JP6718792B2 - Temperature detector - Google Patents

Description

The present invention relates to a temperature sensing element in which a linear conductor containing platinum as a main component is arranged on an insulating substrate.

As a sensor for detecting a temperature in a fluid such as exhaust gas at a high temperature (for example, about several hundreds to one thousand degrees Celsius), a sensor that uses a change in electric resistance of a metal material with temperature is known. As the metal material, a metal material containing platinum is often used from the viewpoint of oxidation resistance at high temperature and temperature dependence of electric resistance.

As a sensor including a metal material for temperature measurement, for example, a thin film resistor made of platinum or the like is provided on a substrate via an insulating layer, and a lead wire for connecting the thin film resistor and a connection lead terminal, and a connection A temperature sensor having a structure in which a lead terminal is covered with a reinforcing material is known (for example, refer to Patent Document 1).

JP-A-8-201313

However, the above-mentioned conventional sensor, when placed in a high-temperature environment, cracks occur inside the reinforcing material due to stress generated by thermal expansion of the lead wire, connecting lead terminals, etc., and the strength of the reinforcing material is increased. There was a problem of lowering.

The temperature sensing element according to one aspect of the present invention is
An insulating substrate,
A linear conductor disposed on the insulating substrate, the linear conductor being made of a metal material containing platinum as a main component,
An electrode pad disposed on the first surface of the insulating substrate and electrically connected to the linear conductor;
A lead made of a metal material containing platinum as a main component, one end of which is joined to the electrode pad;
A protective member disposed on the first surface of the insulating substrate so as to cover a bonding region between the electrode pad and the lead;
When viewed in a cross section perpendicular to the axial direction of the lead, it is a cushioning member arranged between the protective member and the lead, including pores inside, than the softening temperature of the protective member. A cushioning member having a low softening temperature,
It is characterized by including.

According to the temperature sensing element of one aspect of the present invention, when the temperature sensing element is placed in a high temperature environment, the stress generated by the thermal expansion of the lead can be relieved by the buffer member. Thereby, the generation of cracks inside the protective member can be suppressed, and the reliability of connection with the external electric circuit can be improved.

It is an exploded perspective view showing a temperature sensing object concerning an embodiment of the present invention. It is a top view of the temperature sensing element shown in FIG. FIG. 3 is a cross-sectional view showing a part of the cross section of the temperature sensing element taken along the line AA in FIG. 2.

A temperature sensing element according to an embodiment of the present invention will be described with reference to the accompanying drawings. The distinction between upper and lower sides in the following description is for convenience, and does not limit the upper and lower sides when the temperature sensing element is actually used.

FIG. 1 is an exploded perspective view showing a temperature sensing element according to an embodiment of the present invention, FIG. 2 is a top view of the temperature sensing element according to the embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. It is sectional drawing which expands and shows the joining area|region of an electrode pad and a lead in the temperature sensing device which concerns on a form, Comprising: A part of cross section cut|disconnected by the cutting plane line AA line of FIG. 2 is shown.

As shown in FIG. 1, the temperature sensing element 1 includes an insulating substrate 2, a linear conductor 3 provided on the insulating substrate 2, a first surface (upper surface) 2a of the insulating substrate 2, and a linear shape. It includes an electrode pad 4 electrically connected to the conductor 3, and a lead 5 having one end joined to the electrode pad 4.

The insulating substrate 2 is, for example, a flat plate such as a square plate, and is a base portion on which the linear conductor 3 is provided. The insulating substrate 2 is formed of a ceramic sintered body such as an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body, or a glass ceramic sintered body. The insulating substrate 2 is formed by laminating a plurality of insulating layers 2b made of such a ceramic sintered body.

The insulating substrate 2 can be manufactured by the following method, for example, when each insulating layer 2b is made of an aluminum oxide sintered body. First, a slurry prepared by adding and mixing an appropriate organic binder and a solvent to raw material powders such as aluminum oxide, silicon oxide, magnesium oxide and calcium oxide is formed into a sheet by a doctor blade method or the like to form a ceramic green sheet. Create. Next, these ceramic green sheets are cut and processed into appropriate dimensions, and then a plurality of these are laminated to form a laminated body. After that, the insulating substrate 2 can be manufactured by firing this laminate at a high temperature (about 1300 to 1600° C.). Each of the plurality of ceramic green sheets becomes the insulating layer 2b. The insulating substrate 2 may include glass. Moreover, you may include the insulating layer etc. which have glass as a main component.

The linear conductor 3 is formed of platinum or a metal material containing platinum as a main component, which is a metal material whose electric resistance changes according to temperature. In order to detect the change in the electric resistance of the metal material according to the temperature change, it is preferable that the absolute value of the electric resistance of the linear conductor is large in the initial stage (for example, in a state at room temperature of about 25° C.).

This is for the following reason. That is, the change of the electric resistance value according to the temperature change of the linear conductor 3 occurs at a constant ratio regardless of the magnitude (absolute value) of the initial electric resistance value. That is, the larger the initial electric resistance value, the larger the absolute value of the change in the electric resistance due to the temperature change. The larger the absolute value of the change in the electric resistance, the less likely it is to be affected by noise (change in the electric resistance due to factors other than temperature change). Also, the measurement becomes easier. Therefore, the linear conductor 3 preferably has a large initial electrical resistance value. Therefore, a metal material such as platinum is linear (that is, a section in which the electric resistance value is measured is long and is effective in increasing the absolute value of the electric resistance).

Regarding the components other than platinum in the metal material containing platinum as the main component, the components (types) and additions thereof are appropriately added for the purpose of adjusting the temperature resistance coefficient (TCR) of the linear conductor 3 or improving heat resistance. The quantity is selected. Examples of components other than platinum include metal materials of platinum group elements such as palladium, rhodium, and iridium, and gold. In addition, for example, when the linearity of the change of the electric resistance value with respect to the temperature change of the linear conductor 3 is important, it is preferable that the content of platinum is large.

The metal material containing platinum as a main component contains platinum in a ratio of about 80 mass% or more. Platinum and the other components may form an alloy, or may exist as independent crystal grains. The linear conductor 3 may contain an additive other than a metal component such as platinum or a metal material containing platinum as a main component. Examples of the additive material include particles of an inorganic material such as aluminum oxide, which are similar to those contained in the insulating substrate 2. The additive is added, for example, for matching the firing shrinkage between the linear conductor 3 and the insulating layer 2b.

The linear conductor 3 is formed, for example, by applying a metal paste prepared by kneading platinum powder together with an organic solvent and a binder in a predetermined pattern on the main surface of the ceramic green sheet to be the insulating layer 2b and simultaneously firing the same. can do.

The electric resistance value between both ends of the linear conductor 3 is measured by, for example, an external electric circuit (not shown). This electric resistance value changes according to the temperature of the linear conductor 3, and the temperature of the linear conductor 3 changes according to the temperature (external temperature) of the environment in which the temperature sensing element 1 is located. That is, the external temperature is detected by detecting the electric resistance value between both ends of the linear conductor 3.

The external temperature is, for example, the temperature of various combustion exhaust gases, and it may be necessary to detect a high temperature of several hundreds to one thousand degrees Celsius. Since the stability at such a high temperature and the linearity of the change of the electric resistance value depending on the temperature are good, the linear conductor 3 is made of platinum or a metal material containing platinum as a main component. For example, the temperature sensing element 1 is mounted on an external substrate (not shown) including an electric circuit (external electric circuit) for detecting electric resistance as described above, and a temperature measurement object exists together with such an external substrate. It is mounted on the portion to be operated (gas flow path, etc.).

Further, if the linear conductor 3 is exposed to the outside air, it may be damaged due to the adhesion of foreign matter or accidental contact with an external board (not shown) or other components mounted on the external board. Therefore, the electric resistance value may change unnecessarily. In order to prevent this, the linear conductor 3 may be provided between the plurality of insulating layers 2b. In other words, the linear conductor 3 is provided inside the insulating substrate 2 and is not exposed to the outside.

The linear conductor 3 may be a linear conductor that connects two points between the layers of the insulating layer 2b, and the shape of the linear conductor 3 in plan view is not particularly limited. In order to make the linear conductor 3 long and effective in increasing the absolute value of electric resistance, the linear conductor 3 is, for example, a conductor having a meandering pattern (meandering pattern) as shown in FIG. Good.

When the linear conductor 3 is provided between the plurality of insulating layers 2b, one end of the linear conductor 3 has a first portion of the insulating substrate 2 via a through conductor 6 that penetrates the insulating layer 2b in the thickness direction. It is electrically connected to the electrode pad 4 arranged on the surface 2a. The through conductor 6 is, for example, a columnar conductor having a circular shape or the like in a plan view, but in FIG. 1, the through conductor 6 is schematically shown by a broken line.

The electrode pad 4 is a portion for connecting the linear conductor 3 to an external electric circuit. The electrode pad 4 is, for example, a flat member, and one surface thereof is joined to the first surface 2 a of the insulating substrate 2. The electrode pad 4 can be formed, for example, by using the same metal material as that of the linear conductor 3 and by the same method as that of the linear conductor 3. The electrode pad 4 included in the temperature sensing element 1 of the present embodiment has a rectangular pattern made of a metal material containing platinum as a main component, and the electrode pad 4 has, for example, a circular shape, a square shape, or a polygonal shape. Etc., and may have other shapes. Further, the electrode pad 4 may be formed by a lead terminal (not shown) made of gold or the like.

Since the electrode pad 4 may be exposed to an environment of high temperature (for example, several hundreds to 1,000 degrees Celsius), it is made of a metal material having a high oxidation resistance at a high temperature, such as a platinum group metal containing platinum or gold. It is preferably one.

The electrode pad 4 and an external electric circuit (not shown) for measuring an electric resistance value are electrically connected to the other surface of the electrode pad 4 opposite to the one surface bonded to the first surface 2a of the insulating substrate 2. The lead 5 for connecting to is connected.

The lead 5 is a rod-shaped member and has a circular cross section, an elliptical shape, an oval shape, a rectangular cross section when viewed in a cross section perpendicular to the axial direction of the lead 5 (direction perpendicular to the paper surface in FIG. 3). It may have a shape or the like, or may have any other shape. In the present embodiment, the lead 5 has a circular cross-sectional shape. As shown in FIG. 1, a part of the side peripheral surface at one end of the lead 5 is bonded to the surface of the electrode pad 4 opposite to the surface bonded to the first surface 2a of the insulating substrate 2. Further, the lead 5 is made of a metal material containing platinum as a main component, and may be made of pure platinum, like the linear conductor 3, for example. The lead 5 may be joined to the electrode pad 4 by using a brazing method using a brazing material containing gold, or a joining means such as resistance welding.

The temperature sensing element 1 of the present embodiment further includes a protective member 7 for reinforcing the joint between the electrode pad 4 and the lead 5, and a cushioning member 8 arranged between the protective member 7 and the lead 5. Including.

As shown in FIGS. 1 to 3, the protective member 7 is arranged on the first surface 2 a of the insulating substrate 2 so as to cover the bonding area between the electrode pad 4 and the lead 5. The protection member 7 has a coefficient of thermal expansion smaller than that of the lead 5.

In the present embodiment, the protective member 7 is made of crystallized glass, and includes, for example, alumina (Al ₂ O ₃ ), anorthite (CaAl ₂ Si ₂ O ₈ ), diopsite (CaMgSi ₂ O ₆ ), and forsterite ( Mg ₂ SiO ₄ ) and the like are included. In the present embodiment, the thermal expansion coefficient of the protective member 7 made of crystallized glass is set to, for example, 5 ppm/K to 10 ppm/K, which is smaller than the thermal expansion coefficient of the lead 5 containing platinum as a main component.

The buffer member 8 is disposed between the inner surface of the protective member 7 facing the electrode pad 4 and the surface of the lead 5 when viewed in a cross section perpendicular to the axial direction of the lead. The cushioning member 8 includes a large number of pores 9 therein and has a softening temperature lower than the softening temperature of the protective member 7.

In the present embodiment, the buffer member 8 is made of amorphous glass and contains, for example, Al, Si, Ca, Mg, Zn or the like. The buffer member 8 may have a Ca content higher than the Ca content of the protection member 7, and may have an Al content higher than the protection member 7 and an Al content higher than the Mg content, and a Mg content. You may.

The buffer member 8 made of amorphous glass has a softening temperature lower than that of the protective member 7 made of crystallized glass. In the present embodiment, the softening temperature of the protection member 7 is, for example, 1200°C to 1900°C, and the softening temperature of the buffer member 8 is, for example, 500°C to 1200°C.

According to the temperature sensing element 1 of the present embodiment, when the temperature sensing element 1 is placed in an environment of high temperature (for example, several hundred to 1,000 degrees Celsius) and the leads 5 thermally expand, the thermal expansion of the leads 5 causes The stress generated and applied to the protective member 7 can be relieved by the buffer member 8 having the above-described configuration. Thereby, the generation of cracks inside the protective member 7 can be suppressed, and the connection reliability with the external electric circuit can be improved.

The protective member 7 may be disposed on the first surface 2a of the insulating substrate 2 so as to cover the bonding area between the electrode pad 4 and the lead 5. The shape of the protective member 7 when seen in a plan view is not limited to the rectangular shape with the corners chamfered and rounded as shown in FIG. 2, and may be, for example, a circular shape, an elliptical shape, or an oval shape. The shape may be rectangular, or any other shape.

The height of the protective member 7 from the surface of the electrode pad 4 may be 1.1 to 5 times the diameter of the lead 5. When viewed in a cross section perpendicular to the axial direction of the lead 5, the width of the portion of the protective member 7 that abuts the first surface 2a of the insulating substrate 2 is 1.1 to 20 times the diameter of the lead 5. May be the width of. With such a configuration, it is possible to ensure sufficient mechanical strength of the protection member 7.

When the height of the lead 5 with respect to the electrode pad 4 is H, for example, a portion of one end of the lead 5 where the height from the electrode pad 4 is less than H/2 or the height from the electrode pad 4 is H. The buffer member 8 may not be provided at the part of the one end of the lead 5 that is less than /3 or less than H/4, and the protective member 7 may be directly contacted with the part. That is, the part of the surface of the one end of the lead 5 joined to the electrode pad 4 that is close to the electrode pad 4 may not be provided with the buffer member 8 and may be in direct contact with the protective member 7. .. According to such a configuration, when the temperature sensing element 1 is placed in an environment of high temperature (for example, several hundred to one thousand degrees Celsius), a relatively high softening temperature which is equal to or higher than the softening temperature of the buffer member 8 is set. Since the protective member 7 included therein suppresses excessive relative deformation between the electrode pad 4 and the lead 5, it is possible to prevent the lead 5 from peeling off from the electrode pad 4. When the thermal expansion coefficient of the protective member 7 is smaller than the thermal expansion coefficient of the lead 5 as in the temperature sensing element 1 of the present embodiment, the protective member 7 is relatively difficult to deform, so the electrode pad 4 of the lead 5 is formed. The effect of suppressing peeling from the surface can be further improved.

When viewed in a cross section perpendicular to the axial direction of the lead 5, the cushioning member 8 has a greater thickness in the direction perpendicular to the surface of the lead 5 as the distance from the first surface 2a of the insulating substrate 2 increases. May be. That is, as shown in FIG. 3, the thickness of the cushioning member 8 in the direction perpendicular to the surface of the lead 5 may be the largest on the surface of the upper end portion of the lead 5. As shown in FIG. 3, the upper end of the lead 5 is an end opposite to the lower end joined to the electrode pad 4 in the direction perpendicular to the first surface 2a of the insulating substrate 2.

The upper end portion of the lead 5 is a portion where the thickness of the lead 5 is the largest in the direction perpendicular to the first surface 2a of the insulating substrate 2. Further, since the lower ends of the leads 5 are joined to the electrode pads, when the temperature sensing element 1 is placed in an environment of high temperature (for example, several hundreds to 1,000 degrees Celsius), the upper ends of the leads 5 are insulated. This is the portion where the displacement due to thermal expansion is the largest in the direction perpendicular to the first surface 2a of the substrate 2. According to the above configuration of the buffer member 8, the stress due to the thermal expansion of the lead 5 can be effectively relieved. The thickness of the buffer member 8 in the direction perpendicular to the surface of the upper end portion of the lead 5 may be, for example, 0.01 μm or more and 2 μm or less.

A method of manufacturing the protective member 7 and the cushioning member 8 included in the temperature sensing element 1 of this embodiment will be described.

First, the insulating substrate 2 having the linear conductor 3 therein and having the electrode pad 4 electrically connected to the linear conductor 3 through the penetrating conductor 6 on the first surface 2a is manufactured by the method described above. The lead 5 is bonded to the electrode pad 4.

Next, a glass paste containing glass powder is prepared as a raw material for the protective member 7 and the buffer member 8. As a specific composition example of the glass powder, SiO ₂ is 10 to 60 mass% and Al ₂ O ₃ is 5 to 20 mass% as essential components, and CaO is 0 to 50 mass% and MgO as optional components. 0 to 50% by mass, ZnO 0 to 30% by mass, BaO 0 to 60% by mass, SrO 0 to 10% by mass, ZrO ₂ 0 to 20% by mass, SnO ₂ 0 to 10% by mass, La A composition containing 0 to 10% by mass of ₂ O ₃ and 0 to 10% by mass of B ₂ O ₃ can be mentioned.

Next, a glass paste containing the glass powder having the above composition is applied to the first surface 2a of the insulating substrate 2 so as to cover the bonding region between the electrode pad 4 and the lead 5, and then a peak temperature of about 800 to 1200° C. After that, it is naturally cooled. In this cooling step, first, in a state where the lead containing platinum as a main component is thermally expanded, the glass component contained in the glass paste is transferred to the crystallized glass, and then the lead is contracted to form the crystallized glass. A gap is created between the lead and the glass component that has not been crystallized (amorphous glass) is made to enter a part of the gap between the crystallized glass and the lead.

By the method described above, the protective member (crystallized glass) provided on the first surface 2a of the insulating substrate 2 so as to cover the bonding region between the electrode pad 4 and the lead 5 provided in the temperature sensing element 1 of the present embodiment. 7 and a buffer member (amorphous glass) 8 which is disposed between the protection member 7 and the lead 5 and which has pores 9 therein and has a softening temperature lower than the softening temperature of the protection member 7. be able to. Of the gap between the crystallized glass and the lead, the portion where the uncrystallized glass component did not enter becomes the pores 9 included in the inside of the buffer member 8.

The temperature sensing element of the present invention is not limited to the example of the above embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, if the insulating layer 2b forming the insulating substrate 2 is made of a glass ceramic sintered body containing the same glass component as the protective member 7, the adhesion between the insulating substrate 2 and the protective member 7 can be improved. .. The insulating substrate 2 may include three or more insulating layers 2b, and the linear conductor 3 may be disposed between two or more layers. The linear conductor 3 is not limited to the conductor having a meandering pattern as shown in FIG. 1 and may have another pattern.

1 Temperature Measuring Element 2 Insulating Substrate 2a First Surface 2b Insulating Layer 3 Wire Conductor 4 Electrode Pad 5 Lead 6 Penetrating Conductor 7 Protective Member 8 Buffer Member 9 Pore

Claims (6)

An insulating substrate,
A linear conductor disposed on the insulating substrate, the linear conductor being made of a metal material containing platinum as a main component,
An electrode pad disposed on the first surface of the insulating substrate and electrically connected to the linear conductor;
A lead made of a metal material containing platinum as a main component, one end of which is joined to the electrode pad;
A protective member disposed on the first surface of the insulating substrate so as to cover a bonding region between the electrode pad and the lead;
When viewed in a cross section perpendicular to the axial direction of the lead, it is a cushioning member arranged between the protective member and the lead, including pores inside, than the softening temperature of the protective member. A cushioning member having a low softening temperature,
A temperature measuring body characterized by comprising. The part of the surface of the one end of the lead, which is close to the electrode pad, is not provided with the buffer member and is in direct contact with the protective member. Temperature measuring element. When viewed in a cross section perpendicular to the axial direction of the lead, the cross-sectional shape of the lead is circular,
The temperature sensing element according to claim 1, wherein the cushioning member has a thickness that increases in a direction perpendicular to a surface of the lead as the distance from the first surface of the insulating substrate increases. .. The temperature sensing element according to claim 1, wherein the protection member has a coefficient of thermal expansion smaller than a coefficient of thermal expansion of the lead. The temperature sensing element according to claim 1, wherein the protection member is made of crystallized glass. The temperature sensing element according to claim 1, wherein the buffer member is made of amorphous glass.