JP6546084B2 - Printed wiring board substrate and method of manufacturing printed wiring board substrate - Google Patents

Description

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

  For example, a metal layer formed of, for example, a metal or the like is laminated on at least one surface of an insulating base film formed of, for example, a resin, and a conductive pattern is formed by etching the metal layer to form a printed wiring board. Substrates for printed wiring boards to obtain such are widely used.

  A printed wiring board having a large peeling strength between a base film and a metal layer so as not to peel the metal layer from the base film when bending stress acts on the printed wiring board formed using such a printed wiring board Substrates are required.

  Further, in recent years, with the miniaturization and high performance of electronic devices, the densification of printed wiring boards has been required. In the printed wiring board having a high density, the conductive pattern is easily peeled off from the base film as the conductive pattern is miniaturized. Therefore, as a printed wiring board substrate satisfying such a demand for higher density, a printed wiring board substrate capable of forming a fine conductive pattern and having excellent adhesion between a metal layer and a base film is required.

  To meet such requirements, a copper thin film layer is formed on at least one surface of the base film using, for example, a sputtering method, and a copper thick film layer is formed on the copper thin film layer using an electroplating method. Techniques for increasing the adhesion between the layer and the base film are known. However, when the metal layer is directly laminated to the base film, it is known that the metal atoms of the metal layer diffuse into the base film with time and the adhesion between the metal layer and the base film is reduced. .

  Then, the technique of vapor-depositing the chromium thin film by sputtering on the joining surface with respect to the base film of copper foil, and thermocompression-bonding with respect to a base film is proposed (refer Unexamined-Japanese-Patent No. 2000-340911). Thus, by interposing a thin film of a metal different in type from the main metal of the metal layer at the interface between the metal layer and the base film, the transfer of the metal layer to the base film of the main metal is inhibited. The effect of suppressing the decrease in adhesion between the metal layer and the base film due to the diffusion of metal atoms into the base film is obtained.

JP, 2000-340911, A

  In the configuration described in the above publication, since a chromium thin film is formed on one side of the copper foil using a sputtering method, vacuum equipment is required, and the cost for construction, maintenance, operation, etc. of the equipment becomes high. . In addition, there is a limit in increasing the size of the substrate in terms of equipment.

  The present invention has been made based on the above-mentioned circumstances, and is for a printed wiring board and a printed wiring board, which are relatively inexpensive and in which the decrease in adhesion between the base film and the metal layer over time is relatively small. An object of the present invention is to provide a method of manufacturing a substrate.

  A substrate for a printed wiring board according to one aspect of the present invention made to solve the above problems is a printed wiring comprising a base film having an insulating property, and a metal layer laminated on at least one surface of the base film. It is a board | substrate for board | substrates, Comprising: A cobalt atom is contained in surface layer area | region of 1 micrometer in thickness direction from the interface with the metal layer in the said base film, The content rate of this cobalt atom is 1 atomic% or more and 15 atomic% or less.

  In addition, a method for manufacturing a substrate for a printed wiring board according to another aspect of the present invention made to solve the above problems includes a base film having an insulating property, and a metal laminated on at least one surface of the base film. And producing a substrate for a printed wiring board having a layer, wherein at least one surface of the base film is alkali-treated, and at least one surface of the base film after the alkali treatment step is an aqueous solution containing cobalt ions. And a step of contacting, and a step of laminating a metal layer on at least one surface of the base film after the contacting step.

  A substrate for a printed wiring board according to one aspect of the present invention and a substrate for a printed wiring board obtained by the method for producing a printed wiring board according to another aspect of the present invention are a relatively inexpensive base film and metal over time. The decrease in adhesion with the layer is relatively small.

FIG. 1 is a schematic cross-sectional view showing a printed wiring board according to an embodiment of the present invention. FIG. 2 is a detailed schematic cross-sectional view of the printed wiring board of FIG. FIG. 3 is a flow chart showing the procedure of the method of manufacturing the printed wiring board of FIG.

Description of the embodiment of the present invention
A printed wiring board substrate according to one aspect of the present invention is a printed wiring board substrate including a base film having an insulating property, and a metal layer laminated on at least one surface of the base film, A cobalt atom is contained in a surface region of 1 μm in the thickness direction from the interface with the metal layer in the film, and the content of this cobalt atom is 1 atomic% or more and 15 atomic% or less.

  The printed wiring board substrate contains cobalt atoms within the above content range in the surface layer region up to 1 μm in the thickness direction from the interface with the metal layer in the base film, and therefore this cobalt atom is a metal atom of the metal layer Diffusion to the base film. The treatment of causing the base film to contain cobalt atoms can be performed relatively easily, for example, by contacting the base film with a cobalt ion-containing aqueous solution. Therefore, the printed wiring board substrate is relatively inexpensive, but the decrease in the adhesion between the base film and the metal layer due to the change with time is relatively small.

  The metal layer may include a sintered layer of metal particles. Thus, when the said metal layer contains the sintered compact layer of a metal particle, a metal layer can be formed comparatively cheaply.

  The metal layer may include a plating layer. As described above, when the metal layer includes the plating layer, the metal layer can be relatively dense and excellent in conductivity.

  It is preferable that the cobalt atom be chemically bonded to the polymer constituting the base film. Thus, the chemical bonding of the cobalt atom to the polymer constituting the base film prevents the metal atoms of the metal layer from reacting with the functional groups of the polymer constituting the base film and being incorporated into the polymer. Since this can be performed, the diffusion of the metal atoms of the metal layer into the base film can be more reliably prevented, and the decrease in the adhesion between the base film and the metal layer can be suppressed more reliably.

  A method of manufacturing a printed wiring board according to another aspect of the present invention is a method of manufacturing a printed wiring board including a base film having insulation properties and a metal layer laminated on at least one surface of the base film. A method, comprising: alkali treating at least one surface of the base film; contacting an aqueous solution containing cobalt ions with at least one surface of the base film after the alkali treatment; and a base after the contact process. Laminating a metal layer on at least one surface of the film.

  The method for producing a substrate for a printed wiring board includes the step of bringing a cobalt ion-containing aqueous solution into contact with at least one surface of the base film after the alkali treatment step. It is considered that cobalt reacts chemically with the polymer constituting the base film by the reaction between the highly reactive functional group and the cobalt ion in the aqueous solution. Thereby, cobalt atoms can be contained in the surface region of the base film, and the cobalt atoms can suppress the diffusion of metal atoms of the metal layer into the base film. For this reason, although the board | substrate for printed wiring boards obtained by the manufacturing method of the said board | substrate for printed wiring boards is comparatively cheap, the fall of the adhesiveness of the base film and metal layer by a time-dependent change is comparatively small.

  The cobalt ion-containing aqueous solution is preferably a cobalt acetate aqueous solution. As described above, when the cobalt ion-containing aqueous solution is a cobalt acetate aqueous solution, cobalt atoms can be relatively efficiently contained in the surface layer region of the base film, and therefore, the adhesion between the base film and the metal layer due to aging. Can be more effectively suppressed.

  The metal layer laminating step may include the step of applying the metal particle dispersion to at least one surface of the base film and heating the metal particle dispersion. Thus, the metal layer laminating step includes the step of applying the metal particle dispersion to at least one surface of the base film and heating the same, thereby eliminating the need for large-scale equipment and relatively simple and inexpensive. A metal layer can be laminated on at least one surface of the base film.

  Here, “content of atom” means, for example, X-ray photoelectron spectroscopy (ESCA) or X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX) ray spectroscopy or EDS (energy dispersive X-ray spectroscopy), electron probe micro analysis (EPMA), time-of-flight secondary ion mass spectrometry (TOF-SIMS), time-of-flight secondary ion mass spectrometry (TOF-SIMS) two Ion mass spectrometry (SIMS: Secondary Ion Mass Spectrometry), Auger electron spectroscopy can be measured by (AES Auger Electron Spectroscopy) and the like. In the case of X-ray photoelectron spectroscopy, measurement conditions are as follows: K alpha ray of aluminum metal, beam diameter 50 μm, X-ray incident angle to the surface to be analyzed 45 °, and scanning cross section be able to. As a measurement apparatus, for example, a scanning X-ray photoelectron spectrometer "Quantera" manufactured by ULVAC-Phi, etc. can be used.

Details of the Embodiment of the Present Invention
Hereinafter, each embodiment of a printed wiring board and a method for manufacturing the printed wiring board according to the present invention will be described in detail with reference to the drawings.

[Board for printed wiring board]
As shown in FIG. 1, the printed wiring board substrate according to the embodiment of the present invention includes a base film 1 having insulation properties, and a metal layer 2 laminated on one surface (surface) of the base film 1. Prepare.

<Base film>
The base film 1 of the printed wiring board substrate contains cobalt atoms in a surface region A of 1 μm in the thickness direction from the interface with the metal layer 2. The cobalt atoms contained in the surface region A of the base film 1 inhibit the metal atoms constituting the metal layer 2 from diffusing into the base film 1. Moreover, since the process which makes the surface area | region A of the base film 1 contain a cobalt atom is comparatively easy, the said board | substrate for printed wiring boards can be provided comparatively cheaply. Therefore, the printed wiring board substrate is relatively inexpensive, but the decrease in adhesion between the base film 1 and the metal layer 2 due to the change with time is relatively small.

  The lower limit of the content of cobalt atoms in the surface layer region A is 1 atomic%, preferably 2 atomic%, and more preferably 5%. On the other hand, the upper limit of the content of cobalt atoms in the surface layer region A is 15 atomic%, preferably 13 atomic%, and more preferably 12%. When the content of cobalt atoms in the surface region A is less than the above lower limit, the diffusion of metal atoms of the metal layer 2 into the base film 1 can not be sufficiently prevented, and adhesion between the base film 1 and the metal layer 2 due to aging. There is a possibility that the decrease in sex can not be sufficiently suppressed. Conversely, when the content of cobalt atoms in the surface layer region A exceeds the above upper limit, the adhesion between the base film 1 and the metal layer 2 in the initial stage (immediately after the production of the printed wiring board) may be insufficient. is there.

  The thickness of the base film 1 is set by a printed wiring board using the printed wiring board and is not particularly limited. For example, as the lower limit of the average thickness of the base film 1, 5 μm is preferable and 12 μm. Is more preferred. On the other hand, as an upper limit of the average thickness of the base film 1, 2 mm is preferable and 1.6 mm is more preferable. If the average thickness of the base film 1 is less than the above lower limit, the strength of the base film 1 and thus the printed wiring board may be insufficient. On the contrary, when the average thickness of the base film 1 exceeds the above-mentioned upper limit, there is a possibility that the substrate for printed wiring boards may become unnecessarily thick.

  The material of the base film 1 is, for example, a flexible resin such as polyimide, liquid crystal polymer, fluorine resin, polyethylene terephthalate, polyethylene naphthalate, paper phenol, paper epoxy, glass composite, glass epoxy, polytetrafluoroethylene, glass It is possible to use a rigid material such as a base material, a rigid flexible material in which a hard material and a soft material are combined, and the like. Among these, polymers having polyimide as a main component are particularly preferable because they have large bonding strength with metal oxides and the like and are excellent in insulation properties and mechanical strength.

  Thus, when the base film 1 is constituted by a polymer, the cobalt atoms are preferably chemically bonded to the polymer constituting the base film 1. The chemical bonding of the cobalt atoms to the polymer constituting the base film 1 can suppress the metal atoms of the metal layer 2 from reacting with the functional groups of the polymer constituting the base film 1 and being incorporated into the polymer. Thereby, the metal atoms of the metal layer 2 can be more reliably prevented from diffusing into the base film 1, and the decrease in the adhesion between the base film and the metal layer can be more reliably suppressed.

(Polyimide)
As polyimide which is a main component of the base film 1, thermosetting polyimide (also referred to as condensation type polyimide) or thermoplastic polyimide can be used. Among these, thermosetting polyimide is preferable from the viewpoint of heat resistance, tensile strength, tensile elastic modulus and the like.

  The polyimide may be a homopolymer consisting of one structural unit or a copolymer consisting of two or more structural units, or a blend of two or more homopolymers. Although it is preferable, one having a structural unit represented by the following formula (1) is preferable.

  The structural unit represented by the said Formula (1) synthesize | combines the polyamic acid which is a polyimide precursor, using a pyromellitic dianhydride and 4, 4'- diamino diphenyl ether, for example, This is imidated by heating etc. It is obtained by doing.

  As a minimum of content of the above-mentioned structural unit, 10 mass% is preferred, 15 mass% is more preferred, and 18 mass% is still more preferred. On the other hand, as a maximum of content of the above-mentioned structural unit, 50 mass% is preferred, 40 mass% is more preferred, and 35 mass% is still more preferred. If the content of the structural unit is less than the above lower limit, the strength of the printed wiring board and thus the printed wiring board formed using the printed wiring board may be insufficient. In contrast, when the content of the structural unit exceeds the upper limit, the flexibility of the printed wiring board may be insufficient.

  In the base film 1 containing polyimide as a main component, it is preferable that at least the interface with the metal layer 2 be modified to open a part of the imide ring of the polyimide. Such modification can be performed by a known treatment method such as alkali treatment or plasma treatment.

  The lower limit of the ring opening ratio of the imide ring at the interface with the metal layer 2 of the base film 1 is preferably 3%, and more preferably 15%. On the other hand, as an upper limit of the ring-opening rate of the imide ring of the interface with the metal layer 2 of the base film 1, 70% is preferable and 60% is more preferable. If the ring opening ratio of the imide ring at the interface with the metal layer 2 of the base film 1 does not reach the above lower limit, the adhesion between the base film 1 and the metal layer 2 in the initial stage may be insufficient. Conversely, when the ring opening ratio of the imide ring at the interface with the metal layer 2 of the base film 1 exceeds the above upper limit, the strength of the base film 1 may be insufficient, and peeling of the metal layer 2 due to substrate breakage may easily occur. There is.

  In addition, the ring-opening rate of the imide ring at the interface between the base film 1 and the metal layer 2 can be calculated, for example, from the peak intensity indicating the imide ring in the absorption intensity spectrum obtained by infrared absorption analysis. . More specifically, the ring opening ratio of the imide ring at the interface between the base film 1 and the metal layer 2 is measured by infrared total reflection absorption measurement using a single reflection ATR (Attenuated Total Reflection) measurement apparatus using a diamond prism. It can be measured.

In the absorption intensity spectrum at an incident angle of 45 ° by infrared total reflection absorptiometry, the peak intensity at a wavenumber of 1494 cm ^{-1 is} a peak intensity indicating the number of benzene rings, even when the imide ring of polyimide is opened. It is a value that does not change. On the other hand, the peak intensity at a wavenumber of 1705 cm ⁻¹ in the absorption intensity spectrum is a peak intensity indicating the number of carbonyl groups of imide bond, and is a value which decreases as the imide ring of the polyimide is opened. Therefore, it is possible to estimate the ring opening of the polyimide imide ring from the ratio of the peak intensity at a wavenumber of 1705 cm ^-1 to the peak intensity at a wavenumber of 1494cm ^-1 in the absorption intensity spectrum. Specifically, ring-opening of the polyimide of the imide ring is proportional to the ratio of the peak intensity at a wavenumber of 1705 cm ^-1 to the peak intensity at a wavenumber of 1494cm ^-1 in the absorption intensity spectrum, when opening ratio of 0% The ratio of the peak intensities is about 1.1.

  Moreover, the infrared absorption analysis of the interface of the base film 1 and the metal layer 2 becomes possible by removing the metal layer 2 by the etching using an acidic solution.

  As an acidic solution used for the etching for removing the metal layer 2, the acidic etching liquid generally used for metal layer removal can be used, for example, a copper chloride solution, hydrochloric acid, a sulfuric acid, aqua regia etc. are mentioned.

  As a minimum of the temperature of the above-mentioned etching liquid at the time of etching, 10 ° C is preferred and 20 ° C is more preferred. On the other hand, as an upper limit of the temperature of the above-mentioned etching solution, 90 ° C is preferred and 70 ° C is more preferred. When the temperature of the etching solution does not reach the lower limit, the time required for the etching may be long, and the workability may be lowered. Conversely, when the temperature of the etching solution exceeds the upper limit, the energy cost for temperature control may be unnecessarily increased.

  As a minimum of the above-mentioned etching time, 1 minute is preferred, and 10 minutes is more preferred. On the other hand, as an upper limit of the said etching time, 60 minutes are preferable and 30 minutes are more preferable. If the etching time is less than the lower limit, the concentration of the etching solution may be high, which may make it difficult to handle. On the contrary, when the above-mentioned etching time exceeds the above-mentioned upper limit, there is a possibility that workability may fall.

<Metal layer>
In the substrate for a printed wiring board, the metal layer 2 may include a sintered layer of metal particles. The sintered body layer of the metal particles can be formed relatively easily and inexpensively without requiring a large-scale apparatus such as a vacuum facility, so by providing the sintered body layer of the metal particles, for the printed wiring board The manufacturing cost of the substrate can be suppressed.

  In addition, the metal layer 2 may include a plating layer formed by lamination of metals by plating (electroless plating or electroplating). By providing the plating layer, it becomes easy to make the metal layer 2 relatively inexpensive, dense and excellent in conductivity.

  Specifically, as shown in FIG. 2, the metal layer 2 is, for example, a sintered layer 3 laminated on the surface of the base film 1 by sintering a plurality of metal particles, and this sintered layer The electroless plating layer 4 may be laminated on the surface 3 by the electroless plating, and the electroplating layer 5 may be further laminated on the surface of the electroless plating layer 4 by electroplating.

  As a main metal of the metal layer 2, copper, nickel, aluminum, gold, silver etc. can be used, for example. Among them, copper is suitably used as a metal which is excellent in conductivity, excellent in adhesion to the base film 1 and easy to pattern by etching and relatively inexpensive. When the main metal of the metal layer 2 is copper, the effect of suppressing the decrease in adhesion with the metal layer 2 by containing cobalt atoms in the surface region A of the base film 1 is remarkable.

(Sintered body layer)
The sintered body layer 3 is formed by coating a metal particle dispersion liquid (ink) containing a plurality of metal particles mainly composed of a metal serving as a main metal of the metal layer 2 on the modified surface of the base film 1 It can be laminated on the surface of the base film 1 by firing. Thus, the metal layer 2 can be easily and inexpensively formed on the surface of the base film 1 by using the metal particle dispersion.

  As a lower limit of the average particle diameter of the metal particle which forms the sintered compact layer 3, 1 nm is preferable and 30 nm is more preferable. On the other hand, as an upper limit of the average particle diameter of the said metal particle, 500 nm is preferable and 100 nm is more preferable. When the average particle diameter of the metal particles is less than the above lower limit, for example, the dispersibility and stability of the metal particles in the metal particle dispersion decrease, so that they are uniformly laminated on the surface of the base film 1 It may not be easy. Conversely, when the average particle size of the metal particles exceeds the upper limit, the gaps between the metal particles become large, and it may not be easy to reduce the porosity of the sintered body layer 3. The “average particle size” means a particle size at which the volume integrated value is 50% in the distribution of particle sizes measured by the laser diffraction method.

  As a lower limit of the average thickness of the sintered compact layer 3, 50 nm is preferable and 100 nm is more preferable. On the other hand, as an upper limit of the average thickness of the sintered compact layer 3, 2 micrometers is preferable and 1.5 micrometers is more preferable. When the average thickness of the sintered body layer 3 is less than the above-mentioned lower limit, there are many parts where metal particles do not exist in a plan view, and the conductivity may be lowered. Conversely, when the average thickness of the sintered body layer 3 exceeds the above upper limit, it may be difficult to sufficiently reduce the porosity of the sintered body layer 3 or the metal layer 2 may be unnecessarily thick. is there.

(Electroless plating layer)
The electroless plating layer 4 is formed by laminating the same metal as the main metal of the metal particles forming the sintered body layer 3 by electroless plating on the outer surface of the sintered body layer 3. In addition, the electroless plating layer 4 is formed so as to be impregnated into the inside of the sintered body layer 3. That is, by filling the gaps between the metal particles forming the sintered body layer 3 with the main metal by electroless plating, the voids in the sintered body layer 3 are reduced. Thus, the gaps between the metal particles are reduced by filling the gaps between the metal particles with the electroless plating metal, whereby the voids become the fracture origin and the sintered body layer 3 is peeled off from the base film 1 Can be suppressed.

  The electroless plating layer 4 may be formed only inside the sintered body layer 3 depending on the conditions of the electroless plating. As a general theory, the lower limit of the average thickness of the electroless plating layer 4 formed on the outer surface of the sintered body layer 3 (not including the thickness of the plated metal inside the sintered body layer 3) is 0. 2 micrometers is preferable and 0.3 micrometers is more preferable. On the other hand, as an upper limit of the average thickness of the electroless-plating layer 4 formed in the outer surface of the sintered compact layer 3, 1 micrometer is preferable and 0.7 micrometer is more preferable. When the average thickness of the electroless plating layer 4 formed on the outer surface of the sintered body layer 3 is less than the above lower limit, the electroless plating layer 4 is not sufficiently filled in the gaps of the metal particles of the sintered body layer 3 Since the porosity can not be sufficiently reduced, the peel strength between the base film 1 and the metal layer 2 may be insufficient. Conversely, when the average thickness of the electroless plating layer 4 formed on the outer surface of the sintered body layer 3 exceeds the above upper limit, the time required for the electroless plating may be prolonged, and the manufacturing cost may be unnecessarily increased. .

(Electroplated layer)
The electroplating layer 5 is formed by further laminating the above-mentioned main metal on the outer surface side of the sintered body layer 3, that is, the outer surface of the electroless plating layer 4 by electroplating. The thickness of the metal layer 2 can be easily and accurately adjusted by the electroplating layer 5. Moreover, it is possible to increase the thickness of the metal layer 2 in a short time by using electroplating.

  The thickness of the electroplating layer 5 is set according to the type and thickness of the conductive pattern required for the printed wiring board formed using the printed wiring board, and is not particularly limited. In general, the lower limit of the average thickness of the electroplating layer 5 is preferably 1 μm, more preferably 2 μm. On the other hand, as an upper limit of average thickness of electroplating layer 5, 100 micrometers is preferred and 50 micrometers is more preferred. If the average thickness of the electroplating layer 5 is less than the above lower limit, the metal layer 2 may be easily damaged. Conversely, when the average thickness of the electroplating layer 5 exceeds the above upper limit, the printed wiring board substrate may be unnecessarily thick, or the flexibility of the printed wiring board substrate may be insufficient. is there.

[Method of manufacturing printed wiring board substrate]
As a specific example, as shown in FIG. 3, the printed wiring board substrate has a step of subjecting the surface of the base film 1 to alkali treatment (step S1: step of alkali treatment) and a step of alkali treatment on the surface of the base film 1 after the step of alkali treatment. Manufacturing by a method including the step of contacting a cobalt ion-containing aqueous solution (step S2: contacting step) and the step of laminating the metal layer 2 on the surface of the base film 1 after the contacting step (step S3: laminating step) it can.

<Alkali treatment process>
In the alkali treatment step of step S1, the alkali solution is brought into contact with the surface of the base film 1 on which at least the metal layer 2 is to be laminated, thereby weakening the bond of the polymer constituting the base film 1 to impart reactivity. The cobalt film is easily contained in the base film 1 in the contact step described later. Typically, a part of the imide ring of the base film 1 mainly composed of polyimide is opened. In the alkali treatment step, the entire base film 1 may be immersed in an alkali solution.

  As an alkali liquid used at this alkali treatment process, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, etc. are mentioned, for example, Generally, sodium hydroxide aqueous solution is used.

  The pH of the alkaline solution used in the alkaline treatment step can be, for example, 12 or more and 15 or less. Further, the contact time of the base film 1 with the alkaline solution can be, for example, 15 seconds or more and 10 minutes or less. The temperature of the alkaline solution can be, for example, 10 ° C. or more and 70 ° C. or less.

  Moreover, it is preferable that the alkali treatment process has a water washing process of washing the base film 1 with water. In the water washing step, the base film 1 is washed with water to remove the alkaline solution adhering to the surface of the base film 1. Furthermore, it is more preferable that the alkali treatment step has a drying step of drying the washing water after the water washing step. Stabilize the quality of the base film 1 by evaporating the water in the base film 1 to precipitate the ions in the base film 1 as a metal or metal oxide, or by combining it with the resin component of the base film 1 or the like. can do.

<Contact process>
In the contact step of step S 2, a cobalt ion is introduced into the surface layer region A of the base film 1 by bringing the aqueous solution containing cobalt ions into contact with the alkali-treated surface of the base film 1. Specifically, a relatively reactive functional group formed by alkali treatment reacts with a cobalt ion and a polymer constituting base film 1, and a cobalt atom is chemically bonded to a polymer constituting base film 1. Cobalt atoms are considered to be taken into the surface region A of the base film 1 by this. In the contacting step, the entire base film 1 may be immersed in a cobalt ion-containing aqueous solution.

  Examples of the cobalt ion-containing aqueous solution include cobalt acetate aqueous solution, cobalt bromide aqueous solution, cobalt chloride aqueous solution, cobalt benzoate aqueous solution, cobalt nitrate aqueous solution and the like, and a cobalt acetate aqueous solution relatively easy to obtain and handle is preferably used Be Also, these aqueous solutions can be prepared by dissolving a cobalt compound or a hydrate thereof in water.

  As a minimum of cobalt ion concentration of cobalt ion content solution, 0.05 mol / L is preferred, and 0.1 mol / L is more preferred. On the other hand, as a maximum of cobalt ion concentration of cobalt ion content solution, 2 mol / L is preferred and 1 mol / L is more preferred. When the cobalt ion concentration of the cobalt ion-containing aqueous solution is less than the above lower limit, the productivity of the printed wiring board substrate may be insufficient due to the long processing time. Conversely, when the cobalt ion concentration of the cobalt ion-containing aqueous solution exceeds the above upper limit, adjustment of the cobalt atom content may not be easy.

  As a minimum of temperature of cobalt ion content solution, 5 ° C is preferred and 10 ° C is more preferred. On the other hand, as a maximum of temperature of cobalt ion content solution, 60 ° C is preferred and 45 ° C is more preferred. When the temperature of the cobalt ion-containing aqueous solution is less than the above lower limit, the productivity of the printed wiring board may be insufficient due to the long processing time. Conversely, when the temperature of the cobalt ion-containing aqueous solution exceeds the above upper limit, adjustment of the cobalt atom content may not be easy, and energy costs for temperature control may be unnecessarily increased.

  As a minimum of contact time of cobalt ion content solution to base film 1, 0.5 minutes are preferred and 1 minute is more preferred. On the other hand, as an upper limit of contact time of cobalt ion content solution to base film 1, 10 minutes are preferred and 5 minutes are more preferred. When the contact time of the cobalt ion-containing aqueous solution with the base film 1 is less than the above lower limit, the concentration of the cobalt ion-containing aqueous solution needs to be increased, and thus the handling may not be easy. Conversely, when the contact time of the cobalt ion-containing aqueous solution with the base film 1 exceeds the above upper limit, the productivity of the printed wiring board may be insufficient.

  The cobalt ion concentration of the cobalt ion-containing aqueous solution, the temperature and the optimal contact time to the base film 1 mutually affect each other, and also differ depending on the conditions of the alkali treatment. It may be appropriately selected so as to achieve the cobalt atom content.

<Lamination process>
The laminating step of step S3 includes the step of forming the sintered body layer 3 by applying and heating a metal particle dispersion containing a plurality of metal particles, in that the metal layer can be formed relatively inexpensively. preferable. Moreover, it is preferable that a lamination process has the process of forming the electroless-plating layer 4 by electroless plating, and the process of forming the electroplating layer 5 by electroplating.

(Sintered body layer forming process)
As the metal particle dispersion liquid used in this sintered body layer forming step, one containing a dispersion medium of metal particles and a dispersing agent for uniformly dispersing metal particles in the dispersion medium is suitably used. By using the metal particle dispersion liquid in which the metal particles are dispersed uniformly in this manner, the metal particles can be uniformly attached to the surface of the base film 1, and the uniform sintered layer 3 is formed on the surface of the base film 1. It can be formed.

  The metal particles contained in the metal particle dispersion can be produced by a high temperature treatment method, a liquid phase reduction method, a gas phase method or the like, but a liquid phase reduction method capable of producing particles having a uniform particle diameter relatively inexpensively. It is preferred to use those produced by

  The dispersant contained in the metal particle dispersion is not particularly limited, but it is preferable to use a polymer dispersant having a molecular weight of 2,000 or more and 300,000 or less. As described above, by using the polymer dispersant having the molecular weight in the above range, metal particles can be favorably dispersed in the dispersion medium, and the film quality of the obtained sintered body layer 3 is compact and free of defects. Can be If the molecular weight of the dispersant is less than the above lower limit, there is a possibility that the effect of preventing aggregation of the metal particles and maintaining the dispersion may not be sufficiently obtained. As a result, the sintered layer laminated on the base film 1 There is a possibility that 3 can not be made precise and have few defects. Conversely, if the molecular weight of the dispersant exceeds the above upper limit, the bulk of the dispersant is too large, and during the heating after the application of the metal particle dispersion, the sintering of the metal particles may be inhibited to form voids. is there. When the bulk of the dispersant is too large, the density of the film quality of the sintered body layer 3 may be reduced, or the decomposition residue of the dispersant may reduce the conductivity.

  The dispersant preferably contains no sulfur, phosphorus, boron, halogen and alkali from the viewpoint of preventing deterioration of parts. Preferred dispersants are those having a molecular weight in the above range, and polymeric dispersants of amines such as polyethylenimine and polyvinylpyrrolidone, and hydrocarbons based on having carboxylic acid groups in the molecule such as polyacrylic acid and carboxymethylcellulose. Polar group such as polymer dispersant, poval (polyvinyl alcohol), styrene-maleic acid copolymer, olefin-maleic acid copolymer, or copolymer having polyethyleneimine moiety and polyethylene oxide moiety in one molecule The polymer dispersing agent etc. which it has can be mentioned.

  The dispersant can also be added to the reaction system in the form of a solution dissolved in water or a water-soluble organic solvent. As a content rate of a dispersing agent, 1 mass part or more and 60 mass parts or less are preferable per 100 mass parts of metal particles. The dispersing agent prevents aggregation by surrounding the metal particles and disperses the metal particles well. However, when the content ratio of the dispersing agent is less than the above lower limit, the aggregation preventing effect may be insufficient. Conversely, when the content ratio of the dispersant exceeds the above upper limit, an excess of the dispersant may inhibit sintering of the metal particles in the heating step after the application of the metal particle dispersion, and voids may be generated. In addition, the decomposition residue of the polymer dispersant may remain as an impurity in the sintered body layer 3 to lower the conductivity.

  As a content rate of the water used as a dispersion medium in a metal particle dispersion liquid, 20 mass parts or more and 1900 mass parts or less are preferred per 100 mass parts of metal particles. The water of the dispersion medium fully swells the dispersing agent to disperse the metal particles surrounded by the dispersing agent well, but when the content ratio of the water is less than the above lower limit, the swelling effect of the dispersing agent by water May be insufficient. Conversely, when the water content ratio exceeds the upper limit, the metal particle ratio in the metal particle dispersion decreases, and a good sintered body layer 3 having a thickness and a density necessary for the surface of the base film 1 is obtained. There is a possibility that it can not be formed.

  Various organic solvents which are water-soluble can be used as the organic solvent to be added to the metal particle dispersion as required. Specific examples thereof include alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol, ketones such as acetone and methyl ethyl ketone, Examples thereof include polyhydric alcohols such as ethylene glycol and glycerin, and other esters, and glycol ethers such as ethylene glycol monoethyl ether and diethylene glycol monobutyl ether.

  As a content rate of the water-soluble organic solvent in a metal particle dispersion liquid, 30 mass parts or more and 900 mass parts or less are preferable with respect to 100 mass parts of metal particles. If the content ratio of the water-soluble organic solvent is less than the above lower limit, the effects of adjusting the viscosity of the dispersion and adjusting the vapor pressure with the organic solvent may not be sufficiently obtained. On the other hand, when the content ratio of the water-soluble organic solvent exceeds the upper limit, the swelling effect of the dispersing agent by water is insufficient, and there is a possibility that aggregation of metal particles may occur in the metal particle dispersion.

  Examples of the method for applying the metal particle dispersion to the base film 1 include conventionally known coating methods such as spin coating, spray coating, bar coating, die coating, slit coating, roll coating, and dip coating. It can be used. Alternatively, the metal particle dispersion may be applied to only a part of the surface of the base film 1 by screen printing, a dispenser, or the like, for example.

  And the coating film of the metal particle dispersion liquid which apply | coated the metal particle dispersion liquid to the base film 1 is heated. As a result, the solvent dispersant of the metal particle dispersion is evaporated or thermally decomposed, and the remaining metal particles are sintered to obtain a sintered body layer 3 fixed to the surface of the base film 1. In addition, it is preferable to dry the coating film of a metal particle dispersion liquid before the said heating.

  The sintering is preferably performed in an atmosphere containing a certain amount of oxygen. As a minimum of oxygen concentration of atmosphere at the time of sintering, 1 volume ppm is preferred, and 10 volume ppm is more preferred. On the other hand, the upper limit of the oxygen concentration is preferably 10,000 ppm by volume, and more preferably 1,000 ppm by volume. When the oxygen concentration is less than the above lower limit, the amount of metal oxide formed near the interface of the sintered body layer 3 decreases, and the adhesion between the base film 1 and the sintered body layer 3 may not be sufficiently improved. is there. On the other hand, when the oxygen concentration exceeds the upper limit, the metal particles may be excessively oxidized to reduce the conductivity of the sintered body layer 3.

  As a minimum of the above-mentioned sintering temperature, 150 ° C is preferred and 200 ° C is more preferred. On the other hand, as an upper limit of the above-mentioned sintering temperature, 500 ° C is preferred and 400 ° C is more preferred. If the sintering temperature does not reach the above lower limit, the metal particles can not be connected, and there is a possibility that the sintered body layer 3 may collapse at the time of forming the next electroless plating layer 4. Conversely, when the sintering temperature exceeds the upper limit, the base film 1 may be deformed.

(Electroless plating layer formation process)
In the electroless plating layer forming step, the electroless plating layer 4 is formed by performing electroless plating on the surface of the sintered body layer 3 laminated on the surface of the base film 1 in the sintered body layer forming step.

  The above-mentioned electroless plating is preferably performed together with processing such as a cleaner step, water washing step, acid treatment step, water washing step, pre-dip step, activator step, water washing step, reduction step, water washing step and the like.

  In addition, after forming the electroless plating layer 4 by electroless plating, it is preferable to further perform a heat treatment. When heat treatment is performed after the formation of the electroless plating layer 4, metal oxide and the like in the vicinity of the interface between the sintered body layer 3 and the base film 1 further increase, and the adhesion between the base film 1 and the sintered body layer 3 Becomes even larger. The temperature and the oxygen concentration of the heat treatment after the electroless plating can be the same as the heating temperature and the oxygen concentration in the sintered body layer forming step.

(Electroplating layer formation process)
In the electroplating layer formation step, the electroplating layer 5 is laminated on the outer surface of the electroless plating layer 4 by electroplating. In the electroplating layer forming step, the thickness of the entire metal layer 3 is increased to a desired thickness.

  This electroplating is performed using a conventionally known electroplating bath corresponding to the metal to be plated, for example, copper, nickel, silver, etc., and selecting appropriate conditions so that the metal layer 3 of the desired thickness can be rapidly and without defects. It can be done as it is formed.

<Advantage>
As described above, since the printed wiring board substrate contains cobalt atoms within the above content range in the surface region A of 1 μm in the thickness direction from the interface with the metal layer 2 in the base film 1, the cobalt The atoms suppress the diffusion of the metal atoms of the metal layer 2 into the base film 1. Since the above-mentioned contact process for containing cobalt atoms in the base film 2 can be performed relatively easily, the printed wiring board substrate is relatively inexpensive, and the base film 1 and metal layer due to aging change. The decrease in adhesion with 2 is relatively small.

Other Embodiments
It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is not limited to the configurations of the above embodiments, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. Ru.

  The printed wiring board substrate may be manufactured by a method different from the method for manufacturing the printed wiring board shown in FIG. For example, the printed wiring board substrate may be manufactured by omitting the alkali treatment step, and the surface of the base film is modified by, for example, plasma treatment instead of the alkali treatment. May be

  Furthermore, the detailed structure and lamination method of the metal layer in the said board | substrate for printed wiring boards are arbitrary. Specifically, the metal layer of the printed wiring board substrate may not have one or more of a sintered body layer, an electroless plating layer and an electroplating layer, and the metal film is heated to the base film. It may be crimped.

  Further, the printed wiring board substrate may be a double-sided substrate in which metal layers are laminated on both sides of a base fill, or a multilayer substrate comprising a plurality of base films or insulating layers and three or more metal layers. When a plurality of metal layers are provided, the printed wiring board substrate may have a structure in which the content of cobalt atoms in any of the surface layer regions of the base film is within the above range.

  Hereinafter, the present invention will be described in detail based on examples, but the present invention is not to be construed as being limited based on the description of the examples.

  After alkali treatment of the surface of the base film made of polyimide in the following manner, cobalt atoms are contained in the surface layer region, and then a prototype No. 1 of a printed wiring board substrate on which a metal layer is laminated. 1 to No. 14 was produced. Prototype No. of these printed circuit board substrates 1 to No. In the preparation process of 14, the ring opening ratio of the imide ring on the surface of the base film after alkali treatment and the cobalt atom content in the surface region of 1 μm in the thickness direction from the surface of the base film after containing cobalt atoms And were measured. Also, for a prototype of a printed wiring board substrate, 1 to No. The peel strength between the base film and the metal layer immediately after preparation was measured, and the peel strength between the base film and the metal layer after being subjected to a heat resistance test maintained at a temperature of 150 ° C. for 7 days was measured.

(Prototype No. 1)
A polyimide film “Kapton EN-S” (average thickness 25 μm) manufactured by Toray DuPont Co., Ltd. is used as a base film, and first immersed for 90 seconds in an aqueous solution of sodium hydroxide having a concentration of 100 g / L at a temperature of 40 ° C. for 10 seconds. Was washed three times with water and dried. Next, the above-mentioned alkali treatment is performed on a cobalt ion-containing aqueous solution (0.15 mol / L in terms of molar concentration of cobalt ion) having a temperature of 25 ° C. and cobalt acetate tetrahydrate dissolved in water at a ratio of 37.0 g / L. The base film thus obtained was immersed for 90 seconds to contain cobalt atoms in the surface layer region, washed with water for 10 seconds three times, and dried. Furthermore, a printed wiring board is formed by laminating a sintered layer of copper particles, an electroless plating layer, and an electroplating layer in this order on the surface of the base film containing the cobalt atoms. No. of prototypes of printed circuit boards I got one.

  The sinter layer is formed by applying a copper particle dispersion having a copper concentration of 26% by mass, in which copper particles having an average particle size of 70 nm are dispersed in water, on the surface of a base film; It was formed by heating at a temperature of 350 ° C. for 30 minutes in an atmosphere, and its average thickness was 0.15 μm. Electroless copper plating was performed on the sintered body layer to form an electroless plating layer, and the total average thickness of the sintered body layer and the electroless plating layer was 0.45 μm. Furthermore, an electroplating layer having an average thickness of 18 μm was laminated by performing electrolytic copper plating on the electroless plating layer to form a metal layer having a three-layer structure.

(Prototype No. 2 to 7)
Change the alkali treatment time with sodium hydroxide aqueous solution, cobalt acetate tetrahydrate dissolved amount (cobalt ion concentration after dissolution) and immersion time of cobalt ion-containing aqueous solution, and average particle diameter of copper particles forming sintered body layer The other is a prototype No. Prototype No. 1 of a printed wiring board substrate under the same conditions as No. 1 I got 2-7. The average thickness of the metal layer after electroless plating (the total average thickness of the sintered body layer and the electroless plating layer) was also different due to the difference in the average particle diameter of the copper particles. The differences between these conditions are summarized in Table 1.

(Prototype No. 8 to 14)
Furthermore, using a polyimide film “Apical NPI” (average thickness 25 μm) manufactured by Kaneka Corporation as the base film, the alkali treatment time with sodium hydroxide aqueous solution, cobalt acetate tetrahydrate dissolved amount of cobalt ion containing aqueous solution and immersion time , And the average particle diameter of the copper particles forming the sintered body layer (and the average thickness of the metal layer after electroless plating accompanying this), the other is a prototype of a printed wiring board substrate under the same conditions No. I got 8-14. These conditions are also summarized in Table 1.

(Imide ring opening rate)
The ring-opening rate of the imide ring of polyimide is measured using the infrared total reflection absorption measurement (FT-IR) apparatus “Nicolet 8700” manufactured by Thermo Fisher, and the single reflection ATR accessory “Dura Scope” (diamond prism) manufactured by SensIR. The absorption intensity spectrum in the measurement wave number range of 4000 to 650 cm ⁻¹ at an incident angle of 45 ° is measured with the resolution set to 4 cm ⁻¹ as the number of integrations (number of scans) of 16 times. The ratio of the peak intensity of wave number 1705 cm ^{−1 to} the peak intensity of wave number 1494 cm ⁻¹ was calculated from the intensity spectrum, and the ratio of peak intensity of the base film not subjected to the surface treatment was converted to 100%. The imide ring opening ratio is shown in Table 1.

(Cobalt content rate)
The content of cobalt atoms in the surface area of the base film is analyzed using a scanning X-ray photoelectron spectrometer "Quantera" manufactured by ULVAC-Phi, using an X-ray source of K alpha rays of aluminum metal and a beam diameter of 50 μm, The X-ray incident angle to the surface was measured as 45 °. The content of cobalt atoms is shown in Table 1.

(Peeling strength)
Peeling strength was measured by the method according to JIS-K-6854-2 (1999) "Adhesive agent-peeling adhesion strength test method 2 part: 180 degree peeling" by using a resin film as a flexible adherend. The peel strength is shown in Table 1.

  As described above, it is a prototype No. 1 that contains 1 atomic% or more and 15 atomic% or less cobalt atoms in the surface layer region of the base film. 1 to 3 and No. 1 8 to 10 have relatively high peel strength both before and after the heat resistance test, and the change in peel strength before and after the heat resistance test is small, and the adhesion between the base film and the metal layer decreases with time. Was confirmed to be relatively small. On the other hand, prototype No. 1 in which the cobalt atom content in the surface region of the base film is greater than 15 atomic%. 4 and No. 4 In No. 11, although the decrease in peel strength before and after the heat resistance test was small, the peel strength before the heat resistance test was insufficient. In addition, a prototype No. 1 which does not contain cobalt element in the surface region of the base film. 5 to 7 and No. Although the peel strength before the heat resistance test was sufficient, the decrease in peel strength in the heat resistance test was relatively large, and the decrease in adhesion between the base film and the metal layer over time was relatively large. .

  The printed wiring board substrate and the method for manufacturing the printed wiring board substrate according to the embodiment of the present invention can be widely used to manufacture a printed wiring board.

1 Base Film 2 Metal Layer 3 Sintered Layer 4 Electroless Plating Layer 5 Electroplating Layer A Surface Area S 1 Alkaline Treatment Step S 2 Contact Step S 3 Lamination Step

Claims (5)

A base film having an insulating property;
And a metal layer laminated on at least one surface of the base film.
A cobalt atom is contained in a surface region of 1 μm in the thickness direction from the interface with the metal layer in the above base film,
15 atomic% der less content of more than 1 atomic% of the cobalt atoms is,
A substrate for a printed wiring board, wherein the metal layer comprises a sintered layer of metal particles . The printed wiring board substrate according to claim 1, wherein the metal layer includes a plating layer. Printed circuit board substrate according to claim 1 or claim 2 are chemically bonded to the polymer in which the cobalt atom constituting the base film. A base film having an insulating property;
And a metal layer laminated on at least one surface of the base film.
Alkali treating at least one surface of the base film;
Bringing a cobalt ion-containing aqueous solution into contact with at least one surface of the base film after the alkali treatment step;
Laminating a metal layer on at least one surface of the base film after the contact step ;
The manufacturing method of the board | substrate for printed wiring boards whose said cobalt ion containing aqueous solution is cobalt acetate aqueous solution . The method for manufacturing a substrate for a printed wiring board according to claim 4 , wherein the metal layer laminating step includes the step of applying a metal particle dispersion to at least one surface of the base film and heating the metal particle dispersion.

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