JPS6330359A - Manufacture of ceramic green sheet - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (7) Technical field The invention relates to a method for manufacturing a ceramic green sheet.

Ceramic green sheets are produced by adding and mixing a sintering aid, an organic binder, and an organic solvent to ceramic powder, forming the mixture into a sheet, removing the organic binder, and then firing.

The organic binder is used to shape the ceramic powder into any desired shape, and once it is formed into a sheet,
It should be removed. Since it is a type of organic substance, it can be removed by heating, but it is desirable that it can be removed by low-temperature heating and that it is completely removed.

If the organic binder is fired while remaining, voids may occur,
This is because the thermal conductivity becomes low.

Furthermore, the ceramics used for ceramic green sheets include oxide ceramics such as Al2O3, but also non-oxide ceramics such as AIN, TiN 1TiC%Si, and N4.

(a) Prior Art Conventionally, polyvinyl butyral (PVB) and cellulose-based organic materials have been widely used as organic binders for producing ceramic green sheets.

However, PVB1 cellulose and the like have the disadvantage that their thermal decomposition temperature is high and they leave a large amount of carbon as a decomposition residue.

Non-oxide ceramics, such as AIN, TiN,
TiC.

In the case of Si3N4, etc., after forming into a green sheet, the organic binder is removed in some cases in the air or in a non-oxygen atmosphere.

Thermal decomposition of the organic binder in the atmosphere has the advantage that carbon as a decomposition residue can be completely removed.

However, since the non-oxide ceramic is heat-treated at a fairly high temperature in the air, the ceramic is easily oxidized and its properties deteriorate. This is a drawback due to the high thermal decomposition temperature of PVB and cellulose-based organic binders.

A non-oxidizing atmosphere means that the process is carried out in N2 or Ar gas. Pyrolysis treatment in these gases can prevent oxidation of the ceramic. but,
On the other hand, carbon residue cannot be completely removed. For this reason, foaming, cracking, etc. are likely to occur after firing.

In addition, strength properties are significantly impaired. In addition, thermal conductivity also deteriorates.

The above is PVB for non-oxide ceramics.

This was a problem when using a cellulose-based binder.

There were also difficulties with oxide ceramics.

A typical example of oxide ceramic is alumina A4□0
It is 3. Alumina is widely used as a substrate for electronic circuits, a material for IC packages, and the like.

These can be made by firing a simple ceramic plate and then adding a metal film to it.

Instead, firing the ceramic and forming the metal film may be performed simultaneously. This is called co-fired metallization.

In this case, the metal as the metallization layer is, for example, WlM
o -Mn, etc. Since it is a metal, it is easily oxidized.

To prevent metal oxidation, the organic binder is removed by thermal decomposition in a wet reducing atmosphere. In this way, a large amount of organic binder in the sheet formed into a green sheet is not completely removed. It remains in the sheet as carbon. After this, it is fired at a higher temperature. As a result, foaming and cracking are likely to occur, and even if this is not the case, the ceramic becomes weak in strength. In addition to strength, properties such as dielectric constant and thermal conductivity will be severely affected.

As described above, the conventionally used PVB and cellulose-based organic binders have various drawbacks because their thermal decomposition temperatures are too high.

Any oxide ceramic can be used as long as it can be thermally decomposed while being oxidized at a high temperature, but if it is not, it cannot be suitably used.

In the end, it was difficult to completely remove carbon, and in order to remove carbon, the organic binder had to be removed at high temperature in an oxidizing atmosphere.

(1) Problems to be Solved by the Invention Conventional organic binders have a problem in that they cannot be completely removed unless they are thermally decomposed at high temperatures after sheet forming.

If it is possible to find an organic binder for producing green sheets that thermally decomposes at a relatively low temperature regardless of atmospheric or non-oxidizing atmosphere and does not leave any carbon residue after thermal decomposition, its utility value would be extremely large.

Reiterating the conditions required for the organic binder, (a)
Complete thermal decomposition at relatively low temperatures regardless of atmospheric or non-oxidizing atmosphere.

(b) No carbon remains as a decomposition residue.

These are two conditions.

Q. Purpose: By finding an organic binder that completely thermally decomposes at a relatively low temperature and leaves no carbon as a decomposition residue when removing the organic binder, regardless of whether it is in the air or a non-oxidizing atmosphere. It is an object of the present invention to provide a method for producing a good ceramic fired body.

(6) Method of the Invention The present invention is based on the use of polyisobutylene as an organic binder in the production of ceramic green sheets. The organic binder is novel.

The present invention uses polyisobutylene as an organic binder, and forms a ceramic sheet using a slurry obtained by mixing ceramic powder and, if necessary, a sintering aid and an organic solvent. This is a green sheet manufacturing method.

The amount of polyisobutylene to be blended is not particularly limited. It is acceptable as long as it is within the range that allows for good production and processing of green sheets.

About 10 to 60 vol% of polyisobutylene is added to the total of the ceramic powder and the sintering aid added as needed. In particular, a range of 30 to 50 vol% is desirable.

Polyisobutylene alone may also be used. Further, polyisobutylene may be used together with other plasticizers, peptizers, etc. It can likewise serve as an organic binder.

In addition to this, a solvent is required. The present invention does not particularly limit the solvent. A solvent consisting of one or a combination of two or more of conventionally used benzene, toluene, trichlene, alcohols, etc. can be used.

There are also no restrictions on the ceramic powder used.

The present invention can be used with any ceramic powder. AN203, Zr01 as oxide ceramic
Ceramic powders such as BaTiO3 can be used. As a non-oxide ceramic, AIN 1TiN 1
It can also be used for ceramic powders such as TiC1SiC and Si3N4. Furthermore, it can also be used for ceramic powder made of a mixture of two or more of these.

A conventional doctor blade method may be used to form the slurry into a sheet.

(9) Function Polyisobutylene, like conventional organic binders, enables fluidized ceramic powder to be shaped into any desired shape. In this case, it is formed into a sheet shape, but in the function of shaping it into a sheet shape, conventional PVB
It is equivalent to

The problem is thermal decomposition.

The thermal decomposition curves of polyisobutylene used in the present invention and PvB are shown in FIG.

The horizontal axis is the temperature of thermal decomposition. The vertical axis is the weight loss of organic binder. This figure shows the relationship between temperature and weight loss for thermal decomposition in the atmosphere and thermal decomposition in N2.

Since carbon is oxidized in the atmosphere, thermal decomposition proceeds even at lower temperatures. Since carbon is not oxidized in N2, it will only decompose at higher temperatures.

First, let's compare thermal decomposition in the atmosphere.

The temperature at which PVB is completely thermally decomposed in the atmosphere is 600°C.
It is. The temperature is high.

Polyisobutylene is completely thermally decomposed at 350° C. in air. The temperature is extremely low. Furthermore, no carbon remains as a decomposition residue. As described above, the complete thermal decomposition temperature in the atmosphere varies from 250°C to 600°C for J2 and 850°C for polyisobutylene.

Thermal decomposition in an N2 atmosphere will be explained.

Thermal decomposition of PVB in N2 atmosphere is not complete even at 600°C. It is not completely thermally decomposed even at 660°C.

Pyrolysis of polyisobutylene in Nzff atmosphere, 42
The entire process is carried out at 0°C. 250 compared to traditional PVB
It is completely thermally decomposed at temperatures lower than ℃. Even at such a low temperature and in a N2 atmosphere, no carbon remains as a decomposition residue.

The temperature in the organic binder removal process for ceramic green sheets using polyisobutylene was 350°C in the atmosphere and N2
Inside temperature is 420℃. This can be done at a much lower temperature than when conventional P'/B is used. Further, it has the effect of not leaving any carbon as a decomposition residue.

At 350° C. in air, polyisobutylene is completely removed. At temperatures above 350°C, polyisobutylene is completely removed.

Even at 340°C, it is almost completely removed.

In comparison, conventional PVB must be heated above 600°C.

In other words, 340°C to 600°C has been newly established as a temperature range in which the organic binder can be removed in the atmosphere.

Similarly, polyisobutylene can be completely thermally decomposed at 420° C. or higher in an N2 atmosphere. Even at 410°C, it was almost completely removed.

In an N2 atmosphere, PVB cannot be completely removed even at 650°C.

Therefore, in the present invention, a new range of 410° C. to 650° C. has been obtained as a temperature range in which the organic binder can be removed in an N2 atmosphere.

(e) Effects Polyisobutylene is heated at 350°C in the atmosphere and at 42°C in N2.
Complete thermal decomposition at 0°C.

Therefore, when polyisobutylene is used as an organic binder, the following effects can be obtained.

(a) When the ceramic is a non-oxide ceramic and the oxidation temperature of the ceramic is higher than 850°C, the organic binder can be completely removed in the atmosphere. PV
When using B, N! It had to be done inside, and the removal was incomplete.

cb> When the ceramic is a non-oxide ceramic and the oxidation temperature of the ceramic is lower than 350° C., the organic binder is removed in a non-oxidizing atmosphere, such as an N2 atmosphere. The temperature for decomposition may be 420°C. Even in this case, no carbon remains in the green sheet. Therefore, a good ceramic fired body can be obtained through the firing process.

(C) When performing co-fired metallization on oxide ceramics, a non-oxidizing atmosphere (N2,
Remove the organic binder with Ar). Even in this case, unlike PVB, there is no carbon as a decomposition residue, so a good ceramic fired body can be obtained through the firing process.

Example I (+) AIN powder 93wtz (11) Sintering aid 011) for 100 parts by weight of ceramic powder consisting of 2wt%
A slurry was prepared by mixing 15 parts by weight (++++) of polyisobutylene and 100 parts by weight of a luene-isopropyl alcohol mixed solution, and an AIN green sheet with a thickness of 0.8 M was prepared by a doctor blade method.

The above AIN green sheet was punched out into a flat plate of 5cIRX5. This flat plate was placed in an electric furnace, maintained at 350° C. under an atmospheric atmosphere of latm, and heated for 3 hours to thermally decompose and remove polyisobutylene.

At this time, the weight of the flat plate was measured. You can see that polyisobutylene has been completely removed.

Furthermore, carbon analysis was conducted and it was found that no carbon remained in the flat plate.

Next, this flat plate was heated to 1900°C in a N2 atmosphere at latm.
, and baked for 3 hours.

In this way, an AIN fired body was obtained.

This AIN fired body had a density of a, 25 g/d. The surface was shiny. It was a good fired product with no surface roughness.

The thermal conductivity was 140 W/mK.

The unit of thermal conductivity is often cad/cIRsec tE, but the thermal conductivity of materials such as ceramics is W.
/mK is more often expressed as ruko. o 1 cab/se
c = 4.2W.

There are 100 tM = 1772 te, so l cal/c
msec'C=420W/mW.

i) Example ■ A 7'4 AIN green sheet obtained in the same manner as in Example I was heated in an electric furnace at 420°C in a N2 atmosphere atm.
The mixture was heated for 3 hours to thermally decompose and remove the organic binder polyisobutylene.

When the weight was measured, it was found that the polyisobutylene had been completely removed. Carbon analysis revealed that no carbon remained at all.It was fired under the same conditions as in Example I. As a result, a good fired product was obtained. Density is 3.2
At 4 g/-j, the surface was glossy and had no surface roughness.

Thermal conductivity is 140 W/mK and 0 Example 1. 1 at 350 °C in air atmosphere and 42 °C in N2 atmosphere.
It can be seen that polyisobutylene can be completely thermally decomposed and removed by heating at 0°C, and a good fired product can be obtained by subsequent firing.

Next, an example in which conventionally used PVB and dibutyl phthalate are used as the organic binder will be described for comparison.

(B) Comparative Example I (+) AIN powder 98% (11) Sintering aid O++) for 100 parts by weight of ceramic powder consisting of B
12 parts by weight of p V B 3 parts by weight of dibutyl phthalate (111 liters) 100 parts by weight of a mixed solution of toluene and isopropyl alcohol were mixed to prepare a slurry, and a 0.8-thick AdN green sheet was prepared by a doctor blade method.

The above AIN green sheet was punched out into a flat plate of 5 art x 5α.

This flat plate was placed in an electric furnace, and in the atmospheric atmosphere of L ATM.
The mixture was heated at 600° C. for 3 hours, and 6 pv'g and dibutyl phthalate were removed by thermal decomposition using the organic binder.

At that time, we measured the weight and found that the organic binder had been completely removed.

Carbon analysis revealed that there was no carbon left at all.

However, X-ray diffraction revealed that the AβN powder was oxidized and a part of it was converted to AN 20 g. this is,'
This is because the temperature for thermal decomposition is 600°C, which is too high.

Next, this flat plate was heated to 1900 in N2 atmosphere at latm.
The AIN fired body thus obtained had no problems in terms of appearance. However, the thermal conductivity is 7
QW/mK, which was a very low value.

This comparative example shows that because the thermal decomposition temperature is too high, part of the AIH is oxidized partly because it is in the atmosphere. All binding materials have been removed, so there are no problems with strength or roughness.

However, a part of AIH is replaced by A (bos), and Al2O2 has a low thermal conductivity (approximately 4Q W/mK), resulting in a low thermal conductivity as a whole.

When used for semiconductor substrates, materials with low thermal conductivity are undesirable.

(2) Comparative Example■ A green sheet was prepared under the same conditions as Comparative Example I, and the organic binder was removed using an electric furnace with N atm.
The test was carried out by heating at 600° C. for 3 hours in a 2 atmosphere.

The atmosphere simply changes from air to N2.

As a result of weight measurement and carbon analysis, it was found that approximately 2% of the organic binder remained as carbon.

Next, firing was performed under the same conditions as in Comparative Example 1.

Surface roughness and surface microfoaming were observed. This is a big problem in terms of appearance. Well, the thermal conductivity is as low as 5Q W/mK. These defects are caused by firing with carbon remaining.

[Brief explanation of drawings]

Figure 1 shows polyisobutylene used as an organic binder in the present invention and PV conventionally used as an organic binder.
Atmospheric atmosphere with B (polyvinyl butyral), N2
A graph showing a thermal decomposition curve in a medium atmosphere. The horizontal axis is temperature■)
, the vertical axis is the organic binder weight loss. The solid line shows the measured values for polyisobutylene, and the broken line shows the measured values for PVB.

Claims (7)

[Claims] (1) Mix ceramic powder, a sintering aid added as necessary, an organic binder, and an organic solvent, form a sheet using the resulting slurry, and heat the organic binder. A method for producing a ceramic green sheet characterized by using polyisobutylene as an organic binder in the method for producing a ceramic green sheet by decomposition and removal. (2) Thermal decomposition temperature in air is 340℃~600℃
The method for producing a ceramic green sheet according to claim (1), characterized in that the temperature is .degree. (3) Thermal decomposition temperature in non-oxidizing atmosphere is 410℃~65℃
A method for manufacturing a ceramic green sheet according to claim (1), characterized in that the temperature is 0°C. (4) The method for producing a ceramic green sheet according to claim (1), characterized in that the amount of polyisobutylene blended is 10 to 60 vol% with respect to the total of the ceramic powder and the sintering aid. (5) The method for producing a ceramic green sheet according to claim (4), characterized in that the amount of polyisobutylene blended is 30 to 50 vol% with respect to the total of the ceramic powder and the sintering aid. (6) Ceramic powder is Al_2O_3, ZrO, Ba
TiO_3, AlN, TiN, TiC, SiC, Si
Claim No. 3 (
1) Ceramic green sheet manufacturing method described in section 1). (7) Ceramic green according to claim (1), wherein the organic solvent is one or a combination of two or more selected from benzene, toluene, trichlene, alcohols, etc. Seat manufacturing method.