TWI842387B - Method for manufacturing sub-millimeter light-emitting diode backlight panel and its product - Google Patents

Abstract

The present invention provides a method for manufacturing a sub-millimeter light-emitting diode backlight panel, comprising the following steps: (a) bonding a plurality of sub-millimeter light-emitting diode dies to a first circuit layer on a first surface of a flexible substrate; (b) hot-pressing a transparent rigid substrate with a transparent sealing layer attached thereto on the sub-millimeter light-emitting diode dies after step (a), so that the transparent sealing layer covers each sub-millimeter light-emitting diode dies; and (c) bonding a plurality of driver chips to a second circuit layer on a second surface of the flexible substrate opposite to the first surface after step (b); the first circuit layer and the second circuit layer are electrically connected to each other, so that the driver chips are electrically connected to the sub-millimeter light-emitting diode dies on the first circuit layer. The present invention also provides a sub-millimeter light-emitting diode backlight plate manufactured by the above-mentioned manufacturing method.

Description

Method for manufacturing sub-millimeter light-emitting diode backlight panel and its product

The present invention relates to a backlight panel, in particular to a method for manufacturing a sub-millimeter light-emitting diode (mini-LED) backlight panel and its product.

Due to its advantages of high brightness, long life, and fast response speed, the application of LED in the backlight module of liquid crystal display devices has become the mainstream in the industry in the past decade. In addition, with the advancement of optoelectronic semiconductor manufacturing processes and the demand for thinner and smaller liquid crystal display devices, sub-millimeter light-emitting diodes as backlight sources for liquid crystal display devices have also become a development trend in the industry related to liquid crystal display devices.

Referring to FIG. 1 , a conventional sub-millimeter light-emitting diode backlight panel 1 includes a double-sided flexible printed circuit board (FPC) 11, a plurality of sub-millimeter light-emitting diode chips 12, and a plurality of driving chips 13 for driving the sub-millimeter light-emitting diode chips 12. The double-sided flexible printed circuit board 11 has a flexible substrate 110, an upper circuit layer 111 disposed on an upper surface 1101 of the flexible substrate 110, and a lower circuit layer 112 disposed on a lower surface 1102 of the flexible substrate 110 and electrically connected to the upper circuit layer 111. The sub-millimeter light-emitting diode grains 12 are bonded to the upper circuit layer 111 by forming a metal eutectic with solder paste and a bonding pad; the driver chips 13 are also bonded to the lower circuit layer 112 by forming a metal eutectic with solder paste and a bonding pad.

It should be noted here that before the existing sub-millimeter LED backlight panel 1 is actually integrated into the liquid crystal display module to form a liquid crystal display device, it still needs to be packaged through a molding layer (not shown in the figure) to package the sub-millimeter LED chips 12, and a wavelength conversion layer (not shown in the figure) is set above the molding layer covering the sub-millimeter LED chips 12 to provide the sub-millimeter LED chips 12 with a backlight source for mixing light to generate white light before it can be integrated into the liquid crystal display module.

As is known to all, in order to make the liquid crystal display device meet the industry's demand for lightness, thinness and miniaturization, the conventional sub-millimeter light-emitting diode backlight panel 1 generally uses a thin FPC for the double-sided flexible printed circuit board 11 during the manufacturing process. Specifically, the manufacturing method of the conventional sub-millimeter light-emitting diode backlight panel 1 is to first bond the driver chips 13 on the lower circuit layer 112, then flip the double-sided flexible printed circuit board 11 by 180 degrees to place it on a carrier (not shown) provided with a plurality of positioning grooves that can respectively accommodate the driver chips 13, with the upper circuit layer 111 facing upward, and then die-bond the sub-millimeter light-emitting diode dies 12 on the upper circuit layer 111. However, due to the thin thickness of the double-sided flexible printed circuit board 11, it is easily affected by gravity and deformed after being placed on the carrier, so that the sub-millimeter LED chips 12 cannot be accurately connected to the upper circuit layer 111 during the die bonding process. Therefore, it is easy to cause problems such as circuit breakage or uneven brightness (mura) due to component deviation.

From the above description, it can be seen that improving the structure and manufacturing method of the sub-millimeter LED backlight panel 1 to solve the problems of circuit breakage or uneven brightness (mura) caused by component offset is a topic that needs to be broken through by relevant technical personnel in the technical field to which this case belongs.

Therefore, the first purpose of the present invention is to provide a method for manufacturing a sub-millimeter LED backlight panel that can solve the problems of circuit breakage or uneven brightness caused by component misalignment.

Therefore, the method for manufacturing the sub-millimeter light-emitting diode backlight panel of the present invention includes the following steps: step (a), step (b), and step (c).

The step (a) is to solidify a plurality of sub-millimeter light-emitting diode dies on a first circuit layer on a first surface of a flexible substrate.

The step (b) is to heat-press a transparent rigid substrate with a transparent sealing layer attached on the sub-millimeter light-emitting diode die after the step (a), so that the transparent sealing layer covers each sub-millimeter light-emitting diode die.

The step (c) is to bond a plurality of driver chips to a second circuit layer on a second surface of the flexible substrate opposite to the first surface after the step (b); wherein the first circuit layer and the second circuit layer are electrically connected to each other, so that the driver chips are electrically connected to the sub-millimeter light-emitting diode dies on the first circuit layer.

The second purpose of the present invention is to provide a sub-millimeter light-emitting diode backlight panel manufactured by the aforementioned manufacturing method.

The sub-millimeter light-emitting diode backlight panel of the present invention includes a double-sided flexible circuit board, a plurality of sub-millimeter light-emitting diode dies, a plurality of driving chips, and a transparent rigid substrate. The double-sided flexible circuit board includes a flexible substrate, a first circuit layer formed on a first surface of the flexible substrate, and a second circuit layer formed on a second surface opposite to the first surface, and the first circuit layer and the second circuit layer are electrically connected to each other. The sub-millimeter light-emitting diode dies are die-bonded on the first circuit layer. The driving chips are bonded to the second circuit layer. The transparent rigid substrate includes a board body, and a transparent sealing layer attached to the board body, and the transparent sealing layer covers the sub-millimeter light-emitting diode dies.

The effect of the present invention is that the light-transmissive rigid substrate used in step (b) can support the flexible substrate that is susceptible to warping due to gravity, so as to prevent the flexible substrate from warping, which results in the inability to accurately bond the driver chips to the second circuit layer when implementing step (c), thereby solving the problem of circuit breakage or uneven brightness caused by component deviation.

2: Double-sided flexible circuit board

20: Flexible substrate

201: First page

202: Second side

21: First circuit layer

22: Second circuit layer

3: Transparent rigid substrate

31: Plate body

32: Translucent sealing layer

33: Wavelength conversion particles

4: Sub-millimeter LED grains

5:Drive chip

6: Patterned reflective layer

90: Outer frame

91: Optical film

92: Polarizer

93: Lower TFT component array carrier board

94: Color filter carrier

95: Resolution polarizing film

96: LCD signal control circuit

97: Backlight signal control circuit

98: Circuit integrated board

BLP: Sub-millimeter light-emitting diode backlight panel

Other features and effects of the present invention will be clearly presented in the implementation method with reference to the drawings, wherein: FIG. 1 is a schematic diagram illustrating an existing sub-millimeter light-emitting diode backlight plate; FIG. 2 is a schematic diagram illustrating a step (a') of an implementation method of the sub-millimeter light-emitting diode backlight plate of the present invention; FIG. 3 is a schematic diagram illustrating a step (a) of the implementation method of the present invention; FIG. 4 is a schematic diagram illustrating a step (b) of the implementation method of the present invention; FIG. 5 is a schematic diagram illustrating a step (c) of the implementation method of the present invention and a sub-millimeter light-emitting diode backlight plate produced thereby; and FIG. 6 is a schematic diagram illustrating a liquid crystal display device assembled with the sub-millimeter light-emitting diode backlight plate of the implementation method of the present invention.

An embodiment of the method for manufacturing the sub-millimeter light-emitting diode backlight panel BLP of the present invention includes the following steps: step (a), step (b), and step (c).

Referring to FIG. 3 , step (a) is to solidify multiple sub-millimeter light-emitting diode dies 4 on a first circuit layer 21 on a first surface 201 of a flexible substrate 20 .

Referring to FIG. 4 , step (b) is to heat press a light-transmitting rigid substrate 3 with a light-transmitting sealing layer 32 attached thereto on the sub-millimeter light-emitting diode die 4 after step (a), so that the light-transmitting sealing layer 32 can cover each sub-millimeter light-emitting diode die 4 after heat pressing (see FIG. 5 ). Preferably, the light-transmitting rigid substrate 3 includes a light-transmitting plate body 31, the light-transmitting sealing layer 32 attached to the plate body 31, and a plurality of wavelength conversion particles 33 dispersedly packaged inside the plate body 31; a plurality of microparticles (not shown) are dispersed in the light-transmitting sealing layer 32. The particles suitable for being dispersed in the light-transmitting sealant layer 32 may be titanium oxide (TiO ₂ ) particles, and the wavelength conversion particles 33 suitable for the embodiment of the present invention may be fluorescent powder or quantum dots (hereinafter referred to as QDs). In the embodiment of the present invention, the plate body 31, the particles dispersed in the light-transmitting sealant layer 32, and the wavelength conversion particles 33 are respectively illustrated by using glass substrate, TiO ₂ particles, and QDs as examples, but are not limited thereto. For example, the light-transmitting rigid substrate 3 may also be a layered composite structure of glass/wavelength conversion particle layer/glass from bottom to top.

Referring to FIG. 5 , step (c) is to flip the flexible substrate 20 after step (b) by 180°, and bond a plurality of driver chips 5 to a second circuit layer 22 on a second surface 202 of the flexible substrate 20 opposite to the first surface 201; wherein the first circuit layer 21 and the second circuit layer 22 are electrically connected to each other, so that the driver chips 5 are electrically connected to the sub-millimeter light-emitting diode dies 4 on the first circuit layer 21.

In the embodiment of the present invention, the flexible substrate 20, the first circuit layer 21 and the second circuit layer 22 are illustrated by using a commercially available double-sided flexible printed circuit board (FPC), but are not limited thereto. In detail, the double-sided flexible circuit board 2 can also use polyimide (hereinafter referred to as PI) as the main material of the flexible substrate 20, so that PI is coated on a temporary substrate (not shown), and sequentially and repeatedly undergoes yellow light lithography steps, etching steps, thin film deposition steps, and stripping steps to obtain the double-sided flexible circuit board 2. The aforementioned method of using PI to make the double-sided flexible circuit board 2 is not the technical focus of the present invention, and will not be elaborated here.

Preferably, a step (a') is further included before the step (a). As shown in FIG. 2 , the step (a') is to form a patterned reflective layer 6 on the first surface 201 of the flexible substrate 20, and as shown in FIG. 3 , the sub-millimeter light-emitting diode grains 4 are exposed outside the patterned reflective layer 6; after the step (b) is implemented, the patterned reflective layer 6 is covered by the light-transmitting sealing layer 32 (as shown in FIG. 5 ). In the step (a') of the embodiment of the present invention, a patterned white paint (the patterned reflective layer 6) is screen-printed on the first surface 201 of the flexible substrate 20 as an example for illustration, but it is not limited to this.

According to the detailed description of the manufacturing method of the embodiment of the present invention, the sub-millimeter light-emitting diode backlight panel BLP manufactured by the manufacturing method of the embodiment of the present invention is as shown in FIG5, which includes the double-sided flexible circuit board 2, the sub-millimeter light-emitting diode grains 4, the driving chips 5, the light-transmitting rigid substrate 3, and the patterned reflective layer 6.

The double-sided flexible circuit board 2 includes the flexible substrate 20, a first circuit layer 21 formed on the first surface 201 of the flexible substrate 20, and a second circuit layer 22 formed on the second surface 202 opposite to the first surface 201, and the first circuit layer 21 and the second circuit layer 22 are electrically connected to each other.

The sub-millimeter light-emitting diode dies 4 are solid-bonded to the first circuit layer 21, and the driver chips 5 are bonded to the second circuit layer 22.

The transparent rigid substrate 3 includes the board body (glass substrate) 31, a transparent sealing layer 32 attached to the board body 31 and covering the sub-millimeter light-emitting diode grains 4, and wavelength conversion particles (QDs) 33 dispersed in the board body 31. The patterned reflective layer 6 is formed above the first surface 201 of the flexible substrate 20 (because FIG. 5 illustrates the state of the flexible substrate 20 after being flipped 180°, the patterned reflective layer 6 shown in FIG. 5 is formed below the first surface 201 of the flexible substrate 20, which is described in advance), and the sub-millimeter light-emitting diode grains 4 are exposed outside the patterned reflective layer 6 and covered by the transparent sealing layer 32.

Referring to FIG. 6 , when the sub-millimeter light emitting diode backlight panel BLP of the embodiment of the present invention is integrated into a liquid crystal display module, it is placed in an outer frame 90, and an optical film 91, a polarizer 92, a lower TFT element array carrier 93, a liquid crystal layer (not shown), an upper color filter carrier 94, and an analyzer 95 are sequentially stacked on the sub-millimeter light emitting diode backlight panel BLP to make the outer frame 90 have a plurality of layers. The optical film 91, polarizer 92, lower TFT device array carrier 93, liquid crystal layer (not shown), upper color filter carrier 94 and resolution polarizer 95 in the frame 90 together constitute the liquid crystal display module; wherein the liquid crystal display module and the sub-millimeter light-emitting diode backlight panel BLP are respectively electrically connected to a circuit integrated board 98 outside the outer frame 90 via an LCD signal control line 96 and a backlight signal control line 97, thereby constituting a liquid crystal display device.

According to the detailed description of the manufacturing method of the present invention, when the present invention implements step (b) (please refer to FIG. 4 and FIG. 5 at the same time), the plate body (glass substrate) 31 with the light-transmitting sealing layer 32 and the wavelength conversion particles (QDs) 33 dispersed therein is directly hot-pressed on the sub-millimeter light-emitting diode grains 4 after step (a), so that the light-transmitting sealing layer 32 can cover the sub-millimeter light-emitting diode grains 4 after hot-pressing. Therefore, the light-transmitting rigid substrate 3 used in step (b) of the present invention can support the double-sided flexible circuit board 2 which is easily warped by gravity, so as to prevent the double-sided flexible circuit board 2 from warping, which results in the inability to accurately bond the driver chips 5 to the second circuit layer 22 when implementing step (c), thereby solving the problems of disconnection or uneven luminous brightness caused by the offset of the components in the prior art. In addition, the light-transmitting sealing layer 32 is attached to the surface of the board body (glass substrate) 31, and the wavelength conversion particles (QDs) 33 are dispersed inside the board body. Therefore, after the heat pressing mentioned in step (b) is performed, the light-transmitting sealing layer 32 can directly cover the sub-millimeter light-emitting diode chips 4, which can not only directly complete the packaging step of the sub-millimeter light-emitting diode chips 4, but also omit the step of setting the wavelength conversion layer mentioned in the previous technology. The manufacturing method of this embodiment of the present invention is simpler than the existing manufacturing method of the sub-millimeter light-emitting diode backlight plate.

In summary, the manufacturing method and product of the sub-millimeter LED backlight panel of the present invention can avoid the warping problem of the double-sided flexible circuit board 2 during the manufacturing process, thereby accurately bonding the driver chips 5 to the second circuit layer 22 to solve the problems of disconnection or uneven brightness caused by component deviation, and can also be more simplified than the existing process, so the purpose of the present invention can be achieved.

However, the above is only an example of the implementation of the present invention, and it cannot be used to limit the scope of the implementation of the present invention. All simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the patent specification are still within the scope of the patent of the present invention.

2: Double-sided flexible circuit board

20: Flexible substrate

201: First page

202: Second side

21: First circuit layer

22: Second circuit layer

3: Transparent rigid substrate

31: Plate body

32: Translucent sealing layer

33: Wavelength conversion particles

4: Sub-millimeter LED grains

5:Drive chip

6: Patterned reflective layer

BLP: Sub-millimeter light-emitting diode backlight panel

Claims (8)

A method for manufacturing a sub-millimeter light-emitting diode backlight panel comprises the following steps: step (a) is to solidify a plurality of sub-millimeter light-emitting diode dies on a first circuit layer on a first surface of a flexible substrate; step (b) is to hot-press a transparent rigid substrate with a transparent sealing layer attached thereto on the sub-millimeter light-emitting diode dies after step (a), so that the transparent sealing layer Encapsulating each sub-millimeter light-emitting diode die; and step (c), bonding a plurality of driver chips to a second circuit layer on a second surface of a flexible substrate opposite to the first surface after step (b); wherein the first circuit layer and the second circuit layer are electrically connected to each other, so that the driver chips are electrically connected to the sub-millimeter light-emitting diode die on the first circuit layer. The method for manufacturing a sub-millimeter light-emitting diode backlight panel as described in claim 1, wherein the light-transmitting rigid substrate includes a panel body and a plurality of wavelength conversion particles dispersed and encapsulated inside the panel body. The method for manufacturing a sub-millimeter light-emitting diode backlight panel as described in claim 1, wherein a plurality of particles are dispersed in the light-transmitting sealing layer. The method for manufacturing a sub-millimeter light-emitting diode backlight panel as described in claim 1 further includes a step (a') before step (a), wherein a patterned reflective layer is formed on the first surface of the flexible substrate, and the sub-millimeter light-emitting diode dies are exposed outside the patterned reflective layer; after implementing step (b), the patterned reflective layer is covered by the light-transmitting sealing layer. A sub-millimeter light-emitting diode backlight panel, comprising: a double-sided flexible circuit board, including a flexible substrate, a first circuit layer formed on a first surface of the flexible substrate, and a second circuit layer formed on a second surface opposite to the first surface, the first circuit layer and the second circuit layer are electrically connected to each other; a plurality of sub-millimeter light-emitting diode dies, die-bonded on the first circuit layer; a plurality of drive chips, bonded to the second circuit layer; and a transparent rigid substrate, including a board body and a transparent sealing layer attached to the board body, and the transparent sealing layer covers the sub-millimeter light-emitting diode dies. As described in claim 5, the sub-millimeter light-emitting diode backlight panel, wherein the light-transmitting rigid substrate further includes a plurality of wavelength conversion particles dispersedly encapsulated inside the panel body. As described in claim 5, the sub-millimeter light-emitting diode backlight panel has a plurality of particles dispersed in the light-transmitting sealing layer. The sub-millimeter light-emitting diode backlight panel as described in claim 5 further comprises a patterned reflective layer, which is formed above the first surface of the flexible substrate, and the sub-millimeter light-emitting diode dies are exposed outside the patterned reflective layer and are covered by the light-transmitting sealing layer.

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