JP2001339155A - Ceramic circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic circuit board in which a metal circuit board can be bonded rigidly onto a ceramic board without causing any electric short circuit between adjacent metal circuit boards or any cracking in the ceramic board. SOLUTION: A metal circuit board 3 is fixed to the upper surface of a ceramic board 1 through an active metal solder material layer 2 to produce a ceramic circuit board. The active metal solder material layer 2 comprises solder material powder composed of silver powder and copper powder and/or silver-copper alloy powder, and active metal powder composed of at least one kind of titanium, zirconium, hafnium and hydrides thereof and containing 5-20 wt.% of metal powder 2a having a melting point of 1200 deg.C or above and a mean grain size of 1-10 μm.

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 a metal circuit board is joined to a ceramic substrate using an active metal brazing material.

[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, an active metal brazing material obtained by adding titanium, zirconium, hafnium or a hydride thereof to a silver-copper eutectic alloy on a ceramic substrate. There is used a ceramic circuit board in which a metal circuit board made of copper or the like is directly joined through an intermediary.

[0003] Such ceramic circuit boards are generally made of an electrically insulating ceramic material such as a sintered body of aluminum oxide, a sintered body of aluminum nitride, a sintered body of silicon nitride, or a sintered body of mullite as a ceramic substrate. For example, when it is made of an aluminum oxide sintered body, it is specifically manufactured by the following method.

[0004] (1) First, an organic solvent and a solvent are added to an active metal powder obtained by adding at least one of titanium, zirconium, hafnium and a hydride thereof to a silver-copper alloy to prepare a brazing material paste. I do. (2) Next, a ceramic raw material powder such as aluminum oxide, silicon oxide, magnesium oxide and calcium oxide is mixed with an appropriate organic binder, plasticizer, solvent and the like to form a slurry, which is then formed into a well-known doctor blade. After obtaining a plurality of ceramic green sheets by adopting a tape forming technique such as a method or a calendar roll method, forming the ceramic green sheets to a predetermined size, and then laminating the ceramic green sheets vertically as necessary, , About 1600
The ceramic green sheet is fired at a temperature of ° C., and the ceramic green sheets are sintered and integrated to form a ceramic substrate made of an aluminum oxide sintered body. (3) Next, a metal circuit board having a predetermined pattern made of copper or the like is placed on the ceramic substrate with the brazing material paste interposed therebetween. (4) Finally, the brazing material paste disposed between the ceramic substrate and the metal circuit board is heated to a temperature of about 900 ° C. in a reducing atmosphere, and the silver paste is applied to the ceramic substrate via the active metal powder. A ceramic circuit board is manufactured by joining a brazing material made of a copper alloy and joining the brazing material to a metal circuit board.

The active metal brazing material and the exposed surface of the metal circuit board are effectively bonded to an exposed surface of the metal circuit board with an adhesive such as solder for bonding and fixing electronic components such as semiconductor elements to the metal circuit board. Metals such as nickel are applied by using techniques such as plating to make them stronger.

[0006]

However, in this conventional ceramic circuit board, the bonding of the metal circuit board to the ceramic substrate is performed by a metal circuit board having a predetermined pattern made of copper or the like with a brazing material paste interposed therebetween. Is placed in a reducing atmosphere and heated to a temperature of about 900 ° C., and the brazing material paste is heated at a temperature equal to or higher than the liquidus temperature. Viscosity was remarkably reduced, and the molten metal spread greatly, and the melted and spreaded brazing material had a disadvantage of causing an electrical short circuit between adjacent metal circuit boards.

Therefore, in order to solve the above-mentioned drawback, it is conceivable to reduce the thickness of the brazing material paste to, for example, less than 10 μm.

However, when the thickness of the brazing material paste is reduced, when the metal circuit board is mounted on the ceramic substrate, a stress generated between the ceramic substrate and the metal circuit board due to a difference in thermal expansion coefficient between the two. Cannot be effectively absorbed by the brazing material. As a result, cracks and cracks are generated in the ceramic substrate due to the stress.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has as its object to form a metal circuit board on a ceramic substrate without causing an electrical short circuit between the metal circuit boards which are in contact with each other, and to break the metal circuit board. It is an object of the present invention to provide a ceramic circuit board that can be firmly bonded without generating any problem.

[0010]

A ceramic circuit board according to the present invention is a ceramic circuit board having a metal circuit board attached to an upper surface of a ceramic substrate via an active metal brazing material layer. The material layers are silver powder and copper powder and / or
Or a brazing filler metal powder comprising a silver-copper alloy powder, and titanium,
Active metal powder composed of at least one of zirconium, hafnium and hydrides thereof and containing therein 5 to 20% by weight of a metal powder having a melting point of 1200 ° C. or more and an average particle diameter of 1 to 10 μm. It is characterized by the following.

According to the ceramic circuit board of the present invention, the metal active brazing material layer for joining the metal circuit board to the ceramic substrate includes a brazing material powder composed of silver powder and copper powder and / or silver-copper alloy powder; An active metal powder comprising at least one of titanium, zirconium, hafnium and a hydride thereof, and containing therein 5 to 20% by weight of a metal powder having a melting point of 1200 ° C. or more and an average particle diameter of 1 to 10 μm. Therefore, when joining the metal circuit board via the active metal brazing material layer on the ceramic substrate, even if the brazing material is heated to a temperature equal to or higher than the liquidus temperature and melted, the molten brazing material is Viscosity increases due to resistance due to contact with the metal powder contained therein, and as a result, the brazing material does not significantly melt and spread between adjacent metal circuit boards. Electrical independence of the metal circuit plates is maintained can always function properly ceramic circuit board as a product.

At the same time, since the melting and spreading of the brazing material is effectively suppressed by the metal powder, a predetermined amount of the brazing material is interposed between the ceramic substrate and the metal circuit board. Even if the joint with the metal circuit board becomes strong and stress is generated due to the difference in the coefficient of thermal expansion between the ceramic substrate and the metal circuit board, the stress is absorbed by the brazing material, and the ceramic substrate is cracked or broken. And the like can be effectively prevented.

[0013]

Next, the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 show an embodiment of a ceramic circuit board according to the present invention, wherein 1 is a ceramic substrate, 2 is an active metal brazing material layer, and 3 is a metal circuit board.

The ceramic substrate 1 has a square shape,
On its upper surface, a metal circuit board 3 is brazed via an active metal brazing material layer 2.

The ceramic substrate 1 functions as a support member for supporting the metal circuit board 3 joined to the upper surface thereof, and is made of aluminum oxide sintered body, mullite sintered body, silicon carbide sintered body, aluminum nitride It is formed of an electrically insulating material such as a sintered body and a silicon nitride sintered body.

When the ceramic substrate 1 is made of, for example, an aluminum oxide sintered body, aluminum oxide,
An appropriate organic binder, a plasticizer, and a solvent are added to and mixed with raw material powders such as silicon oxide, magnesium oxide, and calcium oxide to form a slurry, and the slurry is subjected to a conventionally known doctor blade method or calendar roll method. By ceramic green sheet (ceramic raw sheet)
Then, the ceramic green sheet is manufactured by subjecting the ceramic green sheet to an appropriate punching process, laminating a plurality of the sheets, and firing at a high temperature of about 1600 ° C.

The ceramic substrate 1 has a metal circuit board 3 joined to the upper surface thereof via an active metal brazing material layer 2. Electronic components such as semiconductor elements are connected to the metal circuit board 3. And the like to supply electric signals and electric power to electronic components such as the electronic parts.

The metal circuit board 3 is made of a metal material such as copper. The ingot (lumps) made of copper or the like is subjected to a conventionally known metal processing method such as a rolling method or a punching method so that the thickness is reduced, for example. It is manufactured in a predetermined pattern shape at 500 μm.

When the metal circuit board 3 is formed of oxygen-free copper, the oxygen-free copper is bonded to the ceramic substrate 1 via the active metal brazing material layer 2 when the surface of the copper is removed. The wettability with the active metal brazing material 2 is improved without being oxidized by oxygen present in the copper, and as a result, the bonding to the ceramic substrate 1 via the active metal brazing material layer 2 becomes strong. Therefore, it is preferable that the metal circuit board 3 is formed of oxygen-free copper.

If the metal circuit board 3 is coated with a metal made of nickel and having good conductivity, good corrosion resistance and good wettability with a brazing material by plating,
A good electrical connection between the metal circuit board 3 and the external electric circuit can be achieved, and an electronic component such as a semiconductor element can be firmly adhered to the metal circuit board 3. Therefore, it is preferable that the metal circuit board 3 is coated with a metal made of nickel and having good conductivity, good corrosion resistance and good wettability with the brazing material by plating.

Further, when a plating layer made of nickel is applied on the surface of the metal circuit board 3, the phosphorous content is 8 to 15% by weight.
If the contained nickel-phosphorus amorphous alloy is used, the surface oxidation of the nickel plating layer is prevented well, and electronic components such as semiconductor elements are securely and firmly electrically connected to the metal circuit board 3 via an adhesive such as solder. Can be connected. Therefore, when a plating layer made of nickel is applied to the surface of the metal circuit board 3, the content of phosphorus is preferably in the range of 8 to 15% by weight, preferably in the range of 10 to 15% by weight. It is preferable to use an amorphous alloy of phosphorus.

Further, when a plating layer made of nickel is applied to the surface of the metal circuit board 3, when the thickness of the nickel plating layer is less than 1.5 μm, the surface of the metal circuit board 3 is completely covered with the nickel plating layer. It becomes difficult to effectively prevent the metal circuit board 3 from being oxidized and corroded, and if it exceeds 3 μm, the internal stress inside the nickel plating layer becomes large and the ceramic substrate 1 There is a risk that warpage or cracks may occur. In particular, when the thickness of the ceramic substrate 1 is as thin as 700 μm or less, warpage or cracking of the ceramic substrate 1 becomes remarkable. Therefore, when a plating layer made of nickel is applied to the surface of the metal circuit board 3, it is preferable that the thickness of the nickel plating layer be in the range of 1.5 μm to 3 μm.

The metal circuit board 3 is joined to the ceramic substrate 1 via an active metal brazing material layer 2, and the active metal brazing material layer 2 acts to directly join the metal circuit board 3 on the ceramic substrate 1. Make

The active metal brazing material layer 2 comprises a brazing material powder composed of silver powder, copper powder and / or silver-copper alloy powder, and an active metal composed of at least one of titanium, zirconium, hafnium and hydrides thereof. Powder, and having a melting point of 1200 ° C. or more and an average particle size of 1
It contains 5 to 20% by weight of a metal powder 2a of 10 to 10 μm.

The joining of the metal circuit board 3 to the ceramic substrate 1 by the active metal brazing material layer 2 is performed by first using a brazing material powder composed of silver powder, copper powder and / or silver-copper alloy powder, titanium, zirconium, An active metal brazing material paste obtained by mixing active metal powder comprising at least one of hafnium and their hydrides, metal powder 2a having a melting point of 1200 ° C. or more and an average particle size of 1 to 10 μm, an organic solvent and a solvent. Then, the active metal brazing paste is printed in a predetermined pattern on the ceramic substrate 1 using a conventionally known screen printing technique, and then the metal circuit board 3 is placed on the printed active metal brazing paste. And then put it in a vacuum or neutral, reducing atmosphere for about 90
Heating is performed at a temperature of 0 ° C. to join a brazing material made of a silver-copper alloy to the ceramic substrate 1 via an active metal powder and to join the brazing material to the metal circuit board 3. In this case, the brazing material melted by heating has an increased viscosity due to resistance due to contact with the metal powder contained therein, and as a result, the brazing material does not melt and spread widely between the adjacent metal circuit boards 3. In addition, the electrical independence between the adjacent metal circuit boards 3 is maintained, and the ceramic circuit board as a product can always function normally. At the same time, the melting and spreading of the brazing material is effectively suppressed by the metal powder 2a, so that a predetermined amount of the brazing material is interposed between the ceramic substrate 1 and the metal circuit board 3, and as a result, the ceramic substrate 1 When the ceramic substrate 1 and the metal circuit board 3 are firmly bonded to each other and a stress is generated due to a difference in thermal expansion coefficient between the ceramic substrate 1 and the metal circuit board 3, the stress is absorbed by the brazing material, and 1 can also effectively prevent the occurrence of cracks and cracks.

The brazing powder composed of silver powder, copper powder and / or silver-copper alloy powder of the active metal brazing material layer 2 is firmly bonded to the metal circuit board 3 and is made of titanium, zirconium, hafnium and the like. At least one of the hydrides
The active metal powder consisting of the seed is solidified on the brazing material made of a silver-copper alloy and on the ceramic substrate 1, thereby joining the metal circuit board 3 to the ceramic substrate 1.

The active metal powder comprising at least one of titanium, zirconium, hafnium and their hydrides constituting the active metal brazing material layer 2 has an absolute amount of active metal of less than 2% by weight. There is a danger that it will be difficult to firmly join the active metal brazing material layer 2 to the ceramic substrate 1, and if it exceeds 5% by weight, the active metal brazing material layer 2 and the ceramic substrate 1 are fragile. The active metal brazing material layer 2 is formed thickly as a result.
There is a risk that the bonding strength between the ceramic substrate 1 and the ceramic substrate 1 may be reduced. Accordingly, it is preferable that the amount of the active metal powder comprising at least one of titanium, zirconium, hafnium and hydrides thereof constituting the active metal brazing material layer 2 be in the range of 2 to 5% by weight.

The active metal brazing material layer 2 contains 5 to 20% by weight of a metal powder 2a having a melting point of 1200 ° C. or more and an average particle diameter of 1 to 10 μm.

The metal powder 2a acts to suppress the melting and spreading of the molten brazing material. The active metal brazing material layer 2 does not melt and spread greatly due to the inclusion of the metal powder 2a. 3 maintain the electrical independence between the ceramic substrate 1 and the metal circuit board 3. The active metal brazing material layer 2 interposed between the ceramic substrate 1 and the metal circuit board 3 can always function normally.
The strength of the ceramic substrate 1 and the metal circuit board 3 is strengthened by setting the amount of the ceramic substrate 1 and the metal circuit board 3 to a predetermined value, and the stress generated due to the difference in thermal expansion coefficient between the ceramic substrate 1 and the metal circuit board 3 is effectively absorbed, Cracks and cracks can be prevented from being generated in the ceramic substrate 1.

The melting point of the metal powder 2a is 1200 ° C.
Since the above metal materials, specifically, tungsten, molybdenum, manganese, etc., have a high melting point of 1200 ° C. or more, when the metal circuit board 3 is bonded to the ceramic substrate 1 via the active metal brazing material layer 2, Even if heat is applied to the powder 2a, the metal powder 2a does not melt, and as a result, the melting and spreading of the brazing material can be effectively suppressed by the metal powder 2a.

When the average particle size of the metal powder 2a is less than 1 μm, the specific surface area of the metal powder 2a increases, and a large amount of oxygen is present in an oxide film formed on the surface of the metal powder 2a. Thereby, the wettability of the active metal brazing material layer 2 to the ceramic substrate 1 and the metal circuit board 3 is reduced, and the metal circuit board 3 can be firmly joined to the ceramic substrate 1 via the active metal brazing material layer 2. On the other hand, if the thickness exceeds 10 μm, the specific surface area of the metal powder 2a decreases, and the resistance of the molten brazing material due to contact with the metal powder 2a decreases, so that the melting and spreading of the brazing material cannot be effectively suppressed. Therefore, the average particle size of the metal powder 2a is specified in the range of 1 to 10 μm.

When the amount of the metal powder 2a is less than 5% by weight, the resistance of the molten brazing material due to contact with the metal powder 2a becomes small, and the melting and spreading of the brazing material cannot be suppressed effectively. If the content exceeds 20% by weight, the bonding area of the brazing material to the ceramic substrate 1 and the metal circuit board 3 becomes narrow, and the metal circuit board 3
The bonding strength is reduced. Therefore, the metal powder 2
The addition amount of a is specified in the range of 5 to 20% by weight.

Thus, according to the above-mentioned ceramic circuit board, electronic components such as semiconductor elements are connected to the metal circuit board 3 joined to the upper surface of the ceramic substrate 1 via the active metal brazing material layer 2, and the metal circuit board is connected. When the external circuit 3 is connected to an external electric circuit, electric signals and electric power are supplied from the external electric circuit to the electronic components such as semiconductor elements via the metal circuit board 3.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. Although an example in which the electronic component generates a large amount of heat and an efficient removal of this heat is described, the ceramic substrate 1 may be formed of an aluminum nitride sintered body having a high thermal conductivity or an aluminum nitride sintered body. The ceramic substrate 1 may be formed of a mullite sintered body having a low dielectric constant when an electric signal is to be propagated to the metal circuit board 3 at high speed.

[0035]

According to the ceramic circuit board of the present invention,
The metal active brazing material for joining the metal circuit board on the ceramic substrate is a brazing material powder composed of silver powder and copper powder and / or silver-copper alloy powder, and at least one of titanium, zirconium, hafnium and hydrides thereof. And containing 5 to 20% by weight of a metal powder having a melting point of 1200 ° C. or more and an average particle diameter of 1 to 10 μm inside the active metal brazing material on a ceramic substrate. When joining a metal circuit board via the same, even if the brazing material is heated to a temperature equal to or higher than the liquidus temperature and melts, the molten brazing material has a viscosity due to resistance due to contact with the metal powder contained therein. Is higher, so that
The brazing material does not significantly melt and spread between the adjacent metal circuit boards, and the electrical independence between the adjacent metal circuit boards is maintained, so that the ceramic circuit board as a product can always function normally.

At the same time, since the melting and spreading of the brazing material is effectively suppressed by the metal powder, a predetermined amount of the brazing material is interposed between the ceramic substrate and the metal circuit board. Even if the joint with the metal circuit board becomes strong and stress is generated due to the difference in the coefficient of thermal expansion between the ceramic substrate and the metal circuit board, the stress is absorbed by the brazing material, and the ceramic substrate is cracked or broken. And the like can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a ceramic circuit board of the present invention.

FIG. 2 is an enlarged view of a main part of the ceramic circuit board shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramic substrate 2 ... Active metal brazing material layer 2a ... Metal powder 3 ... Metal circuit board

Claims (1)

[Claims] 1. A ceramic circuit board having a metal circuit board attached to an upper surface of a ceramic substrate via an active metal brazing material layer, wherein the active metal brazing material layer comprises silver powder, copper powder and / or silver. A brazing filler metal powder composed of a copper alloy powder and an active metal powder composed of at least one of titanium, zirconium, hafnium and hydrides thereof, and having a melting point of 1200 ° C. or more and an average particle diameter of 1 to 10 μm inside
A ceramic circuit board, comprising 5 to 20% by weight of a metal powder of the formula (1).