JP5669917B1 - Power supply - Google Patents

Abstract

An object of the present invention is to obtain a highly reliable and high-performance power supply device that achieves both insulation and heat dissipation. A plurality of terminals (1d, 1s) for flowing a main current project from a side portion, and a plurality of switching elements 1 in which a built-in heat spreader 1 is exposed from one side, and each of the plurality of switching elements 1 A circuit board in which a die pad to be heat-transferred so as to contain 1h is formed of a metal plate integrally with a wiring pattern for electrically connecting between the switching element 1 and the other switching element 1 that are heat-transferred and placed on the die pad 4 and a housing 8 that accommodates the circuit board 4, and the metal plates forming the die pads are thicker than the built-in heat spreader 1 h and are opposite to the circuit surface 4 f with the insulating sheet 7 interposed therebetween. It is joined to the housing 8. [Selection] Figure 1

Description

  The present invention relates to a power supply device having a power circuit composed of a plurality of power semiconductor elements, and more particularly to a structure of a circuit board on which power semiconductor elements are mounted.

  A power supply device that converts an AC voltage into a DC voltage or converts a DC voltage into another DC voltage is widely used in the industry. In particular, a switching power supply having an inverter circuit with a full bridge configuration using a power semiconductor element can be remarkably reduced in size and efficiency as compared with the conventional one, and is used in many power supplies.

  In such a power supply device, the power semiconductor element is often housed in a housing. On the other hand, when the power supply device is used in a high temperature environment, it is important to efficiently cool the power semiconductor element that is a heat source. Therefore, a plurality of power semiconductor elements are fixed to a metal heat dissipator through an insulating material to efficiently diffuse the heat of the power semiconductor elements and establish heat in a high temperature environment (for example, Patent Document 1). reference.).

JP 2013-94022 A (paragraphs 0099 to 0100, FIG. 12)

  However, even if a heat sink having higher heat conductivity than the case is installed between the power semiconductor element and the housing, the insulating material interposed between the heat sink and the power semiconductor element becomes a heat conduction resistance, Heat transfer from the power semiconductor element to the radiator is suppressed. On the other hand, since a plurality of power semiconductor elements have different potentials, if the insulating material is omitted and fixed to the heat radiating plate, insulation is not ensured and reliability is lowered. As a result, it has been difficult to obtain a power supply device that fully exhibits the performance of the power semiconductor element while maintaining high reliability.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to obtain a highly reliable and high-performance power supply device that achieves both insulation and heat dissipation.

  A power supply device according to the present invention is a power supply device that outputs alternating current power to direct current power or direct current power to direct current power of a different voltage and outputs a plurality of terminals projecting from the side portion. A plurality of power semiconductor elements from which heat transfer plates are exposed, and a die pad that heat-mounts each of the plurality of power semiconductor elements so as to enclose the heat transfer plates. A circuit board formed of a metal plate integrally with a wiring pattern that electrically connects a power semiconductor element to be connected to another power semiconductor element, and a housing that accommodates the circuit board, and a metal that forms the die pad Each of the plates is thicker than the heat transfer plate, and is joined to the housing via an insulating sheet on the surface opposite to the surface on which the power semiconductor element is mounted. .

  According to the present invention, the die pad for heat transfer mounting the power semiconductor element and the wiring pattern for electrical connection between the elements are integrally formed of the metal plate, so that the heat received from the power semiconductor element is efficiently transmitted. A power supply device that functions as a heat spreader, achieves both insulation and heat dissipation, and has high reliability and high performance can be obtained.

It is a top view of the circuit board with which the some power semiconductor element which comprises the inverter circuit of the power supply device concerning Embodiment 1 of this invention was mounted. It is a fragmentary sectional view which shows the state which installed the circuit board which mounted the power semiconductor element which comprises the inverter circuit of the power supply device concerning Embodiment 1 of this invention in the housing | casing. 1 is a circuit diagram of a power supply device according to a first embodiment of the present invention and an inverter circuit portion in the power supply device.

Embodiment 1 FIG.
1 to 3 are diagrams for explaining the configuration of the power supply device according to the first embodiment of the present invention and the circuit board constituting the inverter circuit of the power supply device, and FIG. 1 shows the first embodiment of the present invention. FIG. 2 is a plan view of a circuit board on which four power semiconductor elements constituting the inverter circuit of the power supply device are mounted so as to be connected in series and in parallel. FIG. 2 shows the circuit board on which the power semiconductor element is mounted and constitutes the inverter circuit. It is a fragmentary sectional view in the state installed in the housing | casing, and a cutting position respond | corresponds to the AA line of FIG. FIG. 3 is a circuit diagram of the power supply device, FIG. 3A is a circuit diagram of the entire power supply device, and FIG. 3B is a circuit diagram of an inverter circuit portion in the power supply device.

A characteristic part of the power supply device according to the first embodiment of the present invention is the structure of a circuit board on which a plurality of power semiconductor elements for constituting an inverter circuit are mounted. First, the entire power supply device including the inverter circuit The circuit configuration will be described with reference to FIG.
As shown in FIG. 3A, the power supply device 100 according to the first exemplary embodiment of the present invention switches a transformer 21 that changes voltage and DC power supplied from the power source to pulse the primary coil of the transformer 21. Inverter circuit 10 for supplying wave power, rectifier circuit 22 for rectifying AC power transmitted to the secondary coil of transformer 21, output terminal 25 for outputting DC power, center tap and output terminal 25 of transformer 21 And a smoothing capacitor 24 that is connected between the output terminals 25 and smoothes the AC voltage rectified by the rectifier circuit 22. It is what is called an insulation type DC / DC converter provided with.

  As shown in FIG. 3B, the inverter circuit 10 includes a system in which switching elements 1A and 1B, which are power semiconductor elements, are connected in series, and a system in which switching elements 1C and 1D, which are also power semiconductor elements, are connected in series. Connected to form a full bridge. In the circuit shown in FIG. 3, discrete MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) are used for the four switching elements 1A, 1B, 1C, and 1D (collectively switching element 1).

  Specifically, the source terminal 1As of the switching element 1A and the drain terminal 1Bd of the switching element 1B are connected. Similarly, the source terminal 1Cs of the switching element 1C and the drain terminal 1Dd of the switching element 1D are connected. The drain terminal 1Ad of the switching element 1A and the drain terminal 1Cd of the switching element 1C are connected to one terminal of the power supply, and the source terminal 1Bs of the switching element 1B and the source terminal 1Ds of the switching element 1D are connected to the other terminal. Thus, the inverter circuit 10 that switches the DC power supplied from the power source and supplies the pulse wave power to the transformer 21 is formed.

Next, the structure of the circuit board constituting the inverter circuit portion, which is a feature of the power supply device according to the present embodiment, will be described.
As shown in FIG. 1, four circuit patterns 2 </ b> A, 2 </ b> B, 2 </ b> C, and 2 </ b> D (collectively circuit pattern 2) insulated by the resin member 3 are exposed on the circuit surface 4 f of the circuit board 4. The circuit pattern 2A has a function of a wiring pattern that electrically connects the die pad on which the switching element 1A and the switching element 1C are installed, the drain terminal 1Ad of the switching element 1A, and the drain terminal 1Cd of the switching element 1C. The circuit pattern 2B has a function of a wiring pattern for electrically connecting the die pad on which the switching element 1B is installed, the source terminal 1As of the switching element 1A, and the drain terminal 1Bd of the switching element 1B. The circuit pattern 2C has a function of a wiring pattern that electrically connects the die pad on which the switching element 1D is installed, the source terminal 1Cs of the switching element 1C, and the drain terminal 1Dd of the switching element 1D. The circuit pattern 2D has a function of a wiring pattern that electrically connects the source terminal 1Bs of the switching element 1B and the source terminal 1Ds of the switching element 1D.

  That is, the code of each circuit pattern 2 corresponds to the code of the circuit diagram of FIG. In the circuit pattern 2, the circuit pattern 2 connected to the drain terminal (also referred to as the drain terminal 1Xd) of a certain switching element (for example, referred to as the switching element 1X) is used to install the switching element 1X. It has a die pad function.

  The thickness of each circuit pattern 2 is thicker than the thickness of the heat transfer plate 1h of the switching element 1X described later, and is equal to the thickness of the circuit board 4, and the portion exposed on the circuit surface 4f side is opposite as shown in FIG. The side surface is also exposed. The circuit board 4 having such a structure is formed as an integral member by performing insert molding with the resin material constituting the resin member 3 using each circuit pattern 2 as an insert material. Since such a circuit board 4 is conducted to the opposite surface, the circuit board 4 is installed on the metal casing 8 via an insulating heat radiation sheet (insulating sheet 7). Note that cooling water (refrigerant) for radiating heat transmitted to the housing 8 flows on the surface of the housing 8 opposite to the surface on which the circuit board 4 is installed.

  Each switching element 1 is a discrete element having a rectangular plate shape, and from the side, a gate electrode (1Ag to 1Dg: collectively 1g), a drain electrode (1Ad to 1Dd: collectively 1d), and a source electrode (1As to 1Ds: Collectively, the three terminals from 1s) protrude. A built-in heat spreader 1h (in the case of being shown individually, built-in heat spreaders 1Ah to 1Dh) that is electrically connected to the drain electrode 1d is exposed on one of the main surfaces, and the other surface is covered with insulation. 1 and 2, each switching element 1 is placed on the circuit surface 4f so that the built-in heat spreader 1h faces the circuit surface 4f and at least each built-in heat spreader 1h is included in the corresponding die pad. To do. The surface of the opposite side of the built-in heat spreader 1h is pressed by the pressing spring 5 whose one end is fixed to a predetermined position of the housing 8 by the screw 6, and each switching element 1 is fixed on the circuit surface 4f.

  Then, the terminals from the main power electrodes (source electrode 1s and drain electrode 1d) of each element are electrically connected to the circuit pattern 2 to form the inverter circuit 10 shown in FIG. 3B. Further, by providing the circuit pattern 2 with a die pad, a heat transfer path through the circuit pattern 2 from each switching element 1 to the housing 8 (the above-described cooling water) is formed.

Next, the operation will be described.
When the power supply device 100 is operated, a current flows through the switching element 1, and heat corresponding to the voltage loss is generated in the switching element 1. The heat generated in the switching element 1 is transmitted to the circuit pattern 2 that is in direct contact with the built-in heat spreader 1h. The heat transmitted to the circuit pattern 2 is transmitted to the housing 8 through the insulating sheet 7 and is transmitted to the cooling water flowing through the housing 8 (the heat radiation surface thereof).

  At this time, the heat transfer performance of each member in the heat transfer path is proportional to the thermal conductivity and the heat transfer area, and inversely proportional to the path length. In addition, the temperature gradient that becomes the driving force for heat transfer is inversely proportional to the thermal conductivity of the member, and in order to obtain the same amount of heat transfer, the smaller the thermal conductivity, the larger the temperature gradient. Here, the thermal conductivity of the metal members such as the built-in heat spreader 1h, the circuit pattern 2, and the housing 8 is about 398 W / mK for copper and about 92 W / mK and about 100 W / mK for the ADC12 material for aluminum die casting. It is. On the other hand, the material constituting the insulating sheet 7 is, for example, about 10 W / mK, which is about one-tenth of the ADC12 material, even if it contains a thermally conductive filler to increase the thermal conductivity. In order to ensure insulation, it cannot be made extremely thin. Therefore, in the heat transfer path, the heat transfer performance of the insulating sheet 7 is the lowest, and improving the heat transfer performance in the insulating sheet 7 improves the heat transfer performance of the entire heat transfer path.

  Here, when the switching element is connected to the heat transfer plate through the insulating layer as in the conventional case, the heat transfer area in the insulating layer is limited to the area of the switching element having the smallest area in the heat transfer path. Become. Therefore, the heat transfer property of the entire heat transfer path is lowered, and the heat generated in the switching element cannot be removed efficiently. On the other hand, in the power supply device according to the first embodiment, the built-in heat spreader 1h that determines the substantial heat transfer area of the switching element 1 is directly connected to the circuit pattern 2 that is a metal member. Then, the insulating sheet 7 for maintaining the insulating property of the switching element 1 was installed between the circuit pattern 2 and the housing 8 having a larger area and thickness than the built-in heat spreader 1h.

  Therefore, the heat generated in each switching element 1 is transmitted substantially evenly in the exposed surface of the circuit pattern 2 even on the surface opposite to the circuit surface 4f. Therefore, the heat transfer area of the insulating sheet 7 can be expanded without being restricted by the heat transfer area of the switching element 1. As a result, the heat transfer performance of the entire heat transfer path is improved, and the heat generated in the switching element 1 can be efficiently guided to the cooling water and removed (cooled). In addition, when the insulating coating is applied to both surfaces of the switching element, the insulating sheet 7 itself is not necessary. In this case, the insulating coating itself applied to the switching element deteriorates the heat transfer performance. As a result, sufficient cooling cannot be performed.

  That is, the circuit pattern 2 that combines the die pad that is in contact with the built-in heat spreader 1h and the wiring pattern that is connected to the pole that is electrically connected to the built-in heat spreader 1h is used as the heat spreader. As a result, the built-in heat spreader 1h is installed on one surface, and even if the switching element 1 that requires insulation treatment is used, both insulation and heat dissipation can be achieved, and a highly reliable and high-performance power supply device 100 can be obtained. I was able to.

  In addition, by configuring the circuit pattern 2 functioning as a heat spreader as an insert molded component integrated with the circuit board 4, the number of components can be reduced. Further, by configuring the circuit pattern 2 functioning as a wiring pattern as an insert molded part integrated with the circuit board 4, the number of parts can be reduced. Furthermore, the heat spreader that serves both as the wiring pattern and the die pad can be made smaller by using an integral conductor (circuit pattern 2).

  In the first embodiment, nothing is interposed between the switching element 1 and the circuit pattern 2, but heat radiation grease may be applied. Further, although the switching element 1 is shown pressed against the circuit board 4 by a holding spring 5 that is an elastic member, a screw hole is cut in the circuit pattern 2 (die pad portion) to switch the switching element 1 and the circuit pattern 2. May be fixed with screws. Further, when the circuit board 4 is molded, an insert collar or the like may be provided and fixed to the housing 8 with screws.

  In the first embodiment, electrical wiring is performed so as to constitute a full-bridge single-layer inverter, but this is not restrictive. For example, a MOSFET in synchronous rectification may be mounted with the same structure as in the first embodiment. In other words, for a circuit using a plurality of power semiconductor elements having a built-in heat spreader, a die pad that is in contact with the built-in heat spreader and a wiring pattern that is connected to the pole that is connected to the built-in heat spreader are formed as an integrated wiring pattern. Use as a heat spreader. As a result, it is possible to obtain a power supply device 100 having both high insulation and heat dissipation, high reliability, and high performance.

  In the first embodiment, the wiring pattern connected to the switching element 1 and the circuit pattern 2 functioning as a die pad are inserted into the circuit board 4. However, the present invention is not limited to this. For example, the winding of the coil (choke coil 23) connected to the subsequent stage of the inverter circuit 10 or the primary winding of the transformer 21 may be integrally inserted. With this configuration, the number of components that connect the switching element 1 and the winding of the choke coil 23 or the primary winding of the transformer 21 can be reduced, and the assemblability can be improved.

  As described above, according to the power supply apparatus 100 according to the first embodiment of the present invention, the power supply apparatus 100 converts AC power into DC power, or converts DC power into DC power of a different voltage and outputs the power. A plurality of power semiconductor elements (switching element 1) in which a plurality of terminals (1d, 1s) for flowing a main current protrude from the side and a heat transfer plate (built-in heat spreader 1h) is exposed from one side, and a plurality of power semiconductor elements A die pad that heat-places each of the (switching elements 1) so as to enclose a heat transfer plate (built-in heat spreader 1h) between the power semiconductor element placed on the die pad and the other power semiconductor elements. A circuit board 4 formed of a metal plate (circuit pattern 2) integrally with a wiring pattern to be electrically connected, and a housing 8 for housing the circuit board 4, and forming a die pad Each of the metal plates (circuit pattern 2) is thicker than the heat transfer plate (built-in heat spreader 1h), and the surface opposite to the surface (circuit surface 4f) on which the power semiconductor element (switching element 1) is mounted. Thus, since it is configured to be joined to the housing 8 via the insulating sheet 7, not only the die pad portion but also the wiring pattern portion functions as one heat spreader. Therefore, the heat transfer area of the insulating sheet 7 is maximized within the constraints of the area of the substrate and elements, and the heat transfer performance is improved without impairing the insulation. As a result, a built-in heat spreader 1h is installed on one surface, and even if a power semiconductor element (switching element 1) that requires insulation treatment is used, both insulation and heat dissipation are compatible, and a highly reliable and high-performance power supply. Device 100 can be obtained.

  Further, since the circuit board 4 is integrally formed with a resin material (resin member 3) using a metal plate (circuit pattern 2) forming a die pad as an insert material, the number of parts can be reduced and the assemblability can be improved. To do.

  Further, the plurality of power semiconductor elements are four switching elements 1, and the circuit board 4 is formed with the inverter circuit 10 in which the four switching elements 1 are configured as a full bridge, so that high performance and miniaturization are expected. In addition, the effect of achieving both insulation and heat dissipation becomes more prominent.

  Further, the four switching elements 1 constituting the inverter circuit described above are MOSFETs whose drain terminals 1d are electrically connected to the heat transfer plate (built-in heat spreader 1h), and the first MOSFET (switching element 1A) among the plurality of die pads. The die pad for heat transfer mounting and the die pad for electrothermal mounting the second MOSFET (switching element 1C) are connected to the drain terminal 1Ad of the first MOSFET (switching element 1A) and the drain terminal 1Cd of the second MOSFET (switching element 1C). The die pad on which the third MOSFET (switching element 1B) is mounted on heat is integrated with the wiring pattern to be electrically connected (circuit pattern 2A), the drain terminal 1Bd of the third MOSFET (switching element 1B) and the first MOSFET (switching element 1A). ) A die pad for heat transfer mounting the fourth MOSFET (switching element 1D) integrally with the wiring pattern for electrically connecting the first terminal 1As (circuit pattern 2B) and the drain terminal 1Dd of the fourth MOSFET (switching element 1D) Since the metal pattern (circuit pattern 2) is formed integrally with the wiring pattern (circuit pattern 2C) that electrically connects the source terminal 1Cs of the MOSFET (switching element 1C), a main power terminal (circuit pattern 2) is formed on one surface. A built-in heat spreader 1h that is electrically connected to the drain terminal 1d) is installed, and even if a power semiconductor element (switching element 1) such as a MOSFET that requires insulation treatment is used, both insulation and heat dissipation are compatible, and high reliability. A high-performance power supply device 100 can be obtained.

  Further, if the transformer 21 or the choke coil 23 electrically connected to the circuit board 4 is provided and the winding of the transformer 21 or the choke coil 23 is formed integrally with the circuit board 4, a power semiconductor The number of parts connecting the element (switching element 1) and the winding of the choke coil 23 or the primary winding of the transformer 21 can be reduced, and the assemblability is improved.

  1: switching element (power semiconductor element), 1d: drain terminal (terminal for main power), 1h: built-in heat spreader, 1s: source terminal (terminal for main power), 2: circuit pattern, 3: resin member, 4 : Circuit board, 4f: circuit surface, 5: holding spring, 7: insulating sheet, 8: housing, 10: inverter circuit, 100: power supply device.

Claims (5)

A power supply device that converts AC power into DC power, or converts DC power into DC power of a different voltage and outputs the power,
A plurality of power semiconductor elements in which a plurality of terminals for flowing a main current protrude from the side and a heat transfer plate is exposed from one surface,
A die pad that heat-places each of the plurality of power semiconductor elements so as to enclose the heat transfer plate electrically connects the power semiconductor element that is heat-transferred to the die pad and another power semiconductor element. A circuit board formed of a metal plate integrally with the wiring pattern;
A housing for housing the circuit board,
The metal plates forming the die pad are each thicker than the heat transfer plate, and are joined to the housing via an insulating sheet on the surface opposite to the surface on which the power semiconductor element is mounted for heat transfer. A power supply device characterized by that.   The power supply device according to claim 1, wherein the circuit board is integrally formed of a resin material using a metal plate forming the die pad as an insert material. The plurality of power semiconductor elements are four switching elements,
The power supply device according to claim 1, wherein an inverter circuit in which the four switching elements are configured as a full bridge is formed on the circuit board. Each of the four switching elements is a MOSFET whose drain terminal is electrically connected to the heat transfer plate,
Among the plurality of die pads,
A die pad for heat transfer mounting the first MOSFET and a die pad for heat transfer mounting the second MOSFET are integrated with a wiring pattern for electrically connecting the drain terminal of the first MOSFET and the drain terminal of the second MOSFET,
A die pad for heat transfer mounting the third MOSFET is integrated with a wiring pattern for electrically connecting the drain terminal of the third MOSFET and the source terminal of the first MOSFET,
The die pad for heat transfer mounting the fourth MOSFET is integrated with the wiring pattern for electrically connecting the drain terminal of the fourth MOSFET and the source terminal of the second MOSFET,
The power supply device according to claim 3, wherein each of the power supply devices is formed of the metal plate. A transformer or a choke coil electrically connected to the circuit board;
5. The power supply device according to claim 1, wherein a winding of the transformer or a winding of the choke coil is integrally formed with the circuit board.

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