JP3924378B2 - Ceramic heater - Google Patents

Description

【００５８】
【表２】

【００５９】
一方、他の評価用のセラミックヒータについて、電極金具の接合強度及び電極金具の接合部を含むセラミックヒータの抗折強度、及び冷熱サイクル試験後の抵抗変化率を測定すると共に、冷熱サイクル試験後のセラミックヒータを電極金具の接合部を含む部分で切断してその断面を観察した。
【００６０】
前記接合強度は、評価用のセラミックヒータを固定し、セラミック発熱体に接合した電極金具のＮｉリードピンをセラミック発熱体と垂直方向に引っ張り、接合部又はＮｉリードピンあるいは電極金具が破断した時の荷重（Ｎ）を計測して破断モードと共に評価した。
【００６１】
又、前記抗折強度は、評価用のセラミックヒータを把持して電極金具の接合部を加圧することにより、片持ち抗折試験を行い評価した。
【００６２】
更に、前記冷熱サイクル試験は、評価用のセラミックヒータを室温と５００℃の温度雰囲気にそれぞれ曝すのを１サイクルとして繰り返し、３０００サイクル後のセラミックヒータの抵抗値を測定し、該試験前の初期抵抗値に対する抵抗変化率を求めると共に、該試験後のセラミックヒータを電極金具を含む断面で切断してクラックの有無を観察した。
【００６３】
【表３】

【００６４】
表から明らかなように、本発明の請求範囲外である試料番号１、８、１１、１５では、いずれも電極金具の接合強度が７８．５Ｎ（８ｋｇｆ）以下であり、同じく試料番号１０、１４、１７、１８、２７、２８、３０では、電極金具の接合強度は７８．５Ｎ（８ｋｇｆ）を越えるものの、冷熱サイクル試験後の抵抗変化率が３．０以上と大であり、セラミック発熱体にクラックの発生が認められた。
【００６５】
それに対して、本発明では、いずれも電極金具の接合強度は７８．５Ｎ（８ｋｇｆ）を越え、しかも冷熱サイクル試験後の抵抗変化率は２．６以下と小さく、セラミック発熱体にクラックは認められず、電極金具の接合部周囲の応力集中が効果的に緩和されていることが分かる。
【００６６】
尚、前記実施例ではセラミックヒーターについて説明したが、本発明の接合形態は前記実施例に限定されるものではなく、本発明の主旨を逸脱しないものであればいかなるものでも良く、例えばＩＧＢＴ等のパワートランジスター等を実装するセラミック焼結体基板表面に形成したメタライズ部に対する電極等の金属片の接合に適用しても同様の効果を奏するものである。
【００６７】
【発明の効果】
本発明によれば、電極金具と金属層との間に空隙が形成され、該空隙の少なくとも両サイドにおいて前記電極金具と前記金属層が接合され、より好ましくは金属層への金属部材成分の溶出拡散を金属部材との界面から１０μｍ以内に抑制し、該金属部材がセラミック部材との当接面側で２０〜２００μｍの厚さの金属層を接着して接合したときには、両部材間に介在する金属層への金属部材成分の溶出拡散による応力増加が生じず、また金属部材の側面には金属層が接着しておらず、金属部材の接合部周囲への応力集中が抑制されると共に、接合時の物理的な応力が緩和され金属層自体の応力増加が抑制され、室温と高温環境下に繰り返し曝しても、セラミック部材にクラックが発生せず、高い強度を維持した電気的な接続状態の劣化を起こさない極めて信頼性の高いセラミックヒータを提供することができる。
【図面の簡単な説明】
【図１】本発明のセラミック部材と金属部材の接合体を示す一例の要部を拡大し、Ｘ線マイクロアナリシス（ＥＰＭＡ）による金属層に拡散した金属部材成分の面分析の結果を重ねて記載した断面図である。
【図２】本発明のセラミックヒータの一例を示す外観の図である。
【図３】本発明のセラミックヒータの一例の要部の断面を拡大し、Ｘ線マイクロアナリシス（ＥＰＭＡ）による金属層に拡散した電極金具成分の面分析の結果を重ねて記載した断面図である。
【図４】従来のセラミック部材と金属部材の接合体の要部を拡大し、Ｘ線マイクロアナリシス（ＥＰＭＡ）による金属層に拡散した金属部材成分の面分析の結果を重ねて記載した断面図である。
【図５】従来のセラミックヒータの要部の断面を拡大し、Ｘ線マイクロアナリシス（ＥＰＭＡ）による金属層に拡散した電極金具成分の面分析の結果を重ねて記載した断面図である。
【符号の説明】
１ セラミック部材と金属部材の接合体
２ セラミック部材
３ 金属部材
４ 金属層
５ 界面
６ 金属部材成分
７ 厚さ
８ 当接面側
９ セラミックヒータ
１０ セラミック発熱体
１１ 電極金具
１２ 電極金具成分[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a joined body of a ceramic member and a metal member of various oxide or non-oxide type and a ceramic heater, and various industrial machines such as various sensors and measuring instruments, or for heating and ignition. Various internal combustion engine parts such as ceramic heaters used for ceramics, internal combustion engine parts such as glow plugs, or power elements such as semiconductor elements and resistors including power transistors and diodes that generate heat when energized. The present invention is applied to a joined body of a ceramic member and a metal member that require heat resistance, such as an electronic component typified by a heat dissipation board.
[0002]
In particular, it is used for the acceleration of starting direct-injection diesel engines for automobiles aimed at improving fuel efficiency, output, and exhaust gas, as well as ignition assistance for various internal combustion engines such as large diesel engines for ships or power generation. The present invention relates to a high temperature ceramic heater suitable for a heater used for auxiliary heating such as a glow plug to be used or an early activation oxygen sensor for the purpose of improving the exhaust gas.
[0003]
[Prior art]
In addition to oxide-based ceramics that have been used as insulating bases for various electronic components in the past, in recent years, it has outstanding features of high strength and low specific gravity, which are superior in heat resistance and corrosion resistance, wear resistance, and electrical insulation. Non-oxide ceramics having a large number of are widely used as various industrial machine devices including chemical plants and machine tool parts, and as internal combustion engine parts such as automobile diesel engines.
[0004]
For example, when starting a diesel engine or idling, a glow plug for an internal combustion engine used to rapidly preheat the sub-combustion chamber, or an oxygen concentration in the exhaust gas of the internal combustion engine to detect exhaust gas Various auxiliary heaters such as heaters built in to promote the activation of oxygen sensor elements, heat generation that is inferior to conventional rapid temperature rise characteristics and durability such as wear resistance, heat resistance, corrosion resistance, etc. Instead of a sheathed heater in which resistance wires and heat-resistant insulating powder are embedded in a heat-resistant metal cylinder, an electrically insulating ceramic sintered body with good thermal conductivity, a refractory metal, its compound, and their main components Ceramic heating elements integrated by carrying, bonding, or embedding heating resistors made of various inorganic conductive materials are widely used.
[0005]
However, since the ceramic is a brittle material, it is difficult to apply to parts where repeated stress is applied, and in addition, because it is poor in workability, only the parts exposed to high temperatures are resistant to heat resistance, corrosion resistance, and wear resistance. A variety of ceramics and metals, such as a composite structure using a combination of ceramic members and metal members made of high-strength and excellent workability parts made of high-weight lightweight ceramics A zygote is proposed.
[0006]
For joining such a ceramic member and a metal member, a metal layer mainly composed of a refractory metal such as molybdenum (Mo) is deposited on the surface of the ceramic member, and brazing such as silver brazing is performed through the metal layer. It has been widely adopted to braze and join metal members with materials.
[0007]
However, in the joined body of the ceramic member and the metal member by brazing joining, since the thermal expansion coefficients of both the members are greatly different, the distortion caused by the difference in thermal expansion, that is, the residual stress is in the vicinity of the joint portion of both the members. For example, in the glow plug for internal combustion engine and various auxiliary heaters, the bonding strength between the ceramic member and the metal member is generated at the bonding portion between the electrode extraction portion of the ceramic heating element and the electrode fitting, particularly at the bonding interface. There is a drawback in that the ceramic member or the metal member itself is liable to be degraded due to the shrinkage force of the metal member, or to be peeled off from the bonding interface.
[0008]
Therefore, in order to eliminate the difference in thermal expansion between the ceramic member and the metal member and maintain the bonding strength up to a high temperature, gold (Au), silver ( A so-called brazing method in which a metal layer 22 containing active metal such as titanium (Ti), vanadium (V) and the like is melted by heat treatment and contains at least one of Ag), copper (Cu), and nickel (Ni) as a main component. Many contacts have been proposed (see JP-A-6-321648, JP-A-7-25675, and JP-A-7-272832).
[0009]
[Problems to be solved by the invention]
The joined body of the ceramic member 20 and the metal member 21 joined by melting and joining the active metal-containing metal layer 22 by heat treatment is exposed to an initial strength or, for example, a normal temperature and a temperature of 450 ° C. alternately. In the thermal cycle test repeating the above, the bonding strength between the ceramic member 20 and the metal member 21 was satisfactory even at about 3000 cycles.
[0010]
However, for example, ceramic heaters built in the sensors used for recent internal combustion engines are wide-area types that can respond to early activation due to rapid temperature rise and lean burn engines as exhaust gas regulations are tightened. As the heat generation temperature rises, the temperature in the vicinity of the electrode fittings of the ceramic heater reaches 500 ° C, which is higher than the conventional 450 ° C, and the metal layer is melted by heat treatment. The joined body joined in this manner has a problem that it cannot withstand the conditions corresponding to 100,000 miles of traveling.
[0011]
That is, the repetition of the rapid temperature rise under the high temperature condition as described above causes the metal layer 22 to adhere to the contact surface side 33 and the side surface 34 of the metal member 21 and the ceramic member 20 and adhere to the meniscus portion 23 formed. Along with this, there is a problem that a minute crack 24 is generated in the ceramic member 20.
[0012]
Further, as shown in FIG. 5, in a ceramic heating element 26 comprising a heating resistor (not shown) made of an inorganic material and a ceramic sintered body 25, the lead wire 27 connected to the heating resistor is electrically connected. In the ceramic heater 30 in which the electrode fitting 29 is melt-bonded through the metal layer 22 at the exposed portion of the connected electrode lead-out portion 28, the electrode is obtained by repeated heating and cooling over a long period of time under the high temperature conditions as described above. A minute crack 24 is generated in the ceramic heating element 26 along the meniscus portion 23 formed by the metal layer 22 bonded to the contact surface side 33 and the side surface 34 of the metal fitting 29 with the ceramic heating element 26, and the crack 24 is activated. As a result, the electrode fitting 29 peels off from the ceramic heating element 26 with a part of the ceramic sintered body 25 adhered, or the heating resistor is damaged. By or resulting resistance changes giving, causing abnormal heat generation at the electrode portion reduces the life of the heater when energized, there is a problem that eventually results in disconnection.
[0013]
OBJECT OF THE INVENTION
The present invention has been made in view of the above problems, and its purpose is to heat and cool over a long period of time during operation, such as a rapid increase in temperature of the joint between the ceramic member and the metal member to a high temperature as high as 500 ° C. The ceramic member does not crack even if it receives the heat history of the above, or the metal member does not peel from the ceramic member. It does not peel off from the body, or the resistance of the heating element of the ceramic heating element changes abnormally, causing no abnormal heat generation or disconnection, maintaining high bonding strength for a long time, heat resistance, thermal shock resistance, high temperature stability It is an object of the present invention to provide a ceramic member-metal member assembly and a ceramic heater which are excellent in performance and have excellent rapid temperature rise characteristics and which are optimal for high temperatures.
[0014]
[Means for Solving the Problems]
As a result of various studies on the above problems, the present inventor has found that a conventional joined body of a ceramic member and a metal member corresponds to the periphery of the metal member due to a heat history when the metal layer containing the active metal is melt-bonded as a brazing material. X-ray microanalysis (overlaid on the metal layer 22 in the cross-sectional view of the main part shown in FIGS. 4 and 5 when melt bonding is performed in addition to the fact that a slight residual stress is generated in the ceramic member. As a result of the elemental analysis by EPMA), the metal member component 31 and the electrode fitting component 32 are diffused into the metal layer 22 to change its composition. As a result, the hardness of the metal layer 22 increases and the residual stress increases. It became clear.
[0015]
Further, around the joint portion with the metal member 21, from the contact surface side 33 with the ceramic member 20 to the side surface 34 of the metal member 21, the corner portion of the metal member 21 elutes to form an arc shape and melt. It has also been found that the bonded metal layer 22 forms a meniscus portion 23 and the stress 24 concentrates around the joint portion, and as a result, the crack 24 is generated.
[0016]
Therefore, the temperature rise at the time of joining the ceramic member and the metal member is suppressed to prevent the diffusion of the metal member component to the metal layer, the increase in the hardness is suppressed, and the metal layer does not form a meniscus portion. Even if the meniscus portion is removed, or the meniscus portion or the mountain-like bulge is formed around the joint portion of the metal member, the metal member is a metal layer only on the contact surface side with the ceramic member. It has been found that if it is bonded to the side surface of the metal member and is not bonded to the side surface of the metal member, reduction and concentration of the residual stress at that portion can be avoided, and the above-mentioned problems can be solved.
[0017]
That is, the present inventionCeramic heaterIsA ceramic heater in which a ceramic heating element composed of a heating resistor of inorganic conductive material and a ceramic sintered body and an electrode fitting are joined via a metal layer having a thickness of 20 to 200 μm, the electrode fitting comprising the metal layer and the ceramic Bonded only on the contact surface side with the heating element, the metal layer contains an electrode fitting component diffused within 10 μm from the interface with the electrode fitting, and lead pins are bonded to the surface of the electrode fitting. A gap is formed between the electrode fitting and the metal layer at a position facing the lead pin, and the electrode fitting and the metal layer are joined at least on both sides of the gap.It is characterized by that.
[0018]
In particular, the present inventionIn ceramic heaterIs a silicon nitride sintered bodyIs preferred,The metal layer is mainly composed of gold (Au) and nickel (Ni).Is more preferred,Containing one or more of vanadium (V) or molybdenum (Mo)Is more preferred.
[0021]
[Action]
According to the joined body of the ceramic member and the metal member and the ceramic heater according to the present invention, the metal layer interposed between the ceramic member and the metal member has a thickness of 20 to 200 μm and a depth within 10 μm from the interface with the metal member. However, the metal member component is not diffused and contained, and the metal member is bonded only on the contact surface side of the metal layer and the ceramic member, and the metal layer is bonded to the side surface of the metal member. Since the composition change of the metal layer is small, the hardness does not increase, the residual stress will be suppressed, and the stress does not concentrate on the ceramic member corresponding to the periphery of the joint of the metal member, The risk of cracking in the ceramic member around the joint with the metal member or peeling of the metal member from the ceramic member is eliminated even when the heat history of repeated heating and cooling is long. Will be.
[0022]
Further, in the ceramic heater, the ceramic heating element, the electrode fitting, and the metal layer are configured in the same manner as the joined body, so that the ceramic heating element is cracked, and the electrode fitting causes a part of the ceramic sintered body. It does not peel off while it is bonded, the resistance of the heating resistor changes abnormally, or it does not break, maintaining high bonding strength over a long period of time, excellent thermal shock resistance and high temperature stability, and rapid The temperature rise characteristics are good and the durability can be improved dramatically.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a joined body of a ceramic member and a metal member and a ceramic heater according to the present invention will be described in detail with reference to the drawings.
[0024]
FIG. 1 is an enlarged cross-sectional view of a principal part of a joined body of a ceramic member and a metal member according to the present invention, and the results of surface analysis of metal member components diffused in a metal layer by X-ray microanalysis (EPMA) are overlapped. It is.
[0025]
In FIG. 1, reference numeral 1 denotes a joined body of a ceramic member and a metal member obtained by joining a ceramic member 2 and a metal member 3 via a metal layer 4. The metal layer 4 is within a depth of 10 μm from the interface 5 with the metal member 3. The metal member 3 has a thickness 7 of 20 to 200 μm containing the metal member component 6 diffused only in the metal member 3, and the metal member 3 is bonded only at the contact surface side 8 between the metal layer 4 and the ceramic member 2. The side surface 13 of 3 is the one to which the metal layer 4 is not bonded.
[0026]
In the present invention, the material applicable as the ceramic member is alumina (Al₂O_Three) And mullite (3Al₂O_Three・ 2SiO₂), Etc., and non-oxide ceramics include silicon nitride (Si_ThreeN_Four), Silicon carbide (SiC), sialon, aluminum nitride (AlN), and the like.
[0027]
In particular, although the coefficient of thermal expansion is different from that of the metal member and the metal layer, alumina (Al₂O_Three), A silicon nitride sintered body containing rare earth elements such as ytterbium (Yb) and yttrium (Y) in the form of monosilicate and / or disilicate as a matrix component, in terms of strength, fracture toughness and heat resistance From is the best.
[0028]
Moreover, as a metal member joined with the said ceramic member, 3.0-7.5 * 10 which approximated the thermal expansion coefficient of this ceramic member.^-6Metal having a coefficient of thermal expansion of about / ° C., for example, low thermal expansion metal such as molybdenum (Mo) and tungsten (W), Fe—Ni based invar type alloy, Fe—P based Elinvar type alloy, WC— Examples thereof include TiC-Co based cemented carbide, and Fe-Ni-Co based alloys or Fe-Ni based alloys are desirable from the viewpoint of oxidation resistance, workability, and cost.
[0029]
Furthermore, from the viewpoint of ease of plastic deformation of the metal member, the Young's modulus of the metal member is 14 to 15 × 10.^Threekg / mm²Fe-based alloys such as Fe-Ni-Co alloys and Fe-Ni alloys are optimal, and furthermore, the stress generated by the difference in thermal expansion between the two members can be absorbed by plastic deformation of the metal members themselves. It is more desirable to reduce the thickness of the metal member to about 0.1 to 0.5 mm, and the corners of the metal member are chamfered or rounded and curved to avoid stress concentration as is well known. It goes without saying that it is more preferable to apply this.
[0030]
On the other hand, as the metal layer for joining the ceramic member and the metal member, the main component is one or more of gold (Au) or nickel (Ni), copper (Cu), silver (Ag), and palladium (Pd). Even if it is used at a high temperature of 400 ° C. or higher, there is no deterioration due to oxidation. For example, in consideration of prevention of migration under use conditions involving energization of a DC power source, the metal layer is made of gold (Au). An alloy of gold (Au) and nickel (Ni) of 50 to 99% by weight and nickel (Ni) of 1 to 50% by weight is optimal.
[0031]
In addition, the metal layer may include titanium (Ti), vanadium (V), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu) of the Group 4a elements of the periodic table as active metals, It is preferable to contain at least one of molybdenum (Mo), silicon (Si), zirconium (Zr), and hafnium (Hf).
[0032]
In particular, it is optimal to contain one or more of vanadium (V) or molybdenum (Mo) as an active metal from the viewpoint that the wettability of the metal layer to the ceramic member is good and the strength of the ceramic member is not deteriorated. Such an active metal may be contained in the form of nitride, carbide, hydride or the like.
[0033]
Further, if the content of the active metal is less than 1% by weight, the effect of improving the bonding strength is not seen, and if it exceeds 10% by weight, the baking temperature of the metal layer becomes high, and a large residual stress is generated during cooling. 1 to 10% by weight is preferable, and 1 to 5% by weight is particularly optimal.
[0034]
Therefore, as the metal layer made of the noble metal containing the active metal, specifically, gold (Au) and / or silver (Ag) and one or more of nickel (Ni) or palladium (Pd), or copper ( The total amount of any one of Cu), cobalt (Co), and silicon (Si) is 90 to 99 wt%, and the remaining 1 to 10 wt% is vanadium (V), molybdenum (Mo), titanium (Ti), Examples include one containing one or more active metals of zirconium (Zr), hafnium (Hf), and manganese (Mn).
[0035]
In the present invention, when the metal layer contains a metal member component that is dissolved and diffused into the metal layer beyond the depth of 10 μm from the interface with the metal member during bonding, the hardness of the metal layer is remarkably increased. Since the residual stress increases in the portion and causes cracking, it is necessary to control the diffusion range of the metal member component to be within 10 μm..
[0036]
Therefore, coupled with the diffusion range of the metal member component, if the thickness of the metal layer is less than 20 μm, the capacity of the metal layer is insufficient, uneven bonding such as a nest occurs, the bonding strength is insufficient, and the metal member is easily formed. If the thickness exceeds 200 μm, the capacity of the metal layer becomes excessive and the residual stress increases, cracks are generated in the ceramic member in a short time, and the strength is reduced. .
[0037]
Therefore, the thickness of the metal layer is specified to be 20 to 200 μm, and 20 to 150 μm is preferable in consideration of workability in depositing and forming the metal layer.
[0038]
Next, in the present invention, as a bonding form between the metal member and the metal layer, in order to avoid stress concentration on the ceramic member around the joint portion of the metal member, the side surface of the metal member and the metal layer are bonded to each other and the meniscus is bonded. It is most desirable that no portion is formed, and even if the metal layer forms a meniscus portion or a ridge-like bulge, it is sufficient that the metal layer is not adhered to the outer peripheral side surface of the metal member.
[0039]
Therefore, the metal layer is not bonded to the outer peripheral side surface of the metal member, and the metal layer is bonded only on the contact surface side with the ceramic member. Necessary to control conditions, remove unnecessary parts by laser trimming, grinding, etc., or apply a heat-resistant release agent such as BN to the outer peripheral side surface of the metal member in advance and melt-bond Among them, as a simple method, for example, if it is an ultrasonic bonding method in which static vibration is applied and bonded, it is melted greatly, unnecessary portions are removed, or a release agent is applied in advance. The goal can be achieved without any advantage.
[0040]
In addition, it is needless to say that the metal member and the metal layer need not be joined to the entire surface as long as the required strength can be secured. In order to avoid stress concentration due to the difference in thermal expansion, the metal member It is desirable to join so that it does not overlap with any edge of the outer periphery of the metal layer and the outer periphery of the metal layer.
[0041]
Next, FIG. 2 is an external view showing an example of the ceramic heater of the present invention, and FIG. 3 is an enlarged cross-sectional view of the main part of the ceramic heater of the present invention, and a metal layer by X-ray microanalysis (EPMA). It is sectional drawing which overlapped and described the result of the surface analysis of the electrode metal fitting component diffused in.
[0042]
2 and 3, 9 is a ceramic heater in which a ceramic heating element 10 and an electrode fitting 11 are joined via a metal layer 4, and the ceramic heating element 10 is a heating resistor (not shown) made of an inorganic conductive material and a ceramic. A lead wire 15 such as tungsten (W), which is made of an insulator 14 made of a sintered body and connected to the heating resistor, is electrically connected to the electrode lead-out portion 16, and the electrode lead-out portion 16 connects the Ni lead pin 17. A ceramic heater 9 is formed by being electrically joined to the spot-welded electrode fitting 11 via the metal layer 4.
[0043]
In the present invention, for example, the electrode fitting 11 performs ultrasonic bonding while pressing both sides of the electrode fitting 11 substantially perpendicularly to the contact surface with the ceramic heating element 10 while avoiding the spot-welded Ni lead pin 17. As a result, the molten metal layer can be bonded to the side surface 13 of the electrode fitting 11 without bonding.
[0044]
In this case, a gap 18 is generated between the electrode fitting 11 and the metal layer 4 by avoiding the Ni lead pin 17 and the diffusion of the electrode fitting component 12 into the metal layer 4 is caused by the thickness of the metal layer 4. Regardless of the thickness, the depth is within 10 μm from the interface with the electrode fitting 11 and almost no increase in hardness due to a change in the composition of the metal layer 4 is observed. It is.
[0045]
As the electrode fitting 11, any of the metal members already described in detail can be used in the same manner, and further, as a lead pin 17, a soft metal wire such as a Ni wire is connected by spot welding or the like, thereby applying vibration as a ceramic heater. Under such operating conditions, the physical load such as that the vibration is directly transmitted to the joint portion is reduced, so that problems such as separation of the joint portion can be avoided.
[0046]
Further, when the ceramic heater is applied to a glow plug of an internal combustion engine or the like, the ceramic heater is operated by a DC power source, and therefore, from the viewpoint of preventing a short circuit due to migration, A material containing (Au) as a main component and vanadium (V) or titanium (Ti) as an active metal is optimal.
[0047]
The heating resistor made of the inorganic conductive material constituting the ceramic heating element of the present invention is a high melting point metal such as tungsten (W), molybdenum (Mo), titanium (Ti), tungsten carbide (WC), molybdenum silicide. (MoSi₂), A resistor mainly composed of carbide, silicide, nitride, or the like of a high melting point metal such as titanium nitride (TiN), a thermal expansion difference from the nitride ceramic sintered body of the insulator, and high From the standpoint that it does not easily react with them even under temperature, WC or those containing W as a main component are preferable.
[0048]
Needless to say, the components of the inorganic conductive material constituting the heating resistor may be added to the nitride-based ceramic sintered body of the insulator to adjust the difference in thermal expansion and reactivity.
[0049]
On the other hand, with respect to the main component of the inorganic conductive material, silicon nitride (Si) is used as a dispersant in order to prevent the crack due to the difference in thermal expansion from the insulator by controlling the growth and to prevent the resistance from increasing._ThreeN_Four), Boron nitride (BN), aluminum nitride (AlN), or silicon carbide (SiC), and the content thereof is, for example, silicon nitride (Si) relative to 100 parts by weight of the main component._ThreeN_Four) Is 5 to 30 parts by weight, boron nitride (BN) is 1 to 20 parts by weight, aluminum nitride (AlN) is 1 to 15 parts by weight, and silicon carbide (SiC) is 3 to 15 parts by weight. is there.
[0050]
On the other hand, the heating resistor may be in the form of a block, a line, or a layer, and the insulator is bent in a U shape, wound in a coil, or zigzag bent in a plane. When the heating resistor is viewed in plan, it has an arbitrary shape such as a U-shape or a W-shape, and can be supported on, bonded to, or buried in an insulator, It can be applied in various shapes such as a laminated structure of two or more layers via a lead, and a lead material made of a W material or the like may be electrically connected to both ends thereof.
[0051]
【Example】
The invention was then evaluated as detailed below.
First, silicon nitride (Si_ThreeN_Four) Ceramic raw material powder added with a sintering aid made of oxides of rare earth elements such as ytterbium (Yb) and yttrium (Y), and alumina (Al₂O_Three) Powder to silica (SiO₂), Ceramic raw material powder added with calcia (CaO), and aluminum nitride (AlN) with erbium oxide (Er₂O_Three) As a sintering aid is formed into a flat molded body by a known press molding method or the like, and a screen printing method using a paste containing WC as a main component on the surface of one end of the molded body. Thus, the heat generating part is formed in a U-shaped pattern, and the electrode part is similarly formed from the other end side to the side surface of the ceramic molded body.
[0052]
Next, a lead wire is placed so as to electrically connect the heat generating portion and the electrode portion, and another ceramic molded body is stacked thereon, followed by firing at a temperature of 1700 to 1900 ° C. in a reducing atmosphere. A ceramic heating element was produced by integration.
[0053]
Thereafter, the ceramic heating element is processed into a cylindrical shape by grinding, and transferred to the exposed electrode portion by a screen printing method using a paste containing the metal layer component shown in Table 1, and a vacuum atmosphere at 800 to 1300 ° C. A baking process was performed in the inside to deposit and form a metal layer having a width of 3 mm and a length of 4 mm.
[0054]
Electrode fittings in which Ni lead pins were previously connected to an Fe—Ni—Co alloy having a width of 2 mm × length of 3 mm × thickness of 0.2 mm by spot welding were bonded to the ceramic heating element thus obtained by various bonding methods shown in Table 1. Then, using a part of the ceramic heater for evaluation, the part including the joint part of the electrode fitting was cut, the cross section was observed with a scanning electron microscope, and the thickness of the metal layer was measured.
[0055]
In the cross section, the ratio of the length of the metal layer actually bonded to the length of the surface where the electrode fitting contacts the ceramic heating element was determined and evaluated as a bonding area (%).
[0056]
Next, the surface analysis of the electrode fitting component diffused into the metal layer was performed by X-ray microanalysis (EPMA), and the depth of the metal layer containing the electrode fitting component from the interface of the electrode fitting was measured.
[0057]
[Table 1]

[0058]
[Table 2]

[0059]
On the other hand, for the other ceramic heaters for evaluation, while measuring the joint strength of the electrode bracket and the bending strength of the ceramic heater including the joint portion of the electrode bracket, and the resistance change rate after the thermal cycle test, The ceramic heater was cut at a portion including the joint portion of the electrode fitting, and the cross section was observed.
[0060]
The bonding strength is determined by fixing the ceramic heater for evaluation, pulling the Ni lead pin of the electrode fitting bonded to the ceramic heating element in the direction perpendicular to the ceramic heating element, and the load when the bonding portion or Ni lead pin or electrode fitting breaks (N) Was measured and evaluated together with the fracture mode.
[0061]
The bending strength was evaluated by a cantilever bending test by holding a ceramic heater for evaluation and pressurizing the joint of the electrode fitting.
[0062]
Further, in the thermal cycle test, exposure of the ceramic heater for evaluation to room temperature and 500 ° C. temperature atmosphere was repeated as one cycle, the resistance value of the ceramic heater after 3000 cycles was measured, and the initial resistance before the test was measured. The rate of resistance change with respect to the value was determined, and the ceramic heater after the test was cut along the cross section including the electrode fitting, and the presence of cracks was observed.
[0063]
[Table 3]

[0064]
As is clear from the table, in sample numbers 1, 8, 11, and 15 which are outside the scope of the present invention, the bonding strength of the electrode fittings is all78.5N (8kgf)Similarly, for sample numbers 10, 14, 17, 18, 27, 28, and 30, the bonding strength of the electrode fitting is78.5N (8kgf)However, the rate of change in resistance after the thermal cycle test was as large as 3.0 or more, and cracks were observed in the ceramic heating element.
[0065]
In contrast, in the present invention, the bonding strength of the electrode fittings is78.5N (8kgf)Furthermore, the rate of change in resistance after the thermal cycle test is as small as 2.6 or less, and no cracks are observed in the ceramic heating element, and the stress concentration around the joint of the electrode fitting is effectively alleviated. .
[0066]
In addition, although the ceramic heater was demonstrated in the said Example, the joining form of this invention is not limited to the said Example, What kind of thing may be used as long as it does not deviate from the main point of this invention, for example, IGBT etc. Even when applied to the joining of metal pieces such as electrodes to a metallized portion formed on the surface of a ceramic sintered body substrate on which a power transistor or the like is mounted, the same effect can be obtained.
[0067]
【The invention's effect】
The present inventionAccording to the present invention, a gap is formed between the electrode fitting and the metal layer, and the electrode fitting and the metal layer are joined on at least both sides of the gap, more preferablyThe elution and diffusion of the metal member component to the metal layer is suppressed within 10 μm from the interface with the metal member, and the metal member is bonded to the ceramic layer with a thickness of 20 to 200 μm on the contact surface side. didSometimesThe stress does not increase due to the elution and diffusion of the metal member component to the metal layer interposed between the two members, and the metal layer is not adhered to the side surface of the metal member, and the stress concentration around the joint part of the metal member In addition, the physical stress at the time of bonding is relieved and the stress increase in the metal layer itself is suppressed, and cracks do not occur in the ceramic member even if it is repeatedly exposed to room temperature and high temperature environments, and high strength is maintained. Highly reliable without causing deterioration of the electrical connectionTheA ceramic heater can be provided.
[Brief description of the drawings]
FIG. 1 is an enlarged view of an essential part of an example showing a joined body of a ceramic member and a metal member according to the present invention, and the results of surface analysis of metal member components diffused in a metal layer by X-ray microanalysis (EPMA) are described repeatedly. FIG.
FIG. 2 is an external view showing an example of a ceramic heater according to the present invention.
FIG. 3 is an enlarged cross-sectional view of the main part of an example of the ceramic heater of the present invention, and is a cross-sectional view in which the results of surface analysis of the electrode fitting components diffused in the metal layer by X-ray microanalysis (EPMA) are shown superimposed. .
FIG. 4 is a cross-sectional view in which a main part of a conventional ceramic member-metal member assembly is enlarged and the results of surface analysis of metal member components diffused into the metal layer by X-ray microanalysis (EPMA) are overlapped and described. is there.
FIG. 5 is an enlarged cross-sectional view of a main part of a conventional ceramic heater, and is a cross-sectional view in which the results of surface analysis of electrode fitting components diffused into a metal layer by X-ray microanalysis (EPMA) are overlapped.
[Explanation of symbols]
1 Bonded body of ceramic member and metal member
2 Ceramic parts
3 Metal parts
4 Metal layers
5 Interface
6 Metal component components
7 Thickness
8 Contact surface side
9 Ceramic heater
10 Ceramic heating element
11 Electrode bracket
12 Electrode bracket components

Claims (4)

A ceramic heater in which a ceramic heating element composed of a heating resistor of inorganic conductive material and a ceramic sintered body and an electrode fitting are joined via a metal layer having a thickness of 20 to 200 μm , the electrode fitting comprising the metal layer and the ceramic Bonded only on the contact surface side with the heating element, the metal layer contains an electrode fitting component diffused within 10 μm from the interface with the electrode fitting,
A lead pin is joined to the surface of the electrode fitting, and a gap is formed between the electrode fitting and the metal layer at a position facing the lead pin, and the electrode is provided on at least both sides of the gap. A ceramic heater , wherein a metal fitting and the metal layer are joined . The ceramic heater according to claim 1 , wherein the ceramic sintered body constituting the ceramic heating element is a silicon nitride sintered body. The metal layer, a ceramic heater according to claim 1 or 2, characterized in that the main component of gold (Au) and nickel (Ni). The ceramic heater according to any one of claims 1 to 3 , wherein the metal layer contains one or more of vanadium (V) and molybdenum (Mo).

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