JP2010161127A - Wiring board and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board having inexpensive wirings of low resistance. <P>SOLUTION: The wiring board is provided with a substrate, a wettability change layer where a high surface energy region and a low surface energy region are formed on the substrate, a porous conductive layer which is brought into contact with a part of the high surface energy region or the high surface energy region and is formed on the wettability change layer and a conductive layer which is brought into contact with the porous conductive layer and is formed of a conductive material on the high surface energy region of the wettability change layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wiring board and a manufacturing method of the wiring board.

  The electrodes of a flat panel display such as a liquid crystal display device, a PDP (plasma display panel), and an organic EL (Electro Luminescence) display are formed in a predetermined pattern.

  As described above, a photolithography method is generally used as a method for forming electrodes or the like having a predetermined pattern. However, the photolithography method requires expensive equipment and needs to go through a number of processes, which increases the cost of the finished product.

  On the other hand, in recent years, attempts have been made to form electrodes and the like by a printing method in order to reduce manufacturing costs. Among such printing methods, the inkjet method is particularly promising because it does not require expensive equipment and does not waste material.

  Patent Documents 1 and 2 disclose techniques for forming fine wiring by an ink jet method. This is because areas of different surface energies are formed on a substrate by exposure to ultraviolet rays, and the conductive ink droplets are formed on the substrate by an ink jet method in a state where the wettability of a solution (conductive ink) in which conductive particles are dispersed is controlled. In this method, a wiring pattern is formed by dripping onto the substrate, and a low resistance wiring is formed by performing a heat treatment at 200 ° C. or lower. By this method, it is possible to form wiring finer than the diameter of the droplet.

  Further, Patent Document 3 controls the dynamic behavior of the drying speed of the conductive ink and the wetting and spreading of the conductive ink by controlling the dropping position of the droplet of the conductive ink by such an inkjet method. It is possible to form fine wiring.

JP 2006-278534 A JP 2006-134959 A JP 2008-60544 A

  However, in the method disclosed in Patent Document 3, it is necessary to provide a region having a wide wiring width adjacent to the fine wiring region in order to achieve miniaturization. Since spreading is used, the use of low-concentration conductive ink tends to reduce the film thickness and increase the resistance.

  The present invention has been made in view of the above, and an object of the present invention is to provide a wiring board on which fine wiring having low resistance and low resistance is formed and a method for manufacturing the wiring board.

  The present invention includes a substrate, a wettability changing layer in which a high surface energy region and a low surface energy region are formed on the substrate, a part on the high surface energy region, or the high surface energy region. A porous conductive layer formed on the wettability changing layer, and a conductive layer formed of a conductive material in contact with the porous conductive layer and on a high surface energy region of the wettability changing layer. It is characterized by having.

  In the present invention, the wettability changing layer includes a material whose critical surface tension is changed by applying energy and changes from a low surface energy state to a high surface energy state. A high surface energy region and a low surface energy region are formed by the application.

  The present invention also provides a high surface energy region formed on the substrate, a low surface energy region, a part of the high surface energy region or a porous surface formed on the substrate in contact with the high surface energy region. And a conductive layer formed of a conductive material on the high surface energy region of the wettability changing layer.

  In the present invention, the substrate includes a material whose critical surface tension changes by applying energy, and changes from a low surface energy state to a high surface energy state, and by applying the energy, A high surface energy region and a low surface energy region are formed.

  In the invention, it is preferable that the conductive layer is formed by discharging a liquid containing a conductive material with an inkjet head.

  In the present invention, the porous conductor layer includes metal fine particles and a resin binder.

  Further, the present invention is characterized in that the metal fine particles are Ag fine particles, and an average particle diameter R is in a range of 0.1 μm <R ≦ 1 μm.

  In the present invention, the weight ratio of (metal fine particles) / (metal fine particles + resin binder) is 85% or more and 90% or less in the porous conductor layer.

  The present invention also includes a step of forming a high surface energy region and a low surface energy region by applying energy to the wettability changing layer formed on the substrate, and a part of the high surface energy region. Or a step of forming a porous conductive layer in contact with the high surface energy region, and a step of supplying a solution containing a conductive material on the high surface energy region.

  Further, the present invention is characterized in that the application of energy is performed by irradiating with ultraviolet rays.

  In the present invention, the porous conductive layer is formed by a screen printing method.

  Further, the invention is characterized in that the solution containing the conductive material is supplied by being discharged from an inkjet head.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a wiring board by which low-cost fine wiring with low resistance was formed at low cost and a wiring board can be provided.

Top view of wiring board in the present embodiment Cross-sectional view of wiring board in the present embodiment Sectional drawing of the wiring board of another structure in this Embodiment Explanatory drawing of the porous conductive layer of the wiring board in this Embodiment Process drawing of a method of manufacturing a wiring board in the present embodiment Configuration diagram of the photomask used in the examples Explanatory drawing of the manufacturing process of the wiring board in an Example Explanatory drawing of the manufacturing process of the wiring board in a comparative example

  The form for implementing this invention is demonstrated below.

(Configuration of wiring board)
The wiring board according to the present embodiment will be described with reference to FIGS. FIG. 1 is a top view of a wiring board according to the present embodiment, and FIG. 2 is a cross-sectional view of the wiring board according to the present embodiment cut along a broken line 1A-1B in FIG.

  As shown in FIGS. 1 and 2, the wiring board according to the present embodiment has a wettability changing layer 11 formed on the surface of the substrate 10, and the surface of the wettability changing layer 11 will be described later. In addition, a high surface energy region 12 and a low surface energy region 13 are formed by irradiation with ultraviolet light. Immediately after being formed, the wettability changing layer 11 is in a low surface energy state, and only the portion irradiated with ultraviolet light is in a high surface energy state, and the surface of the wettability changing layer 11 has a high surface energy region 12. And a low surface energy region 13 are formed.

  In addition, a porous conductor layer 14 is formed on the wettability changing layer 11 so as to be connected to the high surface energy region 12. The wiring board in the present embodiment is formed by connecting a thin wiring region 22 having a width W1 and a thick wiring region 23 having a width W2 to be the wiring region 21. A connected pad region 24 is formed. The thin wiring region 22 is formed by the conductive layer 15 formed on the high surface energy region 12, and the thick wiring region 23 is formed by the porous conductor layer 14. The wettability changing layer 11 under the porous conductor layer 14 may be either the high surface energy region 12 or the low surface energy region 13.

  With such a configuration, the conductive ink can be selectively flowed on the high surface energy region 12 and the ink fluidity can be assisted by utilizing the ink receptivity in the porous conductor layer 14. In particular, it is preferable to form the main wiring portion where the amount of current increases by the porous conductor layer 14.

  FIG. 3 shows a wiring board having another configuration in the present embodiment. As shown in FIG. 3, the substrate 60 is made of a material that changes from a low surface energy state to a high surface energy state by ultraviolet irradiation, and the surface of the substrate 60 has a high surface energy region 62 by irradiation with ultraviolet light. A low surface energy region 63 is formed. Immediately after the surface of the substrate 60 is formed, it is in a low surface energy state, and only the portion irradiated with ultraviolet light is in a high surface energy state. The surface of the substrate 60 has a high surface energy region 62 and a low surface energy. Region 63 is formed.

  A porous conductor layer 64 is formed on the substrate 60 so as to be connected to the high surface energy region 62. The wiring board having this configuration is formed by connecting a thin wiring region 72 having a width W1 and a thick wiring region 73 having a width W2 to be the wiring region 71. The thin wiring region 72 is formed by the conductive layer 65 formed on the high surface energy region 62, and the thick wiring region 73 is formed by the porous conductor layer 64. The substrate 60 under the porous conductor layer 64 may be either the high surface energy region 62 or the low surface energy region 63.

(substrate)
The substrate 10 constituting the wiring substrate of the present embodiment will be described.

  The substrate 10 is formed of an inorganic material, a metal / alloy, or a resin material. However, it is preferable to have a heat resistance of 100 ° C. or higher, and more preferable to have a heat resistance of 200 ° C. or higher, because firing is performed in the wiring formation process. Examples thereof include inorganic materials such as glass, ceramics, and silicon, resins such as PE, PP, PET, PEN, and polycarbonate, aluminum, and stainless steel. In addition, when using the material which has electroconductivity for the board | substrate 10, the process which coat | covers the surface with an insulator is needed.

  The shape of the substrate 10 is generally a flat plate shape. When a resin material is used as the material constituting the substrate 10, it is possible to reduce the weight by forming a film. In this case, the wiring formed on the substrate 10 by bending or bending needs to have a thickness that does not cause disconnection or the like, and preferably has a thickness of 40 μm or more, more preferably 70 μm or more.

  A wettability changing layer 11 is provided on the substrate 10, and a high surface energy region 12 and a low surface energy region 13 are formed on the surface of the wettability changing layer 11 by performing energy irradiation or the like on the surface. Forming. Examples of the energy irradiation include irradiation with an electromagnetic wave such as ultraviolet rays and radiation, irradiation with an electron beam, and the like.

  When the high surface energy region 12 and the low surface energy region 13 are formed by performing such energy irradiation, a method using a mask or the like is preferable. For example, in the case of irradiating ultraviolet rays as energy irradiation, By using a mask, the high surface energy region 12 and the low surface energy region 13 can be easily formed.

  In addition, the material constituting the wettability changing layer 11 is a polymer material such as polyimide or acrylate, and a hydrophobic functional group (containing fluorine) in the main chain or side chain forming the skeleton of these polymer materials. A fluoroalkyl group or the like) bonded directly or via a linking group is used. These polymer materials are initially brought into a low surface energy state by a hydrophobic functional group. However, the bonds with the hydrophobic functional group are broken by irradiation with ultraviolet rays or the like to become hydrophilic, resulting in a high surface energy state.

  When the surface is in a low surface energy state, the wettability of the conductive ink is poor and it is difficult to form a wiring or the like with the conductive ink. Wiring can be formed using ink. Therefore, the surface of the wettability changing layer 11 on the substrate 10 is exposed to ultraviolet rays or the like using a mask having a predetermined wiring shape pattern, so that only the exposed area becomes a high surface energy area, and the conductive ink. Can wet and spread only in this high surface energy region.

  In addition, such a method may be used as long as the high surface energy region 12 and the low surface energy region 13 can be directly formed on the substrate 10 without using the wettability changing layer 11. For example, a method using a gas phase method such as plasma treatment, etching treatment, sputtering, or vapor deposition treatment using a mask, or a liquid phase method such as dipping or spin coating may be used.

  In addition, the conductive ink used for forming the wiring includes, for example, one in which metal fine particles such as Ag, Ni, and Cu are dispersed in a solution. In particular, a nano metal ink using metal fine particles having a particle diameter of 100 nm or less has high dispersibility and high compatibility with an ink jet method using a fine nozzle. In addition, it is possible to form a low-resistance wiring with a nanometal ink using Ag with a low resistance.

  In the present embodiment, as will be described later, the wiring is formed by an ink jet method, but when formed by this ink jet method, the appropriate concentration of the metal fine particles may be 1 wt% or more and 50 wt% or less. Preferably, it can be adjusted according to the required thickness of the conductive film. The appropriate range of the surface tension of the conductive ink is 0.02 N / m or more and 0.07 N / m or less. If the surface tension is not an appropriate value, the ink landing accuracy and stability deteriorate. End up. The appropriate range of the viscosity of the conductive ink is 1 mPa · s or more and 50 mPa · s or less. If the viscosity is not an appropriate value, the conductive ink adheres to the ink discharge portion and the discharge stability is lowered. It will be.

(Porous conductor layer)
The wiring board in the present embodiment is provided with a porous conductor layer 14. The porous conductor layer 14 has a function of reducing wiring resistance and a function of assisting formation of a fine pattern of wiring. As shown in FIG. 4, the porous conductor layer 14 is formed by agglomeration of a plurality of metal fine particles 41, and in the state where the plurality of metal fine particles 41 agglomerate, minute voids are formed inside and on the surface. In this case, a low-viscosity fluid having high fluidity (liquid exhibiting Newtonian fluid behavior) such as a conductive ink can be taken into the gap and ink can be received.

  The porous conductor layer 14 includes a filler that is metal fine particles and a resin binder. The filler is fine metal particles made of a conductor, and is composed of fine metal or alloy particles. Examples of the filler material include Au, Ag, Cu, Ni, and Al. The particle size of the filler is preferably 1/5 or less, more preferably 1/10 or less of the width and thickness of the wiring to be formed. For example, in order to obtain a wiring having a thickness of 5 μm, the filler particle diameter is preferably 1 μm or less, more preferably 0.5 μm or less. This is because if the particle size of the filler is too large, the shape of the wiring surface or wiring edge portion is deformed, and it becomes difficult to form a uniform wiring pattern. On the other hand, when the particle size of the filler is small, the surface smoothness of the wiring and the edge shape of the wiring pattern are improved, and at the same time, the film density can be lowered and the resistivity of the wiring can be lowered. If the particle diameter of the filler is too small, the voids formed in the porous conductor layer 14 cannot be obtained sufficiently, and the function of receiving a conductive ink described later is deteriorated.

  Furthermore, it is possible to achieve both electrical resistance and conductive ink receptivity by mixing fillers having different particle sizes. Specifically, a method of mixing a minute amount of metal fine particles (nanoparticles) having a diameter of 0.05 μm with metal fine particles having a diameter of 0.5 μm can be mentioned. In this method, voids can be formed by metal fine particles having a diameter of 0.5 μm, and the acceptability of the conductive ink can be increased. By collecting the metal fine particles, the contact area between the particles can be increased.

  The resin binder has a function of forming and holding a filler on the substrate 10. The material used for the resin binder needs to be selected in consideration of the adhesion to the substrate 10 or the wettability changing layer 11. In addition, it is necessary that the solvent is insoluble or has low solubility in the solvent component contained in the conductive ink.

  As a material used for the resin binder, a material used for a printing ink such as a polyvinyl alcohol resin, a phenol resin, an acrylic resin or a resin binder for a paste can be used.

  The mass ratio of the filler (metal fine particles) to the resin binder is 80:20 to 97: 3 for filler: resin binder, that is, the weight ratio of (metal fine particles) / (metal fine particles + resin binder) is 80% to 97. % Is preferable. When the ratio of the filler is too high, the adhesion with the substrate 10 and the wettability changing layer 11 tends to be lowered, and even if the porous conductor layer 14 is formed, there is a possibility of peeling. Also, when stress is applied, cracks etc. are likely to occur in the porous conductor layer 14. On the other hand, when the ratio of the filler is too low, the electrical resistivity is lowered and the wiring resistance is increased. Further, the gap that should be formed between the fillers is filled with the resin binder that is a resin, and the performance of receiving the conductive ink is lowered.

  The porous conductor layer 14 can be formed by preparing a solution in which the above filler and resin binder are dispersed in a solvent, applying the solution, and drying the solution. In the solution in which the filler and the resin binder are dispersed, the filler particles are aggregated to form an aggregate due to the interaction between the fillers. After applying the solution, the degree of freedom of the filler in the aggregates is reduced in the step of drying the solvent, and voids are generated between the plurality of aggregates. By forming such voids in the film or on the surface, the porous conductor layer 14 can be formed. The voids generated in the film surface and on the film surface depend on the filler diameter, filler material, resin binder material, mass ratio of filler to resin binder, and the like. The size of the void is preferably in the range of 0.1 to 10 μm from the viewpoint of the conductive ink receptivity, and further in the range of 0.5 μm to 2 μm in view of electric conductivity and film strength. It is preferable that

  The solvent used in the solution for forming the porous conductor layer 14 needs to be a material that can be volatilized and removed by heating, and does not dissolve the substrate 10 or the wettability changing layer 11. It must be a material. Further, when the porous conductor layer 14 is formed, the viscosity, drying speed, corrosivity, and the like are adjusted according to the forming method.

  As a method for forming the porous conductor layer 14, printing by a printing method is advantageous in terms of cost. Specifically, examples of the printing method include a gravure printing method, a flexographic printing method, a screen printing method, and an inkjet printing method. In particular, a screen printing method that can form the porous conductor layer 14 thick and has high productivity is preferable.

  When the screen printing method is used as a method for forming the porous conductor layer 14, it is necessary to increase the viscosity of the solution to be applied, and it is in the range of 80 to 300 Pa · s with a Brookfield viscometer. Is preferable, and the range of 100 to 150 Pa · s is more preferable. When the viscosity is too low, the shape stability after coating is deteriorated, and the uniformity of the shape tends to deteriorate. On the other hand, if the viscosity is too high, the adhesion between the screen and the substrate becomes high during screen printing, making it difficult to perform stable plate separation, and the pattern transferability of the porous conductive layer 14 is significantly reduced. End up.

  Moreover, it is preferable that the mesh used for screen printing uses a stainless steel mesh from a viewpoint of intensity | strength and body solvent property. At this time, the fineness of the mesh is selected according to the shape of the pattern of the porous conductive layer 14 to be formed. Specifically, it is preferable to use one having a linear density equal to or less than the width of the pattern to be formed. For example, when the pattern of the porous conductive layer 14 having a width of 50 μm is formed, it is preferable to use a mesh having an interval of 50 μm, that is, 500 (500 per inch) or more. If the mesh is too coarse, the uniformity of the pattern width and film thickness is reduced, and a short circuit may occur between the disconnection and the adjacent wiring. On the other hand, if the mesh is too fine, it is necessary to reduce the thickness of the stainless steel wire, the mesh strength will be weakened, and the mesh will be plastically deformed by repeated use, and the accuracy of the pattern formed will be significantly degraded. End up. Although there is a method using a high-tension stainless steel mesh, since the manufacturing cost of such a mesh is high, the cost of the manufactured wiring board is increased.

  In addition, since it is possible to print a highly viscous solution in the screen printing method, the solute component contained in the solvent can be increased, thereby forming the porous conductor layer 14 thick. it can.

  From the above, it is preferable that the porous conductive layer 14 serving as a main wiring through which a large current flows is formed by a screen printing method.

(Production method)
Next, a method for manufacturing a wiring board in the present embodiment will be described with reference to FIG.

  First, as shown in FIGS. 5A and 5B, the surface of the substrate 10 on which the wettability changing layer 11 is formed is irradiated with ultraviolet rays. Specifically, the surface of the wettability changing layer 11 is irradiated with ultraviolet light transmitted through the opening region 31 of the photomask 30 by irradiating the ultraviolet light through the photomask 30. 5A is a top view, and FIG. 5B is a cross-sectional view taken along a broken line 5A-5B in FIG. 5A.

  Next, as shown in FIGS. 5C and 5D, the photomask 30 is removed. On the surface of the wettability changing layer 11 of the substrate 10, a high surface energy region 12 is formed in a region irradiated with ultraviolet rays, and a region not irradiated with ultraviolet rays becomes a low surface energy region 13. That is, the surface of the wettability changing layer 11 on the substrate 10 is in a low surface energy state, and after that, by irradiating with ultraviolet rays, the portion irradiated with the ultraviolet rays changes to a high surface energy state. Region 12 is formed. On the other hand, the portion not irradiated with ultraviolet rays remains in the initial low surface energy state, and this portion becomes the low surface energy region 13. 5C is a top view, and FIG. 5D is a cross-sectional view taken along a broken line 5C-5D in FIG. 5C.

  Next, as shown in FIGS. 5E and 5F, the porous conductive layer 14 is formed. The porous conductive layer 14 is formed on or in contact with the high surface energy region 12. The porous conductive layer 14 is formed in a portion to be a main wiring that requires a particularly low resistance wiring. The porous conductive layer 14 is preferably formed by a screen printing method. 5E is a top view, and FIG. 5F is a cross-sectional view taken along a broken line 5E-5F in FIG. 5E.

  Next, as shown in FIGS. 5G and 5H, a droplet of the conductive ink 33 is dropped by an ink jet method. Specifically, it is dropped on a region where the porous conductor layer 14 and the high surface energy region 12 are in contact with each other. In general, it is difficult to form a wiring finer than the diameter of a droplet dropped by an ink jet method (because the droplet spreads when contacting the substrate), but the porous conductor layer 14 and By dropping the droplet of the conductive ink 33 on the region where the high surface energy region 12 is in contact, the spread of the droplet can be prevented. 5 (g) is a top view, and FIG. 5 (h) is a cross-sectional view taken along a broken line 5G-5H in FIG. 5 (g).

  Next, as shown in FIGS. 5 (i) and 5 (j), the conductive ink 33 dropped by the ink jet method spreads over the high surface energy region 12 and the porous conductor layer 14. Specifically, the amount of wetting and spreading of the droplets of the conductive ink 33 can be adjusted by the ink receiving function of the porous conductor layer 14 and can be spread on the high surface energy region 12. Further, the amount of the solution flowing into the high surface energy region 12 can be adjusted by adjusting the position where the droplet of the conductive ink 33 is dropped between the porous conductor layer 14 and the high surface energy region 12. It is. 5 (i) is a top view, and FIG. 5 (j) is a cross-sectional view taken along a broken line 5I-5J in FIG. 5 (i).

  Next, as shown in FIGS. 5 (k) and 5 (l), the conductive layer is formed on the thick wiring region 23 where the porous conductor layer 14 is formed and the high surface energy region 12 by subsequent drying. A wiring board made of the thin wiring region 22 with the 15 formed thereon is formed. 5 (k) is a top view, and FIG. 5 (l) is a cross-sectional view taken along a broken line 5K-5L in FIG. 5 (k).

  In the wiring board in the present embodiment, the porous conductive layer 14 is used. When such a porous conductive layer 14 is not used, in the case of a wiring pattern having a thick wiring region and a thin wiring region, If even a small amount of the solution is excessively supplied to the thin wiring region, the solution spreads from the thin wiring region. For this reason, it is possible to prevent a case where a desired wiring pattern is not formed or a local thinning of the wiring due to a difference in solvent drying speed between the thin wiring region supplied with the solution and the thick wiring region. be able to.

Example 1
A glass substrate having a thickness of 0.5 μm was used as the substrate 10, and a polyimide resin was formed as the wettability changing layer 11 on the surface of the glass substrate. The wettability changing layer 11 was formed by applying a solution obtained by dissolving PIA-X491-E01 manufactured by Chisso, which is a polyimide resin with a side chain, in N-methylpyrrolidone using a spin coater and then performing heat treatment at 200 ° C. The thickness of the formed wettability changing layer 11 was measured with an ellipsometer and found to be about 2 μm.

Thus, about what formed the wettability change layer 11 on the board | substrate 10, it exposed by irradiating an ultraviolet-ray using the photomask 30 in which the pattern shown in FIG. 6 was formed. The photomask 30 has a pattern formed by openings 31 and a mask portion 32. A mercury lamp with λ = 254 nm is used as an ultraviolet light source to be irradiated, and an irradiation energy density is 5 J / cm ² . did. A wiring region is formed by the pattern of the opening 31 formed in the photomask 30, and a portion that becomes a thin wiring region (leading line) having a width W1 of 15 μm and a thick wiring region having a width W2 of 50 μm It is formed by a portion to be (main wiring), and has a shape in which a portion to be a circular pad region having a diameter D = 30 μm connected to a portion to be a thinner wiring region is formed. The distance S between thin wiring regions (leading lines) is 35 μm, and the length L is 80 μm.

  Next, as shown in FIG. 7, the porous conductive layer 14 was formed on the wettability changing layer after the exposure using the photomask 30 was completed. This porous conductive layer 14 was formed on a high surface energy region. The solution for forming the porous conductive layer 14 uses Ag fine particles having an average particle diameter of 0.2 μm as a filler, a polyvalent acrylate monomer KAYRAD D330 which is a thermosetting resin as a resin binder, and a filler: resin binder The weight ratio was 90:10, that is, the weight ratio of (metal fine particles) / (metal fine particles + resin binder) was 90%. The solute between the filler and the resin binder was dissolved in a solvent of diethylene glycol monobutyl ether acetate (BCA) to form a solution. The weight concentration of the solvent was 90%.

  The solution thus obtained was further dispersed by a planetary mixer and a roll mill to obtain an Ag paste capable of uniform screen printing. The viscosity of this Ag paste was 150 Pa · s when measured with a Brookfield viscometer.

  The porous conductive layer 14 was formed by a screen printing method. The screen used for screen printing was prepared by forming an emulsion pattern on a No. 500 stainless mesh (mesh formed with a density of 500 stainless steel wires having a diameter of 20 μm per inch). The Ag paste was applied on the screen, and a urethane rubber squeegee was scanned to form a pattern of the porous conductor layer 14 using Ag paste.

Thereafter, heat treatment at 150 ° C. was performed to volatilize the solvent contained in the Ag paste, and the porous conductive layer 14 was formed. The thickness of the porous conductive layer 14 formed in this way was measured with a stylus-type film thickness measuring device, and it was in the range of 4 to 5 μm, and the cross-sectional shape was a gently curved surface. Moreover, when the cross section of this porous conductive layer 14 was cut out by FIB (focused ion beam) and observed using a SEM (scanning electron microscope), there were many voids of 1 to 2 μm on the surface and in the film. I confirmed. Moreover, when the electrical resistivity (volume resistivity) of the porous conductor layer 14 after the heat treatment was measured, it was 1 × 10 ⁻⁵ Ω · cm or less, and it was confirmed that it could be used as a wiring material.

  Thus, about the thing in which the porous conductive layer 14 was formed, the nano metal ink was dripped by the inkjet method in the position shown in FIG. The nanometal ink used is one in which Ag fine particles are dispersed in a solvent, and the viscosity is 10 mPa · s. The ink jet apparatus used for the ink jet method is capable of ejecting fine droplets by a piezoelectric element, and the ejected droplets are set to 8 pL (diameter: about 25 μm). In addition, this ink jet apparatus is provided with a movable stage capable of two-dimensional movement for alignment of droplet dropping. After the nanometal ink was dropped, a heat treatment at 200 ° C. was performed to remove the organic material such as a dispersant bonded to the Ag nanoparticles in the nanometal ink by drying.

  In this way, the wiring substrate according to Example 1 having the wiring region composed of the thick wiring region 23 made of the porous conductive layer 14 and the thin wiring region 22 made of the conductive layer 15 and the pad region 24 was formed.

  When the wiring after the heat treatment was observed with an optical microscope, it was confirmed that the wiring having the same pattern as that of the photomask 30 was formed. Thereby, it was confirmed that the wiring was formed only on the high surface energy region 12. Further, when the probe is brought into contact with the porous conductor layer 14 of the circular pad portion and the main wiring portion, and the IV characteristic is measured by a digital multimeter, it is in accordance with Ohm's law and has sufficient electrical properties. It was confirmed that continuity was obtained.

(Comparative Example 1)
As Comparative Example 1, a wiring board as shown in FIG. The wiring board in Comparative Example 1 has a configuration in which a porous conductor layer is not formed in a thick wiring region. By the same method as in Example 1, nanometal ink was dropped by the inkjet method at the position shown in FIG. 8 to form a wiring.

  In this manner, a wiring substrate according to Comparative Example 1 having a wiring region composed of the thick wiring region 123 made of the conductive layer 115, the thin wiring region 122, and the pad region 124 was formed.

  When the wiring board formed in Comparative Example 1 was observed with an optical microscope, the wiring was formed on the high surface energy region, but the thickness of the connection portion between the thick wiring region and the thin wiring region was small. It was formed very thin and it was confirmed that there was a possibility of disconnection in future use. Further, when the probe was brought into contact with the circular pad portion and the main wiring portion which is a thick wiring region and the IV characteristics were measured with a digital multimeter, conduction failure was confirmed in about 20% of the whole. Furthermore, it was confirmed that the resistance value was 10 to 100 times as high as that of Example 1 even in the wiring confirmed to be conductive.

(Example 2)
A wiring board was produced by the same method as in Example 1. However, the ratio of the filler (metal fine particles) and the resin binder used to form the porous conductor layer 14 is such that the filler: resin binder is 85:15, that is, (metal fine particles) / (metal The weight ratio of fine particles + resin binder) was 85% and that of 80:20, that is, the weight ratio of (metal fine particles) / (metal fine particles + resin binder) was 80%. . The wiring resistance of the wiring board manufactured in this way was confirmed to be sufficient electrical continuity, although the value of filler: resin binder of 85:15 was about 60% higher than that of Example 1. On the other hand, when the filler: resin binder was 80:20, electrical continuity was not confirmed. From the results of Example 1 and Example 2, the filler: resin binder is 85:15 to 90:10, that is, the weight ratio of (metal fine particles) / (metal fine particles + resin binder) is 85 to 90%. It has been confirmed that it is necessary to form a wiring board.

(Example 3)
A wiring board was produced by the same method as in Example 1. However, the average particle size of the filler used to form the porous conductor layer 14 is three types: an Ag filler having an average particle size of 0.1 μm, an Ag filler having an average particle size of 1 μm, and an Ag filler having an average particle size of 2 μm. Each wiring board was produced with a filler. An Ag paste made from an Ag filler having an average particle size of 0.1 μm is a high viscosity paste with a Brookfield method exceeding 300 Pa · s. When screen printing is performed using this Ag paste, pattern omission occurs. As a result, normal printing could not be performed. In addition, when screen printing was performed using an Ag paste made of an Ag filler having an average particle diameter of 1 μm and an Ag filler having an average particle diameter of 2 μm, when an Ag filler having an average particle diameter of 2 μm was used, in the formed wiring board The wiring resistance was as high as about 1.5 times the wiring resistance of the wiring board in Example 1. In addition, when an Ag filler having an average particle diameter of 1 μm was used, the wiring resistance in the formed wiring board was not much different from the wiring resistance in the wiring board in Example 1.

  Therefore, the average particle diameter R of the Ag filler is preferably in the range of 0.1 μm <R ≦ 1 μm. Moreover, in Example 1, although a favorable wiring board can be obtained with an Ag filler having an average particle diameter of 0.2 μm, the Ag filler having an average particle diameter of 0.1 μm of this example has a high viscosity. Based on an empirical viewpoint, it is considered that a relatively good wiring substrate can be obtained if the average particle size R of the Ag filler during this period is 0.15 μm or more.

  By increasing the particle size of the metal fine particles of the filler, it is considered that the surface area of the metal fine particles per unit mass is reduced, the influence of the resin binder contained is increased, and the resistance is increased.

  Moreover, although the form which concerns on implementation of this invention was demonstrated, the said content does not limit the content of invention.

DESCRIPTION OF SYMBOLS 10 Board | substrate 11 Wetting property change layer 12 High surface energy area | region 13 Low surface energy area | region 14 Porous conductive layer 15 Conductive layer 22 Thin wiring area 23 Thick wiring area

Claims (12)

A substrate,
On the substrate, a wettability changing layer in which a high surface energy region and a low surface energy region are formed,
A porous conductive layer formed on the wettability changing layer in contact with a part of the high surface energy region or the high surface energy region;
A conductive layer in contact with the porous conductive layer and formed of a conductive material on a high surface energy region of the wettability changing layer;
A wiring board comprising: The wettability changing layer includes a material whose critical surface tension changes by applying energy, and changes from a low surface energy state to a high surface energy state,
The wiring substrate according to claim 1, wherein a high surface energy region and a low surface energy region are formed by applying the energy. A high surface energy region and a low surface energy region formed on the substrate;
A porous conductive layer formed on the substrate in contact with a part of the high surface energy region or the high surface energy region;
A conductive layer formed of a conductive material on a high surface energy region of the wettability changing layer;
A wiring board comprising: The substrate includes a material that changes its critical surface tension by applying energy and changes from a low surface energy state to a high surface energy state,
4. The wiring board according to claim 3, wherein a high surface energy region and a low surface energy region are formed by applying the energy.   The wiring board according to claim 1, wherein the conductive layer is formed by discharging a liquid containing a conductive material with an inkjet head.   The wiring board according to claim 1, wherein the porous conductor layer includes metal fine particles and a resin binder.   The wiring board according to claim 6, wherein the metal fine particles are Ag fine particles, and an average particle diameter R is in a range of 0.1 μm <R ≦ 1 μm.   The wiring substrate according to claim 6 or 7, wherein the porous conductor layer has a weight ratio of (metal fine particles) / (metal fine particles + resin binder) of 85% or more and 90% or less. Forming a high surface energy region and a low surface energy region by applying energy to the wettability changing layer formed on the substrate;
Forming a porous conductive layer in contact with a part of the high surface energy region or the high surface energy region;
Supplying a solution containing a conductive material on the high surface energy region;
A method of manufacturing a wiring board, comprising:   The method for manufacturing a wiring board according to claim 9, wherein the application of energy is performed by irradiating ultraviolet rays.   The method for manufacturing a wiring board according to claim 9 or 10, wherein the porous conductive layer is formed by a screen printing method.   12. The method for manufacturing a wiring board according to claim 9, wherein the solution containing the conductive material is supplied by being discharged from an inkjet head.

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