JP4415647B2 - Power distribution unit manufacturing method - Google Patents

Description

In the present invention, a pair of circuit boards constituting a circuit are arranged at a predetermined interval, and a circuit component in which a circuit component that generates heat upon driving is provided in the power circuit is incorporated in a heat dissipation case. a method of manufacturing a power distribution unit which is formed by being.

  2. Description of the Related Art In recent years, vehicles such as automobiles are equipped with a large number of electronic units, and power distribution units have been widely used to distribute power to each of these electronic units from a common in-vehicle power source. In this power distribution unit, a circuit structure made of a printed circuit board or the like is incorporated, and circuit components such as a large number of semiconductor elements are generally mounted on the circuit structure. Many of these circuit components generate heat when driven, and the heat generated by driving these circuit components adversely affects the performance and reliability of the circuit components. Is often taken.

For example, the power distribution unit described in Patent Document 1 includes an upper opening type heat dissipation case and a pair of upper and lower printed circuit boards arranged in parallel at a predetermined interval in the heat dissipation case. While a large number of circuit components are mounted, each printed circuit board is thermally (thermally conductive) connected to the support column that extends from the bottom of the heat dissipation case, and heat generated by driving each circuit component It is comprised so that heat may mainly be radiated from the bottom side of the heat radiating case.
JP 2002-271058 A

  By the way, in such a power distribution unit, the occupied volume at the time of installation tends to be reduced year by year, and accordingly, downsizing of the power distribution unit and the circuit structure itself incorporated in the power distribution unit is strongly desired. It is where you are. As the power distribution unit is miniaturized in this way, the circuit components mounted on the circuit structure incorporated in the unit inevitably increase in density, and the heat generation density increases accordingly.

  Here, in the power distribution unit described in Patent Document 1, since the heat radiating case is configured as an upper opening type case, the heat generated by the circuit components can be radiated from the peripheral side wall portion, Since the struts that are thermally connected to each printed circuit board are connected to the bottom surface of the heat dissipation case, the heat generated from the circuit components mounted on each printed circuit board passes through the printed circuit boards and the struts. Heat conduction to the bottom surface, mainly dissipated from the bottom side of the heat dissipation case, and in the current situation where the heat generation density is rising as described above, it is difficult to ensure sufficient heat dissipation mainly by only the heat conduction to the bottom side. Of the printed circuit boards, the printed circuit board located away from the bottom surface of the heat radiating case has a problem that the heat transfer path becomes relatively long and the heat dissipation efficiency is poor. That is, in the present situation where the power distribution unit is miniaturized in this way, it is desired that a further heat dissipation measure is taken for the power distribution unit, in particular, a heat dissipation measure is taken for the board away from the bottom surface side of the heat dissipation case.

The present invention aims at providing such circumstances in view, the possible further improve the heat dissipation efficiency by a simple structure distribution unit manufacturing method.

  Here, as a result of earnest research, the applicant of the present application is positioned away from the bottom wall portion of the heat radiating case among the pair of circuit boards arranged at a predetermined interval in order to further improve the heat radiating efficiency in the power distribution unit. Focusing on improving the heat dissipation efficiency of the circuit board, heat generated from at least one circuit component mounted on the circuit board away from the bottom wall is transferred to the wall other than the bottom wall of the heat dissipation case. The heat radiation efficiency is further improved by dissipating heat from the wall portion to the outside of the power distribution unit.

That is, a method for manufacturing a power distribution unit according to the present invention includes a lower case including a bottom wall portion and a side wall portion standing from the periphery of the bottom wall portion, and a heat radiating case having an upper case assembled to the lower case, A circuit structure incorporated in the heat radiating case, and the circuit structure is connected to a circuit of each of these boards and a pair of circuit boards arranged at a predetermined distance from each other, and with driving One of the circuit boards is joined to the bottom wall portion of the heat dissipation case, and the circuit component mounted on the one circuit board is connected to the bottom wall via the one circuit board. On the other circuit board, at least one circuit component is mounted in a posture positioned between the circuit board and the bottom wall portion, and the circuit component is Above heat dissipation cable A method for manufacturing a power distribution unit which is connected in a direct heat can transfer to the side wall by being directly joined to the side wall portion of, assembling the lower case on the circuit structure includes assembling step, as the assembling factory is a preparation step of directly joining at least one circuit component to the side wall of the lower case, one in the lower case of the circuit component is joined by the preparation step A first assembling step for housing the circuit board, and the other circuit board is disposed at a predetermined interval with respect to the one circuit board, and the circuit board of the other circuit board is disposed on the side wall during the disposition. And a second assembling step for mounting the circuit component joined to the part.

According to the power distribution unit manufactured in accordance with the present invention, the circuit component mounted on one circuit board is connected to the bottom wall portion through the one circuit board so as to be able to conduct heat, while the other circuit board is connected. Since the circuit components mounted on the circuit board are joined to the side wall of the heat radiating case and directly connected to the side wall so as to be able to conduct heat, the circuit components connected to the circuit of each circuit board are driven. The heat generated along with the heat can be conducted to different wall parts (different areas) of the heat dissipation case for each circuit board, and can be dissipated mainly for each circuit board in the wall part to be mainly dissipated. The heat dissipation efficiency can be improved with a simple configuration.

  In addition, since at least one circuit component mounted on the other circuit board is joined to the side wall portion of the heat dissipation case, the heat transfer path can be made relatively short, and heat generated by driving the circuit components can be efficiently generated. The heat dissipation case can be thermally conducted.

  Further, since the circuit component mounted on the other circuit board is positioned between the circuit component and the bottom wall portion and this circuit component is joined to the side wall portion of the heat dissipation case, the circuit component is dissipated. By effectively utilizing the space in the case and maintaining a compact structure, the heat generated by the circuit components can be directly transmitted to the side wall portion of the heat radiating case to effectively suppress the temperature rise of the other circuit board.

The power distribution unit manufactured according to the present invention allows heat generated from the circuit components connected to the circuit of each circuit board to mainly conduct heat to a predetermined wall portion of the heat radiating case to radiate heat from the predetermined wall portion of the heat radiating case. However, it does not exclude that the heat is radiated by using a surrounding gas such as heat radiation as a medium.

The specific configuration method of the one circuit board is not particularly limited, but includes, for example, a bus bar board manufacturing step of manufacturing a bus bar board that forms a power circuit by a plurality of bus bars as the one circuit board. the biasing step, connecting a bus bar located on the rear surface of the bus bar substrate fabricated by the bus bar board manufacturing process by Rukoto be bonded to the bottom wall of the heat dissipation case, through the bus bar substrate on the front side of the bus bar substrate circuit components to be not the preferred for to connect so as to allow heat conduction to the bottom wall portion of the heat dissipation case.

  If comprised in this way, a bus-bar board | substrate can be functioned as a heat conductor, and the thermal radiation efficiency of a circuit component can be improved using the component of a power distribution unit effectively.

In this case, the bus bar substrate manufacturing step includes a mounting step of mounting a circuit component having a component main body and leg-shaped terminals extending in a direction from the lower part of the component main body toward the bus bar on the surface side of the bus bar substrate. the implementation process has the preferred to you by welding the leg-like terminals of the circuit component to a predetermined bus bar of the bus bar substrate.

  In other words, when the leg terminals are joined to the bus bar by welding, the heat tolerance can be set wider than that by soldering, and heat conduction to the bus bar efficiently via the leg terminals. This can improve the heat dissipation efficiency.

And a circuit component mounted on the surface side of the circuit board of this one is appropriately determined by the circuit design, it has preferred, for example, to use a relay as the circuit components.

  If comprised in this way, by arranging the relay with good heat dissipation efficiency of the component itself in the space between this pair of circuit boards, heat dissipation by heat conduction and heat dissipation using gas such as heat radiation are efficient. Can dissipate heat.

On the other hand, in the present invention, the other circuit board, constitutes a control circuit board including a control circuit for controlling the driving of the circuit components, the circuit components to be joined to the side wall of the heat dissipation case is the control circuit board a mounted semiconductor element and even not preferable.

  In other words, a relatively large number of circuit components are mounted on the control circuit board, and the heat dissipation efficiency is further improved by efficiently dissipating the heat generated by driving a semiconductor element that generates a relatively large amount of heat among these circuit components. Can be made.

Furthermore, the present invention includes an upper case assembling step for assembling the upper case having the top wall portion to the lower case in a state where the top wall portion is disposed opposite to the other circuit board. Then, by interposing a potting agent in the gap between the other circuit board and the top wall part, the circuit components connected to the circuit board can be thermally conducted to the top wall part via the potting agent. We have preferred that to connect.

  If comprised in this way, while the heat radiation area | region in a heat radiating case can further be expanded by a top wall part, the heat_generation | fever of the circuit components sealed by this with a potting agent can be efficiently carried out from this expanded heat radiation area | region. Heat can be dissipated.

The specific configuration of the heat dissipation case, from the viewpoint of assembling to the circuit structure, the thermal case release is have a lower case and upper case.

On the other hand, according to the manufacturing method of the power distribution unit according to the present invention, a method for manufacturing the power distribution unit, comprising an assembly step of assembling the heat dissipation case and a lower case and an upper case to the circuit structure In this assembling process, one circuit board is housed in a lower case in which at least one circuit component is bonded to the side wall portion in advance, and the other circuit board is arranged at a predetermined interval with respect to the one circuit board. When installing, the circuit component joined to the side wall is mounted on the circuit of the other circuit board.

  According to the present invention, one circuit board is housed in the lower case in which at least one circuit component is bonded to the side wall portion in advance in the assembling process, and the other circuit board is spaced from the one circuit board by a predetermined distance. Since the circuit component bonded to the peripheral wall portion is mounted on the circuit of the other circuit board when being arranged apart from each other, the side wall portion of the heat radiating case and the circuit component bonded to the side wall portion are connected to the lower case and the upper case. Regardless of the assembly with the case, it can be surely connected thermally, and a power distribution unit with excellent heat dissipation efficiency can be manufactured reliably.

The power distribution unit includes a heat radiating case having a pair of opposing wall portions, and a circuit structure incorporated in the heat radiating case, and the circuit structural bodies are arranged at a predetermined interval from each other. In a power distribution unit having at least a pair of circuit boards constituting a circuit and circuit components that are connected to the circuits of these boards and generate heat when driven, the circuit boards are respectively connected to the pair of wall portions of the heat dissipation case. At least one circuit component that is arranged to face each other and is connected to each circuit board is connected so as to be able to conduct heat to the facing wall portion.

According to this power distribution unit , a pair of circuit boards arranged at a predetermined interval between the walls of a pair of opposing heat dissipation cases are respectively arranged to face the walls of the heat dissipation case. Since at least one circuit component connected to each other is connected to the facing wall portion so as to be able to conduct heat, heat generated by driving the circuit components connected to the circuit of each circuit board is generated for each circuit board. It is possible to conduct heat to different wall parts (different areas) of the heat radiating case, and to dissipate mainly on the circuit board in the wall part to dissipate mainly, thereby improving the heat radiation efficiency with a simple configuration. it can. In addition, since the heat generated from the circuit components on the circuit board is radiated by the wall of the heat dissipation case facing the circuit board, the heat transfer path can be made relatively short, and the heat generated by driving the circuit components can be reduced efficiently. Thus, heat can be conducted to the heat radiating case.

  In this case, one of the pair of circuit boards is configured as a bus bar board constituting a power circuit by a plurality of bus bars, and the bus bar located on the back surface of the bus bar board is bonded to the bottom wall portion of the heat dissipation case. Accordingly, it is preferable that the circuit components connected to the front surface side of the bus bar substrate are connected so as to be able to conduct heat to the bottom wall portion of the heat dissipation case using the bus bar substrate as the heat conductor.

  If comprised in this way, a bus-bar board | substrate can be functioned as a heat conductor, and the thermal radiation efficiency of a circuit component can be improved using the component of a power distribution unit effectively.

Further, the power distribution unit, one of the upper Symbol pair of circuit board is configured as a control circuit board including a control circuit for controlling the driving of the circuit component, the gap between the wall portion opposite to the control circuit board to It is preferable that the circuit component connected to the control circuit board by being filled with the potting agent is connected to the wall portion facing the control circuit board by using the potting agent as the heat conductor so as to conduct heat.

  If comprised in this way, the heat_generation | fever from the circuit components sealed by this with a potting agent can be disperse | distributed with respect to the wall part of a thermal radiation case, and can be efficiently transmitted, and the thermal radiation efficiency is improved. be able to.

On the other hand, the manufacturing method of the power distribution unit is a method of manufacturing a power distribution unit for producing the power distribution unit, comprising an assembly step of assembling the heat dissipation case and a lower case and an upper case to the circuit structure, the set In the attaching step, the upper case is filled with a potting agent in advance, and the circuit component connected to the circuit of the control circuit board is sealed after the potting agent has a predetermined elasticity and shape retention. It is characterized by being assembled to the lower case.

  According to this invention, the potting agent can be reliably interposed between one circuit board and the wall of the heat radiating case facing it as a heat conductor, and the power distribution unit can be manufactured reliably. .

According to the power distribution unit, by heat conduction in the wall of the heat dissipation case that faces the circuit board is dispersed in each circuit board heat generated from the circuit components mounted on the pair of the circuit board, a simple structure The heat dissipation efficiency can be improved.

According to the power distribution unit manufacturing method of the present invention , regardless of the assembly of the lower case and the upper case, the peripheral wall portion of the heat radiating case and the circuit components joined to the peripheral wall portion can be reliably thermally connected. And a power distribution unit with excellent heat dissipation efficiency can be manufactured.

Further, according to the method for manufacturing a power distribution unit according to claim 7 , the potting agent as a heat conductor can be reliably interposed between one circuit board and the wall portion of the heat dissipation case facing the circuit board, A power distribution unit with excellent heat dissipation efficiency can be reliably manufactured.

  A preferred embodiment of the present invention will be described with reference to the drawings. In addition, the circuit which comprises the power distribution circuit which distributes the electric power supplied from the common power supply mounted in a vehicle here to several electric loads (for example, a headlight unit, a small light unit, a horn unit, a washer unit, etc.) Although a structure and a power distribution unit are shown, the use of the power distribution unit according to the present invention is not limited to this, and the present invention can be widely applied to cases where on / off switching of energization in a power circuit is performed by a circuit component such as a relay. This circuit structure is incorporated in a power distribution unit 1 as shown in FIG. FIG. 1 is a perspective view showing the power distribution unit upside down.

  The power distribution unit 1 has a substantially rectangular parallelepiped shape and is very compact while having a function of distributing power to a plurality of electrical loads (in this embodiment, five electrical units). In the present embodiment, the power distribution unit 1 is formed so as to be housed in a space having a length of 75 mm, a width of 100 mm, and a height of 25 mm.

  As shown in FIG. 2, the power distribution unit 1 includes a circuit structure 2 including a control circuit board 21, a connector mounting portion 4 and a fuse mounting portion 5 mounted on the circuit configuration body 2, and mounting portions 4, 4. An upper case 6 and a lower case 7 are provided as heat dissipating cases for holding the circuit structure 2 to which 5 is attached from above and below and holding the mounting portions 4 and 5 in an exposed state. In this specification, for convenience of explanation, the side on which the connector mounting portion 4 of the power distribution unit 1 is formed will be referred to as the front side, and the height direction in FIG.

  FIG. 3 is an exploded perspective view of the circuit structure 2. 4 to 6 are sectional views taken along lines IV-IV, VV, and VI-VI in FIG.

  The circuit configuration body 2 constitutes a power circuit that distributes a common in-vehicle power source to each electrical load according to preset conditions. The circuit structure 2 includes a bus bar substrate 20 in which a bus bar layer 30 composed of a plurality of bus bars 22 arranged in a state of being arranged on substantially the same plane is laminated over a plurality of layers via an insulating plate 31. And two kinds of relays 24 and 25 as power circuit components mounted on the bus bar 22 of the bus bar board 20, and the bus bar board 20 so as to interpose the relays 24 and 25 between the bus bar board 20. And a control circuit board 21 arranged at a predetermined interval.

  The circuit structure 2 is a flat block-like body having a substantially square shape in plan view, and a predetermined bus bar 22 is bent in a bowl shape at the front end portion thereof, and a large number of connector terminals 27 are in a square planar area. A predetermined bus bar 22 is bent in the shape of a bowl at the rear end thereof, and a plurality of fuse terminals 28 are protruded rearward while being substantially contained in the rectangular planar area A. In this state, they are lined up over two levels. A plurality (four in this embodiment) of the first relays 24 are mounted along the longitudinal direction (left-right direction) on the surface side of the bus bar substrate 20 between the connector terminals 27 and the fuse terminals 28. ing. The fuse terminals 28 are arranged in a dense state for each one or a plurality of the fuse terminals 28, and the second relay 25 is mounted on the surface side of the bus bar substrate 20 between the dense fuse terminal 28 groups. Yes.

  Specifically, the bus bar substrate 20 is bonded to the upper surface of the bottom wall portion 72 of the lower case 7 by bonding in an electrically insulated state, and is thereby connected to the bottom wall portion 72 of the lower case 7 so as to be able to conduct heat. ing. As the adhesive used for this adhesion, an adhesive having electrical insulation is used, and among them, an adhesive having excellent thermal conductivity is preferably used from the viewpoint of thermal conductivity. The bus bar substrate 20 includes a plurality of bus bar layers 30a to 30c, and a plurality of insulating plates 31a and 31b (insulating layers) are interposed between the bus bar layers 30a to 30c, so that heat on the front side is transferred to the back side. It is. In this embodiment, it is comprised from the 1st thru | or 3rd bus-bar layer 30a-30c, and the 1st and 2nd insulating plates 31a and 31b interposed between these. In the present embodiment, the bus bar substrate 20 in which the bus bar layers 30a to 30c are stacked in three layers is used. However, the number of the bus bar layers is not particularly limited as long as it is a plurality of layers.

  As described above, each of the bus bar layers 30a to 30c is arranged in a state in which a plurality of bus bars 22 are arranged in a predetermined pattern on substantially the same plane, and among the bus bars 22, the predetermined bus bar 22 is bent vertically. Further, the front end of the bent portion is folded back horizontally to be bent into a bowl shape, and the connector terminal 27 and the fuse terminal 28 are formed. In addition, predetermined bus bars 22 in each of the bus bar layers 30 a to 30 c are folded up so that the pin-like terminals 32 protrude from the upper surfaces of the first and second relays 24, 25. Is connected to the control circuit of the control circuit board 21. Then, an electric signal is sent from the control circuit board 21 through the pin-shaped terminal 32, and drive control of the first and second relays 24 and 25 arranged in predetermined bus bar layers 30a to 30c is performed.

  Here, the first and second relays 24 and 25 are mechanical relays, and are substantially rectangular parallelepiped relay bodies 24a and 25a and a plurality of flat plate-like leg terminals provided at the lower ends thereof. 24b, 25b.

  The first relay 24 has a leg-like terminal 24b that extends downward from the lower surface of the relay body 24a and is bent along the layer surface of the bus bar layer 30 to form a superposed portion 24c that is overlapped with a predetermined bus bar 22. . The overlapping portion 24c of the first relay 24 includes an overlapping portion 24c that overlaps the bus bar 22 of the first bus bar layer 30a and an overlapping portion 24c that overlaps the bus bar 22 of the second bus bar layer 30b. Corresponding to each bus bar layer 30a, 30b, a step substantially equal to the step between the layer surfaces of the first bus bar layer 30a and the second bus bar layer 30b is provided between the leg terminals 24b.

  On the other hand, the second relay 25 has leg-like terminals 25b extending along the layer surface of the bus bar layer 30 from the lower surface of the relay body 25a. Therefore, the leg-like terminals 25b are connected to the predetermined bus bar 22 of the third bus bar layer 30c. The overlapping portion 25c is configured to be overlapped.

  The first and second relays 24 and 25 are joined to the predetermined bus bar 22 by welding at the overlapping portions 24c and 25c. In this embodiment, the welding is performed by resistance welding in which the base material is melted and joined by resistance heat generated by sandwiching the joint portion between the electrodes and flowing a large current, but the base material such as laser welding is melted and joined. If it does, the specific method is not specifically limited. Thus, if the 1st and 2nd relays 24 and 25 are joined by welding, compared with the joining by soldering, for example, joining strength can be improved and the heat resistance in a joined part improves, and leg shape. The heat dissipation efficiency through the terminals 24b and 25b can be improved.

  The first and second relays 24 and 25 generate heat as they are driven, and the generated heat is generated from the entire first and second relays 24 and 25 including the relay main bodies 24a and 25a. The heat is dissipated as a medium to be dissipated from a predetermined portion of the heat dissipating case (upper case 6, lower case 7) to the outside of the power distribution unit 1, and most of the heat is transferred to the bus bar substrate 20 via the leg terminals 24b and 25b. Heat is transferred and heat is mainly radiated from the bottom wall 72 of the lower case 7 using the bus bar substrate 20 as a heat conductor.

  On the other hand, the insulating plates 31a and 31b prevent a short circuit between the bus bar layers 30a to 30c and prevent a short circuit between the bus bars 22 arranged in the same bus bar layer 30a to 30c. It is comprised as the flat plate-shaped body formed of the material which has.

  The first insulating plate 31a interposed between the first bus bar layer 30a and the second bus bar layer 30b located above the first bus bar layer 30a is provided on each of the upper and lower (front and back) both surfaces of the first and second bus bar layers 30a and 30b. Are formed, and the bus bar 22 is stored in a positioning state in the bus bar storage groove 310.

  A first terminal insertion hole 311 through which the leg-shaped terminal 24b joined to the bus bar 22 of the first bus bar layer 30a among the leg-shaped terminals 24b of the first relay 24 is inserted at a predetermined position of the first insulating plate 31a. It is formed in a state penetrating in the thickness direction. The first terminal insertion hole 311 is formed substantially corresponding to the shape of the leg-shaped terminal 24b of the first relay 24, and is set to a size substantially equal to the planar shape. In addition, the first terminal insertion hole 311 is set to a size that allows an electrode to be inserted during resistance welding, and resistance welding can be performed by effectively using the first terminal insertion hole 311. Furthermore, when resistance welding is performed on the first insulating plate 31a in the bus bar layer (the second bus bar layer 30b in the present embodiment) above the first insulating plate 31a, the lower electrode is connected to the bus bar layer. An electrode insertion hole 312 is formed so as to contact the predetermined bus bar 22, and a joint portion of the predetermined bus bar 22 of the second bus bar layer 30 b (through the electrode insertion hole 312 (in FIG. 4, the leg-shaped terminal 24 b on the right side of the first relay 24 in FIG. 4). And the joint part) are exposed downward.

  The second insulating plate 31b interposed between the second bus bar layer 30b and the third bus bar layer 30c located above the second bus bar layer 30b accommodates each bus bar 22 of the third bus bar layer 30c individually on the upper surface (front surface). A bus bar storage groove 313 is formed, and the bus bar 22 is stored in the bus bar storage groove 313 in a positioned state. A second terminal insertion hole 314 through which the leg-like terminal 24b of the first relay 24 is inserted is formed at a predetermined location of the second insulating plate 31b in a state of penetrating in the thickness direction. A part of the second terminal insertion hole 314 communicates with the first terminal insertion hole 311 in the vertical direction in a state where the insulating plates 31a and 31b are laminated. Through the terminal insertion holes 311, 314, the joint portions of the predetermined bus bar 22 of the first bus bar layer 30a are exposed.

  Then, electrodes of a predetermined welding machine are inserted through the first and second terminal insertion holes 311 and 314 and the electrode insertion hole 312, the joint portion is sandwiched by these electrodes, and a large current is conducted to the electrodes to make resistance. The first relay 24 is mounted by heat.

  Further, the second insulating plate 31b is provided with a main body insertion hole 315 that communicates with the second terminal insertion hole 314 and allows the relay main body 24a of the first relay 24 to be inserted, and surrounding ribs surround the main body insertion hole 315. 316 is provided.

  On the other hand, the control circuit board 21 includes a control circuit for controlling the driving of the first and second relays 24 and 25 as the circuit components. For example, a printed circuit board (a conductor constituting the control circuit on an insulating board is printed wiring) Are made up of). The control circuit board 21 is a plate-like body that is slightly larger than the bus bar board 20 and is supported by the connector mounting portion 4 and the fuse mounting portion 5 with both front and rear edges facing the top wall portion 61 of the upper case 6. (See FIG. 13). The control circuit board 21 includes a plurality of semiconductor elements 210 mounted on both front and back surfaces (upper and lower surfaces in FIG. 4), a sub-board 211 disposed on the back surface side, and a connector connected to the control circuit. A pin-like terminal 212.

  Specifically, the semiconductor element 210 includes an LSI (Large Scale Integrated Circuit) 210 a as a microprocessor provided at the approximate center on the front surface side of the control circuit board 21, and both left and right end portions on the back surface side of the control circuit board 21. The circuit components (LSI 210a and FET 210b in the present embodiment) that have a relatively large amount of heat generated by the driving are arranged on the peripheral portion of the circuit structure 2. By disposing a circuit component having a relatively large amount of heat generation at the peripheral edge of the circuit structure 2 in this way, heat can be easily diffused to the outside, and the heat dissipation efficiency of the circuit component can be improved. Further, the LSI 210 a is sealed with a potting agent 65 filled between the control circuit board 21 and the top wall portion 61 of the upper case 6. On the other hand, the FET 210b is bonded to a side wall portion 73 (described later) of the lower case 7 with an adhesive, and is directly connected to the side wall portion 73 so as to be capable of conducting heat.

  Similar to the control circuit board 21, the sub board 211 is configured by a printed circuit board, and forms a part of a control circuit that controls the various circuit components. The sub board 211 is a plate-like body arranged between the bus bar board 20 and the control circuit board 21, and is arranged along the longitudinal direction of the control circuit board 21. In this way, a part of the control circuit formed on the control circuit board 21 is formed on the sub board 211, and the sub board 211 is placed between the bus bar board 20 and the control circuit board 21 with respect to the boards 20 and 21. By arranging the first and second relays 24 and 25 so as to be vertical, the space between the boards 20 and 21 on which the first and second relays 24 and 25 are arranged can be effectively used to reduce the size of the circuit component 2. it can. Such a sub-board 211 can be omitted as appropriate, and in this case, all control circuits are formed on the control circuit board 21.

  The control circuit board 21 is provided with through holes (not shown) at predetermined positions, and pin-like terminals 32, connector pin-like terminals 212 and the like standing from the bus bar 22 are inserted into these through-holes. These are joined by soldering at their ends.

  On the other hand, the connector mounting portion 4 is a synthetic resin molded product, and the height and the length in the left-right direction are formed substantially equal to those of the circuit component 2. The connector mounting portion 4 is provided with a connector terminal insertion hole 40 through which the connector terminal 27 and the connector pin-like terminal 212 are inserted, and through the connector terminal insertion hole 40, the connector terminal 27 and the connector pin-like terminal 212 are provided. The front end of the connector protrudes into the connector mounting portion 4 so that it can be connected from the outside. Further, the connector mounting portion 4 is provided with a case fitting groove 41 on the peripheral surface portion thereof, and the front end edges of the upper case 6 and the lower case 7 are fitted into the case fitting groove 41 and assembled to the cases 6 and 7. It is done. Further, the control circuit board 21 is placed on the upper surface of the rear end portion of the connector mounting portion 4.

  On the other hand, the fuse mounting portion 5 is also a synthetic resin molded product, and the height and the length in the left-right direction are formed substantially equal to those of the circuit component 2. The fuse mounting portion 5 is provided with a fuse terminal insertion hole 50 (see FIG. 13) through which the fuse terminal 28 is inserted, and the tip of the fuse terminal 28 can be connected from the outside through the fuse terminal insertion hole 50. It protrudes into the part 5. In addition, the fuse mounting portion 5 is provided with a case fitting groove 51 in the front peripheral surface portion thereof, and the rear end edges of the upper case 6 and the lower case 7 are fitted into the case fitting groove 51 so that the fuse mounting portion 5 It is assembled to the cases 6 and 7 in a state in which most of them are stored. Further, the control circuit board 21 is placed on the upper surface of the front end portion of the fuse mounting portion 5.

  The upper case 6 is a downward-opening dish-like body having a top wall portion 61 having a substantially rectangular shape in plan view, and is made of a material having good thermal conductivity such as an aluminum-based metal. The upper case 6 is filled in advance with a potting agent 65 such as silicon resin, and various circuit components including the LSI 210a mounted on the surface (upper surface) of the control circuit board 21 are sealed by the potting agent 65. The A pair of front and rear locking bulges 60 are provided on the left and right side surfaces of the upper case 6, and locking holes 70 provided on the left and right side walls of the lower case 7 are locked to lock the upper case 6 and the lower case. 7 is assembled in a state in which the circuit structure 2 is accommodated.

  The lower case 7 is an upper opening type box-like body, and is made of a material having good thermal conductivity, such as an aluminum-based metal, like the upper case 6. Specifically, the lower case 7 includes a substantially rectangular bottom wall portion 72 and a peripheral side wall portion 73 erected on the periphery of the bottom wall portion 72, and substantially the entire front and rear side wall portion 73 is large. The cutout portion 71 is formed by cutting out, and the connector mounting portion 4 and the fuse mounting portion 5 are assembled to the cutout portion 71. The bottom wall portion 72 is arranged to face the top wall portion 61 of the upper case 6, and the upper case 6 is fitted on the left and right side wall portions 73 extending upward from the left and right side edges of the bottom wall portion 72. It is supposed to be supportive. A pair of front and rear locking holes 70 for locking the locking bulge portion 60 are provided on the upper portions of the left and right side wall portions 73, and the outer case 6 is assembled in a fixed state. ing.

  As described above, the circuit component 2 is adhered to the upper surface of the bottom wall portion 72 of the lower case 7 with an adhesive having good electrical insulation such as an epoxy resin. The interior of the lower case 7 is also filled with a potting agent such as silicon resin, and the leg-like terminals 24b and 25b of the first and second relays 24 and 25 are sealed with the potting agent.

  According to the power distribution unit 1 configured as described above, the first and second relays 24 and 25 are mounted on the bus bar substrate 20 via the leg-shaped terminals 24 b and 25 b, and the bus bar substrate 20 is bonded to the bottom wall portion 72 of the lower case 7. Therefore, when the first and second relays 24 and 25 generate heat during driving, the heat can be conducted to the bottom wall portion 72 of the lower case 7 via the leg-shaped terminals 24b and 25b and the bus bar substrate 20. The heat can be dissipated mainly through the bottom wall 72 of the lower case 7. In addition, since the bus bar substrate 20 is opposed to the bottom wall portion 72 of the lower case 7 that faces the bus bar substrate 20, the path for heat conduction can be made relatively short, and heat can be radiated efficiently.

  On the other hand, according to the power distribution unit 1, the LSI 210 a is mounted substantially at the center on the surface side of the control circuit board 21, and the potting agent 65 is placed between the surface of the control circuit board 21 and the top wall portion 61 of the upper case 6. If the LSI 210 a generates heat as it is driven, the heat can be conducted to the top wall 61 of the upper case 6 through the potting agent 65, and through the top wall 61 of the upper case 6. Mainly heat can be dissipated. In addition, since the control circuit board 21 is disposed opposite to the top wall portion 61 of the upper case 6 that faces the control circuit board 21, the path for heat conduction can be made relatively short, thereby efficiently dissipating heat. .

  Further, according to the power distribution unit 1, the FET 210b is mounted between the left and right side edges of the back surface of the control circuit board 21 away from the LSI 210a and the bottom wall 72 of the lower case 7, and the FET 210b is mounted on the lower case. 7, the FET 210b can be mounted by effectively using the space in the heat dissipation case, and the heat generated by the FET 210b is directly transmitted to the side wall portion of the heat dissipation case. Thus, the temperature rise of the other circuit board can be effectively suppressed. In addition, since the FET 210b is bonded to the side wall portion 73 of the lower case 7, the path for heat conduction can be made very short, and heat can be efficiently and reliably radiated.

  That is, according to the power distribution unit 1, the first and second relays 24 and 25, the LSI 210 a and the FET 210 b mounted on the bus bar substrate 20 and the control circuit substrate 21 are arranged on the walls of the upper case 6 and the lower case 7 as heat dissipation cases. Since heat conduction is connected to the part, the heat radiation efficiency can be dramatically improved. Moreover, since the heat generated by driving these circuit components 24, 25, 210a, and 210b is mainly dissipated from the wall portion of the heat dissipation case adjacent to each circuit component, the temperature rise of the gas (for example, air) in the heat dissipation case And thereby, heat dissipation using a gas such as heat radiation of the circuit components including the circuit components 24, 25, 210a, and 210b mounted on the bus bar substrate 20 and the control circuit substrate 21 as a medium. There is an advantage that efficiency is also improved.

  In the above description, the LSI 210a and the FET 210b having a relatively large amount of heat generation are described as typical examples of circuit components mounted on the control circuit board 21, but the control circuit board 21 has capacitors and the like on both the front and back sides. Other circuit components are also mounted. The circuit components mounted on the front surface side of the control circuit board 21 are connected to the top wall 61 of the upper case 6 so as to be able to conduct heat, similarly to the LSI 210a, and are mainly dissipated by the heat conduction. In addition, the circuit components mounted on the back surface side of the control circuit board 21 are radiated through the control circuit board 21 while being radiated using the gas in the heat radiating case such as heat radiation as a medium. Even in this case, for example, the LSI 210a and the FET 210b are efficiently dissipated, so that an increase in the gas temperature inside the power distribution unit 1 is suppressed and the heat dissipation efficiency of these circuit components is improved.

  Next, a method for manufacturing the power distribution unit 1 will be described.

  First, the bus bar substrate 20 on which the first and second relays 24 and 25 are mounted is manufactured (bus bar substrate forming step, relay mounting step). In the present embodiment, the second relay 25 is mounted on a predetermined bus bar 22 in the process of forming the bus bar substrate 20, while the first relay 24 is formed after the bus bar substrate 20 on which the second relay 25 is mounted is formed. The relays 24 and 25 may be mounted after the bus bar substrate 20 is formed, or may be mounted together in the manufacturing process of the bus bar substrate 20. However, in the case where at least one of the first and second relays 24 and 25 is mounted after the bus bar substrate 20 is formed, insulation is performed corresponding to the relay mounted after the bus bar substrate 20 is formed, as described above. It is necessary to provide a terminal insertion hole in the plate and, if necessary, an electrode insertion hole for inserting an electrode for resistance welding.

  Specifically, first, the first and second insulating plates 31a and 31b having the above-described configuration are formed, and the first to third bus bar layers 30a to 30c having the above-described configuration are formed. The first to third bus bar layers 30a to 30c are formed by punching a single metal plate or the like so that the bus bars 22 having a predetermined arrangement pattern corresponding to the bus bar layers 30a to 30c are connected to an outer frame (not shown). A bus bar constituting plate (not shown) configured in a plate shape is formed, and the predetermined bus bar 22 is bent to form the connector terminal 27 and the fuse terminal 28.

  Then, the corresponding bus bar 22 is housed and bonded and fixed in a predetermined bus bar housing groove 310 on the front side (upper side) of the first insulating plate 31a, and the connecting portion between the bus bar 22 and the outer frame on the bus bar constituting plate is cut. Then, the second bus bar layer 30b is stacked on the first insulating plate 31a (see FIG. 7A).

  Next, the first insulating plate 31a on which the second bus bar layer 30b is stacked is stacked on the first bus bar layer 30a shown in FIG. 7B. Then, as shown in FIG. 7 (c), the corresponding bus bar 22 is stored in the predetermined bus bar storage groove 310 on the back side (lower side) of the first insulating plate 31a, on the first bus bar layer 30a. The first insulating plate 31a is laminated, the bus bars 22 are bonded and fixed, and the connecting portion between the bus bar 22 and the outer frame of the bus bar constituting plate is cut, and the first and second bus bars are interposed via the first insulating plate 31a. Layers 30a and 30b are stacked.

  Subsequently, in the present embodiment, before the bus bar 22 of the bus bar constituting plate corresponding to the third bus bar layer 30c is laminated on the second insulating plate 31b, the second relay 25 is previously connected to the predetermined bus bar 22 of the bus bar constituting plate. Has been implemented.

  The second relay 25 is mounted by overlapping the second relay 25 with the overlapping portion 25c of the leg-shaped terminal 25b on the predetermined bus bar 22 of the third bus bar layer 30c, and the overlapping portion of the overlapping portion 25c and the bus bar 22 Is sandwiched between the upper electrode D1 and the lower electrode D2 for resistance welding, and both are joined by resistance welding.

  Next, the corresponding bus bar 22 is housed and fixed in a predetermined bus bar housing groove 313 on the front side (upper side) of the second insulating plate 31b, and the connecting portion between the bus bar 22 and the outer frame on the bus bar constituting plate is provided. The third bus bar layer 30c is laminated on the second insulating plate 31b by cutting (see FIG. 7D).

  And the said laminated body of the 1st insulating board 31a and the 1st and 2nd bus-bar layer 30a, 30b and the laminated body of the 2nd insulating board 31b and the 3rd bus-bar layer 30c are assembled | attached on the laminated state, and the bus-bar board | substrate 20 Manufacturing. Note that the second relay 25 is already mounted on the bus bar substrate 20.

  The bus bar substrate 20 manufactured as described above has a leg shape in the bus bar 22 of the first bus bar layer 30a through the first and second terminal insertion holes 311 and 314 provided in the first and second insulating plates 31a and 31b. The joint portion with the terminal 24b is exposed, and the joint portion with the leg terminal 24b in the bus bar 22 of the second bus bar layer 30b is exposed through the second terminal insertion hole 314 provided in the second insulating plate 31b. Yes.

  Then, through this exposed portion, as shown in FIG. 8, the first relay 24 as a circuit component is mounted on the bus bar substrate 20. The first relay 24 is mounted by inserting the first relay 24 through the main body insertion hole 315, the first and second terminal insertion holes 311 and 314, and connecting the predetermined overlapping portion 24c in the leg-shaped terminal 24b to the first. In this state, the bus bar 22 and the overlapping portion 24c are sandwiched between electrodes D indicated by dotted lines and joined together by resistance welding, and the remaining overlapping at the leg-shaped terminal 24b is superposed on the predetermined bus bar 22 of the bus bar layer 30a. The portion 24c is overlapped with the predetermined bus bar 22 of the second bus bar layer 30b, and in this state, the bus bar 22 and the overlapping portion 24c are sandwiched between the electrodes D and joined together by resistance welding. In this resistance welding, the upper electrode D1 is inserted through the first and second terminal insertion holes 311 and 314. In particular, when welding the bus bar 22 of the second bus bar layer 30b and the overlapping portion 24c, the lower electrode D2 is inserted through the electrode insertion hole 312 provided in the first insulating plate 31a.

  Next, after manufacturing the bus bar substrate 20 on which the first and second relays 24 and 25 are mounted, as shown in FIG. 9, the connector is mounted on the bus bar substrate 20 on which the first and second relays 24 and 25 are mounted. The part 4 and the fuse attachment part 5 are attached (attachment part attachment process). Specifically, the connector terminal 27 of the bus bar substrate 20 is inserted into the remaining connector terminal insertion hole 40 of the connector mounting portion 4 in which the connector pin-like terminal 212 is inserted in part of the connector terminal insertion hole 40 in advance. Thus, the connector mounting portion 4 is attached to the front end portion of the bus bar substrate 20. Further, by inserting the fuse terminal 28 of the bus bar substrate 20 into the fuse terminal insertion hole 50 of the fuse mounting portion 5, the fuse mounting portion 5 is attached to the rear end portion of the bus bar substrate 20.

  And the lower case 7 shown in FIG. 10 is attached after the said mounting part attachment process (lower case attachment process). In the present embodiment, in the lower case attaching step, the lower case 7 in which the FET 210b of the control circuit board 21 is attached in advance to a predetermined location on the inner surface of the left and right side walls 73 is used. As described above, since the FET 210b that generates heat as it is driven is attached to the lower case 7 by adhesion, the FET 210b and the lower case 7 can be reliably connected thermally (heat conduction possible), and the heat dissipation efficiency of the FET 210b can be improved. Can be improved.

  The lower case 7 is attached by engaging the edge portions of the cutout portions 71 of the lower case 7 with the case fitting grooves 41 and 51 of the connector mounting portion 4 and the fuse mounting portion 5 attached to the bus bar substrate 20. This is performed by bonding the back surface (lower surface) of the bus bar substrate 20 to the upper surface of the bottom wall 72 of the lower case 7 with an adhesive. In the case where the lower case 7 is formed of a conductive material, an adhesive having an electrical insulation property is used as described above. For example, an adhesive containing an epoxy resin or a silicon resin is used. Can be used. Note that the bus bar substrate 20 and the lower case 7 may be bonded not only by an adhesive but also to the lower case 7 via an insulating layer such as an insulating plate bonded to the back surface of the bus bar substrate 20. Good. Even in this case, the bus bar substrate 20 needs to be connected to the lower case 7 so as to be capable of conducting heat.

  The lower case 7 is filled with a potting agent to a predetermined height, and the leg terminals 24b and 25b of the first and second relays 24 and 25 are sealed. As the potting agent to be filled, one having excellent thermal conductivity is employed, for example, a silicon-based resin having excellent electrical insulation is employed.

  Next, as shown in FIGS. 11A and 11B, the circuit structure 2 is manufactured by assembling the control circuit board 21 to the bus bar board 20 (control board arranging step). That is, the control circuit board 21 on which various circuit components including the LSI 210a are mounted is established above the bus bar board 20 with a predetermined distance from the bus bar board 20 and proper electrical connection is established. Assemble in the state. Specifically, the connector pin-shaped terminal 212 inserted through the connector terminal insertion hole 40 of the connector mounting portion 4, the pin-shaped terminal 32 formed by folding the predetermined bus bar 22, and the FET 210 b bonded to the lower case 7. Are properly connected to the electric circuit including the control circuit of the control circuit board 21 and the front and rear end edges of the control circuit board 21 are supported by the upper surfaces of the connector mounting portion 4 and the fuse mounting portion 5. The substrate 21 is assembled to the bus bar substrate 20. At this time, the sub-board 211 is also attached in a state of being electrically connected to the back side of the control circuit board 21. In the circuit structure 2 manufactured in this way, the bus bar substrate 20 and the control circuit substrate 21 are arranged in a state of being spaced apart by a predetermined interval, and the first and second relays 24, 25 are arranged with high density.

  Finally, as shown in FIG. 12, the upper case 6 is assembled to the lower case 7 to manufacture the power distribution unit 1 (upper case assembling step). Specifically, the upper case 6 is filled with a potting agent 65 in advance, and the potting agent 65 is cured to a state having a certain shape retaining property and elasticity. Assemble. As the potting agent 65 to be filled, a material having excellent thermal conductivity is employed, and for example, a silicon resin having excellent electrical insulation is employed.

  The assembly to the lower case 7 is performed by engaging the front and rear end edges of the upper case 6 with the case fitting grooves 41 and 51 of the connector mounting portion 4 and the fuse mounting portion 5, and the upper case 6 on the left and right side walls 73 of the lower case 7. And the locking bulging portion 60 of the upper case is locked in the locking hole 70 of the lower case 7.

  Then, the fuse H can be attached to the fuse attachment portion 5 to manufacture the power distribution unit 1 having the above-described configuration as shown in FIG.

[Other Embodiments]
Although the power distribution unit and the like according to the present embodiment have been described above, the power distribution unit and the like according to the present invention are not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. is there. For example, the following changes are possible.

(1) In the above-described embodiment, the lower case 7 has the bottom wall portion 72 and the peripheral side wall portion 73 standing on the periphery thereof, and the front and rear side wall portions of the peripheral side wall portion 73 are greatly cut out to provide a cutout portion. 71 is formed, however, the side wall portion of the lower case 7 does not necessarily have to be formed over the entire circumference of the bottom wall portion 73, and may include, for example, only one side wall portion. On the other hand, the notch 71 may not be provided as described above .

  (2) In the above-described embodiment, the overlapping portion 24c of the leg-like terminal 24b of the first relay 24 is exposed through the first terminal insertion hole 311 and the second terminal insertion hole 314 in the circuit configuration body 2, but this circuit configuration The specific configuration of the body 2 is not particularly limited. For example, as shown in FIG. 14, the body 2 is formed on the bus bar 22 below the first bus bar layer 30 c (the first and second bus bar layers 30 a and 30 b). A second insulating plate 310b is laminated on the overlapping portion 24c of the leg-like terminal 24b of the first relay 24 to be bonded so as to cover the connecting portion between the bus bar 22 and the overlapping portion 24c, and the second insulating plate 310b. You may comprise so that the bus-bar 22 of the 3rd bus-bar layer 30c may be arrange | positioned on the top. In this case, also in the manufacturing method of the circuit structure 2, unlike the above-described embodiment, the first relay 24 is mounted on the predetermined bus bar 22 of the bus bar substrate 20 in the process of forming the bus bar substrate 20. In addition, since the first relay 24 is mounted in the process of forming the bus bar substrate 20 as described above, the first insulating plate 310a is not formed with an electrode insertion hole for resistance welding unlike the above embodiment.

  (3) In the above embodiment, the first and second relays 24 and 25, the LSI 210a, and the FET 210b have been described as examples of circuit components, but they are connected to the upper case 6 and the lower case 7 as heat dissipation cases so as to be able to conduct heat. Specific aspects of the circuit components and the thermal connection to be performed are not particularly limited, and may be appropriately changed depending on the designed circuit.

  However, the circuit component bonded to the peripheral side wall portion 73 of the lower case 7 is preferably a semiconductor element having a relatively large calorific value as in the above embodiment. Further, the circuit component disposed between the bus bar substrate 20 and the control circuit substrate 21 is also preferably a mechanical relay having excellent heat dissipation efficiency of the component itself as in the above embodiment.

It is a perspective view shown in the state where the power distribution unit concerning this invention was turned upside down. It is a disassembled perspective view of the power distribution unit. It is a disassembled perspective view of the circuit structure of the power distribution unit. It is the IV-IV sectional view taken on the line of FIG. It is the VV sectional view taken on the line of FIG. It is the VI-VI sectional view taken on the line of FIG. It is explanatory drawing which shows the manufacturing process of the bus-bar board | substrate in the power distribution unit which concerns on this invention. It is explanatory drawing which shows the process of mounting a circuit component on the bus-bar board | substrate. It is explanatory drawing which shows the process of attaching each mounting part to the bus-bar board | substrate. It is sectional drawing which shows the lower case used for the power distribution unit which concerns on this invention. It is explanatory drawing which shows the process of assembling a control circuit board to the bus-bar board | substrate in the power distribution unit. It is explanatory drawing which shows the assembly | attachment process of the upper case in the power distribution unit. It is a figure which shows the completion figure of the same power distribution unit in a cross section different from FIG. It is sectional drawing which shows the bus-bar board | substrate in the power distribution unit which concerns on other embodiment which concerns on this invention in the state by which the circuit component was mounted.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power distribution unit 2 Circuit structure 6 Upper case 7 Lower case 20 Bus bar board | substrate 21 Control circuit board 22 Bus bar 24 1st relay 24a Relay main body 24b Leg-shaped terminal 24c Superposition | polymerization part 25 2nd relay 25a Relay main body 25b Leg-like terminal 25c Superposition part 30 Busbar layer 61 Top wall part 65 Potting agent 72 Bottom wall part 73 Side wall part

Claims (7)

A heat dissipation case having a lower case including a bottom wall portion and a side wall portion standing from the periphery of the bottom wall portion, an upper case assembled to the lower case, and a circuit structure incorporated in the heat dissipation case The circuit structure includes a pair of circuit boards arranged at a predetermined interval from each other, and a circuit component that is connected to the circuit of each of the boards and generates heat when driven. One is joined to the bottom wall of the heat radiating case, and the circuit component mounted on the one circuit board is connected to the bottom wall through the one circuit board so as to be able to conduct heat. On the other circuit board, at least one circuit component is mounted in a posture positioned between the circuit board and the bottom wall portion, and the circuit component is directly joined to the side wall portion of the heat dissipation case. To the side wall Indirectly to a method for manufacturing a power distribution unit which is connected so as to enable heat conduction,
Includes assembling step of assembling the lower case to the circuit assembly, as the assembly factory includes a preparation step of directly joining at least one circuit component to the side wall of the lower case, the circuit component by the preparation step the but the first set with the step of receiving one of the circuit board in the lower case which is joined, as well as arranged at a predetermined distance to the other circuit board to one of the circuit board above the time of this arrangement And a second assembly step of mounting the circuit component joined to the side wall portion on the circuit of the other circuit board.   2. The method of manufacturing a power distribution unit according to claim 1, further comprising: a bus bar board manufacturing step of manufacturing a bus bar board constituting a power circuit with a plurality of bus bars as the one circuit board, wherein the assembly process includes the bus bar board manufacturing step. By adhering the bus bar located on the back surface of the bus bar substrate manufactured by the process to the bottom wall portion of the heat radiating case, circuit components connected to the surface side of the bus bar substrate through the bus bar substrate are connected to the heat radiating case. A method of manufacturing a power distribution unit, characterized in that connection is made to the bottom wall so as to enable heat conduction.   3. The method of manufacturing a power distribution unit according to claim 2, wherein in the bus bar substrate manufacturing step, a circuit component having a component main body and leg-shaped terminals extending in a direction from the lower portion of the component main body toward the bus bar is provided on the surface side of the bus bar substrate. A distribution unit manufacturing method, comprising: a mounting step for mounting the circuit component, wherein the leg-shaped terminals of the circuit components are joined to a predetermined bus bar of the bus bar substrate by welding.   4. The method for manufacturing a power distribution unit according to claim 1, wherein the circuit component mounted on the surface side of the one circuit board is a relay. .   5. The method of manufacturing a power distribution unit according to claim 1, wherein the other circuit board is configured as a control circuit board including a control circuit that controls driving of the circuit component, and the heat dissipation. A circuit component to be joined to a side wall of a case is a semiconductor element mounted on the control circuit board.   6. The method of manufacturing a power distribution unit according to claim 1, wherein an upper case having a top wall portion is disposed on the lower case in a state where the top wall portion is disposed to face the other circuit board. In this upper case assembly process, a potting agent is interposed in the gap between the other circuit board and the top wall portion, and connected to the circuit board via the potting agent. A method of manufacturing a power distribution unit comprising connecting a circuit component to be connected to a ceiling wall so as to enable heat conduction.   7. The method of manufacturing a power distribution unit according to claim 6, wherein in the upper case assembling step, a potting agent is filled in the upper case in advance, and the potting agent has a predetermined elasticity and shape retention. A method of manufacturing a power distribution unit, wherein the circuit component connected to the circuit of the other circuit board is assembled to a lower case in a manner of sealing.

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