JP4032752B2 - Method for manufacturing composite light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flip-chip type composite light emitting device, and more particularly to a composite light emitting device having improved heat dissipation characteristics from a semiconductor light emitting device to a submount device and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, a composite light-emitting element in which a flip-chip type semiconductor light-emitting element is bonded onto a submount element via a bump is often used.
[0003]
As shown in FIGS. 6A and 6B, this composite light-emitting element 70 has a structure in which a GaN-based LED element 72 is joined by Au bumps 73 and 74 on a Zener diode element 71 that is a silicon device, that is, a flip chip. It is an implemented structure. An Au electrode 75 is provided on the lower surface of the Zener diode element 71, and Al electrodes 76a and 76b are provided on the upper surface. Further, in order to use it as a white LED, a blue-emitting GaN LED is covered with a YAG phosphor 77.
[0004]
Compared to the case where a GaN-based LED is used alone, it is possible to perform electrostatic protection of the LED element by bonding with an Au bump, and the effect of improving luminance by taking out light from the sapphire substrate side. was there.
[0005]
The current flowing through the composite light emitting element 70 is currently about I _F = 20 mA, but in recent years, it has been considered to increase the luminance of the composite light emitting element by increasing this to about I _F = 100 mA.
[0006]
[Problems to be solved by the invention]
However, the composite light emitting element 70 has a problem in heat dissipation, and even if the current is increased to a certain extent, the luminance does not increase and may decrease.
[0007]
That is, the ease of flow of heat generated in the LED element can be evaluated by the product (kS) of thermal conductivity (k) and area (S). For example, when a GaN-based LED is used alone and connected to a lead frame, the thermal conductivity k = 42 W / m / K of the sapphire substrate is multiplied by the area S = 0.32 mm × 0.32 mm of the sapphire substrate. KS = 4.3 × 10 ⁻⁶ W · m / K.
[0008]
When the flip-chip type composite light emitting element is connected to the lead frame, it is necessary to consider the heat transfer from the Zener diode to the lead frame and the heat transfer from the GaN-based LED element to the Zener diode.
[0009]
The kS value of the Zener diode is kS = 4.42 × 10 ⁻⁵ W · m / K, and it is considered that the heat flow is more than ten times easier than the heat flow from the GaN-based LED to the lead frame.
[0010]
On the other hand, considering the kS value of the Au bump, if the thermal conductivity k = 319 W / m / K of the Au bump is multiplied by the area of 0.05 mm × 0.05 mm × π × 2 for two Au bumps, kS = 5.01 × 10 ⁻⁶ W · m / K, which is only a little larger than when a GaN-based LED is used alone.
[0011]
Further, compared to the amount of heat generated from the GaN-based LED when I _F = 20 mA, the amount of heat when I _F = 100 mA increases 6.8 times as being proportional to the power consumption I × V. This is because V _F = 3.5 V when the V _F value of the GaN-based LED is I _F = 20 mA, whereas V _F = 4.8 V increases at I _F = 100 mA. Therefore, the conventional composite light emitting device has a heat dissipation characteristic that can ensure sufficient reliability when I _F = 20 mA, but cannot have a sufficient heat dissipation characteristic for a current higher than that. The bottleneck is that in the case of a composite light emitting device, the plane cross-sectional area of the Au bump is small. The total cross sectional area of the Au bumps of the conventional composite light emitting device is about 15% of the flat cross sectional area of the semiconductor light emitting device.
[0012]
Therefore, the flip-chip type composite light emitting element is insufficient when the heat flow through the Au bump is I _F = 20 mA or more, and therefore, the heat generated by the GaN-based LED cannot be sufficiently dissipated and a large current is passed. There is a problem that it is difficult to ensure reliability.
[0013]
Therefore, an object of the present invention is to provide a flip-chip type composite light emitting device with improved heat dissipation.
[0014]
[Means for Solving the Problems]
In the composite light emitting device of the present invention, the total cross sectional area of the first and second large bumps is 30% or more of the cross sectional area of the semiconductor light emitting device.
[0015]
According to the present invention, a flip-chip type composite light emitting device with improved heat dissipation can be obtained.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The first invention of the present application has a semiconductor light emitting element in which a pair of electrodes are formed on one surface of a semiconductor thin film layer laminated on a transparent substrate, and two electrodes, and the pair of electrodes are respectively connected to the two electrodes. A submount element that joins the semiconductor light emitting element in a conductive state, and first and second large bumps that join the semiconductor light emitting element and the submount element;
The first and second large bumps are made of gold stud bumps and gold plating applied around the stud bumps, and the total cross-sectional area of the first and second large bumps is the flat area of the semiconductor light emitting device. The composite light emitting device is characterized by having a cross-sectional area of 30% or more, and the amount of heat generated in the semiconductor light emitting device is efficiently radiated by the first and second large bumps, so that the increased current It has the effect | action that the brightness | luminance according to quantity can be obtained.
[0017]
The second invention of the present application has a semiconductor light emitting element in which a pair of electrodes is formed on one surface of a semiconductor thin film layer laminated on a transparent substrate, and two electrodes, and the pair of electrodes are respectively connected to the two electrodes. In the method of manufacturing a composite light emitting element in which the submount element for joining the semiconductor light emitting element in a conductive state is joined with the first and second large bumps, the semiconductor light emitting element and the submount element are connected to the stud bump. Bonding the first and second small bumps formed by bonding; and applying gold plating to the periphery of the first and second small bumps used for bonding the semiconductor light emitting element and the submount element to form the semiconductor Forming a first and a second large-sized bump whose plane cross-sectional area is expanded to 30% or more of the plane cross-sectional area of the light-emitting element. Since the cross-sectional area of the first and second small bumps can be increased after the semiconductor light emitting element and the submount element are bonded using the first and second small bumps that have been used, the change in the process is reduced. Thus, manufacturing can be easily performed.
[0019]
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0020]
(Embodiment 1)
FIG. 1A is a plan view of the composite light emitting device according to the first embodiment of the present invention, and FIG. 1B is a front sectional view of the composite light emitting device. In FIG. 1, the composite light emitting element 1 includes a semiconductor light emitting element 2, a submount element 3, and first and second large bumps 4 and 5 that join the semiconductor light emitting element 2 and the submount element 3.
[0021]
The submount element 3 is made of an n-type silicon substrate. A p-type semiconductor region is partially formed by implanting and diffusing p-type impurity ions from a part to form a Zener diode. An n-side electrode is formed in a portion corresponding to the n-type semiconductor region, and a p-side electrode is formed in a portion corresponding to the p-type semiconductor region.
[0022]
The semiconductor light emitting element 2 is a blue light emitting flip-chip type using a GaN-based compound semiconductor as in the conventional example, and a p-type layer and an n-type layer are laminated on a sapphire substrate, and the surfaces of these layers are The p-side electrode and the n-side electrode are formed by vapor deposition.
[0023]
The total cross-sectional area of the first and second large bumps 4, 5 provided on the submount element 3 and mounting and joining the semiconductor light emitting element 2 on the submount element 3 is the flat cross sectional area of the semiconductor light emitting element 2. 30% or more. The first and second large bumps 4 and 5 can be provided close to a distance where they do not contact each other.
[0024]
By making the sum of the cross-sectional areas of the first and second large bumps 4 and 5 30% or more of the flat cross-sectional area of the semiconductor light-emitting element 2, the current flowing through the semiconductor light-emitting element 2 is, for example, I _F = 40 mA or more. The luminance can be increased to 1.5 times or more. If the total cross-sectional area of the first and second large bumps 4 and 5 is less than 30% of the flat cross-sectional area of the semiconductor light emitting device 2, the heat dissipation effect is still insufficient and the increase in luminance does not reach 1.5 times. In some cases, it is not preferable.
[0025]
Note that the total cross-sectional area of the first and second large bumps can be set to 63% or more to allow a current of I _F = 80 mA to flow, and the chip size of the semiconductor light emitting element can be reduced to the current 0.32 mm square. It is also possible to increase the current to 0.34 mm square and to set the total cross-sectional area to 68% or more to pass a current of I _F = 100 mA.
[0026]
When the submount element 3 is a Zener diode, an electrostatic protection function can be added by connecting the semiconductor light emitting element 2 and the Zener diode in reverse polarity.
[0027]
That is, with such reverse polarity connection, when an overcurrent due to a high voltage is applied to the submount element 3, the reverse voltage applied to the semiconductor light emitting element 2 is near the forward voltage of the submount element 3, that is, 0. .Bypass opens at 9V. Further, the forward voltage applied to the semiconductor light emitting element 2 sets the zener voltage Vz of the submount element 3 to around 10 V, whereby the bypass is opened at that voltage, and the overcurrent is released respectively. Therefore, destruction of the semiconductor light emitting element 2 due to static electricity can be reliably prevented.
[0028]
Next, a method for manufacturing a composite light emitting device will be described.
[0029]
FIG. 2 is an explanatory view showing a manufacturing procedure of the composite light emitting device.
[0030]
(STB (Stud Bump Bonding) process)
First and second small bumps 6 and 7 made of Au are bonded to two electrodes of each of the plurality of submount elements 3 connected before being cut.
[0031]
(FCB (flip chip bonding) process)
The semiconductor light emitting element 2 is bonded and bonded onto the first and second small bumps 6 and 7 of each submount element 3. At this time, the condition is set so that the distance between the submount element and the semiconductor light emitting element 2 is 10 μm or more, preferably 15 μm or more. The reason is that the Au plating solution easily flows around the Au bump in the next Au plating step.
[0032]
(Au plating process)
Masking is applied to predetermined portions of the connected submount elements 3, and then an electroplating operation is performed by passing an electric current in the plating tank 8, and gold plating is applied to the first and second small bumps 6, 7. First and second large bumps 4 and 5 having an enlarged plane cross-sectional area of 30% or more of the plane cross-sectional area of 2 are formed. The plane cross-sectional areas of the first and second large bumps 4 and 5 do not need to be equal, and only one of the first and second small bumps 6 and 7 may be plated with gold depending on the potential difference between the electrodes. Is possible.
[0033]
By such a method, a composite light emitting device having good heat dissipation characteristics can be obtained.
[0034]
(Embodiment 2)
FIG. 3A is a plan view of a composite light-emitting element according to the second embodiment of the present invention, and FIG. 3B is a front sectional view of the composite light-emitting element. The composite light emitting device 11 uses the first and second large bumps 13 and 12 obtained by a different manufacturing method instead of the first and second large bumps 4 and 5 of the composite light emitting device 1 described above. It was.
[0035]
Next, a method for manufacturing the composite light emitting element 11 will be described.
[0036]
FIG. 4 is an explanatory view showing a manufacturing procedure of the composite light emitting device.
[0037]
(Plating bump formation process)
Masking is applied to a predetermined portion of the plurality of submount elements 3 connected before being cut, and then an electroplating operation is performed by passing an electric current in the plating tank 8 so that two electrodes of the submount element 3 are plated with gold. First and second large bumps 13 and 12 having a plane cross-sectional area of 30% or more of the plane cross-sectional area of the semiconductor light emitting element 2 are formed.
[0038]
(FCB (flip chip bonding) process)
The semiconductor light emitting element 2 is bonded and bonded onto the first and second large bumps 13 and 12 of each submount element 3.
[0039]
By such a method, a composite light emitting device having good heat dissipation characteristics can be obtained.
[0040]
(Embodiment 3)
FIG. 5A is a plan view of a composite light emitting device according to the third embodiment of the present invention, and FIG. 5B is a front sectional view of the composite light emitting device.
[0041]
In the first and second embodiments, the semiconductor light emitting element is described as one single light emitting element. However, the present invention is not limited to this, and, for example, four semiconductor light emitting elements are formed on one block submount element 23. The case where the block light-emitting element 21 in which the block light-emitting element 22 having the element 2 as one block is arranged is also included in the present invention.
[0042]
【The invention's effect】
As described above, according to the present invention, the total cross-sectional area of the first and second large bumps is set to 30% or more of the plane cross-sectional area of the semiconductor light-emitting element, so that the amount of heat generated in the semiconductor light-emitting element can be reduced. The heat is efficiently dissipated by the first and second large bumps, the luminance corresponding to the increased current amount can be obtained, and the performance of the product can be improved.
[0043]
In addition, the first and second small bumps are plated with gold to form the first and second large bumps, so that the first and second small bumps conventionally used can be used to After joining the submount element, the plane cross-sectional area of the first and second small bumps can be increased, and the manufacturing process can be easily performed with fewer changes in the process.
[0044]
Also, by forming a large bump on the submount element by plating and then joining the semiconductor light emitting element, the work can be reduced and the work can be simplified, and the large bump can be accurately formed. It is possible to improve the product quality by preventing the inclination.
[Brief description of the drawings]
FIG. 1A is a plan view of a composite light emitting device according to a first embodiment of the present invention, and FIG. 2B is a front sectional view of the composite light emitting device. FIG. FIG. 3A is a plan view of a composite light emitting device according to a second embodiment of the present invention, and FIG. 4B is a front sectional view of the composite light emitting device. FIG. 4 shows a manufacturing procedure of the composite light emitting device. Explanatory drawing FIG. 5A is a plan view of a composite light emitting device according to a third embodiment of the present invention, FIG. 5B is a front sectional view of the composite light emitting device, and FIG. A plan view (B) of the composite light emitting device is a front sectional view of the composite light emitting device.
DESCRIPTION OF SYMBOLS 1 Composite light emitting element 2 Semiconductor light emitting element 3 Submount element 4 1st large bump 5 2nd large bump 6 1st small bump 7 2nd small bump 8 Plating tank 11 Composite light emitting element 12 2nd large bump 13 First large bump 21 Block composite light emitting element 22 Block light emitting element 23 Block submount element

Claims (1)

A semiconductor light emitting device having a pair of electrodes formed on one surface of a semiconductor thin film layer laminated on a transparent substrate;
A composite light-emitting element having two electrodes and a submount element that joins the semiconductor light-emitting element to the two electrodes in a state where the pair of electrodes are electrically connected to each other by first and second large bumps. In the manufacturing method,
Bonding the semiconductor light emitting element and the submount element with first and second small bumps formed by stud bump bonding;
The first and second small bumps used for joining the semiconductor light emitting element and the submount element are plated with gold to enlarge the plane sectional area to 30% or more of the planar sectional area of the semiconductor light emitting element. And a step of forming a second large bump .

Images