Display panel

Abstract

A display panel including a substrate, a bonding pad, a light-emitting device, a first conductive pattern, an active device and a thermally conductive pattern is provided. The bonding pad is disposed on the substrate. The light-emitting device is disposed on the substrate and is electrically connected to the bonding pad. The first conductive pattern is disposed on the substrate and is electrically connected to the bonding pad. The active device is disposed on the substrate and is electrically connected to the first conductive pattern. The thermally conductive pattern covers and contacts the first conductive pattern. An orthographic projection of the thermally conductive pattern on the substrate partially overlaps an orthographic projection of the light-emitting device on the substrate.

Description

[Technical Field]

[0001] This invention relates to a display technology, and more particularly to a display panel. [Previous Technology]

[0002] Due to their advantages such as high brightness, high contrast, high resolution, low power consumption, durability, and fast response, micro-LED display panels can be widely used in high-end monitors, televisions, wearable devices, and automotive displays. With the reduction in manufacturing costs and the advancement of technology, Micro-LED display panels are considered an important development direction for next-generation display technology.

[0003] In the manufacturing process of Micro-LED display panels, the bonding quality between the light-emitting elements and the circuit backplane is crucial to the operational electrical performance of the display panel. In particular, the selection of metal materials for the circuit backplane is often limited by electrical requirements and the manufacturing capabilities of the factory, which can easily lead to uneven heat distribution on the bonding pads and insufficient solder temperature during the bonding process of the light-emitting elements, thus affecting the bonding yield. [Summary of the Invention]

[0004] The present invention provides a display panel in which the bonding pad has a more uniform heat distribution during the bonding process of the light-emitting element, which helps to improve the bonding yield of the light-emitting element.

[0005] The display panel of the present invention includes a substrate, bonding pads, a light-emitting element, a first conductive pattern, an active element, and a thermally conductive pattern. The bonding pads are disposed on the substrate. The light-emitting element is disposed on the substrate and electrically bonded to the bonding pads. The first conductive pattern is disposed on the substrate and electrically connected to the bonding pads. The active element is disposed on the substrate and electrically connected to the first conductive pattern. The thermally conductive pattern covers and contacts the first conductive pattern. The orthographic projection of the thermally conductive pattern onto the substrate overlaps with the orthographic projection of the light-emitting element onto the substrate.

[0006] In one embodiment of the present invention, the first conductive pattern of the display panel is projected onto the substrate in the same direction as the thermally conductive pattern on the substrate.

[0007] In one embodiment of the present invention, the thermally conductive pattern of the display panel has a first edge in any direction parallel to the surface of the substrate. The first conductive pattern has a second edge closest to the first edge, and the distance between the first edge and the second edge in any direction is greater than or equal to 2 μm.

[0008] In one embodiment of the present invention, the distance between the above-mentioned display panels is less than or equal to 35 μm.

[0009] In one embodiment of the present invention, the thermal diffusivity of the thermally conductive pattern of the display panel is greater than 1.0×10⁻⁶ m² / s.

[0010] In one embodiment of the present invention, the thermal diffusivity of the thermally conductive pattern of the display panel is less than or equal to 1.0×10⁻⁴ m² / s.

[0011] In one embodiment of the present invention, the material of the thermally conductive pattern of the display panel includes SiN x (0 < x < 1.33), AlN, BN, Al 2O 3, ZrO 2, TiO 2, HfO 2, SiC or B 4C.

[0012] In one embodiment of the present invention, the display panel further includes a second conductive pattern, an electrical connection pad, and a first conductive pattern. The orthographic projection of the second conductive pattern on the substrate lies within the orthographic projection of the thermally conductive pattern on the substrate.

[0013] In one embodiment of the present invention, the thermally conductive pattern of the display panel has a first edge in any direction parallel to the surface of the substrate. The second conductive pattern has a second edge closest to the first edge. The distance between the first edge and the second edge in any direction is greater than or equal to 2 μm and less than or equal to 35 μm.

[0014] In one embodiment of the present invention, the active element of the display panel includes a drain electrode electrically connected to the first conductive pattern, and the orthographic projection of the drain electrode on the substrate is within the orthographic projection of the thermally conductive pattern on the substrate.

[0015] Based on the above, in a display panel according to an embodiment of the present invention, the bonding pad for bonding the light-emitting element is electrically connected to the active element via a conductive pattern. By covering and contacting the conductive pattern with a thermally conductive pattern, the uniformity of heat distribution of the bonding pad during the bonding process of the light-emitting element can be effectively improved, and the heating efficiency of the solder can be improved, thereby improving the bonding yield of the light-emitting element.

Implementation Method

[0016] As used herein, “about,” “approximately,” “essentially,” or “substantially” includes the value and the average value within an acceptable range of deviations from a particular value as determined by one of ordinary skill in the art, taking into account the measurement in question and a particular number of errors associated with the measurement (i.e., limitations of the measurement system). For example, “about” may mean within one or more standard deviations of the value, or, for example, within ±30%, ±20%, ±15%, ±10%, ±5%. Furthermore, as used herein, “about,” “approximately,” “essentially,” or “substantially” may be used to select a more acceptable range of deviations or standard deviations depending on the nature of the measurement, the cutting nature, or other properties, and may not apply to all properties with a single standard deviation.

[0017] The ordinal numbers used in the specification and claims, such as "first" and "second," to modify elements do not imply or represent any prior ordinal number for that element (or those elements), nor do they represent the order of one element with another, or the order of manufacturing processes. The use of these ordinal numbers is solely to clearly distinguish one named element from another element with the same name. The same terms may not be used in this specification and the claims; therefore, a first component in the specification may be a second component in the claims.

[0018] In the accompanying drawings, the thicknesses of layers, films, panels, regions, etc., are enlarged for clarity. It should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "connected" to another element, it may be directly on or connected to the other element, or intermediate elements may also be present. Conversely, when an element is referred to as being "directly on" or "directly connected" to another element, no intermediate elements are present. As used herein, "connection" may refer to a physical and / or electrical connection. Furthermore, an "electrical connection" may mean the presence of other elements between two elements.

[0019] Furthermore, relative terms such as “down” or “bottom” and “up” or “top” may be used herein to describe the relationship between one element and another element, as shown in the figures. It should be understood that relative terms are intended to include different orientations of the device other than those shown in the figures. For example, if a device in one figure is flipped, an element described as being “down” to another element will be oriented “up” to the other element. Thus, the exemplary term “down” can include both “down” and “up” orientations, depending on the specific orientation of the figure. Similarly, if a device in one figure is flipped, an element described as being “below” or “under” another element will be oriented “above” the other element. Thus, the exemplary terms “above” or “below” can include both “up” and “down” orientations.

[0020] Exemplary embodiments are described herein with reference to cross-sectional views as schematic representations of idealized embodiments. Therefore, variations in the shape of the illustrations can be anticipated as a result of, for example, manufacturing techniques and / or tolerances. Consequently, the embodiments described herein should not be construed as limited to the specific shapes of the regions shown herein, but rather include, for example, shape deviations caused by manufacturing processes. For example, regions shown or described as flat may generally have rough and / or non-linear characteristics. Furthermore, acute angles shown may be rounded. Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to show the precise shapes of the regions, nor are they intended to limit the scope of the claims.

[0021] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Wherever possible, the same element symbols are used in the drawings and description to denote the same or similar parts.

[0022] FIG1 is a cross-sectional schematic diagram of a display panel according to an embodiment of the present invention. FIG2 is a cross-sectional schematic diagram of the heat distribution of the display panel of FIG1 during the bonding process of the light-emitting elements. FIG3 is a cross-sectional schematic diagram of the heat distribution of the display panel of a comparative example during the bonding process of the light-emitting elements. FIG4 is a temperature rise curve of the solder of FIG1 under various designs of thermally conductive patterns.

[0023] Referring to FIG1, the display panel 10 includes a substrate 100 and a first bonding pad BP1, a second bonding pad BP2, and a light-emitting element 200 disposed on the substrate 100. In this embodiment, the light-emitting element 200 may be a flip-chip type light-emitting diode, which may include an epitaxial structure layer 210, a first electrode 221, and a second electrode 222. For example, the epitaxial structure layer 210 may include a first type semiconductor layer (not shown), a second type semiconductor layer (not shown), and a light-emitting layer (not shown) located between the two semiconductor layers, wherein the first electrode 221 and the second electrode 222 are electrically connected to the first type semiconductor layer and the second type semiconductor layer, respectively.

[0024] In this embodiment, the first electrode 221 and the second electrode 222 of the light-emitting element 200 are electrically bonded to the first bonding pad BP1 and the second bonding pad BP2 on the substrate 100, respectively. However, the present invention is not limited thereto. In other embodiments, the light-emitting element may also be a vertical type light-emitting diode, and the electrode on one side of its epitaxial structure layer is electrically bonded to a bonding pad. In this embodiment, the first electrode 221 and the second electrode 222 of the light-emitting element 200 may each be bonded to the corresponding bonding pad through solder 250, but this is not a limitation.

[0025] Although Figure 1 only shows one light-emitting element 200 and one bonding pad group (i.e., the first bonding pad BP1 and the second bonding pad BP2), it is understood that the number of light-emitting elements 200 disposed on the substrate 100 of the display panel 10 can be multiple, and the number of bonding pad groups can be multiple groups. The multiple light-emitting elements 200 can have multiple light-emitting colors (e.g., red, green and blue, but not limited to these), and multiple light-emitting elements 200 with different light-emitting colors can constitute a display pixel of the display panel 10, but are not limited thereto.

[0026] In this embodiment, the display panel 10 may further include an active element T, a first conductive pattern CP1a, and a second conductive pattern CP2a. The active element T may be electrically connected to the first bonding pad BP1 via the first conductive pattern CP1a and the second conductive pattern CP2a. Specifically, the first conductive pattern CP1a is electrically connected between the active element T and the second conductive pattern CP2a, while the second conductive pattern CP2a is electrically connected between the first conductive pattern CP1a and the first bonding pad BP1. However, the present invention is not limited thereto. In other embodiments, the display panel may not have the second conductive pattern CP2a, and the first conductive pattern CP1a may directly electrically contact the first bonding pad BP1.

[0027] In this embodiment, the method for forming the active element T may include the following steps: sequentially forming a buffer layer 110, a semiconductor pattern SC, a gate insulating layer 120, a gate GE, an interlayer insulating layer 130, a source SE, and a drain DE on a substrate 100, wherein the source SE and drain DE penetrate the interlayer insulating layer 130 and the gate insulating layer 120 to electrically connect two different regions of the semiconductor pattern SC, but this is not a limitation. In this embodiment, the semiconductor pattern SC is made of, for example, polysilicon semiconductor material, but this is not a limitation. In other embodiments, the active element may also be an amorphous silicon thin-film transistor (a-Si TFT), a microcrystalline silicon thin-film transistor (micro-Si TFT), or a metal oxide transistor.

[0028] For example, in this embodiment, the semiconductor pattern SC has a drain region DR, a lightly doped drain region LDR, a channel region CH, a lightly doped source region LSR, and a source region SR, wherein the source SE and drain DE are electrically connected to the source region SR and drain region DR of the semiconductor pattern SC, respectively, and the gate GE is overlapped on the channel region CH. In this embodiment, the gate GE may be selectively disposed above the semiconductor pattern SC to form a top-gate thin-film transistor, but is not limited thereto. In other embodiments, the gate GE may also be disposed below the semiconductor pattern SC to form a bottom-gate thin-film transistor. To prevent the channel region CH of the semiconductor pattern SC from being exposed to light on the substrate 100 side and generating leakage current, a light-shielding pattern 105 may also be provided between the semiconductor pattern SC and the substrate 100, and the light-shielding pattern 105 overlaps the channel region CH of the semiconductor pattern SC along the normal direction (e.g., direction Z) of the substrate surface 100s of the substrate 100, but is not limited thereto.

[0029] It should be noted that the gate GE, source SE, drain DE, buffer layer 110, gate insulating layer 120 and interlayer insulating layer 130 can be implemented by any gate, source, drain, buffer layer, gate insulating layer and interlayer insulating layer known to those skilled in the art for display panels, and the gate GE, source SE, drain DE, buffer layer 110, gate insulating layer 120 and interlayer insulating layer 130 can be formed by any method known to those skilled in the art, so they will not be described in detail here.

[0030] In this embodiment, the display panel 10 may further include a planarization layer 141, a passivation layer 151, a planarization layer 142, a passivation layer 152, a passivation layer 153, and a passivation layer 154 sequentially formed on the interlayer insulating layer 130. Specifically, the planarization layer 141 covers the source SE and drain DE of the active element T. A first conductive pattern CP1a is formed on the passivation layer 151 and is covered by the planarization layer 142. The first conductive pattern CP1a penetrates the passivation layer 151 and the planarization layer 141 to electrically connect the drain DE of the active element T. A second conductive pattern CP2a is formed on the passivation layer 152 and is covered by the passivation layer 153.

[0031] On the other hand, the second conductive pattern CP2a penetrates the passivation layer 152 and the planarization layer 142 to electrically connect with the first conductive pattern CP1a. The first bonding pad BP1 and the second bonding pad BP2 are formed on the passivation layer 153 and are covered by the passivation layer 154. The first bonding pad BP1 can penetrate the passivation layer 153 to electrically connect with the second conductive pattern CP2a. The passivation layer 154 has a plurality of openings 154op exposing the first bonding pad BP1 and the second bonding pad BP2. The first electrode 221 and the second electrode 222 of the light-emitting element 200 are each electrically bonded to their corresponding bonding pads via one opening 154op of the passivation layer 154.

[0032] The materials of planarization layer 141 and planarization layer 142 include, for example, organic materials, such as acrylic materials, siloxane materials, polyimide materials, epoxy resin materials, or stacks of the above materials, but are not limited thereto. The materials of passivation layer 151, passivation layer 152, passivation layer 153 and passivation layer 154 include, for example, inorganic materials, such as silicon oxide, silicon nitride, silicon oxynitride, other suitable materials, or stacks of at least two of the above materials, but are not limited thereto.

[0033] For example, in order to electrically connect different components in the pixel circuit (not shown) (such as another active component, capacitor, or signal line, but not limited thereto), the display panel 10 may also include multiple conductive patterns, such as another first conductive pattern CP1b and another second conductive pattern CP2b, but not limited thereto. The materials of the source SE, drain DE, first conductive pattern CP1a, first conductive pattern CP1b, second conductive pattern CP2a, and second conductive pattern CP2b include, for example, molybdenum, aluminum, titanium, copper, nickel, tungsten, silver, gold, or a stacked layer of at least two of the above materials. The materials of the first bonding pad BP1 and the second bonding pad BP2 include, for example, electroless nickel-immersion gold (ENIG), but not limited thereto.

[0034] In this embodiment, the source SE, drain DE, first conductive pattern CP1a, first conductive pattern CP1b, second conductive pattern CP2a and second conductive pattern CP2b can each be formed by a stacked structure of a first molybdenum layer, an aluminum layer and a second molybdenum layer, wherein the thicknesses of the first molybdenum layer, the aluminum layer and the second molybdenum layer are, for example, 50 nm, 650 nm and 50 nm, respectively, but are not limited thereto.

[0035] It is particularly noteworthy that, in this embodiment, the display panel 10 further includes a thermally conductive pattern 180 that covers and contacts the first conductive patterns CP1a and CP1b. The orthogonal projections of the first conductive patterns CP1a and CP1b onto the substrate 100 are within the orthogonal projection of the thermally conductive pattern 180 onto the substrate 100. On the other hand, the orthogonal projections of the second conductive patterns CP2a and CP2b and the drain DE of the active element T onto the substrate 100 are within the orthogonal projection of the thermally conductive pattern 180 onto the substrate 100. In this embodiment, the thickness of the thermally conductive pattern 180 is, for example, 175 nm, but is not limited thereto.

[0036] The orthogonal projection of the thermally conductive pattern 180 onto the substrate 100 overlaps with the orthogonal projection of the light-emitting element 200 onto the substrate 100. More specifically, the thermally conductive pattern 180 is not formed uniformly on the first conductive pattern CP1a and the first conductive pattern CP1b. Preferably, the thermal diffusivity of the thermally conductive pattern 180 is greater than 1.0 × 10⁻⁶ m² / s and less than or equal to 1.0 × 10⁻⁴ m² / s, and its material includes, for example, SiNx (0 < x < 1.33), AlN, BN, Al₂O₃, ZrO₂, TiO₂, HfO₂, SiC, or B₄C.

[0037] In any direction (e.g., direction X) parallel to the substrate surface 100s of the substrate 100, the thermally conductive pattern 180 has an edge 180e, the first conductive pattern CP1a has an edge CP1e closest to the edge 180e of the thermally conductive pattern 180, and the second conductive pattern CP2a has an edge CP2e closest to the edge 180e of the thermally conductive pattern 180. Preferably, the distance d between the edge 180e of the thermally conductive pattern 180 and the edge CP1e of the first conductive pattern CP1a along this direction is greater than or equal to 2 μm and less than or equal to 35 μm. The distance d” between the edge 180e of the thermally conductive pattern 180 and the edge CP2e of the second conductive pattern CP2a along this direction is greater than or equal to 2 μm and less than or equal to 35 μm.

[0038] First, it should be noted that by using the thermally conductive pattern 180 to cover and contact the first conductive pattern CP1a and the first conductive pattern CP1b, the uniformity of heat distribution of the first bonding pad BP1 and the second bonding pad BP2 during the bonding process of the light-emitting element 200 can be effectively improved, and the heating efficiency of the solder 250 can be improved, thereby improving the bonding yield of the light-emitting element 200.

[0039] For example, in this embodiment, the bonding of the light-emitting element 200 to the bonding pad is achieved using laser bonding technology. During the bonding process, a laser beam LB irradiates the bonding area (i.e., the distribution area of ​​the bonding pad) to raise the temperature of the bonding pad and the solder 250.

[0040] Referring to Figure 3, in a comparative example of the display panel 10C, since the first conductive patterns CP1a and CP1b are not covered with the thermally conductive pattern 180 shown in Figure 1, when the laser beam LB irradiates and heats the bonding area, heat energy is difficult to accumulate on the bonding pads, resulting in the solder 250 on the bonding pads being too cold (e.g., below 200°C), thus affecting the bonding yield. Because the thermal diffusivity of the conductive pattern formed by the stacked structure of the first molybdenum layer, aluminum layer, and second molybdenum layer is too high, most of the heat energy is easily conducted away through the conductive pattern and cannot be concentrated on the bonding pads. For example, in the comparative example, most of the heat energy is concentrated near the film layers of the first conductive patterns CP1a and CP1b, causing their temperature to reach above 300°C. Therefore, the temperature of the bonding pads and the solder 250 on them is below 200°C.

[0041] In other words, in the bonding process of the light-emitting element 200 in the comparative example, the solder 250 has a problem of low heating efficiency. As shown by curve CE in Figure 4, the temperature of the solder 250 can only rise to 122.9°C within the irradiation time of the laser beam (e.g., 7.2 ms).

[0042] Referring to Figures 1 and 2, in order to solve the above-mentioned problems, the display panel 10 of this embodiment is covered with a thermally conductive pattern 180 on the first conductive pattern CP1a and the first conductive pattern CP1b to regulate the heat diffusion and effective total heat capacity of the bonding pad and the underlying film structure. As shown in Figure 2, through the setting of the thermally conductive pattern 180, when the laser beam LB irradiates and heats the bonding area, the heat energy can be distributed more evenly in the area near the bonding pad, wherein the temperature of the bonding pad and the solder 250 on it can reach above 250°C. That is to say, the setting of the thermally conductive pattern 180 can effectively improve the heating efficiency of the solder 250, which helps to improve the bonding yield of the light-emitting element 200.

[0043] Refer to Figures 1 and 4. Curves E1, E2, E3, and E4 respectively show the solder temperature rise curves when the distance d between the edge 180e of the thermally conductive pattern 180 and the edge CP1e of the first conductive pattern CP1a is designed to be 5 μm, 15 μm, 30 μm, and 50 μm. As shown by curves E1, E2, and E3, if the distance d is greater than or equal to 2 μm and less than or equal to 35 μm, the solder temperature 250 can reach approximately 250°C during the laser beam irradiation time.

[0044] However, as shown in curve E4, if the distance d between the edge 180e of the thermally conductive pattern 180 and the edge CP1e of the first conductive pattern CP1a is greater than 35 μm, the temperature of the solder 250 can only reach about 200°C during the irradiation time of the laser beam. That is, the heating efficiency of the solder 250 is slightly worse, but still better than the heating efficiency of the solder in the comparative example in Figure 3.

[0045] In summary, in a display panel according to an embodiment of the present invention, the bonding pads for bonding the light-emitting elements are electrically connected to the active elements via conductive patterns. By covering and contacting the conductive patterns with thermally conductive patterns, the uniformity of heat distribution of the bonding pads during the bonding process of the light-emitting elements can be effectively improved, and the heating efficiency of the solder can be improved, thereby improving the bonding yield of the light-emitting elements. [Simplified Explanation of the Diagram]

[0046] FIG1 is a cross-sectional schematic diagram of a display panel according to an embodiment of the present invention. FIG2 is a cross-sectional schematic diagram of the heat distribution of the display panel of FIG1 during the bonding process of the light-emitting elements. FIG3 is a cross-sectional schematic diagram of the heat distribution of the display panel of a comparative example during the bonding process of the light-emitting elements. FIG4 is a temperature rise curve of the solder of FIG1 under various designs of thermally conductive patterns.

Claims

1. A display panel, comprising: One substrate; A bonding pad is disposed on the substrate; A light-emitting element is disposed on the substrate and electrically bonded to the bonding pad; A first conductive pattern is disposed on the substrate and electrically connected to the bonding pad; an active element is disposed on the substrate and electrically connected to the first conductive pattern. A thermally conductive pattern covers and contacts the first conductive pattern, wherein the orthographic projection of the thermally conductive pattern on the substrate overlaps the orthographic projection of the light-emitting element on the substrate, and the thermal diffusivity of the thermally conductive pattern is greater than 1.0×10-6 m2 / s.

2. The display panel as claimed in claim 1, wherein the orthographic projection of the first conductive pattern on the substrate is located within the orthographic projection of the thermally conductive pattern on the substrate.

3. The display panel as claimed in claim 2, wherein the thermally conductive pattern has a first edge in any direction parallel to a substrate surface of the substrate, the first conductive pattern has a second edge closest to the first edge, and the distance between the first edge and the second edge along the any direction is greater than or equal to 2 μm.

4. The display panel as described in claim 3, wherein the distance is less than or equal to 35 μm.

5. The display panel as claimed in claim 1, wherein the thermal diffusivity of the thermally conductive pattern is less than or equal to 1.0 × 10⁻⁴ m² / s.

6. The display panel as claimed in claim 1, wherein the material of the thermally conductive pattern includes SiNx (0 < x < 1.33), AlN, BN, Al2O3, ZrO2, TiO2, HfO2, SiC, or B4C.

7. The display panel as described in claim 1, further comprising: A second conductive pattern electrically connects the bonding pad and the first conductive pattern, wherein the orthographic projection of the second conductive pattern on the substrate is located within the orthographic projection of the thermally conductive pattern on the substrate.

8. The display panel of claim 7, wherein the thermally conductive pattern has a first edge in any direction parallel to a substrate surface of the substrate, the second conductive pattern has a second edge closest to the first edge, and the distance between the first edge and the second edge along the any direction is greater than or equal to 2 μm and less than or equal to 35 μm.

9. The display panel as claimed in claim 1, wherein the active element includes a drain electrode electrically connected to the first conductive pattern, the drain electrode having an orthographic projection on the substrate within the orthographic projection of the thermally conductive pattern on the substrate.

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