Backlight module for liquid crystal display and production method

Abstract

A backlight module for a liquid crystal display and a production method, the backlight module includes a circuit coating layer, a circuit interconnection layer, a light-emitting diode arrangement layer, a phosphor glue layer, and a transparent protective layer. The present invention uses a light-emitting diode as a point light source, and converts it into a surface light source by coating the phosphor glue. There is no need to use a printed circuit board (PCB) between the light-emitting diodes, and they are directly connected through the circuit. The preparation method of the present invention is characterized in that: no printed circuit board is used, no crystal bonding and reflow soldering processes are required, and the interconnected backlight module is obtained directly on the electrode surface of the light-emitting diode through photolithography and evaporation. The preparation process of the present invention does not require the use of expensive printed circuit boards and supporting high-precision crystal bonding and eutectic reflow soldering equipment. Moreover, the production efficiency is improved, the production cycle is shortened, and the production cost is reduced because no crystal bonding and eutectic reflow soldering are required.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor module packaging technology, and in particular to a light emitting diode backlight module packaging technology used in a liquid crystal display (LCD). Background Art

[0002] As mobile phones tend to be larger screen and virtual reality technology (VR) continues to enter people's lives, the industry has put forward higher requirements for display resolution (ppi) and service life. Although OLED displays have a wider color gamut, they have disadvantages such as insufficient life and large-size support. Small-size light-emitting diodes can greatly improve the resolution of existing displays in the field of backlight display, and can meet the needs of various display fields from wearable devices to large screens of hundreds of inches. In addition, with the characteristics of high brightness, low power consumption, self-luminescence, fast response speed, stable materials, and long service life of light-emitting diodes, compared with OLEDs, they have obvious advantages in quality, contrast, or total price cost.

[0003] The components of the LED backlight module are relatively small in size during production, and the current technology route with high efficiency, low cost and good yield is still in the exploration stage. According to the forecast of foreign organization Yole, the output value of the backlight industry is expected to reach 3.29 billion US dollars by 2025. The market application prospects are huge, but how to achieve the transfer of massive LED components, accurately interconnect with the electrodes of the printed circuit board, and overcome the problems of thermal expansion and failure during the reflow soldering process have become key technical difficulties in the development of the industry. The technical route that uses the existing LED precise arrangement on the printed circuit board and reflow soldering as the core faces huge challenges in terms of production capacity and yield control. Summary of the invention

[0004] The first object of the present invention is to provide a backlight module for a liquid crystal display (LCD), which has the characteristics of high reliability and strong waterproofness.

[0005] The present invention comprises a circuit coating layer, a circuit interconnection layer, a plurality of light emitting diodes arranged in an array, a phosphor glue layer, and a transparent protective layer; the light emitting diodes are arranged in the same layer, a circuit interconnection layer arranged on the same side is arranged between the light emitting diodes, the circuit coating layer is coated on the outside of each circuit interconnection layer, the light emitting diodes on the other side of the circuit coating layer are coated with a phosphor glue layer, and the transparent protective layer is arranged on the outside of the phosphor glue layer.

[0006] As is known to all, water vapor in the environment can not only make the phosphor ineffective but also hinder the reliability of the series-parallel circuit in a micro size. The transparent protective layer and the circuit coating layer provided in the present invention can play the role of isolating water vapor, protecting the phosphor and improving the reliability of the inter-diode interconnection circuit. The inter-diode interconnection circuit and the phosphor of the present invention are in an overall sealed state, so the overall waterproof performance of the backlight module can be effectively improved.

[0007] The present invention has a connecting line in the backlight module, and can form a guaranteed circuit connection between the light emitting diodes without using a printed circuit board (PCB).

[0008] The light emitting diode of the present invention can emit light in a single color (eg, blue) or in multiple colors (eg, red, green, and blue).

[0009] The thickness of the transparent protective layer is 5 μm to 2000 μm. If the thickness of the transparent protective layer is greater than 2000 μm, it will greatly occupy the space of other components, which is not conducive to the thinness of the device and is not recognized by consumers. If the thickness of the transparent protective layer is less than 5 μm, it cannot play a good supporting role, which will have an adverse effect on the yield of the subsequent preparation process and increase the defective output.

[0010] The surface of the transparent protective layer is a transparent protective layer roughening layer.

[0011] The surface of the phosphor glue layer facing the transparent protective layer is a phosphor glue roughening layer. The surface at the interface of the phosphor glue layer and the transparent protective layer is roughened, which can increase the interlayer adhesion, improve the light output rate, reduce the granularity of the light source, and play the role of a diffusion plate.

[0012] In order to facilitate heat conduction, reduce module temperature, and improve product reliability, the present invention provides heat dissipation channels, such as heat dissipation holes, thermal conductive adhesive, etc., in the circuit interconnection layer and the circuit coating layer.

[0013] The row and column spacing of the adjacent light-emitting diodes is less than 2000 μm, and the light-emitting surface size of each light-emitting diode is less than 1 mm. The prominent problem faced by the backlight source is that the light source has a granular feel, so a diffuser is used to scatter the light. According to existing experience, if the row and column spacing of the light-emitting diodes is greater than 2000 μm, the backlight assembly obtained by the process of the present invention will have a serious granular feel, cannot meet the existing industry standards, and cannot be used.

[0014] If the size of the light-emitting surface of the LED is larger than 1mm, the resolution (ppi) of the device display will be reduced, which is inconsistent with the trend of gradually increasing resolution in the display industry, resulting in a competitive disadvantage compared with existing industry products and not being recognized by consumers.

[0015] Another object of the present invention is to provide a method for producing the above product, comprising the following steps:

[0016] 1) Fix a number of light-emitting diodes in an array on the same surface of a fixed film, facing upwards;

[0017] 2) Coating a phosphor glue layer and a transparent protective layer on the light-emitting diode, and peeling off the fixing film after the phosphor glue layer and the transparent protective layer are cured;

[0018] 3) A circuit interconnection layer is made between the electrode surfaces of each light-emitting diode and covered with a circuit coating layer.

[0019] The present invention first uses a fixed film to fix and support each light-emitting diode, a phosphor glue layer, and a transparent protective layer. The transparent protective layer can play a supporting role when making a connecting layer circuit on the electrode surface. Therefore, the backlight module produced by the present invention does not need to be assembled with a diffusion plate, which is more convenient for assembly. If failure occurs in subsequent use, it is convenient to replace the module. The transparent protective layer of the present invention can also isolate water vapor and prevent the phosphor from absorbing water vapor and failing, thereby improving the overall waterproof performance of the module.

[0020] Features of the present invention:

[0021] (1) No need to use expensive printed circuit boards and supporting high-precision die bonding and eutectic reflow equipment; improve production efficiency, shorten production cycle, reduce production costs, and avoid yield loss in the reflow process.

[0022] (2) The product design has high flexibility and reliability. The use of photolithography and evaporation technology is conducive to the design of complex circuits and product differentiation.

[0023] (3) Without using a printed circuit board, the overall thickness of the module is thinner than that of products produced by existing technology routes, which conforms to the trend of thinner and lighter products and saves valuable design space for other modules.

[0024] (4) The module has a high degree of integration and does not require an additional diffusion plate, which makes assembly and subsequent replacement easy and has excellent waterproof performance.

[0025] In short, the manufacturing process of the present invention does not require the use of expensive printed circuit boards and supporting high-precision die bonding and eutectic reflow equipment, thereby achieving the purpose of improving production efficiency, shortening production cycles, reducing production costs, and avoiding yield loss during the process.

[0026] The phosphors in the phosphor glue layer may be mixed powders or single powders stacked side by side or in three dimensions.

[0027] After the fluorescent powder glue layer is coated, the surface of the fluorescent powder glue layer is roughened first, and then a transparent protective layer is coated.

[0028] After the transparent protective layer is coated, the surface coated with the transparent protective layer is roughened to achieve a roughening effect on the outer surface of the transparent protective layer.

[0029] Heat dissipation channels connected to the outside world are set in the circuit interconnection layer and the circuit covering layer to facilitate heat conduction, reduce module temperature and improve product reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figures 1 to 2It is a schematic diagram of the process flow of the present invention.

[0031] Figure 3 The figure is a structural schematic diagram of the product of the present invention.

[0032] Figure 4 Another structural schematic diagram of the product of the present invention. DETAILED DESCRIPTION

[0033] The following description provides an explanation of the embodiments and illustrates the specific details. Obviously, changes in the specific details in actual production should fall within the scope of the present invention.

[0034] Combined with Figures 1 to 3 The specific implementation process is as follows:

[0035] Example 1:

[0036] 1. Fix multiple light-emitting diodes 1 in an array on the upper surface of a fixed film 2 according to the designed spacing, and apply a phosphor glue layer 3 when the fixed film is tightly positioned on the carrier. Figure 1 shown.

[0037] The row and column spacing of LEDs should be less than 2000μm, and the light-emitting surface size of each LED should be less than 1mm.

[0038] The phosphor glue layer can be achieved by hot pressing, bonding or even multi-layer coating.

[0039] 2. After drying the phosphor glue layer 3, a transparent protective layer 4 is coated on the phosphor glue layer 3. Figure 2 shown.

[0040] The transparent protective layer can be formed by layering, using multiple layers of resin or stacking different materials at intervals, with a total thickness of 5μm to 2000μm. It can improve the light output rate, refraction, and reflection interface to better realize diffuse reflection, improve the light uniformity of the light source module, and reduce the granularity of the light source.

[0041] 3. After the transparent protective layer 4 and the phosphor adhesive layer 3 are thoroughly dried, the fixing film 2 is separated.

[0042] 4. Turn it over so that the transparent protective layer faces downward.

[0043] 5. On the electrode surface of each light-emitting diode, a circuit interconnection layer 5 is made by photolithography, evaporation and other process methods. A layer of insulating thermal conductive glue can also be coated on the circuit interconnection layer 5 to facilitate heat dissipation of the device.

[0044] 6. Cover the circuit covering layer 6 after the circuit interconnection layer 5, such as Figure 3 shown.

[0045] A layer of insulating thermal conductive adhesive may also be coated on the outer surface of the circuit coating layer 6 to facilitate heat dissipation of the device.

[0046] 7. The products formed are as follows Figure 3 As shown:

[0047] The light-emitting diodes 1 are arranged in the same layer, and a circuit interconnection layer 5 arranged on the same side is arranged between the light-emitting diodes 1. A circuit covering layer 6 is commonly coated outside each circuit interconnection layer 5, and a phosphor glue layer 3 is commonly coated on the light-emitting diodes 1 on the other side of the circuit covering layer 6. A transparent protective layer 4 is arranged on the outside of the phosphor glue layer 3.

[0048] Example 2:

[0049] 1. A plurality of light emitting diodes 1 are fixed in an array on the upper surface of a fixing film 2 according to a designed spacing, and a phosphor glue layer 3 is coated while the fixing film is tightly positioned on a carrier.

[0050] The row and column spacing of LEDs should be less than 2000μm, and the light-emitting surface size of each LED should be less than 1mm.

[0051] The phosphor glue layer can be achieved by hot pressing, bonding or even multi-layer coating.

[0052] 2. After the phosphor glue layer 3 is dried, in order to improve the light extraction rate and expand the light extraction angle, the surface of the phosphor glue layer 3 is roughened, and then a transparent protective layer 4 is coated on the roughened surface of the phosphor glue layer 3a.

[0053] The transparent protective layer can be formed by layering, using multiple layers of resin or stacking different materials at intervals, with a total thickness of 5μm to 2000μm. It can improve the light output rate, refraction, and reflection interface to better realize diffuse reflection, improve the light uniformity of the light source module, and reduce the granularity of the light source.

[0054] 3. After the transparent protective layer 4 and the phosphor glue layer 3 are completely dried, in order to improve the light output rate and expand the light output angle, the surface of the transparent protective layer 4 is roughened to form a roughened transparent protective layer 4a.

[0055] The fixed membrane 2 is then separated.

[0056] 4. Turn it over so that the transparent protective layer faces downward.

[0057] 5. On the electrode surface of each light-emitting diode, a circuit interconnection layer 5 is made by photolithography, evaporation and other process methods. A layer of insulating thermal conductive glue can also be coated on the circuit interconnection layer 5 to facilitate heat dissipation of the device.

[0058] 6. Cover the circuit covering layer 6 after the circuit interconnection layer 5, such as Figure 3 shown.

[0059] A layer of insulating thermal conductive adhesive may also be coated on the outer surface of the circuit coating layer 6 to facilitate heat dissipation of the device.

[0060] 7. A plurality of heat dissipation channels, such as heat dissipation holes 6a or thermal conductive adhesive, are provided on the circuit interconnection layer 5 and the circuit covering layer 6, so that the outer ends of the heat dissipation holes 6a are connected to the outside world to facilitate heat dissipation of the device.

[0061] 8. The products formed are as follows Figure 4 As shown:

[0062] A circuit interconnection layer 5 arranged on the same side is provided between each light emitting diode 1, and each circuit interconnection layer 5 is covered with a circuit covering layer 6. Heat dissipation holes 6a communicating with the outside are provided in the circuit interconnection layer and the circuit covering layer.

[0063] A phosphor glue layer 3 is coated on the light-emitting diode 1 on the other side of the circuit coating layer 6. The surface of the phosphor glue layer 3 facing the transparent protective layer 4 is a phosphor glue roughening layer 3a. The transparent protective layer 4 is arranged on the outside of the phosphor glue layer 3, and the surface of the transparent protective layer 4 is a roughened transparent protective layer 4a.

Claims

1. A method for producing a backlight module for a liquid crystal display, the backlight module comprising a circuit coating layer, a circuit interconnection layer, a plurality of light-emitting diodes, a phosphor glue layer, and a transparent protective layer; the light-emitting diodes are arranged in the same layer, the circuit interconnection layer arranged on the same side is arranged between the light-emitting diodes, the circuit coating layer is coated on the outside of each circuit interconnection layer, the light-emitting diodes on the other side of the circuit coating layer are coated with a phosphor glue layer, and the transparent protective layer is arranged on the outside of the phosphor glue layer; The production method comprises the following steps: 1) Fix a number of light-emitting diodes in an array on the same surface of a fixed film, facing upwards; 2) Coating a phosphor glue layer and a transparent protective layer on the light-emitting diode, and peeling off the fixing film after the phosphor glue layer and the transparent protective layer are cured; 3) A circuit interconnection layer is formed between the electrode surfaces of each light-emitting diode and covered with a circuit coating layer. The circuit interconnection layer is formed by photolithography or evaporation process, and a heat dissipation channel is set in the circuit interconnection layer and the circuit coating layer.

2. The method for producing a backlight module according to claim 1, characterized in that The transparent protective layer has a thickness of 5 μm to 2000 μm.

3. The method for producing a backlight module according to claim 1 or 2, characterized in that The surface of the transparent protective layer is a transparent protective layer roughening layer.

4. The method for producing a backlight module according to claim 1, characterized in that The surface of the phosphor glue layer facing the transparent protective layer is a phosphor glue roughening layer.

5. The method for producing a backlight module according to claim 1, characterized in that The row and column spacings between adjacent light emitting diodes are less than 2000 μm, and the light emitting surface size of each light emitting diode is less than 1 mm.

6. The method for producing a backlight module according to claim 1, characterized in that A transparent protective layer is applied to the phosphor glue layer in a semi-dried state.

7. The method for producing a backlight module according to claim 1, characterized in that The surface of the transparent protective layer is roughened.

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