JP4769136B2 - Manufacturing method of ceramic joined body and ceramic heater - Google Patents

Description

The present invention relates to a method of manufacturing a ceramic joined body and a ceramic heater motor, in particular a ceramic joined body and a ceramic heater which highly corrosion resistant plated layer is formed of copper in the brazing material portion on mainly the used for joining the connecting terminal The present invention relates to a method for manufacturing a tape .

  Conventionally, a ceramic heater in which a heating resistor made of a high melting point metal such as tungsten or molybdenum is embedded in a ceramic substrate such as alumina has been used. For example, a ceramic heater inserted in a sensor element of a gas sensor is formed by winding a green sheet made of ceramic on which a heating resistor is formed around a ceramic soot tube and firing it integrally.

  A metal pad electrically connected to the heating resistor is provided on the outer peripheral surface of the ceramic heater, and a connection terminal for applying a voltage from the outside to the heating resistor is brazed to the metal pad. This metal pad is made of a refractory metal such as tungsten or molybdenum like the heating resistor, and a plating layer (primary plating layer) for improving wettability with the brazing material is formed on the surface of the metal pad. Has been.

In recent years, ceramic heaters are frequently used in high-temperature environments or environments where temperature changes are severe, and therefore, there is a need for improved thermal durability for brazing filler metal parts. In contrast, by using a brazing material containing copper, it is possible to improve the thermal durability of the brazing material portion. And when a brazing material contains copper, in order to prevent the copper contained in a brazing material from oxidation, the plating layer (secondary plating layer) is formed in the surface. Such a plating layer is heat-treated at, for example, about 600 to 800 ° C. in order to improve adhesion to the brazing material (see, for example, Patent Document 1).
JP-A-2005-190740 (for example, Table 1)

  By the way, as a plating layer (secondary plating layer) for protecting the brazing filler metal portion from oxidation, it is preferable to use a nickel boron plating layer having excellent corrosion resistance as compared with a nickel plating layer, a nickel phosphorus plating layer, or the like. Conceivable. From the viewpoint of effectively protecting the brazing material portion from oxidation, it is considered preferable to increase the thickness of the nickel boron plating layer.

  However, since the nickel boron plating layer has high hardness, cracks are generated during the heat treatment when the thickness is increased. And when a crack exists in a nickel boron plating layer, a brazing | wax material part will be oxidized with the oxygen which penetrate | invaded from there, and brazing intensity | strength will fall remarkably. In addition, the copper contained in the brazing material is diffused in the nickel boron plating layer by the above heat treatment, but if there is a crack in the nickel boron plating layer, the diffused copper is also oxidized. The plated layer itself is also low in corrosion resistance.

  Although it is effective to make the nickel boron plating layer thinner against the occurrence of such cracks, if the nickel boron plating layer is made thinner, the effect of protecting the brazing material portion from oxidation is reduced. In addition, when the nickel boron plating layer is thinned, the copper contained in the brazing material diffuses to the surface of the nickel boron plating layer by the heat treatment, and the copper on the surface is oxidized, so the nickel boron plating layer is also corrosion resistant. Low.

The present invention has been made to solve the above-described problems, and a ceramic joined body in which a brazing material portion is effectively protected by a nickel boron plating layer having excellent corrosion resistance and a decrease in brazing strength is suppressed. and its object is to provide a manufacturing method for manufacturing a ceramic heater motor.

The method for producing a ceramic joined body according to the present invention includes a ceramic base provided with a metal pad on a surface thereof, a connection terminal joined to the metal pad via a brazing filler metal portion, and at least the brazing filler metal. A non-copper diffusion layer in which copper is not diffused exists on the surface side of the plating layer and has a thickness of 1 μm or more, and from the surface of the plating layer, the non-copper layer is provided. A method for manufacturing a ceramic joined body in which cracks exceeding a diffusion layer do not exist , wherein the brazing material and the connecting terminal are brought into contact with a metal pad provided on the ceramic base, and the brazing material is melted. Forming a brazing material portion to join the metal pad and the connection terminal; and forming the plating layer containing nickel boron as a component to have a thickness of 6 μm or more so as to cover at least the surface of the brazing material portion And a step of heat-treating the ceramic substrate on which the plating layer is formed at 900 ° C. or higher.

The method for manufacturing a ceramic heater according to the present invention includes a ceramic base body in which a heating resistor is embedded and a metal pad electrically connected to the heating resistor is provided on the surface, and a brazing material mainly composed of copper. Non-copper diffusion in which copper is not diffused on the surface side of the plating layer, including a connection terminal joined to the metal pad via a portion and a plating layer provided to cover at least the brazing material portion A method of manufacturing a ceramic heater in which a layer is present with a thickness of 1 μm or more and no crack exceeding the non-copper diffusion layer exists from the surface of the plating layer , the brazing material on the metal pad provided on the ceramic base Contacting the connection terminal and melting the brazing material to form the brazing material portion and joining the metal pad and the connection terminal; and at least a surface of the brazing material portion As described above, the method includes a step of forming the plating layer containing nickel boron to a thickness of 6 μm or more, and a step of heat-treating the ceramic substrate on which the plating layer is formed at 900 ° C. or more. .

  By forming the nickel boron plating layer to a thickness of 6 μm or more so as to cover the surface of the brazing material portion as in the method of manufacturing the ceramic joined body of the present invention, the brazing material portion can be effectively protected from oxidation. . And by performing the heat processing at 900 degreeC or more, even if the thickness of a nickel boron plating layer is thickened with 6 micrometers or more, it can suppress that a crack generate | occur | produces. Furthermore, since the nickel boron plating layer has a thickness of 6 μm or more, the copper of the brazing material portion does not diffuse on the surface of the nickel boron plating layer even when heat treatment at 900 ° C. or more is performed. It can also prevent that the corrosion resistance of itself falls.

  Further, as in the method for manufacturing a ceramic heater according to the present invention, by forming a nickel boron plating layer with a thickness of 6 μm or more so as to cover the surface of the brazing material portion, the brazing material portion can be effectively protected from oxidation. it can. And by performing the heat processing at 900 degreeC or more, even if the thickness of a nickel boron plating layer is thickened with 6 micrometers or more, it can suppress that a crack generate | occur | produces. Furthermore, since the nickel boron plating layer has a thickness of 6 μm or more, the copper of the brazing material portion does not diffuse on the surface of the nickel boron plating layer even when heat treatment at 900 ° C. or more is performed. It can also prevent that the corrosion resistance of itself falls.

  Hereinafter, the present invention will be described by taking a ceramic heater as an example. FIG. 1 is a perspective view showing an example of a ceramic heater 100 of the present invention. FIG. 2 is an exploded perspective view of the ceramic substrate 105 of the ceramic heater 100. FIG. 3 is an enlarged cross-sectional view of the vicinity of the electrode portion 120 of the ceramic heater 100. In the following description, the heating part 110 side of the ceramic heater 100 is referred to as the front end side, and the electrode part 120 side is referred to as the rear end side.

  A ceramic heater 100 shown in FIG. 1 is inserted into a sensor element in which an electrode layer is formed on each of inner and outer surfaces of a solid electrolyte tube having a bottomed cylindrical shape (not shown), and heats the sensor element. The ceramic substrate 105 is formed in a round bar shape. The ceramic heater 100 has a heating resistor 141 embedded therein, and a voltage is applied from the electrode portion 120 on the rear end side, and heat is generated in the heating portion 110 on the front end side.

  As shown in FIG. 2, the ceramic substrate 105 is formed by winding green ceramic sheets 140 and 146 made of highly insulating alumina ceramic around the outer periphery of a round rod-like alumina ceramic tube 101 and firing them. A tungsten heating resistor 141 as a heat pattern is formed on the green sheet 140. The heating resistor 141 includes a heating part 142 formed at a position corresponding to the heating part 110 (see FIG. 1), It is composed of a pair of lead parts 143 connected to both ends of the heat generating part 142. Four through holes 144 are formed on the rear end side of the green sheet 140, and the pair of lead portions 143 are electrically connected to the pair of metal pads 121 through the through holes 144.

  As shown in FIG. 1, a connection terminal 130 for applying a voltage from the outside to the ceramic heater 100 is joined on the metal pad 121. The connection terminal 130 is made of a plate-like nickel-based alloy, and the front end side of the body portion 133 that extends straight is bent in a step shape in the thickness direction to form a facing portion 131 and a connection portion 132. A caulking portion 134 to which a lead wire for connecting an external circuit is caulked and fixed is formed at the rear end portion of the body portion 133. In the caulking portion 134, the rear end side barrel portion 133 is twisted at a substantially right angle with respect to the front end side barrel portion 133, and both edges of the rear end side barrel portion 133 are folded back to one surface side. Is formed.

  As shown in FIG. 3, the connection terminal 130 has a facing portion 131 and a connection portion 132 arranged on the metal pad 121, and a brazing material portion 124 is provided and joined so as to cover them. On the surface of the brazing material portion 124, a nickel boron plating layer 125 is formed to protect the brazing material portion 124 from oxidation. The nickel boron plating layer 125 corresponds to the “plating layer” in the claims.

FIG. 4 is an enlarged view of the brazing material portion 124 and the nickel boron plating layer 125. The ceramic heater 100 of the present invention is characterized in that the thickness t of the nickel boron plating layer 125 is 6 μm or more. The nickel boron plating layer 125 is a non-copper diffusion layer 125a in which copper is not diffused on the surface 125s side, and a copper diffusion layer 125b is a layer in which copper is diffused on the brazing filler metal portion 124 side. The thickness t _a of the non-copper diffusion layer 125a is 1 μm or more. Further, when the nickel boron plating layer 125 has a crack 126 continuously progressing from the surface 125s toward the inside thereof, the tip of the crack 126 does not exceed the non-copper diffusion layer 125a, that is, the copper diffusion layer. It is characterized by not reaching 125b.

In the ceramic heater 100 of the present invention, the brazing filler metal portion 124 can be more effectively protected from oxidation by forming the nickel boron plating layer 125 having excellent corrosion resistance so as to have a thickness t of 6 μm or more. Further, by setting the nickel boron plating layer 125 to such a thickness t, when a heat treatment (hereinafter simply referred to as a heat treatment) for improving the adhesion to the brazing material portion 125 is performed, the copper diffusion layer 125b while effectively formed, the thickness t _a of the non-copper diffusion layer 125a may be a 1μm or more, the oxidation of the surface 125s can be suppressed. FIG. 4 shows a state after the heat treatment.

  In general, although the nickel boron plating layer is excellent in corrosion resistance, since it has high hardness, if it has a thickness of 6 μm or more, cracks occur when heat-treated. If the crack reaches the copper diffusion layer from the surface, the copper diffusion layer is oxidized by oxygen that has entered from the crack. In the present invention, the crack 126 extending from the surface 125s of the nickel boron plating layer 125 does not exceed the non-copper diffusion layer 125a, that is, does not reach the copper diffusion layer 125b. Oxidation of the material part 124 and the copper diffusion layer 125b can be suppressed.

  The thickness t of the nickel boron plating layer 125 is not necessarily limited as long as it is 6 μm or more, but is preferably 15 μm or less. From the viewpoint of suppressing the oxidation of the brazing filler metal portion 124, it is sufficient that the thickness t is about 15 μm. If the thickness t is exceeded, the difference in thermal expansion from the brazing filler metal portion 124 becomes large and the peeling easily occurs. Is also unfavorable because it becomes longer. From the viewpoint of harmony such as suppression of oxidation of the brazing filler metal portion 124 and suppression of peeling of the nickel boron plating layer 125, the thickness t of the nickel boron plating layer 125 is preferably 7 μm or more and 10 μm or less.

Without necessarily limited thickness t _b of the copper diffusion layer 125b in the nickel boron plating layer 125 is preferably 1μm or more. When the thickness t _b of the copper diffusion layer 125b is less than 1 μm, the adhesion between the brazing material portion 124 and the nickel boron plating layer 125 becomes insufficient, and the nickel is removed from the brazing material portion 124 when heat is repeatedly applied during use. This is not preferable because the boron plating layer 125 may be peeled off. The non-copper diffusion layer 125a, the thickness t _a of the non-copper diffusion layer 125a is 1μm or more, preferably formed such that the above 2 [mu] m.

  The average particle diameter of the crystal particles in the nickel boron plating layer 125, particularly the non-copper diffusion layer 125a, is preferably 1.5 μm or more, and more preferably 2 μm or more. If the average particle size of the crystal particles is less than 1.5 μm, the crack 126 extending from the surface 125s may exceed the non-copper diffusion layer 125a. Further, if the average particle size of the crystal particles is less than 1.5 μm, the adhesion between the crystal particles may not be sufficient, and copper diffuses from the copper diffusion layer 125b or the like to the surface 125s during use and is oxidized. There is a fear.

  The nickel boron plating layer 125 is distinguished from the non-copper diffusion layer 125a and the copper diffusion layer 125b by using, for example, a cross-section sampler cross section polisher (SM-09010, manufactured by JEOL Ltd.). Can be performed by preparing a cross-sectional sample and examining the presence or absence of copper by EDS element mapping. The presence or absence of the crack 126 can be examined by observing a cross section in which the non-copper diffusion layer 125a and the copper diffusion layer 125b as described above are determined using a scanning electron microscope (SEM). The average particle size of the crystal particles is obtained by observing the cross section in which the non-copper diffusion layer 125a as described above is determined using a scanning electron microscope (SEM), and measuring the particle size of the crystal particles contained per unit area. Can be determined by averaging them.

  The brazing material constituting the brazing material portion 124 is not necessarily limited as long as it contains copper as a main component, that is, contains 50 wt% or more of copper, for example, Cu, Au—Cu, Ag—Cu, etc. Materials. The brazing material preferably has a melting point exceeding the heat treatment temperature (at least 900 ° C. in the present invention). Furthermore, in the case of an Au—Cu brazing material, Au is preferably 2 to 45 wt%.

  Such a ceramic heater 100 can be manufactured through the following manufacturing process. First, the connection terminal 130 is joined to the metal pad 121 provided on the ceramic substrate 105 by the brazing material portion 124 (joining process). Then, a nickel boron plating layer 125 is formed to a thickness of 6 μm or more so as to cover the surface of the brazing material portion 124 (plating process). Further, the ceramic substrate 105 on which the nickel boron plating layer 125 is formed is heat-treated at 900 ° C. or more (heat treatment step). By manufacturing the ceramic heater 100 through the joining process, the plating process, and the heat treatment process, the ceramic heater 100 on which the nickel boron plating layer 125 having the specific structure as described above is formed can be manufactured. Hereinafter, a method for manufacturing the ceramic heater 100 will be specifically described.

  The ceramic substrate 105 may be any ceramic substrate as long as the heating resistor 141 is embedded inside and the metal pad 121 electrically connected to the heating resistor 141 is provided on the surface. Common ceramic substrates can be used. The ceramic substrate 105 can be manufactured, for example, as follows.

  First, as shown in FIG. 2, raw material mixed powder containing alumina as a main component and containing a sintering aid is used as a slurry, and two green sheets 140 and 146 having a predetermined shape are prepared from the slurry by a doctor blade method. The green sheet 140 has four through holes 144 for conduction between the metal pad 121 and the heating resistor 141, and the unfired heat is generated by a metal paste mainly composed of tungsten on one side with the four through holes 144 as a base point. The resistor 141 is printed, and the through hole 144 is filled with a metal paste.

  An unfired metal pad 121 is printed on the opposite surface of the green sheet 140 with a metal paste so as to cover the through hole 144. Then, the green sheet 146 is laminated on the surface of the green sheet 140 on which the unfired heating resistor 141 is printed. Then, these are wound around an alumina ceramic rod 101 prepared separately, and fired at 1500 to 1550 ° C. in a firing furnace to manufacture the ceramic substrate 105.

  A plating layer (primary plating layer) made of nickel or the like is formed on the metal pad 121 of the ceramic base 105 in order to improve the wettability of the brazing material portion 124 prior to the actual connection of the connection terminals 130. It is preferable to keep it.

  Further, the connection terminal 130 to be joined to the metal pad 121 is formed by punching a nickel plate into a substantially T-shaped piece, and as shown in FIG. 1, the front end side of the body portion 133 is stepped in the thickness direction. Folded into a counter part 131 and a connection part 132, and the rear end part of the body part 133 is twisted at a substantially right angle with respect to the front end side, and both edges of the rear end part are folded back to one surface side and caulked. It manufactures by setting it as the part 134.

  As shown in FIG. 3, the connection terminal 130 is joined to the metal pad 121 by disposing the facing portion 131 and the connection portion 132 of the connection terminal 130 on the metal pad 121 and covering the metal pad 121 so as to cover them. In this way, a soldering material mainly composed of copper is melted and applied, and the soldering material is solidified to form a soldering material portion 124.

  The brazing material is not necessarily limited as long as it contains 50 wt% or more of copper as described above. For example, a brazing material such as Cu, Au—Cu, or Ag—Cu can be used. The brazing material preferably has a melting point exceeding the heat treatment temperature (at least 900 ° C.) in the heat treatment step. Furthermore, in the case of an Au—Cu brazing material, Au is preferably 2 to 45 wt%.

  The nickel boron plating layer 125 can be formed on the brazing material portion 124 by electroless plating. This electroless plating treatment is performed using, for example, a nickel compound such as nickel sulfate, nickel chloride, and nickel carbonate, and in addition, a reducing agent such as dimethylamine borane, and a buffering agent such as sodium formate and sodium acetate. Can do. In order to set the thickness t of the nickel boron plating layer 125 to 6 μm or more, the processing time in the electroless plating process is adjusted, the pH value of the plating solution used, the nickel concentration, the content of the reducing agent, etc. are adjusted. It can be done by doing.

  In addition, in the electroless plating process, it is preferable to pre-process the ceramic substrate 105 (including the connection terminals 130 and the like) in advance. For example, in order to prevent the deposition of the nickel boron plating layer on unnecessary portions of the ceramic substrate 105 after degreasing using a chemical having high degreasing performance for the purpose of activating the surface and restoring wettability. In order to activate by removing the metal adhering to unnecessary portions by etching and further removing the oxidation of the surface on which the nickel boron plating layer 125 is formed, it is preferable to perform acid treatment.

The heat treatment is performed on the ceramic substrate 105 on which the nickel boron plating layer 125 is formed. In the present invention, this heat treatment is particularly performed at 900 ° C. or higher. By such heat treatment, as shown in FIG. 4, copper contained in the brazing material portion 124 can be diffused into the nickel boron plating layer 125, and the copper diffusion layer 125b can be formed in the nickel boron plating layer 125. Adhesion between the material part 124 and the nickel boron plating layer 125 can be improved. In the present invention, since the thickness t of the nickel boron plating layer 125 is set to 6 μm or more, even if heat treatment is performed at such a high temperature, copper does not normally diffuse to the surface 125s of the nickel boron plating layer 125. A non-copper diffusion layer 125a having _a thickness ta of at least 1 μm is secured on the surface 125s side.

  In the present invention, the heat treatment temperature is set to 900 ° C. or higher so that the crack 126 extending from the surface 125s toward the inside does not exceed the non-copper diffusion layer 125a, that is, does not reach the copper diffusion layer 125b. be able to.

  Also in the present invention, cracks extending from the surface 125s to the inside may occur in the nickel boron plating layer 125 in the vicinity of 400 to 500 ° C., which is the initial stage of the heat treatment. However, the crystal particles in the nickel boron plating layer 125 grow rapidly to a size 2 to 4 times (2 to 4 μm) near 900 ° C. For this reason, in the present invention, by setting the heat treatment temperature to 900 ° C. or higher, crystal grains are grown, and once generated cracks are made up by the growth of the crystal grains, the cracks 126 extending from the surface 125s toward the inside are not formed. It is possible not to exceed the copper diffusion layer 125a. In the present invention, by growing crystal grains, the adhesion between the crystal grains can be strengthened, and the diffusion of copper from the brazing filler metal portion 124 and the copper diffusion layer 125b to the surface 125s can also be suppressed.

The heat treatment temperature may be 900 ° C. or higher, but is preferably 930 ° C. or higher in order to further promote the growth of crystal grains. Incidentally, the heat treatment temperature is too high, diffusion of copper from the brazing material portion 124 to the nickel-boron plating layer 125 is increased, since the thickness t _a of the non-copper diffusion layer 125a may become less than 1 [mu] m, the heat treatment temperature Is preferably 980 ° C. or lower.

In addition, the growth of crystal grains constituting the nickel boron plating layer 125 mainly depends on the heat treatment temperature and is not necessarily related to the heat treatment time. Therefore, it is not necessary to maintain the temperature at 900 ° C. or higher for a certain period of time. It may be cooled when it reaches 900 ° C. If the heat treatment time is lengthened, the grain size of the crystal particles is averaged and cracks can be further suppressed. However, if the heat treatment time is too long, the brazing material portion 124 is transferred to the nickel boron plating layer 125. diffusion of copper is increased, the thickness t _a of the non-copper diffusion layer 125a may become less than 1 [mu] m.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
A raw material mixed powder containing 93 wt% alumina and 7 wt% sintering aid was used as a slurry, and two green sheets 140 and 146 were prepared from this slurry by a doctor blade method. The green sheets 140 and 146 have a length of 60 mm, a width of 10 mm, and a thickness of 0.3 mm. On the green sheet 140, four through holes 144 for conduction with the metal pad 121 are opened, and the unfired heating resistor 141 is printed with a metal paste mainly composed of tungsten on one side with the four through holes 144 as a starting point. The through hole 144 was filled with a metal paste.

  An unfired metal pad 121 was printed on the opposite surface of the green sheet 140 with a metal paste so as to cover the through hole 144. And the green sheet 146 was laminated | stacked on the surface side in which the unbaking heating resistor 141 of the green sheet 140 was printed. Then, these were wound around a separately prepared alumina ceramic rod 101 having a length of 60 mm, an outer periphery of 10 mm, and an inner diameter of 3 mm, and fired at 1500 to 1550 ° C. in a firing furnace to produce a ceramic substrate 105. Thereafter, nickel plating was performed on the metal pad 121.

  On the other hand, a connecting terminal 130 was manufactured by punching out a small piece having a shape in which a tip having a length of 15 mm and a width of 1 mm swelled in a substantially T-shape from a nickel plate having a thickness of 0.3 mm and processing it into a predetermined shape. Then, the facing portion 131 and the connecting portion 132 of the connecting terminal 130 are arranged on the metal pad 121 of the ceramic base 105, and brazing is performed using a brazing material containing copper (Cu) 62wt% and gold (Au) 38wt%. A brazing filler metal part 124 was obtained.

Next, after degreasing, etching, and acid treatment are performed on the ceramic substrate 105 to which the connection terminal 130 is bonded, brazing material is obtained by electroless plating using nickel and dimethylamine borane as a reducing agent. A nickel boron plating layer 125 having a thickness of 6 μm was formed on the portion 124. Further, the ceramic substrate 105 on which the nickel boron plating layer 125 is formed is heat-treated from room temperature to 900 ° C. in an H ₂ —N ₂ air flow, and is allowed to cool after reaching 900 ° C. A ceramic heater 100 was manufactured.

(Comparative Example 1)
A ceramic heater was manufactured in the same manner as in Example 1 except that the maximum temperature of the heat treatment after forming the nickel boron plating layer was 730 ° C.

  Next, for the ceramic heaters of Example 1 and Comparative Example 1, the surface of the nickel boron plating layer was observed using a scanning electron microscope (SEM), and a cross-section sampler cross section polisher (SM-09010, JEOL Ltd.) A cross-sectional sample was produced using a company company, and the presence or absence of copper was examined by EDS element mapping.

  5 and 6 show scanning electron micrographs (500 times) of the surfaces of the nickel boron plating layers of Example 1 and Comparative Example 1, respectively. 7 and 8 show the results of EDS element mapping of the cross sections of the nickel boron plating layers of Example 1 and Comparative Example 1, respectively. 7 and 8, the upper right is the surface side of the nickel boron plating layer, the lower left is the brazing filler metal part side, and the range indicated by the thick arrow at the center is the range where the nickel boron plating layer is formed. The range indicated by the lower thin arrow is the range where the non-copper diffusion layer is formed.

  As shown in FIG. 6, it was recognized that a lot of streak-like cracks and spot-like cracks were generated on the surface of the nickel boron plating layer for those subjected to heat treatment at 730 ° C. On the other hand, as shown in FIG. 5, it was recognized that the stripe-shaped cracks and the dot-shaped cracks were almost disappeared by the growth of the crystal grains in the case where the heat treatment was performed at 900 ° C.

  In addition, although not shown in figure, about what heat-processed at 730 degreeC, it was recognized that many cracks extended from the surface beyond a non-copper diffusion layer to a copper diffusion layer had generate | occur | produced. On the other hand, in the case of heat treatment at 900 ° C., cracks extending from the surface to the inside are recognized, but all remain in the non-copper diffusion layer, and the substantial cracks reach the copper diffusion layer. Was found not to exist.

  Further, as is apparent from FIGS. 7 and 8, copper diffused from the brazing filler metal part is formed in the heat-treated materials at 730 ° C. and 900 ° C., and a copper diffusion layer is formed. Was recognized. Further, as apparent from FIG. 7, the heat treatment at 900 ° C. has a large amount of copper diffusion from the brazing filler metal part, and the non-copper diffusion layer is thin, but the thickness of the non-copper diffusion layer still remains. The thickness of 1 μm or more was secured, and it was confirmed that a non-copper diffusion layer having a sufficient thickness could be secured even for those subjected to heat treatment at 900 ° C.

  Based on the above, a nickel boron plating layer having a thickness of 6 μm or more is formed on the brazing material portion, and then heat treatment is performed at 900 ° C. or more to form a nickel boron plating layer having excellent corrosion resistance on the brazing material portion. Thus, it can be seen that it is possible to obtain a ceramic heater in which oxidation of the brazing material portion is suppressed and a decrease in brazing strength is suppressed.

The perspective view which shows an example of the ceramic heater of this invention. The disassembled perspective view which shows the base | substrate of the ceramic heater shown in FIG. The expanded sectional view which shows the electrode part vicinity of the ceramic heater shown in FIG. Sectional drawing which shows an example of a nickel boron plating layer. 2 is a scanning electron micrograph of the surface of a nickel boron plating layer according to Example 1. FIG. The scanning electron micrograph of the surface of the nickel boron plating layer concerning the comparative example 1. The figure which shows the result of the EDS element mapping of the cross section of the nickel boron plating layer which concerns on Example 1. FIG. The figure which shows the result of the EDS element mapping of the cross section of the nickel boron plating layer which concerns on the comparative example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Ceramic heater, 101 ... Steel pipe, 105 ... Base | substrate, 110 ... Heating part, 120 ... Electrode part, 121 ... Metal pad, 124 ... Brazing material part, 125 ... Nickel boron plating layer (125a ... Non-copper diffusion layer, 125b ... Copper diffusion layer, 125s ... surface), 130 ... connection terminal, 131 ... facing part, 132 ... connection part, 133 ... body part, 134 ... caulking part, 140 ... green sheet, 141 ... heating resistor, 142 ... heating part , 143 ... read unit, 144 ... through hole, 146 ... green sheets, t ... thickness of the nickel boron plating layer, t a _... non-copper diffusion layer thickness, the thickness of t b _... copper diffusion layer

Claims (2)

A ceramic base provided with a metal pad on the surface, a connection terminal joined to the metal pad via a brazing filler metal part mainly composed of copper, and a plating layer provided so as to cover at least the brazing filler metal part; A non-copper diffusion layer in which copper is not diffused on the surface side of the plating layer, and a crack that exceeds the non-copper diffusion layer from the surface of the plating layer does not exist A manufacturing method of
A step of bringing the brazing material and the connection terminal into contact with each other on a metal pad provided on the ceramic base, and melting the brazing material to form the brazing material portion to join the metal pad and the connection terminal. When,
Forming the plating layer containing nickel boron in a thickness of 6 μm or more so as to cover at least the surface of the brazing material portion;
And a step of heat-treating the ceramic substrate on which the plating layer is formed at 900 ° C. or higher. A heat generating resistor is embedded inside, and a ceramic base provided with a metal pad electrically connected to the heat generating resistor on the surface is joined to the metal pad through a brazing filler metal part mainly composed of copper. A non-copper diffusion layer in which copper is not diffused exists on the surface side of the plating layer, and has a thickness of 1 μm or more. A method for manufacturing a ceramic heater in which there is no crack exceeding the non-copper diffusion layer from the surface of the plating layer ,
A step of bringing the brazing material and the connection terminal into contact with each other on a metal pad provided on the ceramic base, and melting the brazing material to form the brazing material portion to join the metal pad and the connection terminal. When,
Forming the plating layer containing nickel boron in a thickness of 6 μm or more so as to cover at least the surface of the brazing material portion;
And a step of heat-treating the ceramic substrate on which the plating layer is formed at 900 ° C. or higher.