Semiconductor light emitting apparatus

A semiconductor light emitting apparatus can include a housing filled with a wavelength conversion material-containing resin material which seals a semiconductor light emitting device inside the recess of the housing. A transparent resin material can be charged on the wavelength conversion material-containing resin material, and can be configured to prevent the resin materials from being detached from each other or from other portions, such as a housing. Furthermore, such a semiconductor light emitting apparatus can emit light with less color unevenness. The housing can include a first recessed portion and a second recessed portion. The second recessed portion can have a larger diameter than the first recessed portion so as to form a stepped area at the boundary therebetween. The first recessed portion is filled with the wavelength conversion material-containing resin material as a first resin. The first resin extends along from an inner surface of the first recessed portion up to an inner surface of the second recessed portion to cover the inner surface of the second recessed portion. Accordingly, the first resin is recessed at its center area toward the semiconductor light emitting device to form a curved upper surface, and the second resin on the first resin is not in contact with the housing.

This application claims the priority benefit under 35 U.S.C. §119 of Japanese Patent Application No. 2007-205597 filed on Aug. 7, 2007, which is hereby incorporated in its entirety by reference.

BACKGROUND

1. Technical Field

The presently disclosed subject matter relates to semiconductor light emitting apparatuses, and in particular, to a semiconductor light emitting apparatus that uses a semiconductor light emitting device and a wavelength converting material such as a phosphor in combination.

2. Description of the Related Art

Semiconductor light emitting apparatuses have been conventionally known that use a semiconductor light emitting device and a wavelength converting material such as a phosphor in combination in order to emit light in which color (tone) is changed from the original color (tone) originating from the semiconductor light emitting device to a second different color (tone). One example of such a semiconductor light emitting apparatus is shown inFIG. 1.

This type of semiconductor light emitting apparatus can include a resin housing52with which a pair of leads50and51are integrated. Inside the resin housing52a first recessed portion54is formed. Above the first recessed portion54a second recessed portion53with a larger diameter than that of the first recessed portion54is continuously formed.

A semiconductor light emitting device55can be mounted on and/or adjacent to the bottom of the first recessed portion54. Not-shown electrodes of the semiconductor light emitting device55are electrically connected to the respective leads50and51by means of bonding wires56and57.

A transparent resin material is mixed with a particular wavelength converting material such as a particular phosphor to prepare a phosphor-containing resin58, which is charged into the first recessed portion54to resin-seal the semiconductor light emitting device55. On the phosphor-containing resin58and inside the second recessed portion53another transparent resin material59is charged, thereby completing the semiconductor light emitting apparatus (see, for example, Japanese Patent Application Laid-Open No. 2002-33520).

The semiconductor light emitting apparatus configured as described above is referred to as a surface mount type and is used as a light source for use in a portable handy terminal or the like.

This type of semiconductor light emitting apparatus can be configured in such a manner that a soft resin material is used as the transparent resin material for constituting the phosphor-containing resin58which is charged into the first recessed portion54to resin-seal the semiconductor light emitting device55, and a hard resin material is used as the transparent resin material59which is charged into the second recessed portion53on the phosphor-containing resin58. However, the following problems may arise in this configuration.

When the environmental test (heat cycle test) is performed on the semiconductor light emitting apparatus configured as described above, the phosphor-containing resin58can repeatedly expand and contract in accordance with the temperature change during the heat cycle. When the phosphor-containing resin58expands, an external force may be applied to the transparent resin material59which forms the boundary between the phosphor-containing resin58. As a result, the transparent resin material59may become detached and can be peeled from the contact area with the stepped area60where the boundary between the phosphor-containing resin58and the transparent resin material59(between the first and second recessed portions54and53) is formed, thereby easily forming a crack61at that area and adjacent areas.

This phenomenon may occur even during the normal operation conditions. For example, it may occur due to the repeated turning-on and turning-off of the semiconductor light emitting device which leads to repeated generation of heat and cooling of the semiconductor light emitting device.

SUMMARY

The presently disclosed subject matter was devised in view of these and other problems, features and characteristics and in association with the conventional art. According to an aspect of the presently disclosed subject matter, a semiconductor light emitting apparatus can be configured to help prevent the detachment (peeling-off) of used resin materials at their boundary with each other or with other members, while the resin materials are filled into a recessed portion of its housing. Accordingly, a semiconductor light emitting apparatus is disclosed which can include a housing filled with a wavelength conversion material-containing resin material which seals a semiconductor light emitting device inside the recess of the housing and a transparent resin material charged inside the recessed portion on the wavelength conversion material-containing resin material, and which can prevent the resin materials from being detached and/or peeled from each other or from other portions such as a housing. Furthermore, such a semiconductor light emitting apparatus can emit light with less color unevenness.

According to another aspect of the presently disclosed subject matter, a semiconductor light emitting apparatus can include: a housing having an inner space provided thereinside; a semiconductor light emitting device installed in the inner space of the housing; and a resin portion with which the inner space of the housing is filled. Here, the inner space of the housing can include a first recessed portion having a bottom surface and a second recessed portion having an opening. The semiconductor light emitting device can be mounted on and/or adjacent to the bottom surface of the first recessed portion. The second recessed portion can be continuously formed above the first recessed portion. The upper portion of the first recessed portion and the lower portion of the second recessed portion can form a boundary portion, and the second recessed portion can be formed larger in width than the first recessed portion to form a stepped area at the boundary portion. The resin portion can include a first resin and a second resin. The first resin can be formed of a transparent resin material mixed with a wavelength converting material such as a phosphor, and can be charged into the first recessed portion to seal the semiconductor light emitting device. The second resin can be formed of a transparent resin material and charged above the first resin. The first resin can be provided such that the first resin extends along from an inner surface of the first recessed portion up to an inner surface of the second recessed portion to cover the inner surface of the second recessed portion. The first resin can be recessed at its center area toward the semiconductor light emitting device to form a curved upper surface.

In the semiconductor light emitting apparatus configured as described above, the first resin can have a lowermost level of the curved upper surface positioned nearer the semiconductor light emitting device than a level of the stepped area.

In the semiconductor light emitting apparatus configured as described above, the second resin can have a curved upper surface recessed toward the semiconductor light emitting device, with an uppermost level of the curved surface of the second resin being lower than the uppermost edge of the outer periphery of the second recessed portion of the housing.

Alternatively, in the semiconductor light emitting apparatus configured as described above, the second resin can have a curved convex upper surface, and preferably the uppermost level of the curved convex upper surface of the second resin can be lower than the uppermost edge of the outer periphery of the second recessed portion of the housing.

In the semiconductor light emitting apparatus configured as described above, the second resin can have a predetermined hardness harder than that of the transparent resin material constituting the first resin.

In the semiconductor light emitting apparatus configured as described above, the transparent resin material constituting the first resin can have a predetermined elasticity, and is softer than the second resin.

In the semiconductor light emitting apparatus configured as described above, the second resin can have a refractive index lower than that of the transparent resin material constituting the first resin.

In the semiconductor light emitting apparatus configured as described above, the first recessed portion of the housing can be provided with a high reflective film on the inner surface thereof and a corrosion resistance film on the outer surface thereof.

In the semiconductor light emitting apparatus configured as described above, the high reflective film can be formed of a film selected from the group consisting of silver, silver alloys, and aluminum, and the corrosion resistance film can be formed of gold.

In the semiconductor light emitting apparatus configured as described above, the second resin can also contain a wavelength converting material in a concentration less than that in the first resin.

The semiconductor light emitting apparatus of the presently disclosed subject matter can be configured to include a housing having an inner space composed of a first recessed portion and a second recessed portion provided above the first recessed portion, in which a semiconductor light emitting device is mounted on the bottom surface of the first recessed portion. A first resin composed of a transparent resin material and a wavelength converting material such as a phosphor can be charged into the first recessed portion to seal the semiconductor light emitting device. Furthermore, the first resin can be provided such that the first resin extends along from an inner surface of the first recessed portion up to an inner surface of the second recessed portion to cover the inner surface of the second recessed portion. The upper surface of the first resin can be recessed at its center area toward the semiconductor light emitting device to form a curved upper surface. Then, the second resin is charged onto the thus formed first resin.

As a result, the first resin can cover the entire surface of the inner space including the first recessed portion and the second recessed portion of the housing, thereby preventing the second resin formed on the first resin from being in contact with the inner surface of the housing. According to this configuration, the resin portion can be prevented from being detached and/or peeled from the housing, and a semiconductor light emitting apparatus with less color unevenness can be achieved.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A description will now be made below with respect to examples of semiconductor light emitting apparatuses of the presently disclosed subject matter with reference to the accompanying drawings and in accordance with exemplary embodiments.

FIG. 3is a cross sectional view showing a first exemplary embodiment of a semiconductor light emitting apparatus made in accordance with principles of the presently disclosed subject matter. The semiconductor light emitting apparatus1can have a housing2made of a white resin material which has a particular reflectivity. Inside the housing2an inner space can be formed, including a first recessed portion3and a second recessed portion5continuously formed above the first recessed portion3and having an opening4. The upper portion of the first recessed portion3and the lower portion of the second recessed portion5can form a boundary portion, and the second recessed portion5can be formed larger in width than the first recessed portion3to form a stepped area6at the boundary portion.

A semiconductor light emitting device7can be mounted on the bottom of the first recessed portion3. A first resin8can be formed of a transparent resin material mixed with a wavelength converting material such as a particular phosphor, and is charged into the first recessed portion3to seal the semiconductor light emitting device7. The first resin8can be disposed such that the first resin8extends along from an inner surface14of the first recessed portion3up to an inner surface9of the second recessed portion5to cover the inner surface9of the second recessed portion5. The upper surface15of the first resin8can be recessed toward the semiconductor light emitting device7to form a curved upper surface15. The curved upper surface15of the first resin8can have a lowermost level10(at the center area near the optical axis X of the below-positioned semiconductor light emitting device7) positioned nearer the semiconductor light emitting device7than the level of the stepped area6where the boundary between the first recessed portion3and the second recessed portion5is positioned.

A second resin11can be formed of a transparent resin material and charged above the first resin8to form a boundary with the first resin8. As a result, the resin portion can be composed of the first resin8and the second resin11. In the present exemplary embodiment, the upper surface12of the second resin11can be formed to have a planar surface to be flush with the opening edge13of the housing2. According to this configuration, the second resin11is not in contact with both the inner surface14of the first recessed portion3and the inner surface9of the second recessed portion5.

In the semiconductor light emitting apparatus1configured as described above, the first resin8may expand and contract due to the environmental temperature change or the temperature change by the repeated turning-on and -off of the semiconductor light emitting device7. Even in such a case, since the second resin11which forms the boundary with the first resin8is not in contact with both the inner surface14of the first recessed portion3and the inner surface9of the second recessed portion5, the second resin11receives an external force due to the expansion and contraction of the first resin8only at the contact area with the first resin8, but it does not transfer the force to other members, such as the housing2. Accordingly, the second resin11is not detached and/or peeled from the housing2irrespective of the hardness relationship between the different transparent resin materials constituting the first resin8and the second resin11.

In the above configuration, the hardness relationship between the transparent resin material constituting the first resin8and the transparent resin material of the second resin11can be characterized according to the following two exemplary cases:

(1) the transparent resin material constituting the first resin8and the transparent resin material of the second resin11each have a particular elasticity (for example, a combination of silicone resins selected from the group consisting of (or including) soft elastomers (having a superior stress relief property with a low-to-medium hardness (for example, JIS Type A hardness of more than 50)), gels having the same performance as, or similar to, the previous soft elastomers, hard elastomers (serving as a surface layer without stickiness with a JIS Type A hardness of more than 50), high hardness resins with a Shore D hardness of from 60 to 70, and low hardness resins with a Shore D hardness of from 30 to 40); and

(2) the transparent resin material constituting the first resin8has a particular elasticity, and the transparent resin material of the second resin11has a particular hardness (for example, an exemplary combination of a soft elastomer (having a superior stress relief property with a low-to-medium hardness (for example, JIS Type A hardness of more than 50)) or a gel having the same performance as, or similar to, the previous soft elastomer serving as the first resin8and a high hardness epoxy resin with a Shore D hardness of 60 or more serving as the second resin11).

In some cases, if a high power semiconductor light emitting device is used as the device7, the semiconductor light emitting device7may generate a relatively large amount of heat during operation. Even in these cases, the combination of the resin materials (for example, silicone resins) as described in the above item (1) can suppress the deterioration of the transparent resin material constituting the sealing resin for the semiconductor light emitting device7, thereby providing a semiconductor light emitting apparatus1with high reliable optical performances (including stable luminous intensity and less color change).

Furthermore, if the combination of the resin materials as described in the above item (2) is adopted, it is possible to suppress the generation of stress due to heat generation within the sealing resin for sealing the semiconductor light emitting device7. Accordingly, this can also prevent crack generation, thereby improving the reliability of the semiconductor light emitting apparatus1. In addition to this, dust and foreign matters can be prevented from adhering onto the outermost surface of the apparatus because the outermost surface is formed of the second resin8which has a particular hardness suitable for preventing dust and foreign matter adhesion.

Furthermore, in both of the cases as described in the items (1) and (2), the transparent resin material constituting the first resin8includes a resin having a particular elasticity as well as a particular softness. In this case, not-shown bonding wires for electrically connecting the electrodes of the semiconductor light emitting device7to the electrodes provided in the housing2can be prevented from being detached from the electrodes or being cut due to the repeated thermal expansion and contraction of the resin for sealing the device7.

The present inventors have also examined the optical action with regard to the relationship between the transparent resin material constituting the first resin8and the transparent resin material of the second resin11. As a result, the present inventors have found that it is desirable to design the transparent resins such that the transparent resin material constituting the first resin8(for sealing the semiconductor light emitting device7) has a larger refractive index than that of the transparent resin material of the second resin11located above the first resin8. This can make the refractive index of the sealing resin which forms the boundary with the light emitting surface of the semiconductor light emitting device7closer to the refractive index of the crystalline material constituting the semiconductor light emitting device7, thereby increasing the light extraction efficiency from the semiconductor light emitting device7.

Furthermore, in the above configuration, some of the light rays which are emitted at an angle from the semiconductor light emitting device7with respect to the optical axis X of the device7can reach the boundary between the first resin8and the second resin11and enter the boundary at a larger angle than the critical angle, thereby being reflected by the boundary face. Then, the light rays can reach the inner surface14of the first recessed portion3of the housing2as shown inFIG. 3. The light rays are further reflected by the inner surface14to enter the second resin11and be emitted to the outside.

Accordingly, the light rays emitted from the device7in directions other than along the direction of the optical axis X can be re-directed in the illumination direction (along the optical axis X) effectively, thereby increasing the light extraction efficiency. It should be noted that the transparent resin material constituting the first resin8may have a refractive index of 1.5 or more, and that the transparent resin material of the second resin11may have a refractive index of around 1.4. A proper selection of the kinds of transparent resin material can achieve a semiconductor light emitting apparatus1with good optical characteristics.

Examples of the transparent resin materials constituting the first resin8include, but are not limited to, elastomers which are available from Dow Corning Toray Co., Ltd. and have a superior stress relief property with a low-to-medium hardness (for example, JIS Type A hardness of more than 50) and a refractive index of from 1.5 to 1.55, such as JCR6175. Examples of the transparent resin materials of the second resin11include, but are not limited to, hard elastomers which serve as a surface layer without stickiness with a JIS Type A hardness of more than 50 and a refractive index of from 1.4 to 1.45, such as OE-6336, EG-6301, OE-6351 and the like.

It should be noted that means for electrically connecting the semiconductor light emitting device, such as leads and wires, are omitted in the drawings (FIGS. 3 to 6) as a matter of convenience.

FIG. 4is a cross sectional view showing a semiconductor light emitting apparatus in accordance with a second exemplary embodiment of the presently disclosed subject matter. The second exemplary embodiment is different from the first exemplary embodiment at least in that the upper surface12of the second resin11charged on the upper surface15of the first resin8has a convex surface facing toward the semiconductor light emitting device7. The other configuration thereof can be the same as that of the first exemplary embodiment.

The upper surface12of the second resin11is concave facing away from the semiconductor light emitting device and is located lower than the opening edge13of the housing2. This configuration can protect the surface12of the second resin11by using the opening edge13of the housing2to block other parts, such as a substrate, from accidentally hitting the semiconductor light emitting apparatus1during its mounting operation, thereby maintaining a non-defective surface12of the second resin11. Accordingly, it is possible to secure favorable optical characteristics for the semiconductor light emitting apparatus1.

FIG. 5is a cross sectional view showing a semiconductor light emitting apparatus in accordance with the third exemplary embodiment of the presently disclosed subject matter. The third exemplary embodiment is different from the second exemplary embodiment at least in that the upper surface12of the second resin11charged on the upper surface15of the first resin8has a convex surface facing in a direction opposite to the semiconductor light emitting device7. The other configuration thereof can be the same as that of the first exemplary embodiment.

The upper surface12of the second resin11can serve as a lens or similar means for converging the light rays emitted from the device7and which are guided through the second resin11. This can increase the luminous intensity within a predetermined area of light emitted from the semiconductor light emitting apparatus1.

In the first to third exemplary embodiments, the housing2can be formed of a white resin material having a particular reflectivity, although the presently disclosed subject matter is not limited to this configuration. In order to enhance the reflectivity, the inner surface14of the first recessed portion3can be provided with a high reflective layer, for example, made of a metal film. The metal film can be one selected from the group consisting of (or including) silver, silver alloys, and aluminum which each have a high reflectivity with respect to the light rays having visible wavelengths.

In the first to third exemplary embodiments, the housing2is not necessarily formed of a resin material, but may be formed of a metal material, a ceramic material, or a combination of metal and ceramics, or similar materials. When the housing2is formed of a metal material, a corrosion resistance film may be further provided on the outer surface of the housing2. Examples of the corrosion resistance film include Au film and the like. Furthermore, a corrosion resistance film and a high reflective layer of a metal film for enhancing its reflectivity can be provided at the inner surfaces of the first recessed portion3and the second recessed portion5. The metal film can be one selected from the group consisting of (or including) silver, silver alloys, and aluminum which each have a high reflectivity with respect to light rays within the visible wavelength spectrum. Examples of ceramics include AlN, Al2O3, and the like which are commonly utilized. A white material can be used having a high reflectivity with respect to the visible wavelength light rays.

The second resin11can also contain a wavelength converting material as in the case of the first resin8for sealing the semiconductor light emitting device7. In this case, the concentration of the phosphor in the second resin11is less than that in the first resin8. This configuration can reduce the color unevenness of radiated light rays from the semiconductor light emitting apparatus1.

In the first to third exemplary embodiments as described above, the first resin8is charged into the first recessed portion3and extends along from the first recessed portion3up to the inner surface9of the second recessed portion5so as to cover the inner surface9of the second recessed portion5. Accordingly, the upper surface15of the first resin8has a concave curved surface facing away from the below-positioned semiconductor light emitting device7. The present inventors have examined a comparative exemplary semiconductor light emitting device as shown inFIG. 6where the upper surface of the first resin is formed flat. In this case, the first resin8does not extend along the inner surface9of the second recessed portion5, and accordingly, the second resin11charged in the second recessed portion5can be in contact with the inner surface9of the second recessed portion5. As a result, the second resin11may receive external force due to the expansion and contraction of the first resin8so as to be detached and/or peeled from the inner surface9of the second recessed portion5.

With regard to the optical disadvantages, some of the light rays emitted from the semiconductor light emitting device7reach the upper surface15of the first resin8near the inner surface9. Then, the light rays may be reflected by the upper surface15and reach the stepped area6between the first recessed portion3and the second recessed portion5. The light rays are reflected again by the stepped area6toward the upper surface15of the first resin8to enter the second resin11. During the repeated reflection, the light rays passing near the stepped area6where the wavelength converting material is deposited can excite the wavelength converting material. As a result, the light rays that are emitted can include the wavelength converted light rays and can enter the second resin11from the surface15of the first resin8near the stepped area6as illuminated light rays which have a different color tone as compared to the color tone of light rays radiated from other areas. Accordingly, the light emitted from the semiconductor light emitting apparatus1may have color unevenness over the entire surface.

On the contrary, the first to third exemplary embodiments are configured such that the center lowermost level10of the curved surface15of the first resin8is positioned lower than the level of the stepped area6. When the light rays are emitted from the semiconductor light emitting device7, they can enter the second resin11while not passing through the stepped area6where the wavelength converting material may be deposited. Accordingly, a semiconductor light emitting apparatus with less color unevenness can be achieved.

As described above, the semiconductor light emitting apparatus can be configured to include a housing having an inner space composed of a first recessed portion and a second recessed portion provided above the first recessed portion, in which a semiconductor light emitting device is mounted on the bottom surface of the first recessed portion. Here, a first resin composed of a transparent resin material and a phosphor is charged into the first recessed portion to seal the semiconductor light emitting device. Furthermore, the charged first resin is located such that it extends along from an inner surface of the first recessed portion up to an inner surface of the second recessed portion to cover the inner surface of the second recessed portion.

The upper surface of the first resin is recessed at its center area toward the semiconductor light emitting device to form a curved upper surface which is concave facing away from the semiconductor light emitting device. The second resin is charged onto the thus formed first resin. As a result the first resin can cover the entire surface of the first recessed portion and the second recessed portion of the housing, thereby preventing the second resin from being in contact with the inner surface portions of the housing.

According to this configuration, the resin portion (including the first resin and the second resin) charged into the housing is prevented from being detached and/or peeled from the housing, and a reliable semiconductor light emitting apparatus with less color unevenness can be achieved.

The transparent resin material constituting the first resin is selected so as to have at least a particular elasticity. Accordingly, when the second resin has the same level of elasticity as the first resin, or even when the second resin has a certain hardness, it is possible to suppress the generation of stress due to heat generation within the sealing resin for sealing the semiconductor light emitting device7. This can also suppress crack generation, thereby improving the reliability of the semiconductor light emitting apparatus1.

When the housing is made of a metal material, a corrosion resistance film made of gold can be provided at least on the outer surface of the housing. This film can prevent the outer surface of the housing from being corroded or deteriorating in color due to the oxidation of the housing material.

It will be apparent to those skilled in the art that various modifications and variations can be made in the presently disclosed subject matter without departing from the spirit or scope of the presently disclosed subject matter. Thus, it is intended that the presently disclosed subject matter cover the modifications and variations of the presently disclosed subject matter provided they come within the scope of the appended claims and their equivalents. All related art references described above are hereby incorporated in their entirety by reference.