JP4165610B2 - Method for manufacturing light emitting device - Google Patents

Description

  The present invention relates to a light-emitting device, and more particularly to a light-emitting device that can prevent generation of a crack or the like due to thermal expansion between a sealing member and a lead portion due to heat generation accompanying an increase in output of the light-emitting portion.

  As a typical structure of a light emitting device using an LED (Light-Emitting Diode) as a light source, there is one that covers a predetermined range of an LED element and a lead part with a light-transmitting sealing material. As this sealing material, there are resins such as epoxy and silicon, and glass, but resins are generally used in terms of moldability, mass productivity, and cost.

  In recent years, the development of high-intensity blue LEDs equivalent to red and green LEDs has led to use in applications such as LED traffic lights or white light emitting LED lamps. In addition, in order to obtain higher brightness, high-power LEDs are being developed, and a high-power type of several watts has already been commercialized. In a high output type LED element, since a large current flows, heat generation at a level that cannot be ignored from the viewpoint of light emission characteristics and durability occurs.

  In such an LED lamp, when packaging is made of a resin material, the LED element generates heat, causing deterioration of the resin material, such as yellowing, and a crack in the package due to a difference in thermal expansion between the members. It is known that peeling occurs. Moreover, in the high output type LED lamp, since the above-mentioned tendency appears remarkably, an LED lamp excellent in durability is desired.

For example, a glass material is used as a package material to improve the occurrence of yellowing and the like, and the heat resistance and durability, which are characteristic of such a resin package (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-204838 (FIG. 1)

  However, according to the conventional light emitting device, when sealing LED elements and the like with glass, it is generally necessary to soften the glass material and apply pressure processing or to form molten glass and integrate it with the LED elements and the like. Therefore, the object to be sealed is thermally expanded by being exposed to heat during processing. And it integrates in this state, is formed as a thing without stress, and is returned to normal temperature. At this time, if the difference between the coefficient of thermal expansion of the LED element and the bonding substrate is large, excessive stress accompanying the thermal shrinkage difference is brought about at the bonding interface, resulting in bonding failure or a sealing material. There is a problem that cracks occur in glass.

  Accordingly, an object of the present invention is to provide a light-emitting device that is not affected by thermal expansion / shrinkage even when heat-processing using glass as a sealing material.

In order to achieve the above-described object, the present invention arranges a submount on which a light-emitting element is mounted so as to straddle the gap between a pair of flat lead portions formed so that the front ends thereof face each other with a predetermined gap. In doing so, the pair of leads has a recessed portion on the top surface of the tip, and the submount is disposed on the recessed portion of the pair of leads so as to straddle the gap, and above and below the light emitting element. Place the glass sheet on the top, place the upper mold so as to cover the upper glass sheet,
A lower mold is disposed so as to cover the lower glass sheet, and the upper mold and the lower mold are transferred to the light emitting element in a state where the upper and lower glass sheets are heated and softened. By moving the glass sheet on the upper side and the lower side by moving in the direction to go, and integrating the upper and lower glass sheets, the light emitting element, the submount, and the lead portion Provided is a method for manufacturing a light emitting device in which an upper surface and a lower surface in the vicinity of a submount are integrally surrounded by a glass portion.

In the method for manufacturing the light emitting device, before Symbol emitting device has a plurality of said pair of lead portions and the light emitting element, the glass sheets of the upper and lower, have a size that a plurality of the light emitting element can sealing And it is preferable that the said several light emitting element is sealed collectively.

In the method for manufacturing the light emitting device, the recess portion of the lead portion are preferably processed from one step lower other portions of the upper surface of the lead portion.

  According to the light emitting device of the present invention, the stress direction is adjusted and the heat is adjusted by surrounding the light emitting element entirely with the translucent glass portion and the metal portion having a coefficient of thermal expansion of 150% to 500%. It is possible to prevent the occurrence of cracks caused by the difference in shrinkage.

  Further, according to the light emitting device of the present invention, the power supply member and the sealing member are formed to have a large coefficient of thermal expansion relative to the light emitting element, and the light emitting element is entirely surrounded by the sealing member including the power supply member. Therefore, it is possible to prevent the occurrence of cracks and the like caused by the difference in heat shrinkage by adjusting the stress direction.

  Further, according to the light emitting device of the present invention, the power supply member and the sealing member are formed so as to have a large coefficient of thermal expansion with respect to the light emitting element or the submount member. The occurrence of cracks and the like that occur can be prevented.

  FIG. 1 is a cross-sectional view showing a configuration of a light emitting device according to a first embodiment of the present invention. Usually, the lead frame is provided with a belt-like portion connecting the outer side of each lead portion on both sides, but the illustration is omitted here. A plurality of LED elements are usually mounted on the lead frame, but only one of them is shown here. Further, in FIG. 1, the submount is illustrated in a non-cross-sectional state.

The light emitting device 10 is a metal lead mounting type, and a GaN-based LED element 1 (thermal expansion coefficient 4.5 to ⁶ × 10 ⁻⁶ / ° C.) which is flip-chip bonded to the mounting surface via bumps 2, A submount 3 on which the LED element 1 is mounted, and a lead portion made of Cu as a power supply member on which the submount 3 is mounted (thermal expansion coefficient 15 to 17 × 10 ⁻⁶ / ° C., thermal conductivity 400 W · m ⁻¹ K ⁻¹ ) 4A, 4B and a transparent glass sealing member 5 that seals the periphery of the LED element 1 as a center.

For example, AlN (aluminum nitride: thermal expansion coefficient 5 × 10 ⁻⁶ / ° C., thermal conductivity 180 W · m ⁻¹ · k ⁻¹ ) is used for the submount 3, and the electrodes 31 A and 31 B connected to the bumps 2 are used. Are formed on the mounting surface side of the LED element 1, and electrodes 32A and 32B for connecting to the pair of lead portions 4A and 4B are formed on the opposite surface (the surface on the lead frame side). The mounting surface of the LED element 1 on the upper surface of the lead portions 4A and 4B is processed one step lower than the other portions, and the submount 3 is disposed in the recessed portion. A through hole 33 is provided in the submount 3 to connect the electrodes 31A, 31B and the electrodes 32A, 32B.

  The sealing member 5 is made of a sheet-like glass having a characteristic of being transparent and having a low melting point and having a coefficient of thermal expansion close to that of the lead portions 4A and 4B (or within a predetermined range of difference in thermal expansion coefficient). Thereby, the translucent glass part which seals a part of LED element 1, submount 3, and lead part 4A, 4B is formed.

  Assuming that the lead 4A is a positive (+) power supply terminal, the current supplied to the lead 4A is such that the lead 4A, one of the electrodes 32A and 32B, one of the via holes 33, one of the electrodes 31A and 31B, and The current flowing to the anode of the LED element 1 through one of the bumps 2 and further from the cathode of the LED element 1 is caused by the other of the bump 2, the other of the electrodes 31A and 31B, the other of the via hole 33, and the electrodes 32A and 32B. The LED element 1 emits light by flowing to the lead portion 4B through the other.

  FIG. 2 is a plan view showing a state in which the submount is mounted on the lead frame. The submount 3 has the LED element 1 mounted at the center. The lead portions 4A and 4B are formed as a part of the lead frame so as to face each other with a predetermined gap on the inner side from the strip portions on both sides, and a pair is assigned to one LED element.

  FIG. 3 is a diagram showing a state immediately before performing glass sealing using a mold. In the same figure, the state cut | disconnected by the AA part of FIG. 2 is shown. Below, the manufacturing method of the light-emitting device 10 is demonstrated with reference to drawings of FIGS.

  First, the LED element 1 provided with the bumps 2 is positioned on the submount 3 and reflowed to electrically connect the bumps 2 and the electrodes 31 and mechanically fix them.

  Next, the LED element 1 mounted on the submount 3 is disposed in the recesses at the tip portions of the lead portions 4A and 4B so that the energization directions are matched. The submount 3 is one in which the electrodes 31A and 31B, the electrodes 32A and 32B, and the via holes 33 are formed in advance.

  Next, the lead frame 6 is carried into the mold, and the glass sheets 7 and 8 are disposed above and below the LED element 1. The glass sheets 7 and 8 are for forming the sealing member 5 and have a size capable of simultaneously sealing a plurality of LED elements 1.

  Next, the upper mold 11 is arranged so as to cover the glass sheet 7, and further, the lower mold 12 is arranged so as to cover the glass sheet 8. Next, the glass sheets 7 and 8 are moved in the direction of the arrows in FIG. 2 in a vacuum atmosphere while the glass sheets 7 and 8 are heated to 450 ° C. and are softened. When the pressure is applied, the glass sheets 7 and 8 are formed in a dome shape like the sealing member 5 shown in FIG. 1 along the recess 11A of the upper mold 11 and the recess 12A of the lower mold 12.

  Next, unnecessary portions such as strips of the lead frame 4 are removed to separate each of the light emitting devices 10 from the lead frame 4.

  When a forward voltage is applied to the light emitting device 10 via the bump 2 electrically connected to the pad electrode 108 and the n-type electrode 109, hole and electron carrier recombination occurs in the active layer of the LED element 1. The light is emitted and the output light is radiated to the outside of the LED element 1 through the sapphire substrate 101. This output light passes through the sealing member 5 and is emitted to the outside.

  According to the first embodiment described above, the following effects are obtained.

(1) Since the LED element 1 having a small coefficient of thermal expansion is sealed so as to be entirely surrounded by the glass material sealing material 5 having a large coefficient of thermal expansion, the internal stress generated based on the difference in coefficient of thermal expansion is the LED. Adjustment is made so as to go to the center of the element 1. That is, even if an internal stress based on the thermal shrinkage of the glass material occurs after the glass processing, the internal stress becomes a compressive force toward the central direction of the LED element 1, so that the glass material having strength against compression is destroyed. A glass sealing structure can be realized.

(2) Since the LED element 1 having a low thermal expansion coefficient is mounted on the submount 3 having a low thermal expansion coefficient and mounted on the lead portions 4A and 4B having a high thermal expansion coefficient, the sealing member 5 is formed. About the glass material which is doing, the adhesiveness with both LED element 1 with small thermal expansion coefficient and lead part 4A, 4B with large thermal expansion coefficient is requested | required, but the thermal expansion coefficient close | similar to LED element 1 is requested | required. It is preferable to select and seal. Since the lead portions 4A and 4B formed of a soft metal such as Cu are richer in elasticity than the glass material, the difference in thermal expansion coefficient between the LED element 1 and the submount 3 is 150% to 400%. If it is a range, the stress based on a thermal contraction difference can be structurally absorbed, maintaining favorable adhesiveness with a glass material. Therefore, even when the lead portions 4A and 4B are sandwiched between glass materials and sealed, defects such as cracks do not occur.

(3) Even when the input power to the LED element 1 is large and the heat generation temperature is high, the heat generated by the LED element 1 can be dissipated to the outside, and a decrease in luminous efficiency can be effectively prevented. In particular, this can be realized by setting the thermal conductivity of the submount 3 and the lead portions 4A and 4B to 100 W · m ⁻¹ · k ⁻¹ or more.

(4) Since the sealing member 5 is formed using the glass sheets 7 and 8 having a low melting point, the time required for heating can be shortened, a simple heating device can be used, and the glass sealing process is facilitated.

(5) Since defects such as cracks are less likely to occur during processing, high sealing performance with glass can be stably maintained over a long period of time, and light emission characteristics do not deteriorate even under water or in high humidity conditions, and it is excellent over a long period of time. Demonstrate durability.

  In the first embodiment, the configuration using the GaN-based LED element 1 as the LED element 1 has been described. However, the LED element is not limited to the GaN-based one, and other LED elements may be used. Is possible.

In the above-described embodiment, the configuration in which the submount 3 made of AlN is mounted on the lead portions 4A and 4B made of Cu has been described. For example, the lead portion made of brass (thermal conductivity 106 W · m ⁻¹ · A configuration in which a submount 3 (thermal conductivity: 170 W · m ⁻¹ · k ⁻¹ ) made of Si is mounted on k ⁻¹ ) is also possible.

  Further, the sealing member 5 is not limited to the one formed by sealing the plurality of LED elements 1 and the submounts 3 using a sheet-like glass, and a molten glass material is used for the LED. You may make it form by supplying to the circumference | surroundings of the element 1 and the submount 3, and heat-press-molding with the upper metal mold | die 11 and the lower metal mold | die 12. FIG. Further, the glass material to be used is not limited to being transparent as long as it has optical transparency, and may be colored.

  Moreover, the sealing member 5 can be made into various shapes according to a specification etc. For example, in addition to a round shape, an oval shape, a square shape, and the like, shapes with a lens and without a lens are possible.

  In the first embodiment described above, the flip chip type light emitting device using the metal lead as the power supply member has been described. However, the present invention can also be applied to other types of light emitting devices. For example, the present invention can be applied to a face-up (FU) type light emitting device using wire bonding.

  FIG. 4 is a cross-sectional view showing a modification of the light emitting device according to the first embodiment. In the light emitting device 10, the inclined portion 3 </ b> A is provided by removing the corner portion of the submount 3 to prevent cracks due to thermal expansion / contraction of the sealing member 5. By using the submount 3 as described above, it is possible to realize the glass-sealed light emitting device 10 in which cracks are unlikely to occur in addition to the preferable effects of the first embodiment.

  FIG. 5 is a cross-sectional view showing a face-up light emitting device according to the second embodiment of the present invention. The light emitting device 40 is mounted on the top surface of the lead portion 4A, 4B as a power supply member disposed horizontally and in a straight line with a gap at the tip portion, and an adhesive or the like on the top surface of the lead portion 4A. Seals the GaN-based LED element 41, the wire 42 connecting the two electrodes (not shown) on the LED element 41 and the lead portions 4A and 4B, and the tip portions of the LED element 41 and the lead portions 4A and 4B. And a sealing member 5 made of a glass material.

  The sealing member 5 is made of a glass material having transparency, a low melting point, and a coefficient of thermal expansion within a predetermined value. In particular, in the face-up type, by using a wire, the wire 42 and the wire connecting portion 42A that have been softened by heating are easily crushed by pressurization during glass sealing, so that a short circuit or the like is likely to occur. For this reason, it is desirable to use a glass material having a low melting point as much as possible.

  Hereinafter, the assembly of the light emitting device 40 will be described.

  First, in a state before separation of the lead frame, the LED element 41 is mounted on the top surface of the leading end of the lead portion 4A. Next, one electrode on the upper surface of the LED element 41 and the upper surface of the lead portion 4A are connected by a wire 42, and the other electrode on the upper surface of the LED element 41 and the upper surface of the lead portion 4B are connected by a wire 42. Is done. Next, as described in the first embodiment, a glass material is molded by a mold, and the sealing member 5 having a predetermined shape is formed. Finally, unnecessary portions of the lead frame 4 are removed, whereby each of the light emitting devices 40 is separated from the lead frame 4.

  In FIG. 5, for example, if the lead portion 4A is on the anode side, the plus side of a DC power supply (not shown) is connected to the lead portion 4A, and the minus side is connected to the lead portion 4B. By this energization, the LED element 41 emits light. The light is emitted from the upper surface of the LED element 41, most of which is transmitted through the sealing member 5 and emitted to the outside, and the other part is emitted from the sealing member 5 through internal reflection.

  According to the second embodiment described above, in addition to the preferable effects of the first embodiment, the value of the coefficient of thermal expansion between the lead portions 4A and 4B and the sealing member 5 is taken into consideration, and the glass material having a low melting point. By using this, even the face-up type light emitting device 40 can prevent the occurrence of peeling and cracking.

  In each of the above-described embodiments, a reflecting surface may be formed on the surface of the lead portions 4A and 4B to increase the light emission efficiency.

  In addition, a wavelength conversion unit using a phosphor or the like that is excited by light of a predetermined wavelength may be provided in the sealing member 5 above the LED elements 1 and 42.

  Further, in each of the above-described embodiments, the number of LED elements disposed in one sealing member is one, but a multi-light-emitting type light emitting device having two or more LED elements is provided. You can also As a type of the light emitting device in this case, the configuration of FIG. 1 which is a flip chip bonding type is suitable. The plurality of LED elements to be mounted may have a configuration in which a plurality of LED elements having different emission colors are provided or a configuration in which a plurality of LED elements having the same emission color are provided.

  Furthermore, as a drive form of the LED element, all of the plurality of LED elements may be connected in parallel or in parallel in units of groups, may be connected in series in a plurality of units, or all may be connected in series.

  Further, as the shape of the sealing member 5, a hemispherical structure in which a lens portion is formed on the top portion is shown, but the sealing member 5 is not limited to the illustrated shape, and has a shape without a lens portion, Any shape such as a polygonal shape or a cylindrical shape can be used.

  Furthermore, when the sealing member 5 is molded, a glass sheet is used. However, the method is not limited to the method using the glass sheet, and other sealing methods may be used.

  6A and 6B show a flip-chip type light emitting device according to a third embodiment of the present invention. FIG. 6A is a cross-sectional view, and FIG. 6B is a side view seen from the right side of FIG. Note that common reference numerals are given to portions having the same configuration as that of the first embodiment. As shown in FIG. 6A, the light emitting device 10 has a configuration in which the submount element 3 is mounted on a heat radiating portion 50 made of Cu and is integrally sealed with a sealing member 5 made of low melting point glass. The sealing member 5 is formed with a lens 5A.

  The submount element 3 is accommodated in a groove 51 provided in the heat radiating part 50, and the wiring pattern 53 provided on the surface of the submount element 3 and the electrode of the LED element 1 are electrically connected by the bump 2, whereby the power supply part. Part of it. The wiring pattern 53 is solder-bonded to the lead portions 4A and 4B made of soft metal Cu after bonding to the LED element 1. In the lead portion 4B, the sealing member 5 is heated and pressed while being insulated from the heat radiating portion 50 by interposing a rod-like glass material 52 with a rectangular cross section in the groove portion 51 as shown in FIG. 6B. At this time, the lead portion 4A is processed in the same manner as the lead portion 4B. The lead portions 4A and 4B are integrated in a state where they are insulated from the heat radiating portion 50 by the glass material 52 and the sealing member 5 melted based on the heating press.

  According to the third embodiment, since the heat radiating part 50 on which the submount element 3 is mounted is integrally sealed with the sealing member 5 made of a glass material, in addition to the preferable effects of the first embodiment. Thus, the heat dissipation of the heat transmitted from the submount element 3 can be improved. For example, not only when the glass sealing process is performed, but also when the amount of heat generated from the LED element 1 increases due to an increase in current, for example, The light emitting device 1 which is excellent and hardly causes package cracks due to a difference in thermal expansion coefficient can be obtained.

  In the above-described third embodiment, the configuration using the heat radiating portion 50 made of Cu has been described. For example, the thermal conductivity of Cu alloy, aluminum, or the like is good, and the sealing member 5 is used. Those having a small difference in thermal expansion coefficient can also be used. Temporarily, when it is set as the thermal radiation part 50 which consists of aluminum, the difference of a thermal expansion coefficient will be about 500% with respect to the LED element 1 and the submount 3. FIG.

  7A and 7B show a face-up type light emitting device according to a fourth embodiment of the present invention. FIG. 7A is a cross-sectional view, and FIG. 7B is a side view seen from the right side of FIG. Note that common reference numerals are given to portions having the same configuration as the second embodiment. As shown in FIG. 7A, the light emitting device 40 has an LED element 40 bonded to the center of a heat radiating portion 50 made of Cu, and leads 4 A and 4 B that feed power to the LED element 40 and the electrodes of the LED element 40. Are electrically connected by a wire 42. Further, the LED element 40, the wire 42, and the lead portions 4A and 4B are covered with a silicon coat portion 60 made of silicon resin so as to have heat resistance against heat during processing of the low melting point glass. The sealing member 5 covers the silicon coat part 60 and is integrated with the heat dissipation part 50. The sealing member 5 is formed with a lens 5A.

  According to the fourth embodiment, even if it is the face-up type light emitting device 40, the LED element 41 is covered with the silicon coat part 60 having heat resistance and elasticity so that the LED due to the pressure at the time of glass sealing processing Since glass sealing is possible while preventing deformation of the electrode of the element 41 and the wire 42, in addition to the preferable effect of the second embodiment, the LED element 41 is excellent in mountability and not only during glass sealing processing. For example, even when the amount of heat generated from the LED element 41 increases due to an increase in current, the light emitting device 1 is obtained that has good heat dissipation and is less likely to cause package cracking due to a difference in thermal expansion coefficient. Further, the silicon coat part 60 may contain a phosphor.

  In the fourth embodiment described above, the configuration in which power is supplied from the pair of lead portions 4A and 4B to the LED element 41 mounted on the heat dissipation portion 50 has been described. For example, the heat dissipation portion 50 and one lead are provided. It is good also as a structure which integrates a part and insulates the other lead part and the thermal radiation part 50 with the glass material 52. FIG.

  In addition to using a silicon resin as the coating material, other heat-resistant materials such as a ceramic coating material can be used. About the structure which provides this coating material, it is not limited to a face-up type LED element, It can apply also to a flip chip type LED element.

It is sectional drawing which shows the structure of the light-emitting device which concerns on the 1st Embodiment of this invention. It is a top view which shows the state which mounted the submount in the lead frame. It is a figure which shows the state immediately before performing glass sealing using a metal mold | die. In the same figure, the state cut | disconnected by the AA part of FIG. 2 is shown. It is sectional drawing which shows the modification of the light-emitting device which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the face-up type light-emitting device which concerns on the 2nd Embodiment of this invention. The flip-chip type light-emitting device which concerns on the 3rd Embodiment of this invention is shown, (a) is sectional drawing, (b) is the side view seen from the right side surface of (a). The face-up type light-emitting device concerning the 4th Embodiment of this invention is shown, (a) is sectional drawing, (b) is the side view seen from the right side surface of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 LED element 2 Bump 3 Submount 3A Inclined part 4 Lead frame 4A Lead part 4B Lead part 5 Sealing member 5A Lens 6 Lead frame 7 Glass sheet 8 Glass sheet 10 Light emitting device 11 Upper mold | die 11A Concave part 12 Lower mold | die 12A Concave part 31A Electrode 31B Electrode 32A Electrode 32B Electrode 33 Via hole 40 Light emitting device 41 LED element 42 Wire 42A Wire connection part 50 Heat radiation part 51 Groove part 52 Glass material 53 Wiring pattern 60 Silicon coat part

Claims (3)

In arranging the submount on which the light emitting element is mounted on a pair of plate-like lead portions formed so that the tips thereof face each other with a predetermined gap, the pair of leads A concave portion on an upper surface, and the submount is disposed across the gap in the concave portion of the pair of leads ,
A glass sheet is disposed above and below the light emitting element,
Place the upper mold so as to cover the upper glass sheet,
Place the lower mold so as to cover the lower glass sheet,
In the state where the upper and lower glass sheets are heated and softened, the upper mold and the lower mold are moved in a direction toward the light emitting element, whereby pressure is applied to the upper and lower glass sheets. , And the upper and lower glass sheets are integrated, and the light emitting device, the submount, and the upper and lower surfaces of each lead portion in the vicinity of the submount are integrally surrounded by the glass portion. Manufacturing method. The light emitting device includes a plurality of the pair of lead portions and the light emitting element,
The upper and lower glass sheets have a size capable of sealing a plurality of the light emitting elements,
The method for manufacturing a light emitting device according to claim 1 , wherein the plurality of light emitting elements are collectively sealed. The method for manufacturing a light emitting device according to claim 2 , wherein the recessed portion of the lead portion is processed one step lower than other portions on the upper surface of the lead portion.

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