A mounting structure and method for Mini / Micro LED chips

Abstract

The present application discloses a mounting structure and a mounting method for Mini / Micro LED chips. The mounting method includes: arranging a plurality of LED chips on a PET film; aligning and laminating the PET film with a substrate so that the pads of the LED chips correspond to the pads on the substrate one by one; the pads on the substrate are provided with conductive particles, and the conductive particles include metal conductive balls and conductive glue coated on the surface of the metal conductive balls; hot-pressing the PET film to melt the conductive glue through heat conduction, so as to fix the LED chips on the substrate through the conductive glue after cooling. The mounting method adopted in the technical solution of the present application has an implementation temperature of the hot melting temperature of the conductive glue, and further forms a mechanical connection between the LED chips and the substrate after the conductive glue is cured, which is greatly reduced compared with the operation temperature of traditional reflow soldering, so as to effectively prevent thermal damage to the LED chips caused by high-temperature operation.

Description

Technical Field

[0001] This application relates to the technical field of LED chip setting, and particularly relates to a mounting structure and a mounting method for Mini / Micro LED chips. Background Art

[0002] The higher the resolution of a display screen, the more pixel points it has on the screen. For example, a 4K display screen has 8,294,400 pixel points, and an 8K display screen has 33,177,600 pixel points. And each pixel point requires 3 chips (red, green, and blue). In the traditional process, the positive and negative electrodes of each chip need to be welded. Therefore, the number of chip welds reaches tens of millions or even is measured in hundreds of millions.

[0003] In the prior art, the reflow soldering process is usually used to realize the welding of Mini / Micro LEDs. During the operation of reflow soldering, the temperature of reflow soldering can reach 250°C, while the junction temperature Tj (Junction Temperature) of red, green, and blue chips is generally between 125 and 150°C. Therefore, when the welding time exceeds this temperature for a long time (more than 10 seconds), there is a great risk of damaging the LED chips. Summary of the Invention

[0004] This application provides a mounting method for Mini / Micro LED chips, aiming to solve the problem that the process of using reflow soldering to connect LED chips to a substrate in the prior art is prone to damage the chips due to excessive temperature.

[0005] To achieve the above object, this application proposes a mounting method for Mini / Micro LED chips, and the mounting method includes:

[0006] Arrange a plurality of LED chips on a PET film;

[0007] Align and bond the PET film with the substrate, and make the pads of the LED chips correspond to the pads on the substrate one by one; the pads on the substrate are provided with conductive particles, and the conductive particles include metal conductive balls and conductive glue coated on the surface of the metal conductive balls;

[0008] Thermally press the PET film to melt the conductive glue through heat conduction, so as to fix the LED chips on the substrate through the conductive glue after cooling.

[0009] In some embodiments, the arranging a plurality of LED chips on a PET film includes:

[0010] Pretreat the PET film; the pretreatment includes cleaning treatment and antistatic treatment;

[0011] Load and convey a plurality of the LED chips to a die bonder, and arrange the LED chips on the PET film with the pads facing upward in a preset array pattern.

[0012] In some embodiments, aligning and bonding the PET film with the substrate and making the pads of the LED chips correspond to the pads on the substrate one by one includes:

[0013] Invert the PET film so that the pads of the LED chips face downward;

[0014] Based on an alignment system, align the positions of the pads of the LED chips and the pads on the substrate;

[0015] Bond the PET film so that the pads of the LED chips correspond to the pads on the substrate one by one.

[0016] In some embodiments, hot pressing the PET film to melt the conductive adhesive through heat conduction, so as to fix the LED chips on the substrate through the conductive adhesive after cooling includes:

[0017] Set hot pressing parameters, and heat and press the PET film toward the substrate under the hot pressing parameters; the heating temperature in the hot pressing parameters is the hot melting temperature corresponding to the conductive adhesive;

[0018] Perform a cooling treatment at a cooling rate of not less than 10 °C / S, so as to mechanically connect the LED chips on both sides with the substrate through the curing of the conductive adhesive and fix the LED chips on the substrate.

[0019] In some embodiments, after fixing the LED chips on the substrate, a PET film tearing step is further included, and the PET film tearing step includes:

[0020] Set film tearing parameters; the film tearing parameters include a peeling angle, a peeling speed, and a peeling force;

[0021] Perform a film tearing operation on the PET film according to the film tearing parameters, and after completing the film tearing operation, check the state of the LED chips.

[0022] In some embodiments, before setting the film tearing parameters, it is further included to confirm whether the film tearing conditions meet the preset film tearing conditions, and the preset film tearing conditions include:

[0023] The conductive adhesive is completely cured and the edges of the PET film are not adhered or damaged.

[0024] In some embodiments, after fixing the LED chips on the substrate through the conductive adhesive after cooling, it is further included:

[0025] Remove the excess conductive particles and contaminants around the pads of the substrate;

[0026] Attach an LED chip protective film to form protection for the light-emitting performance of the LED chip; the LED chip protective film includes a transparent film and a black semi-solid adhesive formed by compounding;

[0027] Perform quality inspection after the LED chip is mounted and fixed on the substrate.

[0028] In some embodiments, the attaching the LED chip protective film to form protection for the light-emitting performance of the LED chip includes:

[0029] Position and attach the LED chip protective film so that the transparent film in the LED chip protective film corresponds to the light-emitting area of the LED chip, and the black semi-solid adhesive corresponds to the peripheral side of the LED chip;

[0030] Press down the black semi-solid adhesive so that the black semi-solid adhesive separates from the transparent film and flows to the periphery and bottom of the LED chip.

[0031] In some embodiments, the performing quality inspection after the LED chip is mounted and fixed on the substrate includes:

[0032] Detect whether the appearance form is set correctly; the appearance form includes whether the LED chip protective film is attached correctly and whether the LED chip is skewed;

[0033] Test the light-emitting performance of the LED chip; the light-emitting performance of the LED chip includes whether the chip can be lit and whether the chip brightness is consistent.

[0034] This application also provides a mounting structure for a Mini / Micro LED chip, which is prepared by using the mounting method described above.

[0035] The technical solution of this application proposes a method for mounting Mini / Micro LED chips. The mounting method includes: arranging a plurality of LED chips on a PET film; aligning and laminating the PET film with a substrate so that the pads of the LED chips correspond to the pads on the substrate one by one; the pads on the substrate are provided with conductive particles, and the conductive particles include metal conductive balls and conductive glue coated on the surface of the metal conductive balls; hot-pressing the PET film to melt the conductive glue through heat conduction, so as to fix the LED chips on the substrate through the conductive glue after cooling. Based on the structural design of the conductive particles on the substrate, the technical solution of this application can make the conductive glue of the conductive particles melt during the process of one-to-one fitting of the pads of the LED chips and the pads on the substrate and during the hot melting and cooling process, and form a mechanical connection between the LED chips and the substrate after the conductive glue is cured, and conduct the main electrical transmission through the metal conductive balls therein. By using the mounting method provided by the technical solution of this application, the implemented temperature is greatly reduced compared with the temperature of traditional reflow soldering operations, and it can effectively prevent thermal damage to the LED chips caused by high-temperature operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings, where:

[0037] Figure 1 is a schematic flowchart of the method for mounting Mini / Micro LED chips according to an embodiment of this application Figure 1 ;

[0038] Figure 2 is a schematic flowchart of the method for mounting Mini / Micro LED chips according to an embodiment of this application Figure 2 ;

[0039] Figure 3 is a schematic structural diagram of the mounting of Mini / Micro LED chips according to an embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the drawings in the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, rather than all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0041] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present application are only used to explain the relative positional relationship, movement conditions, etc. between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will change accordingly.

[0042] It should also be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time.

[0043] In addition, the descriptions involving "first", "second", etc. in the present application are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present application.

[0044] Referring to Figure 1 As shown, the present application provides a method for mounting Mini / Micro LED chips, aiming to fix the LED chips on a substrate and achieve electrical connection with the substrate. The substrate includes a PCB board and a glass substrate. Among them, pads are correspondingly provided on the substrate and the LED chips, and conductive particles (conductive layers) are provided on the pads of the substrate. The LED is mounted on the substrate, and mechanical connection and electrical connection are achieved through the conductive particles between the pads of the two.

[0045] Among them, the conduction can be achieved by electrostatic adsorption of a plurality of conductive particles on the pads of the substrate. For example, the conductive particles and the pads of the substrate are respectively subjected to static electrode polarization treatment with opposite charge polarities, so as to generate an electrostatic attraction force between the conductive particles and the substrate, further enabling the conductive particles to be quickly and evenly distributed on the pads of the substrate, providing a good basis for the subsequent alignment and bonding of the LED chips.

[0046] Among them, before the conductive particles and the pads of the substrate are respectively subjected to static electrode polarization treatment with opposite charge polarities, the preparation of the conductive particles is also included. The preparation method of the conductive particles includes preparing metal conductive balls, and then uniformly coating conductive glue on the surface of the metal conductive balls.

[0047] Specifically, it includes producing conductive metal balls using a gas injection method or a mechanical separation method. The metal conductive balls include metal balls such as tin balls, silver balls, and nickel balls. The diameter of the metal conductive balls is controlled within 3 - 20 μm, and the particle size error is strictly controlled within ±0.5 μm, so as to ensure that the prepared conductive particles can be set between the pads of the LED chip and the pads of the substrate to form good contact and electrical connection. Among them, the particle size distribution can be detected by a laser particle size analyzer to ensure the particle size consistency of the metal conductive balls.

[0048] Furthermore, CVD chemical vapor deposition or spin coating process is used to form a uniform and dense conductive adhesive on the surface of the metal conductive balls. The thickness of the conductive adhesive is controlled within the range of 3% - 10% of the diameter of the metal conductive balls (preferred thickness), and the maximum thickness does not exceed 25% of the diameter of the metal conductive balls (peak thickness); thus, while ensuring that the conductive adhesive can provide sufficient connection strength, it will not excessively increase the thickness of the packaging structure. Among them, after the conductive adhesive is coated, XPS (X-ray photoelectron spectroscopy) can be used to analyze the energy distribution of photoelectrons to detect the chemical composition, oxidation state, and thickness of the conductive adhesive layer. The XPS detection method has high resolution and can detect thickness changes at the nanometer level. Also, after the conductive adhesive is coated, the microstructure of the conductive adhesive can be detected by SEM (scanning electron microscope). By scanning the surface of the metal conductive balls with a high-energy electron beam and generating a high-resolution image by detecting the reflected electrons, the morphology and uniformity of the conductive adhesive can be observed. Its resolution can reach 1 nm, and the microstructure and defects of the conductive adhesive layer can be clearly observed.

[0049] In this way, through strict particle size control, precise conductive adhesive coating, and advanced detection means in the preparation of conductive particles, the production quality of conductive particles is ensured, providing a high-quality material basis for the packaging of Mini / Micro LED chips.

[0050] Among them, the conductive adhesives include silver-based conductive adhesives, copper-based conductive adhesives, carbon-based conductive adhesives, metal oxide conductive adhesives, conductive polymer adhesives, and mixed filler conductive adhesives, providing a variety of types for selection. Specifically, silver-based conductive adhesives use silver powder as the main conductive filler, with high electrical conductivity and excellent thermal conductivity; they are suitable for high-precision applications, can provide stable electrical connections, and are suitable for hot melt processes at lower temperatures. Copper-based conductive adhesives use copper powder as the conductive filler, with lower costs and good electrical conductivity, suitable for scenarios that are sensitive to costs but require high electrical conductivity, and the antioxidant performance can be improved through surface passivation treatment. Carbon-based conductive adhesives use graphite or carbon nanotubes as fillers, with electrical conductivity slightly inferior to metals, but with flexibility and light weight characteristics, suitable for scenarios with strict weight requirements or high-temperature resistance requirements. Metal oxide conductive adhesives use metal oxides (such as ITO) as fillers, suitable for transparent electronic devices and encapsulation scenarios with requirements for light transmittance. Conductive polymer adhesives are based on conductive polymers (such as polypyrrole or polyaniline), suitable for flexible electronic devices and flexible encapsulation requirements. Mixed filler conductive adhesives mix silver powder, copper powder, and carbon materials, etc., to balance electrical conductivity and costs; they are suitable for scenarios seeking a balance between performance and price.

[0051] After the preparation of the conductive particles is completed, the conductive particles and the pads of the substrate can be statically polarized respectively, so that the two have opposite charge polarities, preparing for the adsorption of the metal conductive balls on the substrate. Among them:

[0052] The static polarization method of the conductive particles can be: placing the prepared conductive particles in an electrostatic pipeline, which is a closed space for generating and maintaining an electrostatic field. Apply a high voltage of 5 - 20 KV in the electrostatic pipeline to make the surface of the conductive particles carry uniform positive or negative charges. To ensure the uniformity and stability of the surface charges of the conductive particles, when applying the voltage, the voltage stability error is controlled within ±5%, and a static voltage meter can be used for real-time monitoring to ensure the uniformity of the surface charges of the conductive particles.

[0053] The static polarization method of the pads of the substrate can be: connecting all the pads on the substrate through a test port, which is an interface for applying voltage and monitoring the charge state. Then apply a charge opposite to the surface of the conductive particles to the pads of the substrate. This means that if the conductive particles carry positive charges, then the pads of the substrate need to carry negative charges; vice versa.

[0054] It should be noted that the absolute value of the voltage used for static polarization of the pads on the substrate is 1.2 to 2.0 times (preferred voltage value) of the voltage value for static polarization of the conductive particles, and the maximum does not exceed 10 times (peak voltage). Exemplarily, when the voltage applied in the electrostatic pipeline is ±5 kv, the static polarization voltage of the pads on the substrate is not less than ±6 kv. The selection of this voltage range can ensure that sufficient electrostatic attraction can be generated between the pads on the substrate and the conductive particles, so as to achieve rapid and uniform adsorption.

[0055] In addition, adsorbing the conductive particles onto the pads on the substrate includes: scanning and capturing the positions of the pads on the substrate to establish pad coordinate data, and these pad coordinate data are used to determine the subsequent placement and positioning of the conductive particles. Among them, a high-precision scanning device is used to comprehensively scan the substrate, such as a CCD camera. Then, according to the pad coordinate data, the number and positions of the pads on the substrate can be determined, and then a certain number of conductive particles with charge polarities are placed on the substrate in a specific area. Under the action of the attraction between opposite charges, the conductive particles start to roll and adsorb onto the pads on the substrate.

[0056] It can be understood that since the size of the pads on the substrate is three to four times the size of the conductive particles, therefore, multiple conductive particles can be simultaneously adsorbed on the pads of the same substrate. When at least one conductive particle contacts the LED chip and the pads on the substrate on both sides at the same time, the connection between the LED chip and the substrate (including mechanical connection and electrical connection) can be achieved.

[0057] Among them, before static polarization of the substrate, the surface of the pads can be pre-treated in advance, such as using a plasma cleaning device to remove the oxide layer and contaminants on the surface of the pads on the substrate with oxygen or argon to improve the adsorption effect of the conductive particles.

[0058] At the end of the arrangement of the conductive particles, the adsorption state of the conductive particles on the pads of the substrate can also be detected by an automatic optical inspection device (AOI); and based on the adsorption state, the arrangement of the conductive particles is adjusted so that the conductive particles meet the adsorption setting requirements.

[0059] Exemplarily, the AOI device uses a high-resolution camera to capture images of the pads on the substrate and the conductive particles thereon. The captured images are processed by an image processing algorithm to identify the positions, shapes, and sizes of the conductive particles. Then, by comparing with the preset adsorption setting requirements, the AOI device can evaluate the adsorption state of the conductive particles, including whether there are omissions, overlaps, or offsets. Based on the detection results of the AOI device, the arrangement of the conductive particles can be adjusted automatically or manually, such as accurately adsorbing, moving, and releasing the conductive particles through a micro-suction device, so as to achieve automatic adjustment of the arrangement of the conductive particles.

[0060] Thus, the setting of the conductive particles (conductive layer) on the pads of the substrate is completed. Compared with the traditional reflow soldering paste setting process, this setting method can achieve precise and rapid coverage of the conductive layer on the pads of the substrate, solve the problem of solder ball contamination, and improve the conductivity and overall reliability of the substrate to the LED chips.

[0061] After the electrostatic adsorption of the conductive particles is completed, the method for mounting Mini / Micro LED chips includes:

[0062] Step S10, arranging a plurality of LED chips on a PET film.

[0063] It can be understood that this application is for the integrated packaging of a plurality of LED chips. There are multiple pads arranged on the substrate, and a plurality of LED chips are packaged on the substrate to form a light-emitting component such as a display screen. Among them, before the LED chips are attached to the substrate, a plurality of LED chips can be automatically arranged in a crystal. This can improve production efficiency, reduce manual intervention and errors, and achieve efficient and accurate arrangement of LED chips, thereby laying a foundation for subsequent mounting operations. Specifically, it includes:

[0064] Pretreat the PET film; the pretreatment includes cleaning treatment and static elimination treatment. Among them, the cleaning treatment can be to use a professional cleaner or solvent to remove impurities such as dirt, dust, and grease on the surface of the PET film to ensure that the LED chips can adhere firmly to the PET film and prevent these impurities from affecting subsequent processing and bonding processes; and removing the static electricity on the surface of the PET film can prevent static electricity from damaging the LED chips or interfering with subsequent bonding processes.

[0065] In addition, load and convey a plurality of LED chips to the crystal arranging device, and arrange the LED chips on the PET film with the pads facing up according to a preset array method. Set the required LED chip array parameters in the crystal arranging device, such as chip pitch, number of rows and columns, etc. It can be to use methods such as vacuum adsorption or mechanical clamping to adsorb the LED chips one by one, and accurately position them according to the preset array parameters, and place the positioned LED chips on the PET film one by one.

[0066] Step S20, align and bond the PET film with the substrate, and make the pads of the LED chips correspond to the pads on the substrate one by one.

[0067] In this step, the aim is to achieve the corresponding relationship between the LED chips and the substrate, so that the pads on the LED chips correspond to the pads on the substrate, in order to facilitate the connection through the conductive particles between the two pads in the subsequent steps. It includes:

[0068] Invert the PET film with the arranged crystals so that the pads of the LED chips face downward for alignment and bonding with the pads on the substrate. Then, use a high-precision alignment system, such as a high-precision camera, to capture the position information of the LED chips on the PET film and compare it with the position information of the pads on the substrate, and control the precise mechanical adjustment structure for fine-tuning to ensure the precise alignment between the LED chips and the pads on the substrate. After alignment, gently bond the PET film to the substrate to ensure that the pads on the LED chips correspond one by one with the pads on the substrate, are in full contact with the conductive particles on the substrate, and avoid damaging the LED chips and the substrate.

[0069] Among them, the entire process needs to be operated in a dust-free clean room, and strictly control environmental parameters such as temperature, humidity, and cleanliness, which can reduce the pollution risk of LED chips.

[0070] Step S30, hot-press the PET film to melt the conductive adhesive through heat conduction, so as to fix the LED chips on the substrate through the conductive adhesive after cooling.

[0071] In this step, after the hot-press operation is completed, stop heating and let the LED chips and the substrate cool. During the cooling process, the conductive adhesive will gradually solidify. The solidified conductive adhesive not only has sufficient mechanical strength to fix the LED chips, but also can provide a reliable electrical connection to ensure that the LED chips can work normally.

[0072] It can be understood that based on the structural setting of the conductive particles, under the action of hot-pressing, the conductive adhesive at both ends of the conductive particles is squeezed to both sides, so that the metal conductive balls in the conductive particles are exposed and contact the pads of the LED chips and the substrate on both sides. In this way, under the condition that the conductive adhesive forms a stable mechanical connection, an electrical connection mainly composed of metal conductive balls is further formed.

[0073] Specifically, this hot-press cooling process includes: setting hot-press parameters, hot-pressing the bonded PCB board and PET film, that is, heating and pressing the LED chips towards the substrate under the hot-press parameters; then using compressed air or other cooling methods to rapidly reduce the temperature.

[0074] Among them, the heating temperature in the hot-press parameters is the hot-melt temperature corresponding to the conductive adhesive, generally between 100 and 150 °C (the peak does not exceed 250 °C), and the hot-press pressure used is between 20 and 100 N (the peak does not exceed 200 N), and the hot-press time is 5 to 10 min (the peak does not exceed 120 min). The cooling and temperature reduction speed is not less than 10 °C / S, which can reduce the influence of thermal stress on the LED chips and the melting points. In this way, by precisely controlling the hot-press parameters and implementing measures such as close contact and rapid cooling, a stable and reliable electrical connection is formed between the LED chips and the substrate, improving the quality and reliability of the product.

[0075] After the contact between the LED chip and the substrate is completed, the PET film can be removed. The PET film removal steps include:

[0076] Set the film removal parameters; the film removal parameters include the peeling angle, peeling speed, and peeling force, and the PET film is removed according to the film removal parameters. Among them, by controlling the peeling curvature, peeling speed, and peeling force of the PET film, a stable film removal process is achieved and the production efficiency is improved. Exemplarily, the peeling angle is controlled between 30° and 45° to reduce the pulling force on the LED chip. The peeling speed is controlled between 0.5 and 1.5 mm / s to remove the PET film evenly and smoothly. The peeling force is controlled between 0.1 and 0.5 N to avoid excessive force causing the displacement or damage of the LED chip.

[0077] And after the film removal operation is completed, check the status of the LED chip. It includes: using an automatic optical inspection device to inspect the chip to promptly discover and eliminate potential quality problems and ensure the qualification rate and reliability of the product. The AOI device can use a high-resolution camera and image processing technology to perform precise visual inspection on the chip. The inspection content includes but is not limited to: whether the LED chip has displacement, damage (such as cracks, fractures, or burns, etc.), and whether there are residues (such as conductive adhesive overflow, dust, or foreign objects, etc.). If the AOI inspection finds contaminants such as residues or dust on the surface of the substrate, it can be cleaned with a lint-free cloth or an ion air gun.

[0078] Among them, before setting the film removal parameters, it also includes confirming whether the film removal conditions meet the preset film removal conditions. The preset film removal conditions include: the conductive adhesive is cured and the edge of the PET film has no adhesion or damage. Based on this, ensure the smooth progress of the removal process.

[0079] Refer to Figure 2 As shown, in some embodiments, after the LED chip is fixed on the substrate by the conductive adhesive after cooling, it further includes:

[0080] Step S31, remove the excess conductive particles and contaminants around the pads of the substrate.

[0081] In this step, the cleaning operation can be carried out by means of plasma cleaning, which has the advantages of good cleaning effect, no chemical residue, and minimal damage to the substrate. The preferred working gas is oxygen or argon. Among them, if the contaminants are mainly organic substances, oxygen can be selected; if the contaminants are mainly inorganic substances or particulate matter, argon or a mixed gas can be selected. Further set the cleaning time and cleaning power to ensure safety and effectiveness during cleaning. Exemplarily, the cleaning time is set between 10 and 20 s, and the power is set between 50 and 200 watts.

[0082] Step S32: Attach the LED chip protective film to form protection for the light-emitting performance of the LED chip. The LED chip protective film includes a transparent film and a black semi-solid adhesive formed by compounding.

[0083] In this step, the transparent film and the black semi-solid adhesive in the LED chip protective film are formed by compounding. The transparent film is used to cover the light-emitting area of the LED chip, while the black semi-solid adhesive is used to fill the periphery and bottom of the LED chip. Among them, the transparent film is usually made of silicone materials (such as epoxy resin or silica gel), which can effectively prevent the LED chip from being damaged by external factors such as dust, moisture, and mechanical shock. The black semi-solid colloid has excellent light-shielding performance and thermal conductivity. Therefore, while improving the light-emitting efficiency and contrast of the LED chip, it can reduce the working temperature of the chip, enabling the applied LED chip to achieve a clearer image display effect and a longer service life.

[0084] The steps for attaching this protective film include: compounding the transparent film and the black semi-solid adhesive, cutting them into sizes suitable for the LED chip, and using a CCD system to accurately position the protective film. Under a slight pressure, such as a pressure of 0.5 - 1 N, the black semi-solid adhesive is made to flow to the periphery and bottom of the chip. Then, the transparent film and the black semi-solid adhesive are fixed by UV curing (wavelength 365 nm, 10 - 30 s) or thermal curing (temperature 80 - 120 °C, time 5 - 10 min). Finally, the mounting effect of the chip protective film is detected.

[0085] Step S33: Conduct quality inspection after the LED chip is mounted and fixed on the substrate.

[0086] In this step, it specifically includes: detecting whether the appearance form is correctly set and the light-emitting performance of the LED chip.

[0087] Among them, the appearance form includes evaluating whether the LED chip protective film is correctly attached to the chip through visual inspection or an automatic optical inspection device, such as no bubbles, wrinkles, or detachment, etc., to ensure that the protective film can effectively protect the LED chip from external environment damage and at the same time does not affect its light-emitting property; and detecting whether the LED chip is skewed, that is, whether the angle between the LED chip and the substrate is within the specified range, to ensure good electrical connection and light-emitting effect.

[0088] The detection of the light-emitting performance of the chip includes applying a specified voltage and current to the LED chip and observing whether it can be normally lit to verify whether the electrical connection of the LED chip is good and whether the chip itself has the ability to emit light; and being able to measure the brightness of multiple LED chips under the same test conditions and compare the differences between them to ensure the brightness consistency of the LED chips and meet the requirements for light uniformity in practical applications.

[0089] It should be noted that the non-conforming LED chips detected can be further removed and replaced. Because the technical solution of this application uses conductive adhesive to complete the mounting of LED chips. When removal and replacement are required, only the defective LED chips need to be heated to melt the conductive adhesive between the chips and the substrate, and then the defective products can be detached. This is simple and convenient, and will not cause thermal damage to other normal chips.

[0090] Finally, ultrasonic cleaning is carried out to remove impurities during the welding process and improve the surface cleanliness of the product.

[0091] In some embodiments, laminating an LED chip protective film to form protection for the light-emitting performance of the LED chip includes:

[0092] Position and laminate the LED chip protective film so that the transparent film in the LED chip protective film corresponds to the light-emitting area of the LED chip, and the black semi-solid adhesive corresponds to the peripheral side of the LED chip;

[0093] Press down the black semi-solid adhesive to make the black semi-solid adhesive separate from the transparent film and flow to the periphery and bottom of the LED chip.

[0094] This application also provides a mounting structure for Mini / Micro LED chips, which is prepared by using the above mounting method.

[0095] As Figure 3 shown is a schematic diagram of the mounting structure. It includes a substrate 10 and an LED chip 20. The LED chip 20 is mounted on the substrate 10. The pads on the LED chip 20 correspond one-to-one with the pads on the substrate 10 (the pads on the substrate are the first pads 11, and the pads on the LED chip are the second pads 21). And a conductive layer 30 is provided between the pads. The conductive layer includes metal conductive balls 31 and conductive adhesive 32 coated on the surface of the metal conductive balls 31. The conductive adhesive 32 is used for mechanically connecting the LED chip 20 and the substrate 10 on both sides, while both ends of the metal conductive balls 31 contact the LED chip 20 and the substrate 10 to form the main electrical connection channels. And a transparent film 40 is laminated on the light-emitting area of the LED chip 20, and black semi-solid adhesive 50 is filled in the peripheral side and bottom. Further, a plastic encapsulation material 60 can be provided to wrap the LED chip 20 to form an encapsulation of the LED chip 20.

[0096] The above are only partial or preferred embodiments of this application. Whether in terms of text or drawings, the scope of protection of this application cannot be limited thereby. All equivalent structural transformations made by using the content of the specification and drawings of this application under the overall concept of this application, or direct / indirect applications in other related technical fields are included in the scope of protection of this application.

Claims

1. A method for mounting a Mini / Micro LED chip, characterized in that: include: Arrange a number of LED chips on a PET film; The PET film and the substrate are aligned and laminated, and the pads of the LED chip correspond to the pads on the substrate one by one; the pads on the substrate are provided with conductive particles, wherein the pads of the substrate and the conductive particles are subjected to electrostatic polarization treatment of opposite charge polarities, so that the conductive particles are quickly and evenly distributed on the pads of the substrate through the electrostatic attraction between the pads of the substrate and the conductive particles, and the conductive particles include metal conductive balls and conductive glue coated on the surface of the metal conductive balls; the conductive glue includes silver-based conductive glue, copper-based conductive glue, carbon-based conductive glue, metal oxide conductive glue, conductive polymer glue and mixed filler conductive glue; The PET film is hot pressed to melt the conductive adhesive by heat conduction, so that the LED chip is fixed on the substrate by the conductive adhesive after cooling.

2. The method for mounting a Mini / Micro LED chip according to claim 1, characterized in that: Arranging a plurality of LED chips on the PET film comprises: The PET film is pretreated; the pretreatment includes cleaning and anti-static treatment; a plurality of the LED chips are fed to a wafer arrangement device, and the LED chips are arranged on the PET film with the solder pads facing upwards according to a preset array.

3. The method for mounting a Mini / Micro LED chip according to claim 2, wherein: Aligning and laminating the PET film and the substrate, and making the pads of the LED chip correspond one-to-one with the pads on the substrate, comprises: The PET film is turned over so that the solder pad of the LED chip faces downward; based on the alignment system, the LED chip is aligned with the solder pad position on the substrate; The PET film is attached so that the solder pads of the LED chip correspond one to one with the solder pads on the substrate.

4. The method for mounting a Mini / Micro LED chip according to claim 1, wherein: The step of hot pressing the PET film to melt the conductive adhesive by heat conduction, so as to fix the LED chip on the substrate by the conductive adhesive after cooling, comprises: The hot pressing parameters are set, and the PET film is heated and pressed toward the substrate under the hot pressing parameters; the heating temperature in the hot pressing parameters corresponds to the hot melting temperature of the conductive adhesive; and a cooling treatment is performed at a cooling rate of not less than 10°C / S, so as to mechanically connect the LED chip and the substrate on both sides through the curing of the conductive adhesive, and fix the LED chip on the substrate.

5. The method for mounting a Mini / Micro LED chip according to claim 4, wherein: After the LED chip is fixed on the substrate, the method further includes performing a PET film tearing step, wherein the PET film tearing step includes: The film-tearing parameters are set; the film-tearing parameters include a peeling angle, a peeling speed and a peeling force; the PET film is torn off according to the film-tearing parameters, and after the tearing off operation is completed, the state of the LED chip is checked.

6. The method for mounting a Mini / Micro LED chip according to claim 5, wherein: Before setting the film tearing parameters, the method further includes confirming whether the film tearing conditions meet the preset film tearing conditions, and the preset film tearing conditions include: The conductive adhesive is completely cured and the edges of the PET film are not adhered or damaged.

7. The method for mounting a Mini / Micro LED chip according to claim 1, wherein: The method further comprises fixing the LED chip on the substrate by the conductive adhesive after cooling: Removing excess conductive particles and contaminants from around the pads of the substrate; Laminating an LED chip protection film to protect the light-emitting performance of the LED chip; the LED chip protection film comprises a composite transparent film and a black semi-solid glue; Perform quality inspection after the LED chip is mounted and fixed on the substrate.

8. The method for mounting a Mini / Micro LED chip according to claim 7, wherein: The step of laminating the LED chip protective film to protect the light emitting performance of the LED chip includes: Positioning and laminating the LED chip protection film so that the transparent film in the LED chip protection film corresponds to the light-emitting area of ​​the LED chip, and the black semi-solid glue corresponds to the peripheral side of the LED chip; The black semi-solid glue is pressed downward to separate the black semi-solid glue from the transparent film and flow to the periphery and bottom of the LED chip.

9. The method for mounting a Mini / Micro LED chip according to claim 7, wherein: The quality inspection after the LED chip is mounted and fixed on the substrate includes: inspecting whether the appearance is correctly set; the appearance includes whether the LED chip protection film is correctly attached and whether the LED chip is skewed; The light-emitting performance of the LED chip is tested; the light-emitting performance of the LED chip includes whether the chip can be lit and whether the brightness of the chip is consistent.

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