Patent Application
20090246357
1. Technical Field
The present invention relates generally to methods of manufacturing printed circuit boards and, particularly, to a method of forming circuits to make a circuit board.
2. Description of Related Art
A popular method for forming circuits on a circuit board uses ink jet printing. Ink jet printing is a non-impact dot-matrix printing technology in which droplets of ink are fired from a small aperture directly to a specified position on a medium to create an image.
A conventional ink jet printing method for manufacturing a circuit is disclosed. In the ink jet printing method, a nano-particle ink is fired by an ink jet printer onto a surface of an insulating substrate to form a circuit pattern. Generally, the nano-particle ink is comprised of nano-scale metal particles. However, in the ink jet printing process, the nano-particle ink directly expose in air and the nano-scale metal particles easily oxidize in air, thereby losing their electrical conductivity. Therefore, the nano-scale metal particles are not suitable for use in the nano-ink used to print circuits.
What is needed, therefore, is a method of printing a circuit to make a circuit board which can overcome the above-described problems.
An exemplary embodiment of a method of forming a circuit on a circuit board includes the steps of: forming a first circuit pattern made of a nano-scale metal oxide material on a surface of an insulating substrate; reducing the nano-scale metal oxide material into a nano-scale deoxidized metal material, thus obtaining a second circuit pattern; and forming an electrically conductive metal layer on the second circuit pattern.
Advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
Many aspects of the present embodiment can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiment. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
An embodiment will now be described in detail below and with reference to the drawings.
Referring to
In a general first step, referring to
In a general second step, a first circuit pattern 200 is formed on a surface 110 of the insulating substrate 100, as shown in
The first circuit pattern 200 is formed on the surface 110 using an ink jet printing method. In an ink jet printing process, an ink jet printer is used to form the first circuit pattern 200 using an ink that includes nano-scale metal oxide material. In the process of forming the first circuit pattern 200, a nozzle of the ink jet printer is disposed close to the surface 110, and the ink is fired onto the surface 110 in the desired pattern, i.e., the first circuit pattern 200. The nano-scale metal oxide contained in the ink can be nano-scale aluminum oxide, nano-scale zinc oxide, nano-scale iron oxide, nano-scale magnesium oxide or nano-scale copper oxide. In the present embodiment, the nano-scale metal oxide contained in the ink is nano-scale copper oxide. Compared with the nano-scale metal particles, particles of the nano-scale metal oxide have an excellent dispersive ability, which can prevent aggregation of the nano-scale metal particles. Therefore, the particles of the nano-scale metal oxide are uniformly dispersed and the first circuit pattern 200 with uniform thickness and width is achieved.
The nano-scale metal oxide particles can be prepared using a sol-gel method, a hydrolysis method, a hydrothermal method, a micro-emulsion method, a precipitation method, a solid-phase reaction method, an electrolytic synthesis method or a plasma method. The ink is prepared by dispersing the nano-scale metal oxide material into an organic solvent or a water-soluble medium. In order to improve strength of the adhesive bond between the first circuit pattern 200 and the surface 110, a surface-active agent, dispersant, binder material or macromolecule polymer can be added to the ink to adjust viscosity, surface tension, and stability of the ink. The organic solvent can be a hydrocarbon having eight to twenty-two carbon atoms or aromatic hydrocarbon. The water-soluble medium can be distilled water, a water-soluble organic compound, or mixture of the distilled water and the water-soluble organic compound. The dispersant is resin polymer. The surface-active agent can be a fatty acid ester or a fatty amine. The binder material can be a polyurethane, a polyvinyl alcohol.
In a general third step, the nano-scale copper oxide particles in the first circuit pattern 200 are reduced into nano-scale copper particles, thus the first circuit pattern 200 is converted or transformed into a second circuit pattern 300 comprised only of nano-scale copper particles, as shown in
Alternatively, if liquid reducing agent, the reducing solution can be chosen from the group comprising sodium borohydride, potassium borohydride, or dimethyl amino borane. It is understood that any reducing agent capable of reducing the chosen metal oxide can be selected. In addition, the reductive reaction parameters such as temperature, pressure can also be predetermined according to the nano-scale metal oxide particles selected.
Alternatively, the first circuit pattern 200 is made of a nano-scale oxide of a first metal. Then, the nano-scale oxide of the first metal is converted or transformed in to a nano-scale oxide of a second metal through a replacement reaction process, and therefore obtaining an intermediate circuit pattern made of the nano-scale oxide of the second metal. Finally, the intermediate circuit pattern is reduced into the second circuit pattern 300 comprised of a nano-scale deoxidized second metal (i.e., nano-scale nano-oxide metal) through a reducing reaction process.
For example, a molecular formula of the nano-scale metal oxide contained in the first circuit pattern 200 is represented by MxOy, the desired second circuit pattern 300 should be made of copper, and the metal M is not copper. The MxOy is combined with a solution to produce a copper oxide through a replacement reaction. In the replacement reaction, a soluble copper salt solution is applied to react with the MxOy. As a result, the metal M of the MxOy is transformed to metal M ion to remain suspended in the solution, and the copper ion in the copper salt solution is oxidized to copper oxide (CuO) and forms the second circuit pattern 200. A reaction equation is expressed as: MxOy+yCu2+=xM2y/x+yCuO. The copper oxide is then reduced to deoxidized/non-oxide copper (i.e., the metal copper). Thus, the first circuit pattern 200 which does not contain copper oxide is transformed to the copper based second circuit pattern 300.
In a general fourth step, a metal layer 400 is plated on the second circuit pattern 300 using an electro-plating method or an electroless-plating method, as shown in
In a plating process, in one aspect, each of the metal particles (e.g., copper particles) in the second circuit pattern 300 is a reaction center, and the metal layer 400 encapsulates each of the metal particles. In another aspect, clearances between adjacent metal particles are filled with the metal layer 400. Therefore, the metal particles of the second circuit pattern 300 are electrically connected to each other by the metal layer 400, through the plating process. In the present embodiment, the metal layer 400 is made of copper, and the second circuit pattern 300 is made of discontinuous or spaced copper particles, so the metal layer 400 electrically connects the copper particles in the second circuit pattern 300.
It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200810300777.4 | Mar 2008 | CN | national |
