JP3347566B2 - Ceramic substrate for electronic components - Google Patents

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 components such as a substrate for a resistor, a substrate for a hybrid IC, and a substrate for a thermal head. The present invention relates to a ceramic substrate for electronic components made of alumina ceramics whose characteristics and electrical characteristics do not change.

[0002]

2. Description of the Related Art Conventionally, a substrate for a resistor, a hybrid IC
Alumina ceramic substrates are used as ceramic substrates for electronic components such as substrates for substrates and thermal heads. In recent years, with the demand for higher density, finer, and multilayered circuit printing, ceramics for electronic components have been used. Tightening of dimensional accuracy in the substrate, particularly, warpage of the substrate has been a problem. For example, in the case of a thick-film circuit board or a hybrid IC board, if the board is warped, printing deviation during circuit printing or variation in the circuit film thickness due to printing occurs, and mounting of IC chips, connection of I / O pins, There was a possibility that it would have a significant effect on hermetic sealing and the like.

[0003] In a thermal head substrate,
If a warped substrate is used, printing misalignment during thin-film printing and variations in the thickness of the thin film may occur.If a thermal head formed using such a substrate is incorporated into a copier or facsimile and used, printing between the paper and the head may occur. Since the distance between them could not be kept constant, there was a possibility that the print would be shaded, resulting in a defective product.

The electrical characteristics of a ceramic substrate for electronic components made of this kind of alumina ceramics have a dielectric constant of 9.0 to 9.8 and a dielectric loss coefficient of 1 × 10 ^-4 to 1 × 10 ^-3. Is required to be within the range. Alumina ceramic substrates having these electrical characteristics are Al ₂ O _{3 in a} proportion of 85 to 96% by weight, and SiO ₂ , CaO and MgO are used as sintering aids.
After adding a solvent and a binder to these to form a slurry, a sheet-like green sheet is formed using a tape forming method such as a doctor blade method, and the green is added. The sheet was dried and punched out with a mold to form a plate-shaped molded body, and then the molded body was fired to obtain an alumina ceramic substrate. Since the substrate is warped as it is, heat treatment is performed to correct the warpage.

[0005]

However, in recent years, the warp standard of the substrate is strict. For example, for a substrate size of 290 × 80 mm, the warpage must be suppressed to 300 μm or less. Warpage could not be corrected, and several heat treatments had to be performed to achieve a predetermined accuracy. As a result, SiO _2, CaO contained as sintering aid components such as MgO are Al ₂
Reacted with O ₃ particles and had only alumina crystals and spinel crystals at the time of firing. Other than these, cordierite (2MgO.2Al ₂ O ₃ .5SiO ₂ ) crystals and mullite (3A)
l ₂ O ₃・ 2SiO ₂ ) crystal, sapphirine (4MgO ・ 5Al ₂ O ₃・ 2SiO ₂ )
There was a problem that crystals and anorthite (CaO.Al ₂ O ₃ .2SiO ₂ ) crystals were crystallized as abnormal crystals.

That is, the dielectric constant of cordierite crystal, sapphirine crystal, mullite crystal, anorthite crystal, etc. is 5.
0 to 6.5, and the dielectric loss coefficient is 4 × 10 ^{−3 to} 5 × 10 ^−3.
Degree and dielectric constant (9.0 to 9.8) or dielectric loss coefficient (1 × 10 ⁻³ to 1 ×) of alumina crystal and spinel crystal.
There is a problem that the electrical characteristics required for the alumina ceramic substrate cannot be satisfied because the value greatly deviates from 10 ^-4 ). In addition, the above-mentioned cordierite crystal, sapphirine crystal, mullite crystal, abnormal crystal growth due to a low crystallization temperature of anorthite crystal and the like, abnormal grain growth occurs, and not only poor electrical characteristics but also poor appearance may occur. These abnormal crystals have thermal expansion coefficients of 2.2 × 10 ^{−6 to} 4.0 × 10 ⁻⁶ / ° C., and the thermal expansion coefficients of alumina crystals and spinel crystals (7.0 × 10 ^{−6 to} 7.0 × 10 ⁻⁶⁾ .
(8 × 10 ⁻⁶ / ° C.), the substrate may be warped more in the cooling process after the heat treatment than in the firing process.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramic substrate for an electronic component made of alumina ceramics in which crystals other than alumina crystals and spinel crystals do not crystallize even if heat treatment is repeatedly performed to correct the warpage of the substrate. Is to provide.

[0008]

In view of the above-mentioned problems, the present invention has been made in view of the above-mentioned problems, and it has been found that 96-98% by weight of Al ₂ O ₃ as the first component and SiO ₂ , CaO, and M as the second component.
It contains three components of gO, and when the total content of the second component is 100, the weight ratio is SiO ₂ : 5.
2.0-68.0, CaO: 2.0-10.5, Mg
O: 25.5 to 42.0, wherein the ceramic substrate for an electronic component is composed of alumina ceramics substantially consisting only of alumina crystals and spinel crystals.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A ceramic substrate for an electronic component according to the present invention is an alumina containing as a first component Al ₂ O ₃ as a main component, and as a second component, _three components of SiO ₂ , CaO and MgO. It is formed of ceramics, and by setting the ratio of the first component and the second component within a certain range, it is substantially composed of only alumina crystals and spinel crystals. In addition to the spinel crystal, the crystal can be free of abnormal crystals such as cordierite crystal, anorthite crystal, mullite crystal, and sapphirine crystal. Therefore, even if the heat treatment is repeatedly performed to correct the warpage of the substrate, it is possible to obtain a ceramic substrate for electronic components made of alumina ceramics, which does not affect the electrical characteristics and has no defective appearance.

[0010] In the present invention, the term "consisting essentially of only alumina crystals and spinel crystals" means that the first peak intensity of alumina crystals is I ₀ , that of abnormal crystals such as cordierite crystals, anorthite crystals, mullite crystals and sapphirine crystals. When the first peak intensity is I, the intensity ratio (I / I ₀ ) is I
/ I ₀ <0.01.

By the way, Al ₂ O ₃ constituting the first component is 9
It is important to contain it in the range of 6 to 98% by weight.

This is because the content of Al ₂ O ₃ is 96% by weight.
If less than the second component (SiO ₂ , CaO, MgO)
Because of the excessively high content of A, abnormal heat treatment such as cordierite, anorthite, mullite, and sapphirine crystals in alumina ceramics with different electrical properties and thermal expansion coefficients besides alumina and spinel crystals in alumina ceramics In order to crystallize, it is necessary to satisfy the electrical properties of a dielectric constant of 9.0 to 9.8 and a dielectric loss coefficient of 1 × 10 ⁻⁴ to 1 × 10 ⁻³ required for a ceramic substrate for electronic components. Because it becomes difficult. When the content of Al ₂ O ₃ exceeds 98% by weight, the second component (SiO 2
₂ , CaO, MgO) to reduce the content.
This is because sintering at a firing temperature of 50 ° C. or less becomes difficult, and mechanical properties as a substrate material are greatly reduced.

The alumina ceramic according to the present invention preferably has a bulk density of 3.7 or more.

Further, SiO ₂ , CaO, which is the second component,
And MgO have a weight ratio of SiO ₂ : 52.0 to 68.0 when the total content of these components is 100,
CaO: 2.0 to 10.5, MgO: 25.5 to 42.
It is important that it be contained so as to be 0.

That is, among the second components, SiO ₂ is an important component for binding the alumina particles to form a grain boundary phase, but when the weight ratio is less than 52.0,
On the other hand, if the sintering temperature is 1650 ° C. or less, sintering cannot be performed sufficiently. If the weight ratio is more than 68.0, mullite crystals as abnormal crystals other than alumina crystals and spinel crystals will be formed by repeated heat treatment. When the amount of the abnormal crystals increases, poor electrical properties and poor appearance of the substrate occur, and the content of CaO and / or MgO decreases, so that the effect of suppressing the growth of alumina particles decreases, This is because sinterability at a temperature of 1650 ° C. or lower is reduced, so that it is difficult to densify.

Further, MgO is an important component for suppressing the growth of alumina particles.
If it is less than 5, the effect of suppressing the growth of the alumina particles is reduced, and the alumina particles cannot be sufficiently densified. Conversely, if the weight ratio is more than 42.0, the other component SiO
₂ and / or 1 due to low CaO content
This is because it becomes difficult to completely fire at a firing temperature of 650 ° C. or less.

Further, CaO is an important component for lowering the sintering temperature. If the weight ratio is less than 2.0, the effect of lowering the sintering temperature is diminished, and sintering at 1650 ° C. or lower becomes difficult. And conversely, the weight ratio is 1
If it exceeds 0.5, abnormal crystals such as cordierite crystal and sapphirine crystal or anorthite crystal are crystallized in addition to the alumina crystal due to repetition of the heat treatment. In addition to the occurrence of poor appearance, the content of SiO ₂ and / or MgO is reduced, so that the sinterability is reduced, and the effect of suppressing the growth of alumina particles is reduced, making it difficult to make them dense.

The alumina ceramic constituting the ceramic substrate for an electronic component according to the present invention is basically composed of Al ₂ O ₃ as the first component and SiO ₂ and Ca as the second component.
Although it is only three components of O and MgO and does not substantially contain impurities, impurities such as Fe ₂ O ₃ and Na ₂ O are mixed in various raw materials and manufacturing processes. The content of these impurities is preferably suppressed to 0.05% by weight or less.

Incidentally, the ceramic substrate for electronic parts made of alumina ceramics according to the present invention can be formed, for example, by the following manufacturing method.

First, 96 to 98% by weight of Al ₂ O ₃ having a purity of 99.7% or more as the first component, and 2 to 4% by weight of three components of MgO, SiO ₂ and CaO as the second component.
Add within the range. However, the weight ratio of each component constituting the second component when the total content is 100 is Si
_{O 2: 52.0~68.0, CaO: 2.0~10} .
5, MgO: added so as to be 25.5 to 42.0.

Then, a solvent and a binder are added to and mixed with these raw materials to produce a slurry, and a green sheet is formed by a tape forming method such as a doctor blade method. After drying the green sheet, the green sheet is cut out to a predetermined size by a mold, and then degreased and then fired in an oxidizing atmosphere at a firing temperature of 1500 to 1650 ° C., whereby the crystal phase is substantially reduced. It consists only of alumina crystals and spinel crystals, has a bulk specific gravity of 3.7 or more, a dielectric constant of 9 to 9.8, and a dielectric loss coefficient of 1 × 10 ^-4 to 1 × 10.
^This makes it possible to obtain a ceramic substrate for electronic components made of alumina ceramics having an electrical property of ^-3 .

[0022]

【Example】

(Example 1) First, the content of Al ₂ O ₃ constituting the first component was fixed at 96.73% by weight, and Si as the second component was fixed.
A ceramic substrate for electronic components made of alumina ceramics in which the weight ratios of O ₂ , CaO, and MgO were respectively changed was prototyped, and the sintered state and the presence or absence of abnormal crystals when heat treatment was performed were measured.

In this experiment, regarding the sintering state, when the ceramic substrate for electronic parts made of alumina ceramics baked at a sintering temperature of 1615 ° C. was not stained when immersed in a penetrating liquid, it was marked with “、”, and when it was stained, it was marked with “X”. The presence or absence of abnormal crystals is determined by measuring the substrate by X-ray diffraction after the heat treatment is repeated 5 times at a temperature of 1350 to 1450 ° C., thereby detecting abnormal crystals such as cordierite crystals, anorthite crystals, mullite crystals, and sapphirine crystals. ○ indicates that no crystallization was found, and X indicates that crystallization of abnormal crystals was observed.

The weight ratios and results of the three components constituting the second component are as shown in Tables 1 and 2.

[0025]

[Table 1]

[0026]

[Table 2]

As a result, the sample No. In No. 1, since the weight ratio of SiO ₂ was as small as less than 52.0, sintering could not be performed completely, and it was stained by the permeating solution.

Sample No. 13 to sample no. In the case of No. 15, although it was possible to completely sinter and did not stain the infiltration solution, heat treatment was applied because the weight ratio of SiO ₂ was more than 68.0. FIG. 2 shows the result of X-ray diffraction. As described above, crystallization of mullite crystal was observed as an abnormal crystal other than the alumina crystal and the spinel crystal.

The sample No. 16 to sample no. In No. 18, since the ratio of CaO is less than 2.0, 1615
At a sintering temperature of ° C., sintering could not be carried out sufficiently, and it was stained by the penetrant.

Further, the sample No. In 29 and 30, Ca
When the heat treatment was applied because the weight ratio of O was more than 10.5, crystallization of cordierite crystals and sapphirine crystals as abnormal crystals other than alumina crystals was observed as shown in the result of X-ray diffraction in FIG. Was.

On the other hand, the sample No. No. 2 to sample no. 1
2 and sample no. 19 to sample no. In the case of No. 28 within the scope of the present invention, sintering was completed completely, and no staining was observed even when immersed in a permeating solution. Even when heat treatment was applied, no crystallization of crystals other than alumina crystals and spinel crystals was observed as shown in the results of the X-ray diffraction in FIG.

(Example 2) Next, the second component SiO
₂ , the total content of the three components CaO and MgO is 100
The weight ratio of each component is expressed as SiO ₂ : CaO: M.
gO = 64.5: 29.9: 5.6, and the content of Al ₂ O ₃ constituting the first component was 90.0 to 99.0% by weight.
A ceramic substrate for electronic components made of alumina ceramics varied in the range of was experimentally manufactured, and the sintering state, the presence or absence of abnormal crystal crystallization when heat treatment was applied, and the electrical characteristics were measured in the same manner as in Experimental Example 1. went.

As for the electrical characteristics, the dielectric constant is 9.0 to 9.0.
9.8 and a dielectric loss coefficient in the range of 1 × 10 ⁻⁴ to 1 × 10 ⁻³ were evaluated as ○, and those out of the range were evaluated as ×.

The content of Al ₂ O ₃ as the first component and the results are as shown in Table 3.

[0035]

[Table 3]

As a result, Sample No. Al is 40 and 41
_Since the content of ₂ O ₃ was too low and the content of the second component was too high, cordierite crystals and sapphirine crystals were crystallized as abnormal crystals as in the result of X-ray diffraction shown in FIG. In addition, since the amount of crystallization of these abnormal crystals is large, the dielectric constant required for ceramic substrates for electronic components is 9 to 9.
9.8, and electrical characteristics of dielectric loss coefficient of 1 × 10 ⁻⁴ to 1 × 10 ⁻³ could not be satisfied.

Sample No. A at 42 and 43
Since the content of l ₂ O ₃ was less than 96.0% by weight, the content of the second component was too large, and although the electrical properties were satisfactory, cordierite crystals and sapphirine crystals were crystallized and the appearance was poor. Was seen.

On the other hand, the sample No. 49-No. In 51,
Since the content of Al ₂ O ₃ was more than 98.0% by weight, the content of the second component was too small, and as a result, sintering could not be completed, and the permeated solution was stained.

On the other hand, the sample No. In the range of the present invention of Nos. 44 to 48, it was possible to completely sinter and did not stain even when immersed in a permeate. Even when heat treatment was applied, no crystallization of crystals other than alumina crystals and spinel crystals was observed as shown in the X-ray diffraction results shown in FIG. Therefore, the dielectric constant required for the ceramic substrate for electronic components is 9 to 9.8, and the dielectric loss coefficient is 1 × 1.
The electrical characteristics of 0 ^-4 to 1 × 10 ^-3 could be satisfied, and no appearance defect occurred.

[0040]

As described above, according to the present invention, SiO ₂ , CaO and MgO are contained as the second component with respect to 96 to 98% by weight of Al ₂ O ₃ as the first component. When the weight ratio of the second component to 100 is Si
_{O 2: 52.0~68.0, CaO: 2.0~10} .
5, MgO: 25.5 to 42.0, and the ceramic substrate for electronic components is composed of alumina ceramics substantially composed of only alumina crystals and spinel crystals, so that even if heat-treated, the ceramics remain in the ceramics. No crystals other than the alumina crystal and the spinel phase are crystallized. Therefore, it is possible to provide a ceramic substrate for an electronic component that does not impair the electrical characteristics and the mechanical characteristics even if the heat treatment is repeatedly performed to correct the warpage of the substrate.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of X-ray diffraction of a heat-treated ceramic substrate for an electronic component according to the present invention.

FIG. 2 is a graph showing the results of X-ray diffraction of a ceramic substrate for electronic components which has been subjected to a heat treatment and is out of the range of the present invention.

FIG. 3 is a graph showing the results of X-ray diffraction of a ceramic substrate for electronic components which has been subjected to a heat treatment and is out of the range of the present invention.

Claims (1)

(57) [Claims] (1) 96 to 98% by weight of Al ₂ O ₃ as a first component
On the other hand, SiO ₂ , CaO, and Mg
O, and the weight ratio of the total content of the second component to 100 is SiO ₂ : 52.
0 to 68.0, CaO: 2.0 to 10.5, MgO: 2
5.5 to 42.0, the first peak of alumina crystals
Strength is I ₀ , cordierite crystal, anorthite crystal,
Let I be the first peak intensity of light crystal and sapphirine crystal.
Intensity ratio electronic component ceramic substrate (I / I ₀₎ is characterized by being formed by I / I ₀ <0.01 der Ru alumina ceramics when the.