JP2008098493A - Thermally conductive substrate, manufacturing method thereof, and circuit module - Google Patents

Abstract

Conventionally, in the case of a heat dissipation board in which wiring is embedded in an insulating layer, it is necessary to make the wiring thinner in order to make the wiring finer (to reduce the wiring width and wiring gap). As the wiring is made finer, the heat dissipation effect of the electronic components mounted on the wiring is more likely to be affected.
An anchor 11 is laminated on a thin lead frame 10 advantageous for fine pattern formation in a thickness direction via an adhesive layer 18 and the like, embedded in a heat transfer layer 12, and fixed on a metal plate 13. Thus, even when the lead frame is made into a fine pattern, a heat conductive substrate, a manufacturing method thereof, and a circuit module are provided which are unlikely to reduce the tensile strength and heat dissipation of the lead frame 10.
[Selection] Figure 1

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).

  12A and 12B are perspective cross-sectional views showing an example of a conventional heat conductive substrate. FIG. 12A is a perspective sectional view of a conventional heat conductive substrate. 12A and 12B, 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. 12B is a perspective cross-sectional view illustrating a heat dissipation mechanism of a conventional heat conductive substrate. In FIG. 12B, 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. 13A to 13C are cross-sectional views of a conventional heat conductive substrate with a fine pattern. 13A to 13C, 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. FIG. 13A corresponds to before fine patterning, FIG. 13B corresponds to after fine patterning, and FIG. 13C corresponds to after further fine patterning. As shown in FIGS. 13A to 13C, 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 narrowed, 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.

  Here, when the wiring 1 (or 1a to 1c) is produced by a general etching method or press method, the wiring thickness 6 (or 6a to 6c) is practically set to the wiring thickness 6 (or 6a to 6c) or the wiring width. This is because the minimum value (or processing limit) of 7 (or 7a to 7c) is obtained. 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. 13B), 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 thicker 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.

  Further, the finer the wirings 1a to 1c, the more rapidly the contact area between the insulating layer 2 and the wiring 1 (or the cross-sectional area of the wiring 1 embedded in the insulating layer 2) becomes smaller. There is a possibility that the tensile strength of the wiring 1 will be lowered.

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, as the wiring 1 becomes finer, the heat dissipation property and tensile strength of the heat dissipation substrate using the wiring 1 may be reduced.

  It is an object of the present invention to provide a heat conductive substrate, a manufacturing method thereof, and a circuit module that are hardly affected by heat dissipation and tensile strength even when the wiring is made into a fine pattern.

  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 anchors are stacked in a thickness direction.

  With such a configuration, even if the lead frame in which at least a part is 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), the lead By fixing the anchor in the thickness direction of the frame and embedding both the lead frame and the anchor in the heat transfer layer, the tensile strength of the finely patterned lead frame is increased. Furthermore, since the heat transmitted to the lead frame can be dissipated through the anchor, even if the wiring pattern of the heat conductive substrate is made fine, the heat dissipating property is not easily 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 lead frame, and 11 is an anchor. 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 by the lead frame 10 and an extraction electrode portion. (A connection part with an external device) etc. are not illustrated. In FIG. 1A, the surface of the heat conductive substrate is covered with a 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 lead frame 10 is exemplified by parallel patterns having different thicknesses. However, it is needless to say that the lead frame 10 corresponds to a general circuit pattern.

  FIG. 1B is a cross-sectional view taken along arrow 14 in FIG. In FIG. 1B, a lead frame 10 and an anchor 11 are embedded and fixed on a metal plate 13 using a heat transfer layer 12 (the surface of the lead frame 10 is exposed). The lead frame 10 and the anchor 11 are fixed by welding or adhesion. In FIG. 1B, the anchor 11 is laminated in the thickness direction only directly below the fine pattern portion of the lead frame 10, but this becomes finer (for example, the lead frame thickness 15 becomes thinner and the lead frame becomes thinner). This is because the lead frame 10 is easily peeled off from the heat transfer layer 12 because the width 16 is reduced.

  In FIG. 1B, the cross section of the anchor 11 is trapezoidal (wide on the metal plate 13 side and narrow on the lead frame 10 side). However, this can be achieved by making the lead frame 10 side narrower. This is to prevent a short circuit between adjacent portions when the lead frame 10 is connected. Moreover, the metal plate 13 side is thickened in order to have an anchor effect (a wrinkle effect). The cross section of the anchor 11 does not need to be trapezoidal. For example, the anchor effect can be obtained by increasing the surface roughness (or making the surface rough) of each side surface of the anchor 11 (the surface in contact with the heat transfer layer 12). It is done.

  In FIG. 1B, the lead frame thickness 15 indicates the thickness of the lead frame 10. In the embodiment, in order to realize the fine patterning of the heat dissipation board, the lead frame 10 exposed on the surface layer is used as the fine pattern for mounting the electronic component. Then, by making the lead frame 10 into a fine pattern, the heat conduction corresponding to the reduced thermal conductivity is supplemented by the anchor 11 laminated using the adhesive layer 18.

  Furthermore, the anchors 11 stacked in the thickness direction of the lead frame 10 do not need to be formed on the entire surface of the lead frame, and as shown in FIG. I can do it. Further, the anchor 11 does not need to be matched with the pattern shape of the lead frame 10 and can have a pattern shape different from the lead frame 10. For example, when the lead frame 10 and the anchor 11 are fixed, the positional deviation is less likely to occur by making the anchor 11 slightly smaller than the lead frame 10.

  Further, both the lead frame 10 and the anchor 11 can be formed of a metal member (for example, Cu, Al, etc.). For example, a fine pattern is required (for example, in the pattern portion of the surface layer as shown in FIG. 1A), and the lead frame 10 is thin (for example, easy to form a fine pattern by a general etching method or a press method) A member having a lead frame thickness of 15 (such as 0.05 mm to 0.10 mm) is used. On the other hand, a metal member thicker than the lead frame 10 is processed to form the anchor 11. The reason why a member thicker than the lead frame 10 is used is that a sufficient anchor effect may not be obtained unless the thickness is substantially the same as or larger than the lead frame 10.

  In this way, in FIGS. 1A and 1B, a thin lead frame 10 that is easy to make fine on the surface layer side (the exposed surface of the lead frame 10) on which an electronic component (not shown) is mounted, On the plate 13 side, a thick anchor 11 (with an excellent anchor effect) is used. In addition, the heat dissipation of the lead frame 10 is enhanced by positively using a highly heat conductive material such as Cu or Al for the anchor 11. Similarly, by using a low-resistance metal material such as Cu or Al for the anchor 11, the effect of reducing the electrical resistance of the lead frame 10 is obtained.

  In the present embodiment, the lead frame 10 and the anchor 11 are fixed to each other (physical, mechanical, electrical, and thermal), thereby affecting the electrical characteristics and heat dissipation characteristics due to the fine patterning on the heat conductive substrate. Will be suppressed.

  Next, a method for fixing the lead frame 10 and the anchor 11 will be described with reference to FIGS.

  2A and 2B are cross-sectional views illustrating the relationship between the lead frame and the anchor. 2A and 2B, reference numeral 18 denotes an adhesive layer. 2A, the lead frame 10 and the anchor 11 are integrated with each other by welding (such as an ultrasonic welding device, a spot welding device, a projection welding device, or laser welding). In FIG. 2B, the lead frame 10 and the anchor 11 are integrated with each other using an adhesive layer 18. In particular, when the lead frame 10 and the anchor 11 are made of a combination of dissimilar metals (for example, Cu and Al), the cost and weight of the heat dissipation substrate can be reduced. Further, here, by using a material having both high thermal conductivity and low electrical resistance as the adhesive layer 18, the electrical resistance between the lead frame 10 and the anchor 11 can be reduced, and the heat dissipation effect can be enhanced. Furthermore, by using a conductive adhesive for the connection of different metals, an effect of preventing the occurrence of galvanic corrosion due to the battery effect between Cu and Al can be obtained.

  3A and 3B are cross-sectional views illustrating the shape of the anchor. 3A and 3B, the anchor 11 of the lead frame 10 is trapezoidal so as to have an anchor effect (throwing effect), but it is not necessary to stick to this shape, and its cross-sectional shape can provide the anchor effect. Anything is fine. Moreover, it is not necessary to form it on all of the lead frames 10, and for example, as shown in FIG. 3A, the anchor 11 may be formed only in a portion where an anchor effect is particularly required. The shape of the anchor 11 may be as shown in FIG. For example, by isotropic etching of a thick metal plate, a shape as shown in FIG. 3B (a trapezoid having curved surfaces on both sides of the cross section) can be created.

  Next, with reference to FIG. 4, the tensile strength increase by the anchor and the improvement of the heat radiation effect will be described. 4A and 4B are perspective sectional views for explaining the strength increase of the heat conductive substrate and the heat dissipation mechanism. FIG. 4A shows a state where an electronic component is mounted on the surface of a heat conductive substrate, and its tensile strength (for example, JIS of a printed circuit board or the like can be referred to for the tensile strength evaluation method) is increased. Reference numeral 19 denotes an electronic component that requires heat dissipation, such as a light emitting diode, a laser, or a power semiconductor. Reference numeral 20 denotes a terminal serving as an external electrode for soldering the electronic component 19, but it is not necessary to be particular about the terminal shape, and for example, a wire used when mounting a bare chip may be used.

  In FIG. 4A, the lead frame 10 and the anchor 11 are embedded in the heat transfer layer 12 in a state where the lead frame 10 and the anchor 11 are laminated in the thickness direction with each other (they are laminated and integrated without using the adhesive layer 18). May be). The lead frame 10 and the anchor 11 are embedded in the heat transfer layer 12 and are fixed on the metal plate 13 in an integrated state. Then, the electronic component 19 is mounted on the surface of the lead frame 10 as indicated by an arrow 14a. A part of the terminal 20 of the electronic component 19 is omitted and not shown. An arrow 14b indicates a force for pulling the electronic component 19 upward. Even if the electronic component 19 is pulled up in the direction of the arrow 14b, the anchor 11 increases its tensile strength.

  FIG. 4B shows a state in which the electronic component 19 mounted on the surface of the heat conducting substrate is dissipated. In FIG. 4B, the electronic component 19 is mounted on the lead frame 10. The heat generated in the electronic component 19 spreads as indicated by arrows 14c and 14d. An arrow 14c indicates that heat generated in the electronic component 19 through the lead frame 10 and the anchor 11 spreads in the plane direction (along the pattern of the lead frame 10 and the anchor 11). An arrow 14 d indicates a state in which heat generated in the electronic component 19 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 19 spreads over a wide range (or a large area) through the anchor 11 as well as the lead frame 10, and further escapes from the anchor 11 to the metal plate 13. . Here, by using a metal with high heat dissipation (for example, copper or aluminum) for the lead frame 10 or the anchor 11, an excellent heat spreader effect (an effect of widening a heat generation portion, for example, a heat-generating electronic component such as a thermo viewer) It means the area of each temperature region when observed in 1. High heat spreader effect means excellent heat dissipation.

  When the adhesive layer 18 (or the adhesive layer 18 formed by curing the adhesive) is used to connect the lead frame 10 and the anchor 11 in addition to welding, the adhesive layer 18 is thermally conductive, conductive, and heat It is desirable to use a member having both conductivity and electrical resistance. With regard to conductivity, commercially available products to which electrode powder (or flaky fine particles, etc.) such as silver, copper, or gold is added are commercially available. Similarly, as an adhesive having thermal conductivity, there is also an electrically insulating adhesive made of a ceramic member such as alumina and an insulating resin, but in this embodiment, both the electrical conductivity and the thermal conductivity are provided. It is desirable to choose what you have. This is because by using an adhesive having conductivity and high thermal conductivity, electrical characteristics and heat dissipation as a thermal conductive substrate can be enhanced. By curing such an adhesive to form an adhesive layer 18, the anchor 11 and the lead frame 10 are fixed. By using a conductive adhesive, the lead frame 10 bonded in the thickness direction and the anchor 11 are electrically connected, so that the wiring resistance of the lead frame 10 can be reduced. Furthermore, by using a highly heat conductive adhesive as the adhesive, the heat conductivity of the lead frame 10 and the anchor 11 bonded in the thickness direction is improved, so that the heat dissipation can be enhanced. In addition, by fixing a plurality of lead frames with an adhesive having conductivity and high thermal conductivity, even between different metals (for example, in the case of Cu and Al, direct connection causes galvanic corrosion due to battery effect) This may prevent problems during joining.

  Next, galvanic corrosion will be briefly described. When joining metal materials with different corrosion potentials, such as copper and aluminum, for example, in the presence of moisture, galvanic corrosion (according to JIS terminology is called stray current corrosion, Some galvanic corrosion) may occur. Here, the galvanic corrosion is corrosion that occurs when a battery is formed between two different metals when they are electrically connected. This corrosion is that if there is moisture between them, a potential is generated and the metal on the minus side is corroded. In the present embodiment, when aluminum (equivalent to base or negative potential) and copper are laminated, a galvanic corrosion does not occur by using a conductive adhesive in the middle. Further, as the conductive powder to be added to the conductive adhesive, the prevention effect can be further obtained by using an inert material (noble or positive potential) such as silver, graphite, gold, or platinum. Alternatively, it is also effective to use sacrificial zinc. In this way, local battery corrosion is prevented by using an adhesive as necessary.

  For example, when the lead frame 10 is made of Cu (copper) and the anchor 11 is made of Al (aluminum), the heat dissipation board can be reduced in weight and cost. This is because Al is cheaper and has a lower specific gravity than Cu. Thus, the advantages of Cu (excellent solderability, low electrical resistance, high thermal conductivity) and Al advantages (low cost, low electrical resistance, high thermal conductivity) can be combined.

  4A and 4B, the mounting method of the electronic component 19 is not limited to soldering using the terminals 20 or the like (solder is not shown), but wires and bumps (both not shown). ) Can be used. There may be a plurality of terminals 20 of the electronic component 19. 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. The anchor 11 may be formed not only on the fine portion of the lead frame 10 but also on a necessary portion.

  For example, in order to mount an electronic component having a plurality of terminals at a high density, it is necessary to make a fine pattern of wiring. In the case of the present embodiment, the anchor 11 can be used only in a portion where the required tensile strength (or necessary heat dissipation) cannot be obtained by the lead frame 10 alone. As a result, as shown in FIGS. 4 (A) and 4 (B) and the like, it is possible to route fine pattern wiring composed of only the thin lead frame 10.

  Here, the thickness of the lead frame 10 is 0.01 mm to 0.40 mm (preferably 0.02 to 0.30 mm, more preferably 0.05 to 0.20 mm, and further 0.05 to 0.10 mm). It is good. 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 lead frame 10 is 0.05 mm, the lead frame width 16 can be 0.05 mm, and the lead frame gap 17 can be 0.05 mm. The minimum pitch (the pitch is the lead frame width 16 and the lead frame). (Corresponding to the sum of the gaps 17) can be 0.1 mm. Further, when the lead frame is thick such as 0.04 mm or more, it is difficult to form a fine pattern. The thickness of the anchor 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.

  It is possible to make the lead frame 10 and the anchor 11 have the same thickness. A plurality of anchors 11 may be stacked in the thickness direction using the adhesive layer 18 or the like (not shown). The number of sheets to be stacked is desirably 10 or less. When the number exceeds 10, it may be difficult to stack a plurality of anchors 11 and lead frames 10 with high accuracy.

  Next, a method for stacking the lead frame and the anchor will be described with reference to FIGS. 5A to 5C are cross-sectional views illustrating the lamination of the lead frame and the anchor. 5A is a cross-sectional view of the lead frame 10, FIG. 5B is a cross-sectional view of the anchor 11, and FIG. 5C illustrates a state in which the lead frame 10 and the anchor 11 are integrated in the thickness direction. It corresponds to a sectional view. In FIG. 5A, a lead frame 10 is formed by a predetermined member (not shown) through a press punching process (not shown) using an etching method or a mold. Next, as shown in FIG. 5B, the anchor 11 is processed in the same manner as the lead frame 10. Here, the anchor 11 is etched (by using side etching by isotropic etching, a taper, that is, an inclination can be formed on the side surface of the anchor). Alternatively, when the anchor 11 is press-molded, the cross-sectional shape of the mold may be a trapezoid. Next, as shown in FIG. 5C, the lead frame 10 and the anchor 11 are aligned with each other, stacked in the thickness direction via the adhesive layer 18, and integrated (or fixed). Here, an arrow 14 indicates a press device (not shown) or a fixing device (or a heat fixing device) used for integration through the adhesive layer 18. In this way, the lead frame 10 and the anchor 11 are laminated in the thickness direction using the adhesive layer 18 and integrated. Note that, for example, welding (spot welding, projection welding, ultrasonic welding, laser welding) or the like may be used without using the adhesive layer 18.

  Next, the manufacturing method of a heat conductive board | substrate is demonstrated using FIGS. 6-8 is sectional drawing explaining an example of the manufacturing method of a heat conductive board | substrate. In FIG. 6, 21 is a pressing device, 22 is a film, and 23 is a heat transfer material. In FIG. 6, the lead frame 10 and the anchor 11 are integrated as shown in FIG. 5, and this is set on the metal plate 13 via the heat transfer material 23. And these are set to the press apparatus 21 as shown in FIG. In FIG. 6, the mold and the like are not shown. Then, the lead frame 10, the anchor 11, the heat transfer material 23, and the metal plate 13 are pressed and integrated in the direction of the arrow 14 using the press device 21.

  FIG. 7 shows a state in which the lead frame 10 and the anchor 11 are pressed and embedded in the heat transfer material 23 and integrated. In FIG. 7, since the heat transfer material 23 can be softened by heating the heat transfer material 23 or the like during pressing, the adhesion to the surface of the lead frame 10, the anchor 11, or the metal plate 13 is improved, or the gap is evenly drawn into the gap. Can be made. As shown in FIGS. 6 and 7, the film 22 is sandwiched between the lead frame 10 and a mold (not shown), so that the heat transfer material 23 is pressed by the pressing device 21 or the mold (FIG. Can be prevented from adhering to the surface (not shown) as dirt.

  FIG. 8 shows a state where the press is finished. As shown by the arrow 14 in FIG. 8, the pressing devices 21 are pulled apart from each other. Further, the film 22 is peeled off from the surface of the lead frame 10. In this way, the lead frame 10 and the anchor 11 are fixed to the surface of the metal plate 13 by the heat transfer material 23. Here, not only the anchor 11 but also the lead frame 10 can be embedded in the heat transfer material 23 by adjusting the pressing conditions. Then, the heat transfer material 23 is thermoset to form the heat transfer layer 12. Thus, the heat dissipation substrate shown in FIGS. 1A and 1B is formed. The heat curing step of the heat transfer material 23 may be performed in the press device 21. However, these members may be formed in a predetermined shape and then cured in a heat curing furnace. Note that an inexpensive (low heat resistance) material can be used for the film 22 by curing the heat transfer material 23 after the film 22 is peeled off. This prevents the film 22 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. By forming the heat transfer layer 12 and the surface of the lead frame 10 on the same plane (preferably a step of 50 μm or less, more preferably 20 μm or less, and even less than 10 μm, a solder resist (not shown) is formed. Becomes easy. By forming a solder resist on the surface of the lead frame 10 that is not soldered, it is possible to prevent the solder from spreading too much on the lead frame 10. Further, since the thickness difference between the heat transfer layer 12 and the 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 peeling off the film 22, it is desirable to buff the surfaces of the lead frame 10 and the heat transfer layer 12 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, the heat from the lead frame 10 and the anchor 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. By using these thermosetting resins (or resins of the same system) as one of the components of the adhesive layer 18, the adhesion or binding property between the adhesive layer 18 and the heat transfer layer 12 can be enhanced.

Next, materials of the lead frame 10 and the anchor 11 (hereinafter referred to as these metal members) will be described. As a material of the lead frame 10 and the anchor 11, 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 by 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, in order to improve workability and thermal conductivity as the lead frame 10, at least one kind selected from the group of at least Sn, Zr, Ni, Si, Zn, P, Fe, etc. other than copper is used for the copper material. It is also possible to use an alloy made of the above materials. For example, it is possible to use a copper material (hereinafter referred to as Cu + Sn) in which Cu is mainly used and Sn is added thereto. In the case of a Cu + Sn copper material (or copper alloy), for example, by adding Sn to 0.1 wt% or more and less than 0.15 wt%, the softening temperature can be increased to 400 ° C. For comparison, when the lead frame 10 is made using copper without Sn (Cu> 99.96 wt%), the conductivity is low, but the formed heat conduction substrate is particularly distorted in the formation portion or the like. was there. As a result, the softening point of the material was as low as about 200 ° C., and it was expected that the material could be deformed during subsequent component mounting (soldering). On the other hand, when a copper-based material with Cu + Sn> 99.96% by weight was used, it was not particularly affected by the heat generation of various mounted parts. There was no effect on solderability and die bondability. Therefore, when the softening point of this material was measured, it was found to be 400 ° C. Thus, it is desirable to add some elements mainly composed of copper. As an element added to copper, in the case of Zr, the range of 0.015 wt% or more and 0.15 wt% is desirable. When the addition amount is less than 0.015% by weight, the effect of increasing the softening temperature may be small. On the other hand, if the amount added is more than 0.15% by weight, the electrical characteristics may be affected. Also, the softening temperature can be increased by adding Ni, Si, Zn, P or the like. In this case, Ni is 0.1 wt% or more and less than 5 wt%, Si is 0.01 wt% or more and 2 wt% or less, Zn is 0.1 wt% or more and less than 5 wt%, and P is 0.005 wt% or more. Less than 0.1% by weight is desirable. And these elements can make the softening point of a copper raw material high by adding single or multiple in this range. In addition, when there are few addition amounts than the ratio described here, the softening point raise effect may be low. Moreover, when there are more than the ratio described here, there exists a possibility of affecting the electrical conductivity. Similarly, in the case of Fe, 0.1% by weight to 5% by weight is desirable, and in the case of Cr, 0.05% by weight to 1% by weight is desirable. These elements are the same as those described above.

  The tensile strength of the copper material used for the lead frame 10 and the anchor 11 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 members may be affected. On the other hand, by setting the tensile strength to 600 N / square mm or less (and if these members require fine and complicated processing, desirably 400 N / square mm or less), the springback (pressure is removed even if bent to the required angle). And the reaction force is repelled), and the formation accuracy can be improved. Thus, as the material of these members, the electrical conductivity can be lowered by mainly using Cu, and the workability can be enhanced by further softening, and further, the heat dissipation effect by the lead frame 10 and the anchor 11 can be enhanced. The tensile strength of the copper alloy used for these members 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 in these lead frames is less than 10 N / square mm, when electronic components are soldered and mounted on these lead frames 10, cohesive failure can occur in these lead frames 10 instead of the solder portions. There is sex. In addition, the lead frame 10 can be made into the copper composition excellent in workability (for example, punching property by press) for fine pattern processing, and can be made into an alloy composition different from the anchor 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. Further, when the compositions of these members are compared, if the element of these impurities is less than 0.1 ppm, it may be affected by the variation of the composition or the analysis may be difficult. 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.

  It is also useful to previously form a solder layer or a tin layer on the surface of the lead frame 10 exposed from the heat transfer layer 12 (the mounting surface of the electronic component or the like) so as to improve solderability. . Note that it is desirable not to form a solder layer on the surface (or embedded surface) of the lead frame 10 or the anchor 11 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 adhesion (or bonding strength) between the lead frame 10 or the anchor 11 and the heat transfer layer 12 is softened. May be affected.

  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.

  9A and 9B 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. 9A and 9B, 24 is a dotted line, a dotted line 24a indicates a general electronic component, and a dotted line 24b indicates a power electronic component. In FIG. 9A, at least the lead frames 10a and 10b and the heat transfer layer 12 are exposed on the surface of the heat conductive substrate (as shown in FIG. 9B, the anchor 11 is under the lead frame 10a. Are integrated together). On the other hand, the anchor 11 is not formed under the lead frame 10b. Accordingly, the anchor 11 can be easily made into a fine pattern. Then, the lead frame 10b is made into a fine pattern, and general electronic components are mounted with high density. Thus, by not forming the anchor 11 under the locally refined lead frame 10b, the alignment of the lead frames 10a, 10b and the anchor 11 and the integration process are facilitated.

  FIG. 9B is a cross-sectional view taken along arrow 14b in FIG. In FIG. 9B, an electronic component 19b such as a power semiconductor is mounted on the lead frame 10a on which the anchor 11 is stacked. The heat generated in the electronic component 19b such as a power semiconductor is dissipated through the anchor 11 as well as the lead frame 10a as indicated by an arrow 14c.

  Thus, when the anchor 11 is laminated under the lead frame 10a (or in the thickness direction), the anchor position can be local. Further, by making the pattern shapes of the lead frame 10a and the anchor 11 different (for example, making the anchor 11 one size smaller than the lead frame 10a), it is possible to prevent positional deviation at the time of stacking. Further, by forming the portion where the tensile strength is not improved and the heat dissipation is not required with only the thin lead frame 10, it is easy to make a fine pattern.

  Next, a circuit module for mounting power electronic components at high density by face-down mounting or the like will be described. FIGS. 10A and 10B are a top view and a cross-sectional view showing a state where the electronic component is mounted face-down. In FIG. 10A, the 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. 10A is FIG. 10B. As shown in FIG. 10B, the lead frame gap 17 can be narrowed as the lead frame 10 is thin. On the other hand, since the anchor 11 is thicker than the lead frame 10, the heat radiation effect can be enhanced. Arrows 14a and 14c in FIGS. 10A and 10B show how heat generated in the electronic component 19 (illustrated by a dotted line 24 in FIG. 10A) spreads. In FIG. 10B, the terminal 20 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. 10A, dotted lines 24a, 24b, and 24c 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. 10A, 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, how the individual anchors 11 are fixed on the lead frame 10 will be described with reference to FIGS. FIGS. 11A and 11B are a top view and a cross-sectional view illustrating a manner in which a piece-shaped anchor is fixed on a lead frame. In FIG. 11A, an anchor 11 is bonded to a necessary portion of the lead frame 10. A dotted line 24 indicates a position where the anchor 11 is set. The anchor 11 is welded or bonded onto the lead frame 10 as indicated by an arrow 14b. FIG. 11B is a cross section taken along arrow 14a in FIG. Note that the anchor 11 may be a plurality of pieces, or may be a single piece as shown in FIG. 11A (for example, the pattern shape shown as the lead frame 10). In this way, the anchor 11 is locally formed in a portion where the anchor effect (and heat dissipation effect) is required. 11A and 11B, the actual lead frame 10 is a fine pattern, but is not shown as a fine pattern because of drafting.

  As described above, heat conduction comprising the metal plate 13, the sheet-like heat transfer layer 12 fixed on the metal plate 13, and the lead frame 10 at least partially embedded in the heat transfer layer 12. The lead frame 10 is a heat conductive substrate in which the anchors 11 are laminated in the thickness direction, so that the influence on the tensile strength and heat dissipation of the lead frame 10 is suppressed even if the heat conductive substrate is made into a fine pattern. Thus, various electronic devices can be miniaturized.

  A heat conductive substrate comprising the metal plate 13, the sheet-like heat transfer layer 12 fixed on the metal plate 13, and the lead frame 10 embedded at least in part in the heat transfer layer 12, Since the lead frame 10 is a heat conductive substrate in which the anchors 11 are laminated in the thickness direction, the influence on the tensile strength and heat dissipation of the lead frame 10 can be suppressed even if the heat conductive substrate is made into a fine pattern. 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 10 having at least a portion embedded in the heat transfer layer 12, A part or more of the lead frame 10 is a heat conductive substrate in which the anchors 11 are laminated in the thickness direction, so that the influence on the tensile strength and heat dissipation of the lead frame 10 can be suppressed even if the heat conductive substrate is made into a fine pattern. Thus, 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 10 having at least a portion embedded in the heat transfer layer 12, A part or more of the lead frame 10 is a heat conductive substrate in which the anchors 11 are laminated in the thickness direction via the adhesive layer 18, so that the tensile strength and heat dissipation of the lead frame 10 can be improved even if the heat conductive substrate is made into a fine pattern. Thus, it is possible to reduce the size of various electronic devices.

  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 10 embedded at least in part in the heat transfer layer 12, At least a part of the lead frame 10 is a heat conductive substrate in which anchors 11 having a pattern different from that of the lead frame 10 are laminated, so that the tensile strength and heat dissipation of the lead frame 10 can be improved even if the heat conductive substrate is made into a fine pattern. Thus, it is possible to reduce the size of various electronic devices.

  The heat transfer layer 12 includes at least one resin selected from the group consisting of epoxy resins, phenol resins, and isocyanate resins, and alumina, magnesium oxide, boron nitride, silicon oxide, silicon carbide, silicon nitride, and aluminum nitride. By suppressing the influence on the tensile strength and heat dissipation of the lead frame 10 even if the heat conductive substrate is made into a fine pattern by using a heat conductive substrate including at least one inorganic filler selected from the group consisting of Therefore, various electronic devices can be miniaturized.

  Here, at least one of the lead frame 10 and the anchor 11 is made of tough pitch copper or oxygen-free copper, so that the lead frame 10 and the anchor 11 can be reduced in material cost and processing cost depending on the use. it can.

  At least one of the lead frame 10 and the anchor 11 is Sn 0.1% by weight or more and 0.15% by weight or less, Zr 0.015% by weight or more and 0.15% by weight or less, Ni is 0.2% by weight or less. 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 a metal material mainly composed of copper containing at least one selected from the group of 0.1 wt% or more and 5 wt% or less, so that the lead frame 10 and the anchor 11 have high electrical conductivity with low electrical resistance. The processability can be improved.

  Also, at least the step of fixing the anchor 11 in the thickness direction with the lead frame 10 aligned, the step of embedding the lead frame 10 and the anchor 11 on the metal plate 13 using a heat transfer material, By providing the manufacturing method of the heat conductive board | substrate including the process of hardening a heat-transfer material, a heat conductive board | substrate can be manufactured stably.

  At least a metal plate 13, a sheet-like heat transfer layer 12 fixed on the metal plate 13, and a lead frame 10 and an anchor 11 at least partially embedded in the heat transfer layer 12 are configured. By providing a circuit module including a heat conductive substrate and electronic components mounted on the lead frame 10, 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 respectively a top view and a cross-sectional view of a heat dissipation board in an embodiment of the present invention. (A) (B) is sectional drawing explaining the relationship between a lead frame and an anchor together (A) and (B) are sectional views for explaining the shape of the anchor. (A) and (B) are perspective cross-sectional views for explaining the strength increase and heat dissipation mechanism of the heat conductive substrate. (A)-(C) are sectional drawings explaining lamination | stacking of a lead frame and an anchor. 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 individual anchors are fixed on a lead frame. (A) (B) is a perspective sectional view showing an example of a conventional heat conductive substrate (A) to (C) are cross-sectional views of a conventional heat conductive substrate with a fine pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Lead frame 11 Anchor 12 Heat transfer layer 13 Metal plate 14 Arrow 15 Lead frame thickness 16 Lead frame width 17 Lead frame gap 18 Adhesive layer 19 Electronic component 20 Terminal 21 Press device 22 Film 23 Heat transfer material 24 Dotted line

Claims (9)

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 anchors are stacked in the thickness direction. 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 anchors are stacked in the thickness direction. 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 anchors are stacked in the thickness direction via an adhesive 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 anchors having a pattern shape different from that of the lead frame are laminated. 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: 5. The heat conducting substrate according to claim 1, wherein at least one of the lead frame and the anchor is tough pitch copper or oxygen-free copper. At least one of the lead frames or anchors is Sn 0.1% to 0.15% by weight, Zr 0.015% to 0.15% by weight, and 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 4, 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 the anchor in the thickness direction with the lead frame aligned,
On the metal plate, the step of embedding the lead frame and the anchor 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 conduction substrate composed of a metal plate, a sheet-like heat transfer layer fixed on the metal plate, and a lead frame and an anchor embedded at least in part in the heat transfer layer;
A circuit module comprising an electronic component mounted on the lead frame.

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