JP2003133673A - Ceramic circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ceramic circuit board in which metal circuit plates formed on both upper and lower surfaces of a ceramic board are connected electrically to each other with a metal column in the through-hole of the ceramic board, and which does not have cracks around the through-hole and has the high junction reliability between the metal circuit plates and the ceramic board and between the metal column and the circuit plates. SOLUTION: This ceramic circuit board has a metal column 5 in a through- hole 4 drilled in a ceramic board 1, first solder layers 2 formed on the upper and lower surfaces of the ceramic board 1 so as to be apart from the outer circumference of the through-hole 4 by a distance not less than 10 μm, metal circuit plates 3 which are bonded to both surfaces of ceramic board 1 with the solder layers 2 respectively so as to close the through-hole 4, and second solder layers 6 with which the metal column 5 and the metal circuit plates 3 are bonded to each other. As the satisfactory junctions between the metal circuit plates 3 and the ceramic board 1 and between the metal circuit plates 3 and the metal column 5 can be obtained, mounted electronic components such as semiconductor devices, etc., can be made to operate normally and stably.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic circuit in which metal circuit boards are attached to both sides of a ceramic substrate and they are connected by metal columns arranged inside the ceramic substrate. It relates to a substrate. 2. Description of the Related Art In recent years, as a circuit board such as a power module board or a switching module board, a metallized metal layer adhered on a ceramic substrate is coated with copper or the like via a brazing material such as a silver-copper alloy. Metal circuit board consisting of a metal circuit board made of copper or a metal circuit made of copper, etc. via an active metal brazing material obtained by adding titanium, zirconium, hafnium or a hydride thereof to a silver-copper eutectic alloy on a ceramic substrate A so-called DBC in which a ceramic circuit board in which plates are directly bonded, or a copper plate is placed on a ceramic substrate and heated to directly bond the ceramic substrate and the copper plate
A ceramic circuit board manufactured by a (Direct Bond Copper) method is used. In order to increase the mounting density of the metal circuit boards, the metal circuit boards are joined to the upper and lower surfaces of the ceramic substrate, and the upper and lower surfaces of the metal circuit boards are connected to the ceramic substrate. Electrical connection is performed by metal pillars arranged in the provided through holes. Incidentally, these ceramic circuit boards, for example, a ceramic circuit board in which a metal circuit board made of copper or the like is directly bonded on a ceramic substrate via an active metal brazing material,
In general, a ceramic substrate made of an electrically insulating ceramic material such as an aluminum oxide sintered body, an aluminum nitride sintered body, a silicon nitride sintered body, a mullite sintered body, and provided with a through hole penetrating in a thickness direction. Then, a metal pillar is arranged in the through hole of the ceramic substrate, and a brazing material paste obtained by adding an organic solvent or a solvent to silver brazing powder (alloy powder of silver and copper) is mixed with a metal brazing paste. A metal circuit board having a predetermined pattern formed by coating on both surfaces and sandwiching a brazing material such as an active metal wax obtained by adding titanium, zirconium, hafnium and at least one of these hydrides to a silver-copper alloy on a ceramic substrate. The metallized metal layer and the metal circuit board are activated by heating this to about 900 ° C in a reducing atmosphere to melt the brazing material paste and brazing material. Through the genus brazing material, and a metal circuit plate and the metal columns are manufactured by joining via the brazing material such as silver solder. [0005] The ceramic circuit board manufactured in this manner is an IGBT (Insulated Gate Bipolar Transistor).
And MOS-FET (Metal Oxide Semiconductor-Fiel
After electronic components such as a semiconductor element such as a d Effect Transistor) are mounted via an adhesive such as solder, external input / output terminals are assembled into a resin case integrally molded to form a semiconductor module. This semiconductor module is used in a wide range of applications from industrial equipment such as robots to drive units for electric trains and electric vehicles, and is required to have high reliability under severe environments. However, in the conventional ceramic circuit board, since the metal circuit board bonding brazing material is attached to the outer periphery of the through hole on the surface of the ceramic substrate to bond the metal circuit board, There was little space between the joint between the metal column and the metal circuit board to the joint between the ceramic substrate and the metal plate. Therefore, when a heat cycle is applied to the circuit board due to the heat history at the time of joining the metal circuit board or the heat generated during the operation of the semiconductor element after the joining or an environmental change, the difference between the thermal expansion of the metal pillar and the thermal expansion of the ceramic substrate causes The pillars dent or push up the upper and lower metal circuit boards, causing thermal stress.At this time, since the metal circuit board located between the joint with the metal pillar and the ceramic board is small, the metal circuit There is a problem that the amount of bending of the plate is small, thermal stress cannot be absorbed, and cracks are easily generated around the through hole of the ceramic substrate due to the thermal stress. To cope with this problem, even if a space is provided between the through hole and the metal column and the portion for absorbing the thermal stress of the metal circuit board is increased, the generation of cracks around the through hole of the ceramic substrate is prevented. In some cases, it could not be suppressed sufficiently. This is because the process of forming a through hole in a ceramic substrate is generally performed by punching in the state of a green sheet. At this time, micro cracks occur around the through hole, and even the substrate after firing is about 50 μm or less. This is considered to be because microcracks remain. That is, the microcracks are present in the portions where the thermal stress generated around the through-holes tends to be concentrated, and the microcracks start from the microcracks to generate the cracks. In the process of attaching the brazing material to the ceramic substrate, a method of applying a brazing material paste to the ceramic substrate by screen printing is usually used. The problem is that the brazing material paste is applied to the through-hole or the brazing material paste drips into the through-hole depending on the positional accuracy of the through-hole in the inside, the accuracy of screen printing, or the viscosity of the brazing-material paste. was there. When the brazing filler metal is heated and melted in such a state, the brazing filler metal and the brazing filler metal attached to the upper and lower surfaces of the metal columns are fused, and the original composition of each brazing filler metal is lost. And the electrical resistance of the brazing material increases. In addition, since the brazing material is interposed between the metal pillar and the inner wall of the through hole, the heat spreads the through hole due to the difference between the radial thermal expansion of the metal pillar and the thermal expansion of the through hole of the ceramic substrate. Stress is generated, and cracks and cracks are easily generated around the through holes of the ceramic substrate. Further, in the above-described punching step for forming the through hole, burrs are generated around the through hole, and the fired ceramic substrate may have a shape in which the periphery of the through hole is raised. is there. When the brazing material paste is applied to the outer periphery of the through hole in such a state, the brazing material paste is applied to the raised burrs, and when placing the metal circuit board on the applied brazing material paste, However, there is a problem that the metal circuit board hardly comes into contact with the brazing material other than the periphery of the through-hole, and voids are generated in the brazing material between the metal circuit board and the ceramic substrate, so that a bonding failure easily occurs. . With these problems, heat generated by a semiconductor element mounted on the metal circuit board cannot be dissipated due to a poor connection between the metal circuit board and the ceramic substrate, and the through-hole starts at the through hole. Cracks reduce the strength and dielectric strength characteristics of the ceramic circuit board, resulting in connection failure due to a change in the composition of the brazing material at the connection between the metal pillar and the metal circuit board, and heat generation at the connection due to an increase in electrical resistance. There has been a problem that electronic components such as semiconductor elements cannot be normally operated stably. The present invention has been devised in order to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a metal circuit board and a ceramic substrate which are free from cracks around through holes. It is an object of the present invention to provide a highly reliable ceramic circuit board having good bonding of a metal column and a metal column and a metal circuit board. According to the present invention, there is provided a ceramic circuit board in which metal pillars are arranged in the through holes of a ceramic substrate having a through hole, and the through holes are closed on both sides of the ceramic substrate. A metal circuit board is attached via a first brazing material, and the metal columns and the metal circuit board are joined via a second brazing material. It is characterized by being arranged at least 100 μm outside the outer periphery of the hole. According to the ceramic circuit board of the present invention, the first brazing material for joining the metal circuit board and the ceramic substrate is arranged at least 100 μm outside the outer periphery of the through hole of the ceramic substrate. The thermal stress due to the difference between the thermal expansion of the pillar and the thermal expansion of the ceramic substrate does not act on microcracks around the through holes of the ceramic substrate to cause cracks or cracks in the ceramic substrate. Since the brazing material does not hang down into the through-hole and fuses with the second brazing material for joining the metal circuit board and the metal pillar, the composition of the brazing material does not change.
It is possible to obtain a highly reliable ceramic circuit board which has good bonding between a metal circuit board and a ceramic substrate and between a metal circuit board and a metal column, and which can normally and stably operate electronic components such as mounted semiconductor elements. It becomes possible. Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a ceramic circuit board according to the present invention, wherein 1 is a ceramic board, 2 is a first brazing material, 3 is a metal circuit board, and 4 is a ceramic board 1. The through holes 5, 5 are metal columns, and 6 is a second brazing material. In this ceramic circuit board, a metal circuit board 3 having a predetermined pattern is formed on both upper and lower surfaces of a ceramic board 1 by a first brazing material 2.
At the same time, a metal column 5 is joined to the metal circuit board 3 via a second brazing material 6 in a through hole 4 provided in the ceramic substrate 1 and penetrating in the thickness direction. It is what is arranged. The metal pillars 5 arranged in the through holes 4 provided in the ceramic substrate 1 are joined at both ends to the metal circuit board 3 via the second brazing material 6, whereby the ceramic columns 1 The metal circuit boards 3 attached to the upper and lower surfaces are electrically connected via the metal columns 5 and the brazing material 6. The ceramic substrate 1 having the through holes 4 is made of an electrically insulating material such as an aluminum oxide sintered body, a mullite sintered body, a silicon nitride sintered body, an aluminum nitride sintered body, or a silicon carbide sintered body. Made of material. For example, in the case of a silicon nitride-based sintered body, an appropriate organic binder, a plasticizer, and a solvent are added to raw material powder such as silicon nitride, aluminum oxide, magnesium oxide, and yttrium oxide to form a slurry. A ceramic green sheet (green ceramic sheet) is formed by applying a well-known doctor blade method or calender roll method to the slurry, and then the ceramic green sheet is subjected to an appropriate punching process to obtain a predetermined shape. At the same time, if necessary, a plurality of sheets are laminated to form a molded body, and after that,
This is 1600-2000 in a non-oxidizing atmosphere such as a nitrogen atmosphere.
It is manufactured by firing at a temperature of ° C. The metal circuit board 3 is made of copper or aluminum. By applying a conventionally known metal working method such as a rolling method or a punching method to a copper or aluminum ingot, a predetermined thickness of, for example, 500 μm is obtained. Formed in a pattern. When the metal circuit board 3 is made of copper, it is preferable that the metal circuit board 3 is formed of oxygen-free copper. In particular, when the first brazing filler metal 2 is made of an active metal brazing filler metal, the oxygen-free copper is used when the surface of the copper is attached to the ceramic substrate 1 via the first brazing filler metal 2. Accordingly, the wettability with the active metal brazing material is improved without being oxidized, so that the joining of the metal circuit board 3 to the ceramic substrate 1 via the active metal brazing material becomes strong. Therefore, the metal circuit board 3
If it is made of copper, it is preferably formed of oxygen-free copper. If the metal pillar 5 is formed of a highly conductive copper (1.72 μΩ · cm) or aluminum (2.65 μΩ · cm) or the like having a very small specific resistance of 3 μΩ · cm or less, the metal pillar 5 Even if a large current flows, a large amount of heat due to Joule heat is not generated from the metal circuit board 3 / the metal pillar 5 and the connection portion thereof. As a result, an adhesive such as solder is used on the metal circuit board 3 An electronic component such as a semiconductor element to be bonded and fixed can always be kept at an appropriate temperature and can be normally and stably operated for a long period of time. When the metal column 5 is made of copper, it is preferable to form the metal column 5 from oxygen-free copper. this is,
In particular, when the first brazing material 2 is made of an active metal brazing material,
At the time of brazing, the surface of the metal circuit board 3 is not oxidized by oxygen present in the copper of the metal columns 5, so that the wettability with the first brazing material 2 is improved and the ceramic of the metal circuit board 3 is This is because bonding to the substrate 1 via the first brazing material 2 becomes strong. It is preferable that the length of the metal column 5 is shorter than the thickness of the ceramic substrate 1 by 0 to 150 μm.
If the metal column 5 is longer than the thickness of the ceramic substrate 1, the metal column 5 pushes up the metal circuit board 3 attached to the top and bottom, and the ceramic substrate 1 and the upper and lower metal circuit boards 3 are not joined well. I will. If the thickness is shorter than 150 μm with respect to the thickness of the ceramic substrate 1, it is necessary to apply a large amount of brazing material 6 to the metal column 5, which increases the cost and
When the brazing material 6 is heated and melted, the metal column 5 moves up and down or tilts, which tends to make it difficult to satisfactorily join the metal column 5 and the metal circuit board 3. The first brazing material 2 is an active metal brazing material when the metal circuit board 3 is directly brazed to the ceramic substrate 1 via the first brazing material 2. If the metal circuit board 3 is made of copper,
A material obtained by adding a metal such as titanium, zirconium, or hafnium or a hydride thereof to a silver-copper eutectic alloy in an amount of 2 to 5% by weight is used. If the metal circuit board 3 is made of aluminum, aluminum-silicon is used. A eutectic alloy to which a metal such as titanium, zirconium, or hafnium or a hydride thereof is added in an amount of 2 to 5% by weight is used. In the case where a metallized metal layer such as tungsten or molybdenum is previously deposited on the surface of the ceramic substrate 1 and the metal circuit board 3 is joined to the metallized metal layer via a brazing material, an active metal component is used. A silver brazing material or an aluminum brazing material that does not contain a metal such as titanium, zirconium, or hafnium or a hydride thereof is used. The second brazing material 6 is a silver brazing material made of a silver-copper eutectic alloy when the metal circuit board 3 is made of copper, and is used when the metal circuit board 3 is made of aluminum. An aluminum brazing material made of an aluminum-silicon eutectic alloy is used. The second brazing material 6 is arranged inside the through hole 4 and joins the metal column 5 and the metal circuit board 3, and is arranged separately from the first brazing material 2. In the ceramic circuit board of the present invention,
It is important that the first brazing material 2 is arranged at least 100 μm outside the outer periphery of the through hole 4. This is because a microcrack of about 50 μm or less exists around the through hole 4 of the ceramic substrate 1. When the first brazing material 2 is arranged at an inner side of 100 μm from the outer periphery of the through hole 4, the thermal stress caused by the difference between the coefficient of thermal expansion of the ceramic substrate 1 and the coefficient of thermal expansion of the metal pillar 5 causes the thermal stress around the through hole 4. This is because the thermal stress acts on the microcracks, and the microcracks start from the microcracks, thereby causing cracks and cracks. Therefore, the first brazing filler metal 2 is formed so that thermal stress does not act on the microcracks.
It is important that the metal is arranged outside the outer periphery of the through hole 4 by 100 μm or more. Further, by arranging the first brazing material 2 at least 100 μm outside the outer periphery of the through hole 4, the brazing material paste made of the first brazing material 2 is applied to the ceramic substrate 1 by screen printing. Can be prevented from dripping into the through-hole 4 of the brazing material paste. Further, when there is a burr generated by punching the green sheet in the vicinity of the through-hole 4 of the ceramic substrate 1, this portion is removed. Since the first brazing material 2 is applied while avoiding the above, it is possible to prevent the occurrence of a bonding failure having defects such as voids between the metal circuit board 3 and the paste of the first brazing material 2. It becomes possible. The width of the space between the inner wall surface of the through hole 4 and the outer wall surface of the metal column 5 (corresponding to the difference between the radius of the through hole 4 and the radius of the metal column 5) is in the range of 30 to 200 μm. Preferably. This is because when the width of this space is less than 30 μm, when the ceramic circuit board is heated, the outer wall surface of the metal column 5 expanded by the difference in the coefficient of thermal expansion between the ceramic substrate 1 and the metal column 5 becomes ceramic. It is difficult to reliably absorb the attempt to expand the inner wall surface of the through hole 4 of the substrate 1 in the space between the inner wall surface of the through hole 4 of the ceramic substrate 1 and the outer wall surface of the metal column 5, This is because the outer wall surface of the metal column 5 pushes and expands the inner wall surface of the through hole 4 of the ceramic substrate 1, which may cause cracks and cracks in the ceramic substrate 1. Also, if the length of this space is 20
If the thickness exceeds 0 μm, the metal column 5 with the brazing material 6 is inclined when the metal column 5 with the brazing material 6 is inserted into the through hole 4 of the ceramic substrate 1, and the metal circuit board 3 is attached to the ceramic substrate 1.
This is because it may not be possible to surely join the semiconductor device. The attachment of the metal circuit board 3 to the ceramic substrate 1 having the through holes 4 using the first brazing material 2 may be performed as follows. First, for example, the metal circuit board 3 is made of copper,
When the first brazing material 2 is made of an active metal brazing material, an organic solvent is prepared by adding a metal such as titanium, zirconium or hafnium or a hydride thereof to a silver-copper eutectic alloy in an amount of 2 to 5% by weight. A solvent is mixed to form a first brazing material paste, and then the first brazing material paste is applied to the upper and lower surfaces of the ceramic substrate 1 by a conventionally well-known screen printing method to a thickness of about 10 to 40 μm. Is printed and applied in a predetermined pattern. Next, the metal columns 5 with the second brazing material 6 are inserted and arranged in the through holes 4 of the ceramic substrate 1, and the first brazing material paste printed and coated on both upper and lower surfaces of the ceramic substrate 1 is formed. Place the metal circuit board 3 on the
This was heat-treated at a predetermined temperature (about 900 ° C. in the case of copper) in a vacuum or in a neutral or reducing atmosphere, and was applied to both end surfaces of the first brazing material paste and the metal column with the brazing material. The brazing material 6 is melted, and the ceramic substrate 1 and the metal circuit board 3 are joined with the molten first brazing material 2, and the metal circuit board 3 and the metal pillar 5 are joined with the second brazing material 6. In the above-described manufacturing method, the metal column 5 with the second brazing material 6 has a thickness of 0 with respect to the thickness of the ceramic substrate 1.
Preferably, the second brazing material 6 is applied to both ends of the metal pillar 5 that is shorter by 150 μm and is longer by 40 to 140 μm than the thickness of the ceramic substrate 1. This is because if the length of the metal column 5 is shorter than the thickness of the ceramic substrate 1 by 0 to 150 μm, as described above, the metal circuit board 3 on which the metal column 5 is vertically mounted does not push up, and the ceramic substrate 1 Because it does not impair the good bonding between the metal circuit board 3 and the metal circuit board 3 on both sides thereof.
The length of the metal column 5 with the brazing material 6 is
If the thickness is 40 to 140 μm longer than the thickness, the brazing material 6 at both ends thereof surely comes into contact with the upper and lower metal circuit boards 3, and the metal pillar 5 and the metal circuit board 3 intervene via the brazing material 6 in a subsequent melting step. This is because a reliable and reliable electrical connection can be obtained. The metal column 5 with the brazing material 6 is formed in a cylindrical shape by subjecting a copper or aluminum ingot (lumps) to a conventionally known metal working method such as a rolling method, a punching method, or a drawing method. Then, a metal pillar 5 is produced, and thereafter, a silver brazing material in the case of copper and an aluminum brazing material in the case of aluminum are applied to the upper and lower end surfaces of the metal pillar 5. As another method, a metal material such as a punching method or a drawing method is applied to a material obtained by laminating a brazing material / a copper plate or an aluminum plate / a brazing material in order and rolling the material to a predetermined thickness. There is a method of producing the same. EXAMPLES Hereinafter, the ceramic circuit board of the present invention will be described in detail with reference to test results of Examples and Comparative Examples, but the present invention is not limited to only the following Examples. First, an aluminum nitride green sheet having a through-hole formed by punching is laminated and fired at a temperature of about 1800 ° C. in a nitrogen atmosphere to obtain a diameter 2 mm.
A ceramic substrate of an aluminum nitride sintered body having a thickness of 0.635 mm and having 20 through-holes of 20 mm was obtained. A first brazing material paste prepared by mixing an organic solvent and a solvent with a material obtained by adding 3% by weight of titanium hydride to a silver-copper eutectic alloy was applied to both surfaces of the aluminum nitride substrate by screen printing. . At this time, the distance from the outer periphery of the through hole of the first brazing material paste pattern is 0 μm, 30 μm, 70 μm.
m, 100 μm were prepared. At this time, when the distance from the outer periphery of the through hole was 0 μm or 30 μm, most of the first brazing material paste dripped into the through hole, but when the distance was 70 μm and 100 μm, there was no dripping. . Next, a metal column on which a silver-copper eutectic alloy is pre-coated as a second brazing material is inserted into the through hole, and a 0.3 mm-thick circuit pattern made of oxygen-free copper is punched out in advance. The processed metal circuit board was placed with a ceramic substrate interposed therebetween so as to cover the through hole. 1.8 m diameter metal columns
m, length 0.635mm, length including second brazing material 0.6
An 85 mm one was used. Finally, the first brazing material paste and the second brazing material are heated in a vacuum to a temperature of about 900 ° C. to melt the metal circuit board and the ceramic substrate, and the metal circuit board and the metal The ceramic circuit board was obtained by joining the pillars. The obtained ceramic circuit board has a temperature of -40 ° C. /
The sample was put into a temperature cycle test at + 125 ° C., and evaluated by observing the cross section of the periphery of the through hole before (initial) and after 1000 cycles of the temperature cycle test. As a result of the evaluation, first, cracks were observed in the periphery of the through hole in the cases where the distance from the outer periphery of the through hole was 0 μm and 30 μm. This is presumably because the thermal stress generated at the time of cooling from the heating state during the production of the ceramic circuit board acted on microcracks around the through-holes, resulting in large cracks. After the temperature cycle test, the narrow portion of the metal circuit board was easily peeled off from the ceramic substrate due to the larger crack. When the distance from the outer periphery of the through hole was 70 μm, cracks were not observed around the through hole in the initial stage, but cracks were observed around the through hole after the temperature cycle test. This is because the connection between the metal circuit board and the ceramic substrate does not exist in the region where the microcrack of about 50 μm or less exists from the outer periphery of the through hole. Although it did not lead to a crack growing into a large crack,
It is considered that a large crack was caused by the repeated thermal stress in the temperature cycle test. In addition,
When the distance from the outer periphery of the through hole was 100 μm, no crack was observed around the through hole even at the initial stage and after the temperature cycle test. From the above results, it can be seen that the first brazing material for joining the metal circuit board and the ceramic substrate is more than 10 mm from the outer periphery of the through hole.
By adopting a structure arranged outside by 0 μm or more,
Even in reliability tests such as temperature cycle tests, cracks and cracks do not occur around the through holes of the ceramic circuit board, and as a result, it has excellent dielectric strength characteristics, high mechanical strength, and It was confirmed that a ceramic circuit board having high bonding reliability was obtained. The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the metal circuit board 3 is directly brazed to the ceramic substrate 1 via the active metal brazing material 2. However, the metal circuit board 3 is preliminarily formed on the surface of the ceramic substrate 1 such as tungsten or molybdenum. The metal circuit board 3 may be bonded to the metallized metal layer via a brazing material. In the above-described embodiment, the metal circuit board 3 previously formed in a circuit wiring pattern shape is brazed to the ceramic substrate 1 via the first brazing material 2 made of an active metal brazing material. Alternatively, a metal plate having substantially the same shape as the ceramic substrate 1 may be brazed, and unnecessary metal portions may be removed by etching to form a circuit wiring pattern, thereby forming the metal circuit plate 3. Furthermore, in the example of the above-described embodiment, the metal column 5 with the second brazing material 6 is inserted and arranged in the through hole 4 of the ceramic substrate 1. A method of applying a brazing material paste to both upper and lower surfaces thereof may be adopted. According to the ceramic circuit board of the present invention,
The first brazing material for joining the metal circuit board and the ceramic substrate is 100 μm from the outer periphery of the through hole of the ceramic substrate.
Due to the arrangement above, the thermal stress due to the difference between the thermal expansion of the metal pillar and the thermal expansion of the ceramic substrate acts on the microcracks around the through holes of the ceramic substrate, which can cause cracks and cracks in the ceramic substrate. In the manufacturing process, the first brazing material hangs down in the through-hole, and is fused with the second brazing material for joining the metal circuit board and the metal pillar, and the composition of the brazing material changes. Since there is no,
It is possible to obtain a highly reliable ceramic circuit board that has good bonding between a metal circuit board and a ceramic substrate and between a metal circuit board and a metal column and that can normally and stably operate electronic components such as mounted semiconductor elements. It becomes possible.

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. [Description of Signs] 1... Ceramic substrate 2... First brazing material 3... Metal circuit board 4. 2 brazing materials

Claims (1)

Claims: 1. A metal pillar is disposed in a through hole of a ceramic substrate having a through hole, and a first brazing material is interposed on both surfaces of the ceramic substrate so as to cover the through hole. The metal column and the metal circuit board are joined via a second brazing material.
Wherein the brazing material is disposed at least 100 μm outside the outer periphery of the through hole.