Flip chip LED and manufacturing method thereof

Abstract

The application provides a flip LED chip and a manufacturing method thereof. The method comprises the following steps: placing a tin electrode of an LED wafer upwards and fixing the LED wafer on a carrier; controlling rotation of a scraping disc on a grinding workpiece table and moving the scraping disc to a position directly above the tin electrode; when the rotation speed of the scraping disc reaches a working speed, moving the carrier to the direction of the grinding workpiece table; when the scraping disc contacts the tin electrode, entering a preparation state; and controlling the carrier to enter a working state from the preparation state, wherein the working state is that the carrier moves at a constant speed to the grinding workpiece table by a certain distance so that the scraping disc contacts the tin electrode and grinding is completed. The method provided by the application can solve the problem of large height difference of the tin electrode prepared by a tin brushing process on a metal bonding layer of a flip LED chip in the prior art.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flip LED chip, and particularly relates to a flip LED chip and a manufacturing method thereof. BACKGROUND

[0002] As a new product in the optoelectronic industry, the light-emitting diode (LED) has the characteristics of small size, high brightness, long service life, rich color, low energy consumption, high safety, etc. and is widely used in general lighting, display screen, signal lamp, backlight, special lighting, indoor display, liquid crystal display, vehicle-mounted lighting, vehicle-mounted display and other fields.

[0003] In recent years, in the chip field, flip chip technology is emerging. The flip LED chip has the advantages of good heat dissipation performance, low voltage, high brightness, high reliability and high saturation current density, and is popular in the application market of high-power and outdoor lighting, and gradually mature.

[0004] The existing flip LED chip prepares a tin electrode on the chip metal bonding layer through a tin brushing process to facilitate packaging. Although the existing tin brushing process is already very mature, under the process limit, there is still a situation that the tin electrode heights on a wafer are not the same, resulting in a large height difference between the lowest and highest chips on a wafer. The large height difference will cause the chip to turn over during the flip-molding process after the chip is cut, damaging the chip. At the same time, the large height difference will also cause the suction nozzle to fail to grab the chip or to grab it crookedly. In order to solve the above problems, the tin electrode height consistency can be achieved by optimizing the tin brushing process and improving the tin brushing precision, but this will undoubtedly greatly increase the cost of chip manufacturing. SUMMARY

[0005] Therefore, in the embodiments of the present application, a flip LED chip and a manufacturing method thereof are provided to solve the problem of large height difference of the tin electrode prepared on the metal bonding layer of the flip LED chip through the tin brushing process in the prior art.

[0006] The first aspect of the embodiments of the present application provides a manufacturing method of a flip LED chip, including the following steps:

[0007] The tin electrode of the LED wafer is upward and fixed on a loading platform;

[0008] The rotation of the scraping disc on the grinding workpiece table is controlled, and the scraping disc is moved to the top of the tin electrode. When the rotation speed of the scraping disc reaches the working speed, the loading platform is controlled to move towards the grinding workpiece table. When the scraping disc contacts the tin electrode, a preparatory state is entered.

[0009] controlling the carrier to enter a working state from the standby state, the working state being that the carrier moves at a constant speed to the grinding workpiece table by a certain distance to make the scraper contact the tin electrode and complete the grinding.

[0010] Preferably, the working rotation speed is 1000 rpm-3000 rpm.

[0011] Preferably, the step of placing the tin electrode of the LED wafer upwards on the carrier specifically includes:

[0012] placing the tin electrode of the LED wafer upwards on the carrier;

[0013] turning on a vacuum generator to adsorb the tin electrode of the LED wafer on the carrier.

[0014] Preferably, in the working state, the moving speed of the carrier to the grinding workpiece table is 500 nm / min.

[0015] Preferably, the material of the scraper is single-crystal diamond.

[0016] Preferably, the step of placing the tin electrode of the LED wafer upwards on the carrier is preceded by:

[0017] obtaining a height requirement value of the tin electrode;

[0018] detecting the height to be ground of all the tin electrodes on the LED wafer and obtaining the maximum height value and the minimum height value of the height to be ground;

[0019] judging whether the minimum height of the height to be ground is greater than or equal to the height requirement value;

[0020] If yes, the step of placing the tin electrode of the LED wafer upwards on the carrier is executed.

[0021] Preferably, the value of the certain distance is the difference between the maximum height value of the height to be ground and the height requirement value.

[0022] Preferably, the moving time can be calculated according to the certain distance and the moving speed.

[0023] Preferably, the step of controlling the carrier to enter a working state from the standby state, the working state being that the carrier moves at a constant speed to the grinding workpiece table by a certain distance to make the scraper contact the tin electrode and complete the grinding is followed by:

[0024] detecting the current height value of all the tin electrodes on the LED wafer and obtaining the maximum height value and the minimum height value of the current height value;

[0025] obtaining a TTV value, the TTV value being a difference between a maximum height value of the current height value and a minimum height value of the current height value;

[0026] determining whether the TTV value is less than a threshold value;

[0027] If yes, the process is completed.

[0028] The second aspect of the embodiment of the present application provides a flip LED chip, which is prepared by the flip LED chip manufacturing method described above.

[0029] Compared with the prior art, the implementation of the present application has the following beneficial effects:

[0030] By fixing the LED wafer with tin electrodes on the stage under the ground of the ground worktable, since the rotating scraping disc is arranged on the ground worktable, when the tin electrodes with different heights contact the scraping disc with a certain rotating speed, the surfaces of the tin electrodes will be ground, and by adjusting the given distance, the tin electrodes with different heights can be ground to the tin electrodes with consistent heights, thereby solving the problem of large height difference of the tin electrodes prepared by the tin brushing process on the metal bonding layer of the flip LED chip. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The flow chart of the flip LED chip manufacturing method for the first embodiment of the present application is shown in the figure.

[0032] Figure 2 The flow chart of the flip LED chip manufacturing method for the second embodiment of the present application is shown in the figure.

[0033] The following specific embodiments will be further described with reference to the above-mentioned figures. DETAILED DESCRIPTION

[0034] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the related drawings. The drawings show several embodiments of the present application. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0035] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can be a middle element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be a middle element. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. The use herein of the terms "and / or" includes a set of one or more associated listed items.

[0037] Embodiment 1

[0038] Please refer to Figure 1 , Figure 1 The method for manufacturing the flip LED chip according to the embodiment of the present application is shown in the figure, and the method specifically comprises steps S01 to S03.

[0039] In step S01, the tin electrode of the LED wafer is upward and fixed on a carrier.

[0040] It should be noted that when the LED wafer is fixed on the carrier, the tin electrode is upward, and meanwhile, the LED wafer is ensured to be relatively parallel to the scraping disc on the grinding workpiece table. In addition, the stability of the fixed LED wafer is also ensured, so that the LED wafer will not shake when the scraping disc rotates to contact the tin electrode, thereby ensuring the grinding precision.

[0041] In step S02, the scraping disc on the grinding workpiece table is controlled to rotate and move to the tin electrode. When the rotating speed of the scraping disc reaches the working speed, the carrier is controlled to move towards the grinding workpiece table. When the scraping disc contacts the tin electrode, the preliminary state is entered.

[0042] In this embodiment, the working environment of the entire grinding process is that the temperature is 20-25°C and the humidity is 50-60%. When the scraping disc on the grinding workpiece table is started, the grinding workpiece table with the scraping disc slowly moves to the tin electrode to be ground, and the rotating speed of the scraping disc gradually increases to the working speed. It should be noted that the working speed is 1000-3000 rpm. When the scraping disc reaches the working speed, the carrier under the grinding workpiece table slowly moves towards the grinding workpiece table. Since the pressure sensing device is arranged on the scraping disc, when the scraping disc contacts the tin electrode, the preliminary state is entered. The preliminary state is that the scraping disc keeps the working speed and the carrier does not continue to move towards the grinding workpiece table. The purpose of the preliminary state is to give the operator enough time to react and stop the further operation of the equipment in case of emergency. On the other hand, the speed of the carrier moving towards the grinding workpiece table is adjusted, because before entering the preliminary state, the speed of the carrier moving towards the grinding workpiece table is relatively fast, which can improve the working efficiency.

[0043] Step S03, control the carrier to enter a working state from the standby state, the working state is that the carrier moves at a constant speed to the grinding workpiece table for a certain distance, so that the scraping disc contacts the tin electrode, and the grinding is completed.

[0044] Specifically, the material of the scraping disc is single crystal diamond, which has high hardness, is not easy to wear, and has good stability, and is suitable for grinding tin electrodes. After entering the working state from the standby state, the carrier moves at a constant speed of 500 nm / min to the grinding workpiece table for a certain distance. It can be understood that the tin electrode is ground by 500 nm per minute, and the certain distance is the distance from the highest tin electrode on a piece of LED wafer to the tin electrode of the target thickness. According to the distance and the moving speed of the carrier, the moving time can be calculated, and the grinding thickness of the tin electrode is adjusted by controlling the moving time.

[0045] In addition, during the grinding process, the tin slag generated by grinding is sucked away by the built-in dust collection device of the carrier and stored in the cavity. The cavity needs to be cleaned regularly.

[0046] In summary, the manufacturing method of the flip LED chip in the above embodiment of the present application fixes the LED wafer with tin electrodes on the carrier below the grinding workpiece table. Since the grinding workpiece table is provided with a rotating scraping disc, when the tin electrodes with different heights contact the scraping disc with a certain rotating speed, the surface of the tin electrode will be ground. By adjusting the certain distance, the tin electrodes with different heights can be ground to tin electrodes with consistent height, thereby solving the problem of large height difference of the tin electrodes prepared by the tin brushing process on the metal bonding layer of the flip LED chip.

[0047] Example 2

[0048] Please refer to Figure 2 , Figure 2 The manufacturing method of the flip LED chip according to the second embodiment of the present application is shown, which specifically includes steps S10 to S18.

[0049] Step S10, obtain the height requirement value of the tin electrode.

[0050] It can be understood that the height requirement value of the tin electrode is the target thickness of the tin electrode, and the target thickness of the tin electrode is different according to different chips.

[0051] Step S11, detect the height to be ground value of all tin electrodes on the LED wafer, and obtain the maximum height value and the minimum height value of the height to be ground value.

[0052] It should be noted that after the tin electrode of the LED wafer is brushed, the height of the tin electrode is 15-150 μm. Due to the limitation of the tin brushing process, the height of the tin electrode will be uneven. If the maximum height value of the tin electrode to be ground is greatly different from the minimum height value, the chip will be damaged in the subsequent mold turning and clamping processes. After most of the LED wafers are brushed, the TVV is greater than 3, wherein the TVV refers to the difference between the maximum height and the minimum height of the tin electrode.

[0053] In step S12, it is determined whether the minimum height of the height to be ground is greater than or equal to the height requirement value. If yes, step S13 is performed.

[0054] Specifically, after the minimum height of the tin electrode to be ground is obtained, it needs to be compared with the height requirement value of the tin electrode. It can be understood that when the height requirement value is greater than the minimum height of the tin electrode to be ground, the stage will transport the LED wafer to the height requirement of the tin electrode. At this time, the scraper will not be able to grind the minimum height of the tin electrode to be ground, and the LED wafer needs to be brushed again to make the minimum height of the tin electrode to be ground reach the height requirement value.

[0055] In step S13, the tin electrode of the LED wafer is upward and fixed on the stage.

[0056] In step S14, the rotation of the scraper on the grinding workpiece table is controlled, and the scraper is moved to the top of the tin electrode. When the rotation speed of the scraper reaches the working speed, the stage is controlled to move towards the grinding workpiece table. When the scraper contacts the tin electrode, the preliminary state is entered.

[0057] In step S15, the stage is controlled to enter the working state from the preliminary state. The working state is that the stage moves at a constant speed to the grinding workpiece table by a certain distance, so that the scraper contacts the tin electrode and completes the grinding.

[0058] In step S16, the current height values of all tin electrodes on the LED wafer are detected, and the maximum height value and the minimum height value of the current height values are obtained.

[0059] In step S17, the TTV value is obtained, which is the difference between the maximum height value and the minimum height value of the current height values.

[0060] In step S18, it is determined whether the TTV value is less than a threshold value. If yes, the process is completed.

[0061] In the embodiment, the threshold value is 3, and when the TTV value is less than 3, it represents that the difference between the maximum height value and the minimum height value of the tin electrode after polishing on the whole wafer is within 3, and the consistency is higher, which can meet the production of the subsequent process and improve the chip yield.

[0062] Embodiment 3

[0063] The manufacturing method of the flip LED chip in the embodiment includes the following steps:

[0064] The LED wafer is placed on the stage, and the vacuum generator is started, and then the LED wafer is adsorbed on the stage, wherein the chip model on the LED wafer is a 4040 chip, the tin electrode height on the 4040 chip is controlled to be 80 μm ± 5 μm, the actual TVV is 8.4, the rotation of the scraping disc on the grinding workpiece table is controlled, and the scraping disc is moved to the top of the tin electrode, when the rotation speed of the scraping disc reaches 2500 rpm, the stage slowly moves upward until it contacts the highest tin electrode and stops moving, and then moves upward at a speed of 500 nm / min for 60 min, after 60 min, the stage is reset, the tin electrode height is ground to 50 μm ± 1.5 μm, and the TTV is 2.8.

[0065] Embodiment 4

[0066] The manufacturing method of the flip LED chip in the embodiment includes the following steps:

[0067] The LED wafer is placed on the stage, and the vacuum generator is started, and then the LED wafer is adsorbed on the stage, wherein the chip model on the LED wafer is a 4040 chip, the tin electrode height on the 4040 chip is controlled to be 80 μm ± 5 μm, the actual TVV is 8.4, the rotation of the scraping disc on the grinding workpiece table is controlled, and the scraping disc is moved to the top of the tin electrode, when the rotation speed of the scraping disc reaches 2500 rpm, the stage slowly moves upward until it contacts the highest tin electrode and stops moving, and then moves upward at a speed of 500 nm / min for 60 min, after 60 min, the stage is reset, the tin electrode height is ground to 50 μm ± 1.5 μm, and the TTV is 2.8.

[0068] Embodiment 5

[0069] The manufacturing method of the flip LED chip in the embodiment includes the following steps:

[0070] Put the LED wafer on the stage, and open the vacuum generator, then the LED wafer is adsorbed on the stage, wherein the chip model on the LED wafer is 0620 chip, the tin electrode height control on the 0620 chip is 30 μm ± 2.5 μm, the actual TTV is 4.2, control the rotation of the scraping disc on the grinding worktable, and move to the tin electrode directly above, when the scraping disc speed reaches 2000 rpm, the stage slowly moves upward, until the highest tin electrode is contacted and stops moving, then moves upward at a speed of 500 nm / min for 20 min, after 20 min, the stage is reset, the tin electrode height is ground to 20 μm ± 1 μm, and the TTV is 2.6.

[0071] Example 6

[0072] The flip LED chip manufacturing method in this embodiment includes the following steps:

[0073] Put the LED wafer on the stage, and open the vacuum generator, then the LED wafer is adsorbed on the stage, wherein the chip model on the LED wafer is 0620 chip, the tin electrode height control on the 0620 chip is 30 μm ± 2.5 μm, the actual TTV is 4.2, control the rotation of the scraping disc on the grinding worktable, and move to the tin electrode directly above, when the scraping disc speed reaches 2000 rpm, the stage slowly moves upward, until the highest tin electrode is contacted and stops moving, then moves upward at a speed of 500 nm / min for 20 min, after 20 min, the stage is reset, the tin electrode height is ground to 20 μm ± 1 μm, and the TTV is 2.6.

[0074] Example 7

[0075] The flip LED chip manufacturing method in this embodiment includes the following steps:

[0076] Put the LED wafer on the stage, and open the vacuum generator, then the LED wafer is adsorbed on the stage, wherein the chip model on the LED wafer is 0620 chip, the tin electrode height control on the 0620 chip is 30 μm ± 2.5 μm, the actual TTV is 4.2, control the rotation of the scraping disc on the grinding worktable, and move to the tin electrode directly above, when the scraping disc speed reaches 2000 rpm, the stage slowly moves upward, until the highest tin electrode is contacted and stops moving, then moves upward at a speed of 500 nm / min for 20 min, after 20 min, the stage is reset, the tin electrode height is ground to 20 μm ± 1 μm, and the TTV is 2.6.

[0077] Example 8

[0078] The flip LED chip manufacturing method in this embodiment includes the following steps:

[0079] The LED wafer is placed on the stage, and the vacuum generator is turned on, and then the LED wafer is adsorbed on the stage, wherein the chip model on the LED wafer is 3535 chip, the tin electrode height control on the 3535 chip is 90 μm ± 5 μm, the actual TTV is 8.7, the rotation of the scraping disc on the grinding worktable is controlled, and it is moved to the tin electrode directly above, when the scraping disc rotation speed reaches 2500 rpm, the stage slowly moves upward, and stops moving after contacting with the highest tin electrode, and then moves upward at a speed of 500 nm / min for 60 min, after 60 min, the stage is reset, the tin electrode height is ground to 60 μm ± 1.5 μm, and the TTV is 2.9.

[0080] Please refer to the following table 1, which shows the parameters corresponding to the above-mentioned embodiments 3-8 of the present application as shown in table 1:

[0081] Table 1

[0082]

[0083]

[0084] As can be seen from the table, after the method is ground, the TTV of the tin electrode is controlled from more than 3 to less than 3, wherein the TTV of the 4040 chip is reduced from 8.4 to 2.8, the TTV of the 1030 chip is reduced from 3.8 to 2.6, the TTV of the 0620 chip is reduced from 4.2 to 2.6, the TTV of the 3939 chip is reduced from 7.9 to 2.8, the TTV of the 3030 chip is reduced from 8.8 to 2.8, the TTV of the 3535 chip is reduced from 8.7 to 2.9, and the improvement effect is obvious.

[0085] Example 9

[0086] The flip LED chip provided by the embodiment 9 of the present application can be prepared by the flip LED chip manufacturing method in the above-mentioned embodiment one.

[0087] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0088] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for fabricating a flip-chip LED, characterized in that, Includes the following steps: The LED chip is fixed on the stage with the tin electrode facing upwards. The scraper on the workpiece grinding table is controlled to rotate and move directly above the tin electrode. When the scraper reaches the working speed, the platform is controlled to move towards the workpiece grinding table. When the scraper contacts the tin electrode, it enters the preparation state. The stage is controlled to enter the working state from the preparatory state. The working state is that the stage moves at a constant speed to the grinding workpiece stage a predetermined distance so that the scraper contacts the tin electrode to complete the grinding. The current height value of all tin electrodes on the LED chip is detected, and the maximum and minimum height values ​​of the current height values ​​are obtained; Obtain the TTV value, where the TTV value is the difference between the maximum height value and the minimum height value of the current height value; Determine whether the TTV value is less than the threshold; If so, then the process is complete; The operating speed is 1000 rpm to 3000 rpm; The specific steps of fixing the LED chip with the tin electrode facing upwards on the stage are as follows: The LED chip is placed on the carrier with the tin electrode facing upwards; Turn on the vacuum generator and attach the tin electrode of the LED chip to the carrier stage; In the aforementioned working state, the moving speed of the stage towards the workpiece grinding stage is 500 nm / min; The step of fixing the LED chip with its tin electrode facing upwards on the stage also includes: Obtain the required height value for the tin electrode; The grinding height values ​​of all tin electrodes on the LED chip are detected, and the maximum and minimum grinding height values ​​are obtained. Determine whether the minimum height of the height to be ground is greater than or equal to the required height value; If so, proceed with the step of fixing the LED chip with the tin electrode facing upwards on the stage; The value of the predetermined distance is the difference between the maximum height value of the height to be ground and the required height value; The travel time can be calculated based on the given distance and the moving speed. When the required height value is greater than the minimum height value of the tin electrode to be ground, the stage will transport the LED chip to the required height position of the tin electrode. At this time, the scraper will not be able to grind the minimum height position of the tin electrode to be ground, and the LED chip needs to be re-tinned so that the minimum height value of the tin electrode to be ground reaches the required height value.

2. The method for fabricating a flip-chip LED according to claim 1, characterized in that, The material of the scraper is single-crystal diamond.

3. A flip-chip LED, characterized in that, The flip-chip LED is prepared by the method for manufacturing a flip-chip LED according to any one of claims 1-2.

Images