JP2000315756A - Bonding structure of heat-radiating wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To bond a ceramic heat-radiating wiring board and a heat sink by screwing firmly without a possibility of destruction. SOLUTION: A substrate 3 which is composed of ceramics containing at least one or more selected from aluminium nitride and silicon nitride as main ingredients and has round holes at four corners and a heat sink (radiator) 4 disposed thereunder are screwed and bonded via the round holes by using washers 7 with a hardness of 25-70 kgf/mm2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric car, a hybrid car, a bullet train, a subway, a commuter train, an elevator,
IGBT (Insulated Gate Bipolar Transisto) is a power device mounted on robots, cranes, air conditioners, etc.
r), and a large current can flow in a semiconductor device housing package in which semiconductor devices are housed and mounted, or in a hybrid integrated circuit device in which various electronic components such as capacitors and resistors are mounted in addition to semiconductor devices. The present invention relates to a heat dissipation wiring substrate having a low-resistance wiring conductor.

[0002]

2. Description of the Related Art Power devices are the oldest semiconductor elements. In recent years, however, high breakdown voltage, large current, high speed and high frequency, and high performance have been remarkably advanced, and IGBT, GTO, ITO
High-speed MOS power devices such as PMs and power MOS FETs have appeared. These power devices include cars, inverter trains, strobes, microwaves,
Widely used for golf carts and the like. However,
In recent years, hybrid vehicles and electric vehicles have been widely spread due to environmental problems, and these power devices, particularly IGBTs, are required to have higher withstand voltage, smaller size, thinner, and lighter weight.

Japanese Patent Laid-Open No. 7-162 discloses a heat dissipation wiring board.
No. 157 discloses a multi-layer structure in which a power element is arranged on a multilayer substrate composed of a plurality of insulating layers, and a heat transfer conductor of the power element is filled in a lower region of the power element of one or more insulating layers. substrate. Has been proposed, and JP-A-63-1
Japanese Patent Application Laid-Open No. 20448 discloses a heat-radiating substrate, "a heat-radiating substrate obtained by impregnating a base material made of a fiber of a low thermal expansion metal material with a metal material having good heat radiation properties. ] Has been proposed.
When these substrates are applied to, for example, a package for accommodating a semiconductor element, the semiconductor element is bonded and fixed to the bottom surface of the concave portion of the insulating base via an adhesive such as glass, resin, or brazing material, and the semiconductor element Each electrode is electrically connected to a wiring conductor located around the recess through wire bonding, and a cover made of metal, ceramics, or the like is joined via a sealing agent similar to the adhesive so as to cover the recess. Then, the semiconductor device is confidentially accommodated in the concave portion of the insulating base, thereby forming a semiconductor device as a final product. These substrates are used as insulating substrates, and are bonded to a heat radiating plate such as a rank side (Al-impregnated SiC fiber) to form a heat radiating wiring substrate. FIG. 7 is a schematic view of a conventional heat dissipation wiring board.

A radiator 4 is joined to a radiator 4 by a screw, and a heat dissipation board 12 made of, for example, a rank side is joined to the radiator 4. An aluminum nitride board 9 having aluminum 8 on both sides is joined thereto as an insulator via a layer made of solder 10. The semiconductor element 1 is mounted thereon.

[0005] The heat radiation wiring board used for these applications naturally needs to efficiently transfer the heat generated in the semiconductor element to a heat sink such as a radiator. Generally, in an automobile, in the structure shown in FIG.
A round hole is made in the heat dissipation board 12, a screw hole is made in the radiator 4, and four corners of the heat dissipation board 12 are formed with M6 screws.
The radiator 4 was fastened and fixed with a torque of 1 Nm.

However, the conventional heat dissipation wiring board having a multi-stage structure has insufficient cooling efficiency, and is used in such a manner as to be directly joined to a radiator through which a coolant flows in order to increase the cooling efficiency, for example, to address environmental issues. It could not be applied to hybrid cars and electric cars that have been forced to appear.

For this reason, the present inventors have proposed a structure in which a heat dissipation wiring board 3 such as aluminum nitride on which a semiconductor element 1 is mounted is directly fixed to a radiator 4 with screws as shown in FIG.

[0008]

However, as shown in FIG. 8, when the heat dissipation wiring board 3 made of ceramics such as aluminum nitride is directly joined by screws 6, a washer between the screw 6 and the heat dissipation wiring board 3 is used. If the hardness of the screw 6 is high, the screw 6 may be partially sheared when the screw 6 is tightened, so that the washer may be cracked or damaged at a portion where the substrate is fastened, and cannot be fixed. Also, it was found that if the hardness of the washer was low, the first problem was that the washer was too deformed and the screw 6 could not be tightened.

Further, in the structure shown in FIG. 8, since the warpage of the heat dissipation wiring board 3 is not taken into consideration, the adhesiveness between the heat dissipation wiring board 3 and the radiator 4 at the central portion of the board is poor, and good heat dissipation characteristics cannot be obtained. There was a second problem.

[0010]

In order to solve the above-mentioned problems, the present invention is directed to a method for mounting a semiconductor element comprising a ceramic mainly containing at least one selected from aluminum nitride and silicon nitride. A heat-dissipating wiring board having a wiring conductor layer and having round holes at four corners, and a heat sink disposed under the heat-radiating wiring board are hardened through the round holes to have a hardness of 25-7.
It is characterized by being joined by screw tightening using a washer of 0 kg / mm ² .

[0011] In order to solve the second problem, the present invention provides a wiring conductor layer for mounting a semiconductor element, comprising a ceramic containing at least one selected from aluminum nitride and silicon nitride as a main component. 0.3mm thick
As described above, the heat dissipation wiring board having an area of 30 cm ² or more is warped in an amount of 20 to 600 so that the bonding surface side with the heat sink becomes convex.
It is characterized in that it is warped by μm.

According to the heat dissipation board of the present invention, since the board having the downwardly projecting warp is fastened to the heat sink, the adhesion between the heat dissipation board and the heat sink is improved, and particularly the adhesion at the center of the heat dissipation board is improved. Thus, a heat dissipation wiring board having low thermal resistance due to screw fastening with a heat sink is provided.

[0013]

1 and 2 are a plan view and a sectional view of a heat dissipation wiring board 3 according to the present invention.

As shown in FIG. 1, screw holes 5 of about M6 (diameter 6 mm) are formed at four corners of the heat dissipation wiring board 3, and a low-resistance wiring for mounting a semiconductor element (not shown) is formed in the center. The conductor layer 2 is placed. FIG. 2A shows a state in which the heat dissipation wiring board 3 of the present invention is directly screwed to the radiator 4 with the screws 6. FIG.
(B) is the top view and side view which showed the structure of the washer 7 of this invention.

The material constituting the heat dissipation wiring board 3 is desirably a ceramic mainly composed of at least one selected from silicon nitride and aluminum nitride having good thermal conductivity and good electrical insulation. The main sintering aid is desirably at least one selected from erbium oxide, yttrium oxide, and ytterbium oxide. The main sintering aids are erbium oxide, yttrium oxide,
The reason for using at least one selected from ytterbium oxide is that, based on the knowledge of the present inventors, the strength and fracture toughness of the heat dissipation wiring board 3 made of aluminum nitride are greatest when these sintering aids are used. Because. And this greatly contributes to prevention of cracking or breakage during fixing.

The heat-dissipating wiring board 3 made of the above-mentioned material and the radiator 4 as a heat sink disposed under the heat-dissipating wiring board 3 are integrated by screwing through the screw holes 5, and a washer used for screw tightening. The hardness of 7 is
It is set to 25 to 70 kg / mm ² .

The reason is that the micro Vickers hardness is 7
When a washer 7 of 0 kg / mm ² or more is used,
As shown in FIG. 6C, since the washer 7 is too hard, the screw 6 is not deformed when the screw 6 is tightened, and the undulation of the tightened portion of the heat radiation wiring board 3 cannot be absorbed. A load is generated, and the heat dissipation wiring board 3 itself cannot withstand this concentrated load, and the heat dissipation wiring board 3 is cracked or damaged.

If the micro Vickers hardness of the washer 7 is 25 kg / mm ² or less, the washer 7 is too soft and deformed too much as shown in FIG.
Fixation becomes impossible.

As a specific material of the washer 7, aluminum or copper having a porosity of approximately 10% is preferably used. In addition, the hardness of the washer 7 referred to herein is a load of 100 g and a time of 1 with a micro Vickers hardness meter.
This is a value measured under the condition of 5 seconds.

The heat radiation wiring board 3 of the present invention
It is desirable that at least one or more metal foils selected from Cu, Al, and Ag are integrated on the ceramic substrate as the wiring conductor layer 2 for mounting. When the present invention is used as a power module, at least one or more metal layers selected from Cu, Al, W, and Mo for a bus bar may be integrated on the heat dissipation wiring board 3. desirable.

Next, the second invention will be described. FIG.
As shown in the figure, as a result of diligent studies on the ideal structure of the heat dissipation wiring board 3 and the adhesion between the heat dissipation wiring board 3 and the mating member to which the heat dissipation wiring board 3 is fixed, aluminum nitride having a thickness of 0.3 mm or more and an area of 30 cm ² or more, A ceramic heat dissipation wiring board 3 made of at least one kind selected from silicon nitride, wherein a direction of warpage of the heat dissipation wiring board 3 is convex toward a bonding surface side with a heat sink, and the amount of warpage is 600 μm or less; It has been found that the heat dissipation wiring board 3 having a thickness of 20 μm or more is optimal.

That is, as shown in FIG. 3A, a radiator wiring board 3 having a downwardly convex warp is used, and the radiator 4 as a heat sink is tightened as shown in FIG. This is because it is possible to improve the adhesiveness at the central portion of the substrate 3 and realize the adhesiveness without a floating portion in the entire heat radiation wiring board 3. Conversely, if it is recessed downward,
This is because even if the four corners are tightened, a floating portion is generated at the central portion, and even if the central portion is further tightened, the floating portion cannot be eliminated from the viewpoint of the entire heat dissipation wiring board 3.

If the amount of warpage of the downward projection is 20 μm or less with respect to the entire substrate, the adhesion at the central portion is impaired, and
Above μm, the heat dissipation wiring board 3 is cracked when the heat dissipation wiring board 3 is fixed by screws. 0.3mm thick
The reason why the shape is limited to the area of 30 cm ² or more is that the heat radiation characteristics of the smaller or thinner heat radiation wiring board 3 do not particularly depend on the warpage of the heat radiation wiring board 3.

When the present invention is used as the heat dissipation wiring board 3, the wiring conductor layer 2 for mounting the semiconductor element 1
Preferably, at least one or more metal foils selected from Cu, Al, and Ag are integrated on the heat dissipation wiring board 3.

Further, when the present invention is used as a power module, Cu, Al, W,
It is desirable that at least one or more metal layers selected from Mo are integrated on the heat dissipation wiring board 3.

The heat sintering wiring board 3 is characterized in that the main sintering aid of aluminum nitride or silicon nitride is at least one selected from yttrium oxide, erbium oxide and ytterbium oxide. According to the findings of the present inventors, the use of this sintering aid for both aluminum nitride and silicon nitride most improves fracture toughness and fracture strength, and is therefore preferred for use in the present invention.

In the embodiment of FIG. 3 described above, there are the following two methods for fixing the heat dissipation wiring board 3 to the mating member.
One is a fixing structure in which one or more screw holes 5 are formed in the heat dissipation wiring board 3 and the M6 screws 6 are tightened to the screw holes 5 with a tightening torque of 5 Nm or more as shown in FIG. As shown in FIG. 5, two or more through-holes are formed in a mating member for fixing the heat dissipation wiring board 3, and M6 screws 6 are used to fasten the fixing bracket 11 to the through-holes with a tightening torque of 5 Nm or more. This is a fixing structure in which the heat dissipation wiring board 3 is fixed by the fixing metal 11.

Hereinafter, a method for manufacturing a heat dissipation wiring board according to the present invention will be described with reference to FIG.

A predetermined binder is added to a ceramic powder comprising aluminum nitride and a sintering aid, and W is formed on a tape obtained by tape forming by a doctor blade method.
Was printed as a main component. Then, after passing through a degreasing step, 1650 to 1800 ° C. in a nitrogen atmosphere
To obtain an aluminum nitride substrate having W metallization. Then, Ni plating on the W metallization,
A copper plate 2 was joined as a low resistance conductor 2 for mounting a semiconductor element by an active metal method. At this time, in order to obtain a “downward convex” warp of 20 μm to 600 μm, the difference between the Young's modulus and the coefficient of thermal expansion between the heat dissipation wiring board 3 made of aluminum nitride and the low resistance conductor 2 when the low resistance conductor 2 is joined. In consideration of the above, it is necessary to predict how much warpage will occur when the heat-dissipating wiring board 3 made of the low-resistance conductor 2 and aluminum nitride is burned. In particular, attention must be paid to the thickness, area, and shape of the low-resistance conductor 2. The amount of warpage is determined by a synergistic effect of the above and the strength and thickness of the heat dissipation wiring board 3 made of aluminum nitride.

[0030]

Embodiment 1 A specific embodiment of the first invention will be described below. A paste containing W as a main component was printed on a tape obtained by adding a predetermined binder to a ceramic powder composed of aluminum nitride and a sintering aid and forming the tape by a doctor blade method. Then, after passing through a degreasing step, it was baked at 1650 to 1800 ° C. in a nitrogen atmosphere to obtain a heat dissipation wiring substrate 3 made of aluminum nitride having W metallization.

Thereafter, Ni plating was applied on the W metallization, and a copper plate was bonded as a wiring conductor layer 2 for mounting a semiconductor element by an active metal method. As shown in FIGS. 1 and 2, the heat dissipation wiring board 3 was fastened with screws at four corners via washers 7 and fixed.

The tightening torques are shown in Table 1. Further, the shape of the washer used in this embodiment is shown in FIG.
Outer diameter 12mm, inner diameter 7mm, thickness 0.5m as shown in
m. The heat dissipation wiring board 3 of the present invention is directly screwed to the radiator 4 by screws 6. The torque measured with a torque wrench when tightening the screw is shown in the column of tightening result.

As shown in Table 1, the washer hardness was 80 k.
g / mm ² . No. 8 was broken by a tightening torque of 2 Nm. In addition, No. ^{2 having} a washer hardness of 20 kg / mm ² . 7 could not be tightened. On the other hand, No. ² having a washer hardness of 25 to 72 kg / mm ² in the range of the present invention. 1 to
In No. 6, good tightening was possible with a tightening torque of 6 to 12 Nm.

In addition, Nd ₂ O _{3 was} used as the main sintering aid.
o. 9 is 50 kg / with a washer hardness within the range of the present invention.
Even when a substrate having a thickness of ² mm ² was used, cracks occurred in the heat dissipation wiring board 3 with a tightening torque of 3 Nm. On the other hand, no. 1 to
6 Y ₂ O ₃ as shown _{in, Yb 2 O 3, Er 2} O 3 that using the Omosho Yuisuke agents, tightening torque 6~12N
m, good tightening was achieved.

[0035]

[Table 1]

Embodiment 2 A specific embodiment according to the second invention will be described below. A paste containing W as a main component was printed on a tape obtained by adding a predetermined binder to a ceramic powder composed of aluminum nitride and a sintering aid and forming the tape by a doctor blade method. After passing through the degreasing process,
It was fired at 1650 to 1800 ° C. in a nitrogen atmosphere to obtain a heat dissipation wiring conductor substrate 3 made of aluminum nitride having W metallization.

Thereafter, Ni plating was applied on the W metallization, and a copper plate was bonded as a wiring conductor layer 2 for mounting a semiconductor element by an active metal method. As shown in FIG. 3, the heat dissipation wiring board 3 was fixed by screwing four corners via washers 7. The thickness of the substrate is 1.5 mm and the area is 5
0 cm ² .

The heat radiation test carried out by the present inventors is as follows. A round hole having a diameter of 8 mm is formed in each of the four corners of a ceramic substrate, an aluminum block having a thickness of 20 mm is prepared as a pseudo radiator, and an M6 screw hole is formed in the aluminum block. M
The heat dissipation wiring board 3 was fixed by tightening a hexagon socket head cap screw to the aluminum block with a torque wrench. Thereafter, heat was actually applied to the heat dissipation wiring board 3 by a heater, the temperature on the heat dissipation wiring board 3 and the temperature on the opposite side of the aluminum block were measured, and the temperature difference was measured. Examples include:
The temperature difference at 600 μm where the heat radiation characteristic was the best was set to 1.00, and the temperature difference was expressed as a ratio. If the heat from the heat-dissipating wiring board is not transmitted to the aluminum block side properly, the temperature of the heat-dissipating wiring board rises. As the ratio of the temperature difference exceeds 1.00, the heat-dissipating characteristics deteriorate. I have.

The results are shown in Table 2. As can be seen from Table 2, the amount of warpage was 250 μm N outside the scope of the present invention.
o. In No. 7, the heat dissipation wiring board 3 is broken by the tightening. In the case of No. 1 in which the warp direction is “convex upward”. In No. 8, the heat radiation characteristic is reduced to 1.50. If the warping direction is “convex downward”, but the amount of warpage is too small, such as 10 μm, the heat radiation characteristic also decreases to 1.65. On the other hand, No. 3 which is within the scope of the present invention. 1 to 6, ie, the warp direction is “convex downward”
Heat dissipation wiring board 3 having a warpage of 20 to 200 μm
It was found that no cracks were generated and the heat radiation characteristics were good at 1.00 to 1.10.

[0040]

[Table 2]

[0041]

According to the present invention, there is provided a heat radiator comprising a ceramic having at least one selected from aluminum nitride and silicon nitride as a main component, having a wiring conductor layer for mounting a semiconductor element, and having round holes at four corners. The wiring board and the heat sink disposed under the wiring board are hardened with a hardness of 2 through the round holes.
By joining with a screw using a washer of 5 to 70 kgf / mm ² , the heat dissipation wiring board and the heat sink can be firmly joined without causing breakage or breakage of the board.

Further, the thickness is 0.3 mm or more, and the area is 30 cm.
Aluminum nitride that is ² or more, a heat dissipation wiring board made of ceramics containing at least one or more selected from silicon nitride as a main component, wherein the warping direction of the substrate is convex on the bonding surface side with the heat sink, The warpage is 6
When the thickness is not more than 00 μm and not less than 20 μm, it is possible to provide a joint structure of a heat radiation wiring board having good heat radiation characteristics without cracking or breakage of the heat radiation wiring board.

[Brief description of the drawings]

FIG. 1 is a plan view showing a joint structure of a heat dissipation wiring board of the present invention.

FIG. 2A is a cross-sectional view showing a joint structure of a heat dissipation wiring board of the present invention, and FIG. 2B is a view showing a washer used for this.

FIG. 3A is a cross-sectional view showing a state before screwing of a heat dissipation wiring board of the present invention, and FIG. 3B is a cross-sectional view showing a state after screwing.

FIG. 4 is a plan view showing a joint structure of the heat dissipation wiring board of the present invention.

FIG. 5 is a plan view showing another embodiment of the joint structure of the heat dissipation wiring board of the present invention.

FIGS. 6A to 6C are cross-sectional views for explaining the hardness and the fixed state of the washer.

FIG. 7 is a cross-sectional view showing a conventional heat dissipation wiring board.

FIG. 8 is a cross-sectional view showing a conventional heat dissipation wiring board.

[Explanation of symbols]

 1: Semiconductor element 2: Low resistance conductor 3: Heat dissipation wiring board 4: Radiator 5: Screw hole 6: Screw 7: Washer 8: Aluminum 9: Aluminum nitride board 10: Solder 11: Fixture 12: Heat dissipation board

Claims (5)

[Claims] 1. A heat-dissipating wiring board comprising a wiring conductor layer for mounting a semiconductor element and having round holes at four corners, comprising a ceramic mainly composed of at least one of aluminum nitride and silicon nitride. And the heat sink having the hardness of 25 to 70 kgf / m through the round hole.
with washer m ^2, the junction structure of heat radiating wiring board, characterized in that joined by screwing. 2. A structure in which a heat-dissipating wiring board made of ceramics containing at least one of aluminum nitride and silicon nitride as a main component and provided with a wiring conductor layer for mounting a semiconductor element is joined to a heat sink disposed thereunder. Wherein the heat dissipation wiring board has a thickness of 0.3 mm or more and an area of 3
A bonding structure for a heat-radiating wiring board, which is not less than 0 cm < ² > and is warped by a warpage of 20 to 600 [mu] m so that a bonding surface side with the heat sink is convex. 3. The heat dissipation wiring board according to claim 1, wherein at least one metal foil of Cu, Al, Ag is formed as a wiring conductor layer for mounting a semiconductor element. Joint structure of heat dissipation wiring board. 4. The heat dissipation wiring board according to claim 1, wherein at least one metal layer of Cu, Al, W, and Mo is formed on the heat dissipation wiring board for bus bars. Joint structure. 5. The bonding of a heat dissipation wiring board according to claim 1, wherein the main sintering aid for ceramics constituting said heat dissipation wiring board is at least one of yttrium oxide, erbium oxide and ytterbium oxide. Construction.