TRANSFER SUBSTRATE AND METHOD OF MANUFACTURING ELECTRONIC APPARATUS

Performance of an electronic component including a plurality of elements is improved. A transfer substrate includes: a support substrate; an adhesive resin layer continuously provided on one surface of the support substrate and having a plurality of holding regions adhesively holding elements; and a coating film provided on a surface of the adhesive resin layer opposite to the support substrate to cover an outer region of the holding region of the adhesive resin layer and having lower surface adhesiveness than surface adhesiveness of the adhesive resin layer.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Japanese Patent Application No. 2023-87200 filed on May 26, 2023, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present disclosure relates to a transfer substrate and a method of manufacturing an electronic apparatus.

BACKGROUND OF THE INVENTION

There is a method of manufacturing an electronic apparatus in which electronic components (elements) are mounted on a plurality of electrodes arranged on a circuit substrate. For example, Japanese Patent Application Laid-open Publication No. 2022-158612 (Patent Document 1) describes a method of mounting an electronic component for mounting a light-emitting element provided on a sapphire substrate on a terminal of a circuit substrate. Further, for example, Japanese Patent Application Laid-open Publication No. 2021-5632 (Patent Document 2) describes a transfer substrate including a plurality of protrusions protruding from a first surface of an elastic body as a transfer substrate for transferring a microLED element on a circuit substrate.

SUMMARY OF THE INVENTION

As described above, an electronic apparatus may be manufactured by adhesively holding elements using an adhesive resin layer of a transfer substrate and collectively mounting the plurality of elements on a circuit substrate. When a plurality of elements are mounted on the circuit substrate as described above, for example, if the circuit substrate or the transfer substrate is warped, the transfer substrate needs to be strongly compressed against the circuit substrate. Accordingly, the adhesive resin layer may be fixed to the circuit substrate.

An objective of the present disclosure is to provide a technique of improving performance of an electronic apparatus including a plurality of elements.

A transfer substrate according to one aspect of the present disclosure includes: a support substrate; an adhesive resin layer continuously provided on one surface of the support substrate and adhesively holding elements in a plurality of holding regions, respectively; and a coating film provided on a surface of the adhesive resin layer opposite to the support substrate to cover an outer region of the holding region of the adhesive resin layer and having lower surface adhesiveness than surface adhesiveness of the adhesive resin layer.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

The following is explanation for each embodiment of the present invention with reference to drawings. Note that only one example is disclosed, and appropriate modification with keeping the idea of the present invention which can be anticipated by those who are skilled in the art is obviously within the scope of the present invention. Also, in order to make the explanation clear, a width, a thickness, a shape, and others of each portion in the drawings are schematically illustrated more than those in an actual aspect in some cases. However, the illustration is only an example, and does not limit the interpretation of the present invention. In the present specification and each drawing, similar elements to those described earlier for the already-described drawings are denoted with the same or similar reference characters, and detailed explanation for them is appropriately omitted in some cases.

In the following embodiments, a microLED display apparatus on which a plurality of microLED elements are mounted will be explained as an example of an electronic apparatus on which a plurality of electronic components are mounted. The microLED display apparatus may be simply referred to as a display apparatus below.

First, an exemplary configuration of a microLED display apparatus as an electronic apparatus according to the present embodiment will be described.FIG.1is a plan view showing the exemplary configuration of the microLED display apparatus as the embodiment of the electronic apparatus. InFIG.1, each of a boundary between a display region DA and a peripheral region PFA, a controlling circuit5, a driving circuit6, and a plurality of pixels PIX is illustrated with a dashed double-dotted line.FIG.2is a circuit diagram showing an exemplary configuration of a circuit around a pixel ofFIG.1.

As shown inFIG.1, a display apparatus DSP1according to the present embodiment includes the display region DA, the peripheral region PFA surrounding the display region DA in a frame form, and a plurality of pixels PIX arranged in a matrix form inside the display region DA. The display apparatus DSP1includes a circuit substrate10having a rectangular planar shape, the controlling circuit5formed on the circuit substrate10, and the driving circuit6formed on the circuit substrate10. The circuit substrate10is made of glass or resin.

The controlling circuit5is a circuit controlling driving of a display function of the display apparatus DSP1. The controlling circuit5is, for example, a driver integrated circuit (IC) mounted on the circuit substrate10. In the example ofFIG.1, the controlling circuit5is arranged along one short side of four sides of the circuit substrate10, in other words, along an X direction in the drawing. In the following explanation, the short side direction of the circuit substrate10may be referred to as X direction, a long side direction of the circuit substrate10may be referred to as Y direction, and a thickness direction of the circuit substrate10may be referred to as Z direction.

In the present embodiment, the controlling circuit5includes a signal-line driving circuit configured to drive a wiring (video signal wiring) VL (seeFIG.2) connected to the plurality of pixels PIX. However, the position and configuration of the controlling circuit5are not limited to those of the example ofFIG.1, and may be variously modified. For example, inFIG.1, a wiring substrate such as flexible circuit board is connected at the position shown as the controlling circuit5, and the driver IC may be mounted on this wiring substrate. Alternatively, for example, the signal-line driving circuit configured to drive the wiring VL may be formed separately from the controlling circuit5.

The driving circuit6includes a circuit configured to drive a scan signal line GL (seeFIG.2) of the plurality of pixels PIX. The driving circuit6includes a circuit configured to supply a reference potential to an LED element mounted on each of the plurality of pixels PIX. The driving circuit6drives the plurality of scan signal lines GL on the basis of a control signal from the controlling circuit5. In the example ofFIG.1, the driving circuit6is arranged along each of the long sides of the four sides of the circuit substrate10. However, the position and exemplary configuration of the driving circuits6are not limited to those of the example ofFIG.1, and may be variously modified. For example, inFIG.1, a wiring substrate such as flexible circuit board may be connected at the position shown as the controlling circuit5, and the driving circuit6may be mounted on the wiring substrate.

Next, an exemplary circuit configuration of the pixels PIX will be explained with reference toFIG.2. Note thatFIG.2shows four pixels PIX. However, each of the plurality of pixels PIX shown inFIG.1includes the same circuit as those of the pixels PIX shown inFIG.2. A circuit of the pixel PIX including a switching element SW and an LED element20may be referred to as a pixel circuit below. The pixel circuit is a circuit of a voltage signal system for controlling a light-emitting state of the LED element20in response to a video signal Vsg supplied from the controlling circuit5(seeFIG.1).

As shown inFIG.2, each pixel PIX includes the LED element20. The LED element20is the micro light-emitting diode. The LED element20includes an anode electrode21EA and a cathode electrode21EK. The cathode electrode21EK of the LED element20is connected to a wiring VSL to which the reference potential (fixed potential) PVS is supplied. The anode electrode21EA of the LED element20is electrically connected to a drain electrode ED of the switching element SW via a wiring31.

Each pixel PIX includes the switching element SW. The switching element SW is a transistor configured to control a connection state (ON/OFF state) between the pixel circuit and the wiring VL in response to a control signal Gs. The switching element SW is, for example, a thin-film transistor. When the switching element SW is in the ON state, the video signal Vsg is input from the wiring VL into the pixel circuit.

The driving circuit6includes a shift register circuit, an output buffer circuit, and the like not illustrated. The driving circuit6outputs a pulse on the basis of a horizontal scanning start pulse transmitted from the controlling circuit5(seeFIG.1), and outputs the control signal Gs.

Each of the plurality of scan signal lines GL extends in the X direction. The scan signal line GL is connected to a gate electrode EG of the switching element SW. By the supply of the control signal Gs to the scan signal line GL, the switching element SW is turned ON to supply the video signal Vsg to the LED element20.

A structure around the LED element20arranged in each of the plurality of pixels PIX shown inFIG.1will be explained below.FIG.3is a transparent enlarged plan view showing an exemplary structure around the LED element arranged in each of the plurality of pixels of the display apparatus ofFIG.1. An inorganic insulative layer14shown inFIG.4is omitted inFIG.3. InFIG.3, each outline of a semiconductor layer, an electrode, and the scan signal line is illustrated with a dotted line.FIG.4is an enlarged cross-sectional view taken along the line A-A ofFIG.3.FIG.5is an enlarged plan view showing a substrate structure from which the LED element ofFIG.3is removed.

As shown inFIG.3, the display apparatus DSP1includes the plurality of pixels PIX (pixels PIX1, PIX2, and PIX3in the example ofFIG.3). Each of the pixels PIX includes the switching element SW, the LED element (light-emitting element)20, the wiring31, and a wiring32. Note that the LED element20configured to emit a visible light of, for example, any one of red, blue, and green is mounted on each of the pixels PIX1, PIX2, and PIX3to form the switching element SW configured to drive the LED element20.

If the visible lights of the respective colors are emitted from the LED elements20of the pixels PIX1, PIX2, and PIX3, color display in the display apparatus DSP1is achieved by controlling the outputs and timings of the visible lights emitted from the LED elements20of the pixels PIX1, PIX2, and PIX3. When the plurality of pixels PIX which emit the visible lights of mutually different colors are combined as described above, a pixel PIX of each color may be referred to as sub-pixel, and a set of the plurality of pixels PIX may be referred to as pixel.

The wiring31is electrically connected to the drain electrode ED of the switching element SW and the anode electrode21EA of the LED element20. The wiring32is connected to a source electrode ES of the switching element SW. In the example ofFIG.3, the wiring32has a bent structure in which one end thereof is connected to the source electrode ES of the switching element SW while the other end thereof is connected to the wiring VL. The scan signal line GL is used as the gate electrode EG of the switching element SW.

The display apparatus DSP1further includes the wiring VL and a wiring VSL. The wiring VL extends over the plurality of pixels (seeFIG.2) along the Y direction, and is electrically connected to the wirings32. The wiring VSL extends over the plurality of pixels PIX along the X direction crossing (inFIG.3, orthogonal to) the Y direction, and is electrically connected to the cathode electrodes21EK of the LED elements20. The wiring VL and the wiring VSL cross with each other via an insulative layer41at a wiring crossing portion LXP shown inFIG.3. The insulative layer41interposes between the wiring VL and the wiring VSL, and thus, the wiring VL and the wiring VSL are electrically isolated from each other.

As shown inFIG.4, the display apparatus DSP1is an electronic apparatus including the LED elements20and a substrate structure SUB1. The substrate structure SUB1is configured to include the circuit substrate10made of glass or resin and a plurality of insulative layers stacked on the circuit substrate10. The plurality of insulative layers of the substrate structure SUB1include an inorganic insulative layer11, an inorganic insulative layer12, an inorganic insulative layer13, and the inorganic insulative layer14which are stacked on the circuit substrate10. The circuit substrate10has a surface10fand a surface10bopposite to the surface10f. The inorganic insulative layers11,12,13, and14are stacked on the surface10fof the circuit substrate10.

The switching element SW includes the inorganic insulative layer12formed on the circuit substrate10, a semiconductor layer50formed on the inorganic insulative layer12, the drain electrode ED connected to a drain region of the semiconductor layer50, the source electrode ES connected to a source region of the semiconductor layer50, and the inorganic insulative layer13covering the semiconductor layer50. Each of the wiring31and the wiring32is a stacked film of, for example, a conductor layer made of titanium or a titanium alloy and a conductor layer made of aluminum or an aluminum alloy. The stacked film including the titanium layers sandwiching the aluminum layer therebetween is referred to as a TAT stacked film.

The example ofFIG.4is an example of a bottom-gate system which the gate electrode EG interposes between the semiconductor layer50and the circuit substrate10. In the bottom-gate system, a part of the inorganic insulative layer12between the gate electrode EG and the semiconductor layer50functions as a gate insulative layer. The inorganic insulative layer12also functions as a base layer for forming the semiconductor layer50. Note that a position of the gate electrode EG is not limited to that of the example ofFIG.4, and, for example, a top-gate system may be applied.

Although a material making each of the inorganic insulative layers11,12,13, and14is not particularly limited, for example, silicon oxide (SiO), silicon nitride (SiN), or the like is exemplified. The semiconductor layer50is a semiconductor film that is a silicon film made of silicon doped with a P-type or N-type conductive impurity.

Each of the source electrode ES and the drain electrode ED is a contact plug for making electric contact with either one of the source region and the drain region of the semiconductor layer50. As a material of the contact plug, for example, tungsten or the like is exemplified. As a modification example ofFIG.4, a contact hole for exposing the source region and the drain region of the semiconductor layer50may be formed in the inorganic insulative layer13, and each of a part of the wiring31and a part of the wiring32may be embedded in the contact hole. In this case, the embedded parts of the wiring31and the wiring32in the contact holes come into contact with the semiconductor layer50, and the contact interfaces between the wirings31,32and the semiconductor layer50can be regarded as the drain electrode ED and the source electrode ES.

As shown inFIG.5, the substrate structure SUB1includes a plurality of bump electrodes33orderly arranged in plan view. The bump electrode33is a terminal for mounting the electronic component on the circuit substrate10(seeFIG.4). In the present embodiment, the bump electrode33is a terminal for mounting the LED element20shown inFIG.4. Thus, two bump electrodes33are adjacently arranged in a region where the LED element20(seeFIG.3) is to be mounted. One of the two bump electrodes33is connected to the anode electrode21EA of the LED element20, and the other is connected to the cathode electrode21EK of the LED element20.

As shown inFIG.4, the bump electrode33is connected to the wiring31at a position overlapping an opening14H formed in the inorganic insulative layer14, and protrudes from the inorganic insulative layer14. The bump electrode33is made of, for example, solder containing tin. Alternatively, the bump electrode33may be a stacking body made of a metal layer made of a metallic material such as copper having higher electric conductivity than solder and a solder layer.

<Method of Manufacturing Electronic Apparatus>

Next, a method of manufacturing an electronic apparatus according to the present embodiment will be explained as a representative example of the method of manufacturing the display apparatus DSP1ofFIG.3.FIG.6is an explanatory diagram showing an example of a process flow of the method of manufacturing the display apparatus as an embodiment of the electronic apparatus.

As shown inFIG.6, the method of manufacturing the electronic apparatus according to the present embodiment includes a substrate-structure preparing step S1, a transfer-substrate preparing step S2, an element holding step S3, an element compressing step S4, a laser emitting step S5, and an element stripping-off step S6.

The substrate structure SUB1ofFIG.7is prepared in the substrate-structure preparing step S1ofFIG.6.FIG.7is a diagram for explaining the substrate-structure preparing step, and is an enlarged cross-sectional view of the substrate structure taken along the line B-B ofFIG.5. In the substrate-structure preparing step S1, as shown inFIG.7, the substrate structure SUB1including the circuit substrate10made of glass or resin, the wiring31formed on the circuit substrate10, and the inorganic insulative layer14covering the wiring31is prepared. The inorganic insulative layer11, the inorganic insulative layer12, the inorganic insulative layer13, and the inorganic insulative layer14are stacked on the circuit substrate10, and the wiring31is arranged between the inorganic insulative layer13and the inorganic insulative layer14. Most of the substrate structure SUB1is covered with the inorganic insulative layer14. The opening14H is formed in the inorganic insulative layer14at a position overlapping the wiring31and a position overlapping the wiring VSL. The wiring31and the wiring VSL are exposed from the inorganic insulative layer14at the bottoms of the openings14H.

Each of the plurality of bump electrodes33is embedded in the opening14H and is connected to the wiring31or the wiring VSL at the bottom of the opening14H. As shown inFIG.5, in plan view of the substrate structure SUB1, the plurality of bump electrodes33are orderly arranged in the region where the electronic component (LED element20ofFIG.3) are to be mounted.

As shown inFIG.7, the bump electrode33is formed to protrude above the inorganic insulative layer14. As described above, a part of the wiring31and a part of the wiring VSL are partially exposed from the inorganic insulative layer14at the openings14H, and thus, the bump electrode33can be selectively formed by, for example, an electroplating method. Note that the bump electrode33may be formed under use of a resist film in order to increase a height of the protrusion of the bump electrode33.

In the transfer-substrate preparing step S2ofFIG.6, a transfer substrate shown inFIGS.8to10is prepared.FIG.8is a perspective view of the transfer substrate prepared in the transfer-substrate preparing step.FIG.9is an enlarged plan view showing a part of the transfer substrate, andFIG.10is an enlarged cross-sectional view taken along the line C-C ofFIG.9.

The transfer substrate70shown inFIGS.8to10includes a support substrate71, an adhesive resin layer72provided on either one surface of the support substrate71, and a coating film73provided on a surface of the adhesive resin layer72opposite to the support substrate71. The support substrate71is a substrate having a substantially rectangular planar shape used for ensuring rigidity of the transfer substrate70. The support substrate71is a synthetic substrate containing, for example, silicon oxide such as quartz or glass, as a main component. Note that the substrate having the rectangular planar shape is exemplified as the transfer substrate70. However, this is one example, and the shape of the transfer substrate70is not particularly limited.

The adhesive resin layer72is a layer used for adhesively holding the plurality of LED elements20in the element holding step S3described below, and is continuously provided on the surface of the support substrate71. More specifically, the adhesive resin layer72(the transfer substrate70) has a plurality of holding regions74in a matrix form adhesively holding the LED elements20. The adhesive resin layer72is provided on the support substrate71in a range including these holding regions74.

Note that the number of the holding regions74of the adhesive resin layer72(the transfer substrate70) is not particularly limited. The number of the holding regions74may be appropriately determined depending on, for example, the number of the LED elements20of the display apparatus DSP1.

The adhesive resin layer72is made of a resin material having adhesiveness capable of adhesively holding the LED elements20, and a surface72f(seeFIG.10) thereof opposite to the support substrate71has adhesiveness capable of adhesively holding the LED elements20. However, the LED elements20adhesively held by the adhesive resin layer72are stripped off from the adhesive resin layer72after being mounted on the substrate structure SUB1. Thus, the adhesiveness of the adhesive resin layer72needs to be appropriately adjusted in consideration of this point. A thickness of the adhesive resin layer72is not particularly limited, but preferably about several tens μm, and is about 20 μm in the present embodiment.

The coating film73is a film used for suppressing adhesion of the adhesive resin layer72to the substrate structure SUB1including the circuit substrate10in the element compressing step S4described below, and the adhesiveness of the surface adhesiveness the coating film73is lower than the adhesiveness of the surface of the adhesive resin layer72. In other words, the coating film73is made of a material having lower adhesiveness than that of the resin material of the adhesive resin layer72. As described above, the adhesive resin layer72has the surface72fhaving the adhesiveness capable of adhering the LED elements20. As a result, the adhesive resin layer72has the surface72fhaving the adhesiveness adhering to the substrate structure SUB1. The adhesiveness of the surface of the coating film73is lower than the adhesiveness of the surface72fof the adhesive resin layer72.

The adhesiveness of the surface of coating film73preferably has the remarkably low, and particularly the surface preferably has no surface adhesiveness. That is, A type of the coating film73having the lower surface adhesiveness than that of the adhesive resin layer72includes not only a type having the lower surface adhesiveness but also a type having no surface adhesiveness.

The coating film73is provided on one surface of the adhesive resin layer72, that is the surface72fof the adhesive resin layer72opposite to the support substrate71in this example. The coating film73is provided to cover an outer region of the holding region74in the surface72fof the adhesive resin layer72. As an example, the coating film73is provided to surround a periphery of each holding region74. In other words, the coating film73is provided over the substantially entire surface72fof the adhesive resin layer72except for a part corresponding to each holding region74. In another words, the coating film73is provided over the substantially entire surface72fof the adhesive resin layer72, and includes an opening73aat a position corresponding to each holding region74.

An opening shape (planar shape) of the opening73ais not particularly limited, but preferably an opening shape formed along the planar shape of the holding region74. Each holding region74is a region adhesively holding the LED element20. As an example, the shape of the holding region74coincides with the planar shape of the LED element20. Thus, it can be also said that the shape of the opening73apreferably has the shape formed along the planar shape of the LED element20. In the present embodiment, the planar shape of the LED element20is rectangular, and thus, the shape of each holding region74is also rectangular. Therefore, the opening shape of the opening73ais preferably also rectangular along the shape of the holding region74.

The opening73aof the coating film73is preferably slightly larger than each holding region74in consideration of positioning accuracy provided when the LED element20is adhesively held by the adhesive resin layer72. For example, when the shape of the LED element20(the shape of the holding region74) is a rectangular shape of about 20 to 30 μm square, a length of one side of the opening73ais about 2 to 5 μm larger than a length of one side of the holding region74. In other words, for example, as shown inFIG.9, a gap80having a predetermined width W1of about 1 to 2.5 μm preferably exists between the periphery of the holding region74and the adhesive resin layer72.

The coating film73is made of, for example, a metallic thin film such as copper or aluminum. However, the material of the coating film73is not limited to such a metallic material. As the material of the coating film73, an inorganic material is preferably used. However, any material capable of suppressing the adhesion of the adhesive resin layer72to the substrate structure SUB1and being endurable to heat applied in the laser emitting step described below is applicable. The material of the coating film73is preferably a material not adhesive to the substrate structure SUB1, particularly a material not having the adhesiveness thereto.

A method of forming the coting film73made of the metallic thin film is not particularly limited. However, for example, a vapor deposition method, a sputtering method, or the like is exemplified. For example, the coating film73may be formed by forming the metallic thin film on a different substrate from the transfer substrate70and then transferring this metallic thin film onto the adhesive resin layer72.

Next, in the element holding step S3ofFIG.6, as shown inFIG.11, the LED element20is adhesively held in each of the plurality of holding regions74of the transfer substrate70by the adhesive resin layer72.FIG.11is a diagram for explaining the element holding step. More specifically,FIG.11is an enlarged cross-sectional view showing a state in which the LED element is held in each holding region of the transfer substrate ofFIG.10by the adhesive resin layer.

In this step, by making the contact of the plurality of LED elements20with the adhesive resin layer72of the transfer substrate70, the plurality of LED elements20are adhesively held by the transfer substrate70. Specifically, the surface of the LED element20opposite to its surface where the electrodes21(the anode electrode21EA and the cathode electrode21EK) are formed is adhesively held by one surface72fof the adhesive resin layer72. In other words, the LED element20is adhesively held by the transfer substrate70such that its surface where the anode electrode21EA and the cathode electrode21EK are formed faces the substrate structure SUB1. Note that the anode electrode21EA and the cathode electrode21EK of the LED element20may be collectively referred to as electrodes21.

Each of the LED elements20adhesively held by the transfer substrate70as described above is first formed on, for example, a sapphire substrate. Each of the plurality of LED elements20completed on the sapphire substrate is temporarily transferred onto a first transfer substrate, and then, is transferred from the first transfer substrate to the transfer substrate70.FIG.11shows a state provided after the plurality of LED elements20are transferred from the first transfer substrate to the transfer substrate70. Since each of the plurality of LED elements20formed on the sapphire substrate is transferred through the first transfer substrate to the transfer substrate70, the LED elements20are held by the transfer substrate70while the electrode21faces the substrate structure SUB1.

Next, in the element compressing step S4ofFIG.6, as shown inFIG.12, the transfer substrate70adhesively holding the plurality of LED elements20is compressed against the substrate structure SUB1prepared in the substrate-structure preparing step S1.FIGS.12and13A to13Care diagrams for explaining the element compressing step. More specifically,FIG.12is an enlarged cross-sectional view showing a state in which the transfer substrate is compressed against the substrate structure in the element compressing step.FIGS.13A to13Care schematic diagrams for explaining the element compressing step provided when the substrate structure SUB1is warped.FIG.14is a cross-sectional view for explaining a modification example of the transfer substrate.

In this step, the transfer substrate70is compressed against the substrate structure SUB1in a state in which the electrodes21of the LED elements20adhesively held by the plurality of holding regions74of the adhesive resin layer72of the transfer substrate70face the plurality of bump electrodes33formed the on substrate structure SUB1, respectively. In the manner, the electrodes21of the plurality of LED elements20held by the transfer substrate70come into contact with the plurality of bump electrodes33, respectively.

Here, it is assumed that, for example, the circuit substrate10configuring the substrate structure SUB1is warped. In this case, in order to make the contact of the electrodes21of the plurality of LED elements20with the corresponding bump electrodes33, the transfer substrate70needs to be more strongly compressed against the substrate structure SUB1than that in no warpage case of the circuit substrate10. Accordingly, there is a risk of adhesion of the adhesive resin layer72to the substrate structure SUB1including the circuit substrate10. However, since the coating film73is provided on the surface of the adhesive resin layer72configuring the transfer substrate70, the adhesion of the adhesive resin layer72to the substrate structure SUB1can be suppressed.

Specifically, for example, as shown inFIG.13A, it is assumed that the substrate structure SUB1is warped to protrude toward the transfer substrate70so that the warpage of the center of the substrate structure SUB1in the X direction is the largest. In this case, when the transfer substrate70is compressed against the substrate structure SUB1, the electrode21of the LED element20comes into contact with the bump electrode33firstly at the center of the substrate structure SUB1in the X direction having the largest warpage as shown inFIG.13B. To the contrary, at both ends of the substrate structure SUB1in the X direction, the electrodes21of the LED elements20do not come into contact with the bump electrodes33.

In order to make the contact of all the electrodes21of the LED elements20with the bump electrodes33, the transfer substrate70needs to be more strongly compressed against the substrate structure SUB1. In the manner, as shown inFIG.13C, all the electrodes21of the LED elements20can come into contact with the bump electrodes33of the substrate structure SUB1. However, for example, at the center of the substrate structure SUB1in the X direction, the adhesive resin layer72is squashed by the LED element20. In other words, the LED element20is compressed into the adhesive resin layer72.

If an area of the substrate structure SUB1is relatively small, a warpage amount is suppressed to be relatively small, and thus, the LED element20is difficult to be compressed into the adhesive resin layer72. To the contrary, if the area of the substrate structure SUB1is relatively large, the warpage amount tends to be large. Accordingly, the LED element20tends to be compressed into the adhesive resin layer72. Since the LED element20is compressed into the adhesive resin layer72as described above, the adhesive resin layer72tends to adhere to the surface of the substrate structure SUB1.

However, the coating film73is provided on the surface of the adhesive resin layer72, the adhesion of the adhesive resin layer72to the substrate structure SUB1can be suppressed. More specifically, even when the LED element20is compressed into the adhesive resin layer72, the coating film73exists between the adhesive resin layer72and the substrate structure SUB1. Thus, the adhesive resin layer72does not directly come into contact with the surface of the substrate structure SUB1. Therefore, the adhesion of the adhesive resin layer72to the substrate structure SUB1can be suppressed.

Particularly, if the thickness of the adhesive resin layer72is larger than the height of the LED element20, when the LED element20is compressed into the adhesive resin layer72, the adhesive resin layer72tends to adhere to the substrate structure SUB1. Even in this case, since the coating film73is provided on the surface of the adhesive resin layer72, the adhesion of the adhesive resin layer72to the substrate structure SUB1can be effectively suppressed.

If the adhesive resin layer72is compressed by the LED element20, the surface of the substrate structure SUB1may come into contact with the coating film73. In this case, the adhesive resin layer72is also pressurized by the coating film73. However, the coating film73is continuously formed in the outer region of the holding region74of the transfer substrate70, and its area is relatively large. More specifically, the contact area of the coating film73with the adhesive resin layer72is larger than the contact area of each LED element20with the adhesive resin layer72. Thus, the coating film73is more difficult to be compressed into the adhesive resin layer72than the LED element20.

The thickness of the coating film73is not particularly limited but is preferably smaller than the height of the LED element20. In other words, when the LED element20is adhesively held by the adhesive resin layer72, the tip of the LED element20is preferably positioned at an outer region of the surface of the coating film73in the Z direction. In the manner, in the element holding step S3, the LED element20is easily adhesively held onto the adhesive resin layer72of the transfer substrate70.

To the contrary, in order to suppress the adhesion of the adhesive resin layer72to the substrate structure SUB1, for example, the thickness of the coating film73is preferably larger than the height of the LED element20as shown inFIG.14. Additionally, the thickness of the coating film73is preferably the same as or slightly larger than a total of the height of the LED element20and a height of the bump electrode33of the substrate structure SUB1.

In the manner, even if the LED element20is compressed into the adhesive resin layer72, a sufficient gap can be ensured between the adhesive resin layer72and the substrate structure SUB1. In the manner, the adhesion of the adhesive resin layer72to the substrate structure SUB1can be securely suppressed. The sufficient gap is ensured between the adhesive resin layer72and the substrate structure SUB1. Therefore, the adhesion of the adhesive resin layer72to the substrate structure SUB1through the gap between the LED element20and the coating film73provided when, for example, the LED element20is compressed into the adhesive resin layer72, is suppressed.

When the thickness of the coating film73is made larger than the height of the LED element20, in the element holding step S3, the LED element20is difficult to be adhesively held by the adhesive resin layer72of the transfer substrate70. However, by, for example, devisal for the shape of the first transfer substrate, the LED element20held on the first transfer substrate can be easily adhesively held onto the adhesive resin layer72of the transfer substrate70. As an example, a portion of the first transfer substrate, the portion facing the holding region74, may be provided with a protrusion having a smaller area than that of the holding region74so that the LED element20is held on this protrusion.

The explanation for the present embodiment has been made in the case in which the substrate structure SUB1is warped to be the curved surface centering the side opposite to the transfer substrate70so that the warpage of the center of the substrate structure SUB1in the X direction is the largest. However, the state of the warpage is not limited to this example. For example, even if the substrate structure SUB1is warped to be a curved surface centering the side of the transfer substrate70, the similar effects can be achieved. Further, even if the transfer substrate70is warped as described above, the similar effects can be achieved.

Next, in the laser emitting step S5ofFIG.6, as shown inFIG.15, laser LZ is emitted from a laser source LZS to the plurality of bump electrodes33and a plurality of contact parts between the bump electrodes33and the electrodes21of the plurality of LED elements20. In the manner, the electrode21of each LED element20is bonded to the bump electrode33.FIG.15is a diagram for explaining the laser emitting step. More specifically,FIG.15is an enlarged cross-sectional view schematically showing a state in which the laser is emitted to the contact part between the electrode21of the LED element20and the bump electrode33.

In this step, since the laser LZ is emitted to the contact part between the bump electrode33and the electrode21of each LED element20, the contact part is heated. More specifically, the heat is applied to the bump electrode33, solder contained in the bump electrode33is melted, and the bump electrode33is bonded to the electrode21of each LED element20by the solder.

Note that a step of previously forming a solder film on the anode electrode21EA and the cathode electrode21EK of the LED element20may be performed prior to this step. The solder-containing bump electrode33can be easily unified with the solder film formed on the anode electrode21EA and the cathode electrode21EK. Thus, by the formation of the solder film on each of the anode electrode21EA and the cathode electrode21EK, the bump electrode33and each electrode21of the LED element20can be made easier to be bond in this step.

Next, in the element stripping-off step S6ofFIG.6, as shown inFIG.16, the plurality of LED elements20are stripped off from the adhesive resin layer72of the transfer substrate70.FIG.16is a diagram for explaining the element stripping-off step. More specifically,FIG.16is an enlarged cross-sectional view showing a state in which the adhesive resin layer72of the transfer substrate70is stripped off from the plurality of LED elements20.

In this step, the transfer substrate70is moved in the Z direction to separate the transfer substrate70from the substrate structure SUB1. At this time, the electrodes21of the plurality of LED elements20are bonded to the bump electrodes33of the substrate structure SUB1. In other words, the plurality of LED elements20are mounted on the substrate structure SUB1, and the fixing strength between the electrodes21of the LED elements20and the bump electrodes33is higher than the adhesive strength between each LED element20and the adhesive resin layer72. Thus, since the transfer substrate70is moved to separate from the substrate structure SUB1, the interface between the adhesive resin layer72and the LED element20is stripped off. This step provides the display apparatus DPS1in which the plurality of LED elements20are mounted on the substrate structure SUB1.

As described above, in the transfer substrate70according to the present disclosure, the coating film73having the lower surface adhesiveness than that of the adhesive resin layer72is provided on the side of the adhesive resin layer72opposite to the support substrate71so as to cover the outer region of the holding region74of the adhesive resin layer72. In the manner, the fixed adhesion of the adhesive resin layer72to the substrate structure SUB1can be suppressed.

As described above, in the element compressing step S4, there is a risk of adhesion of a part of the adhesive resin layer72to the surface of the substrate structure SUB1. In the laser emitting step S5in this state, the emission of the laser LZ causes a risk of fixation of a part (adhesive resin) of the adhesive resin layer72having been adhered on the substrate structure SUB1onto the substrate structure SUB1.

More specifically, in the laser emitting step S5, when the heat is applied to the bump electrode33, the temperature of the substrate structure SUB1also increases. Thus, if the adhesive resin layer72is adhered to the surface of the substrate structure SUB1, the adhesive resin layer72adhered thereto is fixed by heat. If the transfer substrate70is separated from the substrate structure SUB1in this state in the element stripping-off step S6, there is a risk of generation of the fixed and remained adhesive resin layer72on the surface of the substrate structure SUB1.

However, the transfer substrate70according to the present disclosure includes the coating film73provided on the surface of the adhesive resin layer72and having the lower surface adhesiveness than that of the adhesive resin layer72, and the adhesion of the adhesive resin layer72to the substrate structure SUB1in the element compressing step S4is suppressed. Thus, even if the laser LZ is emitted in the laser emitting step S5, the fixation of the adhesive resin layer72to the substrate structure SUB1can be suppressed. Therefore, diffuse reflection of light and the like in the display apparatus DPS1can be suppressed, and the performance of the display apparatus DPS1can be improved.

The embodiments and the typical modification examples have been described above. However, the above-described techniques are applicable to various modification examples other than the exemplified modification examples. For example, the above-described modification examples may be combined.

In the scope of the idea of the present invention, various modification examples and alteration examples could have been easily anticipated by those who are skilled in the art, and it would be understood that these various modification examples and alteration examples are within the scope of the present invention. For example, the ones obtained by appropriate addition, removal, or design-change of the components to/from/into each of the above-described embodiments by those who are skilled in the art or obtained by addition, omitting, or condition-change of the step to/from/into each of the above-described embodiments are also within the scope of the present invention as long as they include the idea of the present invention.

For example, in the transfer substrate preparing step S2of the above-described embodiments, the transfer substrate70including the coating film73provided on the surface of the adhesive resin layer72is prepared. However, the coating film73is not always prepared in the transfer substrate preparing step S2. That is, the coating film73only has to be provided on the surface of the adhesive resin layer72prior to the element compressing step S4. In other words, in the element compressing step S4, the transfer substrate70only has to include the coating film73as described above.

Note that the present technique may employ the following configurations.

A transfer substrate includes: a support substrate; an adhesive resin layer continuously provided on one surface of the support substrate and having a plurality of holding regions adhesively holding elements; and a coating film provided on a surface of the adhesive resin layer opposite to the support substrate to cover an outer region of the holding region of the adhesive resin layer and having lower surface adhesiveness than surface adhesiveness of the adhesive resin layer.

In the transfer substrate according to the Statement 1, the coating film has an opening provided to surround a periphery of the holding region and positioned to face each of the plurality of holding regions.

In the transfer substrate according to the Statement 2, the opening has an opening shape formed along a planar shape of the element held by the holding region.

In the transfer substrate according to the Statement 2 or 3, a size of a gap between the opening and the holding region in plan view is 1 to 2.5 μm.

In the transfer substrate according to any one of the Statements 1 to 4, a thickness of the coating film is smaller than a height of the element.

In the transfer substrate according to any one of the Statements 1 to 4, a thickness of the coating film is larger than a height of the element.

In the transfer substrate according to any one of the Statements 1 to 6, a thickness of the adhesive resin layer is larger than a height of the element.

In the transfer substrate according to any one of the Statements 1 to 7, the coating film is a metallic thin film made of a metallic material.

A method of manufacturing an electronic apparatus includes: a step (a) of preparing a transfer substrate according to any one of the Statements 1 to 8; a step (b) of adhesively holding the elements in the plurality of holding regions of the adhesive resin layer configuring the transfer substrate; a step (c) of preparing a circuit substrate including a plurality of arranged bump electrodes, compressing the transfer substrate adhesively holding the elements in the plurality of holding regions against the circuit substrate, and making contact of the plurality of bump electrodes with electrodes of the elements adhesively held by the plurality of holding regions, respectively; and a step (d) of bonding the bump electrodes and the electrodes of the elements by heat while the plurality of bump electrodes come into contact with the electrodes of the elements adhesively held by the plurality of holding regions, respectively.

A method of manufacturing an electronic apparatus includes: a step (a) of preparing a transfer substrate including a support substrate and an adhesive resin layer continuously provided on one surface of the support substrate and having a plurality of holding regions adhesively holding elements; a step (b) of adhesively holding the elements in the plurality of holding regions of the adhesive resin layer configuring the transfer substrate; a step (c) of preparing a circuit substrate including a plurality of arranged bump electrodes, compressing the transfer substrate adhesively holding the elements against the circuit substrate, and making contact of the plurality of bump electrodes with electrodes of the elements held by the plurality of holding regions, respectively; and a step (d) of bonding the bump electrodes and the electrodes of the elements by heat while the plurality of bump electrodes come into contact with the electrodes of the elements adhesively held by the plurality of holding regions, respectively. In the step (c), the transfer substrate is compressed against the circuit substrate while an outer region of the holding region of the adhesive resin layer is covered with a coating film having lower surface adhesiveness than surface adhesiveness of the adhesive resin layer.

In the method of manufacturing the electronic apparatus according to the Statement 10, the coating film has an opening provided to surround a periphery of the holding region and positioned to face each of the plurality of holding regions.

In the method of manufacturing the electronic apparatus according to the Statement 11, the opening has an opening shape formed along a planar shape of the element held by the holding region.

In the method of manufacturing the electronic apparatus according to the Statement 11 or 12, a size of a gap between the opening and the holding region in plan view is 1 to 2.5 μm.

In the method of manufacturing the electronic apparatus according to any one of the Statements 10 to 13, a thickness of the coating film is smaller than a height of the element.

In the method of manufacturing the electronic apparatus according to any one of the Statements 10 to 13, a thickness of the coating film is larger than a height of the element.

In the method of manufacturing the electronic apparatus according to the Statement 15, the thickness of the coating film is larger than a total of a height of the element and a height of the bump electrode.

In the method of manufacturing the electronic apparatus according to any one of the Statements 10 to 16, a thickness of the adhesive resin layer is larger than a height of the element.

In the method of manufacturing the electronic apparatus according to any one of the Statements 10 to 17, the coating film is a metallic thin film made of a metallic material.

The present invention is applicable to a transfer substrate used for transferring an electronic component (element) and to a method of manufacturing an electronic apparatus on which an electronic component is mounted by use of the transfer substrate.