JP2568305B2 - Method of forming glass coat layer in thin film resistor element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a glass coat layer in a thin-film resistor element, and more particularly, to a method of utilizing the temperature dependence of the resistance of a metal thin film as a resistor. The present invention relates to a method for forming a glass coating layer of a predetermined thickness on the surface of a thin film resistor element suitably used for measurement, flow rate measurement, etc., for example, a flow rate detection element in a hot wire flow meter, for protecting the same.

(Background Art) Conventionally, as a resistor element of this type, a metal thin film of platinum or the like is formed as a resistor on the surface of a ceramic carrier such as a pipe, a bobbin, or a plate, and the metal thin film is externally mounted. Known is a structure in which metal lead wires for establishing electrical continuity with a circuit are connected, and in such an element, a metal thin film provided on the surface of a ceramic carrier is protected. To this end, a glass coat layer having a predetermined thickness is provided on the outer surface of such a metal thin film.

FIG. 1 shows an example of such a thin film resistor element, wherein reference numeral 2 denotes a pipe-shaped bobbin made of a known ceramic material such as alumina, which constitutes a ceramic carrier. . And this bobbin 2
Leads 4 made of a metal wire such as a platinum wire or a stainless wire are bonded and fixed with a glass-based adhesive 6 in a state where they are inserted for a predetermined length. A metal thin film (resistor) 8 made of platinum or the like is provided in a predetermined pattern on the outer peripheral surface of the bobbin 2 in the same manner as in the related art. It is electrically connected to 4. Then, a glass coating layer 12 made of a suitable glass material is formed as a protective coating layer so as to cover at least the outer surface of the metal thin film 8 and reach the entire bobbin 2 by a predetermined thickness (for example, several μm to several tens μm). ).

Incidentally, the formation of the glass coat layer 12 in such a thin film resistor element is generally performed by applying and baking a material obtained by mixing and dispersing glass powder in an appropriate liquid. Coat layer
12 needs to be provided with a uniform thickness, for which,
In JP-A-1-180420, when forming a glass coat layer by a dipping method (dipping method),
It has been proposed to use a highly volatile quick-drying solvent such as an ether, ketone, or ester.

However, such a method of forming a glass coat layer having a predetermined thickness on a resistor element by using such a quick-drying solvent and immersing the slurry in a slurry obtained by mixing glass powder with the solvent is used in such a method. By pulling up the element immersed in the slurry, the thickness of the glass coat layer in the element circumferential direction can be made uniform, but the viscosity of the slurry changes every moment because a quick-drying solvent is used. In addition, since it is necessary to apply the slurry by the desired thickness in one dipping operation, the uniformity of the thickness of the glass coat layer is deteriorated in the pulling direction of the element. It was inherent. However, if the pulling speed of the element is controlled in consideration of the gradually changing slurry viscosity, it is theoretically possible to maintain the uniformity of the film thickness. Control is extremely difficult and poorly practical.

In addition, there is also an inherent problem that the viscosity of the glass coat layer varies among the individual elements in which the glass coat layer is formed by being sequentially immersed in the slurry because the slurry viscosity gradually changes. Was.

(Problem to be Solved) Here, the present invention has been made in view of such circumstances, and an object of the present invention is to solve the above-mentioned disadvantages and to provide a glass having a uniform film thickness even in the pulling direction. It is an object of the present invention to provide a method that can advantageously form a coat layer on a thin film resistor element.

(Solution) In order to solve the above-described problems, the present invention provides a method for forming a predetermined metal thin film on the surface of a ceramics carrier, and providing the metal thin film with electrical continuity with an external circuit. When a glass coat layer having a predetermined thickness is formed on the outer surface of the metal thin film, the thin film resistor element is formed of carbon and hydrogen or carbon, hydrogen and oxygen and has a boiling point of 150. Using a glass paste slurry obtained by mixing glass powder with an organic vehicle at a temperature of at least 0 ° C., immersing the thin-film resistor element in the glass paste, and baking to provide a glass thin layer having a thickness not exceeding 5 μm. The thin-film resistor element is pulled up so as to have a thickness of the glass paste coating layer, and a thin-layer coating step of drying is repeated a plurality of times. It is characterized in that makes with the glass coating layer having a predetermined thickness.

In the present invention, the coating layer of the glass paste formed on at least the outer surface of the metal thin film of the thin-film resistor element is formed during the thin-layer coating step, or a suitable number of times or all of the thin-layer coating step. After the completion of the above, firing is performed.

Further, in the present invention, preferably, the plurality of thin-layer coating steps are configured by a combination of thin-layer coating steps employing pull-up operations in which pull-up directions of the thin-film resistor elements are opposite to each other. As a result, the uniformity of the thickness of the glass coat layer formed can be further improved.

(Operation / Effect) As described above, in the method for forming the glass coat layer of the thin film resistor element according to the present invention, the glass coat layer is not quick-drying and has a boiling point of 15%.
An organic vehicle (solvent) with a temperature of 0 ° C or higher is used, and the thin film resistor element is immersed in a glass paste that is made by mixing glass powder into a slurry, and volatilization of the organic vehicle in the glass paste is immersed. There is almost no change during the work, so that it is no longer necessary to take into account any variation in the coating thickness (film thickness) based on such a change in the viscosity of the glass paste.

Further, in the present invention, even when such a slurry-like glass paste is used, what is necessary is to perform a thin layer coating process of the glass paste such that the thickness of the glass paste obtained by sintering becomes a thin glass layer not exceeding 5 μm. Repeatedly, since the glass paste is applied little by little in order to obtain the desired glass coat layer thickness, the thickness variation of the coating layer due to dripping can be effectively suppressed, A glass coat layer having a more uniform thickness can be advantageously formed on the thin film resistor element.

(Specific Configuration) By the way, according to the present invention, the thin film resistor element on which the glass coat layer is formed includes various examples or structures known in the art including the specific examples shown in FIG. The present invention can be applied to any of these devices.

The present invention provides a slurry-like glass paste coated on at least the outer surface of a metal thin film of such a thin film resistor element, comprising carbon and hydrogen, or carbon, hydrogen and oxygen, and having a boiling point of 150 ° C. or more. It was formed by using an organic vehicle and uniformly mixing the glass powder with the organic vehicle.

Note that the organic vehicle needs to have a boiling point (bp) of 150 ° C. or higher in order to prevent the viscosity of the slurry-like glass paste to be formed from changing over time. Carbon and hydrogen, or carbon,
It must be an organic liquid composed of elements consisting of hydrogen and oxygen, such as terpineol (bp: about 200 ° C.),
Examples thereof include 1-hexanol (bp: 158 ° C), butyl carbitol (bp: 230 ° C), and 2-ethylhexanol (bp: 184 ° C).

Then, according to the present invention, when preparing the slurry-like glass paste by mixing the organic vehicle and the glass powder as described above, the glass powder and the organic vehicle generally have a weight of about 2: 1 to 2: 3. The mixture is blended in a ratio, further blended with an appropriate organic binder, uniformly mixed with a cobblestone in a pot mill, and taken out as a glass slurry. Further, if necessary, an organic vehicle is further added to the obtained glass slurry, and the viscosity is adjusted so that the viscosity is about 1000 to 2000 centipoise (cp).

Next, using the slurry-like glass paste thus obtained, a thin coating layer of the glass paste is formed on at least the outer surface of the metal thin film of the thin-film resistor element according to a normal dipping method (dipping method). Is done.
For example, as shown in FIG. 2, one of the lead wires 22 of the thin-film resistor element 20 is gripped by a jig 24, and in a state where the thin-film resistor element 20 is suspended, a slurry-like glass paste After being inserted and immersed in 26, the slurry glass paste 26 is thinly adhered to the entire surface of the thin film resistor element 20 by lifting it up, and then dried. In the present invention, the adhesion thickness of the glass paste 26 (the coating thickness of the coating layer) is uniform in the axial direction (pulling direction) of the thin film resistor element 20 as well as in the circumferential direction. In order to improve the properties, the thickness is set so as to give a thin glass layer having a thickness not exceeding 5 μm by firing. Note that such a thin adhesive layer of the glass paste 26 can be easily realized by controlling the pulling speed of the thin film resistor element 20 by the jig 24.

Further, in the present invention, a thin layer coating step including application and drying of the glass paste by such immersion,
A glass coat layer having a desired thickness is applied to the thin film resistor element 20.
(At least on the outer surface of the metal thin film) to be formed on the thin film resistor element 20 in the immersion step shown in FIG. By performing the immersion (pulling) operation by inverting the top and bottom, the thin film resistor element 20 is pulled up so that the pulling directions are opposite to each other, so that the outer surface of the thin film resistor element 20 is It becomes possible to make the thickness of the coating layer of the glass paste to be formed, and furthermore, the thickness of the glass coat layer more uniform. Above all, it is desirable to perform such pulling operations in opposite directions alternately.

In the above-mentioned thin layer coating step, the applied layer of the glass paste to be formed needs to be a glass coat layer by firing, and the firing operation is performed every time such an applied layer is formed. It can be carried out during each thin layer coating process, or after a suitable number of thin layer coating processes have been completed, or after all thin layer coating processes have been completed, a multi-layered thin layer of glass paste is applied. This is accomplished by firing all the stacked layers at once.

And such a firing operation is generally performed at 500 ° C. to 900 ° C.
° C, preferably at a temperature of about 600 to 750 ° C. At this time, in order to prevent oxidation of the lead wires of the thin film resistor element, the element body portion where the application amount of the glass paste is formed ( Local heating by light or local heating using an electric heater previously proposed by the present applicant in Japanese Patent Application No. 1-173522 so that only the ceramic carrier portion on which the metal thin film is formed) is heated. ,
It will be suitably adopted.

(Examples) Hereinafter, some examples of the present invention will be shown to clarify the present invention more specifically. However, the present invention should not be construed as being limited to the description of such examples. Needless to say, it is not. It should be understood that various changes, modifications, improvements, and the like can be made to the present invention based on the knowledge of those skilled in the art without departing from the spirit thereof.

Example 1 Using an alumina bobbin as a ceramics carrier, a platinum thin film was formed on the outer peripheral surface by sputtering to a thickness of 0.8 μm.
After forming with a thickness of m, spiral cutting grooves are formed by laser trimming to obtain a resistor thin film of interest, while lead wires made of platinum are inserted into both ends of the alumina bobbin, respectively. By bonding and fixing, a thin-film resistor element having a structure as shown in FIG. 1 was prepared in a size as shown in FIG.

On the other hand, glass powder: 30 parts by weight, acrylic binder: 1.
5 parts by weight and terpineol (organic vehicle): 30 parts by weight were put together with a cobblestone in a pot mill, mixed for 6 hours to obtain a uniform slurry, and then taken out of the pot mill. At this time, the viscosity of the slurry was about 3000 cp. Next, while measuring the viscosity of the obtained slurry with a viscometer, terpineol was added until the viscosity became 1400 cp, and the viscosity was adjusted to obtain a slurry glass for immersing the thin film resistor element. A paste was prepared.

Then, the prepared thin film resistor element was immersed in the slurry glass paste thus prepared as shown in FIG. 2, pulled up at a pulling rate of 0.4 mm / sec, and dried. By performing one thin-layer coating process, and repeating this thin-layer coating process six times, six thin layers of glass paste are laminated on the thin-film resistor element. By heating and baking using an electric heater disclosed in JP-A-1-173522, a thin-film resistor element having a glass coat layer having a thickness of about 25 μm at the center of the element was obtained. The operation of forming such a glass coat layer was performed on ten thin film resistor elements.

For comparison, a dipping operation was performed in which the thin film resistor element was pulled up at a pulling rate of 1 mm / sec using a slurry-like glass paste whose viscosity was adjusted to 2000 cp using acetone as an organic vehicle (solvent). The glass coat layer in which the coating amount of the glass paste applied to the entire surface of the thin film resistor element by the single immersion operation is baked in the same manner as described above, and the film thickness at the central part of the element becomes approximately 25 μm Was formed on the outer surface of the device. The formation of such a glass coat layer was also performed on ten thin film resistor elements.

The thickness of the glass coat layer in 20 of the glass-coated thin film resistor elements thus obtained was measured at points a and b shown in FIG. 3, respectively. The difference in film thickness is shown in Table 1 below as an evaluation criterion indicating the uniformity of the film thickness of the formed glass coat layer.

As is apparent from Table 1, according to the present invention,
A slurry-like glass paste prepared using terpineol as an organic vehicle allows a thin coating layer to be formed on a thin-film resistor element a plurality of times to prepare a low-boiling organic vehicle (acetone). The difference in film thickness between points a and b is smaller than that of the comparative example in which the glass paste was applied in one dipping operation,
Therefore, it is recognized that the glass coat layer formed on the thin film resistor element is excellent in uniformity of film thickness.

Example 2 By using a slurry-like glass paste prepared using terpineol as an organic vehicle in Example 1 and repeating the thin-layer coating step of forming a thin coating layer on a thin-film resistor element six times, such a resistor was obtained. A glass coat layer having a thickness of about 28 μm at the center of the device was formed on the device. In addition, the firing of a thin coating amount of the glass paste formed in each thin layer coating process,
The drying was performed after drying the applied amount of the glass paste in each thin layer coating step. Therefore, the number of firings is six.

About 10 times of the glass-coated thin film resistor element thus obtained, a
The film thickness of the glass coat layer at points and b was measured, and the results are shown in Table 2 below. In Table 2 below, the results of the comparative example obtained in Example 1 are also shown for comparison.

Example 3 In the same manner as in Example 1, the thin-layer coating process using a slurry-like glass paste prepared using terpineol as an organic vehicle was performed six times, and after all the thin-layer coating processes were completed, Example 1 was performed. By baking in the same manner as described above, a glass coat layer having a film thickness of about 25 μm at the center of the device was formed on the thin film resistor device. Also,
Each time the thin layer coating process was completed, the pulling direction of the thin film resistor element was reversed so that the pulling directions of the element were opposite to each other for each dipping operation.

The thickness of the glass coat layer in the glass-coated thin-film resistor element thus obtained was measured at points a and b in the same manner as in Example 1. It is shown in the table. In addition, the third
The table also shows the results of the comparative example obtained in Example 1.

As is apparent from the results of Table 3, the direction of immersion (pulling up) of the thin film resistor element into the glass paste is reversed to repeat the thin layer coating step.
This makes it possible to further uniform the thickness of the formed glass coat layer.

[Brief description of the drawings]

FIG. 1 is an explanatory longitudinal sectional view showing an example of a thin film resistor element which can be used in the present invention, and FIG. 2 is an explanatory view showing a step in an example of an immersion method employed in the method of the present invention. FIG. 3 is an explanatory view showing the measurement points (a, b) of the size of the thin film resistor element used in the example and the thickness of the formed glass coat layer. 2: Bobbin, 4: Lead 6: Adhesive, 8: Metal thin film 10: Conductive paste, 12: Glass coat layer 20: Thin film resistor element 22: Lead wire, 24: Jig 26: Slurry glass paste

Claims (3)

(57) [Claims] 1. A thin-film resistor element comprising a predetermined metal thin film formed on a surface of a ceramic carrier, and a metal lead wire for establishing electrical conduction with an external circuit connected to the metal thin film. Slurry glass obtained by mixing glass powder with an organic vehicle consisting of carbon and hydrogen or carbon, hydrogen and oxygen and having a boiling point of 150 ° C or more when forming a glass coat layer of a predetermined thickness on the outer surface of a metal thin film After the thin film resistor element is immersed in the glass paste using a paste, the thin film resistor element is coated with the glass paste so as to give a thin glass layer having a thickness not exceeding 5 μm by firing. , And a thin layer coating step of drying is repeated a plurality of times to form the glass coat layer having the predetermined thickness. The method of forming the glass coating layer in antibodies element. 2. The glass according to claim 1, wherein the coating layer of the glass paste is fired during the thin-layer coating step or after an appropriate number or all of the thin-layer coating steps. A method for forming a coat layer. 3. The thin-film coating step according to claim 1, wherein the plurality of thin-layer coating steps comprise a combination of thin-layer coating steps employing pull-up operations in which pull-up directions of the thin-film resistor elements are opposite to each other. (2) The method for forming a glass coat layer according to (2).