JP2006294550A - Conductive ink for printed board wiring and wiring method of printed board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a wiring pattern with very fine wire width of 100 nm or less on various kind of printed boards by an ink jet printing process. <P>SOLUTION: The wiring pattern with very fine wire width of 100 nm or less is drawn on various kind of printed boards by an ink jet printer, by using the ink for the ink jet printer containing conductive gold-colloid particles as main component. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive ink for forming wiring on a printed board by a printing method, and also relates to a method for printing a fine wiring pattern on a printed board with an ink jet printer using the conductive ink, and further to the ink. It is related with the printed circuit board product by which the fine wiring pattern was printed on the printed circuit board using this printing machine. Such conductive inks and printed circuit board wiring methods can be applied to a wide range of applications such as flexible printed circuit boards and three-dimensional flip chip mounting.

  In recent years, with the progress of rapid miniaturization of various electronic devices, miniaturization of wiring technology has been required, and studies have been made from various angles, and by using devices such as a masking film, an exposure apparatus, an exposure light source, etc., about 30 μm A bump pitch has been realized, and accordingly, a wiring width of 150 nm has been put into practical use. However, with further progress in integration in the future, a line width of 100 nm or less will be required in the near future, and there is a need for technological development corresponding to that.

  In addition, the demand for higher functionality in a wide range of precision equipment has increased the number of applications that cannot be installed in narrow equipment with conventional printed circuit boards that only have a high degree of integration. Flexible printed circuit boards have been developed for use as printed circuit board bases.

  However, even with such advanced printed circuit boards that are highly integrated or flexible, the surface wiring method is still metal-plated and then a masking film using a photosensitive resin is applied, and exposure and etching are called. Many things go through the process. Some are printed using conductive paint, but considering the ink viscosity, stability, yield due to painting, etc., the line width of the wiring is limited and the cost is high. It is still limited.

  As one of countermeasures, a method for forming a fine wiring pattern by printing using a conductive ink has been proposed. In particular, coupled with recent improvements in the performance of inkjet printers, printed circuit board wiring methods using such a method have rapidly spread.

Inkjet printing itself has been widely used mainly as an output terminal of a personal computer or a personal color printing machine for photographs taken with a digital camera.
Ink jet printers have a mechanism that sprays dedicated ink in the form of minute droplets from the print head toward the substrate.

  Ink-jet exclusive inks are classified into dyes that are excellent in reproducibility of photographic image quality and pigments that are excellent in water resistance and light resistance. In any case, various devices have been devised for the purpose of jetting stability from the print head (preventing nozzle clogging) and long-term stability (preventing sedimentation of particles).

  In particular, in pigment-based inks, the pigment is fined to about 100 nm by mechanical pulverization, so that reaggregation of particles is likely to occur, and various dispersion stabilizers using a surfactant or a block copolymer polymer material can be used. Indispensable, the viscosity becomes high, and the final pigment particle size must be considerably larger than 100 nm. Therefore, in order to print a fine wiring pattern for a printed wiring board by this method, the line width is naturally limited. There will be.

  The present invention does not require many conventional processes in view of the above-mentioned situation related to the printed circuit board wiring, and can be applied not only to the conventional printed circuit board but also to a flexible printed circuit board. The present invention relates to a wiring method having a fine line width of 100 nm or less to a printed board.

  In order to solve the above-described problems, according to a first aspect of the present invention, there is provided a conductive ink for an ink jet printing machine mainly composed of conductive metal colloid particles.

  Furthermore, according to the second aspect of the present invention, the conductive metal colloidal particles are produced by a reaction between a metal compound and a reducing agent of the metal compound. Provided for conductive ink.

  According to a third aspect of the present invention, the method further comprises a step of printing a wiring pattern on a printed board using an ink jet printer using the conductive ink according to claim 1, wherein the printed board has a mutual surface with the metal colloid on the surface. Provided is a printed circuit board wiring method characterized by having a portion to act on.

  Furthermore, according to a fourth aspect of the present invention, there is provided the method according to claim 3, wherein the site interacting with the metal colloid is a functional group containing a hetero atom present on the surface.

  Furthermore, according to a fifth aspect of the present invention, the functional group is at least one of a thiol group, a disulfide group, an amino group, an imino group, a carboxyl group, a carbonyl group, a sulfonyl group, and a phosphoryl group. The described method is provided.

  According to a sixth aspect of the present invention, there is provided a printed circuit board product having wiring printed by the method according to claim 3.

  According to the present invention, it is possible to form fine wiring patterns on various printed circuit boards by a very simple process as compared with the prior art.

  The present invention relates to an ink jet printing ink containing the metal colloid particles as a main component of conductive particles on the printed circuit board having a portion interacting with the metal colloid on the surface by using an ink jet printer. The present inventors have found an excellent method that can form a wiring pattern having a line width of 100 nm or less, which is much simpler than conventional methods, in which only a fine wiring pattern is printed.

  Various conventionally known materials can be used as the material for the printed circuit board in the present invention. For example, conventional printed circuit boards include thermosetting resins such as phenolic resin, bakelite resin, epoxy resin, and alkyd resin, and composite materials obtained by impregnating and curing them in paper, fabric, glass fiber, etc. Examples of flexible printed circuit boards include polyethylene terephthalate (PET), polyethersulfone (PES), polysulfone, polyphenylene sulfate (PPS), nylon, polyester, polystyrene, and copolymers thereof. Etc. are preferably used.

  The metal in the present invention is not particularly limited as long as it is a metal having good conductivity per se, but examples thereof include gold, platinum, palladium, silver, aluminum, copper, etc., among which are preferably used. Includes gold and silver.

  These metals are used in the form of a water-soluble metal compound and can be stirred together with a reducing agent in an aqueous solution to obtain a metal colloid solution, which is preferably used as a main component for the conductive ink in the present invention. The

  Furthermore, as the reducing agent for reducing the metal compound used in the present invention, various conventionally known compounds can be used, such as citric acid, sodium citrate, sodium ascorbate, or aniline, pyrrole, thiophene and derivatives thereof. Is done. In addition, the metal colloid used in the present invention preferably has a diameter of several nm to several tens of nm.

  Since the metal colloidal particles in the present invention are very stable per se, they can be used as an electroconductive ink in an aqueous solution for an ink jet printer. It is preferable to add an activator or the like to adjust conductivity or surface tension. The conductive ink thus obtained has a lower solid content concentration and lower viscosity than conventional ones, and is therefore optimal for printing a wiring pattern having a line width of 100 nm or less.

  As the ink jet printer in the present invention, a commercially available ink jet printer can be used as it is. However, since the conductive ink of the present invention has a lower viscosity than conventional products, the pore diameter of the print head may be 10 μm or less. It is possible to print a wiring pattern with a narrower line width by using such a special print head.

  Examples of functional groups on the printed circuit board surface that interact with the metal colloid in the present invention include thiol groups, disulfide groups, amino groups, imino groups, carboxyl groups, carbonyl groups, sulfonyl groups, phosphoryl groups, and the like. It is preferable to form a wiring pattern with an inkjet printer using a printed circuit board material having When such a printed circuit board does not have the above-described functional group, the desired functional group is printed by various conventionally known methods, for example, a physical method such as plasma treatment or radiation treatment, or a chemical method such as acid or alkali treatment. It can be generated on a substrate.

  Examples of the interaction between the printed board having the functional group on the surface and the metal compound include not only a chemical bond but also van der Waals force, electrostatic interaction, and adsorption force. The method for generating them is simply to print a wiring pattern on a printed circuit board having the above-mentioned functional group on the surface with a normal ink jet printer using the conductive ink mainly composed of the metal colloidal particles of the present invention. To be achieved.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto.

(Example 1) Preparation of gold colloid having a particle diameter of 2 nm To 18 ml of toluene, 0.212 g of tetraoctylammonium bromide (Aldrich) was added, and 1% of tetrachloroauric (III) acid tetrahydrate (Wako Pure Chemical Industries, Ltd.) 3 ml of an aqueous solution is added, and 0.0836 g of sodium borohydride (Wako Pure Chemical Industries, Ltd.) is added. 0.0120 g of naphthalenethiol was added and stirred at room temperature for 5 hours. A colloid of about 2 nm was obtained in the toluene layer.

(Example 2) Preparation of gold colloid having a particle diameter of 12 nm To 183 ml of ultrapure water, 12 ml of a 1% aqueous solution of tetrachlorogold (III) acid tetrahydrate (Wako Pure Chemical Industries) was added and cooled to 4 ° C. Next, 2.4 ml of a 0.5 M aqueous solution of potassium carbonate (Wako Pure Chemical Industries, Ltd.) was added to the solution while cooling and stirring. Under cooling, 2.6 ml of an 8% aqueous solution of sodium ascorbate (Wako Pure Chemical Industries, Ltd.) was added and stirred vigorously for 20 minutes, then heated to 80 ° C. and stirred vigorously for another 20 minutes.

(Example 3) Preparation of gold colloid having a particle size of 30 nm 30 ml of a 1% aqueous solution of tetrachloroauric (III) acid tetrahydrate (Wako Pure Chemical Industries) was added to 148 ml of ultrapure water and heated to 80 ° C. Next, while stirring this solution, 22.5 ml of a 2% aqueous solution of sodium citrate (Katayama Chemical Co., Ltd.) was added thereto and stirred vigorously for another 20 minutes while being heated to 80 ° C.

(Example 4) Preparation of gold colloid having a particle size of 50 nm To 200 ml of ultrapure water, 12 ml of a 1% aqueous solution of tetrachloroauric (III) acid tetrahydrate (Wako Pure Chemical Industries) was added and heated to 80 ° C. Next, while stirring this solution, 20 ml of a 3% aqueous solution of citric acid (Wako Pure Chemical Industries, Ltd.) was added thereto, and the mixture was further stirred vigorously for 20 minutes while being heated to 80 ° C.

Example 5 Printing on Plastic Sheet by Inkjet Method The thiol-coated gold colloid / toluene solution prepared in Example 1 was injected into an ink tank with a syringe and set in an inkjet printer (EPSON PM750C). A printed circuit board wiring masking pattern was created with personal computer drawing software (Adobe Illustrator CS), and the pattern was printed on a plastic sheet with an ink jet printer (EPSON PM750C) incorporating the ink tank of Example 2. It was confirmed that the wiring was formed. This wiring pattern had no disconnection and had an electric resistance of 50Ω and was sufficiently practical.

(Example 6) Printing on thiol group-containing sheet by inkjet method Three types (12, 30, 50 nm) of colloidal gold solutions prepared in Examples 2 to 4 were each injected into an ink tank with a syringe, and an inkjet printer (EPSON) PM750C). When a masking pattern for printed circuit board wiring was created with personal computer drawing software (Adobe Illustrator CS), and a pattern was produced on a thiol group-containing plastic sheet with an ink jet printer (EPSON PM750C) incorporating the ink tank of Example 4, all It was confirmed that a wiring having a line width of 90 nm was formed with the ink. These wiring patterns had no disconnection and had an electrical resistance of 50Ω, which was sufficiently practical.

It is the example which printed the wiring pattern with the inkjet printer on the plastic sheet in Example 5. FIG. 6 is an enlarged digital micrograph (200 × magnification, scalar USB MICROSCOPE M2) of a pattern surface produced on a plastic sheet by an ink jet printer in Example 5. FIG. 6 is a scanning electron microscope (SEM) photograph of the surface of each plastic sheet obtained by electroless plating of colloidal gold having a particle diameter of 50 nm in Example 6 for 10 minutes to 6 hours.

Claims (6)

Conductive ink for ink jet printers mainly composed of conductive metal colloidal particles. The conductive ink according to claim 1, wherein the conductive metal colloidal particles are generated by a reaction between a metal compound and a reducing agent of the metal compound. A printed circuit board wiring comprising a step of printing a wiring pattern on a printed board using an ink jet printer using the conductive ink according to claim 1, wherein the printed board has a portion that interacts with the metal colloid on the surface. Method. The wiring method according to claim 3, wherein the site that interacts with the metal colloid is a functional group containing a hetero atom present on the surface. The method according to claim 4, wherein the functional group is at least one of a thiol group, a disulfide group, an amino group, an imino group, a carboxyl group, a carbonyl group, a sulfonyl group, and a phosphoryl group. A printed circuit board product having wiring printed by the method according to claim 3.