A method for cutting LED chips to prevent back collapse

Abstract

The present invention relates to a method for cutting LED chips to prevent chip back collapse. The method comprises the following steps: (1) laminating; (2) cutting; (3) micro-expanding and shrinking the film; (4) laminating; (5) buckling the film; (6) expanding the film and completing the cutting. The present invention improves the conventional chip cutting process by adding the steps of pre-cutting, micro-expanding, shrinking, laminating and buckling the film, transferring stress in segments, reducing the influence of stress on the inside of the chip, and effectively improving the conventional chip cutting process in which stress is directly transferred from the surface to the inside of the chip at one time, which easily causes chip back collapse. The method overcomes the problem of chip back collapse that is easy to occur during the chip cutting process, greatly improves the qualified rate of chip cutting, and reduces production costs.

Description

Technical Field

[0001] The invention relates to a method for cutting an LED chip for preventing back collapse, and belongs to the technical field of LED chips. Background Art

[0002] As the core component of semiconductor lighting, LED chips play an important role in the lighting industry. LEDs are known as the fourth generation of lighting sources or green light sources. They are energy-saving, environmentally friendly, have a long lifespan, and are compact. They are widely used in various fields such as indication, display, decoration, backlighting, general lighting, and urban nightscapes. According to their different functions, they can be divided into five categories: information display, signal lights, automotive lighting, LCD screen backlights, and general lighting. LED chips have high luminous efficiency, a wide range of colors, and a long service life. They have been widely used in various fields such as large-screen displays, landscape lighting, traffic lights, and car status displays. Therefore, the final appearance of the LED chip will directly affect the quality of its electrical performance parameters. Therefore, the LED industry has very strict requirements on the appearance of the chip, especially the smaller the size, the more obvious it is. The main factor affecting the appearance of the LED chip is the back collapse that occurs after cutting.

[0003] In the LED chip manufacturing process, dicing is the process of separating the entire chip into individual die of the desired size after undergoing basic processes such as photolithography, coating, and thinning. It is an essential back-end process in the semiconductor light-emitting diode chip manufacturing process. The most traditional and widely used dicing method for LED chips is blade dicing. Blade dicing uses a high-speed rotating spindle to drive a blade mounted on it, completely separating the chip into individual die according to a pre-set program. However, blade dicing presents unavoidable challenges: GaAs material is relatively brittle, and the presence of thick metal deposits on both sides of the chip creates significant stress. Furthermore, the blade directly contacts the chip during dicing, subjecting the chip to significant external forces. This can easily lead to chipping, corner chipping, and cracks around the chip edges. Digging deep into the chip, like digging with a forklift, can especially cause cracks on the backside of the chip, commonly known as back chipping. This can severely impact the chip's appearance and reduce yield.

[0004] Chinese patent document CN102709409A discloses a quaternary LED chip and its cutting method, comprising: a first step of using a diamond cutter to half-cut the LED chip on the positive terminal side of the LED chip to form a cutting path, separating the positive terminals of the equally spaced LED chips; a second step of applying a blue film to the positive terminal of the LED chip and a Mylar film to the short negative terminal; a third step of placing the LED chip on the splitting table of a splitter with the positive terminal facing downward and the negative terminal facing upward, and using the splitting knife of the splitter to break the LED chip along the cutting path, thereby processing the LED chip into individual grains. However, the disadvantage of this method is that the positive terminal of the chip is cut with a diamond cutter, and the negative terminal is directly split with the splitting knife. The rigid force directly acting on the chip is large, the chip itself has a large warping stress, and the width of the splitting knife blade is wider than that of the grinding wheel blade, which still causes a large number of back-breaking cases.

[0005] Chinese patent document CN102709171A discloses a method for cutting ultra-small LED chips on GaAs substrates. The method includes: first, performing a full micro-cut on the chip surface, with the half-cut depth being 10% to 20% of the chip's overall height. Then, performing a full-cut through-cut, placing the half-cut chip on a cutting machine and using a diamond knife to completely separate the chip along the cutting path, starting from the edge. However, a disadvantage of this method is that performing a full-cut through-cut along the half-cut path requires a lower blade height and a deeper blade depth, which increases the contact area between the blade back and the chip surface, increasing the probability of back-cutting and significantly affecting chip yield.

[0006] Chinese patent document CN104347760A discloses a method for cutting LED chips, comprising: scratching the back of the chip with a laser, sawing along the scratches with a diamond saw blade, flipping the back-cut chip over, and cutting the front of the chip along the grooves into individual grains with a splitter. However, the disadvantage of this method is that after the back of the chip is scratched with a laser, it is directly cut with a saw blade. However, the groove edges are not smooth and flat, which can easily cause the saw blade to break and crack. In addition, the prepared chip is a chip with a replaced substrate (GaAs material is not suitable for laser ablation and easily produces toxic gases), making it unsuitable for cutting GaAs chips. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention provides a method for cutting LED chips to prevent back collapse.

[0008] The technical solutions of the present invention are as follows:

[0009] A method for cutting LED chips to prevent back-chipping, comprising the following steps:

[0010] (1) Laminating: Place the chip P side down into the laminating machine, cover the N side of the chip with blue film, and heat it until the N side of the chip adheres to the blue film;

[0011] (2) Cutting: Place the chip obtained in step (1) with its P surface facing upward into the saw blade machine, calibrate the level, draw the cutting rows and columns, set the initial blade height to 40-200 μm, select a row for the first pre-cutting, pause after the first pre-cutting is completed, observe the scratches on the blue film on the N side of the chip, adjust the blade height according to the scratches, and continue pre-cutting in another row until there is only a shallow scratch on the blue film on the N side, so that the chip cutting depth is 95-98% of the chip thickness, and then perform normal cutting according to this blade height. The back of the chip will not be completely disconnected after cutting;

[0012] (3) Micro-expansion and shrinkage: The chip obtained in step (2) is placed in a film expansion machine, subjected to micro-expansion treatment, and then heated so that the chip shrinks back to its size before micro-expansion;

[0013] (4) Lamination: placing the chip obtained in step (3) into a laminator, heating, and laminating;

[0014] (5) Buckling the film: buckle the chip in step (4) along the cutting marks in the cutting process so that the blue film is completely fitted with the cutting marks;

[0015] (6) Film expansion: Place the chip obtained in step (5) into a film expansion machine for film expansion processing to obtain independent tube cores, completing the cutting of the LED chip.

[0016] Preferably according to the present invention, in step (1), the heating temperature is 52-58°C.

[0017] Preferably, according to the present invention, in step (1), the blue film model is SPV-224, and the size of the blue film is 220mm*100m~260mm*100m.

[0018] Preferably, according to the present invention, in step (2), the initial height of the blade is set to 60-180 μm and the cutting speed is set to 1-30 mm / s.

[0019] Preferably, according to the present invention, in step (3), the micro-expansion is to set the cylinder of the film expanding machine to lift a stroke of 2 to 3 cm to expand the chip part.

[0020] According to the preferred embodiment of the present invention, in step (3), the heating temperature is 75-80° C., so that the partially opened chips are retracted to the size before micro-expansion, and the degree of disconnection between the chips is increased by partial opening and retraction.

[0021] According to the preferred embodiment of the present invention, in step (4), the heating temperature is 45-55° C. Lamination is to open the chip cracks for the second time, and further increase the degree of disconnection between the chips.

[0022] According to a preferred embodiment of the present invention, in step (5), the buckling process is as follows: along the cutting marks on the chip P surface, pressure is applied to the blue film on the chip N surface, so that the blue film and the cutting marks are completely adhered. That is, after the micro-expansion, shrinkage and lamination processes, the remaining connected portion of the chip is close to breaking, and the cutting marks on the chip P surface can be seen through the transparent blue film. After further pressure is applied along the cutting marks on the chip P surface, the pressure is further released along the cutting marks, and the degree of disconnection between the chips is further increased, so that the chips are on the verge of breaking.

[0023] Preferably, according to the present invention, in step (6), the film expansion is to set the film expansion machine cylinder to lift a stroke of 5 to 6 cm to fully expand the chip.

[0024] Anything not described in detail in the present invention is conventional technology available in this field.

[0025] The beneficial effects of the present invention are:

[0026] 1. The present invention improves the conventional chip cutting process by adding pre-cutting, micro-expanding, shrinking, pressing and buckling steps. The chip is expanded for the first time by pre-cutting and micro-expanding, and then the chip is restored by shrinking. The chip is expanded for the second time by pressing, and finally the blue film is completely fitted with the cutting mark by buckling, so that the cutting mark appears more clearly on the film, further increasing the degree of chip crack opening, so that the chip basically appears to be disconnected. The present invention transmits stress in segments through the pre-cutting, micro-expanding, shrinking, pressing and buckling steps, reducing the impact of stress on the inside of the chip. It effectively improves the conventional chip cutting process that directly transfers stress from the surface to the inside of the chip at one time, which easily causes chip back collapse. It overcomes the problem of chip back collapse that easily occurs during chip cutting, greatly improves the chip cutting qualification rate, and reduces production costs.

[0027] 2. The process of the present invention is simple and easy to operate. It focuses on the degree of opening of chip cracks during blade cutting and does not require the addition of additional mechanical equipment. It is suitable for promotion and application in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the N side of the chip obtained after cutting according to the method of Example 1.

[0029] Figure 2 This is a schematic diagram of the N side of the chip obtained after cutting using the method of Comparative Example 1. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to specific embodiments and the accompanying drawings, but is not limited thereto.

[0031] Example 1

[0032] A method for cutting LED chips to prevent back-chipping, comprising the following steps:

[0033] (1) Laminating: Place the chip P side down into the laminating machine, cover the N side of the chip with blue film, and heat to 58°C so that the N side of the chip adheres to the blue film;

[0034] (2) Cutting: Place the chip obtained in step (1) with the P surface facing upward on the saw machine table, calibrate the level, draw the cutting rows and columns, set the initial blade height to 60 μm, select a row for the first pre-cutting, and the cutting speed is 20 mm / s; after the first pre-cutting is completed, pause and observe if the blade scratch on the blue film is too deep. Adjust the blade height to 85 μm according to the scratch, and continue pre-cutting on another row. Continue to observe if there is no blade scratch on the blue film, continue to adjust the blade height to 82 μm, and continue pre-cutting on another row. There is only a shallow scratch on the N-side blue film, so that the chip cutting depth is 95% of the chip thickness. Then, perform normal cutting according to this blade height. After cutting, the back of the chip will not be completely disconnected;

[0035] (3) Micro-expansion and shrinkage: Place the chip obtained in step (2) into a film expander, set the cylinder lift stroke of the film expander to 2 cm, and perform micro-expansion. Then, place the micro-expanded chip on the heating plate of the film expander and heat it to 80°C, so that the chip shrinks back to its size before micro-expansion.

[0036] (4) Lamination: Place the chip obtained in step (3) on a lamination plate, heat to 50°C, and perform lamination treatment;

[0037] (5) Buckling the film: Place the chip obtained in step (4) along the cutting marks on the P surface, and apply pressure to the blue film on the N surface of the chip so that the blue film and the cutting marks are completely attached. During the pressure application process, you can use your hands or tools such as a ruler to further release the pressure along the cutting direction, and continue to increase the degree of disconnection between the chips, so that the chip is on the verge of breaking;

[0038] (6) Film expansion: Place the chip obtained in step (5) into a film expansion machine, set the cylinder lift stroke of the film expansion machine to 5 cm, and perform film expansion to obtain independent tube cores, thus completing the cutting of the LED chip.

[0039] In step (1), the blue film model is SPV-224, and the size is 220mm*100m.

[0040] This embodiment cuts 408K independent tube cores, 11K independent tube cores have back collapse, and the qualified rate is 97.3%. Figure 1 .

[0041] Example 2

[0042] A method for cutting LED chips to prevent back-chipping, comprising the following steps:

[0043] (1) Laminating: Place the chip P side down into the laminating machine, cover the N side of the chip with blue film, and heat to 55°C so that the N side of the chip adheres to the blue film;

[0044] (2) Cutting: Place the chip obtained in step (1) with the P surface facing upward on the saw machine table, calibrate the level, draw the cutting rows and columns, set the initial blade height to 70 μm, select a row for the first pre-cutting, and the cutting speed is 10 mm / s; after the first pre-cutting is completed, pause and observe whether the blade scratch on the blue film is too deep. Adjust the blade height to 100 μm according to the scratch, and continue pre-cutting on another row. Continue to observe whether there is no blade scratch on the blue film, continue to adjust the blade height to 98 μm, and continue pre-cutting on another row. There is only a shallow scratch on the N-side blue film, so that the chip cutting depth is 98% of the chip thickness. Then, perform normal cutting according to this blade height. After cutting, the back of the chip will not be completely disconnected;

[0045] (3) Micro-expansion and shrinkage: Place the chip obtained in step (2) into a film expander, set the cylinder lift stroke of the film expander to 2 cm, and perform micro-expansion. Then, place the micro-expanded chip on the heating plate of the film expander and heat it to 75°C, so that the chip shrinks back to its size before micro-expansion.

[0046] (4) Lamination: Place the chip obtained in step (3) on a lamination plate, heat to 45°C, and perform lamination treatment;

[0047] (5) Buckling the film: Place the chip obtained in step (4) along the cutting marks on the P surface, and apply pressure to the blue film on the N surface of the chip so that the blue film and the cutting marks are completely attached. During the pressure application process, you can use your hands or tools such as a ruler to further release the pressure along the cutting direction, and continue to increase the degree of disconnection between the chips, so that the chip is on the verge of breaking;

[0048] (6) Film expansion: Place the chip obtained in step (5) into a film expansion machine, set the cylinder lift stroke of the film expansion machine to 5 cm, and perform film expansion to obtain independent tube cores, thus completing the cutting of the LED chip.

[0049] In step (1), the blue film model is SPV-224, and the size is 240mm*100m.

[0050] In this embodiment, 408K independent dies were cut, 10.5K of which showed back-chipping, and the qualified rate was 97.4%.

[0051] Example 3

[0052] A method for cutting LED chips to prevent chipping, the steps are as described in Example 1, except that in step (2), the cutting speed is 30 mm / s.

[0053] In step (3), the lifting stroke of the cylinder of the film expanding machine is set to 3 cm.

[0054] In this embodiment, 408K independent dies were cut, 9.5K of which showed back-chipping, and the qualified rate was 97.7%.

[0055] Example 4

[0056] A method for cutting LED chips to prevent back collapse, the steps are as described in Example 1, except that:

[0057] In step (2), the chip obtained in step (1) is placed with the P surface facing upward on the saw machine table, the level is calibrated, the cutting rows and columns are drawn, the initial blade height is set to 180 μm, and a row is selected for the first pre-cutting, and the cutting speed is 20 mm / s; after the first pre-cutting is completed, pause and observe that there are no blade scratches on the blue film. According to the scratches, the blade height is adjusted to 110 μm, and another row is continued for pre-cutting. It is continued to observe that the blade scratches on the blue film are too deep, and the blade height is continued to be adjusted to 106 μm. Another row is continued for pre-cutting. There is only a shallow scratch on the N-side blue film, so that the chip cutting depth is 96% of the chip thickness. Then, normal cutting is performed according to this blade height. After cutting, the back of the chip will not be completely disconnected.

[0058] In this embodiment, 408K independent dies were cut, 10.2K of which showed back-chipping, and the qualified rate was 97.5%.

[0059] Comparative Example 1

[0060] A method for cutting LED chips, comprising the following steps:

[0061] (1) Laminating: Place the chip P side down in the laminating machine, cover the N side of the chip with blue film, and heat it to 55℃ so that the N side of the chip adheres to the blue film. Use SPV-224 220mm*100m blue film operation.

[0062] (2) Cutting: Place the chip obtained in step (1) with its P surface facing upward on the saw blade. After selecting the product process parameters, cut the chip one by one, cutting the chip into individual dies. The blade height for full cutting is set to 60μm, the cutting speed is 30mm / s, and the full cutting depth is 104% of the chip thickness. Very obvious marks can be seen on the blue film.

[0063] (3) Film expansion: The chip is placed in the film expansion machine, and the cylinder of the film expansion machine is set to lift up to 6cm (the maximum lifting stroke of the cylinder), and the film expansion process is performed to obtain independent tube cores, thus completing the cutting of the LED chip.

[0064] This comparative example cuts 408K independent dies, 22.5K independent dies have back-collapse, and the qualified rate is 94.5%. Figure 2 .

[0065] Depend on Figures 1-2 It can be seen from Examples 1 to 4 and Comparative Example 1 that the LED chip cutting method provided by the present invention improves the conventional chip cutting process, and transmits stress in segments through the pre-cutting, micro-film expansion, film shrinkage, film pressing and film buckling steps, thereby reducing the impact of stress on the inside of the chip, and effectively improving the conventional chip cutting process in which stress is directly transferred from the surface to the inside of the chip at one time, which easily causes chip back collapse. The problem of chip back collapse that is easy to occur during chip cutting is overcome, and the qualified rate is increased from 94.5% in Comparative Example 1 to 97.3%, 97.4%, 97.7% and 97.5% in Examples 1 to 4, with an increase of 2.8% to 3.2%, which effectively improves the qualified rate and reduces production costs.

Claims

1. A method for cutting LED chips to prevent chipping, characterized in that: The steps are as follows: (1) Laminating: Place the chip P side down into the laminating machine, cover the N side of the chip with blue film, and heat it until the N side of the chip adheres to the blue film; (2) Cutting: Place the chip obtained in step (1) with its P surface facing upward into the saw blade machine, calibrate the level, draw the cutting rows and columns, set the initial blade height to 40-200 μm, select a row for the first pre-cutting, pause after the first pre-cutting is completed, observe the scratches on the blue film on the N side of the chip, adjust the blade height according to the scratches, and continue pre-cutting in another row until there is only a shallow scratch on the blue film on the N side, so that the chip cutting depth is 95-98% of the chip thickness, and then perform normal cutting according to this blade height. The back of the chip will not be completely disconnected after cutting; (3) Micro-expansion and shrinkage: The chip obtained in step (2) is placed in a film expansion machine, subjected to micro-expansion treatment, and then heated so that the chip shrinks back to its size before micro-expansion; (4) Lamination: placing the chip obtained in step (3) into a laminator, heating, and laminating; (5) Buckling the film: buckle the chip in step (4) along the cutting marks in the cutting process so that the blue film is completely fitted with the cutting marks; (6) Film expansion: Place the chip obtained in step (5) into a film expansion machine for film expansion processing to obtain independent tube cores, completing the cutting of the LED chip.

2. The LED chip cutting method for preventing back collapse according to claim 1, wherein: In step (1), the heating temperature is 52-58°C.

3. The LED chip cutting method for preventing back collapse according to claim 1, wherein: In step (1), the blue film model is SPV-224, and the size of the blue film is 220mm*100m~260mm*100m.

4. The LED chip cutting method for preventing back collapse according to claim 1, wherein: In step (2), the initial height of the blade is set to 60-180 μm and the cutting speed is set to 1-30 mm / s.

5. The LED chip cutting method for preventing back collapse according to claim 1, wherein: In step (3), the micro-film expansion is to set the film expansion machine cylinder top lifting stroke to 2 to 3 cm.

6. The LED chip cutting method for preventing back collapse according to claim 1, wherein: In step (3), the heating temperature is 75-80°C.

7. The LED chip cutting method for preventing back collapse according to claim 1, wherein: In step (4), the heating temperature is 45-55°C.

8. The LED chip cutting method for preventing back collapse according to claim 1, wherein: In step (5), the buckling process is to apply pressure to the blue film on the N surface of the chip along the cutting marks on the P surface of the chip so that the blue film is completely fitted with the cutting marks.

9. The LED chip cutting method for preventing back collapse according to claim 1, wherein: In step (6), the film expansion is performed by setting the film expansion machine cylinder top lifting stroke to 5 to 6 cm.

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