US-12621936-B2 - Conductive traces

US12621936B2US 12621936 B2US12621936 B2US 12621936B2US-12621936-B2

Abstract

The present disclosure relates to a conductive trace precursor composition comprising a metal salt; 3 to 15 weight % of a reducing solvent selected from a lactam and/or a polyol, and water. Where the reducing solvent is 2-pyrrolidinone, the 2-pyrrolidinone is not present in an amount of 5 weight % or in an amount of 7.5 weight % of the conductive trace precursor composition.

Inventors

Elizabeth Ann GALATI
John Samuel Dilip Jangam
Thomas Craig Anthony
Aja Pariante HARTMAN
Kristopher J. Erickson

Assignees

PERIDOT PRINT LLC

Dates

Publication Date: 20260505
Application Date: 20201201

Claims (10)

1 . A conductive trace precursor composition, consisting of: copper nitrate; water; at least one surfactant present in an amount ranging from about 0.5 weight % to about 3 weight % of a total weight of the conductive trace precursor composition, the at least one surfactant including a non-ionic fluorinated surfactant; and a reducing solvent to reduce the copper nitrate to elemental copper in response to heat, wherein the reducing solvent is 2-pyrrolidone and is present in an amount ranging from 7.5 weight % to 7.75 weight % of the total weight of the conductive trace precursor composition.
2 . The conductive trace precursor composition as defined in claim 1 , wherein the copper nitrate is present in an amount ranging from about 5 weight % to about 70 weight % of the total weight of the conductive trace precursor composition.
3 . The conductive trace precursor composition as defined in claim 1 , wherein the copper nitrate is copper (II) nitrate and is present in an amount ranging from about 35 weight % to about 40 weight % of the total weight of the conductive trace precursor composition.
4 . A method of printing a conductive trace onto a substrate, the method comprising: applying the conductive trace precursor composition of claim 1 to a print substrate; and heating the conductive trace precursor composition to reduce the copper nitrate to the elemental copper.
5 . The method as defined in claim 4 , wherein the conductive trace precursor composition is heated to at least 125 degrees C. to reduce the copper nitrate to the elemental copper.
6 . A method of 3D printing a 3D printed object having a conductive trace, the method comprising: selectively applying a fusing agent to a powder bed material, wherein the fusing agent comprises a radiation absorber and a liquid carrier; selectively applying the conductive trace precursor composition of claim 1 to the powder bed material; reducing the copper nitrate to the elemental copper; and irradiating the selectively applied fusing agent to generate thermal energy to coalesce the powder bed material to form a layer of the 3D printed object.
7 . The method as defined in claim 6 , wherein the reducing of the copper nitrate occurs in the presence of the 2-pyrrolidinone.
8 . The method as defined in claim 6 , wherein the thermal energy generated during the irradiating facilitates the reducing of the copper nitrate to the elemental copper.
9 . A 3D printed object including a conductive trace, the 3D printed object obtained by the method of claim 6 .
10 . A conductive trace precursor composition, consisting of: from about 35 wt % to about 40 wt % of copper nitrate, based on a total weight of the conductive trace precursor composition; from 7.5 wt % to 7.75 wt % of a reducing solvent, based on the total weight of the conductive trace precursor composition, to reduce the copper nitrate to elemental copper in response to heat, wherein the reducing solvent is 2-pyrrolidinone; and a balance of water.

Description

BACKGROUND When manufacturing printed electronics, conductive traces may be printed onto substrates using conductive ink compositions. A conductive ink composition may comprise metal nanoparticles, such as copper nanoparticles, dispersed in a liquid carrier. Once printed, the nanoparticles are deposited on the substrate and these may be sintered at high temperature and pressure to form the conductive trace. Three-dimensional (3D) printing is an additive printing process used to make three-dimensional objects from a digital model. Some 3D printing techniques may be considered additive processes because they involve the application of successive layers of material BRIEF DESCRIPTION OF THE DRAWING Features of examples of the present disclosure will become apparent by reference to the following detailed description and drawings. FIG. 1 shows the exotherm detected with compositions I and II by differential scanning calorimetry (DSC) in Example 1; and FIG. 2 shows the X-ray diffraction patterns of compositions I and II of Example 2 before and after reduction of the copper (II) salt. DETAILED DESCRIPTION The present disclosure relates to a method of 3D printing a 3D printed object having a conductive trace. The method comprises selectively applying a fusing agent and a conductive trace precursor composition to a powder bed material. The fusing agent comprises a radiation absorber and a liquid carrier, and the conductive trace precursor composition comprises a metal salt and a liquid carrier. The method comprises reducing the metal salt; and irradiating the selectively applied fusing agent to generate thermal energy to coalesce the powder bed material to form a layer of the 3D printed object. The present disclosure also relates to a 3D printed object having a conductive trace. The object is obtainable by the method above. In the present disclosure, a conductive trace precursor composition comprising a metal salt is selectively applied to powder bed material during the 3D printing process. A fusing agent comprising a radiation absorber may also be applied to the powder bed material. When the applied fusing agent is irradiated with electromagnetic energy, thermal energy is generated to coalesce the powder bed material to form a layer of the 3D printed object. The heat generated can also facilitate the reduction of the metal salt to metal, leading to the formation of the conductive trace during the course of 3D printing. This can allow conductive traces to be printed within the internal structure of the 3D printed object, and reduce or eliminate the requirement for post-printing treatments to reduce or sinter the metal. It may be possible to reduce the metal salt by applying a reducing agent to the applied conductive trace precursor composition. Alternatively, it may be possible to include a reducing agent in the conductive trace precursor composition. Suitable reducing agents include polyols and lactams. Such compounds can react with the metal salt at elevated temperatures. Accordingly, once printed, conductive trace composition may be heated to facilitate the reduction of the metal salt by the reducing agent. The present disclosure relates to a conductive trace precursor composition comprising a metal salt; 3 to 15 weight % of a reducing solvent selected from a lactam and/or a polyol, and water. Where the reducing solvent is 2-pyrrolidinone, the 2-pyrrolidinone is not present in an amount of 5 weight % or in an amount of 7.5 weight % of the conductive trace precursor composition. The present disclosure also relates to a method of printing a conductive trace onto a substrate. The method comprises applying a conductive trace precursor composition to a print substrate. The conductive trace precursor composition comprises a metal salt, water and 3 to 15 weight % of a reducing solvent selected from a lactam and/or a polyol. The method also comprises heating the conductive trace precursor to reduce the metal salt to metal. In some examples, the metal salt may be a transition metal salt, for instance, a copper salt. Any suitable metal salt may be employed. For example, the salt may be an inorganic or organic salt. The salt may comprise at least one anion selected from the group consisting of hydroxide, carbonate, sulfate, nitrate, acetate, formate, borate, chloride, bromide, and combinations thereof. In one example, the salt is copper nitrate. The salt may be a hydrated metal salt. For example, the salt may be hydrated copper nitrate. The reducing solvent may also act as a humectant. Where the reducing solvent is a lactam, examples of suitable lactams include lactams and polylactams, for instance, 2-pyrrolidinone, 1-(2-hydroxyethyl)-2-pyrrolidone and polyvinylpyrrolidone. Where the reducing solvent is a polyol, examples of suitable polyols include diols and triols. Examples include ethylene glycol, propylene glycol, glycerol, glycerol ethoxylate, ethylhydroxypropanediol, 1,2-butanediol, diethylene glycol and dipropylene gl