JP2012248568A - Heat dissipation substrate, method for manufacturing the same, and semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat dissipation substrate on the surface of which a wiring pattern can be formed and which is capable of dissipating heat from a mounted chip with high efficiency.SOLUTION: A heat dissipation substrate 10 is constituted by laminating a metal layer 11, a composite sheet 12, an insulating sheet 13, and a metal thin-film layer 14. A protrusion 111 having a rectangular shape is formed on the upper surface side of the metal layer 11. On the other hand, an opening 121 shaped to be fitted to the protrusion 111 is formed in the composite sheet 12. The composite sheet 12 is a layer having a structure in which graphite layers (graphite regions) and resin layers (resin regions) are alternately arranged in its in-plane direction.

Description

  The present invention relates to a heat dissipation board used for a semiconductor module and the like, a manufacturing method thereof, and a semiconductor module using the heat dissipation board.

  A diode made of silicon, an IGBT (Insulated Gate Bipolar Transistor), or the like is used as a power semiconductor element that operates with a large current. A semiconductor module using a semiconductor chip on which these elements are formed is configured to efficiently dissipate heat from the semiconductor chip.

  For this reason, in such a case, the semiconductor chip is mounted on a heat dissipation substrate having high thermal conductivity. As a material for the heat dissipation substrate, a metal having high thermal conductivity such as copper or aluminum is generally used. However, graphite has a higher thermal conductivity. However, the thermal conductivity of graphite has anisotropy due to its crystal structure, and the thermal conductivity of graphite in one direction (generally in the in-plane direction of the thin film) is as high as about 1000 to 2000 W / m / K. On the other hand, in the direction perpendicular to this (generally in the thickness direction of the thin film), it is about 1 to 5 W / m / K. The former value is higher than the thermal conductivity of copper, aluminum, etc. (about 300 to 400 W / m / K at most), but the latter value is significantly lower than these. On the other hand, the heat dissipation substrate preferably has a high thermal conductivity in any direction.

  For example, Patent Document 1 describes the structure of a heat dissipation substrate using graphite. In this configuration, a configuration in which graphite layers and metal layers are alternately stacked is used. At this time, high thermal conductivity is obtained in the in-plane direction of the graphite layer, and the thermal conductivity in the film thickness direction is low. However, since the metal layer is laminated in the film thickness direction, the thermal conductivity in the film thickness direction is ensured by the metal layer. Also, if this laminated structure is formed into a sheet shape cut in the lamination direction (direction perpendicular to the in-plane direction of each layer: thickness direction), in this sheet, contrary to the above, the heat conduction in the thickness direction is The heat conduction in the in-plane direction is ensured by the graphite and is ensured by the metal layer. The surface of this laminated structure is further protected with a plating layer, and a semiconductor chip is mounted thereon.

  Patent Document 2 describes a sheet in which graphite sheets and adhesive layers are alternately laminated and this laminated structure is cut in the lamination direction. Thereby, the sheet | seat with the high heat conductivity in the film thickness direction is obtained similarly to the above.

JP 2009-043851 A JP 2009-295921 A

  As described above, the heat dissipation substrate is required to have a function of efficiently radiating heat from the semiconductor chip. On the other hand, a wiring pattern may be formed on a heat dissipation board, and this heat dissipation board may be used as a wiring board. Since the heat dissipation substrate described in Patent Document 1 is conductive, it is difficult to perform such use.

  In the heat dissipation substrate described in Patent Document 2, the thermal conductivity of the adhesive layer is significantly lower than that of graphite. Further, since the in-plane direction of the heat dissipation substrate is the film thickness direction of the graphite layer, the thermal conductivity of the graphite layer itself in the in-plane direction of the heat dissipation substrate is also low. For this reason, although the thermal conductivity in the film thickness direction of the heat dissipation substrate is increased, the thermal conductivity in the in-plane direction is extremely low. For this reason, it is not suitable for the purpose of performing heat dissipation from a semiconductor chip to be mounted with high efficiency, particularly like a power semiconductor module.

  That is, it has been difficult to obtain a heat dissipation substrate that can form a wiring pattern on the surface and can perform heat dissipation from a chip to be mounted with high efficiency.

  The present invention has been made in view of such problems, and an object thereof is to provide an invention that solves the above problems.

In order to solve the above problems, the present invention has the following configurations.
The heat dissipation substrate of the present invention has a structure in which a plurality of graphite regions whose thickness direction is the direction in which the hexagonal ring extends in the in-plane direction are joined via a resin region, and further penetrate the thickness direction. A composite sheet comprising an opening to be formed, a metal layer provided on a lower side of the composite sheet, provided with a convex portion that fits into the opening, an insulating sheet disposed on an upper portion of the composite sheet, It is characterized by comprising a structure in which a metal thin film layer disposed on the insulating sheet is laminated.
In the heat dissipation board of the present invention, the insulating sheet contains an epoxy resin.
In the heat dissipation board of the present invention, the resin layer includes an epoxy resin.
The method for manufacturing a heat dissipation board according to the present invention is a method for manufacturing a heat dissipation board, in which a plurality of graphite layers in which the direction in which the hexagonal ring extends is an in-plane direction and a plurality of resin layers are alternately stacked and pressed. A composite sheet manufacturing process for manufacturing the composite sheet by manufacturing the composite sheet by forming the opening after the laminate is cut and separated along the stacking direction, and the metal layer, the composite sheet, and the insulating sheet And a bonding step in which the metal thin film layers are laminated and thermocompression bonded.
The semiconductor module of the present invention is a semiconductor module using the heat dissipation substrate, wherein the metal thin film layer is patterned and divided into a plurality of regions, and a semiconductor chip is formed on at least one of the metal thin film layers in the region. Is featured.
The semiconductor module of the present invention is characterized in that the opening in the composite sheet is provided immediately below the region of the metal thin film layer on which the semiconductor chip is not mounted.

  Since the present invention is configured as described above, a wiring pattern can be formed on the surface, and heat can be radiated from the mounted chip with high efficiency.

It is a disassembled perspective view which shows the structure of the thermal radiation board which concerns on embodiment of this invention. It is sectional drawing of the composite sheet used in the thermal radiation board which concerns on embodiment of this invention. It is process sectional drawing which shows the manufacturing method of the composite sheet used in the thermal radiation board which concerns on embodiment of this invention. It is sectional drawing which shows the process of manufacturing a semiconductor module using the heat sink which concerns on embodiment of this invention.

  Hereinafter, the structure of the heat dissipation substrate according to the embodiment of the present invention will be described. This heat dissipation substrate is configured by laminating a metal layer, a composite sheet, an insulating sheet, and a metal thin film layer in order from the bottom. Here, in the in-plane direction, the composite sheet has a configuration in which a plurality of graphite regions whose thickness direction is a direction in which the hexagonal ring extends are joined via a resin region. Further, the composite sheet is provided with an opening, and the opening is fitted with a convex portion provided in the metal layer. The uppermost metal thin film layer is etched to form part of the wiring pattern in the semiconductor module.

  FIG. 1 is an exploded perspective view showing the structure of the heat dissipation substrate 10. The heat dissipation substrate 10 is configured by laminating a metal layer 11, a composite sheet 12, an insulating sheet 13, and a metal thin film layer 14. Here, the metal layer 11, the insulating sheet 13, and the metal thin film layer 14 are each uniformly formed of the same material. On the other hand, the composite sheet 12 is composed of a graphite layer and a resin layer, and FIG. 2 is a cross-sectional view of the composite sheet 12 in the AA direction (a portion without an opening).

  A convex portion 111 having a rectangular shape is formed on the upper surface side of the metal layer 11 (the surface to be bonded to the composite sheet 12). On the other hand, the composite sheet 12 is formed with an opening 121 having a shape that fits with the convex portion 111. The height of the convex portion 111 is equivalent to the thickness of the composite sheet 12. The configuration of the convex portion 111 and the opening portion 121 can be appropriately set according to the form of the semiconductor module, as will be described later. In the heat dissipation substrate 10, it is preferable that no gap is formed between the layers in a state where the metal layer 11, the composite sheet 12, the insulating sheet 13, and the metal thin film layer 14 are laminated and integrated. For this reason, the upper surface of the metal layer 11 other than the portion where the convex portion 111 is formed, the surface of the composite sheet 12 other than the portion where the opening 121 is formed, the entire surface of the insulating sheet 13, and the metal thin film layer 14 The lower surface is preferably flat.

  Both the metal layer 11 and the metal thin film layer 14 are made of copper or an alloy containing copper as a main component. When the metal layer 11 is processed into the shape shown in FIG. 1, for example, etching is used. The metal layer 11 is set to be the thickest of the components in FIG. On the other hand, since the metal thin film layer 14 is later formed into a wiring pattern, the thickness thereof is set in consideration of the wiring resistance. Specifically, the thickness of the metal layer 11 (location without the convex portion 111) is, for example, about 2.0 mm, and the thickness of the metal thin film layer 14 is, for example, 0.05 mm.

  The insulating sheet 13 is made of, for example, an epoxy resin that has high insulating properties and can be bonded to the composite sheet 12 and the metal thin film layer 14 by thermocompression bonding, and has a thickness of, for example, 0.2 mm. Moreover, the insulating sheet 13 does not need to be comprised with a single material, and can contain the inorganic filler which consists of thermosetting resin (The hardening | curing agent in this case shall be a thermoplastic resin), an alumina, etc. Furthermore, glass fiber etc. can be included.

  As shown in FIG. 2, the composite sheet 12 is a layer having a structure in which graphite layers (graphite regions) 122 and resin layers (resin regions) 123 are alternately arranged in the in-plane direction. FIG. 2 is a cross-sectional view thereof, but the graphite layer 122 and the resin layer 123 are stretched as they are in the direction perpendicular to the paper surface in FIG. FIG. 3 is a cross-sectional view schematically showing this manufacturing method.

  The composite sheet 12 is manufactured by a laminated sheet manufacturing process described below. First, as shown in FIG. 3A, the graphite layer 122 and the resin layer 123 are laminated. Here, the graphite layer 122 is made of graphite having a crystal structure in which hexagonal rings (a structure in which hexagonal crystals in a hexagonal system are two-dimensionally spread on the turtle shell) are stacked. In graphite, the thermal conductivity in the direction in which the hexagonal ring spreads is high, and the thermal conductivity in the stacking direction is low. The direction in which this hexagonal ring expands is the direction indicated by the arrow in FIG. 3A, which is the in-plane direction (direction perpendicular to the stacking direction) of the graphite layer 122 in this state.

  The resin layer 123 is made of, for example, an epoxy resin as a material that can be pressure-bonded to the graphite layer 122. As shown in the figure, a plurality of graphite layers 122 and resin layers 123 having this configuration are alternately stacked. Similarly to the insulating sheet 13, the resin layer 123 does not need to be composed of a single material, and an inorganic filler made of a thermosetting resin (in this case, the curing agent is a thermoplastic resin) and alumina is used. Can be included. Furthermore, glass fiber etc. can be included.

  As shown in FIG. 3B, the laminated structure is integrated by a heat and pressure treatment to form a laminated body 125.

  Thereafter, as shown in FIG. 3C, the laminated body 125 is thinly cut along the laminating direction to obtain a composite sheet 12 having a sheet shape. In the state of FIG. 3A, the thermal conductivity of the graphite layer 122 was high in the in-plane direction and low in the thickness direction, whereas in the composite sheet 12, the direction of the graphite was changed by 90 °. The conductivity is high in the thickness direction and low in the in-plane direction. In addition, since the heat conductivity of the resin layer 123 is low in any direction, its contribution to the heat conduction in the in-plane direction of the composite sheet 12 is small.

  As shown in FIG. 1, the composite sheet 12 is provided with an opening 121. For example, the opening 121 can be formed by press punching. At this time, as shown in FIG. 2, the composite sheet 12 has a cross-sectional structure in which a large number of thin resin layers 123 are provided along the thickness direction.

  As shown in FIG. 1, the heat dissipation substrate 10 is manufactured by laminating a metal layer 11, a composite sheet 12, an insulating sheet 13, and a metal thin film layer 14 and thermocompression bonding (joining process). In addition, in order to perform this joining firmly, it is preferable that the form in the planar view of the convex part 111 of the metal layer 11 is made slightly larger than the opening part 121 of the composite sheet 12. In this case, the metal which comprises the metal layer 11 softens at the time of this joining process, and this joining can be strengthened.

  As described above, the thermal conductivity in the in-plane direction of the composite sheet 12 is not high. In the heat dissipation substrate 10, in order to complement this, an opening 121 is provided in the composite sheet 12, and the convex portion 111 of the metal layer 11 is fitted into the opening 121. The thermal conductivity of the metal constituting the metal layer 11 is lower than the thermal conductivity in the direction (thickness direction in the composite sheet 12) in which the thermal conductivity of graphite is higher, but the direction in which the thermal conductivity of graphite is lower ( It is significantly higher than its thermal conductivity in the in-plane direction of the composite sheet 12. For this reason, in this composite sheet 12, high heat conduction is obtained in the in-plane direction at the locations where the convex portions 111 exist. In the heat dissipation substrate 10, a region having a high thermal conductivity in the in-plane direction and a region having a high thermal conductivity in the thickness direction can be appropriately set by setting the convex portions 111 (opening portions 121).

  The form at the time of actually forming a semiconductor module using this thermal radiation board | substrate 10 is demonstrated below. FIG. 4 is a cross-sectional view showing this manufacturing process.

  As shown in FIG. 4B, the uppermost metal thin film layer 14 is patterned into a desired pattern with respect to the heat dissipation substrate 10 in the form shown in FIG. This patterning is easily performed by, for example, wet etching using a photoresist as a mask. For example, when the metal thin film layer 14 is made of copper, this etching can be performed using a ferric chloride aqueous solution without adversely affecting the composite sheet 12 or the like. Even when the metal layer 11 and the metal thin film layer 14 are made of the same material, the metal layer 11 is sufficiently thicker than the metal thin film layer 14, and thus the metal layer 11 is not greatly affected by this etching. . If the metal layer 11 is thin, this step can be performed by masking it. 4B, the metal thin film layer 14 is separated into three regions 14a, 14b, and 14c from the left by this process.

  Next, as shown in FIG. 4C, the semiconductor chip 20a is mounted on the metal thin film layer 14a, and the semiconductor chip 20b is mounted on the metal thin film layer 14c by bonding using solder or the like. . Bonding wires 21 connect the electrodes on the semiconductor chip 20a and the metal thin film layer 14b, and the electrodes on the semiconductor chip 20b and the metal thin film layer 14b. As the semiconductor chips 20a and 20b, for example, an IGBT (Insulated Gate Bipolar Transistor), an FRD (Fast Recovery Diode), a control IC, or the like is used. Among these, since a large current flows through the IGBT and the FRD, the amount of heat generated is large.

  Electrodes are also formed on the back surfaces of the semiconductor chips 20a and 20b (sides connected to the metal thin film layers 14a and 14c), and these electrodes are electrically connected to the metal thin film layers 14a and 14c by solder or the like. Connected to. The metal thin film layers 14a, 14b, and 14c and the bonding wire 21 are set so that the electric circuit in the semiconductor module is configured using the semiconductor chips 20a and 20b.

  Finally, as shown in FIG. 4D, a mold layer 30 made of a resin material is formed in a form that seals the heat dissipation substrate 10, the semiconductor chips 20a and 20b, the bonding wires 21, and the like. The leads in this semiconductor module are connected to the metal thin film layers 14a, 14b, 14c, etc., and are taken out in a form protruding from the mold layer 30 in the direction perpendicular to the paper surface in FIG. Thereby, these leads can be used as input / output terminals in the semiconductor module.

  Thus, a semiconductor module can be manufactured using the heat dissipation substrate 10 described above. Here, after forming the heat dissipation substrate 10 before the metal thin film layer 14 is patterned, the metal thin film layer 14 can be used as a wiring pattern by patterning only the uppermost metal thin film layer 14. Under the present circumstances, the manufacturing process after this patterning is the same as that of the case where a normal semiconductor module is manufactured. Moreover, since the insulating sheet 13 exists under the metal thin film layer 14, the metal thin film layer 14 can be used as a wiring pattern.

  At this time, since the heat dissipation substrate 10 having the above-described configuration is used, the heat generated by the semiconductor chips 20a and 20b is efficiently transmitted in the thickness direction and the in-plane direction of the heat dissipation substrate, and heat is released. The structure of the convex part 111 (opening part 121 in the composite sheet 12) of the metal layer 11 in the heat dissipation substrate 10 can be set as appropriate according to the structure of the semiconductor module.

  For example, in the example of FIG. 4D, the heat generation amount in the metal thin film layers 14a and 14c on which the semiconductor chips 20a and 20b are respectively mounted is large, whereas the heat generation in the metal thin film layer 14b on which the semiconductor chips are not mounted. The amount is small. For this reason, it is not necessary to increase the thermal conductivity from the region of the metal thin film layer 14b to the lower side (toward the lower side in the thickness direction of the heat dissipation substrate 10). On the other hand, the heat generation by the semiconductor chips 20a and 20b is large in the regions on both sides, and the heat dissipation efficiency can be increased by transmitting this heat generation in the left and right directions together with the lower side. That is, in the region where the heat conduction from the metal thin film layer side is small, it is preferable to increase the heat conduction in the in-plane direction rather than the thickness direction. On the other hand, in the region where the heat conduction from the metal thin film layer side is large, it is preferable to increase the heat conduction in the thickness direction rather than the in-plane direction. For this reason, the convex part 111 of the metal layer 11 is provided immediately under the metal thin film layer 14b, and the heat conduction in the in-plane direction is set to be more important than the heat conduction in the thickness direction. In the heat dissipation substrate 10, such a setting can be realized particularly in a state where the thermal conductivity in the thickness direction of the composite sheet 12 is particularly increased using graphite.

  Thus, the setting of the convex part 111 (opening part 121) can be suitably performed according to the structure of a semiconductor module. Alternatively, the heat dissipation substrate 10 provided with the convex portion 111 is manufactured with a predetermined setting, and the configuration of the metal thin film layers 14a, 14b, and 14c to be a wiring pattern is determined in consideration of the configuration of the convex portion 111. Can do. Thereby, this heat dissipation board 10 can be adapted to the configuration of the semiconductor chip on which the heat conduction in the thickness direction and the heat conduction in the in-plane direction are mounted.

  In the above configuration, the direction in which the hexagonal ring of graphite spreads in the composite sheet is the thickness direction, but it is not necessary to strictly match the thickness direction. For example, this angle can be set as appropriate in order to provide a certain degree of thermal conductivity in the in-plane direction. This is appropriately performed by adjusting the direction of cutting the laminate in the composite sheet manufacturing process. Moreover, it is also possible to form the heat dissipation substrate of FIG. 1 as a configuration in which the composite sheet 12 is replaced with the graphite layer 122 in FIG. In this case, contrary to the heat dissipation substrate 10, the heat conduction in the in-plane direction is governed by the graphite layer 122, and the heat conduction in the thickness direction is governed by the metal layer 11 (convex portion 111). Is obtained.

  Further, the arrangement and shape of the protrusions (openings) are arbitrary as long as the heat dissipation substrate can be manufactured. In addition, the materials constituting the metal layer, the metal thin film layer, the insulating sheet, and the resin layer are arbitrary as long as the heat dissipation substrate can be manufactured.

DESCRIPTION OF SYMBOLS 10 Heat dissipation board 11 Metal layer 12 Composite sheet 13 Insulating sheets 14, 14a, 14b, 14c Metal thin film layers 20a, 20b Semiconductor chip 21 Bonding wire 30 Mold layer 111 Protruding part 121 Opening part 122 Graphite layer (graphite region)
123 Resin layer (resin area)
125 Laminate

Claims (6)

In the in-plane direction, a composite having a structure in which a plurality of graphite regions in which the direction in which the hexagonal ring spreads is a thickness direction is joined via a resin region, and further includes an opening that penetrates the thickness direction Sheet,
A metal layer provided on the lower side of the composite sheet and provided with a convex portion that fits into the opening;
An insulating sheet disposed on top of the composite sheet;
A metal thin film layer disposed on top of the insulating sheet;
A heat dissipating board having a structure in which is laminated.   The heat dissipation board according to claim 1, wherein the insulating sheet includes an epoxy resin.   The heat dissipation substrate according to claim 1, wherein the resin layer includes an epoxy resin. It is a manufacturing method of a heat dissipation board given in any 1 paragraph of Claims 1-3,
After producing a laminate in which a hexagonal ring spreads in the in-plane direction, a graphite layer and a resin layer alternately laminated and pressure-bonded, and cutting and separating the laminate along the lamination direction, A composite sheet manufacturing process for manufacturing the composite sheet by forming the opening;
A bonding step in which the metal layer, the composite sheet, the insulating sheet, and the metal thin film layer are laminated and thermocompression bonded;
The manufacturing method of the heat sink characterized by comprising. A semiconductor module using the heat dissipation substrate according to any one of claims 1 to 3,
A semiconductor module, wherein the metal thin film layer is patterned and divided into a plurality of regions, and a semiconductor chip is mounted on at least one metal thin film layer in the region.   The semiconductor module according to claim 5, wherein the opening in the composite sheet is provided directly under a region of the metal thin film layer on which the semiconductor chip is not mounted.

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