Ionic liquids for production of metal articles

Abstract

Disclosed are methods for producing articles, articles produced by such methods, and systems for producing such articles.

Description

IONIC LIQUIDS FOR PRODUCTION OF METAL ARTICLESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 631,424, filed April 8, 2024, the entire contents of which are incorporated herein by reference.GOVERNMENT SUPPORT

[0002] This invention was made with government support under DE-AC07- 05ID14517, awarded by the United States Department of Energy. The government has certain rights in the invention.TECHNICAL FIELD

[0003] The present disclosure pertains to synthetic processes for forming articles.BACKGROUND

[0004] A major drawback of particle-based photopolymer additive manufacturing is poor selectivity deposition and of course the simultaneous shrinkage rate variability found in low-temperature or high-temperature cofired ceramic (LTCC or HTCC) parts.SUMMARY

[0005] Provided herein are methods for producing articles, including multi-material articles, articles produced by such methods, and systems for producing such articles.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1A is a top perspective view of an electrical connector constructed in accordance with one example.

[0007] FIG. IB is a bottom perspective view of the electrical connector of FIG. 1A.DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0008] The presently disclosed inventive subject matter may be understood more readily by reference to the following detailed description taken in connection with the accompanying figures and examples, which form a part of this disclosure. It is to beunderstood that these inventions are not limited to the specific products, methods, conditions or parameters described and / or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed inventions.

[0009] The entire disclosures of each patent, patent application, and publication cited or described in this document are hereby incorporated herein by reference. U.S. Patent No. 9,034,568 is attached hereto as Appendix A and therefore represents part of the present disclosure. U.S. Patent No. 10,162,264 is attached hereto as Appendix B and therefore represents part of the present disclosure. U.S. Pub. No. 2021 / 01229364 is attached hereto as Appendix C and therefore represents part of the present disclosure. U.S. Pub. No. 2023 / 0139931 is attached hereto as Appendix D and therefore represents part of the present disclosure.

[0010] As employed above and throughout the disclosure, the following terms and abbreviations, unless otherwise indicated, shall be understood to have the following meanings.

[0011] In the present disclosure the singular forms “a,” “an,” and “the” include the plural reference, and reference to a particular numerical value includes at least that particular value, unless the context clearly indicates otherwise. Thus, for example, a reference to “an anchor” is a reference to one or more of such anchors and equivalents thereof known to those skilled in the art, and so forth. Furthermore, when indicating that a certain element “may be” X, Y, or Z, it is not intended by such usage to exclude in all instances other choices for the element.

[0012] When values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. As used herein, “about X” (where X is a numerical value) preferably refers to ±10% of the recited value, inclusive. For example, the phrase “about 8” preferably refers to a value of 7.2 to 8.8, inclusive; as another example, the phrase “about 8%” preferably refers to a value of 7.2% to 8.8%, inclusive. Where present, all ranges are inclusive and combinable. For example, when a range of “1 to 5” is recited, the recited range should be construed as optionally including ranges “1 to 4”, “1 to 3”, “1-2”, “1-2 & 4-5”, “1-3 & 5”, and the like. In addition, when a list of alternatives is positively provided, such a listing can also include embodiments where any of the alternatives may be excluded. For example, when a range of “1 to 5” is described, sucha description can support situations whereby any of 1, 2, 3, 4, or 5 are excluded; thus, a recitation of “1 to 5” may support “1 and 3-5, but not 2”, or simply “wherein 2 is notincluded.” The phrase “at least about x” is intended to embrace both “about x” and “at least x”.

[0013] In situ, solution-based synthesis routes for metals, alloys, and ceramics have been effectively non-existent through non-particulate means. As noted, a major drawback of particle-based photopolymer additive manufacturing is poor selectivity deposition and of course the simultaneous shrinkage rate variability found in low-temperature or high- temperature cofired ceramic (LTCC or HTCC) parts. Indeed, fabrication of certain parts, including electrical components, has been a challenge. For example, metal lining of vias through a glass or silicon wafer can be difficult to accomplish. To satisfy such ongoing needs, the present inventors have developed solution-based synthetic methods and systems for the production of metal articles. The inventive methods and systems are compatible with all three-dimensional printing techniques, including layer-by-layer, volumetric, two-photon, and stereolithography (SLA) printing.

[0014] Accordingly, provided are methods for making an article comprising exposing to stimulation an ionic liquid comprising solvated metal ions, wherein the stimulation is effective to induce formation of solid conductive material from the metal ions, thereby forming the article comprising the solid conductive material.

[0015] In certain embodiments of the present methods, the stimulation includes one or both of light or heat. For example, the stimulation can include ultraviolet light. In other embodiments, the stimulation includes application of an electrical current. In certain embodiments, the first stimulation includes heat, and the heat is induced by microwave or induction.

[0016] The ionic liquid may be housed in a container during the present synthetic process, and the orientation of the container (e.g., relative to the source of the stimulation) may be kept constant, or the orientation of the container may be changed relative to the source of the stimulation. Changing the orientation of the container relative to a source of stimulation can include rotating the container, moving the container up or down relative to the source of stimulation, moving the container in side-to-side fashion relative to the source of stimulation, or any combination the thereof.

[0017] In some embodiments, the ionic liquid represents a solvent for the solvated metal ions.

[0018] The ionic liquid may comprise metal ions that are complexed with a photoinitiator that induces nucleation and growth of solid metal from the metal ions when the ionic liquid is exposed to the further stimulation.

[0019] The ionic liquid may comprise a single metal ion, or two or more different metal ions, and nucleation and growth of solid metal from the metal ions when the ionic liquid is exposed to the stimulation produces a solid metal representing a single metal, or representing an alloy of two or more different metal alloys are present. For example, the ionic liquid may comprise one or more of ions of silver, aluminum, iron, copper, gold, platinum, palladium, tantalum, lithium, zinc, silver, nickel, tungsten, rhenium, cadmium, molybdenum, titanium, or other metals, such as those that may be used in metal parts, such as electrical components. The respective metal ions may be present in the ionic liquid in a concentration of about 50 mM or greater, such as about 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 325, 350, 375, 400, 425, 450, 475, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000 mM or greater.

[0020] In some embodiments, during the course of exposing the ionic liquid to stimulation that is sufficient to convert the moieties within the ionic liquid to solid material, the ionic liquid (which is typically housed within a container during the process) can be monitored in order confirm that the respective concentrations of the moieties within the ionic liquid (the metal ions) are sufficiently high for the synthetic process to be carried out. As needed, any one of the moieties having a concentration approaching the minimal amount required for the process (e.g., 300 mM for silver ions) can be replenished within the ionic liquid using methodologies that can readily be appreciated among those skilled in the art.

[0021] In certain embodiments of the present methods in which the ionic liquid comprises solvated metal ions, following exposure of the ionic liquid to stimulation in order to induce formation of conductive material from the metal ions, the conductive material may be exposed to inductive heating in order to pulse a current through the conductive material.

[0022] As noted, the present methods may involve the techniques and equipment for any type of three-dimensional printing, including layer by layer, volumetric, two photon, or stereolithography (SLA) printing.

[0023] The present methods may be used to produce any type of article that includes elements that comprise metal.

[0024] It should be appreciated that any metal part, including any number of electrical components and / or their components, housings, or the like can be fabricated using the methods described herein. For instance, referring to Figs. 1A-1B, an electrical connector 22 can be made with any of the methods described herein. The electrical connector 22 configured to mate with a complementary electrical component, such as a second electricalconnector, and mounted to an electrical device which can be configured as a substrate or as one or more electrical cables. The substrate can be configured as a printed circuit board (PCB). PCBs may be constituted of, for example, FR-4. When the electrical connector 22 is mated with the complementary electrical component and mounted to the electrical device, the electrical connector 22 places the complementary electrical component in electrical communication with the electrical device.

[0025] The electrical connector 22 can include a dielectric or electrically insulative connector housing 30 and a plurality of electrical contacts 32 that are supported by the connector housing 30. In other examples, the connector housing 30 can be electrically conductive. The connector housing 30 defines a mating interface 34 at a front end of the connector housing 30. The connector housing 30 can define a mounting interface 36 at a rear end of the connector housing opposite the mating interface 34 along the longitudinal direction L. Further, the mating interface 34 can be aligned with the mounting interface 36 along the longitudinal direction L. The electrical contacts 32 can define respective mating ends at the mating interface 34, and mounting ends at the mounting interface 36. Thus, the electrical contacts 32 can be configured as vertical contacts whose mating ends and mounting ends are opposite each other with respect to the longitudinal direction L. The electrical connector 22 can similarly be referred to as a vertical connector. The mating ends can be configured to mate with the complementary electrical component, for instance along the longitudinal direction L, and the mounting ends can be configured to be mounted to the electrical device. In other examples, the electrical contacts 32 can be configured as right-angle contacts whose mating ends and mounting ends are oriented perpendicular to each other. The electrical connector 22 can similarly be referred to as a right-angle connector.

[0026] The electrical contacts 32 can be arranged in respective linear arrays 47. The linear arrays 47 can be oriented parallel to each other. The electrical connector 22 can include any number of linear arrays as desired. For instance, the electrical connector 22 can include two or more linear arrays 47. The electrical connector 22 can include ground shields disposed between respective adjacent ones of the linear arrays 47.

[0027] The electrical contacts 32 can include a plurality of signal contacts 48 and a plurality of electrical grounds 50 disposed between respective ones of the signal contacts 48. For instance, the adjacent ones of the signal contacts 48 that are adjacent each other along the linear array 47 can define a differential signal pair. While the signal contacts 48 and the grounds 50 can be said to extend along a linear array, it is recognized that at least a portion upto an entirety of the signal contacts and the grounds 50 can be offset with respect to each other along a lateral direction A that is perpendicular to the longitudinal direction.

[0028] The mating ends 48a of adjacent differential signal pairs along the linear array can be separated by at least one ground mating end 54a. In one example, the mating ends 48a of adjacent differential signal pairs can be separated by a plurality of ground mating ends 54a. The mounting ends 48b of adjacent differential signal pairs can be separated by at least one ground mounting end 54b. In one example, the mounting ends 48b of adjacent differential signal pairs can be separated by a plurality of ground mounting ends 54b. For instance, the mounting ends 48b of the signal contacts 48 can be separated by a pair of ground mounting ends 54b. The mounting ends 48b and the ground mounting ends 54b can be configured in any manner as desired, including but not limited to solder balls, press-fit tails, j-shaped leads. Alternatively, and as described above, the mounting ends 48b and the ground mounting ends 54b can be configured as cable mounts that attach to respective electrical conductors and electrical grounds of an electrical cable.

[0029] It is recognized that the grounds 50 can be defined by respective discrete ground contacts. Alternatively, the grounds 50 can be defined by a respective one of a plurality of ground plates. In one example the electrical connector 22 can include a plurality of leadframe assemblies 62 that are supported by the comiector housing 30. Each of the leadframe assemblies 62 can include a dielectric or electrically insulative leadframe housing 64, and a respective linear array 47 of the plurality of first electrical contacts 32. Thus, it can be said that each leadframe assembly 62 is oriented along one of the linear arrays 47 of the first electrical connector 22. The respective signal contacts 48 can be insert molded in the leadframe housing 64. Alternatively, the signal contacts 48 can be stitched into the leadframe housing 64. Further, the grounds of the respective linear array 47 can be defined by a ground plate as described above. The ground plate can include a plate body 68 that is supported by the leadframe housing 64, such that the ground mating ends 54a and the ground mounting ends 54b extend out from the plate body 68. Thus, the plate body 68, the ground mating ends 54a, and the ground mounting ends 54b can all be monolithic with each other. Respective ones of the ground plate bodies 68 can be disposed between respective adjacent linear arrays of the intermediate regions of the electrical signal contacts 48.

[0030] The ground plate can be configured to electrically shield the signal contacts 48 of the respective first linear array 47 from the signal contacts 48 of an adjacent one of the first linear arrays 47 along the lateral direction A. Thus, the ground plates can also be referred to as electrical shields. Further, it can be said that an electrical shield is disposedbetween, along the lateral direction A, adjacent ones of respective linear arrays of the electrical signal contacts 48. In one example, the ground plates can be made of any suitable metal. In another example, the ground plates can include an electrically conductive lossy material. In still another example, the ground plates can include an electrically nonconductive lossy material.

[0031] Also disclosed herein are systems for producing an article, the system comprising: an ionic liquid comprising a solvated ionic precursor; and a source of stimulation that is effective to induce formation of only a single solid material from the ionic precursor. For example, provided are systems for producing an article comprising an ionic liquid comprising solvated metal ions; and, a source of a stimulation that is effective to induce formation of solid conductive material from the metal ions.

[0032] The contents of the ionic liquid may be in accordance with any of the embodiments described supra in connection with the inventive methods.

[0033] For example, the source of the stimulation may be an objective lens that omits ultraviolet light.

[0034] The present systems may further include an inductive heating coil for delivering induction energy to the ionic liquid or a solid structure formed therefrom following stimulation, e.g., in order to pulse a current through conductive material that is formed from the metal ions following exposure to a stimulation that is effective to induce nucleation and growth of solid metal from the metal ions.

[0035] A general description of aspects of the inventive methods and systems is as follows. The ionic liquid (precursor material) should ideally contain metal precursors as solvated ions to achieve the necessary tolerances, rates of production, and simultaneity of synthesis. Ionic liquids (IL) are molten, molecular salts which are liquid at temperatures below 100 °C notably having high polarity, low vapor pressures, thermal and environmental stability, and wide-ranging inorganic and ionic compounds. While slightly different, ILs are referred to herein as including so-called deep eutectic solvents (DES) [1] as functionally identical in use and application. IL (and DES) properties stem from the IL structure having large organic cationic with smaller inorganic / organic anionic structures. With an estimated >1018[2] possible IL formulations the properties of ILs can be tailored to meet specific needs including lubricity, hydrogen bonding tunability, thermal stability, polarizability, electrical conductivity, metal loading capacity, metal binding specificity, and the ability to serve as a redox reaction medium wherein metal ions can be reduced, oxidized, selectively chelated, and selectively deposited.

[0036] Metal TSILs. For the simultaneous nucleation and growth of conductive material, UV-catalyzed (355nm and lower are targeted wavelengths) TSILs at the highest possible concentrations can be used. For example, this can correspond to equal to or greater than 300mM of silver ions. Complexed metal or metal salts produce printable solutions with sufficient concentrations can achieve the needed metal trace volumes. High concentrations of metal in ILs for electroless deposition have been demonstrated using aqueous ILs such as imidazolium

[0014] , though the ILs for use here may be anhydrous silylamide / silylamine substituted ILs or reverse ILs (RIL)

[0015] , In fact, RILs have demonstrated highly controllable electroless gold depositions

[0015] . In the case of complexed metal ions, pho to initiators react with the organic complex to allow local precipitation of the metal. Alternatively, use of a complexing species that is itself light sensitive will provide an electron to reduce the positive metal ion to the neutral metal. In situ heating of the silver traces may be necessary to achieve the maximum conductivity of pure silver, however this is not technically a sintering process. Heating can be achieved by use of induction or microwave fields, and can also provide thermal treatment to the adjacent dielectric polymer with attendant increases in mechanical and thermal stability of the polymers.

[0037] References[1] L. I. N. Tome, V. Baiao, W. Da Silva, and C. M. A. Brett, “Deep eutectic solvents for the production and application of new materials,” Appl. Mater. Today, vol. 10, pp. 30-50, Mar. 2018, doi: 10. 1016 / j.apmt.2017.11.005.[2] I. A. Berezianko and S. V. Kostjuk, “Ionic liquids in cationic polymerization: A review,” J. Mol. Liq., vol. 397, p. 124037, Mar. 2024, doi: 10. 1016 / j.molliq.2024. 124037.[3] L. Chen et al., “Applying basic research on a dialkylphosphoric acid based taskspecific ionic liquid for the solvent extraction and membrane separation of yttrium,” Sep. Purif. Technol., vol. 207, pp. 179-186, Dec. 2018, doi: 10.1016 / j.seppur.2018.06.042.[4] P. Nockemann et al., “Task-Specific Ionic Liquid for Solubilizing Metal Oxides,” J. Phys. Chem. B, vol. 110, no. 42, pp. 20978-20992, Oct. 2006, doi: 10. 102 l / jp0642995.[5] P. Nockemann et al., “Carboxyl-Functionalized Task-Specific Ionic Liquids for Solubilizing Metal Oxides,” Inorg. Chem., vol. 47, no. 21, pp. 9987-9999, Nov. 2008, doi: 10.1021 / ic801213z.[6] G. Durga, P. Kalra, V. Kumar Verma, K. Wangdi, and A. Mishra, “Ionic liquids: From a solvent for polymeric reactions to the monomers for poly(ionic liquids),” J. Mol. Liq., vol. 335, p. 116540, Aug. 2021, doi: 10.1016 / j.molliq.2021.116540.[7] J. Lemus, A. Eguizabal, and M. P. Pina, “UV polymerization of room temperature ionic liquids for high temperature PEMs: Study of ionic moieties and crosslinking effects,” Int. J. Hydrog. Energy, vol. 40, no. 15, pp. 5416 5424, Apr. 2015, doi: 10.1016 / j.ijhydene.2015.01.078.[8] K. R. Hossain, P. Jiang, X. Yao, X. Yang, D. Hu, and X. Wang, “Ionic liquids for 3D printing: Fabrication, properties, applications,” J. Ion. Liq., vol. 3, no. 2, p. 100066, Dec. 2023, doi: 10. 1016 / j.jil.2023. 100066.[9] A. R. Schultz et al., “3D Printing Phosphonium Ionic Liquid Networks with Mask Projection Microstereolithography,” A CS Macro Lett., vol. 3, no. 11, pp. 1205-1209, Nov. 2014, doi: 10.1021 / mz5006316.

[0010] P. Kubisa, “Kinetics of radical polymerization in ionic liquids,” Ear. Polym. J., vol. 133, p. 109778, Jun. 2020, doi: 10.1016 / j.eurpolymj.2020.109778.

[0011] V. Strehmel, “Selection of Ionic Liquids for Free Radical Polymerization Processes,” Macromol. Symp., vol. 254, no. 1, pp. 25-33, Aug. 2007, doi: 10.1002 / masy.200750804.

[0012] S. Harrisson, S. R. Mackenzie, and D. M. Haddleton, “Unprecedented solvent- induced acceleration of free-radical propagation of methyl methacrylate in ionic liquids,” Chem Commun, no. 23, pp. 2850-2851, 2002, doi: 10.1039 / B209479G.

[0013] S. Harrisson, S. R. Mackenzie, and D. M. Haddleton, “Pulsed Laser Polymerization in an Ionic Liquid: Strong Solvent Effects on Propagation and Termination of Methyl Methacrylate,” Macromolecules, vol. 36, no. 14, pp. 5072-5075, Jul. 2003, doi: 10.1021 / ma034447e.

[0014] K. Riaz et al., “Ionic liquid based electroless silver plating bath for Printable circuit boards (PCBs) finishing,” J. Mol. Liq., vol. 394, p. 123704, Jan. 2024, doi:10.1016 / j .molliq.2023.123704.

[0015] Z. Sun, E. Hammond-Pereira, X. Zhang, D. Wu, and S. R. Saunders, “Reversible ionic liquids (RevILs) for the preparation of thermally stable SBA-15 supported gold nanoparticle catalysts,” Appl. Catal. Gen., vol. 643, p. 118725, Aug. 2022, doi: 10.1016 / j.apcata.2022.118725.

Claims

What is claimed:

1. A method for making an article comprising: exposing to stimulation an ionic liquid comprising solvated metal ions, wherein the stimulation is effective to induce formation of solid conductive material from the metal ions, thereby forming the article comprising the solid conductive material.

2. The method according to claim 1, wherein the stimulation includes an electrical current.

3. The method according to claim 1 or claim 2, wherein the stimulation includes light or heat.

4. The method according to any one of claims 1-3, wherein the stimulation includes heat, and the heat is induced by micro wave or induction.

5. The method according to any one of the preceding claims, wherein the ionic liquid represents a solvent for the solvated metal ions.

6. The method according to claim 1 , wherein the ionic liquid comprises metal ions that are complexed with a photoinitiator that induces nucleation and growth of solid metal from the metal ions when the ionic liquid is exposed to the stimulation.

7. The method according to claim 1 or claim 6, wherein the ionic liquid comprises two or more different metal ions, and nucleation and growth of solid metal from the metal ions when the ionic liquid is exposed to the further stimulation produces a solid metal representing an alloy.

8. The method according to any one of claims 1.

6. and 7, wherein the ionic liquid comprises metal ions, and following exposure of the ionic liquid to stimulation in order to induce formation of conductive material from the metal ions, the conductive material is exposed to inductive heating in order to pulse a current through the conductive material.

9. The method according to any one of the preceding claims, wherein exposing the ionic liquid to the stimulation produces the article layer by layer.

10. The method according to any one of claims 1 to 8. wherein exposing the ionic liquid to the stimulation produces the article by volumetric printing.

11. The method according to any one of claims 1 to 8. wherein exposing the ionic liquid to the stimulation produces the article by tw o photon printing.

12. The method according to any one of claims 1 to 8, wherein exposing the ionic liquid to the stimulation produces the article by stereolithography (SLA) printing.

13. The method according to any one of the preceding claims, wherein the article comprises a connector.

14. An article that is produced according to the method according to any one of claims 1 to 12.

15. A system for producing an article, the system comprising: an ionic liquid comprising solvated metal ions; and a source of stimulation that is effective to induce formation of solid conductive material from the metal ions.

16. The system according to claim 15, wherein the ionic liquid comprises metal ions that are complexed with a photoinitiator that induces nucleation and growth of solid metal from the metal ions when the ionic liquid is exposed to the stimulation.

17. The system according to claim 15 or claim 16, wherein the ionic liquid comprises two or more different metal ions, and nucleation and grow th of solid metal from the metal ions when the ionic liquid is exposed to the stimulation produces a solid metal representing an alloy.

18. The system according to any one of claims 15 to 17. further comprising an inductive heating coil.

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