JP2007173441A - Light-emitting module, and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a ceramic substrate has difficulty in processing when the ceramic substrate is used as a heat radiating substrate of an LED. <P>SOLUTION: A heat radiating resin 102 as an insulation layer containing an inorganic filler and a resin compound containing a thermosetting resin, and a lead frame 100 principally containing copper are formed so as to match a concave portion shape of a metal substrate 112 having the concave portion on its one surface, and an LED 108 is mounted on the lead frame 100 portion on the bottom of the concave portion. With this configuration, the heat generated in the LED 108 can spread to the entire light-emitting module via the lead frame 100, and the thickness of the heat radiating resin 102 can be thinned and equalized. Thus, the heat of the lead frame 100 can be efficiently diffused to the metal plate 112. <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. 6 is a cross-sectional view illustrating an example of a light emitting module. In FIG. 6, 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. 6, 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 response to such needs, white LEDs and the like have limitations, and in recent years, red (red), green (green), and blue (blue) single-color light emitting elements, and further purple, orange, red purple, cobalt Attempts have been made to expand the color display range (specifically, the CIE color system, etc.) by adding a special color light emitting element that emits a special color such as blue.

  When such a light emitting module as shown in FIG. 6 responds to such needs, while mounting each of these light emitting elements one by one in the concave portion 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 these reasons, for example, immediately after the liquid crystal TV is turned on (operated), the LED portion is at room temperature (for example, 25 ° C.). (→ 50 ° C. → 60 ° C.), for example, a phenomenon such as a decrease in red light emission efficiency may occur, and the color reproducibility and the brightness of the backlight may also change.

  On the other hand, as shown in FIG. 6, 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 viewpoint of heat dissipation, while a filter or diffusion is used. It becomes difficult to produce a white color by mixing light using a plate or the like (or to produce a white color having high color rendering properties by mixing RGB + special colors).

Therefore, there are a large number of light-emitting elements that can cope with higher luminance of the light-emitting elements (in this case, it is necessary to pass a large current) and multi-LEDs (multiple LEDs are mounted at a high density). There is a demand for a light-emitting module that can be mounted at high density and has high workability 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 uses a metal lead frame, a highly heat-dissipating insulator and a metal plate instead of a ceramic substrate, thereby producing a light-emitting module with good workability and its manufacture. It aims to provide a method.

  In order to solve the above problems, the present invention directly mounts a light emitting element such as an LED on a metal lead frame having a high heat dissipation property, and the heat of the lead frame passes through a heat dissipation resin having a high heat dissipation property. Then, it is transmitted to the metal substrate for heat dissipation formed on the back surface.

  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 in Embodiment 1, in which FIG. 1A is a top view and FIG. 1B is a cross-sectional view taken along an arrow 104a in FIG. 1, 100 is a lead frame, 102 is a heat radiation resin, 104a is an arrow indicating the cross section of FIG. 1B, 104b is an arrow indicating light emitted from the side surface of the LED 108, and 106 is a bent position of the lead frame 100. The dotted line 108 indicates an LED, and the LED 108 is shown as an example of a light-emitting element such as a laser, and needless to say, it can be applied to other light-emitting elements. 110 is a transparent resin, 112 is a metal substrate, 114 is a heat sink for heat dissipation, and 116 is a recess. Then, the metal substrate 112 in which the recesses 116 are formed and the lead frame 100 in which the recesses 116 are formed are integrated via the heat radiation resin 102 so that the recesses overlap each other. The recess 116 formed in the metal substrate 112 is a first recess, and the recess 116 formed in the lead frame 100 is a second recess. In FIG. 1B, the first recess is also the second recess. Both are also shown as recesses 116.

  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 part of the outer periphery of the lead frame 100 is surrounded by the heat radiation resin 102. A dotted line 106 indicates a bending position of the lead frame 100, and the lead frame 100 is bent at the position of the dotted line 106 in FIG. 1A to form a recess 116 as shown in FIG. Then, the LEDs 108 are disposed so as to straddle the plurality of lead frames 100 (note that the LEDs 108 do not necessarily have to be mounted across). Note that members such as a wire wire for mounting the LED 108 (wire wire is in the case of wire bonding connection but conductive resin or solder (in the case of flip chip mounting or the like)) 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 104a in FIG. In FIG. 1B, at least one surface of the metal substrate 112 is processed to be concave. Similarly, the lead frame 100 is also pressed in accordance with the concave shape. Then, as shown in FIG. 1B, the lead frame 100 is fixed on the metal substrate 112 so as to be embedded in the heat radiation resin 102. An arrow 104b in FIG. 1B corresponds to light emitted from the LED. As shown in FIG. 1B, by processing the lead frame 100 into a concave shape (or a parabolic shape, etc.), the light emitted from the side surface of the LED 108 is reflected on the surface of the lead frame 100 as indicated by an arrow 104b. The brightness of the light emitting module can be increased.

  The transparent resin 110 that covers the LED 108 is preferably PMMA (polymethyl methacrylate) or a 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 (that is, flexible) resin material, when the LED 108 generates heat and thermally expands, stress concentration on the connection portion between the LED 108 and the lead frame 100 can be prevented. 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).

  As shown in FIG. 1B, the lead frame 100 and the metal substrate 112 are formed in a concave shape so that the thickness of the heat-dissipating resin 102 that insulates the lead frame 100 and the metal substrate 112 can be reduced (and more uniform). The thermal diffusibility from the frame 100 to the metal substrate 112 can be enhanced. Then, the heat generated in the LED 108 is transmitted to the lead frame 100 and is diffused through the heat radiation resin 102 to the metal substrate 112 and further to the heat sink 114 fixed to the metal substrate 112.

In FIG. 1B, 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). Meanwhile, 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, Al ₂ O ₃ of large particle size small particle size in the gap Al ₂ O ₃ (average particle size 12 microns) (average particle size 3 microns) Therefore, Al ₂ O ₃ can be filled at a high concentration up to nearly 90% by weight. As a result, the thermal conductivity of the heat radiation resin 102 is about 5 W / (m · K). 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 attached to the lead frame 100 can be easily transferred to the metal substrate 112, but conversely, withstand voltage is a problem, and if it is too thick, the heat resistance increases. In consideration of the thermal resistance, the optimum thickness may be set to 50 microns or more and 500 microns or less.

  2A and 2B are a top view and a cross-sectional view illustrating a heat dissipation mechanism in the first embodiment. In FIG. 2, reference numeral 116 denotes a recess, and the LED 108 is mounted on the bottom portion of the recess 116 formed by the lead frame 100 or the metal substrate 112. The arrows 104c and 104d in FIG. 2 indicate the direction of diffusion 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 104c 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. On the other hand, the heat transmitted to the lead frame 100 is transmitted to the metal substrate 112 through the heat radiation resin 102 as indicated by an arrow 104d in FIG. The heat of the metal substrate 112 is transmitted to the heat sink 114 and the like. Thus, since the heat generated in the LED 108 can be diffused at a high speed, the LED 108 can be efficiently cooled.

  As described above, the heat generated by the LED 108 is diffused over a wide range as shown by the arrow 104c through the portion of the lead frame 100 that also serves as the reflection surface on the side surface of the recess 116, and efficient heat diffusion is possible. It becomes.

  2B is a cross-sectional view of the LED 108 portion of FIG. 2A (for example, corresponding to the arrow 104a in FIG. 1A). In FIG. 2B, the state in which the heat generated in the LED 108 diffuses through the lead frame 100 is indicated by an arrow 104c, and the state in which the heat from the lead frame 100 diffuses to the metal substrate 112 through the heat radiation resin 102 is indicated by an arrow 104d. ing. Further, as shown in FIG. 2B, in the first embodiment, the thickness of the heat dissipation resin 102 is increased by matching the shape of the recess 116 of the metal substrate 112 with the shape of the recess 116 of the heat dissipation resin 102 and the lead frame 100. Thin and uniform. Therefore, even when the heat radiating resin 102 having a lower thermal conductivity than the lead frame 100 or the metal substrate 112 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 116 with high density.

  This will be described in more detail. The plurality of LEDs 108 are mounted on the lead frame 100 as shown in FIG. The plurality of LEDs 108 are supplied with current from the plurality of lead frames 100 and emit light in a predetermined color. In FIG. 1, a connection portion (for example, connection by a wire bonder) between the LED 108 and the lead frame 100 is 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.

  The LED 108 is desirably mounted on the bottom of the recess 116 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 a predetermined 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 116, and the lead frame 100 is also widely formed on the side wall surface of the recess 116 (desirably 50% to 95% of the side wall surface). ) When the area ratio of the lead frame 100 in the side wall is less than 50% (that is, the ratio of the heat radiation resin 102 is 50% or more), the heat conduction by the lead frame 100 is affected, and the amount of light reflection by the surface of the lead frame 100 can be reduced. There is sex. 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%), that is, when the interval between the lead frames 100 is narrowed, the possibility of short-circuiting increases. The metal substrate 112 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 radiation resin 102 formed between the metal substrate 112 having the recess 116 and the lead frame 100 is preferably 50 microns or more and 500 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 substrate 112 and the lead frame 100 is lowered, which may affect the reliability. On the other hand, if the thickness exceeds 500 microns, the thermal conductivity (heat dissipation) from the lead frame 100 to the metal substrate 112 may be lowered, affecting the quality (light emission characteristics).

  The thickness variation of the insulating layer is desirably 200 microns or less (more preferably 100 microns or less). As shown in FIG. 1B, in the first embodiment, by forming the recess 116 in the metal substrate 112, the thickness of the heat dissipation resin 102 that insulates between the lead frame 100 and the metal substrate 112 is reduced and uniform. Can be realized. On the other hand, when the thickness variation (or thickness difference) of the heat dissipation resin 102 sandwiched between the lead frame 100 and the metal substrate 112 becomes as large as 200 microns or more, the thermal conductivity (heat dissipation) from the lead frame 100 to the metal substrate 112. The quality (light emission characteristics) may be reduced.

  The shape of the recess 116 is preferably a shape that becomes narrower toward the bottom. This is 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, reference numeral 118 denotes a lens. 3A shows a light emitting module when the transparent resin 110 is processed into a lens shape, and FIG. 3B shows a light emitting module when the lens 118 is mounted on the transparent resin 110.

  3A and 3B, an arrow 104e 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 concave portion 116 (or the wall surface constituting the concave portion 116) of the lead frame 100 and guided to the outside as indicated by an arrow 104e. Here, by performing the high light reflectance treatment of the surface treatment of the lead frame 100, the light reflectance can be increased. 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 the high light reflectivity treatment process is desirably a wide area at least larger than the portion where the concave portion 116 of the lead frame 100 is formed. Furthermore, it is desirable that the lead frame 100 other than the recess 116 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.

  In addition, it is desirable that 50% or more and 95% or less of the area of the side surface forming the recess 116 is the lead frame 100. Note that it is desirable that the heat-dissipating resin 102 be a color having a high light reflectance such as white. However, even when the heat-dissipating resin 102 is white, the lead frame 100 may have a higher light reflectance. In this case, when the area of the lead frame is less than 50%, the light reflection on the side surface is mainly caused by the heat radiation resin 102, which may affect the light emission efficiency (light emission characteristics) of the light emitting module. Further, when the ratio of the lead frame is 95% or more, it may be difficult to manufacture the lead frame 100 because the processing of the lead frame 100 becomes difficult.

  Note that the size of the lens 118 is desirably equal to or larger than the width of the recess 116 as shown in FIG. By increasing the size of the lens 118, a play portion when the lens 118 is mounted can be increased, and thus optical alignment can be easily performed. In particular, by molding the lead frame 100 as described in the third embodiment, the processing accuracy of the lead frame 100 (particularly the parallelism between the bottom of the recess 116 and a plane other than the recess 116) is increased. Therefore, the optical axis can be aligned with high accuracy only by setting the LED 108 at the bottom of the recess 116 and the lens 118 so as to cover the periphery of the recess 116.

  Note that the light-emitting element mounted in the recess 116 is preferably a light-emitting element having at least one or more kinds (more preferably, two or more kinds of light-emitting elements having different emission colors that can improve color rendering properties and reduce costs). By using a plurality of LEDs 108 having different emission colors, the color rendering property can be improved. By mounting a plurality of these LEDs in one recess 116 at a high density, the color mixing property can be improved. 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 property, 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 electrically controlled individually via the lead frame 100 even when the temperature of the light emitting module itself rises.

(Embodiment 3)
Hereinafter, an example of the manufacturing method of the light emitting module in Embodiment 3 of this invention is demonstrated.

  4 and 5 are cross-sectional views showing an example of a method for manufacturing a light emitting module according to the third embodiment. In FIG. 4, 120a and 120b are molds, 122 is a dirt prevention film, and 124 is a burr. 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. This punching process generates burrs 124 in the lead frame 100. Next, as shown in FIG. 4, an uncured heat radiation resin 102 and a metal substrate 112 are set under the lead frame 100. And in the state which positioned these members, it sets between metal mold | die 120a, 120b. Next, the lead frame 100 is pressed against the heat radiation resin 102 by moving the molds 120a and 120b in the direction of the arrow 104f by a press device (not shown in FIG. 4), and the heat radiation resin 102 is moved at a predetermined temperature. Heat cure. Moreover, as shown in FIG. 4, it is desirable to set the antifouling film 122 between the lead frame 100 and the mold 120a. Further, it is desirable that the antifouling film 122 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 120a and 120b, the air can be easily released as indicated by the arrow 104g (the air is passed through the antifouling film 122). 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 substrate 112 and the heat radiation resin 102.

  It should be noted that 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 124 generated at the end of the lead frame 100 is on the dirt prevention film 122 side. In this way, when the lead frame 100 is pressed, the burr 124 bites into the antifouling film 122, 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. 5 is a cross-sectional view after the press working is completed. As shown in FIG. 5, the light emitting module is completed by moving the molds 120a and 120b in the direction of the arrow 104h (note that the LED 108 and the like are not yet mounted in the state of FIG. 5). Then, the LED 108 is mounted on the light emitting module of FIG. 5 and further covered with a resin (transparent resin) 110, whereby the light emitting module as shown in FIG. 1 is completed. The burr 124 can be removed and eliminated during press working, but may 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 have one containing at least one selected from the group consisting of Al ₂ O ₃ , MgO, BN, 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. When BN is used, the linear thermal expansion coefficient can be reduced. Thus, the insulating layer 102 having a thermal conductivity of 1 W / (m · K) to 10 W / (m · K) can be formed. In addition, when heat conductivity is less than 1 W / (m * K), it has the influence which reduces the heat dissipation of a light emitting module. Further, if the thermal conductivity is to be made higher than 10 W / (m · K), it is necessary to increase the amount of filler, which may affect the workability during pressing.

  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 is substantially spherical and has a diameter of 0.1 to 100 microns, but the smaller the particle size, the better the filling rate into the resin. Therefore, the filling amount (or content rate) 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 curing may be reduced, and the adhesiveness between the heat-dissipating resin 102 and the lead frame 100 (for example, lead) Even when the frame 100 is embedded in the heat-dissipating resin 102 or when it is attached to the surface thereof, there is a possibility that the adhesiveness of the frame 100 may be reduced.

  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 insulator made of the heat radiation resin 102 is reduced, the heat generated in the LED 108 mounted on the lead frame 100 can be easily transferred to the metal substrate 112, but conversely, the insulation breakdown voltage becomes a problem. Therefore, in view of the withstand voltage and thermal resistance, the thickness may be set to 50 to 500 microns.

  Next, the material of the lead frame 100 will be described. The lead frame material is preferably an alloy mainly composed 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, at least one selected from the group consisting of copper, which is the lead frame 100, and at least Sn, Zr, Ni, Si, Zn, P, Fe, etc. It is desirable to use an alloy made of the above materials. For example, an alloy (hereinafter referred to as Cu + Sn) in which Cu is a main component and Sn is added thereto 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, when lead frame 100 is manufactured using copper without Sn (Cu> 99.96 wt%), the conductivity is low, but distortion is generated particularly in the formed portion of recess 116 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 alloy with 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% or less is desirable. When the amount added is less than 0.015 wt%, the effect of increasing the softening temperature may be small. Moreover, when there are more addition amounts than 0.15 wt%, it may have the influence which reduces an electrical property. 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 is more than the ratio described here, there exists a possibility of reducing 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 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 spring back is bent to the angle required for bending. However, if the pressure is removed, the reaction force will be returned to the original state to some extent by the reaction force), and the formation accuracy of the recess 116 can be improved. As described above, the lead frame material can be made of Cu alloy to lower the electrical conductivity, and further softened to improve the workability, and the heat dissipation effect of the lead frame 100 can be enhanced.

  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, it is possible to improve the component mountability with respect to the lead frame 100 having a larger heat capacity than the glass epoxy substrate or the like and difficult to solder, and to prevent rust as wiring. 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, the 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 metallic metal substrate 112 is made of aluminum, copper, or an alloy containing them as a main component, which has good thermal conductivity. In particular, in this embodiment, the thickness of the metal substrate 112 is set to 1 mm, but the thickness can be designed according to product specifications such as a backlight (in the case where the thickness of the metal substrate 112 is 0.1 mm or less, heat dissipation properties). (If the thickness of the metal substrate 112 exceeds 5 mm, it is disadvantageous in terms of weight). As the metal substrate 112, not only a plate-shaped substrate but also fin portions (or uneven portions) are formed on the surface opposite to the surface on which the insulator is laminated in order to increase the surface area in order to further improve heat dissipation. You may do it. The linear expansion coefficient is 8 × 10 ⁻⁶ / ° C. to 20 × 10 ⁻⁶ / ° C. By bringing the linear expansion coefficient close to the linear expansion coefficients of the metal substrate 112 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 important from the viewpoint of reliability. The metal substrate 112 can also be screwed to another heat radiating plate (not shown).

  As the lead frame 100, a metal plate mainly made of copper, at least a part of which is punched into a three-dimensional recess 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, a large current of 30 A to 150 A is required to control the LED, which may be further increased depending on the number of LEDs to be driven). Further, when the lead frame 100 is less than 0.10 mm thick, it may be difficult to press due to thinness. Further, if the thickness of the lead frame 100 exceeds 1 mm, there may be an effect of reducing the miniaturization of the pattern at the time of punching by press working. 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 in place of the lead frame 100, the thickness of the copper foil is thinner than that of the lead frame 100, which may make it difficult to thermally diffuse.

  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, a recess was processed by pressing, and an attempt was made to set between the metal substrate 112 on which the recess was formed as shown in FIG. 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 that does not have the recess 116. Then, as shown in FIGS. 4 to 5, the plate-shaped uncured heat radiation resin 102 is set between a metal substrate having a recess and the antifouling film 122, and a mold 120 a having a protrusion on the surface is set. It was heated while being pressed to cure the resin. In this way, the recess 116 was formed in the heat-dissipating resin 102, and a thin copper foil attached to the surface was formed into the recess shape 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 third conventional example, a lead frame 100 that has only been punched into a wiring shape (a concave three-dimensional process has not been performed and a thickness of only 0.3 mm that has not been bent) has been prepared. Affixed on the plate-shaped uncured heat radiation resin 102 prepared in Conventional Example 2, and processing the recess 116 of the lead frame 100 and the recess 116 of the heat dissipation resin 102 as shown in FIGS. I went at the same time. However, since the lead frame 100 is hard, the lead frame 100 could not be processed into the desired shape of the recess 116. It has been found that to form the recess 116 simultaneously with the heat radiation resin 102, it is necessary to use a thinner (softer) copper foil.

  On the other hand, in the case of Embodiment 3, as shown in FIGS. 4 and 5, a lead frame 100 having a stable dimensional shape, which has been molded in advance with the molds 120a and 120b, is used. Therefore, even when a lead frame 100 having a large thickness (for example, 0.1 mm to 1.0 mm, thick and difficult to bend compared to a copper foil) is used, a high-precision one with a predetermined shape ( Punching and three-dimensional processing). Since the lead frame 100 processed and molded in advance and the heat-dissipating resin 102 are integrated, the shape accuracy of the lead frame 100 can be kept high.

  Furthermore, by devising the temperature profile when heat-pressing the heat-dissipating resin 102 and the lead frame 100, the heat-dissipating resin can be softened (decrease in viscosity) and the influence on the lead frame 100 can be suppressed. In this way, a light emitting module using a lead frame having a large thickness and excellent heat dissipation by dividing the molding process of the lead frame 100 alone and the molding process of the lead frame 100 and the heat radiation resin 102 which are molded in advance separately. Can be formed at low cost.

  Further, in the case of the third embodiment, the lead frame 100 is formed on the wall surface of the recess 116 in which the LED 108 is mounted, and the lead frame 100 formed on the wall surface of the recess 116 reflects the light emitted from the LED 108. The heat generated from the LED 108 can be diffused throughout the light emitting module via the side surface of the recess 116, and the light emission efficiency is 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 substrate 112 in the recess 116 in advance, the thickness of the heat radiation resin 102 formed between the lead frame 100 and the metal substrate 112 can be made thin and uniform. Needless to say, the thermal conductivity from the lead frame 100 to the heat radiation resin 102 to the metal substrate 112 can be improved.

  In this way, the metal substrate 112 having the recess 116 (corresponding to the first recess) formed on one side, the lead frame 100 mainly composed of copper having the recess 116 (corresponding to the second recess), and the metal substrate 112. And a heat radiation resin 102, which is an insulating layer containing an inorganic filler and a resin composition containing a thermosetting resin, formed between the lead frame 100 and the insulating layer in the first recess. The second recess is formed through the heat dissipation resin 102, and a part of the outer peripheral portion of the lead frame 100 is surrounded by the heat dissipation resin 102 as the insulator, and the lead frame in the second recess Provided is a light emitting module in which one or more light emitting elements such as LEDs are mounted on 100.

  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.

A top view and a cross-sectional view illustrating the light-emitting module according to Embodiment 1. A top view and a cross-sectional view illustrating a heat dissipation mechanism in the first embodiment. Sectional drawing of the light emitting module in this Embodiment 2. Sectional drawing which shows an example of the manufacturing method of the light emitting module in this Embodiment 3. Sectional drawing which shows an example of the manufacturing method of the light emitting module in this Embodiment 3. Sectional drawing which shows an example of light emitting module

Explanation of symbols

100 Lead frame 102 Heat radiation resin 104 Arrow 106 Dotted line 108 LED
110 Transparent resin 112 Metal substrate 114 Heat sink 116 Concave portion 118 Lens 120 Mold 122 Antifouling film 124 Burr

Claims (14)

A metal substrate having a first recess formed on one side;
A lead frame mainly composed of copper in which a second recess is formed;
An insulating layer formed between the metal substrate and the lead frame and including an inorganic filler and a resin composition including a thermosetting resin;
The second recess of the lead frame is formed in the first recess of the metal substrate via the insulating layer;
A portion of the outer periphery of the lead frame is surrounded by the insulator;
One or more light emitting elements are mounted on the lead frame in the second recess. 2. The light emitting module according to claim 1, wherein the thickness of the insulating layer formed between the metal substrate and the lead frame is not less than 50 microns and not more than 500 microns. 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 substrate 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 the side surface forming the recess. The light emitting module according to claim 1, wherein the light emitting element is a light emitting element having at least one kind of different emission colors. The light emitting module according to claim 1, wherein at least one of the 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 recess before being integrated with the insulating layer. The light emitting module according to claim 1, wherein the thermal conductivity of the insulating layer is 1 W / (m · K) or more and 10 W / (m · K) or less. 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, 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 the recess has a shape that narrows toward the bottom. 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: An uncured insulating resin is set between the metal substrate on which the first recess is formed and the lead frame on which the second recess is formed,
With the antifouling film inserted between the lead frame and the mold, the insulating resin is cured between the metal substrate and the lead frame by pressing, and the second recess is inserted into the first recess. Forming a molded body in which a part of the outer periphery of the lead frame is surrounded by an insulating resin while fitting the recess,
A method for manufacturing a light emitting module, wherein a light emitting element is mounted in a second recess of the molded body and sealed with a resin.

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