JP2008027754A - Ceramic heater manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a ceramic heater in which even in the case brazing work under high temperature is carried out in a jointing process of an electrode pad and a jointing member, precipitation of an adhesion promoting component on the surface of the jointing portion can be suppressed and jointing strength of the jointing portion and the surface plating layer hardly deteriorates. <P>SOLUTION: In the manufacturing method of a ceramic heater 100, a metallic resistor ink to form an electrode pad 121 is made to contain silica. As can be judged by the external view shown in the Fig.4, in the comparison example (the case metallic resistor ink does not contain silica), alumina (adhesion promoting component) contained in the metallic resistor ink precipitates into the surface of the jointing portion in the jointing process, while in the embodiment example, precipitation of alumina into the surface of the jointing portion can be suppressed. Thereby, failure of formation of nickel plated film 125 at the jointing portion can be prevented, and further, deterioration of jointing strength of the jointing portion and the nickel plated film 125 can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes an insulating ceramic substrate having a heating resistor embedded therein, an electrode pad exposed from the ceramic substrate and energizing the heating resistor, and a joint formed by a brazing material. It is related with the manufacturing method of the ceramic heater provided with the joining member joined to an electrode pad.

  Conventionally, an insulating ceramic substrate having a heating resistor embedded therein, an electrode pad that is exposed from the ceramic substrate and energizes the heating resistor, and a joint formed by a brazing material A ceramic heater provided with a joining member (lead member) joined to a pad is known.

  As a method for manufacturing such a ceramic heater, an electrode pad is formed on a ceramic substrate in which a heating resistor is embedded, and then a plating layer is formed on the surface of the electrode pad, and then bonded through a brazing material by heat treatment. There is a manufacturing method of joining members (lead members) (Patent Document 1).

  In addition, since the ceramic heater is frequently used in a high-temperature environment or an environment where temperature changes are severe, an improvement in thermal durability is required for the joining portion between the brazing material plating layer and the joining member. .

In contrast, by using a brazing material having a higher melting point, it is possible to improve the thermal durability of the joint portion.
Note that the melting point of the brazing material that is generally used is about 750 ° C., but it is desirable to use a brazing material having a melting point of 900 ° C. or higher as the brazing material having a high melting point in consideration of the thermal durability of the joint portion. Examples of such a brazing material include a brazing material mainly composed of copper (a brazing material having a copper content of 50% by weight or more).
JP 2005-019339 A (Claim 2)

  However, when a brazing material having a high melting point is used, a brazing operation at a high temperature (900 ° C. or higher) is performed in the bonding process between the electrode pad and the bonding member. Due to the reaction between the component contained in the pad and the component contained in the brazing material, a component that prevents the formation of the surface plating layer is deposited on the surface of the joining portion (brazing portion). May not be able to be formed.

  This surface plating layer is formed to prevent corrosion at the joint when the semi-rack heater is used in a high temperature environment, and is made of a corrosion resistant material such as nickel (Ni). It is formed. The surface plating layer is formed so as to cover the entire surface of the joint portion after the joint portion is formed.

  That is, when the brazing operation is performed at a high temperature and the electrode pad and the brazing material react with each other, the adhesion promoting component added for adhesion between the electrode pad and the ceramic substrate is deposited on the surface of the joint portion. There is a case.

  This adhesion promoting component is the main component of the ceramic substrate and is made of an insulating material. For example, when the ceramic substrate is mainly composed of alumina, alumina as an adhesion promoting component is contained in the electrode pad (specifically, ink for electrodes) to improve the adhesion between the electrode pad and the ceramic substrate. Can be improved.

  When the surface plating layer is formed on the bonding portion (brazing portion), the surface plating layer can be appropriately formed on the portion of the bonding portion where the conductive material of the brazing material is exposed. Of the portion, the portion where the adhesion promoting component (insulating material) is deposited has problems such as a decrease in the thickness of the surface plating layer and the ease of peeling off of the surface plating layer.

  Therefore, the present invention has been made in view of such problems, and even when a brazing operation at a high temperature (900 ° C. or higher) is performed in the bonding process between the electrode pad and the bonding member, the surface of the bonding portion is formed. It is an object of the present invention to provide a ceramic heater manufacturing method that can suppress the adhesion promoting component from precipitating and the bonding strength between the bonding portion and the surface plating layer is unlikely to decrease.

  In order to achieve this object, the method of the present invention according to claim 1 is an insulating ceramic substrate having a heating resistor embedded therein, and is exposed from the ceramic substrate and energizes the heating resistor. And a bonding member bonded to the electrode pad by a bonding portion formed of a conductive brazing material having a melting point of 900 ° C. or higher, and a heating resistor. An electrode pad that includes a main material composed of at least one element selected from tungsten and molybdenum and that contains a main component of the ceramic substrate and is fired is applied to the ceramic substrate on which the electrode is formed. Electrode pad forming step for forming electrode, plating forming step for forming plating layer on the surface of electrode pad, and electrode on which plating layer is formed A bonding step in which the brazing material and the bonding member are placed in contact with each other on the lid and the brazing material is melted by heating to bond the electrode pad and the bonding member to form a bonding portion; A surface plating layer forming step of forming a surface plating layer containing a corrosion-resistant material on the surface of the portion, and the electrode ink is configured to contain silica, Is the method.

  In this ceramic heater manufacturing method, since the electrode ink includes silica, it is possible to suppress the adhesion promoting component contained in the electrode ink from being deposited on the surface of the bonded portion in the bonding step.

  The adhesion promoting component is a component for improving the adhesion between the electrode pad and the ceramic substrate, and the same component as the main component of the ceramic substrate is often used. In addition, since an insulating material is used as the main component of the ceramic substrate, the adhesion promoting component is also an insulating material.

  As described above, the thickness of the surface plating layer can be reduced when forming the surface plating layer on the conductive bonding portion by suppressing the deposition of the insulating adhesion promoting component on the surface of the bonding portion. It can prevent that a dimension becomes thin. In addition, the surface plating layer formed in this manner can prevent the surface plating layer from being easily peeled off because the adhesion promoting component does not precipitate, thereby improving the adhesion with the joint portion.

  Therefore, according to the method of the present invention, even when a brazing operation at a high temperature (900 ° C. or higher) is performed in the bonding process between the electrode pad and the bonding member, the adhesion promoting component is deposited on the surface of the bonding portion. Can be suppressed, and the formation state of the surface plating layer on the joint portion can be prevented from becoming poor.

  Furthermore, since the brazing material used in the method of the present invention has a melting point of 900 ° C. or higher, the ceramic heater manufactured by the method of the present invention is suitable for use in a high temperature environment or in an environment where temperature changes are severe. It has excellent durability in high temperature environments (high temperature durability) and durability against temperature changes (cooling cycle durability).

  An example of such a brazing material is a brazing material mainly composed of copper. Specifically, there are copper-gold solder, copper-silver solder, copper-indium solder, copper-titanium solder, and the like. Some brazing materials mainly composed of copper have a melting point of about 1050 ° C.

  And in the above-mentioned invention method, for example, when the total weight of the main material, the main component of the ceramic substrate, and the silica is 100 parts by weight among the components contained in the electrode ink as described in claim 2 The content of silica can be 2 to 13% by weight.

  That is, in order to surely suppress the deposition of the adhesion promoting component, the content of silica in the electrode ink needs to be a certain level or more. And, as can be seen from the measurement results (evaluation results in FIG. 5) described later, the content of silica in the electrode ink, when the total weight of the main material, the main component of the ceramic substrate, and silica is 100 parts by weight, By setting it to at least 2% or more, it is possible to suppress the deposition of an insulating adhesion promoting component on the surface of the joint portion.

  Also, if the content of silica in the electrode ink is excessive, the silica diffuses more during electrode pad formation (during firing), resulting in the formation of many internal cavities in the electrode pad. There is a possibility that the contact area with the ceramic substrate is reduced, and the bonding strength between the electrode pad and the ceramic substrate is lowered.

  On the other hand, as can be seen from the measurement results described later (evaluation results in FIG. 5), in the electrode ink, when the total weight of the main material, the main component of the ceramic substrate, and silica is 100 parts by weight, By setting the content to 13% or less, it is possible to suppress the formation of a large number of internal cavities in the electrode pad, and it is possible to suppress a decrease in bonding strength between the electrode pad and the ceramic base.

  Next, in the above-described invention method, as described in claim 3, in the electrode pad forming step, as the electrode ink, an ink for a lower layer electrode having a silica content smaller than a main component of the ceramic substrate, and a ceramic An upper electrode ink having a silica content higher than that of the main component, and after applying the lower electrode ink, the upper electrode ink is applied to form a two-layer electrode pad. , Can take the form.

  By using the lower layer electrode ink in which the content of the main component of the ceramic substrate is higher than the content of silica, the lower layer electrode pad obtained by firing the lower layer electrode ink in a portion of the electrode pad close to the ceramic substrate Is formed. Since the lower electrode pad has less silica and has fewer cavities, the contact area with the ceramic substrate is increased, and the bonding state between the electrode pad and the ceramic substrate can be improved.

  Further, by using the upper layer electrode ink in which the silica content is higher than the main component content of the ceramic substrate, the upper layer is formed by firing the upper layer electrode ink in a portion of the electrode pad close to the bonding member and the brazing material. An electrode pad is formed. And since precipitation of an adhesion promoting component can be suppressed by the silica contained in the ink for the upper layer electrode, it is possible to suppress the adhesion promoting component from being deposited on the surface of the joining portion made of the brazing material.

  Note that the silica content in the two-layer electrode pad is not calculated as the content of the upper electrode ink alone, but as the total content of the lower electrode ink and the upper electrode ink. To do. For example, when the content of silica in the electrode pad composed of two layers is in the range of 2 to 13% by weight, the main material among the electrode inks obtained by summing the lower layer electrode ink and the upper layer electrode ink, When the total weight of the main component of the ceramic substrate and silica is 100 parts by weight, the content of silica is adjusted within the range of 2 to 13% by weight.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
In addition, this invention is not limited to the following embodiment at all, and it cannot be overemphasized that various forms may be taken as long as it belongs to the technical scope of this invention.

Embodiments of a ceramic heater and a ceramic heater manufacturing method embodying the present invention will be described with reference to the drawings.
In addition, the ceramic heater of this embodiment can be used for the use etc. for heating a sensor element to activation temperature. In addition, as a sensor element to be heated, a gas sensor that detects a specific gas (oxygen) in a measurement target gas (exhaust gas) for use in various controls (for example, air-fuel ratio feedback control) in an automobile or various internal combustion engines. An element etc. are mentioned.

First, the structure of the ceramic heater 100 will be described with reference to FIGS.
FIG. 1 is a perspective view showing the appearance of the ceramic heater 100. FIG. 2 is an exploded perspective view showing the internal configuration of the ceramic heater 100.

  As shown in FIG. 1, the ceramic heater 100 is configured in a round bar shape (substantially cylindrical shape), and is inserted into a bottomed cylindrical sensor element (not shown) to heat the sensor element. It is. The sensor element is configured by forming electrode layers on the inner and outer surfaces of a solid electrolyte tube having a bottomed cylindrical shape.

  In the ceramic heater 100 of the present embodiment, of the both ends in the longitudinal direction, the side provided with the heat generating portion (the side where the heat generating portion 142 described later is formed) is referred to as the “tip side”, and the opposite end The part is described as “rear end side”.

  The ceramic heater 100 includes a ceramic base 102 having a heating resistor 141, an electrode pad 121 exposed from the ceramic base 102 and energizing the heating resistor 141, and a conductive brazing material having a melting point of 900 ° C. or higher. And a joining member 130 joined to the electrode pad 121.

  The ceramic heater 100 has a configuration in which the heat generating resistor 141 generates heat by energizing the heat generating resistor 141 from the power supply device via the electrode portion 120 provided on the rear end side of the ceramic base 102. A portion of the heat generating resistor 141 that generates heat (a heat generating portion 142 (see FIG. 2) described later) is disposed on the tip side of the ceramic substrate 102. That is, the ceramic heater 100 is configured to heat an object to be heated (such as a sensor element) when the heating unit 110 on the distal end side of the ceramic base 102 generates heat.

  As shown in FIG. 2, the ceramic heater 100 is manufactured by winding green sheets 140 and 146 made of alumina ceramic with high insulating properties around the outer periphery of a round rod-like alumina ceramic tube 101 and firing them. .

  On the green sheet 140, a heating resistor 141 mainly composed of a tungsten-based material as a heat pattern is formed. The heating resistor 141 includes a heating part 142 formed at a position corresponding to the heating part 110 (see FIG. 1), and a pair of lead parts 143 connected to both ends of the heating part 142. The

  In addition, two through holes 144 are formed on the rear end side of the green sheet 140. The pair of lead portions 143 are electrically connected to the two electrode pads 121 formed on the outer surface of the ceramic heater 100 through the two through holes 144.

The green sheet 146 is a sheet that is pressure-bonded to the surface of the green sheet 140 on which the heat generating resistor 141 is formed.
Alumina paste is applied to the surface of the green sheet 146 opposite to the pressure-bonding surface, and the green sheet 140, 146 is wound around the tub tube 101 with this coating surface inside and pressed inward from the outer periphery, A ceramic heater molded body is formed. Thereafter, the ceramic heater molded body is fired to form a ceramic heater.

Note that the soot tube 101 as the ceramic parts constituting the ceramic heater 100 and the green sheets 140 and 146 correspond to the “ceramic substrate” in the present invention.
Next, as shown in FIGS. 1 and 2, two electrode pads 121 on the anode side and the cathode side are formed on the electrode portion 120 of the ceramic heater 100. The electrode pads 121 are provided at two positions on the outer surface of the green sheet 140 corresponding to the two through holes 144 (see FIG. 2). The conduction between the heat generating resistor 141 and the lead portion 143 is performed through a conductive paste filled in the through hole 144. A metal layer (nickel plating film 122 shown in FIG. 3) by plating, which will be described later, is formed on the surface of the electrode pad 121.

Further, in the ceramic heater 100, the joining portion 133 of the joining member 130 is brazed to the electrode pad 121 using a brazing material 124 mainly composed of copper.
The joining member 130 is made of a nickel member, and includes a crimping part 135 cut out in a flat plate shape and a connection part 134 extending from the tip of the crimping part 135.

  The distal end portion of the connection portion 134 is bent in a step shape in the thickness direction, and is formed as a joint portion 133. Further, the joining member 130 is twisted between the connection portion 134 and the crimping portion 135 so as to be twisted at a substantially right angle with the longitudinal direction of the connection portion 134 as an axis.

  The joining member 130 is connected to an external circuit (external power supply device) via the lead wire or the like by fixing a lead wire or the like for connecting an external circuit (not shown) to the caulking portion 135.

  The two joining members 130 configured in such a shape are joined to each of the two electrode pads 121 and function as an anode side terminal and a cathode side terminal when a voltage is applied to the ceramic heater 100.

Next, the structure of the electrode unit 120 will be described with reference to FIG.
Note that the brazing material 124 in the electrode portion 120 corresponds to a joint portion in the claims.

  FIG. 3 is a partial cross-sectional view of the ceramic heater 100 shown in FIG. 1 in the peripheral portion of the electrode portion 120 as viewed in the direction of the arrow along the one-dot chain line A-A ′. In FIG. 3, the direction from the joining member 130 toward the central axis of the ceramic heater 100 (downward on the paper surface in the drawing) is defined as the downward direction, and the direction away from the central axis (upward on the paper surface in the drawing) is described as the upward direction. To do.

  As shown in FIG. 3, the electrode pad 121 formed on the electrode portion 120 is formed on the outer surface (upper surface in FIG. 3) of the green sheet 140 wound around the outer periphery of the soot tube 101, and through the through hole 144. The green sheet 140 is electrically connected to the lead portion 143 of the heating resistor 141 formed on the inner surface (the lower surface in FIG. 3).

  The electrode pad 121 is a pad-like metal layer containing 80% by weight or more of a main material composed of at least one element selected from tungsten and molybdenum. Tungsten and molybdenum are suitable for the composition of the electrode pad 121 because they have good bonding properties to the copper brazing material 124 and have a high melting point and excellent heat resistance.

The joining member 130 is made of a nickel member containing 90% by weight or more of nickel.
As shown in FIG. 3, the bonding member 130 is bonded to the electrode pad 121 by the brazing material 124. Further, a nickel plating film 125 as a metal layer is formed on the bonding member 130 and the electrode pad 121 bonded to each other by the brazing material 124, so that a nickel plating film 125 is formed as a metal layer. Corrosion due to oxidation is prevented. The nickel plating film 125 corresponds to the surface plating layer in the claims.

  The brazing material 124 that joins the electrode pad 121 and the joining member 130 contains copper in an amount exceeding 50% by weight. In the present embodiment, the electrode pad 121 and the bonding member 130 are brazed using a brazing material 124 of 100% by weight of copper.

At the time of brazing, the nickel component of the nickel plating film 122 provided on the electrode pad 121 diffuses into the brazing material 124.
That is, in the ceramic heater 100 of the present embodiment, as shown in FIG. 3, the nickel plating film 122 before brazing has a contour shape indicated by a dashed line 123 at the boundary portion with the brazing material 124. After brazing, a part of the nickel plating film 122 is diffused and melted into the brazing material 124, and the nickel plating film 122 and the brazing material 124 are formed in an integrated state.

Next, the manufacturing method of the ceramic heater of this embodiment is demonstrated.
First, a metal resistor ink (metalized ink) to be the heating resistor 141 and the electrode pad 121 is applied (printed) to the green sheet 140 in a predetermined pattern shape, and the metalized ink ( Alternatively, a process of filling the conductive paste) is performed. Next, the green sheet 146 is pressure-bonded to the green sheet 140, and the green sheet 140 and the green sheet 146 are wound around the soot tube 101 to form a ceramic heater molded body. Subsequently, the ceramic heater molded body is fired to execute a process of forming the ceramic base body 102 in which the green sheets 140 and 146 and the soot tube 101 are integrated.

  The processing so far corresponds to an electrode pad forming step in which the electrode pad 121 is formed by applying metal resistor ink (metallized ink) to the ceramic substrate 102 on which the heating resistor 141 is formed.

Subsequently, a plating formation process for forming a nickel plating film 122 covering the electrode pads 121 is performed (plating formation step).
Next, the brazing material 124 and the joining member 130 are arranged on the nickel plating film 122 so as to contact each other. And in this state, it heats to 900 degreeC or more and fuse | melts the brazing material 124, The process which joins the joining member 130 and the electrode pad 121 by brazing is performed (joining process).

  In this joining step, the brazing material 124 and the region 123 surrounded by the alternate long and short dash line in the nickel plating film 122 are solidified, and the region 123 surrounded by the alternate long and short dash line in the nickel plating film 122 melts into the brazing material 124. A phenomenon occurs.

  Then, a nickel plating film 125 is formed by performing nickel plating by an electroless plating method so as to cover the bonding portion (brazing portion) of the electrode pad 121 and the bonding member 130. As a result, the electrode pad 121 and the bonding portion (the brazing portion) of the bonding member 130 in the electrode portion 120 are protected from corrosion due to oxidation or the like by the nickel plating film 125.

The ceramic heater 100 can be manufactured by executing the above steps.
Next, in order to confirm the effect of the present invention for the ceramic heater 100 of the present embodiment manufactured as described above, the electrode pad 121 and the bonding member 130 are used by using the ceramic heater 100 manufactured based on the conditions described below. The surface state (alumina precipitation state) and the bonding strength at the bonding part (brazing part) were evaluated.

Hereinafter, a description will be given with reference to FIGS.
(A) First, in this embodiment, the green sheets 140 and 146 shown in FIG. 2 were produced by the following method.

93% by weight of alumina (Al ₂ O ₃ ) powder, silica (SiO ₂ ) powder, calcium carbonate (CaCO ₃ ) powder to be calcium oxide (CaO), and magnesium carbonate (MgCO ₃ ) powder to be magnesium oxide (MgO) A raw material powder was prepared by blending 7% by weight of a sintering aid consisting of To 100 parts by weight of the raw material powder, 10 parts by weight of polybutyl vinylal, 5 parts by weight of dibutyl phthalate, and 70 parts by weight of methyl ethyl ketone and toluene are added, respectively, and are slurried with a ball mill (not shown). Mixed. Thereafter, degassing was performed under reduced pressure, and two green sheets of a green sheet 140 having a thickness of 0.2 mm and a green sheet 146 having a thickness of 0.05 mm were produced by a doctor blade method.

Next, a through hole 144 was formed in the green sheet 140 at a predetermined position. Since the green sheet 146 has a thickness of 0.05 mm and is very easy to break, the green sheet 146 is handled in a state of being attached to a transport tape (not shown) until the green sheet 140 is pressed.
(B) Next, a metal resistor ink (metallized ink) for forming the heating resistor 141 and the electrode pad 121 on the green sheet 140 was produced by the following method.

6 parts by weight of a resinous binder and 100 parts by weight of acetone with respect to 100 parts by weight of raw material powder in which 80% by weight of tungsten (W) powder, 10% by weight of alumina powder and 10% by weight of silica (SiO ₂ ) powder are blended. Part by weight and 70 parts by weight of butyl carbitol were added and mixed in a slurry in a pot (not shown). Thereafter, degassing was performed under reduced pressure, and acetone was evaporated to obtain a metal resistor ink (metalized ink).

Alumina contained in the metal resistor ink (metallized ink) is used as an adhesion promoting component for improving the adhesion between the electrode pad 121 and the ceramic substrate 102, and the ceramic substrate 102 (more specifically, green It is the same component as the main component of the sheets 140, 146). Alumina is an insulating material.
(C) Next, the heating resistor 141 and the electrode pad 121 were formed on the green sheet 140 as follows.

A tungsten-based metal resistor ink (metallized ink) prepared in advance as described above was printed on one surface of the green sheet 140 to a thickness of 25 μm by a thick film printing method. That is, each pattern of the heat generating part 142 and the lead part 143 that are fired to form the heat generating resistor 141 was formed on the green sheet 140. Thereafter, two electrode pads 121 were formed at a predetermined position on the other surface of the green sheet 140 by using the above metallized ink by a thick film printing method. Further, metallized ink was filled in the through hole 144 so that each lead portion 143 and each electrode pad 121 were electrically connected.
(D) And the ceramic heater molded object was produced as follows.

On the surface of the green sheet 140 where the heating resistor 141 is formed, the surface of the green sheet 146 on which the conveyance tape is not attached is pressure-bonded. After pressure bonding, the transport tape was peeled off, and an alumina paste (community base) was applied to the surface of the green sheet 146 from which the transport tape was peeled off. Next, with the coated surface as the side of the soot tube 101, green sheets 140 and 146, which were pressure-bonded to each other, were wound around the soot tube 101 and pressed inward from the outer periphery to produce a ceramic heater molded body.
(E) Next, the ceramic heater molded body was fired as follows.

The ceramic heater molded body obtained as described above was heated at 250 ° C. for 6 hours to remove the resin, and then the ceramic heater molded body was fired at 1550 ° C. for 5 hours in a reducing atmosphere. As a result, the rod 101 as a mandrel, the green sheet 146 as a layer surrounding the outer periphery thereof, and the green sheet 140 formed with the heating resistor 141 and the electrode pad 121 as a layer surrounding the outer periphery thereof are integrally fired. A ceramic heater was obtained.
(F) Further, the joining member 130 was brazed as follows to complete the ceramic heater.

  As shown in FIGS. 1 and 3, first, nickel plating was performed on the electrode pad 121 of the fired ceramic heater to form a nickel plating film 122 having a thickness of 2 μm. Thereafter, in order to braze the joint portion 133 of the joining member 130 to the electrode pad 121 with the brazing material 124 made of 100% by weight of copper, the two are joined by holding at 1100 ° C. for 6 minutes in a nitrogen-hydrogen atmosphere. A ceramic heater 100 was produced.

In the present embodiment, the joining member 130 is formed using a material composed of 100% by weight of nickel. Moreover, the thickness dimension of the joining member 130 is 0.3 [mm].
Next, regarding the ceramic heater 100 of the present embodiment manufactured as described above, the evaluation results regarding the surface state (alumina precipitation state) in the bonding portion (brazing portion) of the electrode pad 121 and the bonding member 130 will be described.

  As a comparative example, a ceramic heater manufactured using a metal resistor ink containing no silica as a metal resistor ink (metallized ink) for forming the electrode pad 121 was prepared. And the ceramic heater of this embodiment was compared with the ceramic heater of the comparative example about the surface state in the joining part (brazing part) of an electrode pad and a joining member.

  In the manufacturing process of the ceramic heater of the comparative example, 6 parts by weight of a resin binder and acetone are added to 100 parts by weight of raw material powder in which 90% by weight of tungsten (W) powder and 10% by weight of alumina powder are blended. 100 parts by weight and 70 parts by weight of butyl carbitol were added, mixed in a slurry form in a pot (not shown), degassed under reduced pressure, and acetone was evaporated to obtain a metal resistor ink (metallized ink). It was.

  FIG. 4 is an external view of the ceramic heater 100 according to the present embodiment and the ceramic heater according to the comparative example, in which the surface state of the electrode pad 121 and the bonding portion (the brazing portion) of the bonding member 130 is photographed.

  As shown in FIG. 4, in the ceramic heater of the comparative example, the “alumina precipitation portion” (the dark colored portion of the region surrounded by the dotted line) is present at the joining portion (brazing portion) of the electrode pad 121 and the joining member 130. In contrast, in the ceramic heater 100 of the present embodiment, it can be seen that there is no “alumina precipitation portion” in the bonding portion (brazing portion) of the electrode pad 121 and the bonding member 130.

  According to this evaluation result, the metal resistor ink (metallized ink) containing silica is used as the metal resistor ink (metallized ink) for forming the electrode pad 121, thereby joining the electrode pad 121 and the bonding member 130. It can be seen that it is possible to suppress the precipitation of alumina in the (brazed portion).

  Next, regarding the ceramic heater 100 of the present embodiment manufactured as described above, when the addition amount of silica in the metal resistor ink (metallized ink) is changed, the bonding portion of the electrode pad 121 and the bonding member 130 ( The evaluation result of the surface state (alumina precipitation state) in the brazing portion) and the evaluation result of the bonding strength in the joining portion (brazing portion) will be described.

In this evaluation, five types of ceramic heaters (silica addition amount: 2 wt%, 5 wt%, 10 wt%, 13 wt%, 15 wt%) having different silica addition amounts in the metal resistor ink were used. At this time, the raw material powder of the metal resistor ink adjusts the content of each component by changing the content of tungsten while keeping the content of alumina powder constant as the amount of silica added changes. . For example, when the addition amount of silica is 2% by weight, the raw material powder of the metal resistor ink is 88% by weight of tungsten (W) powder, 10% by weight of alumina powder, and 2% by weight of silica (SiO ₂ ) powder. , And 100 parts by weight of a raw material powder, and when the amount of silica added is 15% by weight, the raw material powder of the metal resistor ink is 75% by weight of tungsten (W) powder and 10% of alumina powder. 100 parts by weight of raw material powder in which 10% by weight and 15% by weight of silica (SiO ₂ ) powder are blended are used.

  As an evaluation method of the surface state (alumina precipitation state) here, an evaluation method is adopted in which it is visually determined whether or not alumina is deposited on the bonding portion (brazing portion) of the electrode pad 121 and the bonding member 130. did.

  In addition, as a method for evaluating the bonding strength here, the ceramic heater 100 is heated from a low temperature (room temperature: 25 ° C.) to a high temperature (500 ° C.), and from the high temperature to the low temperature is taken as one cycle, An evaluation method for determining the bonding strength based on whether or not the bonding member 130 is peeled off from the electrode pad 121 by applying an external force (50 [N]) to the bonding member 130 after performing a temperature change over a cycle. Adopted.

  In the above evaluation, one cycle of temperature change is 10 minutes, and among these, the total of the temperature change time from the low temperature to the high temperature and the high temperature state maintenance time is set to 5 minutes, and the temperature change from the high temperature to the low temperature The sum of the time and the low temperature maintenance time is set to 5 minutes.

FIG. 5 is an explanatory diagram showing the precipitation state of alumina in the joint portion and the evaluation result of the joint strength in the joint portion.
In FIG. 5, the evaluation result of the surface state (alumina precipitation state) is described in the “alumina precipitation suppression effect” column. When alumina is not precipitated, “◯” is described. When it is precipitated, “×” is described. Moreover, in FIG. 5, the evaluation result of joining strength is described in the column of “strength evaluation after cooling cycle”, and “○” is described when the joining member does not peel off, and when the joining member peels off. “X” is described.

  According to the evaluation results of FIG. 5, when the silica addition amount is 2% by weight, 5% by weight, 10% by weight, and 13% by weight, “alumina precipitation suppression effect”, “strength evaluation after cooling cycle” In both cases, since the evaluation result is “◯”, it can be seen that the precipitation of alumina can be suppressed, and it can be seen that the bonding strength after the cooling cycle is excellent.

  However, when the addition amount of silica is 15% by weight, the evaluation result of “strength evaluation after cooling cycle” is “×” although the evaluation result of “alumina precipitation suppression effect” is “◯”. From this, it can be seen that although the precipitation of alumina can be suppressed, there is a difficulty in the bonding strength after the cooling and heating cycle.

  According to this evaluation result, by setting the addition amount of silica in the metal resistor ink within the range of 2 wt% to 13 wt%, it is possible to suppress the precipitation of alumina and to increase the bonding strength after passing the cooling cycle. It can be seen that an excellent ceramic heater can be manufactured.

  In addition, when silica addition amount is 15 weight% or more, it is thought that many internal cavities are formed in an electrode part because a silica diffuses at the time of baking. A ceramic heater having an electrode part in which a large number of internal cavities are formed is subjected to an external force because the strength of the electrode part decreases when used for a long time in an environment where the temperature change is severe. In this case, it is considered that the joining member is peeled off together with the electrode portion.

  As described above, in the method of manufacturing the ceramic heater 100 according to the present embodiment, the metal resistor ink (metallized ink) that forms the electrode pad 121 includes silica.

  As can be seen from the external view shown in FIG. 4, in the comparative example (when the metal resistor ink does not contain silica), alumina (adhesion promoting component) contained in the metal resistor ink in the bonding step is the surface of the bonded portion. In the present embodiment, the alumina contained in the metal resistor ink can be prevented from precipitating on the surface of the joined portion.

  As described above, the nickel plating film 125 (surface plating layer) is formed on the conductive bonding portion by suppressing the deposition of alumina on the surface of the bonding portion (brazing portion) of the electrode pad 121 and the bonding member 130. ) Can be prevented from reducing the thickness of the nickel plating film 125. Further, the nickel plating film 125 formed in this way can prevent the nickel plating film 125 from being easily peeled off because the alumina does not precipitate on the surface of the bonding portion, thereby improving the adhesion with the bonding portion.

  Therefore, according to the ceramic heater manufacturing method of the present embodiment, even when the brazing operation at a high temperature (900 ° C. or higher) is performed in the bonding process of the electrode pad 121 and the bonding member 130, the bonding to the electrode pad 121 is performed. Precipitation of alumina on the surface of the joint portion with the member 130 can be suppressed. For this reason, according to the ceramic heater manufacturing method of this embodiment, it can prevent that the formation state of the nickel plating film 125 with respect to a junction part becomes defective.

  Furthermore, since the brazing material 124 used in the present embodiment is made of 100% by weight of copper and has a melting point of 900 ° C. or higher, the ceramic heater 100 of the present embodiment is used in a high temperature environment or in an environment where temperature changes are severe. Suitable for use below. That is, the ceramic heater 100 is excellent in durability under a high temperature environment (high temperature durability) and durability against temperature change (cooling cycle durability).

  Further, according to the evaluation results shown in FIG. 5, in the above ceramic heater manufacturing method, when the total weight of tungsten, alumina and silica is 100 parts by weight among the components contained in the metal resistor ink, the silica heater The content of is preferably set in the range of 2 to 13% by weight.

  That is, as can be seen from the evaluation results in FIG. 5, by setting the silica content to at least 2% or more, it is possible to suppress the precipitation of alumina on the surface of the joint portion between the electrode pad 121 and the joint member 130. Therefore, in order to reliably suppress the precipitation of alumina at the joint portion between the electrode pad 121 and the joint member 130, it is desirable to set the silica content to at least 2% or more.

  Further, as can be seen from the evaluation results of FIG. 5, by setting the silica content to 13% or less, it is possible to suppress the formation of a large number of internal cavities in the electrode pad 121, and the electrode pad 121, the ceramic substrate 102, It can suppress that the joint strength of this falls.

  In the above embodiment, the metal resistor ink (metallized ink) corresponds to the electrode ink described in the claims, tungsten corresponds to the main material, and the nickel plating film 125 corresponds to the surface plating layer. ing.

  Further, a metal resistor ink to be the heating resistor 141 and the electrode pad 121 is applied (printed) to the green sheet 140, and the ceramic heater molded body in which the green sheet 140 and the green sheet 146 are wound around the soot tube 101 is fired. Thus, the process of forming the ceramic substrate 102 corresponds to the electrode pad forming process.

  Further, the process of performing the plating process for forming the nickel plating film 122 covering the electrode pads 121 corresponds to the plating process, and the brazing material 124 is disposed on the nickel plating film 122 and the bonding member 130 is disposed thereon. The process of performing the process of joining the joining member 130 and the electrode pad 121 by brazing by heating and melting the brazing material 124 corresponds to the joining process. Further, the process of forming the nickel plating film 125 on the brazing material 124 corresponds to the surface plating layer forming process.

  In the above-described embodiment (hereinafter referred to as the first embodiment), the ceramic heater including one electrode pad and the manufacturing method thereof have been described. However, the electrode ink (metal resistor ink, metalized ink) for forming the electrode pad is described. ), It is also possible to manufacture a ceramic heater having a multilayered electrode pad using a plurality of types of electrode ink.

  Therefore, as a second embodiment, a second ceramic heater 150 including a multilayer electrode pad 151 having a multilayer structure will be described. FIG. 6 is an exploded perspective view showing the internal configuration of the second ceramic heater 150 including the multilayer electrode pad 151.

  The second ceramic heater 150 includes a ceramic base 102 having a heating resistor 141, a multilayer electrode pad 151 that is exposed from the ceramic base 102 and energizes the heating resistor 141, and has a melting point of 900 ° C. or higher. And a bonding member (not shown) bonded to the electrode pad 121 by the brazing material.

  The second ceramic heater 150 is different from the ceramic heater 100 of the first embodiment in the configuration of the electrode pads, but the other configurations are the same, and therefore, different parts will be mainly described.

  The multilayer electrode pad 151 has a two-layer structure in which a lower electrode pad 155 and an upper electrode pad 153 are stacked. The multilayer electrode pad 151 is configured such that the lower electrode pad 155 is disposed on the side facing the green sheet 140 and the upper electrode pad 153 is laminated so as to cover the lower electrode pad 155.

  As the electrode ink for forming the multilayer electrode pad 151, the lower layer electrode ink having a lower silica content than the ceramic main component (for example, alumina) and the ceramic main component (for example, alumina). Also, an ink for an upper electrode having a large silica content is used.

Specifically, 6 wt.% Of resin-based binder with respect to 100 wt. Parts of raw material powder containing 85 wt.% Of tungsten (W) powder, 10 wt.% Of alumina powder, and 5 wt.% Of silica (SiO ₂ ) powder. Parts, 100 parts by weight of acetone, and 70 parts by weight of butyl carbitol are added, mixed in a slurry form in a pot (not shown), degassed under reduced pressure, and acetone is evaporated to evaporate the lower layer electrode. Is generated. Further, 6 parts by weight of a resin binder with respect to 100 parts by weight of a raw material powder containing 75% by weight of tungsten (W) powder, 10% by weight of alumina powder, and 15% by weight of silica (SiO ₂ ) powder, 100 parts by weight of acetone and 70 parts by weight of butyl carbitol are added, mixed in a slurry form in a pot (not shown), degassed under reduced pressure, and acetone is evaporated to produce ink for the upper layer electrode. .

  In the electrode pad forming step, after applying the lower layer electrode ink, the upper layer electrode ink is applied over the lower layer electrode ink to form a two-layer electrode ink, By firing, a two-layer electrode pad is formed.

  In this way, by forming the multilayer electrode pad 151 having a two-layer structure using two types of electrode ink, the lower layer electrode pad 155 formed of the lower layer electrode ink, the ceramic substrate 102 (green sheet 140), and the like. The bonding state of can be improved.

  Further, by forming a multilayer electrode pad 151 having a two-layer structure using two types of electrode ink, alumina (adhesion promoting component) is formed on the surface of the joint portion by the upper layer electrode pad 153 formed by the upper layer electrode ink. Can be prevented from precipitating.

The content of silica in the multilayer electrode pad 151 is not calculated as the content of the upper layer electrode ink alone, but as the total amount of the lower layer electrode ink and the upper layer electrode ink. That is, in the second embodiment, the content of each component when the ink for the lower layer electrode and the ink for the upper layer electrode are added is 160 wt% of tungsten (W) powder (= 85 wt% + 75 wt%), alumina It becomes 20% by weight of powder (= 10% by weight + 10% by weight) and 20% by weight of silica (SiO ₂ ) powder (= 5% by weight + 15% by weight). Therefore, the content of silica in the multilayer electrode pad 151 of the second embodiment is 20% by weight of silica powder with respect to 200 parts by weight of raw material powder containing tungsten (W) powder, alumina powder, and silica powder. The content of silica with respect to 100 parts by weight of the raw material powder is 10% by weight.

  Further, for example, when the content of silica in the electrode pad composed of two layers is in the range of 2 to 13% by weight, tungsten among the electrode inks obtained by adding the lower layer electrode ink and the upper layer electrode ink together. When the total weight of alumina and silica is 100 parts by weight, the silica content is adjusted within the range of 2 to 13% by weight.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect can be taken.
For example, the brazing material 124 is not limited to a brazing material composed of 100% by weight of copper, but a brazing material composed of copper and gold (copper-gold brazing), a brazing material composed of copper and silver (copper-silver brazing), copper and indium. A brazing material (copper-indium brazing) made of copper, a brazing material made of copper and titanium (copper-titanium brazing), or the like can be used. In addition, as for a copper-gold brazing, it is desirable to make content of gold into 2-45 weight%. As the brazing material, a brazing material composed of a conductive material having a melting point of 900 ° C. or higher can be used, and some brazing materials mainly composed of copper have a melting point of about 1050 ° C.

Further, the metal resistor ink (metallized ink) may be composed of molybdenum powder instead of tungsten (W) powder. For example, 6 parts by weight of a resin binder with respect to 100 parts by weight of a raw material powder in which 80% by weight of molybdenum (Mo) powder, 10% by weight of alumina powder, and 10% by weight of silica (SiO ₂ ) powder are blended, 100 parts by weight of acetone and 70 parts by weight of butyl carbitol were added and mixed in a slurry in a pot (not shown). Thereafter, the metal resistor ink (metallized ink) can be obtained by degassing under reduced pressure and evaporating acetone.

  Further, although the joining member 130 is formed using a nickel member containing 90% by weight or more of nickel, the joining member 130 may be configured as a clad material in which a nickel member and a SUS member are clad in a laminated form.

  For example, the joining member can be configured by using a nickel member containing 90% by weight or more of nickel and a SUS member containing iron as a main component and containing at least chromium and 30% by weight or less of nickel. Then, by disposing the SUS member on the electrode pad 121 side and joining the joining member and the electrode pad 121 using the brazing material 124, the iron and chromium components contained in the SUS member are diffused into the brazing material 124. Will do. By diffusing the iron component into the brazing material 124 in this manner, the wettability of the brazing material 124 with respect to the electrode pad 121 can be improved, and by diffusing the chromium component into the brazing material 124, the corrosion resistance of the brazing material 124 is improved. Can increase the sex.

  In addition, metallized ink was filled into the through hole 144 and a conductive paste was formed inside the through hole 144. However, a metalized ink was applied to the inner wall of the through hole 144, and a conductive paste was formed on the inner wall of the through hole 144. You may do it.

It is a perspective view showing the appearance of a ceramic heater. It is a disassembled perspective view showing the internal structure of the ceramic heater. It is a fragmentary sectional view in the circumference part of an electrode part seen from a direction of an arrow in dashed-dotted line A-A 'among ceramic heaters shown in FIG. It is the external view which image | photographed the surface state in the junction part (brazing part) of an electrode pad and a joining member about the ceramic heater of this embodiment, and the ceramic heater of a comparative example. It is explanatory drawing which showed the precipitation state of the alumina in a junction part, and the evaluation result of the joint strength in a junction part. It is a disassembled perspective view showing the internal structure of the 2nd ceramic heater.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Ceramic heater, 101 ... Steel pipe, 102 ... Ceramic base | substrate, 110 ... Heating part, 120 ... Electrode part, 121 ... Electrode pad, 122 ... Nickel plating film, 124 ... Brazing material, 125 ... Nickel plating film, 130 ... Joining member , 140 ... green sheet, 141 ... heating resistor, 146 ... green sheet, 150 ... second ceramic heater, 151 ... multilayer electrode pad, 153 ... upper electrode pad, 155 ... lower electrode pad.

Claims (3)

An insulating ceramic substrate having a heating resistor embedded therein;
An electrode pad that is exposed from the ceramic substrate and energizes the heating resistor;
A bonding member bonded to the electrode pad by a bonding portion formed of a conductive brazing material having a melting point of 900 ° C. or higher;
A method for producing a ceramic heater comprising:
Applying to the ceramic substrate on which the heating resistor is formed an electrode ink containing a main material composed of at least one element selected from tungsten and molybdenum and containing the main component of the ceramic substrate; and An electrode pad forming step of firing and forming the electrode pad;
A plating process for forming a plating layer on the surface of the electrode pad;
The brazing material and the joining member are arranged in contact with each other on the electrode pad on which the plating layer is formed, and the brazing material is melted by heating, thereby joining the electrode pad and the joining member. Performing a bonding step of forming the bonding portion;
A surface plating layer forming step of forming a surface plating layer containing a corrosion-resistant material on at least the surface of the joint portion;
Have
The electrode ink comprises silica.
A method for producing a ceramic heater. Among the components contained in the electrode ink, when the total weight of the main material, the main component of the ceramic substrate, and silica is 100 parts by weight, the content of silica is 2 to 13% by weight,
The method for producing a ceramic heater according to claim 1. In the electrode pad forming step,
As the electrode ink, the lower layer electrode ink having a lower silica content than the main component of the ceramic substrate, and the upper layer electrode ink having a higher silica content than the ceramic main component, are used.
Forming the electrode pad comprising two layers by applying the ink for the upper layer electrode after applying the ink for the lower layer electrode;
The method for manufacturing a ceramic heater according to claim 1, wherein: