Microreactor-assisted printing of conductive traces with in-situ reactive inks

Patent metadata

Field	Value
Publication number	US-2016302305-A1
Application number	US-201615093551-A
Country	US
Kind code	A1
Filing date	Apr 7, 2016
Priority date	Apr 7, 2015
Publication date	Oct 13, 2016
Grant date	—

Abstract

Highly conductive silver may be fabricated at room temperature using in-situ reactive silver precursor inks by microreactor-assisted printing without any post-processing. Reactive silver nanoinks, synthesized in-situ from the microreactor, may be directly delivered onto glass and polymeric substrates without any surface treatment to form a highly dense and uniform silver feature. The distribution of the reactive silver nanoinks can be controlled by adjusting the flow rate of the continuous flow. Silver lines may be fabricated using the in-situ reactive precursors delivered via a micro-channel applicator.

First claim

What is claimed is:

1 . A method of printing a conductive trace on a substrate, the method comprising:
transporting a first liquid comprising a first reagent through a first conduit; transporting a second liquid comprising second reagent through a second conduit, wherein one or more of the first and second liquids comprise a metal species; generating a metallic precursor liquid comprising metal nanocrystals by reacting a solution of the first and second liquids as the solution is transported from a union of the first and second conduits through a reaction chamber toward a surface of a substrate; and depositing the metal nanocrystals onto the surface of the substrate by transporting the metallic precursor liquid through a third conduit defining the surface of the substrate over which the conductive trace is to be disposed.

2 . The method of claim 1 , wherein:
the third conduit comprises a microchannel having a lateral width less than 100 μm defined by a molding plate face mated to the substrate surface; and the method further comprises separating the molding plate face from the substrate surface after depositing the metal nanocrystals.

3 . The method of claim 1 , wherein the metal species comprises at least one of Au, Cu, Co, Cr, Ni, Pt, Pd, Rh, CoNiP, CoWP, CoReP, CoMnP, CoNiZnP, CoB, CoFeB, NiFeP, NiMoP, NiWP, or NiZnP.

4 . The method of claim 1 , wherein:
the first reagent comprises a metal compound soluble in a basic aqueous solution; and the second reagent comprises a reductant of the metal species.

5 . The method of claim 4 , wherein:
the first reagent comprises silver nitrate (AgNO3); the first liquid comprises aqueous ammonium hydroxide and [Ag(NH 3 ) 2 ] + complexes; the second reagent comprises formaldehyde (HCHO); and the second liquid comprises aqueous HCHO.

6 . The method of claim 1 , further comprising:
controlling a sum of a first flow rate of the first liquid through the first conduit and a second flow rate of the second liquid through the second conduit to provide a predetermined residence time within the reaction chamber; and controlling the first flow rate relative to the second flow rate to control the composition of the solution of the first and second liquids within the reaction chamber.

7 . The method of claim 6 , wherein the reaction of the first and second liquids occurs at no more than 40° C.

8 . A metallized product, comprising:
a substrate; and a silver trace having a lateral dimension less than 500 μm and a thickness from the substrate surface of less than 150 nm disposed over the substrate, wherein: the silver trace further comprises silver nanocrystals having an average diameter less than 10 nm.

9 . The metallized product of claim 8 , wherein the silver trace is one of a plurality of intersecting traces forming a 2D grid over the substrate surface.

10 . The metallized product of claim 8 , wherein the silver trace is carbon-free.

11 . The metallized product of claim 10 , wherein:
the silver trace has a current carrying cross-sectional area no more than 50 μm 2 ; and the silver trace has a conductivity of at least 3×10 7 S/m.

12 . The metallized product of claim 10 , wherein:
the silver trace has a lateral dimension of approximately 300 μm and a thickness from the substrate surface of less than 150 nm.

13 . The metallized product of claim 11 , wherein the silver trace has a lateral dimension of less than 10 μm and a thickness from the substrate surface of more than 1 μm.

14 . The metallized product of claim 11 , wherein diameters of the silver nanocrystals are between 2 and 10 nm.

15 . The metallized product of claim 14 , wherein a top surface of the silver trace has an average surface roughness no more than 14 nm.

16 . The metallized product of claim 14 , wherein the silver trace has FCC texture.

17 . The metallized product of claim 11 , wherein the substrate has a glass transition temperature below 150° C.

18 . The metallized product of claim 11 , wherein the substrate is polycarbonate.

19 . A continuous flow conductive trace printing apparatus, comprising:
a first liquid conduit; a second liquid conduit; a micromixer in fluid communication with an outlet of the first and second liquid conduits; a reaction chamber in fluid communication with an outlet of the micromixer and having dimensions sufficient to form metal nanocrystals within an aqueous solution of a first reagent supplied through the first liquid conduit and a second reagent supplied through the second liquid conduit as the aqueous solution passes through the reaction chamber; and a microchannel applicator comprising a molding plate disposed opposite a substrate, wherein at least one of the molding plate and substrate comprises a microchannel in fluid communication with an outlet of the reaction chamber, the microchannel to expose at least one surface of the substrate to the metal nanocrystals.

20 . The apparatus of claim 19 , wherein:
the microchannel applicator further comprises a flow cell including a fluid inlet in fluid communication with the outlet of the reaction chamber and in fluid communication with an inlet of the microchannel, and a fluid outlet in fluid communication with an outlet of the microchannel; and the molding plate is disposed between the flow cell and the substrate.

21 . The apparatus of claim 19 , wherein the molding plate comprises a polymer sheet embossed with the microchannel.

22 . The apparatus of claim 21 , wherein the microchannel is one of a 2D grid of intersecting microchannels.

23 . The apparatus of claim 21 , wherein the polymer sheet comprises PMMA or PMDS.

24 . The apparatus of claim 21 , wherein the microchannel has a cross-sectional area no more than 50 μm 2 .

25 . The apparatus of claim 21 , wherein the microchannel has a lateral width less than 100 μm defined by the molding plate face mated to the substrate surface.

26 . The apparatus of claim 19 , further comprising one or more microprocessor controlled dispensing pumps coupled to the first and second fluid conduits and operable to:
control a sum of a first flow rate of the first liquid through the first conduit and a second flow rate of the second liquid through the second conduit to provide a predetermined residence time within the reaction chamber sufficient to form the metal nanocrystals in the aqueous solution prior to entering the microchannel; and control the first flow rate relative to the second flow rate to control the composition of the aqueous solution within the reaction chamber.

27 . The apparatus of claim 26 , wherein the reaction chamber has a length of 10-100 cm and the sum of the first and second flow rates is controlled to provide a volumetric flow rate of approximately 0.4 mL min −1 to an inlet of the microchannel applicator.

28 . The apparatus of claim 19 , further comprising
a first vessel of containing the first reagent and in fluid communication with an inlet of the first conduit; a second vessel containing the second reagent and in fluid communication with an inlet of the second conduit, wherein one or more of the first and second reagents comprise a metal species.

29 . The apparatus of claim 28 , wherein the metal species comprises at least one of Au, Cu, Co, Cr, Ni, Pt, Pd, Rh, CoNiP, CoWP, CoReP, CoMnP, CoNiZnP, CoB, CoF

Assignees

• Univ Oregon State

Inventors

• Chang Chih-Hung
• Choi Chang-Ho

Classifications

• H10F77/935

  for photovoltaic devices or modules · CPC title

• H10F77/211

  for photovoltaic cells · CPC title

• H05K3/0085

  Apparatus for treatments of printed circuits with liquids not provided for in groups H05K3/02 - H05K3/46; conveyors and holding means therefor (apparatus specially adapted for manufacturing assemblages of electric components, e.g. printed circuit boards, H05K13/00) · CPC title

• H05K2201/0257

  Nanoparticles · CPC title

• H05K3/12

  using {thick film techniques, e.g.} printing techniques to apply the conductive material {or similar techniques for applying conductive paste or ink patterns} · CPC title