JP4548317B2 - Insulated circuit board and power module structure including the same - Google Patents

Description

  The present invention relates to an insulated circuit board on which an electronic component such as a semiconductor chip is mounted, and a power module structure including the same.

Conventionally, AlN is used as the insulator ceramics, and DBA in which Al is directly brazed onto the upper and lower surfaces of the insulator ceramics, and Cu is directly bonded to the upper and lower surfaces of the insulator ceramics as the circuit layers and metal layers. An insulated circuit board made of DBC or the like is known.
In such an insulating circuit board, a semiconductor element is mounted on one surface via a solder layer and a circuit layer, and a heat sink is mounted on the other surface via a solder layer. In addition, a heat sink is mounted on the heat radiating plate via a thermally conductive grease layer (see, for example, Patent Document 1).
JP-A-1-286348 (FIG. 1)

  In recent years, even in such an insulating circuit board, it has been desired to flow a large current through the circuit layer and to reduce thermal resistance due to heat generation. For this reason, it is necessary to form a thick circuit layer.

  However, in a conventional insulated circuit board, when the circuit layer is formed thick, the stress generated by the difference in thermal expansion coefficient between the insulator ceramic and the circuit layer is large, so that contact with the circuit layer of the insulator ceramic after the temperature cycle occurs. There is a problem that cracks occur on the surface. At this time, if a semiconductor element is mounted on the upper surface of the circuit layer via a solder layer, there is a problem that cracks occur in the solder layer.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an insulating circuit board that suppresses the occurrence of cracks in the solder layer or the insulating ceramics, and a power module structure including the same.

  The present invention employs the following configuration in order to solve the above problems. That is, the insulated circuit board of the present invention includes an insulator ceramic, a circuit layer formed of Al or Al alloy and provided on one surface of the insulator ceramic, and the insulator formed of Al or Al alloy. In an insulated circuit board comprising a metal layer provided on the other surface of the ceramic, a low thermal expansion high thermal conductivity in which a conductive base material and low thermal expansion high thermal conductivity hard particles are mixed in the upper surface of the circuit layer An electrical conductive layer in which at least one hard particle layer is laminated is provided, and the thickness of any one of the circuit layer and a base material disposed at one end of the electrical conductive layer that is separated from the circuit layer, It is 0.8 mm or less.

According to the present invention, even if the conductive portion through which the current flows is made thicker by arranging the electric conductive layer in which the base material and the low thermal expansion high thermal conductive hard particle layer are laminated one by one on the upper surface of the circuit layer, The thermal expansion coefficient combining the layer and the electrically conductive layer can be kept small.
Here, when the thickness of the circuit layer is 0.8 mm or less, the stress generated due to the difference in thermal expansion coefficient between the circuit layer and the insulating ceramic is reduced. Therefore, even if the temperature cycle is repeated, for example, 3000 times, the occurrence of cracks at the portion of the upper surface of the insulating ceramics to which the circuit layer is bonded is suppressed.
If the thickness of the base material disposed at one end of the electrically conductive layer spaced from the circuit layer is 0.8 mm or less, the stress generated by the difference in the thermal expansion coefficient between the base material and the solder layer is the same as described above. Get smaller. Therefore, even after a semiconductor element or the like is mounted on the base material via the solder layer and the temperature cycle is repeated, for example, 3000 times, occurrence of cracks in the solder layer is suppressed.
Further, by alternately laminating a plurality of base materials and low thermal expansion high thermal conductive hard particle layers, the combined thickness of the circuit layer and the electrical conductive layer can be made desired.

Moreover, it is preferable that the thickness of the base material arrange | positioned at the end spaced apart from the said circuit layer of the said electrically conductive layer is 0.6 mm or less.
According to the present invention, since the thermal expansion coefficient of the circuit layer and the electrically conductive layer can be further reduced, the semiconductor element is disposed on the upper surface of the base material disposed at the upper end of the electrically conductive layer via the solder layer. Etc., and the occurrence of cracks in the solder layer is suppressed even after the temperature cycle is repeated 3000 times, for example.

In the insulated circuit board of the present invention, it is preferable that the insulator ceramics is made of AlN, SiC, Si ₃ N ₄ or Al ₂ O ₃ .
According to the present invention, it is possible to achieve consistency in the thermal expansion coefficient between the insulating ceramics and the portion where the circuit layer and the electrically conductive layer are combined.

In the insulated circuit board of the present invention, the low thermal expansion high thermal conductive hard particles are preferably composed of SiC, diamond, B ₄ C or BN.
According to the present invention, by using SiC, diamond, B ₄ C or BN having a low thermal expansion coefficient and high thermal conductivity, the thermal expansion coefficient of the circuit layer and the electrically conductive layer can be reduced, and the base material Heat can be transferred well between the circuit layer and the circuit layer.

In the insulated circuit board of the present invention, the surface of the low thermal expansion high thermal conductive hard particles is preferably coated with the same material as the base material and the circuit layer.
According to the present invention, the low thermal expansion high thermal conductive hard particles and the base material or the circuit layer are firmly bonded, and even if the temperature cycle is repeated, the base material or the circuit layer and the low thermal expansion high thermal conductive hard particles are The joined state is maintained.

In the insulated circuit board of the present invention, the low thermal expansion high thermal conductive hard particle layer is an alloy layer made of any one of an Al-Si alloy, an Al-Ge alloy, an Al-Cu alloy, and an Al-Mn alloy. And the low thermal expansion high thermal conductive hard particles dispersed in the alloy layer.
According to this invention, since the brazing is performed between the alloy layer, which is an Al-based brazing material having a melting point lower than that of the base material, and the base material and the circuit layer, the low thermal expansion high thermal conductive hard particles are firmly fixed. The

In the insulated circuit board of the present invention, it is preferable that end portions of the low thermal expansion high thermal conductive hard particles penetrate into the base material and / or the circuit layer.
According to the present invention, when the heat of the heating element passes through the heat spreader, heat is transferred from the end of the low thermal expansion high thermal conductive hard particle penetrating the base material and / or the circuit layer to the other end, so that it is good. The heat of the heating element can be transferred.

In the insulated circuit board of the present invention, it is preferable that a terminal structure is formed on at least a part of the base material disposed at one end of the electrically conductive layer that is separated from the circuit layer.
According to this invention, it connects with another electronic circuit etc. via a terminal structure.

Moreover, the power module structure of the present invention is characterized in that a semiconductor element is connected to the base material disposed at one end of the insulating circuit board that is separated from the circuit layer.
According to the present invention, the heat generated from the semiconductor element is satisfactorily transmitted through the electrically conductive layer.

Moreover, it is preferable that the power module structure of this invention is joined to the water cooling or the air cooling heat sink.
According to the present invention, the heat generated from the semiconductor element is transmitted through the electrically conductive layer and cooled by the heat sink, so that the semiconductor element is prevented from reaching a high temperature.

  According to the insulated circuit board and the power module structure including the insulating circuit board according to the present invention, the coefficient of thermal expansion is suppressed to a small value. To prevent. In addition, by stacking a plurality of base materials and low thermal expansion high thermal conductive hard particle layers alternately, it is possible to obtain a desired thickness combining the circuit layer and the electrical conductive layer.

A power module structure according to a first embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the power module structure 1 according to the present embodiment includes an insulating circuit board 2, a semiconductor element 3 mounted on the upper surface of the insulating circuit board 2, and a heat sink disposed on the lower surface of the insulating circuit board 2. 4.

  As shown in FIG. 1, the insulating circuit board 2 includes an insulating ceramic 11, a circuit layer 12 formed on one surface of the insulating ceramic 11, and a metal layer formed on the other surface of the insulating ceramic 11. 13 and an electrically conductive layer 14 provided on the upper surface of the circuit layer 12.

AlN is used for the insulator ceramic 11.
The circuit layer 12 is divided and formed on the upper surface of the insulator ceramic 11, and is bonded to the insulator ceramic 11 by direct brazing. Further, Al having a thickness of 0.6 mm is used for the circuit layer 12.
Similar to the circuit layer 12, the metal layer 13 is directly bonded to the lower surface of the insulator ceramic 11 by brazing. The metal layer 13 is made of Al having a thickness of 0.6 mm.

The electrically conductive layer 14 is formed by laminating a base material 15 and a diamond particle layer (low thermal expansion high thermal conductive hard particle layer) 16 one by one. The circuit layer 12 and the base material 15 form a diamond particle layer 16. It is comprised so that it may pinch | interpose. The semiconductor element 3 is provided on the upper surface of the electrically conductive layer 14 via a solder layer 17.
For the base material 15, Al having a thickness of 0.6 mm is used.
The diamond particle layer 16 has a thickness of 1 μm or more and 500 μm or less, and an Al—Si based alloy layer 18 and diamond particles dispersed in the Al—Si based alloy layer 18 (low thermal expansion high thermal conductive hard particles). 19.
The diamond particles 19 have a particle size of, for example, 200 μm or more and 300 μm or less, and both end portions are penetrated into the circuit layer 12 and the base material 15, respectively.
Examples of the solder layer 17 include 95% Pb-5% Sn and Sn-Ag-Cu solder. Note that a solder containing 95% Pb-5% Sn may contain Ag.

Next, a method for manufacturing the power module structure 1 configured as described above will be described.
First, the circuit layer 12 and the metal layer 13 are respectively bonded to the upper and lower surfaces of the insulator ceramic 11 by direct brazing. Then, diamond particles 19 whose surface is coated with Al on the upper surface of the circuit layer 12 and an Al—Si alloy foil having a thickness of 30 μm are placed, and further an aluminum plate having a thickness of 0.3 mm is placed, for example, The insulating circuit board 2 is formed by pressurizing at a pressure of 0.05 MPa or more and 0.5 MPa or less and bonding at 630 ° C.

At this time, the Al—Si alloy foil is metal-bonded by a eutectic reaction between the circuit layer 12 and Al formed on the surfaces of the base material 15 and the diamond particles 19.
Further, the Al—Si based alloy foil is used as the Al—Si based alloy layer 18, and the diamond particles 19 are firmly bonded in the Al—Si based alloy layer 18. Further, the Al—Si based alloy layer 18 and the circuit layer 12 and the base material 15 are also firmly joined by the eutectic reaction.
Thereafter, the semiconductor element 3 is mounted on the upper surface of the base material 15 via the solder layer 17, and the heat sink 4 is provided on the lower surface of the metal layer 13. As described above, the power module structure 1 is formed.

In the power module structure 1 configured as described above, the heat of the semiconductor element 3 is cooled by the heat sink 4 via the insulating circuit substrate 2 having the electrically conductive layer 14.
That is, since both end portions of the diamond particles 19 are penetrated into the base material 15 and the circuit layer 12 formed on both sides of the diamond particle layer 16, heat conduction is good via the diamond particles 19 of the electrically conductive layer 14. To be done.

  According to the insulated circuit board 2 configured as described above, by laminating the diamond particle layer 16 and the base material 15, the thermal expansion coefficient of the circuit layer 12 and the electrically conductive layer 14 combined can be kept small. Then, by setting the thicknesses of the circuit layer 12 and the base material 15 to 0.6 mm, the thermal expansion coefficient of Al used for the circuit layer 12 and the base material 15 in the conductive portion does not become dominant. Thereby, even if it repeats a temperature cycle, it is suppressed that a crack generate | occur | produces in the site | part to which the circuit layer 12 is joined on the upper surface of the insulator ceramic 11, and the solder layer 17.

Further, since both end portions of the diamond particles 19 are penetrated into the base material 15 and the circuit layer 12, respectively, the heat of the semiconductor element 3 can be transferred to the heat sink 4 well.
Further, since the Al—Si based alloy layer 18, the base material 15, the circuit layer 12, and the diamond particles 19 are bonded together by the eutectic reaction, the temperature cycle from −40 ° C. to 125 ° C. is 3000 times. Even if it is repeated, the bonding state of the Al—Si based alloy layer 18, the base material 15, the circuit layer 12, and the diamond particles 19 can be maintained satisfactorily.

Next, a second embodiment will be described with reference to FIG.
The embodiment described here has the same basic configuration as the first embodiment described above, and is obtained by adding another element to the first embodiment described above. Therefore, in FIG. 2, the same components as those in FIG.

  The difference between the second embodiment and the first embodiment is that, in the power module structure 20 in the second embodiment, the base material 15 in which the insulating circuit board 21 is arranged on the upper end of the electrically conductive layer 14 is a terminal. It has a structure.

  The power module structure 20 configured as described above also has the same operations and effects as the insulating circuit board 2 in the first embodiment described above.

Next, the insulated circuit board according to the present invention will be specifically described with reference to examples.
Insulated circuit boards having configurations as shown in Table 1 and Table 2 were manufactured, and they were designated as Examples 1 to 23 and Comparative Examples 1 to 5, respectively. Table 1 shows the results of performing the temperature cycle of −40 ° C. or more and 125 ° C. or less 3000 times using each insulated circuit board. In Table 1, the number of stacked layers indicates the number of stacked conductive layers 14. Moreover, peeling has shown the case where the interface of the insulator ceramics 11 and the circuit layer 12 is test | inspected using the ultrasonic inspection method, and the joining rate becomes 90% or less. The solder crack indicates the presence or absence of a crack in confirmation using an electron microscope by filling the solder layer 17 under the semiconductor element 3 with resin, then cutting and polishing.

  From Table 1 and Table 2, it was confirmed that cracks in the solder layer and peeling at the interface between the insulating ceramics and the circuit layer did not occur by setting the circuit layer thickness and the base material thickness to 0.8 mm or less. .

In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of this invention, a various change can be added.
For example, in the above-described embodiment, the thickness of both the circuit layer and the base material is 0.6 mm. However, it is not limited to this as long as at least one of them is larger than 0.02 mm and not larger than 0.8 mm.
In addition, although the circuit layer and the base material are both formed of Al, one or both of them may be formed of an Al alloy.
Moreover, although AlN was used as the insulator ceramic, the present invention is not limited to this, and other insulator ceramics such as SiC, Si ₃ N _4, or Al ₂ O ₃ may be used.
Further, although diamond particles are used as the low thermal expansion high thermal conductive hard particles, the present invention is not limited to this, and other conductive particles such as SiC particles and B ₄ C particles may be used.
In addition, the electrically conductive layer has a structure in which a base material and a diamond layer are stacked one by one, but a structure in which a plurality of layers are stacked may be used.
Moreover, although it has the structure where the diamond particle penetrated into the base material, it may be a structure that does not penetrate into the base material, and the depth of penetration may be appropriately changed.

  According to the insulating circuit board and the power module structure including the insulating circuit board according to the present invention, since the thermal expansion coefficient can be matched with the insulating ceramics, the insulating ceramics can be used even if the temperature cycle repeatedly acts during use. Or since the crack does not generate | occur | produce in a solder layer, industrial applicability is recognized.

It is the schematic which showed 1st Embodiment of the insulated heat-transfer structure by this invention. It is the schematic which showed 2nd Embodiment of the insulated heat-transfer structure by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 20 Power module structure 2, 21 Insulated circuit board 3 Semiconductor element 4 Heat sink 11 Insulator ceramics 12 Circuit layer 13 Metal layer 14 Electrically conductive layer 15 Base material 16 Diamond particle layer (low thermal expansion high thermal conductive hard particle layer)
19 Diamond particles (low thermal expansion high thermal conductivity hard particles)

Claims (10)

Insulator ceramics, a circuit layer formed of Al or Al alloy and provided on one surface of the insulator ceramics, and a metal formed of Al or Al alloy and provided on the other surface of the insulator ceramics In an insulated circuit board comprising a layer,
On the upper surface of the circuit layer, there is provided an electrically conductive layer in which at least one layer of a conductive base material and a low thermal expansion high thermal conductive hard particle layer in which low thermal expansion high thermal conductive hard particles are mixed is provided.
The insulated circuit board according to claim 1, wherein a thickness of any one of the circuit layer and a base material disposed at one end of the electrically conductive layer spaced from the circuit layer is 0.8 mm or less.   2. The insulated circuit board according to claim 1, wherein a thickness of a base material disposed at one end of the electrically conductive layer spaced from the circuit layer is 0.6 mm or less. The insulated circuit board according to claim 1 or 2, wherein the insulating ceramic is made of AlN, SiC, Si ₃ N ₄ or Al ₂ O ₃ . 4. The insulated circuit board according to claim 1, wherein the low thermal expansion high thermal conductive hard particles are made of SiC, diamond, B ₄ C, or BN. 5.   5. The insulated circuit board according to claim 1, wherein the surface of the low thermal expansion high thermal conductive hard particles is coated with the same material as the base material and the circuit layer. 6.   The low thermal expansion high thermal conductive hard particle layer is dispersed in the alloy layer made of any one of Al-Si alloy, Al-Ge alloy, Al-Cu alloy, Al-Mn alloy, and the alloy layer. The insulated circuit board according to any one of claims 1 to 5, wherein the insulated circuit board is constituted by low thermal expansion and high thermal conductive hard particles.   7. The insulated circuit board according to claim 1, wherein an end of the low thermal expansion high thermal conductive hard particle penetrates into the base material and / or the circuit layer.   8. The terminal structure according to claim 1, wherein a terminal structure is formed on at least a part of the base material disposed at one end of the electrically conductive layer that is separated from the circuit layer. 9. Insulated circuit board.   9. A power module structure, wherein a semiconductor element is connected to the base material disposed at one end of the insulating circuit board according to claim 1 that is separated from the circuit layer. The power module structure according to claim 9, wherein a water-cooled or air-cooled heat sink is joined.

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