JP6417834B2 - Power module substrate with cooler and method for manufacturing power module substrate with cooler - Google Patents

Description

The present invention, a large current, a method of manufacturing a substrate for a high-voltage power module with a substrate and a condenser power module with a condenser that is used in a semiconductor device for controlling.

  The power module has a circuit layer bonded to one surface of a ceramic substrate and a metal layer bonded to the other surface, and a semiconductor element such as a power element is mounted on the circuit layer via a solder material. Joined to cooler. In such a power module substrate, if a warp occurs, a mounting failure occurs in the mounting process of the semiconductor element, the yield of the power module decreases, and if a warp occurs at the junction temperature with the cooler, it becomes a thermal resistance. Since the heat dissipation performance is hindered during use, it is necessary to use a substrate with less warpage.

  On the other hand, the miniaturization accompanying the increase in the output density of the semiconductor element is progressing, and the demand for module integration is increasing. As a general integration of power modules, a method is known in which a plurality of circuit layers are aligned and bonded to an insulating substrate. However, if a plurality of circuit layers are provided on an insulating substrate, the temperature changes during the manufacturing process or during use. There is a problem that warpage is likely to occur.

  In this regard, Patent Document 1 includes a plurality of insulating substrates (wiring ceramic substrates in which a wiring layer is formed on a ceramic substrate), the plurality of insulating substrates being joined by a lead frame, and the insulating substrate and the power semiconductor element. Has been disclosed that can prevent cracking of the ceramic substrate and peeling of the sealing resin.

JP 2007-27261 A

  However, since the method described in Patent Document 1 imposes a strength on the lead frame, it is not sufficient for eliminating the warp. Even if the warp during semiconductor mounting can be eliminated, other manufacturing processes and Warpage may occur due to temperature changes in the usage environment.

  This invention was made in view of such a situation, and it aims at providing the board | substrate for power modules with a cooler which is excellent in heat dissipation with little shape change by a temperature change also including a manufacturing process and use environment. To do.

The present invention provides a cooler in which a circuit layer is bonded to one surface of a ceramic substrate, and the metal layer of a power module substrate having a metal layer bonded to the other surface of the ceramic substrate is bonded to a cooler. A power module substrate having a first aluminum layer made of aluminum or an aluminum alloy having a purity of 99% by mass or more bonded to one surface of the ceramic substrate, and a solid layer attached to the first aluminum layer. A second aluminum layer comprising a first copper layer made of phase diffusion bonded copper or a copper alloy, the metal layer being made of aluminum or aluminum alloy having a purity of 99% by mass or more, and the second aluminum layer A second copper layer made of copper or a copper alloy solid phase diffusion bonded to the second copper layer, and a third aluminum layer solid phase diffusion bonded to the second copper layer; When the thickness of the first copper layer is t1, the proof stress is σ1, the thickness of the second copper layer is t2, and the proof strength is σ2, (t1 × σ1) / (t2 × .sigma. @ 2) is 0.7 or more and 1.5 or less, t1 + t2 is equal to or greater than 4 mm, the thickness of the third aluminum layer Ri 1mm less der than 0.1 mm, the cooler, made of an aluminum alloy A top plate is provided, and the top plate and the third aluminum layer of the power module substrate are joined by brazing or soldering .

And the manufacturing method of the board | substrate for power modules with a cooler of this invention WHEREIN: While a circuit layer is joined to one surface of a ceramic substrate, the metal layer is joined to the other surface of the said ceramic substrate, The said metal layer In the power module substrate bonded to the cooler, the circuit layer includes a first aluminum layer made of aluminum or an aluminum alloy having a purity of 99% by mass or more bonded to one surface of the ceramic substrate, A laminated structure having a first copper layer made of copper or a copper alloy solid-phase diffusion bonded to the aluminum layer, the second aluminum layer made of aluminum or aluminum alloy having a purity of 99% by mass or more, A second copper layer made of copper or a copper alloy solid-phase diffusion bonded to the second aluminum layer, and solid-phase diffusion bonded to the second copper layer. When the thickness of the first copper layer is t1, the proof stress is σ1, the thickness of the second copper layer is t2, and the proof stress is σ2, (t1 Xσ1) / (t2 × σ2) is 0.7 to 1.5, t1 + t2 is 4 mm or more, and the thickness of the third aluminum layer is 0.1 mm to less than 1 mm . The top plate of the cooler having a top plate made of an aluminum alloy is joined to the third aluminum layer by brazing or soldering.

  A copper layer is laminated symmetrically on both sides of the ceramic substrate via an aluminum layer, but a third aluminum layer made of an aluminum alloy is further laminated on the other side, so a laminated structure on both sides of the ceramic substrate However, it is not a symmetrical structure with a ceramic substrate as the center. However, since the third aluminum layer is thin, the stress generated during heating is small and can be substantially ignored. And this invention comprises the symmetrical structure of an almost stress centering on a ceramic substrate by setting the thickness and proof stress of the 1st copper layer of a circuit layer, and the 2nd copper layer of a metal layer in said range. Can do. As a result, it is difficult for the stress acting on both surfaces of the ceramic substrate during the bonding process of the power module substrate and the cooler to be biased, and it is possible to prevent warping. If warpage occurs during the cooler joining process, there is a risk that voids will occur between the power module substrate and the cooler, but in the present invention warpage can be prevented, so the void ratio can be reduced. it can. As a result, not only the initial warpage during the manufacture of the power module substrate, but also the occurrence of warpage during the semiconductor element mounting process and in the subsequent use environment can be suppressed, and the reliability as an insulating substrate can be improved. Good heat dissipation can be exhibited.

  According to the present invention, it is possible to suppress a change in shape due to a temperature change including a manufacturing process and a use environment, improve reliability as an insulating substrate and connection reliability of a semiconductor element, and exhibit good heat dissipation. be able to.

It is sectional drawing which shows the board | substrate for power modules with a cooler of 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing process of the board | substrate for power modules with a cooler of FIG. It is a front view which shows the example of the pressurization apparatus used for manufacture of the board | substrate for power modules of this invention. It is sectional drawing which shows the board | substrate for power modules with a cooler which is 2nd Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
In the power module substrate 50 with a cooler according to the first embodiment shown in FIG. 1, a plurality of power module substrates 20 are joined to one cooler 80, and the semiconductor element 60 is attached to each power module substrate 20. By joining, the power module 100 is comprised.

  Each power module substrate 20 includes a ceramic substrate 11, a circuit layer 12 bonded to one surface of the ceramic substrate 11 by brazing, and a metal layer 30 bonded to the other surface of the ceramic substrate 11 by brazing. Is provided.

For the ceramic substrate 11, for example, nitride ceramics such as AlN (aluminum nitride) and Si ₃ N ₄ (silicon nitride), or oxide ceramics such as Al ₂ O ₃ (alumina) can be used. The thickness of the ceramic substrate 11 can be set within a range of 0.2 mm or more and 1.5 mm or less.

The circuit layer 12 has a laminated structure including a first aluminum layer 15 bonded to the surface of the ceramic substrate 11 and a first copper layer 16 bonded to the first aluminum layer 15.
The first aluminum layer 15 is made of aluminum (2N—Al) having a purity of 99% by mass or more, aluminum (3N—Al) having a purity of 99.9% by mass or more, and aluminum (4N—Al) having a purity of 99.99% by mass or more. Alternatively, it is formed by bonding a plate material made of an aluminum alloy to the ceramic substrate 11. In the present embodiment, the first aluminum layer 15 has an aluminum plate having a purity of 99% by mass or more brazed to the ceramic substrate 11. The first copper layer 16 is formed by joining a plate material made of pure copper or a copper alloy to the first aluminum layer 15. In the present embodiment, the first copper layer 16 is formed, for example, by solid phase diffusion bonding of an oxygen-free copper plate having a purity of 99.96% by mass or more to the first aluminum layer 15. The thicknesses of the first aluminum layer 15 and the first copper layer 16 are 0.1 mm to 3.0 mm for the first aluminum layer 15 and 2.0 mm to 5.0 mm for the first copper layer 16.

The metal layer 30 includes a second aluminum layer 13 bonded to the surface of the ceramic substrate 11, a second copper layer 31 bonded to the second aluminum layer 13, and a third bonded to the second copper layer 31. A laminated structure having an aluminum layer 32 is formed. The second aluminum layer 13 is formed of the same material as the first aluminum layer 15 of the circuit layer 12. In this embodiment, the second aluminum layer 13 is made of an aluminum plate having the same aluminum purity of 99% by mass or more as the first aluminum layer 15 and having a thickness of 0.1 mm or more and 3.0 mm or less on the ceramic substrate 11. It is attached.
The first aluminum layer 15 and the second aluminum layer 13 are formed in a planar shape having substantially the same size.
The second copper layer 31 is formed by joining a plate material made of pure copper or a copper alloy to the second aluminum layer 13. In the present embodiment, the second copper layer 31 is formed, for example, by solid phase diffusion bonding of an oxygen-free copper plate having a purity of 99.96% by mass or more to the second aluminum layer 13. The thickness of the second copper layer 31 is 2.0 mm or greater and 5.0 mm or less.
The third aluminum layer 32 is made of aluminum (2N—Al) having a purity of 99% by mass or more, aluminum (3N—Al) having a purity of 99.9% by mass or more, aluminum (4N—Al) having a purity of 99.99% by mass or more, It is formed by joining a plate material made of an aluminum alloy such as A3003 or A6063 to the second copper layer 31. In the present embodiment, in the third aluminum layer 32, an aluminum plate of an aluminum alloy A6063 is solid phase diffusion bonded to the second copper layer 31. The third aluminum layer 32 has a thickness of 0.1 mm or more and less than 1.0 mm, and an aluminum foil can be used.

The first copper layer 16 of the circuit layer 12 and the second copper layer 31 of the metal layer 30 have a thickness of the first copper layer 16 of t1, a proof stress of σ1, and the thickness of the second copper layer 31 of the metal layer 30. When the thickness is t2 and the proof stress is σ2, (t1 × σ1) / (t2 × σ2) is set to a relationship of 0.7 to 1.5. For example, the first copper layer 16 is an oxygen-free copper OFC (proof stress σ1 = 190 MPa) having a thickness of t1 = 3.0 mm and a purity of 99.96% by mass or more, and the second copper layer 31 is an object having a thickness of t2 = 2.5 mm. In the case of a combination of oxygen copper OFC (yield strength σ2 = 190 MPa), (t1 × σ1) / (t2 × σ2) = 1.2. In addition, the value of the yield strength in this invention is a value at the time of room temperature (25 degreeC).
The sum (t1 + t2) of the thicknesses of the first copper layer 16 of the circuit layer 12 and the second copper layer 31 of the metal layer 30 is preferably 4 mm or more.

  The cooler 80 is for dissipating the heat of the power module 100 and is made of an aluminum alloy. In the present embodiment, the cooler 80 is formed in a box shape through which a cooling medium such as water flows, but the shape is particularly limited. Not what you want. The power module substrate 20 is fixed by joining the third aluminum layer 32 to the top plate located on the upper surface of the main body of the cooler 80 made of an aluminum alloy by brazing or soldering.

Then, the semiconductor element 60 is soldered to the surface of the circuit layer 12 of each power module substrate 20 constituting the power module substrate 50 with a cooler.
The semiconductor element 60 is an electronic component including a semiconductor, and an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Field Transistor Transistor), a FWD (FelDW, etc.), depending on the function required. Various semiconductor elements are selected. The solder material for joining the semiconductor element 60 is, for example, a Sn—Sb, Sn—Ag, Sn—Cu, Sn—In, or Sn—Ag—Cu solder material (so-called lead-free solder material). It is said.

Next, an example of a method for manufacturing the power module substrate 20 and the power module substrate 50 with a cooler configured as described above will be described.
First, as shown in FIG. 2A, the first aluminum layer 15 of the circuit layer 12 is laminated on one surface of the ceramic substrate 11, and the second aluminum layer 13 of the metal layer 30 is laminated on the other surface. These are joined together. For these joining, a brazing material of an alloy such as Al-Si is used. For example, the ceramic substrate 11 and the first aluminum layer 15 and the second aluminum layer 13 are respectively connected via a brazing material foil 18 of the alloy. The stacked body S is pressed in the stacking direction using the pressurizing device 110 shown in FIG.

3 includes a base plate 111, guide posts 112 vertically attached to the four corners of the upper surface of the base plate 111, a fixed plate 113 fixed to the upper ends of the guide posts 112, Between the base plate 111 and the fixed plate 113, a pressing plate 114 supported by the guide post 112 so as to be movable up and down, and provided between the fixed plate 113 and the pressing plate 114, the pressing plate 114 is urged downward. And an urging means 115 such as a spring.
The fixed plate 113 and the pressing plate 114 are arranged in parallel to the base plate 111, and the above-described laminate S is arranged between the base plate 111 and the pressing plate 114. Carbon sheets 116 are disposed on both sides of the laminate S to make the pressure uniform.
In a state where the pressure is applied by the pressure device 110, the pressure device 110 and the pressure device 110 are installed in a heating furnace (not shown) and heated to a brazing temperature in a vacuum atmosphere for bonding. In this case, the applied pressure is, for example, 0.68 MPa (7 kgf / cm ² ), and the heating temperature is, for example, 640 ° C.

  2B, the first copper layer 16 and the metal layer 30 of the circuit layer 12 are joined to the joined body 19 in which the ceramic substrate 11, the first aluminum layer 15, and the second aluminum layer 13 are joined. The second copper layer 31 and the third aluminum layer 32 are joined. First, the first copper layer 16 is laminated on the first aluminum layer 15 of the joined body 19 via a titanium foil 41 (thickness: 10 μm or more and 20 μm or less) as a diffusion preventing material, and the titanium foil 41 is laminated on the second aluminum layer 13. The second copper layer 31 is stacked via the first copper layer 31, and the third aluminum layer 32 is stacked on the second copper layer 31 via the titanium foil 41. Then, in a state where these laminates are pressurized in the stacking direction using the pressurizing device 110 similar to that shown in FIG. The copper layer 16, the second aluminum layer 13 and the second copper layer 31, and the second copper layer 31 and the third aluminum layer 32 are solid phase diffusion bonded, respectively. The applied pressure in this case is, for example, 0.29 MPa or more and 3.43 MPa or less, and the heating temperature is 500 ° C. or more and less than 548 ° C. The solid state diffusion bonding is performed by holding the pressure and heating state for 5 minutes to 240 minutes.

  Next, the third aluminum layer 32 and the cooler 80 of the power module substrate 20 which is the above-described joined body are laminated via the double-sided brazing clad material 42 and laminated using the pressurizing apparatus 110 similar to FIG. In a state where the pressure is applied in the direction, the entire pressure device 110 is heated in a nitrogen atmosphere to be brazed. As the double-sided brazing clad material, a double-sided brazing clad material 42 in which an Al—Si—Mg based brazing material layer is formed on both surfaces of a core material made of an aluminum alloy (A3003) is used. The heating temperature is set to 0.001 MPa to 0.5 MPa and the heating temperature is set to 580 ° C. to 630 ° C. Moreover, as a joining method of the 3rd aluminum layer 32 and the cooler 80, it is good also as a method of soldering with a Zn-Al type solder material other than brazing. Soldering is performed at a joining temperature of 450 ° C. or lower (for example, 385 ° C. in the case of Zn—Al solder). At this temperature, copper and aluminum do not diffuse, so the first copper layer 16 and the second copper layer 31 The titanium foil 41 as a diffusion preventing material used when the third aluminum layer 32 is bonded is not necessary.

  In the present embodiment, the first aluminum layer 15 and the first copper layer 16, the second aluminum layer 13 and the second copper layer 31, and the joint surfaces of the second copper layer 31 and the third aluminum layer 32, respectively. Is solid phase diffusion bonded after the scratches have been removed and smoothed.

  In the power module substrate 50 with a cooler manufactured in this way, the thickness of the first copper layer 16 is t1, the proof stress is σ1, the thickness of the second copper layer 31 of the metal layer 30 is t2, and the proof strength is Since (t1 × σ1) / (t2 × σ2) is 0.7 or more and 1.5 or less when σ2, the stress generated on both surfaces of the ceramic substrate 11 during heating is centered on the ceramic substrate 11. It becomes the almost symmetrical structure. As a result, the stress acting on both surfaces of the ceramic substrate 11 during heating or the like is less likely to be biased, and it is possible to prevent warping. Therefore, not only the initial warpage at the time of laminating each layer, but also the occurrence of warpage can be suppressed during the mounting process and use environment of the semiconductor element 60, and the reliability as an insulating substrate can be improved, and good heat dissipation can be achieved. It can be demonstrated.

FIG. 4 shows a second embodiment of the present invention.
In the first embodiment, the two power module substrates 20 are separately joined to the cooler 80. However, in the second embodiment, the planar size of the second copper layer 31 of the metal layer 30 of the power module substrate 20 is two. And the second copper layer 31 is shared. In each power module substrate 20, the circuit layer 12 including the first aluminum layer 15 and the first copper layer 16 is bonded to one surface of the ceramic substrate 11, and the second aluminum layer 13 and the second copper are bonded to the other surface. The metal layer 30 composed of the layer 31 and the third aluminum layer 32 is joined.

  In order to manufacture the power module substrate 50 with a cooler, the first aluminum layer 15 of the circuit layer 12 and the second aluminum layer 13 of the metal layer 30 are joined to both surfaces of the ceramic substrate 11 by brazing. The joined body is placed on one second copper layer 31, the first copper layer 16 is laminated on each first aluminum layer 15, and the third aluminum layer 32 is laminated on the second copper layer 31. Then, a power module substrate 20 having two circuit layers 12 is formed by solid-layer diffusion bonding. The power module substrate 20 is formed by joining the power module substrate 20 to the cooler 80 by brazing or soldering. Since this power module substrate 50 with a cooler is integrated by one second copper layer 31, it is difficult to cause displacement and deformation, and it is easy to obtain positional accuracy, so that high integration can be achieved. it can.

  The thickness t1 and proof stress σ1 of the first copper layer 16 at the portion corresponding to the joint between each second aluminum layer 13 and the second copper layer 31, the thickness t2 and proof strength of the second copper layer 31 of the metal layer 30. By setting the relationship of σ2 to (t1 × σ1) / (t2 × σ2) of 0.7 to 1.5 and the thickness of the third aluminum layer 32 to 0.1 mm to less than 1.0 mm, the ceramic substrate 11 to form a substantially stressed target structure. Therefore, the stress acting on both surfaces of the ceramic substrate 11 during heating or the like is less likely to be biased, warpage is hardly generated, and good heat dissipation can be exhibited. The sum (t1 + t2) of the thicknesses of the first copper layer 16 of the circuit layer 12 and the second copper layer 31 of the metal layer 30 is preferably 4 mm or more.

  In the above embodiment, an example of the power module substrate 50 with the cooler having the two circuit layers 12 is shown, but a structure in which three or more circuit layers 12 are mounted may be used.

A ceramic substrate made of AlN having a thickness of 0.635 mm, a first aluminum layer and a second aluminum layer made of aluminum (2N-Al) having a thickness of 0.6 mm and a purity of 99% by mass or more, and a first copper layer The thickness and proof stress shown in Table 1 were prepared for the second copper layer and the third aluminum layer (A6063 is used for the third aluminum layer, and only the thickness is indicated). The first copper layer of sample number 6 uses a ZC alloy (Cu 99.98 mass% -Zr 0.02 mass%) manufactured by Mitsubishi Shindoh Co., Ltd., and the other copper and copper layers have a purity of 99. .96 mass% or more oxygen-free copper (OFC) was used.
And these were joined by the joining method described in the above embodiment, and a sample of a power module substrate was produced.
The planar size of each member was 40 mm × 40 mm for the ceramic substrate, and 37 mm × 37 mm for the circuit layer and the metal layer.

The obtained sample was joined to a cooler by brazing at 615 ° C., and the joining interface between the power module substrate and the cooler was observed with an ultrasonic image measuring machine, and voids (voids) at the joining interface were observed. The area was measured, the total area of voids with respect to the area to be joined was calculated as a void ratio, and those having a void ratio of less than 2% were rated as ◯ and those exceeding 2% as x.
In Table 1, the ratio A indicates (t1 × σ1) / (t2 × σ2), and the thickness B indicates t1 + t2.

  As can be seen from Table 1, (t1 × σ1) / (t2 × σ2) is 0.7 or more and 1.5 or less, t3 is 0.1 mm or more and less than 1.0 mm, and t1 + t2 is 4.0 mm or more. It was confirmed that the power module substrate with a cooler having a good void ratio evaluation and having a small heat-induced change in shape due to a change in temperature is obtained.

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

DESCRIPTION OF SYMBOLS 11 Ceramic substrate 12 Circuit layer 13 Second aluminum layer 15 First aluminum layer 16 First copper layer 18 Brazing material foil 20 Power module substrate 30 Metal layer 31 Second copper layer 32 Third aluminum layer 50 For power module with cooler Substrate 60 Semiconductor element 80 Cooler 100 Power module

Claims (2)

For a power module with a cooler in which a circuit layer is bonded to one surface of a ceramic substrate and a metal layer is bonded to the other surface of the ceramic substrate and the metal layer of the power module substrate is bonded to a cooler A substrate , wherein the circuit layer is bonded to one surface of the ceramic substrate by a first aluminum layer made of aluminum or aluminum alloy having a purity of 99% by mass or more, and solid phase diffusion bonded to the first aluminum layer. A first copper layer made of copper or a copper alloy, wherein the metal layer is a second aluminum layer made of aluminum or an aluminum alloy having a purity of 99% by mass or more, and solid phase diffusion in the second aluminum layer Laminated structure of a second copper layer made of bonded copper or copper alloy and a third aluminum layer bonded to the second copper layer by solid phase diffusion bonding When the thickness of the first copper layer is t1, the proof stress is σ1, the thickness of the second copper layer is t2, and the proof stress is σ2, (t1 × σ1) / (t2 × σ2) There is a 0.7 to 1.5, t1 + t2 is equal to or greater than 4 mm, the thickness of the third aluminum layer Ri 1mm less der than 0.1 mm, the cooler, the top plate made of an aluminum alloy A power module substrate with a cooler , wherein the top plate and the third aluminum layer of the power module substrate are joined by brazing or soldering . In the power module substrate in which the circuit layer is bonded to one surface of the ceramic substrate and the metal layer is bonded to the other surface of the ceramic substrate, and the metal layer is bonded to the cooler, the circuit layer is A first aluminum layer made of aluminum or aluminum alloy having a purity of 99% by mass or more bonded to one surface of the ceramic substrate, and a first made of copper or copper alloy solid-phase diffusion bonded to the first aluminum layer. A laminated structure having a copper layer, wherein the metal layer is made of a second aluminum layer made of aluminum or an aluminum alloy having a purity of 99% by mass or more, and copper or a copper alloy bonded to the second aluminum layer by solid phase diffusion bonding. A laminated structure of a second copper layer and a third aluminum layer solid-phase diffusion bonded to the second copper layer; When the thickness is t1, the proof stress is σ1, the thickness of the second copper layer is t2, and the proof stress is σ2, (t1 × σ1) / (t2 × σ2) is 0.7 or more and 1.5 or less. , T1 + t2 is 4 mm or more, and the thickness of the third aluminum layer is 0.1 mm or more and less than 1 mm, the top of the cooler having a top plate made of an aluminum alloy on the third aluminum layer of the power module substrate. A method for manufacturing a substrate for a power module with a cooler, wherein the plates are joined by brazing or soldering.

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