A novel LED chip packaging structure and its preparation method

Abstract

The present invention provides a novel LED chip packaging structure and a preparation method thereof, which includes a substrate, a dam, an LED chip, a diffusion powder adhesive layer, a phosphor adhesive layer, a white silica gel layer and a transparent silica gel layer. The dam is formed around the outer periphery of the substrate to form a packaging cavity. A raised step is integrally formed on the substrate, and the LED chip is installed on the raised step. The LED chip is electrically connected to the positive and negative electrodes of the substrate through wires respectively. The upper surfaces of the substrate and the LED chip are covered with the diffusion powder adhesive layer, and the upper surface of the diffusion powder adhesive layer is covered with the phosphor adhesive layer. The white silica gel layer is filled in the packaging cavity and is flush with the phosphor adhesive layer above the LED chip. The transparent silica gel layer is filled in the packaging cavity and is flush with the top surface of the dam. The present invention solves the problems of uneven distribution of phosphor, uneven light emission of the LED chip, and structural defects of the package, meeting the requirements of people for high consistency of light-emitting diodes.

Description

Technical Field

[0001] The present invention belongs to the technical field of LED packaging, and particularly relates to a novel LED chip packaging structure and a preparation method thereof. Background Art

[0002] With the wide application of light-emitting diodes in life, people's requirements for light-emitting diodes are not limited to simple requirements such as high brightness and low power consumption. Instead, higher requirements are gradually put forward for the quality of light-emitting diodes, especially for the consistency requirements of white light.

[0003] However, traditional light-emitting diodes usually use a simple mixture of blue chips and phosphors to excite white light. Due to the limitations of process conditions, the following technical defects exist:

[0004] (1) The phosphor cannot be evenly distributed on the blue chip;

[0005] (2) The blue chip itself has uneven light emission due to the shielding of the electrodes;

[0006] (3) The blue light emits from the side of the chip and cannot evenly excite the phosphor;

[0007] The above technical defects result in uneven white light generated by the excitation of the phosphor by blue light at various positions of the blue chip. In addition, defects in the structural design of the package cause the white light emitted by the blue chip to be easily dispersed when passing through these areas, separating the white light into blue and yellow spectra. Therefore, it is difficult to obtain a high-quality homogeneous white light source. Summary of the Invention

[0008] The purpose of the present invention is to provide a novel LED chip packaging structure and a preparation method thereof, which solve the problems of uneven phosphor distribution, uneven light emission of the LED chip, and structural defects of the package, and meet people's requirements for high consistency of light-emitting diodes.

[0009] The specific technical solution of the present invention is as follows:

[0010] A novel LED chip packaging structure includes a substrate, a dam, an LED chip, a diffusion powder glue layer, a phosphor glue layer, a white silica gel layer, and a transparent silica gel layer. The dam is formed around the outer periphery of the substrate to form a packaging cavity. A raised step is integrally formed on the substrate, and the LED chip is mounted on the raised step. The positive and negative electrode solder pads of the LED chip are electrically connected to the positive and negative electrodes of the substrate through wires respectively. The upper surfaces of the substrate and the LED chip are covered with a diffusion powder glue layer, and the upper surface of the diffusion powder glue layer is covered with a phosphor glue layer. The white silica gel layer is filled in the packaging cavity and is flush with the phosphor glue layer above the LED chip. The transparent silica gel layer is filled in the packaging cavity and is flush with the top surface of the dam.

[0011] Preferably, the inner side surface of the dam is a segmented inclined surface structure, including a first inclined surface segment and a second inclined surface segment. The bottom of the first inclined surface segment is connected to the substrate, one side of the second inclined surface segment is connected to the upper surface of the dam 2, and the other side is connected to the first inclined surface segment.

[0012] Preferably, the inclination angle α between the first inclined surface segment and the horizontal plane ranges from 90 < α ≤ 130°.

[0013] Preferably, the inclination angle β between the second inclined surface segment and the horizontal plane ranges from 130 < β < 180°, and the inclination angle β of the inclined surface of the second inclined surface segment is the same as the light-emitting angle of the LED chip.

[0014] Preferably, the substrate includes a positive metal plate and a negative metal plate, and an insulating groove is provided between the positive metal plate and the negative metal plate.

[0015] Preferably, the height of the dam is 0.1 - 2 mm.

[0016] Preferably, the inclined surface length of the second inclined surface segment is 0.05 - 0.3 mm.

[0017] Preferably, the thickness ranges of both the diffusion powder glue layer and the phosphor powder glue layer are 0.01 - 0.15 mm.

[0018] A preparation method for a novel LED chip packaging structure, characterized in that the specific preparation steps of the LED chip packaging structure according to any one of claims 1 - 8 are as follows:

[0019] S1: By means of stamping or etching, a raised step is formed on the substrate.

[0020] S2: An injection molding dam is formed around the substrate to form a packaging cavity, and the inner side wall of the dam is a segmented inclined surface structure.

[0021] S3: The LED chip is fixed on the raised step by using die bonding glue. Among them, the side surface of the LED chip is flush with the side surface of the raised step, and the positive and negative pads of the LED chip are respectively connected to the positive and negative poles of the substrate 1 by using wires.

[0022] S4: The diffusion powder, silica gel, and silica gel solvent are mixed in proportion, and the mixed diffusion powder silica gel solution is sprayed into the packaging cavity to cover the substrate at the bottom of the packaging cavity and the upper surface of the LED chip, and then baked in an oven until the silica gel solvent volatilizes. After the silica gel is cured, the diffusion powder is evenly glued on the LED chip and the upper surface of the substrate to form a diffusion powder glue layer.

[0023] S5: Mix the phosphor, silica gel, and silica gel solvent in proportion, and evenly spray the mixed phosphor silica gel solution on the surface of the diffusing powder gel layer, and bake until the silica gel solvent volatilizes. After the silica gel cures, the phosphor is evenly glued on the upper surface of the diffusing powder gel layer to form a phosphor gel layer.

[0024] S6: Fill the opaque white silica gel on the phosphor gel layer at the bottom and make its liquid level flush with the phosphor gel layer above the LED chip. After baking and curing, a white silica gel layer is formed.

[0025] S7: Fill the transparent silica gel in the encapsulation cavity, covering the white silica gel layer and the phosphor gel layer above the LED chip, and make its liquid level flush with the upper surface of the dam. Then, use an oven to bake and cure to form a transparent silica gel layer, that is, a complete LED chip encapsulation structure is formed.

[0026] Preferably, in the said S4, the diffusing powder silica gel solution is prepared by mixing diffusing powder, silica gel, and silica gel solvent in a weight ratio of 1:0.1:0.2; in the said S5, the phosphor silica gel solution is prepared by mixing phosphor, silica gel, and silica gel solvent in a weight ratio of 1:0.1:0.2.

[0027] Beneficial effects: The present invention discloses a novel LED chip encapsulation structure and its preparation method, having the following advantages:

[0028] (1) In the present invention, a raised step is provided in the encapsulation cavity, and the LED chip is placed on the raised step, making the LED chip closer to the surface and having a higher luminous flux.

[0029] (2) In the present invention, diffusing powder is coated on the surface of the LED chip, making the blue light more evenly scattered before exciting the phosphor. In addition, spraying diffusing powder between the phosphor and the blue light chip can prevent the phosphor from directly contacting the high-temperature blue light chip, making the phosphor less susceptible to hydrolysis by hot water and having a longer service life.

[0030] (3) In the present invention, white silica gel is used to cover the space around the LED chip, which can not only reduce the light emitted from the side of the LED chip and the unevenly distributed phosphor due to the height difference, but also protect the light-emitting diode, so that even if the bottom of the package is affected by moisture or oxidation and discolors, it does not affect the white light efficiency.

[0031] (4) The edge of the package in the present invention adopts a ramp design (i.e., the second inclined plane section), and the ramp angle is parallel to the light-emitting angle of the blue light chip, always avoiding the phenomenon of chromatic dispersion and improving the white light uniformity. Description of the Drawings

[0032] Figure 1 It is a cross-sectional schematic diagram before the substrate is stamped / etched in step S1 of Embodiment 1.

[0033] Figure 2 Schematic cross-sectional view after substrate stamping / etching in step S1 of Example 1;

[0034] Figure 3 Front schematic view of step S2 in Example 1;

[0035] Figure 4 Schematic cross-sectional view of step S2 in Example 1;

[0036] Figure 5 Front schematic view of step S3 in Example 1;

[0037] Figure 6 Schematic cross-sectional view of step S3 in Example 1;

[0038] Figure 7 Schematic cross-sectional view of step S4 in Example 1;

[0039] Figure 8 Schematic cross-sectional view of step S5 in Example 1;

[0040] Figure 9 Schematic cross-sectional view of step S6 in Example 1;

[0041] Figure 10 Schematic cross-sectional view of step S7 in Example 1;

[0042] Figure 11 Schematic diagram of the light emission path of a conventional LED chip packaging structure;

[0043] Figure 12 Schematic diagram of the light emission path of the LED chip packaging structure of Example 1;

[0044] Figure 13 Schematic diagram of the color temperature of a conventional LED chip packaging structure;

[0045] Figure 14 Schematic diagram of the color temperature of the LED chip packaging structure of Example 1;

[0046] Figure 15 Actual light emission diagram of a conventional LED chip packaging structure;

[0047] Figure 16 Actual light emission diagram of the LED chip packaging structure of Example 1;

[0048] In the figure: substrate 1, positive metal plate 1-1, negative metal plate 1-2, raised step 1-3, insulating groove 1-4, dam 2, first inclined surface section 2-1, second inclined surface section 2-2, LED chip 3, diffusion powder adhesive layer 4, phosphor adhesive layer 5, white silica gel layer 6, transparent silica gel layer 7, packaging cavity 8, wire 9. Detailed Implementation Modes

[0049] The following makes several improvements and refinements to the present invention in conjunction with the accompanying drawings, and these improvements and refinements should also be regarded as within the protection scope of the present invention.

[0050] Embodiment 1

[0051] A novel LED chip packaging structure, characterized in that it includes a substrate 1, a dam 2, an LED chip 3, a diffusion powder glue layer 4, a phosphor glue layer 5, a white silica gel layer 6 and a transparent silica gel layer 7;

[0052] The substrate 1 in this Embodiment 1 is a metal plate, preferably a copper alloy plate, including a positive metal plate 1-1 and a negative metal plate 1-2, and an insulating groove 1-4 is provided between the positive metal plate 1-1 and the negative metal plate 1-2;

[0053] The dam 2 is formed around the outer periphery of the substrate 1 to form a packaging cavity 8, and the height of the dam is 0.4 mm. The inner side surface of the dam 2 is a segmented inclined surface structure, including a first inclined surface segment 2-1 and a second inclined surface segment 2-2. The bottom of the first inclined surface segment 2-1 is connected to the substrate 1, and the top of the second inclined surface segment 2-2 is flush with the top surface of the dam 2; the inclination angle α of the first inclined surface segment 2-1 with the horizontal plane is 114°, the inclination angle β of the second inclined surface segment 2-2 with the horizontal plane is 150°, and the inclination angle β of the inclined surface of the second inclined surface segment 2-2 is the same as the light-emitting angle of the LED chip 3, and the inclined surface length of the second inclined surface segment is 0.2 mm.

[0054] A raised step 1-3 is integrally formed on the positive metal plate 1-1, and the raised step 1-3 is located at the center of the packaging cavity 8. The top surface size of the raised step 1-3 is the same as the bottom surface size of the LED chip 3. The LED chip 3 is arranged on the raised step 1-3. The positive and negative solder plates of the LED chip 3 are respectively connected to the positive metal plate 1-1 and the negative metal plate 1-2 through wires 9. The upper surfaces of the substrate 1 and the LED chip 3 are covered with a diffusion powder glue layer 4, the upper surface of the diffusion powder glue layer 4 is covered with a phosphor glue layer 5, the white silica gel layer 6 is filled in the packaging cavity 8 and is flush with the phosphor glue layer 5 above the LED chip 3, the transparent silica gel layer 7 is filled in the packaging cavity 8 for covering the white silica gel layer 6 and the phosphor glue layer 5 above the LED chip 3, and the transparent silica gel layer 7 is flush with the top surface of the dam 2.

[0055] The specific preparation steps of Embodiment 1 are as follows:

[0056] S1: As Figure 1The figure shows a cross-sectional schematic diagram before stamping / etching the substrate. Subsequently, a raised step 1-3 is formed on the positive metal plate 1-1 in the substrate 1 by means of stamping or chemical agent etching. The top surface size of the raised step 1-3 is the same as the bottom surface size of the LED chip 3. The depth of stamping or chemical agent etching is 1 / 2 of the thickness of the positive metal plate 1-1. At this time, the raised step 1-3 is located on the positive metal plate 1-1, as Figure 2 shown.

[0057] S2: Inject and mold the dam 2 around the substrate 1 to form the encapsulation cavity 8. The height of the dam is 0.4 mm. The inner side wall of the dam is a segmented inclined surface structure, including the first inclined surface segment 2-1 and the second inclined surface segment 2-2. Among them, the inclination angle α of the first inclined surface segment 2-1 with the horizontal plane is 114°. Then, an edge slope is designed at a place near the upper surface of the first inclined surface segment 2-1, that is, the second inclined surface segment 2-2. One side of the second inclined surface segment 2-2 is connected to the upper surface of the dam 2, and the other side is connected to the first inclined surface segment 2-1. The best inclined surface length of the second inclined surface segment 2-2 is 0.2 m. The inclination angle β of the second inclined surface segment 2-2 needs to be greater than the inclination angle α of the first inclined surface segment 2-1. The inclination angle β in Embodiment 1 is 150°, so that the dam of the encapsulation body has a gentle transition and is not prone to sharp corners, avoiding the phenomenon of light dispersion caused by the light emitted by the LED chip, as Figure 3 and 4 shown. In this embodiment, the injection molding material of the dam can be made of materials such as PCT, PPA, and EMC.

[0058] S3: Fix the LED chip 3 on the raised step 1-3 with die bonding glue. The side surface of the LED chip 3 is flush with the side surface of the raised step 1-3, and use the wire 9 to connect the positive and negative pads of the LED chip 3 to the positive metal plate 1-1 and the negative metal plate 1-2 of the substrate 1 respectively, as Figure 5 and 6 shown.

[0059] S4: Mix the diffusion powder, silica gel, and silica gel solvent in a certain proportion (weight ratio 1:0.1:0.2). In this Embodiment 1, the diffusion powder is preferably calcium carbonate, and the solvent is preferably ethyl acetate. Spray the mixed diffusion powder silica gel solution inside the encapsulation cavity 8 so that it covers the substrate 1 at the bottom of the encapsulation cavity and the upper surface of the LED chip 3, and use an oven to bake until the silica gel solvent volatilizes. After the silica gel solidifies, the diffusion powder is evenly glued on the upper surface of the LED chip 3 and the substrate 1 to form a diffusion powder glue layer 4. The thickness of the diffusion powder glue layer 4 is preferably 0.05 mm, as Figure 7 shown.

[0060] S5: Mix the phosphor, silica gel, and silica gel solvent in a certain ratio (by weight, 1:0.1:0.2 respectively). The silica gel solvent is preferably ethyl acetate. Spray the mixed solvent evenly on the surface of the diffusion powder glue layer 4, and bake until the silica gel solvent volatilizes. After the silica gel cures, the phosphor is evenly glued on the surface of the diffusion powder glue layer 4 to form a phosphor glue layer 5. The thickness of the phosphor glue layer is preferably 0.05 mm, as Figure 8 shown.

[0061] S6: Since the side surfaces of the raised steps 1-3 and the LED chip 3 are vertical, it is difficult for the diffusion powder glue layer 4 and the phosphor glue layer 5 to evenly wrap them, resulting in uneven light emitted from the side of the LED chip 3. Therefore, opaque white silica gel is filled on the bottom phosphor glue layer 5, and its liquid level is flush with the phosphor glue layer 5 above the LED chip 3 to block the light emitted from the side of the LED chip 3, and then baked and cured in an oven to form a white silica gel layer 6, as Figure 9 shown.

[0062] S7: Fill the encapsulation cavity 8 with transparent silica gel to cover the white silica gel layer 6 and also cover the LED chip 3 covered with the diffusion powder glue layer 4 and the phosphor glue layer 5, and make its liquid level flush with the upper surface of the dam 2. Then, bake and cure it in an oven to form a transparent silica gel layer 7, as Figure 10 shown. After testing this final product, a new type of light-emitting diode is formed.

[0063] In the present invention, the size of the dam 2 can be adjusted according to actual production requirements.

[0064] In this Example 1, the LED chip is a blue light chip.

[0065] The specific structure of a conventional LED chip is as Figure 11 shown: It includes a substrate 1, a dam 2, an LED chip 3, and a phosphor glue layer 4. Among them, the LED chip 3 is arranged at the center of the substrate, and the positive and negative electrode pads of the LED chip 3 are connected to the positive and negative electrodes of the substrate 1 through wires. The dam 2 is arranged along the outer periphery of the substrate 1 to form an encapsulation cavity, and the inner side wall of the dam is a reflective inclined surface. The phosphor glue layer 4 is filled in the encapsulation cavity until it is flush with the top surface of the dam.

[0066] Compare the LED chip encapsulation structure of Example 1 with the conventional LED chip encapsulation structure (both use the same LED chip) as follows:

[0067] (1) Comparison of light emission paths

[0068] As Figure 11 is a schematic diagram of the light emission path of the conventional LED chip encapsulation structure, where L 1is the emission path of normal light, L 2 is the emission path of the light with dispersion occurred from the normal light. This is because there are sharp corners at the top of the dam of the package, causing the light to disperse when passing through the top of the dam of the package. L 3 is the emission path of the uneven light on the side. This is because the phosphor distribution on the side of the chip is uneven, and the light emission is uneven due to the reflection of the inner side of the dam by the reflecting slope.

[0069] As Figure 12 shown, it is a schematic diagram of the light emission path of the LED chip package structure of Embodiment 1. Among them, L 1 is the emission path of normal light, L 4 is the emission path of the uneven light on the side. It can be seen from the figure that the uneven light on the side passes through the white silicone layer and the transparent silicone layer, which can further weaken the light, thereby reducing the color difference caused by the uneven light on the side of the chip. Since the edge slope design (i.e., the second inclined plane section) is performed on the dam in this embodiment, the outer frame of the package is smoothly transitioned, and sharp corners are not easily formed, avoiding the dispersion phenomenon of light when passing through the top of the dam. At the same time, in this Embodiment 1, through the design of the convex steps 1-3, the height of the LED chip 3 is raised, so that the light-emitting surface of the LED chip is lifted upward, making the emitted light less likely to pass through the corner. In addition, the convex steps 1-3 in this Embodiment 1 can not only increase the height of the side of the LED chip 3, facilitating the spraying and filling operations of the diffusion powder glue layer 4, the phosphor glue layer 5, and the white silicone layer, but also raise the LED chip 3 to make it closer to the surface of the package, so that the light emitted by the LED chip 3 is more likely to be emitted, that is, the total luminous flux of the entire LED chip 3 is higher.

[0070] (2) Color difference comparison

[0071] Under the fixed field of view angle FOV (75°), the color temperature of the conventional LED chip package structure and the LED chip package structure of Embodiment 1 are detected respectively. As Figure 13 shown, it is a schematic diagram of the color temperature of the conventional LED chip package structure. It can be seen from the figure that under the fixed field of view angle FOV (75°), the maximum color temperature difference between the four corners and the center of the conventional LED chip package structure is 490K, and the minimum is 310K. As Figure 14As shown, it is the color temperature schematic diagram of the LED chip packaging structure of Embodiment 1. It can be seen from the figure that at a fixed field of view (FOV) angle (75°), the maximum color temperature difference between the four corners and the center of the LED chip packaging structure of Embodiment 1 is 70K, and the minimum is only 14K. Thus, it can be obtained that the color temperature difference of the package obtained by using the preparation method of the LED chip packaging structure of the present invention is much smaller than that of the conventional LED chip packaging structure.

[0072] (3) Comparison of actual light emission diagrams

[0073] As Figure 15 shown, it is the actual light emission photo of the conventional LED chip packaging structure. The light emitted by the LED chip in the figure has a blurred edge, serious dispersion, and uneven light emission color. Under the same test environment, the actual light emission diagram of the LED chip packaging structure of Embodiment 1 is as Figure 16 shown. The light it emits has a uniform color and a clear edge without dispersion.

[0074] The above description is only an illustration of the present invention and is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the premise of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A novel LED chip packaging structure, characterized in that, It includes a substrate, a dam, an LED chip, a diffusing powder glue layer, a phosphor glue layer, a white silica gel layer and a transparent silica gel layer. The dam is formed around the outer periphery of the substrate to form a packaging cavity. A raised step is integrally formed on the substrate. The LED chip is mounted on the raised step. The positive and negative electrode pads of the LED chip are electrically connected to the positive and negative electrodes of the substrate through wires respectively. The upper surfaces of the substrate and the LED chip are covered with a diffusing powder glue layer. The upper surface of the diffusing powder glue layer is covered with a phosphor glue layer. The white silica gel layer is filled in the packaging cavity and is flush with the phosphor glue layer above the LED chip. The transparent silica gel layer is filled in the packaging cavity and is flush with the top surface of the dam; The inner side surface of the dam is a segmented inclined surface structure, including a first inclined surface segment and a second inclined surface segment. The bottom of the first inclined surface segment is connected to the substrate. One side of the second inclined surface segment is connected to the upper surface of the dam, and the other side is connected to the first inclined surface segment; The inclination angle α of the first inclined surface segment with respect to the horizontal plane ranges from 90 < α ≤ 130°; The inclination angle β of the second inclined surface segment with respect to the horizontal plane ranges from 130 < β < 180°, and the inclination angle β of the inclined surface of the second inclined surface segment is the same as the light emitting angle of the LED chip.

2. The novel LED chip packaging structure according to claim 1, characterized in that, The substrate includes a positive electrode metal plate and a negative electrode metal plate, and an insulating groove is provided between the positive electrode metal plate and the negative electrode metal plate.

3. The novel LED chip packaging structure according to claim 1, wherein The height of the dam is 0.1 - 2 mm.

4. The novel LED chip packaging structure according to claim 1, characterized in that, The inclined surface length of the second inclined surface segment is 0.05 - 0.3 mm.

5. The novel LED chip packaging structure according to claim 1, characterized in that, The thickness ranges of both the diffusing powder glue layer and the phosphor glue layer are 0.01 - 0.15 mm.

6. A preparation method of a novel LED chip packaging structure, characterized in that, The specific preparation steps of the LED chip packaging structure according to any one of claims 1 - 5 are as follows: S1: By means of stamping or etching, a raised step is formed on the substrate; S2: The dam is injection - molded around the substrate to form a packaging cavity, and the inner side wall of the dam is a segmented inclined surface structure; S3: The LED chip is fixed on the raised step using die - bonding glue. Among them, the side surface of the LED chip is flush with the side surface of the raised step, and the positive and negative electrode pads of the LED chip are respectively connected to the positive and negative electrodes of the substrate using wires; S4: The diffusing powder, silica gel and silica gel solvent are mixed in proportion, and the mixed diffusing powder silica gel solution is sprayed in the packaging cavity to cover the substrate at the bottom of the packaging cavity and the upper surface of the LED chip, and then baked in an oven until the silica gel solvent volatilizes. After the silica gel is cured, the diffusing powder is uniformly glued on the LED chip and the upper surface of the substrate to form a diffusing powder glue layer; S5: The phosphor, silica gel and silica gel solvent are mixed in proportion, and the mixed phosphor silica gel solution is uniformly sprayed on the surface of the diffusing powder glue layer, and then baked until the silica gel solvent volatilizes. After the silica gel is cured, the phosphor is uniformly glued on the upper surface of the diffusing powder glue layer to form a phosphor glue layer; S6: The opaque white silica gel is filled on the bottom phosphor glue layer and its liquid level is flush with the phosphor glue layer above the LED chip, and after baking and curing, a white silica gel layer is formed; S7: Fill the encapsulation cavity with transparent silicone gel to cover the white silicone layer and the phosphor gel layer above the LED chip, and make its liquid level flush with the upper surface of the dam. Then, bake and cure it using an oven to form a transparent silicone layer, thus forming a complete LED chip encapsulation structure.

7. The preparation method of a novel LED chip packaging structure according to claim 6, characterized in that, In the above S4, the diffused powder silicone solution is prepared by mixing diffused powder, silicone, and silicone solvent in a weight ratio of 1:0.1:0.2; in the above S5, the phosphor silicone solution is prepared by mixing phosphor powder, silicone, and silicone solvent in a weight ratio of 1:0.1:0.2.

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