CN113948624A - LED solder coating method, light emitting device and display device - Google Patents
LED solder coating method, light emitting device and display device Download PDFInfo
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- CN113948624A CN113948624A CN202010688565.9A CN202010688565A CN113948624A CN 113948624 A CN113948624 A CN 113948624A CN 202010688565 A CN202010688565 A CN 202010688565A CN 113948624 A CN113948624 A CN 113948624A
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- 229910000679 solder Inorganic materials 0.000 title claims abstract description 257
- 238000000576 coating method Methods 0.000 title claims abstract description 49
- 239000011553 magnetic fluid Substances 0.000 claims abstract description 163
- 239000000758 substrate Substances 0.000 claims abstract description 109
- 239000002245 particle Substances 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 13
- 230000003075 superhydrophobic effect Effects 0.000 claims description 12
- 239000002923 metal particle Substances 0.000 claims description 8
- 238000001179 sorption measurement Methods 0.000 claims description 6
- 238000002360 preparation method Methods 0.000 claims description 5
- 239000004094 surface-active agent Substances 0.000 claims description 5
- 239000002105 nanoparticle Substances 0.000 claims 1
- 239000011248 coating agent Substances 0.000 abstract description 17
- 238000003466 welding Methods 0.000 abstract description 7
- 239000007788 liquid Substances 0.000 description 9
- 238000010586 diagram Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 229910052759 nickel Inorganic materials 0.000 description 5
- 238000005476 soldering Methods 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
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- 238000007254 oxidation reaction Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
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- 230000005389 magnetism Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000002572 peristaltic effect Effects 0.000 description 2
- 240000007472 Leucaena leucocephala Species 0.000 description 1
- 235000010643 Leucaena leucocephala Nutrition 0.000 description 1
- 102000003691 T-Type Calcium Channels Human genes 0.000 description 1
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- 229910052797 bismuth Inorganic materials 0.000 description 1
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- 229910052738 indium Inorganic materials 0.000 description 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 238000001883 metal evaporation Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
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- 238000004806 packaging method and process Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
- G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
- G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
- G09F9/301—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements flexible foldable or roll-able electronic displays, e.g. thin LCD, OLED
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
- G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
- G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
- G09F9/33—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements being semiconductor devices, e.g. diodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L25/00—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
- H01L25/03—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes
- H01L25/04—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers
- H01L25/075—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00
- H01L25/0753—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00 the devices being arranged next to each other
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/15—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission
- H01L27/153—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission in a repetitive configuration, e.g. LED bars
- H01L27/156—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission in a repetitive configuration, e.g. LED bars two-dimensional arrays
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
- H01L33/62—Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
- H01L2933/0008—Processes
- H01L2933/0033—Processes relating to semiconductor body packages
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
- H01L2933/0008—Processes
- H01L2933/0033—Processes relating to semiconductor body packages
- H01L2933/0066—Processes relating to semiconductor body packages relating to arrangements for conducting electric current to or from the semiconductor body
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- General Physics & Mathematics (AREA)
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- Theoretical Computer Science (AREA)
- Electric Connection Of Electric Components To Printed Circuits (AREA)
Abstract
The invention relates to an LED solder coating method, a light-emitting device and a display device. The magnetic fluid solder balls are prepared from the magnetic fluid solder, then the magnetic fluid solder balls are transferred to the upper side of the circuit substrate in batches through the magnetic field, and the magnetic fluid solder balls drop on the circuit substrate, so that the coating of the solder on the circuit substrate is realized, the reliability of the welding can be improved by adopting the solder, the magnetic fluid solder balls are not easy to oxidize, the magnetic fluid solder balls are convenient to prepare small-sized solder balls and convenient to transport, the applicability of the LED solder coating is greatly improved, and the magnetic fluid solder balls can be particularly applied to micro-LEDs.
Description
Technical Field
The invention relates to the field of semiconductor devices, in particular to an LED solder coating method, a light-emitting device and a display device.
Background
A Light Emitting Diode (micro-LED) is a new generation of display technology, and has higher photoelectric efficiency, higher brightness, higher contrast and lower power consumption compared with a liquid crystal display in the related art, and can realize a flexible display by combining with a flexible panel. In the related art, solder paste is often printed to make the LED display, and the LED and the substrate are soldered by Surface Mount Technology (SMT), which has the problem that the method is only suitable for soldering large-sized LEDs, and small-sized micro-LEDs cannot be used; in the manufacturing of micro-LEDs, the related art usually adopts a huge soldering technique after a solder joint is formed by performing a removal/peeling (lift off) process of In after metal indium (In) is evaporated, but the In is very easy to oxidize, and once the solder is oxidized, the reliability of the photoelectric device is poor.
Therefore, how to realize the connection of the LED chip on the substrate, which is widely and easily used, is a problem to be solved.
Disclosure of Invention
In view of the above-mentioned shortcomings of the related art, the present invention aims to provide an LED solder coating method, a light emitting device and a display device, which are intended to solve the problems of the related art that the way of soldering an LED chip on a substrate is not applicable or convenient for soldering, or the reliability of an optoelectronic device is low.
An LED solder coating method, comprising:
preparing magnetic fluid solder balls with preset sizes from the magnetic fluid solder to be coated;
adsorbing the magnetic fluid solder balls on the lower surface of the transfer substrate in batch through a first magnetic field;
moving the transfer substrate to be coated above the circuit substrate, wherein the magnetic fluid solder ball position on the lower surface of the transfer substrate corresponds to the position of the pad area on the circuit substrate;
and closing the first magnetic field to enable the magnetic fluid solder balls to fall down to the corresponding pad areas on the circuit substrate.
According to the LED solder coating method, the magnetic fluid solder balls are prepared from the magnetic fluid solder, then the magnetic fluid solder balls are transferred to the upper part of the circuit substrate in batches through the magnetic field, and the magnetic fluid solder balls drop on the circuit substrate, so that the coating of the solder on the circuit substrate is realized, the welding reliability can be improved by adopting the solder, the oxidation is not easy, the small-size solder balls can be conveniently prepared by the magnetic fluid solder, the transportation is convenient, the coating applicability of the LED solder is greatly improved, and the LED solder coating method can be particularly applied to micro-LEDs.
Based on the same inventive concept, the invention also provides a light-emitting device, which comprises a circuit substrate and an LED chip, wherein the LED solder coating method is used for coating magnetic fluid solder balls on the bonding pad area of the circuit substrate, and the LED chip is electrically and fixedly connected to the bonding pad area through the magnetic fluid solder balls.
The LED solder coating method with wider application and stronger reliability is adopted in the manufacturing of the light-emitting device, so that the reliability of the light-emitting device is stronger, and the LED chip in the light-emitting device can be a micro-LED chip, so that the display effect of the light-emitting device is better.
Based on the same inventive concept, the present invention also provides a display device including the light emitting device as described above.
The display device includes the light emitting device of the above example, so that the display device is more reliable, and the LED chip in the light emitting device may be a micro-LED chip, so that the display effect of the display device is better.
Drawings
FIG. 1 is a schematic flow chart of a method for coating an LED solder according to an embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating the preparation of magnetic fluid solder balls according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of magnetic fluid solder ball adsorption provided by an embodiment of the present invention;
FIG. 4 is a schematic illustration of a contact angle provided by an embodiment of the present invention;
FIG. 5 is a schematic view of interfacial hydrophobicity provided by an embodiment of the present invention;
FIG. 6 is a schematic diagram of magnetofluid solder ball transfer according to an embodiment of the present invention;
fig. 7 is a schematic diagram of magnetic fluid solder ball dropping provided by the embodiment of the invention;
FIG. 8 is a schematic flow chart of a method for applying solder to an LED according to another alternative embodiment of the present invention;
description of reference numerals:
11-magnetofluid solder, 12-magnetofluid solder ball, 2-transfer substrate, 3-circuit substrate, 31-bonding pad region, 41-first magnetic field, and 42-second magnetic field.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
In the related art, the packaging mode of the LED comprises two modes of traditional solder coating and In metal evaporation; although the traditional solder coating method has better reliability, the adopted screen printing technology can only be used for printing pads with the thickness of more than 50 micrometers, and the corresponding application is usually directed to mini-LEDs and small-pitch display or LEDs with larger size, and cannot be applied to micro-LED light-emitting devices with smaller size; in the scheme of evaporating In metal, the In metal is very easy to oxidize, and after the In metal is oxidized, the reliability of the photoelectric device is poor.
Based on this, the present invention intends to provide a solution to the above technical problem, the details of which will be explained in the following embodiments.
According to the LED solder coating method disclosed by the embodiment, the magnetofluid solder balls are prepared from the magnetofluid solder, then the magnetofluid solder balls are transferred to the upper part of the circuit substrate in batches through the magnetic field, and the magnetofluid solder balls fall on the circuit substrate, so that the coating of the solder on the circuit substrate is realized, the reliability of the welding can be improved by adopting the solder, the oxidation is not easy, the small-sized solder balls can be conveniently prepared by the solder with the magnetofluid property, the transportation is convenient, the applicability of the LED solder coating is greatly improved, and the method can be particularly applied to micro-LEDs. For ease of understanding, the present embodiment will be described below by taking the LED solder coating method shown in fig. 1 as an example for ease of understanding:
referring to fig. 1, the LED solder coating method includes, but is not limited to:
s101, preparing magnetic fluid solder balls 12 with preset sizes from magnetic fluid solder 11 to be coated;
s102, enabling the magnetic fluid solder balls 12 to be adsorbed on the lower surface of the transfer substrate 2 in batch through the first magnetic field 41;
s103, moving the transfer substrate 2 to be coated above the circuit substrate 3, wherein the position of the magnetic fluid solder ball 12 on the lower surface of the transfer substrate 2 corresponds to the position of the pad area 31 on the circuit substrate 3;
s104, closing the first magnetic field 41, and enabling the magnetic fluid solder balls 12 to fall to the corresponding pad areas 31 on the circuit substrate 3.
The LED solder coating method in the embodiment of the invention is mainly used for arranging solder on the pad area 31 in advance on the corresponding position, namely the pad area 31, of the LED chip or other electronic devices on the welding circuit substrate 3; the solder has at least two functions, one is to provide electrical connection between the pad area 31 on the circuit substrate 3 and the LED chip or other electronic device to be soldered, and the other is to provide fixed connection between the LED chip or other electronic device to be soldered and the circuit substrate 3. After the solder coating is completed, the LED chip or other electronic device can be electrically connected to the pad region 31 and fixedly connected thereto by the soldering action of the solder after the solder is cured.
In S101, the solder to be coated is magnetofluid solder. By magnetofluid solder is meant a solder that is itself magnetizable in nature and can move under the influence of a magnetic field. When not solidified, the solder has the characteristic of certain liquid and can flow in a certain range; the magnetic fluid solder adds the characteristic of being magnetized to the solder, and once an external magnetic field acts on the magnetic fluid solder, the magnetic fluid solder can flow under the action of the external magnetic field.
The magnetic fluid is composed of a certain magnetic substance; therefore, the magnetic fluid solder in the embodiment of the invention comprises uniformly mixed nano-scale welding particles and magnetic metal particles. The material of the solder particles of nanometer scale may be a mixture of Sn and/or Bi, wherein the solder particles of nanometer scale represent solder particles having a size range of 1-100 nm, such as 20 nm, 50 nm, 99 nm, etc. The smaller the size of the solder particles, the greater the fluidity thereof and the greater the dimensional freedom of the solder that can be formed, i.e., the magnetic fluid solder balls 12.
Magnetic metal particles means that the particles are of a nature that they can be magnetised under the influence of an externally applied magnetic field to produce an opposing magnetic field and thereby be attracted to the externally applied magnetic field to cause movement. The magnetic metal particles may include at least one of Co particles and Ni particles depending on the material. Co and Ni particles are doped into the solder by utilizing the characteristic of superparamagnetism of the Co and Ni particles under the condition of small size, so that the solder with good magnetic fluid property can be obtained, and the Co and Ni particles move under the action of a magnetic field. In order to achieve a better effect, in the embodiment of the invention, the doping proportion of the magnetic metal particles in the magnetic fluid solder 11 is 0.2-0.8% by mass.
Although the magnetic fluid solder 11 has magnetism and can move under the action of a magnetic field, the magnetic fluid solder 11 itself is in a continuous liquid state if not processed, and needs to be divided into small-size solders corresponding to each pad region 31, namely, the magnetic fluid solder balls 12 in the embodiment of the present invention, according to the pad regions 31 on the circuit substrate 3. The magnetic fluid solder balls 12 also have the characteristics of magnetic fluid, the size of the magnetic fluid solder balls is smaller than that of the magnetic fluid solder 11, for different LED chip sizes, the size of the pad area 31 on the circuit substrate 3 is different, and the size of the magnetic fluid solder balls 12 can be independently set; for example, if the magnetic fluid solder balls 12 are applied in micro-LED applications, the size of the magnetic fluid solder balls 12 can be generally set to be in the order of 5-50 microns.
In some embodiments, preparing the magnetic fluid solder balls 12 with preset sizes in the magnetic fluid solder 11 to be coated may include: a third magnetic field is added on the magnetic fluid solder 11; and under the action of the third magnetic field, dispersing the magnetic fluid solder 11 into magnetic fluid solder balls 12. Due to the fluidity and magnetism of the magnetic fluid solder 11, under the condition of applying the third magnetic field, the applied third magnetic field can guide the movement of the magnetic fluid solder; in the moving process, the dispersed solder balls can be prepared by controlling the flow rate, and the size of the prepared solder balls can be controlled by controlling the speed of the flow rate; the faster the control magnetofluid solder 11 flows, the smaller the size of the prepared solder ball, and the slower the control magnetofluid solder 11 flows, the larger the size of the prepared solder ball. Referring to fig. 2, a schematic diagram of the preparation of magnetic fluid solder balls 12 is shown, which can be combined with microfluidic technology to realize the preparation of magnetic fluid solder balls 12 by means of a peristaltic pump. The microfluidic chip can adopt Y, T type channels, taking a Y-type channel as an example, injecting magnetic fluid at one end of the Y-type channel through a peristaltic pump, injecting organic liquid drops at the other end of the Y-type channel, controlling the flow rate of the organic liquid drops, and preparing different magnetic fluid solder balls 12.
Because the magnetic fluid solder balls 12 in the embodiment of the invention need to be transferred on different platforms, at least the magnetic fluid solder balls 12 need to be transferred between the transfer substrate 2 and the circuit substrate 3, for convenience in the transfer process, the magnetic fluid solder balls 12 can better transfer the substrate 2, and the surfactant can be wrapped around the magnetic fluid solder balls 12 when the solder is dispersed into the magnetic fluid solder balls 12 under the action of the third magnetic field. The surface of the magnetic fluid solder ball 12 is wrapped with a certain amount of surfactant, so that the magnetic fluid solder ball 12 is spherical as much as possible, and is easy to fall off from the transfer substrate 2.
In S102, in order to attach the magnetic fluid solder balls 12 to the lower surface of the transfer substrate 2, the magnetic field direction of the applied first magnetic field 41 should be upward along the plane direction of the transfer substrate 2. When the distance between the transfer substrate 2 and the container for carrying the magnetic fluid solder balls 12 is small to a certain extent, the magnetic fluid solder balls 12 will move upward under the action of the first magnetic field 41, and are blocked by the lower surface of the transfer substrate 2 during the movement process, so as to form the lower surface of the transfer substrate 2, and the effect of adsorbing the magnetic fluid solder balls 12 is not really adsorption, the magnetic fluid solder balls 12 are adsorbed by the additional first magnetic field 41, and the transfer substrate 2 plays a role of preventing the magnetic fluid solder balls 12 from being adsorbed by the first magnetic field 41, please refer to fig. 3.
Because the magnetic fluid solder balls 12 are adsorbed and transferred in batches, the magnetic fluid solder balls 12 can accurately fall on the pad area 31 on the circuit substrate 3 for the convenience of subsequent magnetic fluid solder balls 12, and the distance between the magnetic fluid solder balls 12 can be preset, so that the position of each magnetic fluid solder ball 12 just corresponds to the position of the pad area 31 on the circuit substrate 3. The preset mode can utilize the magnetic property of the magnetic fluid solder balls 12 to adjust the position thereof by an external magnetic field, or the magnetic fluid solder balls 12 are arranged in one step when the magnetic fluid solder balls 12 are prepared, or the magnetic fluid solder balls 12 are arranged in the grooves corresponding to the pad areas 31 on the circuit substrate 3 on the container bearing the magnetic fluid solder balls 12 one by one, and the magnetic fluid solder balls 12 are arranged in the grooves one by one, and the magnetic fluid solder balls 12 are adsorbed under the condition of not influencing the distance between the adjacent magnetic fluid solder balls 12 by the uniform adsorption action of the first magnetic field 41 when the magnetic fluid solder balls are taken. In addition, the magnetic fluid solder balls 12 may be arranged by arranging the shape of the lower surface of the transfer substrate 2.
The transfer substrate 2 only plays a role of transferring the magnetic fluid solder balls 12; in order to reduce the difficulty of falling off the magnetic fluid solder balls 12 from the transfer substrate 2, the magnetic fluid solder balls 12 are wrapped by a surfactant, so that the magnetic fluid solder balls are spherical and are easy to fall off; further, in some embodiments, the lower surface of the transfer substrate 2 may also be provided as a superhydrophobic surface; when the magnetic fluid solder balls 12 are adsorbed on the lower surface of the transfer substrate 2, the shape of each magnetic fluid solder ball 12 is kept spherical. By superhydrophobic surface is meant a surface whose interface has a natural "repelling" effect on the liquid, which has a natural tendency to form a sphere on the superhydrophobic surface. Taking liquid water as an example, a surface with a contact angle with water of less than 90 ° is generally called a hydrophilic surface, and a surface with a contact angle with water of more than 90 ° is generally called a hydrophobic surface; in particular, if the contact angle with water is greater than 150 °, the surface is referred to as a superhydrophobic surface. Please refer to fig. 4, which shows the meaning of the contact angle. The surface free energy of the solid is reduced, the hydrophobicity of the surface of the solid can be improved, the surface of the solid is not flat usually, the rough structure of the surface also has influence on contact angles, and in practical application, the roughness of the surface needs to be considered. Assuming a rough surface with a structure of alternating concave and convex portions, in the wenzel mode theory, the liquid completely penetrates into the grooves of the rough surface, and in the case of the case mode theory, air is trapped in the grooves, and the liquid cannot penetrate into the grooves, so that the air flows straight at the surface depressions, see fig. 5, where a is the wenzel mode and B is the case mode. For highly hydrophobic surfaces, it is difficult for liquids to penetrate into the grooves and push air out, thus being in the cassie mode.
In some embodiments, the superhydrophobic surface, in terms of its structure, can include any one of the following structures: ordered microprotrusion structures, fibrous microstructures, bump structures, or may also include other superhydrophobic structures; in the embodiment of the present invention, the contact angle of the superhydrophobic interface is greater than 150 °, and specifically may be 160 ° or more.
In S103, the transfer substrate 2 is moved to above the circuit substrate 3 to be coated, and since the magnetic fluid solder balls 12 are adsorbed on the lower surface of the transfer substrate 2, when the transfer substrate 2 is moved to above the circuit substrate 3 to be coated, the magnetic fluid solder balls 12 are located below the circuit substrate 3. For the accuracy of the coating position, the position of the magnetic fluid solder ball 12 corresponds to the position of the pad region 31 on the circuit substrate 3.
Referring to fig. 6, during the process of moving the transfer substrate 2 to the circuit substrate 3, the first magnetic field 41 is continuously applied, and the application time of the first magnetic field 41 is at least from the magnetic fluid solder balls 12 being adsorbed on the lower surface of the transfer substrate 2 to the time when the transfer substrate 2 moves above the circuit substrate 3 and before the magnetic fluid solder balls 12 fall down; moreover, in order to ensure that the magnetic fluid solder balls 12 do not fall down during the moving process, the magnetic force applied to the magnetic fluid solder balls 12 by the first magnetic field 41 should be greater than the gravity of the magnetic fluid solder balls 12 themselves.
In S104, when the transfer substrate 2 has moved above the circuit substrate 3, the magnetic fluid solder balls 12 adsorbed on the transfer substrate 2 may be allowed to fall; in order to make the magnetic fluid solder balls 12 fall smoothly, the first magnetic field 41 can be turned off, and the magnetic fluid solder balls 12 can be separated from the transfer substrate 2 under the action of self gravity without the influence of the magnetic force of the first magnetic field 41, so as to fall to the corresponding pad area 31 on the circuit substrate 3, and the coating of the solder is completed.
In some embodiments, if the lower surface of the transfer substrate 2 is not a super-hydrophobic interface, it may be insufficient in hydrophobicity, or even if the lower surface of the transfer substrate 2 is a super-hydrophobic interface, due to the influence of the size, weight, and the like of the magnetic fluid solder balls 12, the magnetic fluid solder balls 12 may not spontaneously fall down when the first magnetic field 41 is turned off; in order to improve the reliability of the magnetic fluid solder balls 12 dropping from the transfer substrate 2, the step of turning off the first magnetic field 41 to drop the magnetic fluid solder balls 12 to the corresponding pad regions 31 on the circuit substrate 3 may further include: turning off the first magnetic field 41 and starting the second magnetic field 42, wherein the magnetic adsorption direction of the second magnetic field 42 to the magnetic fluid solder balls faces to the circuit substrate 3; the magnetic fluid solder balls 12 fall down to the corresponding pad areas 31 on the circuit substrate 3 under the action of the self-weight and the second magnetic field 42, please refer to fig. 7. That is to say, when the first magnetic field 41 is turned off, the second magnetic field 42 is immediately turned on, the magnetic adsorption direction of the second magnetic field 42 to the magnetic fluid solder balls 12 is toward the circuit substrate 3, that is, downward, so that the downward stress of the magnetic fluid solder balls 12 is increased, and the falling reliability of the magnetic fluid solder balls 12 is improved, so that the magnetic fluid solder balls 12 can fall down to the corresponding pad areas 31 on the circuit substrate 3 under the action of magnetic force and self weight. According to different scenarios, the strength of the second magnetic field 42 can be adjusted arbitrarily, and generally, the larger the size of the magnetic fluid solder ball 12, the smaller the strength of the second magnetic field 42 is required.
Therefore, by the coating method of the LED solder provided by the embodiment of the invention, the magnetic fluid solder 11 can be prepared into the magnetic fluid solder balls 12, then the magnetic fluid solder balls 12 are transferred to the upper part of the circuit substrate 3 in batches through the magnetic field, and the magnetic fluid solder balls 12 are dropped on the circuit substrate 3, so that the coating of the solder on the circuit substrate 3 is realized, the reliability of the welding can be improved by adopting the solder, the oxidation is not easy, the magnetic fluid solder is convenient for preparing small-sized solder balls, the transportation is convenient, the applicability of the coating of the LED solder is greatly improved, and the coating method can be particularly applied to micro-LEDs.
Another alternative embodiment of the invention:
the embodiment provides a light-emitting device and a manufacturing method of the light-emitting device, the light-emitting device comprises a circuit substrate 3 and an LED chip, a magnetic fluid solder ball 12 is coated on a pad area 31 of the circuit substrate 3 by an LED solder coating method, and the LED chip is electrically connected and fixedly connected to the pad area 31 through the magnetic fluid solder ball 12. The LED solder coating method can be realized by adopting the solder coating method in the embodiment of the invention.
The embodiment also provides a display device, which can be various electronic devices that use a display back plate made of micro LED chips to perform display, such as but not limited to various smart mobile terminals, PCs, displays, electronic billboards, etc., wherein the light-emitting device of the display device can be made by but not limited to the above-mentioned method for making the light-emitting device.
To further illustrate the LED solder coating method in the embodiment of the present invention, the LED solder coating is specifically described below with reference to fig. 8.
S801, providing a circuit substrate 3 to be coated with solder; wherein on the circuit substrate 3, a pad region 31 for applying solder is provided; the size and number of the pad areas 31 are set according to different LED product sizes, and the pad areas are not limited in this embodiment, and may be LEDs of common size, miniLED products, or micro-LED products.
S802, providing magnetic fluid solder 11 to be coated; the magnetic fluid solder 11 is a solder having a magnetizable property and capable of moving as a fluid under the action of a magnetic field.
The magnetic fluid solder 11 comprises nano Sn and Bi particles, and magnetic metal particles Co and Ni; wherein, the mass ratio of Co and Ni in the magnetic fluid solder 11 is 0.2-0.8%.
S803, preparing magnetic fluid solder balls 12; the magnetic fluid solder ball 12 is magnetic fluid, and the size of the magnetic fluid solder ball is smaller than that of the magnetic fluid solder 11 before preparation and is spherical; a third magnetic field may be applied to the magnetic fluid solder 11, and the magnetic fluid solder 11 is dispersed into magnetic fluid solder balls 12 under the action of the third magnetic field. The dispersed magnetic fluid solder balls 12 are coated with a surfactant so that they can be in a spherical shape.
And S804, applying the first magnetic field 41 to enable the magnetic fluid solder balls 12 to be adsorbed on the lower surface of the transfer substrate 2. When the strength of the first magnetic field 41 is sufficiently large, the magnetic fluid solder balls 12 move upward and stop moving to the lower surface of the transfer substrate 2, and as a result, the magnetic fluid solder balls 12 are adsorbed on the lower surface of the transfer substrate 2.
In order that the magnetic fluid solder balls 12 can be smoothly released from the transfer substrate 2, the lower surface of the transfer substrate 2 is a super-hydrophobic surface.
S805, under the action of keeping the first magnetic field 41, moving the transfer substrate 2 to the position above the circuit substrate 3, wherein the position of the magnetic fluid solder ball 12 corresponds to the position of the pad area 31 on the circuit substrate 3; during the movement of the transfer substrate 2, the first magnetic field 41 continuously applies magnetic force to the magnetic fluid solder balls 12 so that they do not actively fall off.
S806, turning off the first magnetic field 41 and turning on the second magnetic field 42, so that the magnetic fluid solder balls 12 fall down to the corresponding pad areas 31 on the circuit substrate 3 under the action of gravity and the magnetic force of the second magnetic field 42.
Therefore, by the coating method of the LED solder provided by the embodiment of the invention, the magnetic fluid solder 11 can be prepared into the magnetic fluid solder balls 12, then the magnetic fluid solder balls 12 are transferred to the upper part of the circuit substrate 3 in batches through the magnetic field, and the magnetic fluid solder balls 12 are dropped on the circuit substrate 3, so that the coating of the solder on the circuit substrate 3 is realized, the reliability of the welding can be improved by adopting the solder, the oxidation is not easy, the magnetic fluid solder is convenient for preparing small-sized solder balls, the transportation is convenient, the applicability of the coating of the LED solder is greatly improved, and the coating method can be particularly applied to micro-LEDs.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (10)
1. An LED solder coating method, comprising:
preparing magnetic fluid solder balls with preset sizes from the magnetic fluid solder to be coated;
adsorbing the magnetic fluid solder balls on the lower surface of the transfer substrate in batch through a first magnetic field;
moving the transfer substrate to be coated above the circuit substrate, wherein the magnetic fluid solder ball position on the lower surface of the transfer substrate corresponds to the position of the pad area on the circuit substrate;
and closing the first magnetic field to enable the magnetic fluid solder balls to fall down to the corresponding pad areas on the circuit substrate.
2. The LED solder coating method according to claim 1, wherein the magnetic fluid solder comprises nano-sized solder particles and magnetic metal particles uniformly mixed therein.
3. The LED solder coating method according to claim 2, wherein the magnetic metal particles include Co particles and/or Ni particles; the doping proportion of the magnetic metal particles in the magnetic fluid solder is 0.2-0.8% by mass.
4. The LED solder coating method of any one of claims 1-3, wherein turning off the first magnetic field and dropping the magnetic fluid solder balls onto the corresponding pad areas on the circuit substrate further comprises:
closing the first magnetic field and starting a second magnetic field, wherein the magnetic adsorption direction of the second magnetic field to the magnetic fluid solder balls faces to the circuit substrate; and the magnetic fluid solder balls fall into corresponding pad areas on the circuit substrate under the action of self weight and the second magnetic field.
5. The LED solder coating method of any one of claims 1 to 3, wherein the preparation of the magnetic fluid solder balls with preset sizes from the magnetic fluid solder to be coated comprises the following steps:
adding a third magnetic field on the magnetic fluid solder;
and dispersing the magnetic fluid solder into magnetic fluid solder balls under the action of the third magnetic field.
6. The LED solder coating method according to claim 5, wherein when the solder is dispersed into magnetic fluid solder balls under the action of the third magnetic field, the method further comprises:
and a surfactant is wrapped around the magnetic fluid solder balls.
7. The LED solder coating method according to any one of claims 1 to 3, wherein the lower surface of the transfer substrate is a superhydrophobic surface; when the magnetic fluid solder balls are adsorbed on the lower surface of the transfer substrate, the shape of each magnetic fluid solder ball is kept to be spherical.
8. The LED solder coating method of any of claims 1-3, wherein the structure of the superhydrophobic surface comprises any of: ordered micro-convex structure, fibrous micro-structure and convex point structure.
9. A light emitting device comprising a circuit substrate and an LED chip, wherein a solder ball of magnetofluid is coated on a pad region of the circuit substrate by the LED solder coating method according to any one of claims 1 to 8, and the LED chip is electrically and fixedly connected to the pad region by the solder ball of magnetofluid.
10. A display device characterized in that the display device comprises the light-emitting device according to claim 9.
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| CN114783298A (en) * | 2022-05-25 | 2022-07-22 | 苏州华星光电技术有限公司 | Flexible screen leveling device and flexible screen leveling method |
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| CN113948624B (en) | 2023-10-24 |
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