JPH08250823A - Ceramic circuit board - Google Patents

Abstract

PURPOSE: To provide a highly reliable ceramic circuit board which can effectively prevent the occurrence of cracks and strength drops in the circuit board even when a cryogenic cycle is applied to it and can prevent the deformation of metallic plates even when it is subjected to inexpensive machining which is profitable when the manufacturing process is taken into consideration. CONSTITUTION: A ceramic circuit board is constituted by sticking such metallic plates as copper plates 2 and 3, etc., to both surfaces of a ceramic substrate 1 by using a direct sticking method, an active metal method, etc. In the outer peripheral section of the circuit board on the surface opposite to the surface to which the copper plate 2 is stuck, a plurality of holes 7 are formed in lines at prescribed intervals along the outer periphery.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic circuit board having improved reliability with respect to the addition of a cooling / heating cycle.

[0002]

2. Description of the Related Art In recent years, a ceramic circuit board in which a metal plate such as a copper plate is joined to a ceramic substrate has been used as a mounting substrate for semiconductor components such as power transistor modules and switching power supply modules that handle relatively high power. There is.

As a method of manufacturing a ceramics circuit board as described above, that is, a method of joining a ceramics board and a metal plate, an active metal such as Ti, Zr, Hf or Nb is added to an Ag-Cu brazing material or the like in an amount of 1 to 10%. A method using an active metal brazing material with a certain amount of addition (active metal method) or oxygen as a metal plate at 100 to 1000 p
Known is a so-called DBC method (direct bonding copper method) in which a ceramic substrate and a copper plate are directly joined using tough pitch electrolytic copper containing about pm or copper whose surface is oxidized by about 1 to 10 μm.

In the DBC method, for example, a copper circuit board having a thickness of 0.3 mm to 0.5 mm punched into a predetermined shape is first made of an aluminum oxide sintered body, an aluminum nitride sintered body or the like having a thickness of 0.6 to 1.0 mm. After being placed in contact with the ceramics substrate and heated, a eutectic liquid phase of Cu-Cu ₂ O is generated at the bonding interface, and after wetting the surface of the ceramics substrate with this liquid phase,
The ceramic substrate and the copper circuit board are joined by cooling and solidifying the liquid phase. The ceramic circuit board to which such a DBC method is applied has a high bonding strength between the ceramic substrate and the copper circuit board, and has a simple structure that does not require a metallization layer or a brazing material layer, so that it can be miniaturized and highly mounted. It has advantages and can shorten the manufacturing process.

By the way, in the ceramic circuit board in which the metal plate is joined to the ceramic substrate by the above-mentioned DBC method or active metal method, the thickness of the metal plate is thickened to 0.3 to 0.5 mm so that a large current can flow. Therefore, there is a problem in that reliability with respect to thermal history is poor. That is, when a ceramic substrate and a metal plate having a large coefficient of thermal expansion are bonded to each other, a thermal stress due to the thermal expansion difference is generated due to the cooling process after bonding and the addition of a cooling / heating cycle. This stress exists as a residual stress distribution of compression and tension on the ceramics substrate side near the joint, and the principal stress of residual stress acts on the ceramics portion particularly near the outer peripheral end of the metal plate. This residual stress causes cracks in the ceramic substrate or causes the peeling of the metal plate.
Even if the ceramic substrate does not crack,
This has the adverse effect of reducing the strength of the ceramic substrate.

Among the above-mentioned residual stresses, those due to the thermal stress generated in the cooling process after joining the metal plates can be reduced to some extent by adjusting the cooling rate, but the heat generated from the mounted parts in actual use The residual stress caused by the thermal stress due to the above cannot be reduced under external conditions, and is a serious problem.

For this reason, the ceramic circuit board as described above is usually the same as the front surface of the ceramic board, that is, the same as the mounting portion of the semiconductor component, or 5
~ 30% thin metal plates are joined to prevent warpage of the ceramic circuit board, but the problem of residual stress has not been fundamentally solved.

As a measure against the above-mentioned problems due to thermal stress and residual stress, that is, reduction of joint strength and occurrence of cracks, for example, Japanese Patent Publication No. 5-25397 discloses a peripheral edge of a copper plate as a metal plate. It is described that the portion has a thin shape (thin portion), specifically, the outer peripheral end has a stepped shape or a tapered shape. Further, JP-A-3-145748 discloses that a groove is formed inside along the outer peripheral edge of a metal plate. As a result, the stress concentrated on the outer peripheral edge of the metal plate is dispersed in the groove, thereby preventing a decrease in bonding strength and the occurrence of cracks.

[0009]

However, among the techniques for improving the reliability against the thermal history in the above-mentioned conventional ceramic circuit board, the technique disclosed in Japanese Patent Publication No. 5-25397 discloses a metal plate outer peripheral end portion. Since the thin portion is formed by etching or the like at the same time when the circuit pattern is formed, the manufacturing process becomes complicated and the number of manufacturing steps is increased.

Further, in Japanese Patent Laid-Open No. 3-145748,
Similarly, it is mainly described that a groove along the outer peripheral edge of the metal plate is formed by an etching method. According to the etching method, the groove can be formed at the same time when the circuit pattern is formed, but as described above, the etching method has a problem that the process is complicated and the number of manufacturing steps is increased.
Furthermore, although it has been shown that the groove is formed by machining using a mold or the like, when the groove is formed over the entire inner circumference of the outer peripheral edge portion of the metal plate by the method by this machining, the groove is formed by pressing or the like. However, the strength of the formed portion is significantly lower than that of other portions, and the metal plate itself is prone to deformation such as warpage. This deformation of the metal plate causes a decrease in the bonding strength of the metal plate.

From the above, by adding a cooling process or a thermal cycle after joining the metal plates, the thermal stress and residual stress generated in the metal plates are dispersed and alleviated, and the generation of cracks and the reduction in strength of the ceramic substrate are effectively performed. There is a strong demand for a technique capable of preventing the deformation of the metal plate by machining which can prevent the manufacturing process and simplify the manufacturing process.

The present invention has been made to solve such a problem, and even in the case where a cooling / heating cycle is added, the outer circumference of the metal plate is dispersed by dispersing the thermal stress and residual stress generated in the metal plate. Relaxes stress concentration on the edge,
Provided is a ceramic circuit board excellent in reliability and manufacturability, which can effectively prevent cracking and strength reduction of the ceramic board, and can prevent deformation of the metal plate even by machining which is advantageous in the manufacturing process. Is intended.

[0013]

A ceramic circuit board of the present invention is a ceramic circuit board comprising a ceramic substrate and a metal plate bonded to at least the surface of the ceramic substrate as described in claim 1. A plurality of holes are formed inside the outer peripheral edge of the metal plate on the side opposite to the surface to be joined to the ceramics substrate.

According to another aspect of the present invention, there is provided a ceramic circuit board comprising:
In a ceramic circuit board comprising metal plates bonded to both front and back surfaces of the ceramic substrate, a plurality of metal plates are provided inside the outer peripheral edge of the metal plates on both front and back surfaces opposite to the bonding surface with the ceramic substrate. Is characterized in that the holes are formed.

Here, the inside of the outer peripheral edge portion of the metal plate refers to FIG.
As shown in, the width w of the metal plate is used as a reference, and is defined as a portion within 1/3 of the width w of the metal plate from the outer peripheral portion toward the center. That is, with the width w of the metal plate as a reference, the part within 1/3 on both sides from the outer peripheral edge portion not including the outer peripheral edge portion to the inner side is the inner peripheral edge portion, and 1/3 of the width w of the central metal plate Is the central portion (in FIG. 9, the inside of the outer peripheral edge portion is indicated by diagonal lines).

Further, in the present invention, it is preferable that the plurality of holes are formed in all the metal plates bonded on the ceramic substrate, but the plurality of holes are formed in at least one metal plate. If so, it is included in the present invention.

As a preferred form of the above-mentioned ceramic circuit board of the present invention, as described in claim 2, the plurality of holes are formed linearly along the outer peripheral edge of the metal plate. As described in claim 3, the plurality of holes are non-through holes, as described in claim 4, the plurality of holes are through holes, and as described in claim 5. The plurality of holes are holes formed by press molding, the shortest distance between the adjacent holes is L ₁ , and the center-to-center distance between the adjacent holes is L ₂ as described in claim 6. When, 1 / 5L ₂ ≦ L ₁ ≦ 1 / 2L ₂
There is a form that satisfies.

[0018]

In the ceramic circuit board of the present invention, a plurality of holes are formed inside the outer peripheral edge of the metal plate opposite to the bonding surface. Here, the thermal stress generated in the cooling process after joining the metal plates, the thermal stress due to the addition of the thermal cycle, and the residual stress based on them are dispersed by the plurality of holes provided inside the outer peripheral edge of the metal plate. Therefore, stress concentration on the outer peripheral edge of the metal plate is relieved. As a result, the stress value itself at the outer peripheral edge of the metal plate is reduced, so that it is possible to effectively prevent the occurrence of cracks and the reduction in strength of the ceramic substrate, which have been problems in the past. Further, in the present invention, since the above-described stress distribution is achieved by a plurality of holes, the strength-reduced portion (thin portion) of the metal plate becomes discontinuous, so that the metal plate itself may be deformed during machining. It is possible to effectively prevent warpage and the like from occurring. Therefore, it becomes possible to practically form the stress distribution site (hole) by mechanical processing such as press working, and effectively prevent the metal plate itself from being deformed or warped due to press working. It becomes possible to do.

[0019]

EXAMPLES Next, examples of the present invention will be described.

FIG. 1 is a plan view showing the structure of a ceramics circuit board according to an embodiment of the present invention. In the figure, 1 is a ceramic substrate, and a copper plate 2 as a metal plate is bonded to a surface 1a of the ceramic substrate 1. A copper plate 3 is also bonded to the back surface 1b of the ceramics substrate 1 in the same manner, and a ceramics circuit board 4 is constituted by these.

Here, as the ceramic substrate 1, an aluminum oxide sintered body or a mullite sintered body (3Al ₂ O) is used.
₃ -2SiO ₂₎ oxide-based sintered body such as aluminum nitride sintered body, to non-oxide sintered body such as silicon nitride sintered body, the use of substrates made of various ceramics sintered body It is possible to select and use it appropriately according to the intended use and required characteristics. When using a non-oxide type sintered body, it may be preferable to use it after forming an oxide layer on the surface.

The ceramic circuit board 4 shown in FIG.
The copper plates 2 and 3 are bonded to the ceramic substrate 1 by a direct bonding method, a so-called DBC method. As the copper plates 2 and 3 in the case of using such a DBC method, it is preferable to use copper containing oxygen in a ratio of 100 to 3000 ppm such as tough pitch copper, but oxygen-free copper is used depending on the conditions at the time of joining. It is also possible to use. In addition,
Instead of a single plate of copper or copper alloy, a clad plate with another metal member whose bonding surface with the ceramics substrate 1 is made of at least copper can be used.

The copper plate 2 bonded to the front surface 1a side of the ceramic substrate 1 serves as a mounting portion for semiconductor parts and the like, and is patterned into a desired circuit shape. Also,
Copper plate 3 bonded to the back surface 1b side of the ceramics substrate 1
Is to prevent warpage of the ceramics substrate 1 at the time of bonding, and is formed on almost the entire back surface 1b of the ceramics substrate 1 in a state of being divided into two from the vicinity of the center.
The copper plate 3 on the back surface side may have the same thickness as the copper plate 2 which is a mounting part for semiconductor components or the like, but a copper plate having a thickness of 70 to 90% of the thickness of the copper plate 2 is used. It is preferable.

Here, the ceramic circuit board 4 shown in FIG. 1 is one in which copper plates 2 and 3 are bonded to the ceramic substrate 1 by the DBC method. For example, as shown in FIG.
It may be a ceramic circuit board 5 in which the copper plates 2 and 3 are bonded to the ceramic substrate 1 by the active metal method. The above-mentioned active metal method uses the brazing material containing at least one active metal selected from Ti, Zr, Hf, Nb, etc. (hereinafter, referred to as active metal-containing brazing material) layer 6 and the ceramic substrate 1 via the brazing material layer 6. This is a method of joining the copper plates 2 and 3. The brazing filler metal used is, for example, an Ag-Cu eutectic composition (72 wt% Ag-28 wt% Cu) or a composition in the vicinity thereof, which is mainly composed of an Ag-Cu brazing filler metal or a Cu brazing filler metal. Examples thereof include a composition containing at least one selected from the group consisting of Al, Zr, Hf, Nb and the like (active metal). A low melting point metal such as In may be added to the brazing filler metal containing active metal.

The ceramic circuit board 4 shown in FIG. 1 in which the copper plates 2 and 3 are bonded to the ceramic board 1 by the DBC method has a simple structure and high bonding strength, and the manufacturing process can be simplified. And so on. Further, in the case where the copper plates 2 and 3 are joined to the ceramic substrate 1 by the active metal method as in the ceramic circuit board 5 shown in FIG. 2, a high bonding strength is obtained and the active metal-containing brazing material layer 6 is stressed. Since it also functions as a relaxation layer, the reliability can be further improved. From these reasons, it is preferable to select the joining method according to the required characteristics and the application.

When the metal plates (2, 3) are joined to the ceramic substrate 1 by the active metal method, not only copper plates but also various metal plates such as nickel plate, tungsten plate, molybdenum plate are used depending on the application. It is also possible to use these alloy plates and clad plates (including clad plates with copper plates).

In the ceramic circuit boards 4 and 5 described above, as shown in FIGS. 3 and 4, along the outer peripheral edge of the copper plate 2 which is a mounting portion for semiconductor components, that is, each circuit of the copper plate 2 is formed. A plurality of holes 7 are formed inside the pattern portion along the outer peripheral edge portion. The cross-sectional shape of the plurality of holes 7 may be circular as shown in FIG. 3 or rectangular as shown in FIG. Further, the plurality of holes 7 are preferably formed by press working using a mold in order to avoid complication of the manufacturing process and reduce the number of manufacturing steps. However, the application of other forming methods is not necessarily excluded.

The plurality of holes 7 described above are preferably formed linearly at predetermined intervals along the outer peripheral edge of each circuit pattern portion of the copper plate 2. By thus forming the plurality of holes 7 in a linear shape, stress concentration on the outer peripheral end of the copper plate 2 can be effectively relaxed, in other words, stress can be efficiently dispersed. The size of the holes 7 depends on the cross-sectional shape thereof, the size of the copper plate 2, and the interval between the holes 7 to be described later. For example, in the case of a circular shape as shown in FIG. 3, the diameter is 0.1 to 1.0. mm is preferable. If the size of the hole 7 is less than 0.1 mm, the stress may not be sufficiently dispersed, and if it exceeds 1.0 mm, the strength of the copper plate 2 is likely to be reduced and the mounting area is reduced. A more preferable range is 0.3 to 0.7 mm for the same reason. When forming the rectangular hole 7, it is preferable that the length of the long side is set to the above-described size.

Further, the plurality of holes 7 linearly arranged are
1 / 5L ₂ ≤L ₁ ≤1 / 2L, where L _{1 is} the shortest distance between adjacent holes 7 and L ₂ is the distance between the centers of adjacent holes 7.
It is preferable to form so as to satisfy ₂ . If the formation interval of the holes 7 (the shortest distance L ₁ between the adjacent holes 7) is too large, specifically L ₁ > 1 / 2L ₂ , the stress relaxation effect may not be sufficiently obtained. On the other hand, if the formation interval of the holes 7 is too small, specifically L ₁ > 1/5
When L ₂ is set, for example, when a plurality of holes 7 are formed by press working as described above, there is a possibility that strength reduction inside the outer peripheral edge portion (hole forming portion) of the copper plate (metal plate) 2 cannot be sufficiently suppressed. is there. As a result, the copper plate 2 may be deformed and the bonding strength of the copper plate 2 may be reduced.

The plurality of holes 7 described above may be non-through holes 7A as shown in FIGS. 5 and 6, or may be through holes 7B as shown in FIG. For example, non-through hole 7
Since A can be easily formed by press working or the like, it is effective in reducing the number of manufacturing steps and the like, and the through hole 7B is effective for reducing oxygen such as gasified gas that does not contribute to bonding when the DBC method is applied. It also functions as a discharge hole and is effective in further increasing the uniformity of the joined state by preventing swelling.
As described above, since the non-through holes 7A and the through holes 7B have different effectiveness in addition to the stress dispersion / relaxation effect, it is preferable to appropriately select them depending on the joining method, the application, and the like.

Here, when the plurality of holes 7 are non-through holes 7A, the shape in the depth direction may be a substantially uniform shape as shown in FIG. 5 or an inverted conical shape as shown in FIG. It may have a shape (or an inverted pyramid shape). However, its depth d
Is preferably 1/3 to 2/3 of the thickness t of the copper plate 2.
If the depth of the non-through hole 7 is less than 1/3 of the thickness t of the copper plate 2, the stress dispersion effect may be insufficient.

Further, the formation position of the plurality of holes 7, that is, the shortest distance L ₃ from the outer peripheral edge portion of the copper plate 2 to the hole 7 is the copper plate 2
The thickness is preferably 0.3 to 1.0 mm, though it depends on the thickness and size of the material.

The copper plate 2 bonded to the front surface 1a of the ceramics substrate 1 which is a mounting portion for semiconductor components and the like has been described above in detail, but the copper plate 3 bonded to the back surface 1b of the ceramics substrate 1 is described.
As for the copper plate 2 on the front surface side as well, it is preferable to form a plurality of holes 7 inside the outer peripheral edge portion. In particular, when a relatively thick copper plate (metal plate) is used from the viewpoint of heat dissipation, it is desirable to form a plurality of holes 7 also in the copper plate 3 on the back surface side. The shapes and intervals of the holes 7 formed in the copper plate 3 on the back surface side are similar to those of the holes 7 formed in the copper plate 2 on the front surface side.

Ceramic circuit board 4 as described above
Is manufactured, for example, as follows. That is, while processing an oxygen-containing copper plate such as tough pitch copper into a predetermined shape (circuit pattern shape for the copper plate 2),
A plurality of holes 7, for example, are formed linearly inside the outer peripheral edge portion by pressing or the like. Such copper plates 2 and 3 having a plurality of holes 7 are arranged in contact with each other on a ceramic substrate, and the eutectic temperature of copper and copper oxide (13
The ceramic circuit board 4 is manufactured by heating at a temperature of 38 K) or higher. The atmosphere during this heating is preferably an inert gas atmosphere when an oxygen-containing copper plate is used as the copper plate.

The ceramic circuit board 5 is manufactured, for example, as follows. First, similar to the ceramic circuit board 4, copper plates 2 and 3 having a plurality of holes 7 are prepared. On the other hand, a paste of the active metal-containing brazing material as described above is applied to, for example, the ceramic substrate 1 side. The coating thickness of the brazing material layer is preferably set so that the layer thickness of the brazing material layer after heating and joining does not become too large in order to improve the cold cycle characteristics. Next, the copper plates 2 and 3 are laminated on the ceramic substrate coated with the brazing material paste, and heat-treated at a temperature according to the brazing material used, whereby the ceramic circuit board 5 is manufactured.

In the ceramic circuit boards 4 and 5 having the above-described structure, thermal stress generated in the cooling process after joining the copper plates 2 and 3 and thermal stress due to the addition of a cooling / heating cycle,
And the residual stress based on them is dispersed by the plurality of holes 7 provided inside the outer peripheral edge portions of the copper plates 2 and 3,
The stress concentration on the outer peripheral end portions of 3 is relaxed. As a result, the stress value itself at the outer peripheral ends of the copper plates 2 and 3 is reduced, so that it is possible to effectively prevent the occurrence of cracks and the reduction in strength of the ceramic substrate 1 which have been problems in the past. Since the above-described stress distribution is achieved by the plurality of holes 7, the strength-reduced portions of the copper plates 2 and 3 are discontinuous along the outer peripheral edge portion thereof. Therefore, even if mechanical processing such as press working is applied to the formation of the plurality of holes 7, the copper plates 2 and 3 themselves are not deformed or warped. Without inviting, the simplification of the manufacturing process and the reduction of the manufacturing man-hour can be realized.

Next, a concrete example of the above-mentioned embodiment and its evaluation result will be described.

Example 1 First, a 0.7 mm thick aluminum nitride substrate having a 4 μm thick oxide layer on its surface as a ceramic substrate 1 and a plurality of holes 7 were formed along the outer peripheral edge thereof by pressing. , And copper plates 2 and 3 of a predetermined shape made of tough pitch copper (oxygen content: 300 ppm) were prepared. The shape of the hole 7 is shown in FIG.
And the circular shape shown in Fig. 5 (diameter = 0.6 mm, depth = 0.2 mm)
And In addition, the formation intervals of the plurality of holes 7 are set such that
The shortest distance L ₁ between them was 0.25 mm (= 1/2 L ₂ ), and the formation position was such that the distance L ₃ from the copper plates 2 and ₃ was 0.5 mm.

Then, as shown in FIG. 1, two copper plates 2 and 3 are directly placed on both surfaces of the aluminum nitride substrate 1 and heated in a nitrogen gas atmosphere under the condition of 1348K to bond them. The target ceramics circuit board 4 was obtained.

A thermal cycle test (TCT: 233K × 30 minutes + RT × 10 minutes + 398K) was performed on the ceramic circuit board 4 thus obtained.
X 30 minutes is defined as one cycle), and the stress distribution at the time of applying this thermal cycle was measured. FIG. 8 shows the result. The comparative example (shown by the one-dot chain line) in FIG.
Example 1 above except that a copper plate having no holes 7 is used.
For the ceramic circuit board manufactured under the same conditions as
It is a measurement result of stress distribution when a heat cycle is added under the same conditions.

As is apparent from FIG. 8, by forming a plurality of holes 7 along the outer peripheral edges of the copper plates 2 and 3, the stress at the time of applying the cooling / heating cycle is dispersed by the holes 7 and the stress at the outer peripheral edge is increased. Is clearly reduced as compared with the comparative example not having the plurality of holes 7. This makes it possible to prevent the occurrence of cracks in the aluminum nitride substrate 1 and the reduction in strength thereof. By the way, in the ceramic circuit board of Example 1, almost no cracks were generated even after 200 cycles of TCT (cracking occurred at 3%), whereas the ceramic circuit board of the comparative example was aluminum nitride after 200 cycles. 35% of the substrates 1 were cracked.

Further, while the copper plates 2 and 3 having the plurality of holes 7 formed by the press work did not warp or deform during the press work, similarly, the copper plates 2 and 3 were formed along the outer peripheral edge portion of the copper plate by the press work. In a copper plate having grooves formed all around, warping or deformation may occur at the outer peripheral edge of the copper plate during press working. Further, even in the case of a copper plate which is not much deformed during press working, deformation was caused during heat bonding with an aluminum nitride substrate and during cooling. Example 2 Ceramic substrate 1 having a thickness having an oxide layer on its surface
A 0.6 mm aluminum nitride substrate and 0.3 mm thick copper plates 2 and 3 having a predetermined shape in which a plurality of holes 7 were formed by pressing along the outer peripheral edge portion were prepared. The shape of the plurality of holes 7 is the through hole (diameter = 0.5 mm) shown in FIGS. 3 and 7. Further, the formation interval of the plurality of holes 7 is such that the shortest distance L ₁ between the adjacent holes 7 is 0.25 mm (= 1 / 2L ₂ ), and the formation position is such that the distance L ₃ from the copper plates 2 and ₃ is 0.5 mm. I tried to be.

Then, as shown in FIG. 2, In: Ag: Cu: Ti = 14.0: 59.0: 23.0: on both surfaces of the aluminum nitride substrate 1.
A paste of active metal-containing brazing filler metal having a composition of 4.0 is applied, and copper plates 2 and 3 are laminated and arranged through this coating layer, and then heated in a nitrogen gas atmosphere to be joined to obtain a desired ceramic. The circuit board 5 was obtained.

A thermal cycle test was carried out on the ceramic circuit board 5 thus obtained under the same conditions as in Example 1, and good results similar to those in Example 1 were obtained.
It was confirmed that the reliability of the thermal cycle was excellent.
Further, the strength was the same after the plurality of holes 7 were formed in the copper plates 2 and 3 by press working.

[0045]

As described above, according to the ceramic circuit board of the present invention, the thermal stress and the residual stress generated in the metal plate are dispersed by the plurality of holes even when the cooling / heating cycle is applied. The stress concentration on the outer peripheral edge of the metal plate can be relieved, and the deformation of the metal plate can be prevented by the machining which is advantageous in the manufacturing process. Therefore, while simplifying the manufacturing process and reducing the number of manufacturing steps, it is possible to effectively prevent the occurrence of cracks and the reduction in strength of the ceramic substrate due to the addition of a cooling / heating cycle, etc. It becomes possible to provide.

[Brief description of drawings]

1A and 1B are views showing a structure of a ceramics circuit board according to an embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a sectional view thereof.

FIG. 2 is a sectional view showing a structure of a ceramics circuit board according to another embodiment of the present invention.

FIG. 3 is a diagram showing an example of shapes of a plurality of holes and a preferable formation interval in the present invention.

FIG. 4 is a diagram showing another example of the shapes of a plurality of holes in the present invention.

FIG. 5 is a diagram showing an example of a vertical sectional shape of a plurality of holes in the present invention.

FIG. 6 is a diagram showing another example of the vertical cross-sectional shape of a plurality of holes in the present invention.

FIG. 7 is a diagram showing still another example of the vertical cross-sectional shape of a plurality of holes in the present invention.

FIG. 8 is a diagram showing measurement results of stress distribution in the vicinity of an end portion of a copper plate when a thermal cycle is applied to the ceramic circuit board according to the example of the present invention.

FIG. 9 is a diagram showing formation positions of a plurality of holes in the present invention.

[Explanation of symbols]

 1 ... Ceramics substrate 2, 3 ... Copper plate 4, 5 ... Ceramics circuit substrate 6 ... Active metal-containing brazing material layer 7 ... Plural holes

Claims (9)

[Claims] 1. A ceramic circuit board comprising a ceramics substrate and a metal plate bonded to at least the surface of the ceramics substrate, the inside of an outer peripheral edge of the metal plate opposite to the bonding surface to the ceramics substrate. A ceramic circuit board having a plurality of holes formed therein. 2. The ceramic circuit board according to claim 1, wherein the plurality of holes are linearly formed at predetermined intervals along an outer peripheral edge of the metal plate. . 3. The ceramic circuit board according to claim 1, wherein the plurality of holes are non-through holes. 4. The ceramic circuit board according to claim 1, wherein the plurality of holes are through holes. 5. The ceramic circuit board according to claim 1, wherein the plurality of holes are holes formed by press working. 6. The ceramic circuit board according to claim 2, wherein when the shortest distance between the adjacent holes is L ₁ and the center distance between the adjacent holes is L ₂ , 1 / 5L ₂ ≦ L ₁ ≦ 1 / 2L
Ceramic circuit board characterized by satisfying ₂ . 7. The ceramic circuit board according to claim 1, wherein the metal plate is bonded to the ceramic substrate by a direct bonding method. 8. The ceramic circuit board according to claim 1, wherein the metal plate is bonded to the ceramic substrate by an active metal method. 9. A ceramic circuit board comprising a ceramics substrate and metal plates bonded to both front and back surfaces of the ceramics substrate, wherein the metal plates on both front and back surfaces are on the opposite side to the bonding surface to the ceramics substrate. A ceramic circuit board having a plurality of holes formed inside the outer peripheral edge.