JP2007073904A - Circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board which is suitable for mounting a semiconductor device etc. generating heat much like a power element, which is more excellent in radiation property than a conventional technique, and where wiring layer is easily formed to be flat to improve reliability of a soldered part. <P>SOLUTION: The circuit board 10 is provided with wiring layers 12 on a board 11 through insulating layers 13. The board 11 is formed of insulating resin and provided with a cooling medium path 14, and coolers 16 made of aluminum-based metal are buried so as to constitute a part of the cooling medium path 14. The coolers 16 are provided with a plurality of cooling medium channels 16a extending in parallel to channels 14c, and flat parts 16b are formed at places corresponding to the wiring layers 12. For the insulating resin constituting the board 11, resin whose coefficient of thermal expansion is smaller than that of the cooling parts 16. The wiring layers 12 are provided at a plurality of places on the flat parts 16b of the respective cooling parts 16. <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.

In addition, as a printed wiring board (printed wiring board) having excellent heat dissipation and capable of forming a through hole, a printed wiring board having circuit forming conductors on both sides of an insulating layer made of a thermosetting resin cured product. Have proposed that a cooling device for passing a heat medium is embedded in the insulating layer (see Patent Document 1). As shown in FIG. 10A, the printed wiring board disclosed in Patent Document 1 includes a cooling device 52 embedded in an insulating layer 51, and circuit forming conductors (wiring layers) 53 on both surfaces of the insulating layer 51. Is provided. The cooling device 52 is formed, for example, by bending a pipe as shown in FIG. A through hole is formed in a portion of the insulating resin that exists between the flow paths 54 of the thermal refrigerant in the cooling device 52. The cured thermosetting resin constituting the insulating layer 51 can improve thermal conductivity and match the thermal expansion coefficient with the cooling device 52 by blending various fillers.
JP-A-5-299788 (paragraphs [0005] to [0008] of the specification, FIGS. 1 and 2)

  In the technique of Patent Document 1, since the printed wiring board includes the cooling device 52 through which the heat medium passes, the size can be reduced as compared with a configuration in which a heat sink is separately provided. Moreover, the heat dissipation excellent in comparison with the printed wiring board not including the heat sink can be obtained. However, in the configuration of Patent Document 1, the cooling device 52 transmits the heat from the conductor 53 to the outer surface of the pipe constituting the flow path 54 through the insulating layer 51, and then transmits the pipe to the heat medium. In this configuration, the transmitted heat is removed from the portion corresponding to the insulating layer 51 by the heat medium flowing through the flow path 54. Therefore, the heat dissipation (cooling) effect of the conductor 53 differs depending on the positional relationship between the conductor 53 and the tube, and the heat dissipation (cooling) effect of the portion far from the tube or the portion not facing the tube is lower than the portion close to the tube. Become. Further, when the thickness of the thinnest part of the insulating layer 51 existing between the conductor 53 and the tube is, for example, about several tens of μm, the surface of the insulating layer 51 facing the conductor 53 is formed at the time of molding. Difficult to form flat.

  The present invention has been made in view of the above-described conventional problems, and its purpose is suitable for mounting a semiconductor device or the like that generates a large amount of heat, such as a power element, and is superior in heat dissipation than the prior art, An object of the present invention is to provide a circuit board in which a wiring layer can be easily formed flat and the reliability of a solder connection portion is improved.

  In order to achieve the above object, the invention according to claim 1 is provided with a substrate in which a metal cooling portion having a cooling medium flow path is embedded with a resin, and a silicon semiconductor chip can be mounted on the substrate. It is a circuit board in which a wiring layer is provided via an insulating layer. The cooling part is formed with a flat part at least at a position corresponding to the wiring layer, and a resin having a thermal expansion coefficient smaller than that of the cooling part is used for the resin.

  In this invention, since the wiring layer is provided on the flat part constituting the cooling part via the insulating layer, the wiring layer is formed flat, that is, the distance between the wiring layer and the flat part is made constant. By making the distance constant or substantially constant, heat transfer from the wiring layer to the cooling unit becomes better than when the distance between the wiring layer and the cooling unit varies depending on the location. . In addition, the thermal expansion of the metal cooling unit is suppressed by the resin in which the cooling unit is embedded, and the life of the cooling cycle is prolonged, and a semiconductor device (silicon semiconductor chip) is mounted on the wiring layer via solder. This improves the reliability of the solder connection part.

  The invention according to claim 2 is the invention according to claim 1, wherein the resin in which the cooling portion is embedded and the insulating layer are made of the same insulating resin. Therefore, in the present invention, only one type of resin is necessary for the production of the insulating layer, and compared with the case where the insulating layer is formed of a resin different from the insulating resin in which the cooling portion is embedded, Storage becomes easy.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the wiring layer is provided at a plurality of locations on the common flat portion.
When a semiconductor device is mounted on a plurality of wiring layers and used, not all semiconductor devices operate at the same time. When a plurality of wiring layers are provided on a common flat part, the heat of the wiring layer on which the semiconductor device generating heat is mounted is transmitted to the part corresponding to the other wiring layer and cooled. Since the cooling action is received at the part, the heat dissipation (cooling effect) is improved.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the cooling medium flow path is provided so as to extend along an arrangement direction of the wiring layers provided at the plurality of locations. When there are a plurality of cooling medium flow paths and a plurality of wiring layers are arranged so as to correspond to different paths, some semiconductor devices mounted on the wiring layers are partially heated, The cooling medium flowing through the cooling medium flow path flows with little contribution to cooling. However, in the present invention, all the cooling medium flowing through the cooling medium flow path flows in a state that contributes to cooling.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the cooling part is made of an aluminum-based metal. Here, “aluminum-based metal” means aluminum or an aluminum alloy. Aluminum-based metals are inferior to gold, silver, and copper in thermal conductivity, but are higher than iron and magnesium, excellent in workability, light weight, and low cost. Therefore, in this invention, a lightweight circuit board can be manufactured easily and inexpensively.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the wiring layer is made of a metal composite material having a thermal expansion coefficient larger than that of the silicon semiconductor chip and smaller than copper. is there. Here, the “metal composite material” means not a single metal element but a composite of a plurality of metals or metals and ceramics. Since the wiring layer as a whole has a thermal expansion coefficient larger than that of the silicon semiconductor chip and smaller than copper, the difference in the thermal expansion coefficient between the semiconductor device and the wiring layer is smaller than when the wiring layer is formed of copper or aluminum, The life of the cooling / heating cycle becomes longer, and the reliability of the solder connection portion is further improved.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, 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.

  According to the present invention, it is suitable for mounting a semiconductor device or the like that generates a large amount of heat like a power element, has better heat dissipation than the prior art, and it is easy to form a wiring layer flatly and the reliability of the solder connection part The circuit board which improves can be provided.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1A to 1C, the circuit board 10 is provided with a wiring layer 12 on an insulating layer 13 on a substrate 11. The substrate 11 is formed of a resin (insulating resin in this embodiment) and includes a cooling medium passage 14. The cooling medium passage 14 is formed in a rectangular shape in cross section, and includes an inlet portion 14a and an outlet portion 14b, branches from the inlet portion 14a and branches into two flow paths 14c, and then gathers together again. It is formed to be continuous with the outlet portion 14b. Pipes 15a and 15b are cast into the inlet portion 14a and the outlet portion 14b. The pipes 15a and 15b are formed so as to be connectable to a cooling medium circulation path equipped in the vehicle.

  A metal cooling section 16 is embedded in each flow path 14 c so as to constitute a part of the cooling medium passage 14. In this embodiment, the cooling unit 16 is made of an aluminum-based metal. An aluminum-based metal means aluminum or an aluminum alloy. The cooling unit 16 includes a plurality of cooling medium channels 16a having a cross-sectional area smaller than that of the channel 14c and extending in parallel with the channel 14c, and a flat portion 16b is formed at a location corresponding to the wiring layer 12. . A flat portion 16c is also formed on the side opposite to the portion corresponding to the wiring layer 12.

  As the insulating resin constituting the substrate 11, a resin having a thermal expansion coefficient smaller than that of the cooling unit 16 is used. The insulating resin is adjusted so that the thermal expansion coefficient is smaller than that of the cooling unit 16 (in this embodiment, an aluminum-based metal) by mixing (filling) ceramic particles or fibers with a filler. Examples of the filler material include glass, alumina, silicon nitride, and boron nitride.

  The wiring layer 12 is provided at a plurality of locations on the flat portion 16 b of each cooling unit 16. That is, the cooling medium flow path 16a is provided so as to extend along the arrangement direction of the wiring layers 12 provided at a plurality of locations. The wiring layer 12 is generally made of metal (copper in this embodiment) used on a circuit board, and a semiconductor as a silicon semiconductor chip is disposed on a surface of the wiring layer 12 opposite to the insulating layer 13 via a solder 17. A device (semiconductor chip) 18 is mounted (mounted). The semiconductor device 18 is connected to the wiring layer 12 with an aluminum wire (not shown).

  The insulating layer 13 is filled with a ceramic filler that is insulative and has a higher thermal conductivity than the resin in order to increase the thermal conductivity. Further, when the semiconductor device 18 is mounted on the wiring layer 12 via the solder 17, the melting point is 100 ° C. or higher when a thermoplastic resin is used so that the insulating layer 13 is not melted by the heat generated when the solder 17 is melted. (For example, polyamide and polyester) are used. In this embodiment, the resin in which the cooling unit 16 is embedded and the insulating layer 13 are made of the same insulating resin.

  The substrate 11 is formed with a thickness of about 10 mm. The insulating layer 13 is formed to have a thickness of 10 to 300 μm, preferably 20 to 100 μm, because the insulating layer 13 has poor pressure resistance when it is thin, and heat conduction (heat transfer) becomes poor when it is thick. Since the wiring layer 12 is made of copper whose thermal conductivity is sufficiently larger than the thermal conductivity of solder, its thickness is set to an appropriate thickness according to the magnitude of the maximum current flowing through the wiring layer 12.

  Each drawing schematically shows the configuration of the circuit board 10 and the like. For convenience of illustration, some dimensions are exaggerated for easy understanding, so that the width and length of each part are shown. The ratio of dimensions such as thickness is different from the actual ratio. The same applies to other embodiments.

  Next, a method for manufacturing the circuit board 10 configured as described above will be described. The cooling unit 16 is formed by, for example, extrusion molding. Alumite treatment is applied to the outer surface of the formed cooling section 16. As shown in FIG. 3, the cooling unit 16 is placed in a state where the flat portion 16 b is exposed by resin injection molding or transfer molding by placing the cooling unit 16 whose outer surface is anodized at a predetermined position in the mold. A molded product 19 in a state of being cast into is formed. When a thermoplastic resin is used as the resin, injection molding is performed, and when a thermosetting resin is used as the resin, transfer molding is performed. Since the outer surface of the cooling unit 16 is anodized, the resin is firmly bonded to the outer surface of the cooling unit 16 by an anchor effect.

  Next, in order to form the insulating layer 13 in the portion where the flat portion 16b of the molded product 19 is exposed, as shown in FIG. 3, the sheet 20 is disposed so as to face the flat portion 16b, and the sheet 20 is formed by a hot press. Affix. When the sheet 20 is made of a thermoplastic resin, the sheet 20 is simply attached to the flat portion 16b with a heating press. When the sheet 20 is made of a thermosetting resin, a semi-cured sheet is used as the sheet 20 and is attached to the flat portion 16b with a heating press. Thereby, formation of the board | substrate 11 with which the metal cooling part 16 provided with the cooling-medium flow path 16a was embed | buried with insulating resin is completed.

  Next, the wiring layer 12 is formed at a predetermined position on the sheet 20 as the insulating layer 13. The wiring layer 12 is formed by a method used for manufacturing a MID (Molded Interconnect Device), for example, a method in which a copper plate (copper foil) is heated and pressed (hot stamping), or a copper plate (copper foil) is attached by punching press. A method of attaching (IVONDING method), a method of forming a wiring layer by plating, and the like are employed. In this embodiment, a copper plate formed in the shape of the wiring layer 12 is bonded by a hot press. At that time, at least a surface of the copper plate facing the sheet 20 is subjected to blackening treatment. Since the copper plate is blackened, the wiring layer 12 is firmly bonded to the sheet 20 (insulating layer 13) by an anchor effect. Thereby, the manufacture of the circuit board 10 before the semiconductor device 18 is mounted is completed.

  Next, the semiconductor device 18 and passive parts (not shown) such as a chip resistor and a chip capacitor are mounted on the wiring layer 12 via the solder 17 to complete the circuit board 10 on which the semiconductor device 18 is mounted.

  Next, the operation of the circuit board 10 configured as described above will be described. The circuit board 10 is used in communication with a cooling medium circulation path (not shown) through pipes 15a and 15b. The cooling medium circulation path is provided with a pump and a radiator, and the radiator includes a fan that is rotated by a motor so that heat is efficiently radiated from the radiator. For example, water is used as the cooling medium.

  When the semiconductor device 18 mounted on the circuit board 10 is driven and heat is generated from the mounted components, the heat is transmitted to the cooling unit 16 via the solder 17, the wiring layer 12, and the insulating layer 13. The heat transferred to the cooling unit 16 is transferred to the cooling medium flowing through the cooling medium flow path 16a and taken away. That is, since the substrate 11 is forcibly cooled by the cooling medium flowing through the cooling medium flow path 16a, the temperature gradient in the heat transfer path from the semiconductor device 18 or the like to the substrate 11 increases, and the heat generated in the semiconductor device 18 or the like. Is efficiently removed through the substrate 11.

  The wiring layer 12 is provided on the flat portion 16b constituting the cooling unit 16 via the insulating layer 13, and since the distance between the wiring layer 12 and the flat portion 16b is substantially constant, the flat portion 16b is not provided. Compared with the case where the distance between the wiring layer 12 and the cooling unit 16 differs depending on the location, heat transfer from the wiring layer 12 to the cooling unit 16 is improved. In addition, the thermal expansion of the metal cooling unit 16 is suppressed by the insulating resin in which the cooling unit 16 is embedded, and the life of the cooling cycle is extended, and the semiconductor device 18 and the like are provided on the wiring layer 12 via the solder 17. The reliability of the solder connection portion when mounting is improved.

  When a plurality of wiring layers 12 are provided on the substrate 11 and the semiconductor device 18 is mounted on each wiring layer 12 and used, not all the semiconductor devices 18 operate at the same time. When the semiconductor device 18 generates heat, the heat generation is greatest at the center, and the heat is transmitted to the solder 17 and the wiring layer 12, and is transmitted from the wiring layer 12 to the cooling unit 16 through the insulating layer 13. The thermal conductivity of the insulating layer 13 is an order of magnitude smaller than the thermal conductivity of the wiring layer 12 and the cooling unit 16. Since the plurality of wiring layers 12 are provided on the common flat portion 16b, the flat portion 16b is moved to a place where the heat of the wiring layer 12 on which the semiconductor device 18 that generates heat is mounted corresponds to the other wiring layers 12. Since it transmits and receives a cooling action in a cooling part, heat dissipation (cooling effect) improves.

  Since the thermal conductivity of the insulating layer 13 is an order of magnitude higher than the thermal conductivity of the grease, the thermal resistance is lower than that of the configuration in which the heat sink is fixed to the cooling portion having a high cooling function via the grease. Therefore, even if a large current is passed through the semiconductor device 18 and heat generation increases, the heat is efficiently removed, so that the temperature of the semiconductor device 18 is prevented from becoming abnormally high, and the current of the semiconductor device 18 is increased. It becomes possible.

  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 18 or the like. In the circuit board 10 of this embodiment, the heat generated from the semiconductor device 18 and the like is efficiently removed by the cooling medium flowing through the cooling medium flow path 16a 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 14 is communicated with the cooling medium circulation path of the vehicle via pipes 15a and 15b. 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) The circuit board 10 includes a substrate 11 in which a metal cooling portion 16 including a cooling medium flow path 16a is embedded with resin, and the wiring layer 12 on which the silicon semiconductor chip can be mounted is insulated on the substrate 11 It is provided via the layer 13. The cooling part 16 is formed with a flat part 16b at a position corresponding to the wiring layer 12, and a resin having a thermal expansion coefficient smaller than that of the cooling part 16 is used as the resin. Therefore, it becomes easy to make the distance between the wiring layer 12 and the flat portion 16b constant, and when the distance between the wiring layer 12 and the cooling portion 16 varies depending on the location by making the distance constant or substantially constant. In comparison, heat transfer from the wiring layer 12 to the cooling unit 16 is improved. In addition, the thermal expansion of the metallic cooling unit 16 is suppressed by the resin in which the cooling unit 16 is embedded, and the life of the cooling cycle is prolonged, and the semiconductor device (silicon semiconductor chip) is connected to the wiring layer 12 via the solder 17. ) The reliability of the solder connection portion when 18 is mounted is improved.

  (2) The resin in which the cooling unit 16 is embedded and the insulating layer 13 are made of the same insulating resin. Accordingly, only one kind of resin is required for manufacturing the insulating layer 13, and the preparation and storage of materials are possible as compared with the case where the insulating layer 13 is formed of a resin different from the insulating resin in which the cooling section 16 is embedded. Becomes easier.

  (3) The wiring layer 12 is provided at a plurality of locations on the common flat portion 16b. Therefore, compared with the case where the flat part 16b is provided independently for each wiring layer 12, the cooling part 16 receives the cooling action efficiently, so that the heat dissipation (cooling effect) is improved.

  (4) Since the cooling medium flow path 16a is provided so as to extend along the arrangement direction of the wiring layers 12 provided at a plurality of locations, all the cooling medium flowing through the cooling medium flow path 16a contributes to cooling. It flows in. When there are a plurality of cooling medium channels 16a and the plurality of wiring layers 12 are arranged so as to correspond to different passages, in a state where a part of the semiconductor device 18 mounted on the wiring layer 12 is generating heat. The cooling medium flowing through some of the cooling medium flow paths 16a flows with little contribution to cooling. However, this is not the case with this embodiment.

(5) Since the cooling unit 16 is made of an aluminum-based metal, a lightweight circuit board can be easily and inexpensively manufactured.
(6) Since the wiring layer 12 is made of copper and the thermal conductivity is 10 times or more of the thermal conductivity of solder (about 30 W / (mK)), the wiring layer 12 is generated from the semiconductor device 18 or the like mounted on the wiring layer 12 It is avoided that heat is hardly transferred to the substrate 11 side in the wiring layer 12 portion.

(7) Since water is used as the cooling medium, the heat of the substrate 11 can be efficiently removed at low cost.
(8) The cooling medium passage 14 is formed so as to be able to communicate with a cooling medium circulation path equipped in the vehicle. When the circuit board 10 is used for in-vehicle use and is provided, for example, in an engine room or the like, it is necessary to efficiently remove heat generated from the semiconductor device 18 or the like. At that time, the cooling medium flowing through the cooling medium circulation path installed in the vehicle can be used in a state of flowing through the cooling medium passage 14 of the substrate 11, and it is necessary to provide a cooling medium circulation pump dedicated to the circuit board 10. Absent.

  (9) The cooling unit 16 is buried not only in the circumferential surface extending in the longitudinal direction but also in a part of the end surface orthogonal to the longitudinal direction in contact with the insulating resin. Therefore, the thermal expansion of the cooling unit 16 is more effectively suppressed as compared with a configuration in which the end surface is not in contact with the insulating resin.

  (10) When the substrate 11 is manufactured, the cooling unit 16 is set in a mold and the molded product 19 constituting the portion excluding the portion that becomes the insulating layer 13 is manufactured by injection molding or transfer molding, and then the sheet. The part which becomes the insulating layer 13 was formed by pasting 20. Therefore, even when the insulating layer 13 is as thin as several tens of μm, the insulating layer 13 having a desired thickness can be reliably and easily formed.

  (11) Since the wiring layer 12 is made of copper, it can be formed into a circuit pattern by etching and can be easily processed into a circuit pattern. For example, instead of the resin sheet 20, a wiring layer 12 having a predetermined shape can be formed by etching after a resin sheet having a copper layer laminated on one side is attached to the insulating layer 13.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. 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. 4A, the circuit board 10 is provided with a wiring layer 25 on the substrate 11 with an insulating layer 13 interposed therebetween. The wiring layer 25 is 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. “Metal composite material” means not a single metal element but a composite of a plurality of metals or metals and ceramics. In this embodiment, an AlSiC composite material is used as the metal composite material.

  As shown in FIG. 4B, the AlSiC-based composite material 26 has a configuration in which aluminum layers 26b and 26c are arranged on both surfaces with an AlSiC portion 26a interposed therebetween. For example, the AlSiC part 26a is formed by 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 portion 26a has different volume ratios between SiC and Al depending on the particle size, filling rate, and the like of the SiC powder to be used, and has different physical properties such as thermal expansion coefficient and thermal conductivity. The AlSiC-based composite material 26 is provided with an aluminum plate having a desired thickness to be the aluminum layers 26b and 26c so as to sandwich the AlSiC portion 26a having a desired thickness, and heated to the melting temperature of aluminum in a pressurized state to obtain AlSiC. It is formed by laminating and bonding an aluminum plate to the portion 26a.

The thermal expansion coefficient of the wiring layer 25 can be changed in a wide range by changing the overall thickness or the thickness of the AlSiC portion 26a and the aluminum layers 26b and 26c. For example, the ratio t1 / t2 between the thickness t1 of the AlSiC portion 26a and the thickness t2 of the aluminum layers 26b and 26c is t1 / t2 = 3 / 0.4, and the total thickness of the wiring layer 25 is 2.5 mm. Then, the thermal expansion coefficient is 10.5 × 10 ⁻⁶ / ° C., and the thermal conductivity is 240 W / (mK). 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.

  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 effects similar to the effects (1) to (5) and (7) to (10) in the first embodiment.

  (12) Since the thermal conductivity of the wiring layer 25 is more than several times the thermal conductivity of the solder (about 30 W / (mK)), the heat generated from the semiconductor device 18 mounted on the wiring layer 25 or the like. It is avoided that the wiring layer 25 becomes difficult to be transmitted to the substrate 11 side.

  (13) The wiring layer 25 is 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. Therefore, the difference in the thermal expansion coefficient between the semiconductor device 18 and the wiring layer 25 is smaller than when the wiring layer 25 is formed of copper or aluminum, the life of the thermal cycle is longer, and the reliability of the solder connection portion is increased. More improved.

  (14) The metal composite material has a configuration in which aluminum layers 26b and 26c are arranged on both sides of the AlSiC portion 26a. Therefore, for example, by changing the thickness ratio between the AlSiC portion 26a and the aluminum layers 26b and 26c, the thermal expansion coefficient and the thermal conductivity of the wiring layer 25 can be changed so that the semiconductor device 18 and the electronic device mounted on the wiring layer 25 It becomes easy to set to an appropriate value corresponding to a part or the like.

(Third embodiment)
Next, a third embodiment will be described with reference to FIGS. 5 (a), (b) and FIG. This embodiment is the same as the second embodiment in that the wiring layer is made of a metal composite material, but is different from the second embodiment in that the configuration of the metal composite material is changed. The same as in the first and second embodiments. The same parts as those in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 5A, the circuit board 10 is provided with a wiring layer 28 on an insulating layer 13 on a substrate 11. The wiring layer 28 is 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. As shown in FIG. 5B, the metal composite material 29 constituting the wiring layer 28 has a structure in which a copper layer 29b is disposed on both sides of a composite portion 29a of copper and invar. Invar is an alloy composed of 36% by weight of Ni (nickel) and the rest substantially Fe (iron). In addition, the composite part of copper and Invar is not a structure in which a copper layer and an Invar layer are simply laminated, 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.

  As shown in FIG. 6, the metal composite material 29 is formed by rolling and joining an expanded metal 30 formed of invar while being sandwiched between copper plates 31. Specifically, the expanded metal 30 and the expanded metal 30 are surrounded by integrating the copper plate 31 and the expanded metal 30 by heating and rolling with a rolling roll in a state where the expanded metal 30 is disposed between the copper plates 31. A metal composite material 29 composed of the matrix metal copper is formed. As a result, a metal composite material 29 having a thermal expansion coefficient larger than that of the silicon semiconductor chip and smaller than that of the copper is formed. Rolling is performed so that (t12) / (t11) is 0.2 to 0.8, where t11 is the thickness of the metal composite 29 after rolling and joining, and t12 is the thickness of the expanded metal 30 portion. -The thickness of the expanded metal 30 before joining, the thickness of the copper plate 31, and a rolling rate are set. The metal composite material 29 may be formed in accordance with the shape of the wiring layer 12 or may be cut into a predetermined shape after a plate larger than the wiring layer 12 is formed.

In addition, the metal composite material 29 is not limited to the configuration in which the composite portion 29a is a single layer, and the composite portion 29a may have a plurality of layers, for example, the composite portion 29a may have a two-layer configuration. The metal composite material 29 having a composite layer 29a having two layers is formed by rolling and joining three copper plates 31 and two expanded metals 30 alternately stacked. The thermal expansion coefficient of the wiring layer 28 can be changed in a wide range by changing the overall thickness or the thickness of the composite portion 29a and the copper layer 29b. For example, when the composite part 29a is a three-layer product having one layer, the thermal expansion coefficient of the wiring layer 28 is 8.0 × 10 ^{−6 to} 23.5 × 10 ⁻⁶ / in the range of the thickness of 100 μm to 5000 μm. It can be freely changed up to 0 ° C., and when the thickness of the wiring layer 28 is 2000 μm, the thermal expansion coefficient is 11.5 × 10 ⁻⁶ / ° C. and the thermal conductivity is 168 W / (mK). It was.

  The circuit board 10 configured as described above is used in the same manner as the circuit board 10 of the first and second embodiments. The circuit board 10 of this embodiment is similar to the effects (1) to (5), (7) to (10) in the first embodiment and the effects (12) and (13) in the second embodiment. In addition to having the effect, it has the following effect.

  (15) The wiring layer 28 has a configuration in which copper layers 29b are disposed on both sides with the composite portion 29a interposed therebetween. Therefore, it becomes easy to set the thermal expansion coefficient and the thermal conductivity of the wiring layer 28 to appropriate values corresponding to the semiconductor device 18 and electronic components mounted on the wiring layer 28.

(16) Since the wiring layer 28 is a metal composite material, a circuit pattern can be formed by etching, and the processing of the circuit pattern is easier than in the second embodiment.
(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIG. In this embodiment, one cooling unit 16 is provided, and all the wiring layers 12 are provided at locations corresponding to the common flat portion 16b, and at locations that do not correspond to the wiring layer 12, the cooling medium flow path is also provided. The point that 16a is formed is different from the first embodiment, and other configurations are the same as those of the first embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 7 is a schematic cross-sectional view corresponding to FIG. The substrate 11 is provided with one flow path 14c having a width across both rows of the wiring layers 12 arranged in two rows, and one cooling section 16 forms a part of the cooling medium passage 14 in the flow channel 14c. It is buried to do. In the cooling part 16, a plurality of cooling medium flow paths 16a extending in parallel to the flow path 14c (in a direction orthogonal to the paper surface of FIG. 7) are formed at regular intervals, and the flat part 16b corresponds to the two rows of wiring layers 12 It is formed to straddle. A flat portion 16c having the same size as the flat portion 16b is formed on the opposite side of the flat portion 16b across the cooling medium flow path 16a. A plurality of wiring layers 12 are arranged in two rows at a predetermined interval on the flat portion 16b, and the arrangement direction thereof is arranged along the direction in which the cooling medium flow path 16a extends. That is, in this embodiment, all the wiring layers 12 are provided at locations corresponding to the common flat portion 16b. On each wiring layer 12, a semiconductor device 18 and passive parts (not shown) are mounted (mounted) via solder 17.

  The circuit board 10 configured as described above is used in the same manner as the circuit board 10 of the first embodiment. When the semiconductor device 18 mounted on the circuit board 10 is driven and heat is generated from the mounted components, the heat is transmitted to the cooling unit 16 via the solder 17, the wiring layer 12, and the insulating layer 13. The heat transferred to the cooling unit 16 is transferred to the cooling medium flowing through the cooling medium flow path 16a and taken away. Since the flat part 16b is provided so as to straddle the arrangement region of all the wiring layers 12, the heat transferred from the wiring layer 12 corresponding to the heated component through the insulating layer 13 is transmitted to the wiring in the flat part 16b. It is transmitted to a part other than the part corresponding to the layer 12. The heat transmitted through the flat portion 16b is transferred to the cooling medium flowing through the cooling medium flow path 16a and taken away.

Accordingly, the circuit board 10 of this embodiment has the following effects in addition to the effects similar to the effects (1) to (11) in the first embodiment.
(17) Since all the wiring layers 12 are provided at locations corresponding to the common flat portion 16 b, the heat generated from the semiconductor device 18 passes through the solder 17, the wiring layer 12, and the insulating layer 13, and the flat portion 16 b. Is transmitted to the portion other than the portion corresponding to the wiring layer 12 of the heat generating portion in the flat portion 16b. Therefore, the heat transferred to the cooling unit 16 is efficiently removed by the cooling medium flowing through the cooling medium flow path 16a as compared with the first embodiment.

  (18) Since the cooling medium flow path 16a is also formed at a location not corresponding to the wiring layer 12, the heat transferred to the flat portion 16b other than the portion corresponding to the wiring layer 12 of the heat generating portion is more efficiently removed. The

The embodiment is not limited to the above, and may be configured as follows, for example.
○ When the insulating layer 13 is made of a thermosetting resin, instead of pasting the semi-cured sheet 20, after applying an uncured thermosetting resin mixed with a filler to a predetermined thickness with, for example, a squeegee, It may be thermoset. Also in this case, the thin insulating layer 13 can be easily formed to a predetermined thickness.

  The insulating layer 13 does not necessarily need to be formed of the same resin as the insulating resin that constitutes other parts of the substrate 11. However, in order to reduce the thermal resistance of the insulating layer 13, it is preferable that the filler is mixed so that the thermal conductivity is higher than that of the resin alone.

The resin constituting the other part of the substrate 11 excluding the insulating layer 13 need not be formed of an insulating resin. In this case, the filler mixed with the resin of the substrate 11 may be made of metal.
The cooling unit 16 is not limited to extrusion molding, and may be formed by, for example, brazing top plates 34 on both sides of a plate material 33 that has been subjected to bending as shown in FIG. 9B. . In the configuration shown in FIG. 9B, the top plate 34 becomes the flat portions 16b and 16c, and the space surrounded by the plate material 33 and the top plate 34 becomes the cooling medium flow path 16a. The top plate 34 serving as the flat portion 16c disposed on the opposite side of the flat portion 16b facing the insulating layer 13 is not limited to metal but may be made of resin.

  ○ As shown in FIG. 8 (a), a rectangular plate member 35 and a pair of narrow plate members 36 having a rectangular cross section are alternately stacked and joined together by a heat and pressure press to cool the cooling unit. 16 is formed. And as shown in FIG.8 (b), you may make it use the part joined alternately by the board | plate material 35 and the narrow board | plate material 36 as the flat parts 16b and 16c.

  The configuration of the cooling medium passage 14 provided in the substrate 11 is not limited to the configuration in which the inlet portion 14a is provided on one end side in the longitudinal direction of the substrate 11 and the outlet portion 14b is provided on the other end side along the longitudinal direction. For example, as shown in FIG. 9A, the inlet portion 14 a and the outlet portion 14 b are formed so as to extend in a direction orthogonal to the longitudinal direction of the substrate 11, and the pipes 15 a and 15 b protrude from the end surface on the same side of the substrate 11. It may be configured to.

O The cooling part 16 should just have the flat part 16b formed in the location corresponding to the wiring layer 12, and does not need the flat part 16c.
When the cooling unit 16 is cast into an insulating resin by injection molding or transfer molding, the insulating layer 13 may be formed at the same time. In that case, if not only the cooling unit 16 but also the wiring layer 12 is placed at a predetermined position in the mold and molded, the step of bonding the wiring layer 12 onto the insulating layer 13 later can be omitted. Further, when the wiring layer 12 is a single metal or a metal composite material composed of a plurality of metals, the metal layer having a shape corresponding to the flat portion 16b is fixed to the insulating layer 13 instead of the shape of the wiring layer 12. Alternatively, transfer molding may be performed and then processed into the shape of the wiring layer 12 by etching.

  The cooling unit 16 is not limited to the configuration in which the plurality of cooling medium flow paths 16a extend in parallel, and one cooling medium flow path 16a is provided for each of the cooling medium flow paths 16a or the wiring layer 12 arrangement locations. Alternatively, the fins may protrude into the cooling medium flow path 16a.

  The cooling unit 16 is not limited to the extrusion molding, die casting method, plate processing / joining method, etc. For example, the cooling medium flow path 16a is formed by a pipe, and a flat portion is provided at least at a position corresponding to the wiring layer 12. You may manufacture by joining the board | plate material which has. The pipe is not limited to a single bent pipe, and may be configured such that a single pipe is branched into a plurality of pipes in the middle and then gathered again into a single pipe.

The cooling unit 16 may have a configuration in which the inlet portion 14a, the outlet portion 14b, and the flow path 14c are also integrally formed.
A heat pipe may be used as the pipe constituting the cooling medium flow path 16a. 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 a cooling medium circulation path, and the entire configuration is simplified.

The cooling medium flow path 16a is not limited to the configuration extending along the arrangement direction of the wiring layers 12, but may be configured to extend in a direction intersecting with the arrangement direction of the wiring layers 12.
A plurality of inlets and outlets 14a and 14b of the cooling medium passage 14 may be provided.

In the second and third embodiments, the cooling unit 16 including the cooling medium flow path 16a in the fourth embodiment may be used.
In the first and fourth embodiments, the wiring layer 12 may be made of aluminum. However, copper is preferable in terms of electrical resistance.

A plurality of semiconductor devices 18 or other electronic components may be mounted on one wiring layer 12, 25, 28. Therefore, the wiring layer 12 is not limited to a plurality, and may be one.
The wiring layers 12, 25, 28 are not limited to two rows, and may be changed to the number of wiring layers 12, 25, 28 or the number of columns suitable for the shape of the substrate 11, such as one row or three or more rows.

  ○ As long as necessary insulation is ensured, the insulating layer 13 is not limited to insulating ceramics as a filler to be mixed in order to reduce the coefficient of thermal expansion and increase the thermal conductivity. You may use the filler made from.

The insulating layer 13 may be provided only in a portion corresponding to the wiring layer 12. In this case, the flat portion 16b is exposed except for the portion corresponding to the wiring layer 12.
The cooling medium flowing through the cooling medium passage 14 is not limited to water, but may be other liquids or gases.

In the case where the wiring layer 12 is composed of a metal composite material, the metal composite material only needs to have a thermal expansion coefficient larger than that of the silicon semiconductor chip and smaller than that of copper. For example, in the second embodiment, not only a combination of silicon carbide and aluminum, but also other ceramics having good thermal conductivity instead of silicon carbide fine particles, such as boron nitride (BN), magnesium oxide (MgO), Molybdenum disilicide (MoSi ₂ ) or the like may be used, and another metal having high thermal conductivity, such as copper, may be used instead of aluminum. In the third embodiment, the material of the expanded metal 30 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.

○ DBA substrate (Al / AlN / Al) having a structure in which an aluminum nitride (AlN) layer is sandwiched between wiring layers 12 and a copper layer is disposed on both sides of the aluminum nitride layer. A DBC substrate (Cu / AlN / Cu), a silicon nitride (SiN) substrate, an alumina (Al ₂ O ₃ ) substrate, or a silicon carbide (SiC) substrate may be used. The DBA substrate and the cooling unit may be integrally joined at the time of injection molding. At this time, the insulating resin bonds the DBA substrate and the cooling unit.

  ○ Al and Cu are used for the wiring layer 12, AlN, SiN, and alumina are used for the insulating layer 13. The insulating layer 13 and the wiring layer 12 are brazed and bonded in advance by diffusion bonding or the like. You may join with the cooling part 16 at the time of injection molding. At this time, the insulating resin bonds the wiring layer 12 and the cooling unit 16 together.

○ A film is formed by spraying Al ₂ O ₃ (alumina) or AlN on a water-cooled heat sink made of Al. Further, the cooling part 16 sprayed or brazed with Al or Cu is integrally molded by injection molding of a low expansion resin. Also good.

The following technical idea (invention) can be understood from the embodiment.
(1) In invention of Claim 6 or Claim 7, the said metal composite material 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.

(2) In the invention according to claim 6 or claim 7, the metal composite material has a configuration in which an aluminum layer is disposed on both sides of an AlSiC portion.
(3) In the invention according to any one of claims 1 to 7 and the technical ideas (1) and (2), the cooling medium passage communicates with a cooling medium circulation path installed in a vehicle. It is made possible.

  (4) In the invention according to any one of claims 1 to 7 and the technical ideas (1) and (2), the cooling medium passage is constituted by a heat pipe.

(A) is a schematic top view of the circuit board in 1st Embodiment, (b) is an expanded sectional view in the AA line of (a), (c) is sectional drawing in the BB line of (a). Sectional drawing in the CC line of FIG.1 (c). The schematic cross section which shows the manufacturing method of a board | substrate. (A) is a typical fragmentary sectional view of the circuit board in 2nd Embodiment, (b) is the elements on larger scale of (a). (A) is a schematic fragmentary sectional view of the circuit board in 3rd Embodiment, (b) is the elements on larger scale of (a). The model perspective view which similarly shows the manufacturing method of a metal composite material. The schematic cross section of the circuit board in a 4th embodiment. (A) is a schematic cross section which shows another manufacturing method of a cooling part, (b) is a typical fragmentary sectional view of the board | substrate with which the cooling part was cast. (A) is a schematic top view of the circuit board in another embodiment, (b) is a schematic cross section of the cooling part in another embodiment. (A) is sectional drawing of the printed wiring board of a prior art, (b) is a top view which shows the shape of the flow path of a heat carrier.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Circuit board, 11 ... Board | substrate, 12, 25, 28 ... Wiring layer, 13 ... Insulating layer, 16 ... Cooling part, 16a ... Cooling medium flow path, 16b ... Flat part, 18 ... Semiconductor device as a silicon semiconductor chip, 26: AlSiC-based composite material as a metal composite material, 29 ... Metal composite material.

Claims (7)

A circuit board is provided with a substrate in which a metal cooling section having a cooling medium flow path is embedded with a resin, and on which a wiring layer on which a silicon semiconductor chip can be mounted is provided via an insulating layer. And
A circuit board in which the cooling part has a flat part formed at least at a location corresponding to the wiring layer, and the resin uses a resin whose thermal expansion coefficient is smaller than the thermal expansion coefficient of the cooling part.   The circuit board according to claim 1, wherein the resin in which the cooling unit is embedded and the insulating layer are made of the same insulating resin.   The circuit board according to claim 1, wherein the wiring layer is provided at a plurality of locations on the common flat portion.   The circuit board according to claim 3, wherein the cooling medium flow path is provided so as to extend along an arrangement direction of wiring layers provided at the plurality of locations.   The circuit board according to claim 1, wherein the cooling unit is made of an aluminum-based metal.   The circuit board according to claim 1, wherein the wiring layer is 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.   The circuit board according to any one of claims 1 to 6, wherein the wiring layer has a thermal conductivity of 30 W / (mK) or more.

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