JP2011100796A - Circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board free of lamination defect (resin-unfilled part), and having a fewer variations in the sectional area of an electrical circuit, less influence on the resistance, and a fewer variations in impedance between a low density portion and a high density portion of the electrical circuit, thereby having a leeway for circuit design. <P>SOLUTION: The circuit board A has a plurality of circuit grooves 3 on an insulating substrate 1, and electrical circuits 6 formed by plating layers filled in the individual circuit grooves 3. The circuit board A has a high density portion 30 having the electrical circuits 6 formed densely, and a low density portion 31 having the electrical circuits 6 formed nondensely. The surfaces of the insulating substrate 1 and electrical circuits 6 in the high density portion 30 are formed flush with the surfaces of the insulating substrate 1 and electrical circuits 6 in the low density portion 31. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a circuit board used in a portable information terminal device such as a mobile phone; a computer and its peripheral devices; and electrical equipment such as various information home appliances.

  Conventionally, a wiring forming method using a chemical mechanical polishing method (CMP method) has been proposed (see, for example, Patent Document 1). In this method, first, as shown in FIG. 2A, a circuit groove 3 is formed on the surface of the insulating substrate 1 by laser processing or the like. Next, as shown in FIG. 2B, the electroless plating layer 10 is formed on the entire surface of the insulating substrate 1 where the circuit grooves 3 are formed (including the side surfaces and the bottom surface of the circuit grooves 3). The electroless plating layer 10 can be formed by electroless plating of a metal thin film such as copper. Next, as shown in FIG. 2C, an electrolytic plating layer 11 is formed on the surface of the electroless plating layer 10 with a metal such as copper. The electrolytic plating layer 11 is formed so as to fill the circuit groove 3 and cover the entire surface of the electroless plating layer 10. Thereafter, the surface of the insulating substrate 1, the surface of the electrolytic plating layer 11 filled in the circuit groove 3, and the upper end surface of the electroless plating layer 10 attached to the side surface of the circuit groove 3 are flush with each other. Then, unnecessary portions of the electrolytic plating layer 11 are removed. Here, a CMP method in which the electrolytic plating layer 11 is removed by polishing with a polishing machine 20 is employed. Thus, the circuit board A having the electric circuit (wiring) 6 composed of the electroless plating layer 10 and the electrolytic plating layer 11 filled in the circuit groove 3 can be formed.

JP 2000-49162 A

  However, the circuit board formed as described above has a problem that erosion E occurs mainly at the portion where the electric circuit 6 is concentrated. The erosion E refers to a portion where the surface of the electric circuit 6 and the surface of the insulating base material 1 around the electric circuit 6 have been cut into a dish shape or the like. It is considered that this erosion occurs due to a difference in hardness between the electrolytic plating layer 11 and the insulating base 1, a difference in resistance to the polishing machine 20 and the polishing liquid, and the like. The circuit board A in which such erosion E has occurred has the following problems. First, in the build-up method or the like, when an insulating material such as a prepreg is overlaid on the surface of the circuit board A and then formed by heating and pressing to form an insulating layer, the pressure drop at the erosion E increases, and the laminated There was a possibility that a defect (unfilled portion of the resin) would occur. In addition, the surface of the insulating layer corresponding to the erosion may be recessed to reduce the flatness of the surface of the insulating layer. Therefore, when circuit formation is formed on the surface of the insulating layer, the laser processing depth As a result, variations in conductor cross-sectional area (circuit cross-sectional area) and the resistance value of the electric circuit 6 may be affected. Furthermore, since the thickness of the insulating layer varies depending on the concentrated portion (high density portion 30) and the non-concentrated portion (low density portion 31) of the electric circuit 6, the impedance varies between the low density portion and the high density portion of the electric circuit 6. There is no room for circuit design.

  Also, a circuit board similar to the above is formed using a transfer foil, but in this case, when transferring the electric circuit, the concentrated portion (high density portion 30) of the electric circuit 6 is not concentrated. The resin of the prepreg flows unevenly in the portion (low density portion 31), and the thickness of the insulating layer is different between the concentrated portion (high density portion 30) and the non-concentrated portion (low density portion 31) of the electric circuit 6. The above problem could not be solved.

  The present invention has been made in view of the above points, and there is no occurrence of laminating blur, there is little influence on the variation in the cross-sectional area of the electric circuit and the resistance value, and the low-density part and the high-density part of the electric circuit An object of the present invention is to provide a circuit board having a small impedance variation and a sufficient circuit design.

  A circuit board according to claim 1 of the present invention is a circuit board having a plurality of circuit grooves 3 in an insulating base material 1 and an electric circuit 6 formed by a plating layer filled in each circuit groove 3. The electric circuit 6 has a high density portion 30 formed densely and a low density portion 31 formed sparsely, and each surface of the insulating base material 1 and the electric circuit 6 in the high density portion 30 has a low density. The insulating base material 1 and the respective surfaces of the electric circuit 6 in the portion 31 are formed to be flush with each other.

  The circuit board according to claim 2 of the present invention is the circuit according to claim 1, wherein the insulating substrate 1 has a plurality of circuit grooves 3, and an electric circuit 6 is formed by a plating layer filled in each circuit groove 3. It is a board | substrate, The said electric circuit 6 has the high density part 30 formed densely, and the low density part 31 formed sparsely, and is the opposite side to the formation surface of the circuit groove | channel 3 of the insulating base material 1. The distance from the surface to the bottom of the circuit groove 3 in the high-density portion 30 and the distance from the surface opposite to the formation surface of the circuit groove 3 of the insulating substrate 1 to the bottom of the circuit groove 3 in the low-density portion 31 It is characterized by being formed equally.

  The circuit board according to claim 3 of the present invention is the circuit according to claim 1, wherein the insulating substrate 1 has a plurality of circuit grooves 3, and an electric circuit 6 is formed by a plating layer filled in each circuit groove 3. A high-density portion 30 in which the electric circuit 6 is densely formed and a low-density portion 31 that is sparsely formed, the conductor thickness of the electric circuit 6 in the high-density portion 30 and the low density The conductor thickness of the electric circuit 6 in the portion is formed to be equal.

  In the present invention, each surface of the insulating base material and the electric circuit in the high density portion and each surface of the insulating base material and the electric circuit in the low density portion are formed flush with each other. In the case where the insulating layer is formed by heating and pressing after overlapping the insulating materials, it is possible to prevent a pressure drop due to erosion from occurring, and to prevent a stacking defect from occurring. In addition, when the circuit formation is formed on the surface of the insulating layer, it is possible to prevent the laser processing depth from varying, which affects the variation in the conductor cross-sectional area (electric circuit cross-sectional area) and the resistance value of the electric circuit. It is something that can be avoided. Further, since the thickness of the insulating layer is constant between the low density portion and the high density portion of the electric circuit, the impedance does not vary between the low density portion and the high density portion of the electric circuit, and there is a margin for circuit design.

  In addition, the distance from the surface opposite to the circuit groove forming surface of the insulating base in the high density portion to the bottom of the circuit groove, and the circuit from the surface opposite to the circuit groove forming surface of the insulating base in the low density portion The distance to the bottom of the groove is formed to be equal, or the conductor thickness of the electric circuit in the high density portion and the conductor thickness of the electric circuit in the low density portion are formed to be equal. It can be obtained with certainty.

An example of the manufacturing process of this invention is shown, (a)-(e) is sectional drawing. An example of the manufacturing process of a prior art example is shown, (a)-(e) is sectional drawing.

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

  FIG. 1E shows a circuit board A of the present invention. This circuit board A has a plurality of circuit grooves 3 and through holes 4 in the insulating base material 1 and a plurality of electric circuits 6 in which each circuit groove 3 and the through holes 4 are filled with electroless plating. . The surface of the electric circuit 6 is exposed on one or both surfaces of the insulating substrate 1. The width dimension (line width) of the electric circuit 6 is preferably the same for all the electric circuits 6, but this is not limiting, and the width dimension of the electric circuit 6 may be different for each electric circuit 6.

  And the circuit board A of this invention has the high density part 30 in which the electric circuit 6 was formed densely, and the low density part 31 formed sparsely. Here, when the width L of the electric circuit 6 is constant (for example, 5 to 50 μm), the interval WH between the adjacent electric circuits 6 and 6 is 100 μm or less, preferably 70 μm or less, and preferably 50 μm or less (lower limit). 5 μm) is the high density part 30, and the interval WL between the adjacent electric circuits 6, 6 is 50 μm or more, preferably 70 μm or more, more preferably 100 μm or more (the upper limit is not particularly limited). 31 can be formed. Further, in the high density portion 30, the surface of the insulating base 1 and the surface of the electric circuit 6 are substantially flat and substantially flush. Further, in the low density portion 31, the surface of the insulating base 1 and the surface of the electric circuit 6 are substantially flat and substantially flush. The surface of the insulating base 1 in the high density portion 30 and the surface of the insulating base 1 in the low density portion 31 are also substantially flat and substantially flush, and the surface of the electric circuit 6 in the high density portion 30 and the low density portion. The surface of the electric circuit 6 at 31 is also substantially flat and substantially flush. That is, the circuit board of the present invention is such that the surface on the side where the electric circuit 6 is exposed is formed substantially flat over the entire surface, and no dent such as erosion is generated. In addition, although the circuit board of this invention can make the thickness of the insulating base material 1 constant throughout and the thickness of all the electric circuits 6 can be made constant, it is not limited to this.

  In manufacturing the circuit board of the present invention, a film forming step of forming a resin film on the surface of the insulating base material, and forming a recess having a depth equal to or greater than the thickness of the resin film on the basis of the outer surface of the resin film A circuit pattern forming step for forming a circuit pattern portion, a catalyst deposition step for depositing a plating catalyst or a precursor thereof on the surface of the circuit pattern portion and the surface of the resin coating, and the resin from the insulating substrate. A coating removal step for removing the coating; and a plating treatment step for forming an electroless plating film only in a portion where the plating catalyst or its precursor remains after the resin coating is removed.

  FIG. 1 is a schematic cross-sectional view for explaining each step in the circuit board manufacturing method of the present invention. First, as shown in FIG. 1A, a resin film 2 is formed on the surface of the insulating substrate 1. This process corresponds to a film forming process. Next, as shown in FIG. 1B, a circuit pattern portion 32 is formed by forming a recess having a depth equal to or greater than the thickness of the resin coating 2 with the outer surface of the resin coating 2 as a reference. The circuit pattern portion 32 may be the circuit groove 3 in which the insulating base material 1 is dug, or the through hole 4 as the circuit pattern portion 32 in the insulating base material 1 as necessary. Drilling may be performed to form The circuit pattern portion 32 (the circuit groove 3 and the through hole 4) defines a portion where an electroless plating film is formed by electroless plating, that is, a portion where the electric circuit 6 is formed. By this process, the circuit groove 3 and the through hole 4 are formed at a high density in the portion formed as the high density portion 30, and the circuit groove 3 and the through hole 4 are formed at a low density in the portion formed as the low density portion 31. Formed with. This step corresponds to a circuit pattern forming step.

  Next, as shown in FIG. 1C, the bottom and side surfaces of the circuit groove 3, the inner surface of the through hole 4, and the surface of the resin film 2 where the circuit groove 3 and the through hole 4 are not formed are plated. A catalyst or its precursor 5 is deposited. This step corresponds to a catalyst deposition step.

  Next, as shown in FIG. 1 (d), the resin film 2 is removed from the insulating substrate 1. By doing so, the plating catalyst or its precursor 5 can remain only on the surface of the insulating substrate 1 where the bottom and side surfaces of the circuit groove 3 and the inner surface of the through hole 4 are formed. On the other hand, the plating catalyst or its precursor 5 deposited on the surface of the resin film 2 is removed together with the resin film 2 while being supported on the resin film 2. This process corresponds to a film removal process.

  Next, electroless plating is performed on the insulating substrate 1 from which the resin coating 2 has been removed. By doing so, the electroless plating layer 6a is formed only in the portion where the plating catalyst or its precursor 5 remains. That is, as shown in FIG. 1E, an electroless plating layer 6a to be an electric circuit 6 is formed in the portion where the circuit groove 3 and the through hole 4 are formed. And this electric circuit 6 may consist of this electroless plating, or it is a film obtained by further applying electroless plating (fill-up plating) to the electroless plating layer 6a to make it thicker. There may be. Specifically, for example, as shown in FIG. 1 (e), an electric circuit 6 made of an electroless plating layer is formed so as to fill the circuit groove 3 and the whole through-hole 4, and the insulating substrate 1 and A step with the electric circuit 6 may be eliminated. This process corresponds to a plating process.

  Through the above steps, a circuit board A as shown in FIG. The circuit board A thus formed is obtained by forming the electric circuit 6 on the insulating base 1 with high accuracy.

  Hereinafter, each configuration of the present embodiment will be described.

<Film formation process>
As described above, the film forming process is a process of forming the resin film 2 on the surface of the insulating substrate 1.

(Insulating base material)
The insulating base material 1 used in the film forming step is not particularly limited as long as it can be used for manufacturing a circuit board. Specifically, for example, a resin substrate containing a resin can be used.

  Moreover, as said resin, if it is resin which comprises the various organic substrates which can be used for manufacture of a circuit board, it can use without limitation in particular. Specifically, for example, epoxy resin, acrylic resin, polycarbonate resin, polyimide resin, polyphenylene sulfide resin, polyphenylene ether resin, cyanate resin, benzoxazine resin, bismaleimide resin, and the like can be given.

  The epoxy resin is not particularly limited as long as it is an epoxy resin constituting various organic substrates that can be used for manufacturing a circuit board. Specifically, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, aralkyl epoxy resin, phenol novolac type epoxy resin, alkylphenol novolac type epoxy resin, biphenol type epoxy resin, naphthalene type epoxy resin , Dicyclopentadiene type epoxy resins, epoxidized products of condensates of phenols and aromatic aldehydes having a phenolic hydroxyl group, triglycidyl isocyanurate, alicyclic epoxy resins, and the like. Furthermore, the epoxy resin, nitrogen-containing resin, and silicone-containing resin that are brominated or phosphorus-modified to impart flame retardancy are also included. Moreover, as said epoxy resin, said each epoxy resin may be used independently, and may be used in combination of 2 or more type.

  Moreover, when comprising a base material with said each resin, in order to make it harden | cure, a hardening | curing agent is generally contained. The curing agent is not particularly limited as long as it can be used as a curing agent. Specific examples include dicyandiamide, phenolic curing agents, acid anhydride curing agents, aminotriazine novolac curing agents, and cyanate resins. As said phenol type hardening | curing agent, a novolak type, an aralkyl type, a terpene type etc. are mentioned, for example. Further examples include phosphorus-modified phenolic resins or phosphorus-modified cyanate resins for imparting flame retardancy. Moreover, as said hardening | curing agent, said each hardening | curing agent may be used independently, and may be used in combination of 2 or more type.

  In addition, although not particularly limited, it is preferable to use a resin or the like having a good laser light absorption rate in a wavelength region of 10 to 400 nm because a circuit pattern is formed by laser processing. For example, specifically, a polyimide resin or the like can be given.

The insulating base material 1 may contain a filler. The filler may be inorganic fine particles or organic fine particles, and is not particularly limited. By containing the filler, the filler is exposed in the laser processed part, and it is possible to improve the adhesion between the plating due to the unevenness of the filler and the resin.
Specific examples of the material constituting the inorganic fine particles include aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), boron nitride (BN), aluminum nitride (AlN), silica (SiO ₂ ), High dielectric constant fillers such as barium titanate (BaTiO ₃ ) and titanium oxide (TiO ₂ ); magnetic fillers such as hard ferrite; magnesium hydroxide (Mg (OH) ₂ ), aluminum hydroxide (Al (OH) ₂ ), Antimony trioxide (Sb ₂ O ₃ ), antimony pentoxide (Sb ₂ O ₅ ), guanidine salts, zinc borate, molybdate compounds, zinc stannate, and other inorganic flame retardants; talc (Mg ₃ (Si ₄ O ₁₀₎ (OH) 2), barium sulfate (BaSO _4), calcium carbonate (CaCO _3), mica, and the like. As said inorganic fine particle, the said inorganic fine particle may be used independently, and may be used in combination of 2 or more type. These inorganic fine particles have high thermal conductivity, relative dielectric constant, flame retardancy, particle size distribution, color tone flexibility, etc. And high filling can be easily performed. Although not particularly limited, it is preferable to use a filler having an average particle diameter equal to or smaller than the thickness of the insulating layer, more preferably 0.01 μm to 10 μm, and still more preferably a filler having an average particle diameter of 0.05 μm to 5 μm. It is good.

  The inorganic fine particles may be surface-treated with a silane coupling agent in order to improve dispersibility in the insulating base material. The insulating base material may contain a silane coupling agent in order to increase the dispersibility of the inorganic fine particles in the insulating base material. Specific examples of the silane coupling agent include epoxy silane, mercapto silane, amino silane, vinyl silane, styryl silane, methacryloxy silane, acryloxy silane, titanate silane couplings, and the like. Agents and the like. As said silane coupling agent, the said silane coupling agent may be used independently, and may be used in combination of 2 or more type.

  The insulating base material may contain a dispersant in order to enhance the dispersibility of the inorganic fine particles in the insulating base material. Specific examples of the dispersant include alkyl ether-based, sorbitan ester-based, alkyl polyether amine-based, polymer-based dispersants, and the like. As said dispersing agent, the said dispersing agent may be used independently, and may be used in combination of 2 or more type.

  Specific examples of the organic fine particles include rubber fine particles.

  Further, the form of the insulating substrate is not particularly limited. Specifically, a sheet | seat, a film, a prepreg, a molded object of a three-dimensional shape etc. are mentioned. The thickness of the insulating substrate 1 is not particularly limited. Specifically, in the case of a sheet, film, or prepreg, for example, the thickness is preferably 10 to 500 μm, and more preferably about 20 to 200 μm. Further, the insulating base material may contain inorganic fine particles such as silica particles.

(Resin coating)
The resin film 2 is not particularly limited as long as it can be removed in the film removal step. Specifically, for example, a soluble resin that can be easily dissolved in an organic solvent or an alkaline solution, a swellable resin film made of a resin that can be swollen with a predetermined liquid (swelling liquid) described later, and the like. Among these, a swellable resin film is particularly preferable because accurate removal is easy. Moreover, as said swelling resin film, it is preferable that the swelling degree with respect to the said liquid (swelling liquid) is 50% or more, for example. The swellable resin film is not limited to the resin film that does not substantially dissolve in the liquid (swelling liquid) and easily peels off from the surface of the insulating substrate 1 due to swelling. A resin film that swells with respect to the swelling liquid), dissolves at least partly and easily peels off from the surface of the insulating substrate 1 due to the swelling or dissolution, or dissolves in the liquid (swelling liquid). Moreover, the resin film which peels from the said insulating base material 1 surface easily by the melt | dissolution is also contained.

  A method for forming the resin coating 2 is not particularly limited. Specifically, for example, it is formed by applying a liquid material capable of forming a resin film on the surface of the insulating base material 1 and then drying it, or by applying the liquid material to a support substrate and then drying it. And a method of transferring the resin film to be transferred onto the surface of the insulating substrate 1. The method for applying the liquid material is not particularly limited. Specifically, for example, conventionally known spin coating method, bar coater method and the like can be mentioned.

  The thickness of the resin coating 2 is preferably 10 μm or less, and more preferably 5 μm or less. On the other hand, the thickness of the resin coating 2 is preferably 0.1 μm or more, and more preferably 1 μm or more. When the resin coating 2 is too thick, the accuracy of circuit pattern portions such as circuit grooves and through holes formed by laser processing or machining in the circuit pattern forming process tends to be reduced. Moreover, when the thickness of the resin film 2 is too thin, it tends to be difficult to form a resin film having a uniform film thickness.

  Next, a swellable resin film suitable as the resin film 2 will be described as an example.

  As the swellable resin film, a resin film having a swelling degree with respect to the swelling liquid of 50% or more can be preferably used. Furthermore, a resin film having a swelling degree with respect to the swelling liquid of 100% or more is more preferable. In addition, when the said swelling degree is too low, there exists a tendency for a swelling resin film to become difficult to peel in the said film removal process.

  The formation method of the said swellable resin film is not specifically limited, What is necessary is just the method similar to the formation method of the resin film 2 mentioned above. Specifically, for example, a liquid material capable of forming a swellable resin film is applied to the surface of the insulating base material 1 and then dried, or the liquid material is applied to a support substrate and then dried. And a method of transferring the swellable resin film formed by the method to the surface of the insulating substrate 1.

  Examples of the liquid material that can form the swellable resin film include an elastomer suspension or emulsion. Specific examples of the elastomer include a diene elastomer such as a styrene-butadiene copolymer, an acrylic elastomer such as an acrylate ester copolymer, and a polyester elastomer. According to such an elastomer, it is possible to easily form a swellable resin film having a desired degree of swelling by adjusting the degree of crosslinking or gelation of the elastomer resin particles dispersed as a suspension or emulsion.

  The swellable resin film is particularly preferably a film whose degree of swelling changes depending on the pH of the swelling liquid. When such a coating is used, the liquid condition in the catalyst deposition step is different from the liquid condition in the coating removal step, so that the swellable resin can be obtained at the pH in the catalyst deposition step. The coating maintains high adhesion to the insulating substrate, and the swellable resin coating can be easily peeled off at the pH in the coating removal step.

  More specifically, for example, the catalyst deposition step includes a step of treating in an acidic plating catalyst colloid solution (acid catalytic metal colloid solution) having a pH in the range of 1-3, for example, and the coating removal step has a pH of 12-12. When the step of swelling the swellable resin film in an alkaline solution in the range of 14 is provided, the swelling degree of the swellable resin film with respect to the acidic plating catalyst colloid solution is 60% or less, and further 40% or less. The resin film preferably has a degree of swelling with respect to the alkaline solution of 50% or more, more preferably 100% or more, and even more preferably 500% or more.

  Examples of such a swellable resin film include photocuring used for a sheet formed from an elastomer having a predetermined amount of carboxyl groups, a dry film resist (hereinafter also referred to as DFR) for patterning printed wiring boards, and the like. And a sheet obtained by curing the entire surface of a curable alkali-developing resist, and thermosetting or alkali-developing sheet.

  Specific examples of the elastomer having a carboxyl group include a diene elastomer such as a styrene-butadiene copolymer having a carboxyl group in the molecule by containing a monomer unit having a carboxyl group as a copolymerization component; acrylic acid Examples include acrylic elastomers such as ester copolymers; and polyester elastomers. According to such an elastomer, a swellable resin film having a desired alkali swelling degree can be formed by adjusting the acid equivalent, the degree of crosslinking or the degree of gelation of the elastomer dispersed as a suspension or emulsion. . The carboxyl group in the elastomer swells the swellable resin film with respect to the alkaline aqueous solution and acts to peel the swellable resin film from the surface of the insulating substrate. The acid equivalent is the polymer weight per equivalent of carboxyl groups.

  Specific examples of the monomer unit having a carboxyl group include (meth) acrylic acid, fumaric acid, cinnamic acid, crotonic acid, itaconic acid, maleic anhydride, and the like.

  The content ratio of the carboxyl group in the elastomer having such a carboxyl group is preferably 100 to 2000, more preferably 100 to 800 in terms of acid equivalent. When the acid equivalent is too small, the compatibility with the solvent or other composition tends to decrease, whereby the resistance to the plating pretreatment liquid tends to decrease. Moreover, when an acid equivalent is too large, there exists a tendency for the peelability with respect to aqueous alkali solution to fall.

  The molecular weight of the elastomer is preferably 10,000 to 1,000,000, more preferably 20,000 to 60,000. When the molecular weight of the elastomer is too large, the releasability tends to decrease, and when it is too small, the viscosity decreases, so that it is difficult to maintain a uniform thickness of the swellable resin film, and plating pretreatment The resistance to the liquid also tends to deteriorate.

  In addition, as DFR, a photocurable resin containing a photopolymerization initiator containing a predetermined amount of a carboxyl group, an acrylic resin; an epoxy resin; a styrene resin; a phenol resin; A sheet of a resin composition can be used. As specific examples of such DFR, a dry film of a photopolymerizable resin composition as disclosed in JP 2000-231190 A, JP 2001-201851 A, and JP 11-212262 A is used. Sheets obtained by curing, and commercially available as an alkali development type DFR, for example, UFG series manufactured by Asahi Kasei Corporation can be mentioned.

  Furthermore, as another example of the swellable resin film, a resin containing a carboxyl group and containing rosin as a main component (for example, “NAZDAR229” manufactured by Yoshikawa Chemical Co., Ltd.) or a resin containing phenol as a main component (for example, LEKTRACHEM “104F”) and the like.

  The swellable resin film was formed on the surface of the insulating substrate by applying a resin suspension or emulsion using a conventionally known application method such as a spin coat method or a bar coater method, followed by drying or a support substrate. After the DFR is bonded to the surface of the insulating substrate using a vacuum laminator or the like, it can be easily formed by curing the entire surface.

  Moreover, as said resin film, in addition to the above, the following are mentioned. For example, the following are mentioned as a resist material which comprises the said resin film.

  Properties required for the resist material constituting the resin coating include, for example, (1) resistance to a liquid (plating nucleation chemical) in which an insulating substrate on which the resin coating is formed is immersed in a catalyst deposition step described later. (2) The film coating process described later, for example, the resin film (resist) can be easily removed by the step of immersing the insulating base material on which the resin film is formed in alkali, and (3) High film formability. (4) easy dry film (DFR) formation, (5) high storage stability, and the like.

  As the plating nucleating chemical solution, as will be described later, for example, in the case of an acidic Pd—Sn colloid catalyst system, all are acidic (pH 1-2) aqueous solutions. Moreover, in the case of an alkaline Pd ion catalyst system, the catalyst imparting activator is a weak alkali (pH 8 to 12), and the others are acidic. From the above, it is necessary to withstand pH 1 to 11, and preferably pH 1 to 12, as the resistance to the plating nucleating solution. Note that being able to withstand is that when a sample on which a resist is formed is immersed in a chemical solution, swelling and dissolution of the resist are sufficiently suppressed, and the resist serves as a resist. The immersion temperature is generally room temperature to 60 ° C., the immersion time is 1 to 10 minutes, and the resist film thickness is generally about 1 to 10 μm, but is not limited thereto.

  As the alkali stripping chemical used in the film removal step, as will be described later, for example, an aqueous NaOH solution or an aqueous sodium carbonate solution is common. Its pH is 11 to 14, and it is desirable that the resist film can be easily removed preferably at pH 12 to 14. The NaOH aqueous solution concentration is generally about 1 to 10%, the processing temperature is room temperature to 50 ° C., the processing time is 1 to 10 minutes, and the immersion or spray treatment is generally performed, but is not limited thereto.

  Since a resist is formed on an insulating material, film formability is also important. A uniform film formation without repelling or the like is necessary. Moreover, although it is made into a dry film for the simplification of a manufacturing process, reduction of material loss, etc., the flexibility of a film is required in order to ensure handling property. Also, a dry film resist is pasted on the insulating material with a laminator (roll, vacuum). The pasting temperature is room temperature to 160 ° C., and the pressure and time are arbitrary. Thus, adhesiveness is required at the time of pasting. For this reason, the resist formed into a dry film is generally used as a three-layer structure sandwiched by a carrier film and a cover film to prevent dust from adhering, but is not limited thereto.

  The best preservation is that it can be stored at room temperature, but it must also be refrigerated or frozen. As described above, it is necessary to prevent the composition of the dry film from being separated at low temperatures or to be cracked due to a decrease in flexibility.

  The resin coating includes (a) at least one monomer of carboxylic acid or acid anhydride having at least one polymerizable unsaturated group in the molecule and (b) the monomer (a). And a polymer resin obtained by polymerizing at least one monomer that can be polymerized with or a resin composition containing the polymer resin.

  As the resin composition (resin composition of resist material), the polymer resin is an essential component as a main resin (binder resin), and at least one of oligomers, monomers, fillers and other additives may be added. .

  The main resin is preferably a linear polymer with thermoplastic properties. In order to control fluidity and crystallinity, it may be branched by grafting. The molecular weight is about 1,000 to 500,000 in terms of number average molecular weight, preferably 5,000 to 50,000. If the molecular weight is too small, the flexibility of the film and the resistance to the plating nucleation solution (acid resistance) tend to decrease. Moreover, when molecular weight is too large, there exists a tendency for the sticking property at the time of using alkali peelability or a dry film to worsen. Furthermore, a crosslinking point may be introduced to improve resistance to plating nucleus chemicals, suppress thermal deformation during laser processing, and control flow.

  As the composition of the main resin, (a) a carboxylic acid or acid anhydride monomer having at least one polymerizable unsaturated group in the molecule and (b) (a) a monomer that can be polymerized with the monomer It is obtained by polymerizing. Examples of known techniques include those described in JP-A-7-281437, JP-A-2000-231190, and JP-A-2001-201851. Examples of (a) include, for example, (meth) acrylic acid, fumaric acid, cinnamic acid, crotonic acid, itaconic acid, maleic anhydride, maleic acid half ester, butyl acrylate, etc., alone or 2 More than one type may be combined. Examples of (b) are generally non-acidic and have (one) polymerizable unsaturated group in the molecule, but are not limited thereto. It is selected so as to maintain various properties such as resistance in the plating process and flexibility of the cured film. Specifically, for example, methyl (meth) acrylate, ethyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, tert. -Butyl (meth) acrylate, 2-hydroxylethyl (meth) acrylate, 2-hydroxylpropyl (meth) acrylates, etc. are mentioned. Further, esters of vinyl alcohol such as vinyl acetate, (meth) acrylonitrile, styrene, or a polymerizable styrene derivative may be used. It can also be obtained by polymerization of only a carboxylic acid or acid anhydride having one polymerizable unsaturated group in the molecule. Furthermore, a monomer having a plurality of unsaturated groups is selected as a monomer used in the polymer so that it can be three-dimensionally cross-linked, such as an epoxy group, a hydroxyl group, an amino group, an amide group, a vinyl group in the molecular skeleton. Reactive functional groups can be introduced. When the carboxyl group is contained in the resin, the amount of the carboxyl group contained in the resin is preferably 100 to 2000, preferably 100 to 800, as an acid equivalent. Here, the acid equivalent means the weight of the polymer having 1 equivalent of a carboxyl group therein. When the acid equivalent is too low, there is a tendency that compatibility with a solvent or other composition is lowered or plating pretreatment solution resistance is lowered. Moreover, when an acid equivalent is too high, there exists a tendency for peelability to fall. Moreover, the composition ratio of (a) monomer is 5 to 70% by weight.

  Any monomer or oligomer may be used as long as it is resistant to plating nucleation chemicals and can be easily removed with alkali. In order to improve the sticking property of the dry film (DFR), it can be considered that it is used as a plasticizer as a tackifier. Further, a crosslinking agent is added to increase various resistances. Specifically, for example, methyl (meth) acrylate, ethyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, tert. -Butyl (meth) acrylate, 2-hydroxylethyl (meth) acrylate, 2-hydroxylpropyl (meth) acrylates, etc. are mentioned. In addition, esters of vinyl alcohol such as vinyl acetate, (meth) acrylonitrile, styrene, or a polymerizable styrene derivative are also included. It can also be obtained by polymerization of only a carboxylic acid or acid anhydride having one polymerizable unsaturated group in the molecule. Furthermore, a polyfunctional unsaturated compound may be included. Any of the above monomers or oligomers obtained by reacting the monomers may be used. In addition to the above monomers, it is possible to include two or more other photopolymerizable monomers. Examples of this monomer include 1,6-hexanediol di (meth) acrylate, 1,4-cyclohexanediol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, Polyoxyalkylene glycol di (meth) acrylate such as polyoxyethylene polyoxypropylene glycol di (meth) acrylate, 2-di (p-hydroxyphenyl) propane di (meth) acrylate, glycerol tri (meth) acrylate, dipentaerythritol penta (Meth) acrylate, trimethylolpropane triglycidyl ether tri (meth) acrylate, bisphenol A diglycidyl ether tri (meth) acrylate, 2,2-bis (4-methyl) Methacryloxy pentaethoxy phenyl) propane, a polyfunctional (meth) acrylate containing urethane groups. Further, any of the above monomers or oligomers obtained by reacting the monomers may be used.

  Furthermore, you may contain a filler. The filler is not particularly limited. Specifically, for example, silica, aluminum hydroxide, magnesium hydroxide, calcium carbonate, clay, kaolin, titanium oxide, barium sulfate, alumina, zinc oxide, talc, mica, glass, titanic acid. Examples include potassium, wollastonite, magnesium sulfate, aluminum borate, and an organic filler. Moreover, since the resist thickness is generally as thin as 1 to 10 μm, a small filler size is preferable. Although it is preferable to use a material having a small average particle size and cut coarse particles, the coarse particles can be crushed during dispersion or removed by filtration.

  Other additives include, for example, photopolymerizable resins (photopolymerization initiators), polymerization inhibitors, colorants (dyes, pigments, coloring pigments), thermal polymerization initiators, and crosslinking agents such as epoxies and urethanes. Can be mentioned.

  In the printed board processing process, for example, laser processing may be used, but in the case of laser processing in forming the circuit board A of the present invention, it is necessary to impart a laser ablation property to the resist material. As the laser processing machine, for example, a carbon dioxide laser, an excimer laser, a UV-YAG laser, or the like is selected. These laser processing machines have various intrinsic wavelengths, and productivity can be improved by using a material having a high absorption rate for these wavelengths. Among them, the UV-YAG laser is suitable for fine processing, and the laser wavelength is 3rd harmonic 355 nm and 4th harmonic 266 nm. Therefore, it is desirable that the absorption rate is high with respect to these wavelengths. On the other hand, a material having a somewhat low absorption rate may be preferable. Specifically, for example, when a resist having a low UV absorption rate is used, the UV light transmits through the resist, so that energy can be concentrated on the underlying insulating layer processing. That is, since the advantages differ depending on the absorption rate of the laser beam, it is preferable to use a resist in which the absorption rate of the laser beam of the resist is adjusted according to the situation. The resist material desirably has an absorptance of 50% or higher for these wavelengths.

<Circuit pattern formation process>
The circuit pattern forming step is a step of forming the circuit pattern portion 32 such as the circuit groove 3 on the insulating substrate 1. As described above, the circuit pattern portion 32 may be not only the circuit groove 3 but also the through hole 4 penetrating the resin coating 2 and the insulating base material 1 in the thickness direction.

  A method for forming the circuit pattern portion 32 is not particularly limited. Specifically, for example, on the insulating base material 1 on which the resin coating 2 is formed, from the outer surface side of the resin coating 2, machining such as laser processing and dicing processing, and mechanical processing such as embossing processing, etc. The method of forming the circuit groove 3 of a desired shape and depth by giving is mentioned. In the case of forming a highly accurate fine circuit, it is preferable to use laser processing. According to laser processing, the cutting depth or the like can be freely adjusted by changing the output of the laser or the like. Further, as the stamping process, for example, a stamping process using a fine resin mold used in the field of nanoimprinting can be preferably used.

  Further, as the circuit pattern portion 32, a through hole 4 for forming a via hole or the like may be formed.

  By this step, the shape of the circuit pattern portion such as the shape and depth of the circuit groove 3 and the diameter and position of the through hole 4 is defined. The circuit pattern forming step may be performed by dug more than the thickness of the resin film 2, or may be dug by the thickness of the resin film 2 or may be dug beyond the thickness of the resin film 2. Here, when the insulating base material 1 is flat, the distance RH from the surface opposite to the surface of the insulating base material 1 where the circuit groove 3 is formed in the high density portion 30 to the bottom portion 3a of the circuit groove 3, and the low density portion It is preferable that the distance RL from the surface of the insulating base 1 opposite to the surface where the circuit groove 3 is formed to 31 to the bottom 3a of the circuit groove 3 is equal to RL = RL. In addition, the flat insulating base material 1 points out the insulating base material 1 in which the upper surface and the lower surface were formed in the flat surface. Moreover, the formation surface of the circuit groove 3 of the insulating base material 1 means the surface where the circuit groove 3 of the insulating base material 1 opens, and in FIG. Moreover, the surface opposite to the formation surface of the circuit groove 3 of the insulating base material 1 means a surface of the insulating base material 1 where the circuit groove 3 does not open, and in FIG.

  The width of the circuit pattern portion 32 such as the circuit groove 3 formed in the circuit pattern forming step is not particularly limited. When laser processing is used, a fine circuit having a line width of 20 μm or less can be easily formed. Further, the depth of the circuit groove 3 is the thickness dimension of the electric circuit 6 when a step is eliminated between the electric circuit 6 and the insulating substrate 1 by fill-up plating.

<Catalyst deposition process>
The catalyst deposition step is a step of depositing a plating catalyst or its precursor on the surface of the circuit pattern portion such as the circuit groove 3 and the surface of the resin coating 2. At this time, when the through hole 4 is formed, the plating catalyst or its precursor is also deposited on the inner wall surface of the through hole 4.

  The plating catalyst or its precursor 5 is a catalyst that is applied to form an electroless plating film only in a portion where it is desired to form an electroless plating film by electroless plating in the plating treatment step. Any plating catalyst can be used without particular limitation as long as it is known as a catalyst for electroless plating. Alternatively, a plating catalyst precursor may be deposited in advance, and the plating catalyst may be generated after removing the resin film. Specific examples of the plating catalyst include, for example, metal palladium (Pd), platinum (Pt), silver (Ag), etc., or a precursor that generates these.

  Examples of the method of depositing the plating catalyst or its precursor 5 include a method of treating with an acidic Pd—Sn colloidal solution treated under acidic conditions of pH 1 to 3 and then treating with an acid solution. It is done. Specific examples include the following methods.

First, oil or the like adhering to the surface of the insulating base material 1 in which the circuit grooves 3 and the through holes 4 are formed is washed in hot water in a surfactant solution (cleaner / conditioner) for a predetermined time. Next, if necessary, a soft etching treatment is performed with a sodium persulfate-sulfuric acid based soft etching agent. And it pickles further in acidic solutions, such as sulfuric acid aqueous solution of pH 1-2, and aqueous hydrochloric acid. Next, a pre-dip treatment is performed in which a chloride ion is adsorbed on the surface of the insulating base material 1 by being immersed in a pre-dip solution mainly composed of a stannous chloride aqueous solution having a concentration of about 0.1%. Then, Pd and Sn are aggregated and adsorbed by further immersing in an acidic plating catalyst colloid solution such as acidic Pd—Sn colloid having pH 1 to 3 containing stannous chloride and palladium chloride. Then, an oxidation-reduction reaction (SnCl ₂ + PdCl ₂ → SnCl ₄ + Pd ↓) is caused between the adsorbed stannous chloride and palladium chloride. Thereby, the metal palladium which is a plating catalyst precipitates.

  In addition, as an acidic plating catalyst colloid solution, a well-known acidic Pd-Sn colloid catalyst solution etc. can be used, and the commercially available plating process using an acidic plating catalyst colloid solution may be used. Such a process is systematized and sold by Rohm & Haas Electronic Materials Co., Ltd., for example.

  By such catalyst deposition treatment, the plating catalyst or its precursor 5 can be deposited on the surface (bottom surface and side surface) of the circuit groove 3, the inner wall surface of the through hole 4, and the surface of the resin coating 2. it can.

<Film removal process>
The coating removal step is a step of removing the resin coating 2 from the insulating base material 1 subjected to the catalyst deposition step.

  The method for removing the resin coating 2 is not particularly limited. Specifically, for example, after the resin film 2 is swollen with a predetermined solution (swelling liquid), the resin film 2 is peeled off from the insulating substrate 1, or the resin with a predetermined solution (swelling liquid). A method of removing the resin film 2 from the insulating substrate 1 after the film 2 is swollen and further partially dissolved, and a method of removing the resin film 2 by dissolving it with a predetermined solution (swelling liquid) Etc. The swelling liquid is not particularly limited as long as it can swell the resin film 2. The swelling or dissolution is performed by immersing the insulating base material 1 covered with the resin coating 2 in the swelling liquid for a predetermined time. And removal efficiency may be improved by irradiating with ultrasonic waves during the immersion. In addition, when it swells and peels, you may peel off with a light force.

  The case where the swellable resin film is used as the resin film 2 will be described.

  As the liquid (swelling liquid) for swelling the swellable resin film 2, the swellable resin film 2 can be used without substantially decomposing or dissolving the insulating substrate 1 and the plating catalyst or its precursor 5. Any liquid that can be swollen or dissolved can be used without particular limitation. Moreover, the liquid which can swell so that the said swellable resin film 2 can be peeled easily is preferable. Such a swelling liquid can be appropriately selected depending on the type and thickness of the swellable resin film 2. Specifically, for example, the swelling resin film is an elastomer such as a diene elastomer, an acrylic elastomer, and a polyester elastomer, or (a) a carboxylic acid or an acid having at least one polymerizable unsaturated group in the molecule. A polymer resin obtained by polymerizing at least one monomer of an anhydride and (b) at least one monomer that can be polymerized with the monomer (a) or the polymer resin In the case where the resin composition is formed from a carboxyl group-containing acrylic resin, an alkaline aqueous solution such as a sodium hydroxide aqueous solution having a concentration of about 1 to 10% can be preferably used.

  In the case of using a plating process that is performed under acidic conditions as described above in the catalyst deposition step, the swelling resin film 2 has a swelling degree of 60% or less, preferably 40% or less under acidic conditions. Yes, such that the degree of swelling is 50% or more under alkaline conditions, for example, elastomers such as diene elastomers, acrylic elastomers, and polyester elastomers, (a) at least one polymerizable unsaturated group in the molecule Polymer resin obtained by polymerizing at least one monomer of carboxylic acid or acid anhydride having at least one monomer and (b) at least one monomer that can be polymerized with monomer (a) Alternatively, it is preferably formed from a resin composition containing the polymer resin and a carboxyl group-containing acrylic resin. Such a swellable resin film easily swells and peels off with an alkaline aqueous solution having a pH of 12 to 14, for example, a sodium hydroxide aqueous solution having a concentration of about 1 to 10%. In addition, in order to improve peelability, you may irradiate with an ultrasonic wave during immersion. Moreover, you may peel by peeling with a light force as needed.

  In addition, as the resin film, (a) at least one monomer of carboxylic acid or acid anhydride having at least one polymerizable unsaturated group in the molecule, and (b) the (a) single monomer It is preferable to consist of a polymer resin obtained by polymerizing at least one kind of monomer that can be polymerized with a polymer or a resin composition containing the polymer resin. If such a resin film is used, the resin film can be easily formed on the surface of the insulating substrate. Therefore, a highly accurate electric circuit can be more easily formed on the insulating substrate. In addition, many of these resin films can be dissolved by the liquid used in the film removal step, and not only peeling and removal but also dissolution and removal can be used effectively.

  Examples of the method for swelling the swellable resin film 2 include a method of immersing the insulating base material 1 coated with the swellable resin film 2 in a swelling liquid for a predetermined time. Moreover, in order to improve peelability, it is particularly preferable to irradiate with ultrasonic waves during immersion. In addition, when not peeling only by swelling, you may peel off with a light force as needed.

<Plating process>
The plating process is a process of performing an electroless plating process on the insulating substrate 1 after the resin film 2 is removed. In the present invention, an electrolytic plating process may be performed instead of the electroless plating process.

  As a method of the electroless plating treatment, the insulating base material 1 partially coated with the plating catalyst or its precursor 5 is immersed in an electroless plating solution, and the plating catalyst or its precursor 5 is applied. For example, a method of depositing the electroless plating layer 6a only on the portion may be used. The electroless plating layer 6 a is formed so that the circuit groove 3 and the through hole 4 are completely filled, and the surface of the electroless plating layer 6 a does not protrude from the surface of the insulating substrate 1. Further, it is preferable that the thickness TH of the electroless plating layer 6a in the high density portion 30 is equal to the thickness TL of the electroless plating layer 6a in the low density portion 31, and TH = TL is formed. The thickness of the electroless plating layer 6a is the conductor thickness of the electric circuit 6 formed on the circuit board.

  Examples of the metal used for electroless plating include copper (Cu), nickel (Ni), cobalt (Co), and aluminum (Al). In these, the plating which has Cu as a main component is preferable from the point which is excellent in electroconductivity. Moreover, when Ni is included, it is preferable from the point which is excellent in corrosion resistance and adhesiveness with a solder.

  By the plating process, electroless plating is deposited only on the portion where the plating catalyst or its precursor 5 remains on the surface of the insulating base 1. Therefore, it is possible to accurately form a conductive layer only in a portion where the circuit pattern portion 32 is desired to be formed. On the other hand, the deposition of electroless plating on the portion where the circuit pattern portion 32 is not formed can be suppressed. Therefore, even when a plurality of fine electric circuits 6 having a narrow line width with a narrow pitch interval are formed, unnecessary plating does not remain between the adjacent electric circuits 6 and 6. Therefore, the occurrence of a short circuit and the occurrence of migration can be suppressed.

<Desmear treatment process>
In the manufacturing method of said circuit board A, after giving the said plating process process, specifically, before giving a fill-up plating, or after giving, you may further provide the desmear process process which performs a desmear process. By applying desmear treatment, unnecessary resin adhered to the electroless plating film can be removed. Further, when assuming a multilayer circuit board provided with the obtained circuit board, the surface of the insulating base material where the electroless plating film is not formed is roughened, and the adhesion with the upper layer of the circuit board is improved. Can be improved. Further, a desmear process may be performed on the via bottom. By doing so, unnecessary resin adhered to the via bottom can be removed. Moreover, it does not specifically limit as said desmear process, A well-known desmear process can be used. Specifically, the process etc. which are immersed in a permanganic acid solution etc. are mentioned, for example.

  Hereinafter, the present invention will be described specifically by way of examples.

Example 1
A resin film 2 of styrene-butadiene copolymer (SBR) having a thickness of 2 μm was formed on the surface of an insulating substrate 1 having a thickness of 100 μm (R1766 manufactured by Panasonic Electric Works Co., Ltd., using an epoxy resin). The resin coating 2 is formed on the main surface of the insulating substrate 1 by methyl ethyl ketone (MEK) suspension of styrene-butadiene copolymer (SBR) (manufactured by ZEON Corporation, acid equivalent 600, particle size 200 nm, (15% solid content) was applied and dried at 80 ° C. for 30 minutes.

  Then, a plurality of circuit grooves 3 were formed on the insulating base material 1 on which the resin coating 2 was formed by performing groove forming processing of a substantially rectangular cross section having a width of 20 μm and a depth of 30 μm by laser processing. For laser processing, MODEL 5330 manufactured by ESI equipped with a UV-YAG laser was used.

  Next, the insulating base material 1 on which the circuit grooves 3 were formed was immersed in a cleaner conditioner (surfactant solution, pH <1: C / N 3320 manufactured by Rohm & Haas Electronic Materials Co., Ltd.), and then washed with water. Then, soft etching treatment was performed with a sodium persulfate-sulfuric acid-based soft etchant having a pH <1. Then, the pre-dip process was performed using PD404 (Shipley Far East Co., Ltd., pH <1). Next, by immersing in an acidic Pd—Sn colloidal solution (CAT44, manufactured by Shipley Far East Co., Ltd.) having a pH of 1 containing stannous chloride and palladium chloride, palladium serving as the core of the electroless copper plating is tin- It was made to adsorb | suck to the bottom surface and side surface of the circuit groove | channel 3 of the insulating base material 1, and the surface of the resin film 2 in the state of palladium colloid.

  Next, palladium nuclei were generated by immersing in an accelerator chemical solution (ACC19E, manufactured by Shipley Far East Co., Ltd.) having pH <1. Then, the insulating substrate 1 was immersed for 10 minutes in a pH 14 5% aqueous sodium hydroxide solution while being ultrasonically treated. As a result, the resin film (SBR film) 2 on the surface swelled and peeled cleanly. At this time, no fragments or the like of the resin coating 2 remained on the surface of the insulating substrate 1. Next, the insulating substrate 1 was immersed in an electroless plating solution (CM328A, CM328L, CM328C, manufactured by Shipley Far East Co., Ltd.), and an electroless copper plating process was performed. By the electroless copper plating treatment, the electroless copper plating layer 6a was deposited in the circuit groove 3, and the electric circuit 6 was formed. In addition, when the surface of the insulating base material 1 subjected to the electroless copper plating treatment was observed with an SEM (scanning microscope), the electroless plating layer 6a was accurately applied only to the groove-formed portion (the portion of the circuit groove 3). Was formed.

  In the circuit board A thus formed, the line width L of the electric circuit 6 is 20 μm, the distance WH between the adjacent electric circuits 6 and 6 in the high density portion 30 is 20 μm, and the adjacent electric current in the low density portion 31 is formed. The interval WL between the circuits 6 and 6 was 50000 μm. Further, in the circuit board A, no erosion-like dent is formed, and each surface of the insulating base material 1 and the electric circuit 6 in the high density portion 30 and the insulating base material 1 and the electric circuit 6 in the low density portion 31 are formed. These surfaces were formed flush with each other.

  When an insulating layer is formed by superposing a prepreg on the surface of the circuit board A and then forming by heating and pressurizing, it is possible to prevent a pressure drop from occurring, and no stacking defects occur. In addition, when the circuit formation is formed on the surface of the insulating layer, it is possible to prevent the laser processing depth from varying, which affects the variation in the conductor cross-sectional area (electric circuit cross-sectional area) and the resistance value of the electric circuit. I was able to avoid giving it. Furthermore, since the thickness of the insulating layer is constant between the low density portion and the high density portion of the electric circuit, the impedance does not vary between the low density portion and the high density portion of the electric circuit, and there is a margin for circuit design.

(Example 2)
Instead of methyl ethyl ketone (MEK) suspension (manufactured by Nippon Zeon Co., Ltd., acid equivalent 600, particle size 200 nm, solid content 15%) of styrene-butadiene copolymer (SBR), a carboxyl group-containing polymer (Nippon Zeon Co., Ltd.) ), Acid equivalent 500, weight average molecular weight 25000, solid content 20%).

  At this time, the degree of swelling with respect to a 5% aqueous solution of sodium hydroxide at pH 14 was 1000%. On the other hand, the degree of swelling with respect to a 5% hydrochloric acid aqueous solution at pH 1 was 30%.

A Circuit board 1 Insulating substrate 3 Circuit groove 6 Electric circuit 30 High density part 31 Low density part

Claims (3)

  A circuit board having a plurality of circuit grooves in an insulating base material and having an electric circuit formed by a plating layer filled in each circuit groove, wherein the electric circuit is densely formed and a dense portion And the surfaces of the insulating base material and electric circuit in the high density portion and the surfaces of the insulating base material and electric circuit in the low density portion are formed to be flush with each other. Feature circuit board.   A circuit board having a plurality of circuit grooves in an insulating base material and having an electric circuit formed by a plating layer filled in each circuit groove, wherein the electric circuit is densely formed and a dense portion Formed in the low density portion, the distance from the surface opposite to the circuit groove forming surface of the insulating substrate in the high density portion to the bottom of the circuit groove, and the circuit groove of the insulating substrate in the low density portion. 2. The circuit board according to claim 1, wherein the distance from the surface opposite to the formation surface to the bottom of the circuit groove is formed to be equal. A circuit board having a plurality of circuit grooves in an insulating base material and having an electric circuit formed by a plating layer filled in each circuit groove, wherein the electric circuit is densely formed and a dense portion The low-density portion is formed, and the conductor thickness of the electric circuit in the high-density portion is equal to the conductor thickness of the electric circuit in the low-density portion. Circuit board.

Images