JPH02250231A - High temp erature operating element - Google Patents

Abstract

PURPOSE:To eliminate risk of exfoliation from a base board and enhance the long-term reliability by forming a porous high-temp. operating element film having low film density on one side of an insulative member, and a resistance film having a high film density on the other side. CONSTITUTION:On one side of an insulative member 1 a porous high-temp. operating element film 4 having low film density is formed in a specified shape, while on the other side, a resistance film 2 having a higher film density than the abovementioned is formed in a specified figure. With this resistance film 2 a lead is jointed, and an insulative protection film is formed over this insulative member 1 while covering the resistance film 2, and thus a high-temp. operating element is accomplished. Because of its porosity, the element is conformable with the layer provided over it according to the element performance, which can thus be enhanced easily, and is long-term reliability be enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to high-temperature operating elements that operate by being heated to a high temperature of about 1000°C by a heater, such as cathode ray tubes using thermionic emission, hot cathode X-ray tubes, etc. It relates to the structure of high-temperature operating elements such as electron microscopes and electron guns for cathode ray tubes.

[Prior Art] Conventionally, high-temperature operating elements are disclosed in, for example, Japanese Patent Application Laid-Open No. 55-24648.
As described in the publication, the circuit was manufactured using a so-called thick film circuit forming technique such as screen printing. Third
The figure is a cross-sectional configuration diagram showing a conventional high-temperature operating element manufactured in this manner. First, ceramic substrate (10)
A heating element rM (11) in a predetermined pattern is formed on a sheet by a printing technique such as an extrusion method passing between rolls or a casting method. An insulator (12) is formed on the substrate (10) on which this heating element 1 (ll) is formed, and furthermore, this insulator (!2
), a cathode material layer (13
), cathode lead layer (14), base metal layer (15)
) to form a high temperature operating element. Heat generating layer (11
) is formed by screen-printing a paste of a heater material to which a firing aid has been added, and the operating element is similarly formed by screen printing a paste of a desired material to which a firing aid has been added onto a substrate (lO). After screen printing, a firing process is performed at high temperature (1000-2000°C) to form a high temperature operating element.

In this method, a high-temperature treatment process is involved during manufacturing, so when the heater is used at a temperature below this treatment temperature, high-temperature long-term stability as a heater, such as a small change in resistance over time, can be obtained. However, the pattern accuracy obtained by screen printing is low, and it is difficult to control the thickness (thinning) of the heating element layer (11), resulting in high power consumption and large variations in resistance among multiple heaters. Therefore, PVD and CVD are methods that can form patterns with high precision.
The development of a film-forming method was underway.

FIG. 4 shows a conventional method for manufacturing a high-temperature operating element using a thin film forming method. First, a heater resistor (heating element) film (2) is formed on a smooth ceramic substrate (1), and a high-temperature operation element film (4) is formed on the opposite side, and then etched into a predetermined shape. A high-temperature operating element was realized by forming a heater pattern and an element pattern, and joining a lead wire (5) to the heater side.

[Problems to be Solved by the Invention] In the conventional high-temperature operation element formed by the above-described film formation method, a voltage is applied to the lead wire (5) and the resistance changes while the element is used as a heater. This is mainly due to the fact that the resistor (heating element) film (2) is a thin film. Figure 5 shows the change in resistance value over time.

The reason why the resistance initially decreases is because recrystallization of the thin film progresses and the crystal grains in the film become coarser. For example, the resistor (heating element) film (2) is made of W (tungsten), and
When used at 000°C, recrystallization progresses because too°C corresponds to the recrystallization temperature of W.

Next, the reason why the resistance increases over time is due to impurities being mixed into the film or being oxidized due to the atmosphere during use. As a result, the heater was unstable and lacked long-term reliability. Furthermore, there is a problem in that during use, the film peels off from the substrate due to the internal stress of the film, resulting in insufficient performance of both the heater and the element.

In this way, for high-temperature operating elements, either a porous film with low film density is formed on both sides using thick film circuit formation technology, or a dense film with low adhesion and high film density is formed using thin film formation method. However, both the heater and the element were not able to fully demonstrate their performance.

The present invention was made in order to solve the problems of the conventional high-temperature operation elements as described above, and an object thereof is to provide a high-temperature operation element with high long-term reliability.

[Means for Solving the Problems] A high-temperature operating element according to the present invention has a porous high-temperature operating element film with a low film density formed in a predetermined shape on one surface of an insulating member. A resistor film having a higher film density than the high-temperature operation element film is formed on the other surface in a predetermined shape, a lead wire is bonded to the resistor film, and the insulating member is further covered with the resistor film. An insulating protective film is formed on top.

[Function] Since the resistor film in the high-temperature operation element of the present invention is a dense film formed by a thin film formation method, a pattern can be formed with high precision, and the insulating protective film fused to the resistor film is Prevents oxidation of the resistor film due to the usage atmosphere,
It acts to suppress changes in resistance during use. At the same time, it also acts to hold down the substrate and film to prevent them from peeling off during use. On the other hand, since the element side is porous, it is easy to fit in so that a protective layer, an electron emission aid coating layer, an insulating layer, etc. can be easily provided on the element depending on the purpose.

[Example] Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 is a cross-sectional configuration diagram showing a high temperature operating element according to an embodiment of the present invention. In the figure, (1) is a ceramic substrate (insulating substrate), (2) is a dense resistor film with high film density for heaters, (3) is a glassy protective coating N (insulating protective film), (4) ) is a porous film with low film density for a high-temperature operation element film, and (5) is a lead wire. It is desirable for each material to satisfy, for example, the following requirements. The substrate (1) has good thermal conductivity and a coefficient of thermal expansion close to that of the resistor film (2);
It must be a good insulator, not break down at high temperatures, and be smooth. Therefore, considering the manpower, AIN.

A! 203 etc. are possible. The resistor film (2) must have low vapor pressure in a high temperature range and stable electrical characteristics in a high temperature range. Therefore, Mo, W, Pt, Ta, T
Possible examples include iN and TiC. Protective coating N (3
), the diffusion at high temperatures should be small, and the softening point or melting point should be higher than the operating temperature. Therefore, Si
Possible materials include O2, Al2O3, etc., which have a high softening point, a high melting point, and are stable. For example, if it is 5102, the softening point is 1
710℃ (crystal), melting point 1470℃ (crystal), Al2O
3, the melting point is 2030°C. Also, Cab, V2
It may also contain something that scatters to the outside during firing, such as O3.

It is most desirable for the lead wire (5) to have the same characteristics as the resistor film (2), the same diffusion coefficient as the resistor film (2), and the same material as the resistor film (2). Film layer for element 4
) is a porous film that is compatible with a protective layer, an electron emission aid coating layer, an insulating layer, etc., provided to improve its performance.

If the above material is used and the structure is as shown in Figure 1, a voltage is applied to the lead wire (5) to heat the heater, that is, the resistor film (2), and the element film (4) is heated on the back side. It is suitable for improving the performance of high-temperature operating elements that are operated by heating them. For example, if you are trying to obtain a high current density from the element film (4), you can coat the element film (4) with an electron emitting additive so that the change in resistance will be small even when used for a long time. It is stable as a heater, and since it is covered with a glassy protective film, it does not peel off.Furthermore, since the element film is porous, the electron emission aid is well absorbed and a high current density can be obtained.

Here, in view of the above conditions, W/AIN was used as a W co-fired ceramic substrate in which W was coated on the substrate and these were fired at the same time, and W was formed by sputtering as the resistor film (2). As the protective coating layer (3), a glassy "glaze 9" whose main component is 5ilh is used.
A method for manufacturing a high-temperature operating device coated with the following will be described.

Reference photo 1 shows a surface photo of the porous W sintered substrate used in the example, and reference photo 2 shows a surface photo of a dense W sputtered film (reference photo 1 and colleagues).

After etching the W side of a W co-fired ceramic substrate (W/AIM substrate) into a predetermined pattern, W/
The AIN side of the AIM board is mechanically polished to a mirror finish. A mask with a desired heater pattern is set on this substrate (1), and a desired thickness (number + n-n-
A 1O W resistor film (2) is formed. Next, the lead wire (5
) to the desired location using a method such as resistance welding. Next, spray a glassy glass glaze to cover the heater resistor film (2), dry it, and form the coating layer (3).
form. Next, it is fired for 5 to 10 minutes in vacuum or in hydrogen or argon to fuse it to the W resistor film. The processing temperature at this time varies depending on the composition of the "glaze", but is approximately 800 to 1400°C. Here, ``Glaze'' refers to a solution containing oxides, so-called glassy substances.For example, Table 1 shows the composition of three types of glazes, A, B, and C. - This is an example of a commercially available ceramic coating material. The composition of what is called frit in Table 1 is shown in Table 2, and this is a so-called glassy oxide. This glassy material is used as a heater. It dissolves a small amount of metal oxide formed on the resistor film (2) during use, fills the gaps between metals, and acts as a seal coat, so it has excellent adhesion to the resistor film (2). Furthermore, since it is made of glass, it has high electrical insulation properties and does not interfere with its function as a high-temperature heater.

Table 1 Glaze composition (weight ratio) Table 2 Frit composition (weight %) In addition, when providing a protective layer, an electron emission aid coating layer, an insulating layer, etc. on the surface of the element film in the next process, W particles are used as the raw material. Because it is a sintered substrate, it is porous and the layers described above can easily fit into it.

Due to the difference in thermal expansion coefficient during use at high temperatures, the substrate (1)
Distortion may occur between the resistor film (2) and the protective film (3), but as mentioned above, the glass exhibits flexible behavior that fills the gap and acts to alleviate the distortion. Therefore, even if the entire surface is covered, there is no problem of distortion.

Further, if the lead wire (5) is also coated with a similar glass material, the effect will be further improved.

Furthermore, as shown in FIG. 2, it is also possible to process a large area of a ceramic substrate.

In addition, although the method of applying a "glaze" was explained in the above example, it is possible to prepare a glassy target and form a film by a sputtering method, or use a PVD or CVD method to form a glassy protective coating layer (3 ) can be formed.

For glassy compositions, it does not have to be a composite composition as shown in Table 2, but may be a single composition such as 5i()+, Al2O3, etc. For example, if the substrate (1) is Al2O3
If so, coating Ah(h with N(3)) has the advantage of eliminating the need to consider the effects of impurities and diffusion.

In addition, in the above embodiment, the co-fired substrate W/AIN was used,
Although an example has been described in which a high-temperature operation element film of a predetermined shape is obtained by etching W, a W/AIN substrate on which an element pattern is screen printed may also be used. Alternatively, the high-temperature operation element film may be formed by etching a film formed by other methods such as thermal spraying or cladding into a predetermined shape as long as a porous surface is formed.

In addition, in the above embodiment, the method of forming the W resistor film (2) by sputtering method was explained, but so-called PVD methods such as electron beam evaporation, laser PVD method, ion blating method, W Fa, W (Co) s.

Needless to say, it can be formed by a method such as a CVD method using WCIa gas or the like. The same applies to the case where a film other than W, such as Mo, is formed.

Further, since the insulating substrate in the above embodiment was made of AIN, which reacts with water or alkali, a wet process was avoided for forming the heater pattern, but a wet process may be used if the substrate is made of Al2O3 or the like.

[Effects of the Invention] As described above, according to the present invention, a porous high-temperature operation element film with a low film density is formed in a predetermined shape on one surface of the insulating member, while a porous high-temperature operation element film with a low film density is formed on the other surface of the insulating member. forms a resistor film having a higher film density than the high-temperature operation cable film in a predetermined shape,
Since a high temperature operating element is constructed by bonding the lead wire to the resistor film and further covering the resistor film and forming an insulating protective film on the insulating member, there is no problem of peeling from the substrate. This has the effect of providing a high-temperature operating element for mounting a high-temperature heater with high long-term reliability.

Furthermore, since the element film is porous, it is compatible with layers provided on the element depending on the performance of the element, and has the effect that the performance of the element can be easily improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional diagram showing a high-temperature operating element according to one embodiment of the present invention, FIG. 2 is a cross-sectional diagram showing a high-temperature operating element according to another embodiment of the invention, and FIG. 3 is a diagram showing a high-temperature operating element according to another embodiment of the present invention. FIG. 4 is an explanatory diagram showing a method of manufacturing a conventional high-temperature operation element using the thin film formation method, and FIG. 5 is a cross-sectional diagram showing a conventional high-temperature operation element formed using It is a curve diagram showing a change in resistance value over time. In the figure, (1) is an insulating substrate (ceramic substrate),
(2) is a resistor film, (3) is a protective coating layer, (4
) is an element film, and (5) is a lead wire. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] a porous high-temperature operating element film with a low film density formed on one surface of the insulating member in a predetermined shape; a resistor formed in a predetermined shape on the other surface of the insulating member and having a higher film density than the high-temperature operating element film; A high temperature operation element comprising a body film, a lead wire joined to the resistor film, and an insulating protective film formed on the insulating member to cover the resistor film.