JP2007158208A - Light-emitting module and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting module having proper processability which can efficiently cool a light-emitting element, such as LED, by efficiently radiating the heat generated from the light-emitting element, such as LED or semiconductor laser, and to provide its manufacturing method. <P>SOLUTION: A metal plate 110 having a convex portion 114 formed thereon is integrated with a lead frame 100 having a concave portion 112 and principally containing copper, on the midway via a heat-radiating resin 102 containing an inorganic filler and a resin compound containing a thermosetting resin. Then, an LED 108 is mounted on the lead frame 100. In this way, the heat generated from the LED 108 is radiated, and the concave portion 112, formed on the lead frame 100, is used for both a reflection portion and a heat radiation portion, thereby improving light emission efficiency and heat radiation efficiency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light emitting module used for a backlight of a display device having a backlight such as a liquid crystal television and a manufacturing method thereof.

  Conventionally, a cold cathode tube or the like has been used for a backlight of a liquid crystal television or the like, but in recent years, it has been proposed to mount a semiconductor light emitting element such as an LED or a laser on a heat dissipating substrate ( For example, see Patent Document 1).

  FIG. 8 is a cross-sectional view showing an example of a conventional light emitting module. In FIG. 8, the light emitting element 2 is mounted in the recess formed in the ceramic substrate 1. The plurality of ceramic substrates 1 are fixed on the heat sink 3. Further, the plurality of ceramic substrates 1 are electrically connected by a connection substrate 5 having a window portion 4. The light 6 emitted from the LED is emitted to the outside through the window portion 4 formed on the connection substrate 5. In FIG. 8, the wiring in the ceramic substrate 1 having the recesses and the connection substrate 5, the LED wiring, and the like are not shown. Such light emitting modules are used as backlights for liquid crystals and the like. However, since the ceramic substrate 1 is difficult to process and expensive, there has been a demand for a heat dissipation substrate that is less expensive and has excellent workability.

  On the other hand, the display device side including the liquid crystal TV is desired to expand the color display range. In order to meet these needs, white LEDs and the like have limitations. In recent years, red (red), green (green), and blue (blue) single-color light emitting elements, and further purple, orange, red purple, and cobalt blue are used. Attempts have been made to extend the color display range (specifically, the CIE color system or the like) by adding a special color light emitting element that emits a special color.

  When such a light emitting module as shown in FIG. 8 is used for such needs, while mounting such light emitting elements one by one in the recess of the ceramic substrate 1, a uniform color mixture (mixed white color) is produced as a whole, It is necessary to adjust the color balance (for example, white balance described later). On the other hand, it is known that the luminous efficiency of solid light emitting devices such as LEDs decreases as the temperature rises. Furthermore, the degree of decrease in luminous efficiency with respect to temperature varies depending on the emission color of the LED. For this reason, for example, immediately after the liquid crystal TV is turned on, the LED portion is at room temperature (for example, 25 ° C.), so even if white balance is maintained, the temperature of the LED portion increases (for example, 40 ° C. → 50 ° C.). → 60 ° C.), for example, a phenomenon such as a reduction in red light emission efficiency may occur, and color reproducibility and backlight luminance may also change.

  On the other hand, as shown in FIG. 8, when the ceramic substrate 1 on which the light emitting elements 2 such as LEDs are mounted one by one is arranged on the heat radiating plate 3, it is advantageous from the heat radiating surface. It is difficult to create a white color by mixing light using (or create a white color having high color rendering properties by mixing RGB + special colors).

Therefore, it is possible to mount a large number of light-emitting elements that can handle higher brightness of the light-emitting elements (necessary to pass a large current) and multi-LEDs (mounting a plurality of LEDs with high density). There is a demand for light-emitting modules that have high processability and excellent heat dissipation.
JP 2004-311791 A

  However, the conventional configuration has a problem that the heat dissipation substrate on which the light emitting element is mounted is a ceramic substrate, which is disadvantageous in terms of workability and cost.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a light-emitting module with good processability and a method for manufacturing the same by using a lead frame, an insulator, and a metal plate instead of a ceramic substrate. And

  In order to solve the above problems, the present invention directly mounts a light emitting element such as an LED on a lead frame having high heat dissipation, and further heat of the lead frame is formed on the back surface via a heat dissipation resin. It will be conveyed to the metal plate.

  The light emitting module obtained by the light emitting module of the present invention and the manufacturing method thereof can efficiently diffuse the heat generated by the light emitting elements such as LEDs and semiconductor lasers, and can effectively cool the light emitting elements such as LEDs.

(Embodiment 1)
Hereinafter, the light emitting module in Embodiment 1 of this invention is demonstrated using FIG. 1, FIG.

  1A and 1B are a top view and a cross-sectional view illustrating a light-emitting module according to Embodiment 1, in which FIG. 1A is a top view and FIG. 1B is a cross-sectional view taken along an arrow 104 in FIG. In FIG. 1, 100 is a lead frame, 102 is a heat-dissipating resin, 104 is an arrow, 106 is a dotted line, 108 is an LED, and the LED 108 is shown as an example of a light emitting element such as a laser, and is applied to other light emitting elements. Needless to say, you can. Reference numeral 110 denotes a metal plate, 112 denotes a recess, 114 denotes a projection, and 116 denotes a heat sink. In the first embodiment, a lead frame 100 in which a concave portion 112 is formed and a metal plate 110 in which a convex portion 114 is formed are prepared, and the lead frame 100 is placed in a donut-shaped ring made of the convex portion 114. The recess 112 is fitted and insulated and fixed through the heat radiation resin 102.

  First, description will be made with reference to FIG. In FIG. 1A, lead frames 100 are insulated from each other through a heat radiation resin 102 in a state of being divided into a plurality of parts. A dotted line 106 indicates a bent position of the lead frame 100. When the lead frame 100 is bent at the position of the dotted line 106 in FIG. 1A, a recess 112 as shown in FIG. 1B is formed. It shows that The LED 108 is formed so as to straddle the plurality of lead frames 100 (note that the LED 108 does not necessarily have to be mounted straddling). Note that a wire wire for mounting the LED 108 (wire wire is in the case of wire bonding connection, but members such as conductive resin and solder (in the case of flip chip mounting, etc.) are not shown in FIG.

  Next, description will be made with reference to FIG. FIG. 1B corresponds to a cross-sectional view taken along arrow 104 in FIG. In FIG. 1B, a convex portion 114 is formed on a part of the metal plate 110. In FIG. 1B, the two convex portions 114 are visible because the convex portions 114 are formed in a donut shape (or ring shape). A recess 112 is formed in a part of the lead frame 100. The concave portion 112 of the lead frame 100 is inserted into a donut-shaped ring formed by the convex portion 114. Then, as shown in FIG. 1B, the concave portion formed in the lead frame 100 enters the convex portion 114 formed in the metal plate 110, and is insulated and fixed via the heat radiation resin 102. become. Then, one surface of the lead frame 100 embedded in the heat dissipation resin 102 is exposed to the outside, and components that require heat dissipation such as the LED 108 are mounted on the exposed surface. The heat generated from the LED 108 and the like is diffused widely throughout the light emitting module via the lead frame 100.

  As shown in FIG. 1B, the shape of the concave portion 112 of the lead frame 100 and the convex portion 114 of the metal plate 110 are matched to each other, so that the overlapping portion (the concave portion 112 corresponding to a light reflecting surface described later). The thickness of the heat-dissipating resin 102 that insulates the wall surfaces between the lead frame 100 and the metal plate 110 can be increased. Then, the heat generated by the LED 108 is transmitted to the lead frame 100, and to the heat radiating portion (the heat radiating portion is not shown) such as the metal plate 110 and the heat sink 116 fixed to the metal plate 110 through the heat radiating resin 102. Spread.

Note that it is desirable to use a heat dissipation resin 102 in which a highly heat dissipating inorganic filler is dispersed in a curable resin. The inorganic filler has a substantially spherical shape, and its diameter is suitably from 0.1 to 100 microns (if it is less than 0.1 microns, it may be difficult to disperse in the resin, and it exceeds 100 microns) And the thickness of the heat-dissipating resin 102 is increased, which affects the thermal diffusivity). Therefore, the filling amount of the inorganic filler in the heat radiation resin 102 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 Al ₂ O ₃ having an average particle size of 3 microns and an average particle size of 12 microns. By using the Al ₂ O ₃ of the large and small two types of particle size, it is possible to fill the Al ₂ O ₃ of small particle size in the gap Al ₂ O ₃ of large particle size, Al ₂ O ₃ 90 wt% near Can be filled to a high concentration. As a result, the thermal conductivity of the heat radiation resin 102 is about 5 W / (mK). The inorganic filler may include at least one selected from the group consisting of MgO, BN, SiO ₂ , SiC, Si ₃ N ₄ , and AlN instead of Al ₂ O ₃ .

  The thermosetting insulating 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 radiation resin 102 is reduced, heat generated in the LED 108 mounted on the lead frame 100 can be easily transferred to the metal plate 110, but conversely, withstand voltage is a problem, and if it is too thick, the thermal resistance increases. The optimum thickness may be set to 50 microns or more and 1000 microns or less in consideration of withstand voltage and thermal resistance.

  2A and 2B are a top view and a cross-sectional view illustrating a heat dissipation mechanism in the first embodiment. 2A is a top view and FIG. 2B is a cross-sectional view corresponding to FIGS. 1A and 1B, respectively.

  Arrows 104a, 104b, and 104c in FIGS. 2A and 2B indicate the diffusion direction of heat generated in the LED 108, respectively. As shown in FIG. 2A, the heat generated from the LED 108 is transmitted through the lead frame 100 as indicated by an arrow 104a and dissipated at high speed. This is because, in the first embodiment, the lead frame 100 having a high thermal conductivity mainly composed of copper is used. The heat generated in the LED 108 spreads through the lead frame 100 as indicated by an arrow 104b in FIG. 2B, and at the same time, through the heat-dissipating resin 102 as indicated by an arrow 104c in FIG. It is also transmitted to the plate 110. The heat of the metal plate 110 is transmitted to the heat sink 116 or the like as necessary. Thus, since the heat generated in the LED 108 can be widely diffused, the LED 108 can be efficiently cooled.

  Further, as will be described later with reference to FIG. 3 and the like, the lead frame 100 that diffuses the heat generated by the LED 108 is a light reflecting surface that reflects light emitted from the LED 108 forward in the recess 114 (the light reflection is illustrated in FIG. 3). To explain). In this way, the lead frame 100 constituting the recess 114 serves as both a light reflection portion and a heat diffusion portion, and enables efficient light emission and heat diffusion.

  Further, as shown in FIG. 2B, in the first embodiment, the concave portion of the lead frame 100 which becomes a light reflecting surface is obtained by matching the shape of the convex portion 114 of the metal plate 110 and the concave portion 112 of the lead frame 100. The thickness of the heat radiation resin 102 on the side surface portion 112 can be made thin and uniform. Therefore, even when the heat radiating resin 102 having a lower thermal conductivity than that of the lead frame 100 or the metal plate 114 is used, the influence can be minimized.

  As a result, a plurality of LEDs (even LEDs that require high heat dissipation) can be mounted in the recess 112 with high density.

  Next, a case where a plurality of LEDs 108 are mounted in one recess 112 will be described. A plurality of LEDs 108 can be mounted on the lead frame 100 in one recess 112 as shown in FIG. The plurality of LEDs 108 are supplied with current from the plurality of lead frames 100, and each emits light in a predetermined color. In this way, by mounting a plurality of LEDs 108 at a high density, it becomes easy to mix colors with each other, and the cost of the light emitting module can be reduced. In FIG. 1, the connection part between the LED 108 and the lead frame 100 and the connection part (for example, connection by a wire bonder) between the LED 108 and the lead frame 100 b are not shown.

  The color of the heat radiation resin 102 is desirably white (or colorless near white). This is because when the color is black, red, blue, or the like, it is difficult to reflect the light emitted from the light emitting element, which affects the light emission efficiency.

  Alternatively, the LED 108 is preferably mounted on the bottom of the recess 114 formed by the lead frame 100 as shown in FIG. By forming the LED 108 at the bottom of the recess (that is, at the bottom of the recess), the light emitted from the side surface of the LED 108 is caused by the lead frame 100 serving as the wall surface of the recess or the heat dissipation resin 102 exposed between the lead frames 100. The light can be reflected effectively in the desired direction, and the luminous efficiency can be increased.

  In this way, a plurality of light emitting elements are mounted on the lead frame 100 at the bottom surface of the recess 114, and the lead frame is also formed widely on the side wall surface of the recess 114 (desirably 50% to 95% of the side wall surface). ). When the area ratio of the lead frame 100 to the side wall is 50% or less, the heat conduction by the lead frame is affected, and the amount of light reflection by the lead frame surface may be reduced. Further, when it exceeds 95% (that is, when the exposure ratio of the heat radiation resin 102 on the side surface is less than 5%), when the interval between the lead frames 100 is narrowed, the possibility of a short circuit increases. The metal plate 110 is preferably made of aluminum, copper, or an alloy containing them as a main component, which has good thermal conductivity.

  The thickness of the heat-dissipating resin 102 between the convex portion 114 formed on the metal plate 110 and the concave portion 112 formed on the lead frame 100 is desirably 50 microns or more and 1000 microns or less. Furthermore, 100 microns or more and 300 microns or less are desirable. When the thickness of the insulating layer is 50 microns or less, the insulation between the metal plate 110 and the lead frame 100 may be affected. If the thickness exceeds 1000 microns, the thermal conductivity from the lead frame 100 to the metal plate 110 may be affected.

  Also, the thickness variation of the insulating layer (for example, the variation in the thickness of the heat radiation resin sandwiched between the concave portion 112 of the lead frame 100 and the convex portion 114 of the metal plate 110, or the thickness difference between the thick portion and the thin portion is 200 microns or less. 1 (B), the first embodiment insulates between the lead frame 100 and the metal plate 110 by forming the convex portion 114 on the metal plate 110 as shown in FIG. The thickness of the heat-dissipating resin can be made thin and uniform, so that this thickness variation (or thickness difference) can be reduced, and efficient cooling and thinning can be achieved. When the thickness variation (or thickness difference) of the heat radiation resin sandwiched between 110 becomes as large as 200 microns or more, the lead frame 100 is moved to the metal plate 110. Can affect the thermal conductivity.

  The cross-sectional shape of the recess 112 is preferably a mortar shape that narrows toward the bottom. This is because the cross-sectional shape is a mortar shape and becomes narrower toward the bottom to increase the light reflection efficiency.

(Embodiment 2)
Hereinafter, an example of the light emitting module according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view of the light emitting module in the second embodiment. In FIG. 3, 102 is a resin and 120 is a lens. 3A shows a case where the resin 118 is processed into a lens shape, and FIG. 3B shows a case where the lens 120 is mounted on the resin 118. FIG.

  In FIGS. 3A and 3B, an arrow 104 indicates the direction of light emitted from the LED 108. As shown in FIG. 3A, the light emitted from the LED 108 is reflected by the first concave portion 112 (or the wall surface constituting the first concave portion 112) of the lead frame 100, as indicated by an arrow 104, Guided outside. Here, the light reflectance can be increased by performing the high light reflectance treatment of the surface treatment of the lead frame. The surface treatment is preferably silver rather than gold or nickel. This is because silver has a higher light reflectance. Further, the surface treatment may be glossy treatment or matte treatment (such as satin finish). Even if there is no gloss, the reflectance can be increased by using a member having a high reflectance such as silver. Note that it is desirable that the high light reflectivity treatment be performed at least at a portion where the concave portion 112 of the lead frame 100 is formed. Furthermore, it is desirable that the lead frame 100 other than the recess 112 is subjected to a process for improving solder wettability in order to mount a semiconductor, a chip component, or the like. By such treatment, natural oxidation of the lead frame 100 can also be prevented.

  The resin 118 covering the LED 108 is preferably made of PMMA (polymethyl methacrylate) or silicon-based transparent resin. When an epoxy resin is used here, it is necessary to add a UV inhibitor for preventing yellowing of the epoxy. This is because the LED is white, and further, the epoxy resin may be yellowed by blue light. Also, it is desirable to use a soft material such as silicon (having at least a lower hardness than epoxy). By using a soft (flexible) resin material, the LED 108 generates heat and can prevent stress concentration at the connection portion between the LED 108 and the lead frame 100 when the LED 108 is thermally expanded. Similarly, stress concentration on the gold wire when the LED 108 and the lead frame 100 are bonded to each other can be reduced (the gold wire is less likely to be cut).

  It is preferable that 50% or more and 95% or less of the area of the side surface forming the first recess 112 is the lead frame 100. Note that the heat radiation resin 102 is desirably a color having a high light reflectance such as white. However, even when the heat radiating resin 102 is white, the lead frame 100 may have higher light reflectance. In this case, when the area of the lead frame 100 is less than 50%, the light reflection on the side surface is mainly caused by the heat-dissipating resin 102, which may affect the light emission efficiency of the light emitting module. Further, when the proportion of the lead frame is 95% or more, it may be difficult to process the lead frame 100.

  The size of the lens 120 is desirably equal to or larger than the width of the recess 112 as shown in FIG. By increasing the size of the lens 120, the play portion when the lens 120 is mounted can be increased, so that optical alignment can be facilitated. In particular, by processing the lead frame 100 and the metal plate 110 using a technique such as die molding as described later with reference to FIG. As a result, the processing accuracy of the lead frame 100 and the metal plate 110 (particularly the parallelism between the bottom of the first concave portion 112 and the plane of the second convex portion 114) can be increased. Further, the optical axis can be adjusted with high accuracy only by setting the lens 120 on the first recess 112.

  Note that the light-emitting element mounted on the recess 112 (or the bottom of the recess 112) is preferably a light-emitting element having at least one different emission color. Color rendering properties can be improved by using a plurality of LEDs 108 having different emission colors, and color mixing properties can be improved by mounting a plurality of these in a single recess 112 at a high density. In addition, one or more emission colors of the plurality of light emitting elements may be white. As described above, in the configuration of the second embodiment, by utilizing the excellent heat dissipation, even the LED 108 whose light emission efficiency is easily affected by the temperature (or the degree of influence is different) is hardly affected by the temperature. It goes without saying that the LEDs 108 can be individually controlled via the lead frame 100 even when the temperature of the light emitting module itself rises.

(Embodiment 3)
Hereinafter, an example of the structure of the light emitting module according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 4 is a top view of a light emitting module in which the shape of the recess for mounting the LED is an elongated circle (including an ellipse, an oval shape, etc.). As shown in FIG. 4, the number of LEDs 108 mounted and the mounting density can be increased simultaneously with the downsizing of the light emitting module by making the shape of the recesses into elongated recesses.

  In FIG. 4, lead frames 100 a, 100 b, and 100 c are processed in a state of being insulated from each other, and are recessed according to the dotted line 106. The LEDs 108a, 108b, and 108c and a plurality of LEDs are mounted in the recess 112 (or a portion surrounded by the recess 112). And the light radiated | emitted from several LED108a, 108b, 108c is reflected in the wall surface part (doughnut-shaped part enclosed with the dotted line 106 of FIG. 4) of the recessed part 112 of lead frame 100a, 100b, 100c. Further, an arrow 104 in FIG. 4 (only part of which is shown in FIG. 4) indicates a state in which heat generated from the LEDs 108a, 108b, and 108c is transmitted. As described above, the heat generated from the LEDs 108a, 108b, and 108c can be dissipated through the lead frames 100a, 100b, and 100c as shown in FIG. 4, FIG. 2 (A), and FIG. 2 (B). In this way, the luminance of the light emitting module can be increased by increasing the number of mounted LEDs 108.

  Hereinafter, an example of the manufacturing method of the light emitting module in Embodiment 3 of this invention is demonstrated using FIGS. 5-7.

  FIG. 5 is a cross-sectional view illustrating a state in which a part of the metal plate is processed into a convex shape. The metal plate 110a in FIG. 5 (A) is before processing, and the metal plates 110b and 110c in FIGS. 5 (B) and 5 (C) are after processing. Thus, the convex part 114 can be accurately and inexpensively formed by using a metal plate 110 having a constant thickness and pressing it. The cross section of the convex portion 114 may be a vertical triangle as shown in FIG. 5B or a triangle as shown in FIG.

  6 and 7 are cross-sectional views showing an example of a method for molding a light emitting module. In FIG. 6, 124 is a burr, 126a and 126b are molds, and 128 is an antifouling film. First, a predetermined metal plate is punched into a predetermined shape using a press or the like, and this is used as a lead frame 100. Note that burrs 124 may be generated in the lead frame 100 by this punching process. Next, as shown in FIG. 6, an uncured heat radiation resin 102 and a metal plate 110 are set under the lead frame 100. Then, with these members positioned, they are set between the molds 126a and 126b. Next, the lead frame 100 is pressed against the heat-dissipating resin 102 by moving the molds 126a and 126b in the direction of the arrow 104a by a press device (not shown in FIG. 6), and is heated and cured at a predetermined temperature. Also, as shown in FIG. 6, it is desirable to set a dirt prevention film 128 between the lead frame 100 and the mold 126a. Further, it is desirable that the antifouling film 128 is a film having a certain degree of air permeability, such as a nonwoven fabric. In this way, when the lead frame 100 is pressed into the heat-dissipating resin 102 using the molds 126a and 126b, air can be easily removed as indicated by the arrow 104b (the air is passed through the antifouling film 128). Can be prevented from occurring at the interface between the lead frame 100 and the heat radiation resin 102 or at the interface between the metal plate 110 and the heat radiation resin 102.

  When the lead frame 100 is pulled out into a predetermined three-dimensional shape by molding, it is desirable that the direction of the burr generated at the end of the lead frame 100 is on the dirt prevention film 128 side. In this way, when the lead frame 100 is pressed, the burr 124 bites into the antifouling film 128, so that the heat radiation resin 102 can be prevented from entering the surface of the lead frame 100 (for example, the mounting surface of the LED 108 or the like).

  FIG. 7 is a cross-sectional view after the press is completed. As shown in FIG. 7, the light emitting module is completed by moving the molds 126a and 126b in the direction of the arrow 104a (note that the LED 108 and the like are not yet mounted in the state of FIG. 7). Then, the LED 108 is mounted on the light emitting module of FIG. 7 and further covered with a resin 118, whereby the light emitting module as shown in FIG. 1 is completed. The burr 124 can be eliminated during pressing, but can be left after pressing if necessary.

Next, the insulating material will be described in more detail. The heat dissipation resin 102 is composed of a filler and a resin. The filler is preferably an inorganic filler. As the inorganic filler, it is desirable to include one containing at least one selected from the group consisting of Al ₂ O ₃ , Mg, BN, SiO ₂ , SiC, Si ₃ N ₄ , and AlN. When an inorganic filler is used, heat dissipation can be improved, but when using MgO in particular, the linear thermal expansion coefficient can be increased. Further, when SiO ₂ is used, the dielectric constant can be reduced, and when BN is used, the linear thermal expansion coefficient can be reduced. In this way, it is possible to form a heat dissipation resin 102 having a thermal conductivity of 1 W / (m · K) to 20 W / (m · K). In addition, when heat conductivity is less than 1 W / (m * K), it influences the heat dissipation of a light emitting module. 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 resin is preferably a thermosetting resin, and specifically includes at least one selected from the group consisting of an epoxy resin, a phenol resin, and an isocyanate resin.

The inorganic filler has a substantially spherical shape and a diameter of 0.1 to 100 μm. The smaller the particle size, the better the filling rate into the resin. Therefore, the filling amount (or content) of the inorganic filler in the heat radiation resin 102 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 Al ₂ O ₃ having an average particle size of 3 microns and an average particle size of 12 microns. By using the Al ₂ O ₃ of the large and small two types of particle size, it is possible to fill the Al ₂ O ₃ of small particle size in the gap Al ₂ O ₃ of large particle size, Al ₂ O ₃ 90 wt% near Can be filled to a high concentration. As a result, the thermal conductivity of the heat radiation resin 102 is about 5 W / (m · K). In addition, when the filling rate of a filler is less than 70 weight%, thermal conductivity may fall. Further, if the filling rate (or content rate) of the filler exceeds 95% by weight, the moldability of the heat-dissipating resin 102 before uncured may be affected, and the adhesiveness between the heat-dissipating resin 102 and the lead frame 100 (for example, embedded) Case or when pasted on the surface).

  The thermosetting insulating 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.

  Note that if the thickness of the insulator made of the heat radiation resin 102 is reduced, heat generated in the LED 108 mounted on the lead frame 100 can be easily transferred to the metal plate 110, but conversely, the insulation breakdown voltage becomes a problem. Therefore, the optimum thickness may be set in consideration of the withstand voltage and the thermal resistance.

  Next, the material of the lead frame 100 will be described. The lead frame is preferably made mainly of copper. This is because copper has both excellent thermal conductivity and electrical conductivity. In order to improve the workability and thermal conductivity as a lead frame, the copper material used as the lead frame 100 is selected from a group of at least Sn, Zr, Ni, Si, Zn, P, Fe, etc. other than copper. It is desirable to use an alloy comprising at least one material. For example, an alloy containing Cu as a main component and Sn added thereto (hereinafter referred to as Cu + Sn) can be used. In the case of a Cu + Sn alloy, for example, by adding Sn to 0.1 wt% or more and less than 0.15 wt%, the softening temperature can be increased to 400 ° C. For comparison, the lead frame 100 was made using Sn-free copper (Cu> 99.96 wt%). However, although the electrical conductivity is low, distortion is generated particularly in the formed portion of the recess 112 in the completed heat dissipation board. There was a case. As a result of detailed examination, the softening point of the material is as low as about 200 ° C., so that the material is deformed to reliability (repetition of heat generation / cooling, etc.) after mounting a component (when soldering) or after mounting the LED 108. It was expected that there was a possibility. On the other hand, when a copper material of Cu + Sn> 99.96 wt% was used, it was not particularly affected by the heat generated by various mounted components and a plurality of LEDs. 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. In the case of Zr as an element added to copper, a range of 0.015 wt% or more and 0.15 wt% is desirable. When the amount added is less than 0.015 wt%, the effect of increasing the softening temperature may be small. On the other hand, if the amount added is more than 0.15 wt%, 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 preferably 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 preferably 0.005 wt% or more and less than 0.1 wt%. . 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 wt% or more and 5 wt% or less is desirable, and in the case of Cr, 0.05 wt% or more and 1 wt% or less are desirable. These elements are the same as those described above.

The tensile strength of the copper alloy used for the lead frame 100 is desirably 600 N / mm ² or less. In the case of a material having a tensile strength exceeding 600 N / mm ² , the workability of the lead frame 100 may be affected. Further, such a material having a high tensile strength tends to increase its electric resistance, so that it may not be suitable for high current applications such as LEDs used in the first embodiment. On the other hand, by setting the tensile strength to 600 N / mm ² or less (and if the lead frame 100 requires fine and complicated processing, desirably 400 N / mm ² or less), the springback (pressure even if bent to the required angle) If it is removed, the occurrence of rebound by reaction force) can be suppressed, and the formation accuracy of the recess 112 can be improved. As described above, as the lead frame material, the electrical conductivity can be lowered by using Cu as a main component, the workability can be improved by further softening, and the heat dissipation effect by the lead frame 100 can also be enhanced. The tensile strength of the copper alloy used for the lead frame 100 is desirably 10 N / mm ² or more. This is because the copper alloy used for the lead frame 100 needs to have a strength higher than the tensile strength (about 30 to 70 N / mm ² ) of general lead-free solder. When the tensile strength of the copper alloy used for the lead frame 100 is less than 10 N / mm ² , when the LED 108, the driving semiconductor component, the chip component, or the like is soldered and mounted on the lead frame 100, the lead frame 100 portion instead of the solder portion May cause cohesive failure.

  It should be noted that a solder layer or tin is previously applied to the surface of the lead frame 100 exposed from the heat-dissipating resin 102 (the LED 108 or a mounting surface of a control IC or chip component (not shown)). By forming the layer, the heat capacity is larger than that of the glass-epoxy substrate and the like, and soldering can be improved, and the component mountability to the lead frame 100 can be improved, and the rust of the wiring can be prevented. It is desirable that no solder layer be formed on the surface (or embedded surface) of the lead frame 100 that is in contact with the heat radiation resin 102. When a solder layer or a tin layer is formed on the surface in contact with the heat radiation resin 102 in this manner, this layer becomes soft during soldering, which may affect the adhesion (or bond strength) between the lead frame 100 and the heat radiation resin 102. . 1 and 2, the solder layer and the tin layer are not shown.

The metal metal plate 110 is made of aluminum, copper, or an alloy containing them as a main component with good thermal conductivity. In particular, in the present embodiment, the thickness of the metal plate 110 is 1 mm, but the thickness can be designed according to the specifications of the backlight or the like (in addition, if the thickness of the metal plate 110 is 0.1 mm or less, heat dissipation and (If the thickness of the metal plate 110 exceeds 50 mm, it is disadvantageous in terms of weight.) The metal plate 110 is not only a plate-like one, but in order to further improve heat dissipation, a fin portion (or uneven portion) is provided on the surface opposite to the surface on which the heat radiating resin 102 is laminated in order to increase the surface area. It may be formed. The total expansion coefficient is set to 8 × 10 ⁻⁶ / ° C. to 20 × 10 ⁻⁶ / ° C. By bringing the coefficient of expansion close to the linear expansion coefficient of the metal plate 110 and the LED 108, warpage and distortion of the entire substrate 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. Further, the metal plate 110 can be screwed to another heat radiating plate (not shown).

  Further, as the lead frame 100, a metal plate mainly made of copper, at least a part of which is punched into a three-dimensional convex shape in advance, can be used. The thickness of the lead frame 100 is desirably 0.1 mm or greater and 1.0 mm or less (more desirably 0.3 mm or greater and 0.5 mm or less). This is because a large current (for example, 30 A to 150 A, which may further increase depending on the number of LEDs to be driven) is required to control the LEDs. Moreover, when the thickness of the lead frame 100 is less than 0.10 mm, pressing may be difficult. If the thickness of the lead frame 100 exceeds 1 mm, pattern miniaturization may be affected at the time of punching with a press. Here, it is not desirable to use a copper foil (for example, a thickness of 10 to 50 microns) instead of the lead frame 100. In the case of the present invention, the heat generated in the LED is widely diffused through the lead frame 100. Therefore, the greater the thickness of the lead frame 100, the more effective the thermal diffusion through the lead frame 100. On the other hand, when a copper foil is used instead of the lead frame 100, the thickness of the copper foil is thinner than that of the lead frame, which may make it difficult for heat diffusion.

  Next, as a conventional example 1, a sample prototype as shown in FIG. 1 was tried using a copper foil (thickness 10 μm) instead of the lead frame 100. First, after patterning a commercially available copper foil into a predetermined shape, it is processed into a convex shape by pressing, and is set between the metal plate 110 on which the second convex portion 114 is formed and the antifouling film 128 as shown in FIG. Tried. However, the pressed copper foil was soft and difficult to handle.

  Next, as Conventional Example 2, a copper foil was formed in a predetermined pattern on the transfer body, and was affixed to the surface of a plate-like uncured heat-dissipating resin 102 having no recess 112. Next, as shown in FIGS. 6 to 7, this plate-shaped uncured heat-dissipating resin 102 is set between a metal plate having a recess and the antifouling film 128, and a mold 126a having a projection on the surface is set. It was heated while being pressed to cure the resin. Thus, the recess 112 was formed in the heat-dissipating resin 102, and a thin copper foil attached to the surface was formed in the shape of the recess of the heat-dissipating resin 102. And LED108 was mounted on this copper foil, and the heat dissipation test was done. However, since the copper foil is thinner than the lead frame, the rate of thermal diffusion through the copper foil was small.

  Next, as a conventional example 3, a lead frame 100 (not subjected to concave three-dimensional processing, plate thickness is 0.3 mm) prepared only in a wiring shape is prepared, and this is a plate shape prepared in the conventional example 2. 6 to 7, the recess processing of the lead frame 100, the recess processing of the metal plate 110, and the molding processing of the heat dissipation resin 102 were simultaneously performed as shown in FIGS. 6 to 7. . However, since the lead frame 100 and the metal plate 110 are hard, the required concave portion 112 and convex portion 114 cannot be formed.

  On the other hand, in the case of the third embodiment, as shown in FIGS. 6 and 7, the lead frame 100 having the concave portion 112 and the metal plate 110 having the convex portion 114, which are preliminarily molded by the molds 126a and 126b, are used. It will be. Therefore, even when the lead frame 100 or the metal plate 110 is thick (for example, 0.1 mm to 1.0 mm and thick and difficult to bend compared to the copper foil), a highly accurate one is inexpensively specified. Can be processed into a shape (including punching and three-dimensional processing). Since the lead frame 100 and the metal plate 110 processed and molded in this way are integrated by the heat radiation resin 102, a short circuit between the lead frame 100 and the metal plate 110 can be prevented.

  Further, by devising a temperature profile when the heat-dissipating resin 102, the lead frame 100, and the metal plate 110 are hot-pressed, the heat-dissipating resin 102 is softened (decrease in viscosity) and is brought into close contact with each other. Thus, by separating the molding process of the lead frame 100 and the metal plate 110 and the integration process using the heat radiation resin 102 separately, the light emitting module using the lead frame 100 and the metal plate 110 having a large thickness and excellent heat dissipation. Can be formed at low cost.

  Further, in the case of the third embodiment, the recess 112 is formed in the lead frame 100 on which the LED 108 is mounted, and the lead frame 100 formed on the wall surface of the recess 112 reflects the light emitted from the LED 108 and from the LED 108. The generated heat can be diffused throughout the light emitting module via the side surface of the recess 112, and the luminous efficiency is further enhanced and the heat dissipation effect is further enhanced. Since the lead frame 100 also serves as a reflective surface made of metal in this manner, the connection area between the lead frame 100 and the heat-dissipating resin 102 can be expanded, so that heat can be easily transferred from the lead frame 100 to the heat-dissipating resin 102. Further, as shown in FIG. 1 and the like, by forming the metal plate 110 on the convex portion 114 in advance, the thickness of the heat radiation resin 102 formed between the lead frame 100 and the metal plate 110 can be made thin and uniform. Therefore, it goes without saying that the thermal conductivity from the lead frame 100 to the heat radiation resin 102 to the metal plate 110 can be improved.

  Thus, the metal plate 110 having at least a part of the protrusion 114 formed thereon and the lead frame 100 mainly composed of copper having at least a part of the recess 112 formed therein are fitted into the protrusion 114 and the recess 112. In this state, the heat dissipation resin 102, which is an insulating layer made of an inorganic filler and a resin composition containing a thermosetting resin, is fixed, and two or more light emitting elements are mounted on the lead frame 100 of the recess 112, A light emitting module in which a part of the lead frame 100 is a light reflecting surface is provided.

  As described above, since the light emitting module according to the present invention can be used to stably light a large number of light emitting elements, in addition to backlights such as liquid crystal TVs, projectors, projectors, etc. It can also be applied to color rendering applications.

Top view and cross-sectional view illustrating a light-emitting module according to Embodiment 1 Top view and cross-sectional view illustrating a heat dissipation mechanism in Embodiment 1 Sectional drawing of the light emitting module in Embodiment 2 Top view of a light emitting module in which the shape of a convex part for mounting an LED is an oval (including ellipse, oval type, etc.) donut shape Sectional drawing explaining a mode that a part of metal plate is processed into convex shape Sectional drawing which shows an example of the shaping | molding method of a light emitting module Sectional drawing which shows an example of the shaping | molding method of a light emitting module Sectional drawing which shows an example of the conventional light emitting module

Explanation of symbols

100 Lead frame 102 Heat radiation resin 104 Arrow 106 Dotted line 108 LED
DESCRIPTION OF SYMBOLS 110 Metal plate 112 Concave part 114 Convex part 116 Heat sink 118 Resin 120 Lens 124 Burr 126 Mold 128 Anti-stain film

Claims (14)

A metal plate having a convex part formed at least in part;
A lead frame mainly composed of copper having a recess formed at least in part,
In a state where the convex portion and the convex portion are fitted, it is fixed by an insulating layer comprising an inorganic filler and a resin composition containing a thermosetting resin,
Two or more light emitting elements are mounted on the lead frame of the recess,
A light emitting module in which a part of the lead frame is a light reflecting surface. The light emitting module according to claim 1, wherein the insulating layer formed between the metal plate and the lead frame has a thickness of 50 microns or more and 500 microns or less. 2. The light emitting module according to claim 1, wherein the variation in thickness of the insulating layer between the lead frame and the metal plate is 200 microns or less. The light emitting module according to claim 1, wherein the lead frame occupies an area of 50% or more and 95% or less of a side surface forming the convex portion. The light emitting module according to claim 1, wherein the plurality of light emitting elements are light emitting elements having at least two kinds of different light emission colors. The light emitting module according to claim 1, wherein at least one of the plurality of light emitting elements has a white emission color. The light emitting module according to claim 1, wherein the lead frame has a thickness of 0.10 mm to 1.0 mm, and at least a part of the lead frame is processed into a shape having a convex portion before being integrated with the insulating layer. The light emitting module according to claim 1, wherein the insulating layer has a thermal conductivity of 1 W / (m · K) to 20 W / (m · K). The light emitting module according to claim 1, wherein the inorganic filler includes at least one selected from the group consisting of Al ₂ O ₃ , MgO, BN, SiO ₂ , SiC, Si ₃ N ₄ , and AlN. The light emitting module according to claim 1, wherein the thermosetting resin includes at least one selected from the group consisting of an epoxy resin, a phenol resin, and an isocyanate resin. The light emitting module according to claim 1, wherein the insulating layer is white. The light emitting module according to claim 1, wherein a cross section of the convex portion is a trapezoid. Sn is 0.1 wt% to 0.15 wt%, Zr is 0.015 wt% to 0.15 wt%, Ni is 0.1 wt% to 5 wt%, Si is 0.01 wt% to 2 wt%, Zn is Lead frame mainly composed of copper containing at least one selected from the group of 0.1 wt% to 5 wt%, P is 0.005 wt% to 0.1 wt%, and Fe is 0.1 wt% to 5 wt%. The light emitting module according to claim 1, wherein: At least a part of the metal plate with a convex part and a lead frame with at least a part of the concave part are set so that the convex parts are fitted to each other with an insulating resin sandwiched in the middle,
Further, with the antifouling film inserted between the lead frame and the mold, pressing to cure the insulating resin, fixing the metal plate and the lead frame,
A method of manufacturing a light emitting module in which a light emitting element is mounted on the lead frame.

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