Integrated LED device based on flip chip technology

Abstract

The invention relates to an integrated LED device based on a flip-chip process, which comprises a driving chip substrate with a driving circuit on the top surface, an RGB LED chip group is welded on the top surface of the driving chip substrate in a flip-chip manner, and an elastic reinforcing piece is arranged around the flip-chip welding position of the RGB LED chip group; the driving chip substrate, the RGB LED chip set and the elastic reinforcing piece are packaged in the packaging colloid layer, the bottom surface of the driving chip substrate is exposed out of the packaging colloid layer, and the expansion coefficient of the elastic reinforcing piece is smaller than that of the packaging colloid layer; the RGB LED chip set is connected with a heat dissipation piece which is of an inverted-L-shaped structure, arranged in the elastic reinforcing piece and the packaging colloid layer in a penetrating mode and vertically extends downwards to the bottom face of the packaging colloid layer. And a plurality of connecting ends are arranged on the bottom surface of the driving chip substrate. According to the invention, the size of the device is reduced, and the heat dissipation capability and the mechanical stress resistance of the device are improved.

Description

Technical Field

[0001] The present invention relates to the field of LED displays, and in particular to an integrated LED device based on a flip chip process. Background Art

[0002] With the development of technology, LED devices are widely used in the fields of lighting or display. The packaging of existing traditional LED devices usually adopts the methods of wire bonding or indirect driving of a substrate. Such methods have the following problems: 1), low heat dissipation efficiency, and heat is conducted layer by layer through wires or the substrate, which easily leads to an increase in the junction temperature, affecting the light efficiency and lifespan; 2), low space utilization rate, discrete driving chips and LED chips occupy a large area, and it is difficult to meet the miniaturization requirements; thus, there appear LED devices packaged by using the flip chip process. Although the flip chip process can shorten the electrical path through flip-chip soldering, the existing technologies mostly focus on the packaging of a single chip, lacking the optimized design of the integrated structure of the LED chip and the driving chip. Summary of the Invention

[0003] Aiming at the existing deficiencies, the present invention provides an integrated LED device based on a flip chip process.

[0004] The technical solution adopted by the present invention to solve its technical problems is: an integrated LED device based on a flip chip process, including a driving chip substrate with a driving circuit provided on the top surface, an RGB LED chip group connected to the driving circuit is flip-chip soldered on the top surface of the driving chip substrate, and an elastic reinforcing member is arranged on the top surface of the driving chip substrate around the position where the RGB LED chip group is flip-chip soldered; the driving chip substrate, the RGB LED chip group and the elastic reinforcing member are encapsulated in an encapsulation colloid layer and the bottom surface of the driving chip substrate is exposed outside the encapsulation colloid layer, and the expansion coefficient of the elastic reinforcing member is smaller than that of the encapsulation colloid layer; a heat dissipation member in an inverted L-shaped structure is connected to the RGB LED chip group, penetrates through the elastic reinforcing member and the encapsulation colloid layer and extends vertically downward to the bottom surface of the encapsulation colloid layer; and a plurality of connection ends are arranged on the bottom surface of the driving chip substrate.

[0005] Preferably, a plurality of square electrode pad areas are arranged at intervals on the top surface of the driving chip substrate, a positive electrode pad and a negative electrode pad are arranged at intervals along the diagonal on each electrode pad area, and the positive electrode and the negative electrode of the RGB LED chip group are respectively flip-chip soldered to the positive electrode pad and the negative electrode pad.

[0006] Preferably, an isolation groove for isolating the positive electrode pad and the negative electrode pad is arranged on each electrode pad area.

[0007] Preferably, the connection terminal includes a power connection terminal electrically connected to the driving circuit for connecting to a power source and an information connection terminal for transmitting information.

[0008] Preferably, a heat dissipation channel for penetrating a heat dissipation element is provided on the packaging colloid layer.

[0009] Preferably, a filler made of a thermal interface material is filled between the heat sink and the inner wall of the heat dissipation channel.

[0010] Preferably, a heat diffusion layer covering the bottom surface of the driver chip substrate is arranged on the bottom surface of the driver chip substrate around the connection end.

[0011] Preferably, a distributed Bragg reflector is integrated on the bottom surface of the chip of the RGB LED chipset.

[0012] Preferably, the chip surface of the RGB LED chipset is coated with an anti-reflection film with a thickness of 1 / 4 of the emission wavelength.

[0013] Preferably, the elastic reinforcing member is made of silica gel or polyimide material added with optical scattering particles, and the encapsulation colloid layer is made of silica gel or polyimide material.

[0014] The beneficial effects of the present invention are as follows: the present invention realizes vertical stacking of LED chips and driver chips to form an integrated laminated structure through a flip chip process, thereby greatly reducing the volume of the LED device; the provision of the elastic reinforcement improves the ability of the LED device to resist mechanical stress, and ensures the firmness of the welding between the LED chip and the driver chip; at the same time, the structure and provision of the heat sink bypass the thermal resistance of the driver chip substrate, and can also avoid the formation of thermal resistance by the colloidal material in the heat conduction path, thereby improving the heat dissipation capacity of the LED device; the heat sink extends vertically downward without the need for lateral heat dissipation space, and can further reduce the size of the LED device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic structural diagram of an embodiment of the present invention;

[0016] Figure 2 Embodiment of the present invention Figure 1 A is a schematic diagram of the enlarged structure of the middle part;

[0017] Figure 3 It is a schematic diagram of the structure of the electrode welding area on the top surface of the driver chip substrate according to an embodiment of the present invention;

[0018] Names and serial numbers of components in the figure: 1 - Driver chip substrate; 10 - Electrode welding area; 100 - Positive electrode pad; 101 - Negative electrode pad; 102 - Isolation groove; 2 - RGB LED chip group; 20 - Distributed Bragg reflector; 21 - Anti-reflection film; 3 - Elastic reinforcement; 4 - Encapsulation colloid layer; 40 - Heat dissipation channel; 5 - Heat sink; 6 - Connection end; 7 - Filler; 8 - Thermal diffusion layer. Detailed implementation manners

[0019] To more clearly illustrate the objectives, technical solutions and advantages of the embodiments of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The description is clear and complete. Obviously, the described embodiments are partial embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] Embodiments of the present invention are as follows Figures 1 to 3As shown in the figure, an integrated LED device based on a flip-chip process includes a driving chip substrate 1 with a driving circuit (not shown in the figure) provided on its top surface. The driving chip substrate 1 is a square silicon-based or ceramic substrate, and the driving circuit is etched on its top surface. The driving circuit adopts any existing driving circuit for LED devices. An RGB LED chip group 2 connected to the driving circuit is flip-chip welded on the top surface of the driving chip substrate 1. The RGB LED chip group 2 includes a red LED chip, a green LED chip, and a blue LED chip. The red LED chip, the green LED chip, and the blue LED chip are all flip-chip welded on the driving circuit and are arranged in parallel on the driving circuit. An elastic reinforcement member 3 is arranged around the position where the RGB LED chip group 2 is flip-chip welded on the top surface of the driving chip substrate 1. After the LED chips in the RGB LED chip group 2 are flip-chip welded on the top surface of the driving chip substrate 1, there will be a gap between the LED chips and the driving chip substrate 1. At this time, the elastic reinforcement member 3 is used to fill the gap between the LED chips and the top surface of the driving chip substrate 1. In this way, when the LED device is subjected to mechanical stress, the elastic reinforcement member 3 can buffer, ensuring the stability of the welding structure between the LED chips and the driving chip substrate 1 and improving the mechanical stress resistance of the LED device. The driving chip substrate 1, the RGB LED chip group 2, and the elastic reinforcement member 3 are encapsulated in an encapsulation colloid layer 4, and the bottom surface of the driving chip substrate 1 is exposed outside the encapsulation colloid layer 4. The driving chip substrate 1, the RGB LED chip group 2, and the elastic reinforcement member 3 are coated with transparent epoxy resin to form the encapsulation colloid layer 4. At this time, the bottom surface of the driving chip substrate 1 is not coated by the encapsulation colloid layer 4 and is exposed outside, which is convenient for setting connection terminals 6 on the bottom surface of the driving chip substrate 1. That is, a plurality of connection terminals 6 are provided on the bottom surface of the driving chip substrate 1, and the power supply or the transmission of information data is connected through the connection terminals 6. The connection terminals 6 are connected to the driving circuit on the top surface of the driving chip substrate 1. At this time, the connection terminals 6 include a power connection terminal for connecting the power supply and an information connection terminal for transmitting information that are electrically connected to the driving circuit. The power connection terminal includes a VDD connection terminal and a GND connection terminal. The VDD connection terminal and the GND connection terminal are arranged diagonally on the bottom surface of the driving chip substrate 1. The information connection terminal includes an information input terminal and an information output terminal. When the information input terminal and the VDD connection terminal or the GND connection terminal are arranged on the same side of the bottom surface of the driving chip substrate 1, the information output terminal is correspondingly arranged on the same side as the GND connection terminal or the VDD connection terminal.The expansion coefficient of the elastic reinforcing member 3 is smaller than that of the encapsulating colloid layer 4. Thus, during the encapsulation process, the elastic reinforcing member 3 produces a smaller volume change relative to the encapsulating colloid layer 4, thereby avoiding the influence of the volume change of the encapsulating colloid layer 4 on the welding between the LED chip and the driver chip substrate 1, thereby ensuring the stability of the flip-chip welding structure. The elastic reinforcing member 3 is made of silica gel or polyimide material with optical scattering particles added thereto. The optical scattering particles have a low expansion coefficient. When added to the resin material, the expansion coefficient of the resin material will be reduced. For example, the optical scattering particles are made of titanium dioxide, and the encapsulating colloid layer 4 is made of silica gel or polyimide material; RGB The LED chipset 2 is connected with a heat sink 5 in an inverted L-shaped structure, which is inserted into the elastic reinforcement 3 and the encapsulation colloid layer 4 and extends vertically downward to the bottom surface of the encapsulation colloid layer 4; that is, the heat sink 5 is an inverted L-shaped structure composed of a horizontal portion located on the top surface of the driver chip substrate 1 and parallel to the top surface, and a vertical portion parallel to the side wall of the driver chip substrate 1 and perpendicular to the horizontal portion. The heat sink 5 is made of a copper column or a heat-conducting rod. At this time, the middle part of the horizontal portion of the heat sink 5 is interference-fitted in the elastic reinforcement 3 to form a seal for the LED chip. One end of the horizontal portion is connected to the LED chip in the RGB LED chipset 2, and the other end passes through the elastic reinforcement 3 and is connected to the top of the vertical portion of the heat sink 5. The vertical portion of the heat sink 5 is vertically inserted into the encapsulation colloid layer 4, and its bottom end extends to the bottom surface of the encapsulation colloid layer 4. Each LED chip in the LED chip group 2 is provided with a corresponding heat sink 5; this bypasses the thermal resistance of the driver chip substrate 1 and can also prevent the colloid material from being sandwiched in the heat conduction path to form thermal resistance, thereby improving the heat dissipation capacity of the LED device. The heat sink 5 extends vertically downward without the need for horizontal heat dissipation space, and can further reduce the size of the LED device.

[0021] Further improvements, such as Figure 3As shown in the figure, for the flip-chip soldering of the RGB LED chip group 2 on the top surface of the driving chip substrate 1, a plurality of square electrode pad areas 10 are arranged at intervals on the top surface of the driving chip substrate 1. That is, three electrode pad areas 10 are arranged on the top surface of the driving chip substrate 1, and the three electrode pad areas 10 correspond one by one to the red LED chip, green LED chip and blue LED chip in the RGB LED chip group 2. At this time, a positive electrode pad 100 and a negative electrode pad 101 are arranged at intervals diagonally on each electrode pad area 10. The positive electrode pad 100 and the negative electrode pad 101 are both metal pads, and they are all connected to the driving circuit. The electrode pads on the three electrode pad areas 10 are connected in parallel to the driving circuit. Setting the positive electrode pad 100 and the negative electrode pad 101 diagonally makes the distance between the two electrode pads the longest, which can avoid the mutual conduction of the positive electrode and the negative electrode during packaging. The positive electrodes and negative electrodes of the three LED chips in the RGB LED chip group 2 are flip-chip soldered to the positive electrode pad 100 and the negative electrode pad 101 of the three electrode pad areas 10 correspondingly. The red LED chip, green LED chip and blue LED chip in the RGB LED chip group 2 use solder balls or copper pillar bumps as their positive electrodes and negative electrodes, and then are flip-chip soldered to the positive electrode pad 100 and the negative electrode pad 101 through their positive electrodes and negative electrodes. One LED chip corresponds to one electrode pad area for flip-chip soldering, which enables the LED chip and the driving chip to achieve direct electrical connection, reduces the wire resistance, and thus improves the light efficiency of the LED device. At this time, an isolation groove 102 for isolating the positive electrode pad 100 and the negative electrode pad 101 is arranged on each electrode pad area 10. The positive electrode pad 100 and the negative electrode pad 101 are on one diagonal line, and the isolation groove 102 is on the other diagonal line. The isolation groove 102 is used to separate the positive electrode pad 100 and the negative electrode pad 101.

[0022] Further improvement, such as Figure 1 and Figure 2As shown in the figure, a heat dissipation channel 40 for passing through a heat dissipation member 5 is provided on the encapsulation colloid layer 4. The inner diameter of the heat dissipation channel 40 is slightly larger than the outer diameter of the heat dissipation member 5, which avoids the formation of a wrinkled interface between the heat dissipation member 5 and the inner wall of the heat dissipation channel 40 due to thermal expansion of the material, thereby affecting heat transfer. At this time, when the outer edge of the elastic reinforcement member 3 is flush with the top edge of the driving chip substrate 1, the heat dissipation channel 40 is a vertical channel. When the elastic reinforcement member 3 does not completely cover the top surface of the driving chip substrate 1, that is, there is a certain distance between the outer edge of the elastic reinforcement member 3 and the top edge of the driving chip substrate 1, a part of the encapsulation colloid layer 4 covers the position of this interval distance. At this time, the heat dissipation channel 40 is correspondingly set to an inverted L-shaped structure, or the heat dissipation channel 40 is still set to a vertical channel, but the horizontal part of the heat dissipation member 5 is also press-fitted into the part of the encapsulation colloid layer 4 covering the top surface of the driving chip substrate 1. In order to further improve the heat dissipation efficiency, a filler 7 made of a thermal interface material is filled between the heat dissipation member 5 and the inner wall of the heat dissipation channel 40. For example, silver paste is used as the filler to seal between the heat dissipation member 5 and the heat dissipation channel 40 through the filler 7.

[0023] Further improvement, such as Figure 1 As shown in the figure, a heat diffusion layer 8 covering the bottom surface of the driving chip substrate 1 is provided around the connection end 6 on the bottom surface of the driving chip substrate 1. The heat diffusion layer 8 is made of graphene, copper-based composite material or metal-ceramic hybrid material, and is used to laterally and evenly disperse heat to avoid local heat accumulation.

[0024] Further improvement, such as Figure 1 As shown in the figure, a distributed Bragg reflector 20 is integrated on the bottom surface of the chips of the RGB LED chip group 2, that is, a distributed Bragg reflector 20 is provided on the bottom surface of each LED chip in the RGB LED chip group 2 to reduce light loss and reabsorption through it and improve the light extraction efficiency of the LED device. An antireflection film 21 with a thickness of 1 / 4 of the emission wavelength is plated on the chip surface of the RGB LED chip group 2, that is, an antireflection film 21 is electroplated on the surface of each LED chip in the RGB LED chip group 2. For different color LED chips, the thickness of the antireflection film 21 is 1 / 4 of the wavelength of the emitted color light, and it is used to reduce the reflected light and increase the light transmittance, thereby improving the imaging quality and clarity of the LED device.

[0025] Although the present invention has been described in detail with general descriptions and specific embodiments above, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of the present invention claimed.

Claims

1. An integrated LED device based on flip chip process, characterized in that: The invention comprises a driving chip substrate with a driving circuit on the top surface, an RGB LED chipset connected to the driving circuit being flip-chip welded on the top surface of the driving chip substrate, and an elastic reinforcing piece being arranged on the top surface of the driving chip substrate around the position where the RGB LED chipset is flip-chip welded; the driving chip substrate, the RGB LED chipset and the elastic reinforcing piece are encapsulated in an encapsulating colloid layer and the bottom surface of the driving chip substrate is exposed outside the encapsulating colloid layer, and the expansion coefficient of the elastic reinforcing piece is smaller than the expansion coefficient of the encapsulating colloid layer; a heat sink having an inverted L-shaped structure and penetrating through the elastic reinforcing piece and the encapsulating colloid layer and extending vertically downward to the bottom surface of the encapsulating colloid layer is connected to the RGB LED chipset; and a plurality of connection terminals are arranged on the bottom surface of the driving chip substrate.

2. The integrated LED device based on flip chip process according to claim 1, characterized in that: A plurality of square electrode pad areas are arranged at intervals on the top surface of the driving chip substrate, and a positive electrode pad and a negative electrode pad are arranged diagonally at intervals on each electrode pad area, and the positive electrode and the negative electrode of the RGB LED chipset are correspondingly flip-chip welded with the positive electrode pad and the negative electrode pad.

3. The integrated LED device based on flip chip process according to claim 1, characterized in that: An isolation groove for isolating a positive electrode pad from a negative electrode pad is disposed on each of the electrode pad regions.

4. The integrated LED device based on flip chip process according to claim 1, characterized in that: The connection terminal includes a power connection terminal electrically connected to the driving circuit for connecting to a power source and an information connection terminal for transmitting information.

5. The integrated LED device based on flip chip process according to claim 1, characterized in that: The packaging colloid layer is provided with a heat dissipation channel for penetrating a heat dissipation element.

6. The integrated LED device based on flip chip process according to claim 5, characterized in that: A filler made of a thermal interface material is filled between the heat sink and the inner wall of the heat dissipation channel.

7. The integrated LED device based on flip chip process according to claim 1, characterized in that: A heat diffusion layer covering the bottom surface of the driver chip substrate is arranged on the bottom surface of the driver chip substrate around the connection end.

8. The integrated LED device based on flip chip process according to claim 1, characterized in that: A distributed Bragg reflector is integrated on the bottom surface of the chip of the RGB LED chipset.

9. The integrated LED device based on flip chip process according to claim 1, characterized in that: The chip surface of the RGB LED chipset is coated with an anti-reflection film with a thickness of 1 / 4 of the emission wavelength.

10. The integrated LED device based on flip chip process according to claim 1, characterized in that: The elastic reinforcing piece is made of silica gel or polyimide material added with optical scattering particles, and the encapsulation colloid layer is made of silica gel or polyimide material.

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