JP6561886B2 - Manufacturing method of power module substrate with heat sink - Google Patents

Description

  The present invention relates to a method for manufacturing a power module substrate with a heat sink.

In power semiconductor elements for large power control used to control wind power generation, electric vehicles, hybrid vehicles, etc., the amount of heat generated is large, and for example, AlN (aluminum nitride), Al _An insulating substrate made of ceramics such as ₂ O ₃ (alumina), Si ₃ N ₄ (silicon nitride), and a circuit layer formed by bonding a metal plate having excellent conductivity to one surface of the insulating substrate, The power module substrate provided has been widely used. In addition, as a power joule substrate, a substrate having a metal layer formed on the other surface of a ceramic substrate is also provided.

  In addition, in order to efficiently dissipate heat generated from a semiconductor element or the like mounted on a circuit layer, a power module substrate with a heat sink in which a heat sink is bonded to the metal layer side of the power module substrate is provided. As a material for the heat sink, aluminum-based materials such as an aluminum-based composite material in which aluminum or an aluminum alloy is filled in a silicon carbide member typified by aluminum alloy or AlSiC are widely used.

  As a method for joining the power module substrate and AlSiC, a method using a brazing material and a method of melting a part of the AlSiC coating layer (skin layer) are known.

  In Patent Document 1, an AlSiC-based composite formed by impregnating a porous body mainly made of silicon carbide with an aluminum alloy having an initial crystal temperature of 615 ° C. or higher, an AlSiC, and a power module substrate are brazed. It is disclosed to join using a material. In the example of Patent Document 1, the AlSiC composite and the DBA substrate are brazed at 590 ° C. using an aluminum brazing material.

  Patent Document 2 uses an AlSiC composite material in which an aluminum alloy coating layer containing a predetermined amount of Si and Mg is used as a heat sink, and a part of the coating layer of the AlSiC composite material is melted. Then, it is disclosed that the power module substrate and the AlSiC composite material are bonded together.

JP 2003-306730 A JP, 2014-138124, A

  By the way, recently, the output of power semiconductor elements and the like has been increased, and in a power module substrate with a heat sink on which the power semiconductor elements are mounted, the heat generated in the power semiconductor elements etc. is efficiently released to the outside by the heat sink. It is required to bond the power module substrate and the heat sink with high bonding reliability so as to be possible. However, in the method of joining the power module substrate and AlSiC disclosed in Patent Document 1 using an aluminum-based brazing material, the AlSiC base material is partially melted because the brazing joining temperature is high. As a result, AlSiC is distorted and deformed. Further, in the method of melting a part of the AlSiC composite material coating layer described in Patent Document 2, it is difficult to melt only a part of the AlSiC composite material coating layer. May melt partially.

  The present invention has been made in view of the above-described circumstances, and a high-joint between a power module substrate and a heat sink having an aluminum or aluminum alloy such as AlSiC as a base material without melting the base material of the heat sink. An object of the present invention is to provide a method of manufacturing a power module substrate with a heat sink that can be bonded with reliability.

  In order to solve the above-described problems, a method for manufacturing a power module substrate with a heat sink according to the present invention includes an insulating layer, a circuit layer formed on one surface of the insulating layer, and the other surface of the insulating layer. A metal layer of a power module substrate including the formed metal layer and a heat sink are bonded to each other, and the heat sink is made of aluminum or an aluminum alloy having an Si concentration of less than 0.1 at% or an Si concentration of 0. .1at% or more aluminum alloy, or formed from an aluminum-based composite material in which a silicon carbide member is filled with aluminum or an aluminum alloy having a Si concentration of less than 0.1 at% or an Si alloy having an Si concentration of 0.1 at% or more. A method for manufacturing a power module substrate with a heat sink, wherein the heat sink has a Si concentration. When the aluminum layer is formed of an aluminum alloy of 0.1 at% or more, or an aluminum-based composite material in which a silicon carbide member is filled with an aluminum alloy having a Si concentration of 0.1 at% or more, A power module substrate is prepared in which the bonding surface is made of aluminum or an aluminum alloy having a Si concentration of less than 0.1 at% or an aluminum alloy having a Si concentration of 0.1 at% or more. In the case where the metal layer is formed of an aluminum alloy having a concentration of less than 0.1 at%, or an aluminum-based composite material in which a silicon carbide member is filled with aluminum or an aluminum alloy having a Si concentration of less than 0.1 at% The interface between the heat sink and the heat sink has a Si concentration of 0. A step of preparing a power module substrate formed of an aluminum alloy of 1 at% or more, and a bonding surface of at least one of a bonding surface of the metal layer with the heat sink and a bonding surface of the heat sink with the metal layer An Mg layer forming step of forming an Mg layer having a thickness of 0.1 μm or more and 10 μm or less, and a stacking step of stacking the metal layer and the heat sink via the Mg layer to form a stack. The laminated body is heated in a temperature range of 550 ° C. or more and 575 ° C. or less, and a heating step for joining the metal layer and the heat sink is provided.

According to the method for manufacturing a power module substrate with a heat sink having this configuration, the base material of the heat sink is not melted by heating at a low temperature compared to the case of using an aluminum-based brazing material mainly composed of aluminum. A power module substrate with a heat sink in which the metal layer and the heat sink are bonded with high bonding reliability can be obtained. The reason why the metal layer and the heat sink can be joined by heating at a low temperature with the above configuration is considered as follows. In the heating process, when the laminate is heated, Mg in the Mg layer diffuses into the metal layer or the heat sink, and Si contained in the metal layer or the heat sink reacts with Mg diffused from the Mg layer to cause a high concentration. Mg ₂ Si is generated, and a region where Al, Mg ₂ Si, and Mg coexist or a region where Al, Mg ₂ Si, and Si coexist are formed. This region is 575 ° C. or lower, and a sufficient amount of liquid phase can be generated for bonding. Conventional brazing materials such as aluminum-based brazing materials mainly composed of aluminum, Mg-containing Al—Si brazing materials, and clad materials made of Mg-containing brazing materials are used at a temperature of 575 ° C. or less, which is sufficient for bonding. A liquid phase cannot be produced. And since both a metal layer and a heat sink are comprised from the Al member, this liquid phase diffuses into a metal layer and a heat sink, and both are joined.

In addition, since the laminated body has a structure in which an aluminum alloy containing Si or a heat sink and an Mg layer containing Mg are separated, the Mg concentration of the Mg layer can be increased. In order to achieve the effects of the present invention by using a conventional Mg-containing Al—Si brazing material or a clad material made of a Mg-containing brazing material as a skin material, the concentration of Mg must be increased. As a result, the Mg-containing Al—Si brazing material cannot be obtained. Therefore, in this invention, it is set as the structure of the above laminated bodies. Moreover, since it has Mg layer with high Mg density | concentration, Mg can be reliably diffused to the heat sink containing Si.
For the above reasons, according to the method for manufacturing a power module substrate with a heat sink, a power module substrate with a heat sink in which the metal layer and the heat sink are bonded with high bonding reliability by heating at a relatively low temperature. It is thought that you can.

Here, if the Si concentration of both the aluminum alloy of the metal layer and the aluminum alloy of the heat sink is less than 0.1 at%, the region where Al, Mg ₂ Si, and Mg coexist, and Al, Mg ₂ Si, and Si coexist. The amount of the liquid phase generated in the region to be reduced is reduced, and the bondability between the metal layer and the heat sink is reduced.
When the Mg layer thickness is less than 0.1 μm, the amount of Mg 2 Si decreases during heating, and the bondability between the metal layer and the heat sink decreases. When it exceeds 10 μm, a large amount of Al—Mg liquid phase is generated, and a bump is generated.
On the other hand, when the heating temperature is less than 550 ° C., the amount of liquid phase generated is reduced, so that the bondability is lowered. When the temperature exceeds 575 ° C., the solder bump and the heat sink base material melt.

Here, in the method for manufacturing a power module substrate with a heat sink according to the present invention, a thickness of 50 μm from the surface of the joint surface of the metal layer to the heat sink and the joint surface of the heat sink to the metal layer in the laminate. The ratio (Si / Mg) of the amount of Si present in the range up to and the amount of Mg present in the Mg layer is in the range of 0.01 to 99.00 in atomic ratio. It is preferable.
In this case, since the high concentration Mg ₂ Si necessary for bonding the metal layer of the power module substrate and the heat sink can be reliably generated in the heating step, the bonding reliability between the metal layer and the heat sink is high. It becomes possible to join reliably.

Furthermore, in the method for manufacturing a power module substrate with a heat sink of the present invention, in the heating step, the laminate is preferably heated while applying a pressure of 0.1 MPa to 3.5 MPa in the stacking direction. .
In this case, the metal layer of the power module substrate and the heat sink can be reliably bonded with high bonding reliability without causing cracks or damage to the power module substrate and the heat sink.

  According to the present invention, a power module substrate with a heat sink capable of joining a power module substrate and a heat sink having an aluminum alloy such as AlSiC as a base material without melting the base material of the heat sink with high joining reliability. It becomes possible to provide a method.

It is a schematic explanatory drawing of the board | substrate for power modules with a heat sink which concerns on 1st embodiment of this invention. FIG. 2 is an enlarged explanatory view of a joint portion between a metal layer and a heat sink in FIG. 1. It is a schematic explanatory drawing of the manufacturing method of the board | substrate for power modules with a heat sink which concerns on 1st embodiment. It is a schematic explanatory drawing of the board | substrate for power modules with a heat sink which concerns on 2nd embodiment of this invention. It is a schematic explanatory drawing of the manufacturing method of the board | substrate for power modules with a heat sink which concerns on 2nd embodiment.

  Hereinafter, with reference to drawings, the manufacturing method of the board for power modules with a heat sink of the present invention is explained. Each embodiment described below is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, there is a case where a main part is shown in an enlarged manner for convenience, and the dimensional ratio of each component is the same as the actual one. Not necessarily.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic explanatory diagram of a power module substrate with a heat sink according to the first embodiment of the present invention. FIG. 2 is an enlarged explanatory view of a joint portion between the metal layer and the heat sink in FIG. FIG. 3 is a schematic explanatory view of a method for manufacturing a power module substrate with a heat sink according to the first embodiment.

  The power module substrate 10 with a heat sink includes a power module substrate 20 and a heat sink 30 bonded to a metal layer of the power module substrate.

  The power module substrate 20 includes a ceramic substrate 21 serving as an insulating layer, a circuit layer 22 formed on one surface of the ceramic substrate 21 (upper surface in FIG. 1), and the other surface of the ceramic substrate 21 (in FIG. 1). And a metal layer 23 formed on the lower surface.

The ceramic substrate (insulating layer) 21 is made of ceramics such as Si ₃ N ₄ (silicon nitride), AlN (aluminum nitride), and Al ₂ O ₃ (alumina) that are excellent in insulation and heat dissipation. In the present embodiment, the ceramic substrate 21 is made of AlN (aluminum nitride). The thickness of the ceramic substrate 21 is set within a range of 0.2 mm or more and 1.5 mm or less, for example, and is set to 0.635 mm in the present embodiment.

  The circuit layer 22 is formed by joining an aluminum member made of aluminum or an aluminum alloy to one surface of the ceramic substrate 21. As the aluminum member, aluminum (2N aluminum) having a purity of 99% by mass or more and aluminum (4N aluminum) having a purity of 99.99% by mass or more can be used. In this embodiment, a 4N aluminum rolled plate is used. The thickness of the circuit layer 22 is set in a range of 0.1 mm to 1.0 mm, and is set to 0.4 mm in the present embodiment. The circuit layer 22 and the ceramic substrate 21 are joined by, for example, an Al—Si brazing material.

  As a material of the circuit layer 22, a copper member made of copper or a copper alloy can be used in addition to the aluminum member. For example, an oxygen-free copper rolled plate can be joined to the ceramic substrate 21 to form the circuit layer 22. Further, as the circuit layer 22, a joined body in which an aluminum member and a copper member are joined may be used. For example, a joined body in which an aluminum member is joined to the ceramic substrate 21 and a copper member is joined to the aluminum member can be used as the circuit layer 22. When joining an aluminum member and a copper member, it is preferable to interpose a titanium member made of titanium between the aluminum member and the copper member. By interposing the titanium member, the heating step can be performed at a temperature equal to or higher than the eutectic temperature of aluminum and copper (540 ° C.) in the manufacturing method described later.

  The metal layer 23 is formed by bonding an aluminum member made of aluminum or an aluminum alloy bonded to the other surface of the ceramic substrate 21. As the aluminum member, aluminum (2N aluminum) having a purity of 99% by mass or more, aluminum (4N aluminum) having a purity of 99.99% by mass or more, and the like can be used. In this embodiment, a 4N aluminum rolled plate is used. The thickness of the metal layer 23 is set within a range of 0.1 mm to 3.0 mm, and is set to 0.4 mm in the present embodiment. The metal layer 23 and the ceramic substrate 21 are joined by, for example, an Al—Si brazing material. In addition, as an aluminum plate used as the metal layer 23, an aluminum alloy plate containing a Si concentration of 0.1 at% or more can be used.

The heat sink 30 is for dissipating heat on the power module substrate 20 side. The heat sink 30 is made of an aluminum alloy having a Si concentration of 0.1 at% or more, or an aluminum-based composite material in which a silicon carbide member is filled with an aluminum alloy having a Si concentration of 0.1 at% or more. If Si concentration is low, the manufacturing method described later, the liquid phase and the area or Al where Al and Mg 2 _Si and Mg coexisting during the heating step and Mg 2 _Si and Si are generated from a region coexist occurs No longer. As the aluminum based composite material, AlSiC in which an aluminum alloy is filled in silicon carbide (silicon carbide: SiC) can be used. AlSiC may or may not have a coating layer.

A junction 40 is formed between the power module substrate 20 and the heat sink 30. Junction 40, as shown in FIG. 2, has a structure _{in which Mg} 2 Si phase 41 consisting of _Mg 2 Si is dispersed. The joint 40 in which the Mg ₂ Si phase 41 is dispersed is obtained by heating the metal layer 23 and the heat sink 30 of the power module substrate 20 through the Mg layer in the manufacturing method described below, for the power module. It is formed by bonding the substrate 20 and the heat sink 30.

  Here, the manufacturing method of the board | substrate for power modules with a heat sink which concerns on 1st embodiment is demonstrated with reference to FIG.

First, as shown to Fig.3 (a), Mg layer 50 is formed in the joint surface with the heat sink 30 of the metal layer 23 of the board | substrate 20 for power modules (Mg layer formation process).
The thickness of the Mg layer 50 is set in the range of 0.1 μm to 10 μm. If the thickness of the Mg layer 50 becomes too thin, the amount of Mg ₂ Si generated during the heating process described later decreases, and the bondability between the metal layer 23 and the heat sink 30 decreases. On the other hand, if the Mg layer is too thick, an Al—Mg alloy liquid phase is excessively generated during the heating process described later, and a wax is generated at the joint between the metal layer 23 and the heat sink 30. There is a possibility that it becomes easy to do.

The Mg layer 50 preferably has an Mg concentration of 80 at% or more, and particularly preferably 90 at% or more. When Mg concentration of the Mg layer 50 is too low, during the heating step to be described later, the liquid phase from the region or Al and _Mg 2 Si and Si and coexist region where the Al and _Mg 2 Si and Mg coexisting generation There is a risk that it will be difficult.

Further, the ratio of the amount of Si existing in the range from the bonding surface of the metal layer 23 and the bonding surface of the heat sink 30 to the thickness of 50 μm and the amount of Mg existing in the Mg layer 50 (Si / Mg) is preferably in the range of 0.01 to 99.0 in terms of atomic ratio, and particularly preferably in the range of 1.1 to 6.7. When the abundance ratio of Si and Mg is within the above range, high-concentration Mg ₂ Si necessary for joining the metal layer 23 and the heat sink 30 is surely generated during the heating process described later. Therefore, the metal layer 23 and the heat sink 30 can be reliably bonded with high bonding reliability. Note that the amount of Mg present in the Mg layer 50 can be obtained from the thickness, purity, and density of the Mg layer 50. The amount of Si existing in the range from the bonding surface of the metal layer 23 and the surface of the bonding surface of the heat sink 30 to the thickness of 50 μm can be determined from the Si content of the metal layer 23 and the heat sink 30.

  As a method of forming the Mg layer 50 on the metal layer 23, a sputtering method using an Mg target, a method of applying a Mg powder paste and drying, or a vapor deposition method can be used.

  Next, the metal layer 23 and the heat sink 30 are laminated via the Mg layer 50 to form the laminated body 11 (lamination process).

Next, the laminate 11 is heated to join the metal layer 23 and the heat sink 30 (heating step). In the heating step, the stacked body 11 is heated, whereby Mg in the Mg layer 50 diffuses into the aluminum alloy of the heat sink 30, and Si in the aluminum alloy reacts with the diffused Mg to cause a high concentration of Mg ₂ Si. Is formed, and a region where Al, Mg ₂ Si, and Mg coexist or a region where Al, Mg ₂ Si, and Si coexist are formed. This region is 575 ° C. or lower, and a sufficient amount of liquid phase can be generated for bonding. Then, the metal layer 23 and the heat sink 30, because it is the main component of aluminum as described above, the area Al and _Mg 2 Si and Si and the Al and _Mg 2 Si and Mg coexisting is formed from a region coexist The liquid phase diffuses into both the metal layer 23 and the heat sink 30 and joins both.

In the heating step, the heating temperature of the laminated body 11 is a temperature range of 550 ° C. or more and 575 ° C. or less. Since the heating temperature of the laminate 11 is too low, liquid phase and the Al and Mg 2 _Si and Mg and is the area or Al coexisting Mg 2 _Si and Si is formed from a region coexist not generate, bondability Decreases. On the other hand, when the heating temperature of the laminated body 11 becomes too high, melting of the base material of the bump and the heat sink 30 occurs.

  In the heating step, it is preferable to heat the stacked body 11 while applying a pressure of 0.1 MPa or more and 3.5 MPa or less to the stacked body 11 in the stacking direction. If the applied pressure is too low, the liquid phase may not easily diffuse into the metal layer 23 and the heat sink 30 of the power module substrate 20. If the applied pressure becomes too high, the power module substrate 20 and the heat sink 30 may be cracked or damaged.

The heating time is preferably set within a range of 15 minutes to 180 minutes.
The heating is preferably performed by using a vacuum heating furnace and setting the pressure in the vacuum heating furnace within a range of 10 ⁻⁶ Pa to 10 ⁻² Pa.

(Second embodiment)
A second embodiment of the present invention will be described with reference to FIGS.
FIG. 4 is a schematic explanatory diagram of a power module substrate with a heat sink according to the second embodiment of the present invention. FIG. 5 is a schematic explanatory view of a method for manufacturing a power module substrate with a heat sink according to the second embodiment. In addition, about the thing of the same structure as 1st embodiment and 2nd embodiment, the same code | symbol is attached | subjected and described, and detailed description is abbreviate | omitted.

  The power module substrate 60 with a heat sink includes a power module substrate 70 and a heat sink 30 bonded to the metal layer 73 of the power module substrate 70. A joint 40 is formed between the power module substrate 70 and the heat sink 30 as in the case of the first embodiment described above.

  The power module substrate 70 includes a ceramic substrate 71 serving as an insulating layer, a circuit layer 72 formed on one surface of the ceramic substrate 71 (upper surface in FIG. 4), and the other surface of the ceramic substrate 21 (in FIG. 4). And a metal layer 73 formed on the lower surface.

The ceramic substrate (insulating layer) 71 is made of ceramics such as Si ₃ N ₄ (silicon nitride), AlN (aluminum nitride), and Al ₂ O ₃ (alumina) that are excellent in insulation and heat dissipation. In the present embodiment, the ceramic substrate 71 is made of AlN (aluminum nitride). The thickness of the ceramic substrate 21 is set within a range of 0.2 mm or more and 1.5 mm or less, for example, and is set to 0.635 mm in the present embodiment.

  The circuit layer 72 is formed by bonding a copper member made of copper or a copper alloy to one surface of the ceramic substrate 71. As the copper member, oxygen-free copper can be used. In this embodiment, an oxygen-free copper rolled plate is used. The thickness of the circuit layer 72 is set within a range of 0.05 mm to 1 mm, and is set to 0.3 mm in the present embodiment. The circuit layer 72 and the ceramic substrate 71 are bonded by, for example, the DBC method or the active metal brazing method.

  As a material of the circuit layer 72, an aluminum member can be used in addition to the copper member. Further, as the circuit layer 72, a joined body obtained by joining an aluminum member and a copper member may be used. For example, an aluminum member can be joined to the ceramic substrate 71, and a copper member can be further joined to the aluminum member to form the circuit layer 72.

  The metal layer 73 includes a copper member layer 74 bonded to the other surface of the ceramic substrate 71 and a titanium member bonded to the surface of the copper member layer 74 opposite to the surface bonded to the ceramic substrate 71. The layer 75 includes an aluminum member layer 76 bonded to a surface of the titanium member layer 75 opposite to the surface bonded to the ceramic substrate 71.

  The copper member layer 74 is made of copper or a copper alloy. As the copper member, oxygen-free copper can be used. In this embodiment, an oxygen-free copper rolled plate is used. The thickness of the copper member layer 74 is set within a range of 0.05 mm to 1 mm, and is set to 0.3 mm in the present embodiment. The copper member layer 74 and the ceramic substrate 71 are joined by, for example, the DBC method or the active metal brazing method.

  The titanium member layer 75 is made of titanium. The thickness of the titanium member layer 75 is set in the range of 0.003 mm or more and 0.050 mm or less, and is set to 0.3 mm in this embodiment. The titanium member layer 75 and the copper member layer 74 are bonded by, for example, solid phase diffusion bonding.

  The aluminum member layer 76 is made of aluminum or an aluminum alloy. As aluminum or an aluminum alloy, aluminum (2N aluminum) having a purity of 99% by mass or more, aluminum (4N aluminum) having a purity of 99.99% by mass or more, or the like can be used. In this embodiment, a 4N aluminum rolled plate is used. The thickness of the aluminum member layer 76 is set within a range of 0.1 mm or more and 3.0 mm or less, and is set to 0.4 mm in the present embodiment. The aluminum member layer 76 and the titanium member layer 75 are bonded by, for example, solid phase diffusion bonding. In addition, as an aluminum plate used as the aluminum member layer 76, an aluminum alloy plate containing a Si concentration of 0.1 at% or more can be used.

    Next, the manufacturing method of the board | substrate for power modules with a heat sink which concerns on 2nd embodiment is demonstrated with reference to FIG.

  First, as shown in FIG. 5A, the Mg layer 50 is formed on the aluminum member layer 76 (the bonding surface of the metal layer 73 with the heat sink 30) of the power module substrate 70 (Mg layer forming step). The thickness of the Mg layer 50, the Mg concentration, the abundance ratio of Si and Mg (Si / Mg), and the formation method are the same as those in the first embodiment.

  Next, the aluminum member layer 76 and the heat sink 30 are laminated via the Mg layer 50 to form a laminated body 61 (lamination process).

  Next, the laminated body 61 is heated to join the aluminum member layer 76 and the heat sink 30 (heating process). In the heating step, the heating temperature of the laminated body 61, the pressure applied to the laminated body 61, the heating time, and the pressure in the vacuum heating furnace are the same as those in the first embodiment.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, in this embodiment, the heat sink is formed of an aluminum alloy having a Si concentration of 0.1 at% or more, or an aluminum-based composite material in which a silicon carbide member is filled with an aluminum alloy having a Si concentration of 0.1 at% or more. However, the heat sink is an aluminum-based composite material in which aluminum or an Si alloy having an Si concentration of less than 0.1 at%, or a silicon carbide member filled with aluminum or an aluminum alloy having an Si concentration of less than 0.1 at%. It may be formed from. However, in this case, it is necessary to prepare a power module substrate in which the joint surface of the metal layer with the heat sink is made of an aluminum alloy having a Si concentration of 0.1 at% or more.

  For example, in the present embodiment, the Mg layer is a single layer, but the layer configuration of the Mg layer is not limited. The Mg layer may be a laminated structure in which the Mg layer is laminated on each of the front and back surfaces of the aluminum layer.

  Furthermore, the power module substrate is not particularly limited as long as the joining surface of the metal layer to the heat sink is made of aluminum or an aluminum alloy. As long as the circuit layer and the metal layer of the power module substrate are configured not to melt in the heating process of the laminate, they can be joined to various materials.

The power module substrates with heat sinks of the present invention and comparative examples were manufactured by the following method.
First, an aluminum plate (0.6 mmt) having a purity of 99.99% or more to be a circuit layer is laminated on one surface of a ceramic substrate via an Al—Si brazing material, and a metal layer is formed on the other surface. The aluminum plate (0.6 mmt) described in 1 was laminated via an Al—Si brazing material, and was heated and joined while applying a load to obtain a power module substrate.
Next, an Mg layer having the Mg concentration and the layer thickness shown in Table 1 below was formed on the metal layer and / or heat sink of the power module substrate by sputtering. The abundance ratio of Si and Mg (Si / Mg) was measured by the following method. The results are shown in Table 1.

Next, the metal layer of the power module substrate and the heat sink shown in Table 1 were laminated via the Mg layer to form a laminate. This laminated body was put into a vacuum heating furnace and heated at the heating temperature shown in Table 1 for 15 minutes while applying the load shown in Table 1 to produce a power module substrate with a heat sink.
And about the obtained board | substrate for power modules with a heat sink, the joining rate of a heat sink and a board | substrate for power modules and an external appearance were evaluated by the following method. The evaluation results are shown in Table 1.

(Abundance ratio of Si and Mg (Si / Mg))
The Mg amount was calculated by forming the Mg layer on the metal layer and / or the heat sink of the power module substrate, then obtaining the thickness from the cross-sectional SEM observation, obtaining the purity from EPMA, and setting the Mg density to 1.74 g / cm ³ . . When the Mg layer was formed on both the metal layer and the heat sink of the power module substrate, the total amount was defined as the Mg amount.
The amount of Si is the amount of Si within the range of 50 μm in the thickness direction from the surface where the Si concentration in the Al-Si alloy of the heat sink and the metal layer of the power module substrate are joined to the metal layer of the power module substrate. Was calculated. The thickness was measured from cross-sectional SEM observation.
The abundance ratio of Si and Mg (Si / Mg) was obtained from the obtained Mg amount and Si amount. The Si amount is the total amount of Si concentration in the Al—Si alloy of the heat sink and Si concentration of the metal layer of the power module substrate.

(Appearance evaluation of power module substrate with heat sink)
The case corresponding to any of the following was evaluated as x, and the others were evaluated as o.
1. When the joint between the heat sink and the power module substrate is visually observed and a bump is observed.
2. When the heat sink is visually observed and a hump or crack has occurred.

(Joint rate of joint)
The joining rate after the thermal cycle was evaluated. The cooling / heating cycle was performed in the liquid phase (in florinate), and 2000 cycles of −40 ° C. × 5 minutes and 150 ° C. × 5 minutes were performed.
The bonding rate after the thermal cycle was measured using an ultrasonic flaw detector (FineSAT 200, manufactured by Hitachi Power Solutions Co., Ltd.) at the joint between the heat sink and the power module substrate. Calculated.
Here, the initial bonding area is the area to be bonded before bonding, that is, the area of the metal layer of the power module substrate.
(Bonding rate) = {(initial bonding area) − (peeling area)} / (initial bonding area)
In the image obtained by binarizing the ultrasonic flaw detection image, the peeling is indicated by the white portion in the joint portion. Therefore, the area of the white portion is defined as the peeling area.
The evaluation results are shown in Table 1.

Comparative Example 1 in which the thickness of the Mg layer is reduced to less than 0.1 μm, Comparative Examples 3 and 4 in which the Si concentration of the metal layer and the heat sink is 0.1 at% or less and the Si concentration is low, and Comparative Examples in which the bonding temperature is low In No. 5, the joining rate of the joined portion was low.
In Comparative Example 2 in which the thickness of the Mg layer was greater than 10 μm, a bump was generated. In Comparative Example 6 where the bonding temperature was high, the heat sink was cracked.

On the other hand, none of the power module substrates with heat sinks obtained in the examples of the present invention showed a high value of the joint ratio without any occurrence of bumps.
From the above, according to the example of the present invention, it was confirmed that the power module substrate and the heat sink whose base material is aluminum such as AlSiC or the aluminum alloy can be reliably bonded without melting the base material of the heat sink. It was.

10, 60 Power module substrate with heat sink 11, 61 Laminate 20, 70 Power module substrate 21, 71 Ceramic substrate 22, 72 Circuit layer 23, 73 Metal layer 30 Heat sink 40 Joint 41 Mg ₂ Si phase 50 Mg layer 74 Copper member layer 75 Titanium member layer 76 Aluminum member layer

Claims (3)

A metal layer of a power module substrate including an insulating layer, a circuit layer formed on one surface of the insulating layer, and a metal layer formed on the other surface of the insulating layer, and a heat sink, And the heat sink is aluminum or an aluminum alloy having an Si concentration of less than 0.1 at%, an aluminum alloy having an Si concentration of 0.1 at% or more, or an aluminum or Si concentration of 0.1 at% in a silicon carbide member. A method for manufacturing a power module substrate with a heat sink formed from an aluminum-based composite material filled with an aluminum alloy of less than% or an aluminum alloy having a Si concentration of 0.1 at% or more,
When the heat sink is formed of an aluminum alloy having a Si concentration of 0.1 at% or more, or an aluminum-based composite material in which a silicon carbide member is filled with an aluminum alloy having a Si concentration of 0.1 at% or more, Preparing a power module substrate in which a bonding surface of the metal layer to the heat sink is formed of aluminum or an aluminum alloy having a Si concentration of less than 0.1 at% or an aluminum alloy having a Si concentration of 0.1 at% or more; The heat sink is formed of aluminum or an aluminum alloy having a Si concentration of less than 0.1 at%, or an aluminum-based composite material in which a silicon carbide member is filled with aluminum or an aluminum alloy having a Si concentration of less than 0.1 at%. The heat sink of the metal layer. A step bonding surface, providing a power module substrate Si concentration is formed from 0.1 at% or more of aluminum alloy with,
A Mg layer forming step of forming an Mg layer having a thickness of 0.1 μm or more and 10 μm or less on at least one of a joint surface of the metal layer with the heat sink and a joint surface of the heat sink with the metal layer When,
A laminating step of laminating the metal layer and the heat sink via the Mg layer to form a laminate;
Heating the laminated body in a temperature range of 550 ° C. or more and 575 ° C. or less to join the metal layer and the heat sink;
The manufacturing method of the board | substrate for power modules with a heat sink characterized by the above-mentioned.   In the laminate, the amount of Si present in the range from the surface of the joint surface of the metal layer to the heat sink and the joint surface of the heat sink to the metal layer to a thickness of 50 μm, and present in the Mg layer 2. The power module substrate with a heat sink according to claim 1, wherein the ratio (Si / Mg) to the amount of Mg in the range of 0.01 to 99.0 in terms of atomic ratio. Production method.   3. The power module with a heat sink according to claim 1, wherein, in the heating step, the laminated body is heated while applying a pressure of 0.1 MPa to 3.5 MPa in a laminating direction. A method for manufacturing a substrate.

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