circuit board

Abstract

To improve heat dissipation of circuit boards.SOLUTION: One embodiment of a circuit board has a conductive base, an insulating layer disposed on the surface of the conductive base, a circuit part embedded in the insulating layer with a portion exposed, and a heat-dissipating member disposed in the insulating layer and having higher thermal conductivity than the insulating layer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to circuit boards. [Background technology]

[0002] In the field of power electronics, electronic components for power control, such as power semiconductor elements, are used. These electronic components are sometimes mounted on circuit boards on which integrated circuits are formed. For example, Patent Document 1 describes a circuit board including an aluminum metal plate, a resin insulating layer formed on the metal plate, a circuit pattern formed on the insulating layer, and a power semiconductor element mounted on the circuit pattern.

[0003] Furthermore, in the cited document 2, it is described that in order to supply a large current to an electronic component, a thick conductor wiring circuit is used as a circuit pattern on which the electronic component is mounted. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-23223 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-78595 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the amount of heat generated by electronic components such as semiconductor elements has been increasing along with the trend toward higher power output from industrial equipment. In particular, when a thick conductor wiring circuit is used to supply a large current to the electronic components, as in the circuit board described in Cited Document 2, a large amount of heat is generated as the electronic components operate, and therefore the circuit board is required to have high heat dissipation performance.

[0006] Therefore, an object of the present disclosure is to improve the heat dissipation performance of a circuit board. [Means for solving the problem]

[0007] One embodiment of the circuit board comprises a conductive base, an insulating layer disposed on the surface of the conductive base, a circuit portion embedded in the insulating layer with a portion exposed, and a heat dissipation member disposed in the insulating layer and having a higher thermal conductivity than the insulating layer.

[0008] In the circuit board of the above aspect, a heat dissipation member having a higher thermal conductivity than the insulating layer is disposed within the insulating layer, so that heat from the circuit section can be transferred to the conductive base with high efficiency via the heat dissipation member within the insulating layer. The heat transferred to the conductive base is then dissipated to the outside of the circuit board. Therefore, this circuit board can effectively dissipate heat from the circuit board.

[0009] In one embodiment, the heat dissipation member may be in contact with the surface of the conductive base within the insulating layer, in which case heat from the circuit unit can be more efficiently transferred to the conductive base via the heat dissipation member, thereby more effectively dissipating heat from the circuit board.

[0010] In one embodiment, the insulating layer includes a bottom surface in contact with the surface of the conductive base and a top surface opposite the bottom surface, the circuit portion has a side surface along a thickness direction of the insulating layer, the heat dissipation member is disposed within the insulating layer at a position spaced apart from the surface of the conductive base in the thickness direction of the insulating layer and facing the side surface of the circuit portion in a direction intersecting the thickness direction, the distance between the top surface and the heat dissipation member in the thickness direction being 30 μm or more, the distance between the heat dissipation member and the side surface of the circuit portion in the intersecting direction being 30 μm or more and 1000 μm or less, and the distance between the heat dissipation member and the surface of the conductive base in the thickness direction may be greater than 0 and 1000 μm or less. In this case, unlike when the heat dissipation member is disposed between the circuit portion and the surface of the conductive base in the thickness direction, heat from the circuit board can be effectively dissipated without increasing the thickness of the insulating layer.

[0011] In one embodiment, the area of ​​the region where the heat dissipation member faces the conductive base may be 1% or more and 100% or less of the area of ​​the surface of the conductive base covered with the insulating layer. By ensuring the area of ​​the region where the heat dissipation member faces the conductive base in this way, it is possible to preferably realize a configuration in which heat from the circuit unit is transferred to the conductive base via the heat dissipation member with high efficiency.

[0012] In one embodiment, the thermal conductivity of the heat dissipation member may be 50 W / mK or more. In this case, heat from the circuit unit can be more efficiently transferred to the conductive base via the heat dissipation member, thereby more effectively dissipating heat from the circuit board.

[0013] In one embodiment, the heat dissipation member may include aluminum, copper, titanium, magnesium, iron, tungsten, or an alloy containing at least one of these, which can provide the heat dissipation member with high thermal conductivity.

[0014] In one embodiment, the circuit unit is a thick copper circuit unit having a thickness of 500 μm or more. The circuit unit has an exposed upper surface exposed from the insulating layer and an embedded lower surface facing the surface of the conductive base via the insulating layer on the opposite side of the exposed upper surface. The insulating layer includes a bottom surface in contact with the surface of the conductive base and a surface surface opposite the bottom surface. The distance between the surface surface and the embedded lower surface in the thickness direction of the insulating layer may be 50% or more and 130% or less of the thickness of the circuit unit from the embedded lower surface to the exposed upper surface. In this case, the contact area between the circuit unit and the insulating layer can be increased, thereby allowing heat from the circuit unit to be transferred to the insulating layer with high efficiency. The heat transferred to the insulating layer is then transferred to the conductive base with high efficiency, for example, via a heat dissipation member. Therefore, the above configuration allows effective heat dissipation from the circuit board.

[0015] In one embodiment, the circuit board further includes a thin copper circuit portion thinner than the circuit portion, and the insulating layer includes a bottom surface in contact with the surface of the conductive base and a top surface opposite the bottom surface, and the thin copper circuit portion may be disposed on the top surface. In this case, the circuit portion and the thin copper circuit portion thinner than the circuit portion can be mixed on the circuit board, and heat from the circuit portion, through which a larger current may flow than the thin copper circuit portion, can be effectively dissipated.

[0016] The heat dissipation member may be disposed in a position facing the thin copper circuit portion in the thickness direction of the insulating layer, with the insulating layer interposed therebetween, and the distance between the heat dissipation member and the thin copper circuit portion in the thickness direction may be 100 μm or more. In this case, heat from the circuit board can be effectively dissipated while ensuring electrical insulation between the heat dissipation member and the thin copper circuit portion.

[0017] In one embodiment, the insulating layer may contain a curable resin and an inorganic filler, which can impart high insulating properties and heat dissipation properties to the insulating layer.

[0018] In one embodiment, the content of the inorganic filler in the insulating layer may be 50% by volume or more, which can further increase the thermal conductivity of the insulating layer.

[0019] In one embodiment, the inorganic filler may have a thermal conductivity of 10 W / mK or more, which can further increase the thermal conductivity of the insulating layer.

[0020] The inorganic filler may have an average particle size of 1 μm or more and 100 μm or less, in which case the thermal conductivity of the insulating layer can be further increased. [Effects of the Invention]

[0021] According to one aspect and various embodiments of the present disclosure, the heat dissipation performance of a circuit board can be improved. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a perspective view showing a circuit board according to an embodiment. [Figure 2]2 is a cross-sectional view taken along line II-II of the circuit board shown in FIG. [Figure 3] 1 is a cross-sectional view showing a circuit board in which a thick copper circuit portion and a thin copper circuit portion are electrically connected by wires. [Figure 4] 1 is a cross-sectional view showing a step in a method of manufacturing a circuit board according to an embodiment. [Figure 5] 1 is a cross-sectional view showing a step in a method of manufacturing a circuit board according to an embodiment. [Figure 6] 1 is a cross-sectional view showing a step in a method of manufacturing a circuit board according to an embodiment. [Figure 7] FIG. 10 is a cross-sectional view showing a circuit board according to a modified example. [Figure 8] FIG. 10 is a cross-sectional view showing a circuit board according to another modified example. [Figure 9] FIG. 10 is a cross-sectional view showing a circuit board according to yet another modified example. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will not be repeated. The dimensional ratios of the drawings do not necessarily correspond to those in the description.

[0024] Fig. 1 is a perspective view showing a circuit board according to one embodiment. Fig. 2 is a cross-sectional view taken along line II-II of the circuit board shown in Fig. 1. The circuit board 1 shown in Figs. 1 and 2 is, for example, a metal-based circuit board on which electronic components are mounted to form an integrated circuit. The circuit board 1 is suitable for general-purpose applications that use relatively large amounts of power, such as automobiles, industrial robots, and air conditioners. Examples of electronic components that can be mounted on the circuit board 1 include semiconductor elements for power control, such as MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors).

[0025] 1 and 2, the circuit board 1 includes a conductive base 10, an insulating layer 20 laminated on the conductive base 10, a plurality of thick copper circuit portions 30 (circuit portions) embedded in the insulating layer 20, and a heat dissipation member 50 disposed in the insulating layer 20. In the following description, the "thickness direction Z" refers to the thickness direction of the insulating layer 20, and indicates the direction in which the conductive base 10 and the insulating layer 20 are laminated. The "longitudinal direction X" refers to the extension direction of the insulating layer 20, and indicates the direction intersecting with the thickness direction Z (more specifically, the arrangement direction of the plurality of thick copper circuit portions 30). The "lateral direction Y" refers to the extension direction of the insulating layer 20, and indicates the direction intersecting with the thickness direction Z and the longitudinal direction X (intersecting direction).

[0026] The conductive base 10 is a metal base substrate having electrical conductivity. The conductive base 10 is made of, for example, a metal having higher thermal conductivity than the insulating layer 20. Examples of materials for the conductive base 10 include aluminum, iron, copper, stainless steel, and alloys containing at least one of these metals. The conductive base 10 may also contain a non-metallic material. The conductive base 10 has a surface 11 along the XY plane.

[0027] The insulating layer 20 is disposed on the surface 11 of the conductive base 10. The insulating layer 20 is interposed between the conductive base 10 and the thick copper circuit portion 30, thereby physically bonding the conductive base 10 and the thick copper circuit portion 30 and electrically insulating the conductive base 10 and the thick copper circuit portion 30. Furthermore, the insulating layer 20 transfers heat generated by the operation of electronic components mounted on the thick copper circuit portion 30 to the conductive base 10. To achieve these functions, the insulating layer 20 may have high electrical insulation and thermal conductivity. For example, the insulating layer 20 may contain a curable resin and an inorganic filler and may have a thermal conductivity of 3 W / mK or more.

[0028] The curable resin may be, for example, a thermosetting resin material and may contain a resin and a curing agent. Examples of resins contained in the curable resin include epoxy resin, silicone resin, silicone rubber, acrylic resin, phenolic resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamideimide, polyetherimide, polybutylene terephthalate, polyethylene terephthalate, polyphenylene ether, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin.

[0029] The resin content may be 15% by volume or more, 20% by volume or more, or 30% by volume or more, and may be 70% by volume or less, 60% by volume or less, or 50% by volume or less, based on the total volume of the insulating layer 20.

[0030] The curing agent contained in the curable resin is appropriately selected depending on the type of resin. For example, when the resin is an epoxy resin, a phenol novolac compound, an acid anhydride, an amino compound, an imidazole compound, or the like is used as the curing agent. The content of the curing agent may be, for example, 0.5 parts by mass or more or 1.0 parts by mass or more, and 15 parts by mass or less or 10 parts by mass or less, relative to 100 parts by mass of the resin.

[0031] The inorganic filler is filled into the insulating layer 20 to increase the thermal conductivity of the insulating layer 20. The inorganic filler may have a thermal conductivity of, for example, 10 W / mK or more. Examples of inorganic fillers having such a thermal conductivity include boron nitride, aluminum oxide, magnesium oxide, aluminum nitride, and silicon nitride. The inorganic filler may be dispersed in the insulating layer 20 in a powder state. From the viewpoint of increasing the thermal conductivity of the insulating layer 20, the powdered inorganic filler may have an average particle diameter of, for example, 1 μm or more and 100 μm or less. The average particle diameter of the inorganic filler can be adjusted by adjusting the grinding time of the inorganic filler in a lump form.

[0032] The content of the inorganic filler in the insulating layer 20 may be 50% by volume or more, based on the total amount of the insulating layer 20. In this case, the thermal conductivity of the insulating layer 20 tends to be further improved. The content of the inorganic filler in the insulating layer 20 may be 80% by volume or less, preferably 75% by volume or less, and more preferably 70% by volume or less, based on the total amount of the insulating layer 20. In this case, the coatability of the insulating resin composition is further improved, making it easier to obtain an insulating layer 20 with excellent insulating properties.

[0033] The insulating layer 20 is formed, for example, to cover the entire surface 11 of the conductive base 10. As shown in FIG. 2, the insulating layer 20 includes a bottom surface 21 that contacts the surface 11 of the conductive base 10 and a surface surface 22 opposite the bottom surface 21. The distance in the thickness direction Z between the bottom surface 21 and the surface surface 22, i.e., the thickness T1 of the insulating layer 20, is set to, for example, 300 μm or more and 4200 μm or less. A hole 23 is formed in the surface surface 22 for embedding the thick copper circuit portion 30 in the insulating layer 20. The hole 23 is open at the surface surface 22 and extends from the surface surface 22 toward the surface 11 of the conductive base 10 in the thickness direction Z.

[0034] As shown in FIG. 1, a plurality of thick copper circuit portions 30 are arranged at predetermined intervals (i.e., spaced apart from one another) along the vertical direction X. Although three thick copper circuit portions 30 are shown in FIG. 1, the number of thick copper circuit portions 30 is not limited. The circuit board 1 may include one thick copper circuit portion 30, or two or four or more thick copper circuit portions 30. Each thick copper circuit portion 30 has the same configuration. Therefore, in the following description, the configuration of one thick copper circuit portion 30 will be specifically described, but the configurations of the other thick copper circuit portions 30 will also be described in a similar manner.

[0035] The thick copper circuit portion 30 has a structure in which a desired circuit pattern is formed by processing, for example, etching. The thick copper circuit portion 30 is made of copper or a copper-containing alloy. As shown in FIG. 2, the thick copper circuit portion 30 is a circuit conductor that is thicker than a typical circuit conductor, and has a thickness T2 of, for example, 500 μm or more. The thickness T2 of the thick copper circuit portion 30 may be, for example, 600 μm or more, 700 μm or more, or 800 μm or more, and may be 3000 μm or less, 2000 μm or less, or 1000 μm or less.

[0036] The thick copper circuit portion 30 is embedded in the insulating layer 20 with a portion of it exposed. In this embodiment, a portion of the thick copper circuit portion 30 protrudes from and is exposed on the surface 22 of the insulating layer 20, and the remainder of the thick copper circuit portion 30 is embedded in a hole 23 of the insulating layer 20. The state in which the thick copper circuit portion 30 is embedded in the insulating layer 20 refers to a state in which at least a portion of the thick copper circuit portion 30 is embedded below the surface 22 of the insulating layer 20, and thus at least a portion of the thick copper circuit portion 30 is covered by the insulating layer 20. The thick copper circuit portion 30 may have 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more of its surface area covered by the insulating layer 20.

[0037] 2, the thick copper circuit portion 30 has a rectangular cross-sectional shape. The thick copper circuit portion 30 has an exposed upper surface 31 exposed from the surface 22 of the insulating layer 20, an embedded lower surface 32 embedded in the insulating layer 20, and a pair of side surfaces 33, 33 connecting the exposed upper surface 31 and the embedded lower surface 32.

[0038] The exposed upper surface 31 is a surface facing the opposite side to the surface 11 of the conductive base 10 in the thickness direction Z. The exposed upper surface 31 is located at a position protruding from the surface 22 of the insulating layer 20, in other words, at a position higher than the height of the surface 22 from the surface 11 of the conductive base 10. The exposed upper surface 31 provides a mounting surface on which an electronic component 35 (see FIG. 3 described later) is mounted. The exposed upper surface 31 has, for example, a rectangular shape. The width W of the exposed upper surface 31 in the horizontal direction Y may be 5 mm or more, and the width of the exposed upper surface 31 in the vertical direction X may be 5 mm or more.

[0039] The buried lower surface 32 is the surface opposite to the exposed upper surface 31 in the thickness direction Z, i.e., the surface facing the surface 11 of the conductive base 10. The buried lower surface 32 is disposed between the bottom surface 21 and the surface surface 22 of the insulating layer 20 in the thickness direction Z, and faces the surface 11 of the conductive base 10 via the insulating layer 20. In order to ensure electrical insulation between the conductive base 10 and the thick copper circuit portion 30, the buried lower surface 32 is spaced a predetermined distance from the surface 11 in the thickness direction Z. The distance D1 between the buried lower surface 32 and the surface 11 in the thickness direction Z may be set to, for example, 50 μm or more and 3000 μm or less. When the embedding depth of the thick copper circuit portion 30 is represented by the distance D2 in the thickness direction Z between the surface surface 22 and the embedded lower surface 32, the distance D2 may be, for example, 50% or more, 70% or more, or 90% or more of the thickness T2 of the thick copper circuit portion 30, and may be 130% or less or 100% or less of the thickness T2 of the thick copper circuit portion 30.

[0040] The pair of side surfaces 33, 33 extend in the thickness direction Z between the exposed upper surface 31 and the buried lower surface 32, and face each other in the lateral direction Y. A portion of the pair of side surfaces 33, 33 protrudes from and is exposed to the outside surface 22 of the insulating layer 20, and the remaining portions of the pair of side surfaces 33, 33 are embedded in and covered by the insulating layer 20. When the embedding depth of the thick copper circuit portion 30 is expressed by the area of ​​the portion of the side surface 33 that is covered by the insulating layer 20, the area of ​​the covered portion may be, for example, 50% or more, 70% or more, or 90% or more of the total area of ​​the side surface 33, and may be 130% or less or 100% or less of the total area of ​​the side surface 33.

[0041] The heat dissipation member 50 is a member made of a metal having a thermal conductivity higher than that of the insulating layer 20. When the insulating layer 20 contains a filler, the thermal conductivity of the insulating layer 20 may refer to the thermal conductivity of the filler, or may refer to the thermal conductivity of the entire insulating layer 20 including the filler. The heat dissipation member 50 may be made of aluminum, copper, titanium, magnesium, iron, tungsten, or an alloy thereof. Examples of materials for the heat dissipation member 50 include simple metals such as aluminum and copper, and metal alloys such as aluminum alloys, copper-tungsten alloys, and copper-molybdenum alloys. Specific compositions of aluminum alloys include Al-Cu alloys (2000 series), Al-Mn alloys (3000 series), Al-Si alloys (4000 series), Al-Mg alloys (5000 series), Al-Mg-Si alloys (6000 series), and Al-Zn-Mg alloys (7000 series). The heat dissipation member 50 may have a thermal conductivity of, for example, 50 W / mK or more.

[0042] An example of the heat dissipation member 50 is a heat sink. The heat dissipation member 50 is disposed between the bottom surface 21 and the top surface 22 of the insulating layer 20 in the thickness direction Z, and the entire heat dissipation member 50 is covered by the insulating layer 20. The heat dissipation member 50 is disposed around the thick copper circuit portion 30 when viewed from the thickness direction Z, for example. The heat dissipation member 50 is disposed at a position opposite the thick copper circuit portion 30 in the lateral direction Y with the insulating layer 20 interposed therebetween, and is attached to the surface 11 of the conductive base 10, for example.

[0043] By disposing the heat dissipation member 50, which has a higher thermal conductivity than the insulating layer 20, within the insulating layer 20, at least a portion of the heat transferred from the thick copper circuit portion 30 to the insulating layer 20 is transferred with high efficiency to the conductive base 10 via the heat dissipation member 50 within the insulating layer 20. The heat transferred to the conductive base 10 is dissipated to the outside of the circuit board 1. In other words, a heat conduction path is formed in the circuit board 1 that dissipates heat generated by the electronic components 35 to the outside of the circuit board 1 via the thick copper circuit portion 30, the insulating layer 20, the heat dissipation member 50, and the conductive base 10.

[0044] In FIG. 2 , the heat dissipation member 50 has, for example, a substantially rectangular cross-sectional shape. The heat dissipation member 50 has a lower surface 51 facing the surface 11 of the conductive base 10 in the thickness direction Z, an upper surface 52 opposite the lower surface 51, a side surface 53 connecting the lower surface 51 and the upper surface 52 in the thickness direction Z and facing the side surface 33 of the thick copper circuit portion 30 in the lateral direction Y, and a plurality of heat dissipation fins 54 formed on the upper surface 52. The lower surface 51 has, for example, a rectangular shape. The lower surface 51 is in contact with the surface 11 of the conductive base 10, for example. The lower surface 51 may be in indirect contact with the surface 11 of the conductive base 10 via another structure, or may be in direct contact with the surface 11 of the conductive base 10 without another structure. In the example shown in FIG. 2 , the lower surface 51 is in indirect contact with the surface 11 of the conductive base 10 via a solder 60 such as AuSn.

[0045] The lower surface 51 corresponds to the region of the heat dissipation member 50 facing the conductive base 10. The area of ​​the lower surface 51 is set to be equal to or smaller than the area of ​​the surface 11 of the conductive base 10 covered with the insulating layer 20. The area of ​​the surface 11 of the conductive base 10 covered with the insulating layer 20 refers to the area of ​​the portion of the surface 11 of the conductive base 10 covered with the insulating layer 20. In this embodiment, the entire surface 11 of the conductive base 10 is covered with the insulating layer 20. Therefore, in this embodiment, the area of ​​the surface 11 of the conductive base 10 covered with the insulating layer 20 refers to the entire area of ​​the surface 11 of the conductive base 10. The area of ​​the lower surface 51 may be set to be equal to or larger than 1% and equal to or smaller than 100% of the area of ​​the surface 11 of the conductive base 10 covered with the insulating layer 20 (i.e., the entire area of ​​the surface 11). Increasing the area of ​​the lower surface 51 increases the surface area of ​​the heat dissipation member 50 within the insulating layer 20, allowing more heat from the thick copper circuit portion 30 to be transferred to the conductive base portion 10 via the heat dissipation member 50 with high efficiency.

[0046] The upper surface 52 is the surface facing the opposite side to the surface 11 of the conductive base 10. The upper surface 52 is spaced a predetermined distance in the thickness direction Z from the surface surface 22 of the insulating layer 20. A separation distance D3 in the thickness direction Z between the upper surface 52 and the surface surface 22 may be set to, for example, 30 μm or more. In this embodiment, a thin copper circuit portion 40 (described later) is disposed on the surface surface 22, and the upper surface 52 faces the thin copper circuit portion 40 in the thickness direction Z. Therefore, to ensure electrical insulation between the upper surface 52 and the thin copper circuit portion 40, a separation distance D4 in the thickness direction Z between the upper surface 52 and the lower surface 41 of the thin copper circuit portion 40 may be set to, for example, 50 μm or more or 100 μm or more. In this embodiment in which the thin copper circuit portion 40 is disposed on the surface surface 22, the separation distances D4 and D3 are set to be the same. The distance between the upper surface 52 and the lower surface 51 in the thickness direction Z, that is, the thickness T3 of the heat dissipation member 50, is set to be equal to or smaller than the thickness T1 of the insulating layer 20.

[0047] The heat dissipation fins 54 formed on the upper surface 52 have, for example, a rectangular plate shape and are arranged at equal intervals in the lateral direction Y. By providing such heat dissipation fins 54 on the heat dissipation member 50, the surface area of ​​the heat dissipation member 50 can be increased. This increases the contact area between the heat dissipation member 50 and the insulating layer 20, making it easier for much of the heat transferred from the thick copper circuit portion 30 to the insulating layer 20 to be transferred to the conductive base 10 via the heat dissipation member 50. As a result, heat from the circuit board 1 can be dissipated more effectively.

[0048] The side surface 53 extends in the thickness direction Z between the lower surface 51 and the upper surface 52. In order to ensure electrical insulation between the heat dissipation member 50 and the thick copper circuit portion 30, the side surface 53 is spaced a predetermined distance in the lateral direction Y from the side surface 33 of the thick copper circuit portion 30. The separation distance D5 in the lateral direction Y between the side surfaces 53 and 33 may be set to, for example, 30 μm or more, 50 μm or more, or 1000 μm or less. The separation distance D5 may be set to be equal to or greater than the separation distance D1 in the thickness direction Z between the embedded lower surface 32 and the surface 11.

[0049] The circuit board 1 further includes a plurality of thin copper circuit portions 40 arranged on the surface 22 of the insulating layer 20. In FIG. 1, three thin copper circuit portions 40 are arranged at a predetermined distance from one thick copper circuit portion 30 in the horizontal direction Y, for a total of nine thin copper circuit portions 40 arranged in three rows and three columns. The number of thin copper circuit portions 40 is not limited, and the circuit board 1 may include one thin copper circuit portion 40 or no thin copper circuit portions 40. The thin copper circuit portions 40 have the same configuration as each other.

[0050] The thin copper circuit portion 40 is made of, for example, copper or an alloy containing copper. The thin copper circuit portion 40 is a circuit conductor having a thinner wall thickness than the thick copper circuit portion 30. As shown in FIG. 2, the thin copper circuit portion 40 has, for example, a rectangular cross-sectional shape and a thickness T4 of 10 μm or more and less than 500 μm. The thin copper circuit portion 40 has a structure in which a desired circuit pattern is formed by processing, for example, etching or the like.

[0051] The thin copper circuit portion 40 includes a lower surface 41 in contact with the surface 22 of the insulating layer 20 and an upper surface 42 facing the opposite side to the lower surface 41. The lower surface 41 faces the upper surface 52 of the heat dissipation member 50 in the thickness direction Z, with the insulating layer 20 interposed therebetween. The upper surface 42 is disposed, for example, on the same plane as the exposed upper surface 31 of the thick copper circuit portion 30. That is, the upper surface 42 is disposed at the same position as the exposed upper surface 31 in the thickness direction Z. The upper surface 42 may be disposed at a position separated from the exposed upper surface 31 in the thickness direction Z. For example, the separation distance between the upper surface 42 and the exposed upper surface 31 in the thickness direction Z may be set to be equal to or less than the separation distance between the upper surface 42 and the lower surface 41 in the thickness direction Z, i.e., the thickness T4 of the thin copper circuit portion 40. Furthermore, the separation distance D6 between the thin copper circuit portion 40 and the thick copper circuit portion 30 in the lateral direction Y may be set to be equal to or greater than 50 μm.

[0052] As shown in FIG. 3 , the exposed upper surface 31 of the thick copper circuit portion 30, on which the electronic component 35 is mounted, and the upper surface 42 of the thin copper circuit portion 40 may be electrically connected via a wire 45. In this case, the length of the wire 45 can be shortened by reducing the separation distance in the thickness direction Z between the upper surface 42 and the exposed upper surface 31. In this embodiment, the upper surface 42 of the thin copper circuit portion 40 and the exposed upper surface 31 of the thick copper circuit portion 30 are arranged on the same plane, making it possible to shorten the length of the wire 45 as much as possible. By shortening the length of the wire 45 in this way, breakage of the wire 45 can be prevented and the electrical resistance of the wire 45 can be reduced.

[0053] Next, a method for manufacturing the circuit board 1 according to one embodiment will be described. In the following description, the term "resin composition" refers to a resin material containing a curable resin and an inorganic filler before hardening. The insulating layer 20 is formed by hardening this resin composition.

[0054] In a manufacturing method of a circuit board 1 according to one embodiment, first, a conductive base 10, a thick copper circuit portion 30, and a heat dissipation member 50 are prepared. A desired circuit pattern is formed on the thick copper circuit portion 30 by, for example, etching.

[0055] Next, as shown in FIG. 4, a semi-cured (B-stage) resin composition 71 is formed on the embedded lower surface 32 of the thick copper circuit portion 30, and the thick copper circuit portion 30 is pressure-bonded to the conductive base 10 via this resin composition 71. The semi-cured resin composition 71 is formed, for example, by applying a liquid resin composition 71 to a desired thickness on a release film, and then heating the resin composition 71 to semi-cure the resin composition 71. Furthermore, the lower surface 51 of the heat dissipation member 50 is fixed to the surface 11 of the conductive base 10 via solder 60. The heat dissipation member 50 may be fixed to the surface 11 of the conductive base 10 by means of not only the solder 60 but also, for example, by adhesive or screwing.

[0056] 5, a liquid resin composition 72 is filled onto the surface 11 of the conductive base 10 so that the entire heat dissipation member 50 is immersed in the resin composition 72. That is, the resin composition 72 is supplied until the upper surface 52 of the heat dissipation member 50 is covered with the resin composition 72. The resin composition 72 may be supplied onto the surface 11 of the conductive base 10 until the entire heat dissipation member 50 is immersed in the resin composition 72 and until 50% or more of the area of ​​the side surface 33 of the thick copper circuit portion 30 is immersed in the resin composition 72.

[0057] Next, the circuit board 1 is heated, for example, in a heating furnace, until the resin composition 72 is in a semi-cured state. At this time, the circuit board 1 may be heated until the resin composition 72 is completely cured. Next, as shown in FIG. 6, a metal film 73 containing copper or the like is laminated on the resin composition 72. The metal film 73 laminated on the resin composition 72 may have a thickness thinner than the thickness T2 (see FIG. 2) of the thick copper circuit portion 30.

[0058] Next, the circuit board 1 on which the metal film 73 is laminated is heated, for example, using a heating furnace. This hardens the resin compositions 71 and 72 to form the insulating layer 20 (see FIG. 2), and the metal film 73 is pressure-bonded to the surface 22 of the insulating layer 20. Thereafter, a circuit pattern formed on a photoresist by, for example, lithography is transferred to the metal film 73 by etching, and the thin copper circuit portion 40 (see FIG. 2) is formed. In this manner, the circuit board 1 is formed.

[0059] As described above, in the circuit board 1, the heat dissipation member 50, which has a higher thermal conductivity than the insulating layer 20, is disposed within the insulating layer 20, so that at least a portion of the heat transferred from the thick copper circuit portion 30 to the insulating layer 20 can be transferred with high efficiency to the conductive base 10 via the heat dissipation member 50 within the insulating layer 20. The heat transferred to the conductive base 10 is dissipated to the outside of the circuit board 1. Therefore, according to the circuit board 1, the heat of the thick copper circuit portion 30 can be effectively dissipated to the outside of the circuit board 1 via the insulating layer 20, the heat dissipation member 50, and the conductive base 10.

[0060] In a configuration in which the thick copper circuit portion 30 is embedded in the insulating layer 20, as in the present embodiment, the thickness T1 of the insulating layer 20 increases to a certain extent depending on the embedding depth of the thick copper circuit portion 30. When the thickness T1 of the insulating layer 20 increases, for example, the distance that heat from the side surface 33 of the thick copper circuit portion 30 must travel through the insulating layer 20 to reach the conductive base 10 increases, potentially reducing the efficiency of heat transfer from the side surface 33 of the thick copper circuit portion 30 to the conductive base 10. Therefore, by providing a heat dissipation member 50 in the insulating layer 20 at a position facing the side surface 33 of the thick copper circuit portion 30, heat from the side surface 33 of the thick copper circuit portion 30 is efficiently transferred to the conductive base 10 via the heat dissipation member 50. In this way, the heat dissipation member 50 disposed in the insulating layer 20 can compensate for the reduction in the efficiency of heat transfer from the thick copper circuit portion 30 to the conductive base 10, which may occur when the thickness T1 of the insulating layer 20 increases.

[0061] The above embodiment has been described as an embodiment of a circuit board according to the present disclosure. The present disclosure is not limited to the above embodiment, and various modifications are possible without departing from the spirit and scope of the present disclosure.

[0062] In the embodiment shown in FIG. 2, the heat dissipation member 50 is in contact with the conductive base 10. However, as shown in FIG. 7, the heat dissipation member 50 may be spaced apart from the conductive base 10. FIG. 7 shows a YZ cross section of a circuit board 1A according to a modified example. In the example shown in FIG. 7, the lower surface 51 of the heat dissipation member 50 of the circuit board 1A is spaced a predetermined distance from the surface 11 of the conductive base 10 in the thickness direction Z. The distance D7 between the lower surface 51 and the surface 11 in the thickness direction Z may be set to, for example, greater than 0 μm and equal to or less than 1000 μm. The separation distance D7 may be set smaller than the separation distance D4 in the thickness direction Z between the upper surface 52 and the lower surface 41 (i.e., the separation distance D3 in the thickness direction Z between the upper surface 52 and the surface surface 22), or may be set smaller than the separation distance D1 in the thickness direction Z between the embedded lower surface 32 and the surface 11, or may be set smaller than the separation distance D5 in the lateral direction Y between the side surfaces 53 and 33. Even in this configuration, heat from the thick copper circuit portion 30 can be transferred to the conductive base 10 with high efficiency via the heat dissipation member 50, thereby achieving the same effects as the above-described embodiment.

[0063] In the embodiment shown in FIG. 2, a portion of the thick copper circuit portion 30 protrudes from the surface 22 of the insulating layer 20. However, as shown in FIG. 8, the thick copper circuit portion 30 does not have to protrude from the surface 22 of the insulating layer 20. FIG. 8 shows a YZ cross section of a circuit board 1B according to another modification. The thick copper circuit portion 30 of the circuit board 1B is entirely embedded in the insulating layer 20, and the exposed upper surface 31 of the thick copper circuit portion 30 is located on the same plane as the surface 22 of the insulating layer 20. The embedded depth of the thick copper circuit portion 30 may be further increased, so that the exposed upper surface 31 is located lower than the height of the surface 22 of the insulating layer 20 from the surface 11 of the conductive base 10. In other words, the exposed upper surface 31 may be located between the surface 22 and the bottom surface 21 in the thickness direction Z.

[0064] 8 , when the embedding depth of the thick copper circuit portion 30 is represented by the distance D2 in the thickness direction Z between the surface 22 of the insulating layer 20 and the embedded lower surface 32, the distance D2 is set to be the same as the thickness T2 of the thick copper circuit portion 30, that is, 100% of the thickness T2 of the thick copper circuit portion 30. In this case, the entire side surface 33 of the thick copper circuit portion 30 is covered with the insulating layer 20.

[0065] The embedding depth of the thick copper circuit portion 30 can be adjusted by changing the amount of resin composition 72 supplied when forming the resin composition 72 (see FIG. 5) on the surface 11 of the conductive base 10. For example, as shown in FIG. 8, when the exposed upper surface 31 and the surface surface 22 of the insulating layer 20 are arranged on the same plane, the resin composition 72 is supplied onto the surface 11 of the conductive base 10 up to the same height as the exposed upper surface 31. Note that by attaching a release film to the exposed upper surface 31 and supplying the resin composition 72 onto the surface 11 of the conductive base 10 up to the same height as the release film, the exposed upper surface 31 of the thick copper circuit portion 30 can be positioned lower than the surface surface 22 of the insulating layer 20.

[0066] In the above-described circuit board 1B, the thick copper circuit portion 30 is entirely embedded in the insulating layer 20, so that the proportion of the thick copper circuit portion 30 that is covered by the insulating layer 20 can be increased. This increases the contact area between the thick copper circuit portion 30 and the insulating layer 20, so that heat from the thick copper circuit portion 30 can be transferred more efficiently to the insulating layer 20, and the heat transferred to the insulating layer 20 can be transferred more efficiently to the conductive base 10 via the heat dissipation member 50. As a result, the heat dissipation performance of the circuit board 1B can be further improved.

[0067] In the embodiment shown in FIG. 2, the thin copper circuit portion 40 is disposed on the surface 22 of the insulating layer 20. However, as shown in FIG. 9, the thin copper circuit portion 40 may be embedded in the insulating layer 20 with a portion of the thin copper circuit portion 40 exposed, similar to the thick copper circuit portion 30. FIG. 9 is a cross-sectional view showing a circuit board 1C according to yet another modification. In the circuit board 1C, the thin copper circuit portion 40 is embedded in the insulating layer 20, so that the lower surface 41 of the thin copper circuit portion 40 is located at a position lower than the height of the surface 22 of the insulating layer 20 from the surface 11 of the conductive base 10. In other words, the lower surface 41 is located between the surface 22 and the bottom surface 21 in the thickness direction Z. The thin copper circuit portion 40 may have 50% or more, 70% or more, or 90% or more of its surface area covered by the insulating layer 20.

[0068] In order to ensure electrical insulation between the thin copper circuit portion 40 and the heat dissipation member 50, the lower surface 41 of the thin copper circuit portion 40 is spaced a distance D4 from the upper surface 52 of the heat dissipation member 50. In the example shown in Fig. 9, the distance D4 is set to be smaller than the distance D3 in the thickness direction Z between the upper surface 52 and the surface 22. The distance D4 may be set to be equal to or larger than the distance D1 in the thickness direction Z between the embedded lower surface 32 and the surface 11, or may be set to be equal to or larger than the distance D5 in the lateral direction Y between the side surfaces 53 and 33.

[0069] In the circuit board 1C, the thin copper circuit portion 40 is embedded in the insulating layer 20, so that heat from the thin copper circuit portion 40 is transferred with high efficiency to the insulating layer 20 and then transferred with high efficiency to the conductive base 10 via the heat dissipation member 50. The heat transferred to the conductive base 10 is dissipated to the outside of the circuit board 1C. In this way, by embedding both the thick copper circuit portion 30 and the thin copper circuit portion 40 in the insulating layer 20, the heat from the circuit board 1C can be dissipated with high efficiency via the insulating layer 20 and the heat dissipation member 50.

[0070] The present disclosure is not limited to the above-described embodiments and modifications, and various other modifications are possible. For example, the above-described embodiments and modifications may be combined with each other to the extent that they are consistent, depending on the required purpose and effect. In the above-described embodiments and modifications, the "circuit portion" is the thick copper circuit portion 30, but the "circuit portion" is not limited to the thick copper circuit portion 30. For example, the "circuit portion" may be a circuit portion having a thickness of less than 500 μm. The thickness of the "circuit portion" may be, for example, 10 μm or more or 100 μm or more. The cross-sectional shapes of the thick copper circuit portion 30 and the thin copper circuit portion 40 are not limited to the above-described embodiments and modifications, and may, for example, have a partially curved shape.

[0071] The "heat dissipation member" may be a member other than a heat sink, as long as it has a thermal conductivity higher than that of the insulating layer. For example, the "heat dissipation member" may be a heat dissipation plate without heat dissipation fins. In this case, the heat dissipation plate may be configured as a flat plate extending along the XY plane. The "heat dissipation member" may not be configured as a separate member from the conductive base, but may be configured integrally with the conductive base. The material of the "heat dissipation member" may be the same as the material of the conductive base. The "heat dissipation member" may be positioned in the insulating layer facing the circuit portion in the vertical direction X, rather than facing the circuit portion in the horizontal direction Y, or may be positioned so as to surround the circuit portion when viewed from the thickness direction Z. [Explanation of symbols]

[0072] 1,1A,1B,1C...Circuit board, 10...Conductive base, 11...Surface, 20...Insulating layer, 21...Bottom surface, 22...Surface surface, 30...Thick copper circuit part (circuit part), 31...Exposed top surface, 3 2...Buried bottom surface, 33...Side surface, 40...Thin copper circuit section, 50...Heat radiation member, D1, D2, D3, D4, D5, D6, D7...Separation distance, Y...Horizontal direction (cross direction), Z...Thickness direction.

Claims

1. a conductive base; an insulating layer disposed on a surface of the conductive base; a circuit portion embedded in the insulating layer with a portion exposed; a heat dissipation member disposed within the insulating layer and having a higher thermal conductivity than the insulating layer, the insulating layer includes a bottom surface in contact with the surface of the conductive base and a surface surface opposite to the bottom surface, the circuit portion has a side surface along a thickness direction of the insulating layer, The heat dissipation member is arranged within the insulating layer at a position spaced apart from the surface in the thickness direction of the insulating layer and facing the side surface of the circuit portion in a direction intersecting the thickness direction.

2. The circuit board according to claim 1 , wherein the heat dissipation member is in contact with the surface of the conductive base within the insulating layer.

3. the insulating layer includes a bottom surface in contact with the surface of the conductive base and a surface surface opposite to the bottom surface, the circuit portion has a side surface along a thickness direction of the insulating layer, the heat dissipation member is disposed in the insulating layer at a position spaced apart from a surface of the conductive base in a thickness direction of the insulating layer and facing the side surface of the circuit portion in a direction intersecting the thickness direction, a separation distance between the surface and the heat dissipation member in the thickness direction is 30 μm or more; a separation distance between the heat dissipation member and the side surface of the circuit portion in the intersecting direction is 30 μm or more and 1000 μm or less; The circuit board according to claim 1 , wherein a distance in the thickness direction between the heat dissipation member and the surface of the conductive base is greater than 0 and equal to or less than 1000 μm.

4. The circuit board according to any one of claims 1 to 3, wherein the area of ​​the region where the heat dissipation member faces the conductive base is 1% or more and 100% or less of the area of ​​the surface of the conductive base covered with the insulating layer.

5. 5. The circuit board according to claim 1, wherein the heat dissipation member has a thermal conductivity of 50 W / mK or more.

6. 6. The circuit board according to claim 1, wherein the heat dissipation member comprises aluminum, copper, titanium, magnesium, iron, tungsten, or an alloy containing at least one of these.

7. The circuit portion is a thick copper circuit portion having a thickness of 500 μm or more, the circuit portion has an exposed upper surface exposed from the insulating layer and a buried lower surface opposite to the exposed upper surface and facing the surface of the conductive base with the insulating layer interposed therebetween; the insulating layer includes a bottom surface in contact with the surface of the conductive base and a surface surface opposite to the bottom surface, The circuit board according to any one of claims 1 to 6, wherein the distance between the surface and the buried lower surface in the thickness direction of the insulating layer is 50% or more and 130% or less of the thickness of the circuit portion from the buried lower surface to the exposed upper surface.

8. Further provided is a thin copper circuit portion thinner than the circuit portion, the insulating layer includes a bottom surface in contact with the surface of the conductive base and a surface surface opposite to the bottom surface, 8. The circuit board according to claim 1, wherein the thin copper circuit portion is disposed on the surface of the surface.

9. the heat dissipation member is disposed at a position facing the thin copper circuit portion with the insulating layer interposed therebetween in a thickness direction of the insulating layer, 9. The circuit board according to claim 8, wherein the distance between the heat dissipation member and the thin copper circuit portion in the thickness direction is 100 [mu]m or more.

10. 10. The circuit board according to claim 1, wherein the insulating layer contains a curable resin and an inorganic filler.

11. The circuit board according to claim 10 , wherein the content of the inorganic filler in the insulating layer is 50% by volume or more.

12. 12. The circuit board according to claim 10, wherein the inorganic filler has a thermal conductivity of 10 W / mK or more.

13. 13. The circuit board according to claim 10, wherein the inorganic filler has an average particle size of 1 μm or more and 100 μm or less.

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