CN114361064A - Mass transfer method, integrated board packaging method and integrated board - Google Patents

Abstract

The invention relates to the technical field of LED processing, and discloses a bulk transfer method, an integrated board packaging method and an integrated board, which comprise the following steps: and butting the first metal layer on the top of the Micro LED chip with the second metal layer on the surface of the CMOS backboard wafer, and combining by a hot pressing method to form the Micro LED array. The invention has the following advantages and effects: because the Micro LED chip is transferred to the CMOS back plate wafer by utilizing the phenomenon of hot-pressing diffusion between metals, and the metal hot pressing only needs to be heated according to the hot-pressing method after being aligned, the limitation of the service time of the solder paste in the solder paste method is avoided, the Micro LED chip can be used for constructing a larger integrated board, the number of the integrated boards required when the large-size screen is assembled is correspondingly reduced, the abutted seam area of the screen group is correspondingly reduced, and the use feeling of the LED screen is improved. Meanwhile, compared with the traditional solder paste through furnace hardening combination, the metal hot pressing method has higher bonding strength, no bad phenomena of solder ball cracking, tin connection and the like, and better reliability.

Description

Mass transfer method, integrated board packaging method and integrated board

Technical Field

The application relates to the technical field of LED processing, in particular to a massive transfer method, an integrated board packaging method and an integrated board.

Background

At present, compared with Liquid Crystal Displays (LCDs) and Organic Light Emitting Diodes (OLEDs), micron-sized photo-luminescent diodes (Micro LEDs) have the advantages of high contrast, low power consumption, long service life, fast response time and the like, and have attracted extensive attention in Micro-display applications such as Augmented Reality (AR), Virtual Reality (VR), LIFI light sources and the like. However, in the Micro LED flip-chip packaging technology, the use time of the solder paste of the solder brushing process (less than or equal to 8 hours) is limited, a huge amount of technical problems exist, the size of the integrated board for industrialization of the Micro LED is severely limited, so that when a terminal is pasted with a screen, a plurality of small-sized integrated boards can only be selected to be spliced into a large-sized screen group, the splicing seams are more when the large-sized screen is assembled, a large number of technical problems such as full-color are also encountered at the present stage, and the problems seriously affect the visual experience and limit the market popularization and the popularization rate.

Disclosure of Invention

Aiming at the defects in the prior art, the application aims to provide a massive transfer method, an integrated board packaging method and an integrated board, which are not limited by the service time of solder paste, can manufacture an integrated board with larger size, can form an integrated board with higher color purity, have consistent light attenuation of the integrated board and improve the effect after long-term use.

In order to achieve the above purposes, on one hand, the technical scheme is as follows:

the application provides a bulk transfer method, comprising:

growing an epitaxial layer on a sapphire substrate, depositing a first metal layer on the top surface of the epitaxial layer, and then processing to form a plurality of Micro LED chips arranged in an array;

depositing a second metal layer on the surface of the CMOS backboard wafer, and dividing the second metal layer into arrays with the same size according to the size of a single Micro LED chip;

and butting the first metal layer on the top of the Micro LED chip with the second metal layer on the surface of the CMOS backboard wafer, and combining by a hot pressing method to form the Micro LED array.

Preferably, after the epitaxial layer is grown on the sapphire substrate, a silver layer is plated on the epitaxial layer to form a silver plated layer, and then a first metal layer is deposited on the top surface of the silver plated layer

Preferably, the hot pressing method comprises the following steps:

aligning and mutually pressing a first metal layer on the top surface of the Micro LED chip and a second metal layer on the surface of the CMOS backboard wafer to form Micro plastic deformation;

and carrying out annealing treatment in vacuum or protective atmosphere to ensure that the first metal layer and the second metal layer are mutually diffused to form solid solution.

Preferably, the method further comprises the following steps:

after the Micro LED chips are processed and formed, depositing a dielectric passivation layer on the side surface of each chip in the Micro LED chips through a PECVD (plasma enhanced chemical vapor deposition) method;

the n-type common cathode is opened by inductively coupled plasma etching and then an n-contact layer is formed.

The application discloses a packaging method for integrated boards, which comprises the following steps:

completing a Micro LED array according to the method of claim 1;

removing the sapphire substrate of the Micro LED array, and covering the glass substrate provided with the control circuit on one surface of the Micro LED array, from which the sapphire substrate is removed;

uniformly covering a shading layer on the glass substrate;

and quantum dot filling is carried out in the shading layer according to the color intervals of red, green and blue, then the surface layer is covered to form the integrated board, wherein the filling position of each quantum dot corresponds to each Micro LED chip in the Micro LED array.

Preferably, the quantum dot filling comprises the following steps:

quantum dot colloids with corresponding colors are injected into the shading layer according to the color intervals of red, green and blue to form filling areas with corresponding colors, and transparent colloids or vacant filling areas corresponding to blue are injected into the filling areas;

and covering the top surface of the filling area with a filter with a corresponding color.

Preferably, the filling region is of a frustum shape having a top surface and a bottom surface, wherein the bottom surface is larger than the top surface, and the bottom surface faces the glass substrate.

Preferably, the method further comprises the following steps:

and when the filling region is formed, silver is plated on the filling region and the edge of the light shielding layer.

Preferably, the control circuit of the glass substrate is an AM addressing driving circuit implemented by a CMOS driver integrated circuit.

The application also provides a circuit board, which is characterized in that the manufacturing method of the circuit board comprises the method.

The beneficial effect that technical scheme that this application provided brought includes:

the application can realize a huge transfer method, because the Micro LED chip is transferred to the CMOS back plate wafer by utilizing the hot-pressing diffusion phenomenon between metals, and the metal hot pressing only needs to be aligned and then heated according to the hot-pressing method, so that the limitation of the service time of the solder paste in the solder paste method is avoided, the method can be used for constructing a larger integrated board, the number of the integrated boards required when a large-size screen is assembled is correspondingly reduced, the splicing area of the screen group is correspondingly reduced, and the use feeling of the LED screen is improved. Meanwhile, compared with the traditional solder paste through furnace hardening combination, the metal hot pressing method has higher bonding strength, no bad phenomena of solder ball cracking, tin connection and the like, and better reliability.

Meanwhile, the integrated board packaging method and the integrated board provided by the application adopt a quantum dot filling mode to realize full color for the blue LED combined with the CMOS, and the shading layer is utilized to isolate the part filled with the quantum dots, so that the LED light leakage problem is reduced, the color purity is better, and simultaneously, because the blue LEDs directly manufactured in a uniform batch are used as a light emitting basis, the light emitting sources have consistent properties, so that the light attenuation effects of all the LEDs are more consistent, and the display effect of the formed LED integrated board is better.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a Micro LED in the present application.

FIG. 2 is a schematic diagram of a chip array processing flow according to an embodiment of the present application.

FIG. 3 is a schematic view of a CMOS backplane wafer processing flow according to the embodiment shown in FIG. 2.

FIG. 4 is a schematic flow chart illustrating the macro transfer of the Micro LED in the embodiment shown in FIG. 3.

Reference numerals:

1. a sapphire substrate; 11. an epitaxial layer; 12. a first metal layer; 121. a silver coating layer; 2. a Micro LED chip; 21. a dielectric passivation layer; 3. a CMOS backplane wafer; 31. a second metal layer; 4. a glass substrate; 5. a light-shielding layer; 6. a filling area; 61. an optical filter; 7. a surface layer; 8. a common cathode.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In the present application, an embodiment of a method for bulk transfers is provided, comprising the following steps

S1, growing an epitaxial layer 11 on a sapphire substrate 1, depositing a first metal layer 12 on the top surface of the epitaxial layer 11, and then processing to form a plurality of Micro LED chips 2 arranged in an array.

Specifically, as shown in the first step of fig. 2, a P-type GaN layer, a quantum well layer and an N-type GaN layer are respectively formed from bottom to top, and the first metal layer 12 is deposited on the top surface of the N-type GaN layer. Then, a whole epitaxial layer 11 is cut according to an array form through a photoetching process and plasma etching, the single epitaxial layer 11 is the Micro LED chip 2, and tin paste is not used in the method, so that an ITO layer is not correspondingly arranged

In some embodiments, after the epitaxial layer 11 is grown, instead of growing a metal layer directly, a silver layer is plated on the epitaxial layer 11 to form a silver plated layer 121, and then a first metal layer 12 is deposited on the silver plated layer 121. In general technology, the ITO layer on the surface of the chip 2 is used to enhance the conductivity, but at the same time, the light transmittance is high, so that in the flip-chip packaging technology, light is emitted from the bottom of the chip 2, and the light emitting efficiency is reduced. According to the application, the metal layer is used for reflecting bottom light, so that the light output of the Micro LED chip 2 is improved. The further silver plating layer 121 can adjust the conductivity, and can reflect the light escaping to the bottom to the surface of the chip 2 to a greater extent, thereby further enhancing the light output.

In still other embodiments, after the plurality of Micro LED chips 2 are cut and formed, a dielectric passivation layer 21 is deposited on the side surface of each Micro LED chip 2 by using a PECVD deposition method to isolate each Micro LED chip 2 and prevent current leakage and influence the light emitting effect of the Micro LED chips 2, wherein the n-type common cathode 8 is opened by inductively coupled plasma etching, and then an n-contact layer is formed.

S2, depositing a second metal layer 31 on the surface of the CMOS backboard wafer 3, and dividing the second metal layer 31 into arrays with the same size according to the size of the single Micro LED chip 2.

Specifically, referring to fig. 3, the specific materials of the first metal layer 12 and the second metal layer 31 are selected as follows: the diffusion atoms must have a certain solid solubility in the matrix metal to be dissolved into the matrix lattice to form a solid solution, so as to perform solid diffusion, and generally, the first metal layer 12 and the second metal layer 31 may be a combination of tin and zinc or other metal materials with similar structures or properties.

S3, butting the first metal layer 12 on the top of the Micro LED chip 2 with the second metal layer 31 on the surface of the CMOS backboard wafer 3, and combining the two layers by a hot pressing method to form the Micro LED array.

One embodiment of the method comprises hot pressing by:

aligning and pressing the first metal layer 12 on the top surface of the Micro LED chip 2 and the second metal layer 31 on the surface of the CMOS backboard wafer 3 mutually to form Micro plastic deformation;

annealing treatment is performed in a vacuum or a protective atmosphere so that the first metal layer 12 and the second metal layer 31 diffuse into each other to form a solid solution.

Specifically, in the processing process, the first metal layer 12 which is already cut into the array arrangement along with the Micro LED chips 2 is aligned and pressed with the second metal layer 31 which is also cut into the array arrangement on the CMOS backplane wafer 3, so as to prevent the streaming between the adjacent Micro LED chips 2.

The first metal layer 12 and the second metal layer 31 are squeezed to form a diffusion couple on the contact surface, and then the diffusion couple is placed in a vacuum or protective atmosphere furnace for annealing treatment, so that a diffusion interface layer is formed between the two phases, the thickness of the diffusion interface layer can be adjusted by controlling the annealing temperature and the annealing process, and the phase interface required by us can be obtained, wherein the annealing temperature can be 150-.

The present application further provides an embodiment of an integrated board packaging method, which is mainly used for further processing the Micro LED array manufactured in the above embodiment, and a person skilled in the art can also apply the integrated board packaging method to other Micro LED arrays with similar structures according to common knowledge.

As shown in fig. 4, the embodiment of the integrated board packaging method includes the following steps, and the steps of the present embodiment are the subsequent processes of the above-mentioned bulk transfer method embodiment, so the step numbers are continued to the previous embodiment:

and S4, removing the sapphire substrate 1 of the Micro LED array, and covering the glass substrate 4 provided with the control circuit on one surface of the Micro LED array, from which the sapphire substrate 1 is removed.

Specifically, after the sapphire substrate 1 of the Micro LED array is removed, one surface of the Micro LED chip 2 on the Micro LED array is exposed. A specific circuit is formed on the surface of the glass substrate 4 by printing, and the circuit is closely attached to the exposed surface of each Micro LED chip 2 in the Micro LED array to form a closed loop.

In some preferred embodiments, the control loop of the glass substrate 4 is an AM-addressed driving loop implemented by a CMOS driver integrated circuit.

And S5, uniformly covering the shading layer 5 on the glass substrate 4.

Specifically, the light shielding layer 5 is generally made of an insulating material such as a black photoresist or a photoresist, which prevents current leakage and has a good light shielding effect.

S6, quantum dot filling is carried out in the shading layer 5 according to the color interval of red, green and blue, then the surface layer 7 is covered, and an integrated board is formed, wherein each position for quantum dot filling corresponds to each Micro LED chip 2 in the Micro LED array.

Specifically, the Micro LED chip 2 itself emits light, usually blue light, and the blue light needs to be converted to other colors, so that the blue light is absorbed by the quantum dots to emit other primary colors, thereby forming three primary colors of RGB, and finally, the three primary colors are mixed to form full-color display. The integrated board formed by the method restrains the mutual light leakage phenomenon of the light emitting points due to the shielding of the light shielding layer 5, and has purer light emitting effect and higher color purity. Meanwhile, the difference between different Micro LED chips 2 can be amplified by quantum dot luminescence, but as the Micro LED arrays used in the embodiment are formed by growing, cutting and processing in the same batch, the difference between the Micro LED arrays is much smaller than that of the Micro LED chips 2 which are transferred generally, the luminescence property is more uniform, the consistency of the final luminescence effect is stronger, and meanwhile, the light decay effect of the Micro LED chips 2 is closer, so that the display effect of the integrated board after long-term use is far better than that of the prior art.

The surface layer 7 mainly serves to protect the light shield layer 5 and the filling region 6, and is typically glass or sapphire, but may be other suitable transparent materials.

In some further embodiments, the quantum dot filling comprises the steps of:

s61, quantum dot colloid with corresponding colors is injected into the shading layer 5 according to the color intervals of red, green and blue to form a filling area 6 with corresponding colors, wherein the filling area 6 marked with blue is injected with transparent colloid or is vacant;

specifically, the arrangement of the red, green and blue filling positions can be selected according to design requirements, and the blue part is blue light because the Micro LED chip 2 per se emits, so that conversion is not required through quantum dot colloid, a transparent colloid is generally filled to support an exit channel of light emitted by the Micro LED chip 2, and the exit channel of light emitted by the Micro LED chip 2 can be opened by filling gas or digging a light shielding layer 5 in some embodiments.

In some further embodiments, the filling region 6 is of a frustum shape having a top surface and a bottom surface, wherein the bottom surface is larger than the top surface, and the bottom surface faces the glass substrate 4. Specifically, as shown in fig. 1, the filling region 6 is a frustum, which is a quadrangular frustum in the present embodiment, and may be changed into a frustum with another structure according to the process requirement in other embodiments. The frustum bottom surface of the filling region 6 is smaller than the frustum top surface, and the size of the frustum top surface is as large as possible to reduce the occupied area of the shading layer 5, so that the shadow of the light emitting surface is reduced. The bottom surface of the frustum is close to the Micro LED chip 2 so as to receive light emitted by the Micro LED chip 2 as much as possible and reduce waste.

Correspondingly, after the filling region 6 is disposed in the light shielding layer 5, the light shielding layer 5 is naturally divided into a plurality of frustum-shaped structures by the filling region 6, specifically, see fig. 1, in which the surface facing the glass substrate 4 has a smaller area than the surface facing the surface layer 7.

In some further embodiments, silver is plated between the fill region 6 and the light shield layer 5. The silver plating is used to reflect the light emitted to the light shielding layer 5, so as to prevent the light shielding layer 5 from absorbing the light and enhance the emitted light intensity.

S62, covering the top surface of the filling area 6 with the optical filter 61 with the corresponding color. So as to avoid the influence of the emergent purity of a few blue lights which are not converted by the quantum dots.

The present application further provides an embodiment of an integrated board, as shown in fig. 1, including a cmos backplane wafer 3, a Micro LED chip 2, a glass substrate 4, a filling region 6, a light shielding layer 5 and a protection layer, where the description of the up-down and left-right directions in this embodiment is performed according to the up-down and left-right directions in fig. 1.

The Micro LED chips 2 are arranged in an array, and there are several Micro LED chips, wherein fig. 1 shows a part of the Micro LED chips 2 as a representative, and structures such as a common cathode 8 can be seen in fig. 4, a bottom end of each Micro LED chip 2 is provided with a first metal layer 12, and each side surface is provided with a dielectric passivation layer 21 to prevent electric leakage. And the glass substrate 4 is printed with a control circuit, the glass substrate 4 covers the Micro LED chip 2, and a loop is formed among the control circuit, the Micro LED chip 2 and the CMOS backboard wafer 3 to control whether the Micro LED chip 2 emits light.

The surface of the CMOS backplane wafer 3 is provided with a second metal layer 31, the second metal layer 31 is divided into a plurality of layers arranged in an array according to the size of the Micro LED chip 2, and the second metal layer 31 on the top surface of the CMOS backplane wafer 3 and the first metal layer 12 on the bottom surface of the Micro LED chip 2 are integrated through hot pressing.

A light shielding layer 5 is disposed above the glass substrate 4, and the light shielding layer 5 is black glue or insulating glue, and may be other types of black glue in some other embodiments. The light-shielding layer 5 is divided into a plurality of portions arranged in an array by the filling regions 6. The filling regions 6 are arranged according to the three primary colors of red, green and blue, fig. 1 and 4 show an embodiment arranged in a row of red, green and blue, and other embodiments can be arranged according to the requirement, such as the red, green and blue are located on three corners of a triangle.

The Micro LED chip 2 corresponds to the lower portion of each filling area 6, quantum dot colloid is filled in the filling areas 6 corresponding to red and green, transparent colloid is filled in the filling areas 6 corresponding to blue, or the filling areas 6 corresponding to blue are vacant in modes of filling gas, digging and the like, the optical filter 61 corresponding to the color is arranged on the top surface of each filling area 6, and the optical filter 61 does not need to be arranged in the filling area 6 corresponding to blue. The filter 61 is covered by a surface layer 7, in this embodiment the surface layer 7 is sapphire, and in other embodiments the surface layer may be glass or other transparent materials.

The present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements are also considered to be within the scope of the present invention.

Claims (10)

1. A mass transfer method, comprising:

growing an epitaxial layer (11) on a sapphire substrate (1), depositing a first metal layer (12) on the top surface of the epitaxial layer (11), and then processing to form a plurality of Micro LED chips (2) arranged in an array;

depositing a second metal layer (31) on the surface of the CMOS backboard wafer (3), and dividing the second metal layer (31) into arrays with the same size according to the size of a single Micro LED chip (2);

and butting the first metal layer (12) on the top of the Micro LED chip (2) and the second metal layer (31) on the surface of the CMOS backboard wafer (3), and bonding by a hot pressing method to form the Micro LED array.

2. A mass transfer method according to claim 1, wherein:

after an epitaxial layer (11) is grown on a sapphire substrate (1), a silver layer is plated on the epitaxial layer (11) to form a silver plated layer (121), and then a first metal layer (12) is deposited on the top surface of the silver plated layer (121).

3. A mass transfer method according to claim 1,

the hot pressing method comprises the following steps:

aligning and pressing a first metal layer (12) on the top surface of the Micro LED chip (2) and a second metal layer (31) on the surface of the CMOS backboard wafer (3) to form Micro plastic deformation;

and annealing treatment is carried out in vacuum or protective atmosphere, so that the first metal layer (12) and the second metal layer (31) are diffused mutually to form solid solution.

4. A bulk transfer method according to claim 1, further comprising the steps of:

after the Micro LED chips (2) are processed and formed, depositing a dielectric passivation layer (21) on the side face of each Micro LED chip (2) through a PECVD (plasma enhanced chemical vapor deposition) method;

the n-type common cathode (8) is opened by inductively coupled plasma etching and then an n-contact layer is formed.

5. A method for packaging an integrated board is characterized by comprising the following steps:

completing a Micro LED array according to the method of claim 1;

removing the sapphire substrate (1) of the Micro LED array, and covering the glass substrate (4) provided with the control circuit on one surface of the Micro LED array, from which the sapphire substrate (1) is removed;

a light shielding layer (5) is uniformly covered on the glass substrate (4);

and quantum dot filling is carried out in the shading layer (5) according to the color intervals of red, green and blue, and then the surface layer (7) is covered to form the integrated board, wherein the position of each quantum dot filling corresponds to each Micro LED chip (2) in the Micro LED array.

6. The integrated board packaging method of claim 5, wherein the quantum dot filling comprises the following steps:

quantum dot colloids with corresponding colors are injected into the shading layer (5) according to the color intervals of red, green and blue to form filling regions (6) with corresponding colors, the position of each filling region (6) corresponds to one Micro LED chip (2), and transparent colloids or vacant filling regions (6) with corresponding blue colors are injected into the filling regions;

and a filter (61) with corresponding color is covered on the top surface of the filling area (6).

7. The board packaging method according to claim 6, wherein:

the filling area (6) is frustum-shaped and has a top surface and a bottom surface, wherein the top surface is larger than the bottom surface, and the bottom surface faces the glass substrate (4);

the shading layer (5) is divided into a plurality of frustum-shaped structures by the filling regions (6), wherein the area of the surface facing the glass substrate (4) is smaller than that of the surface facing the surface layer (7).

8. The board packaging method of claim 6, further comprising the steps of:

when the filling region (6) is formed, silver is plated on the edges of the filling region (6) and the light shielding layer (5).

9. The board packaging method according to claim 5, wherein: the control loop of the glass substrate (4) is an AM addressing drive loop realized by a CMOS driver integrated circuit.

10. An integrated board, wherein the integrated board is made according to the method of any one of claims 5-9.

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