JP2008192787A - Heat conduction board, circuit module using the same and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat conduction board increasing a heat dissipation effect of a thermal part unit in which an exothermic part connecting with a printed wiring board mounting an electronic part of a signal system is mounted, and also to provide a circuit module using the same and its manufacturing method. <P>SOLUTION: The heat conduction board comprises: a metal plate 15; a sheet-shaped heat conduction layer 14; and a lead frame 13 having a part or more embedded therein, and a module connects a printed wiring board 17 to a lead wire 12. A part of the lead frame 13 is peeled from the heat conduction layer 14 to form a lead fin 16, whereby a heat dissipation property of the heat conduction board is increased, and a stack effect in combination with the other printed wiring board 17 is also simultaneously used while a cooling effect of the circuit module is enhanced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  In recent years, with the demand for higher performance and miniaturization of electronic devices, further miniaturization is required for power supply circuits and drive circuits (for example, sustain circuits for plasma televisions) using a power semiconductor or 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. For this reason, a power system electronic component is conventionally mounted on a heat conductive substrate and is mounted on a heat component unit (for example, the heat component unit 1 in FIG. 10 described later), and a signal system electronic component is a general printed wiring board (for example, in FIG. Japanese Patent Application Laid-Open No. H10-228561 proposes mounting on a printed wiring board 8) and electrically connecting a plurality of substrates thus created to form one circuit module. Next, an example of a conventional circuit module will be described with reference to FIGS.

  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 is composed of a heat conductive substrate 1 and a printed wiring board 8 fixed thereon via a plurality of lead wires 5.

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

  Next, the heat dissipation mechanism in this circuit module will be described with reference to FIG.

  FIGS. 11A and 11B are cross-sectional views illustrating the heat dissipation mechanism of a conventional circuit module. FIG. 11A is a cross-sectional view illustrating a state in which the heat conductive substrate 1 and the printed wiring board 8 are integrated to form a circuit module. In FIG. 11A, an insulator 3 is formed on a metal plate 2 with a metal pattern 4 embedded therein. A part of the metal pattern 4 is bent approximately 90 degrees to form a lead wire 5. A hole 9 is formed in the printed wiring board 8, and a lead wire 5 is inserted into the hole 9 as shown by an arrow 10a and fixed to obtain a circuit module.

FIG. 11B is a cross-sectional view illustrating a problem when the circuit module is air-cooled. In FIG. 11B, an arrow 10b indicates a state in which heat generated in the heat generating component 6 is transferred to the atmosphere (or air) and is convected. As shown in FIG. 10 (B), the heat generated in the heat generating component 6 passes through the gap between the lead wires 5 while staying in the gap between the printed wiring board 8 and the heat conduction board 1 as indicated by the arrow 10b. And discharged outside the circuit module.
JP 2006-308620 A

  However, in the configuration shown in FIG. 11, as indicated by the arrow 10 b, the heat generated in the heat generating component 6 is separated into the air from the surface of the heat generating component 6, the surface of the metal pattern 4, the surface of the lead wire 5, and the like. Therefore, in a narrow space surrounded by the heat conductive substrate 1 and the printed wiring board 8, turbulent flow is likely to occur and it is difficult to obtain an air cooling effect. Further, even when the circuit module shown in FIG. 11 is set up vertically and the chimney effect is generated, the heat source is separated from the heat generating component 6 and the metal pattern 4, so that the air flow is controlled to the optimum value. It is difficult to do so, and the air cooling effect is reduced.

  Thus, the present invention forms a lead fin in the gap between the heat conductive substrate and the printed wiring board to facilitate the transfer of heat generated in the heat-generating component to the air and enhance the air cooling effect (for example, increase the air flow). The purpose is to enhance the air cooling effect of the circuit module by forming a turbulent convection field locally.

  In order to achieve the above object, the present invention provides a heat conduction comprising a metal plate, a sheet-like heat transfer layer fixed on the metal plate, and a lead frame partially embedded in the heat transfer layer. It is a board | substrate, Comprising: It is set as the heat conductive board | substrate which formed the lead fin in a part or more of the lead frame peeled off from the said heat-transfer layer.

  As described above, according to the present invention, the air-cooling effect in the heat conductive substrate and the circuit module using the heat conductive substrate is formed by forming the lead fin made of the lead frame which is a part of the heat conductive substrate on the surface of the heat conductive substrate. To achieve miniaturization of circuit modules and electronic equipment.

  Note that some of the manufacturing steps shown in the embodiments 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)
Hereinafter, a circuit module according to an embodiment of the present invention will be described with reference to the drawings.

  1A and 1B are cross-sectional views of a circuit module according to an embodiment of the present invention. In FIGS. 1A and 1B, reference numeral 11 denotes a heat generating component, for example, a semiconductor element or the like corresponding to a large current such as a power transistor or a power FET. 12 is a lead wire, 13 is a lead frame, 14 is a heat transfer layer, 15 is a metal plate, 16 is a lead fin, 17 is a printed wiring board, 18 is an arrow, and 19 is a fin.

  In FIG. 1A, a heat conductive substrate having lead wires 12 and lead fins 16 includes a lead wire 12 for connecting a part of a lead frame 13 embedded in a heat transfer layer 14 to another printed wiring board 17. The lead fins 16 are used.

  This will be described in more detail. In FIG. 1A, a sheet-like heat transfer layer 14 is formed on a metal plate 15, and a lead frame 13 is embedded in the heat transfer layer 14. Then, a part of the lead frame 13 is peeled off from the heat transfer layer 14 and folded at about 90 degrees to form the lead wires 12 and the lead fins 16. Here, the lead wire 12 is a wiring portion for connecting the heat conductive substrate and the printed wiring board 17. The lead fins 16 function as heat radiating fins for releasing heat generated in the heat generating component 11 to the atmosphere, and can be electrically insulated from the printed wiring board 17 as necessary. In addition, as for the lead fin 16, it is desirable to make some lead frames 13 which implemented the heat-emitting component 11 (for example, power FET etc.) bent about 90 degree | times. By doing so, the heat generated in the heat generating component 11 is directly transmitted to the lead fins 16, which has an effect of enhancing the heat dissipation effect. When the lead fin 16 is formed below the printed wiring board 17 (for example, FIG. 1A), it is desirable that at least the printed wiring board 17 and the lead fin 16 be separated by 1 mm or more. This is to insulate the lead fins 16 from the printed wiring board 17 (or various electronic components mounted on the printed wiring board 17).

  FIG. 1B is a cross-sectional view illustrating a case where a part of the lead fin 16 penetrates the printed wiring board 17. As shown in FIG. 1B, a heat dissipation effect can be obtained on the printed wiring board 17 by penetrating a part of the heat dissipation lead fin 16 through the printed wiring board 17. Further, a fin 19 (for example, a commercially available aluminum cooling fin or the like) can be retrofitted to a part of the lead fin 16 that penetrates. By doing so, the heat dissipation of the lead fins 16 can be further enhanced. In addition, also in the lead fin 16 described in FIG. 1A, FIG. 7, FIG. 8A, FIG. 9B, FIG. 9A, and FIG. The heat dissipating effect can be enhanced (in the drawings described later, the attachment of the fins 19 is not shown). In addition, when attaching the fin 19 to the lead fin 16, fitting (or fitting), screwing, soldering, adhesive fixing, etc. can be selected. Further, by providing an insulating structure on the necessary surface of the fin 19, it is possible to insulate between the lead fin 16 and the fin 19. Further, the insulation stability between the fins 19 and the printed wiring board 17 can be maintained.

  The heat thus generated in the heat generating component 11 is transmitted to the lead fin 16 through the lead frame 13 and the heat transfer layer 14 as indicated by an arrow 18a, and is released from the lead fin 16 to the atmosphere as indicated by an arrow 18b. The

  Note that in FIGS. 1A and 1B, the circuit module is in a laid-down state, but by standing it, the floor area can be reduced and the depth of a device such as a liquid crystal TV or a plasma TV can be reduced. Also, the circuit module shown in FIGS. 1A and 1B is placed vertically (not shown), so that the air layer sandwiched between the heat conductive substrate (or heat transfer layer 14) and the printed wiring board 17 is provided. Is heated by the heat generating component 11 and the lead fin 16, and an effect of positively generating an updraft (hereinafter referred to as a chimney effect) is easily generated. The chimney effect is to move the air whose specific gravity is reduced by being heated by the heat generating component 11 or the lead fin 16 above the space (chimney structure) surrounded by the heat transfer layer 14 and the printed wiring board 17 ( Alternatively, an ascending air current is generated), and cold air is supplied by the suction force generated there to the heat generating component 11, the lead fin 16, or the fin 19 attached to enhance the heat radiation effect of the lead fin 16, and the circuit module This enhances the heat dissipation effect. In this embodiment, as shown in FIG. 1, by forming the lead fins 16 in the chimney structure, the air in the chimney can be efficiently warmed, and the effect of enhancing the chimney effect is obtained. It is done. Further, as will be described later with reference to FIGS. 8 and 9, the efficiency of heat conduction from the heat conducting substrate to the atmosphere is increased by locally forming a turbulent convection field.

  Next, an example of a method for manufacturing a heat conductive substrate used for a circuit module will be described with reference to FIGS. 2A and 2B are cross-sectional views illustrating a method for manufacturing a heat conductive substrate. 2A and 2B, reference numeral 20 denotes a press, and reference numeral 21 denotes a film, which is for preventing dirt. The lead frame 13 is obtained by processing a copper plate or the like into a wiring shape by pressing or the like. 2A, the metal plate 15, the heat transfer layer 14, the lead frame 13, and the antifouling film 21 are set on the press 20. As shown in FIG. 2 (A) and 2 (B), the mold set on the press 20 is not shown.

  Then, as shown in FIG. 2A, the heat transfer layer 14 and the metal plate 15 are pressed and laminated in the direction of the arrow 18 using a press 20. Here, the heat transfer layer 14 is obtained by preforming a heat transfer material, which will be described later, into a sheet shape, for example. In FIG. 2A, the heat transfer layer 14 may have a slightly convex central portion so that air can be easily removed during pressing.

  FIG. 2B is a cross-sectional view illustrating a state after the press is completed. As shown in FIG. 2B, by using the film 21, the heat transfer layer 14 does not adhere to the surface of the press 20 or a mold (not shown) as dirt. Further, by using the film 21 as a cushioning material (or packing or sealing material) between the press 20 or the mold and the lead frame 13, the heat transfer layer 14 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 14 is made to wrap around to a plurality of lead frames 13. Thus, a part or more of the lead frame 13 is embedded in the heat transfer layer 14. By doing so, the mountability of the parts is improved, and the formability (or thinning and fine patterning) of the solder resist or the like is improved. 2A and 2B, the heat transfer layer 14 and the like are heated at the time of pressing, whereby the heat transfer layer 14 can be softened and the adhesion effect with the metal plate 15 is enhanced.

  Then, as shown in FIG. 2B, after forming into a predetermined shape, the film 21 is peeled off from the surface of the heat transfer layer 14. Then, the heat transfer layer 14 in which the lead frame 13 is embedded and integrated on the metal plate 15 is heated and cured in a heating device to obtain a heat conductive substrate. In addition, by thermally curing the heat transfer layer 14 in a state where the film 21 is peeled off, the heat shrinkage (wrinkle generation) of the film 21 can be prevented from affecting the curing of the heat transfer layer 14. In this way, a heat conductive substrate is produced.

  Here, as the sheet-like heat transfer layer 14, 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 thickness of the heat transfer layer 14 is increased Will increase the thermal diffusivity). Therefore, the filling amount of the inorganic filler in the heat transfer layer 14 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 14 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 14 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. If the thickness of the heat transfer layer 14 is reduced, the heat of the lead frame 13 can be easily transferred to the metal plate 15, but conversely, the withstand voltage becomes a problem. Further, if the thickness of the heat transfer layer 14 is too thick, the thermal resistance increases. Therefore, the optimum thickness may be set to 50 μm or more and 1000 μm or less in consideration of the withstand voltage and the thermal resistance.

  In addition, as the heat transfer layer 14, a heat conductive sheet material made by a casting method or the like made of an inorganic filler and a resin (thermosetting resin or thermosoftening resin) can also be used. In this way, a heat conductive substrate is produced.

  Next, a state in which the heat-generating component 11 is mounted on the heat conductive substrate will be described with reference to FIGS. FIGS. 3A to 3C are cross-sectional views illustrating how the heat-generating component 11 is mounted on the surface of the heat conductive substrate. As shown by an arrow 18a in FIG. 3A, the heat generating component 11 (for example, a power semiconductor) is mounted on the lead frame 13 by soldering or the like (note that the terminal electrode of the heat generating component 11 or soldering). The part is not shown). 3A to 3C, the solder resist formed on the lead frame 13 is not shown. FIG. 3B is a cross-sectional view after mounting. It is also possible to make a product in this state.

  And as shown in FIG. 4, the circuit module which consists of a heat conductive board | substrate and the printed wiring board 17 fixed on it with the clearance gap is produced. By forming a circuit module including a heat conductive substrate and a printed wiring board 17 fixed with a gap on the heat conductive substrate, the heat generating component 11 mounted on the heat conductive substrate and the control mounted on the printed wiring board 17 are provided. Since the electronic component (for example, the electronic component 22 in FIG. 4C described later) and the like can be electrically connected in the shortest time, the wiring length can be shortened. Further, since the wiring length is shortened, the wiring portion is less likely to be an antenna, the noise resistance characteristics of the circuit module can be improved, circuit malfunction can be prevented, and power consumption can be suppressed. In addition, after mounting the heat generating component 11 and the like, the lead frame 13 is bent to form the lead wire 12 and the lead fin 16 so that the lead wire 12 and the lead fin 16 do not get in the way when the component is mounted. It becomes possible.

  Next, a method for manufacturing a circuit module will be described. The circuit module is formed by selectively mounting an electronic component such as the heat radiating component 11 on the heat conducting substrate portion and integrating it with a printed wiring board 17 on which other general electronic components are mounted at a high density. is there. By combining the heat conductive substrate and the printed wiring board 17, not only the circuit size can be reduced but also the noise resistance can be improved. Such a circuit module can be produced as shown in FIG. 3C or FIGS. 4A to 4C.

  First, as indicated by an arrow 18b in FIG. 3C, a part of the lead frame 13 is peeled off from the heat transfer layer 14, bent substantially vertically, and as shown in FIG.

  Next, a state in which the heat conductive substrate and the printed wiring board are integrated will be described with reference to FIGS.

  4A to 4C are cross-sectional views for explaining a state in which the heat conductive substrate and the printed wiring board 17 are integrated together. 4A to 4C, 22 is an electronic component (for example, a control semiconductor or chip component that controls the heat-generating component 11 such as a power transistor), and 23 is a hole. FIG. 4A is a cross-sectional view for explaining how a lead wire 12 is formed by bending a part of a lead frame 13a constituting a heat conductive substrate.

  4A, the heat conductive substrate is composed of a metal plate 15 and a heat transfer layer 14 fixed on the metal plate 15 or a lead frame 13a in which a part or more is embedded in the heat transfer layer 14. A part of the lead frame 13a is bent substantially vertically to form a lead wire 12.

  FIG. 4B is a cross-sectional view for explaining how the lead fins 16 are formed by bending a part of the lead frame 13b. As shown in FIG. 4B, a plurality of lead fins 16 are formed by bending the lead frame 13b (partially hidden in the heat transfer layer 14) at a plurality of positions and raising it substantially vertically. The lead fins 16 are desirably formed not only at the peripheral portion of the heat conducting substrate, but also at the central portion thereof (for example, in the vicinity of the heat generating component 11).

  FIG. 4C is a cross-sectional view for explaining how the heat conductive substrate and the printed wiring board 17 are integrated. In FIG. 4C, the lead wire 12 is inserted into the hole 23 formed in the printed wiring board 17 as shown by the arrow 18c and fixed to obtain the circuit module shown in FIG. Here, the electronic component 22 corresponds to, for example, a control semiconductor, a chip resistor, a capacitor, or the like that drives the heat generating component 11 (for example, a power transistor). The printed wiring board 17 is a printed wiring board 17 (single-sided, double-sided, multilayer printed board, etc.) made of glass epoxy or paper phenol. By stacking the circuit module thus created vertically (for example, attached to the back surface of the plasma panel in the plasma TV), the chimney effect by natural convection can be enhanced. In FIG. 4C, some lead fins 16 may penetrate the printed wiring board 17 (not shown). Further, the fin 19 may be attached to a part of the lead fin 16 (not shown).

  It is also useful to previously form a solder layer or a tin layer on the mounting surface of the lead frame 13 such as the electronic component 22 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 14. If a solder layer or a tin layer is formed on the surface in contact with the heat transfer layer 14 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 14. May give.

  The metal plate 15 is made of aluminum, copper, or an alloy mainly composed of aluminum, copper having good heat conductivity. In particular, in the present embodiment, the thickness of the metal plate 15 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 15 is 0. 0). If the thickness is less than 1 mm, heat dissipation and strength may be insufficient, and if the thickness of the metal plate 15 exceeds 50 mm, it is disadvantageous in terms of weight). The metal plate 15 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 14 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.

  The lead wires 12 and the lead fins 16 are preferably formed by peeling off a part of the lead frame 13 from the heat transfer layer 14 and bending (or folding) it approximately 90 degrees as necessary. By doing so, the lead frame 13 that becomes the wiring in the heat conductive substrate and the lead wire 12 can be integrated, and the effect of improving the reliability can be obtained. Further, heat generated in the heat generating component 11 can be radiated from the lead frame 13 directly into the air via the lead fin 16. Further, the heat radiation effect can be enhanced by forming the heat radiation lead fins 16 not only in the peripheral portion of the heat conducting substrate but also in the central portion (particularly in the vicinity of the heat generating component 11). This is because the lead fins 16 are formed from the lead frame 13 made of copper or the like having excellent thermal conductivity. Further, a part of the pattern of the lead frame 13 to which the heat generating component 11 is soldered is peeled off from the heat transfer layer 14 and folded approximately 90 degrees to form the lead fins 16, thereby further radiating effect (or air cooling effect). Can be enhanced. Note that the height of the lead fins 16 at this time is preferably lower than that of the lead wires 12 as shown in FIG. By making it lower than the lead wire 12, the insulation distance can be ensured by setting the distance between the lead fin 16 and the printed wiring board 17 to 1 mm or more (preferably 2 mm or more, further 3 mm or more). In addition, by ensuring the insulation distance, the height of the lead fins 16 may be lowered, but FIG. 8 (described later, while arranging the lead fins 16 in parallel to prevent the air flow from being disturbed) (Acquisition of air cooling effect) and FIG. 9 (the lead fins 16 are comb-blade or staggered comb blades to actively generate turbulence or increase the contact area with air). Thus, an excellent air cooling effect can be obtained.

  As shown in FIG. 3C and FIG. 4A, the lead wire 12 and the lead fin 16 are used as the lead frame 13 peeled off from the heat transfer layer 14, and the peeled portion is used as a metal plate. 15 and the creepage distance between the lead wire 12 or the lead fin 16 and electrical insulation can be enhanced.

  In addition, the lead frame 13 used as the wiring of the lead fin 16, the lead wire 12, or the heat-generating component 11 can be obtained by punching a metal plate mainly made of copper or copper alloy into a predetermined shape. The material of the metal plate constituting the lead frame 13 will be described. Here, the metal 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 100, 200, 300, 500 μm, 1000 μm (1 mm) or the like can be used. Here, when the thickness of the lead frame 13 (or the lead frame 13 constituting the lead fin 16) is less than 100 μm, the strength as the lead fin 16 is insufficient (for example, it becomes easy to bend by external force after being folded). There is. If it exceeds 1 mm, the solderability of the heat-generating component 11 in the lead frame 13 may be reduced. This is because heat at the time of soldering easily escapes due to heat conduction of the lead frame 13. The thickness at the lead fin 16 portion may exceed 1 mm. This is because the heat generated in the heat generating component 11 is easily transmitted to the fins 19 through the lead fins 16 as shown in FIG.

  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 20 (or a mold) is suitable from the viewpoint of pattern identity and mass productivity.

  Various copper alloys can be selected as the lead frame 13. For example, in order to improve the workability and thermal conductivity of 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 as the copper material. It is also possible to use an alloy made of any 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, when Sn-free copper (Cu> 99.96% by weight) is used and the lead frame 13 or a part of the lead frame 13 is a bent lead wire 12, the conductivity is low, but it is particularly formed on the finished heat conductive substrate. There was a case where distortion occurred in a part or the like. 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 electronic component 22 is soldered and mounted on these lead frames 13, it is not the solder portion but the portion of the lead frame 13. There is a possibility of 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 11 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 14. If a solder layer or a tin layer is formed on the surface in contact with the heat transfer layer 14 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 14. May give.

  The metal plate 15 is made of aluminum, copper, or an alloy mainly composed of aluminum, copper having good heat conductivity. In particular, in the present embodiment, the thickness of the metal plate 15 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 15 is 0. 0). If the thickness is less than 1 mm, heat dissipation and strength may be insufficient, and if the thickness of the metal plate 15 exceeds 50 mm, it is disadvantageous in terms of weight). The metal plate 15 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 14 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.

  When the lead frame 13 is bent to form the lead wire 12, the bending angle is preferably substantially vertical (preferably vertical ± 20 degrees or less, preferably ± 10 degrees or less, and further ± 5% or less). When the vertical angle exceeds ± 20 degrees, there is a possibility that the insertability of the printed wiring board 17 into the hole 23 may be affected. Alternatively, since it is necessary to enlarge the hole 23, the printed wiring board 17 is affected in downsizing. The bending angle of the lead fin 16 can be the same as that of the lead wire 12, but it can be designed aerodynamically.

  Next, how the lead frame 13 is bent to form the lead wires 12 and the lead fins 16 will be described with reference to FIGS. 5 to 7 are perspective views for explaining how the lead frame 13 is bent and the lead wires 12 form lead fins 16. 5 to 7 are described as corresponding to, for example, the perspective view of the arrow 18b in FIG. 4B, the formation position is not necessarily limited to the peripheral portion of the heat conductive substrate.

  FIG. 5 is a perspective view for explaining a state in which the lead frame 13 is embedded in the heat transfer layer 14. In FIG. 5, an arrow 18 corresponds to, for example, the arrow 18b in FIG. In FIG. 5, a sheet-like heat transfer layer 14 is formed on a metal plate 15, and a lead frame 13 is embedded in the heat transfer layer 14.

  Next, as shown in FIG. 6, a part of the lead frame 13 is folded as indicated by an arrow 18, and this is used as a lead fin 16.

  FIG. 7 is a perspective view showing a state in which a part of the lead frame 13 is bent into the lead wire 12. In FIG. 7, a step is formed at the tip of the lead frame 13, but when this is used as the lead wire 12, it is easy to insert into the hole 23 formed in the printed wiring board 17 (not shown). It is. Further, by supporting the printed wiring board 17 at this step portion, the contact between the lead fins 16 and the printed wiring board 17 is prevented. The lead frame 13 shown in FIGS. 6 to 7 may be bent in one step. By doing so, the formation cost of the lead wire 12 and the lead fin 16 is reduced. 5 to 7, the lead frame 13 forming the lead fins 16 is illustrated in a floating island shape (insulated from other lead frames 13). By doing so, the lead fins 16 can be floated in a circuit-insulated state. The lead fins 16 may be part of the lead frame 13 that forms the wiring pattern. By doing so, the heat of the heat generating component 11 mounted on the wiring pattern can be directly air-cooled, and the cooling effect can be enhanced.

  Next, an example of the shape of the lead fin 16 will be described with reference to FIG. 8A and 8B are perspective views for explaining the shape of the lead fin 16. FIG. 8A shows the lead fins 16a having the same height and substantially parallel to each other. By doing as FIG. 8 (A), since the flow of the air (illustrated by the arrow 18) flowing through the gap between the lead fins 16a is not hindered, the air cooling effect can be enhanced. In addition, the circuit module thus created (for example, equivalent to FIG. 1) is set up substantially vertically (for example, in a plasma television set so as to be parallel to the back side of the plasma panel), an effect of promoting the generation of the chimney effect is obtained. It is done. FIG. 8B shows the lead fins 16b being substantially parallel to each other while changing the height. For example, in FIG. 8B, the shape of FIG. 8B can be obtained by changing the bending position of the lead frame 13.

  Note that the lead fins 16 shown in FIGS. 8A and 8B can be formed as necessary on a portion of the heat conductive substrate that needs to be radiated (or a portion having a sufficient wiring pattern). By doing so, the circuit module can be optimized and designed electrically and heat transfer engineering.

  Next, an example of the shape of the lead fin 16 will be described with reference to FIG. FIGS. 9A and 9B are perspective views for explaining a state in which the lead fins 16 have a comb blade shape. 9A and 9B, the lead frame 13 integrated with the lead fin 16, the heat transfer layer 14 in which the lead frame 13 is embedded, and the like are not shown. FIG. 9A shows the comb-shaped lead fins 16 arranged in a row, and FIG. 9B shows the comb-shaped lead fins 16 arranged in a plurality of rows (further bent at a certain angle from each other). It corresponds to a perspective view. For example, the comb-shaped lead fins 16a shown in FIG. 9 (A) are staggered as shown by the arrow 18a to obtain FIG. 9 (B), thereby enhancing the air cooling effect. In FIG. 9B, an arrow 18b indicates the flow of air flowing through the gap between the comb-shaped lead fins 16b. As shown in FIGS. 9A and 9B, turbulent flow can be generated locally or the flow of air can be controlled. One lead frame 13 may be processed into a comb blade shape.

  A heat conductive substrate comprising the metal plate 15, the sheet-like heat transfer layer 14 fixed thereon, and the lead frame 13 having a part or more embedded in the heat transfer layer 14 as described above. In addition to the heat conduction, a cooling effect of the heat conduction substrate can be obtained by using the heat conduction substrate in which the lead fins 16 are formed by a part or more of the lead frame 13 peeled off from the heat transfer layer. The degree of freedom of the installation location of the substrate can be increased, and the heat conductive substrate itself can be used as a heat radiating portion (or lead fin 16) of another heating element (for example, a plasma panel or a transformer portion in a plasma TV). It becomes.

  The heat transfer layer 14 includes at least one resin selected from the group consisting of epoxy resins, phenol resins, and isocyanate resins, 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 kind of inorganic filler selected from the group consisting of: heat generated in the heat generating component 11 is transferred to another lead frame 13 or metal plate via the heat transfer layer 14. 15 can dissipate heat. In addition, when the metal plate 15 is fixed to another heating element, the heat generated in the other heating element can be easily transferred to the lead fin 16 via the heat transfer layer 14.

  In addition, the lead frame 13 peeled off from the heat transfer layer 14 is bent by approximately 90 degrees from the heat transfer layer 14 and arranged in a plurality in parallel to form lead fins 16 so that the lead fins 16 are integrated with the lead frame 13. The heat conduction efficiency of the lead fins 16 can be increased, and the air cooling characteristics of the circuit module are improved.

  In addition, the air fining effect of the lead fin 16 can be enhanced by attaching (or retrofitting) the fin 19 to a part of the lead frame 13 peeled off from the heat transfer layer 14.

  A circuit module including a heat conductive substrate and a printed wiring board 17 fixed on the heat conductive substrate with a gap therebetween. The heat conductive substrate includes a metal plate 15 and a sheet-like heat transfer layer 14 fixed thereon. The printed wiring board 17 is formed of a lead wire 12 in which a part of the lead frame 13 is bent substantially vertically. A printed circuit board 17 and a heat conductive substrate are obtained by forming a circuit module in which lead fins 16 are formed in the gap at a part or more of the lead frame 13 fixed substantially parallel to the substrate and peeled off from the heat transfer layer 14. The heat dissipation effect (or the air cooling effect) in the limited gap between the two can be increased, and various electronic devices can be miniaturized.

  The lead frame 13 peeled off from the heat transfer layer 14 is bent by approximately 90 degrees from the heat transfer layer 14 to form lead fins 16, so that the heat transferred to the lead frame 13 having excellent heat conductivity can be directly transferred to the atmosphere. Therefore, the circuit module can be reduced in size and heat dissipation.

  By arranging a plurality of lead frames 13 peeled off from the heat transfer layer 14 substantially in parallel to form a lead fin 16, the heat transferred to the lead frame 13 having excellent thermal conductivity can be directly transferred to the atmosphere. Therefore, the circuit module can be reduced in size and heat dissipation.

  Further, at least one or more lead fins 16 can obtain a heat dissipation effect (or an air cooling effect) through the printed wiring board 17 by penetrating the printed wiring board 17. Further, as shown in FIG. 1B, the fins 19 can be retrofitted as necessary. In the case of FIG. 1B, it is desirable that the fins 19 be attached to the lead fins 16 after the printed wiring board 17 is attached. This is because it is difficult to attach the printed wiring board 17 with the fins 19 attached.

  Since the lead fin 16 is a circuit module that is 1 mm or more lower than the lead wire 12, the insulation distance from the printed wiring board 17 forming the circuit module can be secured, and the heat transmitted to the lead frame 13 having excellent thermal conductivity. Can be released directly into the atmosphere instead of the printed wiring board 17, so that the circuit module can be reduced in size and heat can be increased.

  When the lead wire 12 and the lead fin 16 are made into a circuit module that is substantially parallel, when the heat transmitted to the lead frame 13 having excellent thermal conductivity is directly released into the atmosphere, the lead wire 12 and the lead fin 16 Since the air flow (or the chimney effect) 16 can be prevented from being disturbed, the circuit module can be reduced in size and heat can be increased.

  The heat transfer layer 14 is made of 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 making the circuit module described to include at least one or more types of inorganic fillers selected from the group consisting of, it is possible to increase the heat conduction and heat dissipation effect in the heat conductive substrate constituting the circuit module, and to reduce the size of the circuit module As a result, the chimney effect can be actively utilized.

  Since the lead frame 13 or the lead wire 12 is a circuit module made of copper foil, tough pitch copper, or oxygen-free copper, heat transmitted to the lead frame 13 having excellent thermal conductivity can be directly released into the atmosphere. The circuit module can be reduced in size and heat radiation can be increased.

  In the lead frame 13 or the lead wire 12, 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. In the following, 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, and Fe is 0.1% by weight. By making a circuit module that is a metal material mainly composed of copper, including at least one selected from the group of 5% by weight or less, heat transferred to the lead frame 13 having excellent thermal conductivity can be directly Since it can be released into the atmosphere, it is possible to reduce the size and heat dissipation of the circuit module.

  At least a step of integrating the metal plate 15, the lead frame 13 and the heat transfer layer 14, a step of curing the heat transfer layer 14, and mounting an electronic component such as the heat generating component 11 on the lead frame 13 Thereafter, a step of bending a part of the lead frame 13 substantially vertically to form a lead wire 12, a step of fixing to the printed wiring board 17 using the lead wire 12, and a remaining part of the lead frame 13 A circuit module manufacturing method including the step of folding the lead fins 16 to approximately 90 degrees, and the heat transmitted to the lead frame 13 having excellent thermal conductivity can be directly released into the atmosphere. Enables module manufacturing. Note that the order of these steps may be changed depending on the application.

  At least a step of integrating the metal plate 15, the lead frame 13, and the heat transfer layer 14, a step of curing the heat transfer layer 14, and an electronic component such as the heat generating component 11 on the lead frame 13. After mounting, a step of bending a part of the lead frame 13 substantially vertically to form a lead wire 12, a step of fixing to the printed wiring board 17 using the lead wire 12, and a remaining part of the lead frame 13 The circuit module manufacturing method includes the step of folding the wire to approximately 90 degrees to form the lead fins 16 and the step of attaching the fins 19 to a part of the lead fins 16 to enhance the heat dissipation effect of the circuit modules. An effect is obtained. Note that the order of these steps may be changed depending on the application.

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

(A) (B) is sectional drawing of the circuit module in embodiment of this invention both (A) (B) is sectional drawing explaining the manufacturing method of a heat conductive board | substrate together (A)-(C) is sectional drawing explaining a mode that a heat-emitting component is mounted on the surface of a heat conductive substrate together. (A)-(C) is sectional drawing explaining a mode that a heat conductive board and a printed wiring board are integrated together. A perspective view explaining a state in which the lead frame is embedded in the heat transfer layer A perspective view explaining how a lead frame is bent to form a lead wire A perspective view showing a state in which a part of the lead frame is bent into a lead wire (A) (B) is a perspective view explaining the shape of a lead fin together (A) (B) is a perspective view explaining a state in which both lead fins have a comb blade shape. The perspective view explaining the conventional circuit module (A) (B) is sectional drawing explaining the heat dissipation mechanism of the conventional circuit module together

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Heat generating component 12 Lead wire 13 Lead frame 14 Heat transfer layer 15 Metal plate 16 Lead fin 17 Printed wiring board 18 Arrow 19 Fin 20 Press 21 Film 22 Electronic component 23 Hole

Claims (16)

A heat conductive substrate comprising a metal plate, a sheet-like heat transfer layer fixed thereon, and a lead frame embedded in part or more in the heat transfer layer,
A heat conductive substrate in which lead fins are formed in a part or more of the lead frame peeled off from the heat transfer layer. 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 substrate according to claim 1, comprising: 2. The heat conducting substrate according to claim 1, wherein a plurality of lead frames peeled off from the heat transfer layer are bent at approximately 90 degrees from the heat transfer layer, and a plurality of lead frames are arranged substantially in parallel to form lead fins. The heat conductive substrate according to claim 1, wherein the lead fin is obtained by attaching the fin to a part of the lead frame peeled off from the heat transfer layer. A circuit module comprising a heat conductive substrate and a printed wiring board fixed thereon with a gap therebetween,
The heat conductive substrate is composed of a metal plate, a sheet-like heat transfer layer fixed thereon, and a lead frame in which a part or more is embedded in the heat transfer layer,
The printed wiring board is fixed substantially parallel to the heat conductive substrate by a lead wire formed by bending a part of the lead frame substantially vertically,
A circuit module in which lead fins are formed in the gap at a part or more of the lead frame peeled off from the heat transfer layer. 6. The circuit module according to claim 5, wherein the lead frame peeled off from the heat transfer layer is bent approximately 90 degrees from the heat transfer layer to form a lead fin. The circuit module according to claim 5, wherein a plurality of lead frames peeled off from the heat transfer layer are arranged substantially in parallel to form lead fins. 6. The circuit module according to claim 5, wherein the lead fin is obtained by attaching a fin to a part of the lead frame peeled off from the heat transfer layer. 6. The circuit module according to claim 5, wherein at least one lead fin penetrates the printed wiring board. The circuit module according to claim 5, wherein the lead fin is 1 mm or more lower than the lead wire. 6. The circuit module according to claim 5, wherein the lead wire and the lead fin are substantially parallel to each other. 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 circuit module according to claim 5, comprising: The circuit module according to claim 5, wherein the lead frame or the lead wire is copper foil, tough pitch copper, or oxygen-free copper. In the lead frame or lead wire, 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 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 circuit module according to claim 5, wherein the circuit module is a metal material mainly composed of copper, including at least one selected from the group of wt% or less. at least,
A step of integrating the metal plate, the lead frame, and the heat transfer layer;
Curing the heat transfer layer;
After mounting electronic components on the lead frame, a step of bending a part of the lead frame substantially vertically to form a lead wire;
Fixing to a printed wiring board using the lead wire;
Folding the remaining part of the lead frame to approximately 90 degrees to form a lead fin;
Of manufacturing a circuit module. at least,
A step of integrating the metal plate, the lead frame, and the heat transfer layer;
Curing the heat transfer layer;
After mounting electronic components on the lead frame, a step of bending a part of the lead frame substantially vertically to form a lead wire;
Fixing to a printed wiring board using the lead wire;
Folding the remaining part of the lead frame to approximately 90 degrees to form a lead fin;
Attaching the fin to a part or more of the lead fin;
Of manufacturing a circuit module.

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