JP3192911B2 - Ceramic circuit board - Google Patents

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 against 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 bonded on a ceramic substrate has been used as a substrate for mounting semiconductor components handling relatively high power such as a power transistor module and a switching power supply module. I have.

As a method of manufacturing a ceramic circuit board as described above, that is, a method of joining a ceramic substrate and a metal plate, an active metal such as Ti, Zr, Hf, or Nb is added to an Ag-Cu brazing material at 1 to 10%. The method using the added active metal brazing material (active metal method), or 100 to 1000 ppm of oxygen as a metal plate
A so-called direct bonding method (DBC method: direct bonding copper method) in which a ceramic substrate and a copper plate are directly bonded to each other using a tough pitch electrolytic copper or copper whose surface is oxidized by 1 to 10 μm is known.

For example, in the direct joining method, first, a copper circuit board having a thickness of 0.3 to 0.5 mm stamped into a predetermined shape is replaced with a 0.6 to 1.0 mm thick copper oxide board or aluminum nitride sintered body. After being placed in contact with the ceramic substrate and heated, a eutectic liquid phase of Cu-Cu ₂ O is generated at the joint interface, and after wetting the surface of the ceramic substrate with this liquid phase,
By cooling and solidifying the liquid phase, the ceramic substrate and the copper circuit board are joined. A ceramic circuit board to which such a direct bonding method is applied has a strong bonding strength between the ceramic substrate and the copper circuit board, and can be miniaturized and mounted with a simple structure that does not require a metallization layer or a brazing material layer. And the manufacturing process can be shortened.

In a ceramic circuit board in which a metal plate is joined to a ceramic substrate by the above-described direct joining method or active metal method, the thickness of the metal plate is increased to 0.3 to 0.5 mm so that a large current can flow. Therefore, there is a problem that the reliability of the heat history is poor. That is,
When a ceramic substrate and a metal plate having significantly different coefficients of thermal expansion are joined, a thermal stress due to the above-described difference in thermal expansion is generated due to a cooling process after the joining or addition of a cooling / heating cycle. This stress exists as a compressive and tensile residual stress distribution on the ceramic substrate side near the joint, and the main residual stress mainly acts on the ceramic portion adjacent to the outer peripheral end of the metal plate. This residual stress causes cracks in the ceramic substrate or causes peeling of the metal plate.
Also, even if the ceramic substrate does not crack,
This has the adverse effect of reducing the strength of the ceramic substrate.

[0006] Of the above-mentioned residual stresses, those based on thermal stress generated in the cooling process after joining the metal plates can be reduced to some extent by adjusting the cooling rate or the like, but generate heat from the mounted components during actual use. Residual stress caused by the above cannot be reduced depending on external conditions, and is a serious problem. For this reason, the above-mentioned ceramic circuit board usually has the same or 5 to 30% of the front surface, that is, the mounting part of the semiconductor component, on the back surface of the ceramic substrate.
Although a thin metal plate is joined to prevent the warpage of the ceramic circuit board, the problem of residual stress has not been fundamentally solved.

[0007] As a countermeasure against the above-mentioned problems due to thermal stress and residual stress, that is, a decrease in bonding strength and generation of cracks, for example, Japanese Patent Publication No. 5-25397 discloses an outer peripheral end of a copper plate as a metal plate. It describes that the portion has a thin shape (thin portion), specifically, the outer peripheral end portion has a stepped shape or a tapered shape. Further, Japanese Patent Application Laid-Open No. 3-145748 describes that a groove is formed inside the metal plate along the outer peripheral edge. Thus, the stress concentrated on the outer peripheral end of the metal plate is dispersed by the groove, thereby preventing a decrease in bonding strength and the occurrence of cracks.

[0008]

However, among the above-described methods for improving the reliability of the thermal history of the ceramic circuit board described above, the method described in Japanese Patent Publication No. 5-25397 discloses an outer peripheral end portion of a metal plate. Since the thin portion is formed by etching or the like at the same time as the formation of the circuit pattern, the manufacturing process becomes complicated, resulting in an increase in the number of manufacturing steps.

In Japanese Patent Application Laid-Open No. 3-145748,
Similarly, it is mainly described that a groove along the outer peripheral edge of a metal plate is formed by an etching method. According to the etching method, a groove can be formed simultaneously with the formation of a circuit pattern. However, as described above, the etching method has a disadvantage that the steps are complicated and the number of manufacturing steps is increased.
Further, it is also shown that the groove is formed by machining using a mold or the like.However, when the groove is formed over the entire inner periphery of the outer peripheral edge of the metal plate by this method of machining, the groove is formed by pressing or the like. When forming the metal sheet, plastic deformation occurs in the metal plate around the pressing portion, and accompanying this, deformation such as distortion occurs particularly in the central portion of the metal plate. The deformation of the metal plate causes poor bonding of the metal plate or a decrease in bonding strength.

[0010] From the above, by adding a cooling process or a cooling / heating cycle after joining the metal plates, thermal stress and residual stress generated in the metal plate are dispersed and relaxed, thereby effectively preventing cracks and strength reduction of the ceramic substrate. There is a strong demand for a technique capable of preventing deformation of a metal plate even by machining that can prevent the deformation and simplify the manufacturing process.

The present invention has been made to address such a problem. Even when a cooling / heating cycle is applied, the thermal stress and the residual stress generated in the metal plate are dispersed so that the outer periphery of the metal plate is dispersed. Relieves stress concentration on the edge,
Provided is a ceramic circuit board excellent in reliability and manufacturability, which can effectively prevent cracks and decrease in strength of a ceramics board and can prevent deformation of a metal plate even by machining which is advantageous in a manufacturing process. It is intended to be.

[0012]

According to a first aspect of the present invention, there is provided a ceramic circuit board comprising aluminum nitride.
And a metal plate joined to at least the surface of the ceramic substrate, and a metal plate is provided inside the outer peripheral edge of the metal plate opposite to the joining surface with the ceramic substrate. In a ceramic circuit board on which continuous grooves are formed, when the length of the discontinuous groove is L ₀ and the shortest distance between adjacent discontinuous grooves is L ₁ , 1/10 L ₀ ≦ L ₁ satisfies ≦ 1 / 2L _0, and the depth of the discontinuous grooves is characterized by a 1/3 - 2/3 of the thickness of the metal plate.

According to another aspect of the present invention, there is provided a ceramic circuit board comprising an aluminum nitride sintered body.
A ceramic substrate made of a body , comprising a metal plate bonded to both the front and back surfaces of the ceramic substrate, inside the outer peripheral edge of the metal plate on both the front and back surfaces opposite to the bonding surface with the ceramic substrate, In a ceramic circuit board in which discontinuous grooves are formed, when the length of the discontinuous groove is L ₀ and the shortest distance between adjacent discontinuous grooves is L ₁ , 1/10 L ₀ ≦ satisfies L ₁ ≦ ₁ / 2L _0, and the depth of the discontinuous grooves in the thickness of the metal plate
1/3 to 2/3.

Here, in the ceramic circuit board of the present invention, it is preferable that the discontinuous grooves are formed in all the metal plates bonded to the ceramic substrate.
The present invention is included as long as the discontinuous groove is formed in at least one metal plate bonded to the ceramic substrate. Also, it is included even if it is not the entire circumference of the metal plate.

As described above, in a more preferred embodiment of the ceramic circuit board according to the present invention, the groove is formed at a corner of the metal plate where stress is likely to concentrate. The discontinuous groove is a groove formed by press working, as described in claim 3, and the discontinuous groove is the metal as described in claim 4. An example is a form in which the plate is formed linearly along the outer peripheral edge of the plate .

[0016]

In the ceramic circuit board of the present invention, a discontinuous groove is formed inside the outer peripheral edge on the side opposite to the joining surface of the metal plate. Here, the thermal stress generated in the cooling process after joining the metal plate, the thermal stress due to the addition of cooling and heating cycles, etc., and the residual stress based on them are caused by discontinuous grooves provided inside the outer peripheral edge of the metal plate. Due to the dispersion, the concentration of stress on the outer peripheral edge of the metal plate is reduced. As a result, the stress value itself at the outer peripheral end of the metal plate can be reduced, so that it is possible to effectively prevent the occurrence of cracks and a decrease in strength of the ceramic substrate, which have conventionally been problems.

In the ceramic circuit board of the present invention, since the above-mentioned dispersion of stress is achieved by the discontinuous grooves, even if the grooves are formed by machining, the metal plate is pressed by the mechanical processing. Deformation can be mitigated by the non-groove region between the grooves. Therefore, it is possible to prevent deformation of the metal plate, particularly the central portion of the metal plate during machining. However, a groove is preferably formed in the vicinity of the corner of the metal plate because thermal stress and residual stress are particularly concentrated.

[0018]

Next, an embodiment of the present invention will be described.

FIG. 1 is a view showing the structure of a ceramic circuit board according to one embodiment of the present invention. In the figure, 1
Is a ceramic substrate, and a copper plate 2 as a metal plate is joined to the surface 1a of the ceramic substrate 1. Similarly, a copper plate 3 is formed on the back surface 1b of the ceramic substrate 1.
Are joined, and these constitute a ceramic circuit board 4.

Here, as the ceramic substrate 1, a substrate made of an aluminum nitride sintered body which is a non-oxide based sintered body is used. In addition, when using such a non-oxide-based sintered body, it is preferable to use it after forming an oxide layer on the surface thereof.

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

The copper plate 2 bonded to the front surface 1a of the ceramic substrate 1 is to be a mounting portion for semiconductor components and the like, and is patterned into a desired circuit shape. Also,
Copper plate 3 bonded to back surface 1b side of ceramic substrate 1
Is for preventing warpage of the ceramic substrate 1 at the time of joining, and is joined and formed almost over the entire back surface 1b of the ceramic substrate 1 in a state of being divided into two parts from the vicinity of the center. As the copper plate 3 on the back surface 1b side, a copper plate having the same thickness as the copper plate 2 serving as a mounting portion for semiconductor components or the like may be used, but a copper plate having a thickness of 70 to 90% of the thickness of the copper plate 2 is used. Is preferred.

Here, the ceramic circuit board 4 shown in FIG. 1 is formed by bonding copper plates 2 and 3 to the ceramic substrate 1 by the DBC method. For example, as shown in FIG.
The ceramic circuit board 5 in which the copper plates 2 and 3 are joined to the ceramic substrate 1 by an active metal method may be used. The active metal method includes, for example, a method in which the ceramic substrate 1 is connected to a brazing material layer containing at least one active metal selected from Ti, Zr, Hf, and Nb (hereinafter, referred to as an active metal-containing brazing material) layer 6. This is a method of joining the copper plates 2 and 3. As the composition of the active metal-containing brazing material to be used, for example, a eutectic composition of Ag-Cu (72 wt% A
g-28wt% Cu) or Ag-Cu-based brazing filler metal or its composition
1 to 10% by weight of Ti, Zr, H
Examples of the composition include at least one active metal selected from f, Nb, and the like. In addition, active metal-containing brazing materials
A low-melting-point metal such as In can be added for use.

As shown in FIG. 1, when the copper plates 2 and 3 are joined to the ceramic substrate 1 by the DBC method as in the ceramic circuit board 4 shown in FIG. 1, a simple structure, high joining strength can be obtained, and the manufacturing process can be simplified. And so on. Further, when 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 joining strength can be obtained and the active metal-containing brazing material layer 6 has a high stress. Since it also functions as a relaxation layer, reliability can be further improved. For this reason, it is preferable to select a joining method according to required characteristics, applications, and the like.

When a metal plate is joined to the ceramic substrate 1 by the active metal method, not only a copper plate but also various metal plates, for example, a nickel plate, a tungsten plate, a molybdenum plate, and an alloy plate of these, depending on the application. Alternatively, a clad plate (including a clad plate with a copper plate) or the like can be used.

In the above-mentioned ceramic circuit boards 4 and 5, as shown in FIG. 3, a discontinuous groove 7 is formed in the outer peripheral edge of the copper plate 2 to be a mounting portion for semiconductor components and the like. Along the outer periphery of each circuit pattern portion of the copper plate 2. The discontinuous groove 7
In order to avoid complication of the manufacturing process and to reduce the number of manufacturing steps, it is desirable to form the film by mechanical processing such as pressing using a die. However, application of another formation method is not necessarily excluded.

Here, the inside of the outer peripheral edge of the above-described copper plate 2 (metal plate) refers to the width of the copper plate 2 from the outer peripheral edge toward the center with respect to the width D of the copper plate 2 as shown in FIG. D 1
It is a part within / 3. That is, on the basis of the width D of the copper plate 2, both sides in the center direction from the outer peripheral edge not including the outer peripheral edge
The portion within 1 / 3D is defined as the inside of the outer peripheral edge (indicated by oblique lines in FIG. 4), and the center 1/3 of the width D of the copper plate 2 is defined as the center. If the region where the discontinuous groove 7 is formed reaches the central portion beyond the inside of the outer peripheral edge, the stress concentration at the outer peripheral end of the copper plate 2 cannot be sufficiently reduced, and the mounting area decreases. The above-described discontinuous grooves 7 are preferably formed linearly at predetermined intervals along the outer peripheral edge of each circuit pattern portion of the copper plate 2. Thus, the discontinuous groove 7
Is formed in a straight line, the stress concentration on the outer peripheral end of the copper plate 2 can be efficiently reduced, in other words, the stress can be efficiently dispersed. The shape of each single groove 7a constituting the discontinuous grooves 7, i.e. the width W and the length L ₀ of the single groove 7a, depending on such the size of the single groove 7a of the formation interval and copper plate 2 to be described later, the width W is in the range of 0.2 to 1.0mm, length L
It is preferable that ₀ is within a range of 20 mm or less. Single groove 7a
If the width W is less than 0.2 mm, the stress may not be dispersed sufficiently. If the width W exceeds 1.0 mm, the strength of the copper plate 2 tends to decrease, and the mounting area decreases. A more preferable range of the width W is the same for the same reason.
0.4 to 0.8 mm. In addition, the length L ₀ of each single groove 7a is
If it exceeds 20 mm, there is a possibility that the deformation of the copper plate 2 cannot be sufficiently suppressed with a decrease in the groove non-formed region. Each single groove 7a
Is not particularly limited, but from the viewpoint that stress concentration on the outer peripheral end of the copper plate 2 is efficiently reduced.
It is preferably at least 2 mm.

Further, the discontinuous grooves 7 arranged linearly
It is the shortest distance L ₁ between the single groove 7a close to the length L ₀ of each single groove 7a described _{above, 1 / 10L 0 ≦ L 1} ≦ 1/2
It formed so as to satisfy the L _0. If the interval between the discontinuous grooves 7 (the shortest distance L ₁ between the adjacent single grooves 7 a) is too large, specifically, if L ₁ > 1/2 L ₀ , the effect of dispersing the stress due to the groove formation is reduced. There is a possibility that it is not possible to obtain the copper plate 2 sufficiently. On the other hand, if the formation interval of the discontinuous grooves 7 is too small, specifically, if L ₁ <1 / 10L ₀ , the effect of suppressing the deformation of the copper plate 2 by the groove non-formation region is reduced. There is a possibility that it cannot be obtained sufficiently.

The position of the non-groove-forming region is not particularly limited as long as the discontinuous groove 7 satisfies the above-mentioned formation interval, but a groove is formed near the corner of the copper plate 2. Therefore, it is desirable to arrange each unitary groove 7a. This is because thermal stress and residual stress are particularly concentrated near the corners of the copper plate 2. Further, the lengths L ₀ of the individual grooves 7a constituting the discontinuous grooves 7 do not have to be all the same, and can be appropriately changed within a range satisfying the above-described conditions.

The discontinuous groove 7 may have a substantially uniform longitudinal cross section in the depth direction as shown in FIG.
As shown in FIG. However, the depth d shall be the range of 1/3 - 2/3 of the thickness t of the copper plate 2. If the depth of the discontinuous groove 7 is less than 1/3 of the thickness t of the copper plate 2, the effect of dispersing stress may be insufficient, and if it exceeds 2/3 of the thickness t, the copper plate 2 This tends to cause a decrease in the strength of the steel. The formation position of the discontinuous grooves 7, i.e. the shortest distance L ₂ from the outer peripheral edge portion of the copper plate 2 to the groove 7, varies depending on the thickness and size of the copper plate 2, 0.3～1.0M
m is preferable. When the distance L ₂ showing the formation position of the discontinuous grooves 7 is less than 0.3 mm, and decreased shape retention capability of the copper plate 2 and the distance L ₂ is greater than 1.0mm at the outer peripheral edge portion of the copper plate 2 May not be sufficiently reduced.

The copper plate 2 joined to the front surface 1a of the ceramic substrate 1 serving as a mounting portion for semiconductor components and the like has been described in detail, but the copper plate 3 joined to the back surface 1b of the ceramic substrate 1 has been described.
As with the copper plate 2 on the surface 1a side, it is preferable to form a discontinuous groove 7 inside the outer peripheral edge. In particular, when a relatively thick copper plate (metal plate) is used from the viewpoint of heat dissipation and the like, it is desirable to form discontinuous grooves 7 also in the copper plate 3 on the back surface 1b side. The shape, interval, and the like of the discontinuous grooves 7 formed on the copper plate 3 on the back surface 1b are based on the discontinuous grooves 7 formed on the copper plate 2 on the front surface 1a.

The above-described ceramic circuit board 4 is manufactured, for example, as follows. That is, for example, an oxygen-containing copper plate such as tough pitch copper is processed into a predetermined shape (a circuit pattern shape with respect to the copper plate 2), and a groove 7 that is discontinuous, for example, linearly formed inside the outer peripheral portion thereof by press working. It is formed by processing. Such discontinuous grooves 7
The ceramic circuit board 4 is prepared by placing the copper plates 2 and 3 having the above in contact with each other on a ceramic substrate and heating the same at a temperature lower than the melting point of copper (1356K) and higher than the eutectic temperature of copper and copper oxide (1338K). I do. The atmosphere during this heating is
When an oxygen-containing copper plate is used as the copper plate, an inert gas atmosphere is preferably used.

The ceramic circuit board 5 is manufactured, for example, as follows. First, similarly to the ceramic circuit board 4, the copper plates 2, 3 having the discontinuous grooves 7 are provided.
Prepare 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 such that the thickness of the brazing material layer 6 after the heat bonding is not too large in order to improve the thermal cycle characteristics. Next, the copper plates 2 and 3 are respectively laminated on the ceramic substrate 1 to which the brazing material paste has been applied, and a heat treatment is performed at a temperature corresponding to the brazing material used.
Is prepared.

In the ceramic circuit boards 4 and 5 having the above-described configuration, the thermal stress generated in the cooling process after the joining of the copper plates 2 and 3 and the thermal stress due to the addition of a cooling and heating cycle,
The residual stresses based thereon are dispersed by the discontinuous grooves 7 provided inside the outer peripheral edges of the copper plates 2 and 3, so that the stress concentration on the outer peripheral ends of the copper plates 2 and 3 is reduced. 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, a decrease in strength, and the like of the ceramic substrate 1 which have conventionally been problems.
Since the above-described dispersion of the stress is achieved by the discontinuous grooves 7, even if machining such as press working is applied to the formation of the discontinuous grooves 7, the deformation of the copper plates 2, 3 and particularly the central portion thereof is prevented. Can be prevented. Therefore, the manufacturing process can be simplified and the number of manufacturing steps can be reduced without lowering the bonding strength due to deformation of the copper plates 2 and 3.

Next, specific examples of the above embodiment and evaluation results thereof will be described.

Example 1 First, a 0.7 mm thick aluminum nitride substrate having a 4 μm oxide layer on its surface was prepared as a ceramic substrate 1, and a linear discontinuous groove 7 was formed inside the outer peripheral edge. Thickness of predetermined shape made of tough pitch copper (oxygen content: 300ppm) formed by pressing along the outer peripheral edge 0.3
mm copper plates 2 and 3 were prepared. The shape of the discontinuous grooves 7, a longitudinal section with a substantially uniform shape in the depth direction shown in FIG. 5, 0.5 mm width W of each single groove 7a, the length L ₀ 10 m
m, the depth d is 0.15 mm, the shortest distance L ₁ between each adjacent single groove 7 a is 2 mm (= 0.2 L ₀ ), and the formation position is the distance L ₂ from the outer peripheral edge of the copper plates 2, 3. It was set to 0.5 mm.

Then, as shown in FIG. 1, two copper plates 2 and 3 are placed in direct contact with each other on both surfaces of the aluminum nitride substrate 1 and joined by heating under a condition of 1348 K in a nitrogen gas atmosphere. The intended ceramic circuit board 4 was obtained.

A thermal cycle test (TCT: 233K × 30 minutes + RT × 10 minutes + 398K × 30 minutes is defined as one cycle) is performed on the ceramic circuit board 4 obtained in this manner, and the stress during the addition of the thermal cycle is measured. The distribution was measured. FIG. 7 shows the result. In the comparative example (shown by a dashed line) in FIG. 7, a ceramic circuit board manufactured under the same conditions as in Example 1 above was used under the same conditions except that a copper plate 2 'having no discontinuous grooves was used. It is the measurement result of the stress distribution at the time of adding a cycle.

As is apparent from FIG. 7, by forming the discontinuous grooves 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 discontinuous grooves 7, It can be seen that the stress at the end is clearly reduced as compared to the comparative example having no discontinuous grooves. This makes it possible to prevent cracks and reduction in strength of the aluminum nitride substrate. Incidentally, the ceramic circuit board of Example 1 did not crack even after 100 cycles of TCT, whereas the ceramic circuit board of the comparative example cracked 35% of the aluminum nitride substrate in 100 cycles. .

When the discontinuous groove 7 was formed by press working, no deformation or the like occurred in the copper plates 2 and 3, but similarly, the entire periphery was formed along the outer peripheral edge of the copper plate by press working. In the case where a groove was formed in the copper plate, deformation occurred at the center of the copper plate. In addition, even when the copper plate is small in deformation at the time of the press working, the deformation is generated during the heat bonding to the aluminum nitride substrate and the cooling.

Example 2 An aluminum nitride substrate having a thickness of 0.6 mm was prepared as the ceramic substrate 1, and a linear discontinuous groove 7 was formed inside the outer peripheral edge by press working along the outer peripheral edge. Copper plates 2 and 3 having a thickness of 0.3 mm were prepared. The shape of the discontinuous groove 7 is such that the longitudinal cross-sectional shape is substantially uniform in the depth direction shown in FIG. 5, and the width W of each single groove 7a is
0.5 mm, 10 mm length L _0, and 0.15mm depth d, the shortest distance L ₁ between the single groove 7a close the 2mm (= 0.2L _0), also forming position outside of the copper plate 2 and 3 Distance L from the periphery
₂ was set to 0.5 mm.

Then, as shown in FIG. 2, In: Ag: Cu: Ti = 14.0: 59.0: 23.0: 4.0 on both surfaces of the aluminum nitride substrate.
After applying a paste of the active metal-containing brazing material of the composition, and laminating and arranging the copper plates 2 and 3 via this coating layer,
Heating and bonding were performed in a nitrogen gas atmosphere to obtain a target ceramic circuit board 5.

When a thermal cycle test was performed on the ceramic circuit board 5 thus obtained under the same conditions as in Example 1, good results similar to those of Example 1 were obtained.
It has been confirmed that it has excellent reliability for cooling and heating cycles.
The deformation after the discontinuous grooves 7 were formed in the copper plates 2 and 3 by press working was the same as in Example 1.

[0044]

As described above, according to the ceramic circuit board of the present invention, even when a thermal cycle is applied, the thermal stress and the residual stress generated in the metal plate can be dispersed by the discontinuous grooves. Thus, stress concentration on the outer peripheral end of the metal plate can be reduced, and deformation of the metal plate can be prevented by machining that is advantageous in the manufacturing process. Therefore, after simplifying the manufacturing process and reducing the number of manufacturing steps, it is possible to effectively prevent the occurrence of cracks and a decrease in the strength of the ceramic substrate due to the addition of a cooling / heating cycle and the like. It is possible to provide a circuit board.

[Brief description of the drawings]

FIG. 1 is a view showing a structure of a ceramic circuit board according to one embodiment of the present invention, wherein (a) is a plan view and (b) is a sectional view thereof.

FIG. 2 is a cross-sectional view illustrating a structure of a ceramic circuit board according to another embodiment of the present invention.

FIG. 3 is a diagram showing an example of a shape of a discontinuous groove in the present invention.

FIG. 4 is a diagram showing positions where discontinuous grooves are formed in the present invention.

FIG. 5 is a view showing an example of a longitudinal sectional shape of a discontinuous groove in the present invention.

FIG. 6 is a view showing another example of a longitudinal sectional shape of a discontinuous groove in the present invention.

FIG. 7 is a diagram showing a measurement result of a stress distribution near an end of a copper plate when a thermal cycle is applied to a ceramic circuit board according to an embodiment of the present invention, in comparison with a conventional example.

[Explanation of symbols]

 1 Ceramic substrate 2, 3 Copper plate 4, 5 Ceramic circuit substrate 6 Active metal-containing brazing material layer 7 Discontinuous grooves

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 1/02 H01L 23/12 H05K 1/03 610

Claims (7)

(57) [Claims] 1. A ceramic substrate comprising an aluminum nitride sintered body, and a metal plate bonded to at least a surface of the ceramic substrate, wherein a bonding surface of the metal plate to the ceramic substrate is provided. On the inside of the outer peripheral edge on the opposite side,
In the ceramic circuit board having discontinuous grooves, when the length of the discontinuous grooves is L ₀ and the shortest distance between the adjacent discontinuous grooves is L ₁ , 1 / 10L ₀ ≦ L ₁ ≤ 1/2
Satisfies L _0, and a ceramic circuit board, wherein a depth of said discontinuous grooves is 1/3 - 2/3 of the thickness of the metal plate. 2. The ceramic circuit board according to claim 1, wherein the groove is formed at a corner of the metal plate. 3. The ceramic circuit board according to claim 1, wherein the discontinuous groove is a groove formed by press working. 4. The ceramic circuit board according to claim 1, wherein the discontinuous groove is formed linearly along an outer peripheral edge of the metal plate. 5. The ceramic circuit board according to claim 1, wherein the metal plate is bonded to the ceramic substrate by a direct bonding method. 6. The ceramic circuit board according to claim 1, wherein the metal plate is bonded to the ceramic substrate by an active metal method. 7. A ceramic substrate comprising an aluminum nitride sintered body, and a metal plate joined to both front and back surfaces of the ceramic substrate, respectively, In the ceramic circuit board in which discontinuous grooves are respectively formed on the inner side of the outer peripheral edge on the side opposite to the bonding surface, the length of the discontinuous grooves is L ₀ , and the distance between the adjacent discontinuous grooves is when the shortest distance was _{L 1, 1 / 10L 0 ≦} L 1 ≦ 1/2
Satisfies L _0, and a ceramic circuit board, wherein a depth of said discontinuous grooves is 1/3 - 2/3 of the thickness of the metal plate.