Light board and packaging method thereof

Abstract

The present invention is applicable to the field of LED packaging technology, and provides a lamp board, comprising a substrate, a circuit layer, an LED chip, a first packaging adhesive layer and a second packaging adhesive layer, wherein the circuit layer is arranged on one side of the substrate, and the circuit layer has a soldering pad; the LED chip is connected to the soldering pad; the first packaging adhesive layer is arranged on one side of the substrate and covers the LED chip and the circuit layer, and the first packaging adhesive layer allows the light emitted by the LED chip to pass through; the second packaging adhesive layer is arranged on the other side of the substrate, and is used to partially or completely offset the stress generated by the first packaging adhesive layer on the substrate. The present invention also provides a packaging method for a lamp board. The lamp board and packaging method provided by the present invention effectively improve the delamination, deformation, and poor airtightness caused by the warping of the substrate after the lamp board is packaged, avoid the risk of LED chips peeling, and have low production costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of LED packaging, and in particular relates to a lamp board and a packaging method thereof. Background Art

[0002] In recent years, Mini LED backlight display modules and direct display products have been vigorously promoted in the market and have become the mainstream solution in the future display market. The flip-chip process structure adopted by the light board of Mini LED backlight display module is suitable for the needs of ultra-small space density and is also suitable for packaging substrates of various materials. The substrate material used for packaging Mini LED backlight display module is generally PCB substrate or glass substrate. The packaging glue layer on the surface of Mini LED backlight display module is generally selected from silicone resin or epoxy resin material. The thermal expansion coefficient of PCB substrate or glass substrate is (1~15)×10 -6 / ℃, while the thermal expansion coefficient of silicone resin or epoxy resin is (50~220)×10 -6 / °C, there's a significant thermal expansion mismatch between the substrate and the encapsulant layer, which can cause substrate warping and risks such as delamination, deformation, poor airtightness, and chip peeling. This large difference in thermal expansion coefficients between the substrate and the encapsulant (the encapsulant is much larger than the substrate) causes asynchronous deformation and separation when exposed to cold or heat (for example, during thermal shock tests). Existing technologies reduce this deformation by reducing the difference in thermal expansion coefficients between the substrate and adjacent encapsulant layers, but this doesn't eliminate the stress in the substrate, making it susceptible to deformation. Reducing this difference in thermal expansion coefficients is difficult and expensive. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a lamp board and its packaging method, which effectively improves the problems of delamination, deformation, poor airtightness, etc. caused by the warping of the substrate after the lamp board is packaged. The substrate is not easy to deform, avoiding the risk of peeling of the LED chip and other adverse risks, and the production cost is low.

[0004] The technical solution of the present invention is: a lamp board, including a substrate, a circuit layer, an LED chip, a first encapsulation layer and a second encapsulation layer, the circuit layer is arranged on one side of the substrate, and the circuit layer has a solder pad; the LED chip is connected to the solder pad; the first encapsulation layer is arranged on one side of the substrate and covers the LED chip and the circuit layer, and the first encapsulation layer allows the light emitted by the LED chip to pass through; the second encapsulation layer is arranged on the other side of the substrate, and is used to partially or completely offset the stress generated by the first encapsulation layer on the substrate.

[0005] As a further improvement of the present technical solution, the thickness of the first encapsulation adhesive layer is greater than the thickness of the second encapsulation adhesive layer, the first encapsulation adhesive layer has a first thermal expansion coefficient, and the second encapsulation adhesive layer has a second thermal expansion coefficient greater than the first thermal expansion coefficient.

[0006] As a further improvement of the present technical solution, the first encapsulation adhesive layer and the second encapsulation adhesive layer are made of the same material, which is epoxy resin or silicone resin.

[0007] As a further improvement of the present technical solution, inorganic light-transmitting particles for adjusting the thermal expansion coefficient of the first packaging adhesive layer are dispersed therein.

[0008] As a further improvement of the present technical solution, the inorganic light-transmitting particles are precipitated in the first packaging adhesive layer so that the content of the inorganic light-transmitting particles gradually decreases in a direction away from the substrate.

[0009] As a further improvement of the present technical solution, the particle size of the inorganic light-transmitting particles ranges from 50 nanometers to 5 micrometers.

[0010] As a further improvement of the present technical solution, the inorganic light-transmitting particles are at least one of silicon dioxide powder or aluminum oxide powder.

[0011] As a further improvement of the present technical solution, the thickness of the first encapsulation adhesive layer ranges from 150 microns to 400 microns; and / or the thickness of the second encapsulation adhesive layer ranges from 20 microns to 200 microns.

[0012] As a further improvement of the present technical solution, the lamp board also includes a solder resist layer arranged between the circuit layer and the first packaging adhesive layer, the solder resist layer is provided with a plurality of window structures, and each window structure has at least one pair of solder pads in the area corresponding to the window structure. The LED chip is arranged in the window structure and connected to the solder pads corresponding to the window structure, and the first packaging adhesive layer is in direct contact with the substrate through the window structure.

[0013] The present invention also provides a method for packaging a light panel, comprising the steps of:

[0014] preparing a substrate;

[0015] Disposing a circuit layer having a pad on the substrate;

[0016] Connecting the LED chip to the solder pad;

[0017] A first packaging adhesive layer formed of a first packaging adhesive is provided on one side of the substrate for covering the LED chip and the circuit layer, wherein the first packaging adhesive layer allows light emitted by the LED chip to pass through;

[0018] A second packaging adhesive layer formed by a second packaging adhesive is provided on the other side of the substrate, for partially or completely offsetting the stress generated by the first packaging adhesive layer on the substrate.

[0019] The present invention provides a lamp board and a packaging method thereof. By arranging the first packaging adhesive layer on one side of the substrate and covering the LED chip and the circuit layer, the first packaging adhesive layer allows the light emitted by the LED chip to pass through, and the second packaging adhesive layer is arranged on the other side of the substrate to partially or completely offset the stress generated by the first packaging adhesive layer on the substrate, effectively reducing the warping deformation of the substrate caused by stress, effectively improving the problems of delamination, deformation, poor airtightness, etc. after the lamp board is packaged, avoiding the risk of peeling of the LED chip, and low production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is a structural diagram of a substrate in a light board provided by an embodiment of the present invention;

[0022] Figure 2 This is a schematic structural diagram of a light board provided by an embodiment of the present invention, in which a circuit layer is provided on a substrate;

[0023] Figure 3 This is a schematic diagram of a structure in which an LED chip is connected to a solder pad in a lamp board provided by an embodiment of the present invention;

[0024] Figure 4 This is a structural schematic diagram of a light board provided by an embodiment of the present invention, in which a first encapsulation adhesive layer is provided on one side of a substrate;

[0025] Figure 5 This is a schematic structural diagram of a light board provided by an embodiment of the present invention, in which a second encapsulation adhesive layer is provided on the other side of the substrate;

[0026] Figure 6 This is a schematic diagram of the sedimentation of inorganic light-transmitting particles in the first packaging adhesive layer in a light panel provided by an embodiment of the present invention.

[0027] Numbers in the figure:

[0028] 1-LED chip, 2-solder paste layer, 3-circuit layer, 4-substrate, 5-inorganic light-transmitting particles, 6-first encapsulation adhesive layer, 7-second encapsulation adhesive layer, 8-solder mask layer. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] It should be noted that the terms "setting" and "connecting" should be understood in a broad sense. For example, it can be directly setting or connecting, or it can be indirectly setting or connecting through a central component or a central structure.

[0031] In addition, if there are terms such as "longitudinal", "transverse", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicating orientation or positional relationships in the embodiments of the present invention, they are based on the orientation or positional relationships shown in the drawings or the conventional placement state or usage state, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the structure, feature, device or element referred to must have a specific orientation or positional relationship, nor must it be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0032] The various specific technical features and embodiments described in the specific implementation methods can be combined in any suitable manner unless there is any contradiction. For example, different implementation methods can be formed by combining different specific technical features / embodiments. In order to avoid unnecessary repetition, the various possible combinations of the specific technical features / embodiments in the present invention will not be described separately.

[0033] like Figure 5 As shown, a light board provided by an embodiment of the present invention can be used for Mini LED backlight display modules and direct display products. The light board includes a substrate 4 (such as Figure 1As shown), a circuit layer 3 and an LED chip 1, the circuit layer 3 is arranged on one side of the substrate 4, and the circuit layer 3 has a solder pad; the LED chip 1 is connected to the solder pad. In this embodiment, the LED chip 1 is a flip chip, specifically a flip-chip blue LED chip or a flip-chip RGB LED chip, and the substrate 4 can be an FR4 circuit substrate or a glass substrate; the light board also includes a first packaging glue layer 6 and a second packaging glue layer 7, the first packaging glue layer 6 is arranged on one side of the substrate 4 and covers the LED chip 1 and the circuit layer 3, the first packaging glue layer 6 allows the light emitted by the LED chip 1 to pass through; the second packaging glue layer 7 is arranged on the other side of the substrate 4, and is used to partially or completely offset the stress generated by the first packaging glue layer 6 on the substrate 4. It should be noted that if only the first packaging glue is used to form the first packaging glue layer 6 by dispensing or molding, the first packaging glue layer 6 has a stress acting on the substrate 4, which makes the substrate 4 easy to deform, usually manifested as warping at both ends of the substrate 4 and a depression in the middle, making the LED chip 1 easy to peel off; this embodiment In the figure, the first encapsulation adhesive layer 6 and the second encapsulation adhesive layer 7 are respectively arranged on the two sides of the substrate 4, and a "sandwich" structure is formed with the substrate 4 through the first encapsulation adhesive layer 6 and the second encapsulation adhesive layer 7, wherein the first encapsulation adhesive layer 6 has a tensile stress acting on the substrate 4 and toward one side of the substrate 4, and the second encapsulation adhesive layer 7 has a tensile stress acting on the substrate 4 and toward the other side of the substrate 4, so that the tensile stress acting on both sides of the substrate 4 can be offset to a large extent, effectively reducing the warping deformation of the substrate 4 (especially the substrate 4) caused by the stress applied by the encapsulation adhesive layer, effectively improving the problems of delamination, deformation, poor airtightness after the lamp board is encapsulated, and avoiding the risk of peeling of the LED chip 1. In addition, the first encapsulation adhesive layer 6 and the second encapsulation adhesive layer 7 form a "sandwich" structure with the substrate 4, and there is no need to use multiple layers of encapsulation adhesive layers, the manufacturing process is simple, and the cost is low.

[0034] In a specific application, the projection area of the first encapsulation adhesive layer 6 on the substrate 4 can cover the substrate 4, that is, the first encapsulation adhesive layer 6 can completely cover the surface of one side of the substrate 4, or the first encapsulation adhesive layer 6 can be composed of non-connected first segmented adhesive layers, and the first encapsulation adhesive is formed by dispensing on one side of the substrate 4 (specifically, one side of the circuit layer 3 and the top of the LED chip 1) to form multiple non-connected first segmented adhesive layers. In another embodiment, the second encapsulation adhesive layer 7 can also be composed of non-connected second segmented adhesive layers, and the second encapsulation adhesive is formed by dispensing on the other side of the substrate 4 to form multiple non-connected second segmented adhesive layers, so that the stress between the substrates 4 on both sides of the segmented adhesive layer is offset to prevent deformation of the substrate 4. As an optional embodiment, the first encapsulation adhesive layer 6 can completely cover one side of the substrate 4, and the second encapsulation adhesive layer 7 partially covers the other side of the substrate 4, so that space can be reserved on the back of the substrate 4 to install other components.

[0035] In specific applications, the thickness of the first encapsulation layer 6 is not less than the thickness of the second encapsulation layer 7. Specifically, the first encapsulation layer 6 on one side of the substrate 4 can protect the LED chip 1 and requires a certain thickness. The second encapsulation layer 7 on the other side of the substrate 4 is additionally thick, which increases the overall thickness of the product and does not meet the market trend of overall thinning of LED modules. By controlling the thickness of the first encapsulation layer 6 to be not less than the thickness of the second encapsulation layer 7, it is beneficial to achieve overall thinning of the light panel and miniaturization of the device, meeting market needs.

[0036] In a specific application, the thickness of the first encapsulation layer 6 is greater than the thickness of the second encapsulation layer 7. The first encapsulation layer 6 has a first thermal expansion coefficient, and the second encapsulation layer 7 has a second thermal expansion coefficient, which is greater than the first thermal expansion coefficient. The product of the thickness of the first encapsulation layer 6 and the first thermal expansion coefficient is A, and the product of the thickness of the second encapsulation layer 7 and the second thermal expansion coefficient is B, where A is equal to or approximately equal to B. It should be explained that when the first encapsulation layer 6 has a greater thickness and a smaller first thermal expansion coefficient, while the second encapsulation layer 7 has a smaller thickness and a larger first thermal expansion coefficient, the stresses acting on both sides of the substrate 4 can be balanced and offset. At the same time, the first encapsulation layer 6 can have a certain thickness to protect the LED chip, while the thickness of the second encapsulation layer 7 can be relatively small, which facilitates thinning of the light board. As another embodiment, the thickness of the first encapsulation layer 6 is equal to the thickness of the second encapsulation layer 7. The first encapsulation layer 6 has a first thermal expansion coefficient, and the second encapsulation layer 7 has a second thermal expansion coefficient, which is the same as the first thermal expansion coefficient. In specific applications, the most important parameters for the stress magnitude of the encapsulation adhesive layer on the substrate 4 are the thickness and thermal expansion coefficient of the encapsulation adhesive layer. In specific applications, encapsulation adhesive materials with different thermal expansion coefficients can be selected according to the thickness of the encapsulation adhesive layer, and the adjustment can be flexible so that the stress acting on both sides of the substrate 4 can be offset and the overall product tends to be thinner.

[0037] Furthermore, the materials of the first encapsulation adhesive layer 6 and the second encapsulation adhesive layer 7 are the same, both of which are epoxy resin or silicone resin, which helps to reduce costs. In another embodiment, the materials of the first encapsulation adhesive layer 6 and the second encapsulation adhesive layer 7 can also be different. The first encapsulation adhesive layer 6 is dispersed with inorganic light-transmitting particles 5 for adjusting its thermal expansion coefficient. By adding inorganic light-transmitting particles to the encapsulation adhesive, the thermal expansion coefficient of the encapsulation adhesive layer can be adjusted, which is convenient and low-cost. The inorganic light-transmitting particles 5 settle in the first encapsulation adhesive layer 6 so that the content of the inorganic light-transmitting particles 5 gradually decreases in the direction away from the substrate 4, that is, the added inorganic light-transmitting particles 5 naturally settle in the first encapsulation adhesive, and the closer the area is to the substrate 4, the smaller its thermal expansion coefficient is, which can effectively reduce the deformation of the substrate 4. The particle size range of the inorganic light-transmitting particles 5 is 50 nanometers to 5 microns. Since the inorganic light-transmitting particles 5 are light-transmitting, it is beneficial to ensure the light output of the LED chip. In this embodiment, the inorganic light-transmitting particles 5 are silica powder or alumina powder, or a mixture of silica powder and alumina powder. The inorganic light-transmitting particles 5 are incorporated into the first encapsulating adhesive layer 6. In this embodiment, the inorganic light-transmitting particles 5 preferably have a particle size range of 100 nanometers to 1 micron. Since silica is the primary component of glass and alumina is the primary component of sapphire, both silica powder and alumina powder are light-transmitting particles. The proportion of silica powder or alumina powder incorporated into the first encapsulating adhesive layer 6 is 0 to 100%, preferably 20 to 60%. By controlling the standing time of the first encapsulating adhesive before curing, the silica powder or alumina powder is allowed to naturally settle within the first encapsulating adhesive, forming a stepped distribution. The silica powder content increases closer to the substrate 4, i.e., the thermal expansion coefficient decreases closer to the substrate 4, further reducing deformation of the substrate 4. In addition, the projected area of the encapsulation layer located on the other side of the substrate 4 on the substrate 4 can be flexibly adjusted. Based on cost factors, it does not necessarily fully cover the other side of the substrate 4; the use of translucent particles does not affect the light output of the LED chip 1, and the thermal expansion coefficient is adjusted, with good adjustment effect and low cost.

[0038] As an optional embodiment, the thickness of the first encapsulating adhesive layer 6 ranges from 150 microns to 400 microns; the thickness of the second encapsulating adhesive layer 7 ranges from 20 microns to 200 microns. In specific applications, the thickness of the first encapsulating adhesive layer 6 is not less than the thickness of the second encapsulating adhesive layer 7, and the thickness of the first encapsulating adhesive layer 6 preferably ranges from 250 microns to 300 microns. The first encapsulating adhesive layer 6 can be made of epoxy resin or silicone resin, and the second encapsulating adhesive layer 7 can also be made of either epoxy resin or silicone resin.

[0039] Furthermore, if Figure 4 and Figure 5As shown, the light board also includes a solder resist layer 8 arranged between the circuit layer 3 and the first packaging adhesive layer 6. The solder resist layer 8 is provided with a plurality of window structures. Each window structure has at least one pair of pads in the area corresponding to the window structure. The LED chip 1 is arranged in the window structure and connected to the pads corresponding to the window structure. The first packaging adhesive layer 6 is in direct contact with the substrate through the window structure. Specifically, the first packaging adhesive layer 6 includes an outer adhesive layer located on the outer peripheral side of the LED chip 1 and a bottom adhesive layer located in the window structure. The bottom adhesive layer is formed by filling the window structure with the first packaging adhesive and is directly connected to the substrate 4. It is not only beneficial to solidification, but also improves the light efficiency, helps to increase the backlight brightness, and improves the process yield, with low manufacturing cost.

[0040] An embodiment of the present invention further provides a method for packaging a light board, the method being used to package the light board, comprising the steps of:

[0041] like Figure 1 As shown, a substrate 4 is prepared, and an FR4 circuit substrate or a glass substrate can be selected.

[0042] like Figure 2 As shown, a circuit layer 3 with a solder pad is provided on the substrate 4. In specific applications, a solder resist layer 8 is also provided above the circuit layer 3. The other areas of the circuit layer except the solder pad are provided with the solder resist layer 8, which has the function of insulation and anti-oxidation. The solder resist layer 8 is generally made of ink. When used in backlight products, white ink is used, and when used in direct display products, black ink is used.

[0043] like Figure 3 As shown, the LED chip 1 is connected to the pad; in a specific application, a solder paste layer 2 can be provided on the pad to facilitate soldering.

[0044] like Figure 4 As shown, a first packaging glue layer 6 formed by a first packaging glue is provided on one side of the substrate 4 for covering the LED chip 1 and the circuit layer 3; specifically, the first packaging glue is provided on one side of the substrate 4 by dispensing or molding and is cured to form the first packaging glue layer 6.

[0045] like Figure 5As shown, a second encapsulation adhesive layer 7 formed by a second encapsulation adhesive is provided on the other side of the substrate 4; specifically, the second encapsulation adhesive is provided on the other side of the substrate 4 by dispensing or molding and cured to form the second encapsulation adhesive layer 7. The first encapsulation adhesive layer 6 and the second encapsulation adhesive layer 7 form a "sandwich" structure with the substrate 4, so that the tensile stress acting on both sides of the substrate 4 can be offset to a large extent, effectively reducing the warping deformation of the substrate 4 (especially the substrate 4) caused by the stress applied by the encapsulation adhesive layer, effectively improving the problems of delamination, deformation, poor airtightness, etc. after the lamp board is encapsulated, and avoiding the risk of peeling of the LED chip 1.

[0046] An embodiment of the present invention provides a lamp board and a packaging method thereof, wherein the first packaging adhesive layer 6 is arranged on one side of the substrate 4 and covers the LED chip 1 and the circuit layer 3, and the second packaging adhesive layer 7 is arranged on the other side of the substrate 4. The first packaging adhesive layer 6 and the second packaging adhesive layer 7 form a "sandwich" structure with the substrate 4, so that the stress acting on both sides of the substrate 4 can be offset to a large extent, effectively reducing problems such as warping and deformation of the substrate 4 due to stress, and effectively improving the delamination, deformation, and poor airtightness of the lamp board after packaging, avoiding the risk of peeling of the LED chip 1, and low production cost.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A light board, characterized in that: include: substrate; A circuit layer, the circuit layer is arranged on one side of the substrate, and the circuit layer has a pad; An LED chip, wherein the LED chip is connected to the solder pad; The light board also includes: a first encapsulation adhesive layer, the first encapsulation adhesive layer being disposed on one side of the substrate and covering the LED chip and the circuit layer, the first encapsulation adhesive layer allowing light emitted by the LED chip to pass through; A second packaging adhesive layer is provided on the other side of the substrate and is used to partially or completely offset the stress generated by the first packaging adhesive layer on the substrate.

2. The light board according to claim 1, characterized in that: The thickness of the first encapsulation adhesive layer is greater than that of the second encapsulation adhesive layer. The first encapsulation adhesive layer has a first thermal expansion coefficient, and the second encapsulation adhesive layer has a second thermal expansion coefficient greater than the first thermal expansion coefficient.

3. The light board according to claim 1 or 2, characterized in that: The first packaging adhesive layer and the second packaging adhesive layer are made of the same material, which is epoxy resin or silicone resin.

4. The light board according to claim 2, characterized in that: The first packaging adhesive layer is dispersed with inorganic light-transmitting particles for adjusting its thermal expansion coefficient.

5. The light board according to claim 4, characterized in that: The inorganic light-transmitting particles settle in the first packaging adhesive layer so that the content of the inorganic light-transmitting particles gradually decreases in a direction away from the substrate.

6. The light board according to claim 4, characterized in that: The particle size of the inorganic light-transmitting particles ranges from 50 nanometers to 5 micrometers.

7. The light board according to claim 4, characterized in that: The inorganic light-transmitting particles are at least one of silicon dioxide powder and aluminum oxide powder.

8. The light board according to claim 1, wherein: The thickness of the first packaging adhesive layer ranges from 150 micrometers to 400 micrometers; and / or the thickness of the second packaging adhesive layer ranges from 20 micrometers to 200 micrometers.

9. The light board according to claim 1, wherein: The lamp board also includes a solder resist layer arranged between the circuit layer and the first packaging adhesive layer, the solder resist layer is provided with a plurality of window structures, and each window structure has at least one pair of solder pads in the area corresponding to the window structure. The LED chip is arranged in the window structure and connected to the solder pads corresponding to the window structure, and the first packaging adhesive layer is in direct contact with the substrate through the window structure.

10. A method for packaging a light board, characterized in that: Including steps: preparing a substrate; Disposing a circuit layer having a pad on the substrate; Connecting the LED chip to the solder pad; A first packaging adhesive layer formed of a first packaging adhesive is provided on one side of the substrate for covering the LED chip and the circuit layer, wherein the first packaging adhesive layer allows light emitted by the LED chip to pass through; A second packaging adhesive layer formed by a second packaging adhesive is provided on the other side of the substrate, for partially or completely offsetting the stress generated by the first packaging adhesive layer on the substrate.

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