JP2006210891A - Forming method of inorganic thin film pattern for polyimide resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forming method of an inorganic thin-film pattern for a polyimide resin capable of forming the inorganic thin film pattern on the surface of polyimide resin by ensuring both adhesion reliability and pattern precision. <P>SOLUTION: (1) A process for forming an alkali-proof protection film with a film thickness of 0.01-10 micrometers on the surface of polyimide resin. (2) A process for removing the surface part of the alkali-proof protection film of a pattern formation part and polyimide resin, and for forming a recess. (3) A process for cleaving the imido ring of the polyimide resin of the recess, and generating a carboxyl group by a contact of an alkaline solution. (4) A process for making a metal ion content solution contact to the polyimide resin having this carboxyl group, and generating the metal salt of a carboxyl group. (5) A process for forming an inorganic thin film by depositing the metal salt, as metal, metal oxide or a semiconductor, on the surface of the polyimide resin. From these processes, an inorganic thin film is formed on the surface of polyimide resin into a pattern form. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for forming an inorganic thin film pattern of polyimide resin, in which an inorganic thin film is formed on a surface of a polyimide resin with a fine pattern such as a circuit pattern.

  Various methods have been proposed as a method of forming a circuit pattern on the surface of a substrate formed of a polyimide resin such as a polyimide film. Among them, dry processes such as a vacuum deposition method and a sputtering method are known as methods that can satisfactorily form a fine circuit pattern with excellent adhesion reliability. However, these methods are expensive devices. At the same time, and at the same time, the productivity is low and the cost is high.

  Therefore, at present, the most common circuit pattern formation method is to prepare a metal coating material by previously coating the entire surface of the polyimide resin substrate with a metal film, and then etching the metal film at unnecessary parts by a photolithographic method. Subtractive methods of removing by processing are widely adopted. The adhesion force between the polyimide resin base material and the metal film in the metal coating material is ensured by an anchor effect accompanying the roughening of the surface of the base material or an adhesive. This subtractive method is excellent in productivity and is a method useful for forming a circuit pattern relatively easily. However, since it is necessary to remove a large amount of a metal film when forming a circuit pattern, a metal material is used. There is a problem that a lot of waste occurs. In addition, in recent years, finer circuit patterns have been demanded as electronic circuit boards have increased in density. However, in the subtractive method, unevenness and adhesive due to the occurrence of overetching and roughening of the surface of the base material are required. There is also a problem that it is difficult to cope with the required fine circuit pattern formation due to the presence of the above.

  For this reason, circuit pattern formation methods that replace the subtractive method have been actively studied. For example, the additive method, which is a kind of photolithographic method, applies a photosensitive resin to the entire surface of the base material and cures the portion other than the circuit formation portion by irradiating the portion other than the circuit formation portion with ultraviolet rays. In this method, the cured portion is removed into a circuit pattern shape with a solvent, and the circuit pattern is directly formed on the surface of the substrate using an electroless plating method. The electroless plating method uses a redox reaction in a solution to form a metal film on the surface of a substrate provided with plating catalyst nuclei. This additive method has superior productivity compared to the dry process described above, and can form a fine circuit pattern compared to the subtractive method. Since it is difficult to ensure, there is a problem that adhesion reliability is poor. In addition, the additive method has a complicated process and requires expensive production equipment to form a fine circuit pattern, resulting in high costs.

  Further, an ink jet method has attracted attention as a method for forming a fine circuit pattern easily and inexpensively. In the inkjet method, ink composed of metal nanoparticles is sprayed onto the surface of a substrate in a pattern shape from an inkjet nozzle, applied, and then annealed to form a circuit pattern consisting of a fine metal film. Is. However, when metal nanoparticles are sprayed and applied by the inkjet method, if the number of metal nanoparticles per unit area of the surface of the substrate is insufficient, the shrinkage caused by sintering between the metal nanoparticles during annealing The resulting metal film may break, and conversely, if the number of metal nanoparticles is excessive, the surface smoothness of the metal film formed after annealing may be lost. There is a problem that the control of the coating amount of particles is extremely severe. In addition, it is difficult to obtain sufficient adhesion reliability due to the physical properties of the metal component of the base material and the metal nanoparticles, and further, there is a problem in dimensional accuracy due to shrinkage accompanying sintering between the metal nanoparticles during annealing. Is.

In recent years, as a circuit pattern forming technique having excellent adhesion reliability, the surface of a polyimide resin substrate is treated with an alkaline aqueous solution to generate a carboxyl group, and a metal ion is coordinated to the carboxyl group to form a carboxyl group metal. After forming the salt, the polyimide resin base material is irradiated with ultraviolet rays through a photomask to selectively reduce metal ions to deposit a metal film, and if necessary, apply a metal film by plating. A technique for increasing the film thickness has been proposed (see, for example, Patent Document 1). A part of the metal film formed by this method is embedded in the polyimide resin, and the adhesion reliability of the metal film to the substrate surface of the polyimide resin can be obtained with high reliability.
JP 2001-73159 A

  However, as in the invention of Patent Document 1, it is difficult for the pattern forming method by ultraviolet irradiation through a photomask to cope with extremely fine circuit patterns that are desired as the density of circuit boards increases. Moreover, since the thickness of the metal film obtained is on the order of nm, a film increase is required for most circuit pattern applications. That is, it is necessary to deposit a metal film on the circuit pattern of the formed metal film by a plating method. However, since the metal film isotropically deposits in the plating method, there is a possibility that the pattern accuracy is deteriorated and the adhesion reliability is lowered after the film formation. In order to solve these problems, for example, after a polymer film is formed on the surface of the substrate other than the circuit pattern formation site, a method of increasing the film by plating is proposed, but the process becomes complicated, There is a problem that leads to higher costs.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a polyimide resin inorganic thin film pattern forming method capable of forming an inorganic thin film on a polyimide resin surface with high adhesion reliability and pattern accuracy. Is.

  In the method for forming an inorganic thin film pattern of polyimide resin according to claim 1 of the present invention, when forming an inorganic thin film on the surface of polyimide resin, (1) Alkali resistance protection having a film thickness of 0.01 to 10 μm on the surface of polyimide resin A step of forming a film, (2) a step of removing a surface layer portion of the alkali-resistant protective film and the polyimide resin at the pattern formation site, and a step of forming a recess, and (3) an polyimide resin imide in the recess by contacting with an alkaline aqueous solution. A step of generating a carboxyl group by cleaving the ring, (4) a step of bringing a metal ion-containing solution into contact with the polyimide resin having the carboxyl group to generate a metal salt of the carboxyl group, and (5) using the metal salt as a metal. Or a step of depositing on the polyimide resin surface as a metal oxide or semiconductor to form an inorganic thin film. It is characterized in.

  According to the present invention, an alkaline aqueous solution is allowed to act only on the recess not covered with the alkali-resistant protective film to generate a carboxyl group in the polyimide resin, and a metal, a metal oxide, or a semiconductor is deposited on the inner surface of the recess. An inorganic thin film can be formed, and the inorganic thin film can be formed in the concave portion of the pattern formation site. The inorganic thin film can be formed with high adhesion reliability and high pattern accuracy.

  The invention of claim 2 is characterized in that, in the step (2) of claim 1, the alkali-resistant protective film and the surface portion of the polyimide resin are removed by laser irradiation or vacuum ultraviolet irradiation to form a recess. Is.

  By performing laser irradiation or vacuum ultraviolet irradiation, not only the alkali-resistant protective film but also the surface portion of the polyimide resin can be removed to form a recess.

  According to a third aspect of the present invention, in the step (5) of forming the inorganic thin film of the first or second aspect, the metal salt is deposited on the surface of the polyimide resin as a metal by reducing the metal salt. , A process of forming a metal thin film.

  Metal thin film can be formed on the inorganic thin film formation site by reduction treatment of metal salt, and can be used as an electronic circuit board based on polyimide resin by forming a circuit pattern with metal thin film It is.

  According to a fourth aspect of the present invention, in the step (5) of forming the inorganic thin film according to the first or second aspect, the metal salt is reacted with an active gas, whereby the metal salt is converted into a metal oxide or a semiconductor as a polyimide resin surface. And forming a metal oxide thin film or a semiconductor thin film.

  A metal oxide thin film or a semiconductor thin film can be formed at an inorganic thin film forming site by reacting a metal salt with an active gas, and can be used as various electronic components having a metal oxide thin film or a semiconductor thin film. It can be done.

  The invention of claim 5 is characterized in that, in the step (5) of any one of claims 1 to 4, the deposited inorganic thin film is composed of an aggregate of inorganic nanoparticles.

  According to this invention, the anchoring effect of the inorganic nanoparticle aggregate can be utilized to increase the adhesion strength of the inorganic thin film, and the catalytic activity of the inorganic nanoparticle aggregate can be utilized to Electroless plating can be easily performed on the surface.

  The invention of claim 6 is characterized in that, in the step (5) of claim 5, a part of the aggregate of inorganic nanoparticles is embedded in a polyimide resin.

  According to this invention, the inorganic thin film which consists of an aggregate | assembly of an inorganic nanoparticle can be firmly stuck to a polyimide resin by the high anchor locking effect with respect to the polyimide resin of the aggregate | assembly of an inorganic nanoparticle.

  In addition, the invention of claim 7 is characterized in that, after the step (5) of any one of claims 1 to 6, (6) a step of performing electroless plating on the polyimide resin surface on which the inorganic thin film is deposited. To do.

  According to this invention, the electroless plating film can be increased on the surface of the inorganic thin film to increase the thickness of the inorganic thin film, and the circuit of the electronic circuit board can be formed with the inorganic thin film.

  The invention of claim 8 is characterized in that, in the step (6) of claim 7, electroless plating is performed using an aggregate of inorganic nanoparticles as a plating precipitation nucleus.

  According to the present invention, electroless plating can be selectively deposited on the surface of an inorganic thin film by depositing electroless plating on the surface of the inorganic thin film composed of an aggregate of inorganic nanoparticles. It is generated inside the concave portion where the thin film is formed, and the pattern accuracy can be maintained even after the film increase when the electroless plating film is increased on the inorganic thin film.

  A ninth aspect of the invention is characterized in that, in any one of the first to eighth aspects, the pattern forming portion is a circuit pattern shape.

  According to this invention, a circuit can be formed with an inorganic thin film formed at a pattern formation site, and it can be used as an electronic circuit board having a polyimide resin as a base material.

  According to the present invention, an alkaline aqueous solution is allowed to act only on the concave portion not covered with the alkali-resistant protective film to generate a carboxyl group in the polyimide resin, and a metal, a metal oxide, or a semiconductor is deposited on the inner surface of the concave portion. An inorganic thin film can be formed, and the inorganic thin film can be formed in the concave portion of the pattern formation site. The inorganic thin film can be formed with high adhesion reliability and high pattern accuracy.

  Hereinafter, the best mode for carrying out the present invention will be described.

  Polyimide resin is a polymer having a cyclic imide structure in the main chain, and is obtained, for example, by imidizing polyamic acid. Heat resistance, chemical resistance, mechanical strength, flame resistance, electrical insulation It is a thermosetting resin with excellent properties. In the present invention, this polyimide resin film or molded plate can be used as a substrate, and there is no particular limitation on the form.

  In the present invention, first, in step (1), a protective film 2 having excellent alkali resistance is formed on the entire surface of the polyimide resin substrate 1 as shown in FIG. The material constituting the alkali-resistant protective film 2 is not particularly limited, but is preferably one that can be easily removed in a later step, for example, a resin component or an inorganic polymer component having alkali resistance. Can do. Moreover, when using an acidic solution in a subsequent process, it is desirable to have acid resistance in addition to alkali resistance. For example, polyetherimide, polystyrene, polyethylene, polypropylene, polyacryl, polyvinyl chloride and the like are preferable as the resin component forming the alkali-resistant protective film 2, and polyoxysiloxanes and the like are preferable as the inorganic polymer component.

  The alkali-resistant protective film 2 can be formed by, for example, dissolving a resin component or an inorganic polymer component in a solvent to form a liquid or paste and applying this to the surface of the polyimide resin substrate 1. . The coating method is not particularly limited, and examples thereof include a spin coating method, a dip method, a screen printing method, a flexographic printing method, and a bar coating method. The solvent is appropriately selected depending on the components, the coating method, and the like. Specific examples include THF for polyetherimide, toluene for polystyrene, hot ligroin for polyethylene, and toluene for polypropylene. Ethyl cellulose cannot be used because it has low alkali resistance.

  The alkali-resistant protective film 2 needs to cover the entire surface of the polyimide resin substrate 1, and the film thickness is set to 0.01 to 10 μm, more preferably 0.03 to 4 μm. If the film thickness of the alkali-resistant protective film 2 is less than this range, it may not be able to serve as a protective film. Conversely, if the film thickness is thicker than this range, the following (2) It becomes difficult to form the recess 3 in the polyimide resin substrate 1 in the process.

  After the alkali-resistant protective film 2 is formed on the surface of the polyimide resin substrate 1 as described above, the alkali-resistant protective film 2 and the polyimide resin substrate 1 are formed along a predetermined arbitrary pattern shape in the step (2). The surface layer portion is removed, and the recesses 3 are formed in the pattern shape as shown in FIG.

  The concave portion 3 is formed by irradiating a laser such as a femtosecond laser, an ultraviolet laser, a green laser, or a YAG laser from above the alkali-resistant protective film 2 while scanning along the pattern shape using, for example, a laser drawing apparatus. Further, it can be performed by irradiating vacuum ultraviolet rays from above the alkali-resistant protective film 2 through a photomask using a vacuum ultraviolet (VUV) irradiation apparatus. Thus, not only the alkali-resistant protective film 2 but also the surface layer portion of the polyimide resin substrate 1 therebelow can be removed by laser irradiation or vacuum ultraviolet irradiation. The recessed part 3 can be formed in the surface. Such a recess 3 cannot be formed on the surface of the polyimide resin substrate 1 by a method of removing the alkali-resistant protective film 2 in a pattern shape with a solvent as in a normal photolithographic method.

  Although the depth of the recessed part 3 is not specifically limited, The range of 0.5-15 micrometers is preferable, More preferably, it is the range of 1-10 micrometers. Here, since the alkali-resistant protective film 2 is a chemically stable film and is left without being finally peeled off, the depth of the concave portion 3 includes the film thickness of the alkali-resistant protective film 2, This is the depth from the surface of the alkali-resistant protective film 2 to the bottom surface of the recess 3.

  Next, in the step (3), the surface of the polyimide resin base material 1 is applied to the surface of the polyimide resin base material 1 or the polyimide resin base material 1 is immersed in the alkaline aqueous solution 4 to make the surface of the polyimide resin base material 1 alkaline aqueous solution. 4 is processed. The alkaline aqueous solution 4 is not particularly limited, and examples thereof include a potassium hydroxide aqueous solution, a sodium hydroxide aqueous solution, a calcium hydroxide aqueous solution, a magnesium hydroxide aqueous solution, and an ethylenediamine aqueous solution. Although the density | concentration of the alkaline aqueous solution 4 is not specifically limited, 0.01-10M is preferable, More preferably, it is 0.5-6M. In addition, an auxiliary agent selected from a binder resin, an organic solvent, an inorganic filler, a thickener, a leveling agent, and the like is added to the alkaline aqueous solution 4 to control viscosity, wettability with a polyimide resin substrate, smoothness, and volatility. You may make it do. These are preferably selected according to the shape and line width of the coating pattern.

  Thus, when processing with the alkaline aqueous solution 4, as shown in FIG.1 (c), the alkaline aqueous solution 4 selectively selects only the recessed part 3 which is not coat | covered with the alkali-resistant protective film 2 among the surfaces of the polyimide resin base material 1. FIG. It works. Here, when the alkaline aqueous solution 4 acts on the surface of the polyimide resin substrate 1, as described in Patent Document 1, the cleavage of the imide ring in the molecular structure of the polyimide resin as shown in the chemical reaction formula 1 , A carboxyl group (—COOA: alkali metal salt or alkaline earth metal salt of carboxylic acid) and an amide bond (—CONH—) are formed.

  Accordingly, the surface of the polyimide resin substrate 1 as shown in FIG. 1B is treated with the alkaline aqueous solution 4 so as to selectively contact only the concave portion 3 of the polyimide resin substrate 1 as shown in FIG. Thus, as shown in FIG. 1 (d), a modified layer 5 that is modified by generating a carboxyl group in the surface layer portion of the polyimide resin base material 1 is formed in a pattern along the pattern forming portion.

  Here, as the alkaline aqueous solution 4 penetrates into the surface of the concave portion 3 of the polyimide resin base material 1 as described above, a modification reaction of the polyimide resin proceeds by generating a carboxyl group. The thickness of the modified layer 5 can be increased by increasing the processing time or by heat-treating the polyimide resin substrate 1. 10-80 degreeC is preferable and the process temperature at the time of processing the surface of the polyimide resin base material 1 with the alkaline aqueous solution 4 is 15-60 degreeC more preferably. The treatment time is preferably 5 to 1800 seconds, more preferably 30 to 600 seconds.

  As described above, after forming the modified layer 5 for generating a carboxyl group on the inner surface of the recess 3 of the polyimide resin substrate 1 in the step (3), the surface of the polyimide resin substrate 1 is formed in the step (4). Treat with metal ion-containing solution. In the metal ion-containing solution, the metal ions include gold ions, silver ions, copper ions, platinum ammine complexes, palladium ammine complexes, tungsten ions, tantalum ions, titanium ions, tin ions, indium ions, cadmium ions, vanadium ions, chromium. Examples thereof include at least one selected from ions, manganese ions, aluminum ions, iron ions, cobalt ions, nickel ions, and zinc ions. Among these metal ions, platinum ammine complexes and palladium ammine complexes are used in the state of an alkaline solution, and other metal ions are used in the state of an acidic solution.

Then, by treating the surface of the polyimide resin substrate 1 with the metal ion-containing solution in this way and bringing the metal ion-containing solution into contact with the modified layer 5 that has generated carboxyl groups as described above, for example, —COO ^{- ... M} 2+ ... ^- OOC-
As shown in FIG. 1E, a metal salt (carboxylic acid metal salt) of a carboxyl group can be generated by coordinating a metal ion (M ²⁺ ) to a carboxyl group. The metal ion-containing modified layer 6 can be formed at 5 locations. Here, in order to promote the ligand exchange between the hydroxyl group, alkali metal or alkaline earth metal in the carboxyl group generated in the polyimide resin, and the metal ion, the hydroxyl group, alkali metal or alkaline earth metal The degree of dissociation needs to be increased. For this purpose, it is necessary to keep the polyimide resin substrate 1 in an acidic state. Therefore, in this case, it is preferable to use a metal ion-containing acidic solution as the metal ion-containing solution.

  The metal ion concentration in the metal ion-containing solution shows a close correlation with the ligand substitution reaction between the hydroxyl group, alkali metal or alkaline earth metal in the carboxyl group generated in the polyimide resin, and the metal ion. Although depending on the metal ion species, the metal ion concentration is preferably 1 to 1000 mM, more preferably 10 to 500 mM. A low metal ion concentration is not preferable because it takes time for the ligand substitution reaction to reach equilibrium. The contact time of the metal ion-containing solution to the surface of the polyimide resin substrate 1 is preferably 10 to 600 seconds, more preferably 30 to 420 seconds.

  As described above, the metal ion-containing modification in which the metal ion-containing solution is brought into contact with the modified layer 5 on the inner surface of the concave portion 3 of the polyimide resin substrate 1 in the step (4) to generate a metal salt of a carboxyl group. After the layer 6 is formed, the surface of the polyimide resin substrate 1 is washed with water or alcohol to remove unnecessary metal ions. Then, in the step (5), the metal salt of the metal ion-containing modified layer 6 is deposited as a metal, or deposited as a metal oxide or a semiconductor, and on the inner surface of the polyimide resin substrate 1 recess 3, An inorganic thin film 7 made of metal or an inorganic thin film 7 made of metal oxide or semiconductor can be formed.

  The inorganic thin film 7 is formed on the surface layer of the metal ion-containing modified layer 6 on the inner surface of the recess 3 as shown in FIG. Here, the metal ion-containing modified layer 6 is contained by depositing the metal salt of the metal ion-containing modified layer 6 in this manner on the surface of the metal ion-containing modified layer 6 as a metal, a metal oxide, or a semiconductor. The composition changes so that the metal ions to be reduced. That is, the metal ion-containing modified layer 6 after the step (5) is affected by the thickness of the metal ion-containing modified layer 6 and the method and degree of processing described later, but no metal ions remain. The modified layer 6 'or the modified layer 6' in which some of the metal ions remain has its composition altered.

  In the case where the metal salt is deposited as a metal on the metal ion-containing modified layer 6, it can be performed by reducing the metal salt. The reduction treatment can be performed, for example, by treating the surface of the polyimide resin substrate 1 with a solution containing a reducing agent, or by heat-treating the polyimide resin substrate 1 in a reducing gas or inert gas atmosphere. Although the reduction conditions vary depending on the metal ion species, when treating with a solution containing a reducing agent, for example, sodium borohydride, hypophosphorous acid and its salt, dimethylamine borane, etc. can be used as the reducing agent. When processing with a reducing gas, for example, hydrogen and its mixed gas, borane-nitrogen mixed gas or the like can be used as the reducing gas. When processing with an inert gas, for example, nitrogen gas or argon is used as the inert gas. Gas or the like can be used.

  Moreover, when depositing the metal salt of the metal ion containing modified layer 6 as a metal oxide or semiconductor, it can be performed by treating the metal salt with an active gas. Although the treatment conditions differ depending on the metal ion species, for example, oxygen and a mixed gas thereof, nitrogen and a mixed gas thereof, sulfur and a mixed gas thereof are used as the active gas, and the surface of the polyimide resin substrate 1 is brought into contact with the active gas. Thus, processing can be performed.

  Here, as the metal oxide, for example, titanium oxide, tin oxide, indium oxide, vanadium oxide, manganese oxide, nickel oxide, aluminum oxide, iron oxide, cobalt oxide, zinc oxide, barium titanate, strontium titanate, indium- Tin composite oxide, nickel-iron composite oxide, cobalt-iron composite oxide, etc. can be mentioned, and the inorganic thin film 7 made of metal oxide is thus formed on the surface of the polyimide resin substrate 1. By doing so, for example, it can be used as a capacitor, a transparent conductive film, a heat radiation material, a magnetic recording material, an electrochromic element, a sensor, a catalyst, a light emitting material, and the like.

  Examples of the semiconductor include cadmium sulfide, cadmium telluride, cadmium selenide, silver sulfide, copper sulfide, and indium phosphide. In this way, the inorganic thin film 7 made of a semiconductor is formed of a polyimide resin group. By forming on the surface of the material 1, it can be used as a light emitting material, a transistor, a memory material, and the like.

  As described above, the metal, metal oxide, or semiconductor constituting the inorganic thin film 7 formed in the step (5) is composed of nanoparticles having a particle diameter of 2 to 100 nm. These inorganic nanoparticles are easily aggregated due to their extremely high surface energy and exist as an aggregate of inorganic nanoparticles. At this time, a part of the aggregate of inorganic nanoparticles is stabilized in the resin of the polyimide resin substrate 1 although the degree varies depending on the conditions of the metal ion concentration, the reducing agent concentration, the atmospheric temperature, the active gas concentration, and the like. In other words, a part of the aggregate of inorganic nanoparticles is embedded in the surface portion of the polyimide resin, and is composed of the aggregate of the polyimide resin substrate 1 and the inorganic nanoparticles due to the anchor locking effect at this time. The inorganic thin film 7 can be firmly adhered. In particular, in the general anchor locking effect obtained by chemically or physically roughening the substrate surface, the surface roughness is on the order of μm. The anchor locking effect is excellent in adhesion characteristics with a surface roughness of nanoscale, and is suitable for a wiring material for transmitting an electronic signal in a high frequency region.

  The inorganic thin film 7 can be formed in the concave portion 3 of the polyimide resin substrate 1 as described above, and the circuit pattern is formed with the inorganic thin film 7 by setting the concave portion 3 in a circuit pattern shape. The polyimide resin substrate 1 can be processed as an electronic component such as an electronic circuit board. The inorganic thin film 7 is formed in the recessed part 3 formed in the surface of the polyimide resin base material 1 as mentioned above. Therefore, the inorganic thin film 7 is difficult to peel off from the concave portion 3, and the inorganic thin film 7 can be formed with high adhesion, and the inorganic thin film 7 can be accurately formed along the concave portion 3. When the circuit pattern is formed with the thin film 7, it can be formed with high adhesion reliability and high pattern accuracy.

  Here, the inorganic thin film 7 formed in the step (5) has a thickness of about 10 to 500 nm. On the other hand, in an electronic circuit board, the circuit needs to have a thickness of about μ units. For this reason, when it is used as an electronic circuit board, it is preferable to increase the thickness of the inorganic thin film 7 so as to increase the thickness of the circuit. That is, after the step (5), in the step (6), the surface of the inorganic thin film 7 provided on the polyimide resin substrate 1 is subjected to electroless plating, and the thickness of the inorganic thin film 7 is increased by electroless plating. It is something that can be done.

  The electroless plating can be performed, for example, by immersing the polyimide resin substrate 1 in an electroless plating bath, and the inorganic nanoparticle aggregate forming the inorganic thin film 7 is used as a deposition nucleus of plating. The electroless plating film 8 can be deposited on the surface of the inorganic thin film 7 as shown in FIG. That is, the aggregate of inorganic nanoparticles has an extremely large specific surface area, and thus exhibits excellent catalytic activity. When used as a precipitation nucleus for depositing the electroless plating film 8, from a number of points. Since the deposition of the plating film starts uniformly, the electroless plating film 8 showing good adhesion and electrical characteristics can be obtained. In this way, by depositing the electroless plating film 8 on the surface of the inorganic thin film 7 using the inorganic nanoparticle aggregate as the deposition nucleus of plating, the surface of the polyimide resin substrate 1 is selectively only on the surface of the inorganic thin film 7. The electroless plating film 8 is formed along the inside of the recess 3 in which the inorganic thin film 7 is formed, and the electroless plating film 8 is electrolessly formed on the inorganic thin film 7. When forming the circuit by increasing the plating film 8, the circuit pattern accuracy can be maintained by the recess 3 even after the film is increased. Therefore, the thickness of the electroless plating film 8 is preferably equal to or less than the depth of the recess 3. When the inside of the recess 3 is completely filled with the electroless plating film 8, the thickness of the electroless plating film 8 may be equal to or greater than the depth of the recess 3, and the thickness of the electroless plating film 8 is the depth of the recess 3. When exceeding, it is preferable to polish and remove the electroless plating film 8 exceeding the depth by mechanical means such as grinding or chemical means such as etching. The electroless plating bath is preferably a neutral or weak alkaline electroless plating bath in order to prevent re-modification of the polyimide resin substrate 1.

  Next, the present invention will be specifically described with reference to examples.

Example 1
A polyimide film (trade name “Kapton 200-H” manufactured by Toray DuPont Co., Ltd.) is immersed in an ethanol solution, subjected to ultrasonic cleaning for 5 minutes, and then dried in an oven at 100 ° C. for 60 minutes to obtain a polyimide film. The surface was cleaned.

  On the other hand, a polystyrene solution was prepared by dissolving 50 parts by mass of polystyrene in 180 parts by mass of toluene, and this polystyrene solution was uniformly applied to the surface of the polyimide film by spin coating at 1500 rpm for 30 sec. After that, an alkali resistant protective film of polystyrene was formed on the surface of the polyimide film by holding it in an oven maintained at 60 ° C. for 10 minutes (see FIG. 1 (a)). The thickness of the alkali-resistant protective film was 0.5 μm.

  Next, a circuit pattern having a line width of 5 μm was drawn using an ultraviolet laser device under the following conditions, and the surface layer portion of the alkali-resistant protective film and the polyimide film was removed to form a pattern-shaped recess in the polyimide film (FIG. 1). (See (b)). The depth of the recess was 3 μm.

Laser output: 5W
Wavelength: 355nm
Oscillation operation: Pulse Scan speed: 30mm / sec
Next, the polyimide film was immersed in an aqueous 5M KOH solution adjusted to 50 ° C. for 5 minutes and treated with an alkaline aqueous solution (see FIG. 1C). Thereafter, the polyimide film was immersed in an ethanol solution and subjected to ultrasonic cleaning for 10 minutes. The modified layer was formed in the circuit pattern shape on the surface of the polyimide film (refer FIG.1 (d)).

Next, a 50 mM CuSO ₄ aqueous solution is used as the metal ion-containing acidic solution, the polyimide film is immersed in this aqueous solution for 5 minutes, Cu ions are coordinated to the modified layer, and the metal ion-containing modified layer is formed. It formed (refer FIG.1 (e)). Thereafter, excess CuSO ₄ was removed with distilled water.

Next, a 5 mM NaBH ₄ aqueous solution was used as the reducing solution, and after immersing the polyimide film in this aqueous solution for 5 minutes and washing with distilled water, copper was applied to the surface of the metal ion-containing modified layer on the inner surface of the recess. Thin film deposition was confirmed (see FIG. 1 (f)). The thickness of the copper thin film was 300 nm, the line width was 5 μm, and the electrical resistance of the copper thin film was 5 × 10 ⁻³ Ωcm, and a circuit pattern having the same shape as the concave portion could be formed.

  Thereafter, the polyimide film was immersed in a neutral electroless copper plating bath having the following bath composition whose temperature was adjusted to 50 ° C. for 3 hours.

CuCl ₂ : 0.05M
Ethylenediamine: 0.60M
Co (NO ₃ ) ₂ : 0.15M
Ascorbic acid: 0.01M
2,2′-bipyridyl: 20 ppm
pH: 6.75
The electroless copper plating film was deposited on the copper thin film in the recess, and a uniform copper plating film having a thickness of 3 μm was obtained (see FIG. 1 (g)). The electric resistance of the copper plating film was 3 × 10 ⁻⁵ Ωcm, and the circuit of the electronic circuit board could be formed with the copper thin film and the copper plating film.

(Example 2)
An acrylic resin paste was prepared by dissolving 10 parts by mass of acrylic resin in 80 parts by mass of terpineol. Then, an acrylic resin paste was applied to the surface of the polyimide film whose surface was cleaned in the same manner as in Example 1 by a screen printing method through a screen plate of SUS300 mesh and emulsifier 5 μm, and placed in an oven at 110 ° C. for 30 minutes. By holding, an alkali-resistant protective film of acrylic resin was formed on the surface of the polyimide film (see FIG. 1 (a)). The thickness of the alkali resistant protective film was 10 μm.

  Next, using a YAG laser device, a circuit pattern having a line width of 40 μm was drawn under the following conditions, and the surface layer portion of the alkali-resistant protective film and the polyimide film was removed to form a pattern-shaped recess in the polyimide film (FIG. 1). (See (b)). The depth of the concave portion was 18 μm.

Laser output: 50W
Wavelength: 1064nm
Oscillation operation: Pulse Scanning speed: 100mm / sec
On the other hand, 30 parts by mass of polyethylene glycol as a thickener is added to 100 parts by mass of a 10M concentration KOH aqueous solution, and this is stirred and dissolved to prepare an alkaline aqueous solution. The film was coated with a film thickness of 50 μm and heated in a belt furnace maintained at a peak temperature of 40 ° C. for 30 minutes to perform treatment with an alkaline aqueous solution (see FIG. 1C). Thereafter, the polyimide film was immersed in a propanol solution and subjected to ultrasonic cleaning for 10 minutes. The modified layer was formed in the circuit pattern shape on the surface of the polyimide film (refer FIG.1 (d)).

Next, a 100 mM concentration AgNO ₃ aqueous solution is used as the metal ion-containing acidic aqueous solution, the polyimide film is immersed in this metal ion-containing aqueous solution for 5 minutes, and the silver ions are coordinated to the modified layer on the inner surface of the recess to form a metal. An ion-containing modified layer was formed (see FIG. 1 (e)). Thereafter, excess AgNO ₃ was removed with distilled water.

Next, reduction was performed for 30 minutes in a 50% hydrogen stream at 200 ° C. (N ₂ balance) using hydrogen as the reducing gas. As a result, deposition of a silver thin film was confirmed on the surface portion of the metal ion-containing modified layer. (See FIG. 1 (f)). The thickness of the silver thin film was 300 nm, the line width was 40 μm, and the electric resistance of the silver thin film was 5 × 10 ⁻³ Ωcm, and a circuit pattern having the same shape as the concave portion could be formed.

  Thereafter, the polyimide film was immersed in a neutral electroless nickel plating bath having the following bath composition whose temperature was adjusted to 80 ° C. for 5 hours.

NiSO ₄ : 0.1M
CH ₃ COOH: 1.0M
NaH ₂ PO ₂ : 0.2M
pH: 4.5
The electroless nickel plating film was deposited on the silver thin film in the recess, and a uniform nickel plating film with a film thickness of 16 μm was obtained (see FIG. 1G). The electric resistance of the nickel plating film was 3 × 10 ⁻⁵ Ωcm, and the circuit of the electronic circuit board could be formed with the silver thin film and the nickel plating film.

(Example 3)
A polypropylene solution was prepared by dissolving 30 parts by weight of polypropylene in 180 parts by weight of toluene. Then, by a dip method, a polypropylene solution was uniformly applied to a polyimide film whose surface was cleaned in the same manner as in Example 1 under the condition of a pulling rate of 20 mm / sec, and then placed in an oven maintained at 40 ° C. for 5 minutes. By holding, an alkali resistant protective film of polypropylene was formed on the surface of the polyimide film (see FIG. 1A). The thickness of this alkali-resistant protective film was 0.03 μm.

  Next, using a femtosecond laser device, a circuit pattern having a line width of 3 μm was drawn under the following conditions, and the surface layer portion of the alkali-resistant protective film and the polyimide film was removed to form a pattern-shaped recess in the polyimide film (FIG. 1 (b)). The depth of the recess was 3 μm.

Laser output: 10W
Wavelength: 780 nm
Oscillation operation: Pulse Scan speed: 300mm / sec
Next, the polyimide film was immersed in a 2M concentration KOH aqueous solution whose temperature was adjusted to 70 ° C. for 10 minutes and treated with an alkaline aqueous solution (see FIG. 1C). Then, the polyimide film was immersed in water and ultrasonic cleaning was performed for 10 minutes. The modified layer was formed in the circuit pattern shape on the surface of the polyimide film (refer FIG.1 (d)).

  Next, a 0.1 M concentration indium sulfate aqueous solution and a 0.1 M concentration tin sulfate aqueous solution are mixed to prepare a metal ion-containing acidic aqueous solution in which the molar ratio of indium ions to tin ions is indium / tin = 15/85. Then, the polyimide film was immersed in the aqueous solution containing metal ions for 20 minutes, and indium ions and tin ions were coordinated to the modified layer on the inner surface of the recess to form a modified metal ion-containing layer (FIG. 1 (e )reference). Thereafter, excess metal ions were removed with distilled water.

  Next, this polyimide film was heat-treated in a hydrogen atmosphere at 350 ° C. for 3 hours to obtain a nanoparticle aggregate made of an indium-tin alloy. At this time, the film thickness of the nanoparticle aggregate was 50 nm. Thereafter, the polyimide film was heat-treated in an air atmosphere at 300 ° C. for 6 hours to react the indium-tin alloy with oxygen, thereby forming an ITO thin film on the inner surface of the recess (FIG. 1 ( f)). The ITO thin film had a line width of 3 μm and a sheet resistance of 0.7Ω / □.

Example 4
By adding 35 parts by mass of polyvinylpyrrolidone and 25 parts by mass of glycerin as a thickener to a solution obtained by mixing 50 parts by mass of polydimethylsiloxane with 100 parts by mass of an aqueous 5M ethylenediamine solution, A dimethylsiloxane paste was prepared. Then, this polydimethylsiloxane paste was uniformly applied to the surface of the polyimide film whose surface was cleaned in the same manner as in Example 1 by flexographic printing, and heated in a belt furnace maintained at a peak temperature of 150 ° C. for 10 minutes. By processing, an alkali-resistant protective film of polydimethylsiloxane was formed on the surface of the polyimide film (see FIG. 1 (a)). The thickness of the alkali-resistant protective film was 8 μm.

  Next, a circuit pattern with a line width of 20 μm was drawn under the following conditions using a vacuum ultraviolet irradiation device, and the surface layer portion of the alkali-resistant protective film and the polyimide film was removed to form a pattern-shaped recess in the polyimide film (FIG. 1 (b)). The depth of the concave portion was 10 μm.

Output: 100W
Wavelength: 172 nm
Degree of vacuum: 10 Pa
Irradiation time: 300 min
Next, the polyimide film was immersed in a 7M Mg (OH) ₂ aqueous solution adjusted to 60 ° C. for 50 minutes and treated with an alkaline aqueous solution (see FIG. 1C). Then, the polyimide film was immersed in water and ultrasonic cleaning was performed for 10 minutes. The modified layer was formed in the circuit pattern shape on the surface of the polyimide film (refer FIG.1 (d)).

  Next, the polyimide film is immersed for 3 minutes in a metal ion-containing acidic aqueous solution composed of a 50 mM cadmium nitrate aqueous solution, and cadmium (II) ions are coordinated to the modified layer on the inner surface of the recess, thereby improving the metal ion-containing modification. A quality layer was formed (see FIG. 1 (e)). Thereafter, excess cadmium nitrate was removed with distilled water.

  Next, an aqueous solution having a composition of 100 ppm sodium sulfide, 5 mM disodium hydrogen phosphate, 5 mM potassium dihydrogen phosphate was kept at 30 ° C., and the polyimide film was immersed for 20 minutes for sulfiding treatment. Cadmium nanoparticle aggregates were obtained. And the density | concentration of the nanoparticle aggregate | assembly of a cadmium sulfide was increased by repeating the process after the process by said alkaline aqueous solution 10 times.

  Thereafter, a cadmium sulfide thin film was formed by performing a heat treatment in the atmosphere at 300 ° C. for 5 hours (see FIG. 1F). The cadmium sulfide thin film had a line width of 20 μm and a film thickness of 2.3 μm.

(Comparative Example 1)
A polystyrene solution was prepared by dissolving 10 parts by weight of polystyrene in 180 parts by weight of toluene, and this polystyrene solution was applied to the surface of a polyimide film whose surface was cleaned in the same manner as in Example 1 by spin coating at 3000 rpm. For 30 seconds. Thereafter, an alkali resistant protective film of polystyrene was formed on the surface of the polyimide film by holding in an oven maintained at 60 ° C. for 10 minutes. The thickness of this alkali-resistant protective film was 0.008 μm.

  Next, a circuit pattern having a line width of 5 μm was drawn using an ultraviolet laser device under the following conditions, and the surface layer portion of the alkali-resistant protective film and the polyimide film was removed to form a pattern-shaped recess in the polyimide film (FIG. 1). (See (b)). The depth of the recess was 4 μm.

Laser output: 5W
Wavelength: 355nm
Oscillation operation: Pulse Scan speed: 30mm / sec
Next, the polyimide film was immersed in an aqueous 5M KOH solution adjusted to 50 ° C. for 5 minutes and treated with an alkaline aqueous solution. Thereafter, the polyimide film was immersed in an ethanol solution and subjected to ultrasonic cleaning for 10 minutes. The modified layer was formed in the circuit pattern shape on the surface of the polyimide film.

Next, a 50 mM CuSO ₄ aqueous solution is used as the metal ion-containing acidic solution, the polyimide film is immersed in this aqueous solution for 5 minutes, Cu ions are coordinated to the modified layer, and the metal ion-containing modified layer is formed. Formed. Thereafter, excess CuSO ₄ was removed with distilled water.

Next, a 5 mM NaBH ₄ aqueous solution was used as the reducing solution, and after immersing the polyimide film in this aqueous solution for 5 minutes and washing with distilled water, copper was not only in the recesses but also on the surface of the polyimide film other than the recesses. Deposition of a thin film was observed and a circuit pattern could not be formed.

(Comparative Example 2)
An acrylic resin paste was prepared by dissolving 30 parts by mass of acrylic resin in 80 parts by mass of terpineol. Then, an acrylic resin paste was applied to the surface of the polyimide film whose surface was cleaned in the same manner as in Example 1 through a screen plate of SUS200 mesh and emulsifier 20 μm by screen printing, and placed in an oven at 110 ° C. for 30 minutes. By holding, an alkali-resistant protective film of acrylic resin was formed on the surface of the polyimide film. The thickness of this alkali-resistant protective film was 15 μm.

  Next, using a YAG laser device, a circuit pattern having a line width of 40 μm was drawn under the following conditions to form a pattern-shaped recess. The depth of the recess was 12 μm, did not penetrate the alkali-resistant protective film, and did not reach the surface of the polyimide film.

Laser output: 50W
Wavelength: 1064nm
Oscillation operation: Pulse Scan speed: 20mm / sec
Next, the polyimide film was immersed in an aqueous 5M KOH solution adjusted to 50 ° C. for 5 minutes and treated with an alkaline aqueous solution. Thereafter, the polyimide film was immersed in an ethanol solution and subjected to ultrasonic cleaning for 10 minutes. Formation of the modified layer could not be confirmed on the surface of the polyimide film.

(Comparative Example 3)
An ethylcellulose solution was prepared by dissolving 30 parts by mass of ethylcellulose in 100 parts by mass of terpineol. Then, an ethyl cellulose solution was applied to the surface of the polyimide film whose surface was cleaned in the same manner as in Example 1 through a screen plate of SUS300 mesh and emulsifier 5 μm by screen printing, and kept in an oven at 110 ° C. for 30 minutes. By doing so, an ethyl cellulose film was formed on the surface of the polyimide film. The thickness of this ethyl cellulose film was 5 μm.

  Next, using a YAG laser device, a circuit pattern having a line width of 40 μm was drawn under the following conditions, and the ethyl cellulose film and the surface layer portion of the polyimide film were removed to form a pattern-shaped recess in the polyimide film (FIG. 1B). )reference). The depth of the concave portion was 18 μm.

Laser output: 50W
Wavelength: 1064nm
Oscillation operation: Pulse Scanning speed: 100mm / sec
Next, the polyimide film was immersed in an aqueous 5M KOH solution adjusted to 50 ° C. for 5 minutes and treated with an alkaline aqueous solution. Thereafter, the polyimide film was immersed in an ethanol solution and subjected to ultrasonic cleaning for 10 minutes. As a result of this alkali treatment, the ethyl cellulose film was dissolved in the KOH aqueous solution, and the protective film no longer existed on the surface of the polyimide film.

  INDUSTRIAL APPLICABILITY The present invention can be widely used in the manufacture of electronic parts, mechanical parts, particularly circuit boards such as flexible circuit boards, flex-rigid circuit boards, and TAB carriers.

An example of embodiment of this invention is shown and (a) thru | or (g) is a schematic sectional drawing, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polyimide resin base material 2 Alkali-resistant protective film 3 Recessed part 4 Alkaline aqueous solution 5 Modified layer 6 Metal ion containing modified layer 7 Inorganic thin film 8 Electroless plating film

Claims (9)

  In forming an inorganic thin film on the surface of the polyimide resin, (1) a step of forming an alkali-resistant protective film having a film thickness of 0.01 to 10 μm on the surface of the polyimide resin, (2) an alkali-resistant protective film at a pattern forming site; A step of removing the surface portion of the polyimide resin to form a recess, (3) a step of cleaving the imide ring of the polyimide resin in the recess by contacting an alkaline aqueous solution, and (4) this carboxyl group A step of bringing a metal ion-containing solution into contact with a polyimide resin having a carboxyl group to form a metal salt of a carboxyl group, (5) an inorganic thin film deposited on the surface of the polyimide resin as a metal, or as a metal oxide or semiconductor And forming a polyimide resin inorganic thin film pattern.   2. The polyimide resin inorganic thin film pattern according to claim 1, wherein in the step (2), the concave portion is formed by removing the surface layer of the alkali-resistant protective film and the polyimide resin by laser irradiation or vacuum ultraviolet irradiation. Forming method.   The step of forming the inorganic thin film of (5) is a step of forming a metal thin film by reducing the metal salt to deposit the metal salt as a metal on the surface of the polyimide resin. 3. A method for forming an inorganic thin film pattern of polyimide resin according to 1 or 2.   In the step (5) of forming the inorganic thin film, the metal salt is reacted with an active gas to deposit the metal salt as a metal oxide or semiconductor on the surface of the polyimide resin to form a metal oxide thin film or a semiconductor thin film. The method for forming an inorganic thin film pattern of polyimide resin according to claim 1 or 2, wherein   5. The method for forming an inorganic thin film pattern of polyimide resin according to claim 1, wherein, in the step (5), the deposited inorganic thin film is composed of an aggregate of inorganic nanoparticles.   6. The method for forming an inorganic thin film pattern of polyimide resin according to claim 5, wherein in the step (5), a part of the aggregate of inorganic nanoparticles is embedded in the polyimide resin.   7. The polyimide resin inorganic thin film according to claim 1, further comprising: (6) a step of performing electroless plating on the polyimide resin surface on which the inorganic thin film is deposited. Pattern forming method.   8. The method for forming an inorganic thin film pattern of polyimide resin according to claim 7, wherein in the step (6), electroless plating is performed using an aggregate of inorganic nanoparticles as a plating precipitation nucleus. 9. The method for forming an inorganic thin film pattern of polyimide resin according to claim 1, wherein the inorganic thin film forming portion has a circuit pattern shape.

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