Viscous material printing system using laser-assisted deposition

Abstract

It is an object of the present invention to provide an improved system for digitally depositing material in a manner that is much faster than the best dispensing systems. In a system for printing viscous materials, the printing and post-processing of the viscous material are performed in an alternating sequence. In a first step, the viscous material is printed on a sample placed on a receiving substrate using a donor module and a laser scanner, and then the donor module is replaced with a post-processing system to perform a post-processing operation (or vice versa). Multiple post-processing operations can be performed and multiple different materials can be printed on the same layer. The system allows for improved speed, resolution and variety of materials printed on the same sample, opening up new design possibilities.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Patent Application No. 18 / 065174, filed December 13, 2022, and U.S. Provisional Patent Application No. 63 / 265950, filed December 23, 2021.

[0002] (Technical field) The present invention relates to a system for printing viscous materials, and more particularly to a system in which the printing and post-processing of viscous materials is performed in succession, one after the other. [Background technology]

[0003] Prior art for printing viscous materials has used two main techniques: screen printing and dispensing with a dispensing system. In screen printing, the ink is coated onto a surface by forcing it through a fine-mesh screen that can be formed by stretching silk, synthetic substitutes, or other fabrics taut over a frame. Patterns (i.e., images) of the printed material can be created by blocking parts of the screen with a stencil that is hand-drawn or photographically created. Screen printing is one of the oldest printing techniques. Basic equipment is inexpensive and large dimensions of mesh can be used to print large surfaces. However, for most of today's printed electronics with conductive patterns formed with carbon or silver inks, screen printing could not cope with these types of inks and / or could not produce a layer thick enough in one printing pass to provide the necessary conductivity.

[0004] Therefore, in printed electronics, screen printing is limited to certain applications such as the production of membrane keyboards and radio frequency identification (RFID) antennas. Screen printing is also used to print the dielectric, phosphor, and passivation layers of alternating current (AC) electroluminescent printed large area displays. In contrast to screen printing, many high speed printing processes cannot handle the printing of materials over large areas, making screen printing one of the most important tools for printing materials in microelectronics applications. Rotary screen printing may be preferred over conventional screen printing due to its increased throughput compared to the lower throughput of conventional screen printing.

[0005] However, screen printing has its drawbacks. While screen printing is ideal for mass production, it is not very cost-effective for manufacturing products that are required in small quantities. The setup time for screen printing is complex and involved, so it may not always be cost-effective for printing small quantities. Another problem with screen printing is that only one material can be printed at a time during the printing process. This means that screen printing generally does not allow the printing of a second material before the first material has dried or cured. Furthermore, screen printing cannot be used to print materials that are used as adhesives between components. Another limitation of screen printing is due to the uniform size of the openings located in the screen. Therefore, it is only possible to print materials with the same droplet size in the same printing layer, but often there is a need to print materials with different droplet sizes in the same printing layer. To address such issues, the current solution in the art is to print some of the droplets with a first droplet size with screen printing and other droplets with a second droplet size with another technique.

[0006] Screen printing is less reliable than dispensing with a dispensing system, therefore dispensing is often used in the electronics market. Automated dispensing of electronic materials in fluid form is employed across the full spectrum of electronics manufacturing, from board level assembly to semiconductor applications. Dispensed materials can range in viscosity from very low (like water) to very high (like toothpaste) and encompass many different functions. These include solder pastes to electrically connect components, encapsulants to protect devices from atmospheric conditions, thermal interface materials (TIMs) to help transfer heat away from parts, and adhesives to attach parts to boards or assemblies.

[0007] Each material can be dispensed in a variety of dot sizes or intricate lines and patterns depending on the application requirements. Common applications include underfill, selective coating, fixturing, dam & fill, potting, and dielectric dispensing. The form and function are determined by the type of pump head type attached to the dispenser of the dispensing system. Additionally, a dispenser can be equipped with two or more pump head types to perform multiple dispense operations on a single substrate.

[0008] For example, when electronic materials such as solder paste are screen printed onto printed circuit boards (PCBs), large areas can be printed at one time. Dispensing with a dispensing system almost always takes longer than screen printing because dispensing systems typically print one dot at a time, resulting in reduced throughput. Therefore, minimizing the cycle time between printing each dot with a dispensing system is key to achieving reasonable production throughput. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent Application Serial No. 18 / 065174 [Patent Document 2] U.S. Provisional Patent Application No. 63 / 265950 [Patent Document 3] U.S. Patent No. 10 / 144034 [Patent Document 4] US Patent Application Publication No. 2020 / 0180225 [Patent Document 5] US Patent Application Publication No. 2021 / 0331196 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention improves upon these and other conventional techniques for depositing material onto a sample. [Means for solving the problem]

[0011] The present invention provides an improved system for digitally depositing materials (e.g., via digital / computer control of a laser) with better resolution and repeatability than analog (e.g., manual) screen printing systems, and in a manner much faster than the best dispensing systems. The improved system employs continuous sequence production, greatly increasing production speed and its versatility over conventional systems. Multiple materials can be introduced in each printed layer, and there is no need to clean at the end of production.

[0012] The inventors have recognized that it would be desirable to print viscous materials digitally (e.g., via digital / computer control of a laser) and still maintain high speed production. To that end, the inventors have integrated the printing and post-processing processes into a single system, thereby addressing printing speeds while not limiting the process to a single material deposition or a single post-processing operation.

[0013] In some embodiments of the invention, the printing system employs a donor module that is not laterally translatable, while in other embodiments, the printing system employs a donor module that is laterally translatable. The donor module includes a donor substrate (e.g., a film) that is translated over a number of rollers as printing of the material occurs. The donor module can also include a coating system that is used to evenly spread the material deposited on the donor substrate by the dispensing system. The coating system can be located in a closed cell with a controlled environment to extend the pot life of the material. The coating system can include rollers or knives that form a gap through which the donor substrate is translated by a motor, such translation through the gap exerting pressure on the dispensed material to form a layer of the dispensed material on the donor substrate with a uniform thickness. After coating the donor substrate with material, the rollers or knives are configured to increase the height of the gap before translating the donor substrate from the coating zone to the printing zone.

[0014] In some embodiments of the present invention, the transport unit of the system provides multiple axes of motion for spatially controlling the position of tools utilized in both the calibration process and post-processing operations.

[0015] In some embodiments of the present invention, the donor substrate comprises a film coated with a material. Printing as discussed herein involves directing a laser beam onto the donor substrate coated with the material to eject (or transfer) droplets of the material from the donor substrate onto a sample placed on a receiving substrate. Such a process may be referred to as laser-assisted deposition (LAD).

[0016] In some embodiments of the invention, the receiving substrate is a plate holder that is movable in both X and Y directions on a stage surface that is fixed in the Z direction. The stage surface is the reference surface for all other surfaces in the system, and the receiving substrate can be moved to all areas of the system. In that way, the receiving substrate can hold the sample and be transported to any of the subsystems for both printing and post-processing.

[0017] In embodiments of the invention with a donor module that is not laterally translatable, the only axis of motion of the donor module is in the Z direction. However, the height of the feet on which the donor module rests can be independently adjusted via motors, allowing the surface of the donor substrate to be adjusted in two additional angles (θ and φ relative to the X and Y axes). Using these motors, the surface of the donor substrate can be precisely and reproducibly adjusted to be parallel to the surface of the recipient substrate.

[0018] In some embodiments of the invention, the axis of motion of the laser used to eject (or print) material from the donor substrate onto the sample is also solely in the Z direction, however, similar to the donor module, the laser is mounted on height adjustable legs (controlled by a motor) so that the focal plane of the laser can be adjusted parallel to the surface of the receiving substrate.

[0019] In some embodiments of the invention, the coating process of the donor module comprises dispensing a material onto a donor substrate (e.g., a film) of the donor module and translating the donor substrate through a gap formed by two rollers (or knives) to create a uniform layer of material at a desired thickness on the donor substrate.

[0020] In some embodiments of the invention, the material is dispensed onto a donor substrate (eg, a film) by a syringe containing it, or by any other dispensing device.

[0021] In some embodiments of the present invention, to achieve better uniformity of the material, the material is also dispensed onto the donor substrate (e.g., a film) using a raster motion (i.e., translating the dispensing module back and forth laterally while translating the donor substrate in a direction perpendicular to the lateral motion of the dispensing module), forming lines of deposited material on the donor substrate (compared to other coating methods that dispense dots of material onto the donor substrate).

[0022] In some embodiments of the invention, the donor module includes two donor substrates, so that the donor module can be used to print two different materials onto a sample. The dispense module can then house two dispense units, each of which can be translated laterally back and forth with its own motor to create a raster motion for the corresponding donor substrate that translates in a direction perpendicular to the lateral motion of the respective dispense unit.

[0023] In some embodiments of the invention, a camera is used to inspect the surface of the sample before and / or after printing material onto the sample. In embodiments with a receiving substrate that is translatable in the X and Y directions, the camera may be fixed in the X and Y dimensions, but movable in the Z direction to adjust its focal plane to coincide with the sample surface. The camera may also accommodate a zoom lens to increase the resolution of the inspection.

[0024] In some embodiments, two optional post-processing units are disposed within the system: a UV curing module and a drying unit. The UV curing module is used to cure UV-sensitive materials after they have been deposited on the sample. The drying unit is used to cure heat-sensitive materials after they have been deposited on the sample.

[0025] In some embodiments of the present invention, the UV curing module can contain a UV light source that emits UV light at a desired wavelength and a gas inlet that introduces a gas that enhances the curing rate of the deposited material. In scenarios where oxygen inhibits the UV curing of the deposited material, the gas can be an inert gas that replaces atmospheric oxygen to create a low-oxygen environment directly above the sample in which the newly deposited material is UV cured.

[0026] In embodiments with a donor module that is not laterally translatable, the area between the two donor substrates of the donor module can be utilized for laser post-processing operations including sintering and / or ablation. In other words, such area can define a narrow window through which the laser can be scanned to sinter and / or ablate the sample and / or material deposited on the sample.

[0027] In some embodiments of the invention, the same laser used to print the metal material from the donor substrate onto the sample can be used to sinter the metal material deposited onto the sample by LAD to increase the electrical conductivity of the metal material (e.g., to form better conductive lines). The metal material may be provided in a paste-like substance formed by a mixture of small metal particles and a solvent. After the metal material is deposited onto the sample, the solvent is removed by applying heat to the deposited material, resulting in a small mass of small metal particles. Thus, the electrical conductivity of the metal particles, at least initially, is not the same as that of a homogeneous solid form of the metal, because the electrons of the metal have a long path to travel from one end of the deposited material to the other. Therefore, a laser is used to sinter and melt the particles together to create better interactions between adjacent metal particles and increase the overall electrical conductivity of the printed lines.

[0028] In some embodiments of the invention, ablation of the deposited material is performed to remove portions of unwanted material (e.g., to increase the smoothness of the sample surface). For example, ablation can be used to repair errors in the deposited material resulting from printing errors, or to repair errors in the sample introduced at a previous stage in the sample formation process. Ablation can also be used to improve the resolution of certain portions of the sample that would benefit from improved resolution.

[0029] In some embodiments of the invention, the donor module is laterally translatable, offering several advantages over donor modules in systems that are not laterally translatable, the main advantage being the ability to print, inspect, and post-process a sample while the sample remains fixed in place, thereby allowing for increased resolution and repeatability of various processes (e.g., printing, inspection, and post-processing processes). Specifically, in both embodiments, the donor module may be said to be vertically (Z) translatable, but a laterally translatable donor module may also be translatable in a lateral (X) direction perpendicular to the vertical (Z) direction.

[0030] In some embodiments of the invention, the quality of the coating on the donor substrate can be inspected as the donor module translates from the print zone (i.e., above the receiving substrate) to the coating zone (i.e., below the dispensing system). After coating the top surface of the donor substrate with the dispensing system (e.g., using a syringe containing material), the donor substrate is rotated about 180 degrees around the roller so that the coating side of the donor substrate (upstream of the roller) faces down (downstream of the roller). The coating can then be inspected using a bottom camera (i.e., a camera positioned below the donor substrate) as the donor module translates from the coating zone to the print zone to determine the quality of the coating on the donor substrate. Such an inspection process allows for better control of the print quality.

[0031] In some embodiments of the invention, the dispensing system is not fixedly attached to the coating system. In such embodiments, the donor module (with the coating system) is located in the print zone during the printing operation. When the coating on the donor substrate is worn out, the donor module can be translated to the coating zone (located adjacent to the print zone) where material is dispensed onto the donor substrate, and then the donor substrate is passed through a gap in the coating system to spread the dispensed material into a new uniform coating on the donor substrate. After the donor substrate is coated, it is immediately inspected by the lower camera and sent to the print zone for further printing. If the inspection by the lower camera reveals that the coating quality is not good, the donor substrate can be sent back to the coating zone for recoating. By locating the coating zone away to the side of the print zone, the dispensing system can occupy more space without interfering with the printing process. In such a case, the dispensing system can include more syringes (e.g., five syringes), allowing dispensing of many different materials.

[0032] In some embodiments of the invention, the same transport unit (e.g., including rails) used to laterally translate the donor module can be used to move other subsystems to the print zone. Thus, drying, inspection, or UV curing of the deposited material can occur in the same location as the donor module was located during the print operation. To provide an additional degree of freedom of movement (e.g., so that each subsystem moves throughout the print zone), another axis can be added in the vertical (Y) direction to the transport unit.

[0033] In some embodiments of the invention, the camera is movable about three axes: the Z axis for focusing the camera on the sample surface, and the XY axes for positioning the camera relative to different locations on the sample surface.

[0034] In some embodiments of the invention, the drying unit and UV curing module may also be equipped to move about three axes, although the position axes (X and Y) are of primary importance for those subsystems.

[0035] In some embodiments of the invention, the dispensing system may dispense additional materials or incorporate complex syringe systems. For example, a complex syringe system may be used to dispense two-component (2k) materials such as epoxies that must be mixed in the syringe before being dispensed onto the donor substrate. Such complex syringe systems may require the syringe to be replaced from time to time.

[0036] In some embodiments of the present invention, to reduce the number of syringe changes, the dispensing system may include a purge cup to collect residual material from the complex syringe system.

[0037] In some embodiments of the invention, the drying and suction assembly includes a drying unit configured to perform a drying operation and a suction unit surrounding the drying unit, during the ablation step, the drying unit is turned off and rotated (e.g., flipped up) about a hinge to expose a central cavity (e.g., a window) in the suction unit through which a laser can be passed to perform ablation simultaneously with the suction operation.

[0038] In some embodiments of the invention, drying is performed by delivering heated gas (e.g., hot air) from the drying unit onto the surface of the sample. The heated gas can be distributed evenly onto the sample (and / or print area) via holes on the bottom surface of the drying unit. The heated gas can be evacuated from the sample via holes located on the bottom surface of the suction unit and / or other holes located on the bottom surface of the drying unit. In some embodiments of the invention, the drying and suction assembly is positioned via a transport unit that allows the drying and suction assembly to be transported to and from the area of ​​the sample requiring suction or heating.

[0039] The suction unit can have several uses. First, the suction unit can be used to remove debris from the sample surface while the heating unit and / or the laser scanner are not in use. Second, the suction unit can be used simultaneously with the drying unit. In such a case, the drying unit can deliver hot gas toward the sample surface, and the suction unit can be used to exhaust the hot gas (e.g., treat the hot gas as exhaust gas). Third, the suction unit can be used simultaneously with the laser scanner. In such a case, the drying unit can be flipped up to expose a window in the suction unit; the laser scanner can direct and scan a laser through the suction window to ablate or sinter the sample and / or material deposited on the sample; and the suction unit can collect and remove debris generated by the ablation and / or sintering.

[0040] Specifically, the donor module can be fixed in the lateral (X) direction during printing and coating operations, but can still be translated in the lateral (X) direction during maintenance phases. More specifically, such a donor module can be placed in a drawer mechanism that can translate the donor module in the lateral (X) direction along rails of the drawer mechanism until the donor module reaches a position where it can be lifted out of the drawer and removed for maintenance. Specifically, the drawer of the drawer mechanism can include a bottom support surface that supports a bottom edge of the donor module, but at the same time includes an opening in the bottom support surface. The opening exposes the donor substrate to a top surface of the sample and allows material to be ejected from the donor substrate onto the sample during printing operations.

[0041] In some embodiments of the present invention, after the donor substrate is coated, it is positioned underneath the coating system with the coated side facing towards the receiving substrate.

[0042] In some embodiments of the invention, one or more cameras may be used to inspect the sample before and after the print run at one or more magnification settings.

[0043] In some embodiments of the present invention, a single camera with multiple selectable magnifications may be utilized, or multiple cameras with corresponding fixed magnifications may be utilized for user convenience, and such a camera (in conjunction with a transport unit) may be used to position the donor substrate in the X and Y dimensions.

[0044] In some embodiments of the present invention, the system includes a three-dimensional (3D) sensor to inspect the height of the sample and / or the material printed on the sample. In one embodiment, the 3D sensor is a non-contact sensor that can measure the height of a surface without touching the surface. The 3D sensor can be used in conjunction with a laser scanner to correct errors in the sample (e.g., during circuit board manufacturing) or to repair errors in the printed material. For example, the 3D sensor can measure the height of the sample and / or the printed material and, in response to the height exceeding a desired height, apply laser ablation to reduce the height of the sample and / or the printed material.

[0045] In some embodiments of the invention, the system includes a mechanical height sensor that can measure the height of a sample (e.g., a circuit board) at multiple points by contacting the surface of the sample with the sensor. Both the mechanical and 3D sensors can be used for surface planarization correction and other calibrations of the sample and / or printed material.

[0046] In some embodiments of the present invention, a dispensing system is used to dispense a mixture of two materials. Specifically, the two materials can be dispensed from two different fluid reservoirs into an injection cell of the dispensing system. After mixing in the injection cell, the two materials start to react and have a very short pot life. Therefore, the materials are mixed in the dispensing system only immediately before the mixture is dispensed onto a donor substrate.

[0047] In some embodiments of the invention, material injection from a two-component (2k) dispensing system is performed by mixing the materials in a syringe (i.e., one embodiment of an injection cell), and then moving an interchangeable syringe tip (i.e., also called an interchangeable needle) toward the injection area while moving an injection cup away from the injection area when a coating system of a donor module is positioned under the dispensing system. In some embodiments of the invention, the injection cup is used to collect residual material that may block the syringe tip after the materials react.

[0048] These and further embodiments of the present invention are described in detail below. [Brief description of the drawings]

[0049] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which: [Figure 1] 1 conceptually illustrates a system with a donor module that is not laterally translatable. The system is configured in accordance with an embodiment of the present invention to provide high resolution and high speed printing of viscous materials employing high resolution printing in a narrow gap or contact gap printing system, post-print processing and / or inspection, and a non-digital curing system. "Non-digital" means that all areas of the printed components are cured together (simultaneously) rather than individually (digitally). [Diagram 2] 1 conceptually illustrates a system with a laterally non-translatable donor module configured in accordance with an embodiment of the invention that provides high resolution and high speed printing of viscous materials employing high resolution printing in a narrow gap or contact gap printing system, post-print processing and / or inspection, and a non-digital curing system. [Figure 3A] 14 illustrates the advantage of a laterally translatable donor module compared to a laterally non-translatable donor module: large areas can be printed and post-processed without moving the receiving substrate. [Figure 3B] 14 illustrates the advantage of a laterally translatable donor module compared to a laterally non-translatable donor module: the same area of ​​the sample can be printed and post-processed without moving the receiving substrate. [Figure 4] 1 illustrates the location of the dispense system in both a system with a donor module that is not laterally translatable and a system with a donor module that is laterally translatable. In the former system, the donor module is positioned above the receiving substrate in the print zone, so a dispenser must also be positioned in the print zone to supply material to the donor substrate. In the latter system, however, the dispense system is positioned adjacent to the print zone, simplifying maintenance of the dispense system. [Diagram 5] 1 shows a system with a laterally translatable donor module. The transport unit additionally comprises an X-axis of movement to move the donor substrate back and forth between the print and coating zones, further enabling some post-processing operations to be performed between the print sessions. The additional X-axis of movement also provides the ability to inspect the printed product (e.g., with a camera, 3D sensor, mechanical height sensor, etc.). [Figure 6A] 1 illustrates a drying and suction assembly including a drying unit surrounded by a suction unit in accordance with one embodiment of the present invention, which is turned off and "flip-up" to allow laser ablation to be performed through an opening (i.e., window) in the suction unit while the suction unit is operating. [Figure 6B] 1 illustrates a drying and suction assembly including a drying unit surrounded by a suction unit in accordance with one embodiment of the present invention, which is turned off and "flip-up" to allow laser ablation to be performed through an opening (i.e., window) in the suction unit while the suction unit is operating. [Figure 7]1 shows perspective views of two systems, one with a laterally non-translatable donor module (left) and one with a laterally translatable donor module (right), in accordance with an embodiment of the invention. The system with the laterally non-translatable donor module can include a pull-out mechanism to facilitate maintenance of the donor module. The system with the laterally translatable donor module can include a post-processing system (with one or more post-processing units) that can be translated above the print zone. [Figure 8A] 1 illustrates the movement of certain components of a system with a laterally translatable donor module in accordance with one embodiment of the present invention. The donor module (along with the coating system) can be translated from the print zone to the coating zone to allow the post-processing system to enter the print zone. The axis of movement of the transport unit is also illustrated. [Figure 8B] 1 illustrates how certain components of a system with a laterally translatable donor module can be moved in accordance with one embodiment of the present invention. The system position remains unchanged, and the donor module (together with the coating system) can be translated into the print zone. The axis of movement of the transport unit is also illustrated. [Figure 8C] FIG. 2 is a top view of a donor module and post-processing system in accordance with one embodiment of the present invention. [Figure 8D] FIG. 2 illustrates a more detailed view of the aftertreatment system in accordance with one embodiment of the present invention. [Figure 8E] 2 illustrates the axes of motion of the aftertreatment system, in accordance with one embodiment of the present invention. [Figure 9A] FIG. 2 illustrates a top front perspective view of a portion of the system, in accordance with one embodiment of the present invention. [Figure 9B] FIG. 9B illustrates a close-up view of the dispensing system of the system shown in FIG. 9A dispensing a two-component material (2k material), in accordance with one embodiment of the present invention. [Figure 10A]FIG. 1 illustrates the use of a two-component material (2k material) in the system while simultaneously purging material from the system in accordance with one embodiment of the present invention. [Figure 10B] FIG. 1 illustrates the use of a two-component material (2k material) in the system while simultaneously purging material from the system in accordance with one embodiment of the present invention. [Figure 11A] FIG. 2 illustrates additional details regarding a coating system, in accordance with one embodiment of the present invention. [Figure 11B] FIG. 2 illustrates additional details regarding a coating system, in accordance with one embodiment of the present invention. [Figure 12A] FIG. 2 illustrates additional details regarding a coating system, in accordance with one embodiment of the present invention. [Figure 12B] FIG. 2 illustrates additional details regarding a coating system, in accordance with one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Before describing the invention in detail, it is helpful to refer to FIG. 1, which conceptually illustrates a system 100 with a donor module that is not laterally translatable. The system is configured in accordance with an embodiment of the invention to provide high resolution and high speed printing of a viscous material employing high resolution printing with a narrow gap or contact gap printing system, post-printing processing and / or inspection, and a non-digital curing system. As described further below, the narrow gap or contact gap printing system performs an initial print of the viscous material on a sample 8. As part of the pre-printing processing and / or inspection, the sample 8 may be viewed with one or more imaging devices to monitor and control the initial and subsequent printing process.

[0051] The transport unit (not shown) of system 100 provides multiple axes of motion for spatially controlling the position of tools utilized in both calibration and post-processing operations.

[0052] The receiving substrate 10 can be a plate holder that is movable in both X and Y directions on a surface of stage 11 that is fixed in the Z direction. The surface of stage 11 is the reference plane for all other surfaces in system 100, and the receiving substrate 10 can be moved over the entire area of ​​the surface of stage 11. In that way, the receiving substrate 10 can hold the sample 8 and be transported to any of the subsystems for both printing and post-processing.

[0053] The donor substrates 16a, 16b of the donor module 15 are each coated with a material to be printed onto the sample 8 disposed on the receiving substrate 10. In one embodiment, the material may include a polymeric material or a mixture of polymeric and monomeric materials. In another embodiment, the material may comprise a metal paste, a solder paste, or a ceramic paste. In another embodiment, the material may comprise a high viscosity material, a low viscosity material, a wax material, a heat sensitive material (i.e., a material that hardens when heat is applied), and / or a photosensitive material (i.e., a material that hardens when light is applied). In another embodiment, the material may be curable by ultraviolet (UV) light and / or heat.

[0054] Each donor substrate 16a, 16b can contain a film coated with a material. The film can be a transparent film substrate that is translated using rollers. The transparent film substrate can include a metal layer or a metal layer and a dielectric layer that is different from the coating that is coated on the donor substrate with the coating system. That is, the coating that is coated on the donor substrate with the coating system can be coated on top of the metal layer or the dielectric layer of the transparent thin film substrate. Further details of such transparent film substrates can be found in U.S. Patent No. 10 / 144034 to Michael Zenou.

[0055] In system 100, the only axis of motion for donor module 15 is in the Z direction. However, the height of the legs on which donor module 15 rests can be independently adjusted via motors, allowing the surface of each donor substrate 16a, 16b to be adjusted in two additional angles (θ and φ relative to the X and Y axes). Using these motors, the surfaces of donor substrates 16a, 16b can be precisely and reproducibly adjusted to be parallel to the surface of receiving substrate 10.

[0056] An additional "surface" that can be aligned with the surface of the receiving substrate 10 is the focal plane of a laser 13, which is controlled by a laser scanner 12. The axis of motion of the laser 13 is also solely in the Z direction. However, like the donor module 15, the laser 13 is mounted on height-adjustable legs (controlled by a motor) so that the focal plane of the laser 13 can be adjusted parallel to the surface of the receiving substrate 10.

[0057] In system 100, donor module 15 further includes a coating system 21 and a dispensing system 18 that includes two dispensing units 18a, 18b. For each donor substrate 16a, 16b, material is dispensed onto the donor substrate 16a, 16b as the donor substrate 16a, 16b translates through a gap formed between two rollers, which apply pressure to the material to produce a uniform layer of material at a desired thickness on the donor substrate 16a, 16b.

[0058] For each donor substrate 16a, 16b, a material is dispensed onto each donor substrate 16a, 16b by a syringe containing the material or any other dispensing device. To obtain better uniformity of the material on each donor substrate 16a, 16b, the material is also coated over the entire donor substrate 16a, 16b in lines using a raster motion instead of in dot shapes. The system 100 shown in FIG. 1 has two donor substrates 16a, 16b, so it can be used to print two different materials onto the sample 8. Each dispensing unit 18a, 18b can be equipped with its own motor to translate the dispensing unit 18a, 18b back and forth in the lateral (X) direction.

[0059] Camera 17a is used to inspect the surface of sample 8 before and / or after printing material onto the sample 8. In embodiments with a receiving substrate 10 that is translatable in the X and Y directions, camera 17a may be fixed in the X and Y dimensions, but movable in the Z direction to adjust its focal plane to coincide with the sample surface. Camera 17a may also accommodate a zoom lens to increase the resolution of the inspection.

[0060] Two optional post-processing units are disposed within the system 100: a UV curing module 20 and a drying unit 24. The UV curing module 20 is used to cure UV-sensitive materials after they have been deposited on the sample 8. The drying unit 24 is used to cure heat-sensitive materials after they have been deposited on the sample 8.

[0061] The UV curing module 20 can house a UV light source (not shown) that emits a desired wavelength of UV light, and a gas inlet (not shown) to inject a gas to enhance the cure rate. In scenarios where oxygen inhibits UV curing of the deposited material, the gas can be an inert gas to create a low-oxygen environment directly above the sample 8. Further details of such a UV curing module 20 are provided in U.S. Patent Application Publication No. 2020 / 0180225 to Zenou et al.

[0062] The area 14 between the two donor substrates 16a, 16b can be utilized for laser post-processing operations, including sintering and / or ablation. The same laser 13 used to print the metal material from the donor substrates 16a, 16b onto the sample 8 can be used to sinter the metal material deposited onto the sample 8 by LAD to increase the electrical conductivity of the metal material (e.g., to form better conductive lines). The metal material may be provided in a paste-like substance formed by a mixture of small metal particles and a solvent. After the metal material is deposited onto the sample 8, the solvent is removed by applying heat from a drying unit 24 to the deposited material, resulting in a small mass of small metal particles. Thus, the electrical conductivity of the metal particles is not, at least initially, the same as that of a homogeneous solid form of the metal, because the electrons of the metal have a long path to travel from one end of the deposited material to the other. Therefore, the laser 13 is used to sinter and melt the particles together to create a better interaction between adjacent metal particles and increase the overall electrical conductivity of the printed lines.

[0063] In some embodiments, ablation of the deposited material is performed to remove portions of unwanted material (e.g., to increase the smoothness of the sample surface). Ablation can be used to repair errors in the deposited material resulting from printing errors, or to repair errors in the sample 8 introduced at an earlier stage in the sample formation process. Ablation can also be used to improve resolution in certain portions of the sample 8 that would benefit from improved resolution.

[0064] The donor module 15 of system 101 is laterally translatable, providing several advantages over the donor module 15 of system 100, which is not laterally translatable. The main advantage of system 101 is the ability to print, inspect, and post-process the sample 8 while the sample 8 is fixed in position, which can increase the resolution and repeatability of various processes (e.g., printing, inspection, and post-processing processes). Specifically, in both systems 100 and 101, the donor module 15 can be vertically (Z) translatable. For example, if the sample 8 (e.g., a circuit board) includes regions of different heights, the donor module 15 can be adjusted to one height in one location and another height in another location. However, the donor module 15 of system 101 can also be translated in the lateral (X) direction, which is perpendicular to the vertical (Z) direction.

[0065] Another important advantage of the system 101 is the ability to continuously inspect the coating quality on the donor substrate 16 during printing. The coating quality on the donor substrate 16 can be inspected as the donor module 15 translates between the print zone (i.e., above the receiving substrate 10) and the coating zone (i.e., below the dispensing system 18). After coating the top surface of the donor substrate 16 in the dispensing system 18 (e.g., using a syringe), the donor substrate 16 is rotated approximately 180 degrees around the roller so that the coated side of the donor substrate 16 (upstream of the roller) faces down (downstream of the roller). The coating can then be inspected using the lower camera 17b as the donor module 15 translates from the coating zone to the print zone to determine the quality of the coating on the donor substrate 16. Such an inspection process allows for better control of the print quality.

[0066] In system 101, dispensing system 18 is not fixedly attached to coating system 21. In such an embodiment, donor module 15 (with coating system 21) is located in the print zone during a printing operation. When the coating on donor substrate 16 is worn out, donor module 15 can be translated to a coating zone (located adjacent to the print zone) below dispensing system 18, where material is dispensed onto donor substrate 16, and then donor substrate 16 is passed through a gap in coating system 21 (motion of donor substrate through gap provided by motor) to spread the dispensed material into a new uniform coating on donor substrate 16. After donor substrate 16 is coated, it is immediately inspected by lower camera 17b and sent to the print zone for further printing. If inspection by lower camera 17b reveals that the coating quality is not good, donor substrate 16 can be sent back to the coating zone for recoating. By placing dispensing system 18 away to the side of the print zone, dispensing system 18 can take up more space without interfering with the printing process. In such a case, dispensing system 18 may include more syringes (eg, five syringes) to allow for the dispensing of many different materials.

[0067] An important feature of system 101 is that the same transport unit (e.g., including rails) used to laterally translate donor module 15 can be used to move other subsystems into the print zone. Thus, drying, inspection, or UV curing of deposited material can occur in the same location that donor module 15 was in during the print operation. To provide an additional degree of freedom of movement (e.g., so that each subsystem moves throughout the print zone), another axis can be added in the vertical (Y) direction relative to the transport unit.

[0068] The camera 17a may be movable about three axes: the Z axis for focusing the camera 17a on the sample surface, and the XY axes for positioning the camera 17a relative to different locations on the sample surface. The drying unit 24 and UV curing module 20 may also be equipped to move about three axes, although the position axes (X and Y) are the most important for those subsystems.

[0069] 3A-3B show some advantages of a system 101 with a laterally translatable donor module 15. In the simplified diagrams of FIGS. 3A-3B, only the donor substrate 16 of the donor module 15 is shown. FIG. 3A shows the receiver substrate 10 located in the print area 28. The scan area 26 (e.g., size 200x200 mm) is the area where the laser scanner 12 is equipped to scan the laser beam. The print area 28 (e.g., size 70x100 mm) of the donor substrate 16 is smaller than the scan area 26, so that for the laterally non-translatable donor module 15 (left part of FIG. 3A), printing is restricted to a fixed position in the print area 28. In contrast, for the laterally translatable donor module 15 (right part of FIG. 3B), the print area 28 can be translated over the entire scan area 26 (see, e.g., print positions 1 and 2), allowing printing over a larger part of the laser scan area 26. The main advantage of using a large scan area 26 for printing is the fact that a larger area of ​​the sample 8 can be printed without changing position, improving both the printing speed and the printing resolution. It also allows for a better usage of the material during the printing job.

[0070] FIG. 3B (left) shows that the donor substrate 16 of the laterally fixed donor module 15 is located in the center of the scanning area 26 after printing of one layer is completed. The donor module 15 blocks access to the area of ​​the sample 8 directly below it, and therefore acts as an obstacle for the laser scanner 12, the UV curing module 20, the camera 17a, and other post-processing units during post-processing. If such blocked areas need to be post-processed, the receiver substrate 10 needs to be moved to translate the area of ​​the sample 8 outside the "shadow" of the donor module 15. On the other hand, in a system 101 with a laterally translatable donor module 15, the donor module 15 can be translated away from the scanning area 26 (see the right part of FIG. 3B) and post-processing can be performed over the entire scanning area 26 without moving the receiver stage 10. Thus, the printing and post-processing operations (e.g., sintering or ablation) are aligned with the positional accuracy of the laser scanner 12.

[0071] In both systems 100 and 101, the donor substrates 16, 16a, 16b of the donor module 15 are coated with a coating system 21, where material dispensed onto the donor substrate is forced through a gap between two rollers. Further details regarding the coating system 21 can be found in U.S. Patent Application Publication No. 2021 / 0331196 to Zenou et al. Sometimes, an excessive amount of material is dispensed onto the donor substrate, and the donor substrate translates through the gap, causing the excess material to drip out of the gap and contaminate portions of the donor module 15 and / or the coating system 21. The donor substrates 16, 16a, 16b also need to be replaced from time to time, and maintenance needs to be performed on the donor module 15 and / or the coating system 21.

[0072] In system 100 with a donor module that is not laterally translatable, donor module 15 and dispensing system 18 are located above receiving substrate 10 (see the left half of FIG. 4). Because access to donor module 15 and / or coating system 21 is limited by dispensing system 18, maintenance on donor module 15 and / or coating system 21 typically requires removing donor module 15 and / or coating system 21 from system 100. However, in system 101 with a donor module 15 that is laterally translatable (see the right half of FIG. 4), dispensing system 18 is located to one side of system 101, allowing for easier maintenance of donor module 15 and / or coating system 21, since donor module 15 and / or coating system 21 can be serviced in situ.

[0073] In system 101, it is also possible for dispensing system 18 to dispense additional materials or incorporate a complex syringe system. For example, a complex syringe system may be used to dispense a two-component (2k) material, such as an epoxy, that must be mixed in the syringe before being dispensed onto donor substrate 16. Such complex syringe systems may require the syringe to be replaced from time to time, and such syringe replacement is more easily performed in system 101. In system 101, to reduce the number of syringe replacements, dispensing system 18 may include a purge (or injection) cup 48 (see FIGS. 10A, 10B) that collects residual material from the complex syringe system.

[0074] It is worth emphasizing that the most important feature of the system 101 with the laterally translatable donor module 15 is the ability to post-process the sample 8 immediately after printing the material on it as well as between two successive printing sessions without moving the sample 8. This feature allows both sintering and ablation of the sample 8 and / or the material deposited on it with a very high precision. Since the post-processing can be performed with the laser scanner 12, the registration errors are kept to a minimum, which is determined only by the accuracy of the laser scanner 12. Since the accuracy of the scanner is in the range of 3-5 microns and may be better (scanner dependent), the post-processing can also be performed with that accuracy.

[0075] FIG. 5 illustrates how the post-processing system 30 (e.g., including the drying unit 24, the suction unit 22, the UV curing module 20, the camera 17a, and other inspection tools) can be mounted on a transport unit 34 that can move in both the X and Y directions. As a result, each unit of the post-processing system 30 can reach any area on the sample 8 to dry, cure, and / or inspect that area. In one embodiment, each unit of the post-processing system 30 is mounted on a unique transport unit, and each unit can move independently to post-process any area on the sample 8. As shown in FIG. 5, the donor substrate 16 can be translated laterally away from the receiving substrate 10 by the transport unit 32 prior to post-processing.

[0076] 6A and 6B show an embodiment of a drying and suction assembly that can be used in both systems 100 and 101. Fig. 6A shows a schematic top view of the assembly with the drying unit 24 positioned inside the central cavity 36 of the suction unit 22. During the ablation step, the drying unit 24 is turned off and rotated (e.g., flipped up) about a hinge to expose the central cavity 36 (e.g., a window) of the suction unit 22 through which a laser beam can be scanned to perform ablation simultaneously with the suction operation.

[0077] FIG. 6B shows a detailed view of the drying and suction assembly. Drying can be performed by delivering heated gas (e.g., hot air) from the drying unit 24 onto the surface of the sample 8. The heated gas can be distributed evenly onto the sample 8 via holes 40b located on the bottom surface of the drying unit 24. The heated gas can be exhausted from the sample 8 via holes 40a located on the bottom surface of the suction unit 22 and / or other holes 40b located on the bottom surface of the drying unit 24. In some embodiments, the drying and suction assembly is positioned via a transport unit that allows the post-processing unit to be transported to and from the area of ​​the sample 8 that requires suction or heating. Also shown in FIG. 6B are gas conduits for supplying vacuum to the drying and suction assembly. Conduit 38a can supply vacuum to the suction unit 22, and conduit 38b can supply vacuum to the drying unit 24.

[0078] FIG. 7 shows a detailed view of system 100 with a laterally fixed donor module (top left part of FIG. 7 ) and system 101 with a laterally translatable donor module (bottom right part of FIG. 7 ). Specifically, donor module 15 of system 100 can be fixed in the laterally (X) direction during printing and coating operations, but can be translated in the laterally (X) direction during maintenance phases. More specifically, such donor module 15 can be placed in a drawer mechanism 42, which can translate donor module 15 in the laterally (X) direction along rails of drawer mechanism 42 until donor module 15 reaches a position where donor module 15 can be lifted out of the drawer and removed for maintenance; specifically, the drawer of drawer mechanism 42 can include a bottom support surface that supports a bottom edge of donor module 15, but at the same time includes an opening in the bottom support surface. The openings expose the donor substrates 16a, 16b to the top surface of the sample 8 and allow material to be ejected from the donor substrates 16a, 16b onto the sample 8 during a printing operation.

[0079] In system 101 with a laterally translatable donor module (lower right portion of FIG. 7 ), dispensing system 18 is positioned to one side of system 101. After a printing operation, a portion of coating system 21 is positioned below dispensing system 18 for coating the donor substrate, while post-processing system 30 is positioned inside the printing area (i.e., above receiving substrate 10) for inspecting sample 8 and / or material deposited on sample 8.

[0080] 8A-8B show detailed views of donor module 15, coating system 21, and post-processing system 30. FIGS. 8A and 8B show how donor module 15 and coating system 21 move below dispensing system 18 between a coating position (FIG. 8A) and a printing position (FIG. 8B). Further details regarding coating system 21 can be found in U.S. Patent Application Publication No. 2021 / 0331196 to Zenou et al. For ease of illustration, the donor substrate of donor module 15 is not depicted in FIGS. 8A-8B. Further details regarding coating of the donor substrate can also be found in U.S. Patent Application Publication No. 2021 / 0331196 (wherein the donor substrate is referred to as film 112). FIG. 8A also shows that when the donor module 15 is positioned below the dispensing system 18, the post-processing system 30 can be moved (in the X and Y axes) to an inspection, curing, and / or ablation position above the sample 8 (not shown).

[0081] Figure 8C shows a bottom view of donor module 15 and post-processing system 30. In Figure 8C, donor module 15 is in a coating position and post-processing system 30 is in an inspection, curing, and / or ablation position.

[0082] FIG. 8D shows a bottom view of the post-processing system 30 in more detail. The post-processing system 30 can include the drying and suction assembly (comprising the drying unit 24 and the suction unit 22) described above. The post-processing system 30 can also include the UV curing module 20 described above. The post-processing system 30 can also include cameras 17a, 17c that can inspect the sample 8 before and after printing at one or more magnification settings. In some embodiments of the invention, a single camera with multiple selectable magnifications can be utilized, or multiple cameras with corresponding fixed magnifications can be utilized for user convenience. Such cameras (in conjunction with the transport unit) can be used to position the donor substrate 15 in the X and Y dimensions.

[0083] The post-processing system 30 can also include a three-dimensional (3D) sensor 52 to inspect the height of the sample and / or the material printed on the sample. In one embodiment, the 3D sensor 52 is a non-contact laser sensor that can measure the height of a surface without touching the surface. The 3D sensor 52 can be used in conjunction with the laser scanner 12 to correct errors in the sample 8 or repair errors in the printed material. For example, the 3D sensor 52 can measure the height of the sample 8 and / or the printed material and, in response to the height exceeding a desired height, can apply laser ablation to reduce the height of the sample 8 and / or the printed material.

[0084] The post-processing system 30 may also include a probe 50 (also referred to as a mechanical height sensor) that can measure the height of the sample 8 at multiple points by contacting the surface of the sample 8. Both the probe 50 and the 3D sensor 52 may be used for surface planarization correction and other calibrations on the sample 8 and / or the printed material.

[0085] Figure 8E illustrates the axes of motion of the post-processing system 30. As shown in Figure 8E, the post-processing system 30 can be mounted on rails of a transport unit 34 that allows it to be translated laterally in the X and Y directions.

[0086] 9A and 9B show a coating and dispensing system for two-component (2k) materials. FIG. 9A shows a portion of the coating system 21 located below the dispensing system 18, and FIG. 9B shows a close-up of the dispensing system 18 located above the portion of the coating system 21. Specifically, two materials can be dispensed from two different fluid reservoirs 44a, 44b (corresponding to the two dispensing units 18a, 18b) into the injection cell 45 of the dispensing system 18. After mixing in the injection cell 45, the two materials start to react and their pot life is very short. Therefore, these materials are mixed in the dispensing system 18 only immediately before the mixture is dispensed onto the donor substrate 16.

[0087] 10A and 10B show a cleaning system for the dispensing system 18. Material injection from the two-component dispensing system 18 is performed by mixing the materials in a syringe (i.e., one embodiment of the injection cell 45), and then moving the replaceable syringe tip 46 (i.e., also called a replaceable needle) toward the injection area while moving the injection cup 48 away from the injection area when the coating system 21 of the donor module 15 is placed under the dispensing system 18. In some embodiments of the present invention, the injection cup 48 is used to collect residual material that may block the syringe tip 46 after the material reacts. As shown in FIG. 10B, the syringe tip 46 can protrude into the injection cup 48 through a small hole in the injection cup 48.

[0088] 11A and 11B further illustrate the formation of a uniform layer of material 62 on a donor substrate 16. First, a material 66 can be dispensed onto the donor substrate 16 by a syringe 64 (FIG. 11A) or, more generally, a dispensing system. The donor substrate 16 can be translated by a pair of rollers 54a, 54b rotated about their respective axes by a motor 56. The translation of the donor substrate 16 can cause the dispensed material 66 to pass through a gap 60, thereby forming a uniform layer of material 62 (FIG. 11B). The gap 60 can be created by moving the pair of rollers 58a, 58b toward each other using an appropriate control unit (e.g., a stepper motor or a piezo transducer). The syringe 64 (or, more generally, a dispensing system) can be placed in a closed cell 68 with a controlled environment to extend the pot life of the material 66.

[0089] 12A and 12B are identical to FIGS. 11A and 11B, except that gap 60 is formed using a knife 70 (or other leveling device) and donor substrate 16 instead of a pair of rollers 58a, 58b.

[0090] Thus, a system for printing viscous materials using laser-assisted deposition has been described. Many other embodiments will be apparent to those skilled in the art upon review of the above description. The scope of the invention should therefore be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. [Explanation of symbols]

[0091] 8 Samples 10 Receiving board 11 Stage 12 Laser scanner 13 Laser 14 Laser processing area 15 Donor Module 16, 16a, 16b Donor substrate 17a, 17b, 17c Camera 18 Dispensing System 18a, 18b Dispensing unit 20 UV curing modules 21 Coating System 22 Suction unit 24 Drying Unit 26 Laser scanning area 28 Print area 30 Aftertreatment System 32 Transport unit 34 Transport unit 36 Central cavity in suction unit 38a, 38b Gas pipes 40a,40b opening 42 Drawer mechanism 44a, 44b Fluid reservoir 45 Injection Cell 46 needles 48 Pouring Cup 50 Probes 52 3D Sensor 54a,54b Laura 56 Motor 58a,58b Laura 60 Gap 62 Coating 64 Syringe 66 Dispensed material 68 Closed Cell 70 Knife 100 Systems with non-translatable donor modules 101 System with a translatable donor module

Claims

1. 1. A system comprising a laser and a donor module, The system, wherein the donor module is configured to translate laterally between (i) a coating region, where a coating system is configured to coat material on a donor substrate of the donor module, and (ii) a printing region, where the laser is used to deposit the material from the donor module onto a sample.

2. The system of claim 1 , wherein the coating system is configured to form a uniform layer of the material on the donor substrate.

3. The coating system comprises: a roller or knife defining a gap; a motor for passing the donor substrate through the gap to form a uniform layer of the material having a thickness defined by a height of the gap; Equipped with the roller or knife is configured to increase the height of the gap after the donor substrate is coated with the material and before translating the donor substrate from the coating zone to the printing zone; The system of claim 1 .

4. 10. The system of claim 1, further comprising a dispensing system for dispensing the materials onto the donor substrate, the dispensing system configured to dispense two materials onto the donor substrate in a controlled sequence.

5. 5. The system of claim 4, wherein the dispensing system is disposed within a sealed cell with a controlled environment to extend the pot life of the material.

6. The system of claim 1 , wherein the material comprises (i) a polymeric material, or (ii) a mixture of the polymeric material and a monomeric material.

7. The system of claim 1 , wherein the material is a metal paste, a solder paste, or a ceramic paste.

8. The system of claim 1 , wherein the material is a high viscosity material, a low viscosity material, a wax material, a heat sensitive material, or a light sensitive material.

9. The system of claim 1 , wherein the material is curable by ultraviolet (UV) light or heat.

10. 10. The system of claim 1, wherein the donor substrate comprises a transparent film substrate that is translated using a roller, the transparent film substrate including (i) a metal layer, or (ii) the metal layer and a dielectric layer.

11. 10. The system of claim 1, further comprising one or more of: (i) an ultraviolet (UV) light source configured to cure the deposited material using UV light; or (ii) a heater configured to cure the deposited material using heat.

12. The system of claim 1 , further comprising one or more cameras configured to inspect a surface of the sample.

13. 10. The system of claim 1, further comprising a drying unit and a suction unit, the drying unit configured to dry the deposited material, and the suction unit removing heated air generated by the drying unit.

14. 10. The system of claim 1, further comprising a suction unit, wherein the laser is further configured to ablate the deposited material to increase resolution of the deposited material, and wherein the suction unit is used to remove debris caused by the ablation of the deposited material.

15. 13. The system of claim 1, further comprising a suction unit, wherein the laser is further configured to sinter the deposited material to increase electrical conductivity of the deposited material, and wherein the suction unit is used to remove debris caused by the sintering of the deposited material.

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