JP2023064213A - circuit board - Google Patents

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 and having a thermal conductivity of 3 W/mK or higher, and a circuit section embedded in the insulating layer with a portion exposed, the circuit section has an exposed top surface exposed from the insulating layer and an embedded bottom surface on the opposite side of the exposed top surface facing the surface of the conductive base through the insulating layer, and the area of the embedded bottom surface is larger than the exposed top surface.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to circuit boards.

In the field of power electronics, electronic components for power control such as power semiconductor devices are used. Electronic components of this type are sometimes mounted on a circuit board on which an integrated circuit is formed. For example, Patent Document 1 discloses a metal plate made of aluminum, an insulating layer made of resin formed on the metal plate, a circuit pattern formed on the insulating layer, and a circuit pattern mounted on the circuit pattern. A circuit board with power semiconductor components is described.

Moreover, the cited document 2 describes that a thick conductor wiring circuit is used as a circuit pattern for mounting the electronic component in order to supply a large current to the electronic component.

Japanese Patent Application Laid-Open No. 2003-23223 JP 2008-78595 A

2. Description of the Related Art In recent years, the amount of heat generated from electronic components such as semiconductor elements has increased as the output of industrial equipment has increased. In particular, when a thick conductor wiring circuit is used as in the circuit board described in D2 to supply a large current to electronic components, a large amount of heat is generated as the electronic components operate. Substrates are required to have high heat dissipation performance.

Accordingly, an object of the present disclosure is to improve the heat dissipation performance of a circuit board.

A circuit board according to one aspect includes a conductive base, an insulating layer disposed on the surface of the conductive base and having a thermal conductivity of 3 W/mK or more, and a part of the circuit board being exposed and embedded in the insulating layer. a circuit portion, the circuit portion having 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 area is greater than the area of the exposed top surface.

In the circuit board of the aspect described above, since the area of the embedded lower surface of the circuit portion is larger than the area of the exposed upper surface of the circuit portion, a large contact area between the circuit portion and the insulating layer can be ensured. As a result, the heat of the circuit section can be transferred to the insulating layer with high efficiency. The heat transferred to the insulating layer is radiated from the conductive base to the outside of the circuit board. Therefore, with this circuit board, the heat of the circuit board can be effectively radiated.

In one embodiment, the area of the embedded lower surface may be less than the area of the surface of the conductive base coated with the insulating layer. In this case, by securing the area of the embedded lower surface within the range where the embedded lower surface can be covered with an insulating layer, the heat of the circuit board can be dissipated while ensuring electrical insulation between the circuit section and its surrounding components. Heat can be effectively dissipated through the insulating layer.

In one embodiment, the area of the exposed upper surface may be 0.2% or more and 25% or less of the area of the portion of the surface of the circuit section covered with the insulating layer. In this case, it is possible to increase the ratio of the area of the buried lower surface to the area of the exposed upper surface while ensuring the mounting area of the components on the exposed upper surface. As a result, a larger contact area can be secured between the circuit section and the insulating layer, and the heat of the circuit section can be transferred to the insulating layer with higher efficiency. As a result, the heat of the circuit board can be dissipated more effectively.

In one embodiment, the circuit section may further have an embedded upper surface embedded in the insulating layer, which is an upper surface opposite to the embedded lower surface in the thickness direction of the insulating layer. In this case, a large contact area can be secured between the circuit portion and the insulating layer. Therefore, according to the above configuration, it is possible to more reliably realize a configuration in which the heat of the circuit section is transferred to the insulating layer with high efficiency.

In one embodiment, the circuit portion has a first portion of the circuit portion from the embedded lower surface to the exposed upper surface and a second portion of the circuit portion from the embedded lower surface to the embedded upper surface; The thickness may be 0.01% or more and less than 100% of the thickness of the first portion. In this case, by providing the second portion of the circuit section in the insulating layer, a larger contact area can be secured between the circuit section and the insulating layer. Therefore, according to the above configuration, it is possible to more reliably realize a configuration in which the heat of the circuit section is transferred to the insulating layer with high efficiency.

In one embodiment, the thickness of the first portion may be greater than or equal to 500 μm and less than or equal to 3000 μm. In this case, a circuit section having a first portion and a second portion can be suitably realized.

In one embodiment, the circuit portion has a first portion of the circuit portion from the embedded lower surface to the exposed upper surface and a second portion of the circuit portion from the embedded lower surface to the embedded upper surface; The thickness is thinner than the thickness of the first portion, the first portion is configured in a columnar shape extending in the thickness direction from the buried lower surface to the exposed upper surface, and the second portion is formed within the insulating layer as the first portion. It may be constructed so as to protrude in a direction intersecting the thickness direction. In this case, by projecting the second portion in the insulating layer, a larger contact area can be secured between the circuit section and the insulating layer. Therefore, according to the above configuration, it is possible to more reliably realize a configuration in which the heat of the circuit section is transferred to the insulating layer with high efficiency.

In one embodiment, the insulating layer includes a bottom surface contacting the surface of the conductive base and a surface surface opposite the bottom surface, and the circuit portion comprises a first portion of the circuit portion from the buried bottom surface to the exposed top surface. and a second portion of the circuit portion extending from the embedding lower surface to the embedding upper surface, the thickness of the second portion being the same as the thickness of the first portion, and the first portion and the second portion may be configured in a plate-like shape extending in a direction intersecting the thickness direction in the insulating layer, and the exposed upper surface may form a recess with respect to the surface layer surface. In this case, since the circuit portion extends like a plate in the insulating layer, a larger contact area can be secured between the circuit portion and the insulating layer. Therefore, according to the above configuration, it is possible to more reliably realize a configuration in which the heat of the circuit section is transferred to the insulating layer with high efficiency.

In one embodiment, the insulating layer includes a bottom surface in contact with the surface of the conductive base and a surface layer surface opposite to the bottom surface, and the distance between the embedded lower surface and the surface of the conductive base in the thickness direction of the insulating layer is is 50 μm or more and 300 μm or less, and the distance in the thickness direction between the buried bottom surface and the surface layer surface may be 50% or more and 130% or less of the thickness direction distance between the buried bottom surface and the exposed top surface. In this case, it is possible to more preferably realize a configuration in which the heat of the circuit section is efficiently transmitted to the insulating layer while ensuring electrical insulation between the circuit section and the conductive base.

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 surface layer opposite to the bottom surface. , the thin copper circuit portion may be arranged on the surface layer surface. In this case, the circuit part and the thin copper circuit part thinner than the circuit part are mixed on the circuit board, and the heat of the circuit part through which a larger current can flow than the thin copper circuit part is effectively radiated. becomes possible.

In one embodiment, the insulating layer may contain a curable resin and an inorganic filler. In this case, the insulating layer can be provided with high insulating properties and heat dissipation properties.

In one embodiment, the content of the inorganic filler contained in the insulating layer may be 50% by volume or more. In this case, the thermal conductivity of the insulating layer can be further increased.

In one embodiment, the inorganic filler may have a thermal conductivity of 10 W/mK or higher. In this case, the thermal conductivity of the insulating layer can be further increased.

According to one aspect and various embodiments of the present disclosure, it is possible to improve the heat dissipation of the circuit board.

1 is a perspective view showing a circuit board according to one embodiment; FIG. FIG. 2 is a cross-sectional view of the circuit board shown in FIG. 1 taken along line II-II; FIG. 4 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; FIG. 4 is a cross-sectional view showing one step of a method for manufacturing a circuit board according to one embodiment; FIG. 4 is a cross-sectional view showing one step of a method for manufacturing a circuit board according to one embodiment; FIG. 4 is a cross-sectional view showing one step of a method for manufacturing a circuit board according to one embodiment; It is a cross-sectional view showing a circuit board according to a modification. It is a sectional view showing a circuit board concerning another modification.

Embodiments of the present disclosure will be described below with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference numerals, and redundant description will not be repeated. The dimensional proportions of the drawings do not necessarily match those of the description.

FIG. 1 is a perspective view showing a circuit board according to one embodiment. FIG. 2 is a cross-sectional view of the circuit board shown in FIG. 1 along line II-II. 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 suitably used for general-purpose applications that require relatively large amounts of electric power, such as automobiles, industrial robots, air conditioners, and the like. 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).

As shown in FIGS. 1 and 2, the circuit board 1 includes a conductive base 10, an insulating layer 20 laminated on the conductive base 10, and a plurality of thick copper circuit portions 30 embedded in the insulating layer 20. (circuit part) and In the following description, the “thickness direction Z” is 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” indicates a direction intersecting the thickness direction Z (more specifically, the direction in which the plurality of thick copper circuit portions 30 are arranged) among the extending directions of the insulating layer 20 . The “horizontal direction Y” is the extending direction of the insulating layer 20 and indicates a direction intersecting the thickness direction Z and the vertical direction X. As shown in FIG.

The conductive base 10 is a conductive metal base substrate. The conductive base 10 is made of metal having higher thermal conductivity than the insulating layer 20, for example. 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 contain non-metallic materials. The conductive base 10 has a surface 11 along the XY plane.

An insulating layer 20 is disposed on the surface 11 of the conductive base 10 . The insulating layer 20 is interposed between the conductive base portion 10 and the thick copper circuit portion 30 so as to physically join the conductive base portion 10 and the thick copper circuit portion 30, and to connect the conductive base portion 10 and the thick copper circuit portion 30 together. It has a function of electrically insulating the circuit section 30 . Furthermore, the insulating layer 20 has a function of transferring heat generated by the operation of the electronic components mounted on the thick copper circuit portion 30 to the conductive base portion 10 . In order to achieve these functions, insulating layer 20 has high electrical insulation and thermal conductivity. For example, the insulating layer 20 has higher thermal conductivity than the thick copper circuit section 30 . Specifically, the insulating layer 20 has a thermal conductivity of 3 W/mK or higher. The insulating layer 20 may contain, for example, a curable resin and an inorganic filler.

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 resins, silicone resins, silicone rubbers, acrylic resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluorine resins, polyimides, polyamideimides, polyetherimides, poly Butylene terephthalate, polyethylene terephthalate, polyphenylene ether, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber/styrene) ) resin, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin.

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, based on the total volume of the insulating layer 20. may be:

The curing agent contained in the curable resin is appropriately selected according to 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 may be 15 parts by mass or less or 10 parts by mass or less with respect to 100 parts by mass of the resin.

The inorganic filler fills the insulating layer 20 in order 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 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 powdery 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 pulverization time of the massive inorganic filler.

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. In addition, the content of the inorganic filler in the insulating layer 20 may be 80% by volume or less, preferably 75% by volume or less, more preferably 70% by volume or less, based on the total amount of the insulating layer 20. good. In this case, the coating properties of the insulating resin composition are further improved, making it easier to obtain the insulating layer 20 having excellent insulating properties.

The insulating layer 20 is formed, for example, so as 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 in contact with the surface 11 of the conductive base 10 and a surface layer surface 22 opposite to the bottom surface 21 . A separation distance in the thickness direction Z between the bottom surface 21 and the surface layer surface 22, that is, the thickness T1 of the insulating layer 20 is set to, for example, 300 μm or more and 4200 μm or less. A hole portion 23 for embedding the thick copper circuit portion 30 in the insulating layer 20 is formed in the surface layer 22 . The hole 23 is open on the surface layer 22 , extends in the thickness direction Z from the surface layer 22 toward the surface 11 of the conductive base 10 , and then bends and extends in the horizontal direction Y.

As shown in FIG. 1, the plurality of thick copper circuit sections 30 are arranged along the longitudinal direction X at predetermined intervals (that is, separated from each other). Although three thick copper circuit sections 30 are shown in FIG. 1, the number of thick copper circuit sections 30 is not limited. The circuit board 1 may include one thick copper circuit section 30, or may include two or four or more thick copper circuit sections 30. FIG. Each thick copper circuit section 30 has the same configuration. Therefore, in the following description, the configuration of one thick copper circuit section 30 will be specifically described, but the configurations of the other thick copper circuit sections 30 will also be described in the same manner.

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 section 30 is made of copper or an alloy containing copper. As shown in FIG. 2, the thick copper circuit section 30 is a thicker circuit conductor than general circuit conductors, and has a thickness T2 of 500 μm or more, for example. The thickness T2 of the thick copper circuit portion 30 here refers to the thickness of the thickest portion of the thick copper circuit portion 30 (that is, the maximum thickness). In the example shown in FIG. 2, the thickness T2 of the thick copper circuit portion 30 corresponds to the distance in the thickness direction Z between the exposed upper surface 31 and the buried lower surface 34, which will be described later. 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.

The thick copper circuit section 30 is embedded in the insulating layer 20 with its part exposed. In this embodiment, a portion of the thick copper circuit portion 30 protrudes and is exposed from the surface layer surface 22 of the insulating layer 20 , and the remainder of the thick copper circuit portion 30 is embedded in the hole portion 23 of the insulating layer 20 . The state in which the thick copper circuit portion 30 is embedded in the insulating layer 20 means that at least a portion of the thick copper circuit portion 30 is embedded under the surface layer surface 22 of the insulating layer 20 so that at least a portion of the thick copper circuit portion 30 is embedded in the insulating layer 20 . 20 is covered. 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more of the surface area of the thick copper circuit portion 30 may be covered with the insulating layer 20 .

In FIG. 2, the thick copper circuit portion 30 has a T-shaped cross section. The thick copper circuit portion 30 includes an exposed upper surface 31 exposed from the surface layer surface 22 of the insulating layer 20, an embedded upper surface 32 embedded under the surface layer surface 22 of the insulating layer 20, and the exposed upper surface 31 and the embedded upper surface 32 in the thickness direction. A pair of first side surfaces 33, 33 connected to Z, an embedded lower surface 34 embedded in the insulating layer 20, and a pair of second side surfaces 35 connecting the embedded upper surface 32 and the embedded lower surface 34 in the thickness direction Z, 35 and .

The exposed upper surface 31 and the embedded upper surface 32 are surfaces facing the opposite side of the surface 11 of the conductive base 10 in the thickness direction Z, and constitute the upper surface of the thick copper circuit portion 30 . The exposed upper surface 31 is at a position protruding from the surface layer 22 of the insulating layer 20 , in other words, at a position higher than the height of the surface layer 22 from the surface 11 of the conductive base 10 . Exposed top surface 31 provides a mounting surface on which electronic components 39 (see FIG. 3) are mounted. The area of the exposed upper surface 31 may be, for example, 0.2% or more of the area of the surface 11 of the conductive base 10 covered with the insulating layer 20, and may be 50% or less or 25% or less of the area. . 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. The area of the surface 11 of the conductive base 10 covered with the insulating layer 20 means 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 total area of the surface 11 of the conductive base 10 .

The embedded upper surface 32 is arranged to spread along the XY plane with respect to the exposed upper surface 31 when viewed from the thickness direction Z, and extends along the horizontal direction Y. As shown in FIG. The embedded upper surface 32 has, for example, a rectangular shape surrounding the exposed upper surface 31 . The embedded upper surface 32 is located at a position lower than the height of the exposed upper surface 31 from the surface 11 , specifically, at a position lower than the height of the surface layer surface 22 from the surface 11 . More specifically, the embedded upper surface 32 is located between the surface layer surface 22 and the embedded lower surface 34 in the thickness direction Z. As shown in FIG. An insulating layer 20 is interposed between the buried top surface 32 and the surface layer surface 22 , and the buried top surface 32 is covered with the insulating layer 20 . In this embodiment, a thin copper circuit portion 40, which will be described later, is arranged on the surface layer surface 22, and the embedded upper surface 32 faces the thin copper circuit portion 40 in the thickness direction Z. As shown in FIG. In order to ensure electrical insulation between the thick copper circuit portion 30 and the thin copper circuit portion 40, the embedded upper surface 32 is separated from the surface layer surface 22 in the thickness direction Z by a predetermined distance. A separation distance D1 in the thickness direction Z between the embedded upper surface 32 and the surface layer surface 22 may be set to, for example, 30 μm or more and 3000 μm or less.

The buried lower surface 34 is a surface facing the opposite side of the upper surface of the thick copper circuit portion 30 in the thickness direction Z, that is, the surface 11 side of the conductive base portion 10 , and constitutes the lower surface of the thick copper circuit portion 30 . The buried lower surface 34 is located in a position lower than the height of the buried upper surface 32 from the surface 11 in the insulating layer 20 and faces the surface 11 of the conductive base 10 in the thickness direction Z. As shown in FIG. In order to ensure electrical insulation between the conductive base portion 10 and the thick copper circuit portion 30, the embedded lower surface 34 is separated from the surface 11 in the thickness direction Z by a predetermined distance. A separation distance D2 in the thickness direction Z between the embedding lower surface 34 and the surface 11 may be set to, for example, 50 μm or more and 300 μm or less. Also, the separation distance D2 may be set smaller than the separation distance D1 in the thickness direction Z between the embedded upper surface 32 and the surface layer surface 22 . When the embedding depth of the thick copper circuit portion 30 is represented by the separation distance D3 in the thickness direction Z between the surface layer surface 22 and the embedding lower surface 34, the separation distance D3 is, for example, 50% or more of the thickness T2 of the thick copper circuit portion 30. , 70% or more, or 90% or more, and may be 130% or less or 100% or less of the thickness T2 of the thick copper circuit portion 30 . The separation distance D3 is the separation distance in the thickness direction Z between the embedded upper surface 32 and the embedded lower surface 34, that is, the thickness of the columnar portion P1 described later in the thickness direction Z (equivalent to the thickness T2 of the thick copper circuit portion 30) of 50%. % or more and 130% or less.

The area of the embedded lower surface 34 is set larger than the area of the exposed upper surface 31 . The area of the embedded lower surface 34 may be set to be 1.5 times or more, 2 times or more, or 3 times or more the area of the exposed upper surface 31 . By setting the area of the buried lower surface 34 larger than the area of the exposed upper surface 31 in this way, the ratio of the area of the buried lower surface 34 to the area of the exposed upper surface 31 is increased. As a result, the ratio of the covered portion of the thick copper circuit portion 30 covered with the insulating layer 20 increases, and the contact area between the thick copper circuit portion 30 and the insulating layer 20 increases. As a result, the heat of the thick copper circuit section 30 is transferred to the insulating layer 20 with high efficiency. The heat transferred to the insulating layer 20 is effectively radiated to the outside of the circuit board 1 via the conductive base portion 10 .

The area of the embedded lower surface 34 may be set smaller than the area of the surface 11 of the conductive base 10 covered with the insulating layer 20 . In this case, the embedded lower surface 34 is prevented from protruding from the insulating layer 20 , and the embedded lower surface 34 is reliably covered with the insulating layer 20 . As a result, the heat of the thick copper circuit portion 30 is effectively transferred to the outside of the circuit board 1 while ensuring electrical insulation between the embedded lower surface 34 and surrounding components (for example, the conductive base portion 10). Heat can be dissipated.

The first side surface 33 and the second side surface 35 constitute side surfaces of the thick copper circuit portion 30 that connect the upper surface and the lower surface of the thick copper circuit portion 30 . The pair of first side surfaces 33 extend in the thickness direction Z between the exposed top surface 31 and the buried top surface 32 and face each other in the lateral direction Y. As shown in FIG. A portion of the pair of first side surfaces 33 protrudes and is exposed from the surface layer surface 22 of the insulating layer 20 , and the rest of the pair of first side surfaces 33 is embedded in the insulating layer 20 and covered with the insulating layer 20 . ing. The pair of second side surfaces 35 extend in the thickness direction Z between the embedded upper surface 32 and the embedded lower surface 34 and face each other in the lateral direction Y. As shown in FIG. The entire surfaces of the pair of second side surfaces 35 are embedded in the insulating layer 20 and covered with the insulating layer 20 . When the embedding depth of the thick copper circuit portion 30 is represented by the area of the covered portion covered with the insulating layer 20 of the side surfaces (that is, the first side surface 33 and the second side surface 35) of the thick copper circuit portion 30 , The area of the covering portion may be, for example, 50% or more, 70% or more, or 90% or more of the total area of the side surface of the thick copper circuit portion 30, and may be 130% of the total area of the side surface of the thick copper circuit portion 30. % or less or 100% or less.

The portion of the thick copper circuit portion 30 from the embedded lower surface 34 to the exposed upper surface 31 is divided into a columnar portion P1 (first portion) extending in a columnar shape along the thickness direction Z between the embedded lower surface 34 and the exposed upper surface 31. It's becoming The columnar portion P1 has, for example, a prism shape. One end of the columnar portion P<b>1 (that is, the portion including the exposed upper surface 31 ) protrudes and is exposed from the surface layer 22 of the insulating layer 20 . On the other hand, the rest of the columnar portion P<b>1 (that is, the other portion including the embedded lower surface 34 ) is embedded in the hole portion 23 of the surface layer surface 22 . By adjusting the length (thickness) in the thickness direction Z of the columnar portion P1, the height of the exposed upper surface 31 relative to the surface layer surface 22 of the insulating layer 20 can be easily adjusted. The thickness of the columnar portion P<b>1 in the thickness direction Z corresponds to the thickness T<b>2 of the thick copper circuit portion 30 . The thickness of the columnar portion P1 in the thickness direction Z is set to, for example, 500 μm or more and 3000 μm or less.

A portion of the thick copper circuit portion 30 from the embedded lower surface 34 to the embedded upper surface 32 is a plate-like portion that extends in the lateral direction Y from the columnar portion P1 in a state of being embedded in the insulating layer 20. P2 (second part). The plate-like portion P2 has, for example, a plate shape and extends along the XY plane within the insulating layer 20 . The plate-like portion P2 protrudes in the lateral direction Y to one side of the columnar portion P1 so as to extend in the Y direction, and also slightly protrudes in the lateral direction Y to the other side of the columnar portion P1. The plate-like portion P2 projecting on one side of the columnar portion P1 extends in the lateral direction Y, for example, to a position facing the thin copper circuit portion 40 described later in the thickness direction Z. As shown in FIG. The plate-like portion P2 may not protrude from both sides of the columnar portion P1 in the lateral direction Y, or may protrude from only one side of the columnar portion P1 in the lateral direction Y.

The plate-like portion P2 slightly protrudes on both sides of the columnar portion P1 in the vertical direction X, for example. However, in the vertical direction X, since the other thick copper circuit portions 30 embedded in the insulating layer 20 are arranged, the plate-like portion P2 is electrically connected to the other thick copper circuit portions 30. The plate-like portion P2 is separated from the other thick copper circuit portions 30 by a predetermined distance so as to ensure insulation. On the other hand, in the horizontal direction Y, other thick copper circuit portions 30 are not arranged. Therefore, the plate-like portion P2 can extend from one end to the other end of the insulating layer 20 in the horizontal direction Y. As shown in FIG. Note that the plate-like portion P2 does not have to protrude from the columnar portion P1 in the vertical direction X.

FIG. 2 shows the width W1 of the columnar portion P1 and the overhang amount W2 of the plate-like portion P2. The protrusion amount W2 of the plate-like portion P2 indicates the maximum protrusion amount of the plate-like portion P2 from the plate-like portion P2. In the example shown in FIG. 2, the protrusion amount W2 of the plate-like portion P2 is the first side surface 33 of the columnar portion P1, which is the base end of the plate-like portion P2, and the second side surface 35, which is the tip of the plate-like portion P2. and , in the horizontal direction Y. Also, the width W1 of the columnar portion P1 indicates the separation distance in the horizontal direction Y between the pair of first side surfaces 33, 33. As shown in FIG.

The protrusion amount W2 of the plate-like portion P2 may be set, for example, to 1.1 times or more the width W1 of the columnar portion P1. Also, the protrusion amount W2 of the plate-like portion P2 may be set, for example, to 0.9 times or less the length in the lateral direction Y of the surface 11 of the conductive base 10 covered with the insulating layer 20 . By increasing the amount of protrusion of the plate-like portion P2, the area of the embedding lower surface 34 can be increased. Thereby, the contact area between the thick copper circuit portion 30 and the insulating layer 20 can be increased, and the heat of the thick copper circuit portion 30 can be transferred to the insulating layer 20 with high efficiency.

As shown in FIG. 2, the thickness T3 of the plate-like portion P2, that is, the distance in the thickness direction Z between the embedded lower surface 34 and the embedded upper surface 32 is set thinner than the thickness T2 of the thick copper circuit portion 30. As shown in FIG. For example, the thickness T3 of the plate-like portion P2 may be set to 0.01% or more and less than 100% of the thickness T2 of the thick copper circuit portion 30 . By increasing the thickness T3 of the plate-like portion P2, the surface area of the plate-like portion P2 in the insulating layer 20 can be increased. Thereby, the contact area between the thick copper circuit portion 30 and the insulating layer 20 can be increased, and the heat of the thick copper circuit portion 30 can be transferred to the insulating layer 20 with high efficiency.

The circuit board 1 further includes a plurality of thin copper circuit portions 40 arranged on the surface layer 22 of the insulating layer 20 . In FIG. 1, three thin copper circuit portions 40 are arranged with a predetermined distance from one thick copper circuit portion 30 along the horizontal direction Y, and a total of nine thin copper circuit portions 40 are arranged in three rows. Arranged in 3 columns. The number of the thin copper circuit portions 40 is not limited, and the circuit board 1 may include one thin copper circuit portion 40 or may not include the thin copper circuit portion 40 . Each thin copper circuit section 40 has the same configuration.

The thin copper circuit section 40 is made of, for example, copper or an alloy containing copper. The thin copper circuit portion 40 is a circuit conductor thinner 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 section 40 has a structure in which a desired circuit pattern is formed by processing, for example, etching.

The thin copper circuit section 40 includes a lower surface 41 in contact with the surface layer 22 of the insulating layer 20 and an upper surface 42 facing away from the lower surface 41 . The lower surface 41 faces the embedded upper surface 32 in the thickness direction Z with the insulating layer 20 interposed therebetween. The lower surface 41 may be arranged at a position lower than the surface layer surface 22 of the insulating layer 20 by embedding the thin copper circuit portion 40 in the insulating layer 20 . The upper surface 42 is arranged, for example, on the same plane as the exposed upper surface 31 of the thick copper circuit section 30 . That is, the upper surface 42 is arranged at the same position as the exposed upper surface 31 in the thickness direction Z. As shown in FIG. The upper surface 42 may be arranged at a position spaced apart from the exposed upper surface 31 in the thickness direction Z. For example, the distance in the thickness direction Z between the upper surface 42 and the exposed upper surface 31 may be set to the distance in the thickness direction Z between the upper surface 42 and the lower surface 41, that is, the thickness T4 of the thin copper circuit section 40 or less. Further, the distance D4 in the horizontal direction Y between the thin copper circuit portion 40 and the thick copper circuit portion 30 may be set to 50 μm or more, for example.

As shown in FIG. 3 , the exposed upper surface 31 of the thick copper circuit portion 30 on which the electronic component 39 is mounted and the upper surface 42 of the thin copper circuit portion 40 may be electrically connected via wires 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 . As a result, disconnection of the wire 45 can be prevented, and the electrical resistance of the wire 45 can be reduced. In this embodiment, the thick copper circuit portion 30 has a columnar portion P1 whose thickness in the thickness direction Z can be easily adjusted. Therefore, by adjusting the thickness of the columnar portion P1 (that is, the thickness T2 of the thick copper circuit portion 30), the distance in the thickness direction Z between the upper surface 42 and the exposed upper surface 31 of the thick copper circuit portion 30 is reduced. The height of the exposed upper surface 31 can be set as follows.

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

In the method of manufacturing the circuit board 1 according to one embodiment, first, the conductive base 10 and the thick copper circuit portion 30 are prepared. The thick copper circuit portion 30 is formed, for example, by etching to have a T-shaped cross section having a columnar portion P1 and a plate-like portion P2.

Next, as shown in FIG. 4 , a resin composition 51 in a semi-cured state (B stage) is formed on the embedded lower surface 34 of the thick copper circuit portion 30 , and the thick copper circuit portion 30 is formed through the resin composition 51 . It is crimped onto the conductive base 10 . The semi-cured resin composition 51 is formed by, for example, applying a liquid resin composition 51 to a desired thickness on a release film, and then heating the resin composition 51 to semi-cure the resin composition 51. be done.

Next, as shown in FIG. 5, a liquid resin composition 52 is filled on the conductive base 10 so that the buried upper surface 32 of the thick copper circuit portion 30 is entirely covered with the resin composition 52 . For example, the resin composition 52 is supplied until 50% or more of the total area of the side surfaces (that is, the first side surface 33 and the second side surface 35) of the thick copper circuit portion 30 is immersed in the resin composition 52. The amount of the liquid resin composition 52 supplied onto the conductive base 10 may be adjusted according to the proportion of the side surface of the thick copper circuit section 30 covered with the insulating layer 20 .

Next, the circuit board 1 is heated by, for example, a heating furnace until the resin composition 52 is in a semi-cured state. At this time, the circuit board 1 may be heated until the resin composition 52 is completely cured. Next, as shown in FIG. 6, a metal film 53 containing copper or the like is laminated on the resin composition 52 . The metal film 53 laminated on the resin composition 52 may have a thickness smaller than the thickness T2 (see FIG. 2) of the thick copper circuit portion 30 .

Next, the circuit board 1 on which the metal film 53 is laminated is heated using, for example, a heating furnace. As a result, the resin composition 51 and the resin composition 52 are cured to form the insulating layer 20 (see FIG. 2), and the metal film 53 is pressure-bonded to the surface layer 22 of the insulating layer 20 . After that, as shown in FIG. 2, the circuit pattern formed in the photoresist by, for example, lithography is transferred to the metal film 53 by etching to form the thin copper circuit portion 40 (see FIG. 2). Thus, the circuit board 1 is formed.

As described above, in the circuit board 1 , the area of the embedded lower surface 34 embedded in the insulating layer 20 is set larger than the area of the exposed upper surface 31 . The proportion of the covered portion covered with 20 can be increased, and accordingly, the contact area between the thick copper circuit portion 30 and the insulating layer 20 can be increased. Since the insulating layer 20 has a higher thermal conductivity than air, if the contact area between the thick copper circuit portion 30 and the insulating layer 20 can be increased, the contact between the insulating layer 20 and the thick copper circuit portion 30 can be improved. The heat of the thick copper circuit portion 30 can be transferred to the insulating layer 20 with high efficiency through the portion. The heat transferred to the insulating layer 20 is radiated to the outside of the circuit board 1 through the conductive base portion 10 . Therefore, according to the circuit board 1, the heat of the thick copper circuit portion 30 can be effectively radiated.

The above embodiment describes one embodiment of the circuit board according to the present disclosure. The present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the gist of the present disclosure.

In the embodiment shown in FIG. 2, the case where a part of the thick copper circuit portion 30 protrudes from the surface layer surface 22 of the insulating layer 20 is exemplified. However, as shown in FIG. 7 , the thick copper circuit portion 30A (circuit portion) does not have to protrude from the surface layer surface 22 of the insulating layer 20 . FIG. 7 shows a YZ cross section of a circuit board 1A according to a modification. The thick copper circuit portion 30A of the circuit board 1A is entirely embedded in the insulating layer 20, and the exposed upper surface 31 of the thick copper circuit portion 30A is arranged on the same plane as the surface layer surface 22 of the insulating layer 20. .

In the example shown in FIG. 7, when the embedding depth of the thick copper circuit portion 30A is expressed by the separation distance D3 in the thickness direction Z between the surface layer surface 22 of the insulating layer 20 and the embedding lower surface 34, the separation distance D3 is the thick copper circuit. It is set to be the same as the thickness T2 of the portion 30A, that is, 100% of the thickness T2 of the thick copper circuit portion 30A. In this case, the entire side surfaces of the thick copper circuit portion 30A (that is, the first side surface 33 and the second side surface 35) are covered with the insulating layer 20. FIG. The embedding depth of the thick copper circuit portion 30A can be adjusted by changing the supply amount of the resin composition 52 when forming the resin composition 52 (see FIG. 5) on the conductive base portion 10. . For example, when the exposed upper surface 31 of the thick copper circuit portion 30A and the surface layer surface 22 of the insulating layer 20 are arranged on the same plane as shown in FIG. A resin composition 52 is provided on the surface 11 of the conductive base 10 .

In the circuit board 1A described above, since the entire thick copper circuit portion 30A is embedded in the insulating layer 20, the ratio of the covered portion of the thick copper circuit portion 30A covered with the insulating layer 20 can be increased. can be done. As a result, the contact area between the thick copper circuit portion 30A and the insulating layer 20 can be increased, so that the heat of the thick copper circuit portion 30A can be transferred to the insulating layer 20 with higher efficiency. As a result, it is possible to further improve the heat dissipation of the circuit board 1A.

In the embodiment shown in FIG. 2, the thick copper circuit section 30 is configured to have a T-shaped cross section having a columnar portion P1 and a plate-like portion P2. However, as shown in FIG. 8, the thick-copper circuit portion 30B (circuit portion) may be formed entirely in a plate shape. FIG. 8 shows a YZ cross section of a circuit board 1B according to another modification. The thick copper circuit portion 30B 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 30B is arranged at a position lower than the surface layer surface 22 of the insulating layer 20. .

In the thick copper circuit portion 30B shown in FIG. 8, a portion P3 (first portion) from the embedded lower surface 34 to the exposed upper surface 31 and a portion P4 (second portion) from the embedded lower surface 34 to the embedded upper surface 32 are: It is formed in a plate shape extending along the XY plane within the insulating layer 20 . The thick copper circuit portion 30B including the portion P3 and the portion P4 has, for example, a flat plate shape with a uniform thickness as a whole. The exposed upper surface 31 of the portion P3 is arranged on the same plane as the embedded upper surface 32 of the portion P4. That is, the exposed upper surface 31 is positioned at the same height as the embedded upper surface 32 . Therefore, the exposed upper surface 31 is positioned lower than the surface layer 22 of the insulating layer 20 , that is, between the surface layer 22 and the bottom surface 21 , as is the buried upper surface 32 . The exposed top surface 31 forms a recess with respect to the surface layer surface 22 .

In FIG. 8, the thickness of the portion P3 and the thickness of the portion P4 are the same and are represented by the thickness T2 of the thick copper circuit portion 30B. It can also be said that the thickness of the portion P3 is set to 100% of the thickness T2 of the thick copper circuit portion 30B. When the embedding depth of the thick copper circuit portion 30B is represented by the separation distance D3 in the thickness direction Z between the surface layer surface 22 of the insulating layer 20 and the embedding lower surface 34, the separation distance D3 is 100% of the thickness T2 of the thick copper circuit portion 30B. set to greater than %. The separation distance D3 may be set to, for example, 130% or less of the thickness T2 of the thick copper circuit portion 30B.

When manufacturing the circuit board 1B, when the resin composition 52 (see FIG. 5) is formed on the surface 11 of the conductive base 10, the release film is attached to the exposed upper surface 31 and the release film is attached. A resin composition 52 is supplied onto the surface 11 of the conductive base 10 up to the same height. After the thin copper circuit portion 40 (see FIG. 2) is formed on the insulating layer 20 by etching, the release film is peeled off from the exposed upper surface 31 to obtain the circuit board 1B shown in FIG.

Since the circuit board 1B described above is entirely embedded in the insulating layer 20, the ratio of the covered portion of the thick copper circuit portion 30B covered with the insulating layer 20 is increased as in the case of the circuit board 1A. be able to. Therefore, the heat of the thick copper circuit portion 30B can be transferred to the insulating layer 20 with higher efficiency, and the heat dissipation of the circuit board 1B can be further improved. Further, in the circuit board 1B, unlike the thick copper circuit portion 30 of the above-described embodiment, the thick copper circuit portion 30B is configured in a plate shape. In this case, the process for processing the thick copper circuit portion 30B to have a T-shaped cross section is not necessary, so the manufacture of the thick copper circuit portion 30B is facilitated. Furthermore, since the exposed upper surface 31 of the thick copper circuit portion 30B is arranged at a position lower than the surface layer surface 22 of the insulating layer 20, the thin copper circuit portion 40 is more dense than the thick copper circuit portion 30 of the above-described embodiment. The separation distance in the thickness direction Z between the upper surface 42 and the exposed upper surface 31 is large. By increasing the distance between the thin copper circuit portion 40 and the thick copper circuit portion 30B in this way, the electrical insulation between the thin copper circuit portion 40 and the thick copper circuit portion 30B is ensured more reliably. can do.

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 within a consistent range according to the desired purpose and effect. In the above-described embodiments and modifications, the "circuit section" is the thick copper circuit section 30, but the "circuit section" is not limited to the thick copper circuit section 30. For example, the "circuit section" 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 shape of the thick copper circuit portion 30 and the cross-sectional shape of the thin copper circuit portion 40 are not limited to the above-described embodiments and modifications, and may have, for example, a partially curved shape.

DESCRIPTION OF SYMBOLS 1, 1A, 1B... Circuit board 11... Surface 10... Conductive base 20... Insulating layer 21... Bottom surface 22... Surface layer surface 30, 30A, 30B... Thick copper circuit part (circuit part) 31... Exposed top surface 32 Buried top surface 34 Buried bottom surface 40 Thin copper circuit portion D1, D2, D3, D4 Spacing distance P1 Columnar portion (first portion) P2 Plate portion (second part), P3... part (first part), P4... part (second part), Z... thickness direction.

Claims (13)

a conductive base;
an insulating layer disposed on the surface of the conductive base and having a thermal conductivity of 3 W/mK or higher;
a circuit part embedded in the insulating layer in a partially exposed state,
The circuit section
an exposed upper surface exposed from the insulating layer;
a buried lower surface facing the surface of the conductive base through the insulating layer on the opposite side of the exposed upper surface;
The circuit board, wherein the area of the buried lower surface is larger than the area of the exposed upper surface. 2. The circuit board according to claim 1, wherein the area of the embedded lower surface is smaller than the area of the surface of the conductive base covered with the insulating layer. 3. The circuit board according to claim 1, wherein the area of the exposed upper surface is 0.2% or more and 25% or less of the area of the portion of the surface of the circuit section covered with the insulating layer. 4. The circuit part according to claim 1, further comprising a buried upper surface embedded in the insulating layer, the upper surface of the insulating layer being opposite to the embedded lower surface in the thickness direction of the insulating layer. circuit board. The circuit section has a first portion from the embedded lower surface to the exposed upper surface and a second portion from the embedded lower surface to the embedded upper surface,
5. The circuit board according to claim 4, wherein the thickness of said second portion is 0.01% or more and less than 100% of the thickness of said first portion. 6. The circuit board according to claim 5, wherein the first portion has a thickness of 500 [mu]m or more and 3000 [mu]m or less. The circuit section has a first portion from the embedded lower surface to the exposed upper surface and a second portion from the embedded lower surface to the embedded upper surface,
The thickness of the second portion is thinner than the thickness of the first portion,
the first portion is configured in a columnar shape extending in the thickness direction from the embedded lower surface to the exposed upper surface;
5. The circuit board according to claim 4, wherein said second portion is configured to protrude from said first portion in said insulating layer in a direction crossing said thickness direction. the insulating layer includes a bottom surface in contact with the surface of the conductive base and a surface layer surface opposite to the bottom surface;
The circuit section has a first portion from the embedded lower surface to the exposed upper surface and a second portion from the embedded lower surface to the embedded upper surface,
The thickness of the second portion is the same as the thickness of the first portion,
The first portion and the second portion are formed in a plate shape extending in a direction intersecting the thickness direction in the insulating layer,
5. The circuit board according to claim 4, wherein said exposed upper surface forms a recess with respect to said surface layer. the insulating layer includes a bottom surface in contact with the surface of the conductive base and a surface layer surface opposite to the bottom surface;
a distance between the embedded lower surface and the surface of the conductive base in the thickness direction of the insulating layer is 50 μm or more and 300 μm or less;
9. The distance in the thickness direction between the buried lower surface and the surface layer surface is 50% or more and 130% or less of the distance in the thickness direction between the buried lower surface and the exposed upper surface. or the circuit board according to claim 1. Further comprising 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 layer surface opposite to the bottom surface;
The circuit board according to any one of claims 1 to 9, wherein the thin copper circuit portion is arranged on the surface layer surface. The circuit board according to any one of claims 1 to 10, wherein the insulating layer contains a curable resin and an inorganic filler. 12. The circuit board according to claim 11, wherein the content of said inorganic filler contained in said insulating layer is 50% by volume or more. The circuit board according to claim 11 or 12, wherein the inorganic filler has a thermal conductivity of 10 W/mK or higher.

Images