JP2001177194A - Ceramic circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that a ceramic circuit board is warped and that an electronic component cannot be mounted surely and firmly. SOLUTION: The ceramic circuit board is formed n such a way that a metal circuit board 3 is attached and bonded to the surface of a ceramic board 1. A dummy metal circuit board 4 which corresponds to the metal circuit board 3 is attached and bonded to the rear surface of the ceramic board 1. The outer circumferential position of the dummy metal circuit board 4 is situated to the outside from the metal circuit board 3, and the position is set as Y+0.1 (mm)<=X<=Y when the outer circumferential position of the dummy circuit board 4 is designated as X, the outer circumferential position of the metal circuit plate 3 as Y, and the thickness of the ceramic board 1 as Z.

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 by brazing.

[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 metallized metal layer adhered on a ceramic substrate is formed of a metal made of copper or the like via a brazing material such as a silver-copper alloy. A ceramic circuit board with a circuit board bonded, or silver
A ceramic circuit board is used in which a metal circuit board made of copper or the like is directly joined to a copper eutectic alloy via an active metal brazing material obtained by adding titanium, zirconium, hafnium or a hydride thereof.

[0003] Such a ceramic circuit board, for example, a ceramic circuit board in which a metal circuit board made of copper or the like is joined to a metallized metal layer adhered on the ceramic board via a brazing material, is generally made of an aluminum oxide sintered body. A metallized metal layer is applied to the surface of a ceramic substrate made of an electrically insulating ceramic material such as an aluminum nitride sintered body, a silicon nitride sintered body, a mullite sintered body, etc.
The metallized metal layer is formed by brazing a metal circuit board made of a metal material such as copper via a brazing material such as silver brazing. Specifically, for example, a ceramic substrate is made of an aluminum oxide sintered body. In the case of consisting of, raw material powders such as aluminum oxide, silicon oxide, magnesium oxide and calcium oxide are mixed with an appropriate organic binder, a plasticizer, a solvent and the like to form a slurry, which is then mixed with a conventionally known doctor blade method. A plurality of ceramic green sheets are obtained by adopting a tape forming technique such as or a calender roll method, and then an appropriate organic binder, a plasticizer, and a solvent are added to the high melting point metal powder such as tungsten or molybdenum on the ceramic green sheets. The metal paste obtained by mixing is subjected to a predetermined pattern by employing a thick film forming technology such as screen printing. Then, the ceramic green sheets, on which the metal paste is printed and applied in a predetermined pattern, are laminated one on top of the other as necessary and fired at a temperature of about 1600 ° C. in a reducing atmosphere. To form a ceramic substrate made of an aluminum oxide sintered body having a metallized metal layer on the surface, and finally a metal circuit board of a predetermined pattern made of copper or the like on the metallized metal layer on the surface of the ceramic substrate. And a brazing material such as a silver brazing material is interposed therebetween and heated in a reducing atmosphere at a temperature of about 900 ° C. to melt the brazing material, and the metallized metal layer and the metal circuit board are melted with the molten brazing material. It is produced by joining

In order to effectively prevent oxidative corrosion on the metallized metal layer and the exposed surface of the metal circuit board, and to firmly connect electronic components such as semiconductor elements to the metal circuit board via an adhesive such as solder. In addition, a metal having excellent corrosion resistance such as nickel and having good wettability with respect to an adhesive such as solder is applied to a predetermined thickness by using a technique such as a plating method.

[0005]

However, in this conventional ceramic circuit board, the coefficient of thermal expansion of the ceramic substrate is about 3 ppm / ° C. to 7 ppm / ° C. (aluminum oxide sintered body: about 7 ppm / ° C., aluminum nitride Sintered body: about 4 ppm / ° C, silicon nitride based sintered body: about 3 p
pm / ° C), whereas the coefficient of thermal expansion of a metal circuit board made of copper, aluminum or the like is about 18 ppm / ° C to about 23 ppm.
ppm / ° C (copper: about 18 ppm / ° C, aluminum: about 23 ppm / ° C), and since the thermal expansion coefficients of the ceramic substrate and the metal circuit board are significantly different, the metallized metal layer adhered to the upper surface of the ceramic substrate When a metal circuit board is attached via a brazing material such as silver brazing, a large stress is generated between the ceramic substrate and the metal circuit board due to a difference in the coefficient of thermal expansion between the ceramic substrate and the metal circuit board. Of the semiconductor device, which causes a problem in mounting the semiconductor element. In addition, if the warpage is large, the ceramic substrate is fragile, causing cracks in the ceramic substrate, resulting in a loss of the function as a ceramic circuit substrate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has as its object to effectively prevent warpage and cracking of a ceramic substrate so that electronic components such as semiconductor elements can be mounted with high reliability. Another object of the present invention is to provide a ceramic circuit board capable of stably operating electronic components.

[0007]

According to the present invention, there is provided a ceramic circuit board having a metal circuit board attached to an upper surface of a ceramic substrate, wherein a dummy metal circuit corresponding to the metal circuit board is provided on a lower surface of the ceramic substrate. At the same time, the outer peripheral position of the dummy metal circuit board is located outside the metal circuit board, and the outer peripheral position of the dummy metal circuit board is X, and the outer peripheral position of the metal circuit board is Y. When the thickness of the ceramic substrate is Z, Y + 0.1 (mm) ≦ X ≦
Y + Z.

According to the ceramic circuit board of the present invention, the dummy metal circuit board corresponding to the metal circuit board is symmetrically mounted on the lower surface of the ceramic substrate having the metal circuit board mounted on the upper surface. Between the substrate and the metal circuit board, and between the ceramic substrate and the dummy metal circuit board, stress due to the difference in the coefficient of thermal expansion occurs and warpage occurs, but the directions of the warpage are different from each other, canceling out. As a result, the ceramic substrate does not warp and becomes flat, and electronic components such as semiconductor elements can be securely and firmly mounted on the ceramic circuit substrate.

Further, according to the ceramic circuit board of the present invention, since the outer peripheral position of the metal circuit board is different from the outer peripheral position of the dummy metal circuit board, it is caused by the stress generated between the ceramic substrate and the metal circuit board. The crack generation position on the ceramic substrate is different from the crack generation position on the ceramic substrate caused by the stress generated between the ceramic substrate and the dummy metal circuit board.As a result, the ceramic substrate is effectively prevented from cracking, etc. The reliability of mechanical strength as a substrate can be made high.

Further, according to the ceramic circuit board of the present invention, the outer peripheral position of the dummy metal circuit board is set outside the outer peripheral position of the metal circuit board, and the position is 0.1 mm or more from the outer peripheral position of the metal circuit board. Even when heat acts on the ceramic circuit board, the ceramic circuit board does not warp significantly, and at the same time, the dummy metal circuit board generates heat generated when electronic components such as semiconductor elements are operated. , And efficiently discharge to the outside, so that the electronic component can be operated stably with a good cooling effect of the electronic component.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail based on embodiments shown in the accompanying drawings. FIG. 1 shows an embodiment of a ceramic circuit board according to the present invention, wherein 1 is a ceramic substrate, 2 is a metallized metal layer, 3 is a metal circuit board, and 4 is a dummy metal circuit board.

The ceramic substrate 1 has a square shape,
Metallized metal layers 2 are adhered on both upper and lower surfaces,
A metal circuit board 3 and a dummy metal circuit board 4 are brazed to the metallized metal layer 2.

The ceramic substrate 1 functions as a support member for supporting the metal circuit board 3 and the dummy metal circuit board 4, and is made of a sintered body of aluminum oxide, a sintered body of mullite, a sintered body of silicon carbide, a body of aluminum nitride. It is formed of an electrically insulating material such as a sintered body, a silicon nitride-based sintered body, and a mullite-based sintered body.

When the ceramic substrate 1 is formed of, for example, an aluminum oxide sintered body, a suitable organic binder, a plasticizer, and a solvent are added to a raw material powder such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide. The mixture is added to form a slurry, and the slurry is formed into a ceramic green sheet (ceramic green sheet) by employing a well-known doctor blade method or calender roll method. It is processed and formed into a predetermined shape and, if necessary, a plurality of sheets are vertically stacked to form a molded body. Thereafter, this is fired at a high temperature of about 1600 ° C., or a raw material powder such as aluminum oxide is formed. A suitable organic solvent and a solvent are added and mixed to adjust the raw material powder, and the raw material powder is Molded into a predetermined shape by press forming technique, and thereafter, is manufactured by firing the molded body at a temperature of about 1600 ° C..

The ceramic substrate 1 has metallized metal layers 2 of a predetermined pattern adhered to upper and lower surfaces thereof, and the metallized metal layers 2 are formed by brazing a metal circuit board 3 or a dummy metal circuit board 4 to the ceramic substrate 1. In this case, it acts as a base metal layer.

The metallized metal layer 2 is made of a high melting point metal material such as tungsten, molybdenum, and manganese. For example, a metal paste obtained by adding an appropriate organic binder, a plasticizer, and a solvent to tungsten powder and mixing the resulting mixture is fired. A predetermined pattern and a predetermined thickness (10 to 50 μm) are formed on the upper and lower surfaces of the ceramic substrate 1 by printing and applying a predetermined pattern on the surface of a ceramic green sheet (ceramic raw sheet) serving as the ceramic substrate 1 by a conventionally known screen printing method. ).

The metallized metal layer 2 is coated on its surface with a metal having good conductivity, such as nickel or gold, having good corrosion resistance and good wettability with a brazing material by a plating method of 1 μm to 20 μm.
In this case, the metallized metal layer 2 can be effectively prevented from being oxidized and corroded, and the brazing of the metallized metal layer 2 to the metal circuit board 3 and the dummy metal circuit board 4 is made extremely strong. be able to. Accordingly, in order to effectively prevent the metallized metal layer 2 from being oxidized and corroded, and to firmly braze the metallized metal layer 2 with the metal circuit board 3 and the dummy metal circuit board 4, it is necessary to use nickel or nickel on the surface of the metallized metal layer 2. It is preferable that a metal such as gold having good conductivity, good corrosion resistance and good wettability with the brazing material is applied to a thickness of 1 μm to 20 μm.

On the upper surface of the metallized metal layer 2, a metal circuit board 3 and a dummy metal circuit board 4 are attached via a brazing material 5.

The metal circuit board 3 and the dummy metal circuit board 4
Is formed of a metal material such as copper or aluminum, and a metal circuit board 3 and a dummy metal circuit board 4 are formed on a metallized metal layer 2 formed on the upper and lower surfaces of a ceramic substrate 1 by, for example, a silver brazing material (silver: 72% by weight, 28% by weight of copper) and a brazing material 5 made of aluminum brazing material (88% by weight of aluminum, 12% by weight of silicon), and then placed in vacuum or neutral. In a reducing atmosphere, a heat treatment is performed at a predetermined temperature (about 900 ° C. for a silver brazing material, about 600 ° C. for an aluminum brazing material) to melt the brazing material 5 and to connect the upper surface of each metallized metal layer 2 to the metal circuit. By joining the plate 3 and the lower surface of the dummy metal circuit board 4, they are attached to the upper and lower surfaces of the ceramic substrate 1.

The metal circuit board 3 or the dummy metal circuit board 4 made of copper, aluminum, or the like is obtained by subjecting an ingot (lumps) of copper, aluminum, or the like to a conventionally known metal processing method such as a rolling method or a punching method. For example, the metallized metal layer 2 is manufactured in a predetermined pattern shape corresponding to the pattern shape of the metallized metal layer 2 with a thickness of 500 μm.

The shape of the dummy metal circuit board 4 substantially corresponds to the shape of the metal circuit board 3. The metal circuit board 3 is attached to the lower surface of the ceramic substrate 1 on which the metal circuit board 3 is mounted. Since the corresponding dummy metal circuit boards 4 are mounted symmetrically, stresses caused by the difference in thermal expansion coefficient between the ceramic substrate 1 and the metal circuit board 3 and between the ceramic substrate 1 and the dummy metal circuit board 4. When warping occurs, the directions in which the warping occurs are different from each other, and the directions are offset. As a result, the ceramic substrate 1 is flat without warpage, and electronic components such as semiconductor elements are mounted on the ceramic circuit board. It is possible to surely and firmly mount.

The outer peripheral position of the dummy metal circuit board 4 is located outside the outer peripheral position of the metal circuit board 3;
Further, when the position is X, the outer circumferential position of the dummy metal circuit board 4 is X, the outer circumferential position of the metal circuit board 3 is Y, and the thickness of the ceramic substrate 1 is Z, Y + 0.1 (mm) ≦ X ≦ Y + Z. .

Since the outer peripheral position of the dummy metal circuit board 4 is different from the outer peripheral position of the metal circuit board 3, the ceramic substrate 1 generated by the stress generated between the ceramic substrate 1 and the metal circuit board 3 is formed. Is different from the crack generation position of the ceramic substrate 1 caused by the stress generated between the ceramic substrate 1 and the dummy metal circuit board 4. As a result, it is effective that the ceramic substrate 1 is cracked. And the reliability of the mechanical strength of the ceramic circuit board can be increased.

At the same time, the outer peripheral position of the dummy metal circuit board 4 is set outside the outer peripheral position of the metal circuit board 3, and the position is set at 0.1 mm or more from the outer peripheral position of the metal circuit board 3 and within the thickness of the ceramic substrate 1. Therefore, even if heat acts on the ceramic circuit board, the ceramic circuit board does not warp greatly, and at the same time, the heat generated when the electronic components such as the semiconductor elements operate at 45 ° from the upper surface to the lower surface of the ceramic substrate 1 The dummy metal circuit board 4 efficiently absorbs the spread heat and satisfactorily emits the heat to the outside, so that the cooling effect of the electronic component is improved and the electronic component can be operated stably.

The dummy metal circuit board 4 is located 0.1 mm from the outer peripheral position of the metal circuit board 3 even if its outer peripheral position is located inside or outside the outer peripheral position of the metal circuit board 3. If it is less than the outside, the dummy metal circuit board 4 cannot efficiently absorb the heat generated at the time of operation of the electronic component and can not satisfactorily release the heat to the outside. The outer peripheral position of the dummy metal circuit board 4 is different from the outer peripheral position of the metal circuit board 3
Is located outside the thickness of the ceramic substrate 1 and the dummy metal circuit board 4, the stress generated between the ceramic substrate 1 and the metal circuit board 3 is larger than the stress generated between the ceramic substrate 1 and the metal circuit board 3. As a result, the ceramic circuit board is warped. Accordingly, the outer peripheral position of the dummy metal circuit board 4 is located outside the outer peripheral position of the metal circuit board 3, and the outer peripheral position of the dummy metal circuit board 4 is X, and the outer peripheral position of the metal circuit board 3 is X. Is Y, ceramic substrate 1
Is the thickness of Z, Y + 0.1 (mm) ≦ X ≦ Y +
It is specified in the range of Z.

When the metal circuit board 3 and the dummy metal circuit board 4 are made of copper, if the metal circuit board 3 and the dummy metal circuit board 4 are formed of oxygen-free copper, the oxygen-free copper is brazed. In this case, the copper surface is not oxidized by the oxygen present in the copper, so that the wettability with the brazing material 5 is improved, and the bonding to the metallized metal layer 2 via the brazing material 5 is strengthened. Therefore, the metal circuit board 3 and the dummy metal circuit board 4
Is preferably formed from oxygen-free copper.

The metal circuit board 3 and the dummy metal circuit board 4 are coated on their surfaces with a metal made of nickel and having good conductivity, good corrosion resistance and good wettability with the brazing material by plating. Thus, the electrical connection between the metal circuit board 3 and the dummy metal circuit board 4 and the external electric circuit is good, and the electronic components such as semiconductor elements can be firmly adhered to the metal circuit board 3 via solder. Therefore, the metal circuit board 3 and the dummy metal circuit board 4 may be coated with a metal made of nickel and having good conductivity, good corrosion resistance and good wettability with the brazing material by plating. preferable.

Further, when a plating layer made of nickel is applied to the surfaces of the metal circuit board 3 and the dummy metal circuit board 4, 8 to 15% by weight of phosphorus is contained therein to form a nickel-phosphorus amorphous alloy. Oxidation of the surface of the plating layer made of nickel can be prevented well, and the wettability with the brazing material can be maintained for a long time. Therefore, the metal circuit board 3
When a plating layer made of nickel is applied to the surface of the dummy metal circuit board 4, it is preferable to contain 8 to 15% by weight of phosphorus therein to form a nickel-phosphorus amorphous alloy.

When a plating layer made of a nickel-phosphorus amorphous alloy is applied to the surface of the metal circuit board 3, the content of phosphorus with respect to nickel is less than 8% by weight.
Alternatively, when the content exceeds 15% by weight, it is difficult to form an amorphous alloy of nickel-phosphorus, and there is a risk that the solder cannot be firmly bonded to the plating layer.
Therefore, when a plating layer made of an amorphous alloy of nickel and phosphorus is applied to the surface of the metal circuit board 3, the content of phosphorus with respect to nickel is preferably in the range of 8 to 15% by weight, and more preferably. The range of 10 to 15% by weight is good.

Furthermore, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit 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.

Further, in the above-described embodiment, a metallized metal 2 is previously adhered to the surface of the ceramic substrate 1, and a metal circuit board 3 and a dummy metal circuit board 4 are brazed to the metallized metal layer 2 to form a ceramic circuit. The metal circuit board 3 was directly formed on the surface of the ceramic substrate 1 via an active metal brazing material obtained by adding titanium or titanium hydride to a silver-copper eutectic alloy in an amount of 2 to 5% by weight. The ceramic circuit board may be formed by attaching the dummy metal circuit board 4.

[0032]

According to the ceramic circuit board of the present invention,
Since the metal circuit board and the corresponding dummy metal circuit board are symmetrically mounted on the lower surface of the ceramic substrate having the metal circuit board mounted on the upper surface, the space between the ceramic substrate and the metal circuit board and between the ceramic substrate and the dummy metal Stress due to the difference in the coefficient of thermal expansion between the circuit board and the board causes warping, but the directions of the warping are different from each other, which offset each other, resulting in warping of the ceramic substrate. This makes it possible to securely and firmly mount electronic components such as semiconductor elements on the ceramic circuit board.

Further, according to the ceramic circuit board of the present invention, since the outer peripheral position of the metal circuit board and the outer peripheral position of the dummy metal circuit board are different, it is caused by the stress generated between the ceramic substrate and the metal circuit board. The crack generation position on the ceramic substrate is different from the crack generation position on the ceramic substrate caused by the stress generated between the ceramic substrate and the dummy metal circuit board.As a result, the ceramic substrate is effectively prevented from cracking, etc. The reliability of mechanical strength as a substrate can be made high.

Further, according to the ceramic circuit board of the present invention, the outer peripheral position of the dummy metal circuit board is set outside the outer peripheral position of the metal circuit board, and the position is 0.1 mm or more from the outer peripheral position of the metal circuit board. Even when heat acts on the ceramic circuit board, the ceramic circuit board does not warp significantly, and at the same time, the dummy metal circuit board generates heat generated when electronic components such as semiconductor elements are operated. , And is efficiently released to the outside, and the cooling effect of the electronic component is improved, so that the electronic component can be operated stably.

[Brief description of the drawings]

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

[Explanation of symbols]

 1 ceramic substrate 2 metallized metal layer 3 metal circuit board 4 dummy metal circuit board

Claims (1)

[Claims] A ceramic circuit board having a metal circuit board attached to an upper surface of a ceramic substrate, wherein a dummy metal circuit board corresponding to the metal circuit board is attached to a lower surface of the ceramic substrate; The outer peripheral position of the dummy metal circuit board is located outside the metal circuit board, and the position is X, the outer peripheral position of the dummy metal circuit board is Y, the outer peripheral position of the metal circuit board is Y, and the thickness of the ceramic substrate is Z. When
A ceramic circuit board, wherein Y + 0.1 (mm) ≦ X ≦ Y + Z.