CN101588655B - Ceramic heater and heating iron using it - Google Patents

Abstract

A ceramic heater comprises the following components: a ceramic body which is provided with a conductor and a metal coating layer conducted with the conductor; and a lead wire component which is jointed with the metal coating layer through brazing solder that is composed of more than two metals. The more than two metals exist in the brazing solder with an identificable state. One metal in the more than two metals is a first metal with young's modulus lower than 180 GPa. The first metal is positioned in at least one interface selected from an interface between the brazing solder and the lead wire component and the interface between the brazing solder and the metal coating layer.

Description

Ceramic heater and heating iron using it

This application is based on the divisional application of the patent application with the application number 200580023302.X, the title of the invention is "ceramic heater and soldering iron using it", and the filing date is July 27, 2005.

technical field

The invention relates to a ceramic heater and a soldering iron for heating composed of the ceramic heater.

Background technique

Conventionally, ceramic heaters have been widely used as heat sources for semiconductor heating heaters, soldering irons, curling irons, petroleum fan heaters, and other petroleum gasifiers, or as heat sources in lighting systems. In addition, in recent years, applications such as heating of air-fuel ratio detection sensors (oxygen sensors), especially in-vehicle ceramic heaters, have increased.

In this kind of ceramic heater, there are various shapes such as flat plate shape, cylindrical shape, cylindrical shape, etc., but they are all formed by embedding high melting point metals such as W, Re, Mo, etc., in a ceramic matrix mainly composed of alumina. composed of conductors. FIG. 11 shows a cylindrical ceramic heater as an example. This ceramic heater is composed of a ceramic body in which a conductor is buried, a terminal mounting electrode portion 106 provided on the surface thereof, and a lead member 110 bonded to the surface by solder 111 . The terminal mounting electrode portion 106 is composed of a metallized layer and a Ni plating layer, and connects the buried conductor and the metallized layer in order to supply electric power to the buried conductor (Patent Document 1).

In addition, in recent years, in order to improve reliability, ceramic heaters having the characteristics of the connection of the solder end of the solder outer edge and the point of contact with the solder end of the electrode outer edge have also been proposed. The angle formed by the connection on the above is within the prescribed range (Patent Document 2).

Patent Document 1: Japanese Unexamined Patent Publication No. 8-109063

Patent Document 2: JP-A-2000-286047

However, in recent years, automotive ceramic heaters, which are increasingly in demand, are required to be reliable due to severe operating environments such as high temperature, vibration, and exhaust gas atmosphere. In particular, high reliability is required for the junction of fixed lead parts. sex.

In addition, recently, a rapid temperature rise characteristic is required in a device constituted by a ceramic heater, and in a ceramic heater requiring such a rapid temperature rise, the temperature change of the junction part is also drastic, and high reliability is required for the junction part. That is, due to the difference in thermal expansion between the solder that fixes the lead member to the terminal extraction electrode portion and the ceramic base, stress concentrates on the soldered portion, which lowers the durability of the ceramic heater.

In particular, in ceramic heaters such as hair irons, which have a wide heating area and the entire ceramic heater is sandwiched in the holding member, since the electrode extraction part is rapidly heated simultaneously with the heating, improvement of durability is a major issue.

Contents of the invention

Therefore, an object of the present invention is to provide a ceramic heater that has excellent durability even under severe conditions such as high temperature, vibration, or exhaust gas atmosphere, and has high reliability for rapid heating and cooling.

A further object of the present invention is to provide a heating soldering iron with high durability.

In order to achieve the above object, the first ceramic heater of the present invention is characterized in that: it has: a ceramic body with a built-in conductor and a metal cladding layer connected to the conductor; layer-bonded lead parts, and the coating height of the brazing material covering the covered area of the lead parts is set such that the proximity end on the lead parts closest to the metal coating layer and the distance from the The distance between the farthest upper ends of the metal cladding layer is within the range of 40% to 99% of the lead wire height.

In addition, the second ceramic heater of the present invention is characterized by comprising: a ceramic body having a built-in conductor and a metal coating layer electrically connected to the conductor; and a lead wire bonded to the metal coating layer via solder In addition, the brazing filler metal contains two or more kinds of metals, and the two or more kinds of metals are respectively present in the brazing filler metal in an identifiable state.

In addition, in the present invention, "recognizable" means that two or more kinds of metals are mixed in such a manner that they do not form a solid solution. Metal statue. The magnification at the time of observation is, for example, 50 times or more.

Furthermore, the heating soldering iron of the present invention is characterized in that the first or second ceramic heater of the present invention is used as the heat generating means.

In the first ceramic heater of the present invention constituted as described above, since the range of the solder coating area on the lead member is defined at the joint portion, the joint area between the lead wire and the solder can be ensured, and the stress generated by thermal cycles can be reduced.

Therefore, according to the first ceramic heater of the present invention, it is possible to form a high-reliability junction excellent in durability, and it is possible to provide a highly durable ceramic heater.

Furthermore, in the second ceramic heater of the present invention, since two or more metals are contained as the brazing material, the two or more metals are respectively present in a recognizable state, and one of the two or more metals is A first metal having a Young's modulus of 180 GPa or less, and the first metal is located in at least one of a boundary between the solder and the lead member and a boundary between the solder and the metal cladding layer of the border. Since the components on the lower resistance side of the two or more metals constituting the solder are involved in the conduction of electricity, the resistance value can be reduced. Accordingly, the calorific value of the solder can be reduced, the reliability of the bonding of the solder to the metal coating layer and the lead member can be improved, and a highly durable ceramic heater can be provided.

Description of drawings

FIG. 1(A) is a perspective view of a ceramic heater according to Embodiment 1 of the present invention.

FIG. 1(B) is a cross-sectional view of a ceramic heater according to Embodiment 1. FIG.

FIG. 2 is a cross-sectional view showing a joint portion of the lead member 10 of the ceramic heater according to the first embodiment.

3(A) is a perspective view of a first step in the manufacturing steps of the ceramic heater according to Embodiment 1. FIG.

3(B) is a perspective view of a second step in the manufacturing steps of the ceramic heater according to the first embodiment.

3(C) is a perspective view of a third step in the manufacturing steps of the ceramic heater according to the first embodiment.

3(D) is a perspective view of a fourth step in the manufacturing steps of the ceramic heater according to the first embodiment.

FIG. 4 is a perspective view of ceramic heater 100 according to Embodiment 2 of the present invention.

FIG. 5 is a schematic cross-sectional view of a soldered portion of the ceramic heater 100 shown in FIG. 4 .

6 is a cross-sectional photograph showing an example of a cross section of a soldered portion of ceramic heater 100 according to Embodiment 2. FIG.

FIG. 7 is an enlarged photograph of the area E shown in FIG. 6 .

FIG. 8 is an enlarged photograph of a region D shown in FIG. 6 .

FIG. 9 is an enlarged photograph of area C shown in FIG. 6 .

10 is a perspective view of a heating soldering iron according to Embodiment 1 of the present invention.

Fig. 11 is a perspective view of a conventional ceramic heater.

Fig. 12 is a cross-sectional photograph of a soldered portion of a conventional ceramic heater.

In the figure: 1, 100-ceramic heater, 2-ceramic core material, 3-ceramic sheet, 4-conductor, 5-lead lead-out part, 6-terminal extraction electrode, 6a-metal coating, 6b -plating layer, 7-via hole, 8-adhesive layer, 9-ceramic body, 10-lead parts, 11-solder, 12-electrode extraction part, 13-void, 14-lead Component composition to the diffusion layer of the solder, 16-proximal end, 17-distal end, 18-coating height of the covered area, 22-ceramic core material, 23-ceramic greensheet, 24-conductor , 25-lead lead-out part, 26-metal coating layer, 27-through hole for via hole, 28-electrode extraction part.

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1

1A is a perspective view schematically showing a ceramic heater according to Embodiment 1 of the present invention, FIG. 1B is a sectional view taken along line A-A in FIG. 1A , and FIG. 2 is a sectional view showing a detailed structure of a junction.

The ceramic heater 1 according to Embodiment 1, as shown in FIGS. 1A and 1B , is composed of a cylindrical ceramic core material 2 and a ceramic sheet 3 wound on the ceramic core material 2 through an adhesive layer 8 . Between the core material 2 and the ceramic sheet 3 , the conductor 4 , the lead-out portion 5 and the electrode extraction portion 12 are embedded. Then, the electrode extraction portion 12 is connected to the metal coating layer 6 a provided on the outer side of the ceramic sheet 3 . In addition, a plating layer 6b made of Ni is formed on the surface of the metal coating layer 6a, and the terminal extraction electrode 6 is constituted by the metal coating layer 6a and the plating layer 6b, and the terminal extraction electrode 6 and the lead member 10 are bonded and fixed by solder 11. . In addition, the electrode extraction portion 12 and the metal coating layer 6a are connected through the via hole 7 provided under the metal coating layer 6a of the ceramic sheet 3 as shown in FIG. 1B . In the ceramic heater 1 configured in this way, when electricity is supplied to the metal coating layer 6 a through the lead member 10 , the conductor 4 generates heat, thereby functioning as a heater.

In addition, in the ceramic heater according to Embodiment 1, it is characterized in that the coating height 18 of the coating area, which is the area where the lead member 10 is covered with the solder 11 , is set at the position closest to the terminal mounting electrode 6 of the lead member 10 . 40 to 99% of the distance between the proximal end and the upper end of the lead member 10 farthest from the terminal mounting electrode 6 .

That is, at the joint portion of the terminal mounting electrode 6 and the lead member 10, if the covering height 18 on the cross section of the lead member 10 is lower than the upper end 17 from the proximal end 16 closest to the terminal mounting electrode 6 to the upper end 17 far away from the terminal mounting electrode 6 (hereinafter, this distance is referred to as the lead height in this specification), the initial wire bonding strength is low and the unevenness is large due to the small area of the bonding interface between the lead member 10 and the solder 11. . Therefore, as in Embodiment 1, when the covering height of the solder 11 is 40% to 99% of the lead height, the initial wire bonding strength can be improved and unevenness can be reduced.

In addition, as shown in FIG. 2 , when the lead member 10 is a wire having a circular cross section, the lead wire height becomes the diameter of the circular cross section of the lead member 10 .

In addition, the brazing material 11 covers the coating height 18 of the lead part 10. If it exceeds 99% of the height, in the area covered by the brazing material, in the case of a thermal cycle, the interface between the lead part 10 and the brazing material 11 Cracks are prone to occur, reducing the wire bonding strength.

That is, if the lead member 10 is covered with brazing material to the extent that the covering height 18 exceeds 99% of the lead height, then due to the linear thermal expansion difference between the lead member 10 and the brazing material 11, the interface between the lead member and the brazing material will Stress is generated, and since there is no place for stress release, cracks occur at the interface. In addition, when the values of the linear thermal expansion of the lead member 10 and the solder 11 are compared, the result is that the lead member 10<the solder 11 . Specifically, when the lead member was covered with brazing material in the entire circumferential direction and a thermal cycle test was performed, cracks occurred at the interface between the lead member and the soldering material.

In this regard, if the covering height 18 with respect to the height of the lead wire is set in the range of 40% to 99%, since the solder 11 does not cover a part of the lead member 10, it is possible to alleviate the heat cycle test. Due to the stress generated by the thermal expansion of the lead member 10 and the solder 11, cracks did not occur at the interface between the lead member and the solder 11 in the heat cycle test.

In the present ceramic heater, in order to more effectively prevent cracks at the interface between the lead member and the solder in the heat cycle test, it is preferable to set the coating height 18 within a range of 60% to 99% of the lead height.

The range of the coating height 18 with respect to the height of the lead can be controlled according to the wettability of the lead member 10 and the solder, more specifically, the material and surface roughness of the lead member 10, the material of the solder, and the bonding time. The temperature and protective atmosphere are controlled. In Embodiment 1, it is more preferable to control by the surface roughness of the lead member 10 , and by controlling in this way, the covering height can be relatively easily and reliably set within a predetermined range.

In addition, in the first embodiment, it is preferable that the void 13 exists at the interface between the lead member 10 and the solder. When there are no voids at the interface between the lead member 10 and the solder, when the ceramic heater 1 generates heat, the heat conduction from the ceramic body 9 to the lead member 10 is good, and the surface temperature of the lead member increases, but there are voids at the interface. In the case of holes 13, heat conduction from ceramic body 9 to lead member 10 is inhibited, and the surface temperature of the lead member is lower than when there are no holes. Therefore, if the void 13 exists at the interface between the lead member 10 and the solder, the thermal stress at the junction is reduced, and the deterioration of the wire bonding strength after the heat cycle test can be reduced.

After confirming the size of the void 13 and the initial wire bonding strength, it was found that when the void 13 was 0.1 to 200 μm, the initial wire bonding strength and the wire bonding strength after the thermal cycle test were high and there was almost no difference, but when the void 13 was larger than 200 μm In this case, the wire bonding strength at the initial stage and after the thermal cycle test is low, and when the void 13 is less than 0.1 μm, the surface temperature of the lead member 11 is high, so although the initial wire bonding strength is high, but after the thermal cycle test The wire bond strength is reduced.

In addition, in the case where voids 13 occur in a range greater than 40% of the interface, the initial wire bonding strength is reduced. Therefore, in order to reduce the surface temperature of the lead member and improve the initial wire bonding strength and after the thermal cycle test, Pores 13 of 0.1 to 200 μm are preferably present in the range of 20% to 40% of the interface.

In addition, in the first embodiment, when there is no diffusion layer 14 in which the components of the lead member 10 diffuse into the solder 11, the wire bonding strength at the initial stage and after the thermal cycle test is low, and the presence of the diffusion layer 14 at the interface In this case, the initial wire bonding strength is improved. This is considered to be because a part of the interface changes from physical bonding to chemical bonding due to the diffusion of the components of the lead member 10 into the solder 11, thereby improving the wire bonding strength.

Therefore, in the present invention, it is preferable that the components of the lead member 10 diffuse into the solder 11 .

In order to effectively improve the wire bonding strength, the distance (thickness) of the diffusion layer 14 on the interface is preferably 0.1 to 30 μm, more preferably 3 to 30 μm. When the diffusion layer 14 is less than 0.1 μm, the effect of improving the wire bonding strength is small, and when the diffusion layer is larger than 30 μm, since the components of the lead member 10 diffuse to the solder 11 in a large amount, there is no effect of improving the solder 11. If the hardness is low, after the thermal cycle test, cracks are likely to occur in the solder 11, which may reduce the wire bonding strength.

In addition, in order to stably form the diffusion layer 14, obtain an effective anchor effect, and improve the wire bonding strength, it is preferable that the arithmetic average surface roughness Ra on the surface of the lead member 10 is in the range of 0.05 to 5 μm. If the arithmetic average surface roughness Ra on the surface of the lead member 10 is less than 0.05 μm, the diffusion layer 14 may only be formed in a thickness of 0.05 μm, and the effect of improving the wire bonding strength after the thermal cycle test is small. If the arithmetic average surface roughness Ra If it is larger than 5 μm, there is a possibility that cracks may propagate from the surface due to thermal cycles when measuring the bonding strength of a thick wire due to thermal cycles, which may cause disconnection.

Next, a method of manufacturing ceramic heater 1 according to Embodiment 1 will be described.

When manufacturing the ceramic heater 1, a method including the steps shown in FIGS. 3A to 3D is employed.

First, after the ceramic green sheet 23 is produced, the through-hole 27 for a via hole is formed in the ceramic green sheet 23 (see FIG. 3A ).

Next, after filling the through hole 27 with a conductive paste, a conductive paste layer to be the conductor 24 and the lead-out portion 25 is formed and then dried (see FIG. 3B ).

Then, the ceramic green sheet 23 is reversed, and a conductive paste layer to be the metal coating layer 26 is formed on the back surface (see FIG. 3C ).

Next, the ceramic green sheet 23 is rolled and pasted on the ceramic core material 22 by reversing it once more to produce a green body made of raw materials before sintering (see FIG. 3D ).

The ceramic body 9 is obtained by firing the formed body thus formed in a reducing protective atmosphere at 1500-1650° C., and then, as shown in FIG. , the lead member 10 is fixed by the brazing material 11, and the ceramic heater 1 is obtained.

Alumina, silicon nitride, aluminum nitride, silicon carbide, mullite, etc. can be used for the material of the ceramic heater 1 .

For example, as alumina (Alumina), Al ₂ O ₃ : 88 to 95% by weight, SiO ₂ : 2 to 7% by weight, CaO: 0.5 to 3% by weight, MgO: 0.5 to 3% by weight, ZrO ₂ : Alumina composed of 0 to 3% by weight. If the Al ₂ O ₃ content is smaller than this value, the glassiness increases and the migration at the time of energization increases, so it is not preferable to use it. Conversely, if the Al ₂ O ₃ content is larger than this value, the amount of glass diffused into the metal layer of the built-in heating resistor 4 decreases, and the durability of the ceramic heater 1 deteriorates, so it is not preferable.

As silicon nitride, it may contain Si ₃ N ₄ : 85 to 95% by weight, rare earth element oxides such as Y ₂ O ₃ or Yb ₂ O ₃ , Er ₂ O ₃ : 2 to 12% by weight, Al ₂ O ₃ : 0.3 to 2.0% by weight, and oxygen in terms of SiO ₂ : 0.5 to 3% by weight. As aluminum nitride, the following composition can be used: containing AlN: 85 to 97% by weight, _rare earth element oxides such _{as Y2O3} or _Yb2O3 , _Er2O3 : 2 to 8% by weight _, CaO: 0 to 5% % by weight, wherein oxygen as an impurity in terms of Al ₂ O ₃ : 0.5 to 3% by weight. As mullite, it is possible to use: Al ₂ O ₃ : 58 to 75% by weight, SiO ₂ : 25 to 42% by weight, and 1% by weight or less of unavoidable impurities.

In addition, the shape of the ceramic heater 1 may be a plate shape other than a cylinder and a column shape.

The ceramic heater of the present invention is not limited thereto, and various changes can be made without departing from the gist of the present invention.

Embodiment 2

Next, the ceramic heater 100 according to Embodiment 2 of the present invention will be described with reference to the drawings.

The ceramic heater 100 according to the second embodiment shown in FIGS. 4 and 5 has the same structure as that of the first embodiment, that is, the conductor 4 is provided inside the ceramic base 9 , and the conductor 4 extending to the surface of the ceramic base 9 is configured as follows. A metal coating 6a connected to the electrode extraction part 12 is formed on the electrode extraction part 12, and the lead member 10 is soldered with the solder 11 to the terminal mounting electrode 6 constituted by the metal coating 6a. In addition, if necessary, a plating layer (not shown) is formed on the metal coating layer 6a, and the terminal mounting electrode 6 is constituted by the metal coating layer 6a and the plating layer.

In addition, the ceramic substrate 9 can be obtained, for example, by fabricating a green sheet (the portion that becomes the sheet 3 after firing) by a doctor blade method, and fabricating a molded body that becomes the ceramic core material 2 by an extrusion molding method. , and integrate them to obtain. As the material of the ceramic substrate 9 , oxide ceramics such as alumina, mullite, and forsterite, or non-oxide ceramics such as silicon nitride and aluminum nitride can be used, among which oxide ceramics are preferably used. For example, in the case of using alumina ceramics as the material of the ceramic substrate 9, Al ₂ O ₃ : 88 to 95% by weight, SiO ₂ : 2 to 7% by weight, CaO: 0.5 to 3% by weight, MgO : 0.5 to 3% by weight, ZrO ₂ : 1 to 3% by weight. In addition, not limited to alumina ceramics, silicon nitride ceramics, aluminum nitride ceramics, silicon carbide ceramics, etc. may be used.

At this time, the conductor 4 is printed on the green sheet by the screen printing method, and the electrode extraction portion 12 is formed in the via hole previously formed at a predetermined position on the green sheet by punching or the like. The material of the conductor 4 and the electrode extraction portion 12 is mainly composed of W, Mo, and Re alone, and their alloys, metal silicides, and metal carbides such as TiN, WC, etc. are added. For the conductor 4 and the electrode extraction part 12, it is preferable to adjust these materials so that the resistance of the conductor 4 is increased and the resistance of the electrode extraction part 12 is lowered, and screen-printed respectively.

Here, in order to eliminate the error (level difference) between the green sheet and the conductor 4, and to make the green sheet closely adhere to the cylindrical molded body, it is preferable to coat the conductor 4 with Al ₂ by screen printing or the like. O ₃ is the main component, add SiO ₂ , MgO, etc. to the mixture, add a binder, and use an organic solvent to prepare a paste-like slurry.

Then, by firing the integrated molded body in a reducing atmosphere at 1500°C to 1650°C, a desired sintered body can be obtained.

On the electrode extraction portion 12 of the obtained sintered body, a slurry containing W as a main component was applied, followed by sintering in a vacuum to form the metal coating layer 6a. As for the material of the metal coating layer 6a, it is preferable to contain, as a conductive component, a component composed of a refractory metal such as W, Mo, Re, and alloys thereof. The thickness of the metal coating layer 6 a is preferably set at 10 μm or more. If the thickness is less than 10 μm, the bonding strength between the electrode extraction portion 4 and the ceramic base 9 is low, and the durability against the tensile strength of the lead member 10 during thermal cycles during use is reduced, so it is not preferable. More preferably, the thickness is 15 μm or more, most preferably 20 μm or more. The reason why the thickness of the metal coating layer 6a affects the tensile strength of the lead member 10 is because the metal coating layer 6a is a porous sintered body of a refractory metal composed of W, Mo, Re, etc. The pores diffuse the glass components on the grain boundaries, and the strength is increased by this fixation effect. Therefore, the more the thickness of the metal coating layer 6 a is increased, the more the tensile strength of the bonded lead member 10 is increased.

In addition, after the metal coating layer 6a is formed, plating may be performed on the metal coating layer 6a, and the plating preferably contains Ni as a main component.

Then, the lead member 10 is mounted on the metal coating layer 6a by vacuum brazing.

As the material of the lead member 10 , Ni-based or Fe—Ni-based alloys with good heat resistance are preferably used. This is because there is a possibility that the temperature of the lead member 10 rises during use due to heat conduction from the conductor 4 , causing deterioration. Among them, when a Ni-based or Fe—Ni-based alloy is used as the material of the lead member 10 , it is preferable to set the average crystal grain size to 400 μm or less. If the average particle size exceeds 400 μm, it is not preferable to use the lead member near the soldered portion due to fatigue and cracks due to vibration and heat cycles during use. Regarding other materials, for example, if the grain size of the lead member 10 is larger than the thickness of the lead member 10, stress will concentrate in the crystal grains near the boundary between the solder 11 and the lead member 10 and cracks will occur, so it is not preferable to use it. In order to make the average particle diameter of the lead member 10 smaller than 400 μm, it is only necessary to lower the temperature during brazing as much as possible and shorten the processing time.

Also, the present invention is characterized by the structure in the solder 11 . That is, as shown in FIGS. 6 to 9 , the solder contains two or more kinds of metals, preferably two kinds of metals, and the metals form a mottled structure or a dotted structure. Here, in this specification, "presence in a patchy form" and "presence in a dot form" mean that these two or more kinds of metals exist respectively in a state recognizable by using a microscope or the like, for example. In addition, FIG. 6 shows a cross section by using an example of a rectangular lead member 10a. In addition, it is preferable that the metal which becomes a speckle or exists in a dot shape is selected from at least Group 10 (Ni, Pd, Pt, etc.) or Group 11 (Cu, Ag, Au, etc.) elements as a main component. 2 kinds. This is because the diffusion coefficients of the elements of the 10th and 11th groups are relatively small, which can suppress the diffusion of metals and make it difficult to form a uniform phase, and also have excellent electrical conductivity due to their low intrinsic resistance.

Examples of such brazing material 11 include Ag—Cu brazing material, Au—Cu brazing material, and the like, among which Ag—Cu brazing material is more preferably used.

In this way, after the lead member 10 is soldered to the metal coating layer 6a, since two or more metals (for example, Ag and Cu) exist in spots or dots inside the solder 11, it is necessary to adjust the solder 11. hold time during brazing. For example, when BAg-8 (JIS Z3261) in Ag-Cu brazing material is used, since the melting temperature (melting point) of BAg-8 is about 780°C, it is preferable to keep the soldering temperature from 780°C to 800°C. The time is set at 5 to 40 minutes, and by setting it within this range, Ag and Cu can be made to exist in spots or dots inside the solder 11 .

The brazing material 11 composed of Ag and Cu causes interdiffusion if kept at the brazing temperature for 60 minutes or more, and Ag and Cu tend to form a homogeneously melted alloy. If it is melted uniformly, the electrical resistance inside the solder increases compared to the spot structure where electricity is selectively energized along the lower resistance Ag, and the bonding strength after durability is problematic due to heat generation inside the solder. Therefore, in order to form Ag and Cu plaques in the solder, it is preferable to set the holding time at the brazing temperature to less than 60 minutes. In addition, the retention time at the brazing temperature is at least 5 minutes in order to sufficiently melt the brazing material.

In the past, since the holding time was not adjusted, and the above range was exceeded, it melted uniformly. Fig. 12 is a cross-sectional photograph showing a soldered portion formed by a brazing material 111 in the ceramic heater shown in Fig. 11 . As the brazing material 111 , an Ag—Cu-based or Au—Cu-based brazing material composed of two or more metals is used. As shown in FIG. 12 , the cross section of the solder portion after brazing shows no segregation of the constituent metal composition and exists as a uniform metal. In addition, in the present invention, by adjusting the holding time within the above-mentioned range, the brazing temperature can be lowered below the above-mentioned brazing temperature before uniform melting, so that a patchy structure can be obtained.

In addition, in order to form the spot structure of Ag and Cu in the brazing material, in addition to setting the holding time at the brazing temperature at less than 60 minutes, it is also preferable to set the Ag content at 60 to 90% by weight, and more preferably set the Ag content to 60% by weight. The content is specified at 70 to 75% by weight. As a result, the melting temperature of the Ag-Cu solder is close to the eutectic point (the temperature at which Ag and Cu are fused, and neither side exists as a solid), and since the temperature at which Ag and Cu become liquid phases is lowered, it is possible to reduce the risk of soldering. temperature, also reduces the residual stress after brazing.

In this way, by forming the patch structure inside the solder 11, when the electric power is supplied from the lead member 10 to the ceramic heater 100, since the electricity is selectively energized on the Ag side with a lower resistance value, the resistance value of the solder 11 is lowered, The increase in temperature of the solder 11 is suppressed, and the reliability of the joint is improved.

In addition, the enlarged photo of the area E (near the interface between the brazing material and the metal coating layer) in Figure 6 is Figure 7, and the area D in Figure 6 (the brazing material and the metal coating layer and the brazing material and the lead wire Near the interface of the component) is the enlarged photo shown in Figure 8, and the enlarged photo of the area C (near the interface of the solder and the lead part) in Figure 6 is shown in Figure 9, and the solder 11 and the metal cladding layer 6a At least any one of the interface of the interface, the solder 11 and the lead member 10 is adjacent to each other. It is preferable to form a metal layer that is not patchy and has a Young's modulus of 180 GPa or less. For example, in the solder 11 made of Ag and Cu On it, it is preferable to form a Cu layer 6c. The Cu layer 6c adjacent to the interface between the brazing material 11 and the metal coating layer 6a functions as a stress relaxation layer for the residual stress after brazing, thereby reducing the residual stress in this part and improving the performance of the soldered lead parts. 7 joint strength.

In order to form the Cu layer 6c, it is effective to perform Cu plating on the portions where the metal coating layer 6a and the lead member 10 are in contact with the solder 11 by brazing. Among Ag and Cu, since the surface tension on the Cu side is small, Cu tends to selectively wet the portion where the solder 11 melts and contacts during brazing. Utilizing this phenomenon, it is possible to form the Cu layer 6 c at the portion adjacent to the interface between the metal coating layer 6 a and the lead member which is in contact with the solder.

Furthermore, the Cu layer 6c has irregularities on the side opposite to the interface with the metal coating layer 6a, and the thickness of the irregularities is preferably 10 μm or less, and the thickness of the entire Cu layer 6c including the protrusions is preferably 20 μm or less. Since the Cu layer 6c forms irregularities at the interface of the dissimilar materials in contact with it, the irregularities function as a stress buffer layer, so that the bonding strength after durability is improved.

Here, the concavo-convex surface of the Cu layer 6c is described as a preferable example, but the present invention is not limited to Cu, even if there are protrusions having a height of 10 μm or less on the interface and the thickness of the entire layer including the protrusions is 20 μm Also in the case of the following metal layers other than Cu, the adhesive strength at the interface can be improved, and the reliability and durability can be improved.

However, when the thickness of the protrusions of the Cu layer is 10 μm or more, including the protrusions, the thickness is 20 μm or more, since the adhesive strength of the solder is lowered, it is not preferable to use it. In this case, the holding time at the melting temperature of the solder is preferably set at 5 to 20 minutes.

The metal cladding layer 6a is sintered on the ceramic base 9 in vacuum, but in order to reduce the residual stress formed by the thermal expansion difference with the ceramic base 9, it is preferable to use a conductive material with a small thermal expansion coefficient. The main component of the metal coating layer 6a is more preferably not more than 5.5×10 ^-6 /°C in terms of thermal expansion coefficient. Specifically, it is preferable to use W or Mo having the above-mentioned physical properties as the main component. Thereby, the residual stress at the time of sintering the metal coating layer 6 a generated at the interface between the ceramic base body 9 and the metal coating layer 6 a can be relaxed. That is, by diffusing such a metal in the brazing filler metal, the thermal expansion coefficient of the brazing filler metal is reduced, and the residual stress after brazing that occurs on the interface with the metal coating layer is also reduced, and the electrode extraction part and the brazing filler metal can be improved. The reliability and durability of ceramic heaters can be further improved by improving the bonding reliability of lead parts.

However, since the difference in thermal expansion coefficient is extremely large between the cladding layer 6 a and the brazing material 11 , a large residual stress occurs after brazing. Therefore, it is necessary to reduce the thermal expansion coefficient of the solder. In order to lower the thermal expansion coefficient of the solder, it is sufficient that the main component of the metal coating layer 6a having a small thermal expansion coefficient diffuses into the solder. This can be done by heat treatment after brazing. This heat treatment is preferably performed in a reducing protective atmosphere containing hydrogen or the like, at a temperature below the melting temperature of the solder, more preferably at 700°C to 750°C. Through this heat treatment, the metal or alloy having a thermal expansion coefficient of 5.5×10 ^-6 /°C or less diffuses into the brazing filler metal, thereby lowering the thermal expansion coefficient of the brazing filler metal and improving the strength of the soldered portion after durability.

In addition, it is preferable to form a plated layer made of Ni on the surface of the brazing filler metal 11 for improving the high-temperature durability of the brazing filler metal 11 and preventing corrosion. In order for the Ni plating to function as a protective layer, the grain size of the crystals constituting the plating can be set to 10 μm or less, so that a dense, high-density plating can exist on the surface of the soldered portion. If the particle diameter is set to be 5 μm or less, the plating layer on the surface becomes more dense, and Ni can be diffused into the brazing material 11 at the same time. Since the Young's modulus of Ni is greater than 250Mpa, that is, it is very hard, so the Ni diffused to the inside of the brazing material 11 increases the hardness of the inside of the brazing material 11, and because the internal strength of the brazing material 11 is improved, it can be improved. The initial bonding strength of the electrode extraction part, the solder, and the lead parts, and the bonding strength after durability. Thereby, the reliability and durability of a ceramic heater can be improved.

In addition, as the plating layer, boron-based electroless Ni plating is preferably used. The type of electroless plating can also be coated with phosphorus-based electroless plating in addition to boron-based electroless plating, but when there is a possibility of use in a high-temperature environment, boron-based electroless Ni plating is generally performed.

In addition, FIG. 10 is a perspective view of an example of a heating soldering iron using the ceramic heater 1 or the ceramic heater 100 of the present invention. In this heating iron, hair is inserted between the arms 32 at the front end, and by holding the handle 31, the hair is heated while applying pressure to process the hair. Inside the arm 32, the ceramic heater 1 or the ceramic heater 100 is inserted, and a metal plate 33 such as aluminum, a metal plate coated on the surface, a ceramic plate, etc. are provided on the portion directly in contact with the hair. In addition, a cover made of heat-resistant plastic for preventing burns is attached to the outside of the arm 32 .

Example 1

The ceramic heater of the present invention was produced by the method shown below.

First, a raw material containing alumina as a main component and 6% by weight of SiO ₂ , 2% by weight of MgO, 2% by weight of CaO, and 1.5% by weight of ZrO ₂ as sintering aids was prepared. Using the prepared raw material, a ceramic core material 2 with an outer diameter of 15 mm and a ceramic green sheet 23 with a thickness of 800 μm were prepared by extrusion molding and tape casting.

Next, a conductor 24 made of tungsten (W), a lead lead-out portion 25 , and an electrode lead-out portion 28 are printed on one main surface of the ceramic green sheet 23 . Then, the metal coating layer 26 is printed on the back surface of the end portion of the electrode extraction portion 28 , and then through holes for via holes are formed on the metal coating layer 26 . Then, via holes 7 are formed by embedding a paste made of tungsten (W) in the through holes, and the electrode extraction portion 28 and the metal coating layer 26 are connected.

The prepared raw ceramic body 9 was fired at 1600°C in a reducing protective atmosphere to sinter, and a plated layer 6b with a thickness of 5 μm was formed on the surface of the metal coating layer 6a by electroless plating made of Ni.

On the terminal mounting electrode 6 of the sample obtained as above, the lead member 10 was soldered, but in this embodiment 1, the amount of the brazing material 11 composed of Ag brazing material was changed, and the bonding of the lead member 10 was performed. Samples for evaluation were prepared in which the coating height 18 of the solder on the surface of the lead member 10 was varied within the range of 20 to 100% of the lead height. Then, for these evaluation samples, the initial wire bonding strength, the wire bonding strength after 3000 thermal cycle tests (25° C.·3 minutes to 400° C.·3 minutes), and the crack occurrence rate at the interface were respectively confirmed.

The wire bonding strength was measured by pulling the lead member 10 in a direction perpendicular to the terminal extraction electrode 6 .

Table 1 shows the coating region 18 on the surface of the lead member 10, the initial wire bonding strength, and the results of determination of the wire bonding strength after the heat cycle test (3000 times).

Table 1

Nos. 1 and 6 are samples outside the scope of the present invention. In addition, the data after the heat cycle test in the table are the data after repeating the heat cycle test for 3000 cycles. In addition, the value of "covering height with respect to lead wire height" in Table 1 is the value which measured the part with the highest cover height with respect to lead wire height in the longitudinal direction of a lead member.

The initial wire bonding strength of 85N or more and the wire bonding strength after the thermal cycle test of 35 to 50N were judged as △, the samples of 50 to 60N were judged as ○, and the samples of 60N or more were judged as ◎.

As can be seen from Table 1, the coverage area 18 on the surface of the lead parts 10 of Nos. 2 to 5 within the scope of Example 1 of the present invention is 40 to 99% of the sample, and the wire bonding strength of the initial stage and after the heat cycle test is different. A high average gives good results. Among them, Nos. 3 to 5 were samples in which the coating region 18 on the surface of the lead member 10 was 60 to 99%, and very good results were obtained.

However, No. 1 of the comparative example in which the coated area 18 on the surface of the lead member 10 was 20% had low wire bonding strength at the initial stage and after the thermal cycle test, and No. 6 had a coated area 18 on the surface of the lead member 10 of 100%. % of the samples, the initial wire bonding strength was high, but the wire bonding strength after the heat cycle test was lowered.

In the samples of Nos. 2 to 5 in Example 1 of the present invention, the coating area 18 on the surface of the lead member 10 was 40 to 99%, and since there was no crack at the interface, the decrease in the wire bonding strength was considered to be small.

However, in the sample of No. 6 as a comparative example in which the covered region 18 is 100%, cracks are generated at the interface, so the wire bonding strength is considered to be lowered.

The occurrence of cracks at the interface is considered to be caused by the difference in thermal expansion coefficient between the lead member 10 and the solder 11 . Therefore, it is considered that in the test in which the coverage area 18 is 100%, it is difficult to relax the stress caused by the difference in thermal expansion coefficient, and cracks are likely to occur at the interface.

In addition, the size of voids 13 generated at the interface, the occupancy rate of voids at the interface, the wire bonding strength at the initial stage and after the heat cycle test, and the surface temperature of the lead member when the ceramic heater generates heat at 800°C were confirmed. relation. Judgment results are shown in Table 2. The initial wire bonding strength of 85N or more and the wire bonding strength after the thermal cycle test were 35 to 50N were judged as △, the samples of 50 to 60N were judged as ○, and the samples of 60N or more were judged as △ The sample was judged as ◎.

Table 2

All of the above are samples covered by 60% of the height.

The size of the voids 13 generated at the interfaces of Nos. 13 to 15 and Nos. 17 to 19 in Example 1 of the present invention is 0.1 to 200 μm, and the occupancy rate of the voids 13 at the interface is in the range of 20 to 40%. After the thermal cycle test The wire bonding strength reached over 60N, very good results were obtained.

In addition, the size of the pores 13 generated at the interfaces of Nos. 9 to 11 was 0.1 to 200 μm, and the occupancy rate of the pores 13 at the interfaces was in the range of 0.1 to 20%, and the wire bonding strength after the thermal cycle test was 50 to 60 N. good result. This is considered to be because the voids 13 located at the interface inhibit heat conduction from the ceramic body 9 and the surface temperature of the lead member decreases.

However, No. 7 is considered to be due to the high surface temperature of the lead parts, so the wire bonding strength after the thermal cycle test is reduced; No. 20 to No. 23 are considered to be due to the occupancy rate of voids 13 in the interface exceeding 50%, so although the surface temperature of the lead parts reached - 20° C. or lower, but the bonding strength decreased; No. 12 and No. 16 are considered to be due to the fact that the size of the void 13 was larger than 250 μm, so the wire bonding strength decreased.

In addition, by changing the temperature and time of bonding, a sample was produced to change the distance from the interface to the diffusion layer 14, and the wire bonding strength at the initial stage and after the thermal cycle test was measured. The results are shown in Table 3. The initial wire bonding strength was 85N. In addition, the wire bonding strength after the heat cycle test was judged as △ for the sample of 35 to 50N, ○ for the sample of 50 to 60N, and ◎ for the sample of 60N or more.

table 3

In Example 1 of the present invention, the distance from the interface of Nos. 26 to 29 to the diffusion layer 14 was in the range of 3 to 30 μm, and the wire bonding strength after the heat cycle test was as high as 60 N or more, which was very good. In addition, the distance from the interface of No. 25 to the diffusion layer 14 was 0.1 μm, and the wire bonding strength after the thermal cycle test was 50 to 60 N, and good results were obtained. This is considered to be because the components of the lead member diffused into the solder and the interface changed from physical bonding to chemical bonding, so that the wire bonding strength improved.

However, No. 24, which has no diffusion layer at all, has low wire bonding strength at the initial stage and after the thermal cycle test; No. 30, which has a 45 μm thick diffusion layer 14, diffuses a large amount of components of the lead parts into the solder 11, so the solder 11 The hardness of the solder 11 increases, and after the thermal cycle test, cracks occur in the solder 11, and the wire bonding strength decreases.

In addition, the arithmetic average surface roughness Ra of the lead member 10 used for bonding and the wire bonding strength at the initial stage and after the heat cycle test were measured. A sample with a wire bonding strength of 35 to 50N was judged as △, a sample with 50 to 60N was judged as ◯, and a sample with 60N or more was judged as ◎.

Table 4

The so-called after thermal cycle refers to the data after 3000 thermal cycle tests.

The arithmetic average surface roughness Ra of lead members 10 Nos. 32 to 37 in Example 1 of the present invention was in the range of 0.05 to 5 μm, and the wire bonding strength after the heat cycle test was as high as 60 N or more, which was very good. From the evaluation results, as the arithmetic mean surface roughness Ra of the lead member 10 increases, the diffusion layer 14 tends to form easily from the interface, and as the arithmetic mean surface roughness Ra of the lead member 10 increases, the thermal cycle The wire bonding strength after the test tended to increase due to the anchoring effect.

However, No. 31 is considered to be because the distance from the interface to the diffusion layer 14 is small, and the arithmetic mean surface roughness Ra of the lead member 10 is small, so that a sufficient fixing effect cannot be obtained, so the wire bonding strength after the thermal cycle test is low, and No. 38 is considered to be , the distance from the interface to the diffusion layer is 9 μm, which has sufficient wire bonding strength, but since the arithmetic mean surface roughness Ra of the lead part 10 is 7 μm, a crack propagates from the surface of the lead part 10 through the thermal cycle test, so it is used 36N is destroyed by cutting the lead wire.

Example 2

With Al ₂ O ₃ as the main component, SiO ₂ , CaO, MgO, and ZrO ₂ were adjusted so that the total amount was within 10% by weight, and a green sheet was produced by the doctor blade method, and printed on the surface of the green sheet by W constitutes a paste to form the conductor 4 and the electrode extraction portion 12 .

In addition, a cylindrical molded body was made by extrusion molding, and a ceramic sheet printed with a conductor 4 was tightly wound on the cylindrical molded body, fired in a reducing protective gas at 1600°C, and 20 pieces of ceramics were prepared for heating. device 100.

Then, electroless Ni plating with a thickness of 5 μm was applied to the surface of the electrode extraction portion 12 , and a slurry containing W as a main component was applied to the electrode extraction portion 12 and fired in a vacuum furnace.

Then, a Ni wire of Φ1.0 mm as a lead member was brazed using Ag—Cu brazing material.

At this time, the brazing conditions were defined as brazing temperatures: 780° C., 800° C., and 820° C., and holding times: 5 minutes, 10 minutes, 40 minutes, and 60 minutes, and brazing was performed.

Then, in order to confirm the durability during continuous use, the initial tensile strength and the tensile strength after continuous energization at 400° C. for 800 hours were measured. In the tensile test, the peel strength was measured by pulling the end of the lead member 4 in a direction perpendicular to the main surface of the ceramic heater 100 . In addition, two cross-sections of each lot were observed with an electron microscope to confirm the internal structure of the solder. Table 5 shows the results.

table 5

No. Brazing temperature (℃) Holding time (minutes) Initial tensile strength (N) Tensile strength after durability (N) Spots inside the brazing material The layer at the solder interface ^* 39 780 5 340 178 none Ag/Cu alloy 40 780 10 345 303 have Cu 41 780 40 342 311 have Cu ^* 42 780 60 339 188 none Ag/Cu alloy ^* 43 800 5 338 191 none Ag/Cu alloy 44 800 10 341 307 have Cu 45 800 40 345 305 have Cu ^* 46 800 60 337 183 none Ag/Cu alloy ^* 47 820 5 344 188 none Ag/Cu alloy 48 820 10 348 302 have Cu 49 820 40 339 307 have Cu ^* 50 820 60 343 173 none Ag/Cu alloy

Here, the layer at the solder interface refers to the layer on the interface between the metal coating layer and the solder, and the interface between the lead member and the solder.

In addition, the samples marked with ^* are samples outside the scope of the present invention.

As can be seen from Table 5, Nos. 39, 42, 43, 46, 47, and 50 in which the spot structure shown in Fig. 7 to Fig. 9 was not seen had a tensile strength after the fatigue test that dropped to 200N or less. In contrast, Nos. 40, 41, 44, 45, 48, and 49 of the patch structures shown in FIGS. 7 to 9 were found to have high tensile strengths of 300N or more.

Claims (7)

1. A ceramic heater, characterized in that: It has: a ceramic body, which has a built-in conductor and a metal coating layer that conducts with the conductor; a lead part, which is bonded to the metal coating layer by means of brazing material, The brazing material is composed of two or more metals, and the two or more metals are present in the brazing material in an identifiable state. Each metal image can be confirmed when the reflection electron phase of the partial cross-section, One of the two or more metals is a first metal having a Young's modulus of 180 GPa or less, and the first metal is located at a boundary between the solder and the lead member and between the solder and the lead member. at least one of the boundary portions of the metal coating layer. 2. The ceramic heater according to claim 1, further comprising: a portion of the first metal disposed at a portion where the metal covering layer and the lead member are in contact with the brazing material by brazing. plating. 3. The ceramic heater as claimed in claim 1, characterized in that: The two or more metals are selected from the group consisting of Group 10 metals and Group 11 metals in the periodic table. 4. The ceramic heater as claimed in claim 1, characterized in that: The first metal has a concavo-convex structure on the interface with the lead member or on the opposite side of the interface with the metal coating layer, wherein the height of the protrusions is 10 μm or less, and the thickness of the entire layer including the protrusions is Below 20μm. 5. The ceramic heater as claimed in claim 1, characterized in that: The metal coating layer is composed of a metal having a coefficient of thermal expansion of 5.5×10 ⁻⁶ /°C or less as a main component, and the metal diffuses into the solder. 6. The ceramic heater according to claim 1, wherein Ni is diffused into said brazing material. 7. A soldering iron for heating, characterized in that the ceramic heater according to any one of claims 1-6 is used as the heating mechanism.

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