JP2003283083A - Ceramic circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a large amount of heat is generated by resistance heat generation in brazing filler metal filled in a penetrating hole of a ceramic substrate which metal connects metal circuit plates, and malfunction is generated in electronic components mounted on the metal circuit plates by the heat. <P>SOLUTION: In this ceramic circuit board, metal circuit plates 3 are fixed on both surfaces of the ceramic substrate 1 having the penetrating hole in such a manner that the hole is closed. A metal post 4 wherein content of copper is 50-80 wt.% and content of copper oxide is 20-50 wt.% is arranged in the hole. The metal circuit plates 3 on both the surfaces of the ceramic substrate 1 are connected by using the metal post 4. Resistivity of the metal post 4 is small and resistance heat generation does not occur, so that electronic components can operate stably for a long term. Stress caused by difference of thermal expansion coefficient between the ceramic substrate 1 and the metal post 4 is hard to be generated, so that crack, fracture, etc., are not generated in the ceramic substrate 1. <P>COPYRIGHT: (C)2004,JPO

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 in which metal circuit boards are attached to both surfaces of a ceramic board and these metal circuit boards are connected by metal columns arranged in through holes of the ceramic board. .

[0002]

2. Description of the Related Art In recent years, as a circuit board such as a power module board or a switching module board, a ceramic circuit board in which a metal circuit board made of copper or the like is directly bonded onto a ceramic board via an active metal brazing material or the like has been proposed. It is used.

Further, in these ceramic circuit boards, metal circuit boards are bonded to the upper and lower surfaces of the ceramic board in order to increase the mounting density of the metal circuit boards, and the space between the upper and lower metal circuit boards is provided on the ceramic board. The brazing material filled in the through holes is used for electrical connection.

Specifically, such a ceramic circuit board is manufactured by the following method.

First, an aluminum oxide (Al ₂ O ₃ ) -based sintered body and a mullite (3Al ₂ O ₃ -2SiO ₂ ) -based sintered body
Silicon Carbide (SiC) Sintered Body / Aluminum Nitride (Al
N) A ceramic substrate made of an electrically insulating ceramic material such as a sintered body of silicon or silicon nitride (Si ₃ N ₄ ) and having a through hole penetrating in the thickness direction is prepared. The through hole is filled with a brazing material paste obtained by adding and mixing an organic solvent / solvent to a silver brazing powder (alloy powder of silver and copper), and is printed and applied in a predetermined pattern on the upper and lower surfaces of the ceramic substrate.

Next, a metal circuit board made of copper or the like is placed on the ceramic substrate with a brazing paste interposed therebetween.

Finally, the brazing material paste filled in the through holes of the ceramic substrate and the brazing material paste arranged between the ceramic substrate and the metal circuit board are exposed to each other in a non-oxidizing atmosphere. It is manufactured by heating to a temperature of 900 ° C. to melt the brazing material and joining the ceramic substrate and the metal circuit board with the brazing material.

The ceramic circuit board thus manufactured is used as a semiconductor module by mounting electronic components such as semiconductor elements via an adhesive such as solder and then assembling it in a resin case for external input / output. .

[0009]

However, in the conventional ceramic circuit board as described above, the brazing filler metal filled in the through holes connecting the metal circuit boards joined to the upper and lower surfaces of the ceramic board is used. , When the brazing paste is heated and melted, the air present in the brazing paste is entrapped in the molten brazing material in a large amount and becomes porous,
The conduction resistance was as high as 7 to 10 μΩ · cm in terms of specific resistance.

Therefore, when a large current exceeding 10 A flows through the brazing material in the metal circuit board and the through hole, the brazing material filled in the through hole undergoes resistance heat generation, and the heat is soldered or the like on the metal circuit board. There is a problem that it acts on an electronic component such as a semiconductor element that is adhered and fixed via the adhesive material of (3), and the electronic component cannot be stably operated at a high temperature.

The present invention has been completed in view of the above problems, and an object thereof is to effectively prevent generation of a large amount of heat due to resistance heat generation in a conductor connecting metal circuit boards to each other and to mount the metal circuit boards on the metal circuit board. It is an object of the present invention to provide a ceramic circuit board that can always and normally operate electronic components such as semiconductor elements at an appropriate temperature.

[0012]

In the ceramic circuit board of the present invention, a metal circuit board is attached to both sides of a ceramic substrate having a through hole so as to close the through hole, and the content of copper in the through hole. A metal column having a content of copper oxide of 50 to 80% by mass and a content of copper oxide of 20 to 50% by mass is arranged, and the metal circuit boards on both sides of the ceramic substrate are connected by this metal column. is there.

In the ceramic circuit board of the present invention having the above-mentioned structure, the metal column has a specific resistance of 2.7 to 5 μΩ · c.
It is characterized by being m.

Further, in the ceramic circuit board of the present invention having the above-mentioned structure, the coefficient of thermal expansion of the metal column is 12 × 10 ⁻⁶ /
It is characterized in that it is below ℃.

According to the ceramic circuit board of the present invention, the metal circuit boards attached to both sides of the ceramic board have the same copper content as the through holes of the ceramic board.
Since the connection was made via a metal column having a content of copper oxide of 50 to 80% by mass and a content of copper oxide of 20 to 50% by mass, even if a large current exceeding 10 A flows through the metal circuit board and the metal column, the specific resistance of the metal column However, since it is as low as 2.7 to 5 μΩ · cm, there is almost no resistance heat generation and a large amount of heat is not generated. As a result, an electronic component such as a semiconductor element, which is bonded and fixed on a metal circuit board by using an adhesive such as solder, always has an appropriate temperature, and can operate normally and stably for a long period of time.

Further, according to the ceramic circuit board of the present invention, when the coefficient of thermal expansion of the metal column arranged in the through hole of the ceramic substrate is 12 × 10 ⁻⁶ / ° C. or less, the ceramic substrate and the metal column are The stress due to the difference in the coefficient of thermal expansion is less likely to occur between and. As a result, a highly reliable ceramic circuit board can be obtained without causing cracks or breaks in the ceramic board.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a ceramic circuit board of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of an embodiment of a ceramic circuit board of the present invention. 1 is a ceramic board, 2 is an active metal brazing material, 3 is a metal circuit board, and 4 is a metal column.

Metal circuit boards 3 having a predetermined pattern are attached to both upper and lower surfaces of the ceramic substrate 1 via an active metal brazing material 2, and at the same time, copper is provided in a through hole formed in the ceramic substrate 1 and penetrating in the thickness direction. A metal column 4 made of copper oxide is arranged.

The metal columns 4 made of copper and copper oxide, which are arranged in the through holes provided in the ceramic substrate 1, are connected at their both ends to the upper and lower metal circuit boards 3, respectively. The metal circuit boards 3 attached to the upper and lower surfaces of the above are connected via the metal columns 4.

The ceramic substrate 1 usually has a substantially quadrangular shape and functions as a supporting member for supporting the metal circuit board 3, and is made of an aluminum oxide sintered body, a mullite sintered body, a silicon carbide sintered body, or an aluminum nitride. It is made of an electrically insulating material such as a porous sintered body or a silicon nitride sintered body.

If the ceramic substrate 1 is formed of, for example, an aluminum oxide sintered body, an organic binder, a plasticizer, and a solvent suitable for the raw material powder of aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, etc. Is added and mixed to form a sludge, and a ceramic green sheet (ceramic green sheet) is formed by applying the well-known doctor blade method or calender roll method to the sludge, and then the ceramic green sheet is formed. Through-holes are formed by appropriate punching, and multiple through-holes are stacked to create a through-hole.
It is manufactured by firing at a high temperature of ℃.

On the upper and lower surfaces of the ceramic substrate 1, metal circuit boards 3 are attached via an active metal brazing material 2 so as to close the through holes provided in the ceramic substrate 1.

The ceramic substrate 1 has a thickness of 0.2.
It is preferable that the thickness is ˜1 mm in terms of suppressing cracking of the ceramic substrate 1 when the metal circuit board 3 is joined and heat transferability of heat generated from a semiconductor element (not shown). Thickness is 0.
If it is less than 2 mm, the ceramic substrate 1 tends to be cracked due to the stress generated when the metal circuit board 3 is bonded to the ceramic substrate 1. On the other hand, if the thickness exceeds 1 mm, it tends to be difficult to satisfactorily dissipate heat generated from the mounted semiconductor element.

The metal circuit board 3 is made of a metal material such as copper or aluminum, and is joined to the upper and lower surfaces of the ceramic substrate 1 through the active metal brazing material 2 as follows.

For example, silver brazing powder made of silver-copper alloy powder or aluminum brazing powder made of aluminum-silicon alloy powder is added to at least one active metal such as titanium, zirconium or hafnium and its hydride. An active metal brazing material 2 obtained by adding 2 to 5% by mass of the active metal powder is mixed with an appropriate organic solvent / solvent to obtain an active metal brazing material paste. A predetermined pattern corresponding to the metal circuit board 3 is printed by using a technique.

Thereafter, the metal circuit board 3 is placed on this brazing material pattern, and this is placed in a vacuum, or in a neutral atmosphere or a reducing atmosphere at a predetermined temperature (about 90 degrees for a silver brazing material).
At 0 ° C., about 600 ° C. for an aluminum brazing material), the active metal brazing material 2 is melted to bond the upper and lower surfaces of the ceramic substrate 1 to the metal circuit board 3. This allows
The metal circuit boards 3 are bonded to the upper and lower surfaces of the ceramic substrate 1.

Metal circuit board 3 made of copper or aluminum
Is a 0.5 mm thick, desired circuit wiring pattern shape, for example, by applying a well-known metal processing method such as rolling, punching, or cutting to an ingot (lump) of copper or aluminum. Will be produced.

The thickness of the metal circuit board 3 lowers the electric resistance for transmitting a large current signal, and the ceramic substrate 1
It is preferably 0.1 to 1 mm in order to prevent cracking of the ceramic substrate 1 when joined to. If it is less than 0.1 mm, the electric resistance tends to be large, and it tends to be difficult for a large current signal to flow. On the other hand, if it exceeds 1 mm, the ceramic substrate 1 tends to be cracked or the like due to the stress generated when the ceramic substrate 1 and the metal circuit board 3 are bonded.

The metal columns 4 are arranged so as to fill the through holes in the ceramic substrate 1, and the upper and lower ends thereof are joined to the metal circuit board 3 via the active metal brazing material 2. It is arranged to be done.

The metal column 4 is made of an alloy material of copper and copper oxide, and is joined to the inside of the through hole of the ceramic substrate 1 via the active metal brazing material 2 as follows.

An active metal brazing material paste prepared in the same manner as that used for bonding the metal circuit board 3 is applied to the inside of the through hole of the ceramic substrate 1 by a screen printing method or a dispensing method.

After that, the metal column 4 is inserted and arranged in the through hole,
This is heat-treated at a predetermined temperature (about 900 ° C. for silver brazing material and about 600 ° C. for aluminum brazing material) in a vacuum or in a neutral atmosphere or a reducing atmosphere, and the active metal brazing material 2 is treated. The metal pillars 4 are fused and joined to the through holes of the ceramic substrate 1.

The heat treatment of the metal columns 4 and the heat treatment of the metal circuit board 3 may be performed simultaneously.

Metal column 4 made of an alloy material of copper and copper oxide
For example, after mixing copper powder and copper oxide powder in a predetermined ratio, kneading with a ball mill for, for example, about 24 hours, and then pressure firing at a temperature of 800 to 850 ° C. at about 10 atm for about 3 hours. By making an alloy ingot (lump) of copper and copper oxide by carrying out, and by subjecting it to a conventionally known metal working method such as rolling, punching, and cutting, for example, a diameter of 0.5 mm It is manufactured in a cylindrical shape.

It is important that the metal column 4 has a copper content of 50 to 80% by mass and a copper oxide content of 50 to 20% by mass. This is preferable in terms of suppressing resistance heating and suppressing cracks and cracks due to the difference in thermal expansion coefficient from the ceramic substrate 1.

When the copper content is less than 50% by mass, the metal pillar 4 tends to have a specific resistance of more than 5 μΩ · cm and tends to easily generate resistance heat when a large current flows. On the other hand, when the content of copper exceeds 80% by mass, the coefficient of thermal expansion is 12
The temperature tends to be higher than × 10 ⁻⁶ / ° C., and the ceramic substrate 1 tends to be cracked due to the difference in thermal expansion coefficient from the ceramic substrate 1.

[0038]

EXAMPLES The ceramic circuit board of the present invention will be described in detail below with reference to examples.

First, as a ceramic substrate, the thickness is 0.63.
An aluminum oxide substrate having a size of 5 mm and a size of 75 mm □ was prepared. 20 through holes having a diameter of 0.4 mm were processed in advance on this aluminum oxide substrate.

The metal column is made of an alloy of copper and copper oxide having the composition shown in Table 1 and has a diameter of 0.3 mm and a length of 0.635 mm.
A cylindrical metal column of No. 1 was prepared. Table 1 shows the specific resistance and the coefficient of thermal expansion of the metal columns for each composition at this time.

[0041]

[Table 1]

Next, 97 mass% of silver-copper alloy powder, 3 mass% of titanium hydride powder, an organic binder and a solvent were kneaded to prepare an active metal brazing material paste. Then, this active metal brazing material paste was applied and dried on both upper and lower surfaces of the aluminum oxide substrate and the through holes.

Each metal column was inserted and arranged in the through hole of the aluminum oxide substrate coated with this active metal brazing material paste, and at the same time, oxygen-free copper plates with a thickness of 0.3 mm were arranged on both upper and lower surfaces, and the atmosphere was 10 ^-3 Pa. The aluminum oxide substrate was bonded to the oxygen-free copper plate and the metal columns by the active metal brazing material by performing heat treatment at a temperature of 850 ° C. for 1 hour in vacuum.

For each ceramic circuit board thus produced, a current of 5 A and 10 A per metal column was passed by a DC power source, and the temperature change on the surface of this ceramic circuit board was measured by a surface thermometer. At this time, the ceramic circuit board was covered with a heat insulating material to prevent the generated heat from being dissipated. Then, the temperature rise was measured after 5 minutes by passing an electric current, and the temperature change of less than 10 ° C was evaluated as ◯, and the temperature change of 10 ° C or more was evaluated as x. The results are shown in Table 2.

-40 ° C (30 minutes) to + 125 ° C (30 minutes)
The temperature cycle test of up to 3000 cycles was performed, and after the test, the oxygen-free copper plate and the active metal brazing material on the upper and lower surfaces were peeled off by chemical etching with hydrofluoric acid, and the presence of cracks around the through holes was observed with a metallurgical microscope. did. As a result, the number of cycles in which cracks have occurred is shown in Table 2.

[0046]

[Table 2]

From the results shown in Table 1 and Table 2, in Comparative Examples 1 to 4 in which the content of copper in the metal column is less than 50% by mass, the specific resistance exceeds 5 μΩcm, and a large current exceeding 10 A is applied to this metal column. It can be seen that a temperature rise of 10 ° C or more occurs when flowing.

Further, in Comparative Examples 5 and 6 in which the content of copper in the metal columns exceeds 80 mass%, the coefficient of thermal expansion exceeds 12 × 10 ⁻⁶ / ° C., and heat is generated around the through holes of the ceramic substrate. Cracks due to the difference in expansion coefficient occurred in 2000 cycles or less.

On the other hand, in Examples 1 to 4 which are examples of the present invention, the specific resistance is low at 2.7 to 5 μΩ · cm, and the thermal expansion coefficient is 8.5 to 11.9 × 10 ⁻⁶ / ° C. , 12
At a temperature of × 10 ^-6 / ° C or less, the difference from the coefficient of thermal expansion of the aluminum oxide substrate was small. In addition, the temperature rise after 5 minutes after passing a current of 10 A through the metal column was 0.3 to 9.8 ° C, which was less than 10 ° C, and no cracks were found around the through holes even after the temperature cycle test of 3000 cycles.

It should be noted that the present invention is not limited to the examples of the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

For example, in the example of the above-mentioned embodiment, the metal circuit board is directly brazed to the ceramic substrate through the active metal brazing material to form the ceramic circuit board. Alternatively, a metallized metal layer such as molybdenum may be deposited, and a metal circuit board may be bonded to the metallized metal layer via a brazing material to form a ceramic circuit board.

[0052]

According to the ceramic circuit board of the present invention,
The metal circuit boards attached to both sides of the ceramic substrate,
The metal circuit board and the metal are arranged through the metal columns having a copper content of 50 to 80 mass% and a copper oxide content of 20 to 50 mass% arranged in the through holes of the ceramic substrate. Even if a large current of more than 10 A flows through the pillar, the resistance of the metal pillar is as low as 2.7 to 5 μΩ · cm, so that resistance heat is hardly generated and a large amount of heat is not generated. As a result, an electronic component such as a semiconductor element, which is adhesively fixed to a metal circuit board by using an adhesive such as solder, always has an appropriate temperature, and can operate normally and stably for a long period of time.

Further, according to the ceramic circuit board of the present invention, when the coefficient of thermal expansion of the metal column arranged in the through hole of the ceramic substrate is 12 × 10 ⁻⁶ / ° C. or less, the ceramic substrate and the metal column are The stress due to the difference in the coefficient of thermal expansion is less likely to occur between and. As a result, a highly reliable ceramic circuit board can be obtained without causing cracks or breaks in the ceramic board.

As described above, according to the present invention, it is possible to effectively prevent the generation of a large amount of heat due to resistance heat generation in the conductor connecting the metal circuit boards, and to keep electronic components such as semiconductor elements mounted on the metal circuit boards at all times. It was possible to provide a ceramic circuit board that can be operated normally and stably at an appropriate temperature.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an embodiment of a ceramic circuit board of the present invention.

[Explanation of symbols]

1: Ceramic substrate 2: Active metal brazing material 3: Metal circuit board 4: Metal pillar

Claims (3)

[Claims] 1. A ceramic substrate having a through hole, metal circuit boards are attached to both sides of the ceramic substrate so as to close the through hole, and the content of copper in the through hole is 50 to 80% by mass and the content of copper oxide. Arranging a metal column whose content is 50 to 20% by mass,
A ceramic circuit board, wherein the metal circuit boards on both sides of the ceramic board are connected by the metal columns. 2. The specific resistance of the metal column is 2.7 to 5 μΩ.
The ceramic circuit board according to claim 1, wherein the ceramic circuit board is in cm. 3. The thermal expansion coefficient of the metal column is 12 × 10 ⁻⁶
/ C or less, The ceramic circuit board according to claim 1 characterized by things.