JPH07237966A - Production of ceramics substrate for wiring circuit - Google Patents

Abstract

PURPOSE:To obtain the ceramics substrate low in specific dielectric constant, high in mechanical strength, having a thermal expansion coefficient close to that of metallic tungsten or molybdenum. CONSTITUTION:Mixed powder comprising >=70wt.% of mullite powder <=5mum in average particle diameter, <=30wt.% of silica powder <=2mum in average particle diameter, <=15wt.% of aluminum oxide powder <=1mum in average particle diameter and a total of <=1wt.% of alkali metal oxide and/or alkaline earth metal oxide powder, is molded into a molded form, which is then sintered into a sintered compact to obtain the aimed ceramic substrate. This ceramics substrate is then provided with a conductor layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel ceramic substrate for a wiring circuit, particularly having a high-density wiring, and mounting a pin for inputting / outputting an electric signal or mounting a semiconductor component on a functional module. The present invention relates to a method for manufacturing a ceramic substrate for a wiring circuit suitable for forming

[0002]

2. Description of the Related Art In recent years, integrated circuits such as LSIs have become faster and faster.
Along with the increase in density, a method of directly mounting a chip on a ceramic substrate has been used in order to dissipate heat and increase the speed of elements. However, in this mounting method, as the size of the integrated circuit such as the LSI increases, the stress caused by the temperature change during mounting between the integrated circuit material such as the LSI and the ceramic multilayer wiring circuit board material increases. There was a point. That is, the coefficient of thermal expansion of alumina conventionally used as an insulating material of a ceramic multilayer wiring circuit board is 75 ×
10 ^-7 / ° C (room temperature to 500 ° C), this value is LSI
Thermal expansion coefficient of silicon, which is an integrated circuit material such as
Since it is more than twice as large as 0 to ⁷ / ° C (room temperature to 500 ° C), the stress caused by the temperature change during mounting becomes large.
There was a problem that the reliability of the connection part was reduced. Further, the firing temperature of the alumina-based material is 1500 to 1650 ° C., and the conductor material applicable for forming the wiring circuit at the same time as the structure of the ceramic is tungsten or molybdenum. However, the coefficient of thermal expansion of tungsten or molybdenum is 45 × 10 ^-7 , 54 × 10 ^-7 /
C. (room temperature to 500.degree. C.), and when co-firing with the alumina-based material, there was a problem that cracks were generated inside the wiring board due to the difference in thermal expansion coefficient between them. Further, a problem with a substrate using a sintered body containing alumina as a main component is that the propagation speed of an electric signal is slow. This is because the relative dielectric constant of alumina itself is 9.5%. (1
This is because it is as large as (MHz).

Accordingly, Japanese Patent Laid-Open No. 55-139709 "Mulite Substrate Manufacturing Method" is an example of a substrate in which the coefficient of thermal expansion of a ceramic material is close to that of silicon and the relative dielectric constant is small. According to this publication, cordierite is generated between the mullite main crystals, so that the coefficient of thermal expansion of cordierite is 10 to 20 × 10 ⁻⁷ / ° C. (room temperature to 5).
Since the thermal expansion coefficient of the mullite substrate is lower than that of mullite alone by utilizing the fact that the thermal expansion coefficient is 00 ° C.), a thermal expansion coefficient of 38 to 39 × 10 ⁻⁷ / ° C. close to that of silicon is obtained.

[0004]

However, in spite of such advantages, it is impossible to form a ceramic circuit board by cofiring a ceramic material and a conductor material.
This is because it must be fired at a temperature near 1500 ° C. where the cordierite phase exists, and therefore it cannot be fired at the same time as tungsten or molybdenum, which is a conductor material that is difficult to sinter. Also, since the coefficient of thermal expansion of tungsten or molybdenum is 45 × 10 ⁻⁷ / ° C. and 54 × 10 ⁻⁷ / ° C., respectively, the difference in thermal expansion is large, and cracks occur during simultaneous firing with alumina. .

Therefore, it is an object of the present invention to provide a method of manufacturing a ceramic substrate for a wiring circuit, which has a thermal expansion coefficient close to that of tungsten or molybdenum and has a low relative dielectric constant and high strength.

[0006]

According to the present invention, mullite is the main component, and silicon dioxide, a composite oxide of aluminum oxide and silicon dioxide in a molar ratio of 1: 0.7 to 1, and alkaline earth. A ceramic substrate containing a metal oxide;
Provided is a ceramic substrate for a wired circuit, which has a conductor layer formed on the substrate.

The mullite is aluminum oxide (Al ₂
O ₃ ) and silicon dioxide (SiO ₂ ) have a composition of 3 or more and less than 4 to 2 in a molar ratio, and the content is preferably 70% by weight or more. In particular, mullite has a ratio of Al ₂ O ₃ and SiO ₂ of 3 to
3.5 to 2 is preferred.

The silicon dioxide (SiO ₂ ) is 30% by weight.
It is preferable that it is amorphous (glass) and is formed at the grain boundary of the mullite crystal. Especially 15-30
Weight percent is preferred.

The complex oxide is preferably at least one of andalusite, kyanite and sillimanite. Mullite stoichiometrically aluminum oxide (Al ₂ O ₃₎ rich 3Al ₂ O ₃ · 2SiO ₂ are preferred, composite oxide Al ₂ O ₃ · SiO ₂ is preferred. Al ₂
O ₃ · SiO ₂ is preferably 1 to 15% by weight.

According to the present invention, the main component is mullite,
At least one selected from the group consisting of silicon dioxide, a composite oxide of aluminum oxide and silicon dioxide in a molar ratio of 1: 0.7 to 1, aluminum oxide, and an alkali metal oxide and an alkaline earth metal oxide. Provided is a ceramic substrate for a wiring circuit, which has a contained ceramic substrate and a conductor layer formed on the substrate.

The above ceramic substrate has a weight ratio of mullite (3Al ₂ O ₃ .2SiO ₂ ) of 70% or more, silicon dioxide (SiO ₂ ) of 30% or less, and complex oxide (Al ₂ O ₃ .Si).
It is preferable that the O ₂ ) content is 30% or less, the aluminum oxide content is 15% or less, and the content of at least one selected from alkali metal oxides and alkaline earth metal oxides is 1% or less.

In particular, mullite 70% or more, SiO ₂ 15
% Or less, Al ₂ O ₃ .SiO ₂ 10% or less, Al ₂
It is preferable that 5% or less of O ₃ and 1% or less of an alkaline earth metal oxide or an alkali metal oxide are substantially solid-dissolved in mullite and do not exist as another crystal phase.

It is preferable that substantially all of the alkali metal oxide and the alkaline earth metal oxide be in solid solution in the mullite. Alkali metal oxides include lithium, sodium, potassium, rubidium and cesium oxides, and alkaline earth metal oxides include beryllium, magnesium, calcium, strontium and barium oxides.

According to the present invention, 70% or more by weight of mullite powder having an average particle size of 5 μm or less, 30% or less of silicon dioxide powder having an average particle size of 2 μm or less, 15% or less of aluminum oxide powder having an average particle size of 1 μm or less, and alkali. This is a method for producing a ceramic substrate for a wiring circuit, in which a mixed powder containing 1% or less of an earth metal oxide powder is pressure-molded, fired, and then a conductor layer is formed on the obtained ceramic substrate.

The firing temperature is preferably 1550 to 1680 ° C, and particularly preferably 1580 to 1620 ° C.

[0016]

The aluminum oxide is used as a sintering aid for mullite and produces mullite and sillimanite.

The addition of SiO ₂ lowers the relative dielectric constant and suppresses grain growth during the sintering of mullite to improve the strength.
SiO ₂ is preferably 10 to 30%. 40% is not preferable in terms of strength. In particular, when a ceramic multilayer printed circuit board is manufactured, a high-density wired ceramic multilayer printed circuit board is manufactured by a method of laminating a large number of green sheets printed with conductor wiring materials. However, when an attempt is made to arrange the internal wiring conductors with high density, cracks occur due to the difference in thermal expansion coefficient between the ceramic insulating material and the wiring conductor material. When alumina is used as the ceramic insulating material and tungsten is used as the wiring conductor material, the coefficient of thermal expansion of alumina is 75 × 10 ⁻⁷ when wiring is performed at high density.
/ ° C (room temperature to 500 ° C) and thermal expansion coefficient of tungsten 4
The thermal stress due to the difference of 5 × 10 ⁻⁷ / ° C. (room temperature to 500 ° C.) causes a problem that cracks occur inside the substrate. Therefore, the coefficient of thermal expansion of tungsten or molybdenum used for the internal wiring conductor material is 45 × 10 ⁻⁷ and 54.
It is necessary to develop a ceramic insulating material close to × 10 ^-7 / ° C. Further, a ceramic insulating material having a thermal expansion coefficient close to that of a semiconductor component directly mounted on the ceramic multilayer printed circuit board by soldering or the like is required. Since the coefficient of thermal expansion of the ceramic insulating material containing alumina as a main component is 75 × 10 ⁻⁷ / ° C. (room temperature to 500 ° C.), the coefficient of thermal expansion of the silicon semiconductor element which is a semiconductor component is 35 × 10 ⁻⁷ / ° C. ( Room temperature to 50
The coefficient of thermal expansion is more than twice that of 0 ° C. Therefore, there is a problem that stress generated due to a temperature change at the time of mounting becomes large, reliability of the connecting portion is lowered, and disconnection or the like occurs. Also,
In recent years, gallium-arsenic semiconductor elements have been used for semiconductor parts. The coefficient of thermal expansion of this gallium-arsenic semiconductor device is 65 × 10 ^-7 / ° C. Therefore, when the silicon semiconductor element and the gallium-arsenic semiconductor element are mounted on the same substrate, the ceramic insulating material needs to be close to the coefficient of thermal expansion of these semiconductor elements. A ceramic insulating material having a thermal expansion coefficient of 35 × 10 ⁻⁷ / ° C. of a silicon semiconductor element and a thermal expansion coefficient of 65 × 10 ⁻⁷ / ° C. of a gallium-arsenide semiconductor element, that is, a thermal expansion coefficient of 35 to 65.
× 10 ⁻⁷ / ° C., preferably 40 to 60 × 1
It needs to be 0 ^-7 / ° C. This value is close to the thermal expansion coefficients of 45 × 10 ⁻⁷ / ° C. and 54 × 10 ⁻⁷ / ° C. of tungsten or molybdenum using the internal wiring conductor material. As a ceramic insulating material having such a coefficient of thermal expansion, 3Al having a coefficient of thermal expansion of 42 to 45 × 10 ⁻⁷ / ° C.
_{There are 2} O ₃ .2SiO ₂ and Al ₂ O ₃ .SiO ₂ having a coefficient of thermal expansion of 35 to 75 × 10 ^-7 / ° C. The sintered body containing these crystal phases as a main component has a coefficient of thermal expansion of 40 to 60 × 10.
^-7 / ° C ceramic insulating material. In addition, Al ₂ O ₃ ·
As SiO _2, there are crystal phases of andalusite, kyanite, and sillimanite, but all have the same coefficient of thermal expansion, and the coefficient of thermal expansion hardly changes in any crystal phase. On the other hand, a ceramic multilayer wiring circuit board using a sintered body containing alumina as a main component as a ceramic insulating material has a relative dielectric constant of alumina of 9.5 (1 MH).
Therefore, there is a problem that the propagation speed of the electric signal is slow because it is large. In order to lower the relative permittivity, it is necessary to lower the relative permittivity of the crystal phase constituting the ceramic insulating material. 3Al as an aluminosilicate material with a small relative permittivity that may possibly be formed at the same time as the tungsten or molybdenum conductor material used as the wiring conductor material.
_{2 O 3 · 2SiO 2, Al} 2 O 3 · SiO 2 , etc. is. These ceramic insulating materials have a relative dielectric constant of 6 to 7 by themselves.
(1 MHz). The ceramic insulating material composed of these crystal phases has a small relative permittivity and a ceramic multilayer wiring circuit board having a high electric signal propagation speed can be obtained.

As described above, even when multi-layer wiring is performed,
The ceramic substrate of the present invention is suitable.

Further, 3Al ₂ O ₃ .2SiO ₂ is replaced with Al
₂ O ₃ , SiO ₂ , alkaline earth metal oxides or alkali metal oxides. The amount of SiO ₂ added as a system for sintering is increased to 3Al ₂ O ₃ · 2SiO ₂ and Al ₂ O ₃ after firing.
・ We decided to form a crystalline phase of SiO ₂ . However, when the amount of the alkali metal oxide or the alkaline earth metal oxide is large, the sinterability is improved, but a crystal phase or an amorphous composite oxide of these oxides and Al ₂ O ₃ or SiO ₂ is used. Is generated and the strength of the ceramic insulating material is reduced. Moreover, since the relative permittivity is also high, the total amount of alkali metal oxides and alkaline earth metal oxides is 1 wt% or less, and 3Al ₂ O ₃
· 2SiO may not exceed ₂ and Al ₂ O ₃ · SiO ₂ solid solution limit is required. That is, a ceramic insulating material containing no crystal phase composed of an alkali metal oxide or an alkaline earth metal oxide must be used. Further, in the ceramic insulating material containing more than 1 wt% of the alkali metal oxide and the alkaline earth metal oxide, the firing shrinkage rate varies and a stable sintered body can be obtained in the temperature range where the firing can be sufficiently performed. There wasn't. It was confirmed by X-ray diffraction that this was because the crystal phase in the sintered body was not stable.

Further, alkali metal oxides and alkaline earth metal oxides are substances which are extremely unstable in the atmosphere, and absorb moisture and the like when left to stand. Therefore, when adding these oxides, a method of adding them as a carbonate or a hydroxide is adopted. The carbonate or hydroxide is
Decomposes during the temperature rise process and releases carbon dioxide or water. At this time, the oxide is in an active state, which also has the effect of improving the sinterability.

Silicon dioxide (SiO ₂ ) has the smallest relative permittivity among oxides, and the relative permittivity of the ceramic insulating material can be reduced by increasing the amount added. That is,
By adding SiO ₂ to 3Al ₂ O ₃ · 2SiO _2, it will be lower than the dielectric constant of 3Al ₂ O ₃ · 2SiO _2. Further, Al ₂ O ₃ or by diffusion reaction with 3Al ₂ O ₃ · 2SiO ₂ were added simultaneously by adding SiO _2, to produce a Al ₂ O ₃ · SiO ₂ crystal phase. Therefore, 3Al ₂ O ₃ · 2SiO ₂ in the ceramic insulating material
And a crystal phase of Al ₂ O ₃ .SiO ₂ is formed. These crystalline phases are very stable and do not change at temperatures around 1600 ° C. This makes the firing shrinkage stable by firing at a certain temperature or higher, and is promising as a ceramic multilayer wiring circuit board material. It was also found that the addition of a large amount of SiO ₂ has the effect of suppressing the grain growth of 3Al ₂ O ₃ .2SiO ₂ during firing. As a result, the relative permittivity was lowered and the strength was improved. It was found that the greatest effect was obtained by adding more than 75 wt% of the raw material components other than 3Al ₂ O ₃ .2SiO ₂ as the additive amount of SiO ₂ .

In the method of manufacturing a ceramic multilayer wiring circuit board, it is necessary to first manufacture a green body (green molded body), form wiring conductors on it, and stack a large number of sheets at once to perform simultaneous firing. Other than the green sheet method, there are a slip casting method, a die molding method by a pressing method, an injection molding method, and the like.

The green sheet method is a method in which a solvent and a thermoplastic resin are added to the raw material powder, the agitated slurry is deaerated, and then the green sheet is produced by a green sheet producing apparatus having a doctor blade.

The slip casting method is a method in which water, a dispersant and a resin such as a thermoplastic resin are added to raw material powder and the slurry is stirred and poured into, for example, a gypsum mold.

In the die molding method using a press, a solvent and a resin such as a thermoplastic resin are added to the raw material powder, and the raw material powder is mixed and stirred by a sieving machine or the like, sieved, and then put into a metal to apply a load. In addition, it is a manufacturing method.

The injection molding method is a method in which a thermoplastic resin, wax or the like is added to raw material powder and injection molding is performed.

Of course, a ceramic substrate for a wiring circuit in the case of not forming a multilayer can be manufactured by forming a wiring conductor on a green body and firing it.

[0028]

【Example】

(Embodiment 1) FIG. 1 is a sectional view showing an embodiment of a ceramic substrate for a wiring circuit according to the present invention. In the figure, 1 is a ceramic insulating material, and the thick line in the figure is the wiring conductor material 8. Further, these conductor layers are connected to each other by a predetermined through-hole conductor indicated by a thick line in the vertical direction in the figure. Reference numeral 4 indicates a Kovar pin connected by a gold-indium solder 5, and reference numeral 6 indicates a semiconductor component connected by a solder 7.

Next, an embodiment of the method for manufacturing a ceramic substrate for a wiring circuit according to the present invention will be described. In the following description,
Parts means parts by weight, and% means% by weight.

72 parts of slightly alumina-rich mullite powder (3Al ₂ O ₃ .2SiO ₂ ) having an average particle size of 2 μm, 25.3 parts of quartz powder (SiO ₂ ) having an average particle size of 1 μm, and alumina having an average particle size of 0.4 μm 1.9 parts of powder (Al ₂ O ₃ ) and magnesium carbonate (Mg ₃ (CO ₃ )) having an average particle size of 0.3 μm
₄ (OH) ₃ .5H ₂ O) is converted into MgO in 0.8 parts, and 5.9 parts of polyvinyl butyral having an average degree of polymerization of 1000 as a resin is put in a ball mill and dry mixed for 3 hours. Furthermore, 1.9 ml of butyl phthalyl glycolate as a plasticizer, and trichloroethylene 46 as a solvent.
Part, tetrachloroethylene 17 parts and n-butyl alcohol 18 parts are added and wet mixed for 20 hours to prepare a slurry.
Next, air bubbles are removed from the slurry by vacuum deaeration, and the viscosity is adjusted. Next, the slurry is applied to a silicon film-treated polyester film support with a doctor blade to a thickness of 0.23 mm and dried in an oven to prepare a ceramic green sheet. This ceramic green sheet is removed from the silicon-treated polyester film support and cut at 220 mm intervals. The ceramic green sheet thus produced is cut into 200 mm square pieces using the green sheet punch section, and holes for guides are formed. Then, the ceramic green sheet was fixed using the holes for the guide, and a through hole having a diameter of 0.15 mm was made at a predetermined position by the punch method.
Further, a conductor paste of tungsten powder: nitrocellulose: ethyl cellulose: polyvinyl butyral: trichloroethylene = 100: 3: 1: 2: 23 (weight ratio) was filled in the through holes formed in the ceramic green sheet, and then screen printed. The conductor paste described above is printed according to a predetermined circuit pattern. 30 pieces of these ceramic green sheets are laminated as shown in FIG.
Laminated by pressurizing at ~ 30 kg / cm ² . Next, the laminated ceramic green sheets are put into a firing furnace and hydrogen 3
In a nitrogen atmosphere containing ˜7% by volume and containing a slight amount of water vapor, the temperature was raised to 1200 ° C. at a temperature rising rate of 50 ° C./h to remove the resin component used in producing the ceramic green sheet. After that, the temperature was raised at a heating rate of 100 ° C./h, the maximum temperature was maintained at 1620 ° C. for 1 hour, and the pressureless firing was performed.
Completed a ceramic multilayer wiring circuit board. This mullite multilayer board is about 67% by weight of mullite and Al ₂ O ₃
SiO ₂ 9% and SiO ₂ glass component were about 24%.

After the electroless nickel plating and the gold plating were applied to the thus-prepared wiring circuit ceramic substrate, the Kovar pin 4 was connected with the gold-indium solder 5 by a usual method using a carbon jig. Further, the semiconductor component 6 was mounted face down with the solder 7 directly connected thereto. In this way, the functional module shown in FIG. 1 was produced.

The coefficient of thermal expansion of the ceramic insulating material used for the ceramic substrate for the wiring circuit is 50 × 10 ⁻⁷ / ° C. (room temperature to
500 ° C.), and the thermal expansion coefficient of tungsten used for the internal wiring conductor material is 45 × 10 ⁻⁷ / ° C. (room temperature to 500 ° C.)
The thermal stress due to the difference in thermal expansion coefficient between the ceramic insulating material and the wiring conductor material did not occur, and no cracks occurred. The through hole pitch is 0.3m
High-density wiring of m was also possible. The crystal phase in the ceramic insulating material of the firing method is mullite (3Al ₂ O ₃
· 2SiO ₂₎ and was Al ₂ O ₃ · SiO _2. Since these stable crystal phases have similar thermal expansion coefficients, internal stress is hardly applied. _{Further, Mg 3 (CO 3) 4} (OH) 2 · 5H 3 O was added, Mg in heated
It was confirmed by the X-ray diffraction method and the X-ray microanalyzer that the composite oxide of MgO and other components does not exist in the ceramic insulating material obtained by the firing method although it becomes O.

The tensile strength of the Kovar pin was 4 kg / pin or more, which was a strength that could withstand practical use. Also,
The solder connection part 7 of the semiconductor component 6 did not cause disconnection even after a temperature cycle of -65 ° C. to 150 ° C. for 2000 cycles or more. In this way, the strength was such that a sufficient connection life could be guaranteed even under severe usage conditions. The cause is
3Al ₂ O ₃ · 2SiO ₂ and Al ₂ O ₃ · thermal expansion coefficient of silicon semiconductors thermal expansion coefficient of the SiO ₂ formed of a sintered body is used as the semiconductor components to a ^{50 × 10 -7 / ℃ 35 ×} 1
Close to 0 ^-7 / ° C. (room temperature to 500 ° C.), also, gallium -
Thermal expansion coefficient of arsenic semiconductor 65 × 10 ^-7 / ° C (room temperature to 50
(0 ° C), the difference in the amount of expansion between the substrate and the semiconductor component when heated is small in a ceramic substrate for wiring circuits that mixes a silicon semiconductor and a gallium-arsenic semiconductor, and thermal stress is not so much applied to the solder joint. Is. In the case of the conventional substrate containing alumina as the main component, the coefficient of thermal expansion of alumina is 75 × 10 ⁻⁷ / ° C., which is significantly different from the coefficient of thermal expansion of the silicon semiconductor element, which is the main component currently as a semiconductor component. When heated, thermal stress was applied to the solder joints, resulting in early disconnection.

On the other hand, the signal propagation delay time by the internal wiring conductor 2 was 8.1 ns / m. This value corresponds to the relative dielectric constant of the ceramic insulating material being 6.2. In a conventional printed circuit board made of an insulator containing alumina as a main component, the relative dielectric constant of the ceramic insulating material is about 9.5, and the signal propagation delay time is 10.2 ns /
Therefore, according to this embodiment, the signal propagation delay time is reduced by about 20%.

(Example 2) Example 1 except that the compounding amounts of the ceramic raw material powders are shown in Tables 1 to 3 in% by weight.
A ceramic substrate for a wiring circuit was produced by the same method as described above.
The amounts of alkali metal oxides and alkaline earth metal oxides in Tables 1 to 3 are shown by converting the actually used carbonates or hydroxides into oxides. Using the same method as in Example 1, the functional module shown in FIG. 1 was produced. Addition materials other than mullite are used as flux.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

Table 4 shows the Al ₂ O ₃ .SiO ₂ of the obtained substrate.
The content (% by weight) of the phase is shown, and Table 5 shows the content (% by weight) of the glass component of the substrate obtained similarly.

[0040]

[Table 4]

[0041]

[Table 5]

The texture of the obtained substrate is mullite as a main component, and MgO is in mullite or Al ₂ O ₃ .S
Although it forms a solid solution in iO ₂ , the solid solution amount is 1% or less in terms of MgO as a raw material. If it exceeds that, another crystalline phase is formed, and the coefficient of thermal expansion differs from that of the substrate, which is not preferable. Mullite amount 70 wt% (No. 1 to 7) and 80
FIG. 2 shows the relationship between the amount of SiO _{2 in} the flux and the bending strength for wt% (Nos. 22 to 28). The bending test was a four-point bending method based on JIS. From the figure, it can be seen that the bending strength rapidly increases as the glass component increases. That is, the amount of mullite is 70 wt%
In the case of, the bending strength of 180 MPa or more is the composition in which the amount of SiO _{2 in} the flux is more than 80 wt%, and when the amount of mullite is 80 wt%, the amount of SiO _{2 in} the flux is more than 75 wt%. There are many compositions.

FIG. 3 is a diagram showing the relationship between the amount of added SiO ₂ and the bending strength. As shown in the figure, the addition of SiO ₂ improves the sinterability of mullite and sharply improves the strength. However, when it exceeds 30%, the strength sharply decreases, so it is not preferable to add it excessively. . Especially 40
%, The sinterability decreases and the strength decreases. SiO
It is considered that the addition of ₂ improves the sinterability of mullite and enhances the strength because of the formation of the glass component.

FIG. 4 is a diagram showing the relationship between bending strength and the amount of Al ₂ O ₃ added. As shown in the figure, the strength is drastically lowered by the addition of Al ₂ O ₃ . Therefore, the added amount of Al ₂ O ₃ is preferably 5% or less.

Next, the amount of mullite is 70 wt% and 80 w
FIG. 5 shows the relationship between the amount of SiO ₂ in the flux and the relative dielectric constant with respect to t%. The measurement of the relative permittivity was constant at 1 MHz. The relative dielectric constant tends to decrease as the amount of SiO ₂ in the flux increases. That is, the amount of mullite is 8
In the case of 0 wt%, the relative dielectric constant becomes 6.7 or less.
The composition is such that the amount of SiO ₂ in the flux is more than 85 wt%, and when the amount of mullite is 70 wt%, the relative dielectric constant is smaller than 6.7 even when the amount of SiO _{2 in} the flux is about 50 wt%.

FIG. 6 is a diagram showing the relationship between the relative dielectric constant and the added amount of SiO ₂ . The addition of SiO ₂ significantly reduces the relative dielectric constant. In particular, since the relative dielectric constant rapidly decreases at 15% or more, addition of more than that is preferable.

FIG. 7 is a diagram showing the relationship between the firing temperature and the firing shrinkage of each sample. As shown in the figure, the sample of Example 1 has a constant shrinkage rate at a firing temperature of 1580 ° C. or higher,
The amount of MgO is no. 4.1% and CaO content and Na ₂
If the total amount of O is 2.7%, the firing temperature is 140
It varies between 0 and 1700 ° C and does not become constant. This is unfavorable when a large amount is fired in an electric furnace, since the temperature varies depending on the place in the furnace, and even if the composition is the same, different firing shrinkage ratios are obtained, causing variations in products.

FIG. 8 shows the amount of Al ₂ O ₃ added and A generated on the substrate.
It is a graph showing the relationship between l ₂ O ₃ · SiO ₂ amount. As shown in FIG, Al the addition amount of _{Al 2 O 3 2 O 3 ·} SiO 2
Will increase. This Al ₂ O ₃ .SiO ₂ has the same properties as mullite.

From these results, the composition having a large bending strength and a small relative permittivity is a composition in which the amount of SiO _{2 in} the flux is more than 80 wt% and the amount of mullite is 80 wt% when the amount of mullite is 70 wt%. %, The composition is such that the amount of SiO ₂ in the flux is more than 85 wt%. That is, the composition of the alkaline earth metal oxide (MgO) is 1 wt% or less.

Next, the ceramic insulating materials having these compositions were subjected to X-ray diffraction in order to identify the crystal phase in the sintered body. The amount of alkaline earth metal oxide (MgO) is 1
If more than wt%, Al ₂ O ₃
O and 2Al ₂ O ₃ · 2MgO · 5SiO ₂ are formed, but 3Al is formed at around 1600 ° C, which allows sufficient firing.
₂ O ₃ · 2SiO ₂ and Al ₂ O ₃ · SiO ₂ in addition to Al ₂ O _3,
It cannot be identified because many crystal phases composed of MgO and SiO ₂ are formed. Therefore, there is a problem that the firing shrinkage rate at each temperature is not constant and the variation is large.

On the other hand, alkaline earth metal oxide (MgO)
When the amount is 1 wt% or less, a large amount of SiO ₂ and Al ₂ O ₃ .MgO, 2Al ₂ O ₃ .2Mg added in the firing process.
O · 5SiO ₂ is possible, in 1600 around ℃ capable of performing baking enough, a 3Al ₂ O ₃ · 2SiO ₂ and Al ₂ O ₃ · SiO ₂ only becomes stable crystalline phases. Therefore, at a firing temperature higher than 1550 ° C., that is, at a temperature at which sufficient firing is possible, the crystal phase does not change and the firing shrinkage amount is stable. In addition, Nos. Similar results were obtained for the compositions shown in 29 to 56. That is, the total amount of alkali metal oxides and alkaline earth metal oxides is 1
When it is more than wt%, the bending strength is lower than 180 MPa or the relative dielectric constant is higher than 6.7. Also, the crystal phase after firing is not stable, and 3Al ₂ O ₃ · 2SiO ₂ and Al ₂
An unstable crystal phase was formed in addition to O ₃ · SiO ₂ .

On the other hand, when the total amount of the alkali metal oxide and the alkaline earth metal oxide was 1 wt% or less, the bending strength was 180 MPa or more and the relative dielectric constant was 6.7 or less. Also, the crystalline phase after firing is stable,
At firing temperatures above ℃, 3Al ₂ O ₃ · 2SiO ₂ and Al ₂
There were only two types of crystal phases of O ₃ · SiO ₂ . That is, the added alkali metal oxide and alkaline earth metal oxide are 3Al ₂ O ₃ .2SiO ₂ or Al ₂ O ₃ .Si.
Diffusively dissolved in the O ₂ crystal phase.

The coefficient of thermal expansion of the ceramic insulating material having the composition shown in Tables 1 to 40 is 40 to 60 × 10 ^-7 / ° C. (room temperature to 50).
The thermal expansion coefficient of tungsten used for the internal wiring conductor material is 45 × 10 ⁻⁷ / ° C. (room temperature to 500 ° C.).
C.), the thermal stress due to the difference in thermal expansion coefficient between the ceramic insulating material and the wiring conductor material was small, and no cracks were observed.

In the composition in which the total amount of the alkali metal oxide and the alkaline earth metal oxide is 1 wt% or less (Tables 1 to 3), the tensile strength of the Kovar pin is 4 kg / pin or more, which is a strength enough to endure actual use. Met. Also, the solder connection part of the semiconductor component is 2000 at -65 ° C to 150 ° C.
No disconnection occurred even after the temperature cycle above the cycle. The strength was sufficient to guarantee a sufficient connection life even under such severe use conditions. This is the coefficient of thermal expansion of silicon semiconductor used as a semiconductor component, 35 × 10 ^-7
/ ° C. (room temperature to 500 ° C.), and the thermal expansion coefficient of gallium-arsenic semiconductor is 65 × 10 ⁻⁷ / ° C. (room temperature to 500 ° C.).
This is because even in such a mixed wiring circuit ceramic substrate, the amount of expansion of the substrate and the semiconductor component when heated is small, and stress is not so much applied to the solder connection portion.

On the other hand, the signal propagation delay time due to the internal wiring conductor when the circuit board was multilayered was 8.4 ns / m or less. This value corresponds to the relative dielectric constant of the ceramic insulating material being 6.7 or less. Since the alumina-based ceramic insulating material is about 9.5% and the signal propagation delay time is 10.2 ns / m, according to the present embodiment, the signal propagation delay time is reduced by about 17% or more. It will be.

FIG. 9 is a configuration diagram of semiconductor device mounting using the substrate manufactured in the first embodiment of the present invention. 11: LSI chip, 12: substrate of the present invention, 13: CCB (solder 350
Up to 400 ° C.), 14: silicon carbide sealing body, 15: printed circuit board, 16: backboard (printed circuit board), 1
7: Solder (250 to 300 ° C.), 18: Cooling water, 1
9: Low temperature solder (150 to 200 ° C.).

[0057]

According to the present invention, mullite is a main component, and silicon dioxide, a composite oxide of aluminum oxide and silicon dioxide in a molar ratio of 1: 0.7 to 1, and an alkaline earth metal oxide. By using the contained ceramic substrate, there will be no cracks due to the difference in thermal expansion coefficient between the ceramic insulating material and the wiring conductor material, and there will be no cracks in the substrate caused by thermal stress and disconnection between the substrate and the semiconductor component. And the like, and a high-quality and highly reliable ceramic substrate for wiring circuits can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a wiring circuit ceramic substrate and an insulating module using the same, showing an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the amount of SiO ₂ in the flux and bending strength.

FIG. 3 is a diagram showing the relationship between bending strength and the amounts of SiO ₂ and Al ₂ O ₃ , respectively.

FIG. 4 is a diagram showing the relationship between the bending strength and the amounts of SiO ₂ and Al ₂ O ₃ , respectively.

FIG. 5 is a diagram showing the relationship between the amount of SiO ₂ in the flux and the relative dielectric constant.

FIG. 6 is a diagram showing the relationship between the relative dielectric constant and the amount of SiO ₂ .

FIG. 7 is a diagram showing the relationship between firing temperature and firing shrinkage.

8 is a graph showing the relationship between the Al ₂ O ₃ · SiO ₂ amount and the amount of Al ₂ O _3.

FIG. 9 is a configuration diagram showing an example of a mounting structure of a semiconductor device using the substrate of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ceramic insulating material of this invention, 2 ... Wiring conductor material, 3 ... Ceramic substrate for wiring circuits of this invention, 4 ...
Kovar pin, 5 ... Gold-indium solder, 6 ... Semiconductor component, 7 ... Solder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Shinohara 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi Ltd. Production Engineering Research Laboratory, Hitachi, Ltd.

Claims (3)

[Claims] 1. 70% mullite powder having an average particle size of 5 μm or less
3% by weight of silicon dioxide powder with an average particle size of 2 μm or more
A mixed powder containing 0% by weight or less, 15% by weight or less of aluminum oxide powder having an average particle size of 1 μm or less, and 1% by weight or less in total of at least one powder of an alkaline earth metal oxide and an alkali metal oxide. And a step of forming a conductor layer on the ceramic substrate, and a step of forming a conductor layer on the ceramic substrate. A method of manufacturing a ceramic substrate for a wiring circuit. 2. The firing temperature in the step of obtaining the ceramic substrate according to claim 1,
It is 550-1680 degreeC, The manufacturing method of the ceramic substrate for wiring circuits characterized by the above-mentioned. 3. The ceramic for a wiring circuit according to claim 1, wherein the powder of at least one of the alkaline earth metal oxide and the alkaline metal oxide is an alkaline earth metal oxide powder. Substrate manufacturing method.