JP2003283063A - Ceramic circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that heat cannot be dissipated well because the thickness of a thermally conductive composite increases depending on the warp or waving of a substrate to block the passage for dissipating heat from a semiconductor element. <P>SOLUTION: A metal circuit board 3 for mounting a semiconductor element 7 is fixed to the upper surface of a ceramic substrate 2 having the lower surface fixed with a metal plate 4 being packaged on a heat dissipating member 6 through a thermally conductive composite 5. In such a ceramic circuit board 1, a groove 8 is made in the surface of the metal plate 4 being packaged on the heat dissipating member 6 at a part of distance H of the overall thickness of the ceramic circuit board 1 from the outer circumference of the semiconductor element 7. Since the thermally conductive composite 5 immediately below the semiconductor element 7 or on the periphery thereof intrudes into the groove 8 at the time of bonding the ceramic circuit board 1 to the heat dissipating member 6 through the thermally conductive composite 5, the thermally conductive composite 5 having a relatively low thermal conductivity can be made thinner at the time of bonding resulting in the enhancement of heat dissipation characteristics. <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 obtained by joining a metal circuit board to a ceramic board.

[0002]

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

FIG. 3 is a sectional view showing an example of a semiconductor module using a conventional ceramic circuit board. In FIG.
Reference numeral 11 denotes a ceramic circuit board. The ceramic circuit board 11 includes a ceramic board 12, a plurality of metal circuit boards 13 attached to the upper surface thereof, and a lower surface of the ceramic board 12 facing the metal circuit boards 13. It is composed of a metal plate 14 attached. And such a ceramic circuit board
Reference numeral 11 denotes a heat conductive composition in which an electronic component such as a semiconductor element 17 is mounted on a metal circuit board 13 and a metal plate 14 is provided on a heat dissipation member 16.
It is used as a semiconductor module by being bonded and mounted with 15 interposed.

When the ceramic substrate 12 made of a sintered aluminum oxide material is used, the ceramic circuit board 11 is manufactured by the following method.

First, a raw material powder of aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, etc. is mixed with an appropriate organic binder, a plasticizer, a solvent, etc. to form a sludge, and this is formed by a conventionally known doctor blade method. After obtaining a plurality of ceramic green sheets by adopting tape forming technology such as the calender roll method or the like, they are formed into a predetermined size, and then the ceramic green sheets are laminated on top and bottom as needed and in a reducing atmosphere. A ceramic substrate 12 made of an aluminum oxide sintered body by firing at a temperature of about 1600 ° C. to integrally sinter the ceramic green sheets.
To make.

Next, a brazing paste is prepared by adding and mixing an organic solvent and a solvent to an active metal powder obtained by adding at least one of titanium, zirconium, and hafnium to a silver-copper alloy to prepare a brazing paste. Apply on 12 major surfaces.

Next, a plurality of metal circuit boards 13 made of copper or the like are placed on the upper surface of the ceramic substrate 12 with a brazing paste interposed therebetween, while the lower surface of the ceramic substrate 12 facing the metal circuit boards 13 is similarly soldered. A metal plate 14 made of copper or the like is arranged with a material paste interposed therebetween.

Finally, the brazing paste placed between the ceramic substrate 12 and the metal circuit board 13 and between the ceramic substrate 12 and the metal plate 14 is heated at a temperature of about 900 ° C. in a non-oxidizing atmosphere. It is manufactured by heating to melt the ceramic substrate 12 and the metal circuit board 13 and the ceramic substrate 12 and the metal plate 14 with this brazing material.

Ceramic circuit board manufactured in this way
11 is an IGBT (Insulated Gate Bipolar Transisto)
r) and MOS-FET (Metal Oxide Semiconductor-F
After connecting the electronic components such as the semiconductor element 17 such as the yield effect transistor) via an adhesive such as solder, for example, by joining to the heat dissipation member 16 such as aluminum with the solder, It becomes a semiconductor module that radiates heat well.

However, the coefficient of thermal expansion of the ceramic circuit board 11 (coefficient of thermal expansion of about 3 to 10 × 10 ⁻⁶ / ° C.) and the heat dissipation member 16 (coefficient of thermal expansion of about 18 to 23 × 10 ⁻⁶ / ° C.) Due to the large difference, the solder between the ceramic circuit board 11 and the heat dissipation member 16 may be cracked and peeled off, resulting in a significant deterioration in reliability. For this reason, the ceramic circuit board 11 is replaced with the grease-like heat transfer composition 15 instead of solder.
A structure in which the heat radiation member 16 and the heat radiation member 16 are joined and mounted is adopted.

[0011]

However, since the grease-like heat-conductive composition 15 has low heat conductivity, when the heat-conductive composition 15 between the ceramic circuit board 11 and the heat dissipation member 16 becomes thick, the semiconductor element 17 will be removed. Since the heat radiation path of is blocked, it becomes impossible to dissipate the heat well, which causes the semiconductor element 17 to be thermally destroyed or the characteristics to be deteriorated, so that the semiconductor element 17 cannot be operated stably and reliably. Had.

Further, the ceramic substrate 12 itself has some undulations, the size of the ceramic substrate 12, the circuit pattern of the metal circuit board 13 and the ceramic substrate 12.
Although it is necessary to design the optimum thickness of the metal circuit board 13 and the metal plate 14 depending on the thickness of the ceramic circuit board, it is very difficult to completely flatten the back surface of the ceramic circuit board 11. Therefore, the ceramic circuit board 11 is radiated through the heat transfer composition 15.
Even when the ceramic circuit board 11 is pressed down when bonding to the semiconductor element 17, the semiconductor element 17 which has an influence on the temperature rise of the semiconductor element 17
The heat conductive composition 15 below the heat conductive composition 15 itself has a tendency that the viscosity of the heat conductive composition 15 itself and further the swell of the ceramic substrate 12 impede, so that the heat conductive composition 15 does not sufficiently flow out of the metal plate 14. There is also a problem that it is difficult to reduce the thickness of the heat conductive composition 15 below the element 17.

The present invention has been devised to solve the problems in the prior art as described above, and an object thereof is to reduce the heat resistance of a heat conductive composition having a relatively low thermal conductivity. Can be prevented from increasing, and the heat dissipation characteristics are good,
An object of the present invention is to provide a ceramic circuit board that can stably operate electronic components such as semiconductor elements mounted on a metal circuit board for a long period of time.

[0014]

A ceramic circuit board of the present invention is formed by attaching a metal circuit board on which a semiconductor element is mounted on the upper surface of the ceramic substrate and a metal plate on the lower surface, and the metal plate is heat conductive. A ceramic circuit board mounted on a heat dissipation member via a composition, wherein the metal plate has a groove on a surface mounted on the heat dissipation member at a position at a distance of the entire thickness of the ceramic circuit board from the outer periphery of the semiconductor element. Are formed.

Further, in the ceramic circuit board of the present invention, in the above structure, the groove depth T is 0.01 ≦ T ≦ 0.15.
(Mm) and the width S of the groove is (0.18−0.91T) × L ≦ S ≦ 0 with respect to the length L of the outer side of the semiconductor element.
It is characterized by being 4 L (mm).

According to the ceramic circuit board of the present invention, since the metal plate is provided with the groove on the surface mounted on the heat dissipation member, at a portion of the entire thickness of the ceramic circuit board from the outer periphery of the semiconductor element. , When the ceramic circuit board is joined to the heat dissipation member via the heat transfer composition, the heat transfer composition between the heat dissipation member and under the semiconductor element of the metal plate is allowed to intrude into this groove, Since it is possible to reduce the thickness of the heat transfer composition interposed between the heat dissipation member and the portion of the metal plate immediately below and around the semiconductor element and the heat dissipation member, the metal plate can be bonded. It is possible to prevent an increase in thermal resistance between the heat radiation member and the heat radiation member. As a result, a ceramic circuit board with improved heat dissipation can be provided.

Further, according to the ceramic circuit board of the present invention, the depth T of the groove is 0.01≤T≤0.15 (mm), and the width S of the groove is relative to the length L of the outer side of the semiconductor element. , (0.18
-0.91T) × L ≦ S ≦ 0.4L (mm), a space is formed in the groove just below and around the semiconductor element of the metal plate, which is sufficient for the heat transfer composition to enter. Therefore, when joining the ceramic circuit board to the heat dissipation member via the heat conductive composition, a sufficient amount of the heat conductive composition can be made to enter into this groove from directly under the semiconductor element and its surroundings. Since it is possible to sufficiently thin and bond the heat conductive composition having a relatively low thermal conductivity, which is interposed between the heat dissipation member and the portion immediately below and around the semiconductor element, the metal plate and the heat dissipation member. It is possible to reliably prevent an increase in the thermal resistance between and. Further, the thickness of the metal plate does not become too thin and the strength thereof does not weaken, and the heat load at the time of joining the ceramic circuit board and the metal plate does not deform so that the flatness of the board cannot be maintained.

With such a structure, according to the ceramic circuit board of the present invention, the heat dissipation characteristics are good, and electronic components such as semiconductor elements mounted on the metal circuit board can be stably operated for a long period of time. It will be possible.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an example of an embodiment of a ceramic circuit board of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of a semiconductor module using the ceramic circuit board 1 of the present invention.
Is a ceramic substrate, 3 is a metal circuit board, 4 is a metal plate, 5 is a heat conductive composition, 6 is a heat dissipation member, 7 is a semiconductor element as an electronic component, and 8 is a groove. FIG. 2 is a plan view of the metal plate 4 when the ceramic circuit board 1 of the present invention is viewed from the metal plate 4 side.

The ceramic substrate 2 functions as a support member for supporting the metal circuit board 3 and the metal plate 4, and is made of an aluminum oxide (Al ₂ O ₃ ) based sintered material or mullite (3Al ₂ O _3. ).
2SiO ₂ ) -based sintered body, silicon carbide (SiC) -based sintered body,
Aluminum nitride (AlN) -based sintered material, silicon nitride (Si
₃ N ₄ ) A ceramic material such as a sintered body.

The ceramic substrate 2 has high mechanical strength,
It is preferably made of a high toughness silicon nitride sintered body. In addition, the semiconductor element 7 mounted on the metal circuit board 3
In order to effectively conduct and dissipate the heat generated by the metal circuit board 3 to the metal plate 4 and improve the heat dissipation characteristics of the ceramic circuit board 1, the thermal conductivity of the ceramic board 2 is at least 60 W / m. It is preferably K or more, particularly 80
It is preferably W / m · K or more, more preferably 100 W / m · K or more.

If the ceramic substrate 2 is formed of, for example, a silicon nitride sintered body, first, a sintering aid such as rare earth oxide powder or aluminum oxide powder is added to and mixed with silicon nitride powder. A raw material powder of silicon nitride sintered material is prepared. Next, an organic binder and a dispersion medium are added to and mixed with the raw material powder of a silicon nitride sintered material to form a paste, and the paste is molded into a sheet by an ordinary molding method such as a doctor blade method to obtain a silicon nitride green sheet. Create. Laminating the required number of such silicon nitride green sheets,
A silicon nitride molded body is produced by performing press working and pressure bonding (pressure bonding). After that, the silicon nitride compact is degreased in air or in a non-oxidizing atmosphere such as a nitrogen atmosphere, and then fired in a non-oxidizing atmosphere such as a nitrogen atmosphere to obtain the desired ceramic substrate 2.

The ceramic substrate 2 preferably has a thickness of 0.2 to 1.0 mm in order to improve the mechanical strength of the ceramic circuit substrate 1 and not deteriorate the heat radiation characteristics. If the thickness is less than 0.2 mm, the ceramic substrate 2 tends to be cracked or the like due to the stress generated when the ceramic substrate 2 is bonded to the metal circuit board 3 and the metal plate 4. On the other hand, if it exceeds 1.0 mm, it tends to be difficult to satisfactorily transfer the heat generated from the semiconductor element 7 to the heat dissipation member 6.

The ceramic circuit board 1 of the present invention is formed on the upper and lower surfaces of the ceramic board 2 manufactured as described above.
The metal circuit board 3 and the metal plate 4 made of a metal material having conductivity such as copper and aluminum are integrally bonded to each other by a direct bonding method or an active metal method.

For example, when the active metal method is used, silver braze powder made of silver-copper alloy powder or aluminum braze powder made of aluminum-silicon alloy powder is added to active metal such as titanium, zirconium or hafnium. An active metal brazing material paste obtained by adding and mixing an appropriate organic solvent / solvent to an active metal brazing material containing 2 to 5% by weight of an active metal powder composed of at least one of hydrides and hydrides thereof is used as a ceramic substrate 2 A predetermined pattern corresponding to the metal circuit board 3 and the metal plate 4 is printed on the upper and lower surfaces using a conventionally known screen printing technique.

After that, the metal circuit board 3 and the metal plate 4 are placed on the pattern of the active metal brazing material paste, and this is placed in a vacuum or in a neutral or reducing atmosphere at a predetermined temperature (in the case of silver brazing, it is used). Heat treatment is performed at about 900 ° C. and about 600 ° C. for an aluminum brazing material to melt the active metal brazing material, and the upper and lower surfaces of the ceramic substrate 2 and the metal circuit board 3 are melted.
And the metal plate 4 are joined. As a result, the metal circuit board 3 and the metal plate 4 are attached to the upper and lower surfaces of the ceramic substrate 2.

Metal circuit board 3 made of copper or aluminum
And, the metal plate 4 has a standard thickness of, for example, a standard thickness of .0 by subjecting an ingot (lump) of copper or aluminum to a conventionally known metal working method such as a rolling working method or a punching working method.
5 mm, it is manufactured in a predetermined pattern shape corresponding to the shape of the circuit pattern or the shape between the circuit pattern and the circuit. The standard thicknesses of the metal circuit board 3 and the metal plate 4 suppress the heat generation of the metal circuit board 3 due to a large current, and the ceramic substrate 2 composed of the metal circuit board 3 and a silicon nitride sintered body or the like.
In order to suppress the generation of cracks due to the heat load generated at the joining interface during joining, it is preferably 0.1 to 1.0 mm. If the thickness is less than 0.1 mm, the electric resistance of the metal circuit board 3 increases, and it tends to be difficult for a high current signal from the semiconductor element 7 to propagate. On the other hand, when it exceeds 1.0 mm, the ceramic substrate 2 tends to be cracked or the like due to the stress generated when the ceramic substrate 2 is bonded to the metal circuit board 3 and the metal plate 4.

If the metal circuit board 3 and the metal plate 4 are made of copper, if they are made of oxygen-free copper, the surface of the oxygen-free copper is present in the copper during brazing. Since the wettability with the brazing material is improved without being oxidized by the oxygen, the bonding with the ceramic substrate 2 via the brazing material is strengthened. Therefore, the metal circuit board 3 and the metal plate 4
Is preferably formed of oxygen-free copper.

The standard thicknesses and materials of the metal circuit board 3 and the metal plate 4 are set in order to suppress warpage due to heating at the time of brazing with an active metal or at the time of reflow for mounting an electronic component such as the semiconductor element 7. When the same material is used, the thickness of the metal plate 4 is preferably thinner than that of the metal circuit board 3.

If the metal circuit board 3 is made of nickel and has good conductivity, corrosion resistance, and wettability with the brazing material, it is deposited on the surface of the metal circuit board 3 by plating.
The electric connection between the metal circuit board 3 and the external electric circuit can be improved, and the semiconductor element 7 is provided on the metal circuit board 3.
It is possible to firmly bond electronic components such as the above with solder. Therefore, it is preferable that the surface of the metal circuit board 3 is made of nickel, which has good conductivity, corrosion resistance, and wettability with the brazing material by plating.

The metal plate 4 is provided with a groove 8 on the surface to be mounted on the heat dissipation member 6 at a portion of the entire thickness of the ceramic circuit board 1 from the outer periphery of the semiconductor element 7 (shown by H in FIGS. 1 and 2).
(Indicated by a white portion in FIG. 2) is formed. By forming the groove 8 in this manner, the ceramic circuit board 1
When joining the heat-dissipating member 6 with the heat-transmitting composition 5,
Since the heat-conductive composition 5 penetrates into the groove 8 of the metal plate 4 from the periphery thereof, the thickness of the heat-conductive composition 7 interposed immediately below and around the semiconductor element 7 and having a relatively low thermal conductivity is reduced. Can be joined together. Therefore, it is possible to prevent an increase in thermal resistance and provide the ceramic circuit board 1 with improved heat dissipation.

Since the groove 8 is formed at a portion at a distance H of the entire thickness of the ceramic circuit board 1 from the outer periphery of the semiconductor element 7, the heat generated in the semiconductor element 7 is about to be transferred to the heat dissipation member 6 side. While it spreads at an angle of 45 °, since there is no portion where the thickness of the metal plate 4 is thinned by the groove 8 in the heat conduction path, the groove 8 in which the heat conductive composition 5 has penetrated is present. Since it does not exist, heat conduction in the metal plate 4 is not hindered.

The groove 8 is formed from the portion of the semiconductor element 7 at a distance H from the outer periphery of the semiconductor element 7 to the entire thickness of the ceramic circuit board 1.
On the side, the heat diffusion in the metal plate 4 is hindered by the influence of the groove 8 in which the heat conductive composition 5 is present, so that the thermal resistance tends to increase. Further, when the groove 8 is located away from the outer periphery of the semiconductor element 7 from the portion of the total thickness H of the ceramic circuit board 1, the ceramic circuit board 1 is bonded to the heat dissipation member 6 via the heat conductive composition 5. At this time, it is difficult for the heat conductive composition 5 located immediately below and around the semiconductor element 7 to spread outward and enter the gap between the groove 8 and the heat radiating member 6, and the area directly below the semiconductor element 7 and There is a tendency that the thickness of the heat transfer composition 7 interposed between the surrounding metal plate 4 and the heat dissipation member 6 cannot be made sufficiently thin.

The depth T of the groove 8 is 0.01≤T≤0.15 (m
m) and the width S of the groove 8 is (0.18−0.91T) × L with respect to the length L of the outer side of the semiconductor element 7 (the position of the semiconductor element 7 is shown by a broken line in FIG. 2). It is preferable that ≦ S ≦ 0.4 L (mm).

If the depth T of the groove 8 is smaller than 0.01 mm, the depth T is too shallow. Therefore, the heat transfer member 6 is located directly below the semiconductor element 7 of the metal plate 4 and between the periphery of the semiconductor element 7 and the heat dissipation member 6. There is not enough space for the thermal composition 7 to enter, and there is a tendency that the thickness of the thermally conductive composition 7 immediately below and around the semiconductor element 7 cannot be made sufficiently thin. On the other hand, if the depth T of the groove 8 is larger than 0.15 mm, the thickness of the metal plate 4 becomes too thin at the groove 8 portion, so the strength of the metal plate 4 becomes weak and the ceramic circuit board 1
The metal plate 4 may be deformed due to the deflection of the substrate when mounted on the heat dissipation member 6 or the heat load at the time of joining the ceramic circuit board 1 and the metal plate 4, and the flatness of the substrate may not be maintained. Further, since the depth T of the groove 8 is too deep, when air bubbles enter the inside of the groove 8 when the ceramic circuit board 1 is bonded to the heat dissipation member 6 via the heat conductive composition 5, the semiconductor Due to the deformation caused by the difference in thermal expansion between the ceramic substrate 2 and the metal circuit slope 3 and the metal plate 4 when the element 7 is switched, the bubbles may move directly below the semiconductor element 7 and become an obstacle to heat diffusion.

The width S of the groove 8 is S <(0.18-0.91T).
In the case of × L (mm), the width S is too narrow, so that it is sufficient for the heat conductive composition 7 existing immediately below the semiconductor element 7 of the metal plate 4 and between the periphery and the heat dissipation member 6 to enter. Since such a space is not formed, it tends to be impossible to sufficiently reduce the thickness of the heat conductive composition 7 immediately below and around the semiconductor element 7. On the other hand, S> 0.4L (mm)
In this case, since the width S becomes large, when the ceramic circuit board 1 is bonded to the heat dissipation member 6 via the heat conductive composition 5, bubbles easily enter the groove 8 and the heat diffusion is hindered. Can occur.

The ceramic circuit board 1 of the present invention manufactured as described above is applied to the metal plate 4 with the grease-like heat transfer composition 5 and then bonded to the heat dissipation member 6 made of aluminum or the like to form a semiconductor. It becomes an element module. At this time, if the heat-transfer composition 5 is applied to the metal plate 4 while avoiding the grooves 8 and adjusting the application thickness to be applied uniformly, the heat-transfer composition 5 immediately below and around the semiconductor element 7 is present. Since the metal efficiently penetrates into the groove 8, it becomes possible to reduce the thickness of the heat conductive composition 7 which is interposed immediately below and around the semiconductor element 7 and has a relatively low thermal conductivity, and to bond the same.

[0039]

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.

Here, the ceramic substrate 2 has a thickness of 0.32.
A silicon nitride sintered body having a thickness of 0.5 mm was used, and copper having a thickness of 0.5 mm was used for each of the metal circuit board 3 and the metal board 4. After these are bonded to the upper and lower surfaces of the ceramic substrate 2 by using an active metal brazing material, the metal circuit board 3 is etched.
An unnecessary metal part was removed to form a circuit wiring pattern, and a sample of an example of the ceramic circuit board 1 of the present invention having the structure shown in FIG. 1 was produced. A groove 8 having a depth T and a width S as shown in Table 1 was formed by etching at a position 1.32 mm away from the outer periphery of the semiconductor element 7.

Further, a ceramic circuit board 11 of a comparative example as shown in FIG. 3 is similarly used except that the groove 8 is not formed.
The sample of was produced.

Then, using the above two kinds of samples, the heat-conductive composition 5 was made into an oil compound, and the metal plate 4 was applied to the metal plate 4 with a uniform thickness of 100 μm except for the grooves 8 by using a metal mask. After mounting the ceramic circuit boards 1 and 11 on the heat dissipation member 6, the thickness of the heat conductive composition 5 immediately below the semiconductor element 7 was evaluated, and a power cycle test was further performed.

As a method for evaluating the thickness of the heat transfer composition 5, a hole having a diameter of 1.5 mm is provided in the heat dissipation member 6, and the hole has a diameter of 1.0 mm.
mm displacement sensor is installed, the surface of the heat dissipation member 6 is used as a reference plane (Z = 0 mm), and from that position in the Z-axis direction,
The gap between the back surface of the ceramic circuit board 1 and the front surface of the heat dissipation member 6 is measured (the value when the displacement sensor contacts the back surface of the ceramic circuit board 1 is read), and the oil compound thickness after mounting the ceramic circuit board 1 And

The thermal resistance of each ceramic circuit board 1/11 was evaluated. The thermal resistance was calculated by measuring the temperature of the semiconductor element 7 and the temperature of the heat dissipation member 6 (cooling water side) immediately below the semiconductor element 7 using a thermocouple, and dividing each temperature difference by the applied power. Note that this thermal resistance is the initial thermal resistance immediately after mounting the ceramic circuit boards 1 and 11.
It also includes the thermal resistance of the oil compound. This thermal resistance is shown as a ratio (%) with respect to the length L of the outer side of each semiconductor element 2 when the thermal resistance in the case where the groove 8 is not provided (Nos. 1 and 7) is 100%. It can be judged that the smaller this thermal resistance is, the higher the heat dissipation capability is.

Further, as a method of the power cycle test, it takes 5 seconds after the semiconductor element 7 is turned on in the first cycle.
The applied current is initially set so that it rises to 125 ° C and drops to 25 ° C for 15 seconds after it is turned off, and this is repeated continuously for 5000 cycles and 10000 cycles, and the temperature of the semiconductor element 7 during that time is thermocoupled. It was measured. As a criterion for this, a sample in which the temperature rise of the semiconductor element 7 was 10% or less was judged to be acceptable, and indicated by ◯, and a sample in which the temperature rise was larger than 10% was marked as Δ. The above results are shown in Table 1.

[0046]

[Table 1]

As is clear from Table 1, when the groove 8 is not provided (No. 1 and No. 7), even if the substrate is pressed,
Since the viscosity of the oil compound and the swell of the board interfere, the oil compound does not flow sufficiently out of the metal plate 4, and the thickness of the oil compound after mounting is N
The thickness of o.1 was 0.082 mm and that of No. 7 was 0.080 mm. When the groove 8 of S <(0.18−0.91T) × L (mm) is provided, the oil compound immediately below the semiconductor element 7 of the metal plate 4 and between the periphery of the semiconductor element 7 and the heat radiating member 6 enters. Therefore, a sufficient space was not formed, and the thickness of the oil compound immediately below and around the semiconductor element 7 could not be made sufficiently thin. On the other hand, S> (0.
18-0.91T) x L (mm) groove 8 if provided
Since the oil compound penetrates into the groove and fills the groove 8, the thickness of the oil compound directly below the semiconductor element 7 is 0.05 mm.
When the groove 8 is not provided (No. 1 and No.
Compared to 7), the thermal resistance decreased by 20% or more.

A sample (N with a depth T of the groove 8 of 0.15 mm)
o.6 and No.12) are 5 in the power cycle test.
In 000 cycles, the temperature rise was 10% or less,
There was a temperature increase of more than 10% on cycling. The reason is that the air bubbles contained in the oil compound filled in the groove 8 move between the metal plate 4 located under the semiconductor element 7 and the oil compound, so that the heat dissipation characteristics are deteriorated.

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-mentioned example, the ceramic substrate 2 is made of a silicon nitride sintered material, but when the semiconductor element 7 generates a large amount of heat and it is desired to efficiently dissipate 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.
Further, in the above-mentioned example, the metal circuit board 3 and the metal plate 4 are directly brazed to the ceramic substrate 2 through the active metal brazing material, but this is preliminarily attached to the surface of the ceramic substrate 2 by a metallized metal layer such as tungsten or molybdenum. Alternatively, the metal circuit plate 3 and the metal plate 4 may be bonded to the metallized metal layer via a brazing material. Alternatively, the circuit wiring pattern may be formed by brazing the metal circuit board 3 previously formed in the circuit wiring pattern shape to the ceramic substrate 2 via the active metal brazing material.

[0051]

According to the ceramic circuit board of the present invention,
Since the metal plate has a groove formed on the surface to be mounted on the heat dissipation member at a position at a distance of the entire thickness of the ceramic circuit board from the outer periphery of the semiconductor element, the ceramic circuit board is provided with the heat transfer composition to the heat dissipation member. At the time of joining via a heat conductive composition between the heat dissipation member and a portion immediately below and around the semiconductor element of the metal plate into the groove, the groove immediately below and around the semiconductor element of the metal plate. Since the thickness of the heat conductive composition having a relatively low thermal conductivity interposed between the portion and the heat radiating member can be thinned and joined, the thermal resistance between the metal plate and the heat radiating member is increased. Can be prevented.
As a result, a ceramic circuit board with improved heat dissipation can be provided.

Further, according to the ceramic circuit board of the present invention, the depth T of the groove is 0.01 ≦ T ≦ 0.15 (mm) and the width S of the groove is relative to the length L of the outer side of the semiconductor element. , (0.18
-0.91T) × L ≦ S ≦ 0.4L (mm), a space is formed in the groove just below and around the semiconductor element of the metal plate, which is sufficient for the heat transfer composition to enter. Therefore, when joining the ceramic circuit board to the heat dissipation member via the heat conductive composition, a sufficient amount of the heat conductive composition can be made to enter into this groove from directly under the semiconductor element and its surroundings. Since it is possible to sufficiently thin and bond the heat conductive composition having a relatively low thermal conductivity, which is interposed between the heat dissipation member and the portion immediately below and around the semiconductor element, the metal plate and the heat dissipation member. It is possible to reliably prevent an increase in the thermal resistance between and. Further, the thickness of the metal plate does not become too thin and the strength thereof does not weaken, and the heat load at the time of joining the ceramic circuit board and the metal plate does not deform so that the flatness of the board cannot be maintained.

With such a structure, according to the ceramic circuit board of the present invention, the heat dissipation characteristics are good, and electronic components such as semiconductor elements mounted on the metal circuit board can be stably operated for a long period of time. It will be possible.

[0054]

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a semiconductor module using a ceramic circuit board of the present invention.

FIG. 2 is a plan view of the metal plate 4 when the ceramic circuit board 1 shown in FIG. 1 is viewed from the metal plate 4 side.

FIG. 3 is a sectional view showing an example of a semiconductor module using a conventional ceramic circuit board.

[Explanation of symbols]

1: Ceramic circuit board 2: Ceramic substrate 3: Metal circuit board 4: Metal plate 5: Heat transfer composition 6: Heat dissipation member 7: Semiconductor element 8: Groove T: depth of groove S: Groove width L: Length of outer edge of semiconductor element

Claims (2)

[Claims] 1. A ceramic circuit board is provided with a metal circuit board on which a semiconductor element is mounted, and a lower surface with a metal plate.
A ceramic circuit board in which the metal plate is mounted on a heat dissipation member via a heat transfer composition, wherein the metal plate is formed on the surface mounted on the heat dissipation member from the outer periphery of the semiconductor element to the entire ceramic circuit board. A ceramic circuit board having a groove formed at a portion having a thickness distance. 2. The depth T of the groove is 0.01 ≦ T ≦ 0.1.
5 (mm), and the width S of the groove is (0.18-0.91T) * with respect to the length L of the outer side of the semiconductor element.
The ceramic circuit board according to claim 1, wherein L ≦ S ≦ 0.4 L (mm).