JP2003324167A - Ceramic circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a ceramic circuit board is separated from an external connection board whereby a semiconductor element mounted on the ceramic circuit board cannot be operated normally. <P>SOLUTION: The ceramic circuit board 1 is constituted of a metal circuit board 3 arranged on one main surface of a ceramic board 2, a metal board 4 mounted on the other main surface of the metal circuit board 3 so as to be opposed to the metal circuit board 3, a through conductor 5 connecting the metal circuit board 3 to the metal board 4, and a projected part formed at the center of the main surface opposed to the ceramic board 2 of the metal board 4 so as to have a flat head. The connection of the metal board 4 on which the projection 4a is formed and the external connection board 10 through solder 8 becomes three-dimensional whereby the ceramic circuit board 1 can be surely and rigidly connected to the external connection board 10. <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 on which a power semiconductor element is mounted and which can be surface-mounted on an external connection board with good heat transfer properties.

[0002]

2. Description of the Related Art Conventionally, IGBT (Insulated Gate Bipol)
ar Transistor) and MOS-FET (Metal Oxide Semic)
onductor-A metal circuit made of copper or the like via a brazing material such as a silver-copper alloy on a metallized metal layer deposited on a ceramic substrate as a substrate for mounting a power semiconductor element such as a field effect transistor. A ceramic circuit board bonded to a plate or a metal circuit board made of copper or the like was directly bonded onto the ceramic substrate through an active metal brazing material containing titanium-zirconium-hafnium or its hydrogen compound added to a silver-copper alloy. A ceramic circuit board is used.

Further, when high density mounting is required in this ceramic circuit board, a metal plate is arranged on the other main surface facing the metal circuit board, and the metal circuit board and the metal plate are placed in the ceramic board. There is used a ceramic circuit board which has a structure in which the metal plate is electrically connected by a penetrating conductor provided on the external connection terminal and is used as an external connection terminal, and the mounting area is reduced. In this through conductor, a through hole formed in a ceramic substrate is filled with a metal paste and sintered, or a metal pillar made of copper or the like is placed in the through hole formed in the ceramic substrate, and both ends of the through conductor are made of metal. For example, a circuit board, a metal plate and a brazing material may be joined together.

Incidentally, these ceramic circuit boards, for example, a ceramic circuit board in which a metal circuit board made of copper or the like is directly bonded onto the ceramic board via an active metal brazing material,
Generally, a ceramic substrate made of an electrically insulating ceramic material such as an aluminum oxide sintered body, an aluminum nitride sintered body, a silicon nitride sintered body, and a mullite sintered body, and provided with through holes penetrating in the thickness direction. Then, a metal column is placed in the through hole of this ceramic substrate, and an organic solvent or a solvent is added to and mixed with silver brazing powder (alloy powder of silver and copper) to obtain a brazing material paste. A metal circuit having a predetermined pattern, which is applied on both sides of the metal plate, and a brazing material such as an active metal brazing material in which at least one of titanium, zirconium, hafnium or a hydride of these is added to a silver-copper alloy is sandwiched between ceramic substrates. The plate is placed on and brought into contact with the plate, and then heated in a reducing atmosphere to a temperature of about 900 ° C. to melt the brazing material paste and the brazing material to activate the metallized metal layer and the metal circuit board. Via the metal brazing material, and a metal circuit plate and the metal columns are manufactured by joining via the brazing material such as silver solder.

Further, such a ceramic circuit board is
After mounting a power semiconductor element such as an IGBT or a MOS-FET, it is used by being connected to an external connection board such as a printed board. To join a metal plate to an external connection board such as a printed circuit board, first, a solder paste formed by adding an organic solvent / solvent to a solder powder on the external connection board such as a printed circuit board is printed by a conventionally known screen printing method. By using technology, it is printed and attached to a predetermined pattern, then the ceramic circuit board is placed and abutted on this print-applied solder paste, and then this is heated to a predetermined temperature (about 180 ° C) and the solder paste is applied. The organic solvent, the solvent, etc. are diffused and the solder is melted, and the metal plate and the printed board are joined by the melted solder.

[0006]

However, in this conventional ceramic circuit board, when an external connection board such as a printed board is joined to a metal plate via an adhesive such as solder, the solder is a metal plate. It will melt to a large extent on the surface and become thin with a thickness of less than 50 μm. As a result, it will be difficult to firmly attach the metal plate to the external connection substrate, and the heat generated by the ON / OFF switching operation of the semiconductor element will be generated. When operating, the difference in thermal expansion coefficient between the metal plate and the external connection substrate (for example, alumina: 7 × 10
^-6 / ° C, printed circuit board: 17 × 10 ^-6 / ° C) causes a large thermal stress, and this thermal stress causes the metal plate to peel off from the external connection board. It was

On the other hand, the thickness of the solder as the adhesive is made thick beforehand (for example, about 250 μm), and the amount of the solder interposed between the metal plate and the external connection board is set to an appropriate amount to the metal for the external connection board. It is conceivable to increase the bonding strength of the plates.

However, if the thickness of the solder as the adhesive is increased, the melted solder flows out from the metal plate onto the ceramic substrate when the solder is melted and the metal plate is joined to the external connection substrate. Short-circuiting between adjacent metal plates or thick adhesive between the metal plates and the external connection board, which consists of solder with low thermal conductivity, causes the heat generated during the operation of semiconductor elements to be transferred from the metal plate to the external connection board. However, there is a drawback in that the semiconductor element cannot be efficiently transmitted to the semiconductor element, and the semiconductor element is heated to a high temperature, causing thermal breakdown in the semiconductor element and thermal deterioration in the characteristics.

Further, since the surfaces of the metal plate of the ceramic circuit board and the external connection board such as the printed circuit board are substantially flat, the ceramic circuit board can be bonded to the surface of the external connection board by melting the solder and joining them. There is also a problem that there is a risk of slippage between the two and displacement of the two, which may reduce the mounting accuracy of the ceramic circuit board on the external connection board.

The present invention has been devised in view of the above-mentioned drawbacks of the prior art. An object of the present invention is to firmly bond a ceramic circuit board to an external connection board and to keep the semiconductor element at an appropriate temperature. It is to provide a ceramic circuit board that can be operated normally and stably for a long period of time.

[0011]

In the ceramic circuit board of the present invention, a metal circuit board is arranged on one main surface of the ceramic board, and a metal plate is arranged on the other main surface so as to face the metal circuit board. While the plate and the metal plate are connected by a through conductor arranged in the ceramic substrate,
A convex portion having a flat head portion is formed in a central portion of a main surface of the metal plate opposite to the ceramic substrate.

In the ceramic circuit board of the present invention, in the above structure, the height of the convex portion is 50 μm or more and 200 μm or more.
In the following, the distance from the outer periphery of the metal plate to the outer periphery of the convex portion is 100 μm or more, and the ratio of the area of the head of the convex portion to the area of the metal plate is 40% or more, To do.

Further, the ceramic circuit board of the present invention is
In the above configuration, the plurality of convex portions are provided, and the interval between the adjacent convex portions is 100 μm or more.

According to the ceramic circuit board of the present invention, since a convex portion having a flat head is formed in the central portion of a metal plate to which an external connection substrate such as a printed circuit board is joined, the convex portion is formed. When the bonded metal plate is bonded to the external connection board via solder as an adhesive, a space is formed between the upper surface of the external connection board, the side surface of the convex portion, and the surface of the metal plate around the convex portion. As a result, solder is filled and intervenes in this space and between the upper surface of the external connection board and the surface of the head of the convex portion, and as a result, the metal plate provided with the convex portion is soldered to the external connection board. The joining via the three-dimensional structure becomes three-dimensional, and the ceramic circuit board can be securely and firmly joined to the external connection board.

Further, according to the ceramic circuit board of the present invention, in the above structure, the height of the convex portion is 50 μm or more and 200 μm or more.
The distance from the outer circumference of the metal plate to the outer circumference of the protrusion is 10 m or less.
When it is 0 μm or more and the ratio of the area of the head of the convex portion to the area of the metal plate is 40% or more, the metal plate on which the convex portion is formed is connected to the external connection substrate through solder as an adhesive. When bonded, a space of sufficient volume is formed between the upper surface of the external connection board, the side surface of the convex portion, and the surface of the metal plate around the convex portion, and in the space and the upper surface of the external connection substrate. A sufficient amount of solder is filled and intervenes between the protrusion and the surface of the head, and as a result, the metal plate with the protrusion is soldered to the external connection board more securely and firmly. Can be made.

Further, the upper surface of the external connection board and the surface of the head of the convex portion of the metal plate are in contact with each other with a sufficient area, and the solder interposed between the surface of the head of the convex portion and the upper surface of the external connection board. The heat generated when the semiconductor element mounted on the ceramic circuit board is activated by the metal circuit board / through conductor and metal It is efficiently transmitted to the external connection board through the plate, and as a result, it becomes possible to keep the semiconductor element always at an appropriate temperature and operate the semiconductor element normally and stably for a long period of time.

Further, according to the ceramic circuit board of the present invention, in the above structure, when the plurality of protrusions are provided and the interval between the adjacent protrusions is 100 μm or more, the metal having the protrusions is formed. When the board is joined to the external connection board via solder as an adhesive, a space of sufficient volume is formed between the upper surface of the external connection board and the surface of the metal plate between the adjacent convex portions. Solder is filled in this space,
The solder filled in this space increases friction that acts between the metal plate of the ceramic circuit board and the external connection board such as a printed circuit board. When the ceramic circuit board and the external connection board are melted and joined together, The ceramic circuit board is suppressed from sliding on the surface of the external connection board,
As a result, the positional displacement between the two does not occur, and the mounting accuracy of the ceramic circuit board on the external connection board does not drop significantly.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 are cross-sectional views showing an example of an embodiment of a ceramic circuit board of the present invention. 1 is a ceramic circuit board, 2 is a ceramic board, 3 is a metal circuit board, 4 is a metal plate, and 4a is a convex. Reference numeral 5 is a penetrating conductor, 6 is an active metal brazing material, 7 is a brazing material, 8 is solder, 9 is a semiconductor element, 10 is an external connection board such as a printed board, and 11 is an adhesive.

The ceramic substrate 2 has a substantially quadrangular shape, and the active metal brazing material 6 is provided on one main surface and the other main surface thereof, respectively.
The metal circuit board 3 and the metal plate 4 having a predetermined pattern are attached via the through holes, and the through conductors 5 made of metal columns are provided in the through holes penetrating the ceramic substrate 2 in the thickness direction. It is arranged so as to be joined to the metal circuit board 3 and the metal plate 4 via 7. The metal circuit board 3 and the metal plate 4 attached to the upper and lower surfaces of the ceramic substrate 2 are electrically connected by the through conductors 5 joined to the metal circuit board 3 and the metal plate 4 via the brazing material 7. ing.

The ceramic substrate 2 is formed of an electrically insulating material such as an aluminum oxide sintered body, a mullite sintered body, a silicon nitride sintered body, an aluminum nitride sintered body, and a silicon carbide sintered body. There is. For example, in the case of an aluminum oxide sintered body, a suitable organic binder, a plasticizer, and a solvent are added to and mixed with raw material powders of aluminum oxide, magnesium oxide, yttrium oxide, etc. to form a slurry. A ceramic green sheet (ceramic green sheet) is formed by applying the well-known doctor blade method or calender roll method to the object, and then this ceramic green sheet is punched appropriately to form a predetermined shape, and necessary. According to the above, a plurality of sheets are laminated to form a molded body, and thereafter, this is manufactured by firing at a temperature of about 1600 ° C. in a non-oxidizing atmosphere such as a nitrogen atmosphere.

The metal circuit board 3 and the metal plate 4 are made of copper or aluminum. For example, a copper or aluminum ingot (lump) is subjected to a well-known metal working method such as a rolling working method or a punching working method to obtain, for example, 500 μm.
Is formed into a predetermined pattern.

When the metal circuit board 3 and the metal plate 4 are made of copper, if they are made of oxygen-free copper, the oxygen-free copper is attached to the ceramic substrate 2 via the active metal brazing material 6. Since the surface of the copper is not oxidized by oxygen existing in the copper and the wettability with the active metal brazing material 6 becomes good, the active metal of the metal circuit board 3 and the metal plate 4 on the ceramic substrate 2 is improved. The attachment and joining through the brazing material 6 becomes strong.
Therefore, when the metal circuit board 3 and the metal plate 4 are made of copper, it is preferable that they are made of oxygen-free copper.

Further, the metal plate 4 has a flat head and a convex portion 4a formed on the main surface of the metal plate 4 opposite to the ceramic substrate 2, and the convex portion 4a has the head portion of the external connection substrate 10. The connection conductor (not shown) on the surface is placed on the joint portion where the conductor is formed. The convex portion 4a has a function of supporting the ceramic circuit board 1 and a function of transmitting / diffusing heat generated during the operation of the semiconductor element 9 to the external connection board 10 through the metal plate 4 and the through conductor 5. And external connection board
The 10 and the ceramic circuit board 1 are electrically connected.

Further, when the ceramic circuit board 1 having the metal plate 4 on which the convex portions 4a are formed is joined to the external connection board 10 via the solder 8 as an adhesive, the external connection board 10
A space having an appropriate volume is formed between the upper surface of the metal plate 4, the side surface of the convex portion 4a, and the surface of the metal plate 4 around the convex portion 4a.
The solder 8 is filled and intervenes in this space and between the upper surface of the joint portion of the external connection board 10 and, as a result, the joint portion of the external connection board 10 to the convex portion 4a provided on the metal plate 4 is formed. The bonding via the solder 8 can be made three-dimensional so that the bonding strength can be made extremely strong, and the ceramic circuit board 1 having the metal plate 4 in which the convex portion 4a is formed at the bonding portion of the external connection substrate 10 is formed. Can be joined securely and firmly.

At the same time, when the metal plate 4 on which the convex portion 4a is formed is joined to the joint portion of the external connection substrate 10 via the solder 8 as an adhesive, the joint portion of the external connection substrate 10 and the convex portion 4a are joined together. Means that the heat generated during the operation of the semiconductor element 9 can be efficiently transferred from the metal plate 4 to the external connection board 10 by contacting with each other in an appropriate area. As a result, the semiconductor element 9 can be normally operated for a long period of time, And it becomes possible to operate stably.

The convex portions 4a of the metal plate 4 are formed at the same time when the metal plate 4 is formed, or the main surface of the metal plate 4 is formed by subjecting the metal plate 4 to grinding, pressing, etching or the like. Is formed in a predetermined shape at a predetermined position.

The convex portion 4a has a height of 50 μm or more and 200 or more.
If the distance from the outer periphery of the metal plate 4 to the outer periphery of the convex portion 4a is 100 μm or more, and the ratio of the area of the flat head of the convex portion 4a to the area of the metal plate 4 is 40% or more. Good.

The height of the convex portion 4a is less than 50 μm, and the distance from the outer periphery of the metal plate 4 to the outer periphery of the convex portion 4a is 100 μm.
When it is less than m, the volume of the space formed between the joint portion of the external connection substrate 10 on which the ceramic circuit board 1 is mounted, the side surface of the convex portion 4a, and the surface of the metal plate 4 around the convex portion 4a becomes narrow. Therefore, there is a tendency that the metal plate 4 cannot be firmly bonded to the bonding portion of the external connection board 10. When the height of the convex portion 4a exceeds 200 μm, the volume of the space formed between the bonding surface of the external connection board 10, the side surface of the convex portion 4a, and the surface of the metal plate 4 around the convex portion 4a becomes small. There is a tendency that it becomes too large and the solder 8 cannot be completely filled in this space.

Even if the distance from the outer periphery of the metal plate 4 to the outer periphery of the convex portion 4a is 100 μm or more, the external connection board 10
When the area of the flat head portion of the convex portion 4a of the metal plate 4 joined to is less than 40% of the area of the metal plate 4, the heat generated by the semiconductor element 9 can be efficiently transferred to the external connection substrate 10. Since there is a tendency that the semiconductor element 9 becomes high in temperature and causes the semiconductor element 9 to be thermally destroyed or its characteristics deteriorate, the ratio of the area of the head of the convex portion 4 a to the area of the metal plate 4 is It is preferably 40% or more.

Therefore, the height of the convex portion 4a is 50%.
From the outer periphery of the metal plate 4 to the convex portion 4a in the range from μm to 200 μm
The distance to the outer periphery of the metal plate is 100 μm or more, and the metal plate 4
It is preferable that the ratio of the area of the head of the convex portion 4a to the area of is 40% or more.

As shown in the sectional view of the ceramic circuit board in FIG. 2, when a plurality of convex portions 4a are provided and the distance between the adjacent convex portions 4a is 100 μm or more, the convex portions 4a are formed. When the formed metal plate 4 is joined to the external connection board 10 via the solder 8 as an adhesive, the space between the upper surface of the external connection board 10 and the surface of the metal plate 4 is sufficient between the adjacent convex portions 4a. A space having a large volume is formed and the solder 8 is filled in the space, and the solder 8 filled in the space
Increases the friction acting between the metal plate 4 of the ceramic circuit board 1 and the external connection board 10 such as a printed circuit board, so that the ceramic circuit board 1 and the external connection board 10 are soldered to each other.
It is suppressed that the ceramic circuit board 1 slides on the surface of the external connection board 10 when melting and joining the
There is no possibility that the displacement of the two will occur and the mounting accuracy of the ceramic circuit board 1 on the external connection board 10 will not deteriorate.

When the distance between the adjacent convex portions 4a is less than 100 μm, a space having a sufficient volume is provided between the upper surface of the external connection substrate 10 and the surface of the metal plate 4 between the adjacent convex portions 4a. Is not formed, and the molten solder tends to be difficult to fill in this space. Therefore, in the ceramic circuit board 1 of the present invention, it is preferable that the convex portions 4a are plural and the interval between the adjacent convex portions 4a is 100 μm or more.

When the metal circuit plate 3 and the metal plate 4 are made of copper, the active metal brazing material 6 contains a silver-copper eutectic alloy with a metal such as titanium, zirconium or hafnium or a hydride thereof in an amount of 2-5. What was added by weight% is used. When the metal circuit board 3 and the metal plate 4 are made of aluminum, an aluminum-silicon eutectic alloy to which a metal such as titanium, zirconium, or hafnium or a hydride thereof is added in an amount of 2 to 5% by weight is used. To be

The through conductor 5 made of a metal pillar has a specific resistance of 3
Very low conductive copper (1.72μΩ)
.Cm) or aluminum (2.65 μΩ · cm) or the like, even if a large current flows through the through-conductor 5, the Joule heat is generated from the metal circuit board 3, the metal plate 4, the through-conductor 5 and the connecting portion. A large amount of heat is not generated, and as a result, an adhesive such as solder is attached on the metal circuit board 3.
It is possible to keep the electronic components such as the semiconductor element 9 adhered and fixed using 11 always at an appropriate temperature and operate normally and stably for a long period of time.

When the metal pillar to be the through conductor 5 is made of copper, it is preferable that the metal pillar is made of oxygen-free copper. This is because the surfaces of the metal circuit board 3 and the metal plate 4 are not oxidized by oxygen existing in the copper of the metal column during brazing, and the wettability with the brazing material 7 is good, and the metal circuit board is This is because the bonding to the metal plate 3 and the metal plate 4 via the brazing material 7 becomes strong.

The length of the penetrating conductor 5 made of a metal pillar is preferably 0 to 150 μm shorter than the thickness of the ceramic substrate 2. If the through conductor 5 is longer than the thickness of the ceramic substrate 2, the through conductor 5 pushes up the metal circuit board 3 and the metal plate 4 attached to each main surface of the ceramic substrate 2, and the ceramic substrate 2 and the metal circuit board. 3 and the metal plate 4 tend not to be joined well. Further, if the through conductor 5 is shorter than 150 μm in thickness with respect to the thickness of the ceramic substrate 2, it is necessary to adhere a large amount of the brazing material 7 to both ends of the penetrating conductor 5, which causes an increase in manufacturing cost and also the brazing material. When the through conductor 5 is heated and melted, the penetrating conductor 5 may move up and down or tilt, and it may be difficult to satisfactorily bond the penetrating conductor 5 to the metal circuit board 3 and the metal plate 4.

Through conductor 5, metal circuit board 3, and metal plate 4
The brazing material 7 for joining the
If the metal is made of copper, a silver brazing material made of a silver-copper eutectic alloy is used. If the metal circuit board 3 and the metal plate 4 are made of aluminum, an aluminum brazing material made of an aluminum-silicon eutectic alloy is used. Used. Brazing material 7
Is arranged inside the through hole, and the through conductor 5 and the metal circuit board 3 are
And the metal plate 4 are joined together, and they are arranged separately from the active metal brazing material 6.

The brazing material 7 is preferably spread from the end of the through conductor 5 to the metal circuit board 3 and the metal plate 4 to form a meniscus. Since the brazing material 7 spreads in this manner, the current passing through the through conductor 5 flows smoothly through the meniscus formed in the brazing material 7, and the through conductor 5 and the metal circuit board 3 and the metal plate 4 are connected to each other. An electric current is less likely to be concentrated on the joint portion of the brazing material 7 and local heat generation is reduced. Therefore, an electronic component such as a semiconductor element 9 which is adhesively fixed onto the metal circuit board 3 by using a joint material such as solder. Can always be operated at a proper temperature and can be operated normally and stably for a long period of time.

The thickness of the space between the inner wall surface of the through hole and the outer wall surface of the through conductor 5 (when the cross-sectional shape of both is circular, it corresponds to the difference between the radius of the through hole and the radius of the through conductor 5). Is 30
It is preferably set in the range of up to 200 μm. this is,
When the thickness of this space is less than 30 μm, when heat is applied to the ceramic circuit board 1, the outer wall surface of the through conductor 5 expanded due to the difference in thermal expansion coefficient between the ceramic substrate 2 and the through conductor 5 is the ceramic substrate 2 It becomes difficult for the space between the inner wall surface of the through hole of the ceramic substrate 2 and the outer wall surface of the through conductor 5 to reliably absorb the attempt to spread the inner wall surface of the through hole of 1. This is because the outer wall surface may spread the inner wall surface of the through hole of the ceramic substrate 2 and cause cracks or breaks in the ceramic substrate 2. When the thickness of this space exceeds 200 μm, when the through conductor 5 with the brazing material 7 is inserted into the through hole of the ceramic substrate 2, the through conductor 5 with the brazing material 7 is inclined, and the through conductor 5 This is because it may not be possible to reliably connect the metal circuit board 3 and the metal plate 4.

Further, it is desirable that the active metal brazing material 6 for joining the ceramic substrate 2 to the metal circuit board 3 and the metal plate 4 is arranged 100 μm or more outside the outer periphery of the through hole. As a result, thermal stress due to the difference between the thermal expansion of the through conductor 5 and the thermal expansion of the ceramic substrate 2 may act on the microcracks around the through holes of the ceramic substrate 2 to cause cracks or breaks in the ceramic substrate 2. In addition, the active metal brazing material 6 hangs down in the through hole in the manufacturing process and is fused with the brazing material 7 for joining the metal circuit board 3 and the metal plate 4 to the penetrating conductor 5 to form a brazing material composition. Since it does not change, the metal circuit board 3 and the metal plate 4 are bonded to the ceramic substrate 2, and the metal circuit board 3 and the metal plate 4 are bonded to the through conductor 5, and the mounted semiconductor element 9 is mounted.
It is possible to obtain a highly reliable ceramic circuit board 1 that can normally and stably operate electronic components such as.

A space is provided between the inner wall surface of the through hole and the outer wall surface of the through conductor 5, or the ceramic substrate 2 and the metal circuit board 3 are provided.
When the active metal brazing material 6 that joins the metal plate 4 and the active metal brazing material 6 is arranged outside the outer periphery of the through hole by 100 μm or more, in addition to the above-described effects, the brazing material 7 is connected to the metal circuit board from the end of the through conductor 5. 3 has an effect that it becomes easy to form a meniscus having a shape that spreads over the metal plate 3 and the metal plate 4.

Metal circuit board 3 and metal plate 4 using active metal brazing material 6 on ceramic substrate 2 having through holes.
It is recommended that the attachment be performed as follows.

First, when the metal circuit board 3 and the metal plate 4 are made of copper, the active metal brazing material 6 is made of silver-, for example.
A metal eutectic alloy containing titanium, zirconium, hafnium, or a hydride thereof added in an amount of 2 to 5% by weight is mixed with an organic solvent or solvent to prepare an active metal brazing material paste, and then a ceramic substrate 2 This active metal brazing material paste is printed and applied in a predetermined pattern on the upper and lower surfaces of the same in a thickness of about 10 to 40 .mu.m by employing a conventionally known screen printing method.

Next, the through conductors 5 with the brazing material 7 are inserted and arranged in the through holes of the ceramic substrate 2, and metal circuit boards are respectively placed on the active metal brazing material paste printed and applied on both upper and lower surfaces of the ceramic substrate 2. 3 and the metal plate 4 are placed thereon, and then heat-treated at a predetermined temperature (about 900 ° C. in the case of copper) in vacuum or in a neutral or reducing atmosphere to obtain an active metal brazing paste and brazing material. The brazing material 7 adhered to both end surfaces of the through conductor 5 with 7 is melted,
The molten active metal brazing material 6 joins the ceramic substrate 2 to the metal circuit board 3 and the metal plate 4, and the brazing material 7 joins the metal circuit board 3 and the metal plate 4 to the through conductor 5.

In the above-described manufacturing method, the through conductor 5 with the brazing material 7 has a thickness of 0 to 15 relative to the thickness of the ceramic substrate 2.
A brazing material 7 is provided on both ends of the through conductor 5 composed of a metal pillar having a short length of 0 μm.
40 to 140 relative to the thickness of the ceramic substrate 2.
It is better to have a longer μm. This is because when the length of the through conductor 5 is shorter than the thickness of the ceramic substrate 2 by 0 to 150 μm, the through circuit conductor 5 has the metal circuit board 3 and the metal plate 4 attached to the upper and lower sides of the ceramic substrate 2 as described above. This is because the ceramic substrate 2 is not pushed up and the good bonding between the ceramic substrate 2 and the metal circuit boards 3 and the metal plates 4 on both sides thereof is not impaired. Further, the length of the through conductor 5 with the brazing material 7 is longer than that of the ceramic substrate 2. 40 to 140 μm longer than the thickness of the brazing material, the brazing material 7 on both ends of the metal wiring board 3 and the metal plate 4 are surely arranged.
This is because the through conductor 5 and the metal circuit board 3 and the metal plate 4 are reliably joined to each other through the brazing material 7 in the subsequent melting step, and highly reliable electrical connection is obtained.

The through conductor 5 with the brazing material 7 is formed in a cylindrical shape by subjecting a copper or aluminum ingot (lump) to a conventionally known metal working method such as a rolling method, a punching method or a drawing method. Then, the metal pillar is manufactured, and thereafter, the silver brazing material in the case of copper and the aluminum brazing material in the case of aluminum are applied to both upper and lower end surfaces of the metal pillar. As another method, laminating a brazing material / copper plate or an aluminum plate / brazing material in this order and applying a metal working method such as a punching method or a drawing method to a material having a predetermined thickness by a rolling method. There is a method of making.

The ceramic circuit board 1 of the present invention thus manufactured has an IGBT or a MOS-
Adhesive such as solder for electronic parts such as semiconductor element 9 such as FET
After mounting via 11, the metal plate 4 is joined to the external connection substrate 10 via the solder 8 to form a semiconductor module.

[0048]

EXAMPLES The ceramic circuit boards of the present invention will be described in detail below with reference to the test results of Examples and Comparative Examples, but the present invention is not limited to the following Examples.

(Example 1) First, green sheets of alumina ceramics having through holes formed by punching were laminated and fired at a temperature of about 1600 ° C in a nitrogen atmosphere to form through holes having a diameter of 2 mm. The thickness
A ceramic substrate of 0.635 mm alumina sintered body was obtained. On both surfaces of this alumina substrate, an active metal brazing material paste prepared by mixing 3 wt% of titanium hydride powder to silver-copper eutectic alloy powder with an organic solvent was applied by screen printing. . At this time, the distance between the pattern of the active metal brazing material paste and the outer periphery of the through hole is 100 μm.
And

Next, a metal column to which a brazing material of a silver-copper eutectic alloy was applied in advance was inserted into the through hole and punched into a circuit pattern shape having a thickness of 0.3 mm and made of oxygen-free copper. The metal circuit board and the metal plate were placed with the ceramic substrate sandwiched so as to close the through holes. The diameter of the metal pillar is 1.8m
m, length is 0.635 mm, length including brazing material is 0.685 mm
I used the one.

Finally, the active metal brazing material paste and the brazing material are melted by heating in a vacuum to a temperature of about 900 ° C. to melt the metal circuit board and the metal board and the ceramic board, as well as the metal circuit board and the metal board. The plate and the metal column were joined together to obtain a ceramic circuit board.

Among the ceramic circuit boards obtained by the above manufacturing method, the height of the convex portion formed in the central portion of the main surface of the metal plate on the side opposite to the ceramic substrate and the height of the concave portion from the outer periphery of the metal plate. After bonding the ones with the distance to the outer periphery as shown in Table 1 to the printed circuit board using eutectic solder,
Put into the temperature cycle test of + 125 ℃, and perform the temperature cycle 500
After the cycle and after 1000 cycles, the cross section around the solder at the joint between the metal plate and the printed circuit board was observed and evaluated. The results are shown in Table 1. In addition, sample No.
1 is the case where there is no convex portion.

[0053]

[Table 1]

As is clear from Table 1, when the metal plate is not provided with a convex portion (No. 1), cracks occur in the solder after 500 cycles of the temperature cycle test, and cracks develop after 1000 cycles and the ceramic circuit The peeling from the printed circuit board of the board has occurred. On the other hand, when the metal plate is provided with protrusions, peeling does not occur even after 1000 cycles, and when the height of the protrusions is 50 μm or more and 200 μm or less, no crack is observed even after 1000 cycles. It was Sample with convex height of 30μm (No.2) / 40μ
m sample (No. 3), 230 μm sample (No. 8) and 250 μm sample (No. 9) had cracks at the outermost periphery of the solder after 1000 cycles, but this is the space filled with solder. It is thought that this is because the strength was not so large and the strength was not significantly improved, and the height of the convex portion was high and solder was not filled between the periphery of the convex portion and the printed circuit board, and the strength was not significantly improved.

Further, if the distance from the outer circumference of the metal plate to the outer circumference of the protrusion located on the outer circumference side of the metal plate is 100 μm or more,
No generation of cracks was observed even after 000 cycles.
The distance from the outer periphery of the metal plate to the outer periphery of the protrusion is 50 μm, 80 μ
m and 90 μm samples (No. 10, 11 and 12) are 1000
After the cycle, a crack occurred in the outermost periphery of the solder,
It is considered that this is because the space filled with solder was small and the improvement in strength was not large.

FIG. 3 is a diagram showing the result of measuring the thermal resistance between the metal plate and the printed circuit board for the ceramic circuit board produced in the same manner. Here, the heating chip is eutectic solder on the metal circuit board of the ceramic circuit board in which the height of the projection is 150 μm and the ratio of the area of the head of the projection to the area of the metal plate is 0% to 100%. After mounting and joining the metal plate to the printed circuit board using eutectic solder, the temperature of the metal plate and the surface of the printed circuit board is measured using a thermocouple to calculate the thermal resistance between the metal plate and the printed circuit board. did. Here, the thickness of the eutectic solder between the head of the convex portion of the metal plate and the printed board is about 20 μm, and the ratio of the area of the head of the convex portion to the area of the metal plate is 0%, The case where the thickness of the crystal solder is 150 μm over the entire area between the metal plate and the printed board is shown. The diagram in FIG. 3 shows the thermal resistance when the ratio of the area of the convex head to the area of the metal plate is 0%.
It is a summary that is converted to the thermal resistance ratio when
The horizontal axis represents the ratio (%) of the area of the head of the convex portion to the area of the metal plate, the vertical axis represents the thermal resistance ratio, and the black rhombus plot and the characteristic curve represent the measurement results.

From the results shown in FIG. 3, it can be seen that when the ratio of the area of the convex head to the area of the metal plate is less than 40%, the thermal resistance tends to increase rapidly.

From the above results, by forming a convex portion having a flat head in the central portion of the metal plate, peeling may occur between the metal plate and the printed circuit board even in a reliability test such as a temperature cycle test. And the height of the convex part is 50μ
Temperature cycle test by setting the distance from the outer circumference of the metal plate to the outer circumference of the convex portion to 100 μm or more and the ratio of the area of the head of the convex portion to the area of the metal plate of 40% or more. In a reliability test such as that, cracks are not generated between the ceramic circuit and the printed circuit board, and the rise in thermal resistance between the metal plate and the external connection board is suppressed. It was confirmed that a ceramic circuit board with high bonding reliability with the connection board was obtained.

(Embodiment 2) Next, using the ceramic circuit board and the printed circuit board used in Embodiment 1, the convex portions of the metal plate of the ceramic circuit board are divided into two in the vertical and horizontal directions, respectively, and the head area is Formed the same four convex portions. The height of the protrusion was 150 μm, and the distance from the outer periphery of the metal plate to the outer periphery of the protrusion was 200 μm. Further, sample No. 16 in Table 2 is the case where the convex portion is not divided. The interval between convex parts is 30 ~
Assuming 150 μm, the ceramic circuit board will be misaligned (unit: μm) after the ceramic circuit board and printed circuit board are joined.
I checked. The results are shown in Table 2.

[0060]

[Table 2]

As is clear from Table 2, the interval between convex portions is 100.
The samples (sample Nos. 16 and 17) having a thickness of μm or less had a large positional deviation, and the mounting accuracy tended to decrease. In samples (No. 19 and 20) with a convex interval of 100 μm or more, the molten solder enters between the convex parts of the metal plate, and the friction between the metal plate of the ceramic circuit board and the external connection board such as the printed board increases. It was found that the displacement between the two is unlikely to occur.

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 spirit of the present invention.

For example, in the above example, the ceramic substrate 2 is made of an aluminum oxide sintered body, but
When the semiconductor element 9 generates a large amount of heat and it is desired to efficiently remove this heat, the ceramic substrate 2 may be formed of an aluminum nitride sintered body or a silicon nitride sintered body having a high heat transfer coefficient. When it is desired to propagate an electric signal to the circuit board 3 at high speed, the ceramic substrate 2 may be formed of a mullite sintered body having a low dielectric constant.

Further, in the above example, the metal circuit board 3 and the metal plate 4 are directly brazed to the ceramic substrate 2 via the active metal brazing material 6, but this is preliminarily attached to the surface of the ceramic substrate 2 with tungsten, molybdenum or the like. The metallized metal layer may be deposited, and the metal circuit board 3 and the metal plate 4 may be bonded to the metallized metal layer via a brazing material. The metallized metal layer at this time may be formed by forming a ceramic substrate 2 having through holes and then applying a metal paste such as tungsten or molybdenum and baking it. Alternatively, when forming the ceramic substrate 2, a ceramic green layer is formed. A metal paste such as tungsten or molybdenum may be applied on the sheet and formed simultaneously with the ceramic substrate 2. Further, when forming the metallized metal layer, the through conductor 5 may be formed by filling the through holes with a similar metal paste.

Furthermore, in the above example, the ceramic substrate 2 is used.
The metal circuit board 3 and the metal plate 4 which were previously formed in a circuit wiring pattern shape were brazed to each other via the active metal brazing material 6, but it is unnecessary by etching after brazing a metal plate having substantially the same shape as the ceramic substrate 2. The metal circuit board 3 and the metal plate 4 may be formed by removing the metal portion and forming a circuit wiring pattern.

Further, in the above example, the through conductor 5 with the brazing material 7 is inserted and arranged in the through hole of the ceramic substrate 2. However, the through conductor 5 made of a metal pillar is inserted and arranged in the through hole and the brazing material paste is used. A method of applying to both upper and lower end surfaces may be adopted.

Further, in the above example, the convex portion 4a formed on the main surface of the metal plate 4 is formed integrally with the metal plate 4, but the convex portion 4a is formed as a separate member by the same material and method as the metal plate 4. After being formed, the convex portion 4 is formed on the main surface of the metal plate 4 via an adhesive such as a brazing material.
It may be formed by adhesively fixing a.

[0068]

According to the ceramic circuit board of the present invention,
A metal circuit board is arranged on one main surface of the ceramic substrate, and a metal plate is arranged on the other main surface so as to face the metal circuit board, and the metal circuit board and the metal plate are arranged in the ceramic substrate. A metal plate that is connected to an external connection substrate such as a printed circuit board by forming a convex portion with a flat head in the center of the main surface of the metal plate on the side opposite to the ceramic substrate. Since the central part of the main surface of the main part is a convex shape with a flat head, when the convex part formed on the metal plate is bonded to the external connection board via solder as an adhesive, the external connection A space is formed between the upper surface of the board, the side surface of the convex portion, and the surface of the metal plate around the convex portion, and solder is provided in this space and between the surface of the external connection board and the flat head of the convex portion. Will be filled and intervene, resulting in the formation of convex portions. The solder joint through to the external connection substrate of the metal plate is a three-dimensional, can be a ceramic circuit board bonded securely, firmly to the external connection substrate.

According to the ceramic circuit board of the present invention, the height of the convex portion is 50 μm or more and 200 μm or less, and the distance from the outer periphery of the metal plate to the outer periphery of the convex portion is 100 μm.
When the ratio of the area of the head of the convex portion to the area of the metal plate is 40% or more, the metal plate on which the convex portion is formed is used as an adhesive on the external connection substrate. When joined via solder, a space of sufficient volume is formed between the upper surface of the external connection board, the side surface of the convex portion, and the surface of the metal plate around the convex portion, and the space inside and outside Solder is filled and intervenes between the surface of the board and the head of the convex portion, and as a result, the three-dimensional joining of the metal plate provided with the convex portion to the external connection board via solder is achieved. Therefore, the ceramic circuit board can be securely and firmly joined to the external connection board, and the surface of the external connection board and the head of the convex portion of the metal plate come into contact with each other with a sufficient area,
Solder intervening between the convex portion and the surface of the external connection board is largely melted and spread on the surface of the metal plate and becomes thin with a thickness of less than 50 μm, so it is generated when the semiconductor element mounted on the ceramic circuit board operates. The heat is efficiently transferred from the ceramic circuit board to the external connection board, and as a result, it is possible to keep the semiconductor element at an appropriate temperature and operate the semiconductor element normally and stably for a long period of time.

Further, according to the ceramic circuit board of the present invention, when the number of the convex portions is plural and the interval between the adjacent convex portions is 100 μm or more, the metal plate having the convex portions is formed. When bonded to the external connection board via solder as an adhesive, a space of sufficient volume is formed between the upper surface of the external connection board and the surface of the metal plate between the adjacent convex portions, and this space The inside of the ceramic circuit board is filled with solder, and the solder filled in this space increases the friction that acts between the metal plate of the ceramic circuit board and the external connection board such as a printed circuit board. The ceramic circuit board does not slide on the surface of the external connection board when it is melted and joined, and as a result, the two are displaced, and the accuracy of mounting the ceramic circuit board on the external connection board Not be lowered.

[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.

FIG. 2 is a cross-sectional view showing another example of the embodiment of the ceramic circuit board of the present invention.

FIG. 3 is a diagram showing an example of the results of thermal resistance measurement using samples of Examples and Comparative Examples of the ceramic circuit board of the present invention.

[Explanation of symbols]

1 ... Ceramic circuit board 2 ... Ceramic substrate 3 ... Metal circuit board 4 ... Metal plate 4a ... 5 ... Penetration conductor 6 ... ・ ・ ・ Active metal brazing material 7 ...... brazing material 8 ... ・ ・ ・ Solder 9 ... Semiconductor element 10 ... External connection board

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5E317 AA24 BB04 BB12 CC08 CC15                       CD21 CD32 GG07                 5E338 AA02 AA18 CC04 CC06 CC08                       CD05 CD23 EE02 EE27 EE51                 5F036 BA23 BB08 BC06 BC33 BD01                       BD13

Claims (3)

[Claims] 1. A metal circuit board is disposed on one main surface of a ceramic substrate, and a metal plate is disposed on the other main surface so as to face the metal circuit board. The metal circuit board and the metal plate are disposed in the ceramic substrate. A ceramic circuit board which is connected by through conductors arranged and has a convex portion having a flat head formed in the central portion of the main surface of the metal plate opposite to the ceramic substrate. 2. The height of the convex portion is 50 μm or more and 200 μm or more.
m or less, the distance from the outer periphery of the metal plate to the outer periphery of the protrusion is 100 μm or more, and the ratio of the area of the head of the protrusion to the area of the metal plate is 40% or more. The ceramic circuit board according to claim 1. 3. The ceramic circuit board according to claim 1, wherein a plurality of the convex portions are provided, and an interval between the adjacent convex portions is 100 μm or more.