JP6479382B2 - Metal base substrate - Google Patents

Description

  The present invention relates to a metal base substrate, and more particularly to a metal base substrate which achieves both suppression of delamination and high heat dissipation.

  In an electric circuit board in which a circuit layer on which a circuit pattern is formed and an insulating layer made of resin are laminated, the purpose is to efficiently release the heat generated in the circuit layer by the operation of the electric component attached to the circuit pattern. There is a metal base substrate provided with a heat dissipation layer made of metal on the surface of the insulating layer opposite to the circuit layer. For example, Patent Document 1 describes a metal base circuit board in which a circuit metal layer is formed on a metal heat sink via an insulating layer.

  The heat generated in the circuit layer in such a metal base substrate (metal base circuit board) is conducted to the heat dissipation layer through the insulating layer. Since the heat dissipation layer is made of metal as described above, the heat is efficiently conducted through the heat dissipation layer and released to the air from the open surface of the heat dissipation layer. As a material of the heat dissipation layer, aluminum or copper is adopted in consideration of thermal conductivity and easiness of procurement.

  In recent years, electrical circuits that generate high heat are increasing due to high integration of semiconductor elements and over-density wiring, and the demand for metal base substrates with higher heat dissipation is increasing. When high heat dissipation is required for the metal base substrate, copper having a thermal conductivity higher than that of aluminum is used as the material of the thermal radiation layer (the thermal conductivity of copper is 386 to 402 W / (m · K), aluminum The thermal conductivity of is 226 to 237 W / (m · K)).

Japanese Patent Application Publication No. 2007-150224

  However, in a metal base substrate in which copper is adopted for the heat dissipation layer, delamination is more likely to occur in the joint portion between the heat dissipation layer and the insulating layer than in the case where aluminum is adopted for the heat dissipation layer. This is because the degree of expansion or contraction due to temperature change is largely different between the insulating layer and the heat dissipation layer because the difference in thermal expansion coefficient between copper and resin is large. In particular, when the metal base substrate is used in an environment exposed to severe temperature change such as an automobile engine room, peeling between the heat dissipation layer and the insulating layer is more likely to occur.

  On the other hand, when aluminum is used for the heat dissipation layer in order to suppress the above-described delamination, the heat conductivity of the entire metal base substrate is reduced because the heat conductivity of aluminum is lower than that of copper. Thus, when heat dissipation is enhanced by adopting copper as the material of the heat dissipation layer, delamination is likely to occur, and when aluminum is employed to suppress delamination, the heat dissipation is impaired. . Therefore, in the metal base substrate, there is a problem that the improvement of the heat dissipation and the suppression of the delamination can not be simultaneously achieved.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a metal base substrate that achieves both suppression of delamination and high heat dissipation.

In order to achieve this object, the metal base substrate of the present invention comprises a circuit layer made of a conductor forming a circuit pattern, and an insulating layer which is bonded to the circuit layer and is thermally cured by a thermosetting resin. An insulating layer formed on a surface opposite to the surface to be joined to the circuit layer and laminated with a heat dissipation layer made of metal, the heat dissipation layer forming aluminum to form a surface to be joined to the insulating layer; Material, and a clad material in which a copper material forming the open surface of the heat dissipation layer is joined, a protruding fin is formed on the open surface of the copper material , and the insulating layer has heat conductivity It is characterized in that it has a thermal conductivity of 2 to 12 W / (m · K) and is formed to a thickness of 50 to 200 μm by the addition of an inorganic filler for enhancing alumina or silicon dioxide .

  The thickness of the copper material is 70% or more of the thickness of the heat dissipation layer.

According to the metal base substrate of Claim 1, the following effect is produced. An insulating layer formed by curing a thermosetting resin is joined to a circuit layer on which a circuit pattern is formed, and a heat dissipation layer made of metal for enhancing heat dissipation is joined to the insulating layer. The insulating layer has a thermal conductivity of 2 to 12 W / (m · K) and is formed to a thickness of 50 to 200 μm by the addition of an inorganic filler of alumina or silicon dioxide to enhance heat conductivity. . Thus, the heat from the circuit layer joined to the insulating layer can be efficiently conducted to the insulating layer, and from the insulating layer to the heat dissipation layer joined to the insulating layer. Furthermore, since the thickness of the insulating layer is 50 to 200 μm, the heat from the circuit layer is conducted to the heat dissipation layer without staying in the insulating layer for a long time, so the heat from the circuit layer deforms the insulating layer. It is possible to suppress separation of the bonding between the insulating layer and the circuit layer, or the bonding between the insulating layer and the heat dissipation layer. The heat dissipation layer is formed of a clad material in which an aluminum material bonded to the insulating layer and a copper material forming the open surface of the heat dissipation layer are bonded. The surface of the heat dissipation layer to be bonded to the insulating layer is formed of an aluminum material having a thermal expansion coefficient close to that of the thermosetting resin forming the insulating layer, so peeling between the heat dissipation layer and the insulating layer due to temperature change can be suppressed. On the other hand, the open surface of the heat dissipation layer is formed of a copper material having a high thermal conductivity. Therefore, the heat generated in the circuit layer is conducted to the aluminum material of the heat dissipation layer through the insulating layer, and further conducted to the copper material having a higher thermal conductivity from the aluminum material, and efficiently released from the open surface of the heat dissipation layer. Be done. Furthermore, since a projecting fin is formed on the open surface side of the copper material, the surface area of the copper material can be increased by such a fin, and heat dissipation can be further enhanced. Therefore, there is an effect that suppression of delamination between the insulating layer and the heat dissipation layer can be compatible with efficient release of heat generated in the circuit layer. Further, since the clad material is formed by bonding two metals without a gap, there is no possibility that the bonding portion between the aluminum material and the copper material is peeled off, and the heat conduction at the bonding portion between the aluminum material and the copper material The loss is also small. Therefore, there is an effect of preventing the delamination in the heat dissipation layer and suppressing the loss of heat conduction.

  The metal base substrate of the present invention may be one in which a circuit pattern is formed in a circuit layer, or may be one before a circuit pattern is formed in a circuit layer.

  In addition, although bonding of a metal material may require a temperature higher than the curing temperature of the thermosetting resin, by employing a clad material in which an aluminum material and a copper material are bonded, in the process of manufacturing a metal base substrate There is no need for the step of joining the aluminum material and the copper material, and no heating above the curing temperature of the thermosetting resin is required. Therefore, there is also an effect that the manufacturing of the metal base substrate can be facilitated and the manufacturing cost can be reduced.

  According to the metal base substrate of the second aspect, in addition to the effect of the metal base substrate of the first aspect, the following effect is exerted. Since the thickness of the copper material is 70% or more of the thickness of the entire heat dissipation layer, in the heat dissipation layer, the heat transfer distance of the aluminum material having a thermal conductivity lower than that of the copper material is shortened, and copper having high thermal conductivity The material can be efficiently dissipated as the main heat transfer medium. Therefore, there is an effect that the heat transfer deterioration can be suppressed by using the aluminum material for the heat dissipation layer.

It is a schematic diagram showing the laminated structure of the metal base substrate of this invention. It is explanatory drawing showing the process of laminating | stacking and joining the material which comprises the metal base substrate of this invention. It is explanatory drawing showing the process of forming a circuit pattern and V-shaped groove in the metal base substrate of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. First, the structure of the metal base substrate of the present invention will be described with reference to FIG. FIG. 1 is a schematic view showing a laminated structure of the metal base substrate of the present invention.

  The metal base substrate 1 is obtained by bonding a copper foil 10 and a clad material 30 with a resin material 20 interposed therebetween. In other words, the metal base substrate 1 is a laminate of the copper foil 10, the resin material 20 and the clad material 30.

  The copper foil 10 constitutes a layer on which a circuit pattern to which an electrical component is attached is formed by etching. The method of forming the circuit pattern will be described later with reference to FIG. As copper foil 10 of this embodiment, a thickness of 12 to 600 μm was adopted.

  The resin material 20 is a thermosetting epoxy resin by heating. The resin material 20 has a function of joining the copper foil 10 and the clad material 30, a function of electrically insulating the copper foil 10 and the clad material 30, and heat generated on the surface of the copper foil 10 as a clad material 30. It doubles as a function to conduct. An inorganic filler such as alumina or silicon dioxide for enhancing the heat conductivity is added to the resin material 20 of the present embodiment, and the resin material 20 has a thermal conductivity of 2 to 12 W / (m · K) and a thickness The thing of 50-200 micrometers was employ | adopted.

  The clad material 30 is obtained by laminating and joining together a plate-like aluminum plate 31 and a copper plate 32. In the clad material 30, the surface to which the aluminum plate 31 is exposed is bonded to the resin material 20, and the surface to which the copper plate 32 is exposed is the open surface of the clad material 30.

  As the clad material 30 of this embodiment, a copper plate 31 having a thickness of 70 to 90% of the thickness of the entire clad material 30 is employed. By setting the thickness of the copper plate 31 to 70% or more of the total thickness of the clad material 30, the ratio of the copper plate 32 having high thermal conductivity to the thickness of the clad material 30 increases, and the thickness of the aluminum plate 31 having low thermal conductivity The proportion of the thickness of the cladding material 30 becomes small. Therefore, the heat transfer deterioration in the clad material 30 can be suppressed. Although the thickness of the aluminum plate 31 is 10% or more of the thickness of the clad material 30 in order to stabilize the quality of the clad material 30, the thickness of the aluminum plate 31 is clad in order to further enhance the heat conductivity in the clad material 30. It may be less than 10% of the thickness of the material 30.

  In the metal base substrate 1 having the above configuration, the heat generated in the layer of the copper foil 10 is conducted to the aluminum plate 31 of the clad material 30 through the resin material 20. The heat conducted to the aluminum plate 31 is further conducted to the copper plate 32 having high thermal conductivity, and is released from the open surface of the copper plate 32 (that is, the open surface of the clad material 30). Therefore, in the metal base substrate 1, the heat generated in the copper foil 10 can be efficiently released.

  Further, as the heat dissipation layer of the metal base substrate 1 of the present embodiment, the clad material 30 is adopted. Since the clad material 30 is a material in which two types of metals are firmly joined without a gap, it is possible to prevent the peeling at the joint portion between the aluminum plate 31 and the copper plate 32 and also to suppress the heat conduction loss at the joint portion. In addition, by using the clad material 30 in which the aluminum plate 31 and the copper plate 32 are already bonded, the process of bonding the aluminum plate 31 and the copper plate 32 is omitted in the manufacturing process of the metal base substrate 1 to reduce the manufacturing cost. it can.

  Further, the coefficient of thermal expansion of aluminum is closer to the coefficient of thermal expansion of the epoxy resin forming the resin material 20 than the coefficient of thermal expansion of copper. Accordingly, by bonding the surface of the clad material 30 on which the aluminum plate 31 is exposed to the resin material 20, it is possible to suppress peeling at the bonding portion between the resin material 20 and the clad material 30 due to temperature change.

  Next, the manufacturing process of the metal base substrate 1 will be described with reference to FIGS. 2 and 3. First, with reference to FIG. 2, the process of laminating and joining the materials of the metal base substrate 1 will be described.

  FIG. 2A shows the members to be the material of the metal base substrate 1 and the order in which the members are stacked. The clad material 30 which comprises the thermal radiation layer in the metal base substrate 1 is a clad material with which the aluminum plate 31 and the copper plate 32 were joined as mentioned above. In the surface of the clad material 30 where the aluminum plate 31 is exposed, fine irregularities are formed in advance by chemical polishing. It is desirable that this unevenness be 0.5 to 10 μm in arithmetic mean roughness. As a result, when the clad material 30 and the resin material 20 are bonded in a later step, the bonding strength can be enhanced by the anchor effect.

  The clad material 30 has the upper surface on which the aluminum plate 31 is exposed, and the uncured resin material 20 constituting the insulating layer of the metal base substrate 1 is superimposed thereon. The resin material 20 is a sheet-like material made of epoxy resin as described above. As the resin material 20 of the present embodiment, a resin in which the epoxy resin cures to the C stage by heating to about 150 ° C. or higher was employed.

  On the resin material 20, the copper foil 10 which comprises the circuit layer of the metal base substrate 1 is piled up. The state which the material demonstrated above in FIG.2 (b) was laminated | stacked is shown, and the member of this laminated | stacked state is hereafter called "the lamination | stacking member 1a."

  Next, the prejoining process shown in FIG. 2C is performed on the laminated member 1a. The prebonding process is performed in a vacuum environment. In addition, "a vacuum environment" is the meaning which refers to the environment pressure-reduced below atmospheric pressure, and it is desirable that it is the environment pressure-reduced suitably to 42 hPa.

  At a temperature at which the epoxy resin cures to the C stage while being pressurized to 0.5 MPa to 1.0 MPa from the upper surface and the lower surface, that is, in the direction of the illustrated arrow where the resin material 20 and the clad material 30 are bonded. It is warmed to 80 to 100 ° C. which is lower than about 150 ° C. By this heating, the epoxy resin is melted (gelled) within the range of the B stage from the cured state, whereby the viscosity of the epoxy resin is reduced. As described above, the epoxy resin is melted (gelled) while the lamination member 1a is gently pressed from above and below, so that the air existing between the resin material 20 and the cladding material 30 is reduced due to environmental pressure reduction. As a result, the resin material 20 and the clad material 30 can be brought into close contact with each other.

  Next, the bonding process shown in FIG. 2D is performed on the laminated member 1a on which the preliminary bonding process has been performed. The bonding process is not particularly required to be performed in a reduced pressure environment, but may be performed in a reduced pressure environment. In the bonding process, the epoxy resin hardens to the C stage while being pressurized to 2.0 to 5.0 MPa, which is higher in the direction of the illustrated arrow where the resin material 20 and the clad material 30 bond, than in the preliminary bonding process. The epoxy resin of the resin material 20 is hardened | cured to C stage by heating to 150-250 degreeC more than the temperature to carry out. Each material of the lamination member 1a is joined by the above process, and the metal base substrate 1 is manufactured.

  According to the manufacturing method of the metal base substrate 1 by the preliminary bonding process and the bonding process described above, the resin material 20 and the clad material 30 are brought into close contact in the preliminary bonding process, and then the resin material 20 is obtained by the bonding process. Is completely cured. Therefore, the bonding between the resin material 20 and the clad material 30 can be strengthened, and the metal base substrate 1 in which delamination is less likely to occur can be manufactured.

  The temperature for heating in the pre-joining process and the joining process can be appropriately set in accordance with the property of the thermosetting resin that is the material of the resin material 20. The heating in the pre-joining process may be a temperature lower than the temperature at which the thermosetting resin of the resin material 20 cures to the C-stage, and the heating in the joining process may cure the thermosetting resin of the resin material 20 to the C-stage It is sufficient if the temperature is equal to or higher than the temperature.

  Further, the pressure applied to the laminated member 1a in the pre-joining process and the joining process is not limited to the range of the pressure described above, and the pressure may be 1.0 MPa or less in the pre-joining process. It is sufficient if the pressure is higher than the pressure applied to the laminated member 1a in the bonding process. These pressures can be suitably adjusted according to the property etc. of material.

  Next, with reference to FIG. 3, the formation of the circuit pattern and the formation of the V-shaped groove in the metal base substrate 1 will be described. The member shown in FIG. 3A is obtained by attaching an etching resist 50 (photoresist) on the upper surface of the metal base substrate 1 manufactured by the process shown in FIG. The etching resist 50 in the portion where the circuit pattern is to be formed is irradiated with ultraviolet light to partially cure the etching resist 50 (pattern exposure). Thereafter, a developer is applied to remove the uncured portion of the etching resist 50, that is, the portion which is not formed as a circuit pattern (development). The state in which the etching resist 50 of the part which is not formed as a circuit pattern is removed is shown in FIG.3 (b).

  Next, an etching solution is applied to the metal base substrate 1 in the state of FIG. 3B, and the portion of the copper foil 10 exposed from the remaining etching resist 50 is dissolved to obtain the state of FIG. Do. Thereafter, the etching resist 50 remaining by the stripping solution is removed to obtain the state of FIG. 3D, and a circuit pattern made of the copper foil 10 is formed on the metal base substrate 1.

  After the circuit pattern is formed on the metal base substrate 1, as shown in FIG. 3 (e), V-shaped grooves 60 are formed on both sides of the copper foil 10 and the clad material 30 at desired cutting positions on the metal base substrate 1. Is formed by V-cut processing. The V-shaped groove 60 may be formed on only one of the copper foil 10 side and the cladding material 30 side. By forming the V-shaped groove 60, even if the metal base substrate 1 is thick, it can be easily cut at a desired cutting position. The final cutting of the metal base substrate 1 is performed by manually bending the portion of the V-shaped groove 60. Further, in the V-cut processing, since a large impact is not applied to the joint portion as compared with punching or the like by a die, delamination at the cut portion can be suppressed.

  In the tests conducted by the inventors for the metal base substrate 1 described above, after maintaining the surface temperature of the metal base substrate 1 at 190 ° C. for 6 minutes, in a temperature change experiment in which the surface temperature is heated to 275 ° C. and maintained for 6 minutes. It was confirmed that no delamination occurred. It was also confirmed that delamination does not occur even in a heat cycle experiment in which the environment in which the metal base substrate 1 is placed is alternately changed 100 times at -40 ° C and 125 ° C.

  As mentioned above, although the present invention was explained based on an embodiment, the present invention is not limited at all to the above-mentioned embodiment, and it is easy to be variously modifiable in the range which does not deviate from the meaning of the present invention. It can be guessed.

  For example, in the above embodiment, it has been described that the resin material 20 is composed of an epoxy resin as a thermosetting resin, but various thermosetting resins such as polyimide resin and bismaleimide triazine resin may be used instead of the epoxy resin. It is of course also possible to use a resin. Moreover, although it was described that the inorganic filler is added to the resin material 20, the inorganic filler may not be added. This is because the effect of the present invention that the delamination between the resin material 20 and the clad material 30 can be prevented is the same if the material constituting the insulating layer is made of a thermosetting resin.

  In addition, in the metal base substrate 1 shown in FIG. 1, the bonding of the copper foil 10 and the resin material 20 and the bonding of the resin material 20 and the cladding material 30 are performed on all bonding surfaces. It is also possible that the bonding surface of another layer is bonded to a part of the bonding surface of one layer. For example, the copper foil 10 may be bonded to a part of the surface of the resin material 20, or the resin material 20 may be bonded to a part of the exposed surface of the aluminum plate 31 in the cladding material 30. May be

  Further, although it has been described that the copper foil 10 is to form a circuit pattern by etching, the circuit layer of the metal base substrate of the present invention may be one before the circuit pattern is formed. In addition, the formed circuit pattern may be further coated with a solder resist. In addition to the circuit layer formed by etching as described above (so-called subtractive method), the circuit layer is formed by plating a conductive layer (so-called additive method). ) May be used. The effects of the suppression of delamination and the high heat dissipation according to the present invention are similar regardless of the aspect of the circuit pattern formed on the circuit layer.

  Moreover, although the said embodiment demonstrated using the clad material 30 with which the aluminum plate 31 and the copper plate 32 were joined as a thermal radiation layer of a metal base substrate, methods other than cladding the aluminum plate 31 and the copper plate 32 It is also possible to use what was stuck together. Moreover, although the aluminum plate 31 and the copper plate 32 which comprise the clad material 30 demonstrated that both were plate shape, as long as the surface joined with the resin material 20 is a plane, another shape may be sufficient. . For example, in order to further enhance the heat dissipation, the surface of the clad material 30 where copper is exposed may have a projecting fin structure.

10 Copper foil (circuit layer)
20 Resin material (insulation layer)
30 clad material (heat dissipation layer)
31 Aluminum plate (aluminum material)
32 Copper plate (copper material)

Claims (2)

A circuit layer made of a conductor forming a circuit pattern;
An insulating layer bonded to the circuit layer and formed by thermosetting of a thermosetting resin;
A metal base substrate joined to a surface opposite to the surface joined to the circuit layer of the insulating layer and laminated with a heat dissipation layer made of metal,
The heat dissipation layer is
It is comprised by the clad material which the aluminum material which forms the surface joined to the said insulating layer, and the copper material which forms the open surface of the said thermal radiation layer joined,
Protruding fins are formed on the open surface of the copper material ,
The insulating layer is
It has a thermal conductivity of 2 to 12 W / (m · K) by adding an inorganic filler of alumina or silicon dioxide to enhance heat transfer,
A metal base substrate having a thickness of 50 to 200 μm .   The thickness of the said copper material is 70% or more of the thickness of the said thermal radiation layer, The metal base substrate of Claim 1 characterized by the above-mentioned.

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