JP2007067228A - Circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board which is suitable to carry a semiconductor device generating a large amount of heat, such as power element, etc., and there is no need to provide a radiating board or heat spreader, thus enables reduction in the number of components in assembling a module. <P>SOLUTION: The circuit board 10 is made by forming a wiring layer 12 on a board 11, having waste heat function via an insulating layer 13. The wiring layer 12 has a thermal expansion coefficient that is larger than that of a silicon semiconductor chip and smaller than that of copper. A semiconductor device 15, etc., are mounted on the surface of wiring layer 12 that is located opposite to the insulating layer 13 via solder 14. The board 11 is made of an aluminum-based metal, and has a cooling medium channel through which a cooling medium flows. The wiring layer 12 is constituted of an AlSiC section 12a as an AlSiC-based composite material section, and aluminum layers 12b, 12c which are formed on both the faces of the AlSiC 12a across the AlSiC 12a section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a circuit board on which, for example, a semiconductor device or an electronic component is mounted.

  A heat sink is generally used to dissipate heat generated from a semiconductor device or electronic component mounted (mounted) on a circuit board. When the heat sink is made of metal, the difference in thermal expansion coefficient between the metal and the semiconductor device or the like is large, and the thermal cycle life is shortened. Therefore, a ceramic circuit board with a heat sink provided with a heat sink made of an AlSiC-based composite material has been proposed (for example, see Patent Document 1). In Patent Document 1, first and second aluminum plates are laminated and bonded to both surfaces of a ceramic substrate via an Al—Si brazing material, and a heat sink formed of an AlSiC composite material is laminated and bonded to the surface of the first aluminum plate. Is done. The second aluminum plate becomes a circuit having a predetermined pattern by etching.

In addition, a multilayer printed wiring board that has excellent connection reliability with a small and thin electronic component and can be mounted at high density has been proposed (for example, see Patent Document 2). The multilayer printed wiring board of Patent Document 2 uses a printed circuit board constituted by an insulating substrate made of a mixture of secondary materials such as fibers and particles and a synthetic resin, and a pattern provided on the surface of the insulating substrate. A plurality of substrates are stacked. And the pattern of at least the outermost layer in the multilayer printed wiring board is made of a metal having a smaller thermal expansion coefficient than the insulating substrate. Examples of the metal include 42 alloy, Kovar, copper-invar-copper alloy, and stainless steel.
JP-A-10-65075 (paragraphs [0016] and [0017] in FIG. 1, FIG. 1) JP-A-7-106770 (paragraphs [0015] to [0017] in FIG. 1, FIG. 1)

  However, the configuration of Patent Document 1 requires a heat sink in addition to the substrate (ceramic substrate), which increases the number of components. Further, in a circuit board provided with a heat sink in this way, heat radiation from the heat sink is sufficient when the amount of heat generated from a semiconductor device or an electronic component mounted on the circuit board is small. However, when the amount of heat is large, it is necessary to connect the heat sink to a cooling unit having a higher cooling function. Examples of the cooling unit having a high cooling function include a case and a block having a passage through which a cooling medium is forced. In that case, the heat sink is fixed to the case or the like with screws. At that time, a grease layer is interposed in order to fill up the unevenness of the opposing surfaces of the heat sink and the case. The thermal conductivity of grease is as low as about 0.8 W / (mK), and the thermal resistance between the heat sink and the cooling unit increases, which is an obstacle to increasing the current of semiconductor devices and the size of modules. .

  Further, Patent Document 2 discloses that a metal pattern having a smaller thermal expansion coefficient than that of an insulating substrate is provided on the surface of the substrate, but the object is to reduce the difference in thermal expansion coefficient, and to dissipate heat. No consideration is given to sex. For example, 42 alloy and Kovar have a heat conductivity of about 10 W / (mK), and thus the heat dissipation becomes worse.

  The present invention has been made in view of the above-described conventional problems, and its purpose is suitable for mounting a semiconductor device that generates a large amount of heat, such as a power element, for example, and it is necessary to provide a heat sink and a heat spreader. It is an object of the present invention to provide a circuit board that can reduce the number of components when assembling a module.

  In order to achieve the above object, according to the present invention, a wiring layer made of a metal composite material having a thermal expansion coefficient larger than that of a silicon semiconductor chip and smaller than copper is provided on a substrate having a waste heat function via an insulating layer. Is provided. Here, “having a waste heat function” means not only heat dissipation but also a function of forcibly removing heat by a cooling medium or the like. The “metal composite material” means not a single metal element but a composite of a plurality of metals or metals and ceramics.

  In the present invention, since the substrate itself provided with the wiring layer has a waste heat function, the heat generated from the semiconductor device or electronic component mounted on the wiring layer via the solder provides the heat sink or the heat spreader. Therefore, the semiconductor device mounted on the substrate can be increased in current and the module can be easily downsized. In addition, since the thermal expansion coefficient of the wiring layer as a whole is larger than that of the silicon semiconductor chip and smaller than that of copper, the difference in thermal expansion coefficient between the semiconductor device and the wiring layer is smaller than before, and the life of the cooling cycle is increased. The reliability of the solder connection portion is improved.

  According to a second aspect of the present invention, in the first aspect of the present invention, the wiring layer has a thickness that changes in accordance with a coefficient of thermal expansion of a component mounted on the wiring layer. In this invention, since the thermal expansion coefficient of the material constituting the wiring layer becomes smaller as the thickness of the wiring layer increases, the thermal expansion coefficient is partially different by partially changing the thickness of the wiring layer. A wiring layer is obtained. On the other hand, the thermal expansion coefficients of the semiconductor device and the electronic component mounted on the wiring layer differ depending on objects. Therefore, if the thickness of the wiring layer is changed in accordance with the thermal expansion coefficient of the component mounted on the wiring layer, it is possible to further suppress an excessive force from being applied to the solder connection portion in the thermal cycle. .

The invention according to claim 3 is the invention according to claim 1 or 2, wherein the wiring layer has a thermal conductivity of 30 W / (mK) or more.
If the thermal conductivity of the wiring layer is lower than the thermal conductivity of the solder, it is difficult for heat generated from a semiconductor device or the like mounted on the wiring layer to be transmitted to the substrate side in the wiring layer portion. Since the thermal conductivity of the solder is about 30 W / (mK), in the present invention, the thermal conductivity of the wiring layer becomes higher than the thermal conductivity of the solder, and the wiring layer is suppressed from becoming a heat transfer bottleneck.

The invention according to claim 4 is the invention according to any one of claims 1 to 3,
The said wiring layer is the structure by which the copper layer was arrange | positioned on both surfaces on both sides of the composite part of copper and Invar. Here, Invar is an alloy of 36% by weight of Ni (nickel) and substantially the remainder of Fe (iron). The composite part of copper and Invar is not a structure in which a copper layer and an Invar layer are simply stacked, but a copper region and an Invar region exist in the same layer, and the Invar region is continuous. The copper region means a structure divided into a number of regions. Therefore, the thermal expansion coefficient and thermal conductivity of the composite part of copper and invar vary depending on the area ratio between the copper region and the invar region. In this invention, it becomes easy to set the thermal expansion coefficient and the thermal conductivity of the wiring layer to appropriate values corresponding to the semiconductor device, electronic component, etc. mounted on the wiring layer.

The invention according to claim 5 is the invention according to any one of claims 1 to 3,
The wiring layer has a configuration in which an aluminum layer is disposed on both sides of an AlSiC composite material portion. In this invention, it becomes easy to set the thermal expansion coefficient and the thermal conductivity of the wiring layer to appropriate values corresponding to the semiconductor device, electronic component, etc. mounted on the wiring layer.

The invention according to claim 6 is the invention according to any one of claims 1 to 5,
The substrate includes a cooling medium passage through which a cooling medium flows. In the present invention, heat is removed from the substrate by the cooling medium flowing through the cooling medium passage, the heat of the wiring layer is efficiently transferred to the substrate, and the cooling efficiency of the semiconductor device or electronic component mounted on the wiring layer is improved. .

  According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the cooling medium passage is formed so as to be able to communicate with a cooling medium circulation path installed in a vehicle. For example, when the circuit board of the present invention is used for in-vehicle use, the circuit board is connected to a cooling medium circulation path installed in a vehicle, and the cooling medium flowing through the cooling medium circulation path flows through the cooling medium passage of the board. . Therefore, it is not always necessary to provide a cooling medium circulation pump dedicated to the circuit board.

The invention according to claim 8 is the invention according to any one of claims 1 to 7,
The insulating layer is made of a resin having an adhesive function. In the present invention, the substrate and the wiring layer can be easily joined.

  According to the present invention, for example, it is suitable for mounting a semiconductor device or the like that generates a large amount of heat like a power element, and it is not necessary to provide a heat sink or a heat spreader, and the number of components when assembling a module can be reduced. .

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1A, the circuit board 10 is provided with a wiring layer 12 via an insulating layer 13 on a substrate 11 having a waste heat function. The wiring layer 12 is formed with a smaller coefficient of thermal expansion than a metal (for example, copper or aluminum) conductor pattern generally used for circuit boards. Active components such as a semiconductor device (semiconductor chip) 15 and passive components (not shown) such as a chip resistor and a chip capacitor are mounted on a surface of the wiring layer 12 opposite to the insulating layer 13 via a solder 14 ( Installed). The semiconductor device 15 is connected to the circuit pattern with an aluminum wire (not shown). Although a plurality of semiconductor devices 15 are mounted, only one is shown for convenience of illustration.

  The substrate 11 is made of an aluminum-based metal and includes a cooling medium passage 16 through which a cooling medium flows as shown in FIG. An aluminum-based metal means aluminum or an aluminum alloy. The cooling medium passage 16 includes an inlet portion 16a and an outlet portion 16b, and a plurality of passages 16c are provided between the inlet portion 16a and the outlet portion 16b. Each passage 16c is partitioned by a partition 16d extending in parallel. Pipes 17a and 17b are cast into the inlet portion 16a and the outlet portion 16b. The pipes 17a and 17b are formed so as to be connectable to a cooling medium circulation path equipped in the vehicle. The substrate 11 has a thickness of about 10 mm.

  The wiring layer 12 is generally formed of a metal composite material having a smaller coefficient of thermal expansion than a metal conductor pattern used on a circuit board. Specifically, the aluminum layers 12b and 12c are arranged on both sides of the AlSiC portion 12a as the AlSiC-based composite material portion. The AlSiC portion 12a is formed by, for example, adding an inorganic binder to silicon carbide (SiC) powder, mixing the mixture, forming the mixture, and forming molten aluminum (Al) into a sintered body obtained by firing the obtained formed product. It is formed by injecting under pressure in a mold. The AlSiC part 12a has different volume ratios between SiC and Al depending on the particle size, filling rate, and the like of the SiC powder used, and has different physical properties such as a thermal expansion coefficient and a thermal conductivity. In the wiring layer 12, an aluminum plate having a desired thickness to be the aluminum layers 12b and 12c is disposed so as to sandwich the AlSiC portion 12a having a desired thickness, and heated to the melting temperature of aluminum in a pressurized state to be the AlSiC portion 12a. By laminating and bonding the aluminum plate to each other, the wiring layer 12 made of a metal composite material having a coefficient of thermal expansion larger than that of the silicon semiconductor chip as a whole and smaller than that of copper is formed.

The thermal expansion coefficient of the wiring layer 12 can be changed in a wide range by changing the overall thickness or the thickness of the AlSiC portion 12a and the aluminum layers 12b and 12c. For example, as shown in FIG. 1B, with reference to the wiring layer 12 in which the thickness t1 of the AlSiC portion 12a is 3.0 mm and the thicknesses t2 and t3 of the aluminum layers 12b and 12c are 0.4 mm, respectively. When the overall thickness is changed without changing the ratio of the thickness t1 and the thicknesses t2 and t3, the relationship between the thickness of the wiring layer 12 and the thermal expansion coefficient is as shown in FIG. The thermal expansion coefficient of the wiring layer 12 can be freely changed from 6.5 × 10 ^{−6 to} 25 × 10 ⁻⁶ / ° C. within a thickness range of 100 μm to 5000 μm. In addition, in FIG. 3, E-06 attached | subjected after the number which shows the value of the thermal expansion coefficient of a vertical axis | shaft means * 10 <^-6> , and E-05 means * 10 <^-5> . The value of the thermal expansion coefficient of the silicon semiconductor chip is 2.6 × 10 ⁻⁶ / ° C., and the value of the thermal expansion coefficient of copper is 17.5 × 10 ⁻⁶ / ° C.

In this embodiment, the wiring layer 12 has a thickness of 2.5 mm, a thermal expansion coefficient of 10.5 × 10 ⁻⁶ / ° C., and a thermal conductivity of 240 W / (mK). Yes. In other words, the wiring layer 12 has a thermal expansion coefficient larger than that of the silicon semiconductor chip and smaller than that of copper. The wiring layer 12 is formed with a thermal conductivity of 30 W / (mK) or more.

The insulating layer 13 is made of a resin having an adhesive function. In this embodiment, an epoxy resin is used for the insulating layer 13 and is filled with an aluminum filler in order to increase the thermal conductivity. The insulating layer 13 has a thickness of, for example, 120 μm, a thermal expansion coefficient of 58 × 10 ⁻⁶ / ° C., and a thermal conductivity of about 5 W / (mK).

  Next, a method for manufacturing the circuit board 10 configured as described above will be described. The substrate 11 is formed by casting aluminum using a core corresponding to the shape of the cooling medium passage 16. The wiring layer 12 is formed in the shape of a circuit pattern, and an AlSiC plate serving as the AlSiC portion 12a corresponding to a desired thickness and an aluminum plate serving as the aluminum layers 12b and 12c are laminated and heated in a pressurized state. To be formed. The aluminum layer 12b disposed so as to face the insulating layer 13 is subjected to alumite treatment.

  On the substrate 11 formed as described above, an uncured epoxy resin in which an aluminum filler is dispersed is applied. In a state where the epoxy resin is semi-cured, the wiring layer 12 is arranged so that one aluminum layer 12b faces the epoxy resin layer, and the epoxy resin layer is thermally cured by heat pressing. Since the aluminum layer 12b facing the insulating layer 13 is anodized, the wiring layer 12 is firmly bonded to the insulating layer 13 by an anchor effect. Next, the semiconductor device 15 and passive components (not shown) are mounted on the wiring layer 12 via the solder 14 to complete the circuit board 10.

  Next, the operation of the circuit board 10 configured as described above will be described. FIG. 2 is a schematic diagram showing the relationship between the substrate 11 and the cooling medium circulation path 18. The portion above the insulating layer 13 is not shown. As shown in FIG. 2, the circuit board 10 is used by being connected to a cooling medium circulation path 18 through pipes 17a and 17b. The cooling medium circulation path 18 is provided with a pump 19 and a radiator 20, and the radiator 20 is provided with a fan 22 that is rotated by a motor 21 so that heat radiation from the radiator 20 is efficiently performed. For example, water is used as the cooling medium.

  When the semiconductor device 15 mounted on the circuit board 10 is driven and heat is generated from the mounted components, the heat is transmitted to the substrate 11 via the solder 14, the wiring layer 12, and the insulating layer 13. Since the substrate 11 is forcibly cooled by the cooling medium flowing through the cooling medium passage 16, the temperature gradient in the heat transfer path from the semiconductor device 15 or the like to the substrate 11 increases, and the heat generated in the semiconductor device 15 or the like is efficiently generated. It is removed from the substrate 11.

  Since the thermal conductivity of the insulating layer 13 is an order of magnitude higher than that of grease, the thermal resistance is higher than that of a configuration in which a heat sink is fixed to a cooling portion having a high cooling function via grease as in the prior art. Becomes smaller. Therefore, even if a large current is passed through the semiconductor device 15 and heat generation is increased, the heat is efficiently removed, so that the temperature of the semiconductor device 15 is prevented from becoming abnormally high, and the current of the semiconductor device 15 is increased. It becomes possible.

The components mounted on the wiring layer 12 include a chip resistor and a chip capacitor in addition to the semiconductor device 15. The thermal expansion coefficient of the silicon semiconductor chip is 2.6 × 10 ⁻⁶ / ° C., the thermal expansion coefficient of the chip resistor is about 7 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the chip capacitor is 10 × 10 ^−6. The thermal expansion coefficient of the wiring layer 12 is 10.5 × 10 ⁻⁶ / ° C. whereas it is about / ° C. Therefore, compared with the case where the wiring layer is made of a metal such as copper or aluminum, the difference in thermal expansion coefficient between the mounted component such as the semiconductor device 15 and the wiring layer 12 is used between the mounted component and the circuit board in general. The difference in thermal expansion coefficient with the metal conductor pattern is reduced, and the stress applied to the connection portion of the solder 14 in the cooling cycle is reduced. Therefore, the life of the thermal cycle is prolonged and the reliability of the solder connection portion is improved.

  When the circuit board 10 is used for in-vehicle use, for example, when an in-vehicle inverter device is configured and provided in an engine room or the like, it is necessary to efficiently remove heat generated from the semiconductor device 15 or the like. In the circuit board 10 of this embodiment, the heat generated from the semiconductor device 15 and the like is efficiently removed by the cooling medium flowing through the cooling medium passage 16 as described above. Further, when equipped in a vehicle, since the vehicle is provided with a cooling medium circulation path used for cooling the engine or the like, the cooling medium passage 16 communicates with the cooling medium circulation path of the vehicle via the pipes 17a and 17b. In this case, it is not always necessary to provide a cooling medium circulation pump dedicated to the circuit board 10.

This embodiment has the following effects.
(1) On a substrate 11 having a waste heat function, a wiring layer 12 made of a metal composite material having a thermal expansion coefficient smaller than that of a metal conductor pattern generally used for a circuit board is provided via an insulating layer 13. . Accordingly, the heat generated from the semiconductor device 15 and electronic components mounted on the wiring layer 12 via the solder 14 is efficiently removed without providing a heat sink or a heat spreader, and the semiconductor device mounted on the substrate 11. Therefore, it is easy to increase the current of 15 and downsize the module. Further, since the overall thermal expansion coefficient of the wiring layer 12 is smaller than that of a metal conductor pattern generally used for circuit boards, the difference in thermal expansion coefficient between the semiconductor device 15 and the wiring layer 12 is different from that of the semiconductor device 15. The difference in thermal expansion coefficient with the metal conductor pattern is smaller, the life of the cooling / heating cycle becomes longer, and the reliability of the solder connection portion is improved.

  (2) The wiring layer 12 has a thermal expansion coefficient larger than that of the silicon semiconductor chip and smaller than that of copper. Therefore, the wiring layer 12 in which the difference in thermal expansion coefficient between the semiconductor device 15 and the wiring layer 12 is smaller than the difference in thermal expansion coefficient between the semiconductor device 15 and a metal conductor pattern generally used in a circuit board can be easily formed. Can be manufactured.

  (3) Since the wiring layer 12 has a thermal conductivity of 240 W / (mK) and is larger than the thermal conductivity of solder (about 30 W / (mK)), it is generated from the semiconductor device 15 or the like mounted on the wiring layer 12. Thus, it is possible to prevent the heat from being transmitted to the substrate 11 side at the wiring layer 12 portion.

  (4) The wiring layer 12 has a configuration in which aluminum layers 12b and 12c are arranged on both sides of the AlSiC portion 12a. Therefore, it becomes easy to set the thermal expansion coefficient and the thermal conductivity of the wiring layer 12 to appropriate values corresponding to the semiconductor device 15 and electronic components mounted on the wiring layer 12.

  (5) The substrate 11 includes a cooling medium passage 16 through which the cooling medium flows. Therefore, heat is removed from the substrate 11 by the cooling medium flowing through the cooling medium passage 16, and the heat of the wiring layer 12 is efficiently transferred to the substrate 11, so that the cooling efficiency of the semiconductor device 15 and electronic components mounted on the wiring layer 12 is improved. Will improve.

(6) Since water is used as the cooling medium, the heat of the substrate 11 can be removed efficiently at low cost.
(7) The cooling medium passage 16 is formed to be able to communicate with a cooling medium circulation path installed in the vehicle. When the circuit board 10 is used for in-vehicle use, for example, when an in-vehicle inverter device is configured and provided in an engine room or the like, it is necessary to efficiently remove heat generated from the semiconductor device 15 or the like. At that time, the cooling medium flowing through the cooling medium circulation path equipped in the vehicle can be used in a state where it flows through the cooling medium passage 16 of the substrate 11, and it is necessary to provide a cooling medium circulation pump dedicated to the circuit board 10. Absent.

(8) The insulating layer 13 is formed of a resin having an adhesion function. Therefore, it becomes easier to bond the substrate 11 and the wiring layer 12 than when ceramics are used.
(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. 2 and 4 to 7. This embodiment is different from the first embodiment in that the configuration of the wiring layer is changed, and other configurations are the same. Therefore, the same parts are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 4, the circuit board 10 has a wiring layer 30 provided on a substrate 11 with an insulating layer 13 interposed therebetween. The wiring layer 30 is formed with a smaller coefficient of thermal expansion than a metal (for example, copper or aluminum) conductor pattern generally used for circuit boards. Active components such as a semiconductor device (semiconductor chip) 15 and passive components (not shown) such as a chip resistor and a chip capacitor are mounted on the surface of the wiring layer 30 opposite to the insulating layer 13 via a solder 14 ( Installed). The semiconductor device 15 is connected to the circuit pattern with an aluminum wire (not shown). As shown in FIG. 2, the substrate 11 includes a cooling medium passage 16 similar to that of the first embodiment, and pipes 17a and 17b are cast into the inlet portion 16a and the outlet portion 16b. The pipes 17a and 17b are formed so as to be connectable to a cooling medium circulation path equipped in the vehicle.

  As shown in FIGS. 5A and 5B, the wiring layer 30 is composed of a composite material 31 in which a copper layer 31b is disposed on both sides of a composite portion 31a of copper and invar. The composite material 31 is formed by rolling and joining an expanded metal 32 formed of invar sandwiched between copper plates. Specifically, the composite material 31 is formed by integrating the copper plate and the expanded metal 32 by heating and rolling with a rolling roll while the expanded metal 32 is disposed between the copper plates. By combining the expanded metal 32 and the copper plate, a composite material 31 composed of the expanded metal 32 and the copper of the matrix metal 33 surrounding the expanded metal 32 is formed. As a result, a wiring layer 30 made of a metal composite material having a larger coefficient of thermal expansion than that of the silicon semiconductor chip and smaller than that of copper is formed.

  As shown in FIG.5 (c), when the thickness of the composite material 31 after rolling and joining is set to t11 and the thickness of the part of the expanded metal 32 is set to t12, (t12) / (t11) is 0.2- The thickness of the expanded metal 32 before rolling and joining, the thickness of the copper plate, and the rolling rate are set so as to be 0.8.

  Further, the composite material 31 is not limited to the configuration in which the composite portion 31a is a single layer, and the composite portion 31a may have a plurality of layers, for example, as shown in FIG. The composite material 31 having a composite part 31a having two layers is formed by rolling and joining three copper plates and two expanded metals 32 alternately stacked.

The thermal expansion coefficient of the wiring layer 30 can be changed in a wide range by changing the overall thickness or the thickness of the composite portion 31a and the copper layer 31b. 7 shows that the thickness of the aluminum heat sink (substrate 11) in FIG. 4 is 4 mm, the Young's modulus is 77 GPa, the thermal expansion coefficient is 25 × 10 ⁻⁶ / ° C., and the thickness of the insulating resin (insulating layer 13) is 0. 12 mm, Young's modulus 530 MPa, the thermal expansion coefficient of 25 × ^{10 -6} / ℃, the Young's modulus of the wiring layers 30 110 GPa, the thermal expansion coefficient of 11.5 × ^{10 -6} /℃,8.5×10 ^-6 / ℃ The graph shows the thermal expansion coefficient value of the upper surface of the wiring layer 30 (the bonding interface between the wiring layer 30 and the solder 14) when the thickness of the wiring layer 30 is changed from 100 to 5000 μm.

In the case of the three-layer product shown in FIG. 5B, the thermal expansion coefficient of the wiring layer 30 is 8.0 × 10 ^{−6 to} 23.5 × 10 ⁻⁶ / ° C. in the thickness range of 100 μm to 5000 μm. When the thickness of the wiring layer 30 is 2000 μm, the thermal expansion coefficient is 11.5 × 10 ⁻⁶ / ° C. and the thermal conductivity is 168 W / (mK). Further, in the case of the five-layer product shown in FIG. 6, the thermal expansion coefficient of the wiring layer 30 is free up to 4.0 × 10 ^{−6 to} 23.0 × 10 ⁻⁶ / ° C. in the thickness range of 100 μm to 5000 μm. When the thickness of the wiring layer 30 is 2000 μm, the thermal expansion coefficient is 8.5 × 10 ⁻⁶ / ° C., and the thermal conductivity is 70 W / (mK).

  The manufacturing method of the circuit board 10 configured as described above is the first implementation in that the wiring layer 30 is used in place of the wiring layer 12 and the adhesion between the wiring layer 30 and the insulating layer 13 is increased. The point from which the blackening process with respect to the copper layer 31b is performed corresponding to the alumite process with respect to the aluminum layer 12b in a form differs from 1st Embodiment. Thereby, the wiring layer 30 is firmly bonded to the insulating layer 13 by the anchor effect. The wiring layer 30 is also different from the first embodiment in that the wiring layer 30 is provided on the substrate 11 via the insulating layer 13 and then formed into a predetermined circuit pattern shape by etching.

  The circuit board 10 configured as described above is used in the same manner as the circuit board 10 of the first embodiment. The circuit board 10 of this embodiment has the following effects in addition to the same effects as the effects (1), (2), and (5) to (8) in the first embodiment.

  (9) Since the wiring layer 30 has a thermal conductivity higher than that of the solder (about 30 W / (mK)), heat generated from the semiconductor device 15 or the like mounted on the wiring layer 30 is generated by the wiring layer 30. It is avoided that the portion becomes difficult to be transmitted to the substrate 11 side, and the wiring layer 30 is prevented from becoming a heat transfer bottleneck.

  (10) The wiring layer 30 has a configuration in which the copper layer 31b is disposed on both surfaces with the composite portion 31a interposed therebetween. Therefore, it becomes easy to set the thermal expansion coefficient and the thermal conductivity of the wiring layer 30 to appropriate values corresponding to the semiconductor device 15 and electronic components mounted on the wiring layer 30.

(11) Since the wiring layer 30 is a metal composite material, it can be formed into a circuit pattern by etching, and processing into a circuit pattern is easier than in the first embodiment.
The embodiment is not limited to the above, and may be configured as follows, for example.

  The thickness of the wiring layers 12 and 30 is not limited to a constant thickness, and the thickness varies in accordance with the thermal expansion coefficient of the semiconductor device 15 and electronic components mounted on the wiring layers 12 and 30. It is good also as a structure. Since the thermal expansion coefficient of the material constituting the wiring layers 12 and 30 decreases as the thickness of the wiring layers 12 and 30 increases, the portion corresponding to a part having a large thermal expansion coefficient corresponds to a part having a small thermal expansion coefficient. By partially changing the thickness of the wiring layers 12 and 30 so as to be thinner than the portion to be formed, the wiring layers 12 and 30 having partially different thermal expansion coefficients can be obtained. On the other hand, the thermal expansion coefficients of the semiconductor device 15 and electronic components mounted on the wiring layers 12 and 30 differ depending on the object. Therefore, if the thickness of the wiring layers 12 and 30 is changed in accordance with the thermal expansion coefficient of the components mounted on the wiring layers 12 and 30, an excessive force is applied to the solder connection portion in the thermal cycle. Is more suppressed.

  ○ When the wiring layers 12 and 30 are partially different in thickness, the thermal expansion coefficient is large instead of changing the thermal expansion coefficient corresponding to each component mounted on the wiring layers 12 and 30. It is good also as a structure which formed the part which has many components thinly compared with the part with many components with a small thermal expansion coefficient, and thickness changes in two steps.

  When changing the thermal expansion coefficient by changing the thickness of the wiring layers 12 and 30, the ratio between the thickness of the AlSiC portion 12a and the thickness of the aluminum layers 12b and 12c, or the thickness of the composite portion 31a and the thickness of the copper layer 31b It is good also as a structure which replaces with the structure which makes constant ratio and changes the thermal expansion coefficient by changing ratio of those thickness.

The AlSiC part 12a may be formed by pouring aluminum into the gap between the powders in a state where the powders before firing of SiC are pressed.
The insulating layer 13 is not limited to resin and may be formed of ceramics. Examples of the ceramic include AlN (aluminum nitride) and BN (boron nitride). In this case, since the thermal conductivity is higher than that of the resin, the thermal resistance in the insulating layer 13 is reduced, and the cooling efficiency is improved.

  The configuration of the cooling medium passage 16 provided in the substrate 11 is not limited to a configuration in which a plurality of passages 16c are formed in parallel using a core. For example, a cooling medium passage 16 may be formed by casting a pipe. The pipe is not limited to a single bent pipe, but a plurality of pipes are cast, or a pipe that is divided into a plurality of pipes in the middle and then assembled into a single pipe is cast again. You can do it. In this case, the substrate 11 provided with the cooling medium passage 16 can be manufactured more easily than the manufacturing method using the core.

The cooling medium flowing through the cooling medium passage 16 is not limited to water, but may be other liquids or gases.
The pipe is not limited to a configuration in which both ends project outward from the end surface on the same side of the substrate 11 but may be formed so as to project from a different end surface.

  ○ A heat pipe may be used as the pipe. When the heat pipe is used, the cooling medium is automatically circulated in the pipe, and the heat of the substrate 11 is efficiently released to the outside, so that it is not necessary to provide the cooling medium circulation path 18 and the entire configuration is simplified. .

  The wiring layer 12 may be made of a metal composite material having a thermal expansion coefficient larger than that of the silicon semiconductor chip and smaller than that of copper. For example, in the first embodiment, not only the combination of silicon carbide and an aluminum alloy, but also other ceramics having good thermal conductivity instead of silicon carbide fine particles, such as boron nitride (BN), magnesium oxide (MgO) In addition, molybdenum disilicide (MoSi2) may be used, and another metal having high thermal conductivity, such as copper, may be used instead of the aluminum alloy. In the second embodiment, the material of the expanded metal 32 is replaced with invar, and other invar type alloys such as super invar and stainless invar are used. Or an alloy thereof may be used.

The following technical idea (invention) can be understood from the embodiment.
(1) In the invention according to claim 6, the cooling medium passage is constituted by a heat pipe.

(A) is a schematic cross-sectional view of a circuit board, (b) is a partially enlarged cross-sectional view of a wiring layer. The schematic diagram which shows the relationship between a board | substrate and a cooling-medium circulation path. The graph which shows the relationship between the thickness of a wiring layer, and a thermal expansion coefficient. The schematic cross section of a circuit board. (A) is a schematic cross-sectional view of a composite part, (b) is a longitudinal cross-sectional view of a wiring layer having a three-layer structure, and (c) is a partially enlarged view of (b). The longitudinal cross-sectional view of the wiring layer of 5 layer structure. The graph which shows the relationship between the thickness of a wiring layer, and a thermal expansion coefficient.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Circuit board, 11 ... Board | substrate, 12, 30 ... Wiring layer, 12a ... AlSiC part as AlSiC type composite material part, 12b, 12c ... Aluminum layer, 13 ... Insulating layer, 16 ... Cooling medium channel | path, 18 ... Cooling medium Circuit, 31a ... composite part, 31b ... copper layer.

Claims (8)

  A circuit board in which a wiring layer made of a metal composite material having a thermal expansion coefficient larger than that of a silicon semiconductor chip and smaller than copper is provided on a substrate having a waste heat function via an insulating layer.   The circuit board according to claim 1, wherein the wiring layer has a thickness that changes in accordance with a coefficient of thermal expansion of a component mounted on the wiring layer.   The circuit board according to claim 1, wherein the wiring layer has a thermal conductivity of 30 W / (mK) or more.   The circuit board according to any one of claims 1 to 3, wherein the wiring layer has a configuration in which a copper layer is disposed on both sides of a composite part of copper and invar.   The circuit board according to any one of claims 1 to 3, wherein the wiring layer has a structure in which an aluminum layer is disposed on both sides of an AlSiC-based composite material portion.   The circuit board according to any one of claims 1 to 5, wherein the board includes a cooling medium passage through which a cooling medium flows.   The circuit board according to claim 6, wherein the cooling medium passage is formed to be able to communicate with a cooling medium circulation path installed in a vehicle.   The circuit board according to claim 1, wherein the insulating layer is formed of a resin having an adhesive function.

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