Light emitting diode package structure and manufacturing method thereof

Abstract

A light emitting diode packaging structure and a manufacturing method thereof, the packaging structure comprising a transparent substrate, a light emitting diode and a pad electrode on the transparent substrate, the pad electrode configured to be electrically connected with the light emitting diode by a wire, and a packaging layer covering the light emitting diode and the wire, a light emitting surface of the light emitting diode configured to be towards a side of the transparent substrate. The packaging structure helps to improve the light emitting efficiency of the light emitting diode.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to a light emitting diode (LED) packaging structure and a manufacturing method thereof. BACKGROUND

[0002] Light emitting diodes (LEDs) have high photoelectric conversion efficiency, long service life, high brightness, low heat, environmental protection, and are robust and durable, and thus have been widely used in lighting and display.

[0003] In the packaging process of LEDs, the wire bonding process is a preferred choice due to its high reliability, low cost, and high efficiency. Typically, the LED is fixed on a substrate, and then the chip electrode is connected to the circuit board through the wire bonding process, and finally the packaging is completed. How to optimize the LED packaging structure and packaging process is a problem of concern in the field. SUMMARY

[0004] At least one embodiment of the present disclosure provides a light emitting diode packaging structure, which includes a transparent substrate, a light emitting diode, and a pad electrode on the transparent substrate, the pad electrode being configured to be electrically connected to the light emitting diode through a wire, and a packaging layer covering the light emitting diode and the wire, wherein the light emitting diode is configured to have a light emitting surface facing the side of the transparent substrate.

[0005] In some examples, the packaging structure further includes a light shielding layer on the surface of the transparent substrate, wherein the light shielding layer has an opening, and the light emitting diode is arranged in the opening.

[0006] In some examples, the light emitting diode has a gap with the side wall of the opening; and the gap is filled with a light shielding material.

[0007] In some examples, the packaging structure further includes a contact electrode outside the packaging layer for contact, and the contact electrode is electrically connected to the pad electrode.

[0008] In some examples, the packaging layer further covers the pad electrode, and the packaging structure further includes a contact electrode on the side of the packaging layer away from the transparent substrate, and the contact electrode is electrically connected to the pad electrode through a connecting hole in the packaging layer.

[0009] At least one embodiment of the present disclosure also provides a manufacturing method of a light emitting diode packaging structure, which includes arranging a light emitting diode on a transparent substrate, forming a pad electrode on the transparent substrate, and electrically connecting the pad electrode to the light emitting diode through a wire, and forming a packaging layer covering the light emitting diode and the wire, wherein the light emitting diode is configured to have a light emitting surface facing the side of the transparent substrate.

[0010] In some examples, the manufacturing method further comprises forming a light-shielding layer on the transparent substrate, forming an opening in the light-shielding layer, and disposing the light-emitting diode in the opening.

[0011] In some examples, the light-emitting diode has a gap with a sidewall of the opening; and the manufacturing method further comprises filling a light-shielding material in the gap.

[0012] In some examples, the manufacturing method further comprises forming a contact electrode on the transparent substrate, the contact electrode being located outside the encapsulation layer for contact, and the contact electrode being electrically connected with the pad electrode.

[0013] In some examples, the encapsulation layer further covers the pad electrode, and the manufacturing method further comprises forming a connecting hole in the encapsulation layer and forming a contact electrode on the encapsulation layer, wherein the contact electrode is electrically connected with the pad electrode through the connecting hole.

[0014] The light-emitting diode encapsulation structure and the manufacturing method thereof provided by at least one embodiment of the present disclosure set the light-emitting surface of the light-emitting diode to face the substrate on which the light-emitting diode is located instead of the encapsulation layer, so that the thickness and blackness of the encapsulation layer do not affect the light-emitting efficiency of the device, and the performance of the device is improved. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings needed to be used in the embodiments or related description will be briefly introduced. Obviously, the drawings in the following description only relate to some embodiments of the present disclosure, and are not a limitation on the present disclosure.

[0016] Figure 1 A schematic diagram of a light-emitting diode encapsulation structure provided by some embodiments of the present disclosure;

[0017] Figure 2 A schematic diagram of a light-emitting diode encapsulation structure provided by some other embodiments of the present disclosure; and

[0018] Figures 3A-3C A process step diagram of a manufacturing method of a light-emitting diode encapsulation structure provided by at least one embodiment of the present disclosure. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings shown in the accompanying drawings and the non-restrictive example embodiments shown in the following description, which more fully illustrate the example embodiments of the present disclosure and their various features and advantageous details. It should be noted that the features shown in the drawings are not necessarily drawn to scale. The present disclosure omits the description of known materials, components and process techniques, so as not to obscure the example embodiments of the present disclosure. The examples given are merely intended to facilitate the understanding of the implementation of the example embodiments of the present disclosure, and further enable those skilled in the art to implement the example embodiments. Therefore, these examples should not be understood as limiting the scope of the embodiments of the present disclosure.

[0020] Unless otherwise defined, technical terms or scientific terms used in the present disclosure should be understood as having the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. The terms "first", "second" and similar terms used in the present disclosure do not denote any order, quantity or importance, but are used to distinguish different components. The terms "comprise", "comprise" and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. "Up", "down", "left", "right" and the like are only used to represent relative positional relationships, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly. In the case of no conflict, the embodiments of the present disclosure and the features in the embodiments can be combined to obtain new embodiments.

[0021] Since the wire has a certain height, the packaging layer has a certain thickness. In addition, in order to improve the color consistency and contrast of the device, the packaging layer is usually blackened, which further increases the thickness of the packaging layer. Under the action of high thickness and high blackness, the proportion of light emitted by the LED chip escaping to the air is greatly reduced. In the terminal use, the current needs to be increased to meet the brightness requirement, which increases the load of the chip and reduces the service life of the device.

[0022] A light emitting diode packaging structure, comprising a transparent substrate and a light emitting diode and a pad electrode on the transparent substrate, the pad electrode is configured to be electrically connected with the light emitting diode through a wire, the packaging structure further comprises a packaging layer, the packaging layer covers the light emitting diode and the wire, and the light emitting surface of the light emitting diode is configured to be towards the side of the transparent substrate.

[0023] At least one embodiment of the present disclosure sets the light emitting surface of the light emitting diode to be towards the substrate where it is located instead of the packaging layer, so that the thickness and blackness of the packaging layer do not affect the light emitting efficiency of the device, and the performance of the device is improved.

[0024] In some examples, the light emitting diode can be a multi-faceted light emitter, but in actual application, not all of the light emitting facets can be used, for example, only one light emitting facet can be used. In this case, the light emitting facet of the light emitting diode in the present disclosure specifically refers to the light emitting facet used in actual application.

[0025] For example, in some embodiments, the packaging structure further comprises a light shielding layer on the surface of the transparent substrate, and the light shielding layer is provided with an opening, and the light emitting diode is arranged in the opening.

[0026] The above arrangement improves the light emitting efficiency of the device, and also improves the ink color consistency and contrast of the device by arranging the light shielding layer on the transparent substrate.

[0027] Figure 1 A structural schematic diagram of a light emitting diode packaging structure provided by at least one embodiment of the present disclosure is shown in Figure 1 The light emitting diode packaging structure 10 comprises a transparent substrate 11, a light shielding layer 12 on the surface of the transparent substrate 11, and a light emitting diode 20. The light shielding layer 12 is provided with an opening 120, which exposes at least part of the surface of the transparent substrate 11, and the light emitting diode 20 is arranged in the opening 120. The light emitting diode packaging structure 10 further comprises a packaging layer 15, which covers the light emitting diode 20. The light emitting facet 22a of the light emitting diode 20 is configured to face one side of the transparent substrate 11. In use, the light F emitted by the light emitting diode 20 passes through the transparent substrate 11 to reach the user.

[0028] By arranging the light emitting facet of the light emitting diode to face the substrate where it is located instead of the packaging layer, the thickness and blackness of the packaging layer do not affect the light emitting efficiency of the device, thereby improving the performance of the device.

[0029] For example, the transparent substrate 11 can be a rigid substrate or a flexible substrate; for example, the material of the transparent substrate 11 is glass, sapphire, or transparent resin material, etc., and for example, the transmittance of the transparent substrate 11 reaches 80% or above.

[0030] For example, the light emitting diode 20 is not embedded in the transparent substrate 11.

[0031] For example, at least the light emitting facet 22a of the light emitting diode 20 is located in the opening 120.

[0032] For example, the light shielding layer 12 only exposes the light emitting facet 22a of the light emitting diode 20, but does not expose other non-light emitting facets (for example, the side surface adjacent to the light emitting facet 22a).

[0033] For example, the material of the light shielding layer 12 is a black material such as BT material or polyimide (PI) material.

[0034] For example, the light emitting diode 20 is an inorganic light emitting diode, which is configured to emit red light, green light, blue light, etc.

[0035] For example, the material of the encapsulation layer 15 can be encapsulation glue, such as epoxy resin, silica gel, modified epoxy resin, modified silica gel, etc. In order to improve the color consistency and contrast of the device, the encapsulation layer can be blackened, for example, by injecting black substances such as carbon black. Since the light emitting surface of the light emitting diode 20 does not face the side of the encapsulation layer 15, blackening the encapsulation layer 15 does not affect the light emitting efficiency of the device.

[0036] In other examples, black materials can also be directly used as the material of the encapsulation layer 15, for example, ink can be used as the material of the encapsulation layer 15.

[0037] In at least one embodiment of the present disclosure, the encapsulation layer 15 does not have a transmittance requirement, as long as the encapsulation layer 15 can play a role in encapsulating the light emitting diode.

[0038] For example, as shown in FIG. 1, the light emitting diode 20 has a gap with the side wall of the opening 120, which provides a certain operation margin when the light emitting diode 20 is placed into the opening 120 for die bonding. Figure 1 For example, in some packaging structures, the electrodes of the light emitting diode need to be bonded with the formed pad electrodes during die bonding, in which case the operation precision is required to be high, otherwise poor connection may occur. The packaging structure provided by the embodiment of the present disclosure can reduce the operation precision during die bonding and improve the packaging yield by positioning the opening first and then placing the light emitting diode into the opening for electrical connection.

[0039] The packaging structure can further include a light shielding body 122 filled in the gap.

[0040] For example, the material of the light shielding body 122 is black glue, etc., such as black photoresist. In this way, when a user views from the side of the transparent substrate 11, only the light emitting diode 20 is exposed, thereby bringing the user the extreme contrast. In addition, filling the black glue can also play a role in fixing the light emitting diode chip, preventing the chip from being displaced or the wafer from being damaged during die bonding.

[0041] For example, as shown in FIG. 1, the light shielding body 122 is filled in the gap between the light emitting diode 20 and the side wall of the opening 120.

[0042] Figure 1 ​As shown, for example, the packaging structure can further include an adhesive layer 121 located in the opening 120 and between the transparent substrate surface and the light emitting diode, fixing the light emitting diode 20 on the surface of the transparent substrate 11. For example, the adhesive layer 121 is transparent material, thereby improving the light extraction efficiency of the device. It should be noted that the adhesive layer 121 is not necessary.

[0043] For example, as shown in FIG. 1, the packaging structure 10 further includes a soldering pad electrode 13 located on the side of the light shielding layer 12 away from the transparent substrate 11, and the soldering pad electrode 13 is electrically connected to the light emitting diode 20 through a soldering wire 14. Figure 1

[0044] For example, the soldering pad electrode 13 can include gold (Au), silver (Ag), copper (Cu), aluminum (Al), molybdenum (Mo), magnesium (Mg), tungsten (W), and an alloy material formed by combining the above metals; for example, the soldering pad electrode 13 can also include a metal oxide conductive material, such as zinc oxide, IGZO, etc.

[0045] In the light emitting diode packaging structure provided in at least one embodiment of the present disclosure, when a user looks from the side of the transparent substrate 11, the soldering pad electrode is blocked by the light shielding layer 12, avoiding the contrast reduction caused by the exposure of the soldering pad electrode.

[0046] For example, the light emitting diode 20 can be a normal structure or a flip-chip structure, and the light emitting diode 20 includes a main body part (i.e., a light emitting part) 22 and two electrodes (i.e., an anode and a cathode) 21, and the light emitting part 22 includes, for example, a PN junction or a PIN junction. The two electrodes 21 are located on the same side of the main body part 22 of the light emitting diode, as shown in FIG. 2. Figure 1 For example, as shown in FIG. 2, the two electrodes are both located on the side of the main body part of the light emitting diode away from the transparent substrate 11, and are respectively electrically connected to the corresponding soldering pad electrode 13 through the soldering wire 14.

[0047] For example, as shown in FIG. 2, the packaging layer 15 completely covers the soldering wire 14 and covers a part of the soldering pad electrode 13, and another part of the soldering pad electrode 13 is exposed outside the packaging layer 15 for contact with an external circuit. Figure 1

[0048] For example, in some examples, due to the height difference between the exposed part of the soldering pad electrode 13 and the die bonding area, it is not conducive to terminal use, for example, it is difficult to achieve terminal lamp pasting. As shown in FIG. 2, for example, the packaging structure can further include a contact electrode 16 (e.g., a solder ball) located on the exposed surface of the soldering pad electrode 13 as a pin electrode, thereby compensating for the height difference on the back of the packaging structure and meeting the terminal lamp pasting operation requirements. Figure 1

[0049] Figure 2 ​​​A structural schematic diagram of the light emitting diode packaging structure 30 provided for another embodiment of the present disclosure is shown in FIG. 3, which is similar to the embodiment shown in FIG. 2. Figure 1 and Figure 2 The main difference between the embodiments shown in FIGS. 2 and 3 is the packaging method. For example, as shown in FIG. 2, the light emitting diode can be fully packaged by molding. Figure 2

[0050] As shown in FIG. 3, the packaging layer 15 completely covers the pad electrode 13, and the packaging layer 15 is provided with a connecting hole 17, which is formed by punching a hole in the packaging layer 15 and filling the hole with a conductive material. For example, the conductive material can include gold (Au), silver (Ag), copper (Cu), aluminum (Al), molybdenum (Mo), magnesium (Mg), tungsten (W), and an alloy material formed by combining the above metals. The packaging structure further includes a contact electrode 18 on the packaging layer 15 as a pin, which is electrically connected to the connecting hole 17, thereby leading out two electrodes of the light emitting diode 20. Figure 2

[0051] The present disclosure further provides an electronic device including the light emitting diode packaging structure 10 or 30 provided by any of the above embodiments. The electronic device can be, for example, a display device, which can be a display, an LED panel, an LED television, a mobile phone, a tablet computer, a digital photo frame, a navigator, or any product or component having a display function.

[0052] The present disclosure further provides a manufacturing method of a light emitting diode packaging structure, including: disposing a light emitting diode on a transparent substrate, forming a pad electrode on the transparent substrate, and electrically connecting the pad electrode and the light emitting diode by a bonding wire, and forming a packaging layer to cover the light emitting diode and the bonding wire, wherein an emitting surface of the light emitting diode is configured to face the side of the transparent substrate.

[0053] The manufacturing method of the light emitting diode packaging structure provided by at least one embodiment of the present disclosure packages the light emitting diode from the back side, i.e., the packaging layer is formed on the side opposite to the light emitting surface of the light emitting diode, so that the light emitting efficiency of the device is not affected by the thickness of the packaging layer, thereby improving the light emitting efficiency of the device.

[0054] For example, the manufacturing method further includes: forming a light shielding layer on the transparent substrate, and forming an opening in the light shielding layer, wherein the light emitting diode is disposed in the opening.

[0055] For example, the light emitting diode has a gap with the sidewall of the opening; and the manufacturing method further includes: filling a light shielding material in the gap.

[0056] ​​For example, the manufacturing method further comprises: forming a contact electrode on the transparent substrate, the contact electrode being located outside the encapsulation layer for contact, and the contact electrode being electrically connected with the pad electrode.

[0057] For example, the encapsulation layer further covers the pad electrode, and the manufacturing method further comprises: forming a connecting hole in the encapsulation layer, and forming a contact electrode on the encapsulation layer, wherein the contact electrode is electrically connected with the pad electrode through the connecting hole.

[0058] Figures 3A-3C A process step schematic diagram of a manufacturing method of a light emitting diode packaging structure provided by at least one embodiment of the present disclosure is shown.

[0059] As shown in Figure 3A A transparent material is selected and its surface is cleaned to provide a transparent substrate 11, for example, the transparent substrate 11 can be a flexible substrate or a rigid substrate. For example, the transparent material can be any one of transparent glass, sapphire or transparent high-temperature-resistant material, for example, the transmittance reaches 80-99%. For example, the surface of the transparent substrate can be treated by manual grinding or hydrofluoric acid etching to roughen the surface, so as to reduce the light reflection of the surface of the encapsulation layer and increase the viewing angle of the display screen; or polishing treatment is performed to achieve bright surface effect and increase contrast.

[0060] Then, a light shielding layer 12 is formed on the transparent substrate 11. For example, the light shielding layer 12 can be a black high-temperature-resistant material such as BT or PI, for example, the thickness of the light shielding layer 12 is 1 μm-200 μm. For example, the light shielding layer 12 can be formed on the transparent substrate 11 by using a hot pressing process. For example, the hot pressing process parameters are: heating rate: 3~5℃ / min; contact pressure: 80-100psi; full pressure: 400-500psi; curing time: 120min (>230℃ / material temperature); cooling rate: <3℃ / min.

[0061] Then, a pad electrode and a trace pattern are formed on the light shielding layer 12. For example, a conductive layer can be first formed on the light shielding layer 12, and then a patterning process is performed on the conductive layer to form a conductive pattern of the pad electrode and the trace.

[0062] As shown in Figure 3C The electrode pattern can be formed by copper plating, film pasting, exposure, development and electroplating process.

[0063] Then, a die bonding surface is opened and windowed on the transparent substrate 11 on which the pad electrode pattern is formed, and an opening 120 is formed in the light shielding layer 12, to obtain an overall circuit layout as shown in Figure 3B Figure 3B ​As shown, the pad electrode 13 is arranged around the opening 120 to facilitate connection with the light emitting diode in subsequent processes. For example, a mechanical punching, CNC / laser washing process can be used to open the window for die bonding on the light shielding layer, in preparation for die bonding operation.

[0064] Next, the light emitting diode 20 is placed into the opening 120, which is designed with a certain margin compared to the size of the light emitting diode 20, so as to reduce the operation precision requirement. For example, there is a certain gap between the light emitting diode and the sidewall of the opening.

[0065] For example, an adhesive layer can be formed in the opening 120 to fix the light emitting diode in the opening 120. For example, a transparent adhesive with strong fluidity can be used to flow and fix the die bonding window.

[0066] For example, the light emitting diode 20 is not embedded in the transparent substrate 11.

[0067] The number of light emitting diodes packaged in one opening 120 is not limited in the embodiments of the present disclosure, and can be one or multiple. For example, the packaging structure is a pixel unit configured to emit full-color light. As shown in Figure 3C As shown, three light emitting diodes 20 are arranged in one opening 120, and the three diodes 20 are respectively configured to emit light of three primary colors, i.e., red, green and blue.

[0068] For example, the gap between the light emitting diode and the sidewall of the opening and the gap between the light emitting diodes can also be filled with a light shielding material, such as black photoresist. In this way, when a user views from one side of the transparent substrate 11, only the light emitting diode 20 is exposed, thereby bringing the user the ultimate contrast. In addition, filling the black glue can also play a role in fixing the light emitting diode chip, preventing displacement of the chip or damage to the wafer during packaging of the die bonding area.

[0069] As shown in Figure 3C As shown, four pad electrodes 13 are arranged around the periphery of one opening 120, including one common electrode 13a connected to the cathode or anode of the three light emitting diodes to provide a common cathode voltage or anode voltage, and the other three pad electrodes 13 connected to the other electrodes of the three light emitting diodes.

[0070] Next, wire bonding 14 is used to electrically connect each pad electrode with the corresponding diode electrode. For example, a wire bonder can be used for wire bonding.

[0071] Next, the light emitting diode 20 is packaged to form a packaging layer 15.

[0072] In some examples, a high-precision dispensing machine can be used to identify the marked points on the substrate for targeted dispensing, completing the encapsulation of the back die-bonding area, for example, forming... Figure 1 The packaging structure shown.

[0073] After back-side encapsulation, there is a height difference between the back electrodes and the die-bonding area, making it difficult to attach LEDs to the terminal. Therefore, this invention solves the height difference on the back by forming contact electrodes 16 at the bottom electrodes through printing, wire bonding, and other methods, thus enabling the terminal to attach LEDs.

[0074] In other examples, such as Figure 2 As shown, the LED can be fully encapsulated to form the encapsulation layer 15 by molding. Then, the back encapsulation adhesive is drilled by mechanical / laser drilling. The holes in the encapsulation adhesive are filled by electroplating copper, 3D printing, etc., and the wire bonding pads are connected. A conductive layer (copper, iron, silver and above alloys, etc.) is hot-pressed onto the surface of the encapsulation adhesive. Then, the conductive layer is patterned by etching to form the contact electrode 18.

[0075] In other embodiments of the method for manufacturing a light-emitting diode package structure disclosed herein, the transparent substrate 11 may first be formed on a support substrate. The support substrate may be, for example, a material that is resistant to high temperature, has a low coefficient of thermal expansion, is not easily deformed, and has a low expansion-contraction ratio, such as glass or steel sheet. The support substrate may be opaque. For example, when the transparent substrate 11 has low hardness and is not easy to operate directly, the support substrate may support the transparent substrate and serve as the operating substrate for forming the package structure. After the package structure is completed, the package structure may be peeled off from the support substrate.

[0076] For example, the manufacturing method may further include: forming the transparent substrate 11 on the support substrate, for example by a thermosetting process or an ultraviolet (UV) curing process, and then performing subsequent process steps on the transparent substrate to form the encapsulation structure, and finally removing the encapsulation structure from the support substrate by UV curing or mechanical peeling.

[0077] The above description is merely an exemplary embodiment of this disclosure and is not intended to limit the scope of protection of this disclosure, which is determined by the appended claims.

Claims

1. A light emitting diode packaging structure, comprising a transparent substrate, a light emitting diode and a pad electrode on the transparent substrate, wherein the pad electrode is configured to be electrically connected with the light emitting diode by a wire, the packaging structure further comprises a packaging layer covering the light emitting diode and the wire, an emitting surface of the light emitting diode is configured to face the side of the transparent substrate, and a light shielding layer on the surface of the transparent substrate, wherein the light shielding layer is provided with an opening, and the light emitting diode is arranged in the opening; the light emitting diode has a gap with the sidewall of the opening; the gap is filled with a light shielding material.

2. The package structure of claim 1, further comprising a contact electrode, wherein, the contact electrode is located outside the packaging layer for contact, and the contact electrode is electrically connected with the pad electrode.

3. The package structure of claim 1, wherein, the packaging layer also covers the pad electrode, the packaging structure further comprises a contact electrode on the side of the packaging layer away from the transparent substrate, and the contact electrode is electrically connected with the pad electrode through a connecting hole in the packaging layer. 4.A manufacturing method of a light emitting diode packaging structure, comprising: arranging a light emitting diode on a transparent substrate, forming a pad electrode on the transparent substrate and electrically connecting the pad electrode with the light emitting diode by a wire, forming a packaging layer to cover the light emitting diode and the wire, wherein an emitting surface of the light emitting diode is configured to face the side of the transparent substrate; forming a light shielding layer on the transparent substrate, forming an opening in the light shielding layer, and arranging the light emitting diode in the opening; the light emitting diode has a gap with the sidewall of the opening; the manufacturing method further comprises: filling the gap with a light shielding material. 5.The manufacturing method of claim 4, further comprising: forming a contact electrode on the transparent substrate, the contact electrode is located outside the packaging layer for contact, and the contact electrode is electrically connected with the pad electrode.

6. The production method according to claim 4, wherein the packaging layer also covers the pad electrode, and the manufacturing method further comprises: forming a connecting hole in the packaging layer and forming a contact electrode on the packaging layer, wherein the contact electrode is electrically connected with the pad electrode through the connecting hole.

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