JP4862601B2 - Thermally conductive substrate, manufacturing method thereof, and circuit module - Google Patents

Description

  The present invention relates to a heat conductive substrate used for manufacturing a lighting circuit such as a power supply circuit using a power semiconductor of an electronic device, a backlight using a high-luminance light emitting diode, etc., its manufacturing method, and a circuit module. It is.

  In recent years, with the demand for higher performance and smaller size of electronic devices, it is used for the manufacture of lighting devices such as power circuits using power semiconductors and backlights using light emitting diodes (or semiconductor lasers) with high brightness. The heat conductive substrate is required to have a dense wiring pattern (for example, a fine pattern of a wiring pattern for mounting power semiconductors and light emitting diodes at high density).

  10A and 10B are perspective cross-sectional views showing an example of a conventional heat conductive substrate. FIG. 10A is a perspective sectional view of a conventional heat conductive substrate. 10A and 10B, the wiring 1 is embedded in the insulating layer 2. The insulating layer 2 is fixed on the metal plate 3 with at least a part of the wiring 1 embedded therein. Then, the electronic component 4 is mounted on the wiring 1 as indicated by an arrow 9a. In addition, wiring can be performed between the electronic component 4 and the wiring 1 using a wire 5 or the like.

  FIG. 10B is a perspective cross-sectional view illustrating a heat dissipation mechanism of a conventional heat conductive substrate. In FIG. 10B, the heat generated in the electronic component 4 spreads in the wiring 1 as indicated by an arrow 9b. At the same time, the heat generated in the electronic component 4 is transferred to the metal plate 3 through the insulating layer 2 as shown by the arrow 9c through the wiring 1, and is radiated.

  Next, the fine patterning of the conventional heat conductive substrate will be described with reference to FIGS. FIGS. 11A to 11C are cross-sectional views of a conventional heat conductive substrate with a fine pattern. 11A to 11C, the wirings 1a, 1b, and 1c are embedded in the metal plates 3a, 3b, and 3c in a state of being embedded in the insulating layers 2a, 2b, and 2c, respectively. Here, the differences between the wirings 1a to 1c are the wiring thicknesses 6a to 6c and the wiring widths 7a to 7c. 11A corresponds to before fine patterning, FIG. 11B corresponds to after fine patterning, and FIG. 11C corresponds to after further fine patterning. As shown in FIGS. 11A to 11C, when the wirings 1a to 1c are made into a fine pattern (for example, the gap between the wirings is narrowed, the wiring width is narrowed, the wiring pitch is reduced, etc.), the wiring thickness 6a ~ 6c must be thin. As the wirings 1a to 1c are made into fine patterns in this way, the wiring thicknesses 6a to 6c become thinner and thinner. As a result, when heat generated in the electronic component 4 is radiated through the wirings 1a to 1c, there is a possibility that the thermal conductivity is lowered.

  This is because the wiring thickness 6a is practically the minimum value (or processing limit) of the wiring thickness 6a and the wiring width 7a when the wirings 1a to 1c are produced by a general etching method or press method. For example, when the wiring thickness 6a is 500 μm in order to dissipate heat from the electronic component 4, the minimum value of the wiring width 7a is 500 μm and the minimum width of the wiring interval 8a is 500 μm. Therefore, in order to make the wiring into a fine pattern (for example, as shown in FIG. 11B), when the wiring width 7b is 200 μm and the wiring interval 8b is 200 μm, it is difficult to make the wiring thickness 6b larger than 200 μm. . Similarly, when the wiring width 7c is 100 μm and the wiring interval 8c is 100 μm, the wiring thickness 6c must be as thin as 100 μm. Thus, in order to refine the wiring pattern, the wiring thicknesses 6a to 6c must be reduced. As a result, the cross-sectional areas of the wirings 1a to 1c are reduced, and the heat dissipation effect of the electronic component 4 is reduced.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
Japanese Patent No. 3312723

  As described above, in the conventional heat conductive substrate, it is necessary to reduce the wiring thicknesses 6a to 6c as the wiring 1 becomes finer (for example, the wiring width 7 is narrowed and the wiring interval 8 is narrowed). . As a result, the finer the wiring 1, there is a possibility that the heat dissipation performance of the heat dissipation substrate using the wiring 1 is lowered.

  An object of the present invention is to provide a heat conductive substrate, a manufacturing method thereof, and a circuit module, in which even if the wiring is made into a fine pattern, its heat dissipation is not easily affected.

In order to achieve the object, the present invention provides a heat comprising a metal plate, a sheet-like heat transfer layer fixed on the metal plate, and a lead frame embedded at least in part in the heat transfer layer. A conductive substrate, wherein the lead frame is a heat conductive substrate in which a plurality of lead frames are laminated in the thickness direction and integrated by pressing or welding before being embedded in the heat transfer layer .

  With such a configuration, it is necessary even when the lead frame at least partially embedded in the heat transfer layer is made into a fine pattern (for example, the width of the lead frame is narrowed or the gap between the multiple lead frames is narrowed). Therefore, even if the wiring pattern of the heat conductive substrate is made finer, the heat dissipation is hardly affected, and various circuit modules can be miniaturized.

  As described above, according to the present invention, even when a lead frame having at least a portion embedded in a heat transfer layer is made into a fine pattern, the heat dissipation can be maintained, so that a power semiconductor that requires heat dissipation or a high luminance The light emitting diodes and the like can be mounted with high density, and various circuit modules and devices using these can be miniaturized.

  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 thermally conductive substrate in an embodiment of the present invention will be described with reference to the drawings.

  1A and 1B are a top view and a cross-sectional view, respectively, of a heat dissipation board in an embodiment of the present invention. 1A and 1B, 10 is a first lead frame, and 11 is a second lead frame. 12 is a heat transfer layer, 13 is a metal plate, 14 is an arrow, 15 is a lead frame thickness, 16 is a lead frame width, and 17 is a lead frame gap.

  FIG. 1A is a top view showing a part of the heat conductive substrate, which is illustrated by extracting a part of the heat conductive substrate, and includes a complicated pattern portion formed by the first lead frame 10, The extraction electrode portion (connection portion with an external device) and the like are not shown. In FIG. 1A, the surface of the heat conductive substrate is covered with a first lead frame 10 corresponding to a wiring portion such as an electronic component and a heat transfer layer 12 corresponding to an insulating portion of the wiring. In FIGS. 1A and 1B, a solder resist or the like is not shown in order to explain the characteristics of the heat conductive substrate. In FIG. 1A, the first lead frame 10 has an example of parallel patterns having different thicknesses, but it is not necessary to stick to this, and it corresponds to a general circuit pattern. Needless to say.

  FIG. 1B is a cross-sectional view taken along arrow 14 in FIG. In FIG. 1B, the first lead frame 10 and the second lead frame 11 are embedded on the metal plate 13 using the heat transfer layer 12 (the surface of the first lead frame 10 is exposed). Is fixed. Here, the first lead frame 10 and the second lead frame 11 are laminated and integrated in the thickness direction in order to enhance the heat dissipation of necessary portions.

  In FIG. 1B, the lead frame thickness 15 indicates the thickness of the first lead frame 10. In the embodiment, in order to realize a fine pattern of the heat dissipation board, the first lead frame 10 exposed on the surface layer is used as a fine pattern for mounting electronic components. Then, the first lead frame 10 is formed into a fine pattern, so that the heat conduction is reduced by the laminated second lead frame 11 for the reduced thermal conductivity.

  Here, the thickness of the first lead frame 10 and the second lead frame 11 is positively changed according to the specification application of the heat conductive substrate, or the number of stacked lead frames is changed, or the plurality of lead frames is changed. Change the pattern shape.

  For example, fine patterning is necessary (for example, in the pattern portion of the surface layer as shown in FIG. 1A), and it is easy to form a fine pattern on the first lead frame 10 by a general etching method or press method. A thin member (for example, a lead frame thickness 15 such as 0.05 mm to 0.10 mm) is used.

  In this way, in FIGS. 1A and 1B, the thin first lead frame 10 that is easy to make fine on the surface layer side on which electronic components (not shown) are mounted, and the fine metal plate 13 side is fine. The second lead frame 11 having a wall thickness that is difficult to achieve (that is, excellent in heat conduction) is used. Depending on the application, a thick lead frame (for example, the second lead frame 11) is mounted on the surface side on which an electronic component (not shown) is mounted, and the metal plate 13 is thin and easily refined. The first lead frame 10 may be combined with.

  Next, the heat dissipation mechanism of the heat conductive substrate will be described with reference to FIGS. 2A and 2B are perspective cross-sectional views illustrating a heat dissipation mechanism of the heat conductive substrate. FIG. 2A shows a state in which an electronic component is mounted on the surface of a heat conductive substrate. Reference numeral 18 denotes an electronic component that requires heat dissipation, such as a light emitting diode, a laser, or a power semiconductor. Reference numeral 19 denotes a terminal to be an external electrode for soldering the electronic component 18, but it is not necessary to be particular about the shape of the terminal. For example, a wire used when mounting a bare chip may be used.

  In FIG. 2A, the thin first lead frame 10 and the thick second lead frame 11 are embedded in the heat transfer layer 12 while being laminated in the thickness direction. Then, in a state in which a plurality of lead frames including at least the first lead frame 10 and the second lead frame 11 are laminated in the thickness direction, the heat transfer layer 12 in which at least a part thereof is embedded is formed on the metal plate 13. It is fixed on the top. Then, the electronic component 18 is mounted on the exposed surface of the first lead frame 10 as indicated by an arrow 14a. A part of the terminal 19 of the electronic component 18 is omitted and not shown.

  FIG. 2B shows a state in which the electronic component 18 mounted on the surface of the heat conducting substrate is radiated. In FIG. 2B, the electronic component 18 is mounted on the first lead frame 10. The heat generated in the electronic component 18 spreads as indicated by arrows 14b, 14c, and 14d. The arrow 14b indicates that heat generated in the electronic component 18 through the first lead frame 10 spreads in the plane direction (along the pattern of the first lead frame 10). An arrow 14c indicates that heat generated in the electronic component 18 spreads in the plane direction (along the pattern of the second lead frame 11) through the thick second lead frame 11. Here, the first lead frame 10 and the second lead frame 11 are stacked, adhered, and integrated with each other in the thickness direction, so that the heat generated in the electronic component 18 is not limited to the first lead frame 10, Heat is radiated through the second lead frame 11.

  Further, the heat transmitted to the second lead frame 11 spreads to the metal plate 13 through the heat transfer layer 12. As described above, in the present embodiment, the heat generated in the electronic component 18 spreads over a wide range (or a large area) through the second lead frame 11 as well as the first lead frame 10, and further, The second lead frame 11 escapes to the metal plate 13. Here, by using a metal with high heat dissipation (for example, copper or aluminum) for the first lead frame 10 or the second lead frame 11, an excellent heat spreader effect (an effect of expanding a heat generating portion, for example, heat generation) It means the area of each temperature range when observing an electronic component with a thermo viewer, etc. A high heat spreader effect means excellent heat dissipation.

  2A and 2B, the mounting method of the electronic component 18 is not limited to soldering using the terminals 19 or the like (solder is not shown), but wires and bumps (both not shown). ) Can be used. Further, there may be a plurality of terminals 19 of the electronic component 18. This is because the number of terminals in the case of a high-intensity LED is often two, but more than three in the case of a power transistor and more terminals in the case of a power semiconductor.

  Thus, in order to mount an electronic component having a plurality of terminals with high density, it is necessary to make a fine pattern of wiring. In the case of the present embodiment, the second lead frame 11 can also be used when the first lead frame 10 alone cannot provide the necessary heat dissipation. As a result, as shown in FIGS. 1A and 1B, a fine pattern wiring composed of only the thin first lead frame 10 can be routed.

  Here, the thickness of the first lead frame 10 is preferably 0.01 mm to 0.20 mm (desirably 0.02 to 0.15 mm, more desirably 0.05 to 0.10 mm). When the thickness is less than 0.01 mm, a fine pattern having a lead frame width 16 of about 0.01 mm and a lead frame gap 17 of about 0.01 mm can be obtained, but it is easily affected by dust and foreign matter. For example, when the thickness of the first lead frame 10 is 0.05 mm, the lead frame width 16 can be 0.05 mm, the lead frame gap 17 can be 0.05 mm, and the minimum pitch (the pitch is 16 mm). And the lead frame gap 17) can be set to 0.1 mm.

  The thickness of the second lead frame 11 is preferably 0.10 to 2.00 mm (desirably 0.2 to 1.00 mm, more desirably 0.3 to 0.5 mm). When the thickness is less than 0.10, the heat dissipation effect may be low. Moreover, when thickness exceeds 2.00 mm, a subject may generate | occur | produce in workability.

  Note that the first lead frame 10 and the second lead frame 11 may have the same thickness. A plurality of these lead frames may be stacked. The number of sheets to be stacked is desirably 10 or less. When it exceeds ten sheets, it may be difficult to laminate with high accuracy.

  Next, a method for laminating a plurality of lead frames will be described with reference to FIGS. 3A to 3C are cross-sectional views illustrating the stacking of a plurality of lead frames. 3A is a cross-sectional view of the first lead frame 10, FIG. 3B is a cross-sectional view of the second lead frame 11, and FIG. 3C is a first lead as an example of a plurality of lead frames. This corresponds to a cross-sectional view for explaining how the frame 10 and the second lead frame 11 are integrated in the thickness direction. In FIG. 3A, the first lead frame 10 is a predetermined member (not shown) formed through a press punching process (not shown) using an etching method or a mold. is there. Next, as shown in FIG. 3B, the second lead frame 11 is processed in the same manner as the first lead frame 10. Next, as shown in FIG. 3C, the first lead frame 10 and the second lead frame 11 are aligned with each other, stacked in the thickness direction, and integrated (or fixed). Here, an arrow 14 indicates integration by a press device (not shown) or a welding device (an ultrasonic welding device, a spot welding device, a projection welding device, laser welding, or the like). Thus, the first lead frame 10 and the second lead frame 11 are laminated in the thickness direction and integrated.

  Next, the manufacturing method of a heat conductive board | substrate is demonstrated using FIGS. 4-6 is sectional drawing explaining an example of the manufacturing method of a heat conductive board | substrate. In FIG. 4, 20 is a pressing device, 21 is a film, and 22 is a heat transfer material. In FIG. 4, the first lead frame 10 and the second lead frame 11 are integrated as shown in FIG. 3, and this is set on the metal plate 13 via the heat transfer material 22. . And these are set to the press apparatus 20 as shown in FIG. In FIG. 4, the mold and the like are not shown. Then, the first lead frame 10, the second lead frame 11, the heat transfer material 22, and the metal plate 13 are pressed and integrated in the direction of the arrow 14 using the press device 20.

  FIG. 5 shows how the first lead frame 10 and the second lead frame 11 are pressed and embedded in the heat transfer material 22 and integrated. In FIG. 5, since the heat transfer material 22 can be softened by heating the heat transfer material 22 or the like during pressing, the adhesion with the surfaces of the first lead frame 10, the second lead frame 11, and the metal plate 13 is improved. It can be raised or evenly wrapped around the gap. Further, as shown in FIG. 5, the film 21 is sandwiched between the first lead frame 10 and a mold (not shown), so that the heat transfer material 22 can be used in the press device 20 or the mold (see FIG. 5). Can be prevented from adhering to the surface (not shown) as dirt.

  FIG. 6 shows a state where the press is finished. As shown by the arrow 14 in FIG. 6, the press devices 20 are pulled apart from each other. Further, the film 21 is peeled off from the surface of the first lead frame 10. Thus, the first lead frame 10 and the second lead frame 11 are fixed to the surface of the metal plate 13 by the heat transfer material 22. Here, not only the second lead frame 11 but also the first lead frame 10 can be embedded in the heat transfer material 22 by adjusting the pressing conditions. Then, the heat transfer material 22 is thermally cured to form the heat transfer layer 12. Thus, the heat dissipation substrate shown in FIGS. 1A and 1B is formed. Note that the heat curing step of the heat transfer material 22 may be performed in the press device 20, but may be cured in a heat curing furnace after these members are formed into a predetermined shape. Note that an inexpensive (low heat resistance) material can be used for the film 21 by curing the heat transfer material 22 after the film 21 is peeled off. By doing so, it is possible to prevent the film 21 from undergoing dimensional changes in the heat curing furnace and affecting the surface shape of the heat conductive substrate.

  This will be described in more detail. The heat transfer layer 12 and the surface of the first lead frame 10 are the same surface (preferably a step of 50 μm or less, more preferably 20 μm or less, and even less than 10 μm of each other), so that a solder resist (not shown) ) Is easy to form. In addition, it is possible to prevent the solder from spreading too much on the first lead frame 10 by forming a solder resist on the surface of the first lead frame 10 that is not soldered. Further, since the thickness difference between the heat transfer layer 12 and the first lead frame 10 is small, the thickness variation of the solder resist hardly occurs and the thickness of the solder resist can be set thin. As a result, the film thickness of the solder resist is less likely to affect heat dissipation, and the mountability of electronic components can be improved. Further, after the film 21 is peeled off, it is desirable that the surface of the first lead frame 10 and the heat transfer layer 12 be buffed or the like to further remove burrs and dirt.

  Here, as the sheet-like heat transfer layer 12, a heat transfer composite material made of a resin and a filler can be used. For example, an inorganic filler of 70% by weight to 95% by weight and a thermosetting resin of 5% by weight to 30% by weight are 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 12 is larger Will increase the 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. If the thickness of the heat transfer layer 12 is reduced, heat from the first lead frame 10 and the second lead frame 11 can be easily transferred to the metal plate 13, but conversely, the withstand voltage becomes a problem. Further, if the thickness of the heat transfer layer 12 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.

Next, materials of the first lead frame 10 and the second lead frame 11 (hereinafter referred to as these lead frames) will be described. As a material of these lead frames, a material mainly composed of copper (for example, a copper plate) is desirable. This is because copper has both excellent thermal conductivity and electrical conductivity. For example, it is desirable to use tough pitch copper (alloy symbol: C1100), oxygen-free copper (alloy symbol: C1020), or the like. Such a material is produced by melting the raw material copper. Here, tough pitch copper is refined copper in which oxygen remains in copper, and is excellent in electrical conductivity and workability. In the case of tough pitch copper, for example, Cu 99.90 wt% or more is desirable, and in the case of oxygen-free copper, for example, Cu 99.96 wt% or more is desirable. When the purity of copper is less than these numbers, it is affected not only by workability but also thermal conductivity and electrical conductivity due to the influence of impurities (for example, the content of Cu ₂ O due to the influence of oxygen increases) There is. Such a member is inexpensive and excellent in mass productivity.

Furthermore, various copper alloys can be selected as necessary. For example, the first lead frame 10 is selected from a group of at least Sn, Zr, Ni, Si, Zn, P, Fe, etc. other than copper as the copper material in order to improve workability and thermal conductivity. It is also possible to use an alloy made of at least one material. 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 the first lead frame 10 was made using Sn-free copper (Cu> 99.96 wt%), the conductivity was low, but the formed heat conduction substrate was particularly distorted in the formation portion or the like. It may occur. 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% or less 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 these lead frames 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 may be affected. On the other hand, by setting the tensile strength to 600 N / square mm or less (and, if these lead frames require fine and complicated processing, desirably 400 N / square mm or less), the spring back (pressure even if bent to the required angle) If it is removed, it will be repelled by the reaction force), and the formation accuracy can be improved. Thus, as the material of these lead frames, the conductivity is lowered by mainly using Cu, and the workability is improved by further softening, and the heat dissipation effect by these lead frames is also enhanced. The tensile strength of the copper alloy used for these lead frames is desirably 10 N / square mm or more. This is because the copper alloy used in these lead frames 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 is less than 10 N / square mm, when electronic components are soldered and mounted on these lead frames, there is a possibility of cohesive failure at these lead frame portions instead of the solder portions. There is. For the fine pattern processing, the first lead frame 10 can be made of a copper composition excellent in workability (for example, punchability by press) and an alloy composition different from that of the second lead frame 11. Here, different alloy compositions include at least one element selected from the group consisting of oxygen, sulfur, iron, lead, tin, bismuth, nickel, silver, antimony, arsenic, phosphorus, and silicic acid, which are impurity compositions other than copper. It is desirable to use those having a difference of 0.1 ppm or more, preferably 1 ppm or more. Here, when the composition of the first lead frame 10 and the second lead frame 11 is compared, if the element of these impurities is less than 0.1 ppm, it is affected by the variation of the composition or analysis becomes difficult. Because there is. In addition, when the difference between these impurities is less than 0.1 ppm, it is difficult for differences to occur in electrical characteristics and thermal conductivity.

  Note that a solder layer or a tin layer may be formed in advance on the surface of the first lead frame 10 exposed from the heat transfer layer 12 (the mounting surface of an electronic component or the like) so as to improve solderability. Useful. It is desirable that no solder layer be formed on the surface (or embedded surface) of the first lead frame 10 or the second lead frame 11 that is in contact with the heat transfer layer 12. When a solder layer or a tin layer is formed on the surface in contact with the heat transfer layer 12 in this way, the layer becomes soft during soldering, and the first lead frame 10, the second lead frame 11, and the heat transfer layer 12 It may affect the adhesion (or bond strength).

  The metal plate 13 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 13 is 1 mm (desirably, a thickness of 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 13 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 13 exceeds 50 mm, it is disadvantageous in terms of weight). The metal plate 13 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.

  Next, a circuit module using the heat dissipation board of the present invention will be described with reference to FIGS. Depending on the circuit module, an electronic component that requires heat dissipation (for example, a power semiconductor that is driven with a large current in a power circuit, etc., hereinafter referred to as a power electronic component) and a general electronic component on one heat conductive substrate (Signal semiconductors and the like that are driven with a weak current for signal processing and are hereinafter referred to as general electronic components) must be adjacently mounted at high density. This is because when power electronic components and general electronic components are mounted on separate substrates (for example, power electronic components are mounted on a heat dissipation substrate and general electronic components are mounted on a glass epoxy substrate), it is necessary to connect the substrates to each other via wiring. This wiring is susceptible to noise. As a result, the possibility that the circuit module malfunctions increases.

  7A and 7B are a top view and a cross-sectional view illustrating an example of a circuit module. In these circuit modules, power electronic components and general electronic components are mounted with high density in an adjacent state. 7A and 7B, reference numeral 23 denotes a dotted line, dotted line 23a denotes a general electronic component, and dotted line 23b denotes a power electronic component. In FIG. 7A, at least the first lead frames 10a and 10b and the heat transfer layer 12 are exposed on the surface of the heat conducting substrate (as shown in FIG. 7B, the first lead frame 10a). The second lead frame 11 is laminated and integrated under the bottom). On the other hand, the second lead frame 11 is not formed under the first lead frame 10b. Accordingly, the fine patterning of the second lead frame 11 is facilitated. Then, the first lead frame 10b is formed into a fine pattern, and general electronic components are mounted with high density. Thus, by not forming the second lead frame 11 under the locally refined first lead frame 10b, the first lead frames 10a and 10b and the second lead frame 11 Positioning and integration processes are facilitated.

  FIG. 7B is a cross-sectional view taken along arrow 14b in FIG. In FIG. 7B, an electronic component 18b such as a power semiconductor is mounted on the first lead frame 10a on which the second lead frame 11 is laminated. The heat generated in the electronic component 18b such as a power semiconductor radiates heat not only through the first lead frame 10a but also through the second lead frame 11 as indicated by an arrow 14c.

  Thus, when laminating a plurality of lead frames in the thickness direction, the lamination can be made local. Further, by making the pattern shape of the lead frame different (for example, by making the second lead frame 11 slightly smaller than the first lead frame 10), it is possible to prevent positional deviation at the time of stacking. By forming the portion where heat dissipation is not required with only the thin first lead frame 10, fine patterning is facilitated.

  Next, a circuit module for mounting power electronic components at high density by face-down mounting or the like will be described. 8A and 8B are a top view and a cross-sectional view showing a state where the electronic component is mounted face-down. In FIG. 8A, the first lead frame 10 is insulated via lead frame gaps 17a and 17b. Here, when power electronic components (for example, light-emitting diodes) are surface-mounted, the light-emitting efficiency can be improved by reducing the lead frame gaps 17a and 17b (or a plurality of light-emitting diodes are mounted close to each other). be able to). In such a case, the lead frame gaps 17a and 17b are preferably as small as possible. A cross-sectional view taken along arrow 14b in FIG. 8A is FIG. 8B. As shown in FIG. 8B, the lead frame gap 17 can be narrowed as the first lead frame 10 is thin. On the other hand, since the second lead frame 11 is thicker than the first lead frame 10, the heat dissipation effect can be enhanced. Arrows 14a and 14c in FIGS. 8A and 8B indicate how heat generated in the electronic component 18 (shown by a dotted line 23 in FIG. 8A) spreads. In FIG. 8B, the terminal 19 is a face-down bump or the like.

  Next, an application example to a circuit module using a light emitting diode or the like will be described. For example, in FIG. 8A, dotted lines 23a, 23b, and 23c are mounting positions of, for example, R (red), G (green), and B (blue) light emitting diodes. For example, when the backlight of a liquid crystal television is formed by RGB light emitting diodes (or semiconductor lasers), it is necessary to optically mix these monochromatic lights and synthesize white. In such a case, as shown in FIG. 8A, the heat radiation effect or the wiring resistance can be reduced as the lead frame gaps 17a and 17b are narrowed. Furthermore, by using a heat dissipation board with a narrow lead frame gap 17a, 17b, the RGB color light emitting diodes can be mounted at a higher density, so that the color mixing optical unit can be made smaller. Can be realized.

  Next, with reference to FIGS. 9A and 9B, a state in which the individual second lead frame 11 is bonded onto the first lead frame 10 will be described. FIGS. 9A and 9B are a top view and a cross-sectional view for explaining the manner in which the individual second lead frame is fixed on the first lead frame. In FIG. 9A, the second lead frame 11 is fixed to a necessary portion of the first lead frame 10 by welding or the like. A dotted line 23 indicates a position where the second lead frame 11 is set. The second lead frame 11 is fixed on the first lead frame 10 as indicated by an arrow 14b. FIG. 9B is a cross section taken along arrow 14a in FIG. Even if the second lead frame 11 is a plurality of pieces, the second lead frame 11 is a single piece as shown in FIG. 9A (for example, a pattern shape as shown as the first lead frame 10). May be. In this way, the second lead frame 11 is locally formed in a portion where heat dissipation is necessary. In FIGS. 9A and 9B, the actual first lead frame 10 is a fine pattern, but is not shown as a fine pattern because of drafting.

  As described above, the heat conductive substrate including the metal plate 13, the sheet-like heat transfer layer 12 fixed on the metal plate 13, and the lead frame at least partially embedded in the heat transfer layer 12. The lead frame is a heat conductive substrate in which a plurality of lead frames composed of the first lead frame 10, the second lead frame 11 and the like are laminated in the thickness direction, thereby providing a heat conductive substrate. The effect on heat dissipation due to the fine patterning can be suppressed, and various electronic devices can be miniaturized.

  The heat transfer substrate includes a metal plate 13, a sheet-like heat transfer layer 12 fixed on the metal plate 13, and a lead frame embedded at least in part in the heat transfer layer 12, A part of the lead frame is a heat conductive substrate in which a plurality of lead frames including the first lead frame 10, the second lead frame 11, and the like are laminated in the thickness direction. The influence on heat dissipation by patterning can be suppressed, and various electronic devices can be miniaturized.

  Furthermore, a heat transfer substrate comprising a metal plate 13, a sheet-like heat transfer layer 12 fixed on the metal plate 13, and a lead frame embedded at least in part in the heat transfer layer 12, A part or more of the lead frame is a heat conduction substrate in which a plurality of lead frames having different thicknesses, such as the first lead frame 10 and the second lead frame 11, are stacked in the thickness direction. The influence on heat dissipation due to the fine patterning of the substrate can be suppressed, and various electronic devices can be miniaturized.

  Alternatively, a heat transfer substrate comprising a metal plate 13, a sheet-like heat transfer layer 12 fixed on the metal plate 13, and a lead frame embedded at least in part in the heat transfer layer 12, At least a part of the lead frame is a heat conductive substrate in which a plurality of lead frames with different patterns including the first lead frame 10 and the second lead frame 11 are stacked in the thickness direction. The effect on heat dissipation due to the fine patterning can be suppressed, and various electronic devices can be miniaturized.

  Here, 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 nitride. By including at least one kind of inorganic filler selected from the group consisting of aluminum, the thermal conductivity of the heat transfer layer 12 can be increased, and various electronic devices can be miniaturized.

  Further, at least one of the plurality of lead frames is made of tough pitch copper or oxygen-free copper, so that the plurality of lead frames composed of the first lead frame 10, the second lead frame 11, etc. Depending on the application, material costs and processing costs can be reduced.

  Further, at least one of the plurality of lead frames includes Sn of 0.1 wt% or more and 0.15 wt% or less, Zr of 0.015 wt% or more and 0.15 wt% or less, and Ni of 0.1 wt% or less. % By weight to 5% by weight, Si from 0.01% to 2% by weight, Zn from 0.1% to 5% by weight, P from 0.005% to 0.1% by weight, Fe Is a metal material mainly composed of copper containing at least one selected from the group of 0.1% by weight or more and 5% by weight or less, so that the first lead frame 10, the second lead frame 11, etc. The material cost and processing cost of a plurality of lead frames made of can be reduced depending on the application.

  At least a plurality of lead frames including the first lead frame 10 and the second lead frame 11 are fixed in the thickness direction in an aligned state, and the heat transfer material 22 is used on the metal plate. By providing a method for manufacturing a heat conductive substrate including the step of embedding the plurality of lead frames and the step of curing the heat transfer material 22, the heat conductive substrate can be manufactured stably.

  Furthermore, at least the metal plate 13, the sheet-like heat transfer layer 12 fixed on the metal plate 13, and the first lead frame 10 and the second lead frame embedded at least partially in the heat transfer layer 12 By providing a circuit module including a plurality of lead frames made of 11 and the like, a heat conductive substrate composed of the lead frame, and an electronic component mounted on the lead frame, various devices can be miniaturized. .

  As described above, the heat conductive substrate, the manufacturing method and the circuit module according to the present invention make it possible to reduce the size and performance of a plasma TV, a liquid crystal TV, various in-vehicle electrical components, or a device that requires heat dissipation for industrial use. Can be realized.

(A) and (B) are both a top view and a cross-sectional view of the heat dissipation board in the embodiment of the present invention. (A) and (B) are perspective sectional views for explaining the heat dissipation mechanism of the heat conductive substrate. (A)-(C) are sectional drawings explaining the processing method of a lead frame Sectional drawing explaining an example of the manufacturing method of a heat conductive substrate Sectional drawing explaining an example of the manufacturing method of a heat conductive substrate Sectional drawing explaining an example of the manufacturing method of a heat conductive substrate (A) and (B) are a top view and a cross-sectional view showing an example of a circuit module. (A) and (B) are a top view and a cross-sectional view showing a state in which an electronic component is mounted face-down. (A) and (B) are a top view and a cross-sectional view for explaining a state in which an individual second lead frame is fixed on the first lead frame. (A) (B) is a perspective sectional view showing an example of a conventional heat conductive substrate, respectively. (A) to (C) are cross-sectional views of conventional heat-conducting substrates that are finely patterned

DESCRIPTION OF SYMBOLS 10 1st lead frame 11 2nd lead frame 12 Heat transfer layer 13 Metal plate 14 Arrow 15 Lead frame thickness 16 Lead frame width 17 Lead frame gap 18 Electronic component 19 Terminal 20 Press device 21 Film 22 Heat transfer material 23 Dotted line

Claims (8)

A metal plate,
A sheet-like heat transfer layer fixed on the metal plate;
A lead frame at least partially embedded in the heat transfer layer;
A heat conductive substrate comprising:
The lead frame is a heat conductive substrate in which a plurality of lead frames are laminated in the thickness direction and integrated by pressing or welding before being embedded in the heat transfer layer . A metal plate,
A sheet-like heat transfer layer fixed on the metal plate;
A lead frame at least partially embedded in the heat transfer layer;
A heat transfer board comprising:
At least a part of the lead frame is a heat conductive substrate in which a plurality of lead frames are laminated in the thickness direction and integrated by pressing or welding before being embedded in the heat transfer layer . A metal plate,
A sheet-like heat transfer layer fixed on the metal plate;
A lead frame at least partially embedded in the heat transfer layer;
A heat transfer board comprising:
At least a part of the lead frame is a heat conductive substrate in which a plurality of lead frames having different thicknesses are stacked in the thickness direction and integrated by pressing or welding before being embedded in 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 any one of claims 1 to 3 . Among the plurality of lead frames, at least one is thermally conductive substrate according to any one of claims 1 to 3 is a tough pitch copper or oxygen-free copper. At least one of the plurality of lead frames is Sn 0.1% by weight to 0.15% by weight, Zr 0.015% by weight to 0.15% by weight, Ni 0.1% by weight. 5 wt% or less, Si 0.01 wt% or more and 2 wt% or less, Zn 0.1 wt% or more and 5 wt% or less, P 0.005 wt% or more and 0.1 wt% or less, Fe 0% The heat conductive substrate according to any one of claims 1 to 3 , wherein the heat conductive substrate is a metal material mainly composed of copper, including at least one selected from the group of 1 wt% to 5 wt%. at least,
Fixing a plurality of lead frames in the aligned state in the thickness direction and integrating them by pressing or welding ; and
On the metal plate, the step of embedding the plurality of integrated lead frames in the heat transfer material,
Curing the heat transfer material;
The manufacturing method of the heat conductive board | substrate containing this. At least a heat conductive substrate composed of a metal plate, a sheet-like heat transfer layer fixed on the metal plate, and a plurality of lead frames embedded at least in part in the heat transfer layer,
A circuit module comprising electronic components mounted on the lead frame ,
The lead frame is a circuit module in which a plurality of lead frames are laminated in the thickness direction and integrated by pressing or welding before being embedded in the heat transfer layer .

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