JP2003002750A - Method for manufacturing low temperature fired ceramic substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the insulating property, the strength and the flatness of a low temperature fired ceramic substrate by restriction firing. SOLUTION: Green sheets 12 for restriction, which are not sintered at a sintering temperature of a low temperature firing green substrate 11, are laminated on both surface of the green substrate 11 and restriction-fired at 800-1000 deg.C, and then the green sheets 12 is removed. A resin having a lower pyrolysis temperature than that of a binder of the green substrate 11 is used as a binder of the green sheet 12. As a result, the binder of the green sheet 12 begins thermal pyrolysis to make the green sheet 12 porous before the binder of the green substrate 11 begins the thermal pyrolysis after the firing starts. Then, a gas produced by the pyrolysis of the binder of the substrate 11 is passed through the porous green sheet 12 and is discharged to the outside to prevent the gas produced by the pyrolysis from being confined in the substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a low-temperature fired ceramic substrate in which constraint green sheets are laminated on both surfaces of a low-temperature fired ceramic substrate (raw substrate) before firing and fired by constraint.

[0002]

2. Description of the Related Art In recent years, a constrained firing method has been developed as a firing method for reducing the firing shrinkage in the surface direction of the substrate when firing a low temperature fired ceramic substrate to improve the dimensional accuracy of the substrate. This constrained firing method uses a constrained green sheet (generally an alumina green sheet that is not sintered at the sintering temperature (800 to 1000 ° C.) of the low temperature fired ceramic on both surfaces of the low temperature fired ceramic multilayer substrate (raw substrate) before firing. (Used) is laminated and, in this state, after firing at 800 to 1000 ° C. with or without applying pressure to the green substrate,
The residue of the restraining green sheet is removed from both sides of the fired substrate by blasting or the like to produce a low temperature fired ceramic substrate.

[0003]

By the way, since the green substrate (green sheet laminated body) and the restraining green sheet contain a binder (resin) for ensuring the green strength, the restraint is performed after the start of restraint firing. When the temperature of the green sheet and the green substrate exceeds the thermal decomposition temperature of the binder, the binder is thermally decomposed and scattered to start "debinding".
At this time, if the firing proceeds while the pyrolysis gas of the binder of the raw substrate remains in the raw substrate, many voids are formed inside the fired substrate, and many carbon components remain in the fired substrate. As a result, there arises a problem that the insulating property and strength of the fired substrate are deteriorated or the surface of the substrate is swollen to deteriorate the flatness of the surface of the substrate. Therefore, in the constrained firing step, it is desirable that the pyrolysis gas of the binder of the raw substrate is not trapped inside the substrate.

However, in the constrained firing step, since the raw substrate is sandwiched between two constraining green sheets and fired,
In order to discharge the pyrolysis gas of the binder of the raw substrate to the outside, the pyrolysis gas of the binder of the raw substrate needs to pass through the restraining green sheet. For that purpose, the binding green sheet must be in a porous state at the time when the binder of the green substrate is thermally decomposed, but until the binder removal of the binding green sheet progresses, Since the voids between the ceramic particles in the green sheet are blocked by the binder, it is difficult for the pyrolysis gas to pass through the restraining green sheet.

Since such a situation has not been taken into consideration in the conventional restraint firing, the binder removal from the restraining green sheet (porosification) has not yet progressed sufficiently at the time when the binder of the green substrate is thermally decomposed. No, the passage of pyrolysis gas is bad. Therefore, the pyrolysis gas is confined inside the substrate and many voids are formed inside the fired substrate.
A lot of carbon components remain in the fired substrate, which may result in deterioration of the insulation and strength of the fired substrate, or swelling of the substrate surface, resulting in poor flatness of the substrate surface. was there.

The present invention has been made in view of the above circumstances, and therefore an object thereof is to improve the debinding property of a low temperature fired ceramic substrate when the low temperature fired ceramic substrate is restrained and fired. It is an object of the present invention to provide a method for manufacturing a low temperature fired ceramic substrate, which can improve the insulating property, strength, and flatness.

[0007]

To achieve the above object, the first aspect of the present invention provides a method for constraining firing of a low temperature fired ceramic substrate, wherein the binder of the constraining green sheet is a low temperature fired ceramic before firing. Substrate (raw substrate)
The resin whose thermal decomposition temperature is lower than that of the binder is used. In this way, after the binding firing starts, before the binder of the green substrate begins to thermally decompose, the binder of the binding green sheet begins to thermally decompose, the binding green sheet begins to become porous, and then the green substrate The binder begins to thermally decompose. For this reason, the binder pyrolysis gas of the substrate passes through the porous constraining green sheet at the time of constraining firing and is discharged to the outside, so that the pyrolysis gas is prevented from being trapped inside the substrate. As a result, voids and residual carbon components inside the fired substrate are significantly reduced, and the insulation, strength, and flatness of the fired substrate are improved.

In this case, it is preferable that an acrylic resin (butyl methacrylate copolymer) is used as the binder of the restraining green sheet and a butyral resin is used as the binder of the green substrate. By doing so, the thermal decomposition temperature of the binder (acrylic resin) of the restraining green sheet becomes 370 ° C., while the thermal decomposition temperature of the binder (butyral resin) of the green substrate is 440.
Since the temperature becomes 0 ° C, the difference between the thermal decomposition temperatures of the two becomes 70 ° C.
This difference in thermal decomposition temperature (70 ° C.) is sufficient to advance the thermal decomposition of the binder of the constraining green sheet to make the constraining green sheet porous before the binder of the green substrate begins to thermally decompose. This is the difference in thermal decomposition temperature that can secure the time, and the debinding property of the substrate can be more reliably improved.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A method of manufacturing a low temperature fired ceramic substrate according to an embodiment of the present invention will be described below with reference to FIG.

During firing, the low temperature fired ceramic green substrate 1
Laminating and pressing the restraining green sheets 12 on both sides of 1.
Restrained firing at 800 to 1000 ° C. At this time, the low temperature fired ceramic green substrate 1 is placed on the restraint green sheet 12 from above.
1 may be fired under pressure, or may be fired without pressure.

The low temperature fired ceramic green substrate 11 may be a single layer substrate, or may be a multilayer substrate in which a plurality of green sheets are laminated by a green sheet laminating method. As the low temperature firing ceramic material forming the low temperature firing ceramic raw substrate 11, for example, CaO—SiO ₂ —Al ₂ O ₃ —
B ₂ O ₃ based glass: 50-65% by weight (preferably 60
% By weight) and alumina: 50-35% by weight (preferably 4%)
0% by weight) is preferably used. Besides this, MgO
-SiO ₂ -Al ₂ O ₃ -B ₂ mixture of O ₃ based glass and alumina powder, a mixture of SiO ₂ -B ₂ O ₃ based glass and alumina, PbO-SiO ₂ -B ₂ O ₃ based glass and alumina It is also possible to use a low temperature fired ceramic material that can be fired at 800 to 1000 ° C., such as a mixture thereof with cordierite type crystallized glass. The low temperature fired ceramic green sheet is prepared by mixing the low temperature fired ceramic powder with a binder, a solvent (for example, toluene, xylene, butanol, etc.) and a plasticizer, which will be described later, and thoroughly stirring and mixing to prepare a slurry. The tape is formed by a doctor blade method using a slurry.

When the low-temperature-fired ceramic green substrate 11 is a multilayer substrate, Ag, Ag / Pd, Au, Ag / Pt are formed in the via holes punched in the green sheets of each layer before stacking the green sheets of each layer. , A low melting point metal conductor paste such as Cu is filled, and the inner layer conductor pattern is screen-printed on the green sheet laminated on the inner layer using the same low melting point metal conductor paste. Furthermore, the surface green sheet has a surface conductor pattern A
Printing is performed using a conductor paste of a low melting point metal such as g, Ag / Pd, Au, Ag / Pt, Cu. After this printing step, the green sheets of the respective layers are laminated, thermocompression-bonded, and integrated to manufacture the low-temperature-fired ceramic green substrate 11. still,
The surface layer conductor pattern may be printed after constrained firing.

On the other hand, the restraining green sheet 12 has a firing temperature (800 to 100) of the low temperature firing ceramic green substrate 11.
A high temperature sinterable ceramic powder (for example, alumina powder) that does not sinter at 0 ° C. is used, and this high temperature sinterable ceramic powder is mixed with a binder, a solvent (for example, toluene, xylene, butanol, etc.) and a plasticizer described later. Then, the slurry is prepared by sufficiently stirring and mixing, and the constraining green sheet 12 is tape-molded by using the slurry by a doctor blade method or the like.

As the binder of the restraining green sheet 12, a resin whose thermal decomposition temperature is lower than that of the binder of the low temperature fired ceramic green sheet (low temperature fired ceramic green substrate 11) is used. For example, the restraint green sheet 12
Acrylic resin as a binder of (Pyrolysis temperature: 370
C.) and a butyral resin (pyrolysis temperature: 440.degree. C.) as a binder for the low temperature fired ceramic green sheet (low temperature fired ceramic green substrate 11).

When the low-temperature firing ceramic green substrate 11 is constrained and fired using the constraining green sheet 12,
The constraining green sheets 12 are laminated on both front and back surfaces of the low-temperature fired ceramic green substrate 11, and the laminated body is, for example, 80-
Thermocompression bonding is performed under the conditions of 150 ° C. and 500 to 2500 N / cm ² . After that, firing is performed by one of the following two firing methods.

[Pressureless firing method] The firing temperature of the low temperature firing ceramic green substrate 11 is 8 without pressing the pressure-bonded body of the low temperature firing ceramic green substrate 11 and the restraining green sheet 12.
Bake at 00 to 1000 ° C.

[Pressure firing method] As shown in FIG. 1, a porous setter plate 1 in which a pressure bonded body of a low temperature fired ceramic raw substrate 11 and a restraining green sheet 12 is formed of alumina or the like.
It is sandwiched between 3 and pressed at a pressure of ^{20 to} 200 N / cm ² , and is fired at 800 to 1000 ° C. which is the sintering temperature of the low temperature fired ceramic raw substrate 11.

In either case of the pressureless firing method or the pressure firing method, after the firing is started, 5 to 20 ° C. is required in order to sufficiently remove the binder from the constraining green sheet 12 and the low temperature firing ceramic green substrate 11. 80 at a relatively slow rate of temperature increase per minute
The temperature is raised to 0 to 1000 ° C. In the present embodiment, since the thermal decomposition temperature of the binder of the constraining green sheet 12 is lower than the thermal decomposition temperature of the binder of the low-temperature fired ceramic green substrate 11, the low-temperature fired ceramic green substrate 11 is heated in the temperature rising process after the start of the constraint firing. Before the binder of No. 1 starts to thermally decompose, the binder of the constraining green sheet 12 starts to thermally decompose, and the constraining green sheet 12 starts to become porous,
After that, the binder of the low temperature fired ceramic green substrate 11 starts to be thermally decomposed. For this reason, the binder pyrolysis gas of the low temperature fired ceramic raw substrate 11 will be discharged to the outside through the porous constraining green sheet 12 during the constraining firing, and the pyrolysis gas will be trapped inside the substrate 11. Is prevented. As a result, voids and residual carbon components inside the fired substrate are reduced, and the insulation, strength, and flatness of the fired substrate are improved.

Assuming that the difference in the thermal decomposition temperature of the binder between the low temperature fired ceramic green substrate 11 and the restraining green sheet 12 is A (° C.) and the temperature rising rate after firing is B (° C./min), the restraint is performed. A / B (minutes) is the delay time from the start of thermal decomposition of the binder of the green sheet 12 for use to the start of thermal decomposition of the binder of the low temperature fired ceramic raw substrate 11.
Becomes Therefore, before the binder of the low temperature fired ceramic green substrate 11 begins to be thermally decomposed, the constraining green sheet 1
Green sheet for restraint 1 by thermally decomposing the binder of 2
In order to secure the time required to make 2 porous,
Pyrolysis temperature difference A (° C) and / or heating rate B (° C /
Minutes).

In both the pressureless firing method and the pressure firing method, the binding green sheets 12 (high temperature sinterable ceramics such as alumina) laminated on both surfaces of the low temperature firing ceramic raw substrate 11 are 1500 ° C. or more. Since it does not sinter unless it is heated to 1, the green sheet 12 for restraint is left unsintered if it is fired at 800 to 1000 ° C. However, during the firing process, organic substances such as the binder in the restraining green sheet 12 are thermally decomposed and scattered to remain as ceramic powder.

After firing, the residue (ceramic powder) of the restraining green sheet 12 attached to both sides of the fired substrate is removed by blasting, buffing or the like. This completes the manufacture of the low temperature fired ceramic substrate.

[0022]

EXAMPLE The present inventor has made a low-temperature fired ceramic green substrate 11
A test was conducted to examine the effect of the magnitude of the thermal decomposition temperature of the binder of the restraint green sheet 12 on the insulation, strength, and flatness of the fired substrate. The test results are shown in Tables 1 and 2 below. Show.

[0023]

[Table 1]

[0024]

[Table 2]

In Examples and Comparative Examples shown in Tables 1 and 2, a low temperature fired ceramic green sheet (green substrate) and a constraining green sheet having the same composition except for the type of binder were used.

The low temperature fired ceramic green sheets used in the examples and comparative examples are both CaO--SiO ₂ --Al ₂
O ₃ -B ₂ O ₃ based glass: 60% by weight alumina: 40
It is a low-temperature fired ceramic green sheet consisting of a mixture with a weight percentage, and the binder content is ceramic: 1
15 parts by weight with respect to 00 parts by weight.

The restraining green sheets used in the examples and comparative examples are both alumina green sheets, and the binder content is 1 with respect to 100 parts by weight of ceramic.
5 parts by weight.

In the examples, an acrylic resin (pyrolysis temperature: 370 ° C.) was used as the binder of the constraining green sheet, and a butyral resin (pyrolysis temperature: 440 ° C.) was used as the binder of the low temperature firing ceramic green sheet. Therefore, in the example, the thermal decomposition temperature of the binder of the constraining green sheet is 70 ° C. lower than the thermal decomposition temperature of the binder of the low temperature firing ceramic green sheet.

On the other hand, in the comparative example, butyral resin (pyrolysis temperature: 44) was used as the binder of the restraining green sheet.
Acrylic resin (thermal decomposition temperature: 370 ° C) as a binder for low temperature fired ceramic green sheets
Was used. Therefore, in the comparative example, contrary to the example, the thermal decomposition temperature of the binder of the restraining green sheet is 70 ° C. higher than the thermal decomposition temperature of the binder of the low-temperature fired ceramic green sheet.

In each of the example and the comparative example, a green substrate was prepared by laminating four low temperature fired ceramic green sheets, and a restraining green sheet was laminated on both front and back surfaces of the green substrate, and the green substrate was laminated at 100 ° C. After thermocompression bonding under the conditions of 1000 N / cm ^2, the pressure bonded body is sandwiched between porous setter plates, and heated up to 900 ° C. which is the sintering temperature of the green substrate at a heating rate of 2 ° C./min. Firing was performed while applying a pressure of 50 N / cm ² .

In the embodiment, since the thermal decomposition temperature of the binder of the restraining green sheet is lower than the thermal decomposition temperature of the binder of the green substrate by 70 ° C., the binder of the green substrate is changed in the temperature rising process after the firing is started. Before the thermal decomposition starts, the binder of the constraining green sheet begins to thermally decompose, the constraining green sheet begins to become porous, and then the binder of the green substrate begins to thermally decompose.

At this time, since the difference in thermal decomposition temperature is 70 ° C. and the heating rate is 2 ° C./minute, the binder of the restraining green sheet begins to thermally decompose and then the binder of the green substrate begins to thermally decompose. There is a delay time of 35 minutes, and within this time, the thermal decomposition of the binder of the restraint green sheet progresses sufficiently, the restraint green sheet becomes sufficiently porous, and the restraint green sheet is pyrolyzed. The binder on the raw substrate begins to thermally decompose after the state where it easily passes through. Therefore, the binder pyrolysis gas of the raw substrate is
It is possible to prevent the pyrolysis gas from being trapped inside the substrate after being discharged through the porous green sheet for restraint, and to prevent the formation of voids inside the fired substrate.

On the other hand, in the comparative example, contrary to the example, since the thermal decomposition temperature of the binder of the restraining green sheet is 70 ° C. higher than the thermal decomposition temperature of the binder of the low temperature firing ceramic green sheet, the firing is started. After the thermal decomposition of the binder on the green substrate during the subsequent temperature raising process,
After a delay, the binder of the restraining green sheet begins to thermally decompose. Therefore, at the time when the binder of the green substrate is pyrolyzed, debinding (making porous) of the restraining green sheet has not progressed at all, and the pyrolysis gas does not pass easily. As a result, the pyrolysis gas is confined inside the substrate and many voids are formed inside the fired substrate.

After constrained firing, the amount of generated voids, specific gravity and bending strength of the fired substrate were measured. As shown in Table 2 above, no voids having a diameter of 5 μm or more were generated in the fired substrate in the examples. However, in the comparative example, many voids having a diameter of 5 μm or more were generated in the fired substrate. From this test result, it was confirmed that in the example, the specific gravity of the fired substrate was higher and the transverse rupture strength was considerably higher than in the comparative example.

In other words, there is a relation that the larger the void amount in the fired substrate, the smaller the specific gravity of the fired substrate and the lower the bending strength, and the larger the void amount in the fired substrate, the higher the insulation of the fired substrate. And the flatness are reduced. Therefore, from the test result of this time, it is understood that the example has excellent insulation, strength, and flatness of the fired substrate as compared with the comparative example.

The constraining green sheet is not limited to the alumina green sheet, but may be aluminum nitride (Al
It is also possible to use a green sheet of other high temperature sinterable ceramic such as N).

[0037]

As is apparent from the above description, according to claim 1 of the present invention, the thermal decomposition temperature of the binder of the constraining green sheet used for constraining firing of the low temperature fired ceramic substrate is set to that of the raw substrate. Since it is lower than the thermal decomposition temperature of the binder, after the binding firing starts, before the binder of the raw substrate begins to thermally decompose, the binding of the binding green sheet begins to thermally decompose and the binding green sheet starts to become porous. It is possible to prevent the pyrolysis gas from being trapped inside the substrate, and to improve the insulation, strength, and
Both flatness can be improved.

In the second aspect, since the acrylic resin is used as the binder of the restraining green sheet and the butyral resin is used as the binder of the green substrate, the difference in thermal decomposition temperature between the two binders is 70 ° C. It is possible to secure a sufficient delay time from the start of thermal decomposition of the binding green sheet binder to the start of thermal decomposition of the raw substrate binder, and before the raw substrate binder begins thermal decomposition. In addition, the restraining green sheet can be made porous more reliably.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a state of a low temperature firing ceramic substrate during constrained firing according to an embodiment of the present invention.

[Explanation of symbols]

11 ... Low temperature fired ceramic raw substrate, 12 ... Restraint green sheet, 13 ... Porous setter plate.

Claims (2)

[Claims] 1. A green sheet for restraint which is not sintered at a sintering temperature of the low temperature fired ceramic substrate is laminated on both surfaces of the low temperature fired ceramic substrate before firing and is fired with or without pressure. In the method for producing a low-temperature fired ceramic substrate by removing the residue of the constraint green sheet after restraint firing, the binder contained in the restraint green sheet is more than the binder contained in the low-temperature fired ceramic substrate before firing. A method for producing a low-temperature fired ceramic substrate, characterized in that a resin having a low thermal decomposition temperature is used. 2. The low temperature fired ceramic substrate according to claim 1, wherein an acrylic resin is used as a binder of the restraining green sheet, and a butyral resin is used as a binder of the low temperature fired ceramic substrate before firing. Method.