JP2007088004A - Multilayer circuit board, method of manufacturing the same, electro-optical device, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a multilayer circuit board that can suppress the generation of variance in electric characteristic, a multilayer circuit board, an electro-optical device, and an electronic device. <P>SOLUTION: The method of manufacturing a multilayer circuit board 30 includes a step wherein a droplet discharging method is used to apply a wiring material on a film-like substrate 31, and the wiring material is dried to form wiring layers 32, 34 and 36; a step wherein a droplet discharging method is used to apply an insulating material on the substrate 31, and the insulating material is dried to form insulating layers 51, 52, 54, 56, and 58; and a step wherein the wiring layers 32, 34 and 36 and the insulating layers 51, 52, 54, 56, and 58 are baked at the same time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a multilayer circuit board, a multilayer circuit board, an electro-optical device, and an electronic apparatus.

  For manufacturing a multilayer circuit board having wirings used for an electronic circuit or an integrated circuit, for example, a droplet discharge method is known.

  For example, as disclosed in Patent Document 1, a method of forming a wiring pattern on a substrate using a droplet discharge method in which a functional liquid that is a liquid material is discharged from a droplet discharge head in the form of droplets has been proposed. ing. In this method, a functional liquid in which conductive fine particles such as metal fine particles are dispersed is placed on a substrate, and then a heat treatment or the like is performed to form a thin conductive layer.

JP 2003-309369 A

  However, in the above conventional method, heat treatment is performed every time the wiring layer is formed. Therefore, in the wiring layers formed on the upper layer and the lower layer of the substrate, the heat treatment is performed a plurality of times in the layer close to the substrate. Become. Then, the wiring layers formed on the upper layer and the lower layer of the substrate have a difference in thermal history. As a result, the strength and electrical characteristics of the wiring layer may vary. If the electrical characteristics of the wiring layer vary, the operation of the electro-optical device or an electronic apparatus equipped with the electro-optical device may become unstable.

  An object of the present invention is to provide a method for manufacturing a multilayer circuit board, a multilayer circuit board, an electro-optical device, and an electronic apparatus that can suppress the occurrence of variations in electrical characteristics.

  A method for manufacturing a multilayer circuit board according to the present invention is a method for manufacturing a multilayer circuit board by alternately laminating wiring layers and insulating layers on a substrate, and using a droplet discharge method on the substrate. Applying the wiring material, drying the wiring material to form the wiring layer, applying an insulating material on the substrate using a droplet discharge method, and drying the insulating material to form the insulating material. A step of forming a layer; and a step of collectively baking the wiring layer and the insulating layer.

  According to the present invention, the wiring layer formed on the upper layer and the lower layer of the substrate and the insulating layer formed between the wiring layers are baked together, so that the thermal history of the wiring layer formed on the upper layer and the lower layer of the substrate Since the film quality becomes the same, the film quality can be made almost uniform, so that a wiring layer having stable electrical characteristics can be formed. Similarly, since the film quality of the insulating layer can be made substantially uniform, an insulating layer with good insulating characteristics can be formed. As a result, it is possible to form a multilayer circuit board that can suppress variations in electrical characteristics. Moreover, since the firing process is performed once and the number of firings can be reduced as compared with the conventional method, the processing time can be shortened, which is efficient.

  In the method of manufacturing a multilayer circuit board according to the present invention, it is preferable that the wiring material drying means is a reduced pressure drying method in the step of forming the wiring layer.

  According to the present invention, since the wiring material drying means is the reduced pressure drying method, the solvent in the wiring material can be removed without heating, and therefore, the wiring material can be dried without applying thermal stress. A wiring layer having a uniform film quality can be formed as compared with the heat drying method.

  In the method for manufacturing a multilayer circuit board according to the present invention, it is desirable that in the step of forming the insulating layer, the means for drying the insulating material is a light irradiation method.

  According to this invention, since the drying means for the insulating material is a light irradiation method, the insulating material can be dried by photoreaction without heating, and therefore, the insulating material can be cured without applying thermal stress. Compared with the heat drying method, an insulating layer having a uniform film quality can be formed.

  The multilayer circuit board of the present invention is formed using the above-described method for manufacturing a multilayer circuit board.

  According to the present invention, since a wiring layer having stable electrical characteristics and an insulating layer having excellent insulating characteristics can be formed, a multilayer circuit board capable of reducing variations in electrical characteristics can be provided.

  The electro-optical device of the present invention includes the multilayer circuit board described above.

  According to the present invention, the electro-optical device having stable electrical characteristics can be provided because the multilayer circuit board capable of reducing variations in electrical characteristics is provided.

  An electronic apparatus according to the present invention includes the above-described electro-optical device.

  According to the present invention, since the electro-optical device having stable electrical characteristics is provided, a highly reliable electronic apparatus can be provided.

  Hereinafter, embodiments of the multilayer circuit board forming method, multilayer circuit board, electro-optical device, and electronic apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

(Embodiment)
In the present embodiment, an example in which a functional liquid containing conductive fine particles is discharged in a droplet form from a discharge nozzle of a droplet discharge head by a droplet discharge method to form a wiring composed of a plurality of conductive films on a substrate. It explains using. Here, before describing the characteristic configuration and method of the present invention, first, a wiring material, an insulating material, a substrate, a droplet ejection method, and a droplet ejection apparatus used in the droplet ejection method will be sequentially described.
<About wiring materials>

  The wiring material is made of a dispersion liquid in which conductive fine particles are dispersed in a dispersion medium. In the present embodiment, the conductive fine particles include, for example, metal oxides containing any of gold, silver, copper, iron, chromium, manganese, molybdenum, titanium, palladium, tungsten, and nickel, and oxides thereof. In addition, fine particles of conductive polymer or superconductor are used. These conductive fine particles can be used by coating the surface with an organic substance or the like in order to improve dispersibility. The particle diameter of the conductive fine particles is preferably 1 nm or more and 0.1 μm or less. If it is larger than 0.1 μm, there is a risk of clogging in the discharge nozzle of the droplet discharge head described later. On the other hand, if it is smaller than 1 nm, the volume ratio of the coating agent to the conductive fine particles becomes large, and the ratio of the organic matter in the obtained film becomes excessive.

  The dispersion medium is not particularly limited as long as it can disperse the conductive fine particles and does not cause aggregation. For example, in addition to water, alcohols such as methanol, ethanol, propanol, butanol, n-heptane, n-octane, decane, dodecane, tetradecane, toluene, xylene, cymene, durene, indene, dipentene, tetrahydronaphthalene, decahydro Hydrocarbon compounds such as naphthalene and cyclohexylbenzene, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, 1,2-dimethoxyethane, bis (2- Methoxyethyl) ether, ether compounds such as p-dioxane, propylene carbonate, γ- Butyrolactone, N- methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, can be exemplified polar compounds such as cyclohexanone. Of these, water, alcohols, hydrocarbon compounds, and ether compounds are preferable and more preferable dispersion media in terms of fine particle dispersibility, dispersion stability, and ease of application to the droplet discharge method. Examples thereof include water and hydrocarbon compounds.

  The surface tension of the conductive fine particle dispersion is preferably in the range of 0.02 N / m to 0.07 N / m. When the liquid is discharged by the droplet discharge method, if the surface tension is less than 0.02 N / m, the wettability of the functional liquid composition with respect to the discharge nozzle surface increases, and thus flight bending easily occurs. If it exceeds / m, the shape of the meniscus at the tip of the discharge nozzle is not stable, and it becomes difficult to control the discharge amount and the discharge timing. In order to adjust the surface tension, a small amount of a surface tension regulator such as a fluorine-based, silicone-based, or nonionic-based material may be added to the dispersion within a range that does not significantly reduce the contact angle with the substrate. The nonionic surface tension modifier improves the wettability of the liquid to the substrate, improves the leveling property of the film, and helps prevent the occurrence of fine irregularities in the film. The surface tension modifier may contain an organic compound such as alcohol, ether, ester, or ketone, if necessary.

The viscosity of the dispersion is preferably in the range of 1 mPa · s to 50 mPa · s. When the liquid material is discharged as droplets using the droplet discharge method, if the viscosity is less than 1 mPa · s, the periphery of the discharge nozzle is easily contaminated by the outflow of the functional liquid, and the viscosity is greater than 50 mPa · s. This is because the clogging frequency in the discharge nozzle hole is increased and it becomes difficult to smoothly discharge the droplet.
<Insulation material>

  The insulating material is not particularly limited as long as it is a liquid that can be discharged as droplets at the time of formation and can be solidified thereafter. Examples of such materials include those in which a solution in which a resin is dissolved in a solvent is applied and then the solvent is removed, thermoplastic resins, thermosetting resins, photocurable resins, resin solutions, fine particle dispersions, and the like. And resins and fine particles.

  As the insulating material, organic materials such as polyimide, acrylic resin, and novolac resin are generally used. In addition to the above, polyvinyl alcohol, unsaturated polyester, methyl methacrylic resin, polyethylene, diallyl phthalate, ethylene propylene diene monomer, epoxy resin, phenol resin, polyurethane, melamine resin, polycarbonate, polyvinyl chloride, polyamide, styrene butadiene rubber, An oligomer such as chloroprene rubber, polypropylene, polybutylene, polystyrene, polyvinyl acetate, polyester, polybutadiene, polybenzimidazole, polyacrylonitrile, epichlorohydrin, polysulfide, polyisoprene, a polymer, or the like can be used.

  Since the insulating material should not be dissolved or reacted with the resin or solution to be contacted, the insulating material is preferably a curable resin that is cured by light or heat after ejection.

  Such a photocurable resin usually has at least one functional group, and performs ion polymerization or radical polymerization with ions or radicals generated by irradiating light to the photopolymerization initiator, thereby increasing the molecular weight. If necessary, a resin composition having at least a monomer or oligomer for forming a crosslinked structure and a photopolymerization initiator is cured. The functional group here means an atomic group or a bonding mode that causes a reaction such as vinyl group, carboxyl group, amino group, hydroxyl group, and epoxy group.

  In addition, thermosetting resins usually have at least one functional group and need to increase molecular weight by performing ion polymerization or radical polymerization with ions or radicals generated by applying heat to the thermal polymerization initiator. If present, a resin composition having at least a monomer or oligomer that forms a crosslinked structure and a thermal polymerization initiator is cured. The functional group here means an atomic group or a bonding mode that causes a reaction such as vinyl group, carboxyl group, amino group, hydroxyl group, and epoxy group.

  In addition, a resin solution such as varnish can be used without being cured by light or heat by dissolving a polymer having excellent heat resistance in advance such as polyimide and precipitating it by drying.

  In addition, a fine particle dispersion can also be used in that heat resistance and excellent light transmittance can be obtained. Examples of the fine particles include fine particles of silica, alumina, titania, calcium carbonate, aluminum hydroxide, acrylic resin, organic silicone resin, polystyrene, urea resin, formaldehyde condensate, etc., and one or more of these may be used. Mixed seeds are used. When fine particles are employed, they can be aggregated by being deposited by drying and used as an insulating layer. In order to improve the adhesion between the particles and between the substrate particles, the surface of the particles may be subjected to a photosensitive or heat-sensitive surface treatment.

  A small amount of a surface tension adjusting material such as a fluorine-based material, a silicone-based material, or a nonionic-based material can be added to the droplets of the insulating material as needed within a range that does not impair the intended function. These surface tension modifiers can control the wettability of the applied object, improve the leveling of the applied film, and help prevent the occurrence of coating crushing and the formation of distorted skin. is there.

  The viscosity of the droplet of the insulating material thus prepared is preferably in the range of 1 to 50 mPa · s. When applying a solution with a droplet discharge device, if the viscosity is less than 1 mPa · s, the periphery of the nozzle is easily contaminated by the outflow of the droplet, and if the viscosity is greater than 50 mPa · s, This is because clogging frequency increases and it becomes difficult to smoothly discharge droplets. More preferably, it is in the range of 5 to 20 mPa · s.

Furthermore, it is desirable that the surface tension of the droplet of the insulating material thus prepared falls within the range of 0.02 to 0.07 N / m. When the solution is applied by the droplet discharge device, if the surface tension is less than 0.02 N / m, the wettability of the droplet to the nozzle surface increases, and thus flight bending easily occurs, and 0.07 N / m is set. This is because if it exceeds, the shape of the meniscus at the nozzle tip is not stable, and it becomes difficult to control the discharge amount and the discharge timing of the droplets.
<About substrate>

Various substrates such as glass, quartz glass, Si wafer, plastic film, metal plate, and glass epoxy substrate can be used as the substrate on which the wiring pattern is formed. Also included are those in which a semiconductor film, a metal film, a dielectric film, an organic film or the like is formed as a base layer on the surface of these various material substrates.
<Droplet ejection method>

Here, although there are various ejection techniques for the droplet ejection method, it is preferable to use an inkjet method because a fine wiring pattern can be formed on demand. Examples of the ink jet method include a charge control method, a pressure vibration method, an electromechanical conversion method, an electrothermal conversion method, and an electrostatic suction method. In the charge control method, a charge is applied to a material with a charging electrode, and the flight direction of the material is controlled with a deflection electrode to be discharged from a discharge nozzle. In addition, the pressure vibration method is a method in which an ultra-high pressure of about 30 kg / cm ² is applied to the material and the material is discharged to the tip side of the discharge nozzle. When no control voltage is applied, the material moves straight and the discharge nozzle When a control voltage is applied, electrostatic repulsion occurs between the materials, and the materials are scattered and are not discharged from the discharge nozzle. The electromechanical conversion method utilizes the property that a piezoelectric element (piezoelectric element) is deformed by receiving a pulse-like electric signal. The piezoelectric element is deformed through a flexible substance in a space where material is stored. Pressure is applied, and the material is extruded from this space and discharged from the discharge nozzle.

  In the electrothermal conversion method, a material is rapidly vaporized by a heater provided in a space in which the material is stored to generate bubbles, and the material in the space is discharged by the pressure of the bubbles. In the electrostatic attraction method, a minute pressure is applied to a space in which a material is stored, a meniscus of material is formed on the discharge nozzle, and an electrostatic attractive force is applied in this state before the material is drawn out. In addition to this, techniques such as a system that uses a change in the viscosity of a fluid due to an electric field and a system that uses a discharge spark are also applicable. The droplet discharge method has an advantage that the use of the material is less wasteful and a desired amount of the material can be accurately disposed at a desired position. Note that the amount of one droplet of the liquid material ejected by the droplet ejection method is, for example, 1 to 300 nanograms.

Next, a manufacturing apparatus used when manufacturing the multilayer circuit board according to the present invention will be described. As this manufacturing apparatus, a droplet discharge apparatus that manufactures a multilayer circuit board by discharging (dropping) droplets from a droplet discharge head onto a substrate is used.
<Droplet ejection device>

  FIG. 1 is a perspective view of the droplet discharge device 10. In FIG. 1, the X direction is the left-right direction of the base 12, the Y direction is the front-rear direction, and the Z direction is the up-down direction. The droplet discharge device 10 mainly includes a droplet discharge head 20 and a table 46 on which a substrate 31 is placed. The operation of the droplet discharge device 10 is configured to be controlled by the control device 23.

  The table 46 on which the substrate 31 is placed can be moved and positioned in the Y direction by the first moving means 14, and can be swung and positioned in the θz direction by the motor 44. On the other hand, the droplet discharge head 20 can be moved and positioned in the X direction by the second moving means, and can be moved and positioned in the Z direction by the linear motor 62. The droplet discharge head 20 can be swung and positioned in the α, β, and γ directions by motors 64, 66, and 68, respectively. Thereby, the droplet discharge device 10 is configured to accurately control the relative position and posture between the ink discharge surface 20P of the droplet discharge head 20 and the substrate 31 on the table 46. Yes.

  FIG. 2 is a cross-sectional view of the droplet discharge head 20. The droplet discharge head 20 discharges the liquid 21 from the nozzle 91 by a droplet discharge method. Various known technologies such as a piezo method in which a liquid material is discharged using a piezo element as a piezoelectric element and a method in which a liquid material is discharged by bubbles generated by heating ink are used as a droplet discharge method. Can be applied. Among these, the piezo method has an advantage that it does not affect the composition of the material because no heat is applied to the liquid material. Therefore, the above-described piezo method is employed in the droplet discharge head 20 shown in FIG.

  In the head main body 90 of the droplet discharge head 20, a reservoir 95 and a plurality of liquid chambers 93 branched from the reservoir 95 are formed. The reservoir 95 is a flow path for supplying the liquid 21 to each liquid chamber 93. In addition, a nozzle plate constituting an ejection surface is attached to the lower end surface of the head main body 90. In the nozzle plate, a plurality of nozzles 91 for discharging the liquid 21 are opened corresponding to the respective liquid chambers 93. A flow path is formed from each liquid chamber 93 toward the corresponding nozzle 91. On the other hand, a diaphragm 94 is attached to the upper end surface of the head main body 90. The diaphragm 94 constitutes a wall surface of each liquid chamber 93. Piezo elements 92 are provided outside the diaphragm 94 so as to correspond to the liquid chambers 93. The piezo element 92 is obtained by holding a piezoelectric material such as crystal between a pair of electrodes (not shown). The pair of electrodes is connected to the drive circuit 99.

  When a voltage is applied from the drive circuit 99 to the piezo element 92, the piezo element 92 expands or contracts. When the piezo element 92 contracts and deforms, the pressure in the liquid chamber 93 decreases, and the liquid 21 flows from the reservoir 95 into the liquid chamber 93. Further, when the piezo element 92 expands and deforms, the pressure in the liquid chamber 93 increases and the liquid 21 is discharged from the nozzle 91. Note that the amount of deformation of the piezo element 92 can be controlled by changing the applied voltage. Further, the deformation speed of the piezo element 92 can be controlled by changing the frequency of the applied voltage. In other words, the discharge condition of the liquid 21 can be controlled by controlling the voltage applied to the piezo element 92.

  The capping unit 22 shown in FIG. 1 is for capping the ejection surface 20P when the droplet ejection apparatus 10 is on standby to prevent the ejection surface 20P of the droplet ejection head 20 from drying. The cleaning unit 24 sucks the inside of the nozzle in order to remove clogging of the nozzle in the droplet discharge head 20. The cleaning unit 24 can also wipe the ejection surface 20P in order to remove dirt on the ejection surface 20P in the droplet ejection head 20.

  Next, an example of a multilayer circuit board manufactured using the multilayer circuit board forming method of the present embodiment will be described.

  FIG. 3 is an explanatory diagram of the multilayer circuit board 30. As shown in FIG. 3, the multilayer circuit board 30 includes a lower wiring layer 32 and an upper wiring layer 36 with an insulating layer 54 interposed therebetween. The multilayer circuit board 30 includes a flexible film substrate 31 made of polyimide or the like. An insulating layer 51 is formed on the surface of the film substrate 31. The insulating layer 51 is made of an electrically insulating material such as an acrylic ultraviolet curable resin.

  A wiring layer 32 is formed on the surface of the insulating layer 51. The wiring layer 32 is a conductive material such as Ag. An insulating layer 52 is formed in a region where the wiring layer 32 is not formed on the surface of the insulating layer 51. By adopting the droplet discharge method, the line × space of the wiring layer 32 is miniaturized to about 30 μm × 30 μm, for example.

  An insulating layer 54 is formed so as to cover the wiring layer 32. The insulating layer 54 is also a resin material similar to that of the insulating layer 51. A wiring layer 34 (conduction post) is formed in a column shape so as to penetrate the insulating layer 54 from a part of the wiring layer 32. The wiring layer 34 (conduction post) is the same conductive material such as Ag as the wiring layer 32.

  An upper wiring layer 36 is formed on the surface of the insulating layer 54. Similarly to the lower wiring layer 32, the upper wiring layer 36 is also made of a conductive material such as Ag. The upper wiring layer 36 is connected to the upper end portion of the conduction post 34, and conduction with the lower wiring layer 32 is ensured.

  An insulating layer 56 is formed in a region where the wiring layer 36 is not formed on the surface of the insulating layer 54. Further, an insulating layer 58 as a protective film is formed so as to cover the wiring layer 36. These insulating layers 56 and 58 are also made of the same resin material as that of the insulating layer 51.

  In the present embodiment, the example of the multilayer circuit board 30 including the two wiring layers 32 and 36 has been described. However, the present invention is not limited to this, and the configuration includes three or more wiring layers. It is also possible.

  Next, the formation method of the multilayer circuit board of this embodiment is demonstrated. 4 (a) to 4 (d) and FIGS. 5 (e) to 5 (h) are process cross-sectional views illustrating a manufacturing process of a procedure for forming a multilayer circuit board. FIG. 6 is a flowchart showing an example of a method for forming a multilayer circuit board according to the present embodiment. The multilayer circuit board forming method according to the present embodiment includes a substrate cleaning process, an insulating layer forming process 1, a wiring layer forming process 1, a wiring layer forming process 2, an insulating layer forming process 2, an insulating layer forming process 3, and a wiring layer forming process. The process is roughly composed of a process 3, an insulating layer forming process 4, an insulating layer forming process 5, and a batch firing process. Hereinafter, each step will be described in detail.

  In the substrate cleaning process in step S1 of FIG. 6, the film-like substrate 31 is cleaned. The method for cleaning the substrate 31 is a dry cleaning method using UV. Specifically, excimer UV light having a wavelength of 172 nm is irradiated on the surface of the film-like substrate 31 for about 300 seconds. In addition, you may wash | clean by irradiating the surface of the film-form board | substrate 31 with a normal pressure. Further, although a dry cleaning method using UV light is adopted, this is not particular, and the film-like substrate 31 may be cleaned with a solvent such as water. When a solvent such as water is used, the cleaning effect can be further improved by using ultrasonic waves.

  Next, in the insulating layer forming step 1 in step S2 of FIG. 6, the insulating layer 51 is formed as shown in FIG. The insulating layer 51 is formed by using the droplet discharge device 10 and discharging and disposing the insulating material as droplets from the droplet discharge head 20 onto the substrate 31. The insulating layer 51 is formed on the substrate 31 by curing the arranged insulating material by the UV curing method. As specific UV curing conditions, excimer UV light having a wavelength of 365 nm was irradiated for about 4 seconds. That is, the insulating material was cured without heating, and the insulating layer 51 was formed to a thickness of about 4 μm.

  Next, in the wiring layer forming step 1 of step S3 in FIG. 6, as shown in FIG. 4B, the wiring layer 32 is formed. The wiring layer 32 is formed by using the droplet discharge device 10 to discharge and arrange the wiring material as droplets from the droplet discharge head 20 onto the insulating layer 51. The wiring material thus arranged is dried by a reduced pressure drying method to remove the solvent in the wiring material and form the wiring layer 32 on the insulating layer 51. The specific reduced-pressure drying conditions set the pressure at the time of pressure reduction to the range of 10-100 Pa, and reduced pressure for about 300 seconds. That is, the wiring material was dried without heating, and the wiring layer 32 was formed to a thickness of about 2 μm.

  Next, in the wiring layer forming step 2 in step S4 of FIG. 6, a wiring layer 34 (conduction post) is formed on the wiring layer 32 as shown in FIG. The method for forming the conductive posts 34 is the same as the method for forming the wiring layer 32, and thus the description thereof is omitted. A wiring layer 34 (conduction post) was formed to a height of about 8 μm.

  Next, in the insulating layer forming step 2 in step S5 of FIG. 6, as shown in FIG. 4D, the insulating layer 52 is formed on the insulating layer 51 so as to be substantially the same height as the wiring 32. The reason why the insulating layer 52 is formed to be substantially the same height as the wiring 32 is to maintain flatness. Note that the method for forming the insulating layer 52 is the same as the method for forming the insulating layer 51, and thus the description thereof is omitted. The insulating layer 52 was formed to a thickness of about 2 μm.

  Next, in the insulating layer forming step 3 in step S6 of FIG. 6, as shown in FIG. 5E, the insulating layer is formed on the insulating layer 52 so as to be substantially the same height as the wiring layer 34 (conduction post). 54 is formed. The reason why the insulating layer 54 is formed to be substantially the same height as the wiring layer 34 (conduction post) is to maintain flatness. At this time, in order to obtain conduction between the upper layer and the lower layer, the upper end portion of the conduction post 34 is not covered with the insulating layer 54. Note that the method for forming the insulating layer 54 is the same as the method for forming the insulating layer 51, and thus the description thereof is omitted. Then, the insulating layer 54 was formed to a thickness of about 8 μm.

  Next, in the wiring layer forming step 3 in step S7 of FIG. 6, as shown in FIG. 5F, the wiring layer 36 is formed on the insulating layer 54 so as to be electrically connected to the conductive posts 34. Since the formation method of the wiring layer 36 is the same as the formation method of the wiring layer 32, description is abbreviate | omitted. The wiring layer 36 is electrically connected to the wiring layer 34 (conduction post). Then, the wiring layer 36 was formed to a thickness of about 2 μm.

  Next, in the insulating layer forming step 4 in step S8 in FIG. 6, as shown in FIG. 5G, the insulating layer 56 is formed on the insulating layer 54 so as to be substantially the same height as the wiring 36. The reason why the insulating layer 56 is formed to be substantially the same height as the wiring layer 36 is to maintain flatness. Note that the method for forming the insulating layer 56 is the same as the method for forming the insulating layer 51, and thus the description thereof is omitted. Then, the insulating layer 56 was formed to a thickness of about 2 μm.

  Next, in the insulating layer forming step 5 in step S9 of FIG. 6, as shown in FIG. 5H, an insulating layer 58 as a protective film is formed so as to cover the wiring layer 36 and the insulating layer 56. Note that the method for forming the insulating layer 58 is the same as the method for forming the insulating layer 51, and thus the description thereof is omitted. The insulating layer 58 was formed to a thickness of about 8 μm.

  Finally, in the batch firing step of step S10 in FIG. 6, the wiring layers 32, 34, and 36 and the insulating layers 51, 52, 54, 56, and 58 stacked on the film-like substrate 31 are fired at once. The firing treatment is usually performed in the air, but can be performed in an inert gas atmosphere such as nitrogen, argon, or helium, or in a reducing atmosphere such as hydrogen, if necessary. The treatment temperature of the firing treatment includes the boiling point (vapor pressure) of the dispersion medium, the type and pressure of the atmospheric gas, the thermal behavior such as dispersibility and oxidation of fine particles, the presence and amount of coating material, the heat resistance temperature of the substrate It is determined as appropriate. In the present embodiment, the wiring material and the insulating material were baked at 200 ° C. for about 60 minutes in a clean oven in the atmosphere. As described above, the wiring layers 32, 34, and 36 ensure electrical contact between the fine particles.

Such a baking process can be performed by lamp annealing in addition to a process using a normal hot plate, an electric furnace, or the like. The light source used for lamp annealing is not particularly limited, but excimer laser such as infrared lamp, xenon lamp, YAG laser, argon laser, carbon dioxide laser, XeF, XeCl, XeBr, KrF, KrCl, ArF, ArCl, etc. Can be used as a light source. These light sources generally have a power output in the range of 10 W or more and 5000 W or less, but in this embodiment, a range of 100 W or more and 1000 W or less is sufficient. And the multilayer circuit board 30 as shown in FIG. 3 was obtained.
<Electro-optical device>

  Next, a liquid crystal display device which is an example of the electro-optical device according to the invention will be described.

  FIG. 7 is an exploded perspective view of a liquid crystal display device as an electro-optical device.

  As shown in FIG. 7, the liquid crystal display device 500 includes the multilayer circuit board 30 described in the present embodiment. The liquid crystal display device 500 includes a color display liquid crystal panel 2, a multilayer circuit board 30 connected to the liquid crystal panel 2, and a liquid crystal driving IC 100 mounted on the multilayer circuit board 30. Note that an illumination device such as a backlight and other auxiliary devices are attached to the liquid crystal panel 2 as necessary. The liquid crystal display device 500 has a COF (Chip / On / Film) structure.

  The liquid crystal panel 2 has a pair of substrates 5a and 5b bonded by a sealing material 4, and liquid crystal is sealed in a gap (cell gap) formed between the substrates 5a and 5b. The liquid crystal is sandwiched between the substrate 5a and the substrate 5b. These substrates 5a and 5b are generally formed of a translucent material such as glass or synthetic resin. A polarizing plate 6a is attached to the outer surfaces of the substrate 5a and the substrate 5b.

  An electrode 7a is formed on the inner surface of the substrate 5a, and an electrode 7b is formed on the inner surface of the substrate 5b. These electrodes 7a and 7b are formed of a light-transmitting material such as ITO ((Indium / Tin / Oxide): indium tin oxide). The substrate 5a has a projecting portion that projects from the substrate 5b, and a plurality of terminals 8 are formed on the projecting portion. These terminals 8 are formed simultaneously with the electrodes 7a when the electrodes 7a are formed on the substrate 5a. Accordingly, these terminals 8 are made of, for example, ITO. These terminals 8 include one that extends integrally from the electrode 7a and one that is connected to the electrode 7b via a conductive material (not shown).

  On the other hand, wiring patterns 39a and 39b are formed on the surface of the multilayer circuit board 30 by the wiring pattern forming method according to the present embodiment. That is, an input wiring pattern 39a is formed from one short side to the center of the multilayer circuit board 30, and an output wiring pattern 39b is formed from the other short side to the center. Electrode pads (not shown) are formed at the ends of the input wiring pattern 39a and the output wiring pattern 39b on the center side.

  A liquid crystal driving IC 100 is mounted on the surface of the multilayer circuit board 30. Specifically, a plurality of bump electrodes formed on the active surface of the liquid crystal driving IC 100 are connected to a plurality of electrode pads formed on the surface of the multilayer circuit board 30 by an ACF (Anisotropic Conductive Film). Conductive film) 160. The ACF 160 is formed by dispersing a large number of conductive particles in a thermoplastic or thermosetting adhesive resin. As described above, the so-called COF structure is realized by mounting the liquid crystal driving IC 100 on the surface of the multilayer circuit board 30.

  The multilayer circuit board 30 including the liquid crystal driving IC 100 is connected to the substrate 5 a of the liquid crystal panel 2. Specifically, the output wiring pattern 39b of the multilayer circuit board 30 is electrically connected to the terminal 8 of the board 5a via the ACF 140. Since the multilayer circuit board 30 has flexibility, space saving can be realized by freely folding it.

In the liquid crystal display device 500 configured as described above, a signal is input to the liquid crystal driving IC 100 via the input wiring pattern 39 a of the multilayer circuit board 30. Then, a driving signal is output from the liquid crystal driving IC 100 to the liquid crystal panel 2 via the output wiring pattern 39 b of the multilayer circuit board 30. As a result, an image is displayed on the liquid crystal panel 2.
<Electronic equipment>

  Next, an electronic apparatus equipped with a liquid crystal display device as an electro-optical device of this embodiment will be described.

  FIG. 8 is a perspective view of a mobile phone as an electronic device.

  As shown in FIG. 8, the mobile phone 1000 includes a display unit 1001. The display unit 1001 of the mobile phone 1000 is equipped with a liquid crystal display device 500 as an electro-optical device provided with the multilayer circuit board 30 of this embodiment. Therefore, the mobile phone 1000 with excellent electrical reliability can be provided.

  In the embodiment as described above, the following effects are obtained.

(1) Since the wiring layers 32, 34, and 36 and the insulating layers 51, 52, 54, 56, and 58 are baked at the same time, the thermal history is the same, so the film quality can be made almost uniform. Stable wiring layers 32, 34, and 36 can be formed. Similarly, since the film quality of the insulating layers 51, 52, 54, 56, and 58 can be made almost uniform, the insulating layers 51, 52, 54, 56, and 58 having good insulating characteristics can be formed. As a result, it is possible to form the multilayer circuit board 30 capable of suppressing variations in electrical characteristics. In addition, since the number of times of firing can be reduced as compared with the conventional method because the firing process is performed once, the processing time can be shortened, which is efficient.
(2) Since the drying means of the wiring material is a reduced pressure drying method, the solvent in the wiring material can be removed without heating, and therefore, the wiring material can be dried without applying thermal stress. The wiring layers 32, 34 and 36 having a uniform film quality can be formed as compared with the method.
(3) Since the insulating material drying means is a light irradiation method, the insulating material can be dried by photoreaction without heating, and therefore, the insulating material can be cured without applying thermal stress. Insulating layers 51, 52, 54, 56 and 58 having a uniform film quality can be formed.
(4) Since the wiring layers 32, 34, and 36 having stable electrical characteristics and the insulating layers 51, 52, 54, 56, and 58 having good insulating characteristics can be formed, a multilayer that can reduce variations in electrical characteristics. A circuit board 30 can be provided.
(5) Since the multilayer circuit board 30 capable of reducing variations in electrical characteristics is provided, the liquid crystal display device 500 as an electro-optical device having stable electrical characteristics can be provided.
(6) Since the liquid crystal display device 500 is provided as an electro-optical device with stable electrical characteristics, the mobile phone 1000 as a highly reliable electronic device can be provided.

  The present invention has been described above with reference to preferred embodiments. However, the present invention is not limited to the above-described embodiments, and includes the following modifications and the scope in which the object of the present invention can be achieved. Thus, it can be set to any other specific structure and shape.

  (Modification 1) Although the multilayer circuit board 30 is used in the liquid crystal display device 500 as an electro-optical device in the above-described first embodiment, the invention is not limited to this. For example, in addition to an apparatus having an electro-optic effect that changes the light transmittance by changing the refractive index of a substance by an electric field, an apparatus that converts electrical energy into optical energy is also included. That is, an organic EL (Electro-Luminescence) device, an inorganic EL device, a plasma display device, an electrophoretic display device, a display device using an electron-emitting device (Field-Emission Display, Surface-Conduction-Electron-Emitter Display, etc.) It can also be widely used for light-emitting devices and the like.

  (Modification 2) Although the liquid crystal display device 500 as an electro-optical device is used in the mobile phone 1000 in the above-described embodiment, the present invention is not limited to this. For example, electronic books, personal computers, digital still cameras, LCD TVs, viewfinder type or monitor direct view type video tape recorders, car navigation devices, pagers, electronic notebooks, calculators, word processors, workstations, videophones, POS terminals, touch panels It can be suitably used as an image display means of electronic equipment such as. In either case, an electronic device with excellent electrical reliability can be provided.

1 is a perspective view illustrating a schematic configuration of a droplet discharge device according to an embodiment. Sectional drawing of a droplet discharge head. Explanatory drawing of a multilayer circuit board. (A)-(d) is process sectional drawing which shows the manufacturing process of the procedure which forms a multilayer circuit board. (E)-(h) is process sectional drawing which shows the manufacturing process of the procedure which forms a multilayer circuit board. The flowchart which shows the formation method of a multilayer circuit board. The disassembled perspective view of a liquid crystal display device. The perspective view of a mobile telephone.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Droplet discharge apparatus, 20 ... Droplet discharge head, 30 ... Multilayer circuit board, 31 ... Film-like board | substrate, 32 ... Wiring layer, 34 ... Wiring layer (conduction post), 36 ... Wiring layer, 51 ... Insulating layer 52 ... Insulating layer, 54 ... Insulating layer, 56 ... Insulating layer, 58 ... Insulating layer, 500 ... Liquid crystal display device as electro-optical device, 1000 ... Mobile phone as electronic device.

Claims (6)

A method of manufacturing a multilayer circuit board by alternately laminating wiring layers and insulating layers on a substrate,
Applying a wiring material on the substrate using a droplet discharge method, and drying the wiring material to form the wiring layer;
Applying an insulating material on the substrate using a droplet discharge method, and drying the insulating material to form the insulating layer;
A step of collectively firing the wiring layer and the insulating layer;
A method for producing a multilayer circuit board, comprising: In the manufacturing method of the multilayer circuit board according to claim 1,
In the step of forming the wiring layer, the wiring material drying means is a reduced pressure drying method. In the manufacturing method of the multilayer circuit board according to claim 1,
In the step of forming the insulating layer, the means for drying the insulating material is a light irradiation method.   A multilayer circuit board formed using the multilayer circuit board manufacturing method according to any one of claims 1 to 3.   An electro-optical device comprising the multilayer circuit board according to claim 4. An electronic apparatus comprising the electro-optical device according to claim 5.

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