|United States Patent Application||20080286488|
|Li; Yunjun ; et al.||November 20, 2008|
Forming a conductive film comprising depositing a non-conductive film on a surface of a substrate, wherein the film contains a plurality of copper nanoparticles and exposing at least a portion of the film to light to make the exposed portion conductive. Exposing of the film to light photosinters or fuses the copper nanoparticles.
|Inventors:||Li; Yunjun; (Austin, TX) ; Roundhill; David Max; (Austin, TX) ; Yang; Mohshi; (Austin, TX) ; Pavlovsky; Igor; (Cedar Park, TX) ; Fink; Richard Lee; (Austin, TX) ; Yaniv; Zvi; (Austin, TX)|
|Correspondence Name and Address:|| |
FISH & RICHARDSON P.C.
|Assignee Name and Adress:|| Nano-Proprietary, Inc. |
|Filed:||May 15, 2008|
|U.S. Current Class:||427/541; 427/554; 427/555; 427/557; 427/559|
|U.S. Class at Publication:||427/541; 427/557; 427/559; 427/554; 427/555|
|Intern'l Class:||B05D 3/00 20060101 B05D003/00; B05D 3/06 20060101 B05D003/06|
1. A method of forming a conductive film comprising: depositing a film containing a plurality of copper nanoparticles on a surface of a substrate; and exposing at least a portion of the film to light to make the exposed portion conductive.
2. The method of claim 1, wherein the exposing at least a portion of the film to light causes at least a portion of the copper nanoparticles to fuse together.
3. The method of claim 1, wherein the exposing at least a portion of the film photosinters at least a portion of the copper nanoparticles.
4. The method of claim 3, wherein the photosintering of copper nanoparticles comprises a first transformation of CuO and Cu.sub.2O to Cu.sub.2O and a second transformation of the Cu.sub.2O to Cu.
5. The method of claim 4, wherein during the photosintering process, the copper oxide migrates away from an area where the nanoparticles are fusing.
6. The method of claim 1, wherein exposing at least a portion of the film comprises directing a laser at the film.
7. The method of claim 1, wherein exposing at least a portion of the film comprises exposing the film to a flash lamp.
8. The method of claim 1, wherein exposing at least a portion of the film comprises exposing the film to a focused beam of light.
9. The method of claim 1, wherein the intensity of the light and a time of exposure is sufficient to make the exposed portion conductive.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit under 35 U.S.C. .sctn.119(e) of U.S. provisional application 60/938,975, filed on May 18, 2007, which is incorporated by reference herein in its entirety.
The present disclosure is directed towards metallic ink such as copper. Metal conductors on printed circuit boards (PCB) and flex tape connectors are generally copper (Cu) lines that are either laminated onto the PCBs or are deposited by electroplating techniques. Patterning the copper material to form conducting lines, wire and connecting leads between components requires photolithography and acid etching of blanket copper films. Alternatively, such methods can be used to define copper line patterns during the plating process. In either case, the chemicals used to etch the copper and the resultant chemical waste generated from the processes add significant cost to the products that are made. The cost is further increased due to the time and labor necessary for the etching and photopatterning process steps.
An alternative technique to lamination and electroplating for forming metal conductors on PCB includes printing the metal lines. Silver metal based inks and pastes exist for inkjet printing, screen printing and other printing techniques. Although silver is highly conductive and can be processed at low temperatures, it is an expensive metal, making it cost prohibitive for many applications.
In contrast to silver, copper metal is a standard in the electronics industry and is about one tenth the cost. Accordingly, copper is a suitable alternative to silver for use in applications such as electronic interconnects, radio-frequency ID tags and display manufacturing process, among others.