity of 3.6 to 3.8. .. Furthermore, the center line average roughness (R
a) can be 0.40 μm or less.

[0008]

EXAMPLES Experimental Example 1 An experiment was conducted in which the average particle diameter of the Al ₂ O ₃ raw material was changed and the optimum firing temperature was investigated. All are Al ₂ O ₃
Content 93% by weight, total of SiO ₂ , CaO, MgO 7
SiO ₂ : CaO: MgO = 71: 6: 23 by weight%.
A predetermined binder was added to and mixed with the ceramic raw material prepared as described above, and the mixture was formed into a sheet and fired under predetermined conditions, and the maximum firing temperature at which the specific gravity became maximum was determined as the optimum firing temperature. The results are shown in Table 1.

It can be seen from Table 1 that the optimum firing temperature depends on the average particle size of the Al ₂ O ₃ raw material. And
When the average particle size is 2.5 μm or more, the optimum firing temperature rises dramatically. To set the optimum firing temperature to 1550 ° C. or less, the average particle size is 2.5 μm or less and the optimum firing temperature is 1500 ° C. or less. Therefore, the average particle size needs to be 1.8 μm or less. Further, when the average particle diameter is 0.8 μm or less, although the optimum firing temperature can be lowered, the dispersibility and fluidity at the time of preparing the slurry are poor, and it is particularly difficult to form the tape by the roll compaction method. there were. Therefore, the average particle diameter of the Al ₂ O ₃ raw material is 0.8 to 2.
It is understood that the thickness may be 5 μm, preferably 0.8 to 1.8 μm.

[0010]

[Table 1]

Experimental Example 2 Next, from the above Experimental Example 1, an Al ₂ O ₃ raw material having an average particle diameter of 1.7 μm was used, and the dielectric constant (ε _r ) was changed by changing the Al ₂ O ₃ content. And the dielectric loss tangent (tan δ) were measured. The results are shown in Table 2. From this result, Al
_{As the 2} O ₃ content increases, the dielectric constant tends to increase and the dielectric loss tangent tends to decrease, but the Al ₂ O ₃ content 92 to 96
Almost no significant difference is observed in the range of wt%, and Al ₂ O
It is understood that sufficient electrical characteristics can be obtained even when the content of ₃ is 92 to 94% by weight.

[0012]

[Table 2]

Experimental Example 3 Next, with respect to the Al ₂ O ₃ content of 93% by weight in Experimental Example 2, the sintering aids SiO ₂ , CaO, and
By changing the composition ratio of MgO as shown in Table 3 and FIG.
After being formed into a sheet by the doctor blade method, it was punched into a predetermined shape and fired to obtain a ceramic substrate. For each ceramic substrate, adhesion strength of thick film, presence of abnormal grain growth,
The possibility of low temperature firing was examined. The results are shown in Table 3.

The pressure-membrane adhesion strength was measured by a DuPont method using a copper paste, and 3 kg / mm ² or more was evaluated as ◯ and 3 kg / mm ² or less was evaluated as x. The presence or absence of abnormal grain growth was observed by observing the surface with a microscope, and those with crystals of 10 μm or more were marked with X, and those without crystals were marked with ◯. Further, whether or not low temperature firing is possible was evaluated as ◯ when the optimum firing temperature was 1500 ° C. or lower, and as X when 1500 ° C. or higher.

As can be seen from Table 3, when the amount of CaO is too large, the thick film adhesion strength becomes low and abnormal grain growth occurs, and when the amount of SiO ₂ is too large, low temperature firing becomes difficult. On the other hand, those having SiO _{2 of} 50 to 80% by weight, CaO of 0 to 12% by weight, and MgO of 10 to 40% by weight within the range of the present invention have a thick film adhesion strength of 3 kg / mm ² or more and 10 μm.
It can be seen that there is no abnormal grain growth as described above, and low temperature firing at 1500 ° C. or lower is possible.

[0016]

[Table 3]

Experimental Example 4 Next, No. 1 in Table 3 above. An experiment was carried out for the composition No. 1 to examine the relationship between the firing time from the start of temperature increase to the end of temperature decrease and the average crystal grain size. The results are shown in Table 4.

From this result, it is clear that the tunnel furnace
The average crystal grain size was 7 μm or more for those fired for a period of time, whereas the average crystal grain size for those fired for 6 hours or less using a roller hearth kiln could be as small as 5 μm or less. The average crystal particle diameter of 2 hours was 2 μm. As described above, the ceramic substrate having the firing time of 6 hours or less and the average crystal grain size of 5 μm or less can have a smooth surface as it is fired, and can increase the adhesion strength with the thick film. ..

[0019]

[Table 4]

[0020]

As described above, according to the present invention, 92 to 94% by weight of Al ₂ O ₃ having an average particle size of 0.8 to 1.8 μm is used.
And a total of 6 of sintering aids SiO ₂ , CaO, and MgO.
.About.8% by weight, and the composition ratio of these sintering aids to each other is Si.
O ₂ 50 to 80 wt%, CaO0~12 wt%, MgO
A ceramic raw material in the range of 10 to 40% by weight is formed into a predetermined shape, and is fired at a maximum firing temperature of 1550 ° C. or lower with a firing time of 6 hours from the start of temperature increase to the end of temperature reduction to obtain a ceramic substrate. Since it is manufactured, it can be manufactured at low cost, and Al ₂ O ₃ 9
It is possible to obtain a ceramic substrate having excellent electrical characteristics and thick film adhesion strength comparable to those of about 6% and without abnormal grain growth, and it can be suitably used as a ceramic substrate for electronic parts.

[Brief description of drawings]

FIG. 1 is a ternary diagram showing a composition ratio of a sintering aid in a ceramic substrate of the present invention.

Claims (2)

[Claims] 1. A main component of Al ₂ O ₃ is contained in an amount of 92 to 94% by weight, and sintering aids of SiO ₂ , CaO and MgO in a total of 6 to 8% by weight. Composition ratio is S
iO ₂ 50-80% by weight, CaO 0-12% by weight, M
A ceramic substrate characterized by being in the range of 10 to 40% by weight of gO. 2. Al ₂ O having an average particle diameter of 0.8 to 2.5 μm.
92 to 94% by weight of ₃ and SiO ₂ , C which is a sintering aid.
aO and MgO are contained in a total of 6 to 8% by weight, and the composition ratio of these sintering aids is SiO ₂ 50 to 80% by weight, CaO
A ceramic raw material in the range of 0 to 12% by weight and MgO 10 to 40% by weight is molded into a predetermined shape and the firing time from the start of temperature increase to the end of temperature reduction is 6 hours or less at a maximum firing temperature of 1550 ° C or less. A method for manufacturing a ceramic substrate, characterized by performing high-speed firing.