JPH10144459A - Conductive heating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve defects such as brittleness and softening of electrothermal materials at a high temperature and provide a conductive heating element having its superior adhesion strength of a heater film, release resistance, and oxidation resistance properties by fusing a film made of a micro-tissue resistance heating material consisting of silicide simple tissue, a blended tissue of the silicide and Si, or Si-simple tissue on a surface of a ceramic base material. SOLUTION: A silicide or the silicide and Si, or Si film is fused on a full surface of a pipe-shaped ceramic base material 1, and a fusion layer 2 is formed. Otherwise, the silicide, the silicide and Si, or Si is fused spirally around a ceramics round rod. Still otherwise, one of these is fused around a planar ceramic base material in a circuit pattern. For the base material 1, an aluminum nitride, silicon nitride, alumina, chromia, or the like is employed. At both ends of the fusion layer 2, there is connected to a conductor coupled with an external power source by a mechanical or metallurgical means. This conductive heating element stand steep heating and high-temperature heating and has superior durability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heating element, and more particularly to an electric heating element having a structure in which a coating of a resistance heating material is melt-fused on the surface of a ceramic insulating substrate.

[0002]

2. Description of the Related Art When a heater circuit is baked on a ceramic plate having good heat conductivity, a planar heating element having small temperature unevenness can be obtained. This type of heater, called a ceramic heater, is required to have the following structure and characteristics. High adhesion strength between circuit and ceramic. The heater circuit material has excellent oxidation resistance and can be used even at high temperatures. The heating density of the heater is large. That is, the electric resistance of the heater circuit is high. The most important thing is that large products can be manufactured at low cost. However, at present there are only two types: (1) A type in which an electric heating metal circuit is baked on a ceramic plate that has been sintered in advance. This type has a structure in which a paste obtained by mixing glass with a powder of a noble metal such as platinum, a platinum alloy, or silver is sintered into a circuit pattern. Disadvantage is the type of baking on one side of ceramic (one side baking)
Limited to In other words, the surface where the circuit is baked is exposed, and it is necessary to insulate this part depending on the application. There is a disadvantage that the adhesion strength of the electric heating circuit is weak and it is easily peeled off. The maximum operating temperature is limited by the melting point of the glass used for the binder, and it is at most 400 to 500 ° C, and it is impossible to use a high temperature such as 1000 ° C or more. (2) A type in which an electric heating circuit is integrally baked during ceramic sintering. This type prints a high-melting point metal powder paste such as tungsten on a ceramic green sheet in a circuit pattern.
It has a structure in which a green sheet is further stacked on a printed circuit, and is pressed and sintered integrally. The final structure is a structure in which an electric heating circuit is built in a ceramic plate (both sides are baked)
Then, both sides of the electric heating circuit are ceramic plates. The disadvantage of (1), that is, the disadvantage that the electric heating circuit is exposed, is resolved, but conversely, since the circuit must be wrapped with ceramic, a circuit cannot be formed up to the peripheral end, and the temperature of the peripheral end decreases. There are drawbacks. It is difficult to obtain a uniform temperature distribution. A thin flat plate is warped during firing. Pressure sintering is required to obtain a product without warpage. In this method, there is a fundamental problem of deformation occurring during firing of the ceramic. It is difficult to obtain a large size without deformation. Also, three-dimensional shapes are not possible. Since a mold is required, the cost is extremely high for a small number of products. Electrothermal metals are limited to high melting point metals such as tungsten and molybdenum that do not melt at the firing temperature of the ceramic. Tungsten and molybdenum have a weak point against oxidation, and the ceramic surrounding the electric heating circuit is required to have no defect and complete confidentiality. There is a problem with long-term use at high temperatures in the atmosphere. Tungsten, molybdenum, and the like also have problems in that the electric resistance is small and the heat generation density is small. The ceramic heater has the above problems.

On the other hand, silicides represented by molybdenum disilicide (MoSi ₂ ) are extremely excellent in oxidation resistance,
It is well known as a material capable of conducting and generating heat to a high temperature. The biggest drawback of these silicide heating elements is that they are very brittle. Due to this brittleness, glass powder is usually mixed and sintered into a plate or rod with a certain strength,
Since glass is used for the binder, there is also a problem in heat resistance. In addition, the silicide itself has a property of softening at a high temperature, and there is a problem that the heating element hangs down and is deformed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to use a ceramic which has been sintered in advance as a base material, and to provide an electric heating circuit according to the purpose. It can be applied to both single-sided and double-sided baking, does not require pressure, can eliminate the above-mentioned problem of distortion during ceramic baking, has high adhesion strength between circuit and ceramic, has excellent oxidation resistance, and has high temperature in air. It is intended to provide an electric heating element with a new structure that can be used, and can be manufactured at a low cost even for large items and three-dimensional bodies, and can also be used for heaters with high resistance and high watt density.

[0005]

The above problem can be solved by the following means. That is, 1. The surface of the electrically insulating nitride-based or carbide-based ceramic substrate has a structure in which a coating of a resistance heating material consisting of a silicide simple structure, a mixed structure of silicide and Si, or a Si simple structure is fused to a microstructure. A current-carrying heating element characterized in that: 2. A coating of a resistance heating material containing 0.5% or more active metal and having a microstructure consisting of a silicide simple structure or a mixed structure of silicide and Si was fused to the surface of the electrically insulating ceramic substrate. A current-carrying heating element having a structure. 3. 3. The energization heating element according to any one of 1 or 2, wherein the ceramic substrate is an aluminum nitride-based ceramic, and the microstructure of the resistance heating material is a mixture of silicide and Si. 4. 3. The energization heating element according to any one of 1 or 2, wherein the ceramic substrate is a silicon nitride ceramic, and the microstructure of the resistance heating material is a mixture of silicide and Si. 5. 3. The electric heating element according to the above item 2, wherein the ceramic base is an oxide ceramic. 6. The oxide ceramic is an alumina ceramic,
6. The heating element according to the above item 5, wherein the microstructure of the resistance heating material is a silicide structure.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Aluminum nitride ceramics, silicon nitride ceramics, and silicon carbide ceramics are typical of electrically insulating nitride-based and carbide-based ceramics. The electrically insulating nitride-based or carbide-based ceramic of the present invention refers to these aluminum nitride ceramics, silicon nitride ceramics, silicon carbide ceramics alone, and these ceramics and other nitrides, carbides, borides,
Includes composite ceramics with oxide ceramics. Among these nitride and carbide ceramics, aluminum nitride-based ceramics, in particular, have excellent thermal conductivity, and therefore can be most preferably used as a base material for an electric heating element. In the case of a so-called double-sided baking type current-carrying heating element that uses two ceramics as a base material, sandwiches a film of a resistance heating material between these two ceramics, and fuses them on both sides of the two ceramics The two ceramics do not necessarily have to be the same ceramic, but it is better to select a ceramic having an approximate linear expansion coefficient.

An element which forms a solid solution with Si, for example, Ge
With the exception of Si, most metals form silicides. Assuming that X is an element that forms silicide with Si, Si of the X-Si alloy
The basic change of the microstructure due to the change is as follows. As the Si increases gradually, the first silicide is formed at a certain composition. The composition here is Si (1). In a region of Si <Si (1), a structure in which a silicide phase of a metal X is mixed in a matrix of a metal X. Alternatively, a structure in which a silicide phase of a metal X is mixed in a matrix of a metal X where a certain amount of Si is dissolved. When Si further increases from Si (1), silicides having different compositions appear one after another, and a eutectic mixture of silicide and Si appears after a certain composition Si (2). S
i (1) is the richest silicide of element X, and Si (2) is the richest silicide of Si. In the area of Si (1) ≦ Si ≦ Si (2), this area is a mixed structure of one or more silicides. From Si (2) to less than Si (100%) Si (2) <Si <Si (100%) This area is a mixed structure of Si and silicide. When Si = 100%, a polycrystalline structure of Si results. Here, even if the third, fourth, fifth,... Elements are added to the above-described binary system of X—Si, the basic skeleton of the structure itself, that is, the basic structure in which silicide is present in the matrix. The skeleton does not change. That is, the third, fourth, fifth,... Elements are solid-dissolved in the matrix, are dissolved in silicide to form double silicides, or form other compounds and crystallize in the matrix. Or it is precipitated
At least the silicide (or double silicide) does not disappear from the matrix. In the present invention, "silicide"
The expression is used as a generic term including the original silicide and double silicide.

[0008] A part of the composition range (Si ≥ 5%), when melted, wets and fuses with nitride-based and carbide-based ceramics.

As the current-carrying heating element, a composition for fusing (Si ≧ 5%) and a composition range of can be used. In particular, the composition range of is preferred.
The composition of (1), (2), (3) has a melting property with respect to the above-mentioned electrically insulating nitride and carbide ceramics. The linear expansion coefficient is 4 to 8 × 10 ⁻⁶ (particularly, the composition range is 4 to 6 × 10 ⁻⁶ ), and the linear expansion coefficient is adjusted by adjusting the amount of silicide in the microstructure as necessary. Can be adjusted, and can be matched with the ceramic of the base material, the thermal stress at the fusion interface is suppressed to a minimum, the temperature is stabilized up to a high temperature, and the heating element is extremely advantageous for preventing peeling. In addition, the composition range has an advantage that the melting temperature is low, so that the fusion temperature can be lowered. And silicide is high temperature (approximately 100
(0 ° C. or higher), there is a defect as a heating element that softens and deforms. However, since the deformation is prevented by fusing to the ceramic and stress is relaxed at the fusion interface, the defect becomes a rather advantageous property. . In other words, silicide or a metal having a structure containing silicide is extremely suitable as a coating to be fused to ceramic for the purpose of using a heater at a high temperature. 2. It has excellent oxidation resistance in air and at high temperatures (1000 ° C. or higher). Considering the use in the atmosphere and at a high temperature, the composition range is more excellent in oxidation resistance than in the area of, and 3. Since the electrical resistance is large, the length of the resistor circuit can be shortened,
A heater having a large watt density per unit area can be obtained. For the reasons described above, the composition range, particularly the composition range, is more preferable than the area as the energizing heating element.

[0010] Since the area (1) has a large coefficient of thermal expansion and a small electric resistance, it is necessary to reduce the film thickness in order to reduce the thermal stress and increase the electric resistance. Preferably, the film thickness is 20 μm or less, most preferably 10 μm or less. When the fusion film exceeds 20 μm, it is easy to peel off. In the area (2), Cr-Si-based and Cr-Si-active metal-based alloys are preferable because of their relatively small coefficient of thermal expansion and excellent oxidation resistance.

[0011] As the X element of the above X-Si alloy,
Cr, Mo, W, Fe, Ni, Co, B, P and an active metal, and Pt, Pd, Rh, Ir, Cu, Ag, and other silicide-forming elements can be appropriately selected depending on the purpose. These elements may be used singly or as a mixture of two or more depending on the purpose. For example, the addition of two or more elements is effective in reducing the microstructure of silicide. The amount of addition can be appropriately selected as long as it is within the range for forming the microstructure described above, that is, the range for forming silicide, and the range for forming silicide and Si.
, Ie, a composition range in which silicide and Si are mixed. By adjusting the amount of silicide in the microstructure, the linear expansion coefficient and the electric resistance can be appropriately adjusted, and the melting point is low, and the ceramic can be fused to the ceramic at a low temperature. It is. Among these elements, an active metal element is particularly preferred.

Elements other than the above elements may be added as long as the microstructure is not changed. For example, an element which forms a solid solution with Si and lowers the electrical resistance of Si, or an element which penetrates into silicide and changes the characteristics (electrical resistance, coefficient of linear expansion, melting point, etc.) of the silicide is appropriately determined according to the purpose. May be added. In the production of impurity semiconductors, a very small amount (ppm to ppb unit) of trivalent or pentavalent metal is added to high-purity Si to produce a P-type semiconductor or an N-type semiconductor to lower the electric resistance. However, this is also effective in the present invention, which corresponds to the former case. That is, the method of changing the electric resistance of Si, which constitutes a part of the microstructure, by adding a small amount of trivalent or pentavalent element is an effective method for adjusting the electric resistance of the fused film of the present invention. It is. In addition, as another method of lowering the electric resistance, trace elements (Fe, P, Al, C
It is also effective to use a Si raw material for casting that contains B, Al, P
It is of course also effective to adjust the electric resistance by adding a trivalent or pentavalent element such as the above or a small amount of other elements. In addition,
Both B and P are also dissolved in Si in a trace amount and form silicide at the same time.

Although Si is originally a semiconductor and has a very high resistance, trace elements considered as impurities significantly improve the conductivity of Si. Therefore, the Si raw material of the present invention contains Si as described above. Is rather preferred. Also,
A good example of an element that penetrates into a silicide and changes the characteristics (electrical resistance, linear expansion coefficient, melting point, etc.) of the silicide is MoSi ₂
There is a case in which Al penetrates into and forms a double silicide of (Mo ₅ Al ₃ ) Si ₂ . In this case, the melting point of MoSi ₂ at 2060 ° C. drops to 1800 ° C.

Ge is an element having similar properties to Si.
Since a solid solution can be formed in all proportions without forming a silicide with i, it can be appropriately added depending on the purpose and application. It is effective as an element for controlling the melting point and electric resistance.

The active metal is an element which promotes the wetting and diffusion of the ceramic, and in the present invention, V, Nb, Ta, T
i, Zr, Hf, Y, Mn, Ca, Mg, rare earth elements, aluminum and the like are expressed as active metals. When an active metal is added to Si, wetting is significantly promoted and the wetting angle is reduced. As a result, the thickness of the fusion-bonded film to be fused can be reduced to make it thinner, which has a remarkable effect in increasing electric resistance. Also, the fusion strength is improved. The effect of improving the wettability can be obtained from the addition of a small amount of about 0.1%, but in order to obtain a practical effect, the addition of 0.5% or more is preferable. In the case of a binary alloy of Si-active metal, the amount of Si decreases relatively as the amount of active metal increases. In consideration of the oxidation resistance in the atmosphere, it is preferable to add Si in an amount of at least 3% or more, and most preferably, in a region, that is, a silicide region or more. By the way, in the case of Si-Ti alloy, 8
In the vicinity of 4%, silicide having a composition of Ti ₃ Si is generated.
Ti: A silicide of TiSi ₂ is generated at around 46%. If Ti is less than 46%, that is, Si exceeds 54%, T
A eutectic of iSi ₂ and Si appears. Therefore, the area of Ti ranges from 84% to 100%. Area is Ti: 46-84%, area is 0.5% or more 4
The range is up to less than 6%. Therefore, when oxidation resistance in the atmosphere is considered in a Si-Ti binary alloy, the upper limit of Ti is approximately 84%. If the third, fourth,... Elements are added, the upper limit naturally changes. Of course, Si may be replaced with an oxidation resistance imparting element such as Cr.

In a composition in which Si and an active metal coexist, other than the above-mentioned nitrides and carbides, they are fused to oxide ceramics in general. Therefore, an oxide ceramic can be selected for the base material.

The type of oxide ceramic may be appropriately selected according to the coefficient of linear expansion of the resistance heating material to be fused so as to match the coefficient of linear expansion. Generally (3-9) x 1
From 0 ⁶ oxide having a linear expansion coefficient in the range of, it is sufficient to appropriately select the type. When an alumina-based, chromia-based, or zirconia-based ceramic is used as the base material, the composition of the fused metal is most preferably a silicide composition. Since the linear expansion coefficient of the silicide is generally in the range of 5 to 9 × 10 ⁻⁶ , it is possible to select an alumina-based, chromia-based, or zirconia-based ceramic from these, and to select a linear expansion coefficient. Can be measured.

The fusion layer is provided with a ceramic heating element (SiC, ZrO ₂ or the like) insoluble in the fusion material or other insulating ceramic powder, fiber, or the like, if necessary, mainly for adjusting electric resistance and the like. Powders or fibers of a heating element of an intermetallic compound, such as a high melting point silicide or a hodide, which is hardly soluble in the fusion metal, may be appropriately mixed with a high melting point metal powder or fiber. Alternatively, the powders and fibers of these heating elements may be combined using the fusion material as a binder and simultaneously fused to the base ceramic. The fusion material can also be used as a brazing material, and can be used by bonding a ceramic, metal, or intermetallic compound heat generating resistor foil, plate, or wire to a ceramic substrate.
For example, in the case of using metal foil, W, Mo
And the like, and brazing the whole surface with a brazing material, the problem of oxidation resistance of W and Mo can be solved at the same time.

The thinner the fusion film to be fused to the base ceramic, the more advantageous. There is an advantage that the length of the heat generating circuit can be shortened because the electrical resistance increases as the thickness decreases. Also,
The thermal stress at the fusion interface is reduced, and it can be used at high temperature for a long time. The thickness of the fusion film is about several μm to 500μ
The range of m is best.

The resistance heating film of the present invention can be either a single-sided fusion type in which a single ceramic substrate is fused to one surface or a double-sided fusion type in which the ceramic is sandwiched between two ceramics and fused to both ceramics. Also applicable to

In the double-side fusion type, the molten metal may penetrate into the gap between the circuits, and the circuit may be short-circuited. To solve this problem, it is effective to prevent a short circuit between the circuits by providing a gap between the two ceramics wider than the thickness of the fused metal film. More specifically, it is preferable to form a groove in a portion between circuits before fusion and then overlap and fuse them.

The fusion of the resistance heating film is performed by applying a metal powder adjusted to a predetermined component composition to a ceramic fusion bonding surface, or attaching a metal foil adjusted to a predetermined component to a circuit pattern and heating it. Melt and fuse. Alternatively, a metal film to be fused may be formed on the fusion surface by thermal spraying, sputtering, PVD, CVD, or the like, and then heated, melted, or fused. In addition, some of the components are deposited,
Other elements may be melted and fused by powder coating or metal foil sticking. The atmosphere at the time of fusion is preferably a vacuum, reduction, or inert atmosphere.

In the single-side fusion type in which the resistance heating film is fused to one surface of the ceramic base material and in the double-side fusion type in which the resistance heating film is sandwiched and fused between two ceramics, the uniformity of the thickness of the resistance heating film, the flatness, and the like. The uniform fusion property is superior to the double-side fusion type. Further, in the single-side fusion type, if the linear expansion coefficient of the ceramic base material and the resistance heating film is different, the ceramic may be slightly deformed after fusion. In addition, the ceramic surface may be slightly deformed during heating. On the other hand, when fusion is performed between two ceramics with the same or similar linear expansion coefficients, deformation does not occur after fusion even if there is a slight difference in the linear expansion coefficient between the resistance heating film and the ceramic substrate. There is a feature that deformation does not occur sometimes. From the viewpoint of uniform heating and uniformity of temperature distribution, a double-sided fused structure is preferred.

In the double-sided fusion structure, a portion exposed outside the heat generating circuit is a portion (end face) corresponding to the thickness of the fusion film.
Therefore, the structure is extremely suitable for corrosion resistance and oxidation resistance. Furthermore, the exposed part of the part corresponding to the thickness is covered with a ceramic film by the sol-gel method,
Alternatively, it can be protected from the outside by filling the gap with an inorganic adhesive, sealing with glass, or sealing the periphery of the ceramic substrate with a fusion metal.

The fusion temperature must be at least the temperature at which the melt appears, that is, the solidus temperature or higher, and most preferably the liquidus temperature or higher.

The Si raw material for the fusion metal can be appropriately selected and used from Si used for semiconductors to Si used for component adjustment in metal castings. In casting applications, trace elements such as Fe, C, P, and Al are contained, and these trace elements improve the conductivity of Si, and are effective in the present invention. Further, Si (P-type semiconductor, N-type semiconductor) to which impurities for semiconductor use are added is also effective in the present invention.

Here, the fused film of the resistance heating material of the present invention is appropriately joined to another film of the resistance heating material in the middle (that is, the film of the other resistance heating material is laminated on the fusion film of the invention). Structure which is baked and connected). That is, a structure may be adopted in which a part of a ceramic heater having a structure in which a film of a resistance heating material is baked on a conventional ceramic plate is connected to a fusion film of the resistance heating material of the present invention. Further, a part of the fused film of the resistance heating material of the present invention may be formed by baking a film of the conventional resistance heating material, and used by connecting the films. In particular, it is effective that the terminal portion is a fusion film of the resistance heating material of the present invention. That is, since the fused alloy of the present invention is suitable as a material for joining the terminal to the ceramic, the terminal is fused with the alloy of the present invention, and a film of a conventional resistance heating material is preferably used by baking the terminal. . Alternatively, it is preferable to form a part of the heat generation circuit near the terminal junction and the terminal with a fusion film of the alloy of the present invention, and to use a conventional film of a resistance heating material on the fusion circuit of the present invention. The fused alloy of the present invention is also suitable as a brazing material for terminal joining of a conventional tungsten co-fired structure type ceramic heater.

Next, the structure of the present invention will be described with reference to the drawings. 1 to 3 are views illustrating an embodiment of a single-sided fusion bonding structure according to the present invention. FIG. 1 shows that a silicide or silicide + Si or Si
FIG. 2 shows a structure obtained by spirally fusing a silicide or a silicide + Si or Si film on a ceramic round bar, and FIG. 3 shows a circuit formed on a plate-like ceramic substrate. It is a figure explaining the structure fused to the pattern.

In FIG. 1, reference numeral 1 denotes a substrate made of a ceramic pipe such as aluminum nitride, silicon nitride, alumina, and chromia;
2 is a silicide fused to the base material, or a silicide + Si, or a fused layer of Si. Both ends of the fusion layer are connected to conductors connected to an external power source by mechanical or metallurgical means.

FIG. 2 shows an example in which a spiral fusion film is formed on a base material of a round bar. FIG. 3 shows an example in which a fusion film of a wiring circuit pattern is formed on a plate-like base material. These patterns may be formed by applying a fusion metal powder in the form of a pattern and fusing it, or by forming a fusion film once on the entire surface and removing unnecessary portions by etching, blasting or the like. May be removed to form a desired pattern.

FIGS. 5 to 16 are views for explaining an embodiment of the double-sided fusion bonding structure of the present invention. FIG. 5 is a view showing an example of a heater circuit of a fusion metal. The actual structure is such that this heater circuit is sandwiched between two ceramic substrates and fused to both surfaces of the ceramic. In FIG. 5, reference numeral 1 denotes a fusion metal heater circuit, and reference numerals 2 and 3 denote connection terminals for a power supply. FIG.
FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, which has a structure in which such a heater circuit is sandwiched between two ceramic substrates. FIG. 7 is a diagram showing an example of a manufacturing process of the structure of FIG. FIG. 8 is a diagram illustrating a structure for preventing a short circuit in a heater circuit.

In FIG. 6, the heater circuit 3 for the fusion metal is sandwiched between two ceramic substrates 4 and 5 and is fused.
The fusion metal is not only a heater circuit but also a brazing filler metal for joining the two ceramics. The circuit is formed, for example, by the following method. A metal powder adjusted to the composition of the fusion metal is applied to a circuit pattern on one or both of the two ceramics, and the two ceramics are superposed, heated, melted and fused. Alternatively, one or both of the two ceramics are coated with a film of a fusion metal in a circuit pattern, and the two ceramics are superposed, heated, melted and fused. The film of the fusion metal is formed by a method such as sputtering, PVD, or CVD. A circuit pattern is drawn using a compromise between the two methods, that is, film formation and powder application, and is heated, melted, and fused. Alternatively, a metal is fused in advance to the joint surface of each ceramic to form a fusion film, and this film is removed by a method such as shot blasting to form a circuit pattern. The two ceramics on which the pattern is formed are overlapped with good alignment, heated and re-melted to join the two ceramics. This is the method described above.

As shown in FIG. 7, a fusion film 6 is formed by fusing a metal in advance on the bonding surface of each ceramic, and this film is removed by a method such as shot blasting or etching to form a circuit pattern. After forming
A method of sintering at a temperature equal to or lower than the melting point by heating (pressing and heating as necessary) may be used.

In a structure in which a heater circuit is sandwiched between two ceramics as in the structures shown in FIGS. 6 and 7, the fused metal may penetrate laterally and short-circuit the circuit. As the metal film becomes thicker, a short circuit is more likely to occur. For short circuit,
As shown in FIG. 8, a groove 7 may be formed in the gap between the circuits to widen the gap between the ceramic plates.

When the two ceramics are fused with the heater circuit interposed therebetween, a gap corresponding to the thickness of the heater circuit of the fusion metal remains between the two ceramics. If there is a gap, a foreign matter may be mixed depending on the application, and a short circuit of the circuit may occur. Sealing the gaps at the end faces can be an important issue. For sealing the end face, a closed circuit 8 is formed by surrounding the ceramic end face with a band of a fusion metal as shown in FIG. 9 and sealing is performed by fusing the closed circuit 8 to both surfaces of the ceramic. Is also an effective method. The fusion of the sealing closed circuit 8 is performed simultaneously with the fusion of the heater circuit. The same metal as the fusion metal of the heater circuit may be fused, or a material that can be fused under the same fusion conditions as the fusion metal of the heater circuit may be used. Further, as another sealing method, a ceramic adhesive may be impregnated and solidified.
Further, glass may be fused.

[Explanation of FIG. 9] FIG. 9 shows that one or both heater circuit forming surfaces of two ceramics are coated with a fusion metal of a heater circuit as shown in FIG.
It is a figure showing a structure where the same metal as the fusion metal of the heater circuit or a material that can be fused under the same fusion conditions as the fusion metal of the heater circuit was applied to the pattern, and the pattern was overlapped and heated and fused at the same time. . Since both the heater circuit and the closed circuit 8 are hidden in the ceramic and do not come out of the table, they are indicated by dotted lines. The heater circuit and the closed circuit are electrically insulated from each other.

The following connection structure is effective for connecting the terminal of the heater circuit to an external power supply. A metal terminal having a linear expansion coefficient similar to the linear expansion coefficient of the used ceramic base material is soldered, and the metal terminal is connected to a lead wire. The structure of FIGS. FIG. 10 shows a structure in which a terminal metal is directly brazed to a terminal of a circuit, and FIG. In other words, two holes (for a single phase) and three holes (for a three phase) for drawing out a circuit are drilled in one side of the ceramic substrate, and metallized with a fusion metal along the inner surface of the hole to extend the circuit to the outside. Pull out and braze it when it is pulled out. Alternatively, a structure in which a lead wire of a metal (Mo, W, or the like) having a linear expansion coefficient similar to that of a drawing hole is directly inserted, and a gap between the lead wire and the hole is filled with a brazing material to directly braze the terminal of the circuit. Alternatively, the hole is made into a small diameter hole, and the hole is filled with a fusion metal, and the hole is electrically connected to the outside. In the single-sided fusion bonding structure, a method may be used in which a metal terminal having a metal substrate having a similar linear expansion coefficient to a ceramic base is soldered to a circuit terminal, and the ribbon terminal and an external lead wire are electrically connected. Alternatively, as shown in FIG. 12, the ceramic small piece 9 may be joined to the heater circuit, and a lead wire may be inserted into the hole of the small piece 9 and fixed by brazing. The brazing may be performed by soldering the terminals at the same time as forming the circuit using the fusion metal itself, or by using a high-temperature brazing material having excellent oxidation resistance after forming the circuit, such as Ni brazing. May be. When the ceramic substrate is an aluminum nitride-based ceramic, a silicon nitride-based ceramic, or a silicon carbide-based ceramic, the terminal material is Mo, W, or a fused metal on a porous body of aluminum nitride-based ceramic, silicon nitride-based ceramic, or silicon carbide-based ceramic. Also, a terminal of a composite material made by impregnating with such a material is suitable. Metal terminals and lead wires may be appropriately selected from solid materials, bundled wires, laminated foils, woven fabrics, and the like.

[0038]

The present invention will be described by way of examples. Example 1 (double-side fusion type) Ceramic base material: Use of four types of base materials: aluminum nitride, silicon nitride, silicon carbide, and alumina. Silicon carbide having an electrical resistance of 10 ¹¹ Ω · cm is used. Substrate dimensions: 10 × 30 × 0.6 mm plate. Fusion metal: FIG. 1 on the above ceramic substrate (aluminum nitride, silicon nitride, silicon carbide, alumina)
As shown in FIG. 3, a metal powder prepared in the following composition (Table 1) having a width of 2 mm and a length of 22 mm was mixed with an ethanol solution of polyvinyl alcohol to form a paste, which was applied, and shown in FIG. The same ceramic base material having holes (φ1 mm) at both ends was overlapped, dried, heated and melted and fused as shown in FIG. Distance between holes 20 mm. S
The raw material of i was obtained by crushing a semiconductor substrate into powder and 9
9.999% purity (Al, Mg, Ca, Na ≦ 1 pp
m) Use of powder. The pulverized semiconductor substrate is B-doped P-type Si. The resistance value of B-doped P-type Si is 0.0 to 0.1 Ω · cm. Samples using B-doped P-type Si are indicated as “P-type Si”. 9 samples without indication
9.99% pure powder used. The heating atmosphere is vacuum (5
× 10 ⁻⁵ Torr), argon. The microstructure of the fused metal was selected from the above three ranges, ie, the range of microstructure, namely, the range of silicide formation, the range of forming a mixed structure of silicide and Si, and the Si single structure.

[Table 1] Substrate: ALN is aluminum nitride SiC is silicon carbide SiN is silicon nitride Al ₂ O ₃ is high-purity alumina The atmospheres are numbers 1, 16, and 18 in an argon atmosphere, and others are in a vacuum atmosphere. An electrode for resistance measurement was inserted into the sample.

Example 2 (Heating Test) The sample of Example 1 was subjected to a heating test by applying an AC voltage.
Heat to 500 ° C in 5 minutes and let cool to room temperature. This is 10
Repeated 0 times. No peeling or cracking of the heater was found in any of the samples. Next, the oxidation resistance test of the fused metal was performed. The sample of Example 1 was heated to 1000 ° C. for 5 hours. No change in electrical resistance due to oxidation of the fusion coating was observed.

Example 3 (Comparison of Uniform Fusing Property of Coating) A heater circuit was fused only to one side of a ceramic base material (single-sided fusion structure), and a ceramic circuit was sandwiched between two substrates, and was applied to both ceramics. For the fused structure (double-sided fused structure), the thickness unevenness (unevenness, flatness), width unevenness, and surface properties of the film were compared. Ceramic substrate: Aluminum nitride Dimensions of substrate: 100 × 100 × 0.6 mm plate. Fused metal: Two components having different wettability are selected as the fused metal. High purity Si (99.999%), Si-
25% Ti was selected for comparison. Si powder (particle size: 325 mesh under) was mixed with an ethanol solution of polyvinyl alcohol to form a paste, which was printed on the surface of the aluminum nitride substrate in a circuit pattern shown in FIG. Circuit width: 10 mm, interval between circuits: 5 mm The single-sided fused sample was obtained by drying a sample printed on one side, and then heating and fusing in a vacuum (5 × 10 ⁻⁵ Torr). The double-sided fusion-bonded sample was printed, and the same ceramic plate was further superimposed and aligned, dried, and then dried under vacuum (5 × 10
^-5 Torr). The high-purity Si sample was heated to 1450 ° C. and fused. Si-25% Ti
The sample was heated to 1400 ° C. and fused. Result [Single-sided fusion sample] The high-purity Si sample was a film with a swelling and unevenness. It was also observed that the width of the circuit pattern was narrower than the originally printed width. Si-
The 25% Ti sample formed a flat film with almost no irregularities. The circuit width was almost the same as the originally printed width. It was observed that the single-sided fused sample caused a difference in the flatness of the coating and the degree of unevenness due to the difference in the wettability of the metal to be fused. [Double-side fused sample] On the other hand, a double-side fused sample sandwiched between two ceramics was a high-purity Si sample, Si-25.
Since both the samples of% Ti were sandwiched between the ceramic plates from both sides, the coating was completely fused without swelling of the coating, and a flat coating without unevenness was formed. In addition, the width of the circuit pattern was fused at substantially the same width as the originally printed width.
In the double-sided fused sample, it was observed that a flat and uneven coating was fused even if the wettability of the metal to be fused was different. It was confirmed that the double-sided fusion type was superior to the single-sided fusion type in terms of the flatness of the coating, that is, the uniformity of the thickness and the uniformity of the circuit width.

Example 4 (Comparison test of fusion structure and deformation during heating) Ceramic substrate: Aluminum nitride Dimension of substrate: 10 × 110 × 0.6 mm plate. Fused metal: Si-25% Ti Si raw material: 99.999% purity (Al, Mg,
(Ca, Na ≦ 1 ppm) The powdered metal prepared in the above composition is mixed with an ethanol solution of polyvinyl alcohol to form a paste, which is applied to one entire surface of the ceramic plate (lower plate), dried,
The same ceramic plate (upper plate) having holes 1 mm in diameter (distance between holes: 100 mm) at both ends was overlapped, and heated and melted at 1400 ° C. in a vacuum (5 × 10 ⁻⁵ Torr). The ceramic was fused. For comparison, a sample of single-sided fusion bonding was also applied by applying to the entire surface of one side of the ceramic plate, drying, and then heating and fusing to 1400 ° C. in vacuum (5 × 10 ⁻⁵ Torr). . [Results] After two kinds of samples (two-sided and one-sided fused samples) were fused, an AC voltage was applied to both ends and the temperature was raised to 500 ° C. in 5 minutes. At this time, the single-sided fused sample was warped by 200 microns. On the other hand, there was almost no double-side fusion type. The double-sided fusion structure was found to be more effective in preventing deformation during heating than the single-sided fusion structure.

Example 5 Ceramic substrate: Three types of substrates of aluminum nitride, silicon carbide and silicon nitride were used. Silicon carbide has electrical resistance:
Use 10 ¹¹ Ω-cm. Substrate dimensions: 10 × 30 × 0.6 mm plate. Fused metal: on one side of the ceramic substrate, Fig. 4
As shown in the figure, a metal powder prepared in the following composition (Table 2) having a width of 2 mm and a length of 22 mm was mixed with an ethanol solution of polyvinyl alcohol to form a paste, which was applied very thinly and dried. It was heated, melted and fused. The raw material of S1 is obtained by crushing a semiconductor substrate into powder,
Uses 99.999% pure powder. The pulverized semiconductor substrate is B-doped P-type Si. The resistance value of B-doped P-type Si is 0.0 to 0.1 Ω · cm. Samples using B-doped P-type Si are indicated as “P-type Si”. Unlabeled samples use 99.999% pure powder. The heating atmosphere is vacuum (5 × 10 ⁻⁵ Torr) and argon. The microstructure of the fused metal was selected from the three ranges described above, that is, a range in which a silicide is formed, a range in which a mixed structure of silicide and Si is formed, and a single Si structure. The electric resistance was measured at a distance of 20 mm.

[Table 2] Base material: ALN is aluminum nitride, SiC is silicon carbide, Si
N is silicon nitride, the atmosphere is argon for numbers 1, 3, and 13, and the others are vacuum. The electric resistance measured resistance between 20 mm length.

Example 6 (Heating test) A heating test was performed by applying an AC voltage to the sample of Example 5.
Heat to 500 ° C in 5 minutes and let cool to room temperature. This is 10
Repeated 0 times. No peeling or cracking of the heater was found in any of the samples. Next, the oxidation resistance test of the fused metal was performed. The sample of Example 5 was heated to 1000 ° C. for 5 hours. No peeling of the fused coating due to oxidation and no change in electrical resistance were observed.

[0044]

According to the present invention, as described in detail above, silicides,
An electrothermal material having a composite structure in which a film of an electrothermal material having a mixed structure of Si or silicide and Si is fused to a ceramic base material, and the defect of the electrothermal material being brittle and softening at high temperatures is improved.
In addition, it is a thin film, and the adhesion strength of the heater film,
This is an invention that is extremely industrially significant because it has excellent peeling resistance, oxidation resistance in the atmosphere, withstands rapid heating and high-temperature heating, has excellent durability, has a simple structure and can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram illustrating an embodiment of the present invention.

FIG. 3 is a diagram illustrating an embodiment of the present invention.

FIG. 4 is an explanatory diagram of the embodiment.

FIG. 5 is a diagram showing an example of a heater circuit of a fusion metal.

FIG. 6 is a sectional view taken along line AA of FIG.

FIG. 7 is a view showing one example of a manufacturing process of the structure of FIG. 6;

FIG. 8 is an explanatory diagram of a structure for preventing a short circuit in a heater circuit.

FIG. 9 is an explanatory view of a sealing structure of a ceramic end face.

FIG. 10 is an explanatory diagram of a structure in which terminals are connected to terminals of a heater circuit.

FIG. 11 is an explanatory diagram of a structure in which terminals are connected to terminals of a heater circuit.

FIG. 12 is an explanatory diagram of a structure in which a lead wire is connected to a terminal of a heater circuit.

FIG. 13 is an explanatory diagram of the embodiment.

FIG. 14 is an explanatory diagram of the embodiment.

FIG. 15 is an explanatory diagram of the embodiment.

FIG. 16 is an explanatory diagram of the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ceramic base material 2 ... Fused layer 3 ... Heating circuit 4,5 ... Ceramic base material 6 ... Fused film 7 ... Groove
8 Closed circuit 9 Ceramic piece

 ──────────────────────────────────────────────────続 き Continuation of the front page (31) Priority claim number Japanese Patent Application No. 8-204088 (32) Priority date Hei 8 (1996) June 29 (33) Priority claim country Japan (JP) (31) Priority Claim No. Japanese Patent Application No. 8-279832 (32) Priority Date Hei 8 (1996) September 12 (33) Priority Country Japan (JP)

Claims (6)

[Claims] 1. A coating of a resistance heating material having a microstructure of a silicide simple structure, a mixed structure of silicide and Si, or a single Si structure on a surface of an electrically insulating nitride-based or carbide-based ceramic substrate. A current-carrying heating element characterized by having a worn structure. 2. The method according to claim 1, further comprising the step of:
A current-carrying heating element comprising an active metal of 0.5% or more, and a microstructure having a structure in which a coating of a resistance heating material comprising a silicide simple structure or a mixed structure of silicide and Si is fused. . 3. The ceramic base material is an aluminum nitride ceramic, and the microstructure of the resistance heating material is silicide and Si.
The current-carrying heating element according to claim 1, wherein the current-carrying heating element has a mixed structure. 4. The electric heating element according to claim 1, wherein the ceramic substrate is a silicon nitride-based ceramic, and the microstructure of the resistance heating material is a mixture of silicide and Si. 5. The current-carrying heating element according to claim 2, wherein said ceramic substrate is an oxide ceramic. 6. The electric heating element according to claim 5, wherein the oxide ceramic is an alumina ceramic, and the microstructure of the resistance heating material is a silicide structure.