JP2005268648A - Circuit structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit structure which can suppress heat from being confined therein. <P>SOLUTION: In the circuit structure, a control circuit is formed on one surface of a circuit board 18 by a printed wiring means, and a relay 11 controlled by the control circuit is mounted on one surface of the circuit board. A metallic conductive path 13B (heat transfer layer) is formed on the other surface of the circuit board 18 by the printed wiring means. A lower case 50 also as a heat irradiating member is adhered to the conductive path 13B via an adhesive sheet 16 disposed therebetween. Since the conductive path 13B (heat transfer layer) enables heat generated in the relay 11 mounted on one surface of the circuit board 18 to be quickly transmitted to the other surface of the circuit board 18, heat confinement in the rcircuit structure 10 can be suppressed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a circuit structure.

  Conventionally, a power circuit for distributing power from a common in-vehicle power source to various electronic units, a switching element (for example, a mechanical relay switch, a semiconductor switching element, etc.) provided in the power circuit, and driving of the switching element 2. Description of the Related Art Generally, an electrical junction box is known in which a circuit structure incorporating a control circuit to be controlled is surrounded by a casing (see Patent Document 1).

  In the above circuit structure, a circuit pattern is formed on one surface of the circuit board. On this surface, a switching element for controlling the power circuit and a control circuit for controlling driving of the switching element are provided. Elements (not shown) are mounted, and a control circuit is formed by these circuit patterns, switching elements, and control circuit elements. A bus bar constituting the power circuit is bonded to the other surface of the circuit board via an insulating layer, and the bus bar and the switching element are electrically connected. A heat radiating member is bonded to an opposite surface of the bus bar to the circuit board through an insulating layer.

  In the circuit structure, a relatively large current flows in the power circuit. Since this power circuit is connected to the switching element, a relatively large current also flows through the switching element. For this reason, the amount of heat generated from the switching element is relatively large. Since the control circuit element may be adversely affected by the heat generated from the switching element, it is necessary to quickly remove the heat generated in the switching element. For this reason, a heat radiating member is attached to the circuit structure, and the heat generated by the switching element is radiated to the outside of the electric junction box by the heat radiating member.

However, in the electrical junction box having the above-described configuration, there is a problem that heat generated in the switching element is not sufficiently transmitted to the heat radiating member, and heat may be accumulated.
JP 2003-164040 A

  The heat generated in the switching element is transferred to the switching element → the terminal of the switching element → the circuit pattern constituting the control circuit → the circuit board → the insulating layer → the bus bar → the insulating layer → the heat radiating member, and is radiated from the heat radiating member.

  Among the above paths, the terminals of the switching elements, the circuit patterns constituting the control circuit, and the bus bars are made of metal, so that heat can be conducted relatively easily.

  On the other hand, since the circuit board is made of synthetic resin or ceramic, and the insulating layer is mainly made of synthetic resin, it is difficult to conduct heat. Therefore, in order to prevent heat from being accumulated in the circuit structure, there is a problem of how to increase the heat conductivity of the circuit board and the insulating layer. In particular, when the switching element and the control circuit element are mounted on the same surface of the circuit board, the heat generated by the switching element is quickly transferred to the other surface in order to reduce the influence of heat on the control circuit element. It is required to be able to communicate.

  This invention is completed based on the above situations, Comprising: It is providing the circuit structure body which suppressed heat accumulation.

  As means for achieving the above object, the invention of claim 1 is characterized in that a control circuit is formed on one surface of a circuit board by printed wiring means, and a switching element controlled by the control circuit is formed on one surface thereof. A circuit structure formed by mounting, wherein a heat transfer layer made of metal is formed on the other surface of the circuit board by printed wiring means, and a heat dissipation member is bonded to the heat transfer layer via an adhesive layer. It is characterized by being.

  According to a second aspect of the present invention, in the circuit structure according to the first aspect, the heat transfer layer is formed as a circuit pattern and constitutes a power circuit controlled by the switching element.

  According to a third aspect of the present invention, in the circuit structure according to the first or second aspect, the bus bar constituting the power circuit controlled by the switching element is insulative between the heat transfer layer and the heat radiating member. It is characterized by being bonded through an adhesive layer.

  According to a fourth aspect of the present invention, in the circuit structure according to any one of the first to third aspects, the thickness of the heat transfer layer is not less than 70 μm and not more than 800 μm.

  According to a fifth aspect of the present invention, in the circuit structure according to any one of the first to fourth aspects, the heat transfer layer and the heat radiating member are bonded with an insulating adhesive sheet. .

  According to a sixth aspect of the present invention, in the circuit structure according to any one of the first to fifth aspects, the circuit board is provided with one surface and the other surface of the circuit board in the vicinity of the switching element. Thermal vias that are thermally connected are formed.

  According to a seventh aspect of the present invention, in the circuit structure according to any one of the first to sixth aspects, an opening is formed in the circuit board, and the switching element is accommodated in the opening. It is in contact with the heat transfer layer.

  According to an eighth aspect of the present invention, in the circuit structure according to any one of the second to sixth aspects, an opening is formed in the circuit board, and the switching element is accommodated in the opening. A terminal is provided on the bottom surface of the switching element, and the switching element is mounted on the heat transfer layer in a state where the terminal is electrically connected to the heat transfer layer.

<Invention of Claim 1>
The heat generated in the switching element is transferred from the switching element → the terminal of the switching element → the circuit pattern constituting the control circuit → the circuit board → the metal heat transfer layer. Since the terminal and circuit pattern of the switching element are made of metal, the heat generated by the switching element mounted on one surface of the circuit board is quickly transferred to the circuit board. According to the first aspect of the present invention, since the heat transfer layer made of metal is formed on the other surface of the circuit board, the heat transferred to the circuit board is quickly transferred to the heat transfer layer. Thereby, the heat generated in the switching element can be quickly transferred to the surface on the opposite side from where the switching element is mounted. As described above, according to the first aspect of the present invention, it is possible to obtain a circuit configuration body in which heat is suppressed.

<Invention of Claim 2>
In the invention of claim 2, the heat generated in the switching element is the switching element → the terminal of the switching element → the circuit pattern constituting the control circuit → the circuit board → the metal heat transfer layer (power circuit) → the insulating layer → the heat dissipation. It is transmitted to the member and radiated from the heat radiating member.

  On the other hand, in the conventional example, as described above, switching element → terminal of switching element → circuit pattern constituting control circuit → circuit board → insulating layer → bus bar (power circuit) → insulating layer → heat dissipation member.

  Comparing the two, in the heat transfer path from the circuit board to the power circuit (heat transfer layer or bus bar), the invention of claim 2 has one insulating layer having a lower thermal conductivity than the conventional example. Thereby, since the heat transfer property at the time of transferring the heat generated in the switching element to the heat dissipation member is improved, the heat dissipation property of the circuit structure is improved.

  In addition, when using a bus bar as a power circuit as in the conventional example, since a conductive path is formed by punching out one metal plate, it is necessary to secure an interval between punching jigs. It was necessary to spread some. For this reason, there is a problem that it is difficult to increase the density of the power circuit.

  According to the invention of claim 2, since the heat transfer layer formed on the circuit board constitutes the power circuit, compared with the case where the power circuit is constituted by the bus bar as in the conventional example, the interval between the conductive paths is reduced. Can be narrowed. As a result, the circuit density can be increased.

<Invention of Claim 3>
In the invention of claim 3, the heat generated in the switching element is the switching element → the terminal of the switching element → the circuit pattern constituting the control circuit → the circuit board → the heat transfer layer → the insulating layer → the bus bar (power circuit) → the insulating layer. → It is transmitted to the heat radiating member and radiated from the heat radiating member.

  On the other hand, in the conventional example, as described above, switching element → terminal of switching element → circuit pattern constituting control circuit → circuit board → insulating layer → bus bar (power circuit) → insulating layer → heat dissipation member.

  Comparing the heat transfer paths of the invention of claim 3 and the conventional example, in the invention of claim 3, the heat transfer layer is interposed in the process of conducting heat from the circuit board to the insulating layer and the bus bar (power circuit). ing. With this heat transfer layer, the heat transfer performance of the circuit structure can be improved. This is due to the following reason.

  Since the circuit board has low thermal conductivity, heat generated in the switching element is transferred to the other surface of the circuit board at the part directly below the terminal of the switching element or the part directly below the circuit pattern connected to this terminal. Although the temperature of the board rises, the temperature of the circuit board may not rise sufficiently in a portion away from the terminals and the circuit pattern. Thus, in the conventional example, the temperature distribution tends to occur in the surface direction of the circuit board. As a result, all the heat may not be transmitted to the heat dissipation member directly under the terminal or the circuit pattern, whereas almost no heat is transferred to the heat dissipation member at the part away from the terminal or circuit pattern. There is. Thus, the circuit structure according to the conventional example has a problem that the efficiency of heat conduction from the circuit board to the heat dissipation member is poor.

  According to the invention of claim 3, the metal heat transfer layer is formed on the other surface of the circuit board. The heat generated in the switching element is transmitted from the portion immediately below the terminal of the switching element or the portion directly below the circuit pattern connected to the terminal to the other surface of the circuit board to be transmitted to the heat transfer layer. Then, as a result of heat being quickly transferred through the heat transfer layer, the temperature of the entire heat transfer layer becomes substantially constant. Thereby, the heat generated in the switching element is uniformly distributed in the surface direction over the entire heat transfer layer and is transmitted from the entire heat transfer layer to the heat radiating member, so that the heat transfer property of the circuit structure is improved.

<Invention of Claim 4>
In the conventional printed wiring board, the conductive path (metal layer) generally has a thickness of 18 μm to 35 μm, whereas in the invention of claim 4, the heat transfer layer (metal layer) is used. A substrate having a thickness of 70 μm or more and 800 μm or less is used. When the heat transfer layer is thick in this way, the cross-sectional area of the heat transfer path in the surface direction of the heat transfer layer is increased, so that the amount of heat per unit time conducted in the surface direction through the heat transfer layer increases. For this reason, heat is efficiently dispersed throughout the heat transfer layer, and the temperature distribution in the surface direction of the heat transfer layer is reduced. As a result, heat is transferred from the entire heat transfer layer to the heat radiating member. Will improve.

<Invention of Claim 5>
According to invention of Claim 5, a circuit board and a heat radiating member are adhere | attached with an insulating adhesive sheet. As a result, it is possible to impart insulation to the surface of the heat transfer layer without performing resist treatment (to form an insulating layer by applying an insulating resin) to the heat transfer layer. Can be reduced.

<Invention of Claim 6>
According to the invention of claim 6, the heat generated by the switching element mounted on one surface of the circuit board can be transmitted to the other surface of the circuit board via the thermal via. As a result, the heat generated by the switching element can be transferred to the other surface of the circuit board without going through a circuit board having a low thermal conductivity, so that it is possible to obtain a circuit structure in which heat is suppressed.

<Invention of Claim 7>
According to invention of Claim 7, an opening part is formed in a circuit board, the switching element is accommodated in this opening part, and is in contact with the heat-transfer layer. As a result, the heat generated in the switching element can be directly transferred to the heat transfer layer formed on the other surface of the circuit board without going through the circuit board having a low thermal conductivity, thereby suppressing heat accumulation. Thus, a circuit configuration body can be obtained.

<Invention of Claim 8>
According to the invention of claim 8, the opening is formed in the circuit board, the switching element is accommodated in the opening, and the terminal provided on the bottom surface of the switching element is electrically connected to the heat transfer layer. The switching element is mounted on the heat transfer layer in a state of being connected to. Thereby, the number of terminals protruding from the switching element and connected to the conductive path on the circuit board can be reduced. Then, the number of terminal connection conductive paths formed on the upper surface of the circuit board can be reduced. As a result, since a circuit can be newly formed in a region where the conductive path is not required, the wiring density on the upper surface of the circuit board can be increased.

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the circuit board 18, the relay 11 and the electronic device 12 mounted on the circuit board 18, the connector 30 and the fuse box 40 connected to the circuit board 18 are the lower case 50 that also serves as the heat radiating member 71. The circuit structure 10 surrounded from below is surrounded by an upper case 60 from above to form an electrical connection box 72. In the description of the first embodiment, the vertical direction is based on FIG. 1, the horizontal direction is the right front side of FIG. 1 on the right side, the left back side is the left side, and the front and rear direction is the same as that of FIG. The left side is the front and the right side is the rear.

(Circuit board 18)
A relay 11 (corresponding to a switching element) and an electronic device 12 are mounted on the circuit board 18. This circuit board 18 has a horizontally long plate shape, and has a shape in which two corners on the rear side are cut out in a triangular shape when viewed from above.

  Copper conductive paths 13 are formed on the upper and lower surfaces of the circuit board 18 by printed wiring means. The conductive path 13A formed on the upper surface of the circuit board 18 constitutes a control circuit for controlling the driving of the relay 11, and the conductive path 13B formed on the lower surface (corresponding to the heat transfer layer of claim 1) is mounted on the vehicle. A power circuit connected to a power source (not shown) is configured. The thickness of the conductive path 13 is 18 μm to 35 μm.

  In order to configure the conductive path 13 on both surfaces of the circuit board 18, for example, the following method can be used. Copper foil (not shown) is formed on both upper and lower surfaces of a laminate (not shown) in which a predetermined number of prepregs (not shown) (for example, a cloth made of glass fiber impregnated with a thermosetting resin and made into a semi-cured state) are stacked. A copper-clad laminate in which copper foils (not shown) are directly formed on both sides of the circuit board 18 by superimposing them one by one and curing them by heating and compressing the thermosetting resin. A plate (not shown) is prepared, and an etching resist is applied to both sides of the copper-clad laminate to form the conductive path 13, and then unnecessary copper foils on both sides are simultaneously etched to remove the etching resist. A circuit board 18 having a conductive path 13 formed thereon can be produced (subtractive method).

  Further, a laminate (not shown) in which a predetermined number of prepregs (not shown) are stacked is heated and compressed to cure the thermosetting resin to produce a laminate, and a catalyst (not shown) is formed on the surface of the laminate. ), The portion except the conductive path 13 is coated with a plating-resistant material, and then electroless copper plating is performed to deposit copper plating only on the conductive path 13 so that the conductive path 13 is formed on both sides. The substrate 18 can be produced (additive method).

  A plurality of relays 11 and a plurality of electronic devices 12 are mounted on the upper surface of the circuit board 18. A control circuit that controls driving of the relay 11 is formed by the electronic device 12 and the conductive path 13A.

  The relay 11 has a substantially rectangular parallelepiped shape, and a plurality of terminals 14 (six in this embodiment) protrude from the bottom of the relay 11 and extend downward, and then bent outward at a right angle to form a circuit board. 18 is arranged along the surface. These terminals 14 include a control terminal 14 that is connected to the control circuit and controls driving of the relay 11, and an energization terminal 14 that is connected to the power circuit and controls the power circuit.

  The relay 11 and the electronic device 12 and the conductive path 13A can be connected by, for example, reflow soldering. In this reflow soldering, cream solder (not shown) is applied to a portion of the conductive path 13A formed on the upper surface of the circuit board 18 to which the relay 11 and the terminal 14 of the electronic device 12 are to be connected, for example, by screen printing. The relay 11 and the terminal 14 of the electronic device 12 are placed thereon, and heated and cooled to the solder melting temperature in a reflow furnace (not shown), thereby the relay 11 and the electronic device 12 and the conductive path 13A. This is a method of soldering.

  Of the conductive paths 13A formed on the upper surface of the circuit board 18, the one connected to the energizing terminal 14 of the relay 11 is a conductive path formed on the lower surface of the circuit board 18 by a jumper line (not shown) or a via hole (not shown). 13B. A power circuit is formed by the relay 11, the conductive path 13A, and the conductive path 13B.

  At a position near the front end of the circuit board 18, a plurality of through holes 22A arranged in the left-right direction are formed penetrating in the up-down direction. Terminal fittings 31 to be described later are inserted into these through holes 22A, and the connector 30 is connected to the circuit board 18 via the terminal fittings 31.

  Further, at a position near the rear end of the circuit board 18, a plurality of through-holes 22 </ b> B that are horizontally long when viewed from above are formed in the left-right direction so as to penetrate in the vertical direction. A fuse terminal fitting 41 described later is inserted into these through holes 22B, and the fuse box 40 is connected to the circuit board 18 via the fuse terminal fitting 41.

(Connector 30)
The connector 30 connected to the circuit board 18 includes a connector housing 32, a plurality of terminal fittings 31, and an alignment plate 33.

  The connector housing 32 is made of synthetic resin, has a horizontally long box shape, and includes a hood portion 34 that opens forward. A plurality of terminal fittings 31 are press-fitted into the bottom wall portion 35 of the hood portion 34 so as to penetrate in the front-rear direction. The front end portion of the terminal fitting 31 protrudes into the hood portion 34, and the rear end portion is exposed to the rear of the connector housing 32. The exposed portion of the terminal fitting 31 to the rear is a board connecting portion 31A bent downward, and the lower end portion of the board connecting portion 31A is inserted into the through hole 22A of the circuit board 18 in the vertical direction so that the circuit board 18 Is connected to a power circuit formed on the lower surface.

  The alignment plate 33 is made of resin, and includes a main body portion 33A extending in the left-right direction and a pair of plate-like attachment pieces 33B and 33B extending rearward from both end edges of the main body portion 33A. The rear end portions of both mounting pieces 33B and 33B protrude upward and have a substantially L shape when viewed from the side. The alignment plate 33 is attached to the lower case 50 at a position near the upper ends of the mounting pieces 33B and 33B. An insertion hole 33 </ b> C communicating in the left-right direction for screwing is provided.

  An insertion hole 33 </ b> D communicating in the vertical direction is formed on the upper surface of the main body portion 33 </ b> A side by side in the horizontal direction. The lower end portion of the board connecting portion 31A is inserted into the insertion holes 33D from above, and the lower end portion of the board connecting portion 31A is prevented from being displaced in the front-rear and left-right directions.

(Fuse box 40)
The fuse box 40 connected to the circuit board 18 includes a fuse block 42 and a plurality of fuse terminal fittings 41.

  The fuse block 42 is made of synthetic resin and has a horizontally long box shape. An opening 44 for inserting a fuse (not shown) is provided in the rear wall 43 of the fuse block 42 side by side in the left-right direction. A pair of rectangular attachment portions 45, 45 project outward from the left and right outer surfaces of the fuse block 42, and the insertion portions 46, 45 communicate with the attachment portions 45, 45 in the vertical direction. Is formed.

  On the bottom wall 48 of the fuse block 42, a plurality of slits (not shown) having a substantially L shape when viewed from above are formed in the left-right direction, and a plurality of fuse terminals to be described later are formed in the slits. A metal fitting 41 is inserted from below. The fuse terminal fitting 41 has an elongated plate shape, and includes a fuse connection portion 41A having a plate surface directed in the left-right direction and a substrate connection portion 41B formed to extend downward from the rear end of the fuse connection portion 41A. Become. The fuse terminal fitting 41 is bent at a right angle to the left when viewed from above, with the boundary between the fuse connection portion 41A and the substrate connection portion 41B being a fold line.

  A press-fit groove 47 is provided at the rear end portion of the fuse connection portion 41A, and a fuse terminal (not shown) is inserted and sandwiched so as to be electrically connected.

  On the other hand, the lower end of the board connection portion 41B protrudes downward through the bottom wall 48 of the fuse block 42, and the lower end portion of the board connection portion 41B is inserted vertically into the through hole 22B of the circuit board 18, It is connected to a power circuit formed on the lower surface of the circuit board 18.

(Lower case 50)
The lower case 50 is made of metal (in the present embodiment, made of aluminum), has a horizontally long plate-like bottom wall 51, a rear wall 52 extending upward from the rear end of the bottom wall 51, and both left and right ends of the bottom wall 51. And side walls 53, 53 extending upward from the top.

  A partition wall 54 that protrudes upward from the bottom wall 51 and extends to the left and right is formed at a position retracted rearward from the front end of the bottom wall 51 by a predetermined dimension. When the partition wall 54 and the outer surface of the bottom surface portion 35 of the connector housing 32 abut against each other, the connector housing 32 is prevented from being displaced rearward.

  The bottom wall 51 is formed with a first relief groove 55 </ b> A extending in the left-right direction behind the partition wall 54. A second escape groove 55B extending in the left-right direction is formed at a position retracted forward from the rear end portion of the bottom wall 51 by a predetermined width. When the circuit board 18 is assembled into the lower case 50, the first escape groove 55A prevents the lower end portion of the terminal fitting 31 connected to the circuit board 18 from interfering with the lower case 50. The second escape groove 55 </ b> B prevents the lower end portion of the fuse terminal fitting 41 connected to the circuit board 18 from interfering with the lower case 50.

  The height of the side walls 53, 53 is one step lower than the central portion up to a position retracted rearward by a predetermined dimension, and a first stepped portion 59A standing at a right angle is formed. In each side wall 53, 53, two insertion holes 56A, 56B penetrating in the left-right direction are formed behind the first stepped portion 59A in the front-rear direction. When the circuit board 18 is assembled in the lower case, the insertion hole 56A located on the front side is formed so as to be aligned with an insertion hole 65 of the upper case 60 described later, and a bolt (not shown) is inserted into the insertion hole 56A and the insertion hole from the left and right directions. The lower case 50 and the upper case 60 are fixed by being inserted through the nut 65 and screwed into a nut (not shown). The insertion hole 56B located on the rear side is formed so as to be aligned with the insertion hole 33C of the alignment plate 33, and a bolt (not shown) is inserted through the insertion hole 56B and the insertion hole 33C from the left and right directions. The lower case 50 and the alignment plate 33 are fixed by being screwed into the nuts that are not.

  The height of the region from the rear end portion of the side walls 53, 53 to the position retracted forward by a predetermined length is one step lower than the height dimension of the central portion, and the second vertical A stepped portion 59B is formed. The side walls 53, 53 have a slightly wide rear end at the center portion, and a screw hole 57 is formed in the widened portion so as to face in the vertical direction.

  A pair of screwing portions 58, 58 are formed at both ends of the rear wall 52 so as to be slightly wider forward, and screw holes 58A are formed in the screwing portions 58, 58 in the vertical direction. Yes. The screw holes 58A are formed so as to be aligned with the insertion holes 46 formed in the mounting portions 45, 45 of the fuse block 42 when the circuit board 18 is assembled to the lower case 50. The screw holes 58A and the insertion holes 46 are formed. The fuse block 42 and the lower case 50 are assembled to each other by screwing a bolt (not shown).

  On the upper surface of the bottom wall 51 of the lower case 50, an adhesive sheet cut out in a predetermined shape in a region behind the partition wall 54 and in front of the rear wall 52 (corresponding to the insulating adhesive layer of claim 1). 16 is arranged, and a circuit board 18 is overlaid on the adhesive sheet 16. In this embodiment, a prepreg is used as the adhesive sheet 16. The circuit board 18, the adhesive sheet 16, and the lower case 50 are heated and pressure-bonded in an overlapped state, and the circuit board 18 and the lower case 50 are bonded together by the cured adhesive sheet 16 to form the circuit structure 10. Yes.

(Upper case 60)
The upper case 60 is made of metal (in this embodiment, made of aluminum), has a horizontally long plate-shaped upper surface wall 61, a front wall 62 extending downward from the front end of the upper surface wall 61, and a rear end of the upper surface wall 61. A rear wall 63 extending downward from the right side wall, and side walls 53, 53 extending downward from the left and right ends of the upper surface wall 61.

  A recess 64 is formed in the front wall 62 of the upper case 60 so as to leave both side edge portions of the front wall 62 in an approximately half region from the lower end thereof upward. When the lower case 50 is assembled, the connector 30 is accommodated.

  On both side walls 64, 64 of the upper case 60, rectangular attachment pieces 66 are formed in a state of hanging downward from a front end edge of the side walls 64, 64 by a predetermined dimension. 66 A of insertion holes are formed in the attachment piece 66 facing the left-right direction. The insertion hole 66A is formed so as to be aligned with the insertion hole 56A provided in the side wall 53 of the lower case 50 when the upper case 60 is assembled to the lower case 50. The insertion hole 56A and the insertion hole 66A are formed in the insertion hole 56A. A bolt (not shown) is inserted from the left and right direction, and is screwed into a nut (not shown) to fix the upper case 60 and the lower case 50.

  A pair of screwing portions 67, 67 formed in a square recess shape downward is formed at the two corners located on the rear side of the upper case 60, and each screwing portion 67, 67 has An insertion hole 67A penetrating in the vertical direction is formed. When the upper case 60 is assembled to the lower case 50, the insertion hole 67A formed in the upper case 60 and the screw hole 57 formed in the lower case 50 are aligned, and the insertion hole 67A and the screw hole 57 are aligned. The upper case 60 and the lower case 50 are fixed by screwing a bolt (not shown) from above.

  The operation and effect of the first embodiment will be described below. As described above, in the first embodiment, the heat generated in the relay 11 is transmitted in the order of the relay 11 → the terminal 14 of the relay 11 → the conductive path 13A on the circuit board 18 → the circuit board 18 → the heat transfer layer 13B (power circuit). . Since the terminal 14 and the conductive path 13A of the relay 11 are made of metal, the heat generated by the relay 11 mounted on the upper surface of the circuit board 18 is quickly transferred to the circuit board 18. According to the first embodiment, since the metal conductive path (heat transfer layer) 13A is formed on the lower surface of the circuit board 18, the heat transferred to the circuit board 18 is transferred to the conductive path (heat transfer layer) 13A. It is transmitted quickly. Thereby, since the heat generated in the relay 11 can be quickly transmitted to the surface opposite to the side where the relay 11 is mounted, according to the first embodiment, the circuit in which the heat is suppressed is suppressed. The structure 10 can be obtained.

  Further, in the first embodiment, the heat generated in the relay 11 is generated from the relay 11 → the terminal 14 of the switching element → the conductive path 13A on the circuit board 18 → the circuit board 18 → the heat transfer layer 13B (power circuit) → the adhesive sheet 16. (Insulating layer) → Transfers to the lower case 50 and dissipates heat from the lower case 50 (see FIG. 4).

  Therefore, Embodiment 1 has one less insulating layer with low thermal conductivity in the heat transfer path than in the conventional example. Thereby, since the heat transfer property at the time of transferring the heat generated in the relay 11 to the lower case 50 is improved, the heat dissipation of the circuit component 10 is improved.

  In addition, when using a bus bar as a power circuit as in the conventional example, since a conductive path is formed by punching out one metal plate, it is necessary to secure an interval between punching jigs. It was necessary to spread some. For this reason, there is a problem that it is difficult to increase the density of the power circuit.

  According to the first embodiment, since the conductive path 13B formed on the lower surface of the circuit board 18 constitutes a power circuit, the distance between the conductive paths 13B as compared with the case where the power circuit is configured with a bus bar as in the conventional example. Can be narrowed. As a result, the circuit density can be increased.

  According to the first embodiment, the circuit board 18 and the lower case 50 are bonded by the insulating adhesive sheet 16. Thus, the insulating property can be imparted to the surface of the conductive path 13B without performing a resist process on the conductive path 13B (which forms an insulating layer by applying an insulating resin). The number can be reduced.

Since the power circuit is configured using the relay 11 which is a switching element, the current in the power circuit does not flow constantly but flows intermittently by switching. Therefore, heat is intermittently generated from the relay 11.
This heat is once released from the relay 11 and then stored in the circuit board 18 via the terminal 14 of the relay 11 and the circuit board 18 and gradually radiated from the lower case 50 which also serves as a heat radiating member.

  In the conventional example, heat generated beyond the heat capacity of the circuit board 18 may not be stored in the circuit board 18 and may be trapped inside the circuit structure 10.

  According to the first embodiment, since the conductive path 13B (heat transfer layer) is formed on the lower surface of the circuit board 18, the heat capacity of the circuit board 18 can be increased as a whole. Thereby, the amount of heat once stored in the circuit board 18 can be increased. As a result, heat that could not be stored in the circuit board 18 is prevented from being trapped inside the circuit structure 10.

<Embodiment 2>
Next, a circuit structure according to Embodiment 2 of the present invention will be described with reference to FIGS. In the circuit structure 10 according to the present embodiment, the relay 11 and the electronic device 12 are mounted on the upper surface of the circuit board 18, and a plurality of bus bars 70 are attached to the lower surface of the circuit board 18. The heat radiating member 71 is attached to the surface opposite to the side where it is bonded. Note that the same parts as those of the first embodiment are denoted by the same reference numerals and redundant description is omitted.

(Circuit board 18)
The circuit board 18 in the present embodiment has a rectangular shape, the thickness of the conductive path 13A on the control circuit side formed on the upper surface thereof is 18 to 35 μm, and the conductive path on the power circuit side formed on the lower surface. 13B having a thickness of 70 to 800 μm is used.

  The circuit board 18 according to the present embodiment can be manufactured as follows, for example. The conductive path 13 </ b> A formed on the upper surface of the circuit board 18 can be produced by applying the subtractive method or additive method described in the first embodiment only to the upper surface of the circuit board 18.

  For the conductive path 13B formed on the lower surface of the circuit board 18, a conductive paste (not shown) containing metal powder (for example, copper powder) is applied to the lower surface of the circuit board 13 by screen printing, and the conductive path 13B. Form. Thereafter, the conductive path 13B having a thickness of 70 to 800 μm can be formed on the lower surface of the circuit board 18 by solidifying the conductive paste by heating or the like.

  The conductive path 13 may be formed on the lower surface after being formed on the upper surface of the circuit board 18. Alternatively, a resist (not shown) may be applied to the conductive path 13B formed on the lower surface of the circuit board 18 and protected, and then the conductive path 13A may be formed on the upper surface of the circuit board 18 and then the resist may be removed.

  A plurality of relays 11 and a plurality of electronic devices 12 are mounted on the upper surface of the circuit board 18. A control circuit that controls driving of the relay 11 is formed by the electronic device 12 and the conductive path 13A.

  The relay 11 has a substantially rectangular parallelepiped shape, and a plurality of terminals 14 (six in this embodiment) protrude from the bottom of the relay 11 and extend downward, and then bent outward at a right angle to form a circuit board. 18 is arranged along the surface. These terminals 14 include a control terminal 14 that is connected to the control circuit and controls driving of the relay 11, and an energization terminal 14 that is connected to the power circuit and controls the power circuit.

  Of the conductive paths 13A formed on the upper surface of the circuit board 18, the one connected to the energizing terminal 14 of the relay 11 is a conductive path formed on the lower surface of the circuit board 18 by a jumper line (not shown) or a via hole (not shown). 13B. A power circuit is formed by the relay 11, the conductive path 13A, and the conductive path 13B.

(Bus bar 70)
The plurality of bus bars 70 are made of metal and have an elongated plate shape. One or both ends of each bus bar 70 are bent upward at a right angle. These bus bars 70 are manufactured by punching out a single metal plate by press working and then bending it.

  The bus bars 70 are arranged in a direction perpendicular to the longitudinal direction, with the longitudinal direction directed in the same direction. An adhesive sheet 16 (a prepreg is used in this embodiment) cut into a predetermined shape is placed on the upper surface side of each bus bar 70, and the relay 11 and the electronic device are placed on the adhesive sheet 16. A circuit board 18 on which 12 is mounted is superposed. The circuit board 18, the adhesive sheet 16, and the bus bar 70 are heated and pressed in a stacked state, and the circuit board 18 and the bus bar 70 are bonded to each other by the cured adhesive sheet 16. A portion of the bus bar 70 that protrudes from the circuit board 18 is bent upward at a substantially right angle and inserted into a frame (not shown) from below to be used as a terminal fitting.

(Heat dissipation member 71)
The heat dissipating member 71 is made of metal (in this embodiment, made of aluminum), and extends from the side edge on the right front side in FIG. 5 among the main body 71A having a rectangular shape when viewed from above and the side edges of the main body 71A. And a rectangular mounting portion 71B bent downward in a crank shape.

  The attachment portion 71B is provided with an insertion hole 71C communicating in the vertical direction, and a bolt (not shown) is inserted into the insertion hole 71C so that the attachment portion 71B can be attached to a vehicle body (not shown).

  The heat dissipation member 71 and the bus bar 70 can be bonded as follows, for example. By applying an adhesive having high insulation and high thermal conductivity to the upper surface of the heat radiating member 71, the bus bar 70 side of the bonded circuit board 18 and bus bar 70 is pasted and dried. 70 and the heat dissipation member 71 are bonded together. Thus, the adhesive layer 23 of Claim 3 is formed.

  Hereinafter, the operation and effect of the second embodiment will be described. In the second embodiment, the heat generated in the relay 11 is generated from the relay 11 → the terminal 14 of the relay 11 → the conductive path 13A on the circuit board 18 → the circuit board 18 → the conductive path 13B (heat transfer layer) → the adhesive sheet 16 → the bus bar. 70 (power circuit) → insulating layer 23 → heat radiating member 71 and is radiated from heat radiating member 71 (see FIG. 7). Comparing the heat transfer paths of the second embodiment and the conventional example, in the second embodiment, the conductive path 13B (heat transfer layer) in the process of transferring heat from the circuit board 18 to the adhesive sheet 16 and the bus bar 70 (power circuit). ) Is present.

  Thereby, the heat generated in the relay 11 is transmitted from the portion directly below the terminal 14 of the relay 11 or the portion directly below the conductive path 13A connected to the terminal 14 to the other surface of the circuit board 18 to be transmitted to the conductive path 13B. After being transferred to the (heat transfer layer), the heat is quickly transferred through the conductive path 13B (heat transfer layer). As a result, the temperature of the entire conductive path 13B (heat transfer layer) becomes substantially constant in the plane direction. Then, the heat generated in the relay 11 is uniformly distributed in the surface direction over the entire conductive path 13B (heat transfer layer) and is transmitted from the entire conductive path 13B (heat transfer layer) to the heat radiating member 71. The heat transfer property of the body 10 is improved.

  Moreover, in the conventional printed wiring board, generally, the thickness of the conductive path 13 is 18 μm to 35 μm, whereas in the second embodiment, the thickness of the conductive path 13B (heat transfer layer) is used. Those having a thickness of 70 μm or more and 800 μm or less are used. When the conductive path 13B (heat transfer layer) is thick in this way, the cross-sectional area of the heat transfer path in the direction intersecting the thickness direction of the conductive path 13B (heat transfer layer) increases, so the conductive path 13B (heat transfer layer) ) The amount of heat per unit time conducted in the direction crossing the thickness direction increases. As a result, heat is efficiently dispersed throughout the conductive path 13B (heat transfer layer) and the temperature distribution of the conductive path 13B (heat transfer layer) is reduced. As a result, heat is transferred from the entire conductive path 13B (heat transfer layer) to the heat dissipation member 71. Therefore, the heat transfer performance of the circuit structure 10 is improved.

  In the second embodiment, since the heat radiating member 71 is provided with the attachment portion 71B, it can be directly attached to a vehicle body (not shown). As a result, heat can be transferred to the vehicle body to dissipate heat, thereby improving heat dissipation efficiency.

<Embodiment 3>
In the third embodiment, the opening 17 is formed in the circuit board 18, and the conductive path 13 </ b> B formed on the lower surface of the circuit board 18 is exposed at the bottom of the opening 17. A terminal 20 of a semiconductor switching element 19 (corresponding to a switching element. In the present invention, an FET (electrolytic effect transistor) is used) is connected to the exposed conductive path 13B. Since other configurations are the same as those of the first embodiment, the same parts as those of the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In order to form the opening 17 in which the conductive path 13B is exposed in the circuit board 18, for example, the following may be performed. First, in the same manner as in the first or second embodiment, the circuit board 18 having the conductive paths 13A and 13B formed on the upper and lower surfaces is manufactured. At this time, the conductive path 13A is not formed on the upper surface side of the circuit board 18 and the conductive path 13B is formed on the lower surface side of the portion where the opening 17 is to be manufactured. From the upper surface side of the circuit board 18, a portion where the opening 17 is to be manufactured is drilled so as to leave a base material (remaining margin) of about 0.2 mm on the conductive path 13 </ b> B by router processing, and then laser processing is performed. To scrape off the remaining margin. By this step, an opening that penetrates only the circuit board 18 and exposes the conductive path 13B on the lower surface can be produced.

  The opening 17 formed as described above has a substantially rectangular shape and communicates with the upper surface side of the circuit board. The opening 17 includes an element storage portion 17A that is sized to store the semiconductor switching element 19 and a terminal storage portion 17B that is sized to store the terminal 20 of the semiconductor switching element 19. .

  The semiconductor switching element 19 includes a semiconductor chip (not shown), a gate terminal 20A (control terminal) connected to the semiconductor chip, a drain terminal (energization terminal) and a source terminal 20B (energization terminal) not shown. Is covered with a synthetic resin housing 19A. Among these terminals 20, a drain terminal (not shown) is provided outside the lower surface of the housing 19A, and the source terminal 20B and the gate terminal 20A protrude from the side surface of the housing 19A and extend downward.

  The semiconductor switching element 19 has a housing 19A placed on the element housing portion 17A and a source terminal 20B placed on the terminal housing portion 17B. The drain terminal (not shown) and the conductive path 13B, and the source terminal 20B and the conductive path 13B are in contact with each other, and are mounted by, for example, reflow soldering. The gate terminal 20A is in direct contact with 13A and is mounted by, for example, reflow soldering.

  In the third embodiment, since the drain terminal (not shown) and the source terminal 20B are in contact with the conductive path 13B, the heat generated from the semiconductor switching element 19 is the drain terminal (not shown) and the source terminal 20B. Directly to the conductive path 13B. As described above, the heat generated in the semiconductor switching element 19 can be transmitted to the lower surface of the circuit board 18 without going through the circuit board 18 having a low thermal conductivity.

  Further, since the drain terminal (not shown) is formed on the back surface of the housing 19A of the semiconductor switching element 19 and connected to the conductive path 13B, the drain terminal (on the upper surface side of the circuit board 18 is conventionally provided). It is not necessary to form the conductive path 13A for connection with the control circuit separately from the control circuit. As a result, a new circuit can be formed in a region where there is no need to provide a conductive path for connecting the drain terminal, so that the wiring density on the circuit board 18 can be increased.

<Embodiment 4>
In the fourth embodiment, a thermal via 21 that thermally connects the upper and lower sides of the circuit board 18 is formed in the vicinity of the terminal 20 of the semiconductor switching element 19. Since other configurations are the same as those of the third embodiment, the same parts as those of the third embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The thermal via 21 penetrates the circuit board 18 and is filled with a material having high thermal conductivity. The thermal via 21 is formed so that heat generated on the upper surface or the lower surface of the circuit board 18 can be transmitted to the opposite surface. ing. The shape of the thermal via 21 according to the fourth embodiment is substantially circular when viewed from above, but may be another shape such as an oval or a rectangle.

  The thermal via 21 can be manufactured as follows. First, a through hole 24 that communicates the circuit board 18 and the conductive path 13B vertically is formed by a drill or a laser beam. Next, after filling the through hole 24 with a conductive paste containing metal powder having high thermal conductivity by screen printing, the paste can be solidified to form the thermal via 21.

  Alternatively, a catalyst (not shown) is applied to the through hole 24 drilled in the circuit board 18, and then electroless plating and electrolytic plating are performed, and the through hole 24 is filled with copper plating. it can.

  The thermal via 21 manufactured in this manner is thermally connected to the upper and lower sides of the circuit board 18 with metal powder or copper having high thermal conductivity. For this reason, the heat generated from the semiconductor switching element 19 is transmitted to the lower surface of the circuit board 18 through the thermal via 21 without passing through the circuit board 18 having low thermal conductivity. It is possible to suppress the accumulation.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention, and further, within the scope not departing from the gist of the invention other than the following. Various modifications can be made.

  (1) In this embodiment, the conductive path (heat transfer layer) 13B formed on the lower surface of the circuit board 18 constitutes a power circuit. However, the present invention is not limited to this. For example, the entire lower surface of the circuit board 18 A heat transfer layer made of metal is formed on the circuit board, heat generated by the switching element is dispersed over the entire lower surface of the circuit board 18, and heat is transferred from the entire heat transfer layer to the heat radiating member. Can be improved. At this time, the conductive path 13A connected to the energization terminal of the switching element and the power circuit separately formed by the bus bar or the like may be connected by, for example, a jumper wire across the heat transfer layer, Moreover, it is good also as a structure connected by the via hole insulated with the heat-transfer layer.

  (2) In the first embodiment, the heat radiating member 71 is the aluminum lower case 50, and in the second embodiment, the flat heat radiating member 71 is used. However, the present invention is not limited to this, and an aluminum plate having heat radiating fins formed on one side thereof. May be used.

  (3) In Embodiment 2, the conductive path 13B (heat transfer layer) and the bus bar 70 are bonded by the insulating adhesive sheet 16. However, the present invention is not limited to this, and the conductive path 13B (heat transfer layer) and the bus bar are bonded. 70 may be bonded with an insulating adhesive.

  (4) In the second embodiment, the conductive path 13B (heat transfer layer) and the bus bar 70 are bonded by the insulating adhesive sheet 16, but the present invention is not limited to this, and the pattern of the conductive path 13B (heat transfer layer). The bus bar 70 may have the same pattern, and the conductive path 13B (heat transfer layer) and the bus bar 70 may be bonded in an electrically connected state. As a result, the area of the conductive path of the power circuit is increased, so that the amount of current can be increased. Similarly, since the area of the heat transfer path is increased, the thermal conductivity is also improved.

(5) In the second embodiment, the thickness of the conductive path 13A of the control circuit formed on the upper surface of the circuit board 18 is 18 to 35 μm, and the thickness of the conductive path 13B (heat transfer layer) on the lower surface of the circuit board 18 The thickness of the conductive path 13A formed on the upper surface of the circuit board 18 as well as the conductive path 13B (heat transfer layer) on the lower surface of the circuit board 18 is not limited to this. It is good also as follows. Thereby, the heat dissipation of the circuit structure 10 can be improved.
At this time, it is preferable to set the thickness of the conductive path 13A to about 200 μm because discrete electronic components can be mounted on the upper surface side of the circuit board 18 and heat dissipation can be improved.

  (6) In Embodiment 1, the conductive path 13B (heat transfer layer) and the heat radiating member 71 are bonded by the adhesive sheet 16. However, the present invention is not limited to this, and the conductive path 13B (heat transfer layer) is subjected to a resist treatment. After providing insulation, it is good also as a structure which adhere | attaches the conductive path 13B (heat-transfer layer) and the heat radiating member 71 with an adhesive agent.

  (7) In the third embodiment, the current-carrying terminal (drain terminal, source terminal 20B not shown) of the semiconductor switching element 19 is connected to the conductive path 13B (heat transfer layer) in the opening 17 formed in the circuit board 18. Although it was set as the structure connected, it is not restricted to this, A part of housing | casing of switching elements, such as the relay 11 and the semiconductor switching element 19, is made to contact the electrically conductive path 13B (heat-transfer layer) in the opening part 17, and a terminal is It is good also as a structure connected with the conductive path 13A formed on the circuit board 18. FIG. Thereby, the heat generated by the switching element can be directly transmitted to the conductive path 13B (heat transfer layer) without passing through the circuit board 18 having a low thermal conductivity.

  (8) In the fourth embodiment, the opening 17 is provided in the insulating substrate 18. However, the present invention is not limited to this, and the thermal via 21 is not provided in the circuit board 18 near the terminal of the switching element. It is good also as a structure which forms.

1 is an exploded perspective view of an electrical junction box using the circuit structure according to Embodiment 1. FIG. A plan view of the electrical junction box Similarly, a longitudinal section of the electrical junction box The partially expanded sectional view which shows the heat-transfer path | route of the circuit structure which concerns on Embodiment 1. The disassembled perspective view of the circuit structure based on Embodiment 2. FIG. Similarly, perspective view of the circuit structure Partially enlarged sectional view showing the heat transfer path The partially expanded perspective view which shows the opening part of the circuit board in the circuit structure based on Embodiment 3. FIG. The partially expanded perspective view which shows the structure of the opening part of a circuit board and the thermal via in the circuit structure which concerns on Embodiment 4. FIG. Partially enlarged sectional view showing the structure of the thermal via

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Circuit structure 11 ... Relay (switching element)
13A: Conductive path (control circuit)
13B ... Conductive path (heat transfer layer)
16 ... Adhesive sheet (adhesive layer)
DESCRIPTION OF SYMBOLS 17 ... Opening part 18 ... Circuit board 19 ... Semiconductor switching element (switching element)
21 ... Thermal via 23 ... Adhesive layer 50 ... Lower case (heat dissipation member)
70 ... Bus bar 71 ... Heat dissipation member

Claims (8)

Forming a control circuit by printed wiring means on one surface of the circuit board, and mounting a switching element controlled by the control circuit on one surface thereof;
A circuit structure, wherein a metal heat transfer layer is formed on the other surface of the circuit board by printed wiring means, and a heat radiating member is bonded to the heat transfer layer via an adhesive layer. 2. The circuit structure according to claim 1, wherein the heat transfer layer is formed as a circuit pattern and constitutes a power circuit controlled by the switching element. The bus bar which comprises the electric power circuit controlled by the said switching element is adhere | attached between the said heat-transfer layer and the said heat radiating member through the insulating contact bonding layer. 3. The circuit structure according to 2. 4. The circuit structure according to claim 1, wherein a thickness of the heat transfer layer is 70 μm or more and 800 μm or less. 5. 5. The circuit structure according to claim 1, wherein the heat transfer layer and the heat dissipation member are bonded to each other with an insulating adhesive sheet. 6. The circuit board according to claim 1, wherein a thermal via that thermally connects one surface and the other surface of the substrate is formed in the vicinity of the switching element. The circuit structure according to any one of the above. 7. The circuit board according to claim 1, wherein an opening is formed in the circuit board, the switching element is accommodated in the opening, and is in contact with the heat transfer layer. Circuit structure. An opening is formed in the circuit board, and the switching element is accommodated in the opening,
A terminal is provided on a bottom surface of the switching element, and the switching element is mounted on the heat transfer layer in a state where the terminal is electrically connected to the heat transfer layer. The circuit structure according to any one of claims 2 to 6.

Images