JP2004247512A - Ceramic circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable cracking-free ceramic substrate wherein no thermal stress concentration due to difference in thermal expansion occurs at the junction between a ceramic substrate and an active brazing metal even under repeated thermal impacts inflicted after the bonding of the ceramic substrate and a metal circuit board by the active brazing metal. <P>SOLUTION: The ceramic circuit board comprises a ceramic substrate 1 and a metal circuit board 2 made of copper or a copper alloy which is bonded by an active brazing metal 3 to the top surface of the ceramic substrate 1. Just under the edge of the active brazing metal 3 which is above the top surface of the ceramic substrate 1, a groove in the ceramic substrate 1 and a unbonded region 5 which is free of the active brazing metal 3 are in presence along a bonded edge A, wherein an opening extends from a location facing a bonded edge B formed between the metal circuit board 2 and the active brazing metal 3 to a bonded edge A formed between the ceramic substrate 1 and the active brazing metal 3, with the bonded edge A located further inside the bonded edge B. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ceramic circuit board formed by joining a metal circuit board made of copper or a copper alloy to a ceramic substrate via an active metal brazing material.
[0002]
[Prior art]
In recent years, as a circuit board such as a board for a power module or a board for a switching module, a ceramic circuit board formed by joining a metal circuit board made of copper or a copper alloy on a ceramic board via an active metal brazing material has been used. I have.
[0003]
Such a ceramic circuit board is specifically manufactured by the following method. First, an active metal brazing material paste is prepared by adding an organic solvent and a solvent to an active metal powder obtained by adding at least one of titanium, zirconium, hafnium and a hydride thereof to a silver-copper alloy.
[0004]
Next, for example, when the ceramic substrate is made of an aluminum oxide sintered body, an appropriate organic binder, a plasticizer, a solvent, and the like are added to and mixed with raw material powders of aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, etc. After obtaining a plurality of ceramic green sheets (hereinafter, also referred to as green sheets) by a tape forming technique such as a doctor blade method or a calender roll method, which are well known in the art, these are cut into a predetermined size, and then the green sheets are cut. A plurality of sheets are laminated as necessary and fired at a temperature of about 1600 ° C. in a reducing atmosphere, and the green sheets are sintered and integrated to form a ceramic substrate.
[0005]
Next, the active metal brazing paste is printed in a predetermined pattern on the ceramic substrate and dried, and then a metal circuit board made of copper or a copper alloy is placed on the active metal brazing paste.
[0006]
Finally, the paste of the active metal brazing material disposed between the ceramic substrate and the metal circuit board is heated and melted at a temperature of about 900 ° C. in a non-oxidizing atmosphere. By joining the board, a ceramic circuit board is manufactured.
[0007]
The ceramic circuit board manufactured in this manner is mounted with a semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) or a MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor) via an adhesive such as solder. The terminal for external input / output is mounted in a resin case integrally molded to form a semiconductor module. The semiconductor module is used in a wide range of applications from industrial equipment such as robots to driving parts of trains and electric vehicles, and is required to have high reliability under severe environments.
[0008]
However, the production of the resin case integrally molded with the terminals requires a molding die, and the production cost is high. Therefore, there is a problem that the production cost of the semiconductor module increases. In addition, after incorporating the ceramic circuit board into the resin case with integrated terminals, it is necessary to electrically connect the terminals of the resin case and the metal circuit board of the ceramic circuit board with bonding wires, etc., increasing the number of manufacturing steps. There was a problem of doing.
[0009]
For this reason, a ceramic circuit board in which terminals are directly joined to a metal circuit board by soldering or ultrasonic bonding, or a terminal-integrated ceramic circuit board in which a part of the metal circuit board is extended as a terminal is employed. It is becoming.
[0010]
However, when the terminals are joined to the metal circuit board by soldering, a 90% lead-tin alloy having a melting point higher than the heating temperature is used so that the joining does not come off due to heating when mounting electronic components such as semiconductor elements. Since a high-temperature solder (melting point: about 300 ° C.) is required, cracks are generated in the ceramic substrate due to a difference in thermal expansion between the metal circuit board and the ceramic substrate due to heat history caused by heating and melting the high-temperature solder. Heat resistance of about 250 ° C to protect circuit patterns from the external environment and to prevent solder from adhering to unnecessary parts in the soldering step performed when surface mounting electronic components on printed wiring boards However, there is a problem that an epoxy resin-based solder resist that can only be used cannot be used.
[0011]
Further, when the terminals are joined by ultrasonic joining, for example, since the ultrasonic oscillation horn is pressed with a pressure of 10 to 50 MPa on the surface of the joint portion of the terminal contacted with the metal circuit board, this high pressure is applied to the terminal. The ceramic substrate immediately below the junction is applied via a metal circuit board and brazing material to the ceramic substrate immediately below the junction, and heat of about 500 ° C. or more generated by ultrasonic vibration is instantaneously applied to the ceramic substrate immediately below the junction of the terminal, so that the ceramic In some cases, minute cracks are formed on the substrate, and in that case, there is a problem that the mechanical strength of the ceramic circuit substrate is reduced and the reliability is significantly deteriorated.
[0012]
In order to solve such problems, a terminal-integrated ceramic circuit board with a simpler structure, less number of mounting steps, and higher reliability, with a part of the metal circuit board extended as a terminal part is adopted. It is becoming. This metal circuit board is manufactured into a desired circuit wiring pattern shape by applying a conventionally known metal working method such as a rolling method or a punching method. Alternatively, it is manufactured by brazing a metal plate having substantially the same shape as the ceramic substrate and then removing unnecessary metal portions by etching to form a circuit wiring pattern.
[0013]
In this case, as shown in the cross-sectional view of the conventional ceramic circuit board in FIG. 3, the joining end a between the ceramic substrate 1 and the active metal brazing material 3 and the joining between the metal circuit board 2 and the active metal brazing material 3 It is located at a position facing end b. In other words, the positions are overlapping when the ceramic circuit board is viewed in plan.
[0014]
[Patent Document 1]
JP-A-2002-164461
[Problems to be solved by the invention]
However, in the ceramic circuit board shown in FIG. 3, when the ceramic circuit board is repeatedly subjected to thermal shock by ultrasonic bonding or the like, the ceramic board 1 and the active metal brazing material 3 The thermal stress generated due to the difference in thermal expansion between the active metal brazing material 3 and the thermal stress generated due to the difference in thermal expansion between the metal circuit board 2 and the active metal brazing material 3 is superimposed. Cracks are likely to occur at the joint end a between the ceramic substrate 1 and the active metal brazing material 3, and as a result, the joint strength, thermal conductivity, and electrical insulation are reduced, and the reliability is reduced. There was a problem that.
[0016]
Therefore, the present invention has been completed in view of the above problems, and an object of the present invention is to provide a terminal-integrated ceramic circuit board, which has been heated after bonding the ceramic board and the metal circuit board via an active metal brazing material. Even if the impact is repeatedly applied, the thermal stress generated due to the difference in thermal expansion does not concentrate on the joint end of the ceramic substrate with the active metal brazing material. As a result, the ceramic substrate does not crack and has high reliability. It is to provide a ceramic circuit board.
[0017]
[Means for Solving the Problems]
The ceramic circuit board of the present invention is a ceramic circuit board in which a metal circuit board made of copper or a copper alloy is bonded to an upper surface of the ceramic substrate via an active metal brazing material, and the ceramic substrate has the upper surface thereof. The ceramic substrate and the active metal brazing material, which are located at a position immediately below the end of the active metal brazing material and are located inside the joining end from a position facing the joining end of the metal circuit board and the active metal brazing material. A groove-shaped non-joining region between the ceramic substrate and the active metal brazing material having an opening extending over the joining end thereof is provided along a joining end between the ceramic substrate and the active metal brazing material. I do.
[0018]
In the ceramic circuit board of the present invention, the ceramic substrate is provided at a position directly below the end of the active metal brazing material on the upper surface thereof from the position facing the joint end between the metal circuit board and the active metal brazing material, inside the joint end. A groove-shaped non-joining region between the ceramic substrate and the active metal brazing material having an opening over the joining end between the ceramic substrate and the active metal brazing material is provided along the joining end between the ceramic substrate and the active metal brazing material. Therefore, when the ceramic circuit board is viewed in plan, the joining end between the metal circuit board and the active metal brazing material and the joining end between the ceramic substrate and the active metal brazing material do not overlap. As a result, when a thermal shock is repeatedly applied to the ceramic circuit board, a thermal expansion difference is generated between the ceramic substrate and the active metal brazing material at the joint end between the ceramic substrate and the active metal brazing material. The thermal stress and the thermal stress generated by the difference in thermal expansion between the metal circuit board and the active metal brazing material generated between the metal circuit board and the active metal brazing material do not overlap and are applied. Therefore, a highly reliable ceramic circuit board can be provided in which cracks are not generated at the joining end between the ceramic substrate and the active metal brazing material, and the joining strength, thermal conductivity, and electrical insulation are not reduced.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
The ceramic circuit board of the present invention will be described in detail below. FIG. 1 is a sectional view showing an example of an embodiment of a ceramic circuit board of the present invention, and FIG. 2 is a plan view of the ceramic circuit board of FIG. In these figures, 1 is a ceramic substrate, 2 is a metal circuit board, 3 is an active metal brazing material, 4 is a terminal portion of the metal circuit board 2, 5 is a groove-shaped non-joining area, and A is the ceramic substrate 1 and the active metal. A joint end B with the brazing material 3 is a joint end between the metal circuit board 2 and the active metal brazing material 3. In FIG. 2, the groove-shaped non-joining region 5 is indicated by a dotted line.
[0020]
The ceramic circuit board of the present invention is a ceramic circuit board in which a metal circuit board 2 made of copper or a copper alloy is joined to an upper surface of a ceramic board 1 with an active metal brazing material 3 interposed therebetween. The ceramic substrate 1 and the active metal existing on the upper surface immediately below the end of the active metal brazing material 3 from the position facing the bonding end B between the metal circuit board 2 and the active metal brazing material 3 and inside the bonding end B A non-joining region 5 between the grooved ceramic substrate 1 and the active metal brazing material 3 having an opening extending over the joining end A with the brazing material 3 is provided along the joining end A between the ceramic substrate 1 and the active metal brazing material 3. Have been.
[0021]
The ceramic substrate 1 according to the present invention has a square shape with a side length of about 20 to 200 mm and a thickness of about 0.2 to 1.0 mm, and a metal circuit board 2 made of copper or a copper alloy is activated on its upper surface. It is joined via the metal brazing material 3. The ceramic substrate 1 is a supporting member for supporting the metal circuit board 2, and includes an aluminum oxide (Al ₂ O ₃ ) sintered body (alumina ceramics), a mullite (3Al ₂ O ₃ .2SiO ₂ ) sintered body, It is made of a ceramic which is an electrically insulating material such as a silicon carbide (SiC) based sintered body, an aluminum nitride (AlN) based sintered body, and a silicon nitride (Si ₃ N ₄ ) based sintered body.
[0022]
When the ceramic substrate 1 is made of, for example, an aluminum oxide-based sintered body, an appropriate organic binder, a plasticizer, and a solvent are added to a raw material powder such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide, and the mixture is mixed to form a slurry. None, a ceramic green sheet (ceramic green sheet, hereinafter also referred to as green sheet) is obtained from the slurry by a well-known doctor blade method or calender roll method, and then the green sheet is subjected to an appropriate punching process. It is also manufactured by stacking a plurality of sheets as necessary and firing at a high temperature of about 1600 ° C.
[0023]
The thickness of the ceramic substrate 1 is preferably set to 0.2 to 1.0 mm. In order to satisfy the requirements for downsizing and thinning of the ceramic circuit board, the ceramic substrate 1 when the metal circuit board 2 is bonded is required. This is preferable in terms of suppressing cracks and improving the heat conductivity of heat of 100 ° C. or more generated by a semiconductor element (not shown) to be mounted. When the thickness of the ceramic substrate 1 is less than 0.2 mm, cracks and the like tend to occur easily in the ceramic substrate 1 due to thermal stress generated when the metal circuit board 2 is joined to the ceramic substrate 1. On the other hand, when the thickness exceeds 1.0 mm, it is difficult to cope with the thinning of the ceramic circuit board, and it is possible to satisfactorily radiate heat of 100 ° C. or more generated by the mounted semiconductor element through the ceramic substrate 1. Tends to be difficult.
[0024]
The metal circuit board 2 is made of copper or a copper alloy, and one end of the metal circuit board 2 is a terminal section 4 that is electrically connected to an external electric circuit (not shown). The joining is performed via the brazing material 3 as follows.
[0025]
First, an active metal powder such as titanium, zirconium or hafnium or an active metal powder comprising at least one hydride thereof is added to a silver brazing powder such as a silver-copper alloy powder or an aluminum brazing powder such as an aluminum-silicon alloy powder. An active metal brazing material paste obtained by adding and mixing an appropriate organic solvent and a solvent to the active metal brazing material to which 2 to 5% by mass is added is coated on the upper surface of the ceramic substrate 1 by a conventionally well-known screen printing method. Is printed in a predetermined pattern corresponding to. Since the terminal portions 4 of the metal circuit board 2 are used by being bent substantially perpendicularly to the upper surface of the ceramic substrate 1, active metal brazing material paste is printed on portions corresponding to the terminal portions 4 of the ceramic substrate 1. do not do.
[0026]
Then, the metal circuit board 2 is placed on the pattern of the active metal brazing material paste, or the ceramic substrate 1 on which the active metal brazing material paste is printed is placed on the metal circuit board 2 by the active metal brazing material paste. Are heated in a vacuum or in a neutral or reducing atmosphere at a predetermined temperature (about 900 ° C.) to melt the active metal brazing material paste. The metal circuit board 2 is joined to the upper surface to form a ceramic circuit board.
[0027]
The joining between the ceramic substrate 1 and the metal circuit board 2 is performed so that the active metal brazing material 3 does not flow into the non-joining region 5 of the grooved active metal brazing material 3 on the upper surface of the ceramic substrate 1. It is preferable that the ceramic substrate 1 on which the paste is printed be placed on the metal circuit board 2. Alternatively, an active metal brazing material paste is printed on a joining region of the metal circuit board 2 with the ceramic substrate 1, and the ceramic substrate 1 is placed on the metal circuit board 2 on which the active metal brazing material paste is printed and joined. Is preferred.
[0028]
When the assembly of the ceramic substrate 1 and the metal circuit board 2 is heated to melt the active metal brazing paste as described above, the molten and expanded active metal brazing paste pastes the surface of the metal circuit board 2. Although it wets and spreads outward, it spreads effectively in the non-bonding region 5 of the ceramic substrate 1. That is, the ceramic surface of the ceramic substrate 1 originally has poor wettability of the active metal brazing material 3 (the contact angle of the molten active metal brazing material 3 is large), and the molten active metal brazing material 3 has a molten active Since the contact angle with the metal brazing material 3 is larger, it is possible to effectively suppress the molten active metal brazing material 3 from entering the non-joining region 5. As a result, an inclined meniscus as shown in FIG. 1 is formed at the end of the active metal brazing material 3.
[0029]
The metal circuit board 2 is made of copper or a copper-zinc alloy (a zinc content of 30% by mass or less), a copper-tin alloy (a tin content of 5% by mass or less), a copper-platinum alloy (a platinum content Amount is 5 mass% or less), copper-palladium alloy (palladium content is 5 mass% or less), copper-nickel alloy (nickel content is 5 mass% or less), etc. By applying a conventionally known metal working method such as a rolling working method or a punching working method, a desired circuit wiring pattern shape having a thickness of, for example, 0.5 mm is manufactured. At this time, the terminal portion 4 integrated with the circuit wiring pattern is also formed at the same time.
[0030]
In addition, the thickness of the metal circuit board 2 satisfies the requirements for miniaturization and thinning of the ceramic circuit board, and also satisfies the specification of the electric resistance when a large current signal such as 20 to 50 A flows. From the viewpoint of preventing cracking of the ceramic substrate 1 when joined to the ceramic substrate 1, it is preferably 0.1 to 1.0 mm. When the thickness of the metal circuit board 2 is less than 0.1 mm, a large current signal such as 20 to 50 A tends to be difficult to flow satisfactorily due to an increase in electric resistance. It is difficult to cope with the problem, and cracks and the like tend to be easily generated in the ceramic substrate 1 due to thermal stress generated when the ceramic substrate 1 and the metal circuit board 2 are joined.
[0031]
It is preferable that the metal circuit board 2 is made of oxygen-free copper. In this case, the active metal brazing material 3 is hardly oxidized and the wettability is improved, so that the metal circuit board 2 is strongly bonded to the ceramic substrate 1. Can be.
[0032]
The terminal portion 4 is a part of the metal circuit board 2 and is preferably processed so that its Vickers hardness at room temperature becomes 100 Hv or more. This is because the tough pitch copper used as a normal terminal has a Vickers hardness of 80 Hv or more, so that the terminal portion 4 is not deformed when the terminal-integrated ceramic circuit board is mounted on the resin case. This is because bending is reduced and electronic components such as semiconductor elements to be mounted can be operated stably.
[0033]
As a processing method for setting the Vickers hardness of the terminal portion 4 to 100 Hv or more, electroless nickel plating, impact processing, solder film forming processing, and the like are suitably used.
[0034]
The electroless nickel plating is performed, for example, by applying electroless nickel plating containing phosphorus to the terminal portion 4 and then performing a heat treatment at a temperature of 250 ° C. or more to crystallize the nickel-phosphorus to have a Vickers hardness of 100 Hv or more. It is a processing method. At this time, the amount of phosphorus contained in the nickel film is preferably 8% by mass or more. If the phosphorus content is less than 8% by mass, the nickel-phosphorus compound cannot be sufficiently crystallized, and as a result, the Vickers hardness of the terminal portion 4 tends not to be 100 Hv or more. In addition, other than phosphorus, boron or the like which forms a compound with nickel and has a Vickers hardness of 100 Hv or more may be used.
[0035]
The thickness of the electroless nickel plating is preferably 1.5 μm or more. When the thickness is 1.5 μm or less, the effect of increasing the Vickers hardness of the terminal portion 4 is small, and a Vickers hardness of 100 Hv or more tends to be not obtained. Further, the heat treatment at 250 ° C. or higher is performed because the crystallization of the nickel-phosphorous compound does not proceed at all and the Vickers hardness may not increase unless the heat treatment is performed. This heat treatment may be performed after the formation of the plating film, or may be performed by using a heat treatment when electronic components such as semiconductor elements are mounted on the ceramic circuit board on which the plating film is formed by soldering or the like.
[0036]
Examples of the impact processing on the terminal portion 4 include sand blasting, wet blasting (a method of injecting abrasive grains and water by air pressure), and pressing with a mold. In the case of impact processing by blasting, it may be applied only to the terminal portion 4 or may be subjected to blasting of the entire ceramic circuit board to also serve as a step of removing foreign matter. Pressing with a mold may be performed, for example, by using a device in which the terminal 4 is put into a mold and only the terminal 4 is hit with a hammer or the like.
[0037]
Further, examples of the solder film forming process on the terminal portion 4 include a solder film process by solder plating and a solder film forming process by solder dipping. As the solder, a Pb-Sn-based or Sn-Ag-based solder containing Sn is used, and the Sn forms a Cu-Sn alloy with the copper of the terminal portion 4, whereby the Vickers hardness of the terminal portion 4 increases.
[0038]
In the ceramic circuit board according to the present invention, the ceramic substrate is located at a position directly below the end of the active metal brazing material 3 on the upper surface thereof at a position facing the joining end B between the metal circuit board 2 and the active metal brazing material 3. The non-joining region 5 between the groove-shaped ceramic substrate 1 and the active metal brazing material 3 having an opening extending over the joining end A between the ceramic substrate 1 and the active metal brazing material 3 existing inside the joint end from the joining end is formed. A is provided along A. With this configuration, when the ceramic circuit board 1 is viewed in a plan view, the joining ends A and B do not overlap, and when the ceramic circuit board 1 is repeatedly subjected to thermal shock, the joining end A and the ceramic substrate 1 are activated. The thermal stress generated by the difference in thermal expansion between the metal brazing material 3 and the thermal stress generated by the difference in thermal expansion between the metal circuit board 2 and the active metal brazing material 3 is superimposed. Will not join. As a result, it is possible to obtain a highly reliable ceramic circuit board without cracks occurring at the joint end A and reducing the joint strength, thermal conductivity, and electrical insulation.
[0039]
It is preferable that the width of the groove-shaped non-joining region 5 is 0.05 to 2 times the thickness of the ceramic substrate 1. If the ratio is less than 0.05 times, the active metal brazing material 3 flows into the non-joining region 5, and there is a risk that the joining ends A and B overlap when the ceramic circuit board is viewed in plan. If it exceeds twice, the strength of the ceramic substrate 1 is sharply reduced at the non-bonded region 5, and there is a high risk that the ceramic substrate 1 is broken at the non-bonded region 5 when the terminal portion 4 is bent and used. Become.
[0040]
The depth of the groove-shaped non-joining region 5 is preferably 10 to 40% of the thickness of the ceramic substrate 1. If it is less than 10%, there is a risk that the active metal brazing material 3 easily flows into the non-joining region 5 and the joining ends A and B overlap when the ceramic circuit board is viewed in plan. If it exceeds 40%, the strength of the ceramic substrate 1 is sharply reduced at the portion of the non-joining region 5, and the risk of being broken in the non-joining region 5 when the terminal portion 4 is bent and used is increased.
[0041]
Further, the cross-sectional shape of the groove-shaped non-joining region 5 may be various shapes such as a semicircular shape, a semi-elliptical shape, a triangular shape, and a quadrangular shape. From the viewpoint of dispersing the stress, a polygonal shape such as a semicircular or semielliptical shape having no discontinuous point on the inner peripheral surface, a triangular shape having rounded corners, or a quadrangular shape is preferable.
[0042]
Further, it is preferable that the terminal portion 4 of the metal circuit board 2 has a length from the joining end B to the end of the active metal brazing material 3 of about 5 to 20 mm. If it is less than 5 mm, it tends to be difficult to bend the terminal portion 4 when used by bending it upward, and if it is more than 20 mm, the metal circuit board 3 becomes unnecessarily large, resulting in high cost.
[0043]
In the present embodiment, an example is shown in which the groove-shaped non-joining region 5 is provided between the ceramic substrate 1 and the metal circuit board 2 on the upper surface of the ceramic substrate 1, but is opposed from one end surface of the ceramic substrate 1. It may be formed over the end face. In this case, after joining the metal circuit board 2 to the ceramic substrate 1, the ceramic substrate 1 is divided at the non-joining region 5 and one end is separated and removed, so that the terminal portion 4 is easily extended outside the ceramic substrate 1. The terminal portion 4 can be easily bent. In this case, it is preferable that the cross-sectional shape of the groove-shaped non-joining region 5 is triangular, and the non-joining region 5 can divide the ceramic substrate 1 well.
[0044]
The groove-shaped non-bonding region 5 is formed by applying a pressure process to a predetermined position of a green sheet that becomes the ceramic substrate 1 after firing so that the green sheet becomes a groove shape after firing.
[0045]
Thus, according to the ceramic circuit board of the present invention, the active metal brazing material paste disposed between the ceramic board 1 and the metal circuit board 2 is heated to about 900 ° C. in a non-oxidizing atmosphere to be melted. The semiconductor module is manufactured by bonding a metal circuit board 2 to an electronic component 1 and further mounting an electronic component such as a semiconductor element via an adhesive such as solder, and then mounting the electronic component in a resin case.
[0046]
The present invention is not limited to the above-described embodiment, and various changes can be made without departing from the gist of the present invention.
[0047]
【The invention's effect】
In the ceramic circuit board of the present invention, the ceramic substrate is provided at a position directly below the end of the active metal brazing material on the upper surface thereof from the position facing the joint end between the metal circuit board and the active metal brazing material, inside the joint end. A groove-shaped non-joining region between the ceramic substrate and the active metal brazing material having an opening over the joining end between the ceramic substrate and the active metal brazing material is provided along the joining end between the ceramic substrate and the active metal brazing material. Therefore, when the ceramic circuit board is viewed in plan, the joining end between the metal circuit board and the active metal brazing material and the joining end between the ceramic substrate and the active metal brazing material do not overlap. As a result, when a thermal shock is repeatedly applied to the ceramic circuit board, a thermal expansion difference is generated between the ceramic substrate and the active metal brazing material at the joint end between the ceramic substrate and the active metal brazing material. The thermal stress and the thermal stress generated by the difference in thermal expansion between the metal circuit board and the active metal brazing material generated between the metal circuit board and the active metal brazing material do not overlap and are applied. Therefore, a highly reliable ceramic circuit board can be provided in which cracks are not generated at the joining end between the ceramic substrate and the active metal brazing material, and the joining strength, thermal conductivity, and electrical insulation are not reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of an embodiment of a ceramic circuit board of the present invention.
FIG. 2 is a sectional view of the ceramic circuit board of FIG. 1;
FIG. 3 is a cross-sectional view of a conventional ceramic circuit board.
[Explanation of symbols]
1: ceramic substrate 2: metal circuit board 3: active metal brazing material 4: terminal portion 5: groove-shaped non-joining region A: joining end between ceramic substrate and active metal brazing material B: metal circuit board and active metal brazing material Junction end with

Claims (1)

A ceramic circuit board in which a metal circuit board made of copper or a copper alloy is joined to an upper surface of a ceramic substrate via an active metal brazing material, wherein the ceramic substrate has an upper surface immediately below an end of the active metal brazing material. A groove having an opening extending from a position opposed to a joint end between the metal circuit board and the active metal brazing material to a joint end between the ceramic substrate and the active metal brazing material present inside the joint end. A ceramic circuit board, wherein a non-joining region between the ceramic substrate and the active metal brazing material is provided along a joint end between the ceramic substrate and the active metal brazing material.

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