JP7463153B2 - Mounting method and mounting device - Google Patents

Description

The present invention relates to a mounting method and mounting device for mounting semiconductor chips stably and with high precision.

Semiconductor chips are becoming smaller to reduce costs, and efforts are being made to mount these smaller semiconductor chips with high precision. In particular, LEDs used in displays require semiconductor chips measuring 50 um x 50 um or less, known as micro LEDs, to be mounted quickly and with a precision of a few microns.

Patent Document 1 describes a method for transferring elements in which a laser beam generated from a laser light source is reflected by a galvanometer mirror and selectively irradiated onto elements arranged on an original substrate, causing the elements to peel off from the original substrate as a result of the irradiation and transfer them to a destination substrate. This transfer method makes it possible to transfer minute elements to a destination substrate at high speed, and it is also possible to use this method to mount elements on a circuit board at high speed.

JP 2006-41500 A

However, in a mounting method that only uses the transfer method described in Patent Document 1, there is a risk that repairs after mounting will require a considerable amount of time. Specifically, after checking whether the semiconductor chips are mounted normally on the circuit board by a lighting test, it is necessary to remove any semiconductor chips that are found to be abnormal and mount normal semiconductor chips again (repair them). In contrast, for example, if the circuit board is for a 4K TV, 24.88 million semiconductor chips are used, and even if the defect rate is 0.1%, it is necessary to repair approximately 25,000 chips. This means that the repair alone will take several hundred hours, and there is a problem that even if the mounting process itself is completed quickly, the repairs will have a significant impact on productivity.

In view of the above problems, the present invention aims to provide a mounting method and mounting device that can mount semiconductor chips on a circuit board with high productivity.

To solve the above problem, the mounting method of the present invention is characterized by having a first transfer step of transferring multiple semiconductor chips formed on a carrier substrate to a first transfer substrate, an inspection step of inspecting the state of the semiconductor chips transferred to the first transfer substrate, a second transfer step of transferring only the semiconductor chips determined to be normal by the inspection step from the first transfer substrate to a second transfer substrate, and a mounting step of mounting the semiconductor chips transferred to the second transfer substrate onto a circuit board.

In the mounting method of the present invention, in the second transfer process, only the semiconductor chips that are determined to be normal in the inspection process are transferred from the first transfer substrate to the second transfer substrate, thereby significantly reducing the number of semiconductor chips that require repair after mounting and improving the productivity of circuit boards.

The mounting process also includes a bonding process for bonding the semiconductor chip together with the second transfer substrate to the circuit board, and a separation process for separating the second transfer substrate from the semiconductor chip. It is preferable that the semiconductor chip is selectively transferred in the second transfer process so that the semiconductor chip is arranged on the second transfer substrate that is subjected to the bonding process according to the position where the semiconductor chip is to be arranged on the circuit board.

This makes it possible to mount multiple semiconductor chips on a circuit board at the same time.

The method also includes a post-mounting inspection process for inspecting the performance of the semiconductor chip mounted on the circuit board, and a repair process for adding or replacing a repair semiconductor chip to the circuit board that functions in place of a semiconductor chip determined to be abnormal as a result of the post-mounting inspection process. In the repair process, the semiconductor chip is selectively transferred from the first transfer substrate to the second transfer substrate so that the semiconductor chip is arranged according to the position where the repair semiconductor chip is to be arranged on the circuit board, the semiconductor chip is pressure-bonded to the circuit board together with the second transfer substrate, and the second transfer substrate is separated from the semiconductor chip.

This can reduce the time required for repairs.

In addition, in the inspection process, the state of the semiconductor chip on the first transfer substrate may be inspected by visual inspection using image analysis.

This allows the inspection process to be completed in a short amount of time.

It is also preferable to further include a chip removal process between the inspection process and the second transfer process, in which a semiconductor chip determined to be abnormal is removed from the first transfer substrate.

This prevents abnormal chips from being transferred to the second transfer substrate by mistake.

In order to solve the above problems, the mounting device of the present invention has a transfer unit that transfers multiple semiconductor chips from a carrier substrate to a first transfer substrate and transfers the semiconductor chips from the first transfer substrate to a second transfer substrate, an inspection unit that inspects the state of the semiconductor chips transferred to the first transfer substrate, and a mounting unit that mounts the semiconductor chips transferred to the second transfer substrate onto a circuit board, and is characterized in that only semiconductor chips that are determined to be normal by inspection by the inspection unit are transferred from the first transfer substrate to the second transfer substrate.

In the mounting device of the present invention, only semiconductor chips that are determined to be normal by the inspection by the inspection unit are transferred from the first transfer substrate to the second transfer substrate, which significantly reduces the number of semiconductor chips that require repair after mounting and improves the productivity of circuit boards.

The mounting method and mounting device of the present invention allow semiconductor chips to be mounted on circuit boards with high productivity.

FIG. 2 is a diagram illustrating a mounting device according to the present invention. FIG. 2 is a diagram illustrating a transfer unit in the mounting device according to the present invention. FIG. 2 is a diagram illustrating an inspection unit of the mounting device according to the present invention. FIG. 2 is a diagram illustrating a mounting unit of the mounting device according to the present invention. 1A to 1C are diagrams illustrating a first transfer step of the mounting method according to the present invention. 1A to 1C are diagrams illustrating an inspection step and a chip removal step in the mounting method according to the present invention. 11A to 11C are diagrams illustrating a second transfer step of the mounting method according to the present invention. 1A to 1C are diagrams illustrating a mounting process of a mounting method according to the present invention. 1A to 1C are diagrams illustrating a general lighting inspection process and a general repair process. 1A to 1C are diagrams illustrating a repair process in the present invention.

Figure 1 shows the mounting device that performs the mounting method of the present invention.

The mounting device 100 has a transfer unit 10, an inspection unit 20, and a mounting unit 30. The first and second transfer processes are performed by the transfer unit 10, and the mounting process is performed by the mounting unit 30. In addition, between the first and second transfer processes, the inspection unit 20 inspects the semiconductor chip. In addition, the transportation of the substrates (carrier substrate 2, first transfer substrate 4a, second transfer substrate 4b, circuit substrate 6) between each device is performed by one or more types of robot hands 40.

Details of the transfer unit 10 are shown in Figure 2.

The transfer unit 10 includes a laser irradiation unit 12 that irradiates laser light 11, a transfer substrate holding unit 13 that holds a transfer substrate and is movable in at least the X-axis and Y-axis directions, a transfer substrate holding unit 14 that is located below the transfer substrate holding unit 13 and holds a transfer substrate so as to face the transfer substrate with a gap, and a control unit (not shown).

The laser irradiation unit 12 is a device that irradiates laser light 11 such as an excimer laser, and is fixed to the transfer unit 10. In this embodiment, the laser irradiation unit 12 irradiates spot-shaped laser light 11, and the irradiation position of the laser light 11 in the X-axis direction and Y-axis direction is controlled via a galvanometer mirror 15 and an fθ lens 16, the angles of which are adjusted by a control unit, and the laser light 11 is selectively irradiated to a plurality of semiconductor chips 1 arranged on a transfer substrate held by a transfer substrate holding unit 13. When the laser light 11 is incident on the semiconductor chip 1 of the transfer substrate, laser lift-off occurs, and the semiconductor chip 1 is transferred from the transfer substrate to the transfer substrate.

In this description, the first and second transfer steps described below are carried out by this transfer unit 10. In the first transfer step, the carrier substrate 2 corresponds to the transfer substrate, and the first transfer substrate 4a corresponds to the transferred substrate. On the other hand, in the second transfer step, the first transfer substrate 4a corresponds to the transfer substrate, and the second transfer substrate 4b corresponds to the transferred substrate.

The transfer substrate holding unit 13 has an opening and holds the transfer substrate near its outer periphery by suction. The laser light 11 emitted from the laser irradiation unit 12 can be applied to the transfer substrate held by the transfer substrate holding unit 13 through this opening.

The transfer substrate holding part 13 is moved relative to the transferred substrate holding part 14 at least in the X-axis direction and the Y-axis direction by a movement mechanism (not shown). The control part controls this movement mechanism and adjusts the position of the transfer substrate holding part 13, thereby adjusting the relative position of the semiconductor chip 1 held on the transfer substrate to the transferred substrate.

The transferred substrate holding part 14 has a flat upper surface and holds the transferred substrate during the transfer process of the semiconductor chip 1. The upper surface of the transferred substrate holding part 14 has multiple suction holes, which hold the back surface of the transferred substrate (the surface to which the semiconductor chip 1 is not transferred) by suction force.

In this embodiment, only the transfer substrate holding unit 13 moves in the X-axis and Y-axis directions, thereby causing relative movement between the transfer substrate holding unit 13 and the transferred substrate holding unit 14. However, if the dimensions of the transferred substrate are large and the entire surface of the transferred substrate cannot be positioned directly under the irradiation range of the laser light 11, the transferred substrate holding unit 14 may also be provided with a movement mechanism in the X-axis and Y-axis directions.

Next, details of the inspection unit 20 are shown in Figure 3.

The inspection unit 20 has a camera 21, an inspected substrate holding unit 22, and a control unit (not shown), and uses the camera 21 to capture an image of the inspection object held by the inspected substrate holding unit 22, and performs an appearance inspection of the semiconductor chip 1 by image analysis. In this embodiment, the inspection object is a plurality of semiconductor chips 1 transferred to the first transfer substrate 4a.

Some of the semiconductor chips 1 on the first transfer substrate 4a may not achieve the required performance during the formation process of the semiconductor chips 1 on the carrier substrate 2 described below, and some may develop cracks when transferred to the first transfer substrate 4a. Whether the performance of the semiconductor chips 1 is normal or not can be determined with a high degree of accuracy by checking the color and shape of the semiconductor chips 1.

In this embodiment, the camera 21 is, for example, a CMOS camera that has an image sensor and converts the light imaged on the image sensor into an electrical signal using an external signal as a trigger to create a digital image. The imaging direction of the camera 21 is vertically downward, and images the semiconductor chip 1 from above. The camera 21 is also attached to a moving device (not shown), and the moving device is driven under the control of the control unit to move the camera 21 in the X-axis and Y-axis directions.

The inspection unit 20 also has an illumination unit (not shown). In this embodiment, the illumination unit is an LED light that emits light in synchronization with the movement of the camera 21 by the moving device, and the camera 21 captures images when the illumination unit emits light, thereby continuously capturing images of the external appearance of multiple semiconductor chips 1 arranged in the X-axis and Y-axis directions.

Next, details of the mounting unit 30 are shown in Figure 4.

The mounting unit 30 includes a mounting table 31, a head 32, and a two-view optical system 33, as well as a control unit (not shown).

The mounting table 31 can hold the circuit board 6 by vacuum suction and is configured to be movable in the X and Y axis directions by the XY stage.

In this embodiment, the mounting table 31 has a heater 34, and the temperature of the surface of the mounting table 31 (≈the temperature of the circuit board 6 placed on the mounting table 31) can be controlled by the control unit. In addition, the mounting table 31 is provided with a thermometer (not shown), and the temperature of the mounting table 31 measured by this thermometer can be fed back to perform temperature control.

The head 32 has a substantially flat tip and one or more suction holes, and during the mounting process, suctions and holds the surface of the second transfer substrate 4b on which the semiconductor chip 1 is not transferred. The head 32 can move in the Z-axis direction, and contacts and presses the circuit board 6 held on the mounting table 31 with the bumps of the semiconductor chip 1 transferred to the second transfer substrate 4b held by the head 32. The head 32 also has a heater 35, and the temperature of the head 32, particularly the tip, can be controlled by a control unit. The head 32 is also provided with a thermometer (not shown), and the temperature of the head 32 measured by this thermometer can be fed back to control the temperature.

The head 32 is also configured to be movable in the θ direction (a central direction with the Z-axis direction as the center of rotation), and by linking the movement of the mounting table 31 in the X- and Y-axis directions with the movement of the head 32 in the Z-axis and θ directions, the semiconductor chip 1 can be thermocompression bonded and mounted at a predetermined position on the circuit board 6.

In this embodiment, heaters 34 and 35 are controlled simultaneously so that the temperature of the surface of mounting table 31 and the temperature of the tip of head 32 (≈ the temperature of second transfer substrate 4b) are always equal during the mounting process. By doing so, as described above, even if circuit board 6 and second transfer substrate 4b thermally expand during the mounting process, the relative position between the point of contact with semiconductor chip 1 on second transfer substrate 4b and the point on circuit board 6 where the bumps of semiconductor chip 1 are bonded is unlikely to change, and high-precision mounting can be performed stably.

In this embodiment, the head 32 is configured to move in the Z-axis and θ-directions, and the mounting table 31 is configured to move in the X-axis and Y-axis directions, but this is not necessarily limited to this and can be modified as appropriate depending on the convenience of the device. For example, the head 32 may be configured to move in the X-axis, Y-axis and θ-directions, and the mounting table 31 may move in the Z-axis direction. Also, the θ-direction movement mechanism can be omitted if not necessary. For example, if there is no rotational misalignment in the positions of the semiconductor chip 1 and the circuit board 6, the θ-direction movement mechanism can be omitted.

When the circuit board 6 is placed on the mounting table 31, the two-view optical system 33 can enter between the head 32 and the circuit board 6 to capture images of both. Each captured image is processed by the control unit to recognize the respective positional deviations. The control unit then takes this positional deviation into account and controls each semiconductor chip 1 so that it contacts and is bonded to a predetermined position on the circuit board 6, thereby mounting the semiconductor chip 1 with high precision in the X and Y axis directions.

Next, the mounting method of the present invention will be described with reference to Figs. 5 to 8. Fig. 5 is a diagram for explaining the first transfer step of the mounting method of the present invention. Fig. 6 is a diagram for explaining the inspection step and the chip removal step of the mounting method of the present invention. Fig. 7 is a diagram for explaining the second transfer step of the mounting method of the present invention. Fig. 8 is a diagram for explaining the mounting step in another embodiment.

In the present invention, of the two main surfaces of a semiconductor chip, the surface held by the carrier substrate is defined as the first surface, and the surface opposite the first surface is defined as the second surface, with bumps formed on the second surface, which is to be bonded to the circuit board.

First, the first transfer step in the mounting method of the present invention, which is carried out in the transfer unit 10 shown in FIG. 2, will be described with reference to FIG. 5.

Figure 5 (a) shows multiple semiconductor chips 1 after dicing, with the first surface held by the carrier substrate 2. The carrier substrate 2 also extends in the depth direction of Figure 1, has a circular or rectangular shape, and is made of silicon, gallium arsenide, sapphire, or the like. Multiple semiconductor chips 1 (hundreds to tens of thousands) are also arranged two-dimensionally along the extension of the carrier substrate 2. Small semiconductor chips 1 called micro LEDs have a size of 50 um x 50 um or less, and are arranged at a pitch that is this size plus the dicing width. Such small semiconductor chips 1 are required to be mounted on the circuit substrate 6 with high precision (for example, a precision of 1 um or less). In addition, bumps are formed on the second surface of the semiconductor chip 1.

Figure 5 (b) shows the first transfer substrate attachment process in which the second surface, which is the surface opposite to the first surface held by the carrier substrate 2 of the semiconductor chip 1, is attached to the first transfer substrate 4a. The first transfer substrate 4a is first held by vacuum suction to the transferred substrate portion 14, and an adhesive layer 3a is formed on the surface to which the semiconductor chip 1 is attached. In this first transfer substrate attachment process, the carrier substrate 2 holding the semiconductor chip 1 is adsorbed and handled by the robot hand 40, and the second surface of the semiconductor chip 1 is attached onto the adhesive layer 3a of the first transfer substrate 4a held by the transferred substrate portion 14 shown in Figure 2.

Next, a carrier substrate removal process is performed on the first transfer substrate 4a to which the semiconductor chip 1 is attached together with the carrier substrate 2 as described above. In the carrier substrate removal process, the carrier substrate 2 is peeled off from the semiconductor chip 1 and removed by laser lift-off. Specifically, the first surface of the semiconductor chip 1 is irradiated with laser light 11a emitted from the laser irradiation unit 12 shown in FIG. 2, which penetrates the carrier substrate 2. As a result, part of the GaN layer of the micro LED, which is the semiconductor chip 1, is decomposed into Ga and N, and the semiconductor chip 1 is peeled off from the carrier substrate 2 made of sapphire. The carrier substrate 2 on which all the semiconductor chips 1 have been irradiated with the laser light 11a is removed by moving the robot hand 40, to which the carrier substrate 2 is vacuum-adsorbed, away from the first transfer substrate 4a.

Through this first transfer substrate attachment process and carrier substrate removal process, the semiconductor chip 1 is transferred from the carrier substrate 2 to the first transfer substrate 4a as shown in FIG. 1(c). In this description, the process of transferring the semiconductor chip 1 from the carrier substrate 2 to the first transfer substrate 4a is referred to as the first transfer process.

In the above description, the second surface of the semiconductor chip 1 is attached to the first transfer substrate 4a in the first transfer step, and then the carrier substrate 2 is removed. However, the present invention is not limited to this. In this case, the first transfer substrate 4a is prepared at a position slightly away from the second surface of the semiconductor chip 1, and when the carrier substrate 2 is irradiated with a laser, a part of the GaN layer of the micro LED is decomposed into Ga and N. The propulsive force generated by this decomposition causes the semiconductor chip 1 to fly from the carrier substrate 2 to the first transfer substrate 4a and to be attached to the first transfer substrate 4a.

In addition, in this embodiment, the semiconductor chip 1 is transferred from the carrier substrate 2 to the first transfer substrate 4a by peeling the carrier substrate 2 from the semiconductor chip 1 by laser lift-off, but this is not necessarily limited to this and can be modified as appropriate. For example, the carrier substrate 2 may be removed by scraping off from the side opposite to the side on which the semiconductor chip 1 is provided. This is called back grinding, and this back grinding technique is used in particular in the case of red LEDs, where laser lift-off cannot be applied.

Then, the inspection process shown in FIG. 6(a) is carried out in the inspection unit 20 shown in FIG. 3. In the inspection process, the camera 21 moves above the hundreds to tens of thousands of semiconductor chips 1 arranged in the X-axis and Y-axis directions on the first transfer substrate 4a held by suction on the substrate to be inspected, capturing images. The control unit of the inspection unit 20 analyzes the images obtained by this capture, and performs an appearance inspection of the color, shape, etc. of each semiconductor chip 1. The time required for this inspection process for one first transfer substrate 4a is approximately 30 minutes when the first transfer substrate 4a is a 6-inch wafer.

In addition, in this embodiment, after the inspection process, a chip removal process shown in FIG. 6(b) is carried out. In this chip removal process, the semiconductor chips 1 determined to be abnormal in the inspection process (the two semiconductor chips 1 represented by dots in FIG. 6(b)) are irradiated with laser light 11b, thereby burning off the semiconductor chips 1 and removing them from the first transfer substrate 4a.

This chip removal process may be performed in the transfer unit 10. The laser light 11b at this time is required to burn away the semiconductor chip 1, so it is irradiated from the laser irradiation unit 12 with a power stronger than that of the laser light 11a in the first transfer process described above.

In this way, by removing the abnormal semiconductor chip 1 in the chip removal process, it is possible to prevent the abnormal semiconductor chip 1 from being transferred in error in subsequent processes.

Next, the second transfer process shown in Fig. 7(a) to (c) is carried out in the transfer unit 10 shown in Fig. 2. In the second transfer process, the transfer substrate holding unit 13 (not shown) holds the first transfer substrate 4a so that the adhesive layer 3a and the semiconductor chip 1 face downward as shown in Fig. 7(a), and the transferred substrate holding unit 14 holds the second transfer substrate 4b so that the second transfer substrate 4b having the adhesive layer 3b is positioned below the first transfer substrate 4a.

Then, the control unit of the transfer unit 10 adjusts the angle of the galvanometer mirror 15 to allow the laser light 11c to pass through the first transfer substrate 4a and reach the interface between the adhesive layer 3a and the second surface of a given semiconductor chip 1, thereby laser lifting off the semiconductor chip 1. Specifically, gas is generated from the adhesive layer 3a by irradiation with the laser light 11, and the semiconductor chip 1 is biased by the generation of this gas, so that it flies downward from the first transfer substrate 4a and lands on the second transfer substrate 4b. Note that the first surface of the semiconductor chip 1 transferred to the second transfer substrate 4b in this manner faces the second transfer substrate 4b, and the bumps are exposed on the surface.

In addition, in this second transfer process, the semiconductor chips 1 on the first transfer substrate 4a are not all transferred continuously, but are selectively transferred as shown in FIG. 7(b). The arrangement of the semiconductor chips 1 on the first transfer substrate 4a immediately after the first transfer process is the same as the arrangement of the semiconductor chips 1 on the carrier substrate 2 before the first transfer process, but by selectively transferring the semiconductor chips 1 in this way in the second transfer process, it is possible to transfer the semiconductor chips 1 to the second transfer substrate 4b in any arrangement.

In this embodiment, in preparation for the mounting process described below, the arrangement of the semiconductor chips 1 on the second transfer substrate 4b corresponds to the position where the semiconductor chips 1 are to be placed on the circuit board 6. More specifically, the semiconductor chips 1 are arranged on the second transfer substrate 4b in a layout that is a mirror image of the layout of the semiconductor chips 1 within an area where the semiconductor chips 1 can be mounted on the circuit board 6 in a single mounting process.

On the other hand, as shown by the dashed line on the second transfer substrate 4b in FIG. 7(b), there may be cases where the first transfer substrate 4a does not have a semiconductor chip 1 that can be transferred to the position on the second transfer substrate 4b that is to be transferred. In that case, it is advisable to move the first transfer substrate 4a and the second transfer substrate 4b relative to each other as shown in FIG. 7(c), and then perform laser lift-off. Note that AI may be used to determine how the first transfer substrate 4a and the second transfer substrate 4b should be moved relative to each other to form a predetermined layout on the second transfer substrate 4b with the minimum number of movements.

The power of the laser light 11c used for laser lift-off from the first transfer substrate 4a is sufficient to decompose the adhesive layer 3a, and is lower than the power of the laser light 11a used to decompose the GaN layer in the first transfer step. Therefore, the possibility of the semiconductor chip 1 being destroyed by irradiation with the laser light 11c in the second transfer step is lower than the possibility of the semiconductor chip 1 being destroyed by irradiation with the laser light 11a in the first transfer step, and can be ignored.

Next, the mounting process shown in Fig. 8(a) to (c) is carried out in the mounting section 30 shown in Fig. 4. In the mounting process, as shown in Fig. 8(a), the head 32 shown in Fig. 4 holds the side of the second transfer substrate 4b on which the semiconductor chip 1 is not transferred, and the circuit board 6 placed on the mounting table 31 described later and the semiconductor chip 1 held on the second transfer substrate 4b are opposed to each other.

Then, the head 32 approaches the circuit board 6, and as shown in FIG. 8(b), the bumps on the second surface of the semiconductor chip 1 are brought into contact with the circuit board 6, and further pressure is applied.

In this embodiment, a bonding material 5 such as ACF (anisotropic conductive film) is provided on the surface of the circuit board 6 against which the semiconductor chip 1 abuts, and after the semiconductor chip 1 abuts on the bonding material 5, the semiconductor chip 1 is held by the bonding material 5.

The head 32 is also provided with a heater 35, which operates when the semiconductor chip 1 is pressed to heat the semiconductor chip 1 to a relatively low temperature of 50°C or less, thereby increasing the temperature of the bonding material 5 through the semiconductor chip 1 and increasing the adhesive strength of the bonding material 5 around the bumps of the semiconductor chip 1. As a result, the semiconductor chip 1 is thermocompression-bonded to the extent that it does not shift in position relative to the wiring of the circuit board 6. In other words, the semiconductor chip 1 is temporarily bonded to the circuit board 6. Note that if the semiconductor chip 1 is fixed to the extent that it does not shift in position relative to the wiring of the circuit board 6 simply by embedding the bumps of the semiconductor chip 1 in the bonding material 5, the semiconductor chip 1 does not need to be heated during temporary bonding. Note that in this description, the bonding of the semiconductor chip 1 to the circuit board 6 together with the second transfer substrate 4b is referred to as the bonding process.

Then, the head 32 separates from the circuit board 6 while holding the second transfer substrate 4b, and the second transfer substrate 4b is separated from the semiconductor chip 1. In this description, the separation of the second transfer substrate 4b and the semiconductor chip 1 is called the separation process. In this separation process, if the adhesive strength of the adhesive layer 3b to the semiconductor chip 1 is weaker than the bonding strength between the semiconductor chip 1 and the circuit board 6, it is possible to separate the second transfer substrate 4b and the semiconductor chip 1 simply by separating the second transfer substrate 4b from the circuit board 6. After this separation process, the semiconductor chip 1 is pressed onto the circuit board 6, which is called the main pressing, and is accompanied by heating the semiconductor chip 1 to a temperature (about 150°C) higher than the temperature during the temporary pressing described above, although this is not shown in the figure, so that the bumps of the semiconductor chip 1 melt, and after cooling, the semiconductor chip 1 is mounted at a predetermined position on the circuit board 6 with a strong bonding force. By carrying out the main pressing, a series of mounting methods in the present invention is completed.

In this embodiment, as shown in FIG. 8(b), multiple semiconductor chips 1 are simultaneously bonded in one mounting process. In particular, when the semiconductor chips 1 are micro LEDs, tens of thousands of semiconductor chips 1 are mounted on one circuit board 6. In this case, for example, in a 4K TV panel, 3840×2160×3 semiconductor chips 1 are arranged on one panel, but the time required for mounting can be significantly reduced by transferring multiple semiconductor chips 1 together to one second transfer substrate 4b, holding the second transfer substrate 4b with the head 32, and bonding them together with pressure. The number of semiconductor chips 1 transferred to the second transfer substrate 4b at one time can be specifically 80×80, 120×120, etc.

Here, in this embodiment, as described above, the bonding process before the separation process only involves provisional bonding of the semiconductor chip 1 to the circuit board 6, and the actual bonding is performed separately. Instead, the semiconductor chip 1 may be bonded to the circuit board 6 in the bonding process. In this case, the series of mounting methods in the present invention are completed when the separation process is completed. At this time, it is preferable that the thermal expansion coefficients of at least the surface of the head 32 that contacts the second transfer substrate 4b (the tip of the head 32), the thermal expansion coefficient of the second transfer substrate 4b, and the thermal expansion coefficient of the surface of the circuit board 6 on which the semiconductor chip 1 is mounted are made equivalent. It is also more preferable that the materials of the tip of the head 32, the second transfer substrate 4b, and the surface of the circuit board 6 on which the semiconductor chip 1 is mounted are the same. Specifically, when the material of the circuit board 6 is glass, the material of the tip of the head 32 and the material of the second transfer substrate 4b are glass, just like the circuit board 6. Also, if the material of the circuit board 6 is copper, the material of the tip of the head 32 and the material of the second transfer substrate 4b are SUS304. In this case, the thermal expansion coefficient of copper is 16.8 ppm, while the thermal expansion coefficient of SUS304 is 17.3 ppm, the difference being about 3%.

Heaters 34 are provided not only on the head 32 but also on the mounting table 31, and heaters 34 and 35 are controlled so that the temperature of the head 32 and second transfer substrate 4b and the temperature of the surface of the circuit board 6 on which the semiconductor chip 1 is mounted are always equal during the thermocompression bonding process. By doing so, even if the circuit board 6, head 32, and second transfer substrate 4b thermally expand during the mounting process, the relative position between the contact point with the semiconductor chip 1 on the second transfer substrate 4b and the point on the circuit board 6 where the bumps of the semiconductor chip 1 are bonded is unlikely to change, and high-precision mounting can be performed stably.

Figure 9 is a diagram explaining the lighting inspection process and the repair process.

When the semiconductor chip 1 is a micro LED, in order to check the light emitting performance of the semiconductor chip 1 after mounting on the circuit board 6, the circuit board 6 is placed on a lighting inspection device 41 as shown in FIG. 9(a), and all the semiconductor chips 1 are turned on to inspect the light emitting performance. In this invention, the process of inspecting the performance of the semiconductor chip 1 mounted on the circuit board 6 in this manner is called the post-mounting inspection process.

If, as a result of the post-mounting inspection process (lighting inspection), there is a semiconductor chip 1 that does not light up or has low brightness, such as the second semiconductor chip 1 from the right in FIG. 9(a), then the semiconductor chip 1 is irradiated with laser light 11d as shown in FIG. 9(b) and burned away. The power of this laser light 11d may be the same as the power of laser light 11b in the chip removal process shown in FIG. 6(b), and this process may be performed in the transfer unit 10. Note that even if there is a semiconductor chip 1 with abnormal performance, if it is possible to place a new semiconductor chip 1 near that semiconductor chip 1, the semiconductor chip 1 may be left without being burned away.

When the semiconductor chip 1 is burned in this way, the bonding material 5 may also be burned, in which case the bonding material 5 is applied as shown in FIG. 9(c). Then, as shown in FIG. 9(d), a repair semiconductor chip, which is a new semiconductor chip 1 that functions in place of the semiconductor chip 1 with abnormal performance, is mounted at the location where the semiconductor chip 1 was burned.

In this invention, mounting the repair semiconductor chip in this way is called the repair process, and each repair takes about 30 seconds.

Here, if the circuit board 6 is for use in a 4K television, for example, 24.88 million semiconductor chips 1 are used. If the defect rate of these semiconductor chips 1 is 0.1%, approximately 25,000 chips will need to be repaired. If each repair semiconductor chip were to be repaired one by one, it would take approximately 200 hours just to repair them, and even if the mounting process itself were completed quickly using laser lift-off, repairs would have a significant impact on productivity.

In contrast, the mounting method of the present invention includes an inspection process. Then, only the semiconductor chips 1 that are determined to be normal in this inspection process, i.e., the semiconductor chips 1 with a 100% pass rate in the inspection process, are placed on the second transfer substrate 4b, which are then mounted on the circuit board 6. As a result, the number of chips that fail to light during the lighting inspection is significantly reduced compared to when mounting is performed without the inspection process, and the number of semiconductor chips 1 that need to be repaired after mounting can be significantly reduced, improving the productivity of the circuit board 6.

If, in the above example of a 4K TV, the lighting failure rate were reduced by a factor of 100 by adding an inspection process, the time required for repairs would be approximately 2 hours, a reduction of nearly 200 hours. Compared to conventional mounting methods, the mounting method of the present invention adds an inspection process, but as described above, the time required for the inspection process is approximately 30 minutes. Therefore, by using the mounting method of the present invention, it is possible to significantly reduce time and provide a circuit board 6 with a normal lighting rate of 100%.

In addition, when repairing, the mounting method of the present invention can be further utilized to selectively transfer the semiconductor chip 1 from the first transfer substrate 4a to the second transfer substrate 4b according to multiple repair positions on the circuit board 6 as shown in FIG. 10, and the time required for repair can be further reduced by simultaneously repairing multiple points using this second transfer substrate 4b.

The above mounting method and mounting device make it possible to mount semiconductor chips on circuit boards with high productivity.

The mounting method and mounting device of the present invention are not limited to the above-described form, and may be of other forms within the scope of the present invention. For example, in the above description, the first transfer step and the second transfer step are performed under atmospheric pressure, but the transfer unit 10 may be provided with a decompression unit (not shown) so that the steps may be performed in a decompression environment.

In addition, in the above description, the semiconductor chip is transferred by a laser in the transfer section, but other means may be used. For example, the semiconductor chip may be transferred by attaching it to an adhesive sheet.

In the above explanation, the laser irradiation position in the transfer section is controlled by a galvanometer mirror, but this is not limiting and other known techniques such as a polygon mirror may be used for control. Also, the laser irradiation position may be controlled only by the relative movement of the transfer substrate and the transferred substrate without using mirror reflection.

In addition, in the above description, the first transfer process and the second transfer process are performed by the same transfer unit, but separate transfer units may be provided and each may be performed by the respective transfer units.

In addition, the inspection of semiconductor chips by the inspection unit is not limited to visual inspection using image analysis, but may also be inspection using X-rays, for example.

REFERENCE SIGNS LIST 1 semiconductor chip 2 carrier substrate 3a adhesive layer 3b adhesive layer 4a first transfer substrate 4b second transfer substrate 5 bonding material 6 circuit substrate 10 transfer section 11 laser light 11a laser light 11b laser light 11c laser light 11d laser light 12 laser irradiation section 13 transfer substrate holding section 14 transferred substrate holding section 15 galvanometer mirror 16 fθ lens 20 inspection section 21 camera 22 inspected substrate holding section 30 mounting section 31 placement table 32 head 33 two-view optical system 34 heater 35 heater 40 robot hand 41 lighting inspection device 100 mounting device

Claims (6)

a first transfer step of transferring a plurality of semiconductor chips formed on a carrier substrate via a GaN layer to a first transfer substrate that adhesively holds the semiconductor chips by an adhesive layer by decomposing or back-grinding the GaN layer with a laser ;
an inspection step of inspecting a state of the semiconductor chip transferred to the first transfer substrate;
a second transfer step of transferring only the semiconductor chips determined to be normal in the inspection step from the first transfer substrate to a second transfer substrate by a laser having a power lower than that required for decomposing the GaN layer;
a mounting step of mounting the semiconductor chip transferred to the second transfer substrate on a circuit board;
A mounting method comprising the steps of: The mounting method according to claim 1, characterized in that the mounting process includes a pressure-bonding process for pressure-bonding the semiconductor chip together with the second transfer substrate to the circuit substrate, and a separation process for separating the second transfer substrate from the semiconductor chip, and that the semiconductor chip is selectively transferred in the second transfer process so that the semiconductor chip is arranged on the second transfer substrate that is subjected to the pressure-bonding process according to the position where the semiconductor chip is to be arranged on the circuit substrate. The mounting method according to claim 2, which includes a post-mounting inspection process for inspecting the performance of the semiconductor chip mounted on the circuit board, and a repair process for adding or replacing a repair semiconductor chip that functions in place of a semiconductor chip determined to be abnormal as a result of the post-mounting inspection process to the circuit board, wherein the repair process selectively transfers a semiconductor chip from the first transfer substrate to the second transfer substrate so that the semiconductor chip is arranged according to the position where the repair semiconductor chip is to be arranged on the circuit board, pressure-bonds the semiconductor chip together with the second transfer substrate to the circuit board, and separates the second transfer substrate from the semiconductor chip. The mounting method according to any one of claims 1 to 3, characterized in that in the inspection step, the state of the semiconductor chip on the first transfer substrate is inspected by visual inspection using image analysis. The mounting method according to any one of claims 1 to 4, further comprising a chip removal step of removing a semiconductor chip determined to be abnormal from the first transfer substrate between the inspection step and the second transfer step. a transfer unit that transfers a plurality of semiconductor chips from a carrier substrate on which semiconductor chips are formed via a GaN layer to a first transfer substrate that adhesively holds the semiconductor chips via an adhesive layer by decomposing or back-grinding the GaN layer using a laser, and transfers the chips from the first transfer substrate to a second transfer substrate using a laser with a power lower than that required for decomposing the GaN layer ;
an inspection unit that inspects a state of the semiconductor chip transferred to the first transfer substrate;
a mounting section that mounts the semiconductor chip transferred to the second transfer substrate onto a circuit board;
having
a semiconductor chip that is determined to be normal by an inspection by the inspection unit and that is transferred from the first transfer substrate to the second transfer substrate;

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