WO2023040370A1

WO2023040370A1 - Led chip, led chip manufacturing method, and led chip package method

Info

Publication number: WO2023040370A1
Application number: PCT/CN2022/097774
Authority: WO
Inventors: 张世诚
Original assignee: 深圳市洲明科技股份有限公司
Priority date: 2021-09-14
Filing date: 2022-06-09
Publication date: 2023-03-23
Also published as: CN113889560A; CN113889560B

Abstract

An LED chip, an LED chip manufacturing method, and an LED chip package method. The LED chip comprises a base substrate 100, a light-emitting portion 200 formed on the base substrate 100, and an electrode 300 formed on the light-emitting portion 200. The periphery of the light-emitting portion 200 is coated with a light-absorbing medium 400. According to the LED chip, the periphery of the light-emitting portion 200 is coated with the light-absorbing medium 400, so that in a package process, the situation that a pad on a substrate and the substrate go beyond the light-emitting portion 200 to affect the overall color consistency is avoided, so that the color difference of a finally manufactured display module is reduced, and a display effect can be improved.

Description

LED chip, LED chip manufacturing method and packaging method

cross reference

This application claims the priority of the Chinese patent application filed on September 14, 2021 with application number 202111073670.2 and titled "LED chip and its manufacturing method and packaging method", which is hereby incorporated by reference in its entirety.

technical field

The present application relates to the technical field of LED (light-emitting diode, light-emitting diode), in particular to an LED chip, a method for manufacturing the LED chip, and a packaging method.

Background technique

LED chips are mainly used in ultra-large-screen high-definition display, such as monitoring and command, high-definition broadcasting, high-end cinema, medical diagnosis, advertising display, conference exhibition, office display, virtual reality and other fields, which have high requirements for display effect.

For traditional LED chips, during the packaging process, the differences in the ink color of the pads of the substrate and the substrate itself will affect the overall color consistency, resulting in differences in the color of the display unit and affecting the display effect of the display unit. Therefore, traditional LED chips have the problem of poor color consistency after packaging.

Contents of the invention

According to various embodiments of the present application, an LED chip, an LED chip manufacturing method and a packaging method are provided.

In a first aspect, the present application provides an LED chip, comprising:

Substrate;

a light-emitting portion formed on the substrate; the light-emitting portion is surrounded by a light-absorbing medium; and

An electrode formed on the light emitting part.

In one of the embodiments, the thickness of the light-absorbing medium is less than or equal to the sum of the thicknesses of the substrate and the light emitting part.

In one of the embodiments, the melting point of the light-absorbing medium is lower than the soldering temperature in the LED chip packaging process; the thickness of the light-absorbing medium is less than the sum of the thicknesses of the substrate and the light-emitting part, and the difference between the two The value is less than the preset difference.

In one of the embodiments, the size of the light-emitting part is smaller than the size of the substrate; the area of the substrate not covered by the light-emitting part and the periphery of the substrate are covered with a light-absorbing medium.

In one of the embodiments, the number of the electrodes is multiple, and each of the electrodes is uniformly arranged on the light emitting part.

In one embodiment, the light-absorbing medium is black ink, black hot melt adhesive or black oxide.

In a second aspect, the present application provides a method for preparing an LED chip, comprising:

growing an epitaxial layer on the substrate;

Patterning the epitaxial layer to prepare the light-emitting part;

making electrodes on the light emitting part;

Carry out cutting and sorting to obtain semi-finished chips; the semi-finished chips are separated by a preset distance;

Coating a light-absorbing medium around the semi-finished chip; coating the light-absorbing medium around the light-emitting part; forming an integral semi-finished chip after the light-absorbing medium is cured; and

Slitting the whole semi-finished chip to obtain LED chips.

In one of the embodiments, there are multiple light emitting parts, and each light emitting part array is distributed on the substrate.

In one of the embodiments, before the whole semi-finished chip is cut, the molding process is performed.

In one of the embodiments, before the whole semi-finished chip is cut, the reverse mold treatment is carried out, including:

Carrying out cutting and sorting, after obtaining the semi-finished chip, performing an inversion process on the semi-finished chip, so that the electrode of the semi-finished chip is placed upwards, and the substrate is adhered to the first adhesive film;

Inverting the integral semi-finished chip coated with the light-absorbing medium, and adhering the electrodes of the integral semi-finished chip on the second adhesive film.

In one of the embodiments, the first adhesive film is a blue film.

In one of the embodiments, the substrate is a sapphire substrate, after the epitaxial layer is grown on the substrate, the epitaxial layer is patterned, and before the light-emitting part is prepared, it also includes:

The substrate is back thinned and polished.

In one embodiment, the specific method of coating the light-absorbing medium around the semi-finished chip includes a high-precision inkjet printing process, a mask-blocking spraying process, a silk screen process, and a dispensing process.

In one of the embodiments, the light-absorbing medium is hot-melt adhesive; the coating of the light-absorbing medium around the semi-finished chip includes: using a dispensing process to coat hot-melt glue around the semi-finished chip.

In one of the embodiments, during the process of cutting and sorting to obtain semi-finished chips, the cutting is carried out along the symmetry line between different light emitting parts.

In a third aspect, the present application provides an LED chip packaging method for packaging the above-mentioned LED chip. The LED chip packaging method comprises:

Solder printing on the lamp surface of the PCB (Printed Circuit Board, printed circuit board) substrate;

Bonding the LED chip to the light surface of the PCB substrate;

electrically connecting the LED chip to the PCB substrate by reflow soldering;

Covering the PCB substrate with encapsulation adhesive by compression molding to complete the encapsulation protection; and

Cut off the process side of the packaged PCB substrate to obtain the finished display module.

In one embodiment, the soldering temperature of the reflow soldering is higher than the melting point of the light-absorbing medium.

In one of the embodiments, the packaging glue is a transparent glue.

In one embodiment, the encapsulation glue is transparent glue, epoxy resin glue or silica gel mixed with melanin.

In one of the embodiments, after the LED chip is electrically connected to the PCB substrate through reflow soldering, the encapsulation glue is covered on the PCB substrate through compression molding, and before the encapsulation protection is completed, it also includes:

The LED chip is turned on, aged for a preset time, and overhauled.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the present application will be apparent from the description, drawings and claims.

Description of drawings

In order to better describe and illustrate embodiments and/or examples of the inventions disclosed herein, reference may be made to one or more of the accompanying drawings. Additional details or examples used to describe the drawings should not be considered limitations on the scope of any of the disclosed inventions, the presently described embodiments and/or examples, and the best mode of these inventions currently understood.

Fig. 1 is a schematic structural view of an LED chip in some embodiments;

Fig. 2 is a flow chart of the LED chip preparation method in some embodiments;

Fig. 3 is a schematic diagram of an overall semi-finished chip after being coated with a light-absorbing medium in some embodiments;

Fig. 4 is a schematic diagram of placement direction of semi-finished chips after sorting in some embodiments;

Fig. 5 is a schematic diagram of the overall semi-finished chip after mold inversion in some embodiments;

Fig. 6 is a flowchart of a method for preparing an LED chip in other embodiments;

Fig. 7 is a flow chart of LED chip packaging method in some embodiments;

Fig. 8 is a schematic structural diagram of a display module in some embodiments;

Fig. 9 is a flow chart of LED chip packaging methods in some other embodiments.

Detailed ways

In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the application are given in the drawings. However, the present application can be embodied in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of this application more thorough and comprehensive.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used herein in the specification of the application are only for the purpose of describing specific embodiments, and are not intended to limit the application. The terms "comprising" and "having" and any variations thereof in the specification and claims of the present application and the above descriptions of the drawings are intended to cover non-exclusive inclusion.

It should be noted that when an element is referred to as being “fixed” to another element, it can be directly on the other element or there can also be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and similar expressions are used herein for purposes of illustration only.

In the drawings, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will be understood that when a layer or element is referred to as being "on" another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. layer. In addition, like reference numerals denote like elements throughout.

In the following embodiments, when layers, regions or elements are "connected", it can be interpreted that the layers, regions or elements are connected not only directly but also through other constituent elements interposed therebetween. For example, when layers, regions, elements, etc. are described as being connected or electrically connected, the layers, regions, elements, etc. may not only be directly connected or directly electrically connected, but may also be connected through another layer, region, etc. interposed therebetween. , components, etc. are connected or electrically connected.

It should also be understood that the terms "comprising/comprising" or "having" etc. specify the presence of stated features, integers, steps, operations, components, parts or combinations thereof, but do not exclude the presence or addition of one or more The possibility of other features, integers, steps, operations, components, parts or combinations thereof.

As mentioned in the background technology, the LED chips in the traditional technology have the problem of poor color consistency. The inventors found that this problem is most prominent in the field of Mini LED chips (LED chips with a size between 50 microns and 200 microns). The reason for this problem is: in order to ensure that the welding strength meets the requirements, on the one hand, the size of the pad on the PCB substrate will be larger than the electrode of the LED chip, and on the other hand, the amount of solder will be appropriately increased during welding. In this way, PCB soldering The pads and the solder used in the soldering process will exceed the shielding of the light-emitting layer on the LED chip, and the exposure will affect the contrast. In addition, the position and angle of the chip cannot be guaranteed to be consistent, resulting in unshielded exposed PCB pads and solder The graphics are also inconsistent, and the inconsistency of the reflection will cause ink color differences, which will seriously affect the contrast and consistency of the display module. Adding melanin in the encapsulant can reduce this problem, but the effect is not good. On the one hand, the distribution of melanin in the encapsulant is not uniform and the consistency is poor; Ink or black glue shields the solder at the pad, and the ink or black glue on the side of the chip climbs to a different height, which will have adverse effects due to the side light emission of the chip. Based on this, this application proposes an LED chip and its preparation method and packaging method, which can be applied to the field of conventional LED chips, and can also be applied to the field of Mini LED chips. Covered with light-absorbing medium, it can better shield PCB pads and solder, improve the contrast and ink color consistency of the display module, and improve the display effect.

In one embodiment, as shown in FIG. 1 , an LED chip is provided, including a substrate 100, a light emitting portion 200 formed on the substrate 100, and an electrode 300 formed on the light emitting portion 200; There is a light-absorbing medium 400 .

Wherein, the substrate 100 is used as a growth substrate of the light-emitting part 200 , and its type is determined by the required light-emitting wavelength. For example, LED chips of GaN semiconductor materials such as blue LEDs or white LEDs use substrates such as sapphire, SiC and Si; LED chips using AlInGaP materials such as red LEDs use GaAs substrates. In one embodiment, the substrate is a sapphire substrate. Not only is the production technology mature and the device quality is good, but also the sapphire has good stability and can be used in the high-temperature growth process. It has high mechanical strength and is easy to handle and clean, which is conducive to improving LED performance. chip performance. Further, the light-emitting part 200 , the electrode 300 and the light-absorbing medium 400 are located on the same side of the substrate 100 .

The light emitting part 200 is formed by patterning the epitaxial layer grown on the substrate 100 under proper temperature conditions. In one embodiment, the patterning process specifically includes: cleaning → plating of transparent electrode layer → photolithography of transparent electrode pattern → corrosion → deglue → platform pattern photolithography → dry etching → deglue → annealing → _SiO2 deposition → window pattern photolithography → _SiO2 corrosion → glue removal → N pole pattern photolithography → pre-cleaning → coating → stripping → annealing → P pole pattern photolithography → coating → stripping, where the transparent electrode layer is used as a current diffusion layer, and the semiconductor The layer and the electrode are in 300 ohm contact, which is beneficial to increase the current density. After the patterning process, a light-emitting part 200 is formed that has a PN junction and can emit visible light waves after applying a voltage.

Further, the size of the light emitting part 200 may be the same as that of the substrate 100 , or larger or smaller than that of the substrate 100 . Wherein, the size of the light emitting part 200 is the same as that of the substrate 100 means that the size of the light emitting part 200 is equal to the size of the substrate 100 , or the difference between the two sizes is smaller than a set difference. In the case where the size of the light emitting part 200 is the same as that of the substrate 100 , the surrounding of the light emitting part 200 is covered with a light-absorbing medium, which means that the periphery of the light-emitting part is covered with a light-absorbing medium. When the size of the light-emitting part 200 is smaller than the size of the substrate 100, the surrounding of the light-emitting part 200 is covered with a light-absorbing medium. medium. The area where the substrate 100 does not cover the light-emitting portion 200 refers to the side on which the light-emitting portion 200 is prepared on the substrate 100 . For ease of understanding, as shown in FIG. 1 , the description below will take the light emitting portion 200 smaller than the substrate 100 as an example. It should be noted that the dimensions in this application refer to the dimensions in the non-thickness direction, ie in the length and width directions.

The electrode 300 is a bridge for establishing electrical connection between the light emitting part 200 and the PCB substrate. The number, shape and material of the electrodes 300 are not unique, for example, the number can be two or three, etc., the shape can be circular, square or oval, etc., and the material can be Ag, Au, Ni-Au alloy or ITO ( Indium Tin Oxide, tin-doped indium oxide). Further, the position of the electrode 300 is not unique, for example, it can be arranged at the edge of the light emitting part 200 or in the middle of the light emitting part 200 . In one embodiment, the number of electrodes 300 is multiple, and each electrode 300 is uniformly arranged on the light emitting part 200 to enhance the bonding strength between the chip and the substrate. For example, the LED chip in FIG. 1 includes two square electrodes, and each square electrode is respectively arranged at two side edges of the light emitting part 200 in the longitudinal direction. Specifically, the electrode layer can be formed by evaporation or deposition, and patterned by photolithography and etching to obtain the desired electrode 300 .

The light-absorbing medium 400 refers to a medium material that has a large attenuation of light waves when propagating in the medium, that is, a large value of the absorption coefficient. Generally, the absorption coefficient of black matter is relatively large. Further, the light-absorbing medium 400 can be black ink, black hot-melt adhesive or black oxide, nano-coating, or super-black material made of carbon nanotubes.

Specifically, the light-absorbing medium 400 may be coated around the light-emitting part 200 using a high-precision inkjet printing process, a mask-blocking spraying process, a silk-screening process, or a dispensing process. Furthermore, in order to ensure the smooth progress of the subsequent welding work, the thickness of the light-absorbing medium 400 should be smaller than the thickness of the semi-finished chip composed of the substrate 100 , the light emitting part 200 and the electrode 300 . In one embodiment, the thickness of the light-absorbing medium 400 is less than or equal to the sum of the thicknesses of the substrate 100 and the light-emitting part 200, that is, the thickness of the light-absorbing medium 400 is less than or equal to the semi-finished chip composed of the substrate 100 and the light-emitting part 200 thickness to ensure that the electrode 300 is not attached by the light-absorbing medium 400 and provide conditions for the smooth progress of the subsequent welding work.

In addition, in one embodiment, the melting point of the light-absorbing medium 400 is lower than the soldering temperature in the packaging process of the LED chip, the thickness of the light-absorbing medium 400 is smaller than the thickness of the semi-finished chip composed of the substrate 100 and the light emitting part 200, and the difference between the two is The value is less than the preset difference. On the one hand, after the light-absorbing medium 400 is coated, there is a height difference between the light-absorbing medium 400 and the light-emitting part 200, which can prevent too much light-absorbing medium 400 from affecting subsequent packaging; on the other hand, the difference between the two is smaller than the preset difference, It can also avoid that the amount of the light-absorbing medium 400 is too small, and the light-absorbing medium 400 flows toward the PCB substrate during the encapsulation process, so that the encapsulation of the light-absorbing medium 400 cannot completely wrap around the light-emitting part 200 .

It can be understood that the LED chip may also include two or more light emitting parts 200 and a plurality of electrodes 300 corresponding to the light emitting parts 200 . These light-emitting parts 200 are all disposed on the substrate 100 , and the gap between different light-emitting parts on the substrate 100 is covered with a light-absorbing medium 400 .

The light-emitting part 200 of the above-mentioned LED chip is covered with a light-absorbing medium 400, which can prevent the pads on the substrate, solder and the substrate itself from exceeding the light-emitting part during the packaging process and affect the overall color consistency, so that the final display module The color difference is reduced, which is beneficial to improve the color uniformity, thereby improving the display effect.

Based on the same inventive concept, the present application also provides a method for manufacturing an LED chip. In one embodiment, as shown in FIG. 2 , the preparation method includes step S100 to step S600 .

Step S100: growing an epitaxial layer on the substrate.

Among them, the substrate refers to the growth substrate, and its type is determined by the required emission wavelength. For example, LED chips of GaN semiconductor materials such as blue LEDs or white LEDs use substrates such as sapphire, SiC and Si; LED chips using AlInGaP materials such as red LEDs use GaAs substrates. The epitaxial layer is a structure that grows and deposits on the surface of the substrate under appropriate temperature conditions. By controlling the doping type and doping concentration of the epitaxial layer, a p-type or n-type epitaxial layer can be obtained. Further, the thickness of the epitaxial layer is not unique, for example, it may be 0.5 micron to 5 micron.

Step S300: patterning the epitaxial layer to prepare a light-emitting part.

Wherein, the light-emitting part refers to a structure that can emit visible light waves after voltage is applied. The number of light emitting parts can be one or more. It can be understood that, when the number of light-emitting parts is one, the size of the light-emitting part is the same as the size of the substrate in the semi-finished chip obtained after dicing; In the semi-finished chip, the size of the light emitting part is smaller than the size of the substrate. In one embodiment, there are multiple light emitting parts, and the arrays of the multiple light emitting parts are distributed on the substrate. That is, there is a certain gap between different light emitting parts. In one embodiment, the gap between the light emitting parts is greater than or equal to a preset threshold. The preset threshold can be 20 microns, 25 microns or 30 microns. Increasing the gap between the light-emitting parts, on the one hand, is equivalent to increasing the operable space for subsequent cutting, which is conducive to improving the cutting yield. On the other hand, since the subsequent process will coat the gap between the light-emitting parts with a light-absorbing medium, it can Better shielding of PCB pads and solder is conducive to further improving the contrast and ink color consistency of the display module. Specifically, the epitaxial layer is patterned by semiconductor processes such as photolithography and etching to prepare the light emitting part.

In one embodiment, the epitaxial patterning process specifically includes: cleaning→plating transparent electrode layer→photolithography of transparent electrode pattern→corrosion→removal of glue→photolithography of platform pattern→dry etching→removal of glue→annealing→ _SiO2 Deposition → window pattern photolithography → _SiO2 corrosion → glue removal → N pole pattern photolithography → pre-cleaning → coating → stripping → annealing → P pole pattern photolithography → coating → stripping, where the transparent electrode layer is used as a current diffusion layer, and The semiconductor layer and the electrode are in ohmic contact, which is beneficial to increase the current density. After patterning, a light-emitting part with a PN junction is formed, which can emit visible light waves after applying a voltage.

Step S400: making electrodes on the light emitting part.

Wherein, the electrode light-emitting part establishes a bridge for electrical connection with the PCB substrate. The number, shape and material of the electrodes are not unique, for example, the number can be two or three, the shape can be round, square or oval, and the material can be Ag, Au, Ni-Au alloy or ITO (Indium Tin Oxide , tin-doped indium oxide). Specifically, the electrode layer can be formed by evaporation or deposition, and patterned by photolithography and etching to produce the required electrodes.

Step S500: Carry out dicing and test sorting to obtain semi-finished chips.

Specifically, each LED chip includes one or more light emitting parts, therefore, it needs to be cut to separate different LED chips. Take the case where an LED chip includes a plurality of light emitting parts as an example. In order to avoid damage to the light-emitting parts during cutting, cutting is usually performed at gaps between the light-emitting parts. In one embodiment, cutting is performed along the symmetry line between different light-emitting parts to obtain semi-finished chips, so as to avoid damage to the light-emitting parts during the cutting process due to cutting alignment errors, which is conducive to improving the cutting yield.

Furthermore, after dicing, the semi-finished chips need to be sorted for subsequent work. Among them, the specific methods of chip sorting may include appearance inspection and power-on test. Taking visual inspection as an example, chips with a certain distance between the edge of the light-emitting part and the edge of the substrate can be determined as good products, otherwise they are defective products, so as to avoid damage to the light-emitting part during the cutting process.

Step S600: Coating a light-absorbing medium around the semi-finished chip; coating the light-absorbing medium around the light-emitting part; forming an overall semi-finished chip after the light-absorbing medium is cured.

Wherein, the light-absorbing medium is coated around the light-emitting part. The light-emitting part, electrodes and light-absorbing medium are located on the same side of the substrate. As mentioned above, taking the size of the light-emitting part smaller than the size of the substrate as an example, the light-absorbing medium around the light-emitting part means: the area on the substrate not covered with the light-emitting part and the surrounding of the substrate are covered with light-absorbing medium. The area where the substrate does not cover the light-emitting portion refers to the side where the light-emitting portion is prepared on the substrate, and the area that does not cover the light-emitting portion because the size of the light-emitting portion is smaller than the substrate. The light-absorbing medium refers to a medium material with a large value of absorption coefficient that will be greatly attenuated when the light wave propagates in the medium. Generally, the absorption coefficient of black matter is relatively large. Further, the light-absorbing medium can be black ink, black hot-melt adhesive or black oxide, or nano-coating, or super-black material made of carbon nanotubes.

In addition, in one embodiment, the sum of the thicknesses of the substrate and the light-emitting part is greater than the thickness of the light-absorbing medium, that is, the thickness of the light-absorbing medium is smaller than the thickness of the semi-finished chip composed of the substrate and the light-emitting part, after the light-absorbing medium is coated , there is a height difference between the light-absorbing medium and the light-emitting part, so as to avoid too much light-absorbing medium affecting subsequent packaging. As shown in FIG. 3 , after the light-absorbing medium is coated, the substrate is completely covered by the light-absorbing medium 400 , and the light-emitting part 200 and the electrode 300 are completely exposed. In another embodiment, the sum of the thicknesses of the substrate and the light-emitting part is equal to the thickness of the light-absorbing medium, which can avoid the adverse effect caused by the light emitting from the light-emitting part 200 sideways, and is beneficial to further improve the display effect.

Specifically, the light-absorbing medium can be coated on the area of the substrate not covered with the light-emitting part based on a high-precision inkjet printing process, a mask-blocking spraying process, a silk screen process or a dispensing process. Among them, the high-precision inkjet printing process is a process of coating a light-absorbing medium with a high-precision inkjet printer. High-precision inkjet printers, also known as high-precision microelectronic inkjet printers, have the characteristics of high mechanical strength, good stability, accurate motion accuracy, and strong system compatibility. They are widely used in printed electronics, flexible electronics, organic electronics, and bioelectronics. As well as thin-film packaging printing and OLED (Organic Light-Emitting Diode, organic light-emitting diode) pixel printing and other fields, the ink can be directly sprayed onto the substrate to achieve the required structural layer production. The ink can be based on organic solvents, water solvents, or nanoparticle inks. The mask mask spraying process is a process in which a mask plate is set between the nozzle and the substrate, and then the substrate is selectively sprayed. The specific process of the silk screen printing process includes: using the screen as the plate base, and making a screen printing plate with graphics through the photosensitive plate-making method; reusing the screen printing plate graphics part of the mesh can penetrate the ink, and the non-graphic part of the screen The basic principle of the hole impermeable ink is to carry out ink printing; when printing, pour ink into one end of the screen printing plate, apply a certain pressure on the ink part on the screen printing plate with a scraper, and at the same time move towards the other end of the screen printing plate at a constant speed Moving, the ink is squeezed by the scraper from the mesh of the graphic part to the substrate during the movement. The silk screen printing process can be applied to various types of inks, and is not limited by the size and shape of the substrate. It has the advantages of convenient plate making and low price.

In one embodiment, the light-absorbing medium is hot-melt adhesive, and the hot-melt adhesive is coated around the semi-finished chip by using a dispensing process. Specifically, a glue dispenser can be used to inject hot melt adhesive between the semi-finished chips, and after heating, the hot melt adhesive can be wrapped around the semi-finished chip and cover the surroundings of the light-emitting part to form a whole semi-finished chip, which is conducive to lifting and subsequent mold inversion Job yield. Further, by controlling the glue output of the hot melt adhesive, the sum of the thicknesses of the substrate and the light-emitting part can be greater than or equal to the thickness of the hot melt adhesive, and the difference between the two is smaller than the preset difference. After the melt adhesive is coated and cured, there is a height difference between the hot melt adhesive and the light-emitting part, which can avoid the influence of too much hot melt adhesive on subsequent packaging; on the other hand, the difference between the two is less than the preset difference, and can avoid the The amount of hot melt adhesive used is too small, and the hot melt adhesive flows toward the PCB substrate during the packaging process, resulting in the inability to completely wrap around the light-emitting part after packaging.

Step S700: cutting the whole semi-finished chip to obtain LED chips.

Specifically, laser cutting, plasma cutting or blade cutting can be used to cut the whole semi-finished chip, so that each LED chip is independent of each other to obtain the final LED chip.

In the above LED chip preparation method, the light-absorbing medium is coated around the light-emitting part, which can prevent the solder pads, solder and the substrate on the substrate from exceeding the light-emitting part during the packaging process and affect the overall color consistency, so that the final display module The color difference is smaller, the color is more uniform, and the display effect is better.

Further, in one embodiment, before cutting the whole semi-finished chip, it performs a molding process. Wherein, mold inversion treatment refers to the treatment process of adhering the semi-finished product on the adhesive film. Specific to this application, the semi-finished product may be a semi-finished chip, or may be an entire semi-finished chip. Specifically, on the one hand, a plurality of semi-finished products are adhered to the adhesive film, so that each semi-finished product and the adhesive film form a whole, which can facilitate the subsequent unified processing of each semi-finished product, which is conducive to improving efficiency; Change the placement direction of semi-finished products to improve the operation convenience of subsequent processing, thereby improving efficiency.

In one embodiment, before slitting the whole semi-finished chip, carry out inversion process, including: cutting and sorting, after obtaining the semi-finished chip, perform inversion process on the semi-finished chip, so that the electrodes of the semi-finished chip face upward placing, the substrate is adhered to the first adhesive film; the integral semi-finished chip coated with the light-absorbing medium is subjected to inversion processing, and the electrodes of the integral semi-finished chip are adhered to the second adhesive film.

Specifically, after the test sorting is completed, the semi-finished chip is placed with the electrodes facing upwards. As shown in FIG. 4 , a plurality of semi-finished chips can be placed on the first adhesive film 1 at predetermined distances, the substrate 100 is in direct contact with the first adhesive film 1 , and the electrodes 300 are located away from the first adhesive film 1 . The preset distance can be determined according to the coating method of the light-absorbing medium. For example, for a light-absorbing medium coating method with good resolution and high precision, the preset spacing can be appropriately reduced to reduce the amount of light-absorbing medium used and reduce costs; otherwise, the preset spacing can be appropriately increased to improve yield. Further, a bracket may be used to fix and tighten the first adhesive film 1 , so that the substrate 100 is in close contact with the first adhesive film 1 . In one embodiment, the first adhesive film 1 is a blue film, which has the advantages of good softness and elasticity, and is conducive to improving the convenience of operation.

After the above-mentioned first inversion process is completed, a light-absorbing medium is coated around the semi-finished chip, and the whole semi-finished chip is formed after the light-absorbing medium is cured. The second inversion process is to invert the whole semi-finished chip coated with light-absorbing medium, and adhere the electrodes of the whole semi-finished chip to the second adhesive film 2 . As shown in FIG. 5 , at this time, the substrate 100 of the overall semi-finished chip faces upward. Then, the semi-finished chips after pouring are cut, so that each LED chip is independent of each other, and the final LED chip is obtained. Further, a hard knife is used in the slitting process to reduce the operation requirements and improve the convenience of use. In one embodiment, LED chips are obtained by cutting along the symmetry line between different LED chips, so as to avoid cutting the chip body due to cutting alignment errors, which is beneficial to improve the cutting yield.

In the above embodiment, before cutting the whole semi-finished chip, the mold is reversed, which can improve the convenience of operation and improve the efficiency.

In one embodiment, the substrate is a sapphire substrate. As shown in FIG. 6 , after step S100 and before step S300 , step S200 is further included: Thinning and polishing the backside of the substrate.

Due to the poor thermal conductivity of sapphire, when using LED chips, a large amount of heat will be conducted. In order to prevent the excessive temperature rise of the active area of the LED chip from affecting its light output characteristics and life, it is necessary to conduct a sapphire substrate. The back is thinned to improve the thermal performance of the device. In addition, since the Mohs hardness of sapphire reaches 9.0, in order to meet the requirements of subsequent processes such as scribing and splitting, it is also necessary to reduce the thickness of the substrate to a certain extent. There is a surface damage layer on the back of the thinned substrate, and its residual stress will cause the thinned epitaxial wafer to be bent and deformed and easily cracked in the subsequent process, thereby affecting the yield. Therefore, after thinning, the back of the substrate needs to be polished to remove the above-mentioned surface damage layer and eliminate residual stress. Specifically, a precision grinding and polishing machine can be used to thin and polish the backside of the substrate.

In the above embodiments, the use of sapphire substrate not only has mature production technology and good device quality, but also has good stability and can be used in the high-temperature growth process. It has high mechanical strength and is easy to handle and clean, which is conducive to improving the performance of LED chips. .

Based on the same inventive concept, the present application also provides an LED chip packaging method for packaging the above-mentioned LED chip. In one embodiment, as shown in FIG. 7 , the LED chip packaging method includes step S20 to step S70 .

Step S20: printing solder on the lamp surface of the PCB substrate.

Wherein, the PCB substrate is used as a driving device for the LED chip to provide a driving voltage for the light emitting part. The PCB substrate includes a driving surface and a lamp surface, the driving surface is used for welding the driving circuit, and the lamp surface is used for welding the LED chip. Specifically, the solder can be solder paste or tin-based alloy. The method of solder printing on the lamp surface of the PCB substrate can be stencil printing or glue dispensing.

Further, in one embodiment, before solder printing, the method further includes: soldering the components in the driving circuit to the driving surface of the PCB substrate. Wherein, the devices in the driving circuit include an IC (Integrated Circuit, integrated circuit) control chip, an IC memory chip, resistors, capacitors, connectors, and the like. Specifically, the welding of the driving surface device can be completed through an SMT (Surface Mounted Technology, Surface Mount Technology) process.

Step S30: bonding the LED chip to the light surface of the PCB substrate.

Among them, die bonding, also known as die bonding or die bond, is to bond the chip to the designated area of the bracket through colloid (for LED chips, it is generally conductive glue or insulating glue) to form a thermal path or an electrical path, which is the next step. Links operations that provide conditions. Specifically, after the PCB substrate printed with solder has been tested, a die bonder can be used to bond the LED chip to the light surface of the PCB substrate.

Step S40: electrically connecting the LED chip to the PCB substrate by reflow soldering.

Wherein, the reflow soldering may be vacuum reflow soldering or nitrogen gas reflow soldering, so as to improve soldering quality. Further, in one embodiment, the soldering temperature of reflow soldering is higher than the melting point of the light-absorbing medium. During the soldering process, the light-absorbing medium around the LED chip melts, flows down the chip, passes through electrodes, solder, and PCB pads, Wrapped around the LED chip. Since part of the light-absorbing medium melts and flows to the PCB substrate, there is still a height difference between the light-absorbing medium and the LED chip when the amount of light-absorbing medium is large, which can not only ensure the effective shielding of the side of the chip, but also avoid the light-absorbing medium from adhering It affects the subsequent display effect on the chip surface.

In one embodiment, the light-absorbing medium is black hot-melt adhesive. Taking solder as solder paste as an example, during the soldering process, the soldering temperature of reflow soldering is about 200°C, which is higher than the melting point of black hot melt (about 100°C). After reflow, the black hot sol solidifies at room temperature and wraps the PCB pad and solder, which is conducive to improving the reliability of the package, and is also conducive to further improving the contrast of the display module and the consistency of ink color. It can be understood that the pads and solder feet of the PCB substrate are the window opening area of the PCB. During the reflow soldering process, the PCB substrate outside the window opening area cannot be covered by the black hot melt because it is covered with ink. Therefore, after reflow soldering , although part of the black hot melt flows to the side of the PCB substrate, most of the black hot melt remains around the LED chip due to the effect of surface tension.

Step S60: Making the encapsulation glue cover the PCB substrate by molding to complete the encapsulation protection.

Wherein, the encapsulation glue can be transparent glue, or epoxy resin glue or silica gel mixed with melanin. Compression molding (also known as compression molding or compression molding) is a process in which powdery, granular or fibrous materials are first placed into a mold cavity at molding temperature, and then closed and pressurized to form and solidify. Compression molding can be used for thermosetting plastics, thermoplastics and rubber materials. Specifically, special fixtures can be used to mold the encapsulation adhesive so that the encapsulation adhesive can cover the PCB substrate to complete the encapsulation protection. It can be understood that the number of layers of encapsulant is not unique, and the materials used in each layer may be the same or different. For example, the area between the LED chips can be filled with epoxy resin glue or silica gel mixed with melanin, and then the transparent glue can be used to cover the entire PCB substrate to complete the overall package protection.

Step S70: cutting off the process side of the packaged PCB substrate to obtain a finished display module.

Wherein, the display module can be a single-color module, a two-color module or a full-color module. In one embodiment, the display module is a COB (Chip On Board, chip on board) module, which has a good heat dissipation effect. Specifically, in the manufacturing process of the previous steps, defects such as poor molding are likely to exist at the edge, so the process edge is usually designed on the PCB substrate. After packaging, cut off the process side of the packaged PCB substrate, as shown in Figure 8, the finished display module can be obtained, in the figure, 3 is the packaging glue, and 4 is the LED chip.

In the above LED chip packaging method, the LED chip used is coated with a light-absorbing medium around the light-emitting part, which can prevent the solder pads, solder and the substrate itself from exceeding the light-emitting part on the substrate during the packaging process and affect the overall color consistency, so that the final product The finished display module has less color difference, more uniform color and better display effect.

In one embodiment, as shown in FIG. 9 , after step S40 and before step S60 , step S50 is further included: lighting up the LED chip, aging for a preset time, and performing maintenance. Wherein, the preset time is not unique and can be determined according to the specific type of the LED chip, for example, it can be 3 hours, 4 hours or 5 hours. Specifically, after soldering and before packaging, the LED chips are lit and aged for a preset time, so that LED chips with poor luminous performance can be screened out for decrystallization repair, which is beneficial to improving the reliability of the display module.

It should be understood that although the various steps in the flow chart of the accompanying drawings are displayed sequentially according to the arrows, these steps are not necessarily executed sequentially in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least some of the steps in the drawings may include multiple steps or stages, these steps or stages are not necessarily executed at the same time, but may be executed at different times, and the execution order of these steps or stages is also It is not necessarily performed sequentially, but may be performed alternately or alternately with other steps or at least a part of steps or stages in other steps.

The technical features of the above embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be It is considered to be within the range described in this specification.

The above example only expresses several implementation modes of the present application, and the description thereof is relatively specific and detailed, but it should not be understood as limiting the scope of the patent for the invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the scope of protection of the patent application should be based on the appended claims.

Claims

A kind of LED chip is characterized in that, comprises:

Substrate;

a light-emitting portion formed on the substrate; the light-emitting portion is surrounded by a light-absorbing medium; and

An electrode formed on the light emitting part.
The LED chip according to claim 1, wherein the thickness of the light-absorbing medium is less than or equal to the sum of the thicknesses of the substrate and the light-emitting part.
The LED chip according to claim 2, wherein the melting point of the light-absorbing medium is lower than the soldering temperature in the LED chip packaging process; the thickness of the light-absorbing medium is less than the thickness between the substrate and the light-emitting part. and, and the difference between them is less than the preset difference.
The LED chip according to any one of claims 1 to 3, characterized in that, the size of the light emitting part is smaller than the size of the substrate; the area of the substrate that does not cover the light emitting part, and the The substrate is surrounded by a light-absorbing medium.
The LED chip according to any one of claims 1 to 3, wherein the number of the electrodes is multiple, and each of the electrodes is uniformly arranged on the light emitting part.
The LED chip according to claim 1, wherein the light-absorbing medium is black ink, black hot melt adhesive or black oxide.
A method for preparing an LED chip, characterized in that it comprises:

growing an epitaxial layer on the substrate;

Patterning the epitaxial layer to prepare the light-emitting part;

making electrodes on the light emitting part;

Carry out cutting and sorting to obtain semi-finished chips; the semi-finished chips are separated by a preset distance;

Coating a light-absorbing medium around the semi-finished chip; coating the light-absorbing medium around the light-emitting part; forming an integral semi-finished chip after the light-absorbing medium is cured; and

Slitting the whole semi-finished chip to obtain LED chips.
The LED chip manufacturing method according to claim 7, characterized in that there are multiple light emitting parts, and each light emitting part array is distributed on the substrate.
The method for manufacturing an LED chip according to claim 7, characterized in that before the said integral semi-finished chip is cut, an inversion process is performed.
The LED chip preparation method according to claim 9, characterized in that, before the said overall semi-finished chip is cut, the inversion process is performed, comprising:

Carrying out cutting and sorting, after obtaining the semi-finished chip, performing an inversion process on the semi-finished chip, so that the electrode of the semi-finished chip is placed upwards, and the substrate is adhered to the first adhesive film;

Inverting the integral semi-finished chip coated with the light-absorbing medium, and adhering the electrodes of the integral semi-finished chip on the second adhesive film.
The LED chip manufacturing method according to claim 10, wherein the first adhesive film is a blue film.
The LED chip preparation method according to claim 7, wherein the substrate is a sapphire substrate, after the epitaxial layer is grown on the substrate, the epitaxial layer is patterned, and before the light-emitting part is prepared, further comprising: :

The substrate is back thinned and polished.
According to the LED chip preparation method described in any one of claims 7 to 12, it is characterized in that the specific way of coating the light-absorbing medium around the semi-finished chip includes a high-precision inkjet printing process, a mask blocking spraying process, Silk screen printing process and dispensing process.
The method for preparing an LED chip according to claim 13, wherein the light-absorbing medium is hot melt adhesive; and the coating of the light-absorbing medium around the semi-finished chip includes: using a dispensing process to coat the surrounding of the semi-finished chip Hot melt glue.
The LED chip manufacturing method according to any one of claims 7 to 12, characterized in that, in the process of cutting and sorting to obtain semi-finished chips, cutting is carried out along the symmetry line between different light emitting parts.
A LED chip packaging method, characterized in that it is used to package the LED chip according to any one of claims 1 to 6, the LED chip packaging method comprising:

Solder printing on the lamp surface of the PCB substrate;

Bonding the LED chip to the light surface of the PCB substrate;

electrically connecting the LED chip to the PCB substrate by reflow soldering;

Covering the PCB substrate with encapsulation adhesive by compression molding to complete the encapsulation protection; and

Cut off the process side of the packaged PCB substrate to obtain the finished display module.
The LED chip packaging method according to claim 16, wherein the soldering temperature of the reflow soldering is higher than the melting point of the light-absorbing medium.
The LED chip packaging method according to claim 16 or 17, wherein the packaging glue is a transparent glue.
The method for encapsulating LED chips according to claim 16 or 17, wherein the encapsulating glue is transparent colloid, epoxy resin glue or silica gel mixed with melanin.
The LED chip packaging method according to any one of claims 16 to 19, characterized in that, after the LED chip is electrically connected to the PCB substrate by reflow soldering, the packaging glue is covered by molding The PCB substrate, before the package protection is completed, also includes:

The LED chip is turned on, aged for a preset time, and overhauled.