JPH09208296A - Ceramic substrate for electronic parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ceramics substrate made of alumina ceramics free from defects in electrical characteristics and appearance and not depositing abnormal crystals other than alumina and spinel crystals even when it is repeatedly heat- treated so as to level a warped substrate. SOLUTION: This ceramic substrate is made of alumina ceramics contg. 96-98wt.% Al2 O3 as a 1st component, SiO2 , CaO and MgO as 2nd components and consisting essentially of alumina and spinel crystals. When the total content of the 2nd components is represented by 100, the weight ratio of SiO2 :CaO:MgO is (52.0-68.0):(2.0-10.5):(25.5-42.0).

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 such as a substrate for resistors, a substrate for hybrid ICs, a substrate for a thermal head, and the like, even if heat treatment is repeated to correct warpage of the substrate. The present invention relates to a ceramic substrate for electronic components, which is made of alumina ceramics and whose characteristics and electrical characteristics do not change.

[0002]

2. Description of the Related Art Conventionally, resistor substrates and hybrid ICs
Alumina ceramic substrates have been used as ceramic substrates for electronic parts such as substrates for thermal heads and substrates for thermal heads. In recent years, with the demand for higher density, miniaturization and multilayering of circuit printing, ceramics for electronic parts Tightening of the dimensional accuracy of the substrate, especially warpage of the substrate has been a problem. For example, in a thick film circuit board or a hybrid IC board, if the board is warped, printing deviations in the circuit printing and variations in the circuit film thickness due to printing occur, as well as mounting of IC chips, connection of I / O pins, There is a possibility that it may have a great influence on the tight sealing.

Also in the substrate for the thermal head,
If a warped substrate is used, printing misalignment during thin film printing and variation in thin film thickness will occur.If a thermal head formed using such a substrate is used by incorporating it into a copier or a facsimile machine, the paper and the head will be separated during printing. Since it is not possible to keep the distance between them constant, there is a possibility that the print may have light and shade, resulting in a defective product.

By the way, regarding the electric characteristics of the ceramic substrate for electronic parts made of this kind of alumina ceramics, the dielectric constant is 9.0 to 9.8 and the dielectric loss coefficient is 1 × 10 ⁻⁴ to 1 × 10 ^−3. Is required to be in the range. And, as an alumina ceramic substrate having these electrical characteristics, Al ₂ O _{3 is} 85 to 96 wt%, and as a sintering aid, one of SiO ₂ , CaO and MgO is used.
It is used that more than one kind is added, and after making a slurry by adding and mixing a solvent and a binder to these, a sheet-shaped green sheet is formed using a tape forming method such as a doctor blade method, and the green After the sheet was dried, it was punched with a die to form a plate-shaped molded body, and then the molded body was fired to obtain an alumina ceramic substrate. Then, since the substrate is warped as it is, heat treatment has been performed to correct these.

[0005]

However, in recent years, the warp standard of the substrate has become strict, and for example, for a substrate size of 290 × 80 mm, the warp of 300 μm or less must be suppressed. The warp could not be corrected, and the heat treatment had to be performed several times in order to obtain a predetermined accuracy. As a result, the components such as SiO ₂ , CaO, and MgO contained as the sintering aid are Al ₂
What reacted with O ₃ particles and had only alumina crystals and spinel crystals at the time of firing were 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 is a problem that crystals and anorthite (CaO.Al ₂ O ₃ .2SiO ₂ ) crystals are crystallized as abnormal crystals.

That is, the dielectric constant of cordierite crystals, sapphirine crystals, mullite crystals, anorthite crystals, etc. is 5.
0 to 6.5, the dielectric loss coefficient is 4 × 10 ^{−3 to} 5 × 10 ⁻³
Degree of dielectric constant (9.0 to 9.8) and dielectric loss coefficient (1 × 10 ⁻³ to 1 ×) of alumina crystal and spinel crystal
There is a problem in that the electrical characteristics required for the alumina ceramic substrate cannot be satisfied because it is greatly deviated from 10 ⁻⁴ ). Moreover, abnormal grain growth occurs due to the low crystallization temperature of abnormal crystals such as cordierite crystals, sapphirine crystals, mullite crystals, and anorthite crystals, which may cause not only poor electrical characteristics but also poor appearance, These abnormal crystals have a coefficient of thermal expansion of 2.2 × 10 ^{−6 to} 4.0 × 10 ⁻⁶ / ° C. and a coefficient of thermal expansion of alumina crystals and spinel crystals (7.0 × 10 ^{−6 to} 7.
Since it is larger than 8 × 10 ⁻⁶ / ° C.), the warpage of the substrate may be further increased in the cooling process after the heat treatment than in the baking.

[0007]

An object of the present invention is to provide a ceramic substrate for electronic parts, which is 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 warpage of the substrate. To provide.

[0008]

In view of the above problems, the present invention takes 96 to 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 the weight ratio when the total content of the second component is 100 is SiO ₂ : 5
2.0-68.0, CaO: 2.0-10.5, Mg
O: 25.5 to 42.0, and the ceramic substrate for electronic parts is composed of alumina ceramics that is substantially composed of only alumina crystals and spinel crystals.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A ceramic substrate for electronic parts according to the present invention is an alumina containing Al ₂ O ₃ as a first component and _three components of SiO ₂ , CaO and MgO as a second component. It is formed of ceramics, and by setting the ratio of the first component and the second component within a certain range, it substantially consists of alumina crystals and spinel crystals, and even if the heat treatment is repeated, Other than spinel crystals, it is possible to use those that do not crystallize abnormal crystals such as cordierite crystals, anorthite crystals, mullite crystals, and sapphirine crystals. Therefore, even if the heat treatment is repeatedly performed to correct the warp of the substrate, the electrical characteristics are not affected, and a ceramic substrate for electronic components made of alumina ceramics having no appearance defect can be obtained.

In the present invention, "composed essentially of alumina crystals and spinel crystals" means that the first peak intensity of alumina crystals is I ₀ , and 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, the first component, Al ₂ O _3, is 9
It is important to contain in the range of 6 to 98% by weight.

This has an Al ₂ O ₃ content of 96% by weight.
If it is less than the second component (SiO ₂ , CaO, MgO)
If the heat treatment is performed, abnormal crystals such as cordierite crystals, anorthite crystals, mullite crystals, and sapphirine crystals with different electrical properties and thermal expansion coefficients other than alumina crystals and spinel crystals will appear in the alumina ceramics due to the excessive content of In order to crystallize, the electrical characteristics of the ceramic substrate for electronic parts having a dielectric constant of 9.0 to 9.8 and a dielectric loss coefficient of 1 × 10 ⁻⁴ to 1 × 10 ⁻³ can be satisfied. Because it will be difficult. Further, when the content of Al ₂ O ₃ exceeds 98% by weight, the second component (SiO 2
₂ , due to the reduced content of CaO, MgO) 16
This is because it becomes difficult to sinter at a firing temperature of 50 ° C. or less, and the mechanical properties of the substrate material are significantly reduced.

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

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

That is, among the second components, SiO ₂ is an important component for binding alumina particles to each other to form a grain boundary phase, but when the weight ratio thereof is less than 52.0,
This is because it is not possible to sufficiently sinter at a firing temperature of 1650 ° C. or lower, and conversely, when the weight ratio is more than 68.0, mullite crystals are crystallized as abnormal crystals other than alumina crystals and spinel crystals due to repeated heat treatment. When the amount of the abnormal crystals crystallized increases, the electrical characteristics of the substrate and the appearance of the substrate become poor, and the content of CaO and / or MgO decreases, so that the effect of suppressing the growth of alumina particles decreases, This is because it becomes difficult to densify because the sinterability at a temperature of 1650 ° C. or lower decreases.

Further, MgO is an important component for suppressing the growth of alumina particles, but its weight ratio is 25.
When it is less than 5, the effect of suppressing the growth of alumina particles is lowered and it becomes impossible to sufficiently densify it. On the contrary, when the weight ratio exceeds 42.0, the other component, SiO
₂ and / or 1 due to reduced CaO content
This is because it becomes difficult to perform complete firing at a firing temperature of 650 ° C or lower.

Further, CaO is an important component for lowering the firing temperature, but if its weight ratio is less than 2.0, the effect of lowering the firing temperature is weakened, and sintering at 1650 ° C. or less becomes difficult. And conversely, the weight ratio is 1
If it exceeds 0.5, abnormal crystals such as cordierite crystals and sapphirine crystals or anorthite crystals crystallize out in addition to alumina crystals due to repeated heat treatments, and if the amount of these abnormal crystals crystallizes increases, the electrical characteristics of the substrate become poor. In addition, the appearance is deteriorated, and 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, which makes it difficult to densify.

Further, the alumina ceramics constituting the ceramic substrate for electronic parts 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 contains only three components, O and MgO, and does not substantially contain impurities, since 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.

By the way, 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 molding method such as a doctor blade method. Then, after the green sheet is dried, it is cut into a predetermined size with a mold, and after degreasing, firing is performed at a firing temperature of 1500 to 1650 ° C. in an oxidizing atmosphere, whereby the crystalline phase is substantially It consists of alumina crystals and spinel crystals only, 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.
It is possible to obtain a ceramic substrate for electronic parts, which is made of alumina ceramics and has electric characteristics of ^-3 .

[0022]

【Example】

(Example 1) First, the content of Al ₂ O ₃ forming the first component was fixed at 96.73% by weight, and the second component Si was formed.
A ceramic substrate for electronic parts made of alumina ceramics having different weight ratios of O ₂ , CaO, and MgO was manufactured as a prototype, and the state of sintering and the presence or absence of abnormal crystal crystallization during heat treatment were measured.

In this experiment, regarding the sintered state, the ceramic substrate for electronic parts made of alumina ceramics fired at a firing temperature of 1615 ° C. was not dyed when immersed in the penetrant, and the dyed one was x, and the dyed one was x. The presence or absence of abnormal crystals was measured by X-ray diffraction after heat treatment was repeated 5 times at a temperature of 1350 to 1450 ° C. to determine whether abnormal crystals such as cordierite crystals, anorthite crystals, mullite crystals, and sapphirine crystals were detected. The case where no crystallization was found was marked with ◯, and the case where abnormal crystal crystallization was found was marked with x.

The weight ratios of the three components constituting the second component and the results are 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, it could not be completely sintered and was dyed with the penetrant liquid.

Sample No. 13-Sample No. No. 15 was able to completely sinter and did not stain the permeating liquid, but when heat treatment was applied because the weight ratio of SiO ₂ was more than 68.0, the result of X-ray diffraction is shown in FIG. Thus, in addition to alumina crystals and spinel crystals, mullite crystals were observed as abnormal crystals.

The sample No. 16 to sample no. In No. 18, since the ratio of CaO is less than 2.0, 1615
It could not be sufficiently sintered at a sintering temperature of ℃, and was dyed with the penetrant liquid.

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, as shown in the result of X-ray diffraction in FIG. 3, crystallization of cordierite crystals and sapphirine crystals was observed as abnormal crystals in addition to alumina crystals. It was

On the other hand, sample No. 2 to sample No. 1
2 and sample No. 19-Sample No. No. 28, which is within the scope of the present invention, could be completely sintered and did not stain even when immersed in a penetrant liquid. Further, even if heat treatment was applied, no crystallization of crystals other than alumina crystals and spinel crystals was observed as shown in the result of the X-ray diffraction in FIG.

(Embodiment 2) Next, SiO as the second component
₂ , the total content of the three components CaO and MgO is 100
And the weight ratio of each is SiO ₂ : CaO: M
gO = 64.5: 29.9: 5.6 was fixed, and the content of Al ₂ O ₃ forming the first component was 90.0 to 99.0% by weight.
A ceramic substrate for electronic parts made of alumina ceramics which was changed in each range was prototyped, and the sintering state and the presence or absence of crystallization of abnormal crystals when heat treatment was applied, and the electrical characteristics were measured as in Experimental Example 1. went.

Regarding electrical characteristics, the dielectric constant is 9.0 to 9.0.
A sample having a dielectric loss coefficient of 9.8 and a dielectric loss coefficient of 1 × 10 ⁻⁴ to 1 × 10 ^{−3 was} evaluated as ◯, and a compound having a dielectric loss coefficient outside the range was evaluated as x.

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

[0035]

[Table 3]

As a result, the sample No. Al for 40 and 41
_Since the content of ₂ O ₃ was too small and the content of the second component was too large, there were crystallized cordierite crystals and sapphirine crystals as abnormal crystals similar to the result of X-ray diffraction shown in FIG. Moreover, since the amount of these abnormal crystals crystallized is large, the dielectric constant required for the ceramic substrate for electronic parts is 9 to 9
The electrical characteristics of 9.8 and the dielectric loss coefficient of 1 × 10 ⁻⁴ to 1 × 10 ⁻³ could not be satisfied.

Sample No. A in 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 the electrical characteristics were satisfactory, but cordierite crystals and sapphirine crystals were crystallized, resulting in poor appearance. I was seen.

On the other hand, the sample No. 49-No. At 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, it was not possible to completely sinter it and it was dyed with a penetrant liquid.

On the other hand, the sample No. Those within the range of the present invention of 44 to 48 were able to be completely sintered and did not stain even when immersed in the penetrant liquid. 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 parts 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 defective appearance was caused.

[0040]

As described above, according to the present invention, the first component contains 96 to 98% by weight of Al ₂ O ₃ and the second component contains SiO ₂ , CaO, and MgO. The weight ratio when the second component is 100 is Si
_{O 2: 52.0~68.0, CaO: 2.0~10} .
5, MgO: 25.5 to 42.0, and by configuring the ceramic substrate for electronic parts by alumina ceramics that is substantially composed of only alumina crystals and spinel crystals, even if heat treatment is performed, the ceramic substrate remains in the ceramics. Does not crystallize crystals other than alumina crystals and spinel phase. Therefore, it is possible to provide a ceramic substrate for electronic parts which does not impair the electrical characteristics and mechanical characteristics even when repeatedly subjected to heat treatment to correct the warp of the substrate.

[Brief description of drawings]

FIG. 1 is a graph showing the result of X-ray diffraction in a ceramic substrate for electronic parts according to the present invention that has been heat-treated.

FIG. 2 is a graph showing the results of X-ray diffraction on a heat-treated ceramic substrate outside the scope of the present invention for electronic components.

FIG. 3 is a graph showing the result of X-ray diffraction on a heat-treated ceramic substrate for electronic parts outside the scope of the present invention.

Claims (1)

[Claims] 1. A first component of 96 to 98% by weight of Al ₂ O _{3 and a} second component of SiO ₂ , CaO, and M.
It contains three components of gO, and the weight ratio when the total content of the second component is 100 is SiO ₂ : 5
2.0-68.0, CaO: 2.0-10.5, Mg
O: 25.5 to 42.0, and a ceramic substrate for electronic parts, which is formed of alumina ceramics substantially consisting of alumina crystals and spinel crystals.