JP2001332854A - Ceramic circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ceramic circuit board in which heat-resistance cycle characteristics and bending strength characteristics are improved, to obtain a ceramic circuit board which is improved in reliability in a corrosive atmosphere and prevented from short-circuiting between metal plates, and to obtain a ceramic circuit board which is improved in the soldering yield of an Si chip, etc., in postprocessing. SOLUTION: A ceramic circuit board has a metal plate 2 joined integrally with the top surface of a ceramic substrate 1 across a solder layer 3. The area of the join surface A between the metal plate 2 and solder material layer 3 is smaller than the surface area of the metal plate 2 on the side of a nonjoin surface B, and the area of the join surface C between the solder material layer 3 and ceramic substrate 1 is larger than the area of the join area A between the metal plate 2 and solder material layer 3.

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, and more particularly to a ceramic circuit board having improved heat cycle characteristics, bending strength characteristics, reliability in a corrosive environment, and improved soldering yield.

[0002]

2. Description of the Related Art A ceramic circuit board in which a metal circuit board is bonded to a ceramic substrate has been widely applied to electronic parts, mechanical parts, and the like.

[0003] Since ceramics and metals have different atomic structures, when joining a ceramic substrate and a metal circuit board, chemical properties such as reactivity and physical properties such as thermal expansion coefficient differ greatly. For this reason, conventionally, various methods for joining a ceramic substrate and a metal circuit board have been developed.

For example, a refractory metal method for joining a ceramic substrate and a metal circuit board made of a copper plate using a refractory metal such as Mo and W, and a copper direct joining method for joining using a eutectic reaction of copper and oxygen ( DBC: Direct Bond
ing Copper). In addition, IVa
An active metal method using a group III element or a group V element as a brazing filler metal is exemplified.

[0005] In particular, in the active metal method, Ag is used as a brazing material.
When a silicon nitride (Si ₃ N ₄ ) substrate is used as a ceramic substrate using a Cu—Ti system, Ti as an active metal and N in the silicon nitride substrate are covalently bonded to form a bonding layer. Therefore, extremely high bonding strength can be obtained.

[0006]

In addition to the conventional demands for high bonding strength, in recent years, ceramic circuit boards have high heat resistance and high bending strength, which does not break the ceramic even under a large bending load. (Bending strength) characteristics are required. In the prior art, although high bonding strength can be obtained, it has been difficult to say that the heat cycle resistance and the bending strength sufficiently satisfy the requirements.

A first object of the present invention is to solve this problem, and in particular, to obtain a ceramic circuit board having good heat cycle characteristics and bending strength characteristics.

Further, in the conventional ceramic circuit board, the cross-sectional shape of a metal plate such as copper is gently spread from the non-joining surface side to the joining surface side of the ceramic substrate and the metal plate. Had a shape. For this reason, for example, after joining by the active metal method using an Ag-Cu-Ti-based brazing material, the brazing material is likely to rise on the surface of the metal plate, and when soldering a Si chip or the like in a later process, it is possible to apply a soldering material. Solder wettability such as raised Ti lowers solder wettability, resulting in poor soldering. On the other hand, there is a problem that a metal plate having an area (volume) larger than a required area of the chip is required to mount the chip (corresponding to a foot portion), which hinders improvement in heat cycle resistance. I was

A second object of the present invention is to solve the above-mentioned problems, and a ceramic circuit board with improved heat cycle resistance and improved yield of solder such as Si chips in a later process. The purpose is to obtain.

Further, in a conventional ceramic circuit board, a copper plate bonded to a ceramic substrate is etched and patterned to produce a product as it is, or the entire surface of the copper plate is
The product was plated with i.

If the copper plate is not plated, for example, in a module reliability test in a corrosive atmosphere for automobiles, the side of the copper plate that is not covered with chips or solder is likely to be corroded, leading to a reduction in reliability. I was At the same time, particularly when the pattern is fine, there is a problem that electromigration and stress migration are likely to occur even with an electrical change or a thermal change.

A third object of the present invention is to solve the above-mentioned problems, and it is an object of the present invention to obtain a ceramic circuit board having improved reliability in a corrosive atmosphere and preventing electromigration and stress migration. And

[0013]

Means for Solving the Problems The inventors of the present invention have made various improvements on the side surface of a metal plate in order to solve the above-mentioned problems, and as a result, have reached the present invention.

That is, according to the first aspect of the present invention, in a ceramic circuit board in which a metal plate is integrally joined to a surface of a ceramic substrate via a brazing material layer, the area of the joining surface between the metal plate and the brazing material layer is made of metal. It is characterized in that it is smaller than the surface area of the non-joining surface side of the plate, and the area of the joining surface between the brazing material layer and the ceramic substrate is larger than the area of the joining surface between the metal plate and the brazing material layer.

According to the present invention, the concentration of stress at the joint end is reduced, and the residual stress can be reduced, so that the joint strength and the heat cycle resistance can be improved.

The invention according to claim 2 is characterized in that the horizontal distance between the end of the non-joining surface of the metal plate and the end of the joining surface between the metal plate and the brazing material layer is 50 μm or less. The ceramic circuit board according to claim 1.

In the present invention, the horizontal distance is specified to be 50 μm or less. However, when the horizontal distance exceeds 50 μm, the stress of the ceramic substrate is increased and the heat cycle resistance is lowered.

The horizontal distance between the end of the joining surface between the brazing material layer and the ceramic substrate and the end of the joining surface between the metal plate and the brazing material layer is preferably 20 to 50 μm. The ceramic circuit board according to claim 1, wherein:

In the present invention, the horizontal distance is 20 to 50 μm.
However, if it is less than 20 μm, the stress of the ceramic substrate is increased and the heat cycle resistance is reduced. If it is more than 50 μm, the electrical insulation between the metal circuit patterns is reduced. It is likely to cause a short circuit phenomenon.

According to a fourth aspect of the present invention, the metal plate narrows in width from the non-joining surface side to the joining surface side of the metal plate and the brazing material layer, and the metal plate extends from the surface end on the non-joining surface side of the metal plate. 2. The ceramic circuit board according to claim 1, further comprising an inclined portion inclined toward an end of a joining surface between the plate and the brazing material layer.

According to a fifth aspect of the present invention, the brazing material layer is made of T
2. The method according to claim 1, further comprising at least one active metal selected from i, Zr, Hf, Al and Nb.
It is a ceramic circuit board of said description.

The invention according to claim 6 is the ceramic circuit board according to claim 1, wherein the ceramic substrate is made of silicon nitride.

Since silicon nitride has a high elementary strength, by using silicon nitride as a ceramic substrate, the three-point bending strength of the ceramic circuit substrate is also reduced to 6 as described later.
This is as large as 00 MPa or more.

According to a seventh aspect of the present invention, there is provided the ceramic circuit board according to the sixth aspect, wherein the silicon nitride has a thermal conductivity of 65 W / m · K or more.

In the present invention, the ceramic substrate is used to reduce the thermal resistance when incorporated into a semiconductor module.
It is necessary that the thermal conductivity of silicon nitride is 65 W / (m · K) or more, preferably 85 W / (m · K) or more.

The invention according to claim 8 is the ceramic circuit board according to claim 6, wherein the thickness of the brazing material layer is 60 μm or less.

When aluminum nitride is used as the ceramic substrate, the thickness of the brazing material layer is required to be 40 μm or less, as described in Japanese Patent Application No. 5-49590. In the present invention, since silicon nitride is used as the ceramic substrate, the strength of the silicon nitride is large, so that even if the thickness of the brazing filler metal layer is 60 μm or less, it is possible to exhibit sufficient characteristics.

According to a ninth aspect of the present invention, the three-point bending strength is:
7. The ceramic circuit board according to claim 6, wherein the pressure is 600 MPa or more.

According to a tenth aspect of the present invention, in a ceramic circuit board in which a metal plate is bonded to a surface of a ceramic substrate, the area of the bonding surface between the ceramic substrate and the metal plate is reduced toward the non-bonding surface side of the metal plate. It has a metal plate shape having a large cross-sectional area.

As a method of manufacturing a metal plate having such a shape, a protrusion is provided in advance on the side surface of the metal plate by pressing from above or below, or a metal plate which has been subjected to predetermined patterning by etching or wire electric discharge machining is used. And a method of forming a metal plate having a shape in which the lower end is smaller than the upper end due to the difference in linear expansion coefficient between the ceramics after bonding and the metal plate. To make such a metal plate,
The metal plate needs to have a certain thickness, and preferably has a thickness of 0.1 mm.
1 to 0.8 mm, more preferably 0.2 to 0.5 mm
It is.

According to the eleventh aspect of the present invention, the side surface of the metal plate is wider than a straight line connecting the end of the surface of the metal plate on the non-bonding surface side and the end of the bonding surface between the metal plate and the ceramic substrate. The ceramic circuit board according to claim 10, wherein the ceramic circuit board has a protruding shape.

According to the present invention, the metal plate has a projecting shape on the side surface, that is, the surface end on the non-joining surface side of the metal plate;
Since there is a portion where the metal plate protrudes beyond the straight line connecting the end of the joining surface between the metal plate and the ceramic substrate, the brazing material used for joining to the surface of the metal plate is prevented from rising, and Bonding can be performed without deteriorating solder wettability when mounting a chip or the like in a process.

Conventionally, the cross-sectional shape of the metal plate has been gently spread from the non-bonding surface side to the bonding surface side of the ceramic substrate and the metal plate, and has a shape like the foot of Mt. Fuji. In the present invention, the minimum surface area of the non-bonding surface side necessary for mounting the chip is set, and the metal plate is kept to the minimum necessary size by reducing the cross-sectional area on the bonding surface side. It hardly occurs in ceramics, and the heat cycle resistance can be improved.

According to a twelfth aspect of the present invention, the horizontal distance between the end of the joint surface between the metal plate and the ceramic substrate and the end of the side surface of the metal plate is 5 to 200 μm. It is a ceramic circuit board of said description.

In the present invention, the horizontal distance is 5 to 200 μm.
However, if the horizontal distance is less than 5 μm, the effect of preventing the brazing material from rising cannot be obtained, and if the horizontal distance exceeds 200 μm, the withstand voltage between the patterns becomes small.

According to a thirteenth aspect of the present invention, in a ceramic circuit board in which a metal plate is bonded to a surface of a ceramic substrate, a coating layer is formed on a side surface of the metal plate.

[0037] In the invention according to claim 14, the coating layer is made of A
14. The ceramic circuit board according to claim 13, wherein the ceramic circuit board contains at least one or more alloys of g, Ti, Zr, Hf, Al, Ni, In and Sn.

In the present invention, Ag, T
Although one kind of metal is selected from i, Zr, Hf, Al, Ni, In and Sn, the following effects can be obtained by adding each element. Each element such as Ag can improve the corrosiveness, for example, NOx,
It is possible to exhibit excellent heat cycle resistance even in an environment under corrosive gas such as hydrogen sulfide.

The coating layer may contain two or more kinds of elements, and may further contain an alloy in which these elements are combined. Such an alloy includes an Ag-Sn alloy and the like.

As in the present invention, A
Since at least one metal selected from the group consisting of g, Al, Ni and Sn was deposited and alloyed, the metal plate was extremely stable even in a corrosive atmosphere.

In addition, since the entire surface of the side surface of the metal plate is alloyed, the occurrence of electromigration and stress migration can be prevented even with respect to an electrical change or a thermal change.

According to a fifteenth aspect of the present invention, the thickness of the coating layer is 0.5 μm or more.
It is a ceramic circuit board of said description.

When the thickness of the coating layer is less than 0.5 μm,
Since the stability in a corrosive atmosphere is insufficient and electromigration and stress migration may occur due to electrical or thermal changes, the thickness of the coating layer should be 0.5 μm or more. preferable.

According to a sixteenth aspect of the present invention, there is provided the ceramic circuit board according to the tenth or thirteenth aspect, wherein the metal plate is a Cu plate.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ceramic circuit board according to the present invention will be described below with reference to Tables 1 to 4 and FIGS.

First Embodiment (Tables 1 and 2, FIGS. 1 and 2) In this embodiment, 0.635 mm-thick silicon nitride (Si ₃ N ₄ ) is used as a ceramic substrate, and a thick metal plate is used. A ceramic circuit board was manufactured by an active metal method using a 0.3 mm-thick Cu plate.

First, the Cu plate is previously formed into a narrow shape from the upper end to the lower end by etching, and the side surface of the metal plate is
The shape was inclined from the surface end of the plate upper end to the end of the metal plate lower end.

Next, the weight ratio of Ag: Cu: In: Ti =
63: 23: 10: 4 active metal brazing material paste was screen-printed on a silicon nitride (Si ₃ N ₄ ) substrate with a printing thickness of 30 μm, and a Cu plate was placed on the dried paste to obtain 1 × The bonding was performed in a vacuum of 10 ⁻⁴ Torr or less at a temperature of 760 ° C. for 20 minutes to produce a ceramic circuit board shown in FIG. The obtained ceramic circuit board is shown in FIG. 1 and FIG.

FIG. 1A is a top view showing the front side of the ceramic circuit board, and FIG. 1B is a top view showing the back side thereof. As shown in FIGS. 1A and 1B, a Cu plate 2 is arranged on a ceramic substrate 1.

FIGS. 2A and 2B show cross sections of the front side substrate of the ceramic circuit board. As shown in FIG. 2A, a Cu plate 2a is joined on a ceramic substrate 1 via a brazing material layer 3 made of a brazing material containing an active metal.
The area of the joining surface A between the Cu plate 2a and the brazing material layer 3 is smaller than the surface area of the non-joining surface B side of the Cu plate 2a, and the area of the joining surface C between the brazing material layer 3 and the ceramic substrate 1 is Cu plate 2a. It is larger than the area of the joint surface A with the brazing material layer 3.

FIG. 2B is an enlarged sectional view of one end of the ceramic circuit board.

As shown in FIG. 2 (b), an inclined portion 4 inclined from the surface end on the non-joining surface B side of the Cu plate 2a to the end of the joining surface A between the Cu plate 2a and the brazing material layer 3. Having.

The horizontal distance X between the end of the surface of the Cu plate 2a on the non-bonding surface B side and the end of the bonding surface A between the Cu plate 2a and the brazing material layer 3, and the relationship between the brazing material layer 3 and the ceramic substrate 1
The horizontal distance Y between the end of the joining surface C of the sample No. and the surface end of the Cu plate 2a on the non-joining surface B side was changed variously as shown in Table 1 to obtain a sample No. 1 to No. 1 Ten samples were made.

[0054]

[Table 1]

It should be noted that the sample Nos. 1 to sample N
o. 5, the horizontal distance X was 50 μm or less, and the horizontal distance Y was in the range of 20 to 50 μm. 6 to sample no. In No. 10, the horizontal distance X and the horizontal distance Y are outside the above ranges.

The obtained sample No. 1 to Sample No. 1
In addition to measuring the bonding strength of the ceramic circuit board of No. 0, a TCT test was performed to investigate whether cracks occurred. The measurement conditions were as follows: −40 ° C. × 30 min → RT. (Room temperature) × 10 min → 125 ° C. × 30 min → RT. × 1
A TCT test with 0 min as one cycle was performed, and 200
The presence or absence of cracks in the ceramic substrate after the cycle was checked. Further, the bonding strength (peel strength) of the Cu plate 2 before the TCT test was measured. Table 1 shows the results.

As can be seen from Table 1, the sample Nos. 1 to No. For No. 5, no crack was observed. On the other hand, the sample No. 7-No. 10
The occurrence of cracks was confirmed. This corresponds to Sample No.
7, no. 9, No. This is because the thermal cycle characteristics of Sample No. 10 are insufficient because the Y value is less than 20 μm. In addition, the sample No. As shown in 8, it was confirmed that even when the Y value was within the range of the present invention, when the X value was larger than 50 μm, the heat cycle characteristics deteriorated.

The sample No. For No. 6, the occurrence of cracks was not confirmed as in the other comparative examples. This is because cracks were slightly suppressed even when the X value was out of the range of the present invention because the ceramic used for the substrate was a Si ₃ N ₄ substrate having a higher strength than AlN or Al ₂ O _3. I think. Similarly, for sample no. For example, sample No. 6 has a large X value, It was also found that the bonding strength was considerably lower than that of No. 1.

As described above, it has been found that the ceramic circuit board satisfying the preferable X value and Y value of the present invention exhibits excellent characteristics with respect to both the heat cycle characteristics and the bonding strength.

Next, the horizontal distance X and the horizontal distance Y were set to 30 μm and 40 μm, respectively, and the printing thickness and pattern forming method were variously changed. 11 to sample N
o. Twenty ceramic circuit boards were produced. The three-point bending strength of each of the produced ceramic circuit boards was measured, and the heat cycle resistance was evaluated. The measurement conditions are
In the three-point bending strength, the span was measured at 50 mm, and in the evaluation of the heat cycle resistance, −40 ° C. × 30 min → RT. ×
10 min → 125 ° C. × 30 min → RT. × 10mi
A TCT test was performed with n as one cycle, and the presence or absence of cracks after 200 cycles was evaluated as an index η. The index η indicates that 100% is “no crack due to TCT” and 0% is “crack is generated entirely by TCT”. Table 2 shows the results.

[0061]

[Table 2]

As shown in Table 2, the sample Nos. 1
1 and sample no. In No. 12, the bending strength was 705 MPa or 610 MPa, and the bending strength was improved as compared with the comparative example. Further, since the index η was 100, the heat cycle resistance was improved.

According to this embodiment, the area of the bonding surface A is smaller than the surface area of the non-bonding surface B, and the area of the bonding surface C is larger than the area of the bonding surface A. A ceramic circuit board that can reduce stress concentration at the edges and reduce residual stress, improve bonding strength and heat cycle resistance, and thereby improve the yield of soldering of Si chips and the like in subsequent processes. Can be obtained.

Second Embodiment (Table 3, FIG. 3) In this embodiment, a metal plate is subjected to wire electric discharge machining in advance to have a shape having a projecting portion on a side surface of the metal plate. Using this metal plate, ceramic circuit boards of Examples and Comparative Examples were manufactured by an active metal method or a DBC method.

As shown in Table 3, the ceramic substrate
Silicon nitride (Si ₃ N ₄ ), alumina (Al ₂ O ₃ ), or aluminum nitride (AlN) was used. As the metal plate, a Cu plate, a sample No. 25 is an Al plate, sample N
o. In 26, a Kovar (Ni-Co-Fe alloy) plate was used. In addition, the sample No. of the comparative example. In No. 30, a Ni plate was used. The thickness of each ceramic substrate is 0.635 m
m, and the thickness of the metal plate were unified to 0.3 mm.

[0066]

[Table 3]

In the active metal method, the weight ratio of Ag: Cu: I
An active metal brazing material paste of n: Ti = 63: 23: 10: 4 is screen-printed on a ceramic substrate with a printing thickness of 30 μm, a metal plate is placed on the dried paste, and 760 ° C. in vacuum At a temperature of 20 minutes to produce a ceramic circuit board.

On the other hand, in the DBC method, a Cu plate is placed on a ceramic substrate, and inserted into a heating furnace set at a temperature of 1080 ° C. in a nitrogen gas atmosphere.
A ceramic circuit board in which the plates were directly joined was obtained. DBC
FIG. 3 shows a ceramic circuit board obtained by the method.

FIG. 3A is a top view showing the front side of the ceramic circuit board, in which a Cu plate 2 is arranged on a ceramic substrate 1 and a Si chip 5 is arranged on the Cu plate 2.

FIG. 3B is a cross-sectional view showing one end on the back side of the ceramic circuit board, in which the surface end 6 on the non-bonding surface side of the Cu plate 2 is bonded to the Cu plate 2 and the ceramic substrate 1. The side surface of the Cu plate 2 has a protruding portion 8 whose width is wider than a linear position connecting the end portion 7 of the surface.

Further, the end 7 of the joining surface between the Cu plate 2 and the ceramic substrate 1 and the protrusion 8 formed on the side surface of the Cu plate 2
The horizontal distance Z from the end 9 of the sample No. 21
Or sample No. In No. 28, the range was 5 to 200 μm.

The sample no. 21-
Sample No. Up to 32 ceramic circuit boards were evaluated for wettability and heat cycle resistance. The wettability was evaluated by soldering a Si chip on a metal plate of each ceramic circuit board with a solder 63 to evaluate the wettability. The heat cycle resistance is -4.
0 ° C. × 30 min → RT. × 10 min → RT. × 10
The TCT test was performed with the min as one cycle, and 500
The evaluation was performed by observing the presence or absence of cracks generated in the ceramic after the cycle. Table 3 shows the results.

As shown in Table 3, the active metal method and DB
Even in the joining method using the C method, the horizontal distance Z is set to 5 to 20.
In the case of the ceramic circuit board having a thickness of 0 μm, the solder wettability was good in any case, and no crack was generated in the ceramic.

Therefore, according to the present embodiment, it is possible to obtain a ceramic circuit board having improved heat cycle resistance and improved yield of soldering of a Si chip or the like in a later step. On the other hand, the sample No. 29
-No. In all of the samples of No. 32, voids were generated, and a problem occurred in solder wettability. This is because the brazing material bulges from the side of the metal plate due to the small X value.

Third Embodiment (Table 4, FIG. 4) In the present embodiment, AlN is used as the ceramic substrate.
Using a Cu plate as the substrate and metal plate, the active metal method or D
A ceramic circuit board was manufactured by the BC method.

Further, Ag, Ti, Z
at least one of r, Hf, Al, Ni, In or Sn
As a method of forming a film layer containing a seed or two or more metals, brazing material plating and plating were used.

In the case where the brazing material is used to form a film layer by rising, the brazing material is made of Ag-Cu-Ti-based composition, Ag, Ti, Zr, Hf, Al, Ni, In or Sn.
A small amount of at least one metal is added, and the brazing material is put on the side of the Cu plate by joining at 790 ° C. for 1 hour in a vacuum, and then slowly cooled at 100 ° C./hour or less. An alloyed coating layer was formed.

When a coating layer is formed by plating, the surface of the Cu plate is masked after etching the joined Cu plate, and then Ag and A are applied only to the side surfaces of the Cu plate.
A coating layer was formed on the side surface of the Cu plate by plating with 1, Ni, Sn or the like and sintering at 550 ° C. or lower.

As shown in Table 4, Sample No. 1 was used as a method of forming a coating layer. In the case of Sample No. 33, the brazing material was used. 34 and sample no. In No. 35, plating was performed with Ag. In No. 36, plating was performed with Sn. In addition,
In each of the examples, a coating layer having a thickness of 1 to 2 μm was formed.

[0080]

[Table 4]

Each chip has 6 ceramic chips
After soldering with three solders, a Cu heat sink base was soldered to the back copper plate to form a module.

FIG. 4 shows a ceramic circuit board obtained by the DBC method. FIG. 4 (a) shows the front side of the ceramic circuit board. An Si chip 5 is arranged on the plate 2. FIG. 4B is an enlarged cross-sectional view showing one end of the ceramic circuit board. A coating layer 10 is formed on the side surface of the Cu plate 2 on the ceramic substrate 1.

With respect to the ceramic circuit board in which the coating layer 10 was formed on the side surface of the Cu plate 2, the heat cycle characteristics were examined. Further, between the Cu plates 2, for example, the Cu plate 2a and the C
The presence or absence of a short circuit between the u plate 2b or the Cu plate 2b and the Cu plate 2c was examined. In addition, the heat cycle characteristics were determined in a corrosive gas such as air containing 5 vol% of NOx at -40 ° C. × 30 min → RT. × 10mi
n → 125 ° C. × 30 min → RT. It was investigated by observing the presence or absence of corrosion of the Cu plate 2 after 500 cycles in a TCT test with 1 cycle of × 10 min. The presence or absence of a short circuit between the Cu plates 2 was determined by actually applying a voltage of 1 kV to the module for 150 hours in a constant temperature and high humidity chamber at a relative humidity of 90% and a temperature of 60 ° C. It is a confirmation of the presence or absence. Table 4 shows the results of this investigation.

As shown in Table 4, the sample No. of the embodiment in which the coating layer 10 was formed by brazing or plating was used. 33 to sample no. In No. 36, since no Cu plate corrosion occurred, the heat cycle resistance was improved and the reliability in a corrosive atmosphere was improved. In addition, since no short circuit was observed between the Cu plates 2 in the example, the occurrence of electromigration and stress migration could be prevented.

Therefore, according to the present embodiment, by forming the coating layer 10 on the side surface of the metal plate, the reliability in a corrosive atmosphere can be improved, and a short circuit between the metal plates can be prevented. It is also possible to cope with fine wiring patterns. In particular, it exhibits excellent characteristics even in an atmosphere of a corrosive gas such as NOx, and is therefore effective for ceramic circuit boards mounted on automobile parts and the like.
When the first and second embodiments are combined, a ceramic circuit board having more excellent properties such as heat cycle resistance, bonding strength, corrosion resistance, and short circuit prevention can be formed. In this case, the X value is replaced with the Z value.

[0086]

As described above, according to the ceramic circuit board of the present invention, the heat cycle characteristics and the bending strength characteristics can be improved. Further, the reliability in a corrosive atmosphere is improved, and a ceramic circuit board free of electromigration and stress migration between metal plates can be obtained. Further, it is possible to obtain a ceramic circuit board having an improved soldering yield of a Si chip or the like in a later step.

[Brief description of the drawings]

1A and 1B are diagrams showing a ceramic circuit board according to a first embodiment of the present invention, wherein FIG. 1A is a top view showing the front side, and FIG. 1B is a top view showing the back side.

FIGS. 2A and 2B are views showing a ceramic circuit board according to the first embodiment of the present invention, wherein FIG. 2A is a cross-sectional view showing the entirety, and FIG.

3A and 3B are diagrams illustrating a metal pattern of a ceramic circuit board according to a second embodiment of the present invention, wherein FIG. 3A is a top view illustrating a front side, and FIG.

4A and 4B are diagrams showing a ceramic circuit board according to a third embodiment of the present invention, wherein FIG. 4A is a top view showing the front side, and FIG. 4B is a cross-sectional view showing one end enlarged.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ceramic substrate 2 metal plate 3 brazing material layer 4 inclined portion 5 Si chip 6 surface end of non-joining surface side of Cu plate 7 end of joining surface between Cu plate and ceramic substrate 8 projecting portion 9 end of projecting portion Part 10 Coating layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/24 H05K 3/24 Z F-term (Reference) 4G026 BA03 BA14 BA16 BB28 BD14 BF16 BG02 BG04 BH07 5E343 AA02 AA24 BB13 BB14 BB24 BB28 BB33 BB35 BB67 DD52 EE42 EE55 EE58 GG02 GG16 GG20

Claims (16)

[Claims] In a ceramic circuit board in which a metal plate is integrally joined to a surface of a ceramic substrate via a brazing material layer, an area of a joining surface between the metal plate and the brazing material layer is a surface area on a non-joining surface side of the metal plate. A ceramic circuit board, wherein the area of the bonding surface between the brazing material layer and the ceramic substrate is smaller than the area of the bonding surface between the metal plate and the brazing material layer. 2. The horizontal distance between the end of the surface of the metal plate on the non-joining surface side and the end of the joining surface between the metal plate and the brazing material layer is 50 μm.
The ceramic circuit board according to claim 1, wherein: 3. The horizontal distance between the end of the joining surface between the brazing material layer and the ceramic substrate and the end of the joining surface between the metal plate and the brazing material layer is 20 to 50 μm. 1
The ceramic circuit board as described. 4. The metal plate becomes narrower in width from the non-joining surface side to the joining surface side of the metal plate and the brazing material layer, and the metal plate and the brazing material layer are joined from the surface end of the non-joining surface side of the metal plate. 2. The ceramic circuit board according to claim 1, further comprising an inclined portion inclined toward an end of the joining surface of the ceramic circuit board. 5. The ceramic circuit board according to claim 1, wherein the brazing material layer contains at least one active metal selected from Ti, Zr, Hf, Al and Nb. 6. The ceramic circuit board according to claim 1, wherein the ceramic substrate is made of silicon nitride. 7. The thermal conductivity of silicon nitride is 65 W / m ·
The ceramic circuit board according to claim 6, wherein K is not less than K. 8. The ceramic circuit board according to claim 6, wherein the thickness of the brazing material layer is 60 μm or less. 9. The ceramic circuit board according to claim 6, wherein the three-point bending strength is 600 MPa or more. 10. In a ceramic circuit board in which a metal plate is bonded to a surface of a ceramic substrate, a metal having a cross-sectional area larger than an area of a bonding surface between the ceramic substrate and the metal plate toward a non-bonding surface side of the metal plate. A ceramic circuit board having a plate shape. 11. A protruding shape in which the side surface of the metal plate is wider than a straight line connecting the surface end of the non-bonding surface side of the metal plate and the end of the bonding surface between the metal plate and the ceramic substrate. The ceramic circuit board according to claim 10, wherein: 12. The horizontal distance between the end of the joining surface between the metal plate and the ceramic substrate and the end of the side surface of the metal plate is 5 to 20.
The ceramic circuit board according to claim 10, wherein the thickness is 0 µm. 13. A ceramic circuit board in which a metal plate is bonded to a surface of a ceramic substrate, wherein a coating layer is formed on a side surface of the metal plate. 14. The coating layer is made of Ag, Ti, Zr, Hf,
At least one of Al, Ni, In and Sn or 2
14. The ceramic circuit board according to claim 13, comprising at least one kind of alloy. 15. The ceramic circuit board according to claim 13, wherein the thickness of the coating layer is 0.5 μm or more. 16. The ceramic circuit board according to claim 10, wherein the metal plate is a Cu plate.