JP2011130558A - Electrical junction box - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize an electrical junction box by eliminating a trouble in miniaturization of the electrical junction box. <P>SOLUTION: The electrical junction box 10 includes a circuit board 20 in which an installation recess 20D is created in an opening 20C by arranging an outermost layer sheet 20A with the opening 20C created therein in the outermost layer and stacking another inner layer sheet 20B, a case 30 which houses this circuit board 20, a ceramic capacitor 23 which is mounted in the installation recess 20D, and a heat radiative sheet 24 which is provided between the circuit board 20 and the case 30 and radiates heat from the circuit board 20 to the case 30. The heat radiative sheet 24 is arranged in a position different from the installation recess 20D on the outermost layer sheet 20A. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrical junction box.

  Conventionally, an electrical junction box has been used as a module having a function of distributing power from a common power source to various electrical components. For example, an electrical junction box described in Patent Document 1 is known. The electrical junction box has a circuit board composed of a circuit board, a semiconductor switching element mounted on the circuit board, and the like, and the circuit board is attached to the case via a heat dissipation sheet. According to such an electrical junction box, when the amount of current allowed for each electrical component is exceeded, energization to each electrical component is interrupted by the semiconductor switching element.

JP 2003-164039 A

  However, electronic components such as ceramic capacitors may be mounted on the mounting surface opposite to the semiconductor switching element. In this case, it is necessary to secure at least a space enough to dispose the ceramic capacitor between the circuit board and the case, which is an obstacle to downsizing the electric junction box.

  The present invention has been completed based on the above circumstances, and an object thereof is to reduce the size of an electric junction box.

  The electrical junction box of the present invention includes a circuit board in which a mounting recess is formed in the opening by placing the outermost layer sheet in which the opening is formed in the outermost layer and laminating other sheets, and the circuit board. A case housed inside, an electronic component mounted in the mounting recess, and a heat dissipating sheet provided between the circuit board and the case and dissipating heat from the circuit board to the case. The seat is characterized in that it is arranged at a position different from the mounting recess.

  According to such a configuration, since the electronic component can be mounted in the mounting recess, the outermost layer sheet and the case can be disposed close to each other at least by the depth of the mounting recess. That is, the space to be secured between the outermost layer sheet and the case can be made smaller than the height of the electronic component. Thereby, an electrical junction box can be reduced in size.

The following configuration is preferable as an embodiment of the present invention.
A heat-generating component that generates heat when energized is mounted on the mounting surface of the circuit board opposite to the mounting recess, and the heat-generating component and the heat-dissipating sheet may be arranged side by side in the sheet stacking direction.

  In such a case, heat from the heat generating component is radiated to the case through the circuit board and the heat radiating sheet. Here, since the space formed between the outermost layer sheet and the case is small as described above, the heat dissipation sheet is made thinner than the conventional one. And if a thermal radiation sheet is made thin, thermal conductivity will become high by that much and a thermal radiation effect can be heightened. Therefore, in addition to downsizing of the electrical junction box, a synergistic effect of improving heat dissipation can be exhibited.

  A printed resistor may be disposed on the heat dissipation path in the circuit board, and the electronic component may be a ceramic capacitor that is larger in the sheet stacking direction than the printed resistor.

  Since the printing resistance is generally higher in heat resistance than the ceramic capacitor, there is no problem even when the printing resistance is arranged on the heat dissipation path. Further, since the printing resistance is smaller in the sheet stacking direction than the ceramic capacitor, there is no problem in miniaturizing the electric junction box.

  According to the present invention, the electrical junction box can be reduced in size.

Sectional view of the electrical junction box of the embodiment as viewed from above in the vertical direction Sectional view of the electrical junction box viewed from the front side in the horizontal direction Sectional view of the electrical junction box in the unfolded state as seen from above in the vertical direction Sectional view of the busbar mounted on the circuit board mounting surface and the transistor mounted on the busbar mounting surface (mounting process) as seen from the front side in the horizontal direction Sectional drawing which looked at the state (wire bonding process) wire-bonded using the 1st wire and the 2nd wire from the horizontal front side Sectional view of the state (sealing process) where the bonding part by wire bonding is sealed with a sealing material as seen from the front side in the horizontal direction Sectional view when the circuit board is housed inside the case and the connector housing is placed on the side of the case (case attachment process) as seen from the front side in the horizontal direction Sectional drawing which looked at the state (folding process) which placed the connector housing on the upper surface of the case by folding back the first wire from the front side in the horizontal direction

<Embodiment>
An embodiment of the present invention will be described with reference to the drawings of FIGS. As shown in FIG. 2, the electrical connection box 10 in the present embodiment includes a circuit board 20, a case 30 that accommodates the circuit board 20 therein, a connector 40 attached to the case 30, and the like. . The electrical junction box 10 has a so-called two-story structure in which the connector 40 is mounted on the upper surface of the case 30, and the circuit board 20 and the connector 40 are connected to each other by the first wire W <b> 1.

  The case 30 includes a lower case 31, a case cover 32, and the like. Although not shown, the case cover 32 is fixed to the lower case 31 by fixing means such as screws or an adhesive. A through hole 33 through which the first wire W1 passes is formed at the end of the case cover 32. Further, a guide recess 34 into which the first wire W1 bent in a folded shape is fitted is provided at the opening edge of the through hole 33. When the first wire W1 is fitted into the guide recess 34, the vibration of the first wire W1 in the lateral direction (direction perpendicular to the paper surface in FIG. 2) is restricted.

  On the other hand, the lower case 31 has a box shape with an upper opening, and the circuit board 20 is placed on the bottom surface of the lower case 31. The side wall of the lower case 31 has a shape that is slightly larger than the circuit board 20. Also, the right side wall 35 corresponding to the guide recess 34 in the side wall of the lower case 31 is formed slightly lower. The upper end of the right side wall 35 is set lower than the upper surface of the bus bar 21 mounted on the upper surface of the circuit board 20. Thereby, as shown in FIG. 6, when the circuit board 20 is accommodated in the lower case 31 and the bus bar 21 and the connector terminal 42 described later are arranged side by side, interference between the connector terminal 42 and the right side wall 35 is avoided. It has become so.

  A side case 36 is attached to the side of the case 30. The side case 36 is configured to sandwich the case 30 and the connector 40 from above and below. The inner surface of the side case 36 is in close contact with the upper surface of the connector 40, the lower surface of the lower case 31, and the right side surface of the right side wall 35. For this reason, the inside of the side case 36 is waterproofed from the outside, and water does not enter the inside of the case 30 through the through hole 33. Moreover, since the side case 36 is configured to cover the first wire W1, the first wire W1 can be protected from an external impact.

  The connector 40 has a connector housing 41 made of a synthetic resin, and a fitting recess 43 into which the mating connector can be fitted is formed inside the connector housing 41. The fitting recess 43 has a hood shape, and a metal connector terminal 42 is held on the back wall 44 of the fitting recess 43 by press-fitting or insert molding. The connector terminal 42 has a flat plate shape, and has a plate thickness of, for example, 0.64 mm in this embodiment. The bus bar 21 described later has a plate thickness of, for example, 1.3 mm, and has a plate thickness that is approximately twice that of the connector terminal 42.

  One end of the connector terminal 42 is accommodated in the fitting recess 43, and a mating connector provided in an external device can be fitted in the fitting recess 43. The mating connector is provided with a mating terminal that can be connected to the connector terminal 42. When the mating connector is fitted into the fitting recess 43, the mating terminal is connected to the connector terminal 42 so as to be conductive. The The other end of the connector terminal 42 protrudes outside through the inner wall 44 of the fitting recess 43, and is joined to the first wire W1 by wire bonding. The joint between the connector terminal 42 and the first wire W <b> 1 is embedded with a sealing material 50.

  The circuit board 20 is composed of an inner layer board made up of a plurality of inner layer sheets 20B and an outer layer board made up of a pair of outermost layer sheets 20A arranged on both upper and lower sides of the inner layer board. The circuit board 20 is a ceramic substrate formed by laminating and firing these sheets 20A and 20B. Such a method for forming a ceramic substrate may be generally referred to by a name such as a green sheet lamination method. On the upper mounting surface of the circuit board 20, an electronic component 25 such as a microcomputer or a discrete transistor, a bus bar 21 made of a metal flat plate, and the like are mounted. On the other hand, a plurality of printing resistors 22 are formed on the lower surface of the lower outermost layer sheet 20A by screen printing.

  FIG. 3 is a diagram illustrating the internal structure of the case 30 and corresponds to FIG. 7 illustrating a state in the middle of manufacturing the electrical junction box 10. That is, FIG. 3 is a cross-sectional view showing the electrical junction box 10 in the unfolded state (the state before the connector 40 is mounted on the upper surface of the case 30 and the connector 40 is disposed on the right side of the case 30). It is. The bus bar 21 has a rectangular shape extending along the right edge of the circuit board 20. A plurality of bare-chip transistors 27 are mounted on the mounting surface of the bus bar 21 along the longitudinal direction of the bus bar 21. A plurality of connection lands 26 are provided intermittently along the longitudinal direction of the bus bar 21 on the left side of the bus bar 21 on the upper surface of the circuit board 20. The connection land 26 and the transistor 27 corresponding thereto are arranged side by side in the left-right direction.

  A source pad (not shown) and a gate pad (not shown) are formed on the upper surface of each transistor 27, and a drain pad (not shown) is formed on the lower surface of each transistor 27. Yes. Each transistor 27 is mounted in a state where the drain pad is directly bonded to the mounting surface of the bus bar 21. The source pad and the connector terminal 42 are connected by the first wire W1, and the gate pad and the connection land 26 are connected by the second wire W2.

  The first wire W1 is a bonding wire for energization, and is composed of a metal wire such as aluminum. On the other hand, the second wire W2 is a signal bonding wire and is made of a metal wire such as aluminum. The wire diameter of the first wire W1 is about 400 μm, for example, and the wire diameter of the second wire W2 is about 125 μm, for example. By using the first wire W1 that is thicker than the second wire W2, it is possible to cope with energization. In addition, when one single wire W1 is insufficient, it is possible to deal with a large current application by joining a plurality of first wires W1.

  The connector 40 includes a pair of output connectors 40 </ b> A connected to each electrical component and an input connector 40 </ b> B connected to a power source, and a total of three connectors 40 </ b> A and 40 </ b> B extend along the longitudinal direction of the bus bar 21. They are arranged side by side. The connector terminal 42 of the input connector 40B is a power supply terminal formed wider than the connector terminal 42 of the output connector 40A. The power supply terminal and the bus bar 21 are connected by, for example, three first wires W1. . On the other hand, the connector terminal 42 of the output connector 40A is connected to the transistor 27 by, for example, two first wires W1. The transistor 27 is connected to the connection land 26 by a single second wire W2.

  As shown in FIG. 2, the junction between the transistor 27 and the first wire W1, the junction between the transistor 27 and the second wire W2, and the junction between the second wire W2 and the connection land 26 are commonly sealed. Embedded with material 50. Originally, the sealing material 50 is a protective material that protects the surface of the transistor 27 in a bare chip state, but in this embodiment, it is used as a wire holding material that reinforces the joint between the wires W1 and W2. Thus, by using the sealing material 50 also as a wire holding material, the amount of the sealing material 50 used can be reduced and the sealing operation can be performed at a time. As a result of reinforcing the joints of the wires W1 and W2, it is possible to prevent the connection reliability from being lowered by folding the first wire W1 and causing cracks in the joints.

  FIG. 1 shows the connector terminal 42 projected on the upper mounting surface of the circuit board 20 when the connector terminal 42 is projected in a direction (vertical direction) perpendicular to the mounting surface with respect to the upper mounting surface of the circuit board 20. FIG. As shown in FIG. 1, the projection surface P of the connector terminal 42 is set so as to be within the upper mounting surface of the circuit board 20.

  Further, the pair of output connectors 40A are both arranged to fit within the upper mounting surface of the circuit board 20, and the input connector 40B is also arranged to fit most of the input connector 40B within the upper mounting surface of the circuit board 20. ing. For this reason, when the plane parallel to the upper mounting surface of the circuit board 20 is an XY plane (not shown), the projected area of the electrical connection box 10 projected on the XY plane is increased by both the connectors 40A and 40B. Can be avoided. Since the projection surface P of the connector terminal 42 overlaps the mounting surface of the bus bar 21 in the vertical direction, the distance from the connector terminal 42 to the mounting surface of the bus bar 21 can be shortened.

  Now, as shown in FIG. 2, a mounting recess 20 </ b> D is provided at the center of the lower mounting surface of the circuit board 20. An opening 20C is formed in the lowermost outer layer sheet 20A, and a mounting recess 20D is formed by laminating the opening 20C on the inner layer sheet 20B. A plurality of ceramic capacitors 23 are mounted on the mounting recess 20D by soldering. As described above, in the mounting recess 20D, the lower mounting surface is constituted by the lower surface of the innermost layer sheet 20B which is the lowermost side, and in the portion other than the mounting recess 20D, the lower surface is lowered by the lower surface of the lower outermost layer sheet 20A. The side mounting surface is configured.

  Although the ceramic capacitor 23 is larger in the vertical direction than the printing resistor 22, the ceramic capacitor 23 is mounted in the mounting recess 20 </ b> D, so that the amount protruding downward from the lower surface of the lower outermost layer sheet 20 </ b> A is suppressed to be small. For this reason, the electrical junction box 10 can be made smaller in the vertical direction than when the ceramic capacitor 23 is mounted on the lower surface of the lower outermost layer sheet 20A. This is because the circuit board 20 and the lower case 31 can be arranged closer to each other when the downward protrusion amount of the ceramic capacitor 23 is reduced.

  Further, if the space formed between the circuit board 20 and the lower case 31 is reduced, the heat radiation sheet 24 attached to the lower side of the printed resistor 22 can be made thinner, so that the heat conductivity of the heat radiation sheet 24 is reduced. Can be further enhanced. Here, since the heat dissipation sheet 24 also functions as a fixing member for fixing the circuit board 20 to the bottom surface of the lower case 31, a minimum thickness necessary for fixing the circuit board 20 is secured. Therefore, when the mounting recess 20D is provided, a synergistic effect of improving the heat dissipation characteristics in addition to downsizing of the electrical junction box 10 can be exhibited.

  Since the ceramic substrate generally has a smaller thermal expansion coefficient than that of the resin substrate and has a high thermal conductivity, the ceramic substrate is often used in the technical field of mounting power elements such as the electrical junction box 10. In particular, in this embodiment, the bus bar 21 is mounted on the upper mounting surface of the circuit board 20, and the bare-chip transistor 27 is mounted on the upper surface of the bus bar 21. The transistor 27 is a heat generating component that generates heat when energized. For this reason, the heat generated in the transistor 27 is radiated to the lower case 31 through a heat radiation path including the bus bar 21, the circuit board 20, the printing resistor 22, and the heat radiation sheet 24. In this heat dissipation path, a ceramic substrate is used as the circuit board 20 and a thin heat dissipation sheet 24 is used, so that high heat dissipation characteristics can be realized.

  The present embodiment is configured as described above. Next, a method for manufacturing the electrical junction box 10 will be described. First, as shown in FIG. 4, a plurality of inner layer sheets 20B are laminated, and a pair of outermost layer sheets 20A are laminated on both upper and lower sides of these inner layer sheets 20B. Here, by providing an opening 20C in advance in the lower outermost layer sheet 20A, a mounting recess 20D composed of the opening 20C and the lower surface of the inner layer sheet 20B is formed along with the lamination. Next, by firing the laminated sheets 20A and 20B, the sheets 20A and 20B are in close contact with each other, and the circuit board 20 is formed as an integrated ceramic substrate.

  Next, the bus bar 21 is mounted on the upper mounting surface of the circuit board 20, and the bare-chip transistor 27 is mounted on the mounting surface of the bus bar 21. Thereafter, cream solder is printed on the upper mounting surface of the circuit board 20, and the electronic component 25 is placed on the cream solder. Then, the circuit board 20 is passed through a reflow furnace, and the circuit board 20 is heated at a high temperature to complete the component mounting on the upper mounting surface.

  On the other hand, for the lower mounting surface of the circuit board 20, first, the circuit board 20 is turned upside down and the lower mounting surface is directed upward. Next, the printing resistor 22 and cream solder are printed on the lower mounting surface of the circuit board 20, and the plurality of ceramic capacitors 23 are placed in the mounting recess 20D. From this state, the circuit board 20 is again passed through the reflow furnace, and the circuit board 20 is heated at a high temperature to complete the component mounting on the lower mounting surface, and all the component mounting is completed (mounting process).

  Next, as shown in FIG. 5, the connector 40 is arranged on the right side of the circuit board 20, and the upper surface of the transistor 27 and the upper surface of the connector terminal 42 are arranged in substantially the same plane. The upper surface of the connector terminal 42 and the upper surface of the transistor 27 are connected by wire bonding, and the connection land 26 and the upper surface of the transistor 27 are connected by wire bonding. The connector terminal 42 and the transistor 27 are bonded to both ends of the first wire W1, and the connection land 26 and the transistor 27 are bonded to both ends of the second wire W2 (wire bonding process).

  Next, as shown in FIG. 6, the entire transistor 27 is sealed with a sealing material 50. As a result, the joint between the first wire W1 and the transistor 27, the joint between the second wire W2 and the transistor 27, and the joint between the second wire W2 and the connection land 26 are sealed with the common sealing material 50. Stopped. Thus, since the sealing material 50 for surface protection is also used as a reinforcing material for the joint portion, the amount of the sealing material 50 used can be reduced, and the sealing operation can be performed at a time. On the other hand, the joint portion between the first wire W <b> 1 and the connector terminal 42 is also sealed with the sealing material 50. As a result, each joint is strengthened by the sealing material 50, and it is possible to avoid a decrease in connection reliability due to a crack or the like when the first wire W1 is folded back (sealing step).

  Next, the circuit board 20 is accommodated in the case 30. In the housing operation, the heat dissipation sheet 24 is disposed below the printing resistor 22, and the circuit board 20 and the bottom surface of the lower case 31 are fixed by the plurality of heat dissipation sheets 24. Here, the ceramic capacitor 23 is mounted in the mounting recess 20D, and the amount by which the lower surface of the ceramic capacitor 23 projects downward from the lower surface of the lower outermost layer sheet 20A is suppressed to be small. And the lower case 31 can be arranged closer to each other. Therefore, the electrical junction box 10 can be made shorter than the case where the ceramic capacitor 23 is mounted on the lower surface of the lower outermost layer sheet 20A.

  One of the heat dissipating sheets 24 is disposed below the bus bar 21 so that heat from the bus bar 21 is easily released to the lower case 31 side. Moreover, since the heat radiating sheet 24 is not disposed below the ceramic capacitor 23 which is taller than the printing resistor 22, the electrical junction box 10 is also reduced in height here. Then, the circuit board 20 is protected by closing the upper surface opening of the lower case 31 by the case cover 32, and the first wire W <b> 1 is pulled out of the case 30 from the through hole 33. Since the first wire W1 is fitted into the guide recess 34, the first wire W1 is restricted from shaking in the lateral direction due to vibration or the like (case assembling step).

  Next, the connector 40 is mounted on the upper surface of the case cover 32 as shown in FIG. 8 by turning the first wire W1 upward while rotating the connector 40 in the counterclockwise direction indicated by the arrow in FIG. Put. The lower surface of the connector housing 41 and the upper surface of the case cover 32 are fixed by fixing means such as screwing or adhesive. The connector 40 is in an upside down orientation from the state of FIG. 7, and the fitting recess 43 of the connector housing 41 is opened to the left. Even in this state, the first wire W1 is fitted in the guide recess 34, and its play is restricted (folding step).

  After that, as shown in FIG. 2, the side case 36 is attached from the right side, so that the connector 40 and the case 30 are sandwiched by the side case 36 from above and below. Accordingly, the connector 40 and the case 30 are fixed, the inside of the case 30 is waterproofed, and the first wire W1 is protected from external impact. Thus, the electrical connection box 10 is completed.

  Then, the effect of this embodiment is demonstrated. First, in terms of downsizing in the vertical direction of the electrical junction box 10, since the ceramic capacitor 23 is mounted in the mounting recess 20D, the ceramic capacitor 23 protrudes downward from the lower surface of the lower outermost layer sheet 20A. The amount to be done can be kept small. Thereby, the circuit board 20 and the lower case 31 can be arranged closer to each other in the vertical direction, and the electrical connection box 10 can be downsized in the vertical direction. Further, since the heat radiation sheet 24 is disposed below the printing resistor 22 while avoiding the ceramic capacitor 23, the circuit board 20 can be further downsized in the vertical direction.

  Next, in terms of miniaturization in the lateral direction (direction along the XY plane) of the electrical connection box 10, the connector terminal 42 is formed separately from the bus bar 21. It becomes possible to make it larger than the plate thickness, and the circuit width of the bus bar 21 can be reduced. For this reason, the projected area where the bus bar 21 is projected onto the XY plane can be reduced, and the projected area where the circuit board 20 is projected onto the XY plane can be reduced. In addition, since the connector terminal 42 is disposed so that the projection surface P of the connector terminal 42 is within the upper mounting surface of the circuit board 20, the electrical connection box 10 can be downsized in the lateral direction.

  Next, from the aspect of heat dissipation of the electrical junction box 10, since the circuit board 20 is made of a ceramic substrate, the heat from the bus bar 21 can be efficiently radiated to the circuit board 20. Furthermore, by arranging the circuit board 20 close to the lower case 31, the heat dissipation sheet 24 can be thinned, and the thermal conductivity of the heat dissipation sheet 24 can be increased. In addition to these, since the heat radiation sheet 24 is disposed below the bus bar 21, heat from the circuit board 20 can be efficiently radiated to the lower case 31 via the heat radiation sheet 24. Therefore, high heat dissipation characteristics can be exhibited as the electrical junction box 10 as a whole.

<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.
(1) Although the circuit board 20 is formed by the so-called green sheet laminating method in the above embodiment, the present invention is not limited to the green sheet laminating method and is formed by laminating a plurality of sheets. Other manufacturing methods may be used as long as they are circuit boards.
(2) Although the circuit board 20 made of a ceramic substrate is exemplified in the above embodiment, according to the present invention, a multilayer board formed by laminating a plurality of resin boards using an adhesive sheet such as a prepreg can be used as a circuit board. Good.

(3) Although the heat dissipation sheet 24 is disposed below the printing resistor 22 in the above embodiment, according to the present invention, the heat dissipation sheet 24 may be directly disposed on the lower surface of the lower outermost layer sheet 20A.
(4) Although the bare chip transistor 27 is mounted on the mounting surface of the bus bar 21 as a heat-generating component in the above embodiment, a discrete transistor may be mounted on the mounting surface of the bus bar 21 according to the present invention. Moreover, you may mount electronic components other than a heat-emitting component.

(5) Although the printing resistor 22 is disposed on the lower mounting surface of the circuit board 20 in the above embodiment, the printing resistor may be disposed on the upper mounting surface of the circuit board 20 according to the present invention. A printing resistor may be disposed on the inner layer substrate.
(6) Although the ceramic capacitor 23 is mounted in the mounting recess 20D in the above embodiment, according to the present invention, an electronic component 25 such as a microcomputer or a discrete transistor may be mounted in the mounting recess 20D.

DESCRIPTION OF SYMBOLS 10 ... Electrical junction box 20 ... Circuit board 20A ... Outermost layer sheet 20B ... Inner layer sheet (other sheets)
20C: Opening 20D: Mounting recess 22 ... Printing resistance 23 ... Ceramic capacitor (electronic component)
24 ... Heat dissipation sheet 25 ... Electronic component 30 ... Case

Claims (3)

A circuit board in which a mounting recess is formed in the opening by placing the outermost layer sheet in which the opening is formed in the outermost layer and stacking other sheets;
A case for accommodating this circuit board inside,
An electronic component mounted in the mounting recess;
A heat dissipating sheet provided between the circuit board and the case and dissipating heat from the circuit board to the case;
The said heat dissipation sheet is arrange | positioned in the position different from the said mounting | wearing recessed part in the said outermost layer sheet | seat, The electrical junction box characterized by the above-mentioned.   A heating component that generates heat when energized is mounted on the mounting surface of the circuit board opposite to the mounting recess, and the heating component and the heat dissipation sheet are arranged side by side in the stacking direction of the sheets. The electrical junction box according to claim 1.   3. A printed resistor is disposed on a heat dissipation path in the circuit board, and the electronic component is a ceramic capacitor that is larger in the stacking direction of the sheet than the printed resistor. Electrical connection box as described in.

Images