JPH11121208A - Temperature sensor element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reinforce the adhesive force of a heat-resistant insulating substrate and a metal film by forming a surface of the heat-resistant insulating substrate at a specified surface roughness, and forming the metal film, thereon by electroless plating. SOLUTION: A temperature sensor element 10 is constituted of a heat- resistant insulating substrate 11 comprising aluminum or the like, a metal film 12 having a resistor pattern 13, terminal electrodes 14a and 14b formed at both end parts on the circuit of the resistor pattern 13, lead terminals 15a and 15b attached to both the terminal electrodes and coating material, which covers the connecting parts of the metal film 12 and the terminal electrodes 14a and 14b and the lead terminals 15a and 15b. Then, on the surface of the heat- resistance insulating substrate 11, a surface roughness of 0.5-5 μm in Rz display is formed. The metal film 12 is formed to the deep part of this concave and convex part by electroless plating. When the metal film 12 is formed to the deep part in this way, the adhesive force of the heat-resistant insulating substrate 11 and the metal film 12 is reinforced by anchor effect. The temperature sensor 10 having high durability and reliability with respect to the high temperature is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high temperature sensor element for measuring the temperature of a catalyst or an exhaust pipe of an automobile and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional temperature sensor element has a platinum film formed on a heat-resistant insulating substrate made of alumina by vapor deposition or sputtering. This is because platinum is extremely stable chemically and has very good resistance-temperature characteristics.

A meander-shaped resistance pattern has been formed on the platinum film by laser cutting, dry etching, or the like. Thereafter, terminal electrodes were formed of gold or the like on both ends of the circuit of the resistance pattern, and lead terminals made of platinum or the like were formed on these terminal electrodes. Then, the connection portion between the terminal electrode and the lead terminal on the metal film is coated with a heat-resistant glass paste for mechanical reinforcement and protection from moisture and dust.

A temperature sensor element formed using a platinum film as described above has advantages such as high resistance and small size.

[0005]

By the way, in order to measure the temperature of a catalyst or an exhaust pipe of an automobile, a temperature sensor element capable of withstanding 1000 ° C. is required. However, in the conventional temperature sensor element, since the difference in linear expansion coefficient between the heat-resistant insulating substrate and the platinum film is large, the heat-resistant insulating substrate and the platinum film are separated at a high temperature of about 1000 ° C. If the peeling occurs as described above, the resistance value of the temperature sensor element fluctuates or the resistance pattern is disconnected, and thus there is a problem in the reliability of the temperature sensor element. Therefore, there has been a demand for a temperature sensor element which does not cause separation of the platinum film from the substrate even when used at a high temperature of about 1000 ° C. However, in the conventional temperature sensor element, the surface roughness of the heat-resistant substrate on which the platinum film is formed is
Since it was close to 0 in Rz (JIS-B-0601), there was a problem that the adhesion between the heat-resistant insulating substrate and the platinum film was weak.
Furthermore, in the conventional method of forming a platinum film by vapor deposition or sputtering on a heat-resistant insulating substrate, since platinum is an extremely stable metal that does not easily react, the adhesion between the heat-resistant insulating substrate and the platinum film is high. Had the problem of being weak.

[0006] In view of such a problem, an improvement plan has been considered. For example, there is one in which an intermediate layer is provided between a heat-resistant insulating substrate and a platinum film. In this method, a layer of a metal oxide or the like is formed on a heat-resistant insulating substrate, and a platinum film is formed thereon. By doing so, the adhesion between the heat-resistant insulating substrate and the intermediate layer, and between the intermediate layer and the platinum film is stronger than the adhesion between the heat-resistant insulating substrate and the platinum film, so that peeling at high temperatures can be prevented. . However, when such an intermediate layer is provided and used at a high temperature, the intermediate layer sometimes reacts with platinum. The platinum film is affected by this reaction, and the temperature coefficient of resistance changes from a set value, resulting in a problem that the characteristics of the temperature sensor element deteriorate.

Further, in the method of forming a platinum film by vapor deposition or sputtering, there is a problem that platinum adheres to the device wall other than the substrate, and the use of more platinum than necessary increases the cost. Also, when forming a platinum film on a heat-resistant insulating substrate having a surface roughness, there is a problem that the adhesion between the heat-resistant insulating substrate and the platinum film is weakened because platinum does not reach the deep portion of the concave portion. .

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a temperature sensor element which can be used even at a high temperature of about 1000 ° C. and a method of manufacturing the same. I have.

[0009]

In order to achieve the above object, a temperature sensor element according to the present invention comprises a heat-resistant insulating substrate and a platinum group metal or platinum having a resistance pattern formed on the heat-resistant insulating substrate. A heat-resistant insulating substrate having a surface with a surface roughness of 0.5 to 5 μm, and the metal film is formed on the surface by electroless plating. .

Thus, the adhesion between the heat-resistant insulating substrate and the metal film can be improved without deteriorating the characteristics of the temperature sensor element, and it can withstand use at a high temperature of about 1000 ° C. become.

Further, the metal film is formed of platinum, so that the adhesion between the heat-resistant insulating substrate and the metal film is improved, and the manufacturing cost can be reduced.

A surface roughening step of forming a surface with a surface roughness of 0.5 to 5 μm on the heat-resistant insulating substrate; a step of providing a catalyst nucleus on the surface of the heat-resistant insulating substrate; A manufacturing method including an electroless plating step of forming a metal film on a substrate, a heat treatment step of crystallizing the metal film, and a step of processing the metal film to form a resistance pattern is used.

[0013] Thus, a temperature sensor element which can improve the adhesion between the heat-resistant insulating substrate and the metal film without much trouble and cost and can withstand use at a high temperature of about 1000 ° C is manufactured. be able to.

Further, in the surface roughening step, a manufacturing method in which etching is performed using a hydrofluoric acid solution is used. Thereby, the intended region on the surface of the heat-resistant insulating substrate can be selectively etched.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a temperature sensor element according to an embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the temperature sensor element 10 includes a heat-resistant insulating substrate 11 made of alumina or the like, a metal film 12 having a resistance pattern 13, and terminal electrodes 14 formed at both ends of the circuit of the resistance pattern 13.
a, 14b and lead terminals 15 attached to both terminal electrodes
a, 15b, a coating material (not shown) covering the connection portions of the metal film 12, the terminal electrodes 14a, 14b, and the lead terminals 15a, 15b
It is composed of Note that the heat-resistant insulating substrate 11 and the coating material can withstand use at a high temperature of about 1000 ° C.

The surface of the heat-resistant insulating substrate 11 has an Rz display (JI
SB-0601) has a surface roughness of 0.5-5 μm,
The metal film 12 is formed by electroless plating up to the deep portion of the unevenness. When the metal film 12 is formed to a deep portion in this way, the adhesion between the heat-resistant insulating substrate 11 and the metal film 12 is increased by the anchor effect. Therefore, even when used at a high temperature of about 1000 ° C., the heat-resistant insulating substrate 11 and the metal film 12 do not peel off from each other, and a temperature sensor element 10 having high durability and high reliability at a high temperature of about 1000 ° C. can be obtained. . Figure 2 shows the surface roughness and 1
It is a relation diagram of the resistance value change rate after a standing test at 000 ° C for 100 hours. Note that platinum is used as the metal film. As shown in the figure, the temperature sensor element of the present invention has a resistance change rate of less than 0.1% when the surface roughness is in the range of 0.5 to 5 μm. Even when used at high temperatures, stable characteristics are exhibited.

If the surface roughness is smaller than 0.5 μm in Rz, the anchor effect becomes insufficient and the adhesion between the heat-resistant insulating substrate 11 and the metal film 12 becomes weak. Therefore, the heat-resistant insulating substrate 11 and the metal film 12 can be used at a high temperature.
And the resistance value fluctuates or the resistance pattern 13
However, there is a problem such as disconnection of the wire, and there is anxiety about use at a high temperature of about 1000 ° C. Conversely, if the surface roughness is greater than 5 μm in Rz, the surface irregularities are too large and the mechanical strength of the heat-resistant insulating substrate 11 is reduced. Further, since the metal film 12 can be partially thinned on the heat-resistant insulating substrate 11, the heat-resistant insulating substrate 11 can be used at a high temperature.
And the metal film 12 are peeled off, and the resistance value fluctuates, and the resistance pattern 13 is disconnected.
Anxiety remains for use under moderately high temperatures. Further, when forming the resistance pattern 13 on the metal film 12 by laser cutting or dry etching, the metal film 12
A problem arises in that the removed portion of 12 deviates from the intended portion, causing variations in the characteristics of the temperature sensor element 10.

As the metal film 12, Pt (platinum), R
A platinum group metal consisting of u (ruthenium), Rh (rhodium), Pd (palladium), Os (osmium), and Ir (iridium) is used. This is because platinum group metals are extremely stable, and the resistance-temperature characteristics are also stable. One of these metals may be used, or an alloy of two or more metals may be used. Among them, platinum is the most commonly used metal, and when platinum is used, a temperature sensor element having high characteristics can be manufactured at lower cost than other white metal.

Next, a method for manufacturing the temperature sensor element of the present invention will be described. First, the heat-resistant insulating substrate made of 99.6% alumina is degreased with alkali and washed with water. Thereafter, the surface of the heat-resistant insulating substrate is etched with a 10% hydrofluoric acid solution at room temperature. At this time, impurities such as SiO _{2 at the} grain boundaries are selectively etched, so that fine irregularities are formed on the surface of the heat-resistant insulating substrate. At this time, depending on the case,
By adjusting the hydrofluoric acid concentration and the etching time, a heat-resistant insulating substrate having a surface roughness of 0.5 to 5 μm in Rz is formed.

Next, a catalyst nucleus for plating a metal film on the roughened surface of the heat-resistant insulating substrate having a roughened surface is provided. First, 5 g / dm ^{3 of} SnCl ₂ and 1 cm ³ / dm ^{3 of} HCl
Sensitization of the heat-resistant insulating substrate is performed with an aqueous solution to be used.
Next, the heat-resistant insulating substrate is activated with an aqueous solution of PdCl ₂ at 0.5 g / dm ³ and HCl at 0.1 cm ³ / dm ³ . Further, the same sensitizing and activating processes are performed once again to enhance the effect. In this way, the plating nuclei spread to the deep portions of the irregularities on the surface of the heat-resistant insulating substrate.

Incidentally, the method of providing the catalyst nucleus to the heat-resistant insulating substrate is not limited to the above-mentioned method, and for example, PdCl ₂ , SnC
The catalyst nucleus may be provided by a catalyst treatment using l ₂ , HCl, an accelerating treatment using H ₂ SO ₄ , or the like.

Thereafter, a platinum film is formed on the heat-resistant insulating substrate by electroless plating. By forming the platinum film by electroless plating, the platinum spreads to the deep portion of the irregularities formed on the surface of the heat-resistant insulating substrate, and the adhesion between the heat-resistant insulating substrate and the platinum film is increased by the anchor effect. Then, the platinum film is crystallized by heat treatment in the air at 1300 ° C. for 2 hours to stabilize characteristics such as a resistance value.

Further, a resistance pattern is formed in a meandering shape on the platinum film by a method such as laser cutting or dry etching. Except for both ends of the circuit of the resistance pattern on the platinum film surface, heat-resistant glass paste printing / firing, ceramic sol-gel coating are used for mechanical reinforcement, protection from moisture and dust, and electrical insulation. -A coating is formed by a method such as baking.

Next, terminal electrodes are formed at both ends of the circuit of the resistance pattern by fritless thick film screen printing and baking of platinum or the like in consideration of heat resistance at 1000 ° C. In this case, the glass frit is not used because the temperature sensor element of the present invention is intended for heat resistance of 1000 ° C., and under such use conditions, a problem such as peeling exceeding the heat resistance limit of the glass component occurs. Because. After that, laser trimming is performed to adjust the resistance value of the temperature sensor element to a standard value.

Further, a lead terminal made of a platinum wire or the like is welded on the terminal electrode. Thereafter, for the purpose of mechanical reinforcement, protection from moisture and dust, and electrical insulation again, a coating material made of ceramic or heat-resistant glass paste or the like is applied to the welded portion of the lead terminal and baked.

The plurality of temperature sensor elements formed in this way are separated into individual elements to form an element.

By manufacturing the temperature sensor element by such a method, the manufacturing labor and cost can be reduced relatively easily. Further, in the surface roughening step of the heat-resistant insulating substrate, by using hydrofluoric acid or ammonium fluoride, only changing the conditions such as concentration and time, the surface roughness of 0.5 to 5 μm in Rz display is obtained. A heat-resistant insulating substrate having a surface can be formed relatively easily.
From the viewpoint of general use and cost, it is preferable to use a hydrofluoric acid solution.

[0028]

As described above, according to the present invention, the surface of the heat-resistant insulating substrate is formed to have a surface roughness of 0.5 to 5 μm in Rz, and a metal film is formed thereon by electroless plating. This strengthens the adhesion between the heat-resistant insulating substrate and the metal film,
Even when used at high temperatures, the heat-resistant insulating substrate and the metal film do not peel off. Therefore, at a high temperature of about 1000 ° C., without deterioration of the temperature sensor element characteristics such as a change in the temperature coefficient of resistance caused by providing an intermediate layer such as a metal oxide between the heat-resistant insulating substrate and the metal film. Temperature sensor elements can be used. Further, it is possible to solve problems such as disconnection of the resistance pattern and fluctuation of the resistance value, and to provide a highly reliable temperature sensor element.

By using platinum for the metal film, the temperature sensor element can be manufactured at low cost.

Further, according to the manufacturing method of the present invention, a surface roughness of 0.5 to 5 μm can be formed directly on the surface of the heat-resistant insulating substrate, and the method can be performed at a high temperature of about 1000 ° C. without much trouble and cost. A usable temperature sensor element can be manufactured. In addition, by combining the electroless plating process, the metal film is formed to the deep part of the unevenness of the surface of the heat-resistant insulating substrate, so that the adhesion between the heat-resistant insulating substrate and the metal film is strengthened, and a high temperature of about 1000 ° C. A highly reliable temperature sensor element can be manufactured even when used under the following conditions.

Further, in the surface roughening step, etching with a hydrofluoric acid solution was used. As a result, impurities such as SiO _{2 at the} grain boundaries of the heat-resistant insulating substrate can be selectively etched, and a surface roughness of 0.5 to 5 μm in Rz can be formed relatively easily.

[Brief description of the drawings]

FIG. 1 is a perspective view of a temperature sensor element of the present invention.

FIG. 2 is a graph showing the relationship between the surface roughness of a temperature sensor element of the present invention after etching a heat-resistant insulating substrate and the rate of change in resistance after a standing test at 1000 ° C. for 100 hours.

[Explanation of symbols]

 10 Temperature sensor element 11 Heat resistant insulating substrate 12 Metal film 13 Resistance pattern 14a, 14b Terminal electrode 15a, 15b Lead terminal

Claims (4)

[Claims] 1. A temperature sensor element comprising: a heat-resistant insulating substrate; and a metal film made of a platinum group metal or an alloy containing a platinum group metal, having a resistance pattern formed on the heat resistant insulating substrate. A temperature sensor element, wherein the heat-resistant insulating substrate has a surface having a surface roughness of 0.5 to 5 μm, and the metal film is formed on the surface by electroless plating. 2. The temperature sensor element according to claim 1, wherein said metal film is made of platinum. 3. A surface roughening step of forming a surface having a surface roughness of 0.5 to 5 μm on a heat-resistant insulating substrate; a step of providing a catalyst nucleus on the surface of the heat-resistant insulating substrate; An electroless plating step of forming a metal film on an insulating substrate; a heat treatment step of crystallizing the metal film; and a step of processing the metal film to form a resistance pattern. A method for manufacturing a sensor element. 4. The method according to claim 3, wherein the surface roughening step is performed by etching with a hydrofluoric acid solution.