JP2008235321A - Heat conductive substrate and manufacturing method, and circuit module using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve air-cooling property of a heat conductive substrate itself by fitting a heat generating component to a part where a lead frame is bent and also improve air-cooling property even in combination with a printed circuit board. <P>SOLUTION: In the heat conductive substrate formed of a sheet type heat conductive layer 12 on a metal plate 11 and a lead frame 13 fixed to the heat conductive layer 12, a part of the lead frame 13 is bent almost vertically at the external circumferential part of the heat conductive circuit board and a heat generating component 15 is mounted here (for example, the side of the metal part 20 is located in the side of lead frame 13 and the lead wire 21 is located in the side of the printed circuit board 24). Accordingly, heat radiating effect of the heat conductive substrate can be improved and a floor area of the conductive circuit board can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat conductive substrate used in a power circuit using a power semiconductor or the like of an electronic device, a manufacturing method thereof, and a circuit module using the same.

  In recent years, with the demand for higher performance and miniaturization of electronic devices, further miniaturization is required for power supply circuits using power semiconductors and the like. However, since power system electronic components (for example, power semiconductor elements) generate large current and high heat generation, it is necessary to mount them on a heat conductive substrate corresponding to large current and high heat dissipation. Compared with such power electronic components, signal electronic components (for example, signal semiconductor elements and various chip components) do not generate much heat and can be mounted with high density. Therefore, conventionally, power system electronic components are mounted on a high heat dissipation board, this is mounted on a thermal component unit (for example, thermal component unit 7 in FIG. 10 to be described later), and signal system electronic components are mounted on a general printed wiring board. Japanese Patent Application Laid-Open No. H10-228707 proposes that a plurality of substrates are electrically connected to form a single circuit module. Next, an example of a conventional circuit module will be described with reference to FIG.

  FIG. 10 is a perspective view for explaining a conventional circuit module, which is one of the circuit modules used in a plasma display device, for example. This circuit module includes a thermal component unit and a printed wiring board fixed on the thermal component unit via a plurality of lead wires.

In FIG. 10, the thermal component unit 7 is formed of an insulator 5 fixed on a metal plate 4, a metal pattern 6, a lead wire 1, and the like. On the metal pattern 6, the heat generating component 3 is soldered via the terminal 2. Further, a hole 9 is formed in a part of the printed wiring board 8 so that the lead wires 1 can be inserted all together. The lead wire 1 of the thermal component unit 7 is inserted into the hole 9 of the printed wiring board 8 and integrated into one circuit module.
JP 2006-308620 A

  As described above, in the configuration of FIG. 10, the thermal component unit 7 on which the heat generating component 3 accompanied by heat generation (or needs heat dissipation) and the printed wiring board 8 on which the signal system electronic component or the like is mounted are stacked substantially in parallel. For this reason, the heat generated in the thermal component unit 7 is likely to be trapped in the meantime, so that when the circuit module is used, there is a limit to heat radiation by air cooling.

  Therefore, the present invention aims to enhance the air cooling performance of the heat-generating component by attaching it to the bent part of the lead frame, and improving the air cooling performance of the heat conductive substrate itself even when combined with a printed wiring board.

  In order to achieve the above object, the present invention provides a heat conductive substrate comprising a metal plate, a sheet-like heat transfer layer fixed on the metal plate, and a lead frame fixed to the heat transfer layer. In this case, a part of the lead frame is bent substantially perpendicularly from the heat transfer layer at the outer peripheral portion, and a heat conductive substrate is mounted with a heat generating component mounted on the bent portion.

  As described above, according to the present invention, the heat generating component is mounted on the bent portion of the lead frame, so that the heat dissipation performance (and further the air cooling performance) of the heat conductive substrate can be improved. (Or floor area) can be reduced. As a result, even when a circuit module is combined with a printed wiring board, a small circuit module with good heat dissipation can be provided.

  In addition, heat-generating components that have been individually mounted on the printed wiring board can be mounted together on the heat conductive substrate as necessary, thereby improving the air cooling efficiency when using an air cooling fan or the like. Can do.

  Note that some of the manufacturing steps shown in the embodiment of the present invention are performed using a molding die or the like. However, the molding die is not shown unless it is necessary for explanation. Further, the drawings are schematic views and do not show the positional relations in terms of dimensions.

(Embodiment 1)
Hereinafter, the heat conductive substrate according to Embodiment 1 of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of a heat conductive substrate in an embodiment of the present invention. In FIG. 1, 11 is a metal plate, 12 is a heat transfer layer, 13 is a lead frame, 14 is a transformer or the like (for example, a transformer or a part of a semiconductor with heat generation), 15 is a heat generating component (for example, a power transistor or a power FET). Etc.), 16 is an insulating conductive adhesive, which is an insulating adhesive excellent in thermal conductivity, and a commercially available product can be used. 17 is a fin for heat dissipation, and a commercially available product such as aluminum can be used. Reference numeral 18 denotes an air cooling fan (or a fan), and a commercially available product can be used. 19 is an arrow. The arrow 19 schematically illustrates, for example, the rotation direction of the fan 18, the direction of the wind, the direction in which heat of the heat generating component 15 is transmitted, and the like.

  First, a description will be given with reference to FIG. FIG. 1 shows an example of a circuit module in which a heat-generating component 15, a transformer 14 and the like, and fins 17 and the like for heat dissipation are mounted on a heat conductive substrate in the embodiment. In FIG. 1, a plurality of lead frames 13 are formed on a metal plate 11 by embedding a part or more of them as a kind of wiring via a heat transfer layer 12. A plurality of transformers 14 are mounted on the lead frame 13 (for example, as shown in the center of FIG. 1). On the transformer 14 or the like, a heat radiating fin 17 is fixed using a commercially available insulating conductive adhesive 16 or the like. In some cases, the transformer 14 in the circuit (for example, a DCDC converter) in the embodiment generates heat. In such a case, the transformer and the like 14 are locally cooled by fixing the heat radiation fins 17 on the transformer and the like 14 using the insulating conductive adhesive 16 (see FIG. 3B for details). ) Etc.).

  Further, in FIG. 1, a part of the lead frame 13 (for example, the outer peripheral portion of the heat conducting substrate or the peripheral portion thereof as shown in FIG. 1) is bent substantially vertically, and the bent lead frame 13 (or the portion thereof) is bent. On the outside, a heat generating component 15 (the lead wire formed on the heat generating component 15 is not shown) is mounted. Then, if necessary, the heat dissipating fins 17 are fixed to the inner side (or the side of the lead frame 13 where the heat generating component 15 is not mounted) via the insulating conductive adhesive 16. In this way, the heat generated in the heat generating component 15 is air-cooled through the fins 17. If necessary, the number of fins 17 can be increased, and for example, as shown in FIG. 1, the surface (or upper surface) of the heat conductive substrate can be covered with a plurality of fins 17. The plurality of fins 17 are cooled by the generated wind (shown by the arrow 19b) by rotating the air cooling fan 18 as shown by the arrow 19a. In FIG. 1, it is not necessary to bend all the lead frames 13 on the outer peripheral portion (or the peripheral portion) of the heat conducting substrate. This is for electrically connecting the heat conductive substrate and the printed wiring board in FIGS. 2 and 3 described later.

  In the present embodiment, electronic components that require heat dissipation (for example, the heat generating component 15 and the transformer 14) can be concentrated on the heat conductive substrate. Even when the heat generating components 15 and the transformers 14 serving as heat sources are assembled (or mounted) with high density in this way, as shown in FIG. ) Can be covered with the fins 17 and can be intensively cooled by the fan 18 or the like, and the cooling efficiency can be increased. Although forced air cooling is used in FIG. 1, the same effect can be obtained by other methods (for example, using a heat pipe or a water-cooled circulation facility). And although the heat conductive board in this Embodiment is the thing excellent in the heat dissipation effect by itself, it can raise a utility value further by combining with a printed wiring board and setting it as a circuit module. Next, the heat radiation effect in the circuit module created by combining the heat conductive substrate with the printed wiring board will be described with reference to FIGS.

  Next, an example of a power semiconductor serving as the heat generating component 15 will be described with reference to FIG. FIGS. 2A and 2B are a cross-sectional view and a perspective view, respectively, for explaining the heat generating component 15. In FIG. 2, 20 is a metal part, 21 is a lead wire, and 22 is a resin part. Some of the power semiconductors 15 (for example, depending on the package form such as TO-220C, TO-3P, etc.) are provided with a metal part 20 in a part thereof in order to improve heat dissipation.

  FIG. 2A is a cross-sectional view of the heat generating component 15. For example, a predetermined semiconductor chip is mounted on the metal portion 20 and covered with the resin portion 22 together with the lead wires 21. In addition, the metal part 20 can be used for electric power feeding etc. other than heat dissipation by making the metal part 20 into an active part. Here, the lead wire 21 corresponds to, for example, a source, drain, back gate, or bulk terminal in the power FET, and protrudes from the heat generating component 15. 20 and the same potential.

  FIG. 2B is a perspective view of the heat generating component 15, and it can be seen that the metal portion 20 is formed on substantially the same surface as the resin portion 22. By doing so, the metal part 20 and the resin part 22 can be fixed in close contact with the lead frame 13 as shown in FIG. 1 and the like, and heat dissipation can be improved. The number of lead wires 21 of the heat generating component 15 is generally two to three. However, even if this number is changed, in the case of the present embodiment, it can be dealt with by appropriately dividing the lead frame 13. .

  Note that the shape of the power semiconductor 15 used in this embodiment preferably has a metal portion 20 as shown in FIGS. This is because the metal part 20 that also serves as a live part and a heat dissipation part can be directly fixed to the lead frame 13 having a large current capacity and high thermal conductivity. As a fixing method, it is desirable to select an electrically and mechanically reliable method such as soldering and screwing. This is because the metal part 20 of the power semiconductor 15 is fixed to the lead frame 13 and the lead wire 21 is fixed to the printed wiring board 24, as will be described later with reference to FIGS.

  Next, the heat dissipation effect will be described with reference to FIG. 3A and 3B are a cross-sectional view for explaining how to assemble the circuit module and a cross-sectional view for explaining the heat dissipation effect. 3A and 3B, reference numeral 23 denotes an electronic component such as a chip component (such as a square chip resistor or a multilayer ceramic capacitor) or a semiconductor element for controlling the heat generating component 15. Reference numeral 24 denotes a printed wiring board (for example, a general printed wiring board 24 made of glass epoxy, such as double-sided or multilayered, but an electrode pattern made of copper foil, a through hole, a solder resist, etc. are not shown). Reference numeral 25 denotes a chassis (for example, an aluminum chassis in a plasma TV or a metal housing portion), 26a and 26b are holes, and the holes 26a and 26b are formed in a part of the printed wiring board 24.

  As shown in FIGS. 3A and 3B, the lead wire 21 (or at least a part of the lead wire 21) is inserted into the hole 26b formed in the printed wiring board 24 (or mounted using the hole 26b). Thus, the heat generating component 15 can be mounted on the printed wiring board 24 and mounted close to (or at a high density) the electronic component 23 (for example, a control semiconductor for controlling the power semiconductor). A part of the lead frame 13 extending laterally from the heat conductive substrate can be used for connection between the heat conductive substrate and the printed wiring board 24. Note that the lead frame 13 connecting the heat conductive substrate and the printed wiring board 24 is bent at a substantially vertical end, and this bent portion is inserted into a hole 26b formed in the printed wiring board 24. , Workability and connection stability can be improved.

  The heat conductive substrate is set on the chassis 25 as indicated by an arrow 19a so as to be inserted into the hole 26a formed in the printed wiring board 24. In FIGS. 3A and 3B, the heat conductive substrate is inserted (or set) from the upper side with respect to the printed wiring board 24, but the reverse is also possible. For example, the printed wiring board 24 may be inserted (or set) on the heat conductive substrate. In this case, the lead frame 13 shown in FIGS. 3A and 3B and the insertion portion of the hole 26b of the printed wiring board 24 (or the portion bent so that the tip of the lead frame 13 is inserted into the hole 26b) It may be turned upside down (inserted from bottom to top, or inserted a heat conductive substrate on the printed wiring board 24).

  3A and 3B, it is preferable that the tip of the lead frame 13 inserted into the hole 26b formed in the printed wiring board 24 is bent and inserted into the printed wiring board 24. By inserting (or piercing) into the hole 26b formed in the printed wiring board 24 and soldering, the reliability of the soldered portion between the lead frame 13 and the printed wiring board 24 can be improved. As a result, it is possible to reduce the connection resistance of the solder connection portion, and to cope with an increase in current of the heat conduction substrate. Further, reliability can be further improved by plating through holes 26b as needed.

  This is because it is advantageous for cost reduction and miniaturization to mount the electronic parts 23 and the like that do not generate heat at high density on the printed wiring board 24 side. However, when the heat generating component 15 is mounted close to the electronic component 23, the heat generated in the heat generating component 15 affects the electronic component 23 and the like. However, in the present embodiment, as shown in FIG. 3B, the heat generated in the heat generating component 15 mounted on the printed wiring board 24 using the lead wires 21 as shown in FIG. In addition, heat can be radiated to the heat conductive substrate side, the influence of heat can be suppressed, and the circuit module can be miniaturized.

  FIG. 3B is a cross-sectional view illustrating a heat dissipation mechanism in the circuit module. In FIG. 3B, an arrow 19b indicates how the heat dissipating fan 18 rotates. An arrow 19c indicates a direction in which heat generated in the heat generating component 15, the transformer 14 or the like spreads. In FIG. 3B, the heat generated in the heat generating component 15 is transmitted to the lead frame 13. A part of the heat transferred to the lead frame 13 is transferred to the fins 17 through the insulating conductive adhesive 16 and is air-cooled. A part of the heat of the lead frame 13 is transmitted to the metal plate 11 through the heat transfer layer 12 in which a part or more of the lead frame 13 is embedded. Here, by fixing the metal plate 11 to the chassis 25 with screws or the like (the fixing method is not shown), the heat transmitted to the metal plate 11 spreads to the chassis 25 as indicated by an arrow 19c. .

  Further, by rotating the fan 18 as indicated by an arrow 19b (for example, by sucking wind), air for cooling is supplied from the gap between the chassis 25 and the printed wiring board 24 as indicated by an arrow 19c. You can inhale efficiently. In this case, an efficient air cooling effect due to the chimney effect can be obtained by combining the part of the lead frame 13 bent substantially vertically, the fins 17 and the like to positively configure the chimney structure. Here, the chimney effect is, for example, the effect of inhaling cold air from the bottom of the chimney, when the air is warmed in a chimney-like space, and the air that has become warmer and has a lower density rises above the chimney. That's it. And the heat | fever which generate | occur | produced in the heat-emitting component 15 or the transformer 14 can warm the fin 17 and can generate | occur | produce a chimney effect. By adopting the structure shown in FIGS. 3A and 3B in this way, in addition to direct heat conduction to the chassis 25 and the like, a positive air cooling effect due to the fan 18 and the chimney effect can be utilized.

  Furthermore, as shown in FIG. 3B, the reliability and connection strength with the heat generating component 15 can be improved by soldering directly to the lead frame 13 using the metal portion 20 of the heat generating component 15 as a live part. Further (or at the same time), by connecting the lead wire 21 of the heat generating component 15 to the printed wiring board 24, the circuit pattern routing distance (or line length) can be shortened.

  Note that by separating the printed wiring board 24 and the chassis 25 by a certain distance (for example, 3 to 20 mm, preferably 5 to 10 mm), the heat transferred to the chassis 25 can be sucked out by a positive chimney effect. The cooling effect of the chassis 25 can be obtained as well as the portion.

  3A and 3B, the electrical connection between the heat conductive substrate and the printed wiring board 24 uses the lead wire 21 extending from the heat-generating component 15 and the lead frame 13 in accordance with each application. Needless to say, circuit design and thermal countermeasures can be easily achieved.

  Next, with reference to FIGS. 4A and 4B, the assembly method of the circuit module and the heat dissipation effect thereof will be described. 4A and 4B are a cross-sectional view for explaining how to assemble a circuit module and a cross-sectional view for explaining the heat dissipation effect.

  FIG. 4A is a cross-sectional view showing how the circuit module is assembled, and FIG. 4B is a cross-sectional view illustrating the heat dissipation effect when the circuit module is used. 4A and 4B, the electrical connection between the heat conductive substrate and the printed wiring board 24 is also made by a lead wire 21 (not shown) extending from the heat generating component 15 as necessary. Can do.

  4 (A) and 4 (B), even the heat-generating component 15 conventionally mounted on the printed wiring board 24 can be attached here as a kind of heat-radiating part. . In that case, the bent portion of the lead frame 13 to which the heat generating component 15 is attached can be designed to be insulated from other wirings of the lead frame 13 (designed as a kind of floating island state). Further, by connecting the metal part 20 of the heat generating component 15 directly to the lead frame 13 and connecting the lead wire 21 of the heat generating component 15 to the printed wiring board 24, the circuit pattern routing distance can be shortened and the device can be downsized. enable.

  Next, the state of assembling the heat conductive substrate will be described with reference to FIG. 5 (A) and 5 (B) are cross-sectional views illustrating how the heat conductive substrates are assembled together. FIG. 5A is a cross-sectional view illustrating a state in which the heat-generating component 15 and the fins 17 are attached to the heat conductive substrate, and FIG. 5B is a cross-sectional view illustrating a state in which a part of the heat conductive substrate is bent. In FIG. 5A, the heat conductive substrate is configured by fixing a lead frame 13 on a metal plate 11 via a sheet-like heat transfer layer 12. A part of the lead frame 13 is embedded in the heat transfer layer 12 (this is because even if a thick lead frame 13 is selected, the unevenness does not easily appear on the substrate surface). Protrudes from the heat conductive substrate. Then, the heat generating component 15 is mounted on the protruding portion as necessary as indicated by an arrow 19a, and the fin 17 is fixed with an insulating conductive adhesive 16 or the like. A heat generating component 15 such as a transformer 14 is mounted on the center of the heat conducting substrate. Then, the fins 17 are also fixed on the transformer 14 or the like with an insulating conductive adhesive 16 or the like as necessary. 5A and 5B, mounting solder and the like are not shown. In the heat generating component 15, the metal part 20 and the lead wire 21 are not shown.

  Thereafter, as shown in FIG. 5B, the predetermined portion is bent substantially vertically as shown by an arrow 19b to obtain the shape shown in FIG. In FIG. 5B, it is not necessary to fix the heat generating components 15 and the fins 17 to all of the lead frames 13 protruding left and right from the heat conductive substrate. Further, as shown in FIGS. 3A, 3B, 4A, and 4B, a part of the lead frame 13 protruding left and right is used to electrically connect the heat conductive substrate and the printed wiring board 24 to each other. (And even the shortest distance).

  Next, an example of the manufacturing method of a heat conductive board | substrate is demonstrated using FIG. 6A and 6B are cross-sectional views illustrating a method for manufacturing a heat conductive substrate. 6 (A) and 6 (B), 27 is a press and 28 is a film for preventing dirt. Reference numeral 29 denotes a V-groove, which is a portion processed into a part of the lead frame 13 so as to be easily bent by a press or the like. First, as shown in FIG. 6A, a metal plate 11, a heat transfer layer 12, and a film 28 for preventing dirt are set on a press 27. 6 (A) and 6 (B), a die set on the press 27 is not shown. The lead frame 13 is obtained by punching a predetermined copper plate into a wiring pattern from a metal material such as a copper foil. Further, it is desirable to form the V-groove 29 in advance at a predetermined position of the lead frame 13 (for example, the bending position described with reference to FIG. 5B). Here, the heat transfer layer 12 is obtained by preforming a heat transfer material, which will be described later, into a sheet shape, for example. In FIG. 6A, the central portion of the heat transfer layer 12 may be slightly convex so that air can be easily removed during pressing.

  FIG. 6B is a cross-sectional view illustrating a state after the press is completed. As shown in FIG. 6B, by using the film 28, the heat transfer layer 12 does not adhere to the surface of the press 27 or a mold (not shown) as dirt. Further, by using the film 28 as a cushioning material (or packing or sealing material) between the press 27 and the mold and the lead frame 13, the heat transfer layer 12 is prevented from wrapping around the surface of the lead frame 13. Or press pressure can be increased. As a result, the heat transfer layer 12 can be made to wrap around a narrow gap formed between the lead frames 13.

  6A and 6B, the heat transfer layer 12 and the like are heated at the time of pressing, so that the heat transfer layer 12 can be softened and the adhesion effect with the metal plate 11 is enhanced.

  Then, as shown in FIG. 6B, after forming into a predetermined shape, the film 28 is peeled off from the surface of the heat transfer layer 12. The heat transfer layer 12 in which the lead frame 13 is embedded and integrated on the metal plate 11 is heated and cured in a heating device, and the heat transfer layer 12 shown in FIGS. And In addition, by heating the film 28 in a peeled state, the heat shrinkage (wrinkle generation) of the film 28 can be prevented from affecting the curing of the heat transfer layer 12.

  Here, as the sheet-like heat transfer layer 12, a heat transfer composite material made of a thermosetting resin and a filler can be used. For example, a member composed of 70 to 95% by weight of an inorganic filler and 5 to 30% by weight of a thermosetting resin is desirable. Here, the inorganic filler has a substantially spherical shape, and its diameter is suitably 0.1 μm or more and 100 μm or less (if it is less than 0.1 μm, it becomes difficult to disperse in the resin, and if it exceeds 100 μm, the heat transfer layer 12 Thickness increases and affects thermal diffusivity). Therefore, the filling amount of the inorganic filler in the heat transfer layer 12 is filled at a high concentration of 70 to 95% by weight in order to increase the thermal conductivity. In particular, in the present embodiment, the inorganic filler is a mixture of two types of alumina having an average particle diameter of 3 μm and an average particle diameter of 12 μm. By using alumina having two kinds of large and small particle diameters, it is possible to fill the gaps between the large particle diameters of alumina with small particle diameters, so that alumina can be filled at a high concentration to nearly 90% by weight. As a result, the heat conductivity of the heat transfer layer 12 is about 5 W / (m · K). The inorganic filler may include at least one selected from the group consisting of alumina, magnesium oxide, boron nitride, silicon oxide, silicon carbide, silicon nitride, and aluminum nitride.

  When an inorganic filler is used, the heat dissipation can be improved, but in particular when magnesium oxide is used, the linear thermal expansion coefficient can be increased. Further, when silicon oxide is used, the dielectric constant can be reduced, and when boron nitride is used, the linear thermal expansion coefficient can be reduced. Thus, the heat transfer layer 12 having a thermal conductivity of 1 W / (m · K) or more and 20 W / (m · K) or less can be formed. In addition, when heat conductivity is less than 1 W / (m * K), it influences the heat dissipation of a heat conductive board | substrate. Moreover, when it is going to make thermal conductivity higher than 20 W / (m * K), it is necessary to increase the amount of fillers and may affect the workability at the time of a press. The thermosetting resin contains at least one kind of resin among epoxy resin, phenol resin and cyanate resin. These resins are excellent in heat resistance and electrical insulation.

  Next, the material of the lead frame 13 will be described. Here, the material of the lead frame 13 is preferably a material mainly composed of copper (for example, a copper foil or a copper plate). This is because copper has both excellent thermal conductivity and electrical conductivity. As the copper plate for the lead frame 13, for example, a thickness of 200 μm to 2000 μm (desirably 500 μm to 1000 μm) can be used. When the thickness is less than 200 μm, a predetermined strength may not be obtained when it is bent. On the other hand, if the thickness exceeds 2000 μm, it is difficult to bend with high accuracy, which may increase the cost. As such a copper plate for the lead frame 13, for example, tough pitch copper (alloy symbol: C1100), oxygen-free copper (alloy symbol: C1020), or the like is desirably used. These materials are manufactured by melting the raw copper. Here, tough pitch copper is refined copper in which oxygen remains in copper, and is excellent in electrical conductivity and workability. For example, tough pitch copper is desirably 99.90 wt% or more of Cu, and oxygen free copper is desirably 99.96 wt% or more of Cu, for example. If the purity of copper is less than these numbers, it may be affected not only by workability but also by thermal conductivity and electrical conductivity due to the influence of impurities (for example, the content of Cu2O due to the influence of oxygen increases). . Such a member is inexpensive and excellent in mass productivity. Etching may be used as a patterning method for the lead frame 13, but punching with a press 27 (or a mold) is suitable from the viewpoint of pattern identity and mass productivity.

  Furthermore, various copper alloys can be selected as necessary. For example, in order to improve workability and thermal conductivity as the lead frame 13, at least one kind selected from the group of at least Sn, Zr, Ni, Si, Zn, P, Fe, etc. other than copper is used for the copper material. It is also possible to use an alloy made of the above materials. For example, it is possible to use a copper material (hereinafter referred to as Cu + Sn) in which Cu is mainly used and Sn is added thereto. In the case of a Cu + Sn copper material (or copper alloy), for example, by adding Sn to 0.1 wt% or more and less than 0.15 wt%, the softening temperature can be increased to 400 ° C. For comparison, the lead frame 13 was made using Sn-free copper (Cu> 99.96% by weight), but the conductivity was low, but the formed heat conduction substrate was particularly distorted in the formation area. was there. As a result, the softening point of the material was as low as about 200 ° C., and it was expected that the material could be deformed during subsequent component mounting (soldering). On the other hand, when a copper-based material with Cu + Sn> 99.96% by weight was used, it was not particularly affected by the heat generation of various mounted parts. There was no effect on solderability and die bondability. Therefore, when the softening point of this material was measured, it was found to be 400 ° C. Thus, it is desirable to add some elements mainly composed of copper. As an element added to copper, in the case of Zr, the range of 0.015 wt% or more and 0.15 wt% is desirable. When the addition amount is less than 0.015% by weight, the effect of increasing the softening temperature may be small. On the other hand, if the amount added is more than 0.15% by weight, the electrical characteristics may be affected. Also, the softening temperature can be increased by adding Ni, Si, Zn, P or the like. In this case, Ni is 0.1 wt% or more and less than 5 wt%, Si is 0.01 wt% or more and 2 wt% or less, Zn is 0.1 wt% or more and less than 5 wt%, and P is 0.005 wt% or more. Less than 0.1% by weight is desirable. And these elements can make the softening point of a copper raw material high by adding single or multiple in this range. In addition, when there are few addition amounts than the ratio described here, the softening point raise effect may be low. Moreover, when there are more than the ratio described here, there exists a possibility of affecting the electrical conductivity. Similarly, in the case of Fe, 0.1% by weight to 5% by weight is desirable, and in the case of Cr, 0.05% by weight to 1% by weight is desirable. These elements are the same as those described above.

  The tensile strength of the copper material used for the lead frame 13 is desirably 600 N / square mm or less. In the case of a material having a tensile strength exceeding 600 N / square mm, the workability of these lead frames 13 may be affected. On the other hand, by setting the tensile strength to 600 N / square mm or less (and, if these lead frames 13 require fine and complicated processing, desirably 400 N / square mm or less), the spring back (pressure even if bent to the required angle) The occurrence of rebound by reaction force is suppressed, and the formation accuracy can be improved. As described above, the material of these lead frames 13 is mainly composed of Cu, so that the electrical conductivity can be lowered, and further softening can improve the workability, and further the heat dissipation effect by these lead frames 13 can be enhanced. The tensile strength of the copper alloy used for the lead frame 13 is desirably 10 N / square mm or more. This is because the copper alloy used for the lead frame 13 needs to have a strength higher than the tensile strength (about 30 to 70 N / square mm) of general lead-free solder. When the tensile strength of the copper alloy used for these lead frames 13 is less than 10 N / square mm, when the heat-generating component 15 or the like is mounted on the lead frames 13 by soldering, these lead frame 13 portions are not solder portions. May cause cohesive failure.

  It is also useful to previously form a solder layer or tin layer on the mounting surface of the lead frame 13 such as the heat generating component 15 so as to improve solderability. It is desirable that no solder layer be formed on the surface of the lead frame 13 that contacts the heat transfer layer 12. If a solder layer or a tin layer is formed on the surface in contact with the heat transfer layer 12 in this way, this layer becomes soft during soldering, which affects the adhesion (or bond strength) between the lead frame 13 and the heat transfer layer 12. May give.

  The metal plate 11 is made of aluminum, copper, or an alloy containing them as a main component, which has good thermal conductivity. In particular, in the present embodiment, the thickness of the metal plate 11 is 1 mm (desirably 0.1 mm or more and 50 mm or less), but the thickness can be designed according to product specifications (note that the thickness of the metal plate 11 is 0.2 mm). If the thickness is less than 1 mm, heat dissipation and strength may be insufficient, and if the thickness of the metal plate 11 exceeds 50 mm, it is disadvantageous in terms of weight). The metal plate 11 is not only a plate-like one, but also fin portions (or uneven portions) for increasing the surface area on the surface opposite to the surface on which the heat transfer layer 12 is laminated in order to further improve heat dissipation. May be formed. The total expansion coefficient is 8 to 20 ppm / ° C., and warpage and distortion of the heat conductive substrate of the present invention and the entire power supply unit using the same can be reduced. In addition, when these components are surface-mounted, matching the thermal expansion coefficients with each other is also important in terms of reliability.

(Embodiment 2)
Hereinafter, the heat conductive substrate according to Embodiment 2 of the present invention will be described with reference to the drawings.

  FIG. 7 is a perspective view of the heat conductive substrate in the embodiment of the present invention. The difference between FIG. 7 and FIG. 1 is that a part of the lead frame 13 (for example, the tip thereof) is bent a plurality of times from the heat transfer layer at the outer peripheral portion of the heat conductive substrate, and the heat generating component 15 is mounted on the bent portion (or It is fixed to wrap it around.

  In FIG. 7, a part of the lead frame 13 (for example, the outer peripheral portion of the heat conductive substrate or its peripheral portion as shown in FIG. 1) is bent a plurality of times and bent into the lead frame 13 (or the plurality of bent portions). The heat generating component 15 (the lead wire formed on the heat generating component 15 and the soldered portion thereof are not shown in FIG. 1) is mounted. Then, if necessary, the heat dissipating fins 17 are fixed to the inner side (or the side of the lead frame 13 where the heat generating component 15 is not mounted) via the insulating conductive adhesive 16. In this way, the heat generated in the heat generating component 15 is air-cooled through the fins 17. If necessary, the number of fins 17 can be increased, and for example, as shown in FIG. 1, the surface (or upper surface) of the heat conductive substrate can be covered with a plurality of fins 17. The plurality of fins 17 are cooled by the generated wind (shown by the arrow 19b) by rotating the air cooling fan 18 as shown by the arrow 19a. In FIG. 1, it is not necessary to bend all the lead frames 13 on the outer peripheral portion (or the peripheral portion) of the heat conducting substrate. This is for electrically connecting the heat conductive substrate and the printed wiring board in FIGS. 2 and 3 described later.

  In the second embodiment, electronic components that require heat dissipation (for example, the heat-generating component 15 that generates heat and the transformer 14) can be concentrated on the heat conductive substrate. Even when the heat generating components 15 and the transformers 14 serving as heat sources are assembled (or mounted) with high density in this way, as shown in FIG. Can be covered with the fins 17 and can be intensively cooled by the fan 18 or the like, and the cooling efficiency can be increased. Although forced air cooling is used in FIG. 1, the same effect can be obtained by other methods (for example, using a heat pipe or a water-cooled circulation facility). And although the heat conductive board in this Embodiment is the thing excellent in the heat dissipation effect by itself, it can raise a utility value further by combining with a printed wiring board and setting it as a circuit module.

  Next, the heat dissipation effect will be described with reference to FIG. 8A and 8B are a cross-sectional view for explaining how to assemble the circuit module and a cross-sectional view for explaining the heat dissipation effect.

  As shown in FIGS. 8A and 8B, the lead wire 21 (or at least a part of the lead wire 21) is inserted into the hole 26b formed in the printed wiring board 24 (or mounted using the hole 26b). Thus, the heat generating component 15 can be mounted on the printed wiring board 24 and mounted close to (or at a high density) the electronic component 23 (for example, a control semiconductor for controlling the power semiconductor). A part of the lead frame 13 extending laterally from the heat conductive substrate can be used for connection between the heat conductive substrate and the printed wiring board 24. Note that the lead frame 13 connecting the heat conductive substrate and the printed wiring board 24 has its tip end bent a plurality of times, and the bent portion is inserted into the hole 26b formed in the printed wiring board 24. Workability and connection stability can be improved.

  The heat conductive substrate is set on the chassis 25 as indicated by an arrow 19a so as to be inserted into the hole 26a formed in the printed wiring board 24. In FIGS. 8A and 8B, the heat conductive substrate is inserted (or set) from the upper side with respect to the printed wiring board 24, but the reverse is also possible. For example, the printed wiring board 24 may be inserted (or set) on the heat conductive substrate. In this case, the lead frame 13 shown in FIGS. 8A and 8B and the insertion portion of the hole 26b of the printed wiring board 24 (or the portion bent so that the tip of the lead frame 13 is inserted into the hole 26b) It may be turned upside down (inserted from bottom to top, or inserted a heat conductive substrate on the printed wiring board 24).

  8A and 8B, it is preferable that the tip of the lead frame 13 inserted into the hole 26b formed in the printed wiring board 24 is bent and inserted into the printed wiring board 24. By inserting (or piercing) into the hole 26b formed in the printed wiring board 24 and soldering, the reliability of the soldered portion between the lead frame 13 and the printed wiring board 24 can be improved. As a result, it is possible to reduce the connection resistance of the solder connection portion, and to cope with an increase in current of the heat conduction substrate. Further, reliability can be further improved by plating through holes 26b as needed.

  This is because it is advantageous for cost reduction and miniaturization to mount the electronic parts 23 and the like that do not generate heat at high density on the printed wiring board 24 side. However, when the heat generating component 15 is mounted close to the electronic component 23, the heat generated in the heat generating component 15 affects the electronic component 23 and the like. However, in the present embodiment, as shown in FIG. 8B, the heat generated in the heat generating component 15 mounted on the printed wiring board 24 using the lead wires 21 as shown in FIG. In addition, heat can be radiated to the heat conductive substrate side, the influence of heat can be suppressed, and the circuit module can be miniaturized.

  FIG. 8B is a cross-sectional view illustrating a heat dissipation mechanism in the circuit module. In FIG. 8B, an arrow 19b indicates how the heat dissipating fan 18 rotates. An arrow 19c indicates a direction in which heat generated in the heat generating component 15, the transformer 14 or the like spreads. In FIG. 8B, the heat generated in the heat generating component 15 is transmitted to the lead frame 13. A part of the heat transferred to the lead frame 13 is transferred to the fins 17 through the insulating conductive adhesive 16 and is air-cooled. A part of the heat of the lead frame 13 is transmitted to the metal plate 11 through the heat transfer layer 12 in which a part or more of the lead frame 13 is embedded. Here, by fixing the metal plate 11 to the chassis 25 with screws or the like (the fixing method is not shown), the heat transmitted to the metal plate 11 spreads to the chassis 25 as indicated by an arrow 19c. .

  Further, by rotating the fan 18 as indicated by an arrow 19b (for example, by sucking wind), air for cooling is supplied from the gap between the chassis 25 and the printed wiring board 24 as indicated by an arrow 19c. You can inhale efficiently. In this case, an efficient air cooling effect due to the chimney effect can be obtained by combining the part of the lead frame 13 bent a plurality of times, the fins 17 and the like to positively form the chimney structure. Here, the chimney effect is, for example, the effect of inhaling cold air from the bottom of the chimney, when the air is warmed in a chimney-like space, and the air that has become warmer and has a lower density rises above the chimney. That is. And the heat | fever which generate | occur | produced in the heat-emitting component 15 or the transformer 14 can warm the fin 17 and can generate | occur | produce a chimney effect. By adopting the structure shown in FIGS. 8A and 8B in this way, in addition to direct heat conduction to the chassis 25 and the like, a positive air cooling effect due to the fan 18 and the chimney effect can be utilized.

  Note that by separating the printed wiring board 24 and the chassis 25 by a certain distance (for example, 3 to 20 mm, preferably 5 to 10 mm), the heat transferred to the chassis 25 can be sucked out by a positive chimney effect. The cooling effect of the chassis 25 can be obtained as well as the portion.

  In FIGS. 8A and 8B, the electrical connection between the heat conductive substrate and the printed wiring board 24 uses the lead wire 21 extending from the heat-generating component 15 and the lead frame 13 in accordance with the respective applications. Needless to say, circuit design and thermal countermeasures can be easily achieved.

  Further, as shown in FIG. 8B, the reliability and connection strength with the heat generating component 15 can be improved by soldering directly to the lead frame 13 using the metal portion 20 of the heat generating component 15 as a live part. Further (or at the same time), by connecting the lead wire 21 of the heat generating component 15 to the printed wiring board 24, the circuit pattern routing distance (or line length) can be shortened.

  By connecting the metal part 20 of the heat generating component 15 directly to the lead frame 13 and connecting the lead wire 21 of the heat generating component 15 to the printed wiring board 24, the circuit pattern routing distance can be shortened and the device can be downsized. enable.

  Next, an example of improving the heat dissipation effect of the circuit module will be described with reference to FIGS. FIGS. 9A to 9C are partial cross-sectional views showing examples of improving the heat dissipation effect of the circuit module, and correspond to, for example, the cross-sectional view of the side surface portion (for example, the right side surface) of FIG. 8A described above. . In FIGS. 9A to 9C, (the center portion is omitted) is shown to indicate a partial cross section of the circuit module. FIG. 9A shows a state in which the heat generating component 15, the insulating conductive adhesives 16a and 16b, and the fins 17b are sequentially set in the lead frame 13a formed by bending multiple times as indicated by an arrow 19a. FIG. 9B shows a state in which the heat generating component 15 is set in a lead frame 13a bent (or bent) and bent with an insulating conductive adhesive 16b. And the fin 17b is fixed on this using the insulating conductive adhesive 16b. FIG. 9C is a cross-sectional view for explaining the heat dissipation effect of the circuit module thus created. In FIG. 9C, an arrow 19b indicates how heat generated in the heat generating component 15 is dissipated through the fins 17a, 17b and the like. In addition, as the heat-emitting component 15 in FIGS. 9A to 9C, a resin-molded one can be used. As shown in FIGS. 9B and 9C, a part of the heat generating component 15 (for example, the fin 17c portion) may be surrounded by a lead frame 13a formed by bending multiple times. After further enclosing, screws (screws and the like are not shown in FIG. 4) and fixing with an insulating conductive adhesive 16, heat generated in the heat generating component 15 is multifaceted (or the upper surface of the heat generating component 15). To the lead frame 13a and the fin 17b.

  As described above, the heat conductive substrate includes the metal plate 11, the sheet-like heat transfer layer 12 fixed on the metal plate 11, and the lead frame 13 fixed to the heat transfer layer 12. It is possible to provide a heat conductive substrate in which a part of the lead frame 13 is bent substantially perpendicularly from the heat transfer layer 12 at the outer peripheral portion of the heat conductive substrate, and the heat generating component 15 is mounted on the bent portion. In addition, heat dissipation and miniaturization (or reduction in floor area) of the heat conductive substrate can be realized.

  A heat conductive substrate comprising a metal plate 11, a sheet-like heat transfer layer 12 fixed on the metal plate 11, and a lead frame 13 having a part or more embedded in the heat transfer layer 12, A portion of the lead frame 13 is bent substantially perpendicularly from the heat transfer layer 12 at the outer peripheral portion of the heat conductive substrate, and a fin 17 is attached to the bent portion, thereby forming a heat conductive substrate. Heat dissipation and downsizing (or floor area reduction) can be realized.

  Further, as shown in FIG. 7 and the like, a heat conductive substrate comprising a metal plate 11, a sheet-like heat transfer layer 12 fixed on the metal plate 11, and a lead frame 13 fixed to the heat transfer layer 12. As described above, a part of the lead frame 13 is bent a plurality of times from the heat transfer layer 12 at the outer peripheral portion of the heat conductive substrate, and the heat-radiating component 15 is mounted on the bent portion, thereby improving the heat dissipation. .

  Alternatively, a heat conductive substrate comprising a metal plate 11, a sheet-like heat transfer layer 12 fixed on the metal plate 11, and a lead frame 13 in which a part or more is embedded in the heat transfer layer 12, A part of the lead frame 13 is bent a plurality of times from the heat transfer layer 12 at the outer peripheral portion of the heat conductive substrate, and a heat conductive substrate in which fins 17 are attached to the bent portion, thereby improving the heat dissipation. Can be increased.

  The heat transfer layer 12 includes at least one resin selected from the group consisting of epoxy resins, phenol resins, and isocyanate resins, and alumina, magnesium oxide, boron nitride, silicon oxide, silicon carbide, silicon nitride, and aluminum nitride. By using a heat conductive substrate that includes at least one inorganic filler selected from the group consisting of the above, it is possible to achieve heat dissipation and downsizing (or floor area reduction) of the heat conductive substrate.

  In the lead frame 13, Sn is 0.1 wt% or more and 0.15 wt% or less, Zr is 0.015 wt% or more and 0.15 wt% or less, Ni is 0.1 wt% or more and 5 wt% or less, Si is 0.01% to 2% by weight, Zn is 0.1% to 5% by weight, P is 0.005% to 0.1% by weight, Fe is 0.1% to 5% by weight Realizing heat dissipation and miniaturization (or floor area reduction) of a heat conductive substrate by using a heat conductive substrate that is a metal material mainly composed of copper, including at least one selected from the following group: be able to.

  At least a step of integrating the metal plate 11 and the lead frame 13 via the heat transfer layer 12, a step of curing the heat transfer layer 12, and a heat generating component 15 or a transformer on the surface of the lead frame 13. A method of manufacturing a heat conductive substrate including a step of mounting electronic components such as 14, a step of attaching fins 17 to the surface of the lead frame 13, and a step of bending the lead frame 13 substantially vertically; A small (or small floor area) heat conductive substrate with excellent heat dissipation can be manufactured. Needless to say, the order of these steps (for example, the lead frame 13 is bent after the heat-generating component 15 is mounted) can be changed depending on the application.

  A circuit module comprising at least a printed wiring board 24, a heat conductive substrate, and a heat generating component 15, wherein the heat conductive substrate is a metal plate 11 and a sheet-like heat transfer fixed on the metal plate 11. A layer 12 and a lead frame 13 in which a part or more is embedded in the heat transfer layer 12, and a part of the lead frame 13 is bent substantially perpendicularly from the heat transfer layer 12 at the outer peripheral portion. A part of the heat generating component 15 is mounted, and the heat conductive substrate is inserted into holes 26 a and 26 b formed in the printed wiring board 24, and the heat conductive substrate and the printed wiring board 24 are provided. Is a circuit module that is electrically connected via the lead wire 21 of the heat generating component 15 or the lead frame 13, so that the circuit module can be reduced in size.Further, by reducing the size of the circuit module, the wiring length can be shortened, the wiring length in the DCDC converter or the like can be shortened, or the optimization design can be performed, and the circuit operation can be stabilized.

  And in the heat conductive board which consists of the sheet-like heat-transfer layer 12 on the metal plate 11, and the lead frame 13 fixed to the said heat-transfer layer 12, a part of said lead frame 13 is outer peripheral part of a heat-conductive board | substrate. The heat-generating component 15 (for example, the metal part 20 side on the lead frame 13 side and the lead wire 21 side on the printed wiring board 24 side) is mounted on the heat-generating part 15 here. The effect can be enhanced and the floor area can be reduced.

  As described above, the heat conductive substrate according to the present invention, the manufacturing method thereof, and the circuit module using the substrate can reduce the size of plasma televisions, liquid crystal televisions, various in-vehicle electrical components, or devices requiring industrial heat dissipation. And high performance.

The perspective view of the heat conductive board | substrate in embodiment of this invention (A) and (B) are a sectional view and a perspective view, respectively, for explaining the heat generating component 15. (A) (B) is sectional drawing explaining the assembly method of a circuit module, respectively, and sectional drawing explaining the heat dissipation effect (A) (B) is sectional drawing explaining the assembly method of a circuit module, respectively, and sectional drawing explaining the heat dissipation effect (A) (B) is sectional drawing explaining a mode that a heat conductive board is assembled together. (A) (B) is sectional drawing explaining the manufacturing method of a heat conductive board | substrate together The perspective view of the heat conductive board | substrate in embodiment of this invention (A) (B) is sectional drawing explaining the assembly method of a circuit module, respectively, and sectional drawing explaining the heat dissipation effect (A)-(C) are partial sectional views showing an improvement example of the heat dissipation effect of the circuit module. The perspective view explaining the conventional circuit module

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Metal plate 12 Heat transfer layer 13 Lead frame 14 Transformer etc. 15 Heat generating component 16 Insulating conductive adhesive 17 Fin 18 Fan 19 Arrow 20 Metal part 21 Lead wire 22 Resin part 23 Electronic component 24 Printed wiring board 25 Chassis 26 Hole 27 Press 28 Film 29 V-groove

Claims (6)

A heat conductive substrate comprising a metal plate, a sheet-like heat transfer layer fixed on the metal plate, and a lead frame fixed to the heat transfer layer,
A heat conductive substrate in which a part of the lead frame is bent substantially perpendicularly from the heat transfer layer at an outer peripheral portion of the heat conductive substrate, and a heat generating component is mounted on the bent portion. A heat conductive substrate comprising a metal plate, a sheet-like heat transfer layer fixed on the metal plate, and a lead frame embedded in part or more in the heat transfer layer,
A heat conductive substrate in which a part of the lead frame is bent substantially perpendicularly from the heat transfer layer at an outer peripheral portion of the heat conductive substrate, and fins are attached to the bent portion. The heat transfer layer includes at least one resin selected from the group consisting of an epoxy resin, a phenol resin, and an isocyanate resin;
At least one inorganic filler selected from the group consisting of alumina, magnesium oxide, boron nitride, silicon oxide, silicon carbide, silicon nitride, and aluminum nitride;
The heat conductive board according to claim 1 or 2 containing. In the lead frame, Sn is 0.1% by weight to 0.15% by weight, Zr is 0.015% by weight to 0.15% by weight, Ni is 0.1% by weight to 5% by weight, and Si is 0%. 0.01 wt% or more and 2 wt% or less, Zn is 0.1 wt% or more and 5 wt% or less, P is 0.005 wt% or more and 0.1 wt% or less, Fe is 0.1 wt% or more and 5 wt% or less The heat conductive substrate according to claim 1 or 2, wherein the heat conductive substrate is a metal material mainly composed of copper, including at least one selected from the group consisting of: At least a step of integrating the metal plate and the lead frame via the heat transfer layer;
Curing the heat transfer layer;
Mounting electronic components on the surface of the lead frame;
Attaching fins to the surface of the lead frame;
And a step of bending the lead frame substantially vertically. At least a circuit module comprising a printed wiring board, a heat conductive substrate, and a heat generating component,
The heat conductive substrate comprises a metal plate, a sheet-like heat transfer layer fixed on the metal plate, and a lead frame embedded in part or more in the heat transfer layer,
A part of the lead frame is bent substantially perpendicularly from the heat transfer layer at the outer periphery, and a part of the heat generating component is mounted on the bent part.
The thermally conductive substrate is inserted into a hole formed in the printed wiring board,
The circuit module in which the heat conductive substrate and the printed wiring board are electrically connected via a lead wire of the heat generating component or the lead frame.

Images