JP7801972B2 - LED mounting substrate and manufacturing method thereof - Google Patents

Description

One embodiment of the present invention relates to a light-emitting diode (LED) mounting substrate and a manufacturing method thereof.

In recent years, development has been progressing on so-called micro-LED displays, which feature tiny micro-LEDs arranged within pixels, as next-generation displays. Micro-LEDs are self-emitting elements similar to OLEDs (organic light-emitting diodes). However, unlike OLEDs, they are composed of stable inorganic compounds containing gallium (Ga) or indium (In). Therefore, compared to OLED displays, micro-LED displays are more likely to ensure high reliability. Furthermore, micro-LEDs have high luminous efficiency and can achieve high brightness. Therefore, micro-LED displays are expected to be next-generation displays with high reliability, high brightness, and high contrast.

Conventional manufacturing methods involve forming micro LEDs on a sapphire wafer and then transferring them to a micro LED mounting substrate to manufacture the device. A known method for electrically connecting the micro LED mounting substrate and the micro LED is to bond them using laser irradiation. (See, for example, Patent Document 1.)

Japanese Patent Application Laid-Open No. 2021-157112

When a micro LED chip is flip-chip mounted on a mounting substrate, the connection is hidden by the micro LED chip, making it difficult to inspect the quality of the connection. One method for connecting the electrodes of the micro LED chip to the pad electrodes of the mounting substrate is to bond them using laser irradiation, but the extremely short heating process using laser irradiation makes it difficult to directly measure the temperature, making it difficult to control the quality of the bond.

In view of the above problems, one embodiment of the present invention aims to provide an LED mounting substrate that allows for confirmation of the quality of the connection between the LED electrodes and the mounting substrate. Another aim is to provide a method for manufacturing an LED mounting substrate that allows for temperature control of heating by laser irradiation.

An LED mounting substrate according to one embodiment of the present invention comprises first and second electrode pads disposed on an insulating surface of the substrate and connected to the anode and cathode of an LED chip, third and fourth electrode pads disposed on the insulating surface, and a test pattern including first and second insulating layers, wherein the first insulating layer of the test pattern is in contact with the third electrode pad and is disposed spaced apart from the fourth electrode pad, and the second insulating layer is in contact with the fourth electrode pad and is disposed spaced apart from the third electrode pad.

A method for manufacturing an LED mounting substrate according to one embodiment of the present invention includes forming, on an insulating surface of a substrate, first and second electrode pads connected to the anode and cathode of an LED chip, and third and fourth electrode pads that form a test pattern; forming a first insulating layer in contact with the third electrode pads and a second insulating layer that forms the fourth electrode pads; placing an LED chip on the first and second electrode pads with a bonding conductive layer sandwiched between them; irradiating a laser beam onto an area of the test pattern that includes the third and fourth electrode pads; observing any changes in the appearance of the first and second insulating layers; setting the conditions for the laser beam to be irradiated onto the LED chip; and irradiating the area including the LED chip with the laser beam.

FIG. 1 is a schematic plan view of an LED mounting substrate according to one embodiment of the present invention. FIG. 1 is a schematic plan view of an LED mounting substrate according to one embodiment of the present invention. FIG. 1 is a schematic plan view of an LED mounting substrate according to one embodiment of the present invention. 1 is a schematic cross-sectional view of an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are plan views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are plan views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are plan views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are plan views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. 1A to 1C are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention.

Each embodiment of the present invention will be described below with reference to the drawings. Note that each embodiment is merely an example, and any embodiment that a person skilled in the art could easily come up with by making appropriate modifications while maintaining the spirit of the invention is naturally included within the scope of the present invention. Furthermore, to make the explanation clearer, the drawings may show the width, thickness, shape, etc. of each part more schematically than in the actual embodiment. However, the shapes shown in the drawings are merely examples and do not limit the interpretation of the present invention.

In this specification, expressions such as "α includes A, B, or C," "α includes any of A, B, and C," and "α includes one selected from the group consisting of A, B, and C" do not exclude cases where α includes multiple combinations of A through C, unless otherwise specified. Furthermore, these expressions do not exclude cases where α includes other elements.

For the sake of convenience, the terms "above" or "upper" or "below" or "belower" are used in this specification. However, as a general rule, the substrate on which the structure is formed is used as the reference, and "above" or "upper" refers to the direction from the substrate toward the structure. Conversely, "below" or "belower" refers to the direction from the structure toward the substrate. Therefore, when referring to an LED on a substrate, the surface of the LED facing the substrate is the lower surface, and the surface opposite is the upper surface. Furthermore, when referring to an LED on a substrate, this merely describes the hierarchical relationship between the substrate and the LED, and other components may be disposed between the substrate and the LED. Furthermore, the terms "above" or "upper" or "below" or "belower" refer to the order of stacking in a structure in which multiple layers are stacked, and do not necessarily mean that the layers are overlapping in a planar view.

In this invention, an LED refers to a chip size of several microns to 100 microns, and a mini LED refers to a chip size of 100 microns or more. However, one embodiment of the present invention can use LEDs of either size, and they can be used depending on the pixel size of the LED module and display device.

The following embodiments can be combined with each other unless a technical contradiction occurs.
First Embodiment
1. Overall Configuration This embodiment shows the structure of an LED mounting substrate 10 according to one embodiment. Fig. 1 is a schematic plan view of the LED mounting substrate according to this embodiment.

As shown in FIG. 1, the LED mounting substrate 10 includes a pixel region 110, a drive circuit 112, multiple terminals 113, and a test pattern 116 on a substrate 100. The LED mounting substrate 10 is a drive circuit substrate for driving the LED chips provided in each pixel region 110, and is also called a backplane substrate or active matrix substrate. Although not shown, the LED mounting substrate 10 also includes multiple switching elements, multiple capacitors, various wiring, etc.

As shown in FIG. 1, the LED mounting substrate 10 has a first region 102 and a second region 104. The first region 102 has a display region 106 and a peripheral region 108 surrounding the display region 106.

The first region 102 and the second region 104 are separable. The second region 104 is separated from the first region 102 after the LED chip is mounted in the first region 102 of the LED mounting substrate 10.

In the display area 106, multiple pixel areas 110 are arranged in the X-axis and Y-axis directions. Each of the multiple pixel areas 110 is provided with an LED, and switching elements for driving these LED chips may be provided.

A drive circuit 112 can be provided in the peripheral region 108 to control the light emission state of the LED chips provided in each pixel region 110. Furthermore, a plurality of terminals 113 can be provided at one end of the peripheral region 108 adjacent to the second region. The plurality of terminals 113 function as terminals for electrically connecting a flexible printed circuit board (FPC) or the like to input control signals and power for driving the drive circuit 112.

A plurality of test patterns 116 are arranged in the second region 104. The test patterns 116 may be arranged within the second region 104 in any manner that does not interfere with separating the first region 102 and the second region 104. The test patterns 116 can be separated from the LED mounting substrate 10 by separating the second region 104 from the first region 102 after the LED chips have been mounted on the LED mounting substrate 10. The test patterns 116 are arranged so that the plurality of terminals 113 are located at one end of the peripheral region 108 after the second region 104 has been separated. This allows the test patterns 116 to be provided on the LED mounting substrate 10 without significantly changing the conventional designs of the display region 106 and peripheral region 108.

Next, the pixel region 110 will be described with reference to Figure 2. Figure 2 is a schematic plan view of an LED mounting substrate according to one embodiment of the present invention, and is an enlarged view of the pixel region 110 shown in Figure 1.

Figure 2 shows an example of an LED chip 114 mounted on an LED mounting substrate 10. In the pixel region 110, a first electrode pad 120, a second electrode pad 122, and an LED chip 114 are arranged on an insulating surface 118.

The first electrode pad 120 and the second electrode pad 122 are connected to the anode 124 and cathode 126 of the LED chip 114. The first electrode pad 120 and the second electrode pad 122 are connected to a switching element to drive the LED chip 114 mounted in each pixel region 110.

The first electrode pad 120 and the second electrode pad 122 may be made of, for example, aluminum (Al), titanium (Ti), tin (Sn), chromium (Cr), cobalt (Co), nickel (Ni), molybdenum (Mo), hafnium (Hf), tantalum (Ta), tungsten (W), bismuth (Bi), silver (Ag), copper (Cu), platinum (Pt), gold (Au), or alloys or compounds thereof. Furthermore, the above materials may be used as a single layer or as a multilayer for the first electrode pad 120 and the second electrode pad 122.

The LED chip 114 is a two-terminal element and has an anode 124 and a cathode 126 to enable so-called flip-chip mounting. For example, when the LED chip 114 is mounted on the LED mounting substrate 10, the anode 124 and the cathode 126 are provided on the surface facing the first electrode pad 120 and the second electrode pad 122. One of the anode 124 and the cathode 126 is connected to the p-type semiconductor layer, and the other is connected to the n-type semiconductor layer. Due to this connection, one of the anode 124 and the cathode 126 is also referred to as the p-electrode and the other as the n-electrode. The anode 124 and the cathode 126 are formed using a metal material to improve wettability with fluid conductive materials, and preferably have a metal surface made of gold (Au), silver (Ag), or the like to improve wettability with fluid conductive materials. Such anodes 124 and cathodes 126 are formed to a thickness of approximately 1 μm to 5 μm.

Next, the inspection pattern 116 will be described with reference to Figure 3. Figure 3 is a schematic plan view of an LED mounting board according to one embodiment of the present invention, and is an enlarged view of the inspection pattern 116 shown in Figure 1.

The test pattern 116 includes a third electrode pad 128, a fourth electrode pad 130, a first insulating layer 132, and a second insulating layer 134 on the insulating surface 118 in a plan view.

The third electrode pad 128 is disposed adjacent to the fourth electrode pad 130. The third electrode pad 128 is preferably the same as the first electrode pad 120 disposed in the pixel region 110. It is preferable that the area and/or shape in plan view of the third electrode pad 128 be the same as those of the first electrode pad 120. Here, "the first electrode pad 120 and the third electrode pad 128 having the same area and shape" includes cases where the two do not have exactly the same shape and area due to dimensional errors, etc. Specifically, it is preferable that the difference in area between the first electrode pad 120 and the third electrode pad 128 be ±10% or less, and even more preferably ±5% or less.

The fourth electrode pad 130 is preferably the same as the second electrode pad 122 arranged in the pixel region 110. It is preferable that the area and/or shape in a plan view of the fourth electrode pad 130 be the same as those of the second electrode pad 122. Here, the second electrode pad 122 and the fourth electrode pad 130 being the same means that they are the same in terms of the area of the first electrode pad 120 and the area of the third electrode pad 128.

The third electrode pad 128 and the fourth electrode pad 130 use the same alloy or compound and structure as the first electrode pad 120 and the second electrode pad 122. For example, if the first electrode pad 120 and the second electrode pad 122 use a laminate structure in which Al and Ti are stacked in this order, the third electrode pad 128 and the fourth electrode pad 130 also use a laminate structure in which Al and Ti are stacked in this order.

The first insulating layer 132 and the second insulating layer 134 are arranged adjacent to each other. The third electrode pad 128 and the fourth electrode pad 130 are arranged adjacent to each other. The first insulating layer 132 overlaps the third electrode pad. The second insulating layer 134 overlaps the fourth electrode pad 130. The first insulating layer 132 is arranged spaced apart from the fourth electrode pad 130. The second insulating layer 134 is arranged spaced apart from the third electrode pad 128.

The area of the first insulating layer 132 is larger than the area of the third electrode pad 128. The area of the second insulating layer 134 is larger than the area of the fourth electrode pad 130. Therefore, the first insulating layer 132 has a portion that extends beyond the third electrode pad 128 in a planar view. The second insulating layer 134 also has a portion that extends beyond the fourth electrode pad 130 in a planar view. The portion of the first insulating layer 132 that extends beyond the frame of the third electrode pad 128 in a planar view is located on the third electrode pad 128 side. The portion of the second insulating layer 134 that extends beyond the frame of the fourth electrode pad 130 in a planar view is located on the fourth electrode pad 130 side. In this way, the area of each insulating layer is larger than the area of the electrode pad, making it easier to observe the burning caused by laser light irradiation, as described below. Furthermore, because the portions of the insulating layer that extend outside the frame of each electrode pad are positioned adjacent to each other, it becomes easier to simultaneously irradiate the first insulating layer 132 and the second insulating layer 134 with laser light, as will be described later.

The first insulating layer 132 is made of a different material than the second insulating layer 134. The melting point of the first insulating layer 132 is different from the melting point of the second insulating layer 134. The difference between the melting points of the first insulating layer 132 and the second insulating layer is preferably 100°C or more, and more preferably 50°C or more. Furthermore, the first insulating layer 132 and the second insulating layer 134 preferably have melting points such that the melting point of the bonding conductor (described below) is between the melting points of the first insulating layer 132 and the second insulating layer 134. For example, the melting point A of the first insulating layer 132 is lower than the melting point B of the second insulating layer 134, and the melting point C of the bonding conductor is higher than the melting point A of the first insulating layer 132 and lower than the melting point B of the second insulating layer 134.

The first insulating layer 132 and the second insulating layer 134 can be made of materials used in the preparation process of the substrate 100. The first insulating layer 132 can be made of an organic insulating material, such as a positive photosensitive resin used in planarization films. Specifically, an acrylic organic insulating material with a melting point of 200°C to less than 300°C can be used. The second insulating layer 134 can be made of an inorganic insulating material, such as a silicon-based inorganic insulating material with a melting point higher than that of the material used in the first insulating layer 132. However, the materials used for the first insulating layer 132 and the second insulating layer 134 are not limited to this, as long as the melting point of the bonding conductor, described below, is higher than that of the first insulating layer 132 and lower than that of the second insulating layer 134, as described above.

The film thickness of the first insulating layer 132 and the second insulating layer 134 need only be such that they can be provided with heat capacity by irradiation with laser light.

Next, the cross-sectional structures of the first electrode pad 120, the second electrode pad 122, and the test pattern 116 will be described with reference to Figure 4. Figure 4 is a schematic cross-sectional view of an LED mounting substrate according to one embodiment of the present invention.

Figure 4 is a cross-sectional view taken along the line A1-A2 in Figure 1. As shown in Figure 4, the first electrode pad 120 and second electrode pad 122 on which the LED chip 114 is provided are disposed on an insulating surface 118 on the substrate 100. The insulating surface 118 is formed by an insulating substrate. As shown in Figure 4, the insulating surface 118 may also be formed by an insulating film 136 provided on the substrate 100.

The insulating film 136 is made of an inorganic insulating material such as silicon dioxide (SiO), silicon nitride (SiN), or silicon oxynitride (SiON). Furthermore, each inorganic insulating film is not limited to a single layer and may be a multilayer film.

The LED chip 114 is mounted on the first electrode pad 120 and the second electrode pad 122. The anode 124 and cathode 126 of the LED chip 114 are disposed on the first electrode pad 120 and the second electrode pad 122. Bonding conductors 138 are provided between the first electrode pad 120 and the second electrode pad 122 and the anode 124 and cathode 126 of the LED chip 114, respectively. The anode 124 and cathode 126 are connected to the first electrode pad 120 and the second electrode pad 122, respectively, via the bonding conductors 138, and the LED chip 114 is mounted on the LED mounting substrate 10 by being electrically connected to the first electrode pad 120 and the second electrode pad 122.

The bonding conductor 138 can be made of a material with a melting point lower than that of the first electrode pad 120 and the second electrode pad 122. For example, the bonding conductor 138 can be made of a metal primarily composed of tin (Sn). The first electrode pad 120 can be made of a metal laminate, for example, in which Al and Ti are stacked in this order, and the bonding conductor 138 can be made of Sn, which has a lower melting point than Al, the material of the surface of the first electrode pad 120. Similarly, the second electrode pad 122 can be made of a metal laminate, for example, in which Al and Ti are stacked in this order, and the bonding conductor 138 can be made of a metal primarily composed of Sn, and Sn, which has a lower melting point than Al, the material of the surface of the second electrode pad 122.

Furthermore, the bonding conductor 138 is made of a material whose melting point lies between the melting points of the first insulating layer 132 and the second insulating layer 134 of the test pattern 116. In other words, the melting point of the bonding conductor 138 lies between the melting points of the first insulating layer 132 and the second insulating layer 134 of the test pattern 116. For example, it is preferable to use an organic resin material with a melting point of 200°C to less than 300°C for the first insulating layer 132. Examples of organic resin materials that can be used include acrylic organic compounds. It is preferable to use a material whose melting point is higher than that of the first insulating layer 132 for the second insulating layer 134. For example, it is preferable to use an inorganic material such as silicon nitride, silicon oxynitride, or silicon oxide for the second insulating layer 134. The bonding conductor 138 is preferably made of a conductive material whose melting point is higher than that of the first insulating layer 132 and lower than that of the second insulating layer 134; for example, Sn or a Sn alloy (e.g., a SnAg alloy) can be used as the conductive material for the bonding conductor 138.

In other words, the first insulating layer 132 and the second insulating layer 134 are made of a material that causes the melting point of the bonding conductor 138 to be between the melting points of the first insulating layer 132 and the second insulating layer 134. For example, Sn is used for the bonding conductor 138, and an organic resin is used for the first insulating layer 132 and silicon nitride, an inorganic compound, is used for the second insulating layer 134 so that the melting point of the bonding conductor 138 is between the melting points of the first insulating layer 132 and the second insulating layer 134.

The test pattern 116 is disposed on the insulating film 136. The test pattern 116 includes a third electrode pad 128, a fourth electrode pad 130, a first insulating layer 132, and a second insulating layer 134. The third electrode pad 128 and the fourth electrode pad 130 are disposed on the insulating film 136. The first insulating layer 132 is provided in contact with the surface of the third electrode pad 128 opposite the insulating surface 118. The second insulating layer 134 is provided in contact with the surface of the fourth electrode pad 130 opposite the insulating surface 118. As described above, the test pattern 116 has a layered structure on the insulating film 136 in the order of the third electrode pad 128, the first insulating layer 132, and the order of the fourth electrode pad 130, the second insulating layer 134. Furthermore, as in the modified example described below, the layering order of these layers may be reversed. The test pattern 116 can have a laminated structure in which a first insulating layer 132 and a third electrode pad 128 are stacked in this order on an insulating film 136, and a laminated structure in which a second insulating layer 134 and a fourth electrode pad 130 are stacked in this order.

A portion of the first insulating layer 132 is provided to cover the side surface of the third electrode pad 128. A portion of the first insulating layer 132 is in contact with the insulating film 136. A portion of the first insulating layer 132 is located on the insulating film 136. The side surface of the third electrode pad 128 covered by the first insulating layer 132 faces the side surface of the fourth electrode pad 130. The second insulating layer 134 is provided to cover the side surface of the fourth electrode pad 130. A portion of the second insulating layer 134 is provided to cover the side surface of the fourth electrode pad 130. A portion of the second insulating layer 134 is in contact with the insulating film 136. A portion of the second insulating layer 134 is located on the insulating film 136. The side surface of the fourth electrode pad 130 covered by the second insulating layer 134 faces the side surface of the third electrode pad 128. By arranging the first insulating layer 132 and the second insulating layer 134 in this manner, irradiating them with laser light, and observing the state of the first insulating layer 132 and the second insulating layer 134 after irradiation, it is possible to determine the temperature to which they are heated by the laser light irradiation.

In the LED mounting substrate 10, a test pattern 116 is provided on the insulating surface on which the first electrode pad 120 and second electrode pad 122 of the LED chip 114 are provided, and the test pattern 116 can be used to check the temperature to which the LED chip 114 is instantaneously heated by the laser light when it is mounted. Therefore, by applying this embodiment, an LED mounting substrate 10 is provided that can manage the temperature of the extremely short-term heating process using the laser light used to mount the LED chip 114.

Second Embodiment
In this embodiment, a method for manufacturing an LED mounting substrate 10 according to one embodiment of the present invention will be described. Descriptions of configurations that are the same as or similar to those in the first embodiment may be omitted.

Figures 5a to 5h are cross-sectional and plan views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. After the substrate preparation step of preparing the substrate 100, as shown in Figures 5a to 5h, a test pattern 116 is formed on the previously prepared substrate 100, and an LED chip 114 is mounted thereon.

As shown in FIG. 5a, a first electrode pad 120 and a second electrode pad 122 connected to the anode 124 and cathode 126 of the LED chip 114, and a third electrode pad 128 and a fourth electrode pad 130 forming the test pattern 116 are formed on an insulating surface 118 of the substrate 100.

Next, as shown in FIG. 5b, a first insulating layer 132 and a second insulating layer 134 are formed on the third electrode pad 128 and the fourth electrode pad 130, and the test pattern 116 is formed.

Next, as shown in Figure 5c, the LED chip 114 is placed on the first electrode pad 120 and the second electrode pad 122, with the bonding conductor 138 sandwiched between them.

After the LED chip 114 is placed and before the LED chip 114 is bonded, the temperature to which it will be heated by irradiation with laser light is confirmed using the inspection pattern 116. The process for confirming the temperature to which it will be heated by irradiation with laser light will be described with reference to Figures 5d and 5e.

As shown in Figures 5d and 5e, laser light (indicated by the arrow) is irradiated onto an irradiation area 140 including the third electrode pad 128 and the fourth electrode pad 130. At this time, the first insulating layer 132 and second insulating layer 134 included in the irradiation area 140 are also simultaneously irradiated with the laser light (indicated by the arrow). The first insulating layer 132 irradiated with the laser light includes the third electrode pad 128 and the first insulating layer 132 in contact with the insulating surface between the third electrode pad 128 and the fourth electrode pad 130. The second insulating layer 134 irradiated with the laser light includes the fourth electrode pad 130 and the insulating film 136 in contact with the insulating surface between the third electrode pad 128 and the fourth electrode pad 130.

Next, the change in appearance of the inspection pattern 116 irradiated with the laser light is observed using an optical microscope or the like. Specifically, the change in appearance of the first insulating layer 132 and the second insulating layer 134 is observed using an optical microscope. Figures 5f and 5g show the inspection pattern 116 when the portion of the first insulating layer 132 irradiated with the laser light is burned away.

As shown in Figures 5f and 5g, the portion 142 of the first insulating layer 132 irradiated with the laser light is burned away, while the portion of the second insulating layer 134 irradiated with the laser light remains without any significant change in appearance. Alternatively, the portion of the first insulating layer 132 irradiated with the laser light is carbonized, turning black and undergoing a change in shape due to shrinkage. This change in appearance indicates that the temperature heated by the laser light irradiation is higher than the melting point of the first insulating layer 132 but lower than the melting point of the second insulating layer 134, making it possible to control the temperature heated by the laser light irradiation. Furthermore, because the melting point of the bonding conductor 138 is higher than the melting point of the first insulating layer 132 but higher than the melting point of the second insulating layer 134, the temperature heated by the laser light irradiation is high enough to melt the bonding conductor 138, and it is determined that the first electrode pad 120 and the second electrode pad 122 can be electrically connected to the anode 124 and the cathode 126, respectively, via the bonding conductor 138.

If no change in appearance is observed in the first insulating layer 132 and the second insulating layer 134, it can be inferred that the temperature to which the first insulating layer 132 is heated by irradiation with laser light is lower than the melting point of the first insulating layer 132. Furthermore, if a change in appearance is observed in the first insulating layer 132 and the second insulating layer 134, it can be inferred that the temperature to which the first insulating layer 132 is heated by irradiation with laser light is higher than the melting point of the first insulating layer 132. In these cases, unlike the cases shown in Figures 5f and 5g, it can be determined that the temperature to which the first insulating layer 132 is heated by irradiation with laser light is not within an appropriate range. Therefore, in such cases, it can be determined that the temperature to which the first insulating layer 132 is heated by irradiation with laser light is not suitable for mounting the LED chip 114 to the LED mounting substrate 10. In this embodiment, by using the first insulating layer 132 and the second insulating layer 134 with different melting points and using the change in appearance due to irradiation with laser light as an alternative characteristic, it is possible to appropriately control the temperature suitable for mounting the LED chip 114 to the LED mounting substrate 10.

Next, the conditions for the laser light to be irradiated onto the LED chip 114 are set. The laser light conditions are determined and set by observing the changes in appearance of the first insulating layer 132 and the second insulating layer 134 irradiated with the laser light. Specific changes in appearance of the first insulating layer 132 and the second insulating layer 134 are determined based on, as described above, whether the first insulating layer 132 is burned, or whether there is a change in color or shape, and whether the second insulating layer 134 remains, or whether there is a change in color or shape. Specifically, the laser light conditions under which no burn, color, or shape change of the first insulating layer 132, or no remaining or change in appearance of the second insulating layer 134, are observed, are set as the conditions for the laser light to be irradiated onto the LED chip 114.

Under the set laser light conditions, laser light is irradiated onto an area including the LED chip 114 arranged on the LED mounting substrate 10, as shown in Figure 5h.

<Modification>
6a to 6d, a manufacturing method of a modified example of the LED mounting substrate 10 will be described. The difference from the LED mounting substrate 10 shown in Figures 2 to 5 is the stacking order of the third electrode pad 128 and the fourth electrode pad 130 of the test pattern 116 and the first insulating layer 132 and the second insulating layer 134. Note that descriptions of configurations that are the same as or similar to those of the LED mounting substrate 10 shown in Figures 2 to 5 may be omitted.

Figures 6a to 6d are cross-sectional and plan views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. After the substrate preparation step of preparing the substrate 100, as shown in Figures 5a to 5h, a test pattern 116 is formed on the previously prepared substrate 100, and an LED chip 114 is mounted thereon.

As shown in Figures 6a and 6b, a first insulating layer 132 and a second insulating layer 134 are formed on an insulating surface 118 on a substrate 100. A third electrode pad 128 and a fourth electrode pad 130 are formed on the first insulating layer 132 and the second insulating layer 134. The first insulating layer 132 is provided between the insulating surface 118 and the third electrode pad 128. The second insulating layer 134 is provided between the insulating surface 118 and the fourth electrode pad 130.

Next, the LED chip 114 is placed on the substrate 100, and as shown in Figures 6a and 6b, laser light (indicated by the arrow) is irradiated onto the irradiation area 140, which includes the third electrode pad 128 and the fourth electrode pad 130. The first insulating layer 132 has a portion that is irradiated with the laser light via the third electrode pad 128. The second insulating layer 134 has a portion that is irradiated with the laser light via the third electrode pad 128.

Next, the change in appearance of the inspection pattern 116 irradiated with laser light is observed. Specifically, the change in appearance of the first insulating layer 132 and the second insulating layer 134 is observed. Figures 6c and 6d show the inspection pattern 116 when the portion of the first insulating layer 132 irradiated with laser light is burned away.

As shown in Figures 6c and 6d, the first insulating layer 132 irradiated with laser light is burned away, and the third electrode pad 128 has a portion that is not in contact with the first insulating layer 132. No significant change in appearance is observed in the portion of the second insulating layer 134 irradiated with laser light.

<Modified Process 1>
Next, a modified example of the process of irradiating laser light onto the LED mounting substrate 10 will be described with reference to Figures 7a to 7c. This process differs from the laser light irradiation process shown in Figures 5 and 6 in that the laser light is irradiated onto the inspection pattern 116 before the LED chip 114 is placed on the substrate 100. Note that a description of configurations that are the same as or similar to those of the LED mounting substrate 10 shown in Figures 2 to 6 may be omitted.

Figures 7a to 7c are cross-sectional views for schematically explaining a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. After the substrate preparation step of preparing the substrate 100, a step of forming a test pattern 116 on the previously prepared substrate 100 is carried out, as shown in Figures 5a and 5b.

After the test pattern 116 is formed on the substrate 100, and before the LED chip 114 is placed, the temperature to which the test pattern 116 is heated by irradiation with laser light is confirmed. As shown in Figures 7a to 7c, laser light (indicated by the arrow) is irradiated onto the irradiation area (see Figure 5d) including the third electrode pad 128 and the fourth electrode pad 130.

Next, the change in appearance of the test pattern 116 irradiated with laser light is observed. As shown in Figure 7b, if the portion 142 of the first insulating layer 132 irradiated with laser light is burned away, while the portion of the second insulating layer 134 irradiated with laser light remains without any significant change in appearance, it is clear that the temperature reached by irradiation with laser light is higher than the melting point of the first insulating layer 132 but lower than the melting point of the second insulating layer 134. As described above, the temperature reached by irradiation with laser light is determined to be an appropriate temperature at which the first electrode pad 120 and second electrode pad 122 can be electrically connected to the anode 124 and cathode 126 of the LED chip 114, respectively, via the bonding conductor 138.

After it is determined that the temperature heated by the laser light irradiation is appropriate, the LED chip 114 is placed on the first electrode pad 120 and the second electrode pad 122, with the bonding conductor 138 sandwiched between them, as shown in Figure 7c.

After the LED chip 114 is placed, laser light is irradiated onto the area including the LED chip 114 placed on the LED mounting substrate 10 under laser light conditions determined to be appropriate temperature (see Figure 5h).

<Modified Process 2>
8a and 8b, a modified example of the process of irradiating laser light onto the LED mounting substrate 10 will be described. This process differs from the process of irradiating laser light shown in Fig. 5 and Fig. 6 in that after the LED chip 114 is placed on the substrate 100, the laser light is irradiated onto the inspection pattern 116 and the LED chip 114 simultaneously. Note that a description of configurations that are the same as or similar to those of the LED mounting substrate 10 shown in Fig. 2 to Fig. 6 may be omitted.

Figures 8a and 8b are cross-sectional views for schematically illustrating a method for manufacturing an LED mounting substrate according to one embodiment of the present invention. After the substrate preparation step of preparing the substrate 100, as shown in Figures 5a to 5c, a test pattern 116 is formed on the previously prepared substrate 100, and an LED chip 114 is mounted thereon.

After the test pattern 116 is formed on the substrate 100 and the LED chip 114 is placed, laser light is irradiated onto the test pattern 116 and the LED chip 114, as shown in Figure 8a. The area of the test pattern 116 that is irradiated with laser light is the same as the area shown in Figure 5b. The area of the LED chip 114 that is irradiated with laser light may be the same as the area shown in Figure 5h.

After irradiating the test pattern 116 and the LED chip 114 with laser light, the change in appearance of the test pattern 116 is observed. If no change in appearance of the test pattern 116 as shown in Figure 8b is observed when observing the change in appearance of the test pattern 116, the test pattern 116 and the LED chip 114 are irradiated with laser light again. After irradiating the test pattern 116 and the LED chip 114 with laser light again, the change in appearance of the test pattern 116 is observed again. Irradiation of the laser light and observation of the change in appearance are repeated until a change in appearance of the test pattern 116 is observed, as shown in Figure 8b. If a change in appearance of the test pattern 116 as shown in Figure 8b is observed, it can be determined that the LED chip 114 is sufficiently bonded to the first electrode pad 120 and the second electrode pad 122.

As explained above, in the manufacturing method for the LED mounting substrate 10, before the step of bonding the LED chip 114 to the substrate 100 using laser light, the inspection pattern 116 is irradiated with laser light and the temperature heated by the laser light irradiation can be confirmed by observing the change in the appearance of the inspection pattern 116. By confirming the temperature heated by the laser light irradiation, it is possible to control the temperature heated by the laser light irradiation according to the laser light irradiation conditions. Therefore, by setting the laser light conditions required for bonding the LED chip 114 through temperature control, the LED chip 114 and the substrate 100 can be electrically connected when laser light under those conditions is used for bonding.

Even if there are other effects and advantages different from those achieved by the aspects of the above-described embodiments, those that are clear from the description in this specification or that would be easily predicted by a person skilled in the art are naturally considered to be achieved by the present invention.

10: mounting substrate, 100: substrate, 102: first region, 104: second region, 106: display region, 108: peripheral region, 110: pixel region, 112: driving circuit, 113: terminal, 114: chip, 116: inspection pattern, 118: insulating surface, 120: first electrode pad, 122: second electrode pad, 124: anode, 126: cathode, 128: third electrode pad, 130: fourth electrode pad, 132: first insulating layer, 134: second insulating layer, 136: insulating film, 138: bonding conductor, 140: irradiation region, 142: part

Claims (12)

a first electrode pad and a second electrode pad disposed on an insulating surface of the substrate and connected to an anode and a cathode of the LED chip;
a test pattern including a third electrode pad and a fourth electrode pad arranged on the insulating surface, and a first insulating layer and a second insulating layer;
The test pattern is
the first insulating layer is in contact with the third electrode pad and is spaced apart from the fourth electrode pad;
the second insulating layer is in contact with the fourth electrode pad and is spaced apart from the third electrode pad;
LED mounting board. The LED mounting substrate according to claim 1, wherein the melting point of the first insulating layer is different from the melting point of the second insulating layer. The LED mounting substrate according to claim 1, wherein the first insulating layer is provided in contact with the surface of the third electrode pad opposite the insulating surface, and the second insulating layer is provided in contact with the surface of the fourth electrode pad opposite the insulating surface. The LED mounting substrate according to claim 1, wherein the first insulating layer is provided between the insulating surface and the third electrode pad, and the second insulating layer is provided between the insulating surface and the fourth electrode pad. The area of the third electrode pad is the same as the area of the first electrode pad,
The area of the fourth electrode pad is the same as the area of the second electrode pad.
The LED mounting substrate according to claim 1 . The third electrode pad and the first electrode pad have the same shape,
The fourth electrode pad and the second electrode pad have the same shape.
The LED mounting substrate according to claim 1 . an LED chip mounted on the first electrode pad and the second electrode pad;
a bonding conductor is provided between the anode and the cathode of the mounted LED chip and the first electrode pad and the second electrode pad, respectively;
The LED mounting board according to claim 2 , wherein the melting point of the bonding conductor is between the melting points of the first insulating layer and the second insulating layer. the substrate includes a first region in which the first electrode pads and the second electrode pads are arranged, and a second region in which the test pattern is arranged;
The LED mounting board according to claim 1 , wherein the first region and the second region are separable. forming a first electrode pad and a second electrode pad connected to an anode and a cathode of the LED chip, and a third electrode pad and a fourth electrode pad forming a test pattern on an insulating surface of the substrate;
forming a first insulating layer in contact with the third electrode pad and a second insulating layer on which the fourth electrode pad is formed;
an LED chip is disposed on each of the first electrode pad and the second electrode pad with a bonding conductor sandwiched therebetween;
irradiating a region of the test pattern including the third electrode pad and the fourth electrode pad with laser light;
Observing changes in the appearance of the first insulating layer and the second insulating layer;
Setting conditions for laser light to be irradiated onto the LED chip;
Irradiating a region including the LED chip with laser light;
A manufacturing method of an LED mounting substrate. The method for manufacturing an LED mounting substrate described in claim 9, wherein the laser light conditions are set based on whether the first insulating layer has disappeared and whether the second insulating layer remains. the melting point of the bonding conductor is between the melting points of the first insulating layer and the second insulating layer;
The method for manufacturing an LED mounting substrate according to claim 10 , wherein the laser light is irradiated with the first insulating layer removed and the second insulating layer remaining. The method for manufacturing an LED mounting substrate according to claim 9 , wherein the LED chip is irradiated with laser light under the set laser light conditions.