JP5075157B2 - Wiring substrate manufacturing method and wiring substrate obtained by the manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a wiring substrate and a wiring substrate obtained by the manufacturing method.

  2. Description of the Related Art In recent years, functions of mobile information terminal devices such as mobile phones; computers and peripheral devices; Accordingly, circuit boards mounted on these electrical devices are increasingly required to have higher circuit density. In order to realize such a high density circuit board, a method for accurately forming a circuit having a narrower line width and line spacing is required. In high-density wiring, short-circuiting or migration between wirings easily occurs. Furthermore, as the number of stacked layers increases, it becomes difficult to form a fine circuit due to an increase in unevenness generated on the circuit formation plane.

  Conventionally, a subtractive method and an additive method are known as a method for forming a circuit of a printed wiring board. The subtractive method is a method of forming a circuit by removing an unnecessary portion of the metal foil deposited on the surface of the insulating base material (subtractive) and leaving only the portion of the metal foil where the circuit is to be formed. On the other hand, the additive method is a method of forming a predetermined circuit by performing electroless plating only on a circuit forming portion on an insulating substrate.

  In the subtractive method, by etching a thick copper foil, the metal foil of only the circuit forming part is left, and the other part is removed. Therefore, the copper of the removed part is wasted. This is disadvantageous in terms of manufacturing cost. On the other hand, the additive method is a preferable method because there is no waste of resources because the conductive layer is formed only on the circuit forming portion by using electroless plating.

  A full additive method, which is one of conventional representative additive methods, will be described with reference to schematic cross-sectional views of FIGS. 5 (A) to 5 (E).

  First, as shown in FIG. 5A, a catalytic metal 102 is deposited on the surface of an insulating substrate 100 provided with a through hole 101. Note that the surface of the insulating substrate 100 is roughened in advance. Next, as shown in FIG. 5B, a photoresist layer 103 is formed. Next, as shown in FIG. 5C, the surface of the photoresist layer 103 is exposed through a photomask 110 on which a predetermined circuit pattern is formed. Next, as shown in FIG. 5D, the circuit pattern is developed. Then, as shown in FIG. 5E, the metal wiring 104 is formed by performing electroless copper plating on the surface of the circuit pattern formed by development and the inner wall surface of the through hole 101. A circuit is formed on the insulating substrate 100 by such a process.

  In the conventional additive method described above, the catalytic metal 102 is deposited on the entire surface of the insulating substrate 100. As a result, the following problems have arisen. That is, when the photoresist layer 103 is developed with high accuracy, plating can be formed only on the portions not protected by the photoresist. However, when the photoresist layer 103 is not developed with high accuracy, an unnecessary plated portion 105 may remain in a portion where the plating is not originally formed as shown in FIG. This occurs because the catalytic metal 102 is deposited on the entire surface of the insulating substrate 100. The unnecessary plated portion 105 causes a short circuit or migration between adjacent circuits. Such a short circuit or migration is more likely to occur when a circuit having a narrow line width and line interval is formed.

  In order to solve such a problem, the following Patent Document 1 discloses that the first and second solvent-soluble first photosensitive resin layers and the alkali-soluble second photosensitive resin layer are formed on the insulating substrate. After the photosensitive resin layer is exposed through a photomask having a predetermined circuit pattern, the first and second photosensitive resin layers are developed, and the catalyst is adsorbed on the entire surface including the concave portions generated by the development. A method is described in which an unnecessary catalyst is removed by dissolving an alkali-soluble second photosensitive resin in an alkaline solution, and then an electroless plating is performed to form a circuit accurately only in a portion where the catalyst exists. ing. However, according to such a method, two types of photosensitive resin layers having different solvent solubility are formed, and also during development, after developing with two types of solvent and adsorbing the catalyst, an alkaline solution is further added. The manufacturing process is very complicated, such as the need to dissolve the second photosensitive resin.

  In Patent Document 2 below, a first process of coating a protective film made of resin or metal on an insulating substrate, and a wiring pattern by machining or laser beam irradiation on the insulating substrate coated with the protective film. A second step of drawing and forming the groove and through hole individually or simultaneously, and after forming an activation layer on the entire surface of the insulating substrate, the protective film is peeled off to remove the activation layer on the insulating substrate and remove the groove and A third step of leaving an activation layer only on the inner wall surface of the through hole; and a conductive layer selectively applied only to the inner surface of the activated groove and through hole by plating the insulating substrate without using a plating protective film. And a fourth step of forming the printed wiring board.

  In Patent Document 2, a thermosetting resin is coated on an insulating substrate as a protective film and heated and cured, and the protective film and the insulating substrate are cut according to a predetermined wiring pattern using a scriber, a drilling machine, etc. In addition, an activation process for electroless plating is performed on the entire surface of the protective film and the insulating substrate, and the thermosetting resin on the surface of the insulating substrate is removed with a solvent to leave only the necessary activation layer, and then electroless It is described that a conductive layer is selectively formed only on necessary portions by plating (Patent Document 2, page 2, lower left column, line 16 to lower right column, line 11).

  About the thermosetting resin used as a protective film described in the said patent document 2, the kind in particular is not described. Since general thermosetting resins are hard and have excellent solvent resistance, there is a problem that they are difficult to remove with a simple solvent. Further, such a thermosetting resin has an adhesiveness to the resin base material that is too high, so that only the protective film can be easily and accurately removed without leaving a piece of the protective film on the surface of the resin base material. Was difficult. In addition, if a strong solvent is used for sufficient peeling or if the substrate is immersed for a long time, the catalyst metal and the like on the surface of the base material are also removed, and a conductive layer may not be formed in the portion where the plating is removed. There was a problem that it would disappear and cause a short circuit. In addition, when a strong solvent is used or when immersed for a long time, the protective film made of thermosetting resin may collapse so that the catalyst metal in the protective film is redispersed in the solvent. there were. And the catalyst metal re-dispersed in such a solvent reattaches to the resin base material surface, and there exists a possibility that formation of an unnecessary plating film may be made in the part. For this reason, according to the method disclosed in Patent Document 2, the surface of the insulating substrate is covered with a general thermosetting resin, and later, it is difficult to accurately remove the protective film. It was.

JP-A-57-134996 JP 58-186994 A

  The present invention provides a method of manufacturing a wiring substrate capable of forming a circuit while maintaining the outline of a predetermined circuit pattern with high accuracy by an easy method when forming a fine circuit using the additive method. With the goal.

  The method for producing a wiring substrate of the present invention includes a film forming step of forming a swellable resin film on the surface of an insulating substrate, and the thickness of the film or exceeding the thickness based on the outer surface of the swellable resin film A circuit groove forming step for forming a circuit groove having a depth; a catalyst deposition step for depositing a catalyst metal on the surface of the circuit groove and the surface of the swellable resin film; and the swellable resin film on a predetermined liquid. And a film peeling step for peeling off the swellable resin film from the surface of the insulating substrate, and after peeling off the swellable resin film, an electroless plating film is formed only on the portion where the catalyst metal remains. And a plating process step. According to such a manufacturing method, after a swellable resin film is formed on an insulating substrate, a circuit groove having a predetermined pattern is formed using laser processing or the like, and the plating film is not formed with the swellable resin film In a state in which the catalyst is protected, an unnecessary catalyst metal can be easily removed by applying a catalyst metal to the circuit groove portion and swelling and swelling the swellable resin film. By such a process, electroless plating can be performed only on the circuit groove portion where the catalyst metal remains. As a result, the contour of the circuit pattern formed can be maintained with high accuracy. As a result, for example, even in the case where a plurality of circuit lines are formed with a certain interval, an electroless plating film fragment or the like does not remain between the circuit lines, thereby suppressing the occurrence of short circuits and migration. it can.

  In the production method of the present invention, the catalyst deposition step includes a step of treating in an acidic catalyst metal colloid solution, and the film peeling step includes a step of swelling the swellable resin film in an alkaline solution, and the swelling The conductive resin film is preferably a resin film that does not swell with respect to the acidic catalyst metal colloid solution and swells with respect to the alkaline solution. According to such a manufacturing method, the swellable resin film does not peel in the catalyst deposition process treated under acidic conditions, but selectively peels off in the film peeling process treated with an alkaline solution after the catalyst deposition process. Is done. Therefore, in the catalyst deposition step, the portion where plating is not formed can be accurately protected, and the swellable resin film can be peeled off after deposition of the catalyst, so that more accurate circuit formation is possible. In this case, the swelling resin film preferably has a degree of swelling with respect to the acidic catalyst metal colloid solution of 10% or less and a degree of swelling with respect to the alkaline solution of 50% or more.

  Examples of swellable resin films that are selectively peeled off under alkaline liquid conditions as described above include suspensions or emulsions of elastomers such as diene elastomers, acrylic elastomers, and polyester elastomers having carboxyl groups. A resin film formed by applying and then drying is mentioned. According to such an elastomer, it is possible to easily form a swellable film having a desired degree of swelling by adjusting the acid equivalent, the degree of crosslinking or the degree of gelation. Among these, a diene elastomer comprising a styrene-butadiene copolymer having a carboxyl group is particularly preferable.

  As the swellable resin film, a film mainly composed of a resin composed of an acrylic resin having a carboxyl group with an acid equivalent of 100 to 800 is also preferably used.

  Further, the thickness of the swellable resin film is preferably 10 μm or less from the viewpoint that a fine groove can be formed with high accuracy when the circuit groove is formed.

  In addition, it is preferable that the width of the portion removed by the circuit groove forming step has a portion of 20 μm or less because an antenna circuit or the like that requires fine processing can be formed.

  When the circuit groove forming step is a process of forming a circuit groove by laser processing, a finer circuit can be formed with high accuracy, and the depth of the circuit groove can be increased by changing the laser power. This is preferable because the thickness can be easily adjusted.

  Further, when the circuit groove forming step is a step of forming a circuit groove using a mold pressing method, it is preferable because the circuit groove can be easily formed by stamping a mold.

  In the circuit groove forming step, when a circuit groove having a depth exceeding the thickness of the swellable resin film is formed, the circuit is formed in a deep portion of the insulating base as shown in FIG. be able to. Thereby, damage to the circuit and the like can be suppressed.

  In the circuit groove forming step, a hole for passing through the swellable resin film and establishing conduction between the insulating layers in the insulating base material is used for the via hole or the inner via hole in forming the circuit groove. It is preferable from the point that via holes and inner via holes can be formed by electroless plating on the formed holes.

  The insulating base material has a step surface formed in a step shape, and the film formation step, the circuit groove formation step, the catalyst deposition step, the film peeling step, and the plating treatment step on the step surface. Is also a preferred form. According to such a manufacturing method, a circuit that can overcome a step can be easily formed.

  The swellable resin film contains a fluorescent substance, and further includes an inspection step for inspecting defective film removal using light emitted from the fluorescent substance after the film removal step. preferable. In the manufacturing method as described above, when the wiring width and the wiring interval become extremely small, the film of the portion that should originally be removed between the adjacent wirings cannot be completely removed and remains slightly. This is also a concern. There is also a concern that the resin film fragments removed during the formation of the circuit groove may enter and remain in the formed circuit groove. When the resin film remains between the wirings, a plating film is formed at the portion, which may cause migration or short circuit. In addition, if a resin film fragment remains in the formed circuit groove, it may cause poor heat resistance and propagation loss of the electric circuit. In such a case, the fluorescent resin is contained in the swellable resin film as described above, and after the film removal step, only a portion where the film remains is irradiated with a predetermined light source on the film removal surface. The presence or absence of a film removal failure or the location of a film removal failure can be inspected by emitting light with a reactive substance.

  According to the manufacturing method of the present invention, the outline of a circuit pattern formed by electroless plating can be maintained with high accuracy. Thereby, it can suppress that the fragment | piece etc. of an unnecessary electroless plating film | membrane remain in parts other than a circuit pattern formation part, and, thereby, generation | occurrence | production of a short circuit, migration, etc. can be suppressed.

FIG. 1 is a process diagram for explaining an embodiment of a production method according to the present invention. FIG. 2 is an explanatory diagram for explaining an inspection process for inspecting defective film removal using light emission from the fluorescent substance by adding a fluorescent substance to the swellable resin film. FIG. 3 is a schematic cross-sectional view showing an electroless plating film formed when a circuit groove that digs into an insulating base material is formed beyond the thickness of the swellable resin film in the circuit groove forming step. is there. FIG. 4 is a process diagram for explaining circuit formation using an insulating base material having a stepped surface. FIG. 5 is an explanatory diagram for explaining the contour shape of a circuit formed by a conventional additive method. FIG. 6 is an explanatory diagram for explaining a contour shape of a circuit formed by a conventional additive method.

(First embodiment)
The manufacturing method of the wiring substrate of the present embodiment includes a film forming step of forming a swellable resin film on the surface of the insulating substrate, and the thickness of the film or the thickness based on the outer surface of the swellable resin film. A circuit groove forming step for forming a circuit groove having a depth exceeding, a catalyst deposition step for depositing a catalyst metal on the surface of the circuit groove and the surface of the swellable resin film, and a predetermined amount of the swellable resin film. A film peeling step for peeling the swellable resin film from the surface of the insulating substrate by swelling with a liquid, and an electroless plating film only on a portion where the catalyst metal remains after the swellable resin film is peeled off And a plating process to be formed.

  Hereinafter, the production method of the present invention will be described with reference to the drawings.

  FIG. 1 is a process diagram for explaining an embodiment of a production method according to the present invention. In FIG. 1, 1 is an insulating substrate, 2 is a swellable resin film, 3 is a circuit groove (cutting part), 4 is a through hole, 5 is a catalyst metal (catalyst metal), and 6 is an electroless plating film.

  In the manufacturing method of the present embodiment, as shown in FIG. 1A, first, the swellable resin film 2 is formed on the surface of the insulating substrate 1.

  As the insulating base material 1, various organic substrates that can be used for manufacturing a circuit board can be used without any particular limitation. Specific examples of the organic substrate include base materials made of epoxy resin, acrylic resin, polycarbonate resin, polyimide resin, polyphenylene sulfide resin, and the like. The substrate form is not particularly limited, such as a sheet, a film, a prepreg, and a three-dimensional shaped molded body. The thickness of the insulating substrate 1 is not particularly limited. In the case of a sheet, film, or prepreg, for example, it is preferably about 10 to 200 μm, more preferably about 20 to 100 μm.

  As a method for forming the swellable resin film 2, a liquid material capable of forming the swellable resin film 2 is applied to the surface of the insulating substrate 1 and then dried, or a swellable resin film 2 formed in advance is used. The method of bonding the resin film which becomes is mentioned.

  As a material for forming the swellable resin film 2, it is easily dissolved from the surface of the insulating substrate 1 without being substantially dissolved in the swelling liquid by a step of swelling with a predetermined liquid (swelling liquid) described later. Any resin film that peels can be used without particular limitation. Preferably, a resin film having a swelling degree such that the swelling degree with respect to the swelling liquid is 50% or more, further 100% or more and 1000% or less is used. If the degree of swelling is too low, the swellable resin film tends to be difficult to peel in the film peeling step described later, and if it is too high, the film strength is reduced and it is broken when peeled off. Tends to be difficult to peel.

  Such a swellable resin film is particularly preferably a film whose degree of swelling varies depending on the pH of the swelling liquid. When such a film is used, the pH in the catalyst deposition process can be changed by making the liquid conditions in the catalyst deposition process described later different from the liquid conditions in the film peeling process described later. The swellable resin film 2 maintains a high adhesion to the insulating substrate 1, and the swellable resin film 2 can be easily peeled off at the pH in the film peeling step.

  More specifically, for example, the catalyst deposition step described later includes a step of treating in an acidic catalyst metal colloid solution having a pH in the range of 1 to 3, for example, and the film peeling step described later is alkaline in the range of pH 12 to 14. When the step of swelling the swellable resin film in the solution is provided, the swellable resin film has a swelling degree of 25% or less, further 10% or less with respect to the acidic catalyst metal colloid solution, and with respect to the alkaline solution. A resin film having a swelling degree of 50% or more, further 100% or more, and more preferably 500% or more is preferable.

  Examples of such swellable resin films include photocuring used for sheets formed from elastomers having a predetermined amount of carboxyl groups, dry film resists for patterning printed wiring boards (hereinafter also referred to as DFR), 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 degree of alkali swelling can be formed by adjusting the acid equivalent, the degree of crosslinking, the degree of gelation, etc. 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 small, 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. Specific examples of such DFR include a dry film of a photopolymerizable resin composition as disclosed in JP-A-2000-231190, JP-A-2001-201851, and JP-A-11-212262. Sheets obtained by curing, and commercially available as an alkali development type DFR, for example, UFG series manufactured by Asahi Kasei Kogyo Co., Ltd. can be mentioned.

  Furthermore, examples of other swellable resin films include rosin-based resins containing carboxyl groups (for example, “NAZDAR229” manufactured by Yoshikawa Chemical Co., Ltd.) and phenol-based resins (for example, And “104F” manufactured by LEKTRACHEM).

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

  The thickness of the swellable resin film 2 is 10 μm or less, further 5 μm or less, preferably 0.1 μm or more, more preferably 1 μm or more. When the thickness is too thick, the accuracy tends to decrease when forming fine circuit grooves, and when the thickness is too thin, it tends to be difficult to form a film having a uniform thickness.

  Next, as shown in FIG. 1 (B), a circuit groove having a predetermined circuit pattern having a thickness corresponding to the thickness of the coating or a depth exceeding the thickness on the insulating base material 1 on which the swellable resin coating 2 is formed. Form. Further, drilling for forming the through hole 4 is performed as necessary (circuit groove forming step).

  The width of the circuit groove is not particularly limited, but when laser processing is used, a fine circuit having a line width of 20 μm or less can be easily formed. By forming such a fine circuit, an antenna circuit or the like that requires high-precision processing can be easily formed.

  Further, in the circuit groove forming step, forming a through-hole for passing through the swellable resin film 2 and establishing conduction between the insulating layers in the insulating base material 1 is a via hole when a plurality of wiring base materials are stacked. A hole that can be used for an inner via hole can be formed when the circuit groove 3 is formed, and via holes and inner via holes are easily formed by conducting electroless plating on the formed hole. It is preferable from the point which can be performed.

  The processing method for forming the circuit groove 3 is not particularly limited, and cutting or stamping by laser processing or dicing is used. Laser processing is preferable in order to form fine circuit grooves with high accuracy. According to laser processing, the depth of the circuit groove and the like can be freely adjusted by changing the laser power. In addition, a fine mold or the like used in the field of nanoimprint can be preferably used for the embossing process.

  In the circuit groove forming process, electroless electrolysis described later is performed by selectively removing only a portion of the insulating base material 1 where a conductive layer such as a circuit, an electrode, a via hole or an inner via hole is to be formed. A region to which the metal catalyst 5 which is a portion where the electroless plating film 6 is formed by the plating treatment process is defined.

  Next, as shown in FIG. 1C, a catalyst metal (on the surface where the circuit groove 3 and the through hole 4 are formed and on the entire surface of the swellable resin film 2 where the circuit groove 3 and the through hole 4 are not formed). (Plating catalyst) 5 is deposited (catalyst deposition step).

  The catalyst metal 5 is a catalyst or a precursor thereof that is imparted in order to sufficiently and effectively form an electroless plating film only on a portion where the catalyst is activated in a plating process described later. Any known catalyst can be used without particular limitation. Specific examples thereof include, for example, metallic palladium (Pd), platinum (Pt), silver (Ag), etc., or precursors that generate these.

  Examples of the method of depositing the catalytic metal 5 include a method of treating with an acidic Pd—Sn colloid solution treated under acidic conditions of pH 1 to 3, and then treating with an acid solution. Specifically, the following methods can be mentioned.

First, oil and 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 are washed with 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 and hydrochloric acid aqueous solution of pH1-2. Then, 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 containing a stannous chloride aqueous solution having a concentration of about 0.1%. Thereafter, Pd and Sn are aggregated and adsorbed by further dipping in an acidic catalytic metal colloid solution such as acidic Pd—Sn colloid having pH 1 to 3 containing stannous chloride and palladium chloride. Then, metal palladium is formed by causing an oxidation-reduction reaction (SnCl ₂ + PdCl ₂ → SnCl ₄ + Pd ↓) between the adsorbed Pd and Sn.

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

  By such plating deposition treatment, the catalyst metal 5 can be deposited on the surfaces of the circuit grooves 3 and the through holes 4 and the surface of the swellable resin film 2 as shown in FIG.

  Next, as shown in FIG. 1D, the swelling resin film 2 is peeled from the surface of the insulating base material 1 by swelling the swelling resin film 2 with a predetermined liquid (film peeling step). According to this process, only the catalyst metal 5 on the surface of the formed circuit groove 3 and the through-hole 4 is insulated in the circuit groove forming process by peeling off the swellable resin film 2 covering the surface of the insulating substrate 1. The catalyst metal 5 deposited on the surface (the surface of the swellable resin film 2) that is left on the base material 1 and on which no other circuit grooves are formed can be removed while being supported on the swellable resin film 2. it can.

  The swelling liquid for swelling the swellable resin film 2 swells the swellable resin film 2 without substantially decomposing or dissolving the insulating base material 1, the swellable resin film 2 and the catalytic metal 5, and preferably has a degree of swelling. Any liquid can be used as long as it can be swollen to 50% or more. Such a swelling liquid can be appropriately selected depending on the type and thickness of the swellable resin film 2.

  In addition, when the plating process treated under acidic conditions as described above is used in the catalyst deposition step, the swelling resin film 2 has a swelling degree of 10% or less under acidic conditions, and under alkaline conditions. It is preferably formed from an elastomer such as a diene elastomer, an acrylic elastomer, and a polyester elastomer having a degree of swelling of 50% or more. Such a swellable resin film easily swells and peels off with an alkaline aqueous solution having a pH of 12 to 14, such as 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.

  Next, as shown in FIG. 1 (E), an electroless plating film 6 is formed only on the portion where the catalyst metal 5 remains (plating process). By such a process, the electroless plating film 6 can be deposited only on a portion where a predetermined circuit pattern is to be formed, that is, a portion where the catalytic metal 5 is deposited.

  As an electroless plating method, the insulating substrate 1 with the catalytic metal 5 deposited only on the portion where the circuit pattern is to be formed is immersed in the electroless plating solution, and only the portion on which the catalytic metal 5 is deposited is electroless. A method of depositing the plating film 6 can be used.

  Examples of the metal used for electroless plating include Cu (copper), Ni (nickel), Co (cobalt), and Al (aluminum). Among these, plating containing Cu as a main component is preferable from the viewpoint of excellent conductivity, and when Ni is contained, it is preferable from the viewpoint of excellent corrosion resistance and adhesion to solder or the like.

  The thickness of the electroless plating film 6 to be formed is not particularly limited, but is preferably about 0.1 to 10 μm, more preferably about 1 to 5 μm.

  By such a plating process, the electroless plating film 6 can be deposited only on the portion of the surface of the insulating substrate 1 where the circuit is to be formed, that is, the portion where the catalytic metal 5 is deposited. In the electroless plating film 6 formed by such a method, the catalytic metal is deposited only on the part where the circuit is to be formed, and the catalytic metal 5 in the other part is removed by peeling off the swellable resin film 2. Has been. Therefore, it is possible to accurately form a conductive layer made of electroless plating only on a portion where a circuit is to be formed. Therefore, since it is possible to suppress the deposition of the electroless plating film on an unnecessary portion, for example, even when a plurality of fine circuits having a narrow line width and a narrow line width are formed, adjacent circuits are formed. There is no unnecessary plating residue in between, so that the occurrence of short circuits and migration can be suppressed.

  In addition, in the manufacturing method of the wiring base material mentioned above, the fluorescence by irradiating ultraviolet light or near-ultraviolet light to a test object surface after a film | membrane peeling process by making the swelling resin film 2 contain a fluorescent substance. The film peeling failure can be inspected by using light emission from the active substance. In the manufacturing method of the present embodiment, a metal wiring having an extremely small wiring width and wiring interval can be formed. In such a case, for example, as shown as the residue 2a of the swellable resin film 2 in the enlarged top view of the circuit 8 formed on the surface of the insulating base 1 in FIG. There is a concern that it remains without being completely removed. When the residue 2a of the swellable resin film 2 remains between the metal wirings, a plating film is formed on the portion, which may cause migration or short circuit. In such a case, the swellable resin film 2 is made to contain a fluorescent substance, and after the film removal step, the film removal surface is irradiated with a predetermined light source and only the portion where the film remains is emitted by the fluorescent substance. By doing so, it is possible to inspect the presence or absence of film removal failure and the location of film removal failure.

  The fluorescent substance that can be contained in the swellable resin film 2 used in this inspection process is not particularly limited as long as it exhibits light emission characteristics when irradiated with light from a predetermined light source. Specific examples thereof include Fluoresceine, Eosine, Pyronine G and the like.

  The portion where light emission from the fluorescent substance is detected by this inspection process is a portion where the residue 2a of the swellable resin film 2 remains. Therefore, by removing the portion where light emission is detected, it is possible to suppress the formation of a plating film on that portion. Thereby, generation | occurrence | production of a migration or a short circuit can be suppressed beforehand.

  Through such steps, a wiring substrate 10 as shown in FIG. 1E is formed.

  In addition, if the manufacturing method which concerns on this invention mentioned above is used, the circuit which has predetermined depth in the insulating base material 1 by forming a circuit groove deeper than the thickness of the swellable resin film 2 in a circuit groove formation process. The groove 3 can be formed. Then, by forming a circuit groove 3 having a predetermined depth in the insulating base material 1, an electroless plating film 6a that becomes a circuit is formed in a deep portion of the insulating base material as shown in FIG. Circuits can also be formed at positions having different depths between the conductive layers (for example, 6a and 6b in FIG. 3). Also, as shown in 6c and 6d of FIG. 3, after forming a circuit groove having a predetermined depth in the insulating substrate 1, a circuit is formed so that the circuit groove is embedded by electroless plating. Since a circuit having a large area can be easily formed, it is preferable in that the electric capacity of the circuit can be increased.

(Second embodiment)
In the first embodiment, the method of forming a circuit on a flat insulating substrate has been described, but the method of the present invention is particularly applicable to a three-dimensional insulating substrate having a stepped three-dimensional surface. Accurate circuit formation is possible.

 A method for forming a circuit on the three-dimensional insulating substrate 51 of the present embodiment will be described with reference to the drawings.

  4A to 4E are schematic cross-sectional views for explaining each step of the method of forming a circuit on the three-dimensional insulating base material 51 of the present embodiment.

  In this embodiment, as shown in FIG. 4A, first, the swellable resin film 2 is formed on the surface of the three-dimensional insulating substrate 51 having a stepped portion.

  As the three-dimensional insulating base material 51, various resin molded bodies that can be used for manufacturing a three-dimensional circuit board conventionally known can be used without any particular limitation. It is preferable from the viewpoint of production efficiency that such a molded body is obtained by injection molding. Specific examples of the resin material for obtaining the resin molding include polycarbonate resin, polyamide resin, various polyester resins, polyimide resin, polyphenylene sulfide resin, and the like.

  The method for forming the swellable resin film 2 is not particularly limited. Specifically, for example, a method of drying after applying a liquid material for forming the swellable resin film 2 on the stepped surface of the three-dimensional insulating substrate 51 can be mentioned. The method for applying is not particularly limited. Specifically, conventionally known spin coating methods, bar coater methods, spray methods, electrostatic coating, electrodeposition coating, and the like can be used without particular limitation.

  Next, as shown in FIG. 4B, by removing only a predetermined portion of the swellable resin film 2 from the outer surface side of the formed swellable resin film 2 using, for example, a laser, a predetermined pattern is formed. A circuit groove 3 is formed. The method for forming the circuit groove 3 is not particularly limited.

  Thus, by forming the circuit groove 3 in accordance with a predetermined circuit pattern, a portion where the circuit is formed is defined.

  Next, as shown in FIG. 4C, the metal catalyst 5 is deposited on the entire surface where the circuit groove 3 is formed and the surface where the circuit groove 3 is not formed (catalyst deposition step). By such a catalyst deposition process, the metal catalyst 5 can be deposited on the surface of the circuit groove 3 and the surface of the swellable resin film 2 as shown in FIG.

  Next, as shown in FIG. 4D, the swellable resin film 2 is swollen with a predetermined liquid and peeled from the surface of the three-dimensional insulating substrate 51 (film peeling step). According to this step, the metal catalyst 5 can be left only in the portion of the stepped surface of the three-dimensional insulating base material 51 where it is desired to form a circuit.

  Then, as shown in FIG. 4E, the electroless plating film 6 is formed only on the portion where the metal catalyst 5 remains (plating process). By such a process, the electroless plating film 6 is deposited only on the portion where the circuit groove 3 is formed.

  Through such a process, the three-dimensional circuit board 60 in which the circuit 6 is formed on the three-dimensional insulating base 51 as shown in FIG. According to the circuit formation method of the present embodiment, a circuit can be accurately and easily formed on the surface of the three-dimensional circuit board having the stepped portion.

Example 1
Using a spin coat method on the surface of an epoxy resin base material (R1766 manufactured by Panasonic Electric Works Co., Ltd.) having a thickness of 100 μm, a methyl ethyl ketone (MEK) suspension of styrene-butadiene copolymer (SBR) (manufactured by Nippon Zeon Co., Ltd., acid) Equivalent 600, particle diameter 200 nm, solid content 15%) was applied and dried at 80 ° C. for 30 minutes to form a 2 μm thick resin film.

  And the circuit groove | channel of the predetermined shape which has a substantially rectangular cross section of width 20micrometer and depth 30micrometer was formed by laser processing with respect to the epoxy resin base material in which the said resin film was formed. For laser processing, MODEL 5330 manufactured by ESI equipped with a UV-YAG laser was used.

  Next, the epoxy resin base material in which the circuit groove was 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. And after water washing, the pre-dip process was performed using PD404 (Shipley Far East Co., Ltd. product, pH <1). Then, 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 electroless copper plating is tin-palladium. It was made to adsorb | suck to an epoxy resin base material in the state of a colloid.

  Next, palladium nuclei were generated by immersing in an accelerator chemical solution (ACC19E, manufactured by Shipley Far East Co., Ltd.) having a pH <1. Then, the epoxy resin substrate was immersed for 10 minutes in a pH 14 5% aqueous sodium hydroxide solution while being ultrasonically treated. As a result, the SBR film on the surface swelled and peeled cleanly. At this time, no fragments of the SBR film remained on the surface of the epoxy resin substrate. Then, the epoxy resin base material was immersed in an electroless plating solution (CM328A, CM328L, CM328C, manufactured by Shipley Far East Co., Ltd.) to perform electroless copper plating.

  An electroless copper plating film having a thickness of 5 μm was deposited by the electroless copper plating treatment. When the surface of the epoxy base material subjected to the electroless copper plating treatment was observed with an SEM (scanning microscope), the electroless plating film was accurately formed only in the portion where the circuit groove was formed.

  The swelling degree of the swellable resin film under alkaline conditions and acidic conditions was determined as follows.

  An SBR suspension applied to form a swellable resin film on the release paper was applied and dried at 80 ° C. for 30 minutes. As a result, a 2 μm thick resin film was formed. Then, a sample was obtained by forcibly peeling the formed film.

  And about 0.02 g of the obtained sample was weighed. The weight of the sample at this time is defined as the weight m (b) before swelling. Then, the weighed sample was immersed in 10 ml of a 5% aqueous sodium hydroxide solution (pH 14) at 20 ± 2 ° C. for 15 minutes. Similarly, another sample was immersed in 10 ml of a 5% hydrochloric acid aqueous solution (pH 1) at 20 ± 2 ° C. for 15 minutes.

  Then, each of the samples was centrifuged at 1000 G for about 10 minutes using a centrifuge to remove moisture and the like attached to the sample. And the weight of the swollen sample after centrifugation was measured, and it was set as the weight m (a) after swelling. From each of the obtained weight m (b) before swelling and weight m (a) after swelling, “swelling degree SW = (m (a) −m (b)) / m (b) × 100 (%)” The degree of swelling was calculated from the formula. Other conditions were performed in accordance with JIS L1015 8.27 (measurement method of alkali swelling degree).

  At this time, the degree of swelling with respect to a sodium hydroxide 5% aqueous solution at pH 14 was 750%. On the other hand, the degree of swelling with respect to a 5% hydrochloric acid aqueous solution at pH 1 was 3%.

  As described above, when the method according to the present invention is used, the catalytic metal can be deposited only on a specific portion of the substrate surface by peeling the swellable resin film. Therefore, the electroless plating film is formed accurately only on the portion where the catalyst metal is deposited. Moreover, since the swellable resin film can be easily peeled off by the swelling action, it can be seen that the peeling step can be easily and accurately performed.

DESCRIPTION OF SYMBOLS 1,100 Insulating base material 2 Swellable resin film 2a Residue of swelling resin film 3 Circuit groove 4 Through-hole 5 Catalytic metal 6,6a-6d, Electroless plating film 8 Circuit 10 Wiring base material 51 Three-dimensional shape insulating base Material 101 Through-hole 102 Catalytic metal 103 Photoresist layer 104 Conductive layer 105 Unnecessary portion 110 Photomask

Claims (15)

A film forming step of forming a swellable resin film on the surface of the insulating substrate;
Forming a circuit groove having a depth corresponding to the thickness of the swellable resin film based on the outer surface of the swellable resin film or a depth exceeding the thickness; and
A catalyst deposition step of depositing a catalyst metal on the surface of the circuit groove and the surface of the swellable resin film;
A film peeling step of peeling the swellable resin film from the surface of the insulating substrate by swelling the swellable resin film with an alkaline solution ;
And a plating treatment step of forming an electroless plating film only on a portion where the catalytic metal remains after peeling off the swellable resin film. The catalyst deposition step includes a step of treating in an acidic catalyst metal colloid solution, and the film peeling step includes a step of swelling the swellable resin film in an alkaline solution;
The swellable resin film, the degree of swelling against the acidic catalyst metal colloidal solution is below 10%, method for manufacturing a wiring substrate according to claim 1 for the said alkaline solution is a resin film that swells. The swellable resin coating method for producing a wiring substrate according to claim 1 or 2 degree of swelling before Symbol alkaline solution is 50% to 1000%.   The method for manufacturing a wiring substrate according to claim 2 or 3, wherein the swellable resin film is a resin film formed by applying an elastomer suspension or emulsion and then drying.   The method for producing a wiring substrate according to claim 4, wherein the elastomer has a carboxyl group and is selected from the group consisting of a diene elastomer, an acrylic elastomer, and a polyester elastomer.   The method for producing a wiring substrate according to claim 5, wherein the diene elastomer is a styrene-butadiene copolymer.   The method for producing a wiring substrate according to claim 2 or 3, wherein the swellable resin film is mainly composed of a resin made of an acrylic resin having a carboxyl group with an acid equivalent of 100 to 800. The method for manufacturing a wiring substrate according to claim 1, wherein the swellable resin film has a thickness of 0.1 to 10 μm or less. The circuit groove forming step, the manufacturing method of the wiring substrate according to any one of claims 1-8 is a step of forming a circuit grooves by laser processing. Manufacturing method of the circuit groove-forming step is, the wiring substrate according to any one of claims 1-8 is a step of forming a circuit groove with a mold押法. The method for manufacturing a wiring substrate according to any one of claims 1 to 10 , wherein in the circuit groove forming step, a circuit groove having a depth exceeding a thickness of the swellable resin film is formed. The method for manufacturing a wiring substrate according to any one of claims 1 to 11, wherein, in the circuit groove forming step, the insulating substrate is perforated through the swellable resin film. The insulating substrate has a step surface formed in a step shape, and the film formation step, the circuit groove formation step, the catalyst deposition step, the film peeling step, and the plating treatment step on the step surface, a method for manufacturing a wiring substrate according to any one of claims 1 to 1 2 for performing. The said swellable resin film contains a fluorescent substance, and further comprises an inspection step for inspecting defective film removal using light emission from the fluorescent substance after the film removal step. 14. The method for manufacturing a wiring substrate according to any one of 1 to 3 . The wiring base material obtained by the manufacturing method of any one of Claims 1-4 .

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