JP6926018B2 - Transfer substrate, mounting method using it, and manufacturing method of image display device - Google Patents

Description

The present invention relates to a transfer substrate for transferring a chip component, and a mounting method for mounting the chip component on a wiring board using the transfer substrate.

Semiconductor chips are becoming smaller due to advances in microfabrication technology, and LED chips are becoming smaller due to improved luminous efficiency of LEDs. Therefore, a large number of chip components such as semiconductor chips and LED chips can be densely formed on one wafer substrate.

In recent years, the chip component C densely formed and diced on the wafer substrate W as shown in FIG. 8A is rearranged on the wiring board S at a predetermined interval and mounted at high speed and with high accuracy (FIG. 8A). c)) There are uses. For example, in the manufacture of micro LED displays, which are attracting attention as image display devices, it is necessary to mount millions of LED chips at predetermined positions on a TFT substrate at intervals.

Although the enlarged views of FIG. 8B showing the cross section of the wafer substrate W and FIG. 8D showing the cross section of the wiring board S are shown in FIGS. 9A and 9B, the chip component C is shown. In order to reliably join the bump electrode B to the electrode (not shown) of the wiring board S, an accuracy of about several μm is required.

Therefore, the chip components C densely formed on the wafer substrate W as shown in FIG. 8 (a) are spaced apart from the wiring board S as shown in FIG. 8 (c) at predetermined intervals (FIG. 8 (c)). Various processes for mounting with high accuracy are being studied.

In particular, the laser lift-off method (hereinafter referred to as the LLO method) has been studied a lot (for example, Patent Document 1).

FIG. 10 shows an example in which the chip component C is transferred and arranged from the wafer substrate W to the wiring substrate S by the LLO method. FIG. 10A shows a state in which the leftmost chip component C is irradiated with the laser beam L and transferred to the wiring board S. Here, the leftmost chip component C is aligned with the upper portion of the wiring board S at a predetermined position. Further, the wavelength of the laser beam L in FIG. 10A is selected from a range suitable for peeling the chip component C from the wafer W. For example, if a wavelength absorbed by the material of the chip component C is used, the chip component C is peeled from the wafer substrate W by the gas generated by the decomposition of the material as the temperature rises.

FIG. 10B shows a state in which the leftmost chip component C peeled off from the wafer substrate W by irradiation with the laser beam L is transferred to the wiring substrate S. Here, since the leftmost chip component C is transferred directly below, it is arranged at a predetermined position on the wiring board S. If the moving distance d directly below the chip component due to transfer is made larger than the total height of the chip component C and the bump B, the wafer substrate W is transferred even if the chip component C is transferred to the wiring board S. Is possible to move horizontally.

FIG. 10C shows a state in which the laser beam L is irradiated after the predetermined positions of the chip component C to be transferred next and the wiring board S are arranged directly under the laser beam L. By this laser irradiation, the next chip component C is transferred and arranged at a predetermined position on the wiring board S at a distance from the chip component C previously transferred and arranged.

After that, by arranging the chip component C to be transferred and the predetermined position of the wiring board S (the position where the chip component C should be mounted) at any time directly under the laser beam L and transferring the chip component C, FIG. The chip component C can be transferred and arranged on the wiring board S as shown in c).

However, as shown in FIGS. 10A to 10B, in order to separate the chip component C from the wafer substrate W, a large amount of energy due to the laser beam L is applied to the chip component C. Therefore, the chip component C reaches the wiring board S in an accelerated state even during the moving distance d shown in FIG. 10B. On the other hand, the electrode portion of the wiring board S is made of metal, and the chip component C may be damaged as shown in FIG. 11 due to the impact when the bump electrode B of the accelerated chip component C comes into contact with the metal electrode. In order to alleviate such an impact, it is conceivable to coat the bump of the chip component C or the electrode of the wiring board C with a thermosetting adhesive (uncured used for sealing), but the coating thickness is high. It is 5 μm or less, which is insufficient to alleviate the impact.

As described above, since the impact applied to the chip component C is large in the direct transfer from the wafer substrate W to the wiring substrate S, a transfer method using a transfer substrate is generally used.

Japanese Unexamined Patent Publication No. 2010-161221

In the transfer method using a transfer substrate, first, as shown in FIG. 12A, the first transfer substrate 1 is brought into close contact with the chip component C of the wafer substrate W, and the chip component C is peeled off by laser light or the like. 1 Transfer to the transfer substrate 1. The first transfer substrate 1 has adhesiveness on the side holding the chip component C. Here, since the chip component C is transferred in close contact with the first transfer substrate, it is transferred to the first transfer substrate 1 without being accelerated.

By the way, as shown in FIG. 12B, since the bump B of the chip component C is in close contact with the first transfer board 1, even if the chip component C is transferred from this state to the wiring board S, the bump B is still formed. It cannot be brought into contact with the electrodes of the wiring board S. Therefore, as shown in FIG. 12C, the chip component C of the first transfer board 1 is transferred to the second transfer board 2 again. The second transfer board 2 has adhesiveness on the side holding the chip component C.

Through the above steps, as shown in FIG. 12D, the second transfer substrate 2 holds the side opposite to the bump B of the chip component C. Here, by adjusting the adhesiveness between the second transfer substrate 2 and the chip component C, the transfer substrate 2 holding the chip component C as shown in FIG. 12D can be used as a substitute for the wafer substrate W in FIG. Therefore, the impact of the chip component C at the time of transfer can be alleviated.

However, it is difficult to control the adhesive strength between all the chip parts C and the second transfer board 2 to be constant, and on the other hand, the laser beam L so as to surely peel off all the chip parts from the second transfer board 2. It is necessary to set the strength of. Therefore, it is extremely difficult to transfer all the chip components C from the second transfer board 2 to the wiring board S without damaging them. If the laser beam L is intended to have an adhesive force that allows peeling even at a low intensity, there is a concern that the chip component C may spontaneously peel from the second transfer substrate 2 or that the chip component C may be displaced during transfer.

The present invention has been made in view of the above problems, and when the chip components arranged in a dense state are mounted on the wiring board at a predetermined interval, the chip components are not damaged and are predetermined. It provides a transfer substrate and a transfer substrate used for reliably mounting at a position, a mounting method using the transfer substrate, and a method for manufacturing an image display device.

In order to solve the above problems, the invention according to claim 1 holds a plurality of chip parts having bump electrodes from the opposite side of the surface on which the bump electrodes are formed and connects them to the bump electrodes. A transfer substrate used for transferring and mounting on a wiring board having electrodes, which includes a base substrate and an adhesive layer formed on the base substrate and holding the chip components, and the material used for the base substrate is The adhesive layer meets the conditions of a Young ratio of 1 GPa or more, a softening temperature of 200 ° C. or more, and a thermal conductivity of 1 W / m · K or more. A transfer substrate having a leave hardness of 50% or more and 90% or less.

The invention according to claim 2 is the transfer substrate according to claim 1, wherein a silicone resin or an acrylic resin is used as the adhesive layer.

The invention according to claim 3 transfers a chip component having a die-dipped bump electrode to a first transfer board holding the bump electrode side, and transfers the chip component to a second transfer board holding the opposite side of the bump electrode. Then, it is a mounting method of transferring and mounting on a wiring board having an electrode to be connected to the bump electrode, wherein the transfer substrate according to claim 1 or 2 is used as the second transfer substrate, and the chip is used. At the stage of transferring the components from the first transfer board to the second transfer board, the spacing between the chip components is changed to the mounting interval on the wiring board, and the surface of the second transfer board holding the chip components. This is a mounting method in which the transfer substrate is peeled off from the chip component after heating while pressurizing from the opposite side.

The invention according to claim 4 is to manufacture an image display device using the mounting method according to claim 3, using an LED chip as the chip component and a TFT substrate as the wiring board. The method.

By mounting using the transfer board of the present invention, chip components arranged in a dense state can be reliably mounted on a wiring board at predetermined intervals, and this transfer board and mounting method can be used. By mounting the LED chip on the TFT substrate, a high-quality image display device can be obtained.

It is a figure which shows the state which the transfer substrate (second transfer substrate) which concerns on embodiment of this invention holds a chip component. According to an embodiment of the present invention, (a) a diagram showing a step of transferring a chip component from a wafer substrate to a first transfer substrate, and (b) a diagram showing a state in which the chip component is transferred to the first transfer substrate. be According to an embodiment of the present invention, it is a diagram showing (a) a step of peeling a chip component from a first transfer substrate, (b) a diagram showing a state in which the chip component is transferred to the transfer substrate 2, and (c). It is a figure which shows the process of peeling the next chip component from a 1st transfer board, and (d) is a figure which shows the state which the next chip component is transferred to the 2nd transfer board. It is a figure which shows the state which (a) the 2nd transfer board holding a chip component is arranged on the wiring board, and (b) the chip component held by the 2nd transfer board is used as a wiring board in accordance with the embodiment of this invention. It is a figure which shows the state of heat-bonding. According to the embodiment of the present invention, it is a figure which shows the state after the heat crimping of a chip component to a wiring board is completed, and (d) the 2nd transfer substrate is peeled off from a chip component, and the mounting is completed. It is a figure which shows the state. It is a modification of the embodiment of the present invention, in which (a) the thermal crimping head is arranged on the wiring board while holding the second transfer board, and (b) the chip component to the wiring board wiring board. It is a figure which shows the state after the thermal pressure bonding is completed. According to the embodiment of the present invention, (a) transfer of chip components from a wafer substrate to a first transfer substrate, (b) transfer of chip components from a first transfer substrate to a second transfer substrate, and (c) second transfer. It is a top view which shows the mounting of a chip component on a wiring board using a board. (A) Top view showing a wafer substrate and chip parts, (b) Cross-sectional view, (c) Top view showing a wiring board and chip parts, and (d) Cross-sectional view. (A) is an enlarged view of a cross section of a wafer substrate and a chip component, and (b) is an enlarged view of a cross section in which a chip component is mounted on a wiring board. The process of directly transferring the chip component from the wafer substrate to the wiring board will be described. (A) The process of peeling the chip component from the wafer substrate, (b) The state in which the chip component is transferred to the wiring board (c) The wafer substrate It is a figure which shows the process of peeling off the next chip component from 1 (d), and (d) the state where the next chip component is transferred to the wiring board. It is a figure explaining how the chip component peeled off from a wafer substrate is damaged by the impact by a collision with a wiring board. The transfer of a chip component using a transfer substrate is described, and is a diagram showing a process of transferring a chip component from a wafer substrate to a first transfer substrate. (B) A state in which the chip component is transferred to the first transfer substrate is shown. It is a figure which shows (c) a process which transfers a chip component from a 1st transfer substrate to a 2nd transfer substrate, and (d) is a figure which shows the state which the chip component was transferred to the 2nd transfer substrate. ..

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a second transfer board 2 which is a transfer board according to an embodiment of the present invention, and shows a state in which a chip component C is held.

As shown in FIG. 1, the second transfer substrate 2 has an adhesive layer 21 laminated on the base substrate 20, and the adhesive layer 21 holds a surface opposite to the bump B of the chip component C.

The base substrate 20 controls the mechanical and thermal characteristics of the second transfer substrate 2, and it is desirable that the base substrate 20 has excellent dimensional stability, heat resistance, and high thermal conductivity. Specifically, it is desirable that the softening temperature is 200 ° C. or higher, the Young's modulus is 1 GPa or higher, and the thermal conductivity is 1 W / m · K or higher. As long as this condition is satisfied, glass, metal, ceramic, or resin may be used, and translucency is not required.

The adhesive layer 21 holds the chip component C, but uses a material more flexible than the base substrate 20 in order to reduce the impact in the process of transferring the chip component C from the first transfer board 1 (details will be described later). .. As an index of flexibility, it is preferable that the leave hardness determined by the repulsion type hardness tester is 50% or more and 90% or less of the base substrate 20. Further, it is desirable that the melting point is 200 ° C. or higher. As a specific main component, it can be selected from silicone resin and acrylic resin.

Hereinafter, embodiments in which the second transfer board 2 having the configuration shown in FIG. 1 is used in the process of mounting the chip components on the wafer board W on the wiring board S at predetermined intervals are shown in FIGS. 2 to 5. Will be described using.

2 (a) and 2 (b) explain the process of transferring the chip component C on the wafer substrate W to the first transfer substrate 1, but FIGS. 12 (a) and 12 (b) show. It is the same as the conventional technique shown in. Here, the chip component C is diced to a size of 1 mm or less on each side. In the description of this embodiment, a GaN-based LED chip is assumed, but a semiconductor integrated circuit chip (IC chip) made of a material such as Si may be used.

In a GaN-based LED, an LED chip is formed on a GaN layer laminated on a sapphire substrate. Therefore, by irradiating light energy with a laser from the side of the wafer substrate W where the chip component C is not formed, the GaN layer that has absorbed the light and overheated is decomposed to generate nitrogen gas, and the sapphire substrate and the sapphire substrate are formed. The GaN layer is peeled off at the interface of. At this time, since the first transfer board 1 and the chip component C are in close contact with each other, if the first transfer board 1 is fixed, no impact force is applied to the chip component C.

A top view of the chip component C from the wafer substrate W to the first transfer substrate 1 is shown in FIG. 7A, but the intervals between the chip components C do not change and the dense state is maintained.

After that, the step of transferring the chip component C from the first transfer substrate 1 to the second transfer substrate 2 will be described with reference to FIG. By the way, unlike the example shown in FIG. 12 (c), the feature of the present invention is that at the stage of transferring from the first transfer board 1 to the second transfer board 2, the space between the chip components C is widened and mounted on the wiring board S. Do the same as when you do. The difference in the arrangement of the chip component C on the first transfer board 1 and the second transfer board is shown in FIG. 7 (b) in a top view. Here, the distance between the chip components C on the second transfer board 2 is the same as that of the wiring board S, and when the chip component C of the second transfer board 2 faces the electrode side of the wiring board S, all the chip components are simultaneously placed. It can be aligned at a predetermined position on the wiring board S.

FIG. 3A shows a state in which the surface on which the chip component C of the first transfer board 1 is arranged and the adhesive layer 21 of the second transfer board 2 face each other with a gap from each other to the leftmost chip component C. It shows a state of irradiating a laser beam and transferring it to the second transfer substrate 2. Here, the distance between the chip component C (non-bump surface) on the first transfer board 1 and the adhesive layer 21 needs to be larger than the height of the chip component C including the bump B. This is because the spacing between the chip components C is changed between the first transfer board 1 and the second transfer board 2, so that the relative positions are changed in the plane direction with the first transfer board 1 and the second transfer board 2 facing each other. Because it is necessary to do.

In FIG. 3A, the laser beam L heats the bump surface side of the chip component C and emits it from the second transfer substrate 2, and the wavelength absorbed by the GaN constituting the chip component C is preferable. However, if a material that absorbs light and emits gas can be used as the adhesive layer of the first transfer substrate 1 with the chip component C, the wavelength of the laser beam may be selected according to the material of the adhesive layer.

FIG. 3B shows a state in which the chip component C irradiated with the laser beam L is emitted from the first transfer substrate 1 and held by the second transfer substrate 2. Here, the chip component C arrives at the second transfer substrate 2 after being accelerated in the space between the first transfer substrate 1 and the second transfer substrate 2, although the chip component C has a slight interval. The adhesive layer 21 needs to cushion the impact when the chip component C arrives. Therefore, as a result of searching for a condition that the chip component C is not damaged when it arrives at the second transfer substrate 2, as described above, the leave hardness determined by the repulsive hardness tester is 50% or more and 90% or less of the base substrate 20. I found the condition that. If this value exceeds 90%, the chip parts may be damaged. On the other hand, if it is less than 50%, the chip parts will not be damaged, but inconvenience may occur due to viscosity or the like when heating in a subsequent process.

In FIG. 3C, the first transfer substrate is arranged so that the chip component C to be transferred next and the predetermined position of the second transfer substrate 2 (predetermined distance from the chip component C transferred earlier) are arranged directly under the laser beam. It shows a state in which the laser beam L is irradiated after adjusting the relative positions of the first and the second transfer substrate 2. By this laser irradiation, the next chip component C is transferred and arranged on the second transfer substrate 2 at a predetermined interval from the chip component C previously transferred and arranged (FIG. 3 (d)).

After that, the chip component C to be transferred directly under the laser beam L and the predetermined position of the second transfer substrate 2 (by arranging them at any time to transfer the chip component C, as shown in FIG. 1) The chip component C can be obtained on the second transfer substrate 2 on which C is transferred and arranged.

A state in which the chip component C is mounted on the wiring board S using the second transfer board 2 will be described with reference to FIGS. 4 and 5.

FIG. 4A shows a state in which the second transfer board 2 is arranged in a state where the chip mounting position on the wiring board S arranged on the stage 3 and the chip component C are aligned. Here, the chip component arrangement on the second transfer board 2 and the chip component mounting position on the wiring board S are as shown in the top view in FIG. 7 (c), and all the chips arranged on the second transfer board 2 are shown. The components can be aligned with the mounting position of the wiring board S at the same time.

From this state, the heat crimping head 4 is brought closer from the base board 20 side of the second transfer board 2 and heat crimped as shown in FIG. 4B to electrically attach the chip component C to the electrode of the wiring board S. Can also be mechanically joined and mounted. Further, if the thermosetting adhesive is arranged in advance between the chip component C and the wiring board S, the resin sealing of the chip component C can be performed at the same time.

Since the thermocompression bonding is performed by sandwiching it between the stage 3 and the thermocompression bonding head 4, the stage 3 may have a heating function.

Further, in the heat crimping, when the second transfer substrate 2 is thermally deformed, the mounting accuracy of the chip component C is lowered. Therefore, the base substrate 20 constituting the second transfer substrate 2 is required to have a softening temperature of 200 ° C. or higher, a Young's modulus of 1 GPa or higher, and a thermal conductivity of 1 W / m · K or higher. Further, the adhesive layer 21 is required to have a melting point of 200 ° C. or higher because it must be avoided to be fused during heat pressure bonding.

FIG. 5C shows a state after the heat crimping of FIG. 4B is completed, in which the heat crimping head 4 is raised, and then the second transfer substrate is peeled off from the chip component C. The state is shown in FIG. 5 (d).

In FIGS. 4 and 5, an example in which the second transfer board 2 is arranged on the wiring board S and then the heat crimping head 4 is lowered and heat-pressed is described. However, as a modification of the present embodiment, heat is generated. FIG. 6 shows an example in which the crimping head 4 sucks and holds the second transfer substrate 2. FIG. 6A shows a state in which the heat crimping head 4 sucks and holds the second transfer board 2 and aligns the second transfer board 2 with the wiring board S. FIG. 6B shows a state after the heat crimping is completed. It is shown that the second transfer substrate 2 can be peeled from the chip component C at the same time by raising the heat crimping head 4.

As described above, in the present invention, the transfer of the chip component C from the second transfer board 2 to the wiring board S is not performed by the LLO method, but is transferred and mounted at the same time by heat crimping. Therefore, when the chip component C is transferred from the second transfer board 2 to the wiring board S, the chip component C is not impacted. Therefore, even if the material and electrodes of the wiring board S are hard, the chip component It is possible to prevent C from being damaged. Further, although the LLO method is used for transferring the chip component C from the first transfer substrate 1 to the second transfer substrate 2, the second transfer layer can be obtained by appropriately selecting the adhesive layer constituting the second transfer substrate 2. It is possible to alleviate the impact during transfer to the transfer substrate 2 and prevent damage to the chip component C.

Therefore, in an application in which a large number of chip parts are mounted at intervals, the chip breakage rate in the process can be suppressed to an extremely low level, and the cost required for repair can be significantly reduced. Therefore, the present invention is suitable as a method for manufacturing an image display device in which a TFT substrate is used as a wiring board and an LED chip is used as a chip component, and a method for manufacturing a high-quality image display device using millions of LEDs. It is extremely suitable as.

1 1st transfer board 2 2nd transfer board 3 Stage 4 Thermocompression bonding head 20 Base board 21 Adhesive layer B Bump C Chip component L Laser light S Wiring board W Wafer board

Claims (4)

A transfer substrate used for holding a plurality of chip components having bump electrodes from the opposite side of the surface on which the bump electrodes are formed and transferring them to a wiring board having electrodes connected to the bump electrodes. hand,
A base substrate and an adhesive layer formed on the base substrate to hold the chip components are provided.
The material used for the base substrate satisfies the conditions of Young's modulus of 1 GPa or more, softening temperature of 200 ° C. or more, and thermal conductivity of 1 W / m · K or more.
The adhesive layer is a transfer substrate having a melting point of 200 ° C. or higher and a leave hardness measured by a repulsive hardness tester of 50% or more and 90% or less of the leave hardness of the base substrate. The transfer substrate according to claim 1.
A transfer substrate using a silicone resin or an acrylic resin as the adhesive layer. A chip component having a diced bump electrode is transferred to a first transfer board holding the bump electrode side, transferred to a second transfer board holding the opposite side of the bump electrode, and then connected to the bump electrode. It is a mounting method that transfers and mounts on a wiring board that has electrodes to be used.
The transfer substrate according to claim 1 or 2 is used as the second transfer substrate.
At the stage of transferring the chip component from the first transfer board to the second transfer board, the interval of the chip component is changed to the mounting interval on the wiring board.
A mounting method in which the transfer substrate is peeled off from the chip component after heating while pressurizing from the side opposite to the surface holding the chip component of the second transfer substrate. Using an LED chip as the chip component and a TFT substrate as the wiring board,
A method for manufacturing an image display device, which manufactures an image display device using the mounting method according to claim 3.

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