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Semiconductor light emitting device

Semiconductor light emitting device description/claims

The present invention relates to a semiconductor light emitting device in which a flip chip semiconductor light emitting element is mounted on a submount substrate, and particularly to a technique for setting a semiconductor light emitting device in a smaller space than the conventional ones.

In recent years, with an improvement of a technique of semiconductors, semiconductor light emitting devices that output white light to be equipped in lighting apparatuses have become widely used.

Especially, semiconductor light emitting devices are compact and require low electric power. Therefore, semiconductor light emitting devices are suitable for installing in portable devices such as cellular-phones and cameras, and should explosively prevail in the near future.

A semiconductor light emitting device comprises: a semiconductor light emitting element that emits blue light; and translucent resin scatteredly including luminescent substance that converts blue light into greenish yellow light, greenish yellow being a complementary color of blue. The semiconductor light emitting device outputs light that looks white by outputting (a) a part of blue light that is emitted by a semiconductor light emitting element and transmits translucent resin without being converted by the luminescent substance, and (b) greenish yellow light that is generated as a result of conversion by the luminescent substance, at the same time in a proper proportion.

The details about the aforementioned semiconductor light emitting device are disclosed in Japanese Patent Publication No. 3257455 and No. 3399440 filled by the applicants of the present invention.

The aforementioned semiconductor light emitting device comprises a submount substrate and a flip chip semiconductor light emitting element that is mounted on the submount substrate, and needs a space for wire bonding on the submount substrate. Therefore, the submount substrate needs to be larger than the semiconductor light emitting element, and the semiconductor light emitting element is mounted on the submount substrate in an unbalanced position where a center of the semiconductor light emitting element does not coincide with a center of the submount substrate. It should be noted here that generally a main surface of the semiconductor light emitting element is substantially square and a main surface of the submount substrate is substantially rectangular.

Also, it is preferable that the semiconductor light emitting device is equipped with a cup-like reflection member to reflect the light emitted in parallel with a main light emitting surface by the semiconductor light emitting element so that the light travels in a direction perpendicular to a main light emitting surface.

The reflection member is a metal plate that has a conical-trapezoidal-shaped hole, as one example. On a bottom of the reflection member, the semiconductor light emitting element is provided. Radius of the reflection member decreases from a top toward a bottom.

Also a lens made of transparent resin or the like is provided over the reflection member to improve light distribution characteristic, and it is preferable to keep a radius on a bottom as small as possible taking the amount of materials and light focusing efficiency into account.

However, taking a light distribution characteristic into consideration, if a center of main light emitting surface of the semiconductor light emitting element is adjusted to coincide with a center of the reflection member, a space for wire bonding sticks out from the main light emitting surface. This would make a radius on a bottom of the reflection member considerably larger than a shape of the submount substrate. Nonetheless, adjusting a center of the submount substrate to coincide with a center of the reflection member should be avoided because it causes a degradation of light distribution characteristic. Also, reducing a space for wire bonding should be avoided because it increases bonding defects, lowers a yield ratio, and diminishes productivity due to an effort to improve accuracy.

The aim of the present invention is to provide a semiconductor light emitting device that can be set in a smaller space than the conventional ones without sacrificing light distribution characteristic and productivity and to provide a method for manufacturing the semiconductor light emitting device.

The semiconductor light emitting device of the present invention comprises an element to emit light and a substrate on a main surface of which the element is mounted. The main surface of the substrate composed of two areas, (i) a mount area which is rectangular and on which the element is mounted, and (ii) a pad area that is equipped with a pad for wire bonding. Here, the pad area is contiguous to the mount area on one side of the mount area, and the pad area decreases in width continuously or stepwise in a direction away from the one side.

With this structure, a width of the pad area decreases with the distance from the element. This enables to keep a space for wire bonding without being inferior to the prior art, and to decrease a radius of a bottom of a cup-like reflection member with attention to light distribution characteristic by adjusting a center of a main light emitting surface of the element to coincide with a center of the reflection member. Therefore, it is possible to reduce the amount of materials and to improve light focusing efficiency.

Also, this structure has only two areas, the mount area and the pad area, on the main surface of the substrate. In other words, there is no wasted space on the substrate. This allows greater flexibility to cut off substrates from an array substrate such as a silicon wafer and to increase the number of substrates that can be cut off from an array substrate, compared with circular or polygonal substrates (a hexagon substrate, for one example) on which an element needs to be mounted in a middle.

Consequently, according to the present invention, it is possible to set a semiconductor light emitting element in a smaller space than the conventional ones without sacrificing light distribution characteristic and productivity.

A shape of the pad area of the semiconductor light emitting device can be an isosceles trapezoid whose long base coincides with the one side.

With this arrangement, since the pad area is an isosceles trapezoid, it is possible to make the pad area easily just by cutting off diagonally two corners of the conventional rectangle pad area.

Also, a shape of the pad area of the semiconductor light emitting device can be an isosceles triangle whose base coincides with the one side.

With this arrangement, since the pad area is an isosceles triangle, it is possible to make the pad area easily just by cutting off diagonally two corners of the conventional rectangle pad area.

Also, a shape of the pad area of the semiconductor light emitting device can be a circular arc whose chord coincides with the one side.

• Provisional Patent
• Utility Patent

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