JPH06256067A - Compound for joining ceramic - Google Patents

Abstract

PURPOSE:To provide a compound for joining ceramics, capable of strongly joining the various ceramics in a simple process, and capable of forming joined layers and joined products having sufficient joining strengths also in processes before calcination and in calcination processes and excellent in high purity, heat resistance, high chemical resistance, etc. CONSTITUTION:A compound used for joining ceramics and formed by kneading a polysilazane compound and a polycarbosilazane compound with ceramic powder and a solvent is used as a joining material for the ceramics, the polysilazane compound and the polycarbosilazane compound being known as the precursors of silicon carbide(SiC) and silicon nitride(SiN).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a wide range of ceramics such as silicon, silicon carbide, silicon nitride, aluminum nitride and non-oxide ceramics such as composites thereof, and oxide ceramics such as alumina, zirconia and mullite. The present invention relates to a compound suitable for joining and filling those voids.

[0002]

2. Description of the Related Art Ceramics have advantages such as high heat resistance and solidity, are chemically inert, and can be prepared with extremely high purity, and are used in various fields as advanced materials. . Generally, the processing of these ceramics is performed at the stage of forming the material before firing. But,
Since a large volume change occurs before and after firing the ceramic molded body, it is difficult to improve the dimensional accuracy only by processing before firing. Therefore, it can be reprocessed to obtain a desired shape and accuracy after firing, but the shape and size of ceramics are limited because they are solid, brittle and poor in workability as described above.

Further, it has been conventionally practiced to form a complex shaped body or a large-sized product by assembling and joining the respective component materials divided so as to form a desired ceramic shaped body. In this case, if the respective ceramic fired component materials cannot be joined in a predetermined shape or the like while maintaining the advantages of ceramics excellent in heat resistance and chemical durability, the original utility value as ceramics is impaired. Therefore, various methods having heat resistance have been carried out as ceramics joining methods. For example, there are a joining method using solder glass and a metal joining method using metallizing. Further, a part of cement-based inorganic material such as alumina cement is also used as a high heat resistant bonding material.

[0004]

However, the materials applicable to both the solder glass bonding method and the metal bonding method are limited, and the heat resistance and the corrosion resistance are not sufficient. Moreover, in addition to requiring advanced technology when joining,
The shape of the joint is also limited to a simple shape. Further, the inorganic material-based bonding material has an advantage that it can be fixed at room temperature, but in order to have fire resistance, it is usually necessary to bake at a high temperature of 1000 ° C. or higher, and the fixing force is remarkably reduced in the baking process, cracks, etc. It was often generated and damaged, and it could only be used for extremely limited materials and applications.
Further, the inorganic material-based bonding material often contains various elemental components as components and impurities, and it may not be possible to achieve a predetermined high degree of purification.

In view of the present situation of the above-mentioned conventional ceramics joining method, the present invention can firmly join various ceramics in a simple process, has sufficient joining strength before and during firing, and The purpose is to provide a ceramic bonding material capable of forming a bonding layer and a bonded body excellent in high purity, high heat resistance, high chemical resistance, and the like, that is, a compound for ceramic bonding, and further firmly fix it. The object is to easily form a large-sized ceramic product and a complex shaped body that are joined and integrated.

The present inventor has completed the present invention as a result of various studies on the requirements as a bonding material for achieving the above object, and in particular as a result of intensive studies so as to satisfy the following two points. That is, (1) the bonding material is a bonding material capable of exhibiting a sufficiently strong bonding force at room temperature during bonding and maintaining the bonding force even during the firing process. In other words, there is no risk of the joints coming off during the firing process, and no special firing jig is required. Further, there is no restriction on the shape or size of the bonded body. Further, in some cases, the firing step after joining can be omitted by setting the operating temperature of the ceramic joined body in the firing temperature range. (2) As the ceramic bonding material that requires high purity, for example, contaminants such as transition metals and alkali metal ions should not be included as components or impurities.
Ceramics are very often used in high-purity applications such as electronic parts and semiconductor element manufacturing members. In these applications, the above contaminants do not mix even in the manufacturing process and processing stage of raw materials and ceramics. Need to do so. Therefore, when the joined ceramic joined body is used particularly for the treatment of semiconductor elements, Si, O, N, C, H
All other elements are pollutants and should be reduced as much as possible.

[0007]

According to the present invention, there is provided a compound for ceramic bonding which comprises a polysilazane compound, a polycarbosilane compound, a ceramic powder and a solvent.

[0008]

The present invention is constituted as described above, and polysilazanes and polycarbosilane compounds are dissolved in a predetermined solvent to form an adhesive solution, and the solution is applied to the joint portion of the ceramics to be joined. The ceramics can be easily fixed and joined by drying, and the fixing force can be maintained even during the subsequent firing. In addition, the polysilazanes and polycarbosilane compounds can be heated in an inert gas or oxygen-containing gas atmosphere to produce SiN, SiC, SiO depending on the atmosphere.
It is possible to produce a heat-resistant and chemically stable compound such as N, Si, and SiO ₂ and form a firm bonding layer with the mixed ceramic powder to obtain a strong bonded body of ceramics. In addition, polysilazanes and polycarbosilane compounds can be chemically synthesized, can be easily purified, do not contain polluting elements harmful to semiconductors, etc., as a bonding material for various ceramics such as semiconductor members, It does not become a pollution source.

The present invention will be described in detail below. The polysilazanes and polycarbosilane compounds used in the present invention are well known as precursors of silicon carbide (SiC) and silicon nitride (SiN). As the polysilazanes, compounds generally used as precursors of SiN or SiC, such as polymers of various molecular weights of perhydropolysilazane and various polymers of methylpolysilazane, can be used.
Further, polycarbosilanes are [RR'SiCH ₂ ] _n
(However, R and R ′ are R ≠ R ′, and H, CH ₃ , C ₆
It is one of H ₅ . A compound represented by the general formula (n = 5 to 5000 or more) and conventionally used as a precursor of SiC can be used.

According to the knowledge of the inventor, both of the above polysilazanes and polycarbosilane compounds have a certain degree of fixing force at room temperature when they are dissolved in an organic solvent such as xylene and then the solvent is removed. The sticking force changes as the temperature rises. That is, the relationship between the temperature and the bonding strength was experimentally examined for each of the polysilazane compound, the polycarbosilane compound, and the mixture of both ratios of about 1: 1. The results are shown schematically in FIG. According to FIG. 1, the adhesion force of the polysilazane compound, that is, the adhesive strength is about 100 to 200.
Almost disappeared at ℃, but increased sharply from around 200 ℃,
The rate of increase decreases from around 500 ° C, 900 to 10
At 00 ° C., it again tends to rise. The polysilazane compound is a solid to viscous liquid at around room temperature depending on its type and degree of polymerization, and when the temperature rises, a low-viscosity liquid is generated and a decomposition reaction occurs to form an extremely brittle gel, which reduces the adhesive strength. . At 200 ° C or higher, the polymerization progresses and the gel solidifies to increase the adhesive strength, but from around 500 ° C, the thermal decomposition is intense and a large amount of organic substances are desorbed and the residue becomes porous, so the increase in the adhesive strength becomes slow. . Also,
It is estimated that at about 900 to 1000 ° C., the thermal decomposition reaction is completed, the inorganic compound produced is sintered and crystallized, and the adhesive strength is further rapidly increased.

On the other hand, the polycarbosilane compound loses its sticking force at about 200 to 400 ° C. as shown in FIG. 1, but at about 400 ° C. or higher, the sticking force increases with temperature.
When it exceeds 00 ° C, the rate of increase in strength becomes small, and like the polysilazane compound, it tends to rise again at 900 to 1000 ° C. Most of the polycarbosilane compounds are solid at around room temperature, and are usually stable up to around 200 ° C. and the adhesive strength is maintained. However, when the temperature is raised to 200 ° C. or higher, it becomes a low-viscosity liquid and a polymerization reaction starts to occur, and the adhesive strength is lost. However, at 400 ° C. or higher, the polymer is polymerized and the adhesive strength increases with temperature. In addition, since gelation reaction does not usually occur, the strength is higher than that of polysilazane. When the temperature exceeds 600 ° C, the rate of increase in strength decreases because the thermal decomposition reaction of the solidified substance progresses to become porous, as in the case of polysilazane, but the adhesive strength is re-heated when the thermal decomposition reaction is completed at about 900 to 1000 ° C. Rises sharply with.

On the other hand, as is apparent from FIG. 1, when the polysilazane compound and the polycarbosilane compound are used alone, a temperature range in which the sticking force almost disappears appears during the temperature rise. It can be seen that when the two are mixed and used, the adhesive strength exceeding the average value of the both is obtained in almost the entire temperature range. The reason for this is not clear, but the adhesion of polysilazane is lost 100 to 20
At around 0 ° C., polycarbosilane solidifies or is a highly viscous liquid, which prevents gelation of polysilazane,
In addition, the polymerization reaction progresses in the direction in which the polymer is polymerized and the viscosity increases, so that the fixing force does not decrease. On the other hand, in the vicinity of 200 to 400 ° C., where the polycarbosilane has no adhesiveness, the polycarbosilane melted in the polymerized and solidified polysilazane acts as a plasticizer to compensate brittleness and increase strength. At a high temperature of 600 ° C. or higher, rapid decomposition of gas does not occur as a whole because the decomposition temperatures of both are different, and solidification is completed without destroying the structure. Moreover, since the properties of the reaction product are different between the two, it is considered that the interaction due to the complexation contributes to the increase in the sticking force.

As described above, a predetermined high adhesive strength can be maintained over the entire application temperature range due to the interaction caused by the combined use of both the polysilazane compound and the polycarbosilane compound in the present invention. In the present invention, the polysilazane compound and the polycarbosilane compound are each added to the other compound in an amount of 5% by weight or more, and the weight ratio is 1: 0.05 to 40, preferably 1: 100.
It is preferable to use a mixture of 0.1 to 20.

In the ceramic bonding compound of the present invention, ceramic powder is further added and mixed to the mixture of the polysilazane compound and the polycarbosilane compound. As the ceramic powder to be added, it is preferable to use a ceramic powder of the same type as the ceramic to be joined or a different ceramic powder having a thermal expansion coefficient matching that of the ceramic to be joined within a predetermined range. When the ceramic bonding compound is composed only of the mixture of the polysilazane compound and the polycarbosilane compound, a good bonded body can be obtained when the bonding surface of the ceramics is extremely small, but peeling occurs when the area is large, which is good. It was difficult to obtain a bonded body. The inventor has found that the main cause is that these compounds change to compounds such as SiN, SiC, and SiO ₂ during firing of ceramics after joining, and at that time, organic substances such as hydrogen and hydrocarbons are released or burned and volatilized. It was found that volume contraction occurs and gaps and cracks occur at the joints. INDUSTRIAL APPLICABILITY In the present invention, by adding ceramic powder to a mixture of a polysilazane compound and a polycarbosilane compound, it is possible to reduce the volume shrinkage at the time of firing and improve the bonding strength. .

In the present invention, if a ceramic powder of the same type as the ceramic to be bonded is used, a particularly good bonded state can be obtained. It is presumed that the difference in thermal expansion between the bonding layer and the ceramics to be bonded is eliminated, so that the thermal strain of the ceramic bonded body is reduced. Further, a bonded body having a high bonding strength can be obtained even if the ceramic powder is not the same as the ceramics to be bonded, but has a similar thermal expansion coefficient or a ceramic powder having a difference of 1 × 10 ⁻⁶ or less. The ceramic powder of the same kind as the ceramics to be joined, which is added to the mixture of the polysilazane compound and the polycarbosilane compound, means the same ceramic powder as the ceramics to be joined. For example, for joining silicon, silicon powder, S
SiC powder is used for iC, SiN powder is used for SiN, alumina powder is used for alumina, and zirconia powder is used for zirconia. On the other hand, different types of ceramic powders having matching thermal expansion coefficients are ceramic powders having a difference in average thermal expansion coefficient of 1 × 10 ⁻⁶ or less, which is different from the ceramics to be bonded, such as silicon, SiC, SiN, It can be appropriately selected from various ceramic materials such as aluminum nitride. For example, it is possible to select powder of SiN, silicon, or the like for aluminum nitride which is the ceramic to be bonded. If the difference in the average thermal expansion coefficient between the ceramics to be bonded and the different type ceramic powder exceeds 1 × 10 ⁻⁶ , the resulting ceramic bonded body will have a large thermal strain, and peeling or other inconvenience will occur, such being undesirable.

The amount of the ceramic powder added is 1: 2 to 40, preferably 1: 4, by weight based on the compound mixture.
Add ~ 20. If the weight ratio of the ceramic powder to the total amount of the compound mixture is 2 or less, the effect of preventing cracks during firing is not sufficient, and if it exceeds 40, the bonding strength decreases and it is not practical. The particle size of the ceramic powder to be added can be appropriately selected depending on the application means to be applied, the shape of the bonded article, and the like. Further, by using a ceramic powder having a large particle size for filling a large gap or the like, good results can be obtained with less shrinkage after drying. In this case, problems such as easy precipitation and separation of the ceramic powder may occur during kneading and storage of the produced bonding compound, and it is usually preferable to use the ceramic powder having an average particle size of 100 μm or less.

The compound of the present invention comprises a powder mixture obtained by adding the above-mentioned ceramic powder to the above-mentioned polysilazane and polycarbosilane compound mixture, and an organic solvent such as xylene to be sufficiently kneaded to form a slurry. To do.
The kind of solvent and the mixing ratio of the solid content and the solvent can be appropriately selected according to each condition at the time of bonding. These are related to workability such as coating, and generally, the smaller the amount of the solvent is, the easier the drying is, and the less volume is reduced after the drying, and good results can be obtained. However, if the amount of the solvent is too small, the fluidity is lowered and the coating work becomes difficult. Therefore, usually
The powder mixture of the polysilazanes and polycarbosilane compound mixture and the ceramic powder and the solvent were mixed with each other in a ratio of 1:
It is advisable to mix them in a weight ratio of 0.05 to 40. In order to impart high fluidity, it is preferable to add the solvent such that the liquid component of the solvent is 20% by weight or more. In the present invention, for the purpose of improving workability, an appropriate amount of a surfactant or a thickener may be added in addition to the above powder mixture and solvent.

The ceramic bonding compound of the present invention obtained as described above uses a brush, a dispenser or the like, and forms a bonding portion by applying or injecting a fixed amount on the bonding surface of each ceramic ceramic to be bonded. can do.
After coating and the like, before the solvent evaporates and solidifies, the joints of the respective ceramics to be joined are butted, and heated and dried if necessary. After that, by further heating and firing to a predetermined temperature in an atmosphere of an inert gas such as nitrogen or argon or in an atmosphere of an oxygen-containing gas such as air, a desired ceramic joint having high heat resistance and high strength joining is obtained. Obtainable.

[0019]

EXAMPLES The present invention will now be described in detail based on examples. However, the present invention is not limited to the following examples. Examples 1 to 9 and Comparative Example 1 Polycarbosilane obtained by heating polysilane in an autoclave was mixed with perhydropolysilazane having a molecular weight of 1700 to 2100 at each weight ratio shown in Table 1 to obtain a compound mixture. Obtained. The resulting mixture has an average particle size of 20
A silicon powder of μm was added at a weight ratio of 1: 5 with the mixture to obtain a mixed powder of polysilazane, polycarbosilane and silicon. Further, xylene was added to the obtained mixed powder solid content in a weight ratio of 1: 0.5, and the mixture was kneaded with a ball mill for 4 hours to prepare bonding compounds. The bonding compounds thus prepared were each about 30 g.

Further, the diameter of the end surface is finished to be 10 mm.
A silicon rod having φ and a length of 30 mm was prepared. Next, each bonding compound obtained above was applied to the end face of one silicon rod by a quartz glass rod to form a joint, and then the end faces of the other silicon rods were joined together and pressed and bonded. The bonded silicon bonded body was dried at 70 ° C. for 3 hours to fix the bonded portion. Then, the adhered silicon bonded body was fired at each temperature shown in Table 1 in a nitrogen gas atmosphere. Each tensile strength of the fired and formed silicon bonded body was measured. The results are shown in Table 1.

[0021]

[Table 1]

As is clear from the above Examples and Comparative Examples, when the bonding compound was prepared from the compound of polysilazane alone without adding polycarbosilane, the tensile strength was low at any firing temperature, and particularly 120
It can be seen that the tensile strength after firing at ° C and 1350 ° C is extremely low. On the other hand, the bonding compound mixed at a polycarbosilane / polysilazane weight ratio of 0.2 to 40, particularly 0.1 to 20, is
It can be seen that the tensile strength after treatment at the firing temperature of 120 to 1350 ° C. is improved.

Example 10 A bonding compound was prepared in the same manner as in Example 1 except that the polycarbosilane / polysilazane weight ratio was 0.3. The obtained bonding compound was applied to the end face of one silicon nitride rod having a diameter of 10 mmφ, and was butt-bonded to the end faces of other silicon nitride rods. Then, it was dried at room temperature and further heat-treated at 250 ° C. in air. The bonded silicon nitride rod after the heat treatment had a bonding strength of 0.5 MPa measured in the same manner as in Example 1. Then, the bonded silicon nitride rod obtained above was fired at 1000 ° C. in a nitrogen gas atmosphere, and as a result, it had a bonding strength of 10 MPa in tensile strength. At a firing temperature of 1350 ° C., a tensile strength of 100 MPa and a bonding strength of 100 MPa were obtained.

Examples 11 to 17 and Comparative Examples 2 to 3 The polycarbosilane used in Example 1 was added to the hexamethylcyclotrisilazane polymer having an average molecular weight of about 1300 at a weight ratio of 1: 0.2. Weighed and added to give a mixture of compounds. Silicon carbide powder having an average particle size of 2 μm was added to the obtained mixture at a weight ratio shown in Table 2 to obtain a mixed powder. Further, the mixed powder having the same weight as that of the mixed solvent was added to a mixed solvent having a toluene / hexane ratio of 5/1 and kneaded well with a ball mill to prepare a bonding compound. On the other hand, a 5 × 5 × 25 (mm) silicon carbide ceramic square bar was prepared, and the bonding compound prepared as described above was used.
(Mm) was applied to the end face, and two silicon carbide ceramic square rods were adhered to the end face. Then, after drying at room temperature, it was fired at each temperature shown in Table 2 in an argon gas atmosphere, and the bending strength was measured by a four-point bending weighting method. The results are shown in Table 2.
It was shown to.

[0025]

[Table 2]

As is clear from the above Examples and Comparative Examples, the bonding compound of Comparative Example 2 in which the ceramic powder SiC was not added to the compound mixture of polysilazanes and polycarbosilanes was burned by the bonding compound of the present invention. The flexural strength increases as the temperature rises, but the flexural strength after firing is low and does not change regardless of the firing temperature. In addition, for the compound mixture, SiC
It can be seen that the bonding compound of Comparative Example 3 in which the addition amount was more than 40 times and 50 times was not exhibited the adhesive ability itself.

Example 18 5 g of perhydropolysilazane used in Example 1, 5 g of polysilastyrene having an average molecular weight of about 40,000, and an average particle size of 2
80 g of 0 μm alumina powder, 45 g of alumina powder having an average particle size of 1 μm, and 30 g of xylene were mixed and kneaded with a ball mill to obtain a bonding compound. Meanwhile, 5x
A square rod of alumina ceramics of 5 × 25 (mm) was prepared, and using the bonding compound prepared as described above, coating was applied to the end face of 5 × 5 (mm) in the same manner as in Example 1, and two rods were applied. The end faces of the alumina ceramics square rods were bonded.
Then, it was dried and fixed at room temperature. Each alumina ceramic stick was fired in air at 500 ° C. and 1200 ° C., and the bending strength was measured in the same manner as in Example 11.
As a result, they had bending strengths of 3 MPa and 60 MPa, respectively.

Example 19 50 g of trimethylhydropolysilazane having an average molecular weight of about 2000, 5 g of polycarbosilane, 200 g of silicon powder having an average particle size of 5 μm, 60 g of diethylene glycol butoxyacetate and 30 g of xylene were mixed and sufficiently kneaded with a ball mill to obtain a bonding compound. I got a pound. Using the obtained bonding compound, in a 30 × 30 (mm) square,
Screen printing was performed on an aluminum nitride ceramic plate having a thickness of 0.8 mm, a silicon ceramic plate of the same size was placed thereon, and the plate was pressure-welded, dried, and fixed. As a result of heating and firing the obtained ceramic fixing plate at 1200 ° C. in a nitrogen gas atmosphere, a strong bonded body of aluminum nitride and silicon was obtained.

[0029]

The ceramic bonding compound of the present invention has a sufficient adhesive strength when dried at room temperature, retains the adhesive strength even during high temperature heat treatment such as firing, and increases the adhesive strength. Various ceramics can be obtained in a large size and in a complicated shape as a strong ceramic bonded body in a simple process without causing damage or peeling of the bonded portion. Further, the ceramic bonding compound of the present invention is
In addition to ceramic powder, compounds mainly composed of Si, O, N, C and H elements can be used as constituent components, and contamination of semiconductor contaminants can be suppressed as much as possible, and various semiconductor manufacturing processes can be performed. It is also useful as a bonding material or a filler for ceramic members. Further, the formed bonding layer portion is excellent in high purity, high heat resistance, high chemical resistance and the like.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the firing temperature and the adhesive strength in a polysilazane compound, a polycarbosilane compound, or an equal mixture of a polysilazane compound and a polycarbosilane compound.

Claims (4)

[Claims] 1. A ceramic bonding compound comprising a polysilazane compound, a polycarbosilane compound, a ceramic powder and a solvent. 2. The compound for ceramic bonding according to claim 1, wherein the ceramic powder has the same kind of thermal expansion coefficient as the ceramic to be bonded or a coefficient of thermal expansion similar to that of the ceramic to be bonded. 3. The compound for ceramic bonding according to claim 1, wherein the weight ratio of the polysilazane compound to the polycarbosilane compound is 1: 0.05 to 40. 4. The ceramic bonding compound according to claim 1, wherein the weight ratio of the total amount of the polysilazane compound and the polycarbosilane compound to the ceramic powder is 1: 2-40.