JP2006179544A - Led light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LED light source in which luminous flux lowers little even in case of an LED light source having relatively high power consumption per LED and a long lifetime is realized. <P>SOLUTION: In the LED light source mounting an LED chip on a substrate, the LED chip is covered with first translucent resin which is covered with second translucent resin. The first resin is silicon resin, the second resin has a glass transition point of 100°C or above, and power consumption per LED chip is 0.1 W or above. A small LED light source having a high luminous flux in which lifetime characteristics are improved can thereby be provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an LED light source that realizes a long service life with little decrease in luminous flux even in an LED light source with relatively large power consumption per LED.

Since white LEDs do not use mercury like fluorescent lamps, they are being developed as next-generation illumination light sources because they are a light source that is easier on the environment, and because glass is not used and glass fragments are not scattered. Yes. As an example of a conventional LED light source, one in which a fluorescent layer 20 is disposed in the periphery of an LED (GaN die) 12 and a lens 24 is disposed thereon is known. In addition, a translucent epoxy resin is generally introduced as a member constituting the lens (for example, Patent Document 1).
JP 2000-244021 A (see paragraph 0004)

  The LED as described above is generally designed so that the size of the LED chip is about 0.3 mm square and the power consumption is 0.07 W (= 3.5 V × 0.02 A) per LED. ing. However, it has been found that if the input power to the LED is increased in order to obtain a large amount of light and is 0.1 W or more, the luminous flux maintenance factor of the LED is extremely lowered. When the cause was analyzed, it was found that the resin around the LED deteriorates and turns yellow.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an LED light source that has a long luminous flux and has improved life characteristics.

  In order to solve the above-described conventional problems, an LED light source according to the present invention is an LED light source in which an LED chip is mounted on a substrate, and the LED chip is covered with a first translucent resin, The first resin is covered with a second translucent resin, the first resin is a silicone resin, and the glass transition temperature of the second resin is 105 ° C. or higher, and the LED The power consumption per chip is 0.1 W or more.

  In a preferred embodiment, when the refractive index of the first resin is n1 and the refractive index of the second resin is n2, the relationship of n1 <n2 is satisfied.

  In a preferred embodiment, the second resin has a configuration that is an epoxy resin.

  In a preferred embodiment, the LED light source has an LED chip mounted on a substrate, wherein the LED chip is covered with a first translucent resin, and the first resin is a second translucent resin. The second resin is covered with a third translucent resin, the first resin is a silicone resin, and the second resin has a glass transition temperature. The resin is 105 ° C. or higher, and the power consumption per LED chip is 0.1 W or higher.

  In a preferred embodiment, when the refractive index of the first resin is n1, the refractive index of the second resin is n2, and the refractive index of the third resin is n3, n1 <n2 <n3 This relationship holds.

  In a preferred embodiment, the second resin has a configuration that is a resin whose main material is epoxy.

  In a preferred embodiment, the third resin has a configuration that is a resin whose main material is epoxy.

  In a preferred embodiment, the power consumption per LED chip is 1 W or more, and the glass transition temperature of the third resin is 105 ° C. or more.

  In a preferred embodiment, the first resin includes a fluorescent material.

  In a preferred embodiment, the first resin has an average thickness of 0.05 to 2 mm.

  In a preferred embodiment, the average thickness of the first resin is 0.5 mm or less.

  In a preferred embodiment, the light emission center wavelength of the LED chip is 350 to 500 nm, and the LED chip is configured to light white in combination with the light emission of the fluorescent material.

  As described above, the present invention is an LED light source in which an LED chip is mounted on a substrate, the LED chip is covered with a first light-transmitting resin, and the first resin is a second light-transmitting resin. Covered with a translucent resin, the first resin is a silicone resin, the glass transition temperature of the second resin is 105 ° C. or more, and the power consumption per one LED chip is With the configuration of 0.1 W or more, it is possible to provide an LED light source with a large luminous flux and a small LED light source with improved life characteristics.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 shows an LED light source 104 according to the first embodiment of the present invention.

  In FIG. 1, LEDs 102 are arranged on a substrate 101. A total of 64 LEDs 102 are arranged in a range of 2 × 2 cm, 8 × 8. Reference numeral 103 denotes an electrode for supplying power to the LED light source 104.

  FIG. 2 shows an enlarged cross-sectional view of the LED light source 104 on the A-A ′ plane. An LED chip 201 is flip-chip mounted on the substrate 101, and a first resin 202 is formed so as to cover the LED chip 201. A second resin 203 is formed so as to cover the first resin 202, and a third resin 204 is formed so as to cover the second resin 203.

  In addition, a reflection plate 205 is installed around the LED on the substrate so as to be able to extract light toward the light emitting direction at the top in the drawing so as to surround the LED chip.

  The LED element 201 is a GaN-based LED element having a light emission center wavelength of 350 to 500 nm. The size of the light emitting surface is 0.3 to 5 mm square. In the present embodiment, the emission center wavelength is 460 nm, and the size of the light emitting surface is 0.3 mm square.

  The substrate 101 is a substrate mainly made of aluminum, and is made of a composite layer including an insulating layer and an Al layer. The thickness is about 0.01 to 0.5 mm for the composite layer and about 0.5 to 5 mm for the Al layer. In addition, the board | substrate of this Embodiment used the thing whose thickness of a composite layer is 0.3 mm, and Al layer is 1 mm. 64 LEDs 201 are arranged at equal intervals in a 20 mm square area of the substrate. The first resin is a silicone resin mixed with a phosphor that absorbs blue light and emits yellow light. The resin thickness (average thickness) is in the range of 0.05 to 2 mm, and is 0.2 mm in the present embodiment. Adjustment to this range is preferable because light absorption by the resin is relatively small and wavelength conversion by the phosphor can be sufficiently performed.

  For example, YAG yellow phosphor is used as the phosphor. It is an LED light source that outputs white color by blue light emission of LED and yellow light emission of phosphor.

  The second resin 203 is a resin whose main material is epoxy, and has a glass transition point of 105 ° C. Moreover, the thickness of resin is 0.5-5 mm, and is 0.8 mm in this Embodiment.

  The third resin 204 is a resin whose main material is epoxy and has a composition different from that of the second resin. Moreover, it has a lens shape. In particular, these epoxy resins are characterized by having a glass transition point of 105 ° C. or higher, unlike conventional epoxy resins. The glass transition point was measured by the DSC method (= Differential Scanning Calibration).

  The reflection plate 205 has a surface with high reflectivity, and for example, a metal plate, such as a silver plate, can be used as a reflection process on a base such as an aluminum plate or a resin plate. In the case of this embodiment, it is an aluminum plate. The thickness of the reflecting plate varies depending on the size of the chip, but about 10 to 50 times the chip size is appropriate. Since the reflector of this embodiment is a 0.3 mm square chip, a reflector having a thickness of 1 mm was used.

  Although not shown, 32 LED chips configured as described above are connected in series, and are configured in a total of 64 in 2 parallel, and are designed to light up with a direct current of about 100V. Here, since a current of 80 mA is supplied at a voltage of 3.5 V per LED, the power is designed to be supplied with a power of 3.5 V × 0.04 A = 0.14 W.

  In the LED light source 104 of the present embodiment, an Al heat sink having a size of 10 cm × 10 cm × 15 cm (not shown) is mounted on the substrate surface opposite to the surface on which the LEDs are mounted, and the ambient temperature is 60 ° C. Life test was conducted in the environment.

  Moreover, several types of conventional LED light sources were prepared as comparative examples. The conventional LED light source has the same configuration as the LED light source of the first embodiment, the second resin 203 is an epoxy resin, and the glass transition temperature is only 105 to 95 ° C., which is 60 to 95 ° C. Is different.

  When these LED light sources were continuously lit with the above power and the luminous flux maintenance factor was measured, as shown in FIG. 4, the conventional LED light source is extremely luminous flux-maintaining as compared with the LED light source of the present embodiment. It was found that the rate decreased. Further, in detail investigation, it was found that the second resin may be a resin having a glass transition temperature of 105 ° C. or higher. Many epoxy resins having different compositions have been developed and sold, and some have different properties such as thermal expansion coefficient, refractive index, specific gravity, hardness, and bending strength. Products that have silicones bonded to epoxy groups that are close to the properties of silicone resins have been developed. Here, the epoxy resin is a resin whose main material is epoxy, and refers to all resins having an epoxy group. Further, the glass transition temperature is a temperature at which the elastic modulus of the resin rapidly decreases. These resins have many glass transition point temperatures ranging from several tens of degrees Celsius to close to 200 degrees Celsius, but conventionally they have not been considered to be related to the luminous flux maintenance factor of the resins. The resin is yellowed and deteriorates, for example, the bond in the molecule is broken due to various causes. However, it has been found from the results of this embodiment that an LED light source with a higher luminous flux maintenance factor can be obtained by defining the glass transition temperature.

  Here, since the temperature simulation of the LED light source of this Embodiment was performed, it shows below.

  The simulation conditions are as follows. The size of each constituent material is as in the above embodiment. The first resin 202 has a thickness of 0.2 mm, and the second resin 203 has a thickness of 0.8 mm, and is injected to the same height as the reflector. The third resin 204 has a lens shape that is equal to the size of the opening of the reflecting plate 205.

  The physical properties shown in Table 1 were used. Although the physical property values of the respective resins are strictly different, since the differences are relatively small compared to other constituent materials (reflecting plates, substrates, etc.), they were treated as the same.

  The ambient temperature is 60 ° C. air, and the back surface of the substrate is connected to an Al heat sink having the same size as described above. Simulation calculation was performed assuming that 3.5V × 0.04A = 0.14W was charged per LED and 90% of the LED was released as heat.

  FIG. 5 shows the temperature distribution simulation result of the cross section of the LED light source of the present embodiment. As a result, with the LED as a heat source, an isothermal line appears around the LED, and the first resin part has an isothermal line of 70 ° C. or higher, and most of the portions become 70 ° C. or higher during lighting. I understand that. Further, it can be seen that the second resin portion has a temperature range of about 70 ° C. at the maximum and below 63 ° C. at the minimum. The third resin has a temperature of 63 ° C. to about 60 ° C. of the ambient temperature. Further, since the substrate has high thermal conductivity, the temperature gradient is steep (the interval between the isothermal lines is narrow).

  As a result of the above studies, it has been found that if the glass transition point of the second resin is 105 ° C. or higher, the heat resistance of the resin is increased and the deterioration during the lifetime is reduced. In the case of an LED using a phosphor, since the thickness of the first resin is substantially determined from the concentration of the phosphor, the second resin temperature is increased, and the type of the second resin is the LED. It has been found that the lifespan will be greatly determined.

  From the above examination, when the second resin temperature at the time of rated lighting becomes 70 ° C. or more, the influence of the glass transition temperature of the second resin on the lifetime of the LED light source becomes large.

  The second resin temperature becomes 70 ° C. or more when the power consumption of the LED is 0.1 W or more and the thickness of the first resin is less than 2 mm. Further, the thickness of the first resin is required to be at least about 0.05 mm from the accuracy of general manufacturing processes, and therefore, the thickness range of about 0.05 mm to 2 mm is suitable as the thickness range of the first resin. In the case where the first resin contains a phosphor, partially absorbs light emitted from the LED, and is mixed with the wavelength-converted light, the first resin thickness is set to 0.5 mm or less. It is more preferable because it has an effect of reducing light absorption in the resin. As such a preferable example, there is one in which the emission center wavelength of the LED chip is 350 to 500 nm, the phosphor is contained in the first resin, and is lit white.

  Examples of combinations of LED chips and phosphors are those in which the emission wavelength of the chip is about 350 to 400 nm and those in which phosphors that emit light in RGB colors are combined, or the emission wavelength of the chip is about 400 to 500 nm. And a combination with a phosphor exhibiting a fluorescence having a wavelength corresponding to a complementary color, or an example of one or more phosphors emitting light of 500 to 800 nm with the chip of about 400 to 500 nm.

  In the present embodiment, the case of a resin containing epoxy as a main material has been described as the second resin, but it has been confirmed that the same effect can be obtained even with a silicone resin.

  In addition, it has been found that such an effect occurs when the power per LED is 0.1 W or more. When the power is 0.1 W or less, since the light from the LED and the thermal energy are both small, the decrease in the luminous flux maintenance factor is not remarkable. However, when it exceeds 0.1 W, the decrease of the luminous flux maintenance factor increases rapidly. When the conventional LED light source exceeds 0.1 W, yellowing starts in several hundred hours and the luminous flux begins to deteriorate, whereas the LED light source according to the present embodiment does not show yellowing even after 5000 hours or more. It was.

  Moreover, since it is desirable that the third resin is hard in order to cope with an external force or the like, an epoxy resin or the like is preferable. Preferably, the third resin also has a glass transition temperature of 105 ° C. or higher. This is because in the case of an LED having a large output of 1 W or more per LED, the third resin also becomes high temperature, and the third resin will turn yellow unless the glass transition temperature is defined. .

  The upper limit of the glass transition temperature that can be realized by the epoxy resin is substantially about 250 ° C.

  In the present embodiment, the case where an epoxy resin is used as the third resin has been described, but other resins may be used.

  In this embodiment, the DSC method is used as the glass transition point measurement method, but the TMA method may be used. Also, any one of the methods has the same effect if it falls within the scope of the present claims.

  In the present embodiment, the case where the first resin, the second resin, the third resin, and three kinds of resins are used has been described, but the same effect can be obtained even when there is no third resin. I can do it. However, in the case where the refractive index of each resin is the first resin <the second resin <the third resin, the difference in the refractive index between the resins is small, so that the light from the LED chip is taken out. It is preferable because efficiency is improved. The refractive indexes of the present embodiment are the first resin: 1.41, the second resin: 1.45, and the third resin: 1.50. The first resin and the third resin Since the second resin has a refractive index approximately in the middle of the refractive index difference, it is more preferable.

  In this embodiment, the case where the LED chip is flip-chip mounted on the substrate is described. However, as another method of mounting the LED on the other substrate, there is a method of mounting by wire bonding. As shown in this embodiment, it was found that flip chip mounting is preferable. This is because, in flip chip mounting, there is no wire, so there is no failure mode of wire breakage. When various experiments were conducted, especially when the second resin and the third resin had wires, the higher the glass transition point of the resin, the more likely the wire to break due to expansion and contraction due to the heat of the resin. Because it was found that there is.

  Since the LED light source of the present invention can obtain an LED light source having a high luminous flux and a good luminous flux maintenance factor, it is useful for lighting applications such as general lighting and accent lighting. Further, it can also be used as a backlight light source such as a liquid crystal and various light sources for automobiles.

The figure which shows the outline of the LED light source in Embodiment 1 of this invention. The figure which shows the cross section of the LED light source in Embodiment 1 of this invention. The figure which shows the luminous flux maintenance factor of the LED light source Figure showing a conventional LED The figure which shows the temperature simulation result of the LED light source of this invention

Explanation of symbols

101 Substrate 102 LED
DESCRIPTION OF SYMBOLS 103 Electrode 104 LED light source 201 LED chip 202 1st resin 203 2nd resin 204 3rd resin 205 Reflector

Claims (12)

An LED light source having an LED chip mounted on a substrate,
The LED chip is covered with a first translucent resin,
The first resin is covered with a second translucent resin;
The first resin is a translucent silicone resin,
The glass transition temperature of the second resin is 105 ° C. or higher,
The LED light source, wherein power consumption per LED chip is 0.1 W or more. The refractive index of the first resin is n1, and the refractive index of the second resin is n2.
When
2. The LED light source according to claim 1, wherein a relationship of n1 <n2 is established. The LED light source according to claim 1, wherein the second resin is a resin whose main material is epoxy. An LED light source having an LED chip mounted on a substrate,
The LED chip is covered with a first translucent resin,
The first resin is covered with a second translucent resin;
The second resin is covered with a third translucent resin,
The first resin is a silicone resin,
The second resin is a resin having a glass transition temperature of 105 ° C. or higher,
The LED light source, wherein power consumption per LED chip is 0.1 W or more. The refractive index of the first resin is n1, and the refractive index of the second resin is n2.
And when the refractive index of the third resin is n3,
5. The LED light source according to claim 4, wherein a relationship of n1 <n2 <n3 is established. 6. The LED light source according to claim 4, wherein the second resin is a resin whose main material is epoxy. The LED light source according to claim 4, wherein the third resin is a resin whose main material is epoxy. 8. The LED light source according to claim 4, wherein the power consumption per LED chip is 1 W or more, and the glass transition temperature of the third resin is 105 ° C. or more. The LED light source according to claim 4, wherein the first resin contains a fluorescent material. The LED light source according to claim 9, wherein the average thickness of the first resin is 0.05 to 2 mm. The LED light source according to claim 9, wherein an average thickness of the first resin is 0.5 mm or less. 12. The LED light source according to claim 9, wherein a light emission center wavelength of the LED chip is 350 to 500 nm, and is lit in white in combination with light emission of the fluorescent material.

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