JP6264150B2 - Power module substrate and power module substrate with heat sink - Google Patents

Description

  The present invention relates to a power module substrate and a power module substrate with a heat sink used in a semiconductor device that controls a large current and a high voltage.

  Conventional power module substrates are known in which a circuit layer is laminated on one surface of a ceramic substrate and a metal layer is laminated on the other surface, and an electronic circuit such as a semiconductor chip is formed on the circuit layer. A component is soldered and a heat sink is bonded to a metal layer, thereby being used as a power module.

  In this type of power module substrate manufacturing method, a circuit layer is laminated on one surface of a ceramic substrate via a brazing material, and a metal layer is laminated on the other surface of the ceramic substrate via a brazing material. Are heated in a state of being pressed in the laminating direction, thereby bonding the ceramic substrate, the circuit layer, and the metal layer. Then, a heat sink is laminated on the surface opposite to the surface on which the ceramic substrate of the metal layer is bonded via a brazing material, and the metal layer and the heat sink are bonded by pressing and heating in the stacking direction. Thus, a power module substrate with a heat sink is manufactured.

Moreover, as a joining method of a metal layer and a heat sink, as described in, for example, Patent Document 1 or Patent Document 2, an expensive facility is unnecessary, and a fluoride system that can be relatively easily and stably brazed. The flux brazing method using the flux is applied.
In this flux brazing method, the power module substrate and the heat sink are heated and joined in a non-oxidizing atmosphere by applying a fluoride-based flux to the brazing material surface to remove the oxide on the brazing material surface. can do.

JP 2012-28472 A JP 2012-49436 A

  However, when a brazing method using a flux is used to join the metal layer and the heat sink, the excess flux travels along the side surface of the heat dissipation layer, or the flux evaporates, and the joint between the ceramic substrate and the metal layer is formed. It can erode and cause debonding at the joint.

Therefore, in Patent Document 1, a porous portion is provided on the side surface of the metal layer, and the flux reaches the joint by absorbing the excess flux to the porous portion when traveling along the side surface of the metal layer. It has been proposed to prevent. Patent Document 2 proposes preventing the flux from reaching the joint between the ceramic substrate and the metal layer by reacting the high oxygen concentration portion provided on the side surface of the metal layer with the flux.
However, even if it is possible to prevent the flux from reaching the side surface of the metal layer, in a closed space such as in a heating furnace, the evaporated flux should not contact the junction between the ceramic substrate and the metal layer. It is difficult to prevent completely, and it is difficult to reliably prevent peeling of the joint.

  The present invention has been made in view of such circumstances, and it is possible to increase the bonding reliability by bonding the metal layer and the heat sink without causing separation at the bonding portion between the ceramic substrate and the metal layer. An object is to provide a power module substrate and a power module substrate with a heat sink.

The present invention provides a power module substrate in which a circuit layer is formed on one surface of a ceramic substrate and a metal layer is brazed and bonded to the other surface, and a collar portion extending from a side surface of the metal layer has the rib portion. It is formed over the entire circumference of the side surface of the metal layer, and the flange portion has an extension length from the base end portion connected to the side surface of the metal layer to the tip end portion, and the side surface of the metal layer and the base end So that the tip of the collar portion covers the periphery of the opposite surface of the metal layer. It is provided .

The collar portion provided on the side surface of the metal layer is disposed in a state of covering the periphery of the joint portion between the metal layer and the heat sink when the metal layer and the heat sink are joined. As a result, not only the flux that flows out from the joint between the metal layer and the heat sink, but also the evaporated flux can be confined in the space surrounded by the side surface of the metal layer and the flange portion and the heat sink, and the flux is a ceramic substrate. Intrusion into the joint between the metal layer and the metal layer can be prevented.
Therefore, the metal layer and the heat sink can be bonded without causing separation at the bonded portion between the ceramic substrate and the metal layer, and the bonding reliability of the power module substrate can be improved.
It should be noted that the brim portion of the metal layer only needs to be arranged so as to cover the periphery of the joint portion between the metal layer and the heat sink when the metal layer and the heat sink are joined. For example, in a state before the metal layer is bonded to the ceramic substrate, the collar portion is formed in a state extending perpendicularly to the side surface of the metal layer. And, by heating at the time of bonding the ceramic substrate and the metal layer, the collar portion can be provided in a skirt shape that covers the periphery of the bonding portion between the metal layer and the heat sink by the tip portion side hanging down by its own weight. . Further, the collar portion can be deformed in advance into a state where the collar portion is bent toward the joint surface with the heat sink.

  The power module substrate with a heat sink according to the present invention is characterized in that a heat sink is brazed and joined to the metal layer of the power module substrate, and a tip portion of the collar portion is in contact with the heat sink. .

In the power module substrate with a heat sink of the present invention, it is preferable that a brazing material is provided so as to fill a space portion surrounded by the flange portion, the side surface of the metal layer, and the heat sink.
At the time of joining the metal layer and the heat sink, the brazing material can be fastened in the space surrounded by the side surface of the metal layer and the flange portion and the heat sink, so that the metal layer and the heat sink are filled with the brazing material. Can be joined. Therefore, the contact area between the metal layer and the heat sink can be increased, and heat dissipation can be improved.

  According to the present invention, the flux can be prevented from entering the bonded portion between the ceramic substrate and the metal layer, so that the metal layer and the heat sink can be separated without causing separation at the bonded portion between the ceramic substrate and the metal layer. The bonding reliability of the power module substrate can be improved.

It is sectional drawing which shows the power module manufactured using the board | substrate for power modules of embodiment which concerns on this invention. It is principal part sectional drawing of the board | substrate for power modules with a heat sink. It is sectional drawing explaining the manufacturing method of the board | substrate for power modules, Comprising: (a) Before joining of each member, (b) shows the state after joining. It is sectional drawing explaining the manufacturing method of the board | substrate for power modules with a heat sink, Comprising: (a) is before joining of a power module board | substrate and a heat sink, (b) shows the state after joining.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a power module 1 using a power module substrate 10 according to an embodiment of the present invention. The power module 1 of FIG. 1 includes an electronic component 20 such as a semiconductor chip mounted on the front surface of a power module substrate 10 and a heat sink 30 attached to the back surface.

  The power module substrate 10 includes a ceramic substrate 11, a circuit layer 12 laminated on one surface of the ceramic substrate 11, and a metal layer 13 laminated on the other surface of the ceramic substrate 11. The substrate 11, the circuit layer 12, and the metal layer 13 are brazed and joined. Then, the power module substrate 50 with heat sink is configured by bonding the heat sink 30 to the surface of the metal layer 13 of the power module substrate 10. The electronic module 20 is soldered to the surface of the circuit layer 12 of the power module substrate 50 with a heat sink to configure the power module 1.

The ceramic substrate 11 is formed of a ceramic material such as AlN (aluminum nitride), Si ₃ N ₄ (silicon nitride), Al ₂ O ₃ (alumina), and has a thickness of 0.2 mm to 1 mm, for example.
The circuit layer 12 is formed of pure aluminum having a purity of 99.00% by mass or more, an aluminum alloy, an aluminum alloy having a purity of 95% by mass or more such as A3003, or pure copper or a pure alloy such as oxygen-free copper or tough pitch copper. The thickness is set to 1 mm to 3 mm.

  The metal layer 13 is made of pure aluminum having a purity of 99.00% by mass or more, an aluminum alloy, or an aluminum alloy having a purity of 95% by mass or more, and has a thickness of 0.4 mm to 1.6 mm, for example. In addition, a flange portion 15 extending from the side surface 13 a is formed at the central portion in the thickness direction of the side surface 13 a of the metal layer 13 over the entire circumference of the side surface 13 a of the metal layer 13. The collar portion 15 is formed away from both surfaces of the metal layer 13, is provided thinner than the thickness of the metal layer 13, and is formed to a thickness of 0.2 mm to 0.4 mm, for example. Further, as shown in FIG. 2, the flange portion 15 has an extension length 15L from the base end portion connected to the side surface 13a of the metal layer 13 to the tip end portion, and the side surface 13a and the base end portion of the metal layer 13 The distance from the connecting position to the surface opposite to the bonding surface of the metal layer 13 to the ceramic substrate 11 is greater than 13M. The connection position between the side surface 13a of the metal layer 13 and the base end portion of the collar portion 15 is based on the center position of the collar portion 15 in the thickness direction. That is, the distance 13M is a distance from the surface opposite to the bonding surface of the metal layer 13 to the ceramic substrate 11 to the center position in the thickness direction of the base end portion of the collar portion 15.

  And as a preferable combination example of each member in the board | substrate 10 for power modules of this embodiment, the ceramic board | substrate 11 is 0.635 mm-thick AlN, and the circuit layer 12 is 1 mm-thick pure aluminum board (purity 99.99 mass% or more 4N-Al), the metal layer 13 is made of an aluminum plate having a thickness of 1.6 mm. The ceramic substrate 11, the circuit layer 12, and the metal layer 13 are made of an alloy such as Al—Si, Al—Ge, Al—Cu, Al—Mg, Al—Si—Mg, or Al—Mn. The brazing material is brazed and joined.

The heat sink 30 is formed of an aluminum alloy, for example, a flat plate having a thickness of 0.3 mm or more and 5 mm or less of a 6000 series aluminum alloy. Then, the metal layer 13 of the power module substrate 10 and the heat sink 30 are brazed and joined, for example, with a brazing material of an Al—Si alloy.
Note that the shape of the heat sink 30 is not particularly limited, and includes a heat sink having an appropriate shape such as a flat plate heat sink or a flat plate heat sink formed with fins.

Next, a method for manufacturing the power module substrate 50 with a heat sink will be described.
First, as shown in FIG. 3B, the circuit layer 12 and the metal layer 13 are brazed to the ceramic substrate 11. Specifically, as shown in FIG. 3A, the circuit layer 12 and the metal layer 13 are laminated on both surfaces of the ceramic substrate 11 with the brazing filler metal foil 14 interposed therebetween. As shown in (b), the ceramic substrate 11, the circuit layer 12, and the metal layer 13 are brazed by heating in a vacuum while being pressurized, and the power module substrate 10 is manufactured. The brazing temperature is set to 620 ° C. to less than the melting point in the case of aluminum and an aluminum alloy, and to 620 ° C. to 850 ° C. in the case of pure copper or a copper alloy.

  When the ceramic substrate 11 is joined to the circuit layer 12 and the metal layer 13, the flange portion 15 of the metal layer 13 extends from the vertically extending state shown in FIG. As shown in FIG. 2, the tip end side is formed in a suspended state. Specifically, in a state before joining the ceramic substrate 11 and the metal layer 13, the collar portion 15 extends perpendicularly to the side surface 13 a of the metal layer 13 as shown in FIG. It is formed in a state. However, by heating at the time of joining the ceramic substrate 11 and the metal layer 13, as shown in FIG. 3B, the tip end side of the collar portion 15 hangs down by its own weight. At this time, the extension length 15L of the collar portion 15 is longer than the distance 13M from the connection position between the side surface 13a of the metal layer 13 and the base end portion to the surface opposite to the bonding surface of the metal layer 13 to the ceramic substrate 11. Since the flange portion 15 is provided large, the tip portion of the collar portion 15 comes into contact with the surface of the pressurizing jig 80 to form the space portion 17 inside the collar portion 15, and the collar portion 15 is the lower surface of the metal layer 13. It is provided in a skirt shape so as to cover the periphery of the (opposite surface).

Next, the power module substrate 10 thus configured and the heat sink 30 are brazed and bonded using a flux. Specifically, fluoride (KAlF ₄ , K ₂ AlF ₅ , K ₃ AlF _6, etc.) flux is applied to the brazing material surface to remove the oxide on the brazing material surface, and a non-oxidizing atmosphere (for example, N ₂ atmospheres) and heated to 580 to 620 ° C. for bonding. At this time, the region where the flux is applied is set to be inside the outer periphery of the flange portion 15. The brazing material for joining the metal layer 13 of the power module substrate 10 and the heat sink 30 is clad in advance on the surface of the heat sink 30 or in the form of a brazing material foil 16 as shown in FIG. It is supplied by being superimposed on the heat sink 30.

  When the power module substrate 10 and the heat sink 30 are laminated when the power module substrate 10 and the heat sink 30 are joined, the tip of the collar portion 15 of the metal layer 13 comes into contact with the heat sink 30. The collar portion 15 is arranged in a state of being covered so as to cover the periphery of the joint portion between the metal layer 13 and the heat sink 30. As a result, as shown in FIG. 4B, a space portion 17 surrounding the periphery of the joint portion between the metal layer 13 and the heat sink 30 is formed by the side surface 13 a and the flange portion 15 of the metal layer 13 and the heat sink 30. . Therefore, when the metal layer 13 and the heat sink 30 are joined, when the excess flux flows out, the flux 15 is blocked by the flange portion 15 even if it tries to scoop up along the side surface 13a of the metal layer 13. The flux can be confined in the space 17. Moreover, since not only the flux that has flowed out but also the evaporated flux can be confined in the space portion 17, it is possible to prevent the flux from entering the joint between the ceramic substrate 11 and the metal layer 13.

  As described above, in the power module substrate 10 and the power module substrate 50 with the heat sink of the present embodiment, the flux can be prevented from entering the joint portion between the ceramic substrate 11 and the metal layer 13. The power module substrate 10 and the heat sink 30 can be bonded to each other without causing separation at the bonding portion between the metal layer 13 and the metal layer 13, and the bonding reliability of the power module substrate 10 can be improved.

Note that the space portion 17 surrounded by the side surface 13a of the metal layer 13 and the flange portion 15 and the heat sink 30 has an amount of flux that flows out from the joint surface in order to prevent excess flux from flowing out of the space portion 17. The size is sufficient to ensure a sufficient space. For this reason, flux does not flow out of the space portion 17 and enter the joint portion between the ceramic substrate 11 and the metal layer 13.
In addition, when the metal layer 13 and the heat sink 30 are joined, the brazing material can be fastened in the space portion 17, so that the metal layer 13 and the heat sink 30 are joined in a state where the brazing material is filled. The flange portion 15 and the heat sink 30 are also brazed. Therefore, the contact area between the metal layer 13 and the heat sink 50 can be increased, and heat dissipation can be improved.

Moreover, in the said embodiment, although the collar part 15 of the metal layer 13 was provided in the skirt shape by the heating at the time of manufacture of the board | substrate 10 for power modules, the collar part 15 of the metal layer 13 is provided with the metal layer 13 ( When the power module substrate 10) and the heat sink 30 are joined, the tip of the power module substrate 10 is placed in contact with the heat sink 30 so as to cover the periphery of the joint between the metal layer 13 and the heat sink 30. It only needs to be possible.
For example, the flange portion 15 of the metal layer 13 is deformed in advance into a state of being bent to the joint surface side with the heat sink 30 by press working, so that it is formed in a skirt shape before joining with the ceramic substrate 11. You can also.

  In addition, this invention is not limited to the thing of the structure of the said embodiment, In a detailed structure, it is possible to add a various change in the range which does not deviate from the meaning of this invention.

DESCRIPTION OF SYMBOLS 1 Power module 10 Power module board | substrate 12 Circuit layer 13 Metal layer 13a Side surface 14 Brazing material foil 15 Brim part 16 Brazing material foil 17 Space part 20 Electronic component 30 Heat sink 50 Power module board 80 with a heat sink Pressure jig

Claims (3)

A power module substrate in which a circuit layer is formed on one surface of a ceramic substrate and a metal layer is brazed to the other surface, and a collar portion extending from a side surface of the metal layer is a side surface of the metal layer The flange portion extends from the base end portion connected to the side surface of the metal layer to the tip end portion, and the connection between the side surface of the metal layer and the base end portion is formed. It is provided to be larger than the distance from the position to the surface opposite to the surface of the metal layer bonded to the ceramic substrate, and the tip of the collar portion is provided so as to cover the periphery of the opposite surface of the metal layer . A power module substrate.   2. A power module substrate with a heat sink, wherein a heat sink is brazed and joined to the metal layer of the power module substrate according to claim 1, and a tip portion of the collar portion is provided in contact with the heat sink.   3. The power module substrate with a heat sink according to claim 2, wherein a brazing material is provided so as to fill a space surrounded by the flange portion, the side surface of the metal layer, and the heat sink.

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