Patent Application
20250145845
The present disclosure relates to convertible inks, and more specifically, to conductive convertible inks.
Convertible inks can be used to fabricate electronic structures. Examples of convertible inks include composite materials with an insulating phase after curing but which can be selectively converted to a conductive or resistive phase by methods such as a thermal treatment or laser sintering.
According to one or more embodiments, a printable ink provided. In one embodiment, the ink includes silver nanoparticles coated with a polymer. The ink can be cured at a low temperature (e.g, 100-120 C) after which the ink is not conductive. Later, application of further energy, (e.g., laser light) can decompose polymer molecules and lead to spontaneous coalescence of silver nanoparticles to create conductive pattern.
In one embodiment, a method of forming a convertible ink is disclosed. The method includes: performing a polyol process with a metal salt, a capping agent and a solvent to produce encapsulated nanospheres in a first aqueous solution; reducing the amount of capping agent in the solution. The capping agent can be reduced by: adding solvent soluble with the capping agent and agitating the mixture via centrifugation to form a supernatant and a precipitate that includes the encapsulated nanospheres; removing the supernatant; adding a second solvent to the precipitate to form a second solution; agitating the second solution to form a second supernatant and a precipitate that includes the encapsulated nanospheres; and removing the second supernatant.
In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the capping agent can be Polyvinylpyrrolidone (PVP).
In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the first reducing agent can be ethanol.
In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the second reducing agent can be acetone.
In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the solvent can be a polyol.
In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the first reducing agent can be different than the second reducing agent.
In one embodiment, a method of forming conductive traces on a substrate is disclosed. The method can include: forming a convertible ink according to any prior method; applying the convertible ink to the substrate; curing the convertible ink to form cured ink; and forming the conductive traces by exposing the cured ink to laser light.
In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the laser light can be produced by an 830 nm laser.
In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the conductive traces can be formed due to a net reduction in the capping agent in the convertible ink from exposure to the laser light.
In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the method of forming the traces can include heating the substrate, wherein the convertible ink is cured by applying it to heated substrate.
In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the convertible ink can be cured in a vacuum oven.
In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the convertible can be applied by aerosol jet printing.
Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure. For a better understanding of the disclosure with the advantages and the features, refer to the description and to the drawings.
For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts:
Convertible inks are composite materials with an insulating phase after being cured but which are selectively converted to a conductive or resistive phase by methods such as a thermal treatment or laser sintering. Convertible inks can include, for example, a composite blend of conductive particles and insulating particles/agents. A non-limiting example of a convertible ink includes polyvinylpyrrolidone (PVP) encapsulated silver nanoparticles.
As disclosed herein, a method of synthesizing an ink is disclosed. The synthesized ink will include metal nanoparticle spheres capped (e.g., surrounded) by a nonconductive, volatile capping agent. This ink can be synthesized such that it cures after a thermal treatment, into a non-conductive film. Advantageously, the synthesized ink can be effectively applied by an aerosol jet process to apply a non-conductive film of the ink onto a surface.
Application of a higher energy laser process, such as by selectively laser sintering the film using an ultraviolet or near infrared (NIR) laser, can cause the capping material to volatilize and results in the formation of a conductive trace. The laser process can be performed using any laser of any wavelength such that the output energy density is sufficient to volatilize the capping agent and initiate sintering of the conductive particles.
For example,
Exposure of the ink 102 leads to volatilization of the capping material/agent 120 which causes the localized conductive particles 122 to pack more tightly and fuse to become conductive to form traces 106 as illustrated in
It should be noted that several traces 106 can formed from the film 102 as shown in
The convertible inks can be used as printable inks that are printed as films that can be easily patterned to create conductive traces by application of localized energy (e.g. thermal energy or laser). As opposed to some prior inks, the insulating material is included as part of the synthesis as the dispersant and is mostly absent from the final conductive traces. This property is useful should the ink need to be tuned to higher conductance since any insulating material present will hinder its conductivity and raise the dielectric constant.
The conductive particles 122 in the convertible ink include conductive metal particles. Non-limiting examples of conductive metal particles include silver particles, gold particles, copper particles, or a combination thereof. In the following figures, silver will be illustrated.
In each embodiment, the conductive particles 122 are in the convertible ink in an amount of about 2 to about 6 weight % (wt. %).
In each embodiment, the average diameter of the conductive particles 122 is about 20 to about 100 nanometers (nm). The concentration of capping material should be high enough to see a homogenous dispersion without being so high that the particles are suspended far apart in the film as shown in
The insulating portion 102 in the convertible ink includes an insulating material. A non-limiting example of the material of the insulating portion 102 is a polymeric capping agent such as polyvinylpyrrolidone (PVP). As noted above, application of a laser to the film 102 removes the capping agent 120 and allows conductive particles 122 to provide a path for electrical conduction.
With reference now to
In
With reference now to
Finally, the concentrated precipitate can be redispersed in tripropylene glycol methyl ether (TGME) using an agitator such as a probe scintillator. The resultant ink can then be used to form traces.
In practice, the precipitate (e.g., TGME and precipitate mixture) can be applied to a substrate (see., e.g.,
Curing is performed by, for example, heating for a period of time. The temperature and time for curing will depend on the composition of the convertible ink. According to one or more embodiments, curing is performed by heating at a temperature of about 75 to about 150 degrees Celsius. In other embodiments, curing is performed by heating at a temperature of about 80 to about 100 degrees Celsius. The ink can be cured by an oven, a vacuum over, or by applying it to a heated substrate, for example.
It shall be understood that the final mixture will include PVP, TGME and the metal (e.g., silver). Application of the laser causes the weight percentage of PVP and TGME to start to decrease as the temperature of the film increases due to exposure to the laser as shown in
The following definitions and abbreviations are to be used for the interpretation of the claims and the specification. As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains” or “containing,” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, a mixture, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus.
Additionally, the term “exemplary” is used herein to mean “serving as an example, instance or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms “at least one” and “one or more” are understood to include any integer number greater than or equal to one, i.e. one, two, three, four, etc. The terms “a plurality” are understood to include any integer number greater than or equal to two, i.e. two, three, four, five, etc. The term “connection” can include an indirect “connection” and a direct “connection.”
References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described can include a particular feature, structure, or characteristic, but every embodiment may or may not include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
For purposes of the description hereinafter, the terms “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” and derivatives thereof shall relate to the described structures and methods, as oriented in the drawing figures. The terms “overlying,” “atop,” “on top,” “positioned on” or “positioned atop” mean that a first element, such as a first structure, is present on a second element, such as a second structure, wherein intervening elements such as an interface structure can be present between the first element and the second element. The term “direct contact” means that a first element, such as a first structure, and a second element, such as a second structure, are connected without any intermediary conducting, insulating or semiconductor layers at the interface of the two elements.
The terms “about,” “substantially,” “approximately,” and variations thereof, are intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±10%, 9%, 8%, 7%, 6%, or 5%, 4%, 3%, 2%, or 1% of a given value.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form detailed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiments were chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the various embodiments with various modifications as are suited to the particular use contemplated.
While the preferred embodiments have been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the disclosure as first described.
