Low dielectric constant and low dielectric loss dielectric compositions for aerosol jet printing

Abstract

The printable dielectric ink composition includes an inhibited catalyst polymer complex and a crosslinker, the printable dielectric ink composition having a viscosity of about 1 to about 10 cP.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 330,806, filed Apr. 14, 2022, which is hereby incorporated by reference in its entirety.

Background Art

[0002] The present disclosure relates to additive manufacturing, and more particularly, to a dielectric composition having a low dielectric constant and low dielectric loss for aerosol jet printing.

[0003] Additive manufacturing (AM) has opened new paths for the assembly and prototyping of electronic devices. In conventional manufacturing, the same equipment used to manufacture the final parts is also used to generate prototypes. However, bottlenecks occur in such methods, and even a small change in the design of a part at the prototype stage requires a long time for tool and setup reconfiguration.

[0004] In contrast, AM technology removes bottlenecks, facilitates a rapid and iterative approach to prototyping, and enables modifications to the prototype architecture to be implemented and tested in a short time. However, for AM prototyping to be effective, the materials used in manufacturing need to exhibit performance similar to that of the materials used in large - scale manufacturing processes.

[0005] Direct write is a powerful technology in the AM field and has been demonstrated to be able to quickly create prototypes of very complex electronic devices. To manufacture layered electronic devices using a direct write printer, both conductive ink and dielectric ink are required. Conductive inks have attracted much research interest and significant progress has been made in improving resolution, conductivity, and mechanical performance, but printable dielectric materials have received less attention.

Summary of the Invention

[0006] According to one or more embodiments, the printable dielectric ink composition comprises an inhibited catalyst polymer complex and a crosslinking agent, and the printable dielectric ink composition has a viscosity of about 1 to 10 cP.

[0007] According to other embodiments, a method for producing a printable dielectric ink composition includes combining a monomer and a catalyst for a certain period of time to form a monomer-catalyst complex, and initiating polymerization to form a catalyst-polymer complex. This method may optionally include adding an inhibitor to the catalyst-polymer complex to inhibit the catalyst and polymerization, thereby forming an inhibited catalyst-polymer complex. This method may also include adding a crosslinking agent to the catalyst-polymer complex to form a printable composition. This method includes printing the printable composition and optionally activating the crosslinking agent to form a crosslinked material on a substrate.

[0008] Further features and advantages are realized through the technology of this disclosure. Other embodiments and aspects of this disclosure are described in detail herein and are considered to be part of the claimed disclosure. Refer to the description and drawings for a better understanding of this disclosure, including its advantages and features. [Brief explanation of the drawing]

[0009] [Figure 1] This is a flowchart illustrating a method for manufacturing and using dielectric ink according to an embodiment. [Figure 2] This is a schematic diagram of a printing apparatus for printing dielectric ink according to an embodiment. [Figure 3] This is a schematic diagram of a printing apparatus for printing dielectric ink according to an embodiment. [Figure 4A] This graph shows the dielectric loss of dielectric ink. [Figure 4B] This is a graph showing the dielectric constant of dielectric ink. [Modes for carrying out the invention]

[0010] Commercial dielectric inks used in direct-write systems present two challenges. The first challenge relates to the performance of the dielectric material. Dielectric materials used in direct-write printers are often photopolymers, which exhibit high dielectric loss at RF and microwave frequencies. The dielectric loss in these materials is due to the large dipole properties of vinyl ether, epoxy, or acrylate functional groups. To mitigate the loss, nonpolar polymers are required. However, nonpolar polymers cannot be produced by the same strong radical or cation-based photopolymerization reactions that work so well with vinyl ether, epoxy, and acrylate. For this reason, nonpolar polymer compositions are often used as dispersions of pre-formed polymers in nonpolar solvents.

[0011] The use of dispersions of such polymers in nonpolar solvents presents a second challenge. While it is possible to produce dispersible dielectric materials based on pre-formed nonpolar polymers and associated solvents, the resulting mixtures contain a large solvent fraction to facilitate dispersibility. Consequently, during processing of solvent-based materials, the film size ultimately shrinks and releases toxic nonpolar volatile organic compounds (VOCs).

[0012] Due to the aforementioned challenges, prototyping high-frequency devices using direct-write technology results in device performance that does not match that achieved with conventional manufacturing procedures, or requires a level of complexity and control in the printing process that hinders the adoption of large-scale formats. To overcome these inefficiencies, solvent-free techniques are needed to form non-polar polymers in situ. For such techniques to be adopted in actual industrial applications, it is necessary to develop technologies with reaction mechanisms that can withstand common manufacturing conditions such as oxygen and moisture, and with a pot life that enables stable printing over long periods.

[0013] Accordingly, in several aspects, this specification describes solvent-free, low dielectric constant, low-loss reactive dielectric ink compositions specifically designed for the manufacture of aerosol jet high-frequency devices. In particular, potential organometallic ring cleavage metathesis reactions are used in combination with photo-induced thiol-ene crosslinking or increased monomer reactivity to address the aforementioned challenges of solvent-free technology. The inks can be aerosolized, printed, and rapidly cured into ultra-low polarity films as required, achieving high resolution. The viscosity of the inks can be adjusted to suit use with various dispensing devices. Furthermore, since the inks are designed for use in outdoor environments, they are suitable for adoption in large formats, and the thermomechanical and dielectric properties of the inks can be integrated into the construction of RF and microwave devices.

[0014] Figure 1 is a flow chart showing a method for manufacturing and using a dielectric ink according to an embodiment. As shown in box 102, this method involves bonding a monomer and a catalyst for a certain period of time to form a monomer-catalyst complex, initiating polymerization, and forming a catalyst-polymer complex.

[0015] The monomer has low viscosity. In one or more embodiments, the viscosity of the monomer is about 1 to about 10 centipoise (cP).

[0016] In some embodiments, the monomer comprises a distorted bicyclic carbon ring having an unsaturated bond within the ring. In other embodiments, the monomer comprises an alkene group (e.g., a primary alkene group) pendanted to the bicyclic ring. The pendanted alkene group is in the exo conformation, endo conformation, or both. A non-limiting example of the monomer is 5-vinyl-2-norbornene.

[0017] The catalyst has an affinity for the monomer and is selected based on the type of monomer and its suitability for catalyzing olefin metathesis. Non-limiting examples of catalysts include transition metal carbene complexes, such as ruthenium carbene complexes, or Grubbs catalysts, including first-generation Grubbs catalysts (I) and second-generation Grubbs catalysts (II).

[0018] [Chemical]

[0019] The catalyst forms a complex with the monomer and initiates polymerization and growth. The monomer and the catalyst are mixed and incubated for a time sufficient to grow the polymer to the desired viscosity. In one or more embodiments, this time is from about 1 hour to about 10 hours. In other embodiments, this time is from about 2 to about 8 hours, or 3 to about 6 hours.

[0020] The growth of the polymer is continued until the target viscosity and / or the desired number of monomers (n) is reached. In one or more embodiments, the number of monomers (n) in the polymer is from about 5 to about 10,000. In other embodiments, the number of monomers (n) is from about 5 to about 1,000.

[0021] In one or more embodiments, the target viscosity is from about 5 to about 2000 mPa·s. In other embodiments, the target viscosity is from about 10 to about 100 mPa·s.

[0022] As shown in Box 104, when the desired viscosity and / or the number of monomers is reached, the method can include, if necessary, adding an inhibitor to the catalyst-polymer complex to inhibit the catalyst and polymerization to form an inhibited catalyst-polymer complex. An inhibitor is a compound that binds to the catalyst and renders it inactive.

[0023] In one or more embodiments, the catalyst is a transition metal carbene complex, such as a ruthenium carbene complex or a Grubbs catalyst, and the inhibitor is a phosphite-containing compound that forms a complex with the transition metal in the catalyst to inactivate the catalyst, and is a reversible inhibitor that can be expelled (i.e., the complex formation is released) from the transition metal of the catalyst by heating. Non-limiting examples of phosphite compounds include phosphites having methyl, ethyl, and propyl substituents in any combination. For example, in one or more embodiments, the phosphite compound is trimethyl phosphite, triethyl phosphite, or tripropyl phosphite.

[0024] In some embodiments, the trialkyl phosphate inhibitor can be omitted, and thus step 104 can be omitted. In such cases, reliance can be placed on the vinyl pendant group of 5-vinyl-2-norbornene. This group slows viscosity drift by opening an alternative cross-metathesis reaction pathway that competes with ring-opening metathesis (ROMP). An example of the process is shown below.

[0025]

Chemical formula

[0026] As shown in Box 106, this method includes adding a crosslinking agent to the inhibited catalyst-polymer composite to form a printable composition. The crosslinking agent is one or more compounds that crosslink the printable composition and form a crosslinked material on the substrate when printed using an additive manufacturing device such as an aerosol jet printer.

[0027] The crosslinking agent is a composition of one or more compounds. The crosslinking agent includes at least one compound that binds to the inhibited catalyst-polymer composite and forms crosslinks within the polymer. Crosslinking increases the viscosity of the polymer and also improves the elastic modulus and thermal stability of the final cured material.

[0028] In one or more embodiments, the crosslinking agent comprises a dithiol compound. In other embodiments, the crosslinking agent comprises a dithiol compound that enables photoactivation and a photosensitizer. Non-limiting examples of dithiols include 1,2-dithiol, 1,3-dithiol, 1,4-dithiol, 1,5-dithiol, 1,6-dithiol, 1,7-dithiol, 1,8-dithiol, 1,9-dithiol, 1,10-dithiol, 1,11-dithiol, 1,12-dithiol, 1,13-dithiol, 1,14-dithiol, 1,15-dithiol, 1,16-dithiol, 1,17-dithiol, 1,18-dithiol, 1,19-dithiol, and 1,20-dithiol.

[0029] A photosensitizer is a photosensitizing compound that is excited by light of a desired wavelength. In some embodiments, the photosensitizer is excited by ultraviolet light with a wavelength of about 200 to about 400 nanometers. Non-limiting examples of photosensitizers include isopropylthioxanthone and benzophenone.

[0030] In one or more embodiments, a photosensitizer in the printing composition is excited by light, such as ultraviolet light, while it is being printed on the substrate. The excited photosensitizer extracts radicals from compounds in the crosslinking agent, forming a radical crosslinking agent that removes and bonds unsaturated bonds, such as unsaturated alkenes, in the polymer of the inhibited catalyst polymer complex.

[0031] In some embodiments, light having a wavelength of about 200 to about 400 nanometers (nm) is irradiated to activate the crosslinking agent and, optionally, the photosensitizer (if present) to induce crosslinking of the polymer. In other embodiments, the wavelength of the light is between about 200, 250, 300, 350, and 400 nm, or any range between these. In such methods, the light source irradiates the printable composition with light while the printable composition is being deposited on the surface of the substrate or after it has been deposited. Non-limiting examples of the light source include light-emitting diodes (LEDs).

[0032] In one or more embodiments, the crosslinking agent is activated by heat, and when heat is applied, the crosslinking agent induces crosslinking within the polymer. In some embodiments, heat is applied by depositing the printable composition onto a heated substrate. In some embodiments, the temperature of the heated substrate is about 60°C to about 120°C. In other embodiments, the temperature of the heated substrate is about 60°C to about 90°C. Furthermore, a secondary heat treatment at 140°C for 8 hours may be performed to improve the mechanical properties of the film.

[0033] As shown in Box 108, this method further includes printing a printable composition and activating a crosslinking agent as needed to form a crosslinked material on a substrate. Printing is performed by an additive manufacturing (AM) device or printer, such as an aerosol jet printer.

[0034] In an embodiment where a printable composition is printed using an aerosol jet printer, the printable composition is atomized or aerosolized into droplets and deposited on the surface of a substrate, as shown in Figure 2. Figure 2 is a schematic diagram of a printing apparatus for printing dielectric ink according to an embodiment. The deposition head 208 of the printing apparatus deposits the printable composition onto the surface of the substrate 202. The printable composition is cured by one or more methods that induce crosslinking in the printed composition, forming a cured layer of material 204 on the substrate 202.

[0035] The printable composition is cured, for example, by applying heat, light, or both heat and light. In the embodiment shown in Figure 2, one or more light sources 206 (e.g., LED lamps) irradiate the printable composition deposited on the substrate 202 with light. The printable composition is cured by the printed material layer 204 by heating the substrate 202 as needed.

[0036] Figure 3 is a schematic diagram of a printing apparatus for printing dielectric ink according to an embodiment. The printable composition is deposited on the surface of a heated substrate 202, and is cured by heat without exposure to light, forming a cured material layer 204.

[0037] The dielectric printable compositions described herein are formed by inactivating and then reactivating catalysts bonded to polymer chains, and provide compositions that can be cured by gentle heating, photoactivation, or a combination thereof. By employing a photoactivation crosslinking mechanism as needed and adding highly reactive monomers, the resolution of the print line is improved.

[0038] The dielectric ink composition is solvent-free or substantially solvent-free. In one or more embodiments, the dielectric ink composition contains 0% by weight of solvent. In other embodiments, the dielectric ink composition contains 10, 9, 8, 7, 6, 5, 4, 3, 2, or less than 1% by weight of solvent.

[0039] In some embodiments, the cured dielectric material has a dielectric constant of about 2.2 to about 3.0. In other embodiments, the cured dielectric material has a dielectric constant of about 2.2 to about 2.5.

[0040] In one or more embodiments, the cured dielectric material has a dielectric loss of about 0.0005 to about 0.01 between 8.2 and 12.4 GHz. In other embodiments, the cured dielectric material has a dielectric loss of about 0.001 to about 0.005 between 8.2 and 12.4 GHz. [Examples]

[0041] Various methods can be used to measure the dielectric constant and dielectric loss tangent, including the transmission / reflection line (TRL) method, the open-ended coaxial probe method, the free-space method, and the resonance method. The TRL method was selected because it combines accuracy and practicality for broadband measurements of solid materials. This method uses the Keysight X11644 WR90 waveguide calibration kit, the Keysight material measurement software suite, and the FieldFox N9918A vector network analyzer (VNA). In the TRL method, two-port S-parameter measurements are performed to extract the dielectric constant and dielectric loss tangent. The Keysight software suite allows selection of the most accurate method for converting the S-parameters to complex dielectric constant values. The Nicholson-Ross-Weir (NRW) method was selected due to its widespread use. The WR-90 waveguide characterization technique characterizes the dielectric constant and dielectric loss between 8.2 and 12.4 GHz. The inhibiting polynorbornene ink described herein was tested and compared with the commercially available dielectric ink NEA121. NEA121 is a photocurable mixture of benzophenone, 1,3,5-trialyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and pentaerythritol tetrakis(3-mercaptopropionate). Both inks were poured into aluminum trays and cured on a hot plate set to 60°C. The cured material was removed from the hot plate after 6 hours, cut into rectangular structures, and characterized.

[0042] The inhibited polynorbornene ink showed a dielectric loss of 0.00322 (Figure 4A, bottom trace) and a dielectric constant of 2.31 at 10 GHz (Figure 4B, bottom trace). The commercially available ink NEA121 showed a dielectric loss of 0.0221 (Figure 4A, top trace) and a dielectric constant of 2.95 at 10 GHz (Figure 5B, top trace).

[0043] All means or step-plus-function elements in the following claims are intended to include any structures, materials, or actions for performing a function in combination with other specifically claimed elements. While the descriptions in this disclosure have been presented for illustrative and explanatory purposes, they are not intended to be exhaustive or to limit the disclosure in a detailed form. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of this disclosure. The selection and description of embodiments have been made to best illustrate the principles and practical applications of this disclosure and to enable other those skilled in the art to understand the various embodiments, along with various modifications suitable for specific intended uses.

[0044] While preferred embodiments have been described, those skilled in the art should understand that various improvements and enhancements within the scope of the following claims are possible both now and in the future. These claims should be interpreted as maintaining appropriate protection over the disclosure described initially.

Claims

1. A method for manufacturing a printable dielectric ink composition, The process involves bonding a monomer and a catalyst for a certain period of time to form a monomer-catalyst complex, then initiating polymerization to form a catalyst-polymer complex, and An inhibitor is added to the catalyst-polymer composite to inhibit the catalyst and polymerization, thereby forming an inhibited catalyst-polymer composite. A crosslinking agent is added to the catalyst-polymer composite to form a printable composition, A method comprising printing the printable composition and, if necessary, activating the crosslinking agent to form a crosslinked material on a substrate.

2. The method further includes adding an inhibitor to the catalyst-polymer composite to inhibit the catalyst and polymerization, thereby forming an inhibited catalyst-polymer composite. The method according to claim 1, wherein the crosslinking agent is added to the inhibited catalyst-polymer composite.

3. The method according to claim 1, wherein the crosslinking agent is activated by light having a wavelength of 200 to 400 nanometers (nm).

4. The method according to claim 3, wherein activation is performed by a photosensitizer to induce crosslinking in the polymer.

5. The method according to claim 3, wherein the light is irradiated by a light source during or after deposition on the surface of the substrate.

6. The method according to claim 5, wherein the light source includes a light-emitting diode (LED).

7. The method according to claim 1, wherein the crosslinking agent is activated by heat, and after the addition of heat, the crosslinking agent induces crosslinking within the polymer.

8. The method according to claim 7, wherein heat is applied by depositing the printable composition onto a heated substrate.

9. The method according to claim 8, wherein the temperature of the heated substrate is 60°C to 120°C.

10. The method according to claim 9, further comprising performing a secondary heat treatment.

11. The method according to claim 10, wherein the secondary heat treatment is performed at 140°C.

12. The method according to claim 11, wherein the secondary heat treatment is performed for 8 hours.

13. A printable dielectric ink composition, A catalyst-polymer composite in which the catalyst and polymerization are inhibited by an inhibitor, Contains a crosslinking agent, An ink composition wherein the viscosity of the printable dielectric ink composition is about 5 to about 2000 mPa·s.

14. The ink composition according to claim 13, wherein the catalyst-polymer composite comprises a monomer polymerized in combination with the catalyst.

15. The ink composition according to claim 14, wherein the viscosity of the monomer before it is polymerized by bonding with the catalyst is about 1 to about 10 centipoise (cP).

16. The ink composition according to claim 14, wherein the monomer comprises a distorted bicyclic carbon ring having an unsaturated bond within the ring.

17. The ink composition according to claim 14, wherein the monomer comprises an alkene group.

18. The ink composition according to claim 17, wherein the monomer comprises 5-vinyl-2-norbornene.

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