Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/38—Improvement of the adhesion between the insulating substrate and the metal
  • H05K3/381—Improvement of the adhesion between the insulating substrate and the metal by special treatment of the substrate
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/38—Improvement of the adhesion between the insulating substrate and the metal
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/03—Use of materials for the substrate
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
  • H05K3/14—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using spraying techniques to apply the conductive material, e.g. vapour evaporation
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/03—Use of materials for the substrate
  • H05K1/0393—Flexible materials
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
  • H05K3/022—Processes for manufacturing precursors of printed circuits, i.e. copper-clad substrates

Definitions

• the present invention relates to a two-layer flexible substrate and a manufacturing method thereof, more specifically, a base metal layer (hereinafter sometimes referred to as a seed layer) is formed on an insulator film by a dry plating method, and then a copper layer
• a base metal layer hereinafter sometimes referred to as a seed layer
• the present invention relates to a two-layer flexible substrate with few pinholes and concave defects and a method for manufacturing the same.
• LCDs, mobile phones, digital cameras, and various electric devices are required to be thin, small, and lightweight, and electronic components mounted thereon are moving toward miniaturization and form electronic circuits.
• a hard plate-like “rigid printed wiring board” and a “flexible printed wiring board (hereinafter sometimes referred to as FPC)” which is flexible in the form of a film and can be freely bent.
• FPC flexible printed wiring board
• LCD driver wiring HDD (hard disk drive), DVD (digital versatile disk) modules
• mobile phone hinges taking advantage of its flexibility. That demand is increasing.
• a material used for the FPC is a copper clad laminate (hereinafter sometimes referred to as CCL) in which a copper foil (conductor layer) is pasted on an insulating film such as polyimide or polyester.
• CCL copper clad laminate
• One is CCL (usually referred to as “three-layer CCL”, hereinafter referred to as three-layer CCL) in which an insulating film and copper foil (conductor layer) are bonded with an adhesive, and the other is an insulating film.
• CCL in which copper foil (conductor layer) is directly combined by casting method, laminating method, metalizing method or the like without using an adhesive usually referred to as “two-layer CCL”, hereinafter referred to as “two-layer CCL”) It is.
• the manufacturing cost is lower in price because the 3-layer CCL is easier to manufacture, such as material costs and handling properties of insulating films, adhesives, etc. It is.
• the two-layer CCL is superior in characteristics such as heat resistance, thin film thickness, and dimensional stability. The two-layer can be thinned although it is expensive due to fine patterning and high-density mounting of the circuit. Demand for CCL is expanding.
• the manufacturing method of the two-layer CCL having such characteristics is roughly classified into three.
• the first is a method of attaching an insulating film to electrolytic copper foil or rolled copper foil by a casting method
• the second is a method of attaching electrolytic copper foil or rolled copper foil to an insulating film by a lamination method.
• the dry plating method refers to a sputtering method, an ion plating method, a cluster ion beam method, a vacuum deposition method, a CVD method, etc.
• the third method is usually called “metalizing method”.
• the thickness of the metal layer can be freely controlled by using a dry plating method and a wet plating method (for example, electroplating), so that the metal layer is made thinner than the casting method or the laminating method. And easy. Moreover, since the smoothness of a polyimide and a metal layer interface is high, it is generally said that it is suitable for a fine pattern.
• CCL obtained by the metalizing method has a smooth metal-insulating film interface, so it cannot be expected to have an anchor effect generally used in the adhesion between metal and insulating film, and the adhesion strength of the interface is sufficiently developed. There is a problem of not doing.
• the two-layer CCL formed using this metallizing method is subjected to a “PCT test (Pressure Cooker Test)” that is left for a long time at 121 ° C., 95% RH, 2 atm, high humidity, and high pressure.
• PCT test Pressure Cooker Test
• the adhesion strength tends to decrease significantly. Therefore, heat of about 100 to 150 ° C. is applied at the time of drying after applying the liquid resist in the pattern forming process, and heat of about 250 ° C. is also used for bonding and soldering when mounting an IC or the like on the formed pattern.
• the two-layer CCL manufactured by the conventional metalizing method is used for fine pattern formation at high temperatures and COF mounting. Inadequate, improving heat resistance and moisture resistance has become an indispensable issue.
• Patent Document 1 proposes a method of forming a metal alloy layer mainly composed of Ni and Cr as an intermediate layer (seed layer) between an insulating film and a copper layer.
• a metal alloy layer mainly composed of Ni and Cr as an intermediate layer (seed layer) between an insulating film and a copper layer.
• the copper thin film in a flexible printed circuit board having a copper thin film made of copper or an alloy containing copper as a main component directly on at least one surface of a plastic film substrate, the copper thin film includes a surface layer having a crystal structure, It has a two-layer structure of a bottom layer having a polycrystalline structure between the surface layer and the plastic film substrate.
• the peak intensity at the crystal lattice plane index (200) is expressed as the crystal lattice plane index.
• the X-ray relative intensity ratio (200) / (111) which is a value divided by the peak intensity in (111), is 0.1 or less
• the bottom layer is a plastic film substrate by plasma treatment using a mixed gas containing nitrogen.
• a functional group is formed on top, and a metal made of copper or a copper-based alloy is formed.
• a metal made of copper or a copper-based alloy is formed.
• the atoms formed is configured by a chemical bond, a method of improving the moisture resistance have been described.
• the present invention is brought about by the combined effect of control of the crystal lattice plane and plasma treatment, and it is technically difficult to control the crystal lattice plane, and it is difficult to stably mass-produce.
• the thickness of the copper conductive film necessary for wiring is considered to be more than 35 ⁇ m and up to 50 ⁇ m, but the width of the formed wiring is about several hundred ⁇ m. Therefore, the presence of pinholes of several tens of ⁇ m rarely causes defects in the wiring portion.
• the thickness of the copper coating for forming the wiring portion is 15 ⁇ m or less, Preferably, the thickness is preferably as thin as 8 ⁇ m or less, ideally about 5 ⁇ m, which increases the possibility of defects in the wiring portion.
• a resist layer having a desired wiring portion pattern is provided on the copper conductor layer so that only the wiring portion is masked and the copper conductor layer of the non-wiring portion is exposed.
• the exposed copper conductor layer is removed by a chemical etching process.
• the resist layer is peeled off.
• a wiring board having a narrow wiring width and a narrow wiring pitch such as a wiring width of 15 ⁇ m and a wiring pitch of 30 ⁇ m, for example, by using a substrate formed with a very thin copper coating layer of, for example, 5 ⁇ m.
• a substrate formed with a very thin copper coating layer of, for example, 5 ⁇ m Is an electro copper plating film having a thickness of about 5 ⁇ m because a large one of the pinholes generated in the base metal layer of the substrate by dry plating processing reaches the order of several tens to several hundreds of ⁇ m. Since the insulator film exposed part by the pinhole can hardly be filled, the exposed part, that is, the missing part of the conductor layer is applied to the wiring part, and the wiring part is missing at the position of the pinhole. If it becomes a defect or it is not so, it will cause the adhesion defect of a wiring part.
• Patent Document 3 discloses a technique for defining the number of pinholes in a metal polyimide film laminate. However, Patent Document 3 does not disclose pinholes in the deposited film, but defines pinholes after electrolytic copper plating, and does not mention pinholes in the deposited film or the base metal layer.
• Patent Document 4 as a method for solving the above problem, a base metal layer is formed on an insulator film by a dry plating method, and a copper coating layer by electroless plating is further applied as an intermediate metal layer to form a pin. A method for coating exposed portions of an insulator film with holes is described.
• the exposed portion of the insulator film due to pinholes can be eliminated to some extent, but on the other hand, the plating solution used for the electroless copper plating treatment or its pretreatment solution has already been formed. It penetrates between the insulator film and the base metal layer from various pinhole parts, which causes the adhesion of the base metal layer and the conductor layer by the electrolytic copper plating formed thereafter. It has been found that there is a possibility and has not been a sufficient solution. Also, even if the exposed part of the insulator film can be filled by electrolytic copper plating, the adhesion between the insulation film and the copper layer is low, so if there are pinholes in the underlying metal layer, poor adhesion and reduced insulation reliability It has become a cause of inviting.
• JP 2006-13152 A Japanese Patent No. 3563730 Japanese Patent Laid-Open No. 11-92917 Japanese Patent Laid-Open No. 10-195668
• the present invention solves the above-described problems in the production of a two-layer flexible substrate using a dry plating method, and a copper foil film layer resulting from pinholes formed when a base metal layer is formed by dry plating on an insulator film.
• a two-layer flexible substrate excellent in adhesion, corrosion resistance, and water resistance between the insulator film and the underlying metal layer, particularly suitable for fine pattern formation and COF mounting
• Another object of the present invention is to provide a two-layer flexible substrate and a manufacturing method thereof.
• the inventors of the present invention formed a base metal layer by dry plating without using an adhesive on at least one surface of an insulator film, and formed a copper thin film layer and / or a copper layer having a desired layer thickness on the base metal layer.
• the insulator film is subjected to a surface treatment, and by using a two-layer flexible substrate in which the oligomer amount is 70% or less of the oligomer amount before the surface treatment, a base metal layer is formed.
• a base metal layer is formed by dry plating on at least one surface of an insulator film without using an adhesive, and a copper thin film layer is formed on the base metal layer by dry plating 2
• the insulator film has a surface treatment applied to at least one surface, and the amount of oligomer after the surface treatment is applied to only one surface of the insulator film is an oligomer before the surface treatment. It is a two-layer flexible substrate characterized by being 70% or less of the amount.
• the copper thin film layer in the first invention has a thickness of 50 nm to 500 nm, and there are no pinholes having a diameter exceeding 30 ⁇ m. Further, pinholes having a diameter of 5 ⁇ m or more and 30 ⁇ m are The number is 45,000 or less per square meter.
• a third invention of the present invention is a two-layer flexible substrate according to the first and second inventions, wherein a copper wet plating layer is formed on the copper thin film layer by a wet plating method.
• the copper wet plating layer in the third aspect has a thickness of 0.5 ⁇ m to 12 ⁇ m, and there are no concave defects with a diameter or maximum defect length exceeding 20 ⁇ m.
• the number of concave defects having a maximum defect length of 10 ⁇ m or more and 20 ⁇ m or less is 2200 or less per square meter.
• the underlying metal layer has a layer thickness of 5 nm to 50 nm, contains 6 wt% to 22 wt% of an additive element mainly composed of chromium, and the remaining nickel 2 layers characterized in that the layer thickness of the copper thin film layer and the copper wet-plated conductor layer (copper layer) made of a nickel-chromium-based alloy is 50 nm to 12 ⁇ m It is a flexible substrate.
• the insulator film according to the first to fifth aspects is a polyimide film, a polyamide film, a polyester film, a polytetrafluoroethylene film, a polyfinylene sulfide film, a polyethylene film. It is a resin film selected from a phthalate film and a liquid crystal polymer film.
• the surface treatment according to the first to sixth aspects is performed by plasma with a DC voltage of 1500 V to 3000 V against the surface of the insulator film in an inert atmosphere at a pressure of 0.8 Pa to 4.0 Pa. It is a discharge process.
• the eighth invention of the present invention is characterized in that the inert atmosphere of the surface treatment in the seventh invention is a nitrogen atmosphere, and the PCT peel strength after the surface treatment is 70% or more of the initial peel strength.
• the surface treatment according to the first to sixth aspects is performed by plasma with a high frequency voltage of 800 V to 2000 V on the surface of the insulator film in an inert atmosphere at a pressure of 0.8 Pa to 4.0 Pa. It is a discharge process.
• the tenth invention of the present invention is characterized in that the inert atmosphere of the surface treatment in the ninth invention is a nitrogen atmosphere, and the PCT peel strength after the surface treatment is 70% or more of the initial peel strength.
• a base metal layer is formed by dry plating on at least one surface of an insulator film without using an adhesive, and a copper thin film layer is formed on the base metal layer by dry plating.
• the surface of the insulator film is subjected to surface treatment by plasma discharge applied for 2 to 100 seconds between the counter discharge electrodes of the plasma electrode in an inert atmosphere at a pressure of 0.8 Pa to 4.0 Pa. After applying, the base metal layer is formed.
• the twelfth invention of the present invention is characterized in that the surface treatment by plasma discharge in the eleventh invention applies a DC voltage of 1500 V to 3000 V between the discharge electrodes of the plasma electrode.
• the thirteenth invention of the present invention is characterized in that the surface treatment by plasma discharge in the eleventh invention applies a high frequency voltage of 800 V to 2000 V between the discharge electrodes of the plasma electrode.
• a base metal layer is formed on at least one surface of an insulator film by a dry plating method without using an adhesive, and a copper thin film layer is formed on the base metal layer by a dry plating method.
• a method for producing a two-layer flexible substrate according to the invention of claim 8 wherein the surface of the insulator film is subjected to a direct current voltage of 1500 V to 3000 V between the counter electrode of the plasma electrode in a nitrogen atmosphere at a pressure of 0.8 Pa to 4.0 Pa.
• a base metal layer is formed after surface treatment with plasma generated by applying for 2 to 100 seconds.
• a base metal layer is formed by dry plating on at least one surface of an insulator film without using an adhesive, and a copper thin film layer is formed on the base metal layer by dry plating.
• a method for producing a two-layer flexible substrate according to the invention of claim 10 wherein the surface of the insulator film is subjected to a high frequency voltage of 800 V to 2000 V between the counter electrode of the plasma electrode in a nitrogen atmosphere at a pressure of 0.8 Pa to 4.0 Pa.
• a base metal layer is formed after surface treatment with plasma generated by applying for 2 to 100 seconds.
• the sixteenth invention of the present invention is characterized in that the dry plating method in the eleventh to fifteenth inventions is any one of a vacuum deposition method, a sputtering method, and an ion plating method.
• the insulator film according to the eleventh to sixteenth aspects is a polyimide film, a polyamide film, a polyester film, a polytetrafluoroethylene film, a polyfinylene sulfide film, a polyethylene film. It is a resin film selected from a phthalate film and a liquid crystal polymer film.
• the present invention there is no lack of the copper foil film layer and the copper wet plating layer due to the pinhole generated when the base metal layer is formed, the lack of the base metal layer is small, and the insulator film, the base metal layer, A two-layer flexible substrate having excellent adhesion and corrosion resistance can be obtained. Since this two-layer flexible substrate is also suitable for a flexible wiring board having a wiring portion having a narrow width and a narrow pitch, it has a remarkable industrial effect.
• the two-layer flexible substrate of the present invention has a base metal layer by dry plating on at least one surface of an insulator film without using an adhesive, and has a copper thin film layer on the base metal layer.
• the insulator film has a structure in which the amount of oligomer is 70% or less of the amount of oligomer before the surface treatment by performing a surface treatment. By performing the treatment to obtain a surface having an oligomer amount of 70% or less compared to the amount of oligomer before the surface treatment, the generation of coarse pinholes is suppressed.
• the two-layer flexible substrate of the present invention has a copper thin film layer with a thickness of 50 nm to 500 nm, has no pinholes with a diameter of 30 ⁇ m, and has no more than 45,000 pinholes with a diameter of 5 ⁇ m to 30 ⁇ m per square meter. It is desirable.
• the thickness of the copper thin film layer is preferably 50 nm to 500 nm. If the thickness of the copper foil film layer is less than 50 nm, the copper thin film layer is formed when the copper wet plating layer is formed on the surface of the copper thin film layer by the electrolytic copper plating method which is one of the subsequent wet plating methods. The electrical resistance value is high, and the plating appearance on the surface of the copper layer may be deteriorated. In addition, when forming a copper wet plating layer by the electrolytic copper plating method, the copper thin film layer functions as a cathode, and the resistance value of the copper thin film layer becomes a problem. On the other hand, if the thickness of the copper thin film layer exceeds 500 nm, pinholes in the copper thin film layer are reduced, but the copper thin film layer is formed by the dry plating method, so that time is required and the economy is inferior.
• a two-layer flexible substrate is manufactured by providing a copper wet plating layer on the surface of the copper thin film layer by a wet plating method having a film formation rate faster than that of the dry plating method.
• the number of pinholes on the surface becomes minute by wet plating.
• the pinholes in the base metal layer and the copper thin film layer are not filled.
• the pinholes in the copper thin film layer are filled by wet plating, but if there are pinholes in the copper thin film layer, the underlying metal layer is exposed to the atmosphere before wet plating, so the underlying metal layer is altered and wiring defects And may cause a poor adhesion of the wiring part.
• the size thereof is in the range of 45,000 or less pinholes having a diameter of 5 ⁇ m to 30 ⁇ m per square meter.
• the number is not specified because pinhole wiring defects with a diameter of less than 5 ⁇ m and poor adhesion are rarely caused and detection is difficult.
• the surface treatment of the insulator film on the base material is performed using plasma treatment.
• the surface treatment may be performed on one side of the insulator film, but it is more effective when performed on both sides.
• the treatment condition is a pressure of 0.8 Pa to 4.0 Pa under an inert atmosphere. Under an inert atmosphere where the pressure is less than 0.8 Pa, the plasma discharge becomes difficult to stabilize, and in an inert atmosphere where the pressure exceeds 4.0 Pa, the treatment becomes too strong, so that the insulating film may be wrinkled during the treatment. There is not preferable.
• a direct current voltage (1500V to 3000V) is applied between the counter electrodes of the plasma electrode to perform direct current plasma (DC plasma) treatment. If this DC voltage is less than 1500 V, the plasma treatment is too weak to increase the initial adhesion strength, and if it exceeds 3000 V, the treatment becomes too strong, and the insulating film is likely to be wrinkled or deformed during the treatment. On the contrary, the heat resistant adhesion strength and PCT peel strength are lowered, which is not preferable.
• DC plasma direct current plasma
• a high frequency voltage of 800 to 2000 V is applied between the counter discharge electrodes of the plasma electrode to perform a high frequency plasma (RF plasma) treatment.
• RF plasma high frequency plasma
• the plasma treatment is too weak to increase the initial adhesion strength, and if it exceeds 2000V, the treatment becomes too strong, so that the insulating film is likely to be wrinkled or deformed during processing.
• the inert atmosphere is a group 18 gas such as nitrogen gas or argon, and may be a mixed gas of nitrogen and argon.
• the PCT peel strength can be 70% or more of the initial peel strength.
• the treatment time by plasma discharge is preferably 2 to 100 seconds. If the plasma discharge treatment time is less than 2 seconds, the treatment is too weak to contribute to an increase in the initial adhesion strength, and if the treatment is continued for more than 100 seconds, the influence becomes too great and the insulating film is likely to be wrinkled or deformed. On the contrary, it is not preferable because it results in a decrease in heat-resistant adhesion strength and PCT adhesion strength. On the other hand, a long processing time exceeding 100 seconds is not desirable from the viewpoint of productivity.
• the amount of oligomer in the base insulator film is large, pinholes in the copper thin film layer increase.
• the amount of oligomer in the insulator film after the surface treatment is desirably 70% or less compared to the amount of oligomer before the surface treatment.
• it is desirable that the oligomer amount of the insulator film after the surface treatment is 35% or less compared to the oligomer amount before the surface treatment.
• the oligomer is a molecule having a molecular weight in the range of 300 to 14000, and is a molecule remaining in the film without sufficiently proceeding polymerization when an insulator film is produced.
• the determination of the oligomer amount is obtained by measuring the oligomer amount as follows.
• the oligomer may be extracted from the insulator film using a solvent such as tetrahydrofuron, and the molecular weight distribution of the extract may be measured using a size exclusion chromatograph (SEC method).
• the layer thickness of the base metal layer is preferably 5 nm to 50 nm. If the layer thickness of the base metal layer made of a nickel-chromium-based alloy mainly containing chromium as an additive element obtained by the dry plating method is less than 5 nm, the long-term adhesion of the base metal layer is improved even after the subsequent processing steps. Problems arise. Furthermore, if the layer thickness of the base metal layer is less than 5 nm, an etching solution infiltrate when performing wiring processing and the wiring part floats, which causes problems such as a significant decrease in wiring peel strength.
• the layer thickness of the base metal layer exceeds 50 nm, it is difficult to remove the base metal layer during the processing of the wiring portion, and further, it may cause a hair crack or warp, resulting in a decrease in adhesion strength. Further, if the layer thickness is greater than 50 nm, it is difficult to perform etching, which is not preferable.
• the component composition of the base metal layer is such that the chromium content is 12 wt% to 22 wt%. That is, if the chromium content is less than 12% by weight, the heat resistance is lowered. On the other hand, if the chromium content exceeds 22% by weight, it is difficult to remove the underlying metal layer during the processing of the wiring portion, which is not preferable. . Furthermore, a transition metal element can be appropriately added to this nickel-chromium alloy in accordance with the target characteristics for the purpose of improving heat resistance and corrosion resistance. In the case of such a base metal layer, in the two-layer flexible substrate of the present invention, the layer thickness of the base metal layer is preferably 15 nm to 50 nm.
• the base metal layer is preferably an alloy containing 4 to 22% by weight of chromium, 5 to 40% by weight of molybdenum, and the balance being nickel.
• the chromium content of 4 to 22% by weight is necessary to prevent the heat-resistant peel strength from significantly lowering due to thermal degradation, and when the chromium content is lower than 4% by weight, Even if it is added, it is not preferable because the heat-resistant peel strength cannot be prevented from significantly decreasing due to thermal deterioration.
• the chromium content exceeds 22% by weight, etching becomes difficult, which is not preferable. Therefore, in the case of chromium, it is more preferably 4 to 15% by weight, and particularly preferably 5 to 12% by weight.
• the ratio of molybdenum is preferably 5 to 40% by weight in order to improve corrosion resistance and insulation reliability.
• the proportion of molybdenum is less than 5% by weight, the effect of addition does not appear and corrosion resistance and insulation reliability are not improved, which is not preferable.
• the proportion of molybdenum exceeds 40% by weight, the heat-resistant peel strength tends to be extremely lowered, which is not preferable.
• the sputtering target composition has a nickel content of 93% by weight or less. Film formation rate can be obtained.
• a transition metal element can be appropriately added to the nickel-chromium-molybdenum alloy in accordance with the intended characteristics for the purpose of improving heat resistance and corrosion resistance.
• this base metal layer may contain 1% by weight or less of unavoidable impurities contained by being taken in during the production of the target.
• a dry plating method is used for forming the base metal layer and the copper thin film layer, it is preferable to use any one of a vacuum deposition method, a sputtering method, and an ion plating method in this dry plating method.
• Insulator film (base material) Furthermore, in the two-layer flexible substrate of the present invention, as a base insulator film, a polyimide film, a polyamide film, a polyester film, a polytetrafluoroethylene film, a polyfinylene sulfide film, a polyethylene naphthalate system It is desirable to use a resin film selected from a film and a liquid crystal polymer film. For example, an insulator film having a film thickness of 25 to 75 ⁇ m can be suitably used. Note that a substrate containing an inorganic material is preferably not used because an inorganic material such as glass fiber becomes an obstacle to laser processing and chemical etching.
• Copper layer In the two-layer flexible substrate of the present invention, a copper thin film layer is formed on a base metal layer by a dry plating method, and then a copper wet plating layer is provided on the copper thin film layer by a wet plating method. A copper layer having a thickness of 10 nm to 12 ⁇ m including the plating layer is laminated and formed.
• the dry plating method is either a vacuum deposition method, a sputtering method, or an ion plating method, but the deposition rate is slower than the wet plating method. It is also suitable for forming a relatively thin copper layer.
• the two-layer flexible substrate of the present invention has a pinhole number of 5 to 30 ⁇ m in diameter of 45,000 or less per square meter, and if the outermost surface is a copper wet plating layer, the diameter or maximum defect length
• the number of concave defects of 10 ⁇ m to 20 ⁇ m is limited to 2200 or less per square meter, which is suitable for manufacturing a flexible wiring board with narrow pitch wiring.
• the substrate is a resin film selected from a polyimide film, a polyamide film, a polyester film, a polytetrafluoroethylene film, a polyphenylene sulfide film, a polyethylene naphthalate film, and a liquid crystal polymer film.
• a base metal layer is formed on one or both sides of the insulator film without using an adhesive, and a copper thin film layer is formed on the base metal layer.
• the insulator film of the base material usually contains moisture, and is present in the insulator film by air drying or vacuum drying before forming the base metal layer made of nickel-chromium alloy by dry plating. It is necessary to remove moisture. If this is insufficient, the adhesion with the underlying metal layer will be deteriorated.
• the base metal layer is formed by dry plating
• a target having the composition of the base metal layer is attached to the sputtering cathode.
• nitrogen, argon, or a mixed gas of nitrogen and argon is introduced, and the inside of the apparatus is maintained in an inert atmosphere at a pressure of 0.8 Pa to 4.0 Pa.
• a DC voltage of 1500 V to 3000 V or a high frequency voltage of 800 V to 2000 V is applied between the counter discharge electrodes of the plasma electrode, and surface treatment with plasma is performed for 2 seconds to 100 seconds.
• argon gas is introduced, the inside of the apparatus is held at about 1.3 Pa, and the insulator film mounted on the winding roll and unwinding roll in the apparatus is conveyed at a speed of about 3 m / min.
• Power is supplied from a sputtering direct current power source connected to the substrate to start sputtering discharge, and a base metal layer made of nickel-chromium alloy or nickel-chromium-molybdenum alloy is formed on the insulator film.
• the copper thin film layer is formed using a sputtering apparatus in which a copper target is mounted on the sputtering cathode, as in the case of the base metal layer.
• the base metal layer and the copper thin film layer are preferably formed continuously in the same vacuum chamber.
• the film is taken out into the atmosphere, and the copper thin film layer is formed using another sputtering apparatus. In this case, it is necessary to perform sufficient dehydration before film formation.
• an electroless copper plating process forms an electroless copper plating layer on the entire flexible substrate, thereby covering the exposed surface and making the entire flexible substrate surface a good conductor even if pinholes exist. It is possible to minimize the influence of pinholes.
• an electroless copper plating process it is necessary to set conditions in consideration of permeation by an electroless plating solution or its pretreatment solution.
• the layer thickness of the plated copper wet plating layer by this electroless copper plating solution is such that defects can be repaired by pinholes on the substrate surface and is not dissolved by the electrolytic copper plating solution when the electrolytic copper plating solution treatment is performed.
• the thickness may be any layer, and it is preferably in the range of 0.01 ⁇ m to 1.0 ⁇ m.
• the substrate on which the electrolessly plated copper wet plating layer is formed in this manner is subjected to an electrolytic copper plating process so as to finally form a copper wet plating layer having a desired thickness, and is generated when the base metal layer is formed. It is possible to obtain a two-layer flexible substrate that is not affected by the large and small pinholes and that has good adhesion and high adhesion.
• the thickness of the copper wet plating layer formed on the base metal layer and the copper thin film layer in this way is desirably 12 ⁇ m or less. Such a layer thickness is used to obtain a wiring board having a narrow wiring width and a narrow wiring pitch.
• the copper wet plating layer is formed on the surface of the copper thin film layer by a wet plating method is appropriately selected depending on the method of manufacturing the wiring portion pattern.
• the wiring part is formed by a base metal layer, a copper thin film layer, and a copper wet plating layer, so that the layer thickness required for the wiring part becomes It is necessary to form a copper wet plating layer.
• the subtractive method is a method in which a resist layer is provided on the surface of the copper layer of the two-layer flexible substrate, a mask having a predetermined wiring pattern is provided on the resist layer, and ultraviolet rays are irradiated from above to be exposed.
• the copper wet plating layer may be provided by the wet plating method on the copper thin film tank or may not be provided.
• the semi-additive method is to provide a resist layer on the surface of the metal layer of the two-layer flexible substrate (a metal layer comprising a base metal layer and a copper thin film layer or a base metal layer, a copper thin film layer and a copper wet plating layer). Then, a mask having a predetermined wiring pattern is provided on the resist layer, exposed to ultraviolet rays from the resist layer, developed, and a plating mask for forming a wiring portion by electrodepositing copper on the surface of the metal layer.
• the wiring layer is formed by electroplating using the metal layer exposed in the opening as a cathode, and then the resist layer is removed and soft etching is performed on the surface of the two-layer flexible substrate other than the wiring portion. This is a method of forming a wiring part pattern by removing a metal to complete a wiring part.
• the pinhole is measured by specifying the position of the laminate of the base metal layer and the copper thin film layer obtained by the dry plating method by a transmission method, measuring the size with an optical microscope, and having a diameter of 5 ⁇ m to 30 ⁇ m. The number of pinholes per square meter was measured.
• the oligomer amount is evaluated by extracting the plasma-treated insulating film with tetrahydrofuron, measuring the ratio of oligomers having a molecular weight of 380 to 13500 using a size exclusion chromatograph (SEC method), and performing plasma treatment. The previous value was taken as 100% and compared to give the amount of oligomer.
• SEC method size exclusion chromatograph
• the peel strength was measured by a method based on IPC-TM-650 and NUMBER 2.4.9 to obtain an initial peel strength.
• the lead width was 1 mm and the peel angle was 90 °.
• the lead was formed by a subtractive method.
• a film substrate on which a 1 mm lead film is formed is left in an oven at 150 ° C. for 168 hours, and is taken out by evaluating the 90 ° peel strength until it reaches room temperature, Heat-resistant peel strength was used.
• a film substrate on which a 1 mm lead film is formed is allowed to stand for 96 hours in an autoclave at 121 ° C. and 2 atm. To obtain PCT peel strength.
• the method for measuring the concave defect was to observe the surface of the copper wet plating layer obtained by the electroplating method using an optical microscope and measure the size of the concave defect.
• the concave defect is circular, the diameter is 10 ⁇ m to 20 ⁇ m.
• the maximum value of the length of the defective portion of the concave defect is “maximum defect length”, the number of concave defects of 10 ⁇ m to 20 ⁇ m per square meter It was measured.
• Comparative Example 1 First, as Comparative Example 1, characteristics of a two-layer flexible substrate in which film formation was performed without performing plasma treatment are shown. Using a 20 wt% Cr—Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the base metal layer on one side of a 38 ⁇ m thick polyimide film (registered trademark “Kapton 150EN” manufactured by Toray DuPont) A 20 wt% Cr—Ni alloy base metal layer was deposited at a deposition rate of 0.7 nm / sec by direct current sputtering in an Ar atmosphere.
• a 20 wt% Cr—Ni alloy target manufactured by Sumitomo Metal Mining Co., Ltd.
• a 20 wt% Cr—Ni alloy base metal layer was deposited at a deposition rate of 0.7 nm / sec by direct current sputtering in an Ar atmosphere.
• a part of the film formed under the same conditions was measured using a transmission electron microscope (TEM: manufactured by Hitachi, Ltd.), and the layer thickness was 0.02 ⁇ m.
• TEM transmission electron microscope
• a Cu target manufactured by Sumitomo Metal Mining Co., Ltd.
• a copper thin film layer was formed to a thickness of 100 nm by sputtering, and then copper electroplating Was formed to a thickness of 8 ⁇ m.
• the obtained two-layer flexible substrate has an initial peel strength of 471 N / m, a PCT peel strength of 253 N / m, a dry substrate has 76714 pin holes / m 2 , an oligomer amount of 100%, and a sufficient initial peel strength is obtained. I could't.
• a 20 wt% Cr—Ni alloy base metal layer was formed at 7 nm / sec. Separately, a part of the film formed under the same conditions was measured using a transmission electron microscope (TEM: manufactured by Hitachi, Ltd.), and the layer thickness was 0.02 ⁇ m.
• a copper thin film layer having a thickness of 100 nm is formed on the 20 wt% Ni—Cr film as a second layer by sputtering using a Cu target (manufactured by Sumitomo Metal Mining Co., Ltd.), and then copper electroplating. Was formed to a thickness of 8 ⁇ m.
• the obtained two-layer flexible substrate has an initial peel strength of 624 N / m, a PCT peel strength of 434 N / m, and the number of pinholes in dry plating (a laminate of a base metal layer and a copper thin film layer, hereinafter referred to as dry plating).
• dry plating a laminate of a base metal layer and a copper thin film layer, hereinafter referred to as dry plating.
• a part of the film formed under the same conditions was measured using a transmission electron microscope (TEM: manufactured by Hitachi, Ltd.), and the layer thickness was 0.02 ⁇ m.
• a copper thin film layer having a thickness of 100 nm is formed on the 20 wt% Ni—Cr film as a second layer by sputtering using a Cu target (manufactured by Sumitomo Metal Mining Co., Ltd.), and then copper electroplating. Was formed to a thickness of 8 ⁇ m.
• a 38- ⁇ m thick polyimide film (registered trademark “Kapton 150EN” manufactured by Toray DuPont Co., Ltd.) was applied for 50 seconds with a DC voltage of 2000 V between the plasma electrode and the discharge electrode in an atmosphere with a nitrogen gas pressure of 3.1 Pa. Then, the plasma treatment was performed only on the surface of the base metal layer. Next, a 20 wt% Cr—Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) is used as the first layer of the base metal layer on the polyimide-treated surface, and DC sputtering is used in an Ar atmosphere. A 20 wt% Cr—Ni alloy base metal layer was formed at a film speed of 0.7 nm / sec.
• a part of the film formed under the same conditions was measured using a transmission electron microscope (TEM: manufactured by Hitachi, Ltd.), and the layer thickness was 0.02 ⁇ m.
• a copper thin film layer having a thickness of 100 nm is formed on the 20 wt% Cr—Ni film as a second layer by sputtering using a Cu target (manufactured by Sumitomo Metal Mining Co., Ltd.), and then copper electroplating The film was formed to a thickness of 8 ⁇ m by the method.
• the resulting two-layer flexible substrate had an initial peel strength of 632 N / m, a PCT peel strength of 467 N / m, the number of pin holes in dry plating was 8236 holes / m 2 , there were no pinholes exceeding 30 ⁇ m in diameter, and the amount of oligomer was 50 %, 2005 / m 2 , and there were no concave defects with a diameter or maximum defect length exceeding 20 ⁇ m.
• Comparative Example 2 Apply a DC voltage of 500 V for 15 seconds between the counter electrode and the plasma electrode in a 38 ⁇ m thick polyimide film (registered trademark “Kapton 150EN” manufactured by Toray DuPont) under an atmosphere of nitrogen gas pressure of 0.7 Pa. However, the discharge was unstable and could not be processed.
• a polyimide film registered trademark “Kapton 150EN” manufactured by Toray DuPont
• a two-layer flexible substrate according to Example 4 was produced in the same manner as in Example 1 except that the argon gas pressure was 3.6 Pa, the plasma treatment was performed for 6 seconds by applying a direct current of 2800 V to the plasma electrode.
• a two-layer flexible substrate according to Example 5 was produced in the same manner as in Example 1 except that the argon gas pressure was 1.6 Pa, the plasma treatment was performed for 6 seconds by applying a direct current of 2200 V to the plasma electrode.
• the resulting two-layer flexible substrate had an initial peel strength of 627 N / m, the number of pin holes in dry plating was 5142 / m 2 , there were no pin holes exceeding 30 ⁇ m in diameter, and the oligomer amount was 70%.
• the measurement of the concave defect of the two-layer flexible substrate which concerns on Example 5 was not performed.
• a two-layer flexible substrate according to Example 6 was produced in the same manner as in Example 1 except that the argon gas pressure was 3.6 Pa, the plasma treatment was performed for 6 seconds by applying a direct current of 1600 V to the plasma electrode.
• the obtained two-layer flexible substrate had an initial peel strength of 626 N / m, the number of pinholes in dry plating was 6428 / m 2 , no pinholes exceeding 30 ⁇ m in diameter, and the oligomer amount was 70%.
• the measurement of the concave defect of the two-layer flexible substrate which concerns on Example 6 was not performed.
• the resulting two-layer flexible substrate has an initial peel strength of 599 N / m, the number of pin holes in dry plating is 7143 / m 2, there are no pin holes exceeding 30 ⁇ m in diameter, the oligomer amount is 50%, and the number of concave defects is 1554 / m 2, and recessed defect diameter or maximum defect length exceeds 20 ⁇ m was none.
• Example 2 was carried out in the same manner as in Example 1 except that the gas pressure of the mixed gas of 50% by volume of argon and 50% by volume of nitrogen was 1.6 Pa, plasma treatment was performed for 50 seconds by applying DC 3000V to the plasma electrode.
• a layer flexible substrate was prepared.
• the resulting two-layer flexible substrate had an initial peel strength of 572 N / m, the number of pin holes for dry plating was 15286 / m 2, there were no pin holes exceeding 30 ⁇ m in diameter, the amount of oligomer was 30%, and the number of concave defects was 1861 / m 2, and recessed defect diameter or maximum defect length exceeds 20 ⁇ m was none.
• the obtained two-layer flexible substrate had an initial peel strength of 583 N / m, the number of pin holes for dry plating was 21286 / m 2 , had no pinholes exceeding 30 ⁇ m in diameter, the oligomer amount was 40%, and the number of concave defects was 1889. / m 2, and recessed defect diameter or maximum defect length exceeds 20 ⁇ m was none.
• the resulting two-layer flexible substrate had an initial peel strength of 608 N / m, the number of pin holes for dry plating was 15098 / m 2 and had no pinholes exceeding 30 ⁇ m in diameter, the oligomer amount was 63%, and the number of concave defects was 2017. / m 2, and recessed defect diameter or maximum defect length exceeds 20 ⁇ m was none.
• the resulting two-layer flexible substrate had an initial peel strength of 614 N / m, the number of pin holes for dry plating was 19713 / m 2 and had no pinholes exceeding 30 ⁇ m in diameter, the amount of oligomers was 70%, and the number of concave defects was 1798 / m 2, and recessed defect diameter or maximum defect length exceeds 20 ⁇ m was none.
• a two-layer flexible substrate according to Example 19 was prepared in the same manner as in Example 1 except that the argon gas pressure was 1.6 Pa, and a plasma treatment was performed for 12 seconds by applying a high frequency of 600 V to the plasma electrode.
• the resulting two-layer flexible substrate had an initial peel strength of 569 N / m, the number of pin holes for dry plating was 24384 / m 2 and had no pinholes exceeding 30 ⁇ m in diameter, the amount of oligomers was 62%, and the number of concave defects was 1720. / m 2, and recessed defect diameter or maximum defect length exceeds 20 ⁇ m was none.
• a two-layer flexible substrate according to Example 22 was produced in the same manner as in Example 1 except that the nitrogen gas pressure was 1.6 Pa, the plasma treatment was performed for 12 seconds by applying a high frequency of 600 V to the plasma electrode.
• Table 1 summarizes the results of the above examples and comparative examples.
• the insulator film is subjected to a surface treatment of plasma treatment under predetermined conditions according to the present invention, whereby the oligomer amount of the insulator film is reduced to 70% or less of the oligomer amount before the surface treatment. It is possible to suppress the number of pinholes in dry plating to 45000 / m 2 or less and the number of concave defects in the copper wet plating layer to 2200 / m 2 or less. Moreover, when the atmospheric pressure of the plasma treatment of the surface treatment is less than 0.8 Pa, it is confirmed that the discharge becomes unstable, and the insulator film cannot be subjected to the surface treatment. It is also clear that if the voltage applied to the plasma electrode is too high, the insulator film is wrinkled and a two-layer flexible substrate cannot be produced.

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