JP2005183847A - Method for forming wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily forming a fine conductive layer having a low electric resistance in a through-hole of a substrate. <P>SOLUTION: Through-holes are made in a substrate 10, coated with droplets by ink jetting, and then heated to thereby form a conductive layer 30. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for forming a wiring board.

  A method has been developed in which a conductive fine particle dispersion is discharged onto a substrate by an inkjet method (droplet discharge method) to form wirings included in various electro-optical devices in a predetermined pattern. For example, US Pat. No. 5,132,248 proposes a method in which a liquid material in which conductive fine particles are dispersed is directly applied to a substrate by an ink-jet method and then converted into a conductive film pattern by heat treatment or laser irradiation. . According to this method, there is a merit that the process of wiring formation is greatly simplified.

  Incidentally, in recent years, along with miniaturization of elements and low power consumption, it has been required to miniaturize conductive layers used in various electro-optical devices and to form conductive layers having low electric resistance values. In order to satisfy this requirement by the inkjet method, the blending ratio of the conductive fine particles contained in the conductive fine particle dispersion is increased, and the coating film is finely stacked to form a fine and low electric resistance value. Attempts have been made to form conductive layers.

However, this method has problems such as an increase in wiring width and an increase in manufacturing time due to an overlay accuracy problem. (See Patent Document 1)
US Pat. No. 5,132,248

  An object of the present invention is to provide a method of forming a wiring board that can be formed by a simple method and is fine and has a low electric resistance value.

The method for forming a wiring board according to the present invention includes a step of forming a through hole at a predetermined position of the board,
Applying a droplet to the through hole by a droplet discharge method;
Heat treating the substrate coated with the droplets to form a conductive layer in the through hole;
At least.

  The through hole may be formed by laser irradiation.

  According to the method for forming a wiring substrate of the present invention, a fine conductive layer having a low electric resistance value can be formed by a simple method.

  According to the present invention, a through hole can be opened in a substrate by laser light irradiation. According to this method, a fine conductive layer corresponding to the laser spot diameter can be formed on the substrate.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  1 to 4 are plan views or cross-sectional views schematically showing the steps of the method for forming a wiring board according to the first embodiment to which the present invention is applied. FIG. 1B is a view showing a cross section taken along the line AA in FIG. 1A, and shows a substrate 10 made of a plastic substrate for forming a wiring substrate.

  In the wiring substrate forming method according to the present embodiment, the through hole 20 is formed in the substrate 10 by irradiating the substrate 10 with the laser light 40 as shown in FIG. The substrate formed by laser irradiation is as shown in FIG. A laser beam 40 output from the laser beam irradiation device is irradiated to a predetermined position of the substrate 10. In this case, a fine through hole is formed in the substrate 10 as the spot diameter of the laser beam 40 is reduced.

  FIG. 3 is a plan view of the substrate 10 in which the through holes are formed, and a cross-sectional view taken along the line CC. Through holes are opened in the substrate 10 as shown.

  A droplet is applied to the substrate on which the through hole is formed by a droplet discharge method (inkjet method). The applied droplet is a conductive fine particle dispersion having re-solubility. Any material (droplet) containing conductive fine particles can be used.

  According to the method for forming a wiring board of the present embodiment, it can be used without being restricted by the blending ratio of the conductive fine particles used in the application process by inkjet.

  Next, after applying droplets in the through holes, a heating process is performed. Heating is performed by applying heat of about 180 to 200 degrees. By heating the substrate including the applied droplets, the conductive layer 30 can be formed in the through hole.

  A wiring substrate can be formed by forming a conductive layer in a through hole formed in a substrate and further forming a wiring on the surface of the substrate by an inkjet process.

  Further, after applying droplets on one surface (front surface) by an inkjet process and drying (heating), the other surface (rear surface) is similarly applied by droplets by an inkjet process, thereby wiring on both sides of the substrate. Can be formed.

  Regarding the formation of the wiring, a lyophilic process is performed on the substrate surface by a predetermined method, the lyophilic process is performed at a place where the wiring is to be formed, and the lyophobic process is performed on other areas. Further, the droplets are applied at intervals where the droplets applied by the ink jet method are not connected. Then, a drying (heating) step is performed. By repeating the step of applying droplets by inkjet coating and the drying step, it is possible to draw on the entire surface of the wiring, and it is possible to form a thick wiring by repeating this step more than once. Become.

  In order to form the conductive layer 30, a predetermined amount is applied so that the amount of droplets to be applied is substantially the same as the surface of the substrate. By doing so, it is possible to form a wiring substrate having a flat surface without forming irregularities on the substrate surface.

  It is also possible to apply a predetermined amount of droplets on the substrate surface so that the conductive layer is convex (see FIG. 4). In this case, since it becomes convex from the surface of the substrate, the surface is more uneven than the above structure in terms of flatness. However, in consideration of the connectivity with the wiring formed on the surface of the substrate, connection with high adhesion can be performed.

  Instead of the lyophobic treatment as described above, it is also possible to form a wiring by forming a bank made of resin in a region other than a region to be a wiring and applying a droplet to a region surrounded by the bank. It is. In this case, unlike the above-described droplet applying process, wiring can be formed by continuously drawing a predetermined amount of material (liquid) and performing a drying process.

  Examples of improvements are shown below.

  In the example using the plastic substrate (flexible substrate) as described above, the substrate is exemplified in a state in which nothing is formed, but wiring or the like may be formed on one surface (or both surfaces). Even in the case where the wiring is formed, a conductive layer can be formed by opening a through hole at a predetermined position by laser irradiation and applying a droplet by an ink jet method as described above. Furthermore, depending on the positional relationship between the front surface and the back surface, the conductive layer formed in the through hole can also serve to connect the front surface wiring and the back surface wiring. According to the present invention, conduction between the front and back sides is also possible.

  By mounting a semiconductor chip on one surface of such a wiring board, a semiconductor device on which the semiconductor chip is mounted can be formed. The semiconductor chip may be any type of chip, for example, a stack type in which semiconductor chips are stacked. Such semiconductor devices can be mounted on optical devices (display devices) such as liquid crystal devices and organic EL devices, and these display devices can also be mounted on electronic devices such as mobile phones and mobile devices. is there.

  Furthermore, a laminated wiring board in which an insulating film is formed on a wiring formed by ink jet and a wiring is further formed thereon by an ink jet method may be used. When forming the multilayer wiring board, for example, the wiring first formed on the substrate by the ink jet method is used as the first wiring, and the wiring formed by the ink jet method through the insulating film forming the interlayer is used as the second wiring. In this case, the conductive layer connecting the first wiring and the second wiring can be formed by the ink jet method as described above.

  In that case, the insulating film is opened only in a predetermined region, and droplets are applied to the opened portion by an ink jet method. Further, a region to be a wiring can be formed by applying droplets by an ink jet method. In addition, it is also possible to perform by the same process regarding application | coating to an opening part and application | coating in the case of 2nd wiring formation.

  In this way, a multilayer wiring board can be formed by forming a plurality of layers in which an insulating layer is arranged between each wiring, such as the first wiring, the insulating layer, and the second wiring. Also in this case, the conductive layer and the wiring can be formed by applying the above-described droplets to the openings of the wiring and the insulating layer by an ink jet method and drying by heating. Note that the insulating layer can also be formed by an ink-jet method by selecting a material. In that case, an inkjet process can be efficiently performed by preparing an inkjet apparatus for forming a wiring and an inkjet apparatus for forming an insulating layer and adopting a continuously arranged line configuration. Furthermore, in the case of wiring formation, inkjet coating must be performed a plurality of times in order to apply to the entire region and to form a wiring having a large film thickness. In that case, a method of preparing a plurality of sets of ink-jet devices for forming wirings and ink-jet devices for forming insulating layers, and arranging them in a continuous manner can also be applied.

  Further, when the apparatus is continuously arranged and formed in a line shape in this way, a reel-to-reel manufacturing method can be applied if the substrate is a tape-like material.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to these, Various aspects can be taken within the scope of the summary of this invention.

FIG. 1A is a plan view schematically showing one step of a method for forming a conductive layer according to a first embodiment to which the present invention is applied. FIG.1 (b) is a figure which shows typically the cross section in AA of Fig.1 (a). Sectional drawing which shows typically 1 process of the formation method of the wiring board which concerns on 1st Embodiment to which this invention is applied. The top view which shows typically 1 process of the formation method of the conductive layer which concerns on 1st Embodiment to which this invention is applied. The top view which shows typically 1 process of the formation method of the conductive layer which concerns on 1st Embodiment to which this invention is applied.

Explanation of symbols

10 substrate, 30 conductive layer, 40 laser light

Claims (5)

Forming a through hole at a predetermined position of the substrate;
Applying a droplet to the through hole by a droplet discharge method;
Heat treating the substrate coated with the droplets to form a conductive layer in the through hole;
A method of forming a wiring board having at least In the formation method of the wiring board of Claim 1,
A method for forming a wiring board, comprising: forming the through hole by laser irradiation. In the formation method of the conductive layer of Claim 1,
Forming a coating layer on a part of the substrate on which the conductive layer is formed. In the formation method of the wiring board of Claim 3,
A method of forming a wiring board, wherein the coating layer is formed by a droplet discharge method. In the formation method of the wiring board in any one of Claims 1-4,
A method for forming a wiring board, wherein the droplets formed by the droplet discharge method are droplets in which conductive fine particles are dispersed.

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