JP2004172282A - Method of manufacturing circuit, and circuit board equipped with the circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce waste of material and to enable a circuit which is extremely excellent in electrical conductivity to be easily manufactured through a simple process. <P>SOLUTION: A colloidal solution Q where conductive nano metal powder 20 having 0.1 to 100 nm of an average grain diameter is dispersed is applied on the surface of a board 14 where an ink resin 13 is printed through a printing method, the colloidal solution Q and the ink resin 13 are heated up, the ink resin 13 is decomposed and sublimated, the conductive nano metal powder 20 residing thereon is removed, a liquid present in the colloidal solution Q on the surface of a non-printed area 14B is evaporated, and the conductive nano metal powder 20 is fused together to form a conductive metal layer 21 made of only nano metal powder on the surface of the non-printed areas 14B of the board 14 for the formation of a circuit. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a circuit and a circuit board provided with the circuit, and more particularly, a circuit having a fine and high-precision printing pattern, which is used as an electromagnetic wave shield or the like from an electric device, is formed from a conductive nano metal powder. To form.
[0002]
[Prior art]
Conventionally, as a method of forming a circuit pattern, there is a photolithographic method of performing exposure using a photosensitive resist when forming a pattern, and the photolithographic method includes a subtractive method and an additive method as described below. It can be divided into two types.
[0003]
In the above subtractive method, a conductive layer is previously formed on a substrate by copper foil, electroless copper plating or electrolytic copper plating, and then a photosensitive resist (photoresist) is formed on the conductive layer. The photosensitive resist is exposed only to a predetermined pattern through a photomask. Then, the unexposed portion of the photoresist is washed and cured by development, and then the electrically conductive layer is immersed in an etching solution (such as ferric chloride) to expose the unexposed portion of the conductive layer. Only the portion is corroded (etched), and finally the photoresist is peeled off with alkali (KOH) to form a circuit having only a predetermined pattern.
[0004]
In the additive method, a layer of a photosensitive resist is previously formed on a substrate, as opposed to the subtractive method, and the photosensitive resist is exposed only to a predetermined pattern through a photomask. The photoresist in the unexposed portions is washed by development, and a pattern of the photosensitive resist is formed only in the exposed portions. Next, the entire surface is subjected to electroless copper plating and subsequently to electrolytic plating, and finally the photoresist is peeled off to form a non-exposed portion as a circuit pattern.
[0005]
A printing method similar to the above-described additive method is also used. In this printing method, a circuit is formed by printing a predetermined pattern using conductive ink. This method is expected to be an inexpensive process because the material cost is low and the manufacturing equipment is cheap.
[0006]
Further, various proposals have conventionally been made as a method of forming a fine circuit pattern. For example, Japanese Patent Application Laid-Open No. H10-242141 proposes a fine oxide film pattern in which a fine pattern composed of an electric field assisting oxide film is formed in a fine pattern formation region by applying a predetermined voltage between nanoprobes. ing.
[0007]
[Patent Document 1]
JP-A-10-242141
[0008]
[Problems to be solved by the invention]
However, the biggest problem of the subtractive method is that a large amount of harmful waste liquid used for etching is generated. This waste liquid contains a large amount of metal, so that waste liquid treatment is costly and is not good for the environment. In addition, the conductive layer is an expensive layer, and it is very wasteful to discard an excess portion. Further, a device for exposing through a photomask is very expensive, so that there is a problem in that the cost is high. In addition, since the etching corrodes the conductive layer not only in the thickness direction but also in the plane direction, when the thickness of the conductive layer is large, side etching proceeds, the line width becomes narrower than a predetermined pattern, and the extreme In some cases, disconnection may occur.
[0009]
The problem of the additive method is that the materials are expensive for both electroless copper plating and electrolytic copper plating, and the cost increases because the number of processes increases. Further, since an exposure process is involved, very expensive equipment is required as in the subtractive method.
[0010]
In addition, the above printing method uses a conductive ink dispersed in a resin as the conductive ink. Particularly, when the printing object is a resin or the like, a high temperature cannot be applied, and as a result, Poor conductivity may limit applications. Further, if a large amount of conductive metal powder is added to the ink to improve the conductivity, the printability deteriorates, and if electrolytic copper plating or the like is applied to the print pattern, the number of steps increases and the cost increases.
[0011]
Further, in Japanese Patent Application Laid-Open No. Hei 10-242141, good conductivity may not be obtained depending on the thickness of the electric field assisting oxide film or the state of the film formation, or an expensive device for applying a voltage or the like is required. This leads to higher costs.
[0012]
An ink jet method or the like in which ink is ejected in the form of dots is also conceivable, but it is difficult to form a linear pattern such as a circuit, and pinholes and disconnections are likely to occur. In addition, the printing speed of the ink jet method is low. For this reason, attempts have been made to improve the printing speed by increasing the number of heads. However, when the number of heads is increased, the frequency of ink clogging failures increases, and management becomes extremely difficult.
[0013]
The present invention has been made in view of the above-described problems, and has as its object to provide a method for manufacturing a circuit that can easily form a circuit with extremely good conductivity by reducing waste of materials in a simple process. I have.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, the present invention prints an ink resin made of a thermoplastic resin on a non-circuit pattern area on a substrate surface,
Next, the entire surface of the ink resin printed portion of the substrate and the non-printed portion to be a circuit pattern region, the average particle diameter is coated with a colloid solution in which conductive nano metal powder of 0.1 nm to 100 nm is dispersed,
Next, the substrate is heated, and the ink resin is decomposed and sublimated in the ink resin printed portion to remove the conductive nanometal powder on the surface thereof, and the colloid solution is removed in the non-printed portion of the circuit pattern region. The present invention provides a method for manufacturing a circuit in which a conductive nanometal powder is fused by evaporating only a liquid therein to form a circuit with a conductive metal layer composed of only the nanometal powder.
[0015]
The method of manufacturing a circuit according to the present invention has been made based on the inventor's intensive research and found the following.
By reducing the particle size of the conductive metal powder to about 0.1 nm to 100 nm, the activity of the metal surface becomes extremely high, the fusion temperature of the metal is significantly reduced, and the metal powders can be fused at a low temperature. I found out. For example, in the case of silver, the melting point of the bulk is 963 ° C., but when the nano silver powder is about 0.1 nm to 100 nm, the fusion temperature is remarkably lowered to about 200 ° C.
Therefore, a circuit consisting of a conductive metal layer can be formed by fusing the nano metal powders together.However, when the nano metal powder becomes finer, the danger of dust explosion increases, so that the nano metal powder is dispersed colloidally in a solvent. It is necessary to stabilize and use. However, the colloidal dispersion of this nanometallic powder in a solvent has a very low viscosity, so rather than forming circuits by printing this colloidal solution of nanometallics, we combine printing and lift-off technologies. That's how it works.
[0016]
In the manufacturing method of the present invention, as described above, as a colloid solution in which nano metal powder is dispersed in a liquid, the surface of the ink resin printed portion of the non-circuit pattern region and the surface of the non-printed portion of the circuit pattern region Because of the application, the metal colloid of very fine nanoparticles having excellent conductivity can be applied uniformly and workability is improved.
By heating after application, first, the ink resin is sublimated and decomposed, and the conductive nano metal powder applied to the surface of the printed portion of the ink resin by the sublimation decomposition can be removed. At the same time, due to the heating, the non-printed portions fuse the nano metal powders together to form a conductive metal layer consisting of only the very conductive nano metal powder, thereby forming a circuit composed of the conductive metal layer. can do.
[0017]
The particle size of the conductive nanometal powder is an important factor that greatly affects the fusing temperature, and as a result of various studies, the average particle size of the conductive nanometal powder is 0.1 nm to 100 nm. This is because, if the thickness is smaller than 0.1 nm, the activity becomes extremely high even at room temperature, agglomeration and the like occur partially between the conductive nanometal powders, and the oxidation of the surface increases, and a metal oxide film is formed. is there. On the other hand, if it is larger than 100 nm, the fusion temperature is not lowered, the metal film cannot be formed at a low temperature, and it is difficult to scatter with the ink resin at the time of heating in the printed portion. Further, the smaller the particle size, the lower the fusion temperature, so the preferred particle size is 1 nm to 50 nm, more preferably 1 nm to 10 nm. In addition, the conductive nanometal powder can be made to have a very low resistance by melting each other and forming a metal film.
[0018]
Further, the thickness of the metal coating is preferably 1 μm to 15 μm without fusing the conductive nano metal powder. If the thickness is less than 1 μm, disconnection is likely to occur and the conductivity is not good. On the other hand, even if the thickness is more than 15 μm, the conductivity is sufficiently satisfied, the material cost is increased and waste is caused, and the surface flatness is deteriorated.
[0019]
The decomposition sublimation temperature of the thermoplastic resin used as the ink resin is lower than the fusion temperature between the conductive nanometal powders.
This is because, before the nano metal powder in the nano metal colloid solution applied to the surface of the ink resin was fused and formed a metal film, the ink resin was decomposed and sublimated to be applied to the surface of the ink resin. This is for removing the nano metal powder.
Therefore, it is preferable to gradually heat from a low temperature state in which the ink resin is decomposed and sublimated to a temperature at which the metal powders fuse together.
[0020]
The ink resin is preferably a thermoplastic resin that decomposes at a temperature as low as possible, and may be at least one resin selected from the group consisting of thermoplastic acrylic resins, butyral resins, cellulose resins, and polyester resins. Preferably, the selection can be made in accordance with printability.
[0021]
The conductive nanometal powder is preferably made of any one of gold, silver, copper, platinum, and palladium, or a mixture thereof. These metals have some degree of conductivity and can be nanoparticles. In particular, silver is preferable in terms of cost and conductivity. The shape of the metal powder can be various shapes such as a sphere, an oval sphere, a column, a scale, and a fiber.
[0022]
It is preferable that the above-mentioned heating temperature is 200 ° C to 350 ° C. When the temperature is lower than 200 ° C., the metal powder is not melted, the metal film is not easily formed, and the ink resin is hardly decomposed and sublimated. On the other hand, if the temperature is higher than 350 ° C., the substrate may be thermally degraded. The temperature is more preferably from 200C to 250C. The heating temperature and the heating time can be appropriately set so that the formation of the metal film and the decomposition and sublimation of the ink resin can be performed efficiently. The heating time is preferably 5 minutes to 120 minutes, more preferably 10 minutes to 60 minutes.
[0023]
The liquid contained in the colloid solution as a medium is preferably aqueous or a solvent such as toluene or alcohol, and is preferably a liquid having high volatility and easily evaporating.
[0024]
It is preferable that the conductive nano metal powder is uniformly dispersed in the colloid solution at a volume ratio of 10% to 95% of the total volume of the colloid solution. Thereby, nano metal powder can be efficiently and uniformly contacted.
The reason why the above range is set is that when the range is smaller than the above range, the metal powders are difficult to sufficiently adhere to each other, and it is difficult to form a metal film during heating. On the other hand, if it is larger than the above range, the colloid aggregates without being stabilized. For this reason, there is a problem that the particle diameter becomes large and it becomes difficult to melt at a low temperature. In addition, it is more preferably 30% to 80%.
[0025]
The colloid solution can be applied by a method selected from a bar coat, spin coater, screen printing, roll coater, and the like.
The colloid solution can be prepared by a usual method. For example, when a reducing agent such as an amine is used for an aqueous solution of chloroauric acid, gold is reduced and precipitated. At this time, a surfactant or a polymer can be adsorbed as a protective colloid on the surface of the gold particles to stabilize the colloid.
[0026]
As a printing method of the ink resin on the substrate, it is preferable to use an intaglio offset printing method in which the ink resin is once transferred from the intaglio to the blanket, and then the ink resin is transferred from the blanket to the substrate. Further, conventionally known printing methods such as flat plate offset printing and relief printing can also be used. The printing thickness of the ink resin is preferably 1 μm to 10 μm in order that the printed portion can be easily decomposed and sublimated and the non-printed portion becomes a good circuit pattern.
[0027]
In the intaglio offset printing using an intaglio printing plate, the thickness of the ink can be freely controlled by changing the depth of the intaglio printing, and printing with a relatively large thickness is possible. In addition, the resolution of the intaglio printing is very high, and it is possible to faithfully reproduce a very fine pattern of about 10 μm by printing.
[0028]
Preferably, the surface rubber of the blanket is made of silicone rubber, the intaglio is made of glass, and the ink resin contains a solvent having a small degree of swelling with respect to the blanket.
[0029]
In the case of intaglio offset printing, in particular, if silicon rubber is used as the surface rubber of the blanket, it is possible to transfer 100% of the ink transferred from the intaglio to the blanket to the substrate, and to perform printing with a sufficiently thick ink in one pass. Is also possible. Moreover, since the ink is separated only once, the shape of the printed matter is very good, and a very fine shape of about 10 μm can be reproduced by printing. Therefore, good printing can be performed so that the non-printed portion becomes a circuit pattern.
[0030]
In addition, the intaglio plate can form a very good intaglio plate by etching a metal or glass by photolithography, so a very good printing can be performed by combining a blanket with a smooth and good transferability. It becomes possible. In the present invention using nano metal powder, intaglio offset printing was found to be a very suitable printing method.
[0031]
As a result of studying the intaglio, it was found that the smoothness of the surface was very important. If the smoothness of the surface is poor, ink remains on the surface of the intaglio when doctoring the ink, and stains (ground stains) occur in non-image areas. In order to produce an intaglio with good surface smoothness at the lowest cost, etching is performed using glass. Glass can be used with both soda glass and non-alkali glass. However, since non-alkali glass is very expensive, soda glass is sufficient in fields where high dimensional accuracy is not required. It is also possible to create an intaglio by etching a metal material. As the metal material, various materials can be used. In particular, materials such as stainless steel, 42 alloy (Fe—Ni alloy (Ni 42%)), copper, brass, and invar which have good etching properties can be used. In the case of an intaglio using these metals, it is necessary to improve the smoothness by lapping and polishing the surface to mirror finish. Further, in order to improve the mechanical strength of the metal surface, it is conceivable to perform a surface strengthening treatment such as hard chrome plating on the outermost surface. It is necessary to design the depth of the intaglio according to the desired thickness of the ink film, but usually it is preferably about 1 to 50 μm. About half the depth of the intaglio ink is transferred to the blanket, and almost 100% is printed on the substrate using a silicone rubber blanket.
[0032]
If the surface rubber hardness of the blanket is high, it is difficult to sufficiently transfer the ink of the plate without deforming the rubber. On the other hand, if the hardness is low, the deformation of the rubber becomes large, and it is difficult to perform printing with high accuracy. Therefore, from the above-mentioned viewpoint, the rubber hardness of the blanket is JIS-A hardness of 70 to 20, more preferably 60 to 30. In addition, the surface shape of the blanket has a great influence on the print shape, especially as the print pattern becomes finer. For forming a fine pattern having a line width of about 20 μm, the surface roughness is preferably 1.0 μm or less as a 10-point average roughness, more preferably 0.5 μm or less. When silicone rubber is used as the material, ink transfer is good.
[0033]
The solvent contained in the ink is an important factor that governs printability in offset printing. Particularly, during printing, the solvent in the ink always contacts the blanket, so that the surface rubber of the blanket swells with the solvent and the wettability of the surface changes. In general, if a solvent having a small swelling is used, the surface wettability of the blanket has little change and stable printing can be performed. However, it is better to select a solvent which swells a little in consideration of the acceptability with the blanket. However, continuous printing greatly changes the wettability of the surface due to swelling, so that stable printing cannot be performed. Problems such as an increase in surface wettability and an increase in the line width of printing, transfer of minute stains on the plate surface, and poor transfer to a printing medium occur. The solvent in the surface rubber is evaporated and dried by heating the surface rubber, and can be completely returned to the original surface state. Therefore, the ease of evaporation and drying depends on the heating temperature, the boiling point of the solvent and the thickness of the rubber. However, if the heating temperature is 40 ° C. to 200 ° C., it is possible to dry effectively. For heating and drying, it is effective to directly heat the blanket cylinder. However, the heating is not particularly limited, and drying may be performed by blowing hot air from outside the blanket. In addition, the drying can be always heated, but the heating and cooling may be repeated irregularly.
[0034]
After drying, if the surface temperature of the blanket is high, there is a problem that the plate swells due to heat due to contact with the plate, and the printing accuracy is deteriorated. For this reason, the surface temperature of the plate usually needs to be kept within ± 1 ° C., and of course, it is assumed that the room temperature in the clean room is also kept within that range, but the temperature of the blanket surface needs to be kept within + 5 ° C. The reason why the variation is larger than the surface temperature of the printing plate is that heat is released to the intaglio when the blanket contacts and rolls. If the temperature is + 5 ° C or more, the temperature of the intaglio becomes + 1 ° C or more and adversely affects printing accuracy. . The most effective way to keep the surface temperature of the blanket at + 5 ° C. or higher is to forcibly cool the surface of the blanket with cold air, and the blanket cylinder is also made of metal and has a large heat capacity, so it can be cooled effectively. . In addition, it is also possible to rapidly cool the blanket surface temperature by rolling on a metal platen. In addition, there is no particular limitation, and various methods are possible.
[0035]
The substrate is a resin having transparency, and the ink resin is printed so that a non-printed portion becomes a circuit pattern, and the circuit pattern can be a mesh having a line width of 5 to 40 μm and a line interval of 50 to 500 μm. . This is particularly suitable for forming a circuit having many high-density line portions. The printing of the ink resin may be performed on only one side of the substrate, or may be performed on both sides.
[0036]
As the transparent resin, a resin that can be continuously processed into a roll is preferable. Polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene, polypropylene and polystyrene, and vinyls such as polyvinyl chloride (PVC) and polyvinylidene chloride are preferred, although those having high transparency and high heat resistance are preferred. , Polyethersulfone, polycarbonate, polyamide, polyimide, acrylic resin and the like. Among these, PET films having very good permeability and being inexpensive are most desirable.
[0037]
It has been found that it is important to print and form as fine a pattern as possible in order to improve the electromagnetic wave shielding performance particularly at 1 to 1000 MHz for the print pattern. As a result of intensive research, it has been found that a line width of 5 to 40 μm is good. If the line width exceeds 40 μm, the aperture ratio cannot be improved and the transmittance decreases. In addition, the geometrical pattern of the pattern is confirmed with the naked eye and visibility is poor. On the other hand, if the line width is smaller than 5 μm, the electromagnetic wave shielding effect is deteriorated and disconnection is apt to occur when forming a pattern, and it is extremely difficult to stably produce a good product. In consideration of PDP (plasma display panel) applications, it is necessary to sufficiently cut the electric field component at 1 to 1000 MHz as an electromagnetic wave shielding characteristic. If the line spacing is 50 to 500 μm, both transparency and electromagnetic shielding properties can be achieved. When the line spacing is smaller than 50 μm, the transmittance sharply decreases. On the other hand, if it is larger than 500 μm, the electromagnetic wave shielding property is deteriorated.
[0038]
As another printing method, it is preferable to obtain high printing accuracy equivalent to that of the photolithographic method because the application is widened. In screen printing, if the line width is smaller than 100 μm, it may be difficult to faithfully reproduce the shape of the plate. Further, in principle, the screen gauze exerts different forces on the central part and the peripheral part of the screen, and the elongation is different. For this reason, the printing accuracy of the pattern may be deteriorated in the central portion and the peripheral portion.
[0039]
In letterpress printing (or flexographic printing), the thickness of a single ink film is as thin as 0.1 μm to 1.0 μm, and the resolution of the plate itself is slightly lower. In order to clarify the non-printed portion, a certain ink film thickness is required. In the relief printing plate, there is a phenomenon called a marginal zone in which ink spreads around the pattern, and similarly, it may be difficult to faithfully reproduce the pattern.
[0040]
Lithographic offset printing using a lithographic plate and, in recent years, a waterless lithographic plate (trade name TAN manufactured by Toray) using silicone rubber in a non-image area have been increasingly used as a plate. Resolution is higher than using PS plate with water.
[0041]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, an ink resin is printed on the surface of the substrate by a printing method. As shown in FIGS. 1A, 1B, 1C, and 1D, a printing method uses a flat-plate intaglio offset printing press 10 to transfer the ink resin 13 from the intaglio 11 to the blanket 12 once. Intaglio offset printing for transferring the ink resin 13 from the blanket 12 to the substrate 14 is employed.
[0042]
The surface 12a of the blanket 12 is made of silicone rubber (rubber hardness JIS-A 40, room temperature-curable silicone rubber addition type, rubber thickness 300 μm), and the surface roughness is 0.1 μm as a 10-point average roughness. The intaglio 11 is a glass intaglio made of soda lime glass.
[0043]
The substrate 14 is a polyimide film having a thickness of 100 μm, and the ink resin 13 is an acrylic resin which is a thermoplastic resin, the viscosity of which is adjusted to 50 to 100 P with a solvent (butyl carbitol acetate) having a small degree of swelling with respect to the blanket 12. ing.
[0044]
When printing of ten sheets on the substrate 14 is completed, the flatbed-type intaglio offset printing press 10 applies hot air to the blanket 12 from the air outlet 15a of the heating device 15 to heat the blanket 12. The adjustment is performed for 5 minutes by adjusting the surface temperature of the blanket 12 to 80 ° C. The temperature in the clean room where the printing machine is installed is controlled at 23 ° C. ± 1 ° C., and the surface temperature of the intaglio 11 is also adjusted at 23 ° C. ± 1 ° C. Thus, the hot air is applied to the surface every ten printings to perform drying.
After the drying, cooling is performed for 5 minutes by blowing cold air to the blanket 12 from the air outlet 16a of the cooling device 16. The temperature of the blanket surface after cooling is adjusted within room temperature + 3 ° C. within the surface.
[0045]
According to the above-described method, the ink resin 13 made of a thermoplastic acrylic resin is printed on the surface 14a of the substrate 14 in the non-circuit pattern area that does not become a circuit. The printing pattern of the ink resin is a stripe pattern having a line width W1 of 200 μm, a line interval W2 of 20 μm, and a film thickness of 3 μm in an uncured state (unfired).
The ink resin 13 transferred on the blanket 12 is completely transferred to the substrate 14 by 100%, and a pattern having a very good pattern shape and a stable film thickness is obtained. On the substrate 14, the printed portion 14A of the ink resin 13 becomes a non-circuit pattern region, and the non-printed portion 14B becomes a circuit pattern region.
[0046]
Next, as shown in FIG. 2, a substantially spherical conductive particle made of silver having an average particle diameter of 10 nm is formed on the entire surface of the substrate 14, that is, on the entire surface of the printed portion 14A and the non-printed portion 14B of the ink resin 13. The colloid solution Q in which the nano metal powder 20 is dispersed is applied. Specifically, the colloid solution Q is uniformly applied with a thickness of 10 μm by a coating method using a roll coater.
[0047]
Thereafter, the substrate 14 on which the printing of the ink resin 13 and the colloid solution Q are applied is heated, and the colloid solution Q and the ink resin 13 are heated at 250 ° C. for 1 hour.
By this heating, the ink resin 13 is thermally decomposed and sublimated, and the conductive metal powder 20 present in the colloid solution Q applied to the surface of the ink resin 13 is scattered and removed. Further, by heating, the liquid existing in the colloid solution Q on the surface of the non-printing portion 14B is evaporated, and the conductive nano metal powders 20 are fused together. The conductive metal layer 21 is formed. A very fine circuit pattern having a line width of 20 μm and a thickness of 3 μm is formed by the conductive metal layer 21, and a circuit board 30 made of only the conductive nano metal powder 20 is formed on the substrate 14.
[0048]
As described above, according to the manufacturing method of the present invention, since the particle size of the nano metal powder is extremely small as 0.1 nm to 100 nm, the conductive metal which becomes a circuit by fusing the nano metal powders together. A layer can be formed, and the circuit is made of only the nano metal powder, and thus has excellent conductivity. In addition, although fine nano metal powder is used, it is applied to the substrate surface as a colloid solution in which the nano metal powder is dispersed, so that workability is good and a highly accurate circuit can be easily formed. .
[0049]
The present invention is not limited to the above embodiment, and as the conductive nanometal powder, any of gold, copper, platinum, palladium or a mixture thereof can be used, and the liquid of the colloid solution includes toluene, alcohol, and the like. A solvent may be used. As the ink resin, a thermoplastic resin such as a butyral resin, a cellulose resin, or a polyester resin may be used. Further, printing may be performed by another printing method such as lithographic printing.
[0050]
Hereinafter, examples and comparative examples of the circuit manufacturing method of the present invention will be described in detail.
[0051]
(Example 1)
The viscosity of a thermoplastic acrylic resin (manufactured by Kyoei Chemical Co., Ltd.) was adjusted to 50 to 100 P with a solvent (butyl carbitol acetate) on the surface of a 100-μm-thick polyimide film (manufactured by Dupont, trade name: Kapton) as a substrate. The ink resin was printed by the intaglio offset printing method. A glass intaglio plate was used for printing, and the printing pattern was a stripe pattern having a line width of 200 μm and a line interval of 20 μm.
[0052]
Blanket (surface roughness 10-point average roughness) having silicone rubber (rubber hardness JIS-A 40, room temperature curing type silicone rubber addition type (KE1600, manufactured by Shin-Etsu Chemical Co., Ltd.), rubber thickness 300 μm) on the surface rubber. 1 μm), and hot air was applied to the surface every 10 sheets of printing to dry at 80 ° C. for 5 minutes. The clean room was controlled at room temperature of 23 ° C. ± 1 ° C., and the surface temperature of the intaglio was also adjusted to 23 ° C. ± 1 ° C. After drying, the surface of the blanket was forcibly blown with cold air to cool for 5 minutes. The blanket surface temperature after cooling was adjusted within room temperature + 3 ° C within the surface.
[0053]
After that, continuous printing was performed, but the surface temperature of the intaglio plate hardly changed, and no influence on printing accuracy was observed. Since the ink transferred on the blanket was completely transferred to the glass substrate 100%, an ink having a very good pattern shape and a stable film thickness was obtained. The printed pattern had a line width of 200 μm and a film thickness (unfired) of 3 μm. After printing the ink resin, a colloid solution (manufactured by Nippon Paint Co., Ltd.) in which silver powder having an average particle diameter of 10 nm is dispersed as a conductive nanometal colloid is screened on the entire surface of the printed and non-printed portions of the ink resin on the substrate. It was applied by a printing method. The coating amount was set to be about 3 μm in average surface thickness, and the silver powder used was one that was uniformly dispersed in the colloid solution at a volume ratio of 60% of the total volume of the colloid solution.
[0054]
Thereafter, by baking at 250 ° C. for 1 hour, the silver powders were completely fused together, and a metal coating was formed on the non-printed portion. In the printed portion, the ink resin was thermally decomposed and sublimated, and the surface of the printed portion was The colloidal solution containing the silver powder scattered and evaporated. As a result, a conductive circuit pattern made of a very fine 1 μm-thick metal film having a line width of 20 μm can be formed only on the non-printed portion. ^-6 Very good conductivity of Ω · cm was developed.
[0055]
(Comparative Example 1)
A photosensitive photoresist film (dry film) was vacuum-adhered to a 16 μm thick copper foil attached to a 100 μm thick polyimide film, exposed through a photomask, and developed to form a 30 μm resist pattern. Next, etching was performed with an etchant, and finally, the resist was peeled off with an alkali to form a copper foil pattern having a line width of 20 μm.
[0056]
The conductivity is almost the same as in Example 1 (1.8 × 10 ^-6 Ω · cm), which was good, but the line width was very small, and a problem of partial disconnection occurred. Further, since a very large amount of waste liquid is generated at the time of etching, the cost of processing the waste liquid is high. Furthermore, in the photolithography process (exposure, development, and drying), expensive production equipment is required, and equipment depreciation costs are added. Therefore, the production cost is 5 to 10 in the case of Example 1 as 1.
[0057]
(Comparative Example 2)
Using a conductive silver paste on a polyimide film having a thickness of 100 μm, printing was performed by screen printing with a line width of 20 μm and a line interval of 360 μm. The printed matter was cured at 200 ° C. for 1 hour to produce a circuit board.
[0058]
Although the waste liquid and the production equipment cost were the same as in Example 1 and could be produced at a very low cost, the line width of 20 μm could not be formed stably by screen printing, there were many disconnections, etc., and the printing accuracy was low. Very bad. The conductivity is 6 × 10 ^-4 It was very poor at Ω · cm, and it was found that practical application was difficult.
[0059]
From Example 1 and Comparative Examples 1 and 2, a very good circuit pattern can be formed only by printing according to the present invention, and further, no waste liquid is generated, and no expensive manufacturing equipment is required. It was confirmed that a circuit board with a stable resistance can be manufactured.
[0060]
【The invention's effect】
As is clear from the above description, according to the present invention, since the particle size of the conductive nano metal powder is reduced to about 0.1 nm to 100 nm, the surface activity of the metal powder becomes extremely high, Of the metal powder is remarkably lowered, and the metal powders can be fused at a low temperature. In addition, since a resin that can be decomposed and sublimated by heating is used as an ink resin, and the ink resin is previously applied to a non-circuit pattern area, the nano metal on the surface of the ink resin is heated by thermal decomposition and sublimation of the ink resin. The powder can be removed, and a metal layer in which the nano metal powder is fused can be formed only on the non-printed portion of the substrate surface, so that a circuit having extremely good conductivity can be easily manufactured by a simple process.
[0061]
In addition, since there is no development step or the like as compared with the conventional photolithography method, there is no waste liquid flowing out and there is no need to worry about the influence on the environment. Further, since the ink resin is printed by the printing method, the structure of the apparatus is simpler and relatively inexpensive than the photolithographic method.
Therefore, a circuit board provided with a circuit manufactured by the manufacturing method of the present invention is irradiated from a circuit having a high-density line portion or an electronic device such as a CRT (CRT) or a PDP (plasma display panel). It can be suitably used as an electromagnetic wave shield for shielding electromagnetic waves.
[Brief description of the drawings]
FIGS. 1A, 1B, 1C, and 1D are explanatory views of a printing process by intaglio offset printing.
FIG. 2A is a diagram illustrating a state in which a colloid solution is applied to a substrate, and FIG. 2B is a diagram illustrating a configuration of a circuit.
[Explanation of symbols]
11 Intaglio
12 blanket
13 Ink resin
14 Substrate
20 Conductive nano metal powder
21 Conductive metal coating
Q Colloid solution

Claims (7)

Printing an ink resin made of thermoplastic resin on the non-circuit pattern area on the substrate surface,
Next, the entire surface of the ink resin printed portion of the substrate and the non-printed portion to be a circuit pattern region, the average particle diameter is coated with a colloid solution in which conductive nano metal powder of 0.1 nm to 100 nm is dispersed,
Next, the substrate is heated, and the ink resin is decomposed and sublimated in the ink resin printed portion to remove the conductive nanometal powder on the surface thereof, and the colloid solution is removed in the non-printed portion of the circuit pattern region. A method for manufacturing a circuit, wherein only a liquid inside is evaporated to fuse conductive nano metal powders together, and a circuit is formed by a conductive metal layer composed of only the nano metal powder. The circuit manufacturing method according to claim 1, wherein a decomposition sublimation temperature of the thermoplastic resin used as the ink resin is lower than a fusion temperature of the conductive nanometal powders. 3. The circuit manufacturing method according to claim 1, wherein the ink resin is at least one resin selected from the group consisting of a thermoplastic acrylic resin, a butyral resin, a cellulose resin, and a polyester resin. The method according to any one of claims 1 to 3, wherein the conductive nanometal powder is made of any one of gold, silver, copper, platinum, and palladium or a mixture thereof. The method according to claim 1, wherein the heating temperature is 200 ° C. to 350 ° C. 6. 2. An intaglio offset printing method in which the ink resin is once transferred from the intaglio to a blanket, and then the ink resin is transferred from the blanket to the substrate as a printing method of the ink resin on the substrate surface. A method for manufacturing a circuit according to claim 5. A circuit board manufactured by the manufacturing method according to any one of claims 1 to 6 and provided with a circuit having a pattern made of only nano metal powder on a substrate.

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