Mini LED backlight device and preparation method thereof

Abstract

The application provides a Mini LED backlight device and a preparation method thereof, wherein the Mini LED backlight device comprises two mutually isolated rigid conductive substrate structures respectively welded with positive and negative electrodes of a Mini LED chip, and the spacing between the lower surfaces of the two rigid conductive substrate structures opposite to the electrodes of the Mini LED chip is greater than the spacing between the chip electrodes; high-reflection white glue is arranged around the Mini LED chip; and a lens is pressed above the Mini LED chip. Technical problems such as the fact that exposed copper in the existing Mini LED backlight device affects the lamp bead performance due to oxidation, and the fact that the cutting process causes great loss of blades are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a Mini LED backlight device and its fabrication method. Background Technology

[0002] An LED (Light Emitting Diode) is a solid-state semiconductor device that converts electrical energy into visible light. Its light-emitting principle is electroluminescence, where a forward current is applied to a PN junction, causing free electrons and holes to recombine and emit light, thus directly converting electrical energy into light energy. LEDs, especially white LEDs, are widely used as a new lighting source material. They have developed rapidly due to their advantages such as fast response, good shock resistance, long lifespan, energy saving, and environmental friendliness, and are now widely used in landscaping and indoor / outdoor lighting.

[0003] In LED packaging, the substrate typically uses copper supports as the circuitry. Multiple LED chips are placed on this substrate for packaging. After packaging, an abrasive wheel is used to cut and separate the chips to obtain the LED beads. During this process, the copper supports of each individual LED bead are connected, resulting in exposed copper on the sides of the supports after the individual LED beads are cut. Long-term exposure can affect the performance of the LED beads due to copper oxidation, and the cutting process also causes significant wear on the abrasive wheel. Summary of the Invention

[0004] To overcome the above shortcomings, this invention provides a Mini LED backlight device and its preparation method, which effectively solves the technical problems in existing Mini LED backlight devices, such as the oxidation of exposed copper affecting the performance of LED beads and the large wear on the cutting blade during the cutting process.

[0005] The technical solution provided by this invention is as follows:

[0006] This invention provides a Mini LED backlight device, comprising:

[0007] Two mutually isolated rigid conductive substrate structures are respectively welded to the positive and negative electrodes of the Mini LED chip, and the distance between the lower surfaces of the two rigid conductive substrate structures opposite to the Mini LED chip electrodes is greater than the distance between the chip electrodes.

[0008] High-reflectivity white adhesive surrounding the Mini LED chip; and

[0009] A lens pressed against the Mini LED chip.

[0010] The present invention also provides a method for fabricating a Mini LED backlight device, comprising:

[0011] A rigid conductive substrate is prepared on the surface of a rigid support substrate, and the distance between the lower surfaces of the two rigid conductive substrates opposite to the chip electrodes is greater than the distance between the chip electrodes.

[0012] Solder resist portions and solder portions are formed on the surface of each rigid conductive substrate, and the solder portions are located at the ends and are adapted to the positive and negative electrodes of the Mini LED;

[0013] The Mini LED chip is soldered to the solder joint of the rigid conductive substrate;

[0014] High-reflectivity white glue is placed around the Mini LED chip;

[0015] A lens is pressed on top of the Mini LED chip;

[0016] Remove the rigid support substrate and cut to obtain a single Mini LED backlight device.

[0017] The Mini LED backlight device and its fabrication method provided by this invention can bring at least the following beneficial effects:

[0018] 1. The rigid conductive substrates are independent of each other, and there is no exposure of the rigid conductive substrates. Therefore, there is no oxidation problem, and the cutting process will not cause significant wear to the blade (there is no connection between the rigid conductive substrates of different Mini LED chips). This saves consumables and costs while improving the service life of Mini LED backlight devices.

[0019] 2. The conductive substrate structure serves only as a support structure for the Mini LED chip, without any plastic or ceramic components, and can be reused, thereby reducing costs.

[0020] 3. By increasing the distance between the electrodes of the Mini LED chip through this rigid conductive substrate structure, subsequent applications are facilitated, the probability of chip welding problems caused by the small spacing between the Mini LED chip electrodes is reduced, thereby expanding the application of the chip. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the Mini LED backlight device structure in one embodiment of the present invention;

[0022] Figure 2 For the purposes of this invention Figure 1 The diagram shows the rigid conductive substrate structure in the Mini LED backlight device.

[0023] Figure 3 This is a schematic diagram of a rigid conductive substrate structure in another embodiment of the present invention;

[0024] Figure 4 For the purposes of this invention, such as Figure 4 A schematic diagram of a Mini LED backlight device structure on a rigid conductive substrate is shown.

[0025] Figures 5(a) to 5(j) This is a flowchart of a method for fabricating a Mini LED backlight device in an example of the present invention. Attached image description:

[0027] 11 / 26 - Mini LED chip, 12 - Rigid conductive substrate structure, 13 / 28 - High reflectivity white glue, 14 / 27 - Lens, 15 - Welding part, 16 - Solder resist part, 17 - Spacing extension part, 18 - Rigid conductive substrate, 21 - First conductive layer, 22 - Conductive connection layer, 23 - Second conductive layer, 24 / 25 - Insulating material. Detailed Implementation

[0028] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0029] like Figure 1 The figure shows a schematic diagram of an embodiment of the Mini LED backlight device provided by the present invention. As can be seen from the figure, the Mini LED backlight device includes: two mutually isolated rigid conductive substrate structures 12 respectively welded to the positive and negative electrodes of the Mini LED chip 11, and the distance between the lower surfaces of the two rigid conductive substrate structures opposite to the electrodes of the Mini LED chip is greater than the distance between the electrodes of the chip; a high reflectivity white adhesive 13 surrounding the Mini LED chip; and a lens 14 pressed on top of the Mini LED chip.

[0030] For Mini LED chips, the distance between the positive and negative electrodes is typically 100–200 μm. This small spacing presents challenges when soldering them onto the substrate for subsequent backlight applications. Therefore, in this embodiment, a rigid conductive substrate structure is used to widen the distance to 300–350 μm for easier application. Furthermore, currently, the copper in the copper supports of different LED chips is interconnected, resulting in exposed copper on the sides of the supports after cutting individual LED chips. This leads to copper oxidation affecting chip performance and significant wear on the cutting blade during the cutting process. The rigid conductive substrate structures used in this embodiment are independent, avoiding this exposure and minimizing wear on the cutting blade during the cutting process.

[0031] The Mini LED backlight device uses flip-chip Mini LEDs, and this embodiment only provides an exemplary structure of the Mini LED backlight device. In other embodiments, the device may include other structures, such as a phosphor layer disposed on the light-emitting side surface of the Mini LED chip, or other light-emitting structures designed to improve light output brightness. The high-reflectivity adhesive is silicone doped with light-reflecting particles (such as titanium dioxide) and has a reflectivity greater than 95%. It is placed around the Mini LED chip to reflect the light emitted from the surrounding area of ​​the chip back, thereby improving the light output efficiency of the chip.

[0032] like Figure 2 As shown, each rigid conductive substrate structure includes a rigid conductive substrate 18, a soldering portion 15, and a spacing extension portion 17. The soldering portion 15 is located on the upper surface of the rigid conductive substrate 18 and at one end, for soldering the Mini LED chip 11. The spacing extension portion is located on the lower surface of the rigid conductive substrate 18 at the end opposite to the soldering portion, formed on the body of the rigid conductive substrate 18, and filled with insulating material. In another embodiment, each rigid conductive substrate structure further includes a solder resist portion 16, which is the area on the upper surface of the rigid conductive substrate excluding the soldering portion, and is prepared by forming a solder resist material on the surface of the rigid conductive substrate.

[0033] In this rigid conductive substrate structure, the rigid conductive substrate (thickness 20–150 μm) can be selected according to requirements, preferably a copper sheet. The extension portion (thickness 2–10 μm) at the end of the rigid conductive substrate can be prepared by etching. Conventional insulating material can be filled into the etched extension portion; this insulating material can be selected according to the actual application, such as photoresist or polyimide. The extension portion and the soldering portion are located on different surfaces of the same side of the rigid conductive substrate. During the soldering process, the extension portions of the two rigid conductive substrates are positioned opposite each other. Solder paste is printed on the soldering portion, and the Mini LED chip is die-bonded to the solder paste surface for reflow soldering. This widens the spacing between the chip electrodes and increases the area of ​​the chip pads, facilitating subsequent backlight applications. The solder resist portion is prepared by printing a solder resist layer on the surface of the rigid conductive substrate, with a thickness of 10–50 μm.

[0034] In another embodiment, such as Figure 3 As shown, the rigid conductive substrate includes, from bottom to top, a first conductive layer 21, a second conductive layer 23, and at least one conductive connection layer 22 for connecting the first conductive layer and the second conductive layer. The end of the first conductive layer 21 includes a spacing portion, and the end of the second conductive layer corresponding to the first conductive layer includes a welding portion. Furthermore, in the rigid conductive substrate structure of the MiniLED backlight device, the spacing portion of the first conductive layer in the two rigid conductive substrates is filled with an insulating material 24, and the conductive connection layers are filled with an insulating material 25.

[0035] In this rigid conductive substrate structure, the rigid conductive substrate consists of three parts: a first conductive layer, a second conductive layer, and at least one conductive connecting layer for connecting the first and second conductive layers. The first conductive layer has a thickness of 2–10 μm, the connecting layer has a thickness of 10–30 μm, and the second conductive layer has a thickness of 20–100 μm. The Mini LED chip is fixed to the welding portion of the second conductive layer by soldering. The width of the insulating material between the two first conductive layers is the spacing, preferably 300–350 μm. Since the welding portion is located at the end of the second conductive layer, the spacing between the second conductive layers is adapted to the distance between the Mini LED chip electrodes, without specific limitations, ensuring that the chips can be soldered normally while remaining independent. The number (can be 1, 2, or even more), size, and other parameters of the electrode connecting layers between the first and second conductive layers can be set according to actual conditions, ensuring that the first and second conductive layers in the same rigid conductive substrate structure are connected together. The insulating material 24 filling the space between the extended portions of the first conductive layer and the insulating material 25 filling the space between each conductive connection layer can be selected according to the actual application, such as photoresist, polyimide, etc. To facilitate fabrication, other structures can be selectively added to this rigid conductive substrate structure, such as filling the space between each conductive connection layer with insulating material 25 and plating a palladium metal layer (thickness of 0.1-1 μm) on the surface where the second conductive layer is connected; or depositing tin on the surface of the second conductive layer and printing a solder resist layer on the tin surface, etc.

[0036] Similar to the previous embodiment, during the soldering process, solder paste is printed on the soldering portion of the second conductive layer. The Mini LED chip is then die-bonded onto the solder paste surface and reflow soldered to fix it in place. Next, high-reflectivity white adhesive 28 is applied around the Mini LED chip using a dispensing method. Finally, silicone is pressed directly above each Mini LED chip 26 to form a hemispherical lens 27 to increase the light emission angle. The final product is then cut to obtain the desired shape. Figure 4 The image shows a single Mini LED backlight device.

[0037] The present invention also provides a method for fabricating a Mini LED backlight device, comprising:

[0038] S10 prepares mutually isolated rigid conductive substrates on the surface of a rigid support substrate, and the distance between the lower surfaces of the two rigid conductive substrates for the same Mini LED chip that are opposite to the chip electrodes is greater than the distance between the chip electrodes.

[0039] S20 forms solder resist portions and solder portions on the surface of each rigid conductive substrate. The solder portions are located at the ends and are adapted to the positive and negative electrodes of the Mini LED. The solder resist portions are prepared by printing a solder resist layer on the surface of the rigid conductive substrate, with a thickness of 10–50 μm.

[0040] The S30 solders the Mini LED chip to the solder joint of a rigid conductive substrate;

[0041] S40 surrounds the Mini LED chip with a high-reflectivity white adhesive.

[0042] The S50 has a lens pressed on top of the Mini LED chip;

[0043] The S60 removes the rigid support substrate and cuts it to obtain a single Mini LED backlight device.

[0044] The Mini LED backlight device uses flip-chip Mini LEDs, and the fabrication method described herein is merely an illustrative example of the fabrication process. In other embodiments, the device may include other structures, such as a phosphor layer disposed on the light-emitting side surface of the Mini LED chip, or other light-emitting structures designed to enhance light output brightness. The high-reflectivity adhesive is silicone doped with light-reflective particles (such as titanium dioxide), with a reflectivity greater than 95%. It is placed around the Mini LED chip to reflect light emitted from the chip's periphery back, improving the chip's light output efficiency. The supporting substrate can be selected according to the actual application, such as steel sheets.

[0045] In one embodiment, step S10, which involves fabricating mutually isolated rigid conductive substrates on the surface of a rigid support substrate, includes:

[0046] S11 forms an extended spacing portion on one end of a rigid conductive substrate;

[0047] S12 attaches a first insulating layer to the surface of a rigid support substrate;

[0048] S13 fixes the rigid conductive substrate with the extended spacing portion to the surface of the first insulating layer and the rigid support substrate, wherein the first insulating layer matches the extended spacing portion on the rigid conductive substrate, the extended spacing portion is filled by the first insulating layer, and the two rigid conductive substrates for the same Mini LED chip are symmetrically fixed on both sides of the first insulating layer.

[0049] In the rigid conductive substrate structure of this embodiment, the rigid conductive substrate (thickness 20-150 μm) can be selected according to the requirements of the substrate, preferably a copper sheet. The extension portion (thickness 2-10 μm) at the end of the rigid conductive substrate can be prepared by etching. The etched extension portion is filled with a conventional insulating material, which can be selected according to the actual application, such as photoresist, polyimide, etc. After the extension portion is formed, the rigid conductive substrate is fixed to the support substrate according to the formed first insulating layer; then, a solder resist layer is printed on the surface of the second conductive layer to form a solder joint and a solder resist layer. Then, solder paste is printed on the solder joint, and the Mini LED chip is die-bonded to the solder paste surface for reflow soldering. The extension portion and the solder joint are set on different surfaces on the same side of the rigid conductive substrate. During the soldering process, the extension portions of the two rigid conductive substrates are arranged opposite each other, thereby widening the distance between the chip electrodes and increasing the area of ​​the chip pads, which is convenient for subsequent backlight applications. The solder resist layer is prepared by printing a solder resist layer on the surface of a rigid conductive substrate, with a thickness of 10–50 μm.

[0050] In another embodiment, step S10, which involves fabricating mutually isolated rigid conductive substrates on the surface of a rigid support substrate, includes:

[0051] S14 attaches a first insulating layer to the surface of a rigid support substrate. This rigid conductive substrate (thickness 20-150 μm) can be selected as needed, preferably a copper sheet.

[0052] S15 forms a first conductive layer on the surface of a rigid support substrate, with the same height as the first insulating layer. The thickness of the first conductive layer is 2–10 μm, and it is preferably a copper layer.

[0053] S16 forms a second insulating layer on the surfaces of the first conductive layer and the first insulating layer, the second insulating layer at least covering the first insulating layer. The insulating materials used for both the first and second insulating layers can be selected according to the actual application, such as photoresist or polyimide. The thickness of the second insulating layer is 10–30 μm.

[0054] S17 forms a conductive connection layer on the surface of the first conductive layer with the same height as the second insulating layer. The function of this conductive connection layer is to connect the first conductive layer and the second conductive layer; its quantity and size can be set according to actual conditions.

[0055] In step S18, a second conductive layer is formed on the surface of the conductive connection layer, which is separated from each other. The second conductive layer at least covers the conductive connection layer, and the spacing between the two second conductive layers for the same Mini LED chip is adapted to the positive and negative electrodes of the Mini LED chip and is smaller than the spacing between the corresponding first conductive layers. The thickness of the second conductive layer is 20-100 μm, and it is preferably a copper layer.

[0056] In addition, to improve the adhesion between materials, after forming a conductive connection layer with the same height as the second insulating layer on the surface of the first conductive layer, the method further includes forming a palladium metal layer with a thickness of 0.1 to 1 μm on the formation area of ​​the second conductive layer.

[0057] In one example, taking a steel sheet as the rigid support substrate and a copper sheet as the rigid conductive substrate, the fabrication process of a Mini LED backlight device is explained:

[0058] A release layer 32 is attached to the surface of the steel sheet 31, as shown in Figure 5(a);

[0059] The edge release layer is removed by photolithography, leaving the first insulating layer 33 formed by photoresist, as shown in Figure 5(b);

[0060] In the area of ​​the steel sheet 31 excluding the first insulating layer 33, an Ag layer with a thickness of 1 to 2 μm, a Ni layer with a thickness of 2 to 5 μm, and a Cu layer with a thickness of 2 to 10 μm are electroplated sequentially to form the first conductive layer 34, as shown in Figure 5(c).

[0061] A polyimide layer is coated on the surface of the first insulating layer 33 and the first conductive layer 34, and a second insulating layer 35 with a thickness of 10 to 30 μm is left after photolithography and development, as shown in Figure 5(d); the second insulating layer 35 at least covers the first insulating layer 33, and the surface area of ​​the first conductive layer is reserved for subsequent preparation of the conductive connection layer.

[0062] A Cu layer with the same height as the second insulating layer 35 is electroplated in the reserved area to form a conductive connection layer 36 with a thickness of 10-30 μm, as shown in Figure 5(e).

[0063] A palladium layer with a thickness of 0.1–1 μm is deposited on the surface of the second insulating layer and the second conductive layer (chemical plating method); and a copper layer with a thickness of 0.1–1 μm is deposited on the entire surface of the palladium layer (chemical plating method), as shown in Figure 5(f) (palladium and copper are indicated by the symbol 37);

[0064] Metal Cu was electroplated on the surface of the copper metal and photolithography was performed according to the distance between the electrodes of the Mini LED chip to form a second conductive layer 38 with a thickness of 20-100 μm, as shown in Figure 5(g).

[0065] Tin 39 is deposited on the surface of the second conductive layer, as shown in Figure 5(h);

[0066] A solder resist layer 40 with a thickness of 10 to 50 μm is printed on the surface of the tin layer to form a solder resist part and a solder part, as shown in Figure 5(i);

[0067] Solder paste is printed on the soldering part of the second conductive layer. The Mini LED chip 41 is then die-bonded to the solder paste surface and reflow soldered to fix it, as shown in Figure 5(j). Next, high-reflectivity white glue is applied around the Mini LED chip using a dispensing method. Finally, silicone is pressed directly above each Mini LED chip 41 to form a hemispherical lens. The lens is then cut to obtain the desired shape. Figure 4 The image shows a single Mini LED backlight device.

[0068] It should be noted that the above embodiments can be freely combined as needed. The above description is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a Mini LED backlight device, characterized in that, The method comprises the following steps: Preparation of mutually isolated rigid conductive substrates on the surface of a rigid support substrate, and the distance between the lower surfaces of the two rigid conductive substrates opposite to the electrodes of the same Mini LED chip is greater than the distance between the electrodes of the chip; Forming a soldering part on the surface of each rigid conductive substrate, and the soldering part is located at the end part and is adapted to the positive and negative electrodes of the Mini LED; Soldering the Mini LED chip to the soldering part of the rigid conductive substrate; Surrounding the Mini LED chip with high reflectivity white glue, and the high reflectivity white glue covers the side wall of the rigid conductive substrate at the same time; Pressing a lens above the Mini LED chip; Removing the rigid support substrate to obtain a single Mini LED backlight device by cutting; Cutting along the high reflectivity white glue between the rigid conductive substrates.

2. The method of claim 1, wherein the Mini LED backlight device is prepared by a process comprising: The preparation of mutually isolated rigid conductive substrates on the surface of a rigid support substrate comprises the following steps: ​ Forming a distance-expanding part on one side end part of the rigid conductive substrate; Attaching a first insulating layer on the surface of the rigid support substrate; Fixing the rigid conductive substrate with the distance-expanding part formed thereon to the first insulating layer and the surface of the rigid support substrate, wherein The first insulating layer matches the distance-expanding part on the rigid conductive substrate, fills the distance-expanding part through the first insulating layer, and is fixed to the two sides of the first insulating layer symmetrically for the two rigid conductive substrates of the same Mini LED chip.

3. The method of claim 2, wherein the Mini LED backlight device is prepared by a process comprising: providing a plurality of Mini LEDs on a substrate; providing a plurality of micro LEDs on the substrate; and providing a plurality of micro LED drivers on the substrate. The forming of a distance-expanding part on one side end part of the rigid conductive substrate comprises the following steps:

4. The method for fabricating a Mini LED backlight device as described in claim 1, characterized in that, Forming the distance-expanding part on one side end part of the rigid conductive substrate by etching. The preparation of mutually isolated rigid conductive substrates on the surface of a rigid support substrate comprises the following steps: Attaching a first insulating layer on the surface of the rigid support substrate; Forming a first conductive layer with the same height as the first insulating layer on the surface of the rigid support substrate; Forming a second insulating layer on the surface of the first conductive layer and the first insulating layer, and the second insulating layer covers at least the first insulating layer; Forming a conductive connecting layer with the same height as the second insulating layer on the surface of the first conductive layer; 5. The method for fabricating a Mini LED backlight device as described in claim 4, characterized in that, Forming mutually separated second conductive layers on the surface of the conductive connecting layer, and the second conductive layers cover at least the conductive connecting layer, and the distance between the two second conductive layers for the same Mini LED chip is adapted to the positive and negative electrodes of the Mini LED chip and is smaller than the distance between the corresponding first conductive layers.

6. A Mini LED backlight device, characterized in that, After forming the conductive connecting layer with the same height as the second insulating layer on the surface of the first conductive layer, the method further comprises the following step: Forming a palladium metal layer on the formation area of the second conductive layer. The method comprises the following steps: Two mutually isolated rigid conductive substrate structures respectively soldered to the positive and negative electrodes of the Mini LED chip, and the distance between the lower surfaces of the two rigid conductive substrate structures opposite to the electrodes of the Mini LED chip is greater than the distance between the electrodes of the chip; High reflectivity white glue surrounding the Mini LED chip, and the high reflectivity white glue covers the side wall of the rigid conductive substrate at the same time; And A lens pressed above the Mini LED chip.

7. The Mini LED backlight device of claim 6, wherein, Each of the rigid conductive substrate structures comprises a rigid conductive substrate, a soldering portion and a spacing portion, wherein the soldering portion is located on the upper surface of the rigid conductive substrate and at one end portion for soldering the Mini LED chip; the spacing portion is located on the lower surface of the rigid conductive substrate opposite to the soldering portion and is formed on the body of the rigid conductive substrate and filled with insulating material.

8. The Mini LED backlight device of claim 7, wherein, Each of the rigid conductive substrate structures further comprises a solder mask portion, which is the area of the upper surface of the rigid conductive substrate except the soldering portion and is prepared by forming a solder mask material on the surface of the rigid conductive substrate.

9. The Mini LED backlight device of claim 7 or 8, wherein, The rigid conductive substrate comprises a first conductive layer, a second conductive layer and at least one conductive connection layer for connecting the first conductive layer and the second conductive layer from bottom to top, wherein the end portion of the first conductive layer comprises a spacing portion, the corresponding end portion of the second conductive layer surface comprises a soldering portion; and the spacing portions of the first conductive layers of the rigid conductive substrates of the two rigid conductive substrate structures of the Mini LED backlight device are filled with insulating material, and the conductive connection layers are filled with insulating material.

10. The Mini LED backlight device of claim 9, wherein, The surface of the insulating material filled between the conductive connection layers and the second conductive layer is further plated with a palladium metal layer.

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