JP2007273533A - Method and device for forming conductive pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a conductive pattern which can ensure ample electrical continuity, even if a resin substrate is employed. <P>SOLUTION: A pattern is formed of a liquid with as micro particles of metal dispersed in a solvent on the surface of a substrate. The solvent is evaporated by making a light beam impinge on the pattern, while controlling so that the light beam will not be incident on a region where the pattern thus formed is not arranged. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for forming a conductive pattern, and more particularly, to a method and apparatus for forming a conductive pattern on a printed circuit board without using a mask corresponding to the pattern to be formed.

  Known methods for drawing a circuit pattern on a photoresist film on a printed circuit board include contact exposure, reduced projection exposure, and proximity exposure using a photomask on which a circuit pattern is formed. In these methods, as the number of printed circuit boards is increased and the number of products is increased, a photomask must be prepared for each type of printed circuit board.

  As a method not using a photomask, a direct drawing method has attracted attention. In the direct drawing method, a latent image is formed by making a laser beam incident on a desired region of a resist film via a polygon mirror or a digital micromirror device (DMD). By developing the resist film, a pattern made of a resist material is formed.

  Patent Document 1 below discloses a method for directly forming a conductive pattern on a substrate without using a resist film. Hereinafter, the method disclosed in Patent Document 1 will be described.

  A dispersion liquid in which silver particles are dispersed is ejected from an ink jet nozzle toward a printed circuit board and attached in a wiring pattern. The substrate is held at about 250 ° C. to evaporate the solvent of the dispersion adhering to the substrate. Thereby, silver particles remain on the substrate, and a wiring pattern is formed.

JP 2004-304129 A

  In some cases, sufficient electrical continuity between the fine particles may not be ensured simply by evaporating the solvent from the dispersion liquid containing silver fine particles adhering to the substrate. In order to ensure sufficient electrical continuity, the heat treatment temperature after depositing the dispersion must be increased. For this reason, a substrate material that can withstand high-temperature heat treatment must be used, and an inexpensive resin substrate cannot be used.

  The objective of this invention is providing the formation method of the conductive pattern which can ensure sufficient electrical continuity even if it uses a resin-made board | substrate. Another object of the present invention is to provide a conductive pattern forming apparatus suitable for this forming method.

  According to one aspect of the present invention, (a) a step of forming a pattern on the surface of a substrate with a liquid in which metal fine particles are dispersed in a solvent, and (b) the pattern formed in the step a is disposed. There is provided a method for forming a conductive pattern, which includes a step of controlling a light beam not to enter an unexposed region, causing the light beam to enter the pattern, and evaporating the solvent.

  According to another aspect of the present invention, a stage that holds a substrate and moves the held substrate in a direction parallel to the surface thereof, and a liquid liquid in which metal fine particles are dispersed on the surface of the substrate held on the stage. A nozzle head that ejects droplets and adheres to the surface; a light source that causes a light beam to enter the surface of the substrate held on the stage; and movement of the stage based on image data; There is provided a conductive pattern forming apparatus having a control device for controlling ejection and emission of a laser beam from the light source.

  The laser beam does not enter the region where the pattern is not formed by the liquid in which the metal fine particles are dispersed. For this reason, it is possible to prevent the substrate from being damaged by the laser beam. In addition, since it is not necessary to heat the entire substrate, it is possible to use a resin substrate having low heat resistance.

  FIG. 1A shows a schematic diagram of a conductive pattern forming apparatus according to an embodiment. An XY stage 2 is attached on the base 1. An XYZ orthogonal coordinate system is defined which is fixed to the base 1 and has a horizontal plane as an XY plane. The XY stage 2 holds the substrate 20 so that the surface thereof is parallel to the XY plane. The XY stage 2 includes a drive mechanism 3 and can translate the held substrate in the X-axis direction and the Y-axis direction. The drive mechanism 3 is controlled by the control device 10. A nozzle head 5 and a laser light source 6 are disposed above the XY stage 2. The nozzle head 5 has a plurality of nozzles 5 a on the surface facing the XY stage 2. The laser light source 6 has a plurality of light emitting pixels 6 a on the surface facing the XY stage 2.

  FIG. 1B shows a plan view of the nozzle head 5, the laser light source 6, and the XY stage 2. The nozzles 5a of the nozzle head 5 are arranged in the Y-axis direction. Each nozzle 5a discharges a droplet of a dispersion liquid in which metal fine particles, for example, copper fine particles are dispersed in a solvent. The discharged droplets adhere to the surface of the substrate 20 held on the XY stage 2. As the nozzle head 5, for example, an inkjet nozzle used in a known inkjet method (droplet discharge method) can be used. In order to arrange the nozzles 5a densely in the Y-axis direction, a plurality of nozzle rows in which a plurality of nozzles are arranged at an equal pitch are arranged, and the nozzle rows are arranged so that the nozzles in the plurality of nozzle rows do not overlap in the Y-axis direction. You may mutually shift in the Y-axis direction.

The light emitting pixels 6a of the laser light source 6 are arranged in the Y-axis direction. The light emitting pixels 6a and the nozzles 5a have a one-to-one correspondence. A laser beam is emitted from each of the light emitting pixels 6 a and is incident on the surface of the substrate 20 held on the XY stage 2. The Y coordinate is the same at the position where the droplet ejected from a certain nozzle 5a is attached and the position where the laser beam emitted from the light emitting pixel 6a corresponding to the nozzle 5a is incident. As the laser light source 6, for example, a semiconductor laser can be used. Note that another light source capable of obtaining sufficient power, for example, a light emitting diode, a CO ₂ laser, an excimer laser, or a solid state laser such as Nd: YAG may be used.

  The planar dimension of the droplet discharged from the nozzle 5a and adhering to the surface of the substrate 20 is, for example, about 25 μm. The beam spot size of the laser beam emitted from the light emitting pixel 6a on the surface of the substrate 20 is slightly smaller than the plane dimension of the droplet.

  The control device 10 controls the timing at which droplets are ejected from the nozzle 5a and the timing at which a laser beam is emitted from the light emitting pixels 6a. By moving the substrate 20 in the X-axis direction and discharging droplets from the nozzles 5a based on the image data, a pattern of the dispersion liquid can be formed on the surface of the substrate 20. The light emission timing of the light emitting pixels 6a is controlled so that the laser beam is incident on the droplets discharged from the corresponding nozzles 5a and attached to the surface of the substrate 20. For this reason, the laser beam is incident on the position where the droplet discharged from the nozzle 5a is attached, but is not incident on the position where the droplet is not attached.

  The board | substrate 20 is a resin-made core board | substrate for producing a printed circuit board, for example. The metal fine particles dispersed in the dispersion discharged from the nozzle 5a are, for example, copper fine particles having a diameter of about several μm. For example, toluene or the like can be used as the solvent. The viscosity of the dispersion is adjusted to about 10 mPa · s, for example. The size of the droplet and the size of the metal fine particles are appropriately selected according to the size of the pattern to be formed and the required resolution.

  Next, the conductive pattern forming method according to the first embodiment will be described with reference to FIGS. 2A to 2C.

  As shown in FIG. 2A, the XY stage 2 is controlled to place the substrate 20 at the initial position. The following steps are performed while moving the substrate 20 at a constant speed in the X-axis direction. Droplets are ejected from a predetermined nozzle 5a of the nozzle head 5 at a predetermined timing. The nozzle 5a that discharges the droplet and its timing are determined based on the image data. The discharged droplet 30a adheres to the position of one pixel constituting the pattern to be formed on the surface of the substrate 20.

  As shown in FIG. 2B, following the droplet 30a, the droplets 30b and 30c adhere to the positions of the pixels constituting the pattern to be formed on the surface of the substrate 20.

  As shown in FIG. 2C, when the droplet 30a attached in the step of FIG. 2A is arranged on the path of the laser beam emitted from the corresponding light emitting pixel 6a, the laser beam is emitted from the light emitting pixel 6a. As a result, the solvent of the droplet 30a evaporates and at least the surface layer portion of the metal fine particles is melted, and the fine particles in contact with each other are integrated to form the metal film 31a. The metal film 31a is firmly attached to the substrate 20.

  Each time the droplets 30b, 30c, etc. discharged from the nozzle 5a and adhered to the substrate 20 are arranged at the irradiation position of the corresponding light emitting pixel 6a, a laser beam is emitted from the light emitting pixel 6a. As a result, a conductive pattern made of integrated metal fine particles can be formed on the surface of the substrate 20.

  Since only the droplets are locally heated by the laser beam irradiation, the temperature of the entire substrate 20 does not increase. For this reason, a conductive pattern can be formed also on the surface of a resin substrate having low heat resistance.

  Next, a method for forming a conductive pattern according to the second embodiment will be described with reference to FIGS.

  As shown in FIG. 3A, the XY stage 2 is controlled to place the substrate 20 at the initial position. The following steps are performed while moving the substrate 20 at a constant speed in the X-axis direction. Based on the image data, droplets are ejected from a predetermined nozzle 5a of the nozzle head 5 at a predetermined timing. The discharged droplet 30a adheres to the position of one pixel constituting the pattern to be formed on the surface of the substrate 20.

  As shown in FIG. 3B, the laser beam is incident on the droplet 30a attached to the surface of the substrate 20. Thereby, the solvent of the droplet 30a evaporates, and at least the surface layer portion of the metal fine particles is melted, and the fine particles in contact with each other are integrated. Furthermore, the integrated metal fine particles 31 a are firmly attached to the substrate 20.

  As shown in FIG. 3C, the next droplet 30b is ejected from the predetermined nozzle 5a of the nozzle head 5 at a predetermined timing based on the image data. As shown in FIG. 3D, the laser beam is incident on the droplet 30b attached to the surface of the substrate 20. Thereby, the metal film 31b in which the metal fine particles are integrated is formed. As described above, by alternately repeating the discharge of the droplet and the irradiation of the laser beam, a conductive pattern made of the metal films 31a, 31b and the like is formed.

  In the second embodiment, after the droplet 30a discharged from the nozzle 5b adheres to the surface of the substrate 20, the laser beam enters the droplet 30a attached to the substrate before the next droplet 30b adheres. Thus, the nozzle head 5 and the laser light source 6 are controlled. Thereby, the mutual interference between the two droplets in contact with each other can be suppressed.

  In the first and second embodiments, the droplets of the dispersion liquid are ejected in parallel with the incidence of the laser beam, but after the pattern made of the dispersion liquid is formed on the entire surface of the substrate 20. The laser beam may be incident along the pattern.

  Next, a method for forming a conductive pattern according to the third embodiment will be described with reference to FIGS. 4A to 4D.

  As shown in FIG. 4A, a metal particle dispersion film 25 is formed on the surface of the substrate 20 by applying a paste in which metal fine particles are dispersed. The substrate 20 is placed on the XY stage 2.

  As shown in FIG. 4B, while moving the substrate 20 in the X-axis direction, a laser beam is emitted from a predetermined light emitting pixel 6a at a predetermined timing based on image data. In the region where the laser beam is incident, the solvent of the metal particle dispersion film 25 evaporates, and the surface layer portion of the metal particles dissolves so that the metal particles are integrated. Thereby, the metal film 26 is formed. As shown in FIG. 4C, a pattern corresponding to the image data is formed by the metal film 26.

  As shown in FIG. 4D, the metal fine particle dispersion film 26 in the region where the metal film 26 is not formed is removed. Thereby, a conductive pattern made of the metal film 26 is obtained.

  In any of the above embodiments, the laser beam does not enter the exposed surface of the substrate 20. For this reason, it is possible to prevent the substrate 20 from being damaged by the laser beam. Further, since the entire substrate 20 is not heated, a resin substrate having low heat resistance can be used.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

(1A) is a schematic view of a conductive pattern forming apparatus according to an embodiment, and (1B) is a plan view of the main part thereof. It is a figure in the middle of the process for demonstrating the formation method of the conductive pattern by a 1st Example. It is a figure in the middle of a process for demonstrating the formation method of the conductive pattern by a 2nd Example. It is a figure in the middle of a process for demonstrating the formation method of the conductive pattern by a 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base 2 XY stage 3 Drive mechanism 5 Nozzle head 5a Nozzle 6 Laser light source 6a Light emission pixel 10 Control apparatus 20 Substrate 25 Metal fine particle dispersion film 26, 31a, 31b Metal film 30a, 30b, 30c Droplet

Claims (10)

(A) forming a pattern on the surface of the substrate with a liquid in which metal fine particles are dispersed in a solvent;
(B) controlling the light beam not to enter the region where the pattern formed in the step a is not arranged, causing the light beam to enter the pattern, and evaporating the solvent. Forming method.   2. The method for forming a conductive pattern according to claim 1, wherein in step b, at least a surface layer portion of the metal fine particles is melted by irradiation with a light beam and the metal fine particles in contact with each other are integrated.   3. The method of forming a conductive pattern according to claim 1, wherein in the step a, the pattern is formed by ejecting liquid droplets from a nozzle and adhering them to the surface of the substrate.   The method for forming a conductive pattern according to claim 3, wherein the formation of the pattern in the step a and the incidence of the light beam in the step b are performed in parallel.   In the steps (a) and (b), after a droplet ejected from the nozzle adheres to the surface of the substrate, a light beam is incident on the droplet adhered to the substrate before the next droplet adheres. 4. A method for forming a conductive pattern according to 3. (A) applying a paste in which metal fine particles are dispersed in a solvent on the surface of the substrate;
(B) A step of drawing on the paste applied in the step a by using a light beam, melting at least the surface layer portion of the metal fine particles in the region where the light beam is incident, and integrating the metal fine particles in contact with each other. When,
(C) A method of forming a conductive pattern including a step of removing paste in a region not irradiated with the light beam in the step b. A stage that holds the substrate and moves the held substrate in a direction parallel to the surface;
A nozzle head that discharges liquid droplets in which metal fine particles are dispersed and adheres to the surface of the substrate held on the stage;
A light source that makes a light beam incident on the surface of the substrate held by the stage;
A conductive pattern forming apparatus comprising: a control device that controls movement of the stage, ejection of droplets from the nozzle, and emission of a laser beam from the light source based on image data.   The nozzle head includes a plurality of nozzles, the laser light source includes a plurality of light emitting pixels, the nozzles correspond to the light emitting pixels on a one-to-one basis, and each of the corresponding nozzle and light emitting pixel pairs The conductive position according to claim 7, wherein the attachment position of the droplet discharged from the nozzle and the incident position of the laser beam emitted from the light emitting pixel corresponding to the nozzle are arranged at the same position in the first direction. Pattern forming device.   9. The control device according to claim 7, wherein the control device controls the light source so that a light beam is incident on a position where a droplet discharged from the nozzle is attached and a light beam is not incident on a position where the droplet is not attached. The conductive pattern forming apparatus described.   After the droplet ejected from the nozzle adheres to the surface of the substrate held on the stage, the control device makes the light beam incident on the droplet adhered to the substrate before the next droplet adheres. The conductive pattern forming apparatus according to claim 7, wherein the light source is controlled to do so.

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