Thick copper embedded circuit board structure

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 conductive base, and a thick copper circuit part embedded in the insulating layer with a portion of the thick copper circuit part exposed, and the thick copper circuit part is embedded in the insulating layer with more than 50% of its surface area covered by the insulating layer.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a circuit board.

Background Art

[0002] In the field of power electronics, electronic components for power control such as power semiconductor devices are used. Such electronic components may be mounted on a circuit board on which an integrated circuit is 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 device mounted on the circuit pattern.

[0003] Also, Citation Document 2 describes using a thick conductor wiring circuit as a circuit pattern for mounting an electronic component in order to supply a large current to the electronic component.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, with the increase in the output of industrial equipment, the amount of heat generated from electronic components such as semiconductor devices has been increasing. In particular, when a large current is supplied to an electronic component using a thick conductor wiring circuit as in the circuit board described in Citation Document 2, a large amount of heat is generated with the operation of the electronic component, so high heat dissipation performance is required for the circuit board.

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

Means for Solving the Problems

[0007] One embodiment of a circuit board comprises a conductive base, an insulating layer disposed on the conductive base, and a thick copper circuit portion embedded in the insulating layer with a portion exposed, wherein the thick copper circuit portion is embedded in the insulating layer with 50% or more of its surface area covered by the insulating layer.

[0008] In the circuit board according to the above embodiment, more than 50% of the surface area of ​​the thick copper circuit portion is covered by an insulating layer, so heat from the thick copper circuit portion is transferred to the insulating layer with high efficiency. The heat transferred to the insulating layer is dissipated from the conductive base to the outside of the circuit board. Therefore, this circuit board can effectively dissipate heat.

[0009] In one embodiment, the insulating layer may have a thermal conductivity of 3 W / mK or higher. Having a thermal conductivity of 3 W / mK or higher allows the heat from the thick copper circuit section to be transferred to the insulating layer with high efficiency. Therefore, in this embodiment, heat from the circuit board can be dissipated more effectively.

[0010] In one embodiment, the thickness of the thick copper circuit portion may be 500 μm or more. By setting the thickness of the thick copper circuit portion to 500 μm or more, the current capacity of the circuit board can be increased, and the heat generated from the electronic components mounted thereon can be transferred to the insulating layer with high efficiency.

[0011] In one embodiment, the thick copper circuit portion includes an embedded lower surface facing the conductive base and an exposed upper surface on the opposite side of the embedded lower surface that is exposed from the insulating layer, and the insulating layer includes a bottom surface in contact with the conductive base and a surface on the opposite side of the bottom surface, and the distance from the surface surface of the insulating layer to the embedded lower surface may be 50% or more and 130% or less of the thickness of the thick copper circuit portion. By setting the distance from the surface surface of the insulating layer to the embedded lower surface to 50% or more and 130% or less of the thickness of the thick copper circuit portion, the contact area between the thick copper circuit portion and the insulating layer is increased, so that the heat from the thick copper circuit portion is transferred to the insulating layer with high efficiency. As a result, it becomes possible to effectively dissipate the heat from the circuit board.

[0012] In one embodiment, the distance from the conductive base to the buried bottom surface may be 50 μm or more and 300 μm or less. By setting the distance from the conductive base to the buried bottom surface to 50 μm or more and 300 μm or less, it becomes possible to electrically insulate the conductive base from the thick copper circuit.

[0013] In one embodiment, a thin copper circuit section, which is thinner than the thick copper circuit section, may be further provided, and the thin copper circuit section may be arranged on the surface of the insulating layer. In this embodiment, the thick copper circuit section and the thin copper circuit section are mixed on the circuit board, and heat can be effectively dissipated from the thick copper circuit section through which a large current flows.

[0014] In one embodiment, a thin copper circuit section, which is thinner than the thick copper circuit section, may be further provided, and the thin copper circuit section may be embedded in the insulating layer with a portion exposed. In this embodiment, the heat from the thin copper circuit section can be transferred to the insulating layer with high efficiency, so that the heat from the circuit board can be effectively dissipated.

[0015] In one embodiment, the insulating layer may contain a curable resin and an inorganic filler. By including a curable resin and an inorganic filler in the insulating layer, high insulating properties and heat dissipation properties can be imparted to the insulating layer.

[0016] In one embodiment, the inorganic filler content in the insulating layer may be 50% by volume or more. By including 50% by volume or more of inorganic filler, the thermal conductivity of the insulating layer can be further increased.

[0017] In one embodiment, the thermal conductivity of the inorganic filler may be 10 W / mK or higher. By setting the thermal conductivity of the inorganic filler to 10 W / mK, the thermal conductivity of the insulating layer can be further increased.

[0018] The average particle size of the inorganic filler may be 1 μm or more and 100 μm or less. By making the average particle size of the inorganic filler 1 μm or more and 100 μm or less, the thermal conductivity of the insulating layer can be increased. [Effects of the Invention]

[0019] According to one aspect and various embodiments of the present invention, the heat dissipation performance of a circuit board can be improved.

Brief Description of the Drawings

[0020] [Figure 1] It is a perspective view showing a circuit board according to an embodiment. [Figure 2] It is a cross-sectional view taken along line II-II of the circuit board shown in FIG. 1. [Figure 3] It 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 a wire. [Figure 4] It is a cross-sectional view showing a step of a method for manufacturing a circuit board according to an embodiment. [Figure 5] It is a cross-sectional view showing a step of a method for manufacturing a circuit board according to an embodiment. [Figure 6] It is a cross-sectional view showing a step of a method for manufacturing a circuit board according to an embodiment. [Figure 7] It is a cross-sectional view showing a step of a method for manufacturing a circuit board according to an embodiment. [Figure 8] It is a cross-sectional view showing a circuit board according to another embodiment. [Figure 9] It is a cross-sectional view showing a circuit board according to yet another embodiment.

Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions are not repeated. The dimensional ratios in the drawings do not necessarily match those in the description.

[0022] Figure 1 is a perspective view showing a circuit board according to one embodiment. Figure 2 is a cross-sectional view of the circuit board shown in Figure 1 along line II-II. The circuit board 1 shown in Figures 1 and 2 is a metal-based circuit board on which electronic components are mounted to form an integrated circuit, and is suitable for general-purpose applications that use relatively large amounts of power, such as automobiles, industrial robots, and air conditioning equipment. Examples of electronic components mounted on the circuit board 1 include power control semiconductor elements such as MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors).

[0023] As shown in Figures 1 and 2, the circuit board 1 comprises a conductive base 10, an insulating layer 20, and a plurality of thick copper circuit sections 30. The conductive base 10, the insulating layer 20, and the thick copper circuit sections 30 are stacked in this order. In the following description, the stacking direction of the conductive base 10, the insulating layer 20, and the thick copper circuit sections 30 may be referred to as the "thickness direction," the arrangement direction of the plurality of thick copper circuit sections 30 may be referred to as the "length direction," and the direction perpendicular to the thickness direction and length direction may be referred to as the "width direction."

[0024] The conductive base 10 is a conductive metal base substrate. The conductive base 10 is made of a metal having higher thermal conductivity than, for example, the insulating layer 20. Examples of materials for the conductive base 10 include aluminum, iron, copper, stainless steel, or an alloy containing at least one of these metals. The conductive base 10 may also contain non-metallic materials.

[0025] The insulating layer 20 is disposed on the conductive base 10. By interposing the insulating layer 20 between the conductive base 10 and the thick copper circuit 30, the insulating layer 20 physically joins the conductive base 10 and the thick copper circuit 30 while electrically insulating them. The insulating layer 20 also has the function of transferring heat generated by the operation of the semiconductor element mounted on the thick copper circuit 30 to the conductive base 10. To achieve these functions, the insulating layer 20 has high electrical insulation and thermal conductivity. For example, the insulating layer 20 may contain a curable resin and an inorganic filler and have a thermal conductivity of 3 W / mK or higher.

[0026] The curable resin contained in the insulating layer 20 is, for example, a thermosetting resin material and contains a resin and a curing agent. Examples of resins included in the curable resin are 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, fully 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.

[0027] The resin content may be 15% or more by volume, 20% or more by volume, or 30% or more by volume, and may be 70% or less by volume, 60% or less by volume, or 50% or less by volume, based on the total volume of the insulating layer 20.

[0028] The curing agent included in the curable resin is appropriately selected depending on the type of resin. For example, when the resin is an epoxy resin, phenol novolac compounds, acid anhydrides, amino compounds, and imidazole compounds can be used as curing agents. The curing agent content may be, for example, 0.5 parts by mass or more, or 1.0 part by mass or more, or 15 parts by mass or less, or 10 parts by mass or less, per 100 parts by mass of resin.

[0029] The inorganic filler is filled into the insulating layer 20 to enhance its thermal conductivity. The inorganic filler contained in the insulating layer 20 may have a thermal conductivity of, for example, 10 W / mK or higher. Examples of inorganic fillers having such 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 powder form. From the viewpoint of increasing the thermal conductivity of the insulating layer 20, the powdered inorganic filler may have an average particle size of, for example, 1 μm or more and 100 μm or less. The average particle size of the inorganic filler can be adjusted by adjusting the grinding time of the bulk inorganic filler.

[0030] The inorganic filler content in the insulating layer 20 is 50% by volume or more, based on the total amount of the insulating layer 20. This tends to further improve the thermal conductivity of the cured body. Alternatively, the inorganic filler content in the insulating layer 20 is 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. This further improves the coatability of the insulating resin composition and makes it easier to obtain a cured body with superior insulating properties.

[0031] As described above, the insulating layer 20 is formed to cover the upper surface of the conductive base 10. The insulating layer 20 includes a bottom surface 21 that is in contact with the upper surface of the conductive base 10 and a surface 22 that is opposite to the bottom surface 21. The distance between the bottom surface 21 and the surface 22, i.e., the thickness T1 of the insulating layer 20, is set to, for example, 300 μm or more and 1600 μm or less.

[0032] Multiple thick copper circuit sections 30 are arranged on an insulating layer 20. The multiple thick copper circuit sections 30 are arranged in the width direction of the circuit board 1, spaced apart from each other. Note that the circuit board 1 does not necessarily need to have multiple thick copper circuit sections 30; it is sufficient to have at least one thick copper circuit section 30. The thick copper circuit section 30 has a structure in which a desired circuit pattern is formed by processing, for example, etching. The thick copper circuit section 30 is made of copper or an alloy containing copper. The thick copper circuit section 30 is a thicker circuit conductor compared to a general circuit conductor, and has a thickness T2 of, for example, 500 μm or more. Note that the thickness T2 of the thick copper circuit section 30 may be, for example, 600 μm or more, 700 μm or more, 800 μm or more, or 2000 μm or less, or 1000 μm or less.

[0033] Each of the multiple thick copper circuit sections 30 is embedded in the insulating layer 20 with a portion of it exposed. In the embodiment shown in Figure 2, the thick copper circuit section 30 has a substantially rectangular cross-sectional shape and includes an embedded lower surface 31, an exposed upper surface 32, and four side surfaces 33.

[0034] The embedded lower surface 31 is positioned between the bottom surface 21 and the surface layer 22 in the thickness direction of the circuit board 1, and is positioned to face the upper surface of the conductive base 10. In order to ensure electrical insulation between the conductive base 10 and the thick copper circuit section 30, the embedded lower surface 31 of the thick copper circuit section 30 is spaced apart from the conductive base 10. The separation distance D1 between the embedded lower surface 31 of the thick copper circuit section 30 and the conductive base 10 may be set to, for example, 50 μm or more and 300 μm or less.

[0035] The exposed upper surface 32 is the surface opposite to the buried lower surface 31 and is exposed from the insulating layer 20. The exposed upper surface 32 provides a mounting surface on which heat-generating elements such as electronic components are mounted. The exposed upper surface 32 may have a width W of 5 mm or more in the width direction of the circuit board 1, and may have a length of 5 mm or more in the length direction of the circuit board 1.

[0036] The four sides 33 extend in the thickness direction of the circuit board 1 and connect the buried lower surface 31 and the exposed upper surface 32. By embedding the thick copper circuit section 30 within the insulating layer 20, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more of the surface area of ​​each side 33 may be covered by the insulating layer 20. The embedding depth of the thick copper circuit section 30, i.e., the distance D2 from the surface layer 22 of the insulating layer 20 to the buried lower surface 31, may be 50% or more and 130% or less of the thickness T2 of the thick copper circuit section 30.

[0037] As described above, the thick copper circuit section 30 is embedded in the insulating layer 20, so that the entire surface of the embedded lower surface 31 of the thick copper circuit section 30 and at least a portion of the pair of side surfaces 33 are covered by the insulating layer 20. More specifically, 50% or more of the surface area of ​​the thick copper circuit section 30 is covered by the insulating layer 20. In one embodiment, 60% or more, 70% or more, 80% or more, or 90% or more of the surface area of ​​the thick copper circuit section 30 may be covered by the insulating layer 20. Since the insulating layer 20 has a higher thermal conductivity than air, the heat from the thick copper circuit section 30 is transferred to the insulating layer 20 with high efficiency via the embedded lower surface 31 and the pair of side surfaces 33. The heat transferred to the insulating layer 20 is dissipated from the conductive base 10 to the outside of the circuit board 1. In other words, the circuit board 1 has heat conduction paths that dissipate heat generated by electronic components to the outside of the circuit board 1 via the thick copper circuit section 30, the insulating layer 20, and the conductive base section 10.

[0038] In one embodiment, the circuit board 1 may further include thin copper circuit sections 40. In the embodiment shown in Figure 2, a plurality of thin copper circuit sections 40 are arranged on the surface 22 of the insulating layer 20 and are aligned in the longitudinal direction of the circuit board 1. The number of thin copper circuit sections 40 is not limited, and the circuit board 1 may have one or more thin copper circuit sections 40, or it may not have any thin copper circuit sections 40 at all. The thin copper circuit sections 40 are spaced apart from the thick copper circuit sections 30. The spacing D3 between the thin copper circuit sections 40 and the thick copper circuit sections 30 may be set to, for example, 50 μm or more.

[0039] The thin copper circuit section 40 is made of, for example, copper or a copper-containing alloy. The thin copper circuit section 40 is a circuit conductor with a thinner wall thickness than the thick copper circuit section 30, and has a thickness T3 of, for example, 10 μm or more and less than 500 μm. The thin copper circuit section 40 has a structure in which a desired circuit pattern is formed by processing, for example, etching.

[0040] In the embodiment shown in Figure 2, the thin copper circuit section 40 has a substantially rectangular cross-sectional shape and includes a bottom surface 41, an top surface 42, and four side surfaces 43. The bottom surface 41 of the thin copper circuit section 40 is in contact with the surface surface 22 of the insulating layer 20. That is, multiple thin copper circuit sections 40 are arranged on the surface surface 22 of the insulating layer 20. The top surface 42 of the thin copper circuit section 40 is located on the opposite side of the bottom surface 41 and is coplanar with the exposed top surface 32 of the thick copper circuit section 30. The four side surfaces 43 extend in the thickness direction of the circuit board 1 and connect the bottom surface 41 and the top surface 42.

[0041] Note that the upper surface 42 of the thin copper circuit section 40 and the exposed upper surface 32 of the thick copper circuit section 30 do not necessarily have to be on the same plane. For example, the distance between the upper surface 42 of the thin copper circuit section 40 and the exposed upper surface 32 of the thick copper circuit section 30 in the thickness direction of the circuit board 1 may be set to be less than or equal to the thickness T3 of the thin copper circuit section 40. As shown in Figure 3, the exposed upper surface 32 of the thick copper circuit section 30 on which the electronic components 35 are mounted and the upper surface 42 of the thin copper circuit section 40 may be electrically connected by a wire 45. In this case, by reducing the distance between the upper surface 42 of the thin copper circuit section 40 and the exposed upper surface 32 of the thick copper circuit section 30 in the thickness direction of the circuit board 1, it is possible to shorten the length of the wire 45. As a result, it is possible to prevent the wire 45 from breaking and to reduce the electrical resistance of the wire 45.

[0042] Next, a method for manufacturing the circuit board 1 according to one embodiment will be described. In the following description, "resin composition" refers to a resin material before curing that contains a curable resin and an inorganic filler, and the insulating layer 20 is formed when this resin composition cures.

[0043] In a manufacturing method for a circuit board 1 according to one embodiment, a conductive base portion 10 and a thick copper circuit portion 30 are first prepared. A desired circuit pattern is formed on the thick copper circuit portion 30, for example, by etching.

[0044] Next, as shown in Figure 4, a semi-cured (Stage B) resin composition 51 is formed on the embedded lower surface 31 of the thick copper circuit section 30, and the thick copper circuit section 30 is pressed onto the upper surface of the conductive base section 10 via this resin composition 51. The semi-cured resin composition 51 is formed, for example, by applying a liquid resin composition 51 to a desired thickness onto a release film, and then heating the resin composition 51 to semi-cure it.

[0045] Next, as shown in Figure 5, liquid resin composition 52 is filled onto the conductive base 10 so that more than 50% of the surface area of ​​the thick copper circuit section 30 is covered. For example, the resin composition 52 is supplied until more than 50% of the surface area of ​​a pair of side surfaces 33 of the thick copper circuit section 30 is immersed in the resin composition 52. The amount of liquid resin composition 52 supplied onto the conductive base 10 is adjusted according to the proportion of the surface area of ​​the thick copper circuit section 30 that is covered by the insulating layer 20.

[0046] Next, the circuit board 1 is heated, for example, in a heating furnace, until the resin composition 52 is semi-cured. Alternatively, the circuit board 1 may be heated until the resin composition 52 is completely cured. Next, as shown in Figure 6, a copper-containing metal film 53 is laminated onto the resin composition 52. The metal film 53 laminated onto the resin composition 52 may have a film thickness thinner than the thickness T2 of the thick copper circuit portion 30.

[0047] Next, the circuit board 1 with the metal film 53 laminated on it is heated, for example, using a heating furnace. This causes the resin composition 51 and resin composition 52 to harden, forming an insulating layer 20, and pressing the metal film 53 against the surface 22 of the insulating layer 20. Then, as shown in Figure 7, for example, the circuit pattern formed on the photoresist by lithography is transferred to the metal film 53 by etching, forming the thin copper circuit portion 40. In this way, a circuit board 1 having a conductive base portion 10, an insulating layer 20, a thick copper circuit portion 30, and a thin copper circuit portion 40 is formed.

[0048] In the circuit board 1 manufactured in this manner, more than 50% of the surface area of ​​the thick copper circuit section 30 is covered by the insulating layer 20. Since this insulating layer 20 has a higher thermal conductivity than air, heat from the thick copper circuit section 30 can be transferred to the insulating layer 20 with high efficiency through the contact area between the insulating layer 20 and the thick copper circuit section 30. The heat transferred to the insulating layer 20 is dissipated to the outside of the circuit board 1 from the conductive base 10. Therefore, the circuit board 1 can effectively dissipate heat from the thick copper circuit section 30.

[0049] Although circuit boards according to various embodiments have been described above, various modified forms can be constructed without being limited to the embodiments described above, as long as the gist of the invention is not changed.

[0050] For example, in the embodiment shown in Figure 2, only a portion of the thick copper circuit portion 30 is embedded in the insulating layer 20 in the thickness direction of the circuit board 1, but the entire thick copper circuit portion 30 may be embedded in the insulating layer 20. Figure 8 is a cross-sectional view showing a circuit board 1A according to another embodiment. In the circuit board 1A, the entire thick copper circuit portion 30 is embedded in the insulating layer 20, and the exposed upper surface 32 of the thick copper circuit portion 30 is located on the same plane as the surface 22 of the insulating layer 20. The embedding depth of the thick copper circuit portion 30 may be further increased so that the exposed upper surface 32 of the thick copper circuit portion 30 is located between the bottom surface 21 and the surface 22 in the thickness direction of the circuit board 1.

[0051] The embedding depth of the thick copper circuit section 30 can be adjusted by changing the amount of resin composition 52 supplied when forming the resin composition 52 on the conductive base 10 (see Figure 5). For example, as shown in Figure 8, when the exposed upper surface 32 of the thick copper circuit section 30 and the surface layer 22 of the insulating layer 20 are placed on the same plane, the resin composition 52 is supplied to the same height as the exposed upper surface 32 of the thick copper circuit section 30. Furthermore, by attaching a release film to the exposed upper surface 32 of the thick copper circuit section 30 and supplying the resin composition 52 to the same height as the release film, it is possible to position the exposed upper surface 32 of the thick copper circuit section 30 between the bottom surface 21 and the surface layer 22 in the thickness direction of the circuit board 1.

[0052] In the circuit board 1A described above, the entire surface of the embedded lower surface 31 and the pair of side surfaces 33 of the thick copper circuit section 30 are covered with an insulating layer 20. Therefore, heat from the thick copper circuit section 30 can be transferred to the insulating layer 20 with greater efficiency, further improving the heat dissipation performance of the circuit board 1A.

[0053] Figure 9 is a cross-sectional view showing a circuit board 1B according to yet another embodiment. In circuit board 1B, the thin copper circuit portion 40 is embedded in the insulating layer 20 with a portion of it exposed, similar to the thick copper circuit portion 30. In circuit board 1B, the lower surface 41 of the thin copper circuit portion 40 is positioned between the bottom surface 21 and the surface layer 22 in the thickness direction of the circuit board 1, and is positioned to face the upper surface of the conductive base portion 10. In order to ensure electrical insulation between the conductive base portion 10 and the thin copper circuit portion 40, the lower surface 41 of the thin copper circuit portion 40 is spaced apart from the conductive base portion 10. The separation distance D4 between the lower surface 41 of the thin copper circuit portion 40 and the conductive base portion 10 may be set to be larger than the separation distance D1 between the embedded lower surface 31 of the thick copper circuit portion 30 and the conductive base portion 10.

[0054] In the circuit board 1B, the thin copper circuit portion 40 has a surface area of ​​50% or more covered by the insulating layer 20. In one embodiment, the thin copper circuit portion 40 may have a surface area of ​​60% or more, 70% or more, 80% or more, or 90% or more covered by the insulating layer 20. By covering the surface of the thin copper circuit portion 40 with the insulating layer 20, the heat from the thin copper circuit portion 40 is transferred to the insulating layer 20 with high efficiency and released from the conductive base portion 10 to the outside of the circuit board 1. As described above, by embedding both the thick copper circuit portion 30 and the thin copper circuit portion 40 within the insulating layer 20, the heat from the circuit board 1B can be dissipated with high efficiency through the insulating layer 20.

[0055] In the above embodiment, the thick copper circuit section 30 and the thin copper circuit section 40 have a substantially rectangular cross-sectional shape. However, the cross-sectional shape of the thick copper circuit section 30 and the thin copper circuit section 40 is not limited to a rectangular shape, and may, for example, have a partially curved shape. The various embodiments described above can be combined within a non-contradictory range. [Explanation of Symbols]

[0056] 1,1A,1B...Circuit board, 10...Conductive base, 20...Insulating layer, 21...Bottom surface, 22...Surface layer surface, 30...Thick copper circuit section, 31...Buried bottom surface, 32...Exposed top surface, 40...Thin copper circuit section.

Claims

1. A conductive base and An insulating layer disposed on the conductive base, A thick copper circuit section embedded in the insulating layer with a portion exposed, It comprises a thin copper circuit section that is thinner than the thick copper circuit section, The thick copper circuit portion is embedded in the insulating layer with 50% or more of its surface area covered by the insulating layer. The thick copper circuit portion includes a buried lower surface facing the conductive base, an exposed upper surface on the opposite side of the buried lower surface and exposed from the insulating layer, and a side surface connecting the buried lower surface and the exposed upper surface. The insulating layer includes a bottom surface in contact with the conductive base and a surface opposite to the bottom surface. The thickness of the thick copper circuit portion is greater than the distance from the surface of the insulating layer to the buried bottom surface. A portion of the side surface of the thick copper circuit section is exposed from the insulating layer. The thin copper circuit section is a circuit board arranged on the insulating layer.

2. The circuit board according to claim 1, wherein the insulating layer has a thermal conductivity of 3 W / mK or more.

3. The circuit board according to claim 1 or 2, wherein the thickness of the thick copper circuit portion is 500 μm or more.

4. The circuit board according to claim 1, wherein the distance between the conductive base and the buried lower surface is 50 μm or more and 300 μm or less.

5. The circuit board according to claim 1, wherein the thin copper circuit portion is embedded in the insulating layer with a portion of it exposed.

6. The circuit board according to any one of claims 1 to 5, wherein the insulating layer contains a curable resin and an inorganic filler.

7. The circuit board according to claim 6, wherein the inorganic filler content in the insulating layer is 50% by volume or more.

8. The circuit board according to claim 6 or 7, wherein the thermal conductivity of the inorganic filler is 10 W / mK or more.

9. The circuit board according to any one of claims 6 to 8, wherein the average particle size of the inorganic filler is 1 μm or more and 100 μm or less.

10. The thin copper circuit portion is arranged on the surface of the insulating layer, The circuit board according to claim 1, wherein the distance between the upper surface of the thin copper circuit portion and the exposed upper surface of the thick copper circuit portion in the thickness direction of the circuit board is less than or equal to the thickness of the thin copper circuit portion.

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