JP6201297B2 - Power module substrate with copper plate and method for manufacturing power module substrate with copper plate - Google Patents

Description

  The present invention relates to a power module substrate with a copper plate used in a semiconductor device that controls a large current and a high voltage, and a method for manufacturing a power module substrate with a copper plate.

Among semiconductor elements, a power module for supplying power has a relatively high calorific value, and for example, AlN (aluminum nitride), Al ₂ O ₃ (alumina), Si ₃ N ₄ ( A circuit layer formed by bonding a first metal plate to one surface side of an insulating substrate made of silicon nitride), and a metal layer formed by bonding a second metal plate to the other surface side of the insulating substrate; The board for power modules provided with is used.
In such a power module substrate, a semiconductor element of a power element is mounted on a circuit layer via a solder material.
And the heat sink for cooling the board | substrate for power modules is joined to the other surface side of a metal layer.

For example, Patent Document 1 proposes a power module substrate in which a first metal plate constituting a circuit layer is a copper plate and a second metal plate constituting the metal layer is an aluminum plate.
In the power module substrate having this configuration, since the circuit layer is made of a copper plate, it is possible to sufficiently spread and dissipate heat from a heating element such as an electrical component mounted on the circuit layer. . In addition, since the metal layer is made of an aluminum plate, thermal strain caused by the difference in thermal expansion coefficient between the heat sink and the insulating substrate can be sufficiently relaxed in the metal layer, and cracking of the insulating substrate is suppressed. It becomes possible.

JP 2003-197826 A

  By the way, in the board | substrate for power modules described in patent document 1, a copper plate is joined to one surface of an insulated substrate, and an aluminum plate is joined to the other surface of an insulated substrate. Here, since the bonding temperature when bonding the copper plate and the insulating substrate is higher than the bonding temperature when bonding the aluminum plate and the insulating substrate, first, after bonding the copper plate and the insulating substrate, The insulating substrate is bonded.

Here, when a copper plate is bonded to one surface of the insulating substrate, the thermal expansion coefficients of the copper plate and the insulating substrate are greatly different, so that a large warp occurs after bonding. In this state, even if an aluminum plate is to be bonded to the other surface side of the insulating substrate, the aluminum plate and the insulating substrate are not in close contact with each other, and there is a possibility that the bonding cannot be performed satisfactorily.
Further, even when the aluminum plate is bonded by correcting the warp by applying pressure, the warp still occurs because different metals are bonded on one surface and the other surface of the insulating substrate. . In particular, when the aluminum plate is thicker than the copper plate, warping becomes significant.
When the power module substrate is warped in this way, a gap is generated at the bonding interface when the semiconductor element is bonded on the circuit layer or when the heat sink is bonded to the metal layer side. There was a possibility that it could not be performed well.

  The present invention has been made in view of the above-described circumstances, and suppresses the occurrence of warping even when the circuit layer is made of copper or a copper alloy and the metal layer is made of aluminum or an aluminum alloy. An object of the present invention is to provide a power module substrate with a copper plate and a method for manufacturing a power module substrate with a copper plate.

Such problem solution to the, in order to achieve the above object, a substrate for the copper plate with a power module of the present invention, a ceramic substrate, a circuit layer formed on one surface of the ceramic substrate, the ceramic substrate A metal layer formed on the other surface of the ceramic substrate , wherein the metal layer is formed by joining an aluminum plate made of aluminum or an aluminum alloy to the other surface of the ceramic substrate , and the circuit layer includes: A copper plate made of copper or a copper alloy is brazed to one surface of the ceramic substrate , and the copper plate includes a die pad to which a semiconductor element is bonded, a lead portion extending from the die pad, and the lead portion. has a guide frame for connecting said die pad of the copper plate are brazed on one surface of the ceramic substrate, before Relationship between the thickness t ₂ of the thickness t ₁ of the circuit layer metal layer, is characterized in that there is a t 1 _{<t 2.}

In the power module substrate with a copper plate of this configuration, a copper layer die pad made of copper or a copper alloy is joined to one surface of the ceramic substrate to form a circuit layer, and the copper plate die pad has a lead portion. Since it is connected to the guide frame via the via, the warpage is suppressed by ensuring the rigidity of the copper plate. Therefore, even when the circuit layer is made of copper or a copper alloy and the metal layer is made of aluminum or an aluminum alloy, warpage does not occur and the semiconductor element and the heat sink can be bonded well.

In addition, when a heat sink is bonded to the metal layer side of the power module substrate with a copper plate, the thermal strain caused by the difference in thermal expansion coefficient between the ceramic substrate and the heat sink is reduced by aluminum or an aluminum alloy having a relatively small deformation resistance. Since the metal layer comprised of can be relaxed by deformation, cracking of the ceramic substrate can be suppressed.
Moreover, in the above power module substrate with a copper plate, the circuit layer having the mounting surface on which the electronic component is mounted is made of copper or a copper alloy, so that the heat generated from the electronic component can be sufficiently expanded. It becomes possible to promote heat dissipation. Therefore, durability when a power cycle is loaded can be improved.
Further, the relationship between the thickness t _{1 of the} circuit layer and the thickness t ₂ of the metal layer is t ₁ <t _2, and the thickness of the circuit layer made of copper or a copper alloy having a relatively large deformation resistance. Since the thickness t ₁ is formed thinner than the thickness t _{2 of the} metal layer made of aluminum or aluminum alloy having a relatively small deformation resistance , the occurrence of warpage in the power module substrate with a copper plate can be further suppressed. .

Here, it is preferable that the copper plate is formed in a strip shape, has a plurality of die pads in the longitudinal direction, and the ceramic substrate is bonded to the die pads.
In this case, since the copper plate is formed in a strip shape and has a plurality of die pads in the longitudinal direction, a semiconductor element is mounted on the die pad, and the lead portion is continuously cut from the guide frame. A semiconductor device can be manufactured.

Furthermore, method of manufacturing a substrate for the copper plate with a power module of the present invention, a ceramic substrate, a circuit layer formed on one surface of the ceramic substrate, a metal layer formed on the other surface of the ceramic substrate, A power module substrate manufacturing method comprising: a die pad; a lead portion extending from the die pad; and a guide frame connecting the lead portion; and a copper plate made of copper or a copper alloy is prepared. The die pad is brazed to one surface of the ceramic substrate, the die pad is brazed to the insulating substrate, and then an aluminum plate made of aluminum or an aluminum alloy is bonded to the other surface of the ceramic substrate. It is characterized by.

In the method of manufacturing a power module substrate with a copper plate having this configuration, the ceramic substrate is bonded to a copper plate having a die pad, a lead portion extending from the die pad, and a guide frame connecting the lead portion. Therefore, it is possible to suppress the occurrence of warpage of the joined body between the copper plate and the ceramic substrate . Furthermore, after bonding the copper plate to the ceramic substrate, since joining the aluminum plate made of aluminum or an aluminum alloy to the other side of the ceramic substrate, it is possible to improve the reliability of the bonding between the aluminum plate and the ceramic substrate.

  According to the present invention, even if the circuit layer is made of copper or a copper alloy and the metal layer is made of aluminum or an aluminum alloy, the power module substrate with a copper plate capable of suppressing the occurrence of warpage and The manufacturing method of the board | substrate for power modules with a copper plate can be provided.

It is a schematic explanatory drawing of the power module using the board | substrate for power modules with a copper plate which is embodiment of this invention. It is a schematic explanatory drawing of the board | substrate for power modules with a copper plate which is embodiment of this invention. It is a schematic explanatory drawing of the frame used for the board | substrate for power modules with a copper plate which is embodiment of this invention. It is a flowchart of the manufacturing method of the board | substrate for power modules with a copper plate which is embodiment of this invention. It is a schematic explanatory drawing of the manufacturing method of the board | substrate for power modules with a copper plate which is embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a power module substrate 10 with a copper plate and a power module 1 using this power module substrate 10 with a copper plate according to an embodiment of the present invention.
The power module 1 is bonded to a power module substrate 10 with a copper plate on which a circuit layer 12 is disposed, and a surface on one side (upper side in FIG. 1) of the power module substrate 10 with a copper plate via a solder layer 2. And a heat sink 41 disposed on the other side (lower side in FIG. 1) of the power module substrate 10 with a copper plate. The power module substrate 10 with the copper plate and the semiconductor element 3 are sealed by the exterior resin 6, and a lead portion 33 of the copper plate 30 described later is configured to protrude outward from the exterior resin 6. .
Here, the solder layer 2 is made of, for example, a Sn—Ag, Sn—In, or Sn—Ag—Cu solder material. In the present embodiment, a Ni plating layer (not shown) is provided between the circuit layer 12 and the solder layer 2.

As shown in FIGS. 1 and 2, the power module substrate 10 with a copper plate includes a ceramic substrate 11 and a circuit layer 12 disposed on one surface (the upper surface in FIGS. 1 and 2) of the ceramic substrate 11. And a metal layer 13 disposed on the other surface (the lower surface in FIGS. 1 and 2) of the ceramic substrate 11.
The ceramic substrate 11 prevents electrical connection between the circuit layer 12 and the metal layer 13. In this embodiment, it is comprised with AlN (aluminum nitride) with high insulation. In addition, the thickness of the ceramic substrate 11 is set within a range of 0.2 to 1.5 mm, and in this embodiment is set to 0.635 mm.

The circuit layer 12 is formed by bonding a copper plate 30 made of copper or a copper alloy to one surface of the ceramic substrate 11.
The copper plate 30 includes a die pad 32 to which the semiconductor element 3 is bonded, a lead portion 33 extending from the die pad 32, and a guide frame 31 that connects the lead portion 33. The die pad 32 is bonded to one surface of the ceramic substrate 11 to constitute the circuit layer 12. Further, the lead portion 33 of the copper plate 30 is disposed so as to protrude outward from the exterior resin 6.
In the present embodiment, as the copper plate 30, as shown in FIG. 3, a strip material in which a plurality of die pads 32 are connected in the extending direction of the guide frame 31 is used.

As shown in FIG. 5, the metal layer 13 is formed by bonding an aluminum plate 23 to the other surface of the ceramic substrate 11.
In this embodiment, the aluminum plate 23 to be the metal layer 13 is a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99% by mass or more. The aluminum plate 23 has a 0.2% proof stress of 30 N / mm ² or less.

Here, in the present embodiment, as shown in FIG. 2, the thickness t ₁ of the circuit layer 12 (the die pad 32 of the copper plate 30) is set within a range of 0.1 mm ≦ t ₁ ≦ 0.6 mm. The thickness t _{2 of} the metal layer 13 (aluminum plate 23) is set in the range of 0.6 mm ≦ t ₂ ≦ 6 mm, and the thickness t ₁ of the circuit layer 12 and the thickness of the metal layer 13 are set. The relationship with t ₂ is t ₁ <t ₂ . The relationship between the thickness _{t 2} of the thickness _{t 1} and the metal layer 13 of the circuit layer _12, which is preferably a t 2 / _{t 1} ≧ 2.5.
In the present embodiment, the thickness t ₁ of the circuit layer 12 (die pad 32 of the copper plate 30) is set to t ₁ = 0.3 mm, and the thickness t _{2 of} the metal layer 13 (aluminum plate 23) is set to t ₂ = 2.0 mm. T ₂ / t ₁ = 6.67

The heat sink 41 is for dissipating heat from the power module substrate 10 with a copper plate described above.
In the present embodiment, the heat sink 41 is made of aluminum or an aluminum alloy, and specifically, is a rolled plate of A6063 alloy. Further, the thickness of the heat sink 41 is set within a range of 1 mm or more and 10 mm or less, and is set to 5 mm in the present embodiment. The heat sink 41 and the metal layer 13 are joined using an Al—Si brazing material.

  Below, the manufacturing method of the board | substrate 10 for power modules with a copper plate of the above-mentioned structure is demonstrated with reference to FIG. 4, FIG.

First, the copper plate 30 (die pad 32) to be the circuit layer 12 and the ceramic substrate 11 are joined (circuit layer forming step S01). Here, the ceramic substrate 11 and the copper plate 30 (die pad 32) to be the circuit layer 12 were joined by a so-called active metal brazing method.
In this embodiment, as shown in FIG. 5, the die pad 32 of the copper plate 30 which becomes the circuit layer 12 is joined to one surface side of the ceramic substrate 11 via the active brazing material 24 (lamination step S11). In the present embodiment, an active brazing material 24 made of Ag-27.4 mass% Cu-2.0 mass% Ti was used.

In this state, the ceramic substrate 11, the copper plate 30 (die pad 32) the stacking direction ^{9.8 × 10 4 Pa (1kgf /} cm 2) or more ^{343 × 10 4 Pa (35kgf /} cm 2) was pressurized with the following ranges In a state, it is charged into a heating furnace and heated (heating step S12). Then, the active brazing material 24 and a part of the copper plate 30 (die pad 32) are melted, and a molten metal region is formed at the interface between the copper plate 30 (die pad 32) and the ceramic substrate 11. Here, the heating temperature is 850 ° C. and the heating time is 10 minutes.

And the ceramic substrate 11 and the copper plate 30 (die pad 32) are joined by solidifying the molten metal area | region formed in the interface of the copper plate 30 (die pad 32) and the ceramic substrate 11 (solidification process S13).
As a result, the circuit layer 12 is formed.

Next, an aluminum plate 23 to be the metal layer 13 is joined to the other surface side of the ceramic substrate 11 (metal layer forming step S02). In the present embodiment, as shown in FIG. 5, an aluminum plate 23 to be the metal layer 13 is disposed on the other surface side of the ceramic substrate 11 with a brazing material foil 25 having a thickness of 5 to 50 μm (14 μm in this embodiment). Are stacked (stacking step S21). In the present embodiment, the brazing material foil 25 is an Al—Si based brazing material containing Si which is a melting point lowering element.
In this state, the ceramic substrate 11, heated in the range of the aluminum plate 23 below the laminating direction to ^{9.8 × 10 4 Pa (1kgf /} cm 2) or more ^{343 × 10 4 Pa (35kgf /} cm 2) with pressurized state The furnace is charged and heated (heating step S22). Then, the brazing filler metal foil 25 and a part of the aluminum plate 23 are melted, and a molten metal region is formed at the interface between the aluminum plate 23 and the ceramic substrate 11. Here, the heating temperature is 550 ° C. or more and 650 ° C. or less, and the heating time is 30 minutes or more and 180 minutes or less.
And the ceramic substrate 11 and the aluminum plate 23 are joined by solidifying the molten metal area | region formed in the interface of the aluminum plate 23 and the ceramic substrate 11 (solidification process S23).
Through this process, the power module substrate 10 with a copper plate according to the present embodiment is produced.

  According to the power module substrate 10 with a copper plate according to the present embodiment configured as described above, the circuit layer 12 is formed by bonding the die pad 32 of the copper plate 30 to the ceramic substrate 11. The rigidity of the circuit layer 12 is secured by the 30 guide frames 31 and the like, and the warp of the power module substrate 10 with a copper plate can be suppressed. Therefore, even when a copper plate 30 made of copper or a copper alloy is bonded to one surface of the ceramic substrate 11 and an aluminum plate made of aluminum or an aluminum alloy is bonded to the other surface of the ceramic substrate 11, The warpage of the module substrate 10 can be suppressed.

Since the warpage is suppressed in this way, even when the semiconductor element 3 is soldered on the circuit layer 12, it is possible to suppress the strain from being applied to the solder layer 2 and to improve the bonding reliability. Can be made.
Further, even if the metal layer 13 and the heat sink 41 are laminated, no gap is generated between them, and the heat sink 41 can be satisfactorily bonded to the metal layer 13.

Further, since the heat sink 41 is bonded to the metal layer 13 side of the power module substrate 10 with a copper plate, the thermal distortion caused by the difference in thermal expansion coefficient between the ceramic substrate 11 and the heat sink 41 is relatively reduced in deformation resistance. Since the metal layer 13 made of the small aluminum plate 23 can be relaxed by deformation, it is possible to suppress cracking of the ceramic substrate 11 when a heat cycle is applied.
Furthermore, in the power module substrate 10 with a copper plate according to the present embodiment, the circuit layer 12 having the mounting surface on which the semiconductor element 3 is mounted is made of copper or a copper alloy. Can be sufficiently expanded, and heat dissipation can be promoted. Therefore, durability when a power cycle is loaded can be improved.

  In the present embodiment, the die pad 32 of the copper plate 30 is joined to the ceramic substrate 11 to form the circuit layer 12, and the lead portion 33 is disposed so as to protrude outward from the exterior resin 6. Therefore, the lead portion 33 can be used as an external terminal, and a semiconductor device such as the power module 1 can be easily configured.

Furthermore, in the present embodiment, the relationship between the thickness t ₂ of the thickness t ₁ and the metal layer 13 of the circuit layer 12, t 1 _<because there is a t _2, the warpage in the substrate 10 for power module with copper Occurrence can be suppressed. Further, the ceramic layer 11 is not restrained more than necessary by the circuit layer 12 made of copper or copper alloy having a relatively large deformation resistance, and the metal layer 13 made of an aluminum plate 23 having a relatively small deformation resistance. It is sufficiently thick to relieve stress applied to the power module substrate 10 with a copper plate, and to suppress cracking of the ceramic substrate 11.
In the present embodiment, the relationship between the thickness _{t 2} of the thickness _{t 1} and the metal layer 13 of the circuit layer _12, since there is a t 2 / _{t 1} ≧ 2.5, substrate copper with a power module 10 It is possible to reliably suppress the occurrence of warping.

  Moreover, in this embodiment, since the strip | belt material with which the several die pad 32 was connected in the longitudinal direction of the guide frame 31 is used, this board | substrate 10 for power modules with a copper plate can be manufactured efficiently.

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, the circuit layer made of copper or copper alloy and the ceramic substrate have been described as being bonded using a so-called active metal brazing method, but the present invention is not limited to this, and the bonding is performed using the DBC method or the like. May be.
Although it demonstrated as what joins the metal layer which consists of aluminum or aluminum alloy, and a ceramic substrate using a brazing material, it is not limited to this, Transient liquid phase bonding method (Transient Liquid Phase Bonding), casting method, You may join using a metal paste method etc.

Moreover, although the ceramic substrate made of AlN is used as the insulating substrate, the present invention is not limited to this, and other ceramic substrates such as Al ₂ O ₃ , Si ₃ N ₄ may be used. It may be composed of a resin or the like.
Furthermore, the structure of the exterior resin, the heat sink, and the like is not limited to the present embodiment, and may have another structure.

10 Copper Module Power Module Substrate 11 Ceramic Substrate (Insulating Substrate)
12 circuit layer 13 metal layer 30 copper plate 23 aluminum plate

Claims (3)

Comprising: a ceramic substrate, a circuit layer formed on one surface of the ceramic substrate, and a second surface which is formed on the metal layer of the ceramic substrate,
The metal layer is configured by joining an aluminum plate made of aluminum or an aluminum alloy to the other surface of the ceramic substrate ,
The circuit layer is configured by brazing a copper plate made of copper or a copper alloy to one surface of the ceramic substrate ,
The copper plate includes a die pad to which a semiconductor element is bonded, a lead portion extending from the die pad, and a guide frame for connecting the lead portion, and the die pad of the copper plate is one of the ceramic substrates . Brazed to the surface,
The thickness t ₁ and the relationship between the thickness t ₂ of the metal layer, t 1 _<copper plate with a power module substrate, characterized in that there is a t ₂ of the circuit layer. The said copper plate is formed in strip | belt shape, has a some die pad in the longitudinal direction, The said ceramic substrate is joined to the said die pad, The power module with a copper plate of Claim 1 characterized by the above-mentioned. Substrate. A ceramic substrate, wherein a circuit layer formed on one surface of a ceramic substrate, a method of manufacturing a substrate for the copper plate with a power module and a metal layer formed on the other surface of the ceramic substrate,
A copper plate made of copper or a copper alloy, having a die pad, a lead part extending from the die pad, and a guide frame connecting the lead part, is prepared,
Brazing the die pad to one surface of the ceramic substrate ;
After brazing the die pad to the ceramic substrate , an aluminum plate made of aluminum or an aluminum alloy is joined to the other surface of the ceramic substrate .

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