KR20060085523A - Packaging apparatus of high-power led using laser - Google Patents

Abstract

The present invention relates to a packaging device of a high-power LED using a laser, the conventional method of bonding a high-power LED using a heater by a utero method or an ultrasonic method using an ultrasonic device using a heat source as a laser The present invention relates to a high power LED packaging device using laser for achieving high reliability and high productivity.

To this end, the present invention, the mobile bonding tool for picking up and seating the LED chip on the substrate to be bonded to the LED chip is located, and transfers the laser beam generated from the laser oscillator generating a predetermined laser output to the upper portion of the substrate Is provided with an optical fiber, the optical fiber is configured to be dually installed in a position opposite to each other to face the bonding site.

Description

Packaging apparatus of high-power LED using laser}             

1 to 4 are diagrams for explaining a conventional eutectic bonding method.

5 is a view for explaining a conventional ultrasonic bonding method.

6 is a view for explaining the problem of the ultrasonic bonding method.

7 shows a bonding apparatus according to the present invention.

8 is a view for explaining a wafer level eutectic bonding method according to the present invention.

9 through 11 illustrate various embodiments of the present invention.

12 is a flowchart showing a bonding method for implementing the present invention.

<Description of the symbols for the main parts of the drawings>

1: LED chip 2: substrate wafer

30: LED chip upper camera 31: LED chip transfer unit

32: bonding head portion 33: bonding tool

34: upper substrate camera 35: lower camera

36 controller 37 laser oscillator

38 substrate wafer transfer portion 39 optical fiber

40: total reflection mirror

The present invention relates to a packaging device of a high-power LED using a laser, the conventional method of bonding a high-power LED using a heater by a utero method or an ultrasonic method using an ultrasonic device using a heat source as a laser The present invention relates to a high power LED packaging device using laser for achieving high reliability and high productivity.

LED chip is generally manufactured by the following process.

Epi Process-Photolithography-Etching-Metallization-Lapping / Polishing-Dicing

Finally, the separated LED chip is die-bonded in various package types.

Recently, as high-power LEDs are developed in earnest for lighting purposes, heat generation problems in LEDs are emerging.

As shown in FIG. 1, since the high power LED 1 emits a lot of heat during light emission, the thermally conductive materials A LN and SiC are generally used so that heat can be diffused outward and discharged through the package 3. Alternatively, a substrate 2 made of Si or the like is used.

How fast and evenly the heat of the high power LED (1) is the key technology of the high power LED (1) is the key technology of the high output LED (1) and the bonding method between the high output LED (1) and the substrate (2) have.

One method is to join as a heat using a heater, and the other method is to join using ultrasonic waves.

The former is called an eutectic bonding method, and the latter is called an ultrasonic bonding method.

First, the utero joining method will be described.

The eutectic bonding method is a bonding method that focuses on the fact that the melting point of metals is quite high, but the melting points of different kinds of compositions are considerably lowered.

For example, the melting point of gold (Au) is 1064 degrees, but if 20% of tin (Sn) is contained here, the melting point is lowered to 283 degrees.

This is used to bond the LED and the substrate. In order to bond the two, a thin film of Au and AuSn is coated on the lower surface of the LED 1 and the upper surface of the substrate 2, respectively, as shown in FIG.

In the eutectic joining process, heat is required to melt dissimilar metals.

In general, tin (Sn) is easily oxidized in the air, so in the eutectic bonding method, the space where the chips are bonded is preferably operated under the atmosphere of nitrogen gas.

There are many heat sources used, but in general, raising and lowering the temperature is not fast.

In the process of picking and placing the LED chip 1 and the substrate 2, heat should not be applied. Therefore, heat must be applied from the moment the LED chip 1 and the substrate 2 touch each other. Therefore, in order to raise the chip at room temperature to at least 300 degrees, the heat source type or heating method should be considered.

FIG. 3 is a diagram illustrating a conventional eutectic bonding process, in which a substrate 2 and an LED 1 that are separated one by one are supplied to a device (a), and then the substrate chip is picked up by a bonding tool and the camera The attitude correction is performed by (b).

Subsequently, the bonding tool is moved to seat the substrate 2 on the seating plate (c), the LED 1 is picked up by the pick-up tool, and posture correction is performed by the camera (d). It moves toward (2) and rests on the upper portion of the substrate (2) (e).

Then, heat is applied to the mounting plate to bond the LED 1 to the substrate 2 (f).

By the way, as shown in Fig. 4 is a method of joining the substrate 2 by applying heat under the substrate 2 using a heater, but the time corresponding to the heater temperature is not fast. Mass production is not high.

Ultrasonic bonding method is as follows.

As shown in FIG. 5, Au Bumps 4 are first formed on the upper surface of the substrate 2, and the Au PADs 5 of the LED chips corresponding to the Au Bumps 4 of the substrate 2 are matched. Let's do it.

The LED chip 1 is brought into close contact with the substrate 2, the pressure 7 and the ultrasonic energy 6 are simultaneously applied using the ultrasonic head 8, and the Au PAD 5 and the substrate under the LED chip 1 are applied. As Au Bump (4) of (2) touches, Au Bump (4) is distorted and the surface of Au is activated by ultrasonic energy (6), so that the bonding between Au PAD (5) and Au Bump (4) is made. do.

As the LED is getting higher and higher, the heat generation problem is seriously raised, and how much stable and fast heat is emitted to the outside is important, but the ultrasonic method requires the interval between Au Bumps (4) as shown in FIG. You can't get the heat out of space. The heat that could not be drained will accumulate and eventually cause the LED to fail. Therefore, the ultrasonic bonding method has a structural defect.

In addition, since the ultrasonic bonding does not completely melt and bond the Au Bump (4), it may be a problem for many heat dissipation generated during long time use of the LED.

On the other hand, the eutectic method melts and pastes AuSn completely, and Au and AuSn are spread evenly on the LED chip 1 and the substrate 2, thereby stably acting on heat diffusion.

At present, the high-power LED is considered to be superior to the ultrasonic method over the ultrasonic bonding method.

However, since the eutectic method joins by applying heat, a heat rising time is necessary and a heater capable of locally applying heat between the LED chip 1 and the substrate 2 is required. In addition, deterioration of the device due to uneven heating becomes a problem. Also, the first chip should not be melted again by the subsequent heating process. To solve this problem, the tool itself may be heated, but in reality, accurate control is difficult.

Ultrasonic generation in ultrasonic bonding operates for less than 1 second, so the productivity is considerably higher than that of the eutectic.

If the eutectic bonding method can achieve higher productivity as the ultrasonic method, the eutectic bonding method is advantageous for the high power LED bonding method.

In summary, these joining methods have the following problems.

First, in order to raise the temperature of the substrate and the LED chip by the conventional eutectic bonding method, the heater was heated. However, it takes much time to raise and lower the temperature. Therefore, productivity is not high.

Second, the conventional ultrasonic bonding method has high productivity due to the short bonding time, but the ultrasonic bonding method tends to be less reliable in the high output LED than the ultrasonic bonding method.

In other words, in the eutectic bonding method, Au and AuSn are completely melted to form an alloy, and thus the bonding strength between the LED and the substrate is excellent, and thus heat dissipation is desired.

However, since the ultrasonic bonding method is a partial bonding consisting of surface activation between Au and Au, the bonding force or heat emission is lower than that of the eutectic bonding method.

Third, the conventional bonding method is difficult at the wafer level.

In other words, it is difficult to bond each LED chip onto the substrate supplied to the wafer by means of a eutectic. If you melt all the LEDs at once by raising the temperature of the board without putting each LED chip on the board and melting the LEDs at once, the LED chip is not fixed on the board. It is wrong. If the attitude of the LED chip is incorrect, that is, the degree of bonding is reduced, heat dissipation is not smooth, and thus the reliability of the high power LED cannot be guaranteed. In addition, when the LED chip is placed on the substrate and the temperature is melted to apply a slight pressurization to the LED, the bonding strength is excellent, so if the LED is simply placed on the substrate and melted, the bonding strength is reduced. When the bonding force is lowered, heat dissipation is not performed smoothly, and thus the reliability of the high power LED is lowered.

Fourth, the problem of the conventional ultrasonic bonding method is that Au bumps must be formed on the substrate, but if the height between the Au bumps is not constant, the lower surface of the LED chip does not touch evenly, so that only one side melts as shown in FIG. 6. do. The height of Au Bump must be managed uniformly. This is not an extremely easy process and it is difficult to manage the equipment because the LED chip must be balanced to Au Bump even if Au Bump is formed uniformly.

Also, it is very difficult to manage the Au bump shape because the characteristics of the LED vary depending on the shape of the Au bump.

The present invention has been made in view of the above problems, and the present invention aims to achieve higher productivity as the ultrasonic bonding method even in the eutectic bonding method, and has an object of using a laser as a heat source.

In order to achieve the above object, a packaging device for a high power LED using a laser according to the present invention,

The mobile bonding tool for picking up and seating the LED chip is positioned on the upper part of the substrate to which the LED chip is to be bonded, and an optical fiber for delivering the laser beam generated from the laser oscillator generating a predetermined laser output to the upper part of the substrate, The optical fiber is characterized in that it is configured so as to face the bonding site is installed in a double in a position opposite to each other.

The present invention configured as described above will be described in detail with reference to the accompanying drawings.

As shown in FIG. 7, the laser is a device capable of output on / off at a considerably fast response speed and is the most optimal method for raising the temperature at the junction of the high power LED 1 and the substrate 2 extremely. . In general, the laser uses a fiber coupled semiconductor laser, and considering the heat absorption with the LED substrate material, the 808 nm band is preferable.

In the present invention, the laser oscillator 11 is used to greatly reduce the temperature rise of the heater. The oscillation time of the laser oscillator 11 is considerably fast and has the advantage of raising the temperature locally.

By focusing the laser beam on the LED chip 1 and the substrate 2, when the laser is oscillated within a short time, the temperature of the LED 1 rises rapidly, and the appropriate power can be output from the laser oscillator 11 The LED 1 is bonded by adjusting the eutectic temperature.

In addition, Heater-1 is built into the bonding tool so that it can always be maintained at a temperature of about 150-200 degrees, and Heater-2 can always be maintained at a temperature of about 150-200 degrees. When the temperature of the substrate 2 is to be increased and bonded, it may be used as an auxiliary heater for heat to give excellent bonding force.

In addition, in the conventional method, the following eutectic bonding method is impossible at the wafer level. The conventional method was a 1: 1 bonding method for bonding one LED chip to one substrate chip, but the present invention proposes a wafer level bonding method.

The wafer-level eutectic bonding method means that the substrate is supplied to the equipment as a wafer itself rather than as a single piece, and the LED chips are directly bonded onto the wafer by the eutectic bonding method.

Therefore, in the existing method of bonding one LED to one board, a device of a very complicated shape is included, including a mechanism configuration and control for supplying the boards one by one and extracting the bonded LEDs. However, in the present invention, since the substrate is used as the wafer, such a transfer structure is not necessary, and thus a simpler system can be manufactured than the existing apparatus.

Next, a wafer level bonding method will be described with reference to FIG.

First, the wafer to be used as a substrate is supplied as shown in (a), and then, as shown in (b), the LED chip is picked up using a bonding tool, and then moved to the upper part of the wafer as shown in (c). Let's go.

Thereafter, as shown in (d), the laser beam transmitted through the optical fiber is irradiated toward the LED, whereby the temperature rises and the LED and the wafer are bonded.

In the case of (e)-(g), a process of repeating the process of (b)-(d) is shown. Through this process, a plurality of LED chips are bonded onto the wafer level substrate as shown in (h).

Apparatus implementation for the method of the present invention is as follows, it can be divided into three types, dual irradiation type, fixed type, mobile type according to the laser beam irradiation method.

First, in the dual irradiation type, as shown in FIG. 9, the bonding tool 33 picks up the LED chip 1 placed on the LED chip transfer part 31 by the bonding head part 32 to form an upper portion of the substrate 2. Moved to and placed.

After that, the laser beam oscillated from the laser oscillator 37 is irradiated onto the LED chip 1 through the optical fiber 39 positioned to irradiate both ends of the junction and is bonded.

In this case, the upper camera 30 is a camera for accurately determining the position of the chip before the contact head 32 picks up the LED chip 1, and the substrate upper camera 34 is picked up by the bonding head 32. It is a camera for recognizing the position and pattern of the substrate before bonding the LED chip 1 to the substrate 2, and the lower camera 35 freezes the posture of the LED chip 1 picked up by the bonding head 32. It is a camera to print.

The controller 36 is for integrated control of the apparatus of the present invention.

The substrate wafer transfer unit 38 is an X-Y transfer unit for moving the substrate based on the positional information recognized by the upper camera 34.

Next, as shown in FIG. 10, the laser beam oscillated from the laser oscillator 37 on the side is oriented at a 90 degree angle by the total reflection mirror 40 inside the junction, so that the substrate 2 may be rotated. This is the way to irradiate to the top.

As shown in Fig. 11, the movable type is similar to the fixed type, but the laser beam oscillated from the laser oscillator 37 is connected to the side of the joint through the optical fiber, and the total reflection mirror 40 is positioned inside the joint to adjust the angle. As a method of converting and irradiating to the upper portion of the substrate 2, the bonding portion is a method of moving irradiation while attracting the optical fiber.

FIG. 12 is a flowchart illustrating a method of bonding LEDs using the apparatus of the present invention. First, the next camera of the LED chip 1 is photographed in the upper camera 30 positioned above the LED chip 1, and then the controller ( The image is processed at 36 and, accordingly, the LED chip transfer unit 31 is moved to match the center of the LED chip 1 with the center of the upper camera 30.

The bonding head 32 is moved to the upper part of the LED chip 1 to pick up the LED chip 1, and then picked up to the position where the lower camera 35 is located, and the lower camera 35 is By taking this action, the posture of the LED chip 1 picked up by being processed by the controller 36 is aligned once again.

In this case, the upper camera 34 of the substrate photographs the posture of the substrate 2, and processes the image on the controller 36 so that the center of the substrate 2 coincides with the center of the upper camera 34. ) Is moved. Changing the optical system of such image processing generally enables not only the die bonder but also the flip chip process.

Subsequently, when the pickup head 32 moves to the upper portion of the substrate 1, that is, the position where the LED chip 1 is to be bonded, descends and places the LED chip 1 on the upper portion of the substrate 1, the laser oscillator 36 The laser beam is bonded to the LED chip 1 until it is turned on to reach a predetermined power set point.

When the bonding is completed, the laser oscillator 37 is turned off, the bonding head 32 is raised, and the plurality of LED chips are bonded onto the substrate using the laser beam through the above processes. The wafers in the substrate state in which the bonding is completed are separated after a suitable dicing process.

As described above, the packaging device of the high power LED using the laser of the present invention has the following effects.

First, it uses the eutectic bonding method which has better bonding strength and bonding reliability than the ultrasonic bonding method. While heating, the laser can be used to overcome the low productivity, which is the biggest disadvantage of the eutectic bonding method.

Second, since the wafer itself is supplied instead of the substrates one by one, the device structure for picking and placing the substrates is not necessary, so the device is not complicated and the transport of the substrates is not necessary, thereby achieving high productivity.

Third, a reliable and fast temperature profile can be achieved by using a laser as the main heat source and using an auxiliary heater in the bonding tool and the mounting plate of the substrate to achieve the eutectic bonding process.

Fourth, the ultrasonic method, which is one of the existing bonding methods, is required to apply a high pressure when bonding the LED chip and the substrate, so that the pressing structure is complicated and damage to the chip may occur. The bonding to the non-high eutectic method has little effect on the chip.

Claims (5)

The mobile bonding tool for picking up and seating the LED chip is positioned on the upper part of the substrate to which the LED chip is to be bonded, and an optical fiber for delivering the laser beam generated from the laser oscillator generating a predetermined laser output to the upper part of the substrate, The optical fiber is a packaging device for a high-power LED using a laser, characterized in that it is installed in a dual position in the opposite position to face the bonding site. 2. The packaging apparatus of high power LED using a laser according to claim 1, wherein a heating means is mounted on the lower part of the substrate and / or inside the bonding tool. A mobile bonding tool for picking up and seating an LED chip on the substrate to be bonded is located, and receives a laser beam generated from a laser oscillator generating a predetermined laser output from the side of the bonding tool. The packaging device of high power LED using a laser, characterized in that configured to direct the laser beam to the junction portion of the LED chip located on the upper substrate through the total reflection mirror provided.  4. The packaging apparatus of high power LED using a laser according to claim 3, wherein the laser beam is transmitted to the side of the bonding tool through an optical fiber. 4. The packaging apparatus of high power LED using a laser according to claim 3, wherein a heating means is mounted on a lower portion of the substrate and / or inside the bonding tool.

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