JP5957862B2 - Power module substrate - Google Patents

Description

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

  As a conventional power module, a metal layer serving as a circuit layer is laminated on one surface of a ceramic substrate, and an electronic component such as a semiconductor chip is soldered on the circuit layer, and on the other surface of the ceramic substrate. A structure in which a metal layer to be a heat dissipation layer is formed and a heat sink is joined to the metal layer is known.

  And in the power module substrate used for such a power module, various measures are taken in order to improve the insulation between the circuit layer and the heat dissipation layer bonded to both sides of the ceramic substrate. In addition, when the current flowing through the electronic component is large, not only the heat of the electronic component itself but also Joule heat is generated in the wiring portion such as a bonding wire. For this reason, a temperature change repeatedly acts in a short time (generally referred to as a power cycle) due to heat generation of the electronic components and the wiring part when energized and cooling by a heat sink when not energized. For this reason, peeling and voids develop mainly at the wiring joint and the solder joint, and the rise in thermal resistance becomes a problem, and improvement in power cycle resistance is required.

For example, in Patent Document 1, by providing a step around the joint surface between the ceramic substrate and the heat dissipation layer (metal base plate), the insulation distance (creeping distance) between the circuit layer and the heat dissipation layer is increased, thereby providing insulation. As well as improving power cycle resistance.
In Patent Document 2, by disposing a heat spreader on an electronic component and joining a metal foil of a wiring lead, heat dissipation from the upper surface side of the electronic component is enhanced and power cycle resistance is improved. In Patent Document 3, the solder joint between the electronic component and the circuit layer is provided thin at the center and thick at the outer periphery to absorb and relieve the stress caused by the difference in thermal expansion coefficient, thereby reducing the power cycle. Improves tolerance.

Japanese Patent No. 4496404 JP 2006-135270 A JP 2011-159994 A

  However, while countermeasures against power cycle resistance due to thermal resistance at wiring joints and solder joints have been taken, there are few countermeasures against power cycle tolerance at the substrate constituting the power module substrate.

  The present invention has been made in view of such circumstances, and provides a power module substrate capable of improving power cycle resistance while maintaining insulation without increasing the size of the power module substrate. The purpose is to do.

In the present invention, a circuit layer to which an electronic component is bonded is laminated on one surface of a ceramic substrate, and a heat dissipation layer is stacked on the other surface, and the heat dissipation layer is opposite to the bonding surface with the ceramic substrate. In addition, a power module substrate on which a heat sink bonding surface to which a heat sink is bonded is formed, and an area of an electronic component mounting surface to which an electronic component opposite to the bonding surface between the ceramic substrate and the circuit layer is bonded An overhanging portion is formed on the electronic component mounting surface side of the side surface of the circuit layer, and the area of the heat sink joint surface opposite to the joint surface between the ceramic substrate and the heat dissipation layer is increased. projecting portion is formed on the heat sink bonding surface side of the heat dissipation layer, overhanging portions of the circuit layer, the distance t11 in the thickness direction from the joint surface between the ceramic substrate The thickness t10 of the circuit layer is set to be ¼ or more and ½ or less of the circuit layer, and the projecting portion of the heat dissipation layer has a distance t21 in the thickness direction from the bonding surface with the ceramic substrate. It is set so that it may become 2/5 or more and 7/10 or less of the plate | board thickness t20 of a layer .

By laminating a circuit layer with an overhang on one surface of a ceramic substrate and laminating a heat dissipation layer with an overhang on the other surface of the ceramic substrate, the creepage between the circuit layer and the heat dissipation layer A distance can be secured and insulation can be maintained.
Moreover, since the heat capacity can be increased by increasing the volume of the circuit layer by the overhanging portion, it is possible to suppress an increase in temperature due to heat generation of the electronic component. Also in the heat dissipation layer, the volume of the main surface can be increased by the overhanging portion, and the heat capacity can be increased, and the area of the heat sink, heat sink and other heat dissipation members can be increased, so that the heat dissipation can be improved. it can. Therefore, power cycle tolerance can be improved.
In addition, when the circuit layer and the heat dissipation layer are bonded to both surfaces of the ceramic substrate, the area of the bonding surface is small with respect to the pressure surface, so that the pressure load acts on the bonding surface sufficiently, and the circuit layer and the heat dissipation layer The bonding reliability with the ceramic substrate can be improved. Furthermore, the overhanging portions provided in the circuit layer and the heat dissipation layer suppress the wrapping of the brazing material to the electronic component mounting surface of the circuit layer and the heat sink joint surface (main surface) of the heat dissipation layer due to the excess brazing material at the time of bonding. Further, the occurrence of surface stains due to adhesion of the brazing material can be prevented, and the joining properties of electronic parts and the like can be improved.

In the power module substrate of the present invention, a plate thickness t10 of the circuit layer is less than 1.0mm 2.0mm or less, the thickness t20 of the previous SL radiating layer is set to be 1.0mm or more 2.0mm or less It is good to have.
By using such a circuit layer and a heat dissipation layer, it is possible to reliably improve insulation and power cycle resistance of the power module substrate.

  Further, in order to prevent a short circuit with another power module substrate adjacent in the module such as an IGBT and improve the mounting density, in the power module substrate of the present invention, the circuit layer and the heat dissipation layer are extended. The size of the outer peripheral edge of the part may be set to be equal to or smaller than the size of the outer peripheral edge of the ceramic substrate.

  ADVANTAGE OF THE INVENTION According to this invention, power cycle tolerance can be improved, maintaining insulation, without enlarging the board | substrate for power modules.

It is a longitudinal cross-sectional view which shows one Embodiment of the board | substrate for power modules of this invention. It is a principal part longitudinal cross-sectional view explaining the board | substrate for power modules of an Example. It is a figure which shows the relationship between the maximum temperature of the electronic component upper surface at the time of providing the overhang | projection part in either a circuit layer or a thermal radiation layer, and the thickness of an overhang | projection part. It is a figure which shows the relationship between the maximum temperature of the electronic component upper surface at the time of changing the protrusion length of the overhang | projection part of a circuit layer or a thermal radiation layer, and the protrusion length of an overhang | projection part. It is a principal part longitudinal cross-sectional view explaining the board | substrate for power modules of a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a power module using a power module substrate according to an embodiment of the present invention. The power module 1 includes a power module substrate 3 having a ceramic substrate 2 made of ceramics, an electronic component 4 such as a semiconductor chip mounted on the surface of the power module substrate 3, and a back surface of the power module substrate 3. The heat sink 5 is joined.

  In the power module substrate 3, metal layers are laminated on both surfaces of the ceramic substrate 2, the metal layer laminated on one surface of the ceramic substrate 2 becomes the circuit layer 6, and the electronic component 4 is soldered to the surface. The Moreover, the metal layer laminated | stacked on the other surface of the ceramic substrate 2 is made into the thermal radiation layer 7, and the heat sink 5 is attached to the surface.

  On the side surface of the circuit layer 6, an overhanging portion 6 c is formed to increase the area of the electronic component mounting surface 6 b on the opposite side from the bonding surface 6 a with the ceramic substrate 2. In addition, a protruding portion 7c is formed on the side surface of the heat dissipation layer 7 so that the area of the heat sink bonding surface 7b (main surface) on the opposite side is larger than the bonding surface 7a with the ceramic substrate 2. The sizes of the outer peripheral edges of the overhang portions 6c and 7c are set to be the same as or smaller than the outer peripheral edge of the ceramic substrate 2.

The circuit layer 6 has a plate thickness t10 of 1.0 mm or more and 2.0 mm or less, and a distance t11 in the thickness direction from the joint surface 6a to the overhanging portion 6c to the ceramic substrate 2 is 1 of the plate thickness t10. It is set to be / 4 or more and ½ or less. The heat dissipation layer 7 has a thickness t20 of 1.0 mm or more and 2.0 mm or less, and a distance t21 in the thickness direction from the bonding surface 7a to the overhanging portion 7c with the ceramic substrate 2 is equal to the thickness t20. It is set to be 2/5 or more and 7/10 or less.
In the present embodiment, the protruding length w11 of the overhanging portion 6c of the circuit layer 6 is provided with the same size as the distance t11, and the protruding length w21 of the overhanging portion 7c of the heat radiation layer 7 is equal to the distance t21. Are provided in the same size.

The ceramic substrate 2 is made of, for example, nitride ceramics such as AlN (aluminum nitride), Si ₃ N ₄ (silicon nitride), oxide ceramics such as Al ₂ O ₃ (alumina), SiC (silicon carbide), or the like. For example, in the case of AlN, the thickness is 0.635 mm, 1.0 mm, etc., and in the case of Al ₂ O ₃ or Si ₃ N ₄ , the thickness is 0.32 mm.
The circuit layer 6 and the heat dissipation layer 7 can be made of aluminum having a purity of 99.00% by mass or more (so-called 2N aluminum). In particular, aluminum having a purity of 99.90% by mass or more is desirable, and JIS standard uses 1N90 (purity 99.90% by mass or more: so-called 3N aluminum) or 1N99 (purity 99.99% by mass or more: so-called 4N aluminum). Can do. The circuit layer 6 and the heat dissipation layer 7 may be made of aluminum alloy, copper, and copper alloy in addition to aluminum. Further, the overhang portions 6c and 7c of the circuit layer 6 and the heat dissipation layer 7 can be formed by punching out to a desired outer shape by press working and crushing leaving the outer peripheral edge portion.

The circuit layer 6 and the heat dissipation layer 7 and the ceramic substrate 2 are joined by brazing. As the brazing material, an alloy such as Al—Si, Al—Ge, Al—Cu, Al—Mg, or Al—Mn is used.
For joining the circuit layer 6 and the electronic component 4, a solder material such as Sn—Cu, Sn—Ag—Cu, Zn—Al, or Pb—Sn is used. Reference numeral 8 in the figure indicates the solder joint layer. The electronic component 4 and the terminal portion of the circuit layer 6 are connected by a wire made of aluminum or the like, ribbon bonding, or the like (not shown).

Further, the heat sink 5 has an appropriate shape, such as a flat plate, one in which a large number of pin-shaped fins are integrally formed by hot forging or the like, and one in which strip-like fins are formed in parallel by extrusion. Can be adopted. Further, a heat radiating plate or a stress buffer layer made of a metal plate such as aluminum, aluminum alloy, copper, or copper alloy can be provided between the heat sink 5 and the heat radiating layer 7.
As a joining method between the heat radiation layer 7 and the heat sink 5, a brazing method using a brazing material of an alloy such as Al—Si, Al—Ge, Al—Cu, Al—Mg, or Al—Mn can be used. , Nocolok brazing method using flux for Al-Si brazing material, Ni plating on heat dissipation layer and heat sink, and soldering with solder material such as Sn-Ag-Cu, Zn-Al or Pb-Sn The method is used, or is mechanically fixed with screws in a state of being in close contact with silicon grease.

And in order to manufacture the board | substrate 3 for power modules comprised in this way, first, the joining surface 6a of the circuit layer 6 and the surface of the ceramic substrate 2, and the joining surface 7a of the thermal radiation layer 7 and the back surface of the ceramic substrate 2 are first made. The ceramic substrate 2, the circuit layer 6, and the heat dissipation layer 7 are brought into contact with each other with a brazing material interposed therebetween, and heated at 615 ° C. or more and 645 ° C. or less while pressurizing the laminated ceramic substrate 2, the circuit layer 6, and the heat dissipation layer 7 with 1 to 5 kgf / cm ² in the thickness direction. By brazing in a vacuum or an inert gas atmosphere.
Next, the heat sink 5 is bonded to the heat dissipation layer 7 of the power module substrate 3 manufactured as described above. In general, an electronic component such as a semiconductor chip mounted on the circuit layer 6 is soldered. Therefore, in order to improve solder wettability, the joined body of the power module substrate 3 and the heat sink 5 is subjected to electrolysis or electroless Ni or Ni alloy plating on the surface, and then the electronic component is soldered.

Like the power module substrate 3 shown in FIG. 1, the circuit layer 6 provided with the overhanging portion 6 c is laminated on one surface of the ceramic substrate 2, and the overhanging portion 7 c is provided on the other surface of the ceramic substrate 2. When the heat radiation layer 7 is laminated, the creeping distance between the circuit layer 6 and the heat radiation layer 7 can be sufficiently secured. In addition, by setting the size of the outer peripheral edge of the overhang portions 6c and 7c of the circuit layer 6 and the heat dissipation layer 7 to be equal to or smaller than the size of the outer peripheral edge of the ceramic substrate 2, the circuit layer 6 and the heat dissipation A short circuit with the layer 7 can be prevented more reliably.
Moreover, since the volume of the circuit layer 6 can be increased by the overhang | projection part 6c and a heat capacity can be increased, the temperature rise by the heat_generation | fever of the electronic component 4 can be suppressed. Also in the heat dissipation layer 7, the volume can be increased by the overhanging portion 7 c to increase the heat capacity, and the area of the joint surface 7 a with the heat sink 5 can be increased, so that the heat dissipation can be improved. Therefore, power cycle tolerance can be improved.

  In addition, when the circuit layer 6 and the heat dissipation layer 7 are laminated on both surfaces of the ceramic substrate 2, since the area of the bonding surfaces 6a and 7a is smaller than the pressing surface, the pressing load sufficiently acts on the bonding surfaces 6a and 7a. The bonding reliability between the circuit layer 6 and the heat dissipation layer 7 and the ceramic substrate 2 can be improved. Further, the overhang portions 6c and 7c provided in the circuit layer 6 and the heat dissipation layer 7 allow the brazing material to be bonded to the electronic component laminated surface 6b of the circuit layer 6 and the main surface 7b of the heat dissipation layer 7 by the excess brazing material at the time of joining. The wraparound is suppressed, the occurrence of surface stains due to the adhesion of the brazing material is prevented, and the bondability of electronic components and the like can be improved.

The circuit layer 6 has a thickness t10 of 1.0 mm or more and 2.0 mm or less, and a distance t11 in the thickness direction from the joint surface 7a to the overhanging portion 6c with the ceramic substrate 2 is 1 of the thickness t10. / 4 or more and 1/2 or less, the heat dissipation layer 7 has a plate thickness t20 of 1.0 mm or more and 2.0 mm or less, and from the joint surface 7a to the overhanging portion 7c to the ceramic substrate 2. It is preferable that the distance t21 in the thickness direction is set to be 2/5 or more and 7/10 or less of the plate thickness t20.
By using the circuit layer 6 and the heat dissipation layer 7 as described above, it is possible to improve power cycle resistance while maintaining insulation.

In order to confirm the effect of the present invention, the following experiments were conducted on the examples and comparative examples.
(Experiment 1)
A metal plate having an aluminum purity of 99.99% by mass was used for both the circuit layer and the heat dissipation layer. Further, AlN was used for the ceramic substrate, and power module substrates (samples 1 to 6) were manufactured under the conditions shown in Table 1. As shown in FIG. 2A, the power module substrates of Samples 1 to 3 have a protruding portion 6 c only in the circuit layer 6, and the heat radiating layer 7 has no protruding portion. It is manufactured. In addition, as shown in FIG. 2B, the power module substrates of Samples 4 to 6 have a protruding portion 7 c only in the heat dissipation layer 7, and the heat dissipation layer 6 is not formed with a protruding portion. It was manufactured using.

  In these samples 1 to 6, as shown in Table 1, the bonding surface 6a of the circuit layer 6 with the ceramic substrate 2 is formed in 19 mm square, and the bonding surface 7a of the heat dissipation layer 7 with the ceramic substrate 2 is formed in 21 mm square. did. Further, the protruding length w11 of the overhanging portion 6c of the circuit layer 6 is set to the same size as the distance t11, and the protruding length w21 of the protruding portion 7c of the heat radiation layer 7 is set to the same size as the distance t21.

Then, a plurality of power module substrates having different sizes of the distance t11 of the circuit layer 6 or the distance t21 of the heat dissipation layer 7 are manufactured, and after attaching a heat sink to each of the power module substrates, an electronic component is mounted on the power module. The maximum temperature of the upper surface of the electronic component when the electronic component was energized was measured. FIG. 3 shows the measurement results summarized for each sample.
The ceramic substrates 2 of the samples 1 to 6 are 25 mm square and 0.635 mm thick, and the heat sink 5 is a 30 mm square and 1 mm thick JIS standard A6063 aluminum alloy metal plate. It was.
In Table 1, the distance t11 and the distance t21 vary the distance in the thickness direction from the joint surfaces 6a, 7a to the overhang portions 6c, 7c with the ceramic substrate 2 as shown on the horizontal axis of the graph of FIG. It has been made.

As shown in FIG. 3, it can be seen that the heat radiation can be improved by providing the overhang portions 6 c and 7 c in an appropriate range on the circuit layer 6 or the heat radiation layer 7 of the power module substrate. In the samples 1 to 3 provided with the overhang portion 6c, when the plate thickness t10 is 1.0 mm or more and 2.0 mm or less, high heat dissipation is obtained when the distance t11 is 1/4 or more and 1/2 or less of the plate thickness 10. Sex was obtained. In the samples 4 to 6 in which the overhang portion 7c is provided on the heat dissipation layer 7, when the thickness t20 is 1.0 mm or more and 2.0 mm or less, the distance t21 is 2/5 or more and 7/10 or less of the plate thickness 20 High heat dissipation was obtained. Moreover, it turned out that the samples 4-6 which provided the overhang | projection part 7c in the heat radiating layer 7 can obtain higher heat dissipation than the samples 1-3 which provided the overhang | projection part 7c in the circuit layer 6. FIG. .

(Experiment 2)
For both the circuit layer and the heat dissipation layer, a power module substrate (samples 21 and 22) was manufactured using a metal plate having a plate thickness of 2.0 mm and an aluminum purity of 99.99 mass%. In both of these samples 21 and 22, the bonding surface 6a of the circuit layer 6 with the ceramic substrate 2 was formed in 19 mm square, and the bonding surface 7a of the heat dissipation layer 7 with the ceramic substrate 2 was formed in 21 mm square.
As shown in FIG. 2A, the power module substrate of the sample 21 has only the overhanging portion 6c. Further, the power module substrate of the sample 22 has an overhanging portion 7c only in the heat dissipation layer 7, as shown in FIG. 2 (b).

In the sample 21, a plurality of power module substrates in which the distance t11 of the circuit layer 6 was 1.2 mm and the length of the protruding length w11 of the overhang portion 6c was variously changed were produced. Further, in the sample 22, a plurality of power module substrates in which the distance t21 of the heat radiation layer 7 was 1.2 mm and the size of the protruding length w21 of the overhang portion 7c was variously changed were produced. And after joining a heat sink to each power module substrate, an electronic component was mounted to manufacture a power module, and the maximum temperature of the upper surface of the electronic component when the electronic component was energized was measured. FIG. 4 shows the measurement results summarized for each sample.
The ceramic substrate 2 of each of the samples 21 and 22 has a 25 mm square and a plate thickness of 0.6 mm, and the overhanging portion 6c of the circuit layer 6 has a protruding length w11 exceeding 3.0 mm. When the protruding length w21 of the overhanging portion 7c exceeds 2.0 mm, the heat dissipation layer 7 protrudes from the outer peripheral edge of the ceramic substrate 2.
The heat sink 5 was a 30 mm square and 1 mm thick JIS A6063 aluminum alloy metal plate.

As can be seen from FIG. 4, the greater the length w11 of the overhang portion 6c and the length w21 of the overhang portion 7c, the higher the heat dissipation.
Further, even when the overhanging portion 6c is set to 3.0 mm or less, which is a size that does not exceed the outer peripheral edge of the ceramic substrate 2, the circuit layer 6 can obtain sufficiently high heat dissipation. Similarly, even if the heat dissipation layer 7 is set to 2.0 mm or less, which is a size in which the overhanging portion 7c does not exceed the outer peripheral edge of the ceramic substrate 2, sufficiently high heat dissipation can be obtained. In this way, the outer peripheral edges of the overhang portions 6a and 7a are made larger than the outer peripheral edge of the ceramic substrate 2 in order to prevent short circuit with other power module substrates adjacent in the module such as IGBT and to improve the mounting density. Even if it is set to be equal to or smaller than that, a sufficient heat radiation effect can be obtained.

(Experiment 3)
A power module substrate (samples 31 to 39) was manufactured under the conditions shown in Table 2 using a metal plate having an aluminum purity of 99.99 mass% for both the circuit layer and the heat dissipation layer. Among these, samples 31, 34, and 37 were manufactured using the circuit layer 6 and the heat dissipation layer 7 in which no overhang was formed (FIG. 5). Further, the power module substrates of the samples 32, 35, and 38 were manufactured by using only the heat dissipation layer 7 in which the overhanging portion 7c was formed (FIG. 2B). Samples 33, 36, and 39 were manufactured using the circuit layer 6 and the heat dissipation layer 7 in which the overhang portions 6c and 7c were formed (FIG. 1).

In these samples 31 to 39, the bonding surface 6a of the circuit layer 6 with the ceramic substrate 2 was formed in 19 mm square, and the bonding surface 7a of the heat dissipation layer 7 with the ceramic substrate 2 was formed in 21 mm square. For the sample in which the overhang portions 6c and 7c are provided on the circuit layer 6 or the heat dissipation layer 7, the protruding length w11 of the overhang portion 6c of the circuit layer 6 is set to the same size as the distance t11. The protruding length w21 of the overhang portion 7c is set to the same size as the distance t21.
The samples 31 to 33 have a plate thickness t10 of the circuit layer 6 and the plate thickness t20 of the heat dissipation layer 7 of 1.0 mm, the samples 34 to 36 have a plate thickness t10 and a plate thickness t20 of 1.6 mm, and the samples 37 to 39 have It formed using the metal plate whose plate | board thickness t10 and plate | board thickness t20 are 2.0 mm. The ceramic substrates 2 of the samples 21 to 29 are 25 mm square and 0.6 mm thick, and the heat sink 5 is a 30 mm square and 1 mm thick JIS A6063 aluminum alloy metal plate. It was.

  A power module was manufactured by mounting an electronic component on the power module substrate of each of the samples 31 to 39 formed in this manner, after bonding a heat sink. And the temperature of the electronic component upper surface 2 second after energization to the electronic component of each sample 21-29 was measured. Table 2 shows the measurement results. The “temperature difference on the upper surface of the electronic component” in Table 2 indicates the temperature difference between the upper surface of the electronic component of each sample and the temperature of the samples 31, 34, and 37 as a reference.

  As can be seen from Table 2, at least the heat radiation layer 7 is provided with the overhanging portion 7c, so that the heat dissipation can be improved. In the case where the overhang portions 6c and 7c are formed on both the circuit layer 6 and the heat dissipation layer 7 (samples 33, 36, and 39), higher heat dissipation is obtained.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, the metal layer used for the circuit layer 6 and the heat dissipation layer 7 can use aluminum alloy, copper, or copper alloy in addition to aluminum.

Further, the ceramic substrate and the metal plate may be joined by a transient liquid phase joining method called TLP joining method (Transient Liquid Phase Bonding) in addition to brazing. In this transient liquid phase bonding method, a copper layer deposited on the surface of the metal plate is interposed at the interface between the metal plate, the ceramic substrate, and the heat sink. By heating, copper diffuses into the aluminum of the metal plate, the copper concentration in the vicinity of the copper layer of the metal plate increases and the melting point decreases, and a metal liquid phase forms at the bonding interface in the eutectic region of aluminum and copper Is done. If the temperature is kept constant in a state in which this metal liquid phase is formed, the metal liquid phase reacts with the ceramic substrate or the heat sink, and copper further diffuses into the aluminum. The copper concentration gradually decreases, the melting point increases, and solidification proceeds with the temperature kept constant. Thereby, strong joining with a metal plate, a ceramic substrate, and a heat sink is obtained.
Moreover, the method of joining a ceramic board | substrate and a copper metal plate using an active metal brazing material is also employable. For example, using an active metal brazing material (Ag-27.4 mass% Cu-2.0 mass% Ti) containing Ti as an active metal, a laminate of a copper metal plate and a ceramic substrate is pressed. It can be heated in a vacuum and Ti, which is an active metal, can be preferentially diffused in the ceramic substrate, and the metal plate and the ceramic substrate can be joined via the Ag-Cu alloy.

  In addition, the heat sink should have an appropriate shape, such as a flat plate, one in which a large number of pin-shaped fins are integrally formed by hot forging, etc., one in which strip-shaped fins are formed integrally in parallel by extrusion. Can be adopted. Further, a heat radiating plate or a stress buffer layer made of a metal plate such as aluminum, aluminum alloy, copper, or copper alloy can be provided between the heat sink and the heat radiating layer.

DESCRIPTION OF SYMBOLS 1 Power module 2 Ceramic substrate 3 Power module substrate 4 Electronic component 5 Heat sink 6 Circuit layer 6a Joint surface 6b Electronic component mounting surface 6c Overhang part 7 Heat radiation layer 7a Joint surface 7b Main surface 7c Overhang part 8 Solder joint layer

Claims (3)

A circuit layer to which electronic components are bonded is laminated on one surface of the ceramic substrate, and a heat dissipation layer is stacked on the other surface, and a heat sink is provided on the opposite side of the heat dissipation layer from the bonding surface with the ceramic substrate. A power module substrate on which a heat sink bonding surface to be bonded is formed, wherein the electronic component mounting surface to which the electronic component on the opposite side of the bonding surface between the ceramic substrate and the circuit layer is bonded is increased. A protruding portion is formed on the electronic component mounting surface side of the side surface of the circuit layer, and an overhang portion that increases the area of the heat sink bonding surface on the opposite side of the bonding surface between the ceramic substrate and the heat dissipation layer wherein the heat dissipation layer is formed on the heat sink junction surface, the overhang portion of the circuit layer, the circuit layer distance t11 in the thickness direction from the joint surface between the ceramic substrate The thickness t10 is set to be ¼ or more and ½ or less of the thickness t10, and the protruding portion of the heat dissipation layer has a thickness direction distance t21 from the bonding surface with the ceramic substrate of the thickness of the heat dissipation layer. It is set so that it may become 2/5 or more and 7/10 or less of t20, The board | substrate for power modules characterized by the above-mentioned. Claims, characterized in that the thickness t10 of the circuit layer is in 1.0mm or more 2.0mm or less, the thickness t20 of the previous SL radiating layer is set to be 1.0mm or more 2.0mm or less 1. The power module substrate according to 1.   The size of the outer peripheral edge of the overhanging portion of the circuit layer and the heat dissipation layer is set to be equal to or smaller than the size of the outer peripheral edge of the ceramic substrate. The board | substrate for power modules as described.

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