JP2002009403A - Ceramic circuit board and semiconductor element module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate deterioration in heat dissipating due to permeation of bubbles in a heat conducting composition layer between a ceramic circuit board and a heat dissipating member, which is caused by warp of the ceramic circuit board due to heat generated by a semiconductor element. SOLUTION: In this ceramic circuit board, metal circuit board 2 is attached on the upper surface of a ceramic board 1, a dummy metal circuit board 3 corresponding to the metal circuit board 2 is attached on the lower surface of the board 1, and the dummy metal circuit board 3 is mounted on the heat dissipating member 5 via heat conducting composition 4. When an outer peripheral position of the metal circuit board 2 is set to X, an outer peripheral position of the dummy metal circuit board 3 is set to Y and the thickness of the ceramic board 1 is set to Z, a relation of 0<|X-Y|<=z/2 is held.

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, and a semiconductor device module.

[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 to a ceramic board via an active metal brazing material has been used. Have been.

Such a ceramic circuit board is generally manufactured by the following method in the case of a ceramic board generally made of an aluminum oxide sintered body.

First, at least one of titanium, zirconium, hafnium and hydrides thereof is added to a silver-copper alloy.
An organic solvent and a solvent are added and mixed with the seeded active metal powder to prepare a brazing material paste.

Next, a raw material powder such as aluminum oxide, silicon oxide, magnesium oxide and calcium oxide is mixed with a suitable organic binder, a plasticizer, a solvent and the like to form a slurry, which is mixed with a conventionally known doctor blade method. After obtaining a plurality of ceramic green sheets by adopting a tape forming technique such as calendering or calender roll method, the ceramic green sheets are formed into a predetermined size, and then the ceramic green sheets are stacked up and down as needed, and about 1600 in a reducing atmosphere. 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.

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

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 non-oxidizing atmosphere to melt the brazing material.
It is manufactured by joining a ceramic substrate and a metal circuit board with this brazing material.

[0008] The ceramic circuit board manufactured in this manner is bonded to an electronic component such as a semiconductor element such as an IC or an LSI via an adhesive such as solder and then mounted on a heat dissipation member such as aluminum by soldering. Thus, a semiconductor element module (hereinafter, referred to as a semiconductor module) that satisfactorily radiates heat generated during operation of the semiconductor element is obtained.

However, the ceramic circuit board (having a coefficient of thermal expansion of about 3 to 10 ppm / ° C.) and the heat dissipating member (having a coefficient of thermal expansion of about 18 to 23 ppm / ° C.) are significantly different from each other. Cracks may occur in the solder between the heat dissipating members, and peeling may occur, which may significantly deteriorate the reliability.

For this reason, a configuration is adopted in which a ceramic circuit board and a heat radiating member are joined and mounted via a grease-like heat conductive composition instead of solder.

[0011]

However, in the conventional semiconductor module as described above, since the balance of the thermal expansion coefficient is different in the portion of the upper surface of the ceramic circuit board where the metal circuit board is not joined, the electronic component is not used. When heat is generated, the ceramic substrate warps and deforms due to the temperature rise. For example, when the ceramic substrate is deformed and the peripheral portion is deformed upward, the end of the heat conductive composition is concaved in a U-shape, and then when the deformation of the ceramic substrate returns, the end of the heat conductive composition also returns to the original state. Then, the above-mentioned concave portion is closed, and bubbles (air) enter.

As a result, air bubbles (air) penetrate into the heat conductive composition between the ceramic circuit board and the heat radiating member, and the heat radiating path from the electronic component is cut off, resulting in thermal destruction of the electronic component and deterioration of characteristics. Therefore, there has been a problem that the electronic component cannot be operated stably and reliably.

Accordingly, the present invention has been completed in view of the above problems, and an object of the present invention is to suppress the deformation of a ceramic circuit board due to warping and to stably operate an electronic component such as a semiconductor element. It is to provide a substrate and a semiconductor module.

[0014]

According to the present invention, a metal circuit board is mounted on an upper surface of a ceramic substrate, and a dummy metal circuit plate corresponding to the metal circuit plate is mounted on a lower surface. A ceramic circuit board mounted on a heat radiating member via a thermal composition, wherein the outer peripheral position of the metal circuit board is X, the outer peripheral position of the dummy metal circuit board is Y, and the thickness of the ceramic substrate is Z. , 0 <| X−Y | ≦ Z /
2.

According to the ceramic circuit board of the present invention, a dummy metal circuit board corresponding to the metal circuit board is attached to the lower surface of the ceramic board having the metal circuit board attached to the upper surface. There is no stress between the metal circuit board and the ceramic substrate and the dummy metal circuit board due to the difference in the coefficient of thermal expansion, and warpage of the ceramic circuit board due to heat generated during operation of electronic components such as semiconductor elements. Deformation does not occur, air bubbles do not enter the heat conductive composition between the ceramic circuit board and the heat radiating member, and the heat radiation does not deteriorate, so that a highly reliable semiconductor module can be obtained.

According to the ceramic circuit board of the present invention, the outer peripheral position of the dummy metal circuit board is made different from the outer peripheral position of the metal circuit board. The position where the crack occurs on the ceramic substrate and the position where the crack occurs on the ceramic substrate due to the stress generated between the ceramic substrate and the dummy metal circuit board are different. As a result, cracking of the ceramic substrate is effectively prevented, and the ceramic circuit is effectively prevented. The reliability of mechanical strength as a substrate can be made high.

Further, according to the semiconductor module of the present invention, a semiconductor element is mounted on the metal circuit board of the ceramic circuit board of the present invention, and the heat dissipation of the dummy metal circuit board is performed through the heat conductive composition. It is mounted on a member.

With such a configuration, the heat dissipation is good as described above, the reliability is high in terms of mechanical strength, and the semiconductor element can be stably operated for a long period of time.

[0019]

Next, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the ceramic circuit board of the present invention, wherein 1 is a ceramic board, 2 is a metal circuit board, 3 is a dummy metal circuit board, 4 is a heat conductive composition, 5 is a heat radiating member, 6 is a semiconductor element.

The ceramic substrate 1 has a square shape, and a metal circuit board 2 and a dummy metal circuit board 3 are brazed on both upper and lower surfaces thereof.

The ceramic substrate 1 acts as a support member for supporting the metal circuit board 2 and the dummy metal circuit board 3, and is made of an aluminum oxide (Al ₂ O ₃ ) sintered body, mullite (3Al ₂
O ₃ · 2SiO ₂ ) sintered body, silicon carbide (SiC) based sintered body, aluminum nitride (AlN) based sintered body, silicon nitride (Si ₃ N ₄ ) based sintered body, etc. Have been.

When the ceramic substrate 1 is formed of, for example, an aluminum oxide sintered body, an appropriate 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 slurry is mixed to form a slurry, and the slurry is formed into a ceramic green sheet (green ceramic sheet) by employing a conventionally known doctor blade method or calender roll method. It is manufactured by performing a punching process, laminating a plurality of these, and firing at a high temperature of about 1600 ° C.

The ceramic substrate 1 has a metal circuit board 2 and a dummy metal circuit board 3 attached to the upper and lower surfaces thereof through brazing material.

The ceramic substrate 1 has a thickness of 0.1 mm.
It is preferable to set it to 2 to 1.0 mm. If the thickness is less than 0.2 mm, cracks or the like are likely to occur in the ceramic substrate 1 due to stress generated when the ceramic substrate 1 is bonded to the metal circuit board 2 or the dummy metal circuit board 3. If it exceeds 1.0 mm, the heat generated from the semiconductor element 6 can be satisfactorily dissipated to the heat radiating member 5.
It is difficult to communicate to.

The metal circuit board 2 and the dummy metal circuit board 3 are made of a metal material such as copper or aluminum. The metal circuit board 2 and the dummy metal circuit board 3 are joined to the upper and lower surfaces of the ceramic substrate 1 as follows. Is done.

For example, silver braze powder composed of silver-copper alloy powder, aluminum braze powder composed of aluminum-silicon alloy powder, and the like, and at least one active metal such as titanium, zirconium, hafnium or a hydride thereof. An active metal brazing material paste obtained by adding and mixing an appropriate organic solvent and a solvent to an active metal brazing material to which 2 to 5% by weight of an active metal powder is added is applied to the upper and lower surfaces of the ceramic substrate 1 by a conventionally known screen printing technique. Printing is performed in a predetermined pattern corresponding to the metal circuit board 2 and the dummy metal circuit board 3 by using the same.

Thereafter, the metal circuit board 2 and the dummy metal circuit board 3 are placed on the pattern, and are placed in a vacuum, a neutral atmosphere, or a reducing atmosphere at a predetermined temperature (about 900 in the case of silver brazing material). ℃, about 600 in case of aluminum brazing material
C.), the active metal brazing material is melted, and the upper and lower surfaces of the ceramic substrate 1 are joined to the metal circuit board 2 and the dummy metal circuit board 3. As a result, the upper and lower surfaces of the ceramic substrate 1, the metal circuit board 2, and the dummy metal circuit board 3 are attached.

Metal circuit board 2 made of copper, aluminum, etc.
The dummy metal circuit board 3 has a thickness of, for example, 0.1 mm by subjecting an ingot such as copper or aluminum to a conventionally known metal processing method such as a rolling method or a punching method.
It is manufactured in a predetermined pattern shape corresponding to the pattern shape at 5 mm. The thickness of the metal circuit board 2 or the dummy metal circuit board 3 is preferably 0.1 to 1.0 mm. If the thickness is less than 0.1 mm, the electric resistance increases, so that it becomes difficult to transmit a high current signal from the semiconductor element. When the thickness is 1.0 mm or more, cracks or the like are likely to occur in the ceramic substrate 1 due to stress generated when the ceramic substrate 1 is bonded to the metal circuit board 2 or the dummy metal circuit board 3.

The thickness and the material of the metal circuit board 2 and the dummy metal circuit board 3 are the same thickness and the same material in order to suppress warpage due to heating at the time of active metal brazing or solder reflow for mounting the semiconductor element 6. Is preferred.

A semiconductor element 6 is soldered to a predetermined position of the metal circuit board 2, and an electrode of the semiconductor element 6 and an electrode of the metal circuit board 2 are electrically connected by a bonding wire such as aluminum. ing.

The heat dissipating member 5 is made of a high heat conductive material such as copper or aluminum, and more specifically, has a heat conductivity of 100 W / m · K (W ·
m ⁻¹ · K ⁻¹ ) or more, and is preferably bonded and mounted to the dummy metal circuit board 3 via the heat conductive composition 4.

Heat dissipating member 5 made of copper, aluminum, etc.
Is manufactured in a rectangular shape having a thickness of, for example, about 3 mm by subjecting an ingot such as copper or aluminum to a conventionally known metal working method such as a rolling method or a punching method.

The heat conductive composition 4 is in the form of a grease. For example, the heat conductive composition 4 is prepared by adding an appropriate amount of a powder of a heat conductive material such as aluminum, copper, zinc, aluminum nitride or the like to silicone oil and mixing. Is applied in a predetermined pattern and a predetermined thickness on the upper surface of the heat radiating member 5 by a screen printing method, a dispensing method or the like. The thickness is preferably from 50 to 300 μm. If it is less than 50 μm,
It becomes difficult to distribute the heat conductive composition 4 uniformly. When the thickness is 300 μm or more, the heat transfer composition 4 is too thick, so that the heat transfer property is reduced.

The shape of the dummy metal circuit board 3 substantially corresponds to the shape of the metal circuit board 2, and the metal circuit board 2 is mounted on the lower surface of the ceramic substrate 1 on which the metal circuit board 2 is mounted.
Since the dummy metal circuit board 3 corresponding to the metal circuit board 2 is attached to a vertically symmetrical position (corresponding position), even if the semiconductor element 6 mounted on the metal circuit board 2 operates and generates heat, the ceramic substrate 1 and the metal The occurrence of warpage due to the difference in the coefficient of thermal expansion between the circuit board 3 and the dummy metal circuit board 3 is suppressed, and the heat transfer composition 4 is free of air bubbles (air) and satisfactorily radiated.
And a highly reliable semiconductor module can be obtained.

When the outer peripheral position of the dummy metal circuit board 3 is located outside or inside the half of the thickness Z of the ceramic substrate 1 with respect to the outer peripheral position of the metal circuit board 2, the semiconductor element 6 operates to generate heat. However, the occurrence of warpage due to the difference in thermal expansion coefficient between the ceramic substrate 1, the metal circuit board 2, and the dummy metal circuit board 3 cannot be suppressed. In addition, the dummy metal circuit board 3 and the metal circuit board 2 are located at the same position (| X-Y
It is difficult to fabricate and install them so that | = 0). Therefore, it is preferable to secure a difference of 50 μm or more between the outer peripheral positions of the dummy metal circuit board 3 and the metal circuit board 2. Therefore, assuming that the thickness Z of the ceramic substrate 1, the outer peripheral position X of the metal circuit board 2, and the outer peripheral position Y of the dummy metal circuit board 3, the range is 0 <| XY− ≦ Z / 2.

X and Y are relative positions in the horizontal direction. For example, one of X and Y is a reference position and the other is a position (distance) in the horizontal direction with respect to the reference position.
Or each position (distance) in the horizontal direction from a separate reference position (not shown).

When the metal circuit board 2 and the dummy metal circuit board 3 are made of copper, if the metal circuit board 2 and the dummy metal circuit board 3 are formed of oxygen-free copper, the oxygen-free copper is In addition, the wettability of the active metal brazing material is improved without being oxidized by oxygen present in the copper, and the bonding to the ceramic substrate 1 is strengthened. Therefore, it is preferable that the metal circuit board 2 and the dummy metal circuit board 3 are formed of oxygen-free copper.

The present invention is not limited to the above-described embodiment, and various changes can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the metal circuit board 2 and the dummy metal circuit board 3 are brazed directly to the ceramic substrate 1 via the active metal brazing material to form a ceramic circuit board. A ceramic circuit board may be formed by previously attaching a metallized metal layer such as tungsten or molybdenum, and attaching the metal circuit board 2 and the dummy metal circuit board 3 to the metallized metal layer via a brazing material.

[0040]

According to the ceramic circuit board of the present invention,
When the outer peripheral position of the metal circuit board is X, the outer peripheral position of the dummy metal circuit board is Y, and the thickness of the ceramic substrate is Z, 0 <|
Since X−Y | ≦ Z / 2, heat transfer between the ceramic substrate, the metal circuit board, and the dummy metal circuit board due to a difference in thermal expansion coefficient between the heat dissipation member and the heat dissipation member does not occur. Air bubbles (air) do not enter the composition, and as a result, heat generated from the semiconductor element can be transmitted to the heat radiating member satisfactorily, and the electronic component such as the semiconductor element can be operated stably without heat radiation deterioration.

According to the semiconductor module of the present invention, the semiconductor element is mounted on the metal circuit board of the ceramic circuit board, and is mounted on the heat dissipating member via the heat conductive composition on the dummy metal circuit board. As described above, the electronic components such as the semiconductor elements can be operated stably for a long time without deterioration of the heat radiation.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a semiconductor module using a ceramic circuit board of the present invention.

[Explanation of symbols]

 1: Ceramic substrate 2: Metal circuit board 3: Dummy metal circuit board 4: Heat conductive composition 5: Heat dissipation member 6: Semiconductor element

Claims (2)

[Claims] A metal circuit board is mounted on an upper surface of a ceramic substrate, and a dummy metal circuit board corresponding to the metal circuit board is mounted on a lower surface, and the dummy metal circuit board is provided with a heat dissipating member via a heat conductive composition. Wherein the outer peripheral position of the metal circuit board is X, the outer peripheral position of the dummy metal circuit board is Y, and the thickness of the ceramic substrate is Z, 0 <| X−Y | ≦ Z / 2. A ceramic circuit board. 2. A semiconductor element comprising: a semiconductor element mounted on the metal circuit board of the ceramic circuit board according to claim 1; and a dummy metal circuit board mounted on the heat radiating member via the heat conductive composition. module.