KR20190109133A - Method for arraying micro LED chips for manufacturing a LED display. - Google Patents

Abstract

Disclosed is a method for arraying micro LED chips, configured to array a plurality of micro LED chips in a predetermined arrangement on a substrate, wherein the method comprises the steps of: forming a plurality of solder portions in the predetermined arrangement on the substrate; preparing a tray in which recesses having an arrangement corresponding to the predetermined arrangement are formed; inserting micro LED chips into the recesses such that the micro LED chips are arrayed in the predetermined arrangement; bonding the micro LED chips inserted into the recesses to a chip transfer film; transferring the micro LED chips onto the substrate such that each of the micro LED chips can be placed on each of the solder portions with the chip transfer film; and bonding the micro LED chips onto the substrate by heating the solder portions. According to the present invention, it is possible to accurately re-array the micro LED chips.

Description

LED chip array method for LED display panel manufacturing {Method for arraying micro LED chips for manufacturing a LED display.}

The present invention relates to LED display panel manufacturing technology, and more particularly, to an LED chip array method for manufacturing a micro LED display panel.

In order to make a micro LED module for implementing a micro LED display panel, a vertical or flip chip type micro LED chips are bonded to a substrate such as a printed circuit board (PCB) and arrayed. For this purpose, it is required to bond the micro LED chips sorted on the chip holding portion to the solder portions on the substrate to be bonded accurately.

As shown in FIG. 1, the spacing of the micros 3 sorted on the chip holding section 2 is different from the spacing of the solder sections 5 on the substrate 4. 5) After confirming the positions one by one, a method of bonding the micro LED chip 3 to the corresponding solder 5 on the substrate 4 using the die bonder 6 has been proposed. However, this method requires a large number of micro LED chips 3 to be transported one by one and bonded to the substrate 4, so that excessive processing time is required. In addition, the above method can be used in a process having a precision error of 100 um or more, but is not suitable in a process requiring precision of several to several tens of um. In addition, in transferring and bonding the LED chip sorted on the chip holding part such as blue tape to the substrate, it is difficult to correct the LED chip in the bonding process in the case of misaligned LED chips in the sorting or picking process.

In addition, there is a method of rearranging the micro LED chip to a pixel size and then transferring the entire micro LED chips by, for example, a roll to roll method or an electrostatic bonding method. When using this method, in order to mass-produce a micro LED display panel, the chip-to-chip spacing of the micro LED chips must be precisely within a few um and be fast. Even in the mass production of a mini LED display panel using LED chips having a larger size than a micro LED chip, the chip-to-chip spacing precision between LED chips must satisfy within 10 μm, but this was also difficult to achieve.

In addition, in the case of transferring the LED chips, such as the roll roll method or the electrostatic adhesive method, in general, the adhesive sheet must be attached to the upper portion of the rearranged LED chips (ie, the LED emitting surface) to transfer the adhesive sheet. There is a problem in that the luminous efficiency is lowered even though a little adhesive remains on the LED chip.

In addition, various methods that have been examined to transfer LED chips to a substrate do not meet the X / Y / Z alignment level of the LED chips sufficient to realize the display, and the LEDs also have to be used in the reflow process for bonding the LED chips. There was a high possibility that the chips would have an undesired rotation or distortion.

The problem to be solved by the present invention is to prepare a tray formed with recesses of a predetermined arrangement, and to insert the LED chips into the recesses of the tray, to precisely rearrange the LED chips having a fine size, And a method for easily reordering LED chips having a fine size.

According to an aspect of the present invention, there is provided a micro LED chip array method for arranging a plurality of micro LED chips in a predetermined arrangement on a substrate, wherein the micro LED chip array method includes: Forming a plurality of solder portions in a crystal arrangement; Preparing a tray in which recesses of an arrangement corresponding to the predetermined arrangement are formed; Inserting the micro LED chips into the recesses such that the micro LED chips are in the predetermined arrangement; Bonding the micro LED chips inserted into the recesses to a chip transfer film; Transferring the micro LED chips onto the substrate such that each of the micro LED chips is placed on each of the solder portions with the chip transfer film; And bonding the micro LED chips onto the substrate by heating the solder portions.

According to one embodiment, the depth of each of the recesses is less than or equal to the height of each of the microLED chips such that each of the microLED chips protrudes out of each of the recesses.

According to one embodiment, the bonding step uses a reflow process or a process of raising the temperature of the heating block in contact with the substrate.

According to one embodiment, preparing the tray may be made of a semiconductor substrate, a ceramic substrate, or a metal substrate, using an etching process to form the recesses.

According to an embodiment, the preparing of the tray may include fabricating a tray from a semiconductor substrate, a ceramic substrate, or a metal substrate, wherein dry etching, wet etching, laser processing, and ion milling are performed to form the recesses. Or use a physical drilling process.

According to an embodiment, the recesses are grouped into a plurality of groups, and each of the plurality of groups includes a plurality of recesses having a plurality of micro LED chips having different wavelengths.

According to an embodiment, the spacing between neighboring recesses among neighboring groups of the plurality of groups is greater than the spacing between neighboring recesses in one group.

In accordance with another aspect of the present invention there is provided a micro LED chip array method for arranging micro LED chips on a substrate in a predetermined arrangement, wherein the micro LED chip array method comprises an arrangement of a corresponding arrangement with the predetermined arrangement. Preparing a tray in which recesses are formed; Inserting the micro LED chips into the recesses such that the micro LED chips are in the predetermined arrangement; Forming solder portions on the micro LED chips inserted into the recesses; Placing the substrate such that electrodes of the substrate contact the solder portions; And heating the solder part to bond the micro LED chips onto the substrate.

According to an embodiment, the forming of the solder portions may include: placing a mask on the tray, the mask including openings exposing the micro LED chips; And filling solder material into the openings to form the solder portions.

According to one embodiment, the top height of the tray and the top surface of the micro LED chips inserted into the recesses are on the same plane.

According to one embodiment, the bonding step uses a reflow process or a process of raising the temperature of the heating block in contact with the tray.

According to one embodiment, the bonding is performed with each of the micro LED chips constrained inside each of the recesses.

The micro LED chip array method according to the present invention can precisely rearrange the micro LED chips by manufacturing a tray in which the recesses are formed in a predetermined arrangement and in a precise size, and inserting the micro LED chips into the recesses. In this way, there is an effect of enabling the implementation of an LED display of high quality.

Other objects, advantages and effects of the present invention will be better understood from the following description of the embodiments.

1 is a view for explaining the prior art.
2 is a flowchart illustrating an overall method of an LED chip array according to a first embodiment of the present invention.
3A, 3B, and 3C are diagrams illustrating red, green, and blue micro LED chips held in a chip holding unit, respectively.
4 is a view for explaining the step of forming solder portions on a substrate in a predetermined arrangement, according to a first embodiment of the present invention.
FIG. 5 is a diagram for explaining a step of preparing a tray in which recesses of an arrangement corresponding to a predetermined arrangement are formed according to the first embodiment of the present invention.
FIG. 6 is a diagram for explaining a step of inserting micro LED chips into recesses such that the micro LED chips are in a predetermined arrangement according to the first embodiment of the present invention.
FIG. 7 is a view for explaining the step of bonding the micro LED chips inserted in the recesses to the chip transfer film according to the first embodiment of the present invention.
8 is a diagram for describing a step of transferring the micro LED chips onto the substrate with the chip transfer film so that each of the micro LED chips is placed on each of the solder portions, according to the first embodiment of the present invention.
FIG. 9 is a diagram for describing a step of bonding the micro LED chips to the substrate by heating solder parts according to the first embodiment of the present invention.
FIG. 10 is a flowchart illustrating an LED chip array method according to a second embodiment of the present invention.
FIG. 11 is a view for explaining a step of preparing a tray and inserting micro LED chips into recesses formed in the tray according to the second embodiment of the present invention.
FIG. 12 is a diagram for describing a step of forming solder parts on micro LED chips inserted in recesses according to a second exemplary embodiment of the present invention.
FIG. 13 is a view for explaining a step of arranging a substrate such that electrodes of the substrate contact solder parts according to a second embodiment of the present invention.
FIG. 14 is a diagram for explaining a process of bonding microLED chips onto a substrate by heating solder portions interposed between the microLED chips and the substrate according to the second embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]

2, the LED chip array method according to the first embodiment of the present invention is an LED chip array method for arranging micro LED chips on a substrate in a predetermined array, wherein the substrate is arranged in the predetermined crystal array. Forming a solder portion on the substrate; preparing a tray on which the recesses of the array corresponding to the predetermined array are formed; and s2 the microLED chips to form the predetermined crystal array. Inserting micro LED chips s3, adhering the micro LED chips inserted in the recesses to a chip transfer film, and each of the micro LED chips to be placed on each of the solder portions, the chip transfer film Transferring the micro LED chips onto the substrate by s5, and heating the solder portions, It includes the step s6 of bonding the micro LED chip to the substrate.

 In addition, before performing the above steps, as shown in (a), (b) and (c) of FIG. 3, the red micro LED chips 30R, the green micro LED chips 30G, and the blue micro LED chip. The chip holders 2a, 2b, and 2c (commonly referred to as 2), in which the 30Bs are bonded and held, are prepared in advance. The micro LED chips 30R, 30G, and 30B are held in the chip holding portions 2a, 2b, and 2c at non-uniform intervals, so rearrangement is necessary. In addition, in order to arrange the micro LED chips 30R, 30G, and 30B (commonly 30) on a substrate in units of pixels, the micro LED chips may be rearranged into groups including red chips, green chips, and blue chips. It is necessary.

Step s1 forms a mask 9 including openings 9a on the top surface of the substrate 40, such as a PCB, as shown in FIG. The solder metal 50 is filled to form solder portions 50, each of which includes one or more solder bumps on the substrate 40. After the solder portions 50 are formed on the substrate 40, the mask 9 is removed from the top surface of the substrate 40. In this embodiment, each of the solder portions 50 includes two solder bumps to correspond to the two electrode pads of the flip chip type micro LED chip, but has only one electrode pad on the side where the micro LED chip is connected to the substrate. In this case, a solder portion consisting of only one solder bump may be employed. The mask 9 may be a metal mask or a PR film mask in which the openings 9a are formed by a photolithography process, and the solder part 50 may be a deposition apparatus such as an E-beam apparatus or a thermal deposition apparatus. It may be formed by the deposition process used.

A plurality of solder groups G corresponding to the plurality of LED pixels is formed on the substrate. The spacing between the solder portions 50 between neighboring solder groups G is greater than the spacing between the solder portions 50 in the solder group G.

Step s2 is a step of preparing a tray in which the recesses of the array corresponding to the predetermined arrangement of the above-described LED chip on the substrate, as shown in FIG. 5, are prepared, such as Si, sapphire, GaAs, AlN, etc. It is produced by preparing a semiconductor or ceramic substrate or a metal substrate and forming recesses 62 having a predetermined depth by using a semiconductor process including a photolithography process and an etching process on the prepared substrate. Various methods for forming the recesses 62 may be used, for example dry etching, wet etching, laser, ion milling, physical drilling, or the like. In this embodiment, each of the recesses 62 has the same cross-sectional area throughout its depth.

Further, as will be described below, the recesses 62 are recessed so that each of the micro LED chips inserted in each of the recesses 62 can protrude out of each of the recesses 62. It is formed to a depth smaller than the height of the field.

The size (width) of each of the recesses 62 may be about 10-30 μm larger than the size (width) of the corresponding micro LED chip. In addition, the thickness of the tray 60 is preferably in the range of several tens of micrometers to several hundred micrometers in consideration of the thickness of the micro LED chip and the height of the micro LED chip mounted on the substrate. Since the recesses 62 are formed by a semiconductor process or a milling process, the tolerances can be almost eliminated in size, spacing or pitch.

In addition, the recesses 62 are grouped into a plurality of groups g, and each of the plurality of groups g has a plurality of micro LED chips 30 having different wavelengths, that is, a red micro LED chip. (30R; see FIG. 3), the green micro LED chip 30G (see FIG. 3) and the blue micro LED chip 30B (see FIG. 3) are inserted into three recesses 62, 62 and 62. The interval between neighboring recesses 62 and 62 between neighboring groups G and G among the plurality of groups G is adjacent to the recesses 62 and 62 in one group G. Greater than the interval between.

Step s3 is a step of inserting the micro LED chips 30R, 30G, 30B into the recesses 60 so as to be in the predetermined arrangement, as shown in FIG. In this case, the micro LED chips 30R, 30G, and 30B may be inserted one by one or several may be inserted at a time. Each of the micro LED chips 30R, 30G, 30B includes electrode pads bonded to solder portions on a substrate in a subsequent step to be described below, with the micro LED chips 30R facing the bottom of the recess. 30G, 30B are inserted into the recesses 62. As mentioned above, each of the recesses 62 is preferably formed at a depth equal to or smaller than the height of the micro LED chips 30R, 30G, and 30B, and thus, the recesses 62 Each of the micro LED chips 30R, 30G, and 30B inserted into each of the plurality of protrusions protrudes out of each of the recesses 62. The red micro LED chip 30R, the green micro LED chip 30G, and the blue LED chip 30B are respectively inserted into each of the three recesses 62 consecutive to each other in one group G. Between two neighboring recess groups G and G, the spacing 30B and 30R between two micro LED chips inserted into two neighboring recesses 62 and 62 is equal to two neighboring groups within one group G. It is larger than the spacing between the two micro LED chips 30R and 30G or 30G and 30B inserted in the recesses 62 and 62.

In operation S4, the micro LED chips 30R, 30G, and 30B inserted into the recesses 62 are bonded to the chip transfer film 70, as shown in FIG. 7. The chip transfer film 70 is adhesive to the first surface in contact with the micro LED chips 30R, 30G, and 30B. In addition, the chip transfer film 70 may have adhesiveness to a second surface opposite to a surface contacting the micro LED chips 30R, 30G, and 30B. When the chip transfer film 70 is used for a roll-to-roll transfer method, the second surface of the chip transfer film 70 is attached to the roll and used for transfer. The adhesion to the first surface may be implemented by applying an adhesive material that may be weakened by, for example, UV application.

In step s5, the micro LED chip (with the chip transfer film 70) is placed so that each of the micro LED chips 30R, 30G, and 30B is placed on each of the solders 50, as shown in FIG. 8. Transferring 30R, 30G, 30B onto the substrate 40 is performed. First, the chip transfer film 70 is positioned above the substrate 40, and then the chip transfer film 70 is pressed by, for example, a stamp or a roller, so that the micro LED chips 30R, 30G, and 30B are soldered ( 50) to be placed on each of them. The micro LED chips 30R, 30G, and 30B may be separated from the chip transfer film 70 to be bonded to the solder part 50 through an adhesive material in advance in the solder part 50. In this case, it may also be considered to irradiate the chip transfer film 70 with UV, which weakens the adhesive force of the chip transfer film 70.

In operation S6, as shown in FIG. 9, the solder portions 50 are heated to bond the micro LED chips 30R, 30G, and 30B to the substrate 40. In this embodiment, the temperature of the heating block 90 disposed in contact with the lower surface of the substrate 40 is raised, and the solder is heated by the heat transferred from the heating block 90 to the solder parts 50 through the substrate 40. By heating the sections 50, bonding to the micro LED chips 30R, 30G, 30B is performed. In order to prevent the alignment of the micro LED chips 30R, 30G and 30B, it is preferable to heat using the heating block 90 with the positions of the micro LED chips 30R, 30G and 30B fixed. It may also be considered to heat the solder portions 50 by passing the substrate 40 through a ripple-ow oven.

Second Embodiment

Now, a second embodiment of the present invention will be described. In the description of the second embodiment, the content overlapping with the first embodiment may be omitted, and the omitted content is considered to be the same as or similar to the first embodiment.

Referring to FIG. 10, the LED chip array method according to the second embodiment of the present invention is an LED chip array method in which micro LED chips are arrayed on a substrate in a predetermined array, which corresponds to the predetermined crystal array. Preparing a tray in which recesses of the recesses are formed; inserting the microLED chips into the recesses so that the microLED chips are the predetermined arrangement; and the recesses Forming solder portions on the LED chips inserted into the substrate; and placing the substrate so that the electrodes of the substrate contact the solder portions; and heating the solder portions to heat the LED chips onto the substrate. Bonding step S5.

In step S1, a tray 60 including a structure as shown in FIG. 11 is prepared. Similar to the previous embodiment, the tray 60 is prepared using a semiconductor process including a photolithography process and an etching process by preparing a semiconductor or ceramic substrate such as Si, sapphire, GaAs, AlN, or a metal substrate. It is produced by forming recesses 62 of a predetermined depth in the prepared substrate. Various methods for forming the recesses 62 may be used, for example dry etching, wet etching, laser, ion milling, physical drilling, or the like. In this embodiment, each of the recesses 62 has the same cross-sectional area throughout its depth.

Referring back to FIG. 11, step S2 inserts the micro LED chips 30R, 30G, 30B into the recesses 62 such that the micro LED chips 30R, 30G, 30B are in the predetermined crystal arrangement. It's a step. At this time, the upper surface of the tray 60 and the upper surface of the micro LED chip 30R, 30G, 30B inserted into the recesses 62 are on the same plane, which is the plane on which the mask is formed in a subsequent step To be In addition, electrode pads are provided on an upper surface of the micro LED chips 30R, 30G, and 30B, that is, a surface on which the micro LED chips 30R, 30G, and 30B are exposed to the outside of the recesses 62. This is different from the electrode pad of the micro LED chip facing the bottom of the recess in the first embodiment.

In operation S3, as shown in FIG. 12, solder parts 50 are formed in the micro LED chips 30R, 30G, and 30B inserted into the recesses 62, and the micro LED chip ( Disposing a mask 9 on the tray 60 including exposed openings 9a exposing the top surface with electrode pads of 30R, 30G and 30B, and soldering into the openings 9a; Filling the material to form the solder portions 50. When the solder portions 50 are formed, the mask 9 is removed. Even after the mask 9 is removed, the tray 60 is not removed in order to prevent the recesses 62 from moving the micro LED chips 30R, 30G, and 30B in a subsequent step.

More specifically, in step S3, after forming the mask 9, for example, one of the micro LED chips 30R, 30G, and 30B is filled with a metal material for soldering through the openings 9a through screen printing. Solder portions 50 including the solder bumps described above are formed. The mask 9 may be a metal mask or a PR film mask in which the openings 9a are formed by a photolithography process, and the solder part 50 may be a deposition apparatus such as an E-beam apparatus or a thermal deposition apparatus. It may be formed by the deposition process used.

In operation S4, as illustrated in FIG. 13, the substrate 40 is disposed so that the electrodes (not shown) of the substrate 40 contact the solder portions 50. In this case, an adhesive material is formed on the solder portions 50 or the substrate 40, and the gap between the substrate 40 and the micro LED chips 30R, 30G, and 30B is maintained until the solder portion 50 participates in bonding. It is desirable to remain fixed.

In step S5, as shown in FIG. 14, the solder portions 50 interposed between the micro LED chips 30R, 30G and 30B and the substrate 40 are heated to heat the micro LED chips 30R and 30G. , 30B) is bonded to the substrate 40. In the present embodiment, the step S5 increases the temperature of the heating block 90 disposed in contact with the lower surface of the tray 60, is generated in the heating block 90 and passes through the tray 60 to the solder portion ( And applying the solder portions 50 to the heat transferred to 50. Thus, the tray 60 preferably has sufficient thermal conductivity. In this case, step 5 is performed in a state where each of the micro LED chips 30R, 30G, and 30B is constrained in each of the recesses 62, and thus, the unwanted tilt or shift of the micro LED chips is performed. You can prevent the same movement. Since the bonding step is performed while the micro LED chips are constrained to the recesses 62, instead of the above-described bonding method using the heating block, a method of heating the solder portions 50 by passing through the ripple-o oven may be useful. Can be used.

30 ....................... LED chip
40 ............
50 .......................... Solder
60 ...

Claims (18)

A micro LED chip array method, in which a plurality of micro LED chips are arrayed in a predetermined array on a substrate.
Forming a plurality of solder portions in the predetermined array on the substrate;
Preparing a tray in which recesses of an arrangement corresponding to the predetermined arrangement are formed;
Inserting the micro LED chips into the recesses such that the micro LED chips are in the predetermined arrangement;
Bonding the micro LED chips inserted into the recesses to a chip transfer film;
Transferring the micro LED chips onto the substrate such that each of the micro LED chips is placed on each of the solder portions with the chip transfer film; And
And heating the solder parts to bond the micro LED chips onto the substrate. The method of claim 1, wherein the depth of each of the recesses is less than or equal to the height of each of the microLED chips such that each of the micro LED chips protrudes out of each of the recesses. The method of claim 1, wherein the bonding step comprises using a reflow process or a process of raising the temperature of the heating block in contact with the substrate. The method of claim 1, wherein the preparing of the tray comprises fabricating a tray from a semiconductor substrate, a ceramic substrate, or a metal substrate, and using an etching process to form the recesses. The method of claim 1, wherein the preparing of the tray comprises fabricating a tray from a semiconductor substrate, a ceramic substrate, or a metal substrate, and forming the recesses by using dry etching, wet etching, laser processing, or ion milling. Or using a physical drilling process. The method of claim 1, wherein the recesses are grouped into a plurality of groups, and each of the plurality of groups includes a plurality of recesses of a plurality of micro LED chips having different wavelengths. . The method of claim 6, wherein the spacing between neighboring recesses among neighboring groups of the plurality of groups is greater than the spacing between neighboring recesses in one group. A micro LED chip array method, in which a plurality of micro LED chips are arrayed in a predetermined array on a substrate.
Preparing a tray in which recesses of an arrangement corresponding to the predetermined arrangement are formed;
Inserting the micro LED chips into the recesses such that the micro LED chips are in the predetermined arrangement in the recesses;
Forming a plurality of solder portions on the micro LED chips inserted into the recesses;
Placing the substrate such that electrodes of the substrate contact the solder portions;
Heating the solder portion to bond the micro LED chips onto the substrate. The method of claim 8, wherein the forming of the solder portion,
Disposing a mask on the tray, the mask including openings exposing the micro LED chips; And
Filling the solder material into the openings to form the solder portions. 10. The method of claim 9, wherein the mask is a metal mask. 10. The method of claim 9, wherein the mask is a PR film in which the openings are formed by a photolithography process. The method of claim 8, wherein the top height of the tray and the top surface of the micro LED chips inserted into the recesses are on the same plane. The method of claim 8, wherein the bonding comprises using a reflow process or a process of increasing a temperature of a heating block in contact with the tray. The method of claim 8, wherein the bonding is performed while each of the micro LED chips is confined within each of the recesses. The method of claim 8, wherein preparing the tray comprises fabricating a tray from a semiconductor substrate, a ceramic substrate, or a metal substrate, and using an etching process to form the recesses. The method of claim 8, wherein the preparing of the tray comprises fabricating the tray from a semiconductor substrate, a ceramic substrate, or a metal substrate, and forming the recesses by using dry etching, wet etching, laser processing, or ion milling. Or using a physical drilling process. The method of claim 8, wherein the recesses are grouped into a plurality of groups, and each of the plurality of groups includes a plurality of recesses having a plurality of micro LED chips having different wavelengths. . 18. The method of claim 17, wherein an interval between neighboring recesses among neighboring groups of the plurality of groups is greater than an interval between neighboring recesses in one group.

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