JP5766095B2 - Semiconductor light emitting device - Google Patents

Description

  The present invention relates to a semiconductor light emitting device for flip chip mounting.

  A semiconductor light emitting device cut out from a wafer (hereinafter referred to as an LED die unless otherwise specified) often has a configuration in which a semiconductor layer including a light emitting layer is provided on a transparent insulating substrate. In a semiconductor light emitting device in which such an LED die is mounted on a circuit board (hereinafter referred to as an LED device unless otherwise specified), a protruding electrode is provided on the surface of the LED die opposite to the transparent insulating substrate (hereinafter referred to as an electrode surface). In some cases, flip chip mounting (also referred to as face-down mounting) is performed in which the LED die and the electrode of the circuit board are conductively connected through the protruding electrodes. This flip chip mounting is characterized in that it has better thermal conductivity and light emission efficiency than a mounting method using wire bonding (also referred to as face-up mounting).

  In an LED die having an n-side electrode (cathode) and a p-side electrode (anode) on the electrode surface, the n-side electrode and its surroundings do not emit light. It was provided in the part or side. On the other hand, recently, the area of the LED die has been increased, and a large amount of current is supplied to increase the light emission amount. In order to cope with such a situation, it is effective to make the current distribution uniform, and as one means there is a case where the n-side electrode is arranged at the center of the electrode surface.

  For example, FIG. 1A of Patent Document 1 shows an LED chip 10 (semiconductor light emitting element) including an N-side electrode 15 at the center of an electrode surface and p-side electrodes 16 at four corners of the electrode surface. Although there is no description regarding improvement of current distribution in Patent Document 1, if the n-side electrode is arranged at the center of the electrode surface and the p-electrode is arranged symmetrically, the current distribution becomes uniform and the luminance is improved even when a large current flows. Is known to be easier to plan. FIG. 2 of Patent Document 1 shows a state where the LED chip 10 is flip-chip mounted on a lead frame.

Japanese Patent No. 3365787 (FIGS. 1 and 2)

  As in the LED die (LED chip 10) shown in FIG. 1 of Patent Document 1, there is an n-side electrode (N-side electrode 15) at the center of the electrode surface, and p-side electrodes (P-side electrode 16) at the four corners of the electrode surface. ), The circuit board on which the LED die is mounted has a complicated electrode pattern. In other words, since the p-side electrodes are separated, all the p-side electrodes must be connected by the electrode pattern on the flip chip mounting surface side when the LED die is mounted on the circuit board, or surrounded by the p-side electrodes. The electrode pattern connected to the n-side electrode must be extracted from the electrode pattern connected to the p-side electrode. When the electrode pattern becomes complicated in this way, not only the circuit board becomes difficult to manufacture, but also the mounting becomes difficult or the circuit board becomes large.

  Therefore, in order to solve this problem, an object of the present invention is to provide a semiconductor light emitting device that can provide a uniform current distribution and simplify an electrode pattern of a circuit board even when the n-side electrode is in the center of the electrode surface. And

In order to solve the above problems, a semiconductor light emitting device of the present invention includes an n-type semiconductor layer and a p-type semiconductor layer, and a semiconductor light emitting device including an n-side electrode and a p-side electrode connected to the n-type semiconductor layer and the p-type semiconductor layer. In the element
Having a rectangular electrode surface;
The n-side electrode and the p-side electrode are arranged one by one on the electrode surface,
The n-side electrode is in the center of the electrode surface;
The p-side electrode is on one short side of the electrode surface with respect to the n-side electrode,
There is a floating electrode on the other short side of the electrode surface with respect to the n-side electrode,
The entire p-type semiconductor layer is connected to the p-side electrode with a low resistance.

  The circuit board on which the semiconductor light emitting element having the above-described structure is flip-chip mounted only needs to have the electrode pattern of the circuit board connected to the p-side electrode on the flip chip mounting surface side on one side with respect to the n-side electrode. Similarly, the electrode pattern of the circuit board connected to the n-side electrode need only be on the other side of the n-side electrode on the flip chip mounting surface. This electrode pattern is connected to the n-side electrode at the center, and is also connected to the floating electrode. Thus, since the electrode patterns on the flip chip mounting surface side of the circuit board need only be provided on one side and the other side, the shape and arrangement are simplified. At this time, since the p-side electrode and the entire p-type semiconductor layer are connected with low resistance, the current distribution does not become non-uniform.

A reflective metal layer may be provided on the electrode surface side of the n-side electrode, the p-side electrode , and the floating electrode .

The n-side electrode, the p-side electrode , and the floating electrode may be formed by electrolytic plating.

A floating electrode separated from the floating electrode may be disposed on the one short side where the p-side electrode is disposed.

  As described above, the semiconductor light emitting device of the present invention has a uniform current distribution and simplifies the electrode pattern of the circuit board even when the n-side electrode is at the center of the electrode surface.

The bottom view of the LED die in 1st Embodiment of this invention. Sectional drawing of the LED die | dye shown in FIG. The bottom view of the state which peeled off the insulating film from the LED die | dye shown in FIG. Sectional drawing of the LED apparatus containing the LED die shown in FIG. The top view of the circuit board contained in the LED device shown in FIG. The bottom view of the LED die in 2nd Embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted. For the sake of explanation, the scale of the members is changed as appropriate. Furthermore, the relationship with the invention specific matter described in the claims is described in parentheses.
(First embodiment)

The electrode surface of the LED die 20 (semiconductor light emitting device) in the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a bottom view of the LED die 20 of this embodiment. When the LED die 20 is viewed from the bottom side, two floating electrodes 25, an n-side electrode 26, and a p-side electrode 27 can be seen in the region occupied by the insulating film 24. The insulating film 24 is open around the n-side electrode 26 and the p-side electrode 27. In the figure, the n-side electrode 26 is in the center of the electrode surface, and the n-type semiconductor layer 22 is visible around the n-side electrode 26. The p-side electrode 27 is on the right side (one side) of the electrode surface, and the p-type semiconductor layer 23 can be seen around the p-side electrode 27. The floating electrode 25 is on the left side (the other side) of the electrode surface. Details of the floating electrode 25 will be described later.

  In the present embodiment, the LED die 20 will be described as a widely used face-up mounting LED die converted to a face-down mounting (flip chip mounting) LED die. In face-up mounting, the surface opposite to the electrode surface is die-bonded on the circuit board, Au electrodes are formed in the two openings of the insulating film 24, and n-side wire bonding and p-side wire bonding are applied to the respective electrodes. I do. In the LED die 20 of the present embodiment, an n-side electrode 26 and a p-side electrode 27 are formed on the electrode portion for wire bonding. When a wafer in which LED dies for face-up mounting are connected and arranged is obtained, an Au electrode for wire bonding may be formed in the opening of the insulating film 24 in some cases. In this case, since the n-side electrode 26 and the p-side electrode 27 are formed on the Au electrode, a part of the Au electrode can be seen around the n-side electrode 26 and the p-side electrode 27.

  The stacked structure of the LED die 20 will be described with reference to FIG. FIG. 2 is a cross-sectional view of the LED die 20 drawn along the line AA in FIG. An n-type semiconductor layer 22 is formed under the sapphire substrate 21, and a p-type semiconductor layer 23 is formed under the n-type semiconductor layer 22. In the drawing, the p-type semiconductor layer 23 is illustrated as being divided, but the divided portion is an opening of the p-type semiconductor layer 23 and the left and right p-type semiconductor layers 23 are connected. The insulating film 24 covers the n-type semiconductor layer 22 and the p-type semiconductor layer 23 except for the opening. The floating electrode 25 is formed so as to be connected to the lower surface of the insulating film 24. The n-side electrode 26 is connected to the n-type semiconductor layer 22 in the openings of the insulating film 24 and the p-type semiconductor layer 23. The p-side electrode 27 is connected to the p-type semiconductor layer 23 at the opening of the insulating film 24 through the metal layer 28. As will be described later with reference to FIG. 3, the metal layer 28 is laid on the periphery of the p-type semiconductor layer 23, and a part of the metal layer 28 appears below the p-type semiconductor layer 23 on the left side of FIG. 2.

  The sapphire substrate 21 is a transparent insulating substrate and has a thickness of 80 to 120 μm. The n-type semiconductor layer 22 is composed of a GaN buffer layer and an n-type GaN layer and has a thickness of about 5 μm. The p-type semiconductor layer 23 includes a metal multilayer film including a transparent electrode layer and the like and a p-type GaN layer, and has a thickness of about 1 μm. Although not shown, the light emitting layer is at the boundary between the p-type semiconductor layer 23 and the n-type semiconductor layer 22, and the planar shape is substantially the same as that of the p-type semiconductor layer 23. The insulating film 24 is made of SiO2 or polyimide and has a thickness of about several hundred nm to 1 [mu] m. The floating electrode 25, the n-side electrode 26 and the p-side electrode 27 are bumps having Au or Cu as a core, and are formed by electrolytic plating and have a thickness of about 10 to 30 μm. In the electrolytic plating method, since a common electrode in which a highly reflective aluminum layer, a TiW layer, and an Au layer are sequentially laminated is used, the floating electrode 25, the n-side electrode 26, and the p-side electrode 27 have a reflective layer on the electrode surface side. ing. The metal wiring 28 is made of Au and has a thickness of several hundred nm.

  In FIG. 3, the electrode surface of the LED die 20 will be described in more detail. FIG. 3 is a bottom view of the LED die 20 with the floating electrode 25, the n-side electrode 26, the p-side electrode 27, and the insulating film 24 removed. There is a p-type semiconductor layer 23 inside the n-type semiconductor layer 22, and the n-type semiconductor layer 22 is also visible from the opening of the central p-type semiconductor layer 23. On the right side of the drawing, a metal wiring 28 extends along the side of the p-type semiconductor layer 23 from the place where the p-side electrode 27 (see FIG. 2) is located. The metal wiring 28 is in ohmic contact with the p-type GaN layer via a transparent electrode (not shown), and functions so that a current flows to the end of the p-type semiconductor layer 23 with a low resistance. That is, by connecting the peripheral portion of the p-type semiconductor layer 23 and the p-side electrode with metal, the entire p-type semiconductor layer 23 is connected to the p-side electrode 27 with a low resistance.

  As described above, the LED die 20 is obtained by diverting an LED die for face-up mounting for flip chip mounting. When the LED die that is the basis of the LED 20 is mounted face up, light is emitted to the p-type semiconductor layer 23 side. For this reason, a transparent electrode is formed on the surface of the p-type semiconductor layer 23, and a thin metal wiring 28 is provided in order to reduce resistance so as not to have a large influence on light emission. However, the reduction in resistance in the LED die of the present invention is not limited to metal wiring. For example, the resistance of the transparent electrode may be reduced. Also, if the LED die can be designed exclusively for flip chip, a metal layer can be laminated on the p-type semiconductor layer for various purposes such as a reflective layer, and this metal layer can reduce the resistance over the entire p-type semiconductor layer.

  The LED device 30 (semiconductor light emitting device) including the LED die 20 will be described with reference to FIG. FIG. 4 is a cross-sectional view of the LED device 30. The LED die 20 is flip-chip mounted on the circuit board 38. The floating electrode 25 and the n-side electrode 26 are connected to an internal connection electrode 32 (the other electrode pattern) formed on the upper surface of the circuit board 38, and the p-side electrode 27 is an internal connection electrode 35 formed on the upper surface of the circuit board 38. (One electrode pattern) is connected. The internal connection electrodes 32 and 35 are connected to external connection electrodes 34 and 37 through through-hole electrodes 33 and 36, respectively. The upper surface of the circuit board 38 and the periphery of the LED die 20 are covered with a fluorescent resin 31. The internal connection electrodes 32 and 35 and the external connection electrodes 34 and 37 are copper foils having Ni and Au layers on the surfaces and a thickness of several μm to several tens of μm. The through-hole electrodes 33 and 36 are filled with metal paste in through-holes having a diameter of about 100 to 300 μm. In addition, when aiming at a brightness improvement, it is good for the internal connection electrodes 32 and 35 to provide the metal layer with high reflectances, such as Ag, on the surface.

  Next, the upper surface (flip chip mounting surface) of the circuit board 38 will be described with reference to FIG. FIG. 5 is a top view of the circuit board 38 included in the LED device 30. Inside the circuit board 38, rectangular internal connection electrodes 32 and 35 are formed. As shown in FIG. 4, the floating electrode 25 and the n-side electrode 26 are connected to the internal connection electrode 32, and the p-side electrode 27 is connected to the internal connection electrode 35.

  The floating electrode 25 supports the LED die 20 so that it does not tilt when pressure is applied to the LED die 20 during flip-chip mounting. Further, part of heat generated by the light emitting layer is released to the internal connection electrode 32 of the circuit board 14 through a path including the p-type semiconductor layer 23, the insulating film 24, and the floating electrode 25. Further, the floating electrode 25 strengthens the connection between the LED die 20 and the circuit board 14. In order to achieve these functions, the floating electrode may be formed along the region occupied by the p-type semiconductor layer 23. However, in order to make the internal connection electrode 32 of the circuit board 14 in a simple shape, it must be formed on the left side of the n-side electrode 26 in FIG.

As shown in FIG. 2 and the like, the n-side electrode 26 is separated from the corner of the insulating film 24. The corners of the insulating film 24 are cracked or have pinholes. That is, the LED die 20 prevents the p-type semiconductor layer 23 and the n-type semiconductor layer 22 from being short-circuited due to cracks or pinholes in the insulating film 24 because the n-side electrode 26 is separated from the corner of the insulating film 24. .
(Second Embodiment)

  In the LED die 20 shown in FIG. 1, the floating electrode 25 has a circular planar shape. However, the planar shape of the floating electrode is not limited to a circle. Further, in order to achieve a horizontal balance at the time of mounting, it is sufficient that a floating electrode is provided at least on the side opposite to the p-side electrode. Therefore, an additional floating electrode may be disposed in the vicinity of the p-side electrode. Therefore, as a modification of the floating electrode, an electrode surface of the LED die 60 (semiconductor light emitting element) in the second embodiment of the present invention will be described with reference to FIG.

  FIG. 6 is a bottom view of the LED die 60. On the electrode surface of the LED die 60, there are an n-side electrode 26, a p-side electrode 27, and floating electrodes 61, 62, 63 inside the insulating film 24. Similar to the electrode surface of the LED die 20 in FIG. 1, there is an n-side electrode 26 at the center of the electrode surface of the LED die 60, a p-side electrode 27 on the right side (one side), and an opening in the insulating film 24. The n-type semiconductor layer 22 and the p-type semiconductor layer 23 can be seen around the n-side electrode 26 and the p-side electrode 27. The floating electrode 61 is on the left side (the other side) of the electrode surface and has a U-shape and occupies a large area. Further, floating electrodes 62 and 63 are arranged on the right side of the electrode surface so as to be aligned with the p-side electrode 27. The n-side electrode 26, the p-side electrode 27, and the floating electrodes 61, 62, and 63 are plated bumps as in the LED die 20 of FIG. That is, in the LED die 60, the n-side electrode 26 and the p-side electrode 27 having the same shape are formed on the same LED die (before bump formation) as the LED die 20, and the floating electrodes 61, 62, 63 having different shapes are formed. Is. The LED die 60 can be flip-chip mounted on the circuit board 38 (see FIGS. 4 and 5). At this time, the floating electrode 61 is connected to the internal connection electrode 32 together with the n-side electrode 26, and the internal connection electrode 35 is connected to the internal connection electrode 35. Are connected to the floating electrodes 62 and 63 together with the p-side electrode 27.

  The main purpose of enlarging the floating electrode 61 and adding the floating electrodes 62 and 63 is to improve the heat dissipation characteristics and brightness of the LED die. Since the LED die 60 generates heat mainly in the light emitting layer, the p-type semiconductor layer 23 (see FIGS. 2 and 3) laminated with the light emitting layer has a large area between the circuit board 38 (see FIGS. 4 and 5) and conducts heat. A good heat dissipation path is required. Since the floating electrodes 61, 62, and 63 have a large area and are made of metal, they have a good thermal conductivity, and thus become an excellent discharge path. Further, the floating electrodes 61, 62, and 63 have a reflective layer on the electrode surface side like the floating electrode 25, and occupy a wide area, so that the light emission efficiency of the LED die 60 can be improved.

In the LED 20 of the first embodiment and the LED 60 of the second embodiment, the p-side electrode 27 was circular. The shape of the p-side electrode is not limited to a circle. For example, if the opening on the p-side of the insulating film 24 is an oval, an oval p-side electrode may be formed.

20, 60 ... LED die (semiconductor light emitting element),
21 ... sapphire substrate,
22 ... n-type semiconductor layer,
23 ... p-type semiconductor layer,
24. Insulating film,
25, 61, 62, 63 ... floating electrodes,
26 ... n-side electrode,
27 ... p-side electrode,
28 ... Metal wiring,
30 ... LED device (semiconductor light emitting device),
31 ... Fluorescent resin,
32, 35 ... internal connection electrodes (electrode patterns),
33, 36 ... through-hole electrodes,
34, 37 ... external connection electrodes,
38. Circuit board.

Claims (4)

In a semiconductor light emitting device comprising an n-type semiconductor layer and a p-type semiconductor layer, and an n-side electrode and a p-side electrode connected to the n-type semiconductor layer and the p-type semiconductor layer,
Having a rectangular electrode surface;
The n-side electrode and the p-side electrode are arranged one by one on the electrode surface,
The n-side electrode is in the center of the electrode surface;
The p-side electrode is on one short side of the electrode surface with respect to the n-side electrode,
There is a floating electrode on the other short side of the electrode surface with respect to the n-side electrode,
The semiconductor light-emitting element, wherein the entire p-type semiconductor layer is connected to the p-side electrode with a low resistance. The semiconductor light emitting element according to claim 1, further comprising a reflective metal layer on the electrode surface side of the n-side electrode, the p-side electrode , and the floating electrode . 3. The semiconductor light emitting device according to claim 2 , wherein the n-side electrode, the p-side electrode , and the floating electrode are formed by an electrolytic plating method. Wherein the one short side portion disposed p-side electrode, the semiconductor light-emitting device according to any one of claims 1 to 3, wherein the floating electrode, characterized in that a floating electrode separated.

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