CN113948502A - LED chip, preparation method thereof and preparation method of LED display module - Google Patents

Abstract

The invention provides a manufacturing process of an LED chip and the LED chip, wherein the LED chip comprises a luminous layer, a substrate and an electrode; the substrate is arranged between the light-emitting layer and the electrode; welding a substrate on a first electrode of the initial LED chip; connecting a second electrode to one side of the substrate far away from the first electrode to obtain an LED chip; the base plate has strengthened the bottom intensity of LED chip, avoid appearing the condition that the bottom was hindered by the top in the connection process with the PCB board, the height of the luminescent layer on the LED chip can be lifted to the base plate simultaneously, make the distance increase of luminescent layer and PCB board, thereby make follow-up use shelter from the material and shelter from the PCB base plate part of exposure easier to operate, then shelter from the material and appear climbing phenomenon and also can only shelter from the base plate when sheltering from the PCB board, and can not shelter from the luminescent layer, thereby realize COB product display effect's promotion.

Description

LED chip, preparation method thereof and preparation method of LED display module

Technical Field

The invention relates to the field of LEDs, in particular to an LED chip, a preparation method thereof and a preparation method of an LED display module.

Background

Because of the continuous increase of the demand of market to the screen booth apart from, indoor booth apart from product has become the main technical expansion space in display field to along with the demand interval is littleer and more, even the limit of accomplishing current technology also can't be realized to traditional disconnect-type device, the demand of product below the traditional device can't satisfy P0.7 promptly. At this moment, the COB (Chip On Board) product has a texture in the small-space market due to the characteristics of low cost, high reliability, high protection, easiness in cleaning and the like, but the problems of ink color consistency, module-to-module bright lines, color lines and the like of the COB product cannot be well solved all the time, so that the COB whole-screen effect is not good in the traditional SMD product effect, and the market popularization of the COB product is influenced.

At present, the thickness of a conventional LED chip is about 85 μm, wherein the light emitting layer 32 is ten and several micrometers, please refer to fig. 7, and the thickness of the other top is sapphire 31. When the conventional LED chip is used, in the die bonding process, the top damage often occurs because the light-emitting layer at the bottom of the chip is fragile; in order to solve the ink color consistency and improve the contrast, ink is sprayed or black glue is sprayed between chips, but due to the capillary phenomenon, the ink or the black glue covers the electrodes 33 and simultaneously ascends along the side surfaces of the chips, and the ascending heights are inconsistent, so that the side surface luminescence is inconsistent, and the side surface viewing effect of a COB product is influenced; in order to optimize the light emitting effect of the COB, an optical structure is generally made on the light emitting surface or an optical film is attached to the light emitting surface, so that the COB packaging surface is too thick, and the problems of bright lines and color lines between modules are caused.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the LED chip, the preparation method thereof and the preparation method of the LED display module are provided, and the display effect of COB products is improved.

In order to solve the technical problems, the invention adopts a technical scheme that:

an LED chip includes a light emitting layer, a substrate, and an electrode;

the substrate is disposed between the light emitting layer and the electrode.

In order to solve the technical problem, the invention adopts another technical scheme as follows:

a preparation method of an LED chip comprises the following steps:

welding a substrate on a first electrode of the initial LED chip;

and connecting a second electrode to one side of the substrate far away from the first electrode.

In order to solve the technical problem, the invention adopts another technical scheme as follows:

a preparation method of an LED display module is characterized by comprising the following steps:

connecting a second electrode of at least one LED chip to the lamp surface of the PCB substrate;

coating shielding materials in gaps of the LED chips;

packaging the PCB substrate provided with the LED chip to obtain the LED display module

The invention has the beneficial effects that: connect the second electrode after the welding base plate on the first electrode of initial LED chip again at the opposite side of base plate and obtain the LED chip, the base plate has strengthened the bottom intensity of LED chip, avoid appearing the condition that the bottom was hindered by the top in the connection process with the PCB board, the height of the luminescent layer on the LED chip can be lifted to the base plate simultaneously, make the distance increase of luminescent layer and PCB board, thereby make follow-up use shelter from the PCB base plate part that the material sheltered from the exposure easy operation more, then shelter from the material and appear climbing phenomenon also only can shelter from the base plate when sheltering from the PCB board, and can not shelter from the luminescent layer, thereby realize COB product display effect's promotion.

Drawings

FIG. 1 is a flowchart illustrating steps of a method for manufacturing an LED chip according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of an LED chip according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a wafer capable of generating a plurality of LED chips according to an embodiment of the present invention;

FIG. 4 is a schematic view of a substrate according to an embodiment of the invention;

FIG. 5 is a schematic diagram of a combination of an LED chip die and a substrate according to an embodiment of the present invention;

FIG. 6 is a schematic illustration of a portrait print according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a prior art LED chip;

FIG. 8 is a schematic diagram illustrating a comparison between climbing of a prior art LED chip and a prior art LED chip of the present invention with an equal amount of shielding material;

description of reference numerals:

1. an LED chip; 11. a first electrode; 12. a protective layer; 13. a light emitting layer; 14. a substrate; 141. a pad on the substrate; 15. a second electrode; 16. printing red LED chips; 17. printing a green LED chip; 18. printing blue LED chips;

2. a shielding material.

Detailed Description

In order to explain technical contents, achieved objects, and effects of the present invention in detail, the following description is made with reference to the accompanying drawings in combination with the embodiments.

As mentioned in the background art, the problem of poor light-emitting effect of the LED chip in the prior art is found by the research of the inventor, and the problem is most prominent in the field of Mini LED chips (LED chips with the size between 50 and 200 μm), and the reason for the problem is that: in order to solve the ink color consistency and improve the contrast, ink jet or black glue spraying among chips is a common technical means, but due to the capillary phenomenon, the climbing heights of ink or black glue on the side surface of the chip are different, and adverse effects are brought by the side light emitting of the chip. Based on this, the application provides an LED chip and preparation method and packaging method thereof, can be applied to conventional LED chip field, also can be applied to Mini LED chip field, and is specific, the base plate is welded before the LED chip is cut, and the height of the luminescent layer on the LED chip can be lifted to the base plate, makes the distance increase of luminescent layer and PCB board, avoids ink or black glue to shelter from the luminescent layer to improve COB module display module's contrast and black consistency, promote display effect.

Referring to fig. 2 and 8, an embodiment of the present invention is:

an LED chip includes a light emitting layer 13, a substrate 14, an electrode 15, and a protective layer 12; the substrate 14 is disposed between the light-emitting layer 13 and the electrode 15; the protective layer 12 is arranged on the side of the light-emitting layer 13 away from the substrate 14; the electrode 15 is used for connecting with a pad on the PCB; the thickness of the substrate 14 is 5-85 μm;

in an alternative embodiment, the electrodes comprise a first electrode 11 and a second electrode 15; one end of the first electrode 11 is arranged on the side of the light-emitting layer 13 far away from the protective layer 12, and the other end is connected with one side of the substrate 14; the other side of the substrate 14 is provided with a second electrode 15;

in an alternative embodiment, the substrate and the second electrode are integrated, that is, only the first electrode and the side of the substrate where the second electrode is not arranged need to be connected in the process;

referring to fig. 8, the top light-emitting surface of the LED chip of the present invention has no sapphire, the bottom strength of the LED chip is enhanced by adding the substrate, the bottom top damage during the die bonding process is avoided, the light-emitting layer is raised at the same time, sufficient climbing space is provided for the black ink or black glue, so that the black ink or black glue cannot block the light-emitting layer to affect the side light emission, the top sapphire is removed, more operable space can be provided for the COB surface treatment, the display effect is optimized, and the problems of bright lines and color lines between modules due to excessive thickness are avoided.

Based on the same inventive concept, please refer to fig. 1-5, the present application further provides a method for manufacturing an LED chip, comprising steps S100 to S500:

s100, welding a substrate on a first electrode of an initial LED chip;

wherein the initial LED chip comprises a substrate layer, a light emitting layer and a first electrode on the light emitting layer. The substrate layer is used as a growth substrate of the light emitting layer, and the type of the substrate layer is determined by the required light emitting wavelength. For example, for an LED chip of GaN semiconductor material such as blue LED or white LED, sapphire, SiC, Si, or other types of substrates are used; for an LED chip using an AlInGaP-based material such as a red LED, a GaAs-type substrate is used. In one embodiment, the substrate is a sapphire substrate, so that the production technology is mature, the device quality is good, the stability of sapphire is good, the sapphire substrate can be applied to a high-temperature growth process, the mechanical strength is high, the processing and the cleaning are easy, and the improvement of the performance of an LED chip is facilitated. The first electrode is a bridge for establishing electric connection between the luminous layer and the PCB substrate. The number, shape and material of the first electrodes 11 are not exclusive, for example, the number may be two or three, the shape may be circular, square or oval, and the like, and the material may be Ag, Au, Ni — Au alloy or ITO (Indium Tin Oxide ), and the like. Further, the position of the first electrode 11 is not exclusive, and may be disposed at an edge of the light emitting layer or in the middle of the light emitting layer, for example. In one embodiment, the first electrodes 11 are square electrodes, and the number of the first electrodes is two, and the first electrodes are disposed at the edge of the light emitting layer in the length direction, so as to be beneficial to enhancing the welding strength of the chip and the substrate. Specifically, the electrode layer may be formed by evaporation or deposition process, and patterning may be performed by photolithography and etching, so as to obtain the desired first electrode 11.

In an alternative embodiment, the process for preparing the initial LED chip comprises the following steps:

plating a transparent electrode on the epitaxial wafer, photoetching a preset pattern on the transparent electrode through a photoetching machine, corroding the preset pattern, photoetching a platform pattern after removing photoresist, carrying out dry etching, removing the photoresist and carrying out annealing treatment;

depositing silicon dioxide, photoetching a window pattern on the deposited silicon dioxide, corroding the silicon dioxide according to the window pattern, removing photoresist, photoetching an N pole pattern, pre-cleaning, plating a film after the pre-cleaning, namely plating an N/P pole material, stripping the film, namely stripping redundant N/P pole material, and then carrying out annealing operation;

photoetching a P pole graph, coating a film, stripping the film, and grinding the substrate layer to thin the substrate layer to obtain an initial LED chip required by S100;

in this embodiment, the polishing step may be omitted.

And S200, connecting a second electrode 15 to one side of the substrate 14 far away from the first electrode 11.

In an alternative embodiment, the side of the substrate 14 facing away from the first electrode 11 is provided with a second electrode 15;

and S500, cutting according to a preset size to obtain the required LED chip.

And cutting the whole connected substrate and wafer according to the size of a single LED chip to obtain the required LED chip.

Further, after dicing, the chips are required to be tested and sorted for subsequent work. The specific mode of chip sorting may include appearance inspection and power-on test. For example, in the case of visual inspection, a chip having a certain distance between the edge of the light-emitting portion and the edge of the substrate can be determined as a good product, or a bad product, so as to avoid damage to the light-emitting portion during dicing.

In one embodiment, the step S100 includes the steps of:

s110, planting metal balls on the first electrode 11 of the initial LED chip to form a bonding pad of the initial LED chip.

Referring to fig. 3, a schematic diagram of a wafer is shown, in which a plurality of initial LED chips are disposed on the wafer, each of the initial LED chips includes two first electrodes 11; the metal ball is a metal simple substance or an alloy;

and S120, welding the substrate 14 on the bonding pad of the initial LED chip.

The substrate 14 is welded on the bonding pad through eutectic welding, laser welding or high-temperature reflow soldering, so that the electrode on the surface of the substrate is conducted with the chip;

in an alternative embodiment, the substrate 14 is provided with corresponding pads 141, and the pads of the LED chip and the pads 141 on the substrate 14 are soldered;

referring to fig. 4, a plurality of bonding pads 141 are disposed on a substrate 14, that is, a substrate can be combined with a plurality of initial LED chips on a wafer;

in an alternative embodiment, the substrate 14 includes a BT resin substrate or a glass substrate;

in an alternative embodiment, the thickness of the substrate 14 is 5-85 μm, and the thickness of the substrate 14 is less than the length and width dimensions thereof;

in one embodiment, after step S200 and before step S500, the method further includes step S300: stripping the substrate layer of the initial LED chip to expose the light-emitting layer 13;

specifically, the substrate layer of the initial LED chip is stripped through laser, and because the substrate layer of the chip is gallium nitride, the gallium nitride can be vaporized through the laser, so that the substrate layer and the light-emitting layer are stripped, the thickness of the chip is reduced, and the light-emitting efficiency is improved;

FIG. 5 is a schematic view showing the substrate layer being peeled off after the wafer and the substrate 14 are bonded;

in an alternative embodiment, S3 further includes: stripping the substrate layer of the initial LED chip and exposing the light-emitting layer below the substrate layer; the substrate layer may be sapphire;

in one embodiment, after step S200 and before step S500, the method further includes step S400: plating a protective layer 12 with a preset thickness on the luminous layer 13;

specifically, the surface of the light-emitting layer 13 is plated with silicon dioxide with a preset thickness to serve as the protective layer 12, and the silicon dioxide is transparent and firm, so that the light transmittance of the light-emitting layer 13 is not affected while the light-emitting layer is protected, and the light-emitting efficiency of the light-emitting layer is ensured;

based on the same inventive concept, the present application further provides a method for manufacturing an LED display module, please refer to fig. 6, which includes steps S20 to S70.

And S20, connecting the second electrode of the LED chip to the lamp surface of the PCB substrate.

The LED chip can be an LED chip mentioned in the specification or an LED chip prepared by an LED chip preparation method in the specification;

the PCB substrate is used as a driving device of the LED chip and used for providing driving voltage for the light emitting part. The PCB substrate comprises a driving surface and a lamp surface, the driving surface is used for welding a driving circuit, and the lamp surface is used for welding an LED chip.

Specifically, in one embodiment, the step S20 includes the steps of:

s21: and printing solder on the lamp surface of the PCB substrate. The solder may be a solder paste or a tin-based alloy. The method for printing the solder on the lamp surface of the PCB substrate can be steel mesh printing or dispensing by a dispenser.

Further, before solder printing, the method further comprises the following steps: and welding the devices in the driving circuit to the driving surface of the PCB substrate. The devices in the driving Circuit include an IC (Integrated Circuit) control chip, an IC memory chip, a resistor, a capacitor, a connector, and the like. Specifically, the bonding of the driving Surface device may be performed by an SMT (Surface mount Technology) process.

S22: and connecting a second electrode of the LED chip on a lamp surface bonding pad of the PCB to form an LED chip 1 array.

And the PCB is electrically connected with the LED chip through reflow soldering.

S30, a shielding material is applied to the gaps of the array of LED chips 1.

Wherein, a high precision ink jet printer, a mask masking spray process, a screen printing process or a dispensing process may be used to coat the masking material around the LED chip 1. In one embodiment, a high-precision printing device is used for longitudinally and sequentially printing three colors of RGB (red, green and blue) on one side, far away from a PCB (printed circuit board), of an LED chip 1, each LED chip 1 is printed with one color, at the moment, a shielding material 2 is diffused towards two sides, covers a bonding pad and soldering tin on the PCB substrate and climbs onto the substrate of the LED chip 1, and as a light emitting part of the LED chip 1 is lifted by the substrate, the shielding material 2 cannot climb onto the light emitting part, particularly shields the side face of the light emitting part to influence the light emitting of the light emitting part, so that the light emitting effect of the LED chip is ensured;

referring to fig. 6, a schematic diagram of longitudinal printing is shown, in which a red LED chip 16, a green LED chip 17 and a blue LED chip 18 are sequentially arranged along a longitudinal direction;

in an alternative embodiment, the masking material 2 may be black ink or black glue;

and S50, covering the PCB substrate with the packaging glue by compression molding to complete packaging protection.

And directly molding the packaging adhesive through a mould pressing process to complete the packaging of the PCB provided with the LED chip 1.

Furthermore, a functional optical film is added on the surface of the packaging adhesive according to specific process requirements;

in an alternative embodiment, the encapsulation adhesive is a transparent or black-pigmented epoxy resin; or transparent or melanin-doped silica gel;

and S60, cutting off the process edge of the packaged PCB substrate to obtain the finished product display module.

In one embodiment, the display module is a COB (Chip On Board) module.

In one embodiment, after step S30 and before step S50, the method further includes step S40: and (4) lighting the LED chip 1 and aging for a preset time.

The preset time is not unique and may be determined according to the specific type of the LED chip, and may be 4 hours or 5 hours, for example. Specifically, after welding and before packaging, the LED chips are lightened, the LED chips with poor light-emitting performance can be screened out for aging preset time, and accordingly the LED chips are subjected to crystal removal and repair, and the reliability of the display module is improved.

In summary, the invention provides a manufacturing process of an LED chip and an LED chip, wherein a substrate is welded on a first electrode of an initial LED chip, a second electrode is connected on a side of the substrate away from the first electrode, a substrate layer of the initial LED chip is peeled off to expose a light-emitting layer, a protective layer is arranged on the light-emitting layer to reduce the overall thickness of the initial LED chip, and obtain a desired LED chip, the intensity of the bottom of the LED is enhanced by adding the substrate on the bottom of the initial LED chip close to the first electrode, thereby avoiding bottom top damage during die bonding when connecting with a PCB, and even if the substrate is damaged, the light-emitting layer can still be protected without affecting the light-emitting of the light-emitting layer, and simultaneously the substrate raises the height of the light-emitting layer relative to the PCB, so as to provide enough climbing space for black ink or black glue arranged when shielding the bottom of the PCB, and prevent the light-emitting layer from being shielded to affect the side light-emitting, meanwhile, the top sapphire substrate layer is omitted, so that more operable spaces can be provided for COB surface treatment, the display effect is optimized, and the problems of bright lines and color lines among modules due to over-thickness are avoided.

It should be understood that, although the steps in the flowcharts of the figures are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in the figures may include multiple steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, which are not necessarily performed in sequence, but may be performed alternately or at least partially in sequence with other steps or other steps.

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent changes made by using the contents of the present specification and the drawings, or applied directly or indirectly to the related technical fields, are included in the scope of the present invention.

Claims (10)

1. An LED chip is characterized by comprising a light-emitting layer, a first electrode and a substrate;

one side of the light-emitting layer is connected with one end of the first electrode, and the other end of the first electrode is connected with one side of the substrate;

and a second electrode is arranged on the other side of the substrate.

2. The LED chip of claim 1, further comprising a protective layer;

the protective layer is arranged on one side of the light-emitting layer far away from the substrate.

3. A preparation method of an LED chip is characterized by comprising the following steps:

welding a substrate on a first electrode of the initial LED chip;

and connecting a second electrode to one side of the substrate far away from the first electrode.

4. The method of claim 3, further comprising, after the step of bonding the substrate to the first electrode of the initial LED chip:

stripping the substrate layer of the initial LED chip to expose the light-emitting layer;

and plating a protective layer with a preset thickness on the luminous layer.

5. The method of claim 3, further comprising, before the step of bonding the substrate to the first electrode of the initial LED chip:

implanting metal balls on the first electrode to form a bonding pad of the initial LED chip;

the welding of the substrate on the first electrode of the initial LED chip is specifically:

and welding the substrate on the bonding pad.

6. The method of claim 3, wherein the step of bonding the substrate to the first electrode of the LED chip comprises:

and welding a BT resin substrate or a glass substrate on the first electrode of the initial LED chip.

7. The method for preparing the LED chip according to claim 3, wherein the step of bonding the substrate on the first electrode of the initial LED chip comprises:

and welding the substrate on the first electrode of the initial LED chip through eutectic welding, laser welding or high-temperature reflow welding.

8. The method of claim 4, wherein said peeling the substrate layer of the initial LED chip comprises:

and stripping the substrate layer of the initial LED chip by laser.

9. The method as claimed in claim 4, wherein the step of coating a protective layer with a predetermined thickness on the light-emitting layer comprises:

and plating silicon dioxide with a preset thickness on the luminous layer.

10. A preparation method of an LED display module is characterized by comprising the following steps:

connecting a second electrode of at least one LED chip to the lamp surface of the PCB substrate;

coating shielding materials in gaps of the LED chips;

and packaging the PCB substrate provided with the LED chip to obtain the LED display module.

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