JP2017126523A - heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance bonding strength between an electrode and a lead terminal, thereby improving reliability.SOLUTION: A heater 10 according to the present invention comprises: a ceramic body 1; a heating resistor 2 provided in the ceramic body 1; an electrode 3 provided on the surface of the ceramic body 1 so as to be connected to the heating resistor 2; and a lead terminal 4 bonded to the electrode 3 via a bonding material 5. The lead terminal 4 comprises: a first portion 41 erecting from the electrode 3; and a second portion 42 extending along the length direction of the ceramic body 1. The first portion 41 has an outer peripheral surface at least part of which is covered with the bonding material 5, and has a recess 43, in a region on the outer peripheral surface covered with the bonding material 5, which is recessed in the length direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heater used for a liquid heating heater, a powder heating heater, a gas heating heater, an oxygen sensor heater, and the like.

  As a heater used in a liquid heating heater, a powder heating heater, a gas heating heater, an oxygen sensor heater, and the like, for example, a heater disclosed in Patent Document 1 is known. The heater device disclosed in Patent Document 1 includes a ceramic body in which a heating resistor is embedded, an electrode pad provided on the surface of the ceramic body, and a terminal member joined to the electrode pad.

JP 2011-60712 A

  In the heater device disclosed in Patent Document 1, one end portion of the terminal member is provided so as to rise from the electrode, and the other end portion is provided extending along the length direction of the ceramic body. One end of the terminal member is joined to the electrode pad by a brazing material, and the other end of the terminal member is fixed to the heater device body. In the heater device having such a configuration, vibration in a direction perpendicular to the length direction of the ceramic body is easily absorbed by deformation of the other end portion of the terminal member, whereas a direction parallel to the length direction of the ceramic body. The vibration is easily transmitted to one end. Therefore, the stress due to vibration is repeatedly applied due to long-term use, and the brazing material may peel off between the terminal member and the brazing material, particularly in the portion facing the length direction of the ceramic body on the outer surface of the terminal member. was there. If peeling occurs, there is a risk of disconnection, which may result in low reliability.

  The heater according to one aspect of the present invention includes a rod-shaped or cylindrical ceramic body, a heating resistor provided inside the ceramic body, and an electrode provided on a surface of the ceramic body and connected to the heating resistor. And a lead terminal joined to the electrode with a joining material, the lead terminal comprising: a first part rising from the electrode; a second part extending along the length direction of the ceramic body; The first portion has at least a part of an outer peripheral surface covered with the bonding material, and has a concave portion recessed in the length direction in a region of the outer peripheral surface covered with the bonding material. doing.

  According to the heater of one embodiment of the present invention, the bonding strength between the lead terminal and the bonding material can be increased and the reliability can be increased.

It is a perspective view which shows one Embodiment of a heater. It is sectional drawing which shows the cross section in the AA line of the heater shown in FIG. FIG. 3 is an enlarged cross-sectional view showing the vicinity (C portion) of the joint portion of the lead terminal in FIG. 2. It is an expanded sectional view which shows the junction part vicinity of the lead terminal in a modification. It is the side view which looked at the heater shown in FIG. 1 from the B direction. It is an expanded sectional view which shows the junction part vicinity of the lead terminal in a modification. (A) And (b) is an expanded sectional view which shows the junction part vicinity of the lead terminal in a modification, respectively. It is an expanded sectional view which shows the junction part vicinity of the lead terminal in a modification. It is an expanded sectional view which shows the junction part vicinity of the lead terminal in a modification. It is sectional drawing which shows the modification of a heater.

  The heater 10 according to an embodiment of the present invention will be described in detail.

  FIG. 1 is a perspective view showing an example of an embodiment of the heater 10 of the present invention, FIG. 2 is a longitudinal sectional view showing a section taken along line AA in FIG. 1, and FIG. 3 is a view of a lead terminal in FIG. It is an expanded sectional view which expands and shows a junction part neighborhood (C section). As shown in FIGS. 1 to 3, the heater 10 includes a rod-shaped or cylindrical ceramic body 1, a heating resistor 2 provided inside the ceramic body 1, and an electrode provided on the surface of the ceramic body 1. 3 and a lead terminal 4 joined to the electrode 3.

  The ceramic body 1 is a member provided to protect the heating resistor 2. The shape of the ceramic body 1 is rod-shaped or cylindrical. Examples of the rod shape include a column shape such as a column shape or a prism shape. In addition, the column shape here includes, for example, a plate shape extending in a specific direction. Examples of the cylindrical shape include a cylindrical shape and a rectangular tube shape. In the heater 10 shown in FIG. 1, the ceramic body 1 has a cylindrical shape.

  The ceramic body 1 is made of an insulating ceramic material. Examples of the insulating ceramic material include alumina, silicon nitride, and aluminum nitride. From the viewpoint of excellent thermal conductivity, it is preferable to use aluminum nitride. In particular, when aluminum nitride is used, the thermal conductivity of the ceramic body 1 can be increased to 150 W / (m · K), so the heat generated by the heating resistor 2 formed inside the ceramic body 1 Can communicate efficiently to the surface. Accordingly, the heater 10 can be rapidly heated.

  From the viewpoint of ease of production, it is preferable to use alumina. When the ceramic body 1 is cylindrical, the dimensions of the ceramic body 1 can be set, for example, to a length of 100 mm and an outer diameter of 20 mm. When the ceramic body 1 is plate-shaped, the dimensions of the ceramic body 1 can be set, for example, to a length of 80 mm, a width of 50 mm, and a thickness of 2 mm. When the ceramic body 1 is cylindrical, the dimensions of the ceramic body 1 can be set, for example, to a length of 100 mm, an outer diameter of 20 mm, and an inner diameter of 14 mm.

  The heating resistor 2 is a resistor that generates heat when a current flows. The heating resistor 2 is provided inside the ceramic body 1. That is, the heating resistor 2 is embedded in the ceramic body 1. The heating resistor 2 in the heater 10 of the present embodiment has a folded shape. Both ends of the heating resistor 2 are connected to a pair of extraction electrodes 21. The extraction electrode 21 is extracted to one end portion of the ceramic body 1, and is extracted to the outer peripheral surface of the ceramic body 1 at the end portion. A folded portion of the heating resistor 2 is provided at the other end of the ceramic body 1. That is, the extraction electrode 21 is provided in a region of the ceramic body 1 opposite to the folded portion of the heating resistor 2. Both ends of the heating resistor 2 are electrically connected to the electrodes 3 provided on the outer peripheral surface of the ceramic body 1 via the extraction electrodes 21.

In the example shown in FIG. 2, the folded portion of the heating resistor 2 has a single U shape, but may have a so-called meander shape having a plurality of folded portions. In the example shown in FIG. 2, the heating resistor 2 is provided in one cross section, that is, on one virtual plane inside the ceramic body 1. The heating resistor 2 may be provided on a virtual curved surface along the outer peripheral surface of the ceramic body 1 inside the ceramic body 1. Thereby, the soaking | uniform-heating property in the outer peripheral surface of the ceramic body 1 improves.

  The heating resistor 2 is made of a metal material. Examples of the metal material include tungsten, molybdenum, rhenium, and the like. The dimensions of the heating resistor 2 can be set, for example, to a width of 1 mm, a total length of 300 mm, and a thickness of 0.02 mm. The extraction electrode 21 can be formed simultaneously with the heating resistor 2 by using the same metal material as that of the heating resistor 2. The extraction electrode 21 can also be formed separately using a material different from that of the heating resistor 2.

  The electrode 3 is provided on the surface of the ceramic body 1. The electrode 3 is connected to the heating resistor 2 via the extraction electrode 21. The electrode 3 is made of a metal material. Examples of the metal material include tungsten, molybdenum, rhenium, and the like. The dimensions of the electrode 3 can be set, for example, such that the length along the length direction of the ceramic body 1 is 9 mm, the width is 5 mm, and the thickness is 0.02 mm. In the present embodiment, the electrode 3 is connected to the heating resistor 2 via the extraction electrode 21, but is not limited thereto. Specifically, the heater 10 may not have the extraction electrode 21 and the electrode 3 and the heating resistor 2 may be directly connected.

  The lead terminal 4 is a member for supplying power to the heating resistor 2. The lead terminal 4 is used by being electrically connected to an external power source (not shown). As the lead terminal 4, a wire or plate made of nickel or copper metal can be used. In the present embodiment, the cross section of the lead terminal 4 (the cross section of the first portion 41 and the second portion 42) is circular. Other shapes of the cross section of the lead terminal 4 include, for example, an elliptical shape, a polygonal shape such as a triangular shape or a rectangular shape, or a hollow shape of these shapes.

  The lead terminal 4 can be attached on the surface of the electrode 3 using a bonding material 5. As the bonding material 5, for example, a brazing material can be used. Examples of the brazing material include Au brazing, AuCu brazing, AgCu brazing, and Ag brazing.

  The lead terminal 4 includes a first portion 41 rising from the electrode 3 and a second portion 42 extending along the length direction from the first portion 41 outside the outer peripheral surface of the ceramic body 1. The dimension of the lead terminal 4 can be set as follows, for example. The length of the first portion 41 can be set to 2.3 mm. The length of the second portion 42 can be set to 3.5 mm in the direction parallel to the length direction of the ceramic body 1. Further, if the cross sections of the first portion 41 and the second portion 42 are circular, the diameter can be set to 0.8 mm.

  At least a part of the outer peripheral surface of the first portion 41 of the lead terminal 4 is covered with the bonding material 5. That is, the first portion 41 of the lead terminal 4 and the electrode 3 are joined by the joining material 5. And the 1st part 41 has the recessed part 43 dented in the length direction of the ceramic body 1 in the area | region covered with the bonding | jointing material 5 among the outer peripheral surfaces. That is, the 1st part 41 has the recessed part 43 in the site | part which has faced the length direction of the ceramic body 1 among the area | regions covered with the bonding | jointing material 5 of the outer peripheral surface.

Vibration in a direction parallel to the length direction of the ceramic body 1 is easily transmitted to the first portion 41 of the lead terminal 4. Due to the vibration in the direction parallel to the length direction of the ceramic body 1, the first portion 41 of the lead terminal 4 is subjected to repeated bending stress in the direction parallel to the length direction of the ceramic body 1, A tensile stress is repeatedly applied to a portion of the outer surface of the one portion 41 facing the length direction of the ceramic body 1. Therefore, the stress due to vibration is generated between the lead terminal 4 and the bonding material 5, particularly the ceramic body 1 on the outer surface of the first portion 41 of the lead terminal 4.
There is a possibility that peeling between the lead terminal 4 and the bonding material 5 may occur due to repeated application of stress due to long-term use. This peeling is likely to occur at the outermost end of the interface between the lead terminal 4 and the bonding material 5, that is, the farthest from the outer peripheral surface of the ceramic body 1. It progresses to the ceramic body 1 side along the interface. When the tip of the peeling reaches the electrode 3, it may develop along the surface of the electrode 3 and peeling may occur between the electrode 3 and the bonding material 5. Alternatively, there is a possibility that a crack is generated in the electrode 3 starting from the peeling tip, and the electrode 3 is peeled off from the ceramic body 1 or a crack is generated in the ceramic body 1. In some cases, the lead terminal 4 and the heating resistor 2 are disconnected. In particular, when used in a high-temperature and high-humidity atmosphere, galvanic corrosion is likely to occur at the outermost end of the interface between the lead terminal 4 and the bonding material 5 that is in contact with the atmosphere. This corrosion site becomes a starting point of peeling, and the peeling tends to progress along the interface between the portion of the first portion 41 of the lead terminal 4 facing the length direction of the ceramic body and the bonding material 5 where a large stress is applied.

  In the heater 10 of this embodiment, the recessed part 43 is provided in the site | part which has faced the length direction of the ceramic body 1 among the area | regions covered with the bonding | jointing material 5 of the outer peripheral surface of the 1st part 41. FIG. Therefore, even if peeling occurs at the end of the bonding material 5 due to vibration in a direction parallel to the length direction of the ceramic body 1, the progress of the peeling to the ceramic body 2 side can be suppressed by the recess 43, Since the length of the interface between the lead terminal 4 and the bonding material 5, which is a peeling progress path, is increased, the progress of the peeling can be suppressed. In addition, the anchor effect due to the part of the bonding material 5 entering the concave portion 43 increases the bonding strength between the lead terminal 4 and the bonding material 5, thereby suppressing the progress of peeling. Therefore, the reliability of the heater 10 is improved.

  The recessed part 43 is good to be located in the heating resistor 2 side among the outer peripheral surfaces of the 1st part 41 like the example shown in FIG. Since the temperature close to the heating element 2 in the joint portion between the lead terminal 4 and the joint material 5 becomes high, galvanic corrosion is more likely to occur. That is, by providing the recess 43 on the heat generating body 2 side, which is more likely to be peeled out of the portion of the outer surface of the first portion 41 facing the length direction of the ceramic body 1, the progress of the peeling is achieved. Can be suppressed.

  As in the example illustrated in FIG. 5, the concave portion 43 may have a shape in which the shape of the opening portion has a length direction, and the length direction of the opening portion may be along the axial direction of the first portion 43. The length direction of the opening portion is along the axial direction of the first portion 43, that is, the opening portion has a long shape along the peeling progress direction. For this reason, since the separation path of peeling becomes further longer, it becomes easier to suppress the progress of peeling. Further, when a tensile stress is applied to the lead terminal 4, the stress applied to the bonding material 5 entering the lead terminal 4 is caused by the shape of the opening of the recess 43 being along the axial direction of the first portion 41 of the lead terminal 4. Since it can disperse | distribute in the longitudinal direction of the lead terminal 4, the joining strength of the lead terminal 4 becomes large. If the size of the opening including the width is simply increased, the strength of the lead terminal 4 is lowered. In order to obtain the above-described effect while suppressing the strength reduction of the lead terminal 4, the shape of the opening is a shape having a length direction as described above, and the length direction of the opening is the first portion 43. It should be along the axial direction.

In addition, as in the example illustrated in FIG. 6, it is preferable that there is a gap 6 between the inner surface of the recess 43 and the bonding material 5 that covers the recess 43. Even if a thermal stress due to a thermal expansion difference between the lead terminal 4 and the bonding material 5 occurs due to a thermal cycle caused by the heater 10 being turned on and off, the gap 6 positioned between the lead terminal 4 and the bonding material 5 Since thermal stress is relaxed, durability is improved. In addition, since the interface that is the progress path of peeling is interrupted in the middle, the progress of peeling tends to stop. Here, the inner surface of the recess 43 is a bottom portion of the inner surface of the recess 43. That is, the bonding material 5 is not filled in the concave portion 43 as in the example shown in FIG. 4 (the bonding material 5 enters the bottom of the concave portion 43), but the bonding material as in the example shown in FIG. 5 is that it has entered only the opening side of the recess 43 (part of the way from the opening to the bottom of the recess 43). Such a gap 6 can be formed by, for example, pre-treating the bottom portion of the recess 43 so that the bonding material 5 does not get wet when the lead terminal 4 is bonded to the electrode 3. it can. Specifically, if AgCu brazing is used as the bonding material 5, a boron nitride film may be formed on the bottom of the recess 43 of the lead terminal 4. Such a film can be formed, for example, by applying a paste in which boron nitride powder is mixed with a solvent such as a solvent or water to form a slurry, and drying the recess. Note that the gap 6 exists between the inner surface of the recess 43 and the bonding material 5 covering the recess 43 only when the bonding material 5 does not exist at the bottom of the recess 43 as in the example shown in FIG. In addition, a thin bonding material 5 is present at the bottom, and a gap 6 is present between the bottom and the opening side of the recess 43.

  The size of the concave portion 43 may be set such that the larger the length of the interface between the lead terminal 4 and the bonding material 5, which is the peeling propagation path, the longer the length, but the strength of the lead terminal 4 is also taken into consideration. For example, it can be set as follows. The length of the opening (the length of the first portion 41 in the axial direction) is 10% to 50% of the length of the region covered with the bonding material 5 of the first portion 41. The width of the opening is 5% to 30% of the outer peripheral length of the first portion 41 if the cross-sectional shape of the lead terminal 4 is circular, and if the cross-sectional shape of the lead terminal 4 is rectangular, It is 5% to 50% of the width of the surface of the first portion 41 facing the length direction of the ceramic body 1. The depth of the opening is 5% to 40% of the diameter of the first portion 41 if the cross-sectional shape of the lead terminal 4 is circular, and if the cross-sectional shape of the lead terminal 4 is rectangular, It is 5% to 40% of the length of the cross section in the length direction of the ceramic body 1. More specifically, when the first portion 41 has a diameter of 0.8 mm, a length of 2.3 mm, and the length of the region covered with the bonding material 5 is 1.5 mm, the length of the opening 0.5 mm, width 0.2 mm, and depth 0.2 mm. Note that the length, width, and depth of the opening are the maximum length, the maximum width, and the maximum depth, respectively.

  The position in the axial direction of the first portion 41 of the recess 43 is not particularly limited as long as it is a region covered with the bonding material 5. In order to keep the progress of peeling as small as possible, it may be arranged on the side closest to the outermost end, that is, the side far from the outer peripheral surface of the ceramic body 1, which is the starting point of peeling.

  The cross-sectional shape of the recess 43 is a semi-elliptical shape in the examples shown in FIGS. 2 to 4, but a semicircular shape like the example shown in FIG. 6, or a triangular shape like the example shown in FIG. A polygonal shape such as a rectangular shape as shown in FIG. 7B may be used, and there is no particular limitation. If it is a semi-ellipse or a semi-circle, the inner surface of the recess 43 becomes a curved surface, so that when the tensile stress is applied to the lead terminal 4, the stress is easily dispersed, so that the bonding strength of the lead terminal 4 is increased. The cross-sectional shape of the recess 43 shown in FIG. 2 and the like is a cross-sectional shape (longitudinal cross-section) in the direction along the axial direction of the first portion 41, but a cross-section (transverse cross-section) in the width (diameter) direction of the first portion 41. Similarly, there is no particular limitation on the shape of).

  Further, in the example shown in FIG. 2 and the like, only one recess 43 is provided at a portion facing the length direction of the ceramic body 1 on the outer surface of the first portion 41. is not. For example, as in the example shown in FIG. 8, a plurality of recesses 43 may be provided side by side in the axial direction of the first portion 41. In the example shown in FIG. 8, the first portion 41 has two recesses 43 whose axial length is smaller (about one half) than the recess 43 in the example shown in FIG. They are arranged side by side. By doing so, the number of the recesses 43 for suppressing the progress of the peeling increases, and the interface between the lead terminal 4 and the bonding material 5 is the progressing path of the peeling even if the total length of the recesses 43 is the same. The length of becomes longer. Therefore, it becomes easier to suppress the progress of peeling. The size of the plurality of recesses 43 may be the same or different from each other. The length of the concave portion 43 in the direction along the axial direction of the first portion 41 is the length of the region covered by the bonding material 5 of the first portion 41 as the total length of the plurality of concave portions 43. Of 10% to 50%.

  Further, in the example shown in FIG. 4, the recess 3 is provided at one portion of the outer peripheral surface of the first portion 41 on the side of the heating resistor 2, and in the example shown in FIG. One of the outer peripheral surfaces is provided on the opposite side of the heating resistor 2 side. As described above, stress due to vibration in a direction parallel to the length direction of the ceramic body 1 is mainly generated in a portion of the outer surface of the first portion 41 of the lead terminal 4 facing the length direction of the ceramic body 1. To do. That is, it occurs in a portion of the outer peripheral surface of the first portion 41 on the side of the heating resistor 2 and a portion on the opposite side to the side of the heating resistor 2. Therefore, as in the example shown in FIG. 9, the recess 43 may be provided in both the portion on the side of the heating resistor 2 on the outer peripheral surface of the first portion 41 and the portion on the side opposite to the side of the heating resistor 2. Good. At this time, the number of the concave portions 43 in each portion may be one or plural. Moreover, the position of the recessed part 43 in the axial direction of the 1st part 41 may be the same between both parts, and may differ. In order to suppress a decrease in strength of the lead terminal 4, the concave portions 43 may be arranged at different positions in each part. In the example shown in FIG. 9, one recess 43 having the same size is disposed on the side of the heating resistor 2 and two on the side opposite to the heating resistor 2 side. The positions of the recesses 43 in the axial direction of the first portion 41 are different from each other and do not overlap with each other in the length direction of the ceramic body 1. The number of the recesses 43 on the side of the heating resistor 2 where the possibility of peeling is greater is increased so as to suppress the strength reduction of the lead terminal 4 as much as possible.

  The lead terminal 4 has a shape in which a metal wire is bent to have a first portion 41 and a second portion 42, and the surface of the first portion 41 has a protrusion having a shape corresponding to the recess 43. The concave portion 43 can be formed by pressing a mold or the like. The wire rod in which the recess 43 is formed in advance may be bent, the wire rod may be bent and then the recess 43 may be formed, or when the wire rod is bent, the recess 43 may be used as a bending device or a tool. Bending and forming the recess 43 may be performed at the same time by using a projection provided with a projection corresponding to.

  The lead terminal 4 may include a curved portion 44 between the first portion 41 and the second portion 42 as in the example shown in FIG. When the vibration is generated in a direction parallel to the length direction of the ceramic body 1, the bending portion 43 bends, whereby the stress applied to the first portion 41 of the lead terminal 4 by the vibration can be reduced. As a result, the possibility of peeling between the lead terminal 4 and the bonding material 5 can be reduced. In the example shown in FIG. 10, the curved portion 43 is thinner than the first portion 41 and the second portion 42. Thereby, the bending part 43 can be made to bend more easily and the stress added to the 1st part 41 of the lead terminal 4 by vibration can be reduced.

1: Ceramic body 2: Heating resistor 21: Lead electrode 3: Electrode 4: Lead terminal 41: First part 42: Second part 43: Recess 5: Bonding material 6: Air gap 10: Heater

Claims (4)

A rod-shaped or cylindrical ceramic body, a heating resistor provided inside the ceramic body, an electrode provided on the surface of the ceramic body and connected to the heating resistor, and a bonding material to the electrode With joined lead terminals,
The lead terminal includes a first portion rising from the electrode, and a second portion extending along the length direction of the ceramic body,
The first portion has at least a part of an outer peripheral surface covered with the bonding material, and has a recess recessed in the length direction in a region of the outer peripheral surface covered with the bonding material. A heater characterized by that.   2. The heater according to claim 1, wherein the recess is located on the heat generating resistor side of the outer peripheral surface of the first portion.   The heater according to claim 1 or 2, wherein the recess has an opening having a length direction, and the length direction is along an axial direction of the first portion.   The heater according to any one of claims 1 to 3, wherein there is a gap between an inner surface of the recess and the bonding material covering the recess.

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