JP5330156B2 - Circuit board manufacturing method and circuit board obtained by the manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a circuit board, which forms the circuit board with high precision on an insulation base material, even for an electrical circuit having a narrow line width and a line interval. <P>SOLUTION: The manufacturing method of a circuit board includes: a film formation process to form a resin film 2 in the surface of the insulation base material 1; a circuit pattern formation process to form a circuit pattern portion of a circuit groove 3 of a predetermined shape and depth by applying laser processing or machine processing to the insulation base material 1 from the outside surface of the resin film 2; a catalyst adhesion process to adhere a plating catalyst or its precursor 5 to the surface of the circuit pattern portion and the surface of the resin film 2; a film peeling process to peel off the resin film 2 from the insulation base material 1; and a plating processing process to apply electroless plating to the insulation base material 1 of which the resin film 2 is peeled off. The film formation process uses, as the insulation base material 1, a material which has a smooth surface having a 0.5 &mu;m or less surface roughness (Ra), and the resin film 2 is formed on the smooth surface side. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a circuit board manufacturing method and a circuit board obtained by the manufacturing method.

  In mobile information terminal devices such as mobile phones, computers and peripheral devices, and electrical devices such as various information home appliances, high functionality is rapidly progressing. Accordingly, circuit boards mounted on these electric devices are required to have higher density of electric circuits. In order to satisfy such a demand for higher circuit density, there is a method capable of accurately forming wiring of an electric circuit with a narrower line width and line interval (width of a portion between adjacent electric circuits). It has been demanded. In high-density circuit wiring, short-circuiting or migration between wirings is likely to occur.

  As a method for manufacturing a circuit board, a method of forming an electric circuit on an insulating substrate by a subtractive method or an additive method is known. The subtractive method is a method of forming an electric circuit by removing (subtractive) a metal foil other than a portion where the electric circuit on the surface of the metal foil-clad laminate is desired to be formed. On the other hand, the additive method is a method of forming an electric circuit by performing electroless plating only on a portion where a circuit on an insulating substrate is to be formed.

  The subtractive method is a method in which the metal foil on the surface of the metal foil-clad laminate is etched to leave only the portion where the electric circuit is to be formed, and the other portion is removed. This method is disadvantageous from the viewpoint of manufacturing cost because the portion of the metal to be removed is wasted. On the other hand, in the additive method, metal wiring can be formed by electroless plating only in a portion where an electric circuit is desired to be formed. For this reason, metal is not wasted and resources are not wasted. Also from such a point, the additive method is a preferable circuit forming method.

  A method of forming an electric circuit made of metal wiring by a full additive method, which is one of conventional representative additive methods, will be described with reference to FIG. FIG. 5 is a schematic cross-sectional view for explaining each step of forming a metal wiring by a conventional full additive method.

  First, as shown in FIG. 5A, a plating catalyst 102 is deposited on the surface of the insulating base material 100 on which the through holes 101 are formed. 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 on the insulating base material 100 on which the plating catalyst 102 is deposited. Next, as shown in FIG. 5C, 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 exposed photoresist layer 103 is developed to form a circuit pattern 104. Then, as shown in FIG. 5E, by performing electroless plating such as electroless copper plating, the metal wiring 105 is formed on the surface of the circuit pattern 104 and the inner wall surface of the through hole 101 formed by development. . By performing each process as described above, a circuit made of the metal wiring 105 is formed on the insulating base material 100.

  In the conventional additive method described above, the plating catalyst 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 a portion that is not protected by the photoresist. However, when the photoresist layer 103 is not developed with high accuracy, an unnecessary plated portion 106 may remain in a portion where the plating is not originally formed as shown in FIG. This occurs because the plating catalyst 102 is deposited on the entire surface of the insulating substrate 100. The unnecessary plated portion 106 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. FIG. 6 is a schematic cross-sectional view for explaining the contour shape of a circuit formed by a conventional full additive method.

  Moreover, as a manufacturing method different from the manufacturing method of said circuit board, the manufacturing method of patent document 1 and patent document 2 etc. are mentioned, for example.

  Patent Document 1 discloses the following method as another additive method.

  First, a solvent-soluble first photosensitive resin layer and an alkali-soluble second photosensitive resin layer are formed on an insulating substrate (insulating base material). Then, the first and second photosensitive resin layers are exposed through a photomask having a predetermined circuit pattern. Next, the first and second photosensitive resin layers are developed. Next, after the catalyst is adsorbed on the entire surface including the concave portions generated by development, only the unnecessary catalyst is removed by dissolving the alkali-soluble second photosensitive resin with an alkali solution. Then, after that, electroless plating is performed to accurately form a circuit only in a portion where the catalyst exists.

  Patent Document 2 below discloses the following method.

  First, a protective film of resin is coated on an insulating substrate (insulating base material) (first step). Next, a groove and a through hole corresponding to the wiring pattern are drawn or formed on the insulating substrate coated with the protective film alone or simultaneously by machining or laser beam irradiation (second step). Next, an activation layer is formed on the entire surface of the insulating substrate (third step). Next, the protective film is peeled off, the activation layer on the insulating substrate is removed, and the activation layer is left only on the inner wall surface of the groove and the through hole (fourth step). Next, the insulating substrate is plated without using a plating protective film, and a conductive layer is selectively formed only on the inner surfaces of the activated grooves and through holes (fifth step).

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

  However, according to the method described in Patent Document 1, 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, Furthermore, the manufacturing process is very complicated, such as the need to dissolve the second photosensitive resin with an alkaline solution.

  Patent Document 2 describes that after a thermosetting resin is coated on an insulating substrate as a protective film and heated and cured, the protective film and the insulating substrate are cut according to a predetermined wiring pattern, or the surface of the insulating substrate is heated. It is described that the curable resin is removed with a solvent (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 patent document 2, the kind in particular is not described. Since general thermosetting resins have excellent solvent resistance, there is a problem that they are difficult to remove with a simple solvent. Also, such a thermosetting resin has too high adhesion to the resin substrate, and it is difficult to accurately remove only the protective film without leaving a fragment of the protective film on the surface of the resin substrate. there were. In addition, when a strong solvent is used for sufficient peeling or when the substrate is immersed for a long time, the plating catalyst on the surface of the substrate is also removed. In this case, the conductive layer is not formed in the portion where the plating catalyst is removed. In addition, if a strong solvent is used or if it is immersed for a long time, the protective film made of thermosetting resin may collapse so that the plating catalyst in the protective film is redispersed in the solvent. there were. Thus, the plating catalyst redispersed in the solvent may be reattached to the surface of the resin base material, and an unnecessary plating film may be formed in that portion. Therefore, according to a method such as the method disclosed in Patent Document 2, it is difficult to form a circuit having an accurate contour.

  The present invention has been made in view of such circumstances, and provides a method of manufacturing a circuit board that can be formed on an insulating base material with high precision even in an electric circuit with a narrow line width and line spacing. The purpose is to do. Moreover, it aims at providing the circuit board obtained by the manufacturing method of the said circuit board.

  In order to form an electric circuit on an insulating base material with high accuracy, the present inventors firstly formed a resin film on the surface of the insulating base material, and the insulating group from the outer surface side of the resin coating. A circuit pattern forming step of forming a circuit pattern portion by forming at least one of a circuit groove and a hole having a desired shape and depth by laser processing or machining on the material; and a surface of the circuit pattern portion; There is no catalyst deposition step for depositing a plating catalyst or its precursor on the surface of the resin coating, a coating stripping step for stripping the resin coating from the insulating substrate, and an insulating substrate from which the resin coating has been stripped. A method of manufacturing a circuit board different from the conventional one, which includes a plating process for performing electrolytic plating, has been developed. And the present inventors paid attention to the surface roughness of the insulating base material and the resin coating, particularly the insulating base material used in the method for manufacturing the circuit board as described above.

  Usually, when manufacturing a circuit board, the surface roughness of the insulating base material used is not often considered. In addition, even if the surface roughness of the insulating base material is taken into account, in general, in the case of the conventional method of forming an electric circuit on the insulating base material, in order to improve the adhesion between the electric circuit and the insulating base material In addition, it has been considered that it is preferable that the surface roughness is large to some extent. In addition, when an electric circuit is formed by partially removing the metal foil on the surface of the metal-clad laminate obtained by laminating a metal foil on a prepreg and heating and pressing, when removing the metal foil There was a tendency for the smoothness of the insulating base material, which is the supporting base material for the electric circuit, to decrease. In view of such circumstances, as an insulating base material to be used, it is general to use a material having a relatively large surface roughness as it is without intentionally reducing the surface roughness by performing a smoothing treatment or the like. It is thought that it was the target.

  However, the present inventors have a phenomenon that it is difficult to form an electric circuit with high accuracy when an insulating base material having a relatively large surface roughness is used in the method of manufacturing a circuit board as described above. I have found that it happens.

  The present inventors have inferred that this phenomenon is due to the following.

  When an insulating substrate having a relatively large surface roughness is used, a resin film having a uniform film thickness is formed when a resin film, particularly a resin film having a film thickness of 5 μm or less, is formed on the surface of the insulating substrate in the film forming step. It is considered difficult to form. This is considered to cause the above phenomenon.

  Specifically, when an insulating base material having a relatively large surface roughness, for example, an insulating base material having a surface roughness of 0.6 μm Ra and 7 μm Rz, is used on the surface of the insulating base material. When a resin film, particularly a thin resin film, is formed, it is considered that the insulating substrate is easily exposed from the resin film. And if the part which the said insulating base material exposed from the said resin film exists, although the exposed part is not a location which wants to form an electrical circuit, it is thought that a plating layer will be formed.

  Furthermore, even if the insulating substrate is not exposed from the resin coating, it is considered that only a specific portion of the resin coating formed on the surface of the insulating substrate is thinned. And, for example, if there is a place where the resin film is thin in a place near the place where the circuit groove or hole is formed, the resin near the place where the circuit groove or hole is formed when the circuit groove or hole is formed. It is considered that the resin coating at the thin coating is also removed. And it is thought that a plating layer will be formed also in the location around the circuit groove or hole which is not the location where the electric circuit is to be formed.

  The above-mentioned problem can be solved by increasing the resin film formed on the surface of the insulating substrate, for example, by setting the film thickness to 10 μm. However, if the resin film is increased, the circuit pattern In the forming process, for example, in laser processing, it tends to be difficult to form circuit grooves and holes with high accuracy. Therefore, in the above-described method for manufacturing a circuit board, in order to form an electric circuit with high accuracy, the film thickness of the resin coating is preferably 5 μm or less. Conceivable.

  Therefore, the present inventors, when using an insulating base material having a relatively large surface roughness in the above-described circuit board manufacturing method, has high accuracy regardless of the film thickness of the resin film formed on the surface of the insulating base material. We thought it would be difficult to form an electrical circuit.

  Therefore, the present inventors have arrived at the present invention as described below by intentionally using an insulating base material having a relatively low surface roughness in the circuit board manufacturing method as described above. .

  A method of manufacturing a circuit board according to an aspect of the present invention includes: a film forming step of forming a resin film on the surface of an insulating base; and laser processing or machining on the insulating base from the outer surface side of the resin film. A circuit pattern forming step of forming a circuit pattern part by forming at least one of a circuit groove and a hole having a desired shape and depth, and a plating catalyst or its surface on the surface of the circuit pattern part and the surface of the resin film A catalyst deposition step for depositing the precursor; a coating stripping step for stripping the resin coating from the insulating substrate; and a plating treatment step for performing electroless plating on the insulating substrate from which the resin coating has been stripped. In the coating film forming step, the insulating base material having a smooth surface with a surface roughness Ra of 0.5 μm or less is used, and the resin coating film is formed on the smooth surface side. To.

  According to such a configuration, even an electric circuit with a narrow line width and line interval can be formed on an insulating base with high accuracy.

  This is thought to be due to the following.

  First, since the surface roughness of the smooth surface, which is the surface on the side on which the resin coating is formed, of the insulating base material is as high as 0.5 μm or less in Ra, it is formed on the smooth surface of the insulating base material. Even if the resin film to be formed is thin, it is considered that the resin film can be formed uniformly. Specifically, it is considered that the insulating base material is not easily exposed from the resin film, and that only a specific portion of the resin film is less likely to be thin. Therefore, it is considered that the occurrence of the above-described problems due to the exposure of the insulating base material and the fact that only a specific portion of the resin coating is thin is suppressed.

  Moreover, it is preferable that the surface roughness represented by Ra of the said smooth surface is 1/10 or less with respect to the thickness of the said resin film. According to such a configuration, the electric circuit can be formed on the insulating base material with higher accuracy.

  This is because it is possible to further suppress the occurrence of the above problems due to the exposure of the insulating base material and the like because it is possible to further suppress the exposure of the insulating base material and the specific part of the resin coating from becoming thin. Conceivable.

  Moreover, it is preferable that the surface roughness represented by Rz of the said smooth surface is below the thickness of the said resin film. According to such a configuration, the electric circuit can be formed on the insulating base material with higher accuracy.

  This is because it is possible to further suppress the occurrence of the above problems due to the exposure of the insulating base material and the like because it is possible to further suppress the exposure of the insulating base material and the specific part of the resin coating from becoming thin. Conceivable.

  Moreover, it is preferable that the insulating base material used in the said film formation process is obtained by pressurizing with a smooth plate, a smooth film, a smooth sheet, or a smooth foil.

  According to such a configuration, even when an insulating base material having a relatively large surface roughness is used, the insulating base material obtained by pressing with a smooth plate, a smooth film, a smooth sheet, or a smooth foil By using this, an electric circuit can be easily formed on an insulating substrate with high accuracy.

  A circuit board according to another embodiment of the present invention is obtained by the method for manufacturing a circuit board. According to such a configuration, a circuit board formed on an insulating substrate with high accuracy can be obtained even with an electric circuit having a narrow line width and line spacing.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is an electrical circuit with a narrow line | wire width and line | wire space | interval, the manufacturing method of the circuit board which can be formed on an insulating base material with high precision can be provided. Moreover, the circuit board obtained by the manufacturing method of the said circuit board is provided.

It is a schematic cross section for explaining each process in a manufacturing method of a circuit board concerning a 1st embodiment. It is drawing for demonstrating the state of the insulation base material 1 after each process in 1st Embodiment. It is drawing for demonstrating the state of the insulation base material 21 at the time of using the insulation base material 21 with comparatively large surface roughness. It is a schematic cross section for demonstrating each process of manufacturing the three-dimensional circuit board concerning 3rd Embodiment. It is a schematic cross section for demonstrating each process of forming the metal wiring by the conventional full additive method. It is a schematic cross section for demonstrating the outline shape of the circuit formed by the conventional full additive method.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

(First embodiment)
The method for manufacturing a circuit board according to the present embodiment includes a film forming step of forming a resin film on the surface of the insulating base material, and laser processing or machining on the insulating base material from the outer surface side of the resin film. Forming a circuit pattern part by forming at least one of a circuit groove and a hole having a shape and depth, and a plating catalyst or precursor thereof on the surface of the circuit pattern part and the surface of the resin film A catalyst deposition step for depositing, a coating stripping step for stripping the resin coating from the insulating substrate, and a plating treatment step for performing electroless plating on the insulating substrate from which the resin coating has been stripped, In the film forming step, the insulating base material is a surface having a smooth surface with a surface roughness Ra of 0.5 μm or less, and the resin film is formed on the smooth surface side. .

  First, a method for manufacturing a circuit board according to the first embodiment of the present invention will be described. FIG. 1 is a schematic cross-sectional view for explaining each step in the circuit board manufacturing method according to the first embodiment.

  First, as shown in FIG. 1A, a resin coating 2 is formed on the surface of the insulating base 1. Although the details will be described later, the insulating substrate 1 is one having a smooth surface with a surface roughness Ra of 0.5 μm or less. And the said resin film 2 is formed on the said smooth surface. This process corresponds to a film forming process.

  Next, as shown in FIG. 1B, a desired shape and depth are obtained by laser processing or machining the insulating base material 1 on which the resin coating 2 is formed from the outer surface side of the resin coating 2. At least one of the circuit groove 3 and the through hole 4 is formed. That is, if necessary, only the circuit groove 3 may be formed, only the through hole 4 may be formed, or both the circuit groove 3 and the through hole 4 may be formed. Good. The laser processing or machining for forming the circuit groove 3 is performed by cutting beyond the thickness of the resin coating 2 on the basis of the outer surface of the resin coating 2. The laser processing or machining for forming the through hole 4 is a drilling process that cuts beyond the thickness of the resin coating 2 and the insulating substrate 1. The circuit groove 3 and the through hole 4 correspond to a circuit pattern portion, and this process corresponds to a circuit pattern forming process.

  Next, as shown in FIG. 1C, a plating catalyst or its surface is formed on the surface of the circuit groove 3 or the through hole 4 and the surface of the resin film 2 where the circuit groove 3 or the through hole 4 is not formed. The precursor 5 is deposited. This step corresponds to a catalyst deposition step.

  Next, as shown in FIG. 1D, the resin film 2 is peeled from the insulating base material 1. By doing so, the plating catalyst or its precursor 5 can remain only on the surface of the insulating base material 1 where the circuit grooves 3 and the through holes 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 peeling process.

  Next, electroless plating is performed on the insulating substrate 1 from which the resin coating 2 has been peeled off. By doing so, a plating layer is formed only in the portion where the plating catalyst or its precursor 5 remains. That is, as shown in FIG. 1E, a plating layer that becomes the 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 plating layer, and may give the said plating layer further electroless plating (fill-up plating), and also made it thicker. . Specifically, for example, as shown in FIG. 1 (E), an electric circuit 6 made of a plating layer is formed so as to fill the circuit groove 3 and the whole through-hole 4, and the insulating base 1 and the electric substrate You may make it eliminate the level | step difference with a circuit. This process corresponds to a plating process.

  Through the above steps, a circuit board 10 as shown in FIG. 1E is formed. The circuit board 10 formed in this way is formed with high accuracy on an insulating base material even if it is an electric circuit with a narrow line width and line spacing. That is, according to the manufacturing method described above, even an electric circuit with a narrow line width and line interval can be formed on the insulating substrate with high accuracy.

  In addition, after giving a plating process, specifically, before giving a fill-up plating, or after giving, you may give a desmear process. By applying a desmear process, unnecessary resin adhered to the plating layer can be removed. Further, when a multilayer circuit board including the obtained circuit board is assumed, the surface of the insulating base material where the plating layer is not formed is roughened to improve the adhesion with the upper layer of the circuit board. be able to. 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.

  The effect of improving the accuracy of the electric circuit formed on the insulating base as described above is presumed to be due to the following mechanism. In addition, FIG. 2 is drawing for demonstrating the state of the insulating base material 1 after each process in 1st Embodiment. 2A shows the state of the insulating base material 1 after the film forming step, FIG. 2B shows the state of the insulating base material 1 after the circuit pattern forming step, and FIG. Shows the state of the insulating base material 1 after the catalyst deposition step, FIG. 2 (D) shows the state of the insulating base material 1 after the film peeling step, and FIG. 2 (E) shows the plating treatment. The state of the insulating base material 1 after the process is shown. FIG. 2 shows a case where the circuit groove 3 is formed as a circuit pattern portion. Hereinafter, the case where the circuit groove 3 is formed will be described, but the same applies to the case where the through hole 4 is formed.

  First, as shown in FIG. 2A, the insulating base material 1 after the film forming step is considered to form a resin film 2 having a relatively uniform film thickness on the insulating base material 1. . This is considered to be because the surface roughness of the smooth surface, which is the surface on the side on which the resin coating 2 is formed, of the insulating base material 1 is high, with Ra being 0.5 μm or less. More specifically, it is considered that it is difficult for the insulating base material 1 to be exposed from the resin coating 2 and that only a specific portion of the resin coating 2 is thin.

  Next, as shown in FIG. 2B, the insulating base material 1 after the circuit pattern forming step is formed with the circuit groove 3 by subjecting the insulating base material 1 to laser processing or mechanical processing. And also about the said resin film 2 currently formed in the said insulating base material 1, it is thought that only the resin film of the location corresponding to the position in which the said circuit groove 3 was formed is removed with high precision. That is, it is considered that the resin coating 2 other than the portion corresponding to the position where the circuit groove 3 is formed remains with high accuracy.

  Then, by applying the catalyst deposition step, as shown in FIG. 2C, a plating catalyst or a precursor thereof is formed on the surface of the circuit groove 3 and the surface of the resin film 2 where the circuit groove 3 is not formed. The body 5 is applied.

  Then, it is considered that the plating catalyst or its precursor 5 remains with high accuracy only on the surface of the circuit groove 3 as shown in FIG.

  And by performing the said plating process process, as shown to FIG.2 (E), it is thought that the plating layer 7 used as an electric circuit can be formed with high precision.

  From the above, according to the method for manufacturing a circuit board according to the present embodiment, an electric circuit is formed with high accuracy even when an electric circuit with a narrow line width and line spacing is formed on an insulating base material. I think it can be done.

  On the other hand, when the insulating base material 21 having a relatively large surface roughness such that the surface roughness exceeds 0.5 μm in Ra, an electric circuit is formed by the same method as in this embodiment. However, the present inventors have found that it is difficult to form an electric circuit with high accuracy, that is, the phenomenon that the accuracy of the formed electric circuit is lowered occurs. And it is guessed that the phenomenon that the precision of the electric circuit formed becomes low is as follows.

  FIG. 3 is a drawing for explaining the state of the insulating base material 21 when the insulating base material 21 having a relatively large surface roughness is used. 3A to 3E are drawings corresponding to FIGS. 2A to 2E, respectively.

  First, when a resin film is formed on the surface of the insulating base material 21 having a relatively large surface roughness, it is considered that the film thickness and the like of the formed resin film 22 become non-uniform. Specifically, for example, it is considered that the insulating base material 21 is exposed from the resin coating 22 or that the resin coating 22 is thinned as shown in FIG. Hereinafter, the case where the resin film 22 is thinned will be described.

  In such a case, if there is a thin portion of the resin coating 22 at a location close to the location where the circuit groove 23 is formed, the circuit groove 23 is formed when the circuit groove 23 is formed as shown in FIG. The nearby resin coating 22 is also removed. That is, when the resin film other than the resin film at the position corresponding to the position where the circuit groove 23 is formed is also removed, and the exposed portion 23a of the insulating base material is formed at a position other than the position where the circuit groove 23 is formed. Conceivable.

  Then, by applying the catalyst deposition step, as shown in FIG. 3C, not only the surface of the circuit groove 23 and the surface of the resin film 22 where the circuit groove 23 is not formed, but also the insulation. It is considered that the plating catalyst or its precursor 25 is also deposited on the surface of the exposed portion 23a of the substrate.

  Thereafter, by performing the film peeling step, as shown in FIG. 3D, not only the plating catalyst or its precursor 25 remains on the surface of the circuit groove 23, but also the exposed portion of the insulating substrate. It is considered that the plating catalyst or its precursor 25a remains on the surface of 23a.

  Then, by performing the plating treatment step, as shown in FIG. 3E, not only the plating layer 26 to be an electric circuit is formed, but also the plating layer 26a resulting from the exposed portion 23a of the insulating base material. Is also considered to be formed.

  From the above, it is considered that a plating layer is formed other than the portion where the circuit is to be formed. That is, it is considered difficult to form an electric circuit with high accuracy on the insulating base material.

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

  The insulating substrate 1 used in the film forming step is a substrate having a smooth surface with a surface roughness Ra of 0.5 μm or less. Specific examples of the substrate include a resin substrate containing a resin. The insulating base material 1 may have a smooth surface with a surface roughness Ra of 0.5 μm or less, and a resin substrate having a smooth surface with a surface roughness Ra of 0.5 μm or less. It may be used as it is, or may be obtained by subjecting a resin base material having a relatively large surface roughness to a smoothing treatment described later. In the film forming step, a resin film is formed on the smooth surface side. Therefore, the surface of the insulating base material on which the resin film is not formed, that is, the surface other than the smooth surface may have a relatively large surface roughness.

  Further, the surface roughness of the smooth surface may be 0.5 μm or less in Ra, but is more preferably 0.3 μm or less. When the surface roughness of the smooth surface is too large, as described above, there is a tendency that an electric circuit cannot be formed with high accuracy. Moreover, since the smaller the better the surface roughness of the smooth surface, the lower limit may be any surface roughness that can be produced. For example, if it can be manufactured, it may be 0.01 μm or the like.

  The resin can be used without particular limitation as long as it is a resin constituting various organic substrates that can be used in the manufacture of circuit boards. Specifically, for example, an epoxy resin, an acrylic resin, a polycarbonate resin, a polyimide resin, a polyphenylene sulfide 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 phenolic hydroxyl groups, triglycidyl isocyanurate, finger ring type epoxy resins and the like. Furthermore, in order to impart flame retardancy, the above-mentioned epoxy resin or the like that is brominated or phosphorus-modified is 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 the like. As said phenol type hardening | curing agent, a novolak type, an aralkyl type, a terpene type etc. are mentioned, for example. 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.

  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.

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. Since these inorganic fine particles have high thermal conductivity, relative dielectric constant, flame retardancy, particle size distribution, color tone freedom, etc., when selectively exerting a desired function, appropriate blending and particle size design should be performed. And high filling can be easily performed.

  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 200 μm, and more preferably about 20 to 100 μm. Further, the insulating base material may contain inorganic fine particles such as silica particles.

  The resin film 2 is not particularly limited as long as it can be removed in the film peeling step. Specifically, for example, a soluble resin that can be easily dissolved by an organic solvent or an alkaline solution, a resin film made of a swellable resin that can be swollen by a predetermined liquid (swelling liquid) described later, and the like. Among these, a swellable resin film is particularly preferable because accurate removal is easy. Examples of the swellable resin film include a resin film that does not substantially dissolve in a predetermined liquid (swelling liquid), which will be described later, and easily peels from the surface of the insulating base material 1 by swelling. .

  A method for forming the resin coating 2 is not particularly limited. Specifically, for example, a liquid material is applied to the main surface of the insulating base material 1 and then dried, or the resin coating 2 such as a resin film previously formed on the main surface of the insulating base material 1 is formed. The method of bonding what is obtained is mentioned. 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 thickness of the resin coating 2 is too thick, the accuracy of grooves and holes formed by laser processing or machining tends to decrease. 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. In the present embodiment, as described above, even if the resin film 2 is thin, A uniform resin film is easily formed.

  Further, as described above, it is preferable that the smooth surface has a small surface roughness. More specifically, in relation to the thickness of the resin film formed on the smooth surface, the following range is more preferable.

  The surface roughness expressed by Ra of the smooth surface is preferably 1/10 or less, more preferably 1/15 or less, with respect to the thickness of the resin coating. Moreover, the surface roughness represented by Rz of the smooth surface is preferably not more than the thickness of the resin coating, and more preferably not more than 2/3 of the thickness of the resin coating.

  As described above, by doing so, an electric circuit can be formed on the insulating substrate with higher accuracy. This means that even if a thin resin film that can form circuit grooves and through holes with high accuracy, for example, a resin film having a film thickness of 5 μm or less is formed, the insulating base material is exposed and a specific portion of the resin film is formed. This is considered to be because it is possible to further suppress only the thinning. Therefore, it is considered that the occurrence of the above-described problems caused by the exposure of the insulating base material can be further suppressed.

  In the present invention, Ra is the arithmetic average height of the roughness curve defined by JIS B 0601: 2001. In the present invention, Rz is the maximum height roughness defined by JIS B 0601: 2001. Ra and Rz can be measured using, for example, a surface roughness measuring machine, a laser microscope, an atomic force microscope, and the like. Specifically, it can be measured using surface roughness analysis or the like using a scanning confocal laser microscope (LEXT OLS3000 manufactured by Olympus Corporation).

  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. Further, a resin film having a degree of swelling with respect to the swelling liquid of 100% or more is more preferable, and a resin film having 1000% or less 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 peeling process. Moreover, when the said swelling degree is too high, there exists a tendency for peeling to become difficult by tearing at the time of peeling, etc., when the film strength falls.

  The method for forming the swellable resin film is not particularly limited. Specifically, for example, a liquid material capable of forming a swellable resin film is applied to the smooth surface of the insulating substrate 1 and then dried, or the liquid material is applied to a support substrate and then dried. For example, a method of transferring the coating film formed on the smooth surface of the insulating substrate 1 may be used.

  Examples of the liquid material capable of forming the swellable resin film include elastomer suspensions and emulsions. 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 stripping step, so that a 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 peeling 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 to 3, for example, and the film peeling step has a pH of 12 to 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 25% or less, and further 10% 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 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. 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.

A swellable resin film is formed on a surface of an insulating substrate by applying a resin suspension or emulsion on the surface of the insulating substrate using a conventionally known application method such as a spin coat method or a 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.

  Further, the widths of the circuit grooves and through holes formed in the circuit pattern forming step are not particularly limited. Specifically, for example, the circuit groove preferably includes a portion having a line width of at least 5 to 30 μm. The circuit groove 3 defines a portion where a plating layer is formed by electroless plating, that is, a portion where an electric circuit is formed. Specifically, for example, the width of the circuit groove formed here is the line width of the electric circuit formed in the present embodiment. That is, in the case of such an electric circuit with a narrow line width, a circuit board having a sufficiently high density circuit can be obtained. Note that the depth of the circuit groove is the depth of the electric circuit formed in this embodiment when a step is eliminated between the electric circuit and the insulating base material by fill-up plating. In addition, when laser processing is used, a fine circuit having a line width of 20 μm or less can be easily formed.

  The said plating catalyst or its precursor 5 is a catalyst provided in order to form a plating layer only in the part which wants to form a plating layer by electroless plating in the said plating process process. 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 the resin film is peeled off. 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.

  As a method for removing the resin film 2, a method in which the resin film 2 is dissolved or removed by swelling by immersing the insulating base material 1 coated with the resin film 2 in a liquid such as an alkaline solution for a predetermined time. Is mentioned. As the alkaline solution, for example, an aqueous sodium hydroxide solution having a concentration of about 1 to 10% can be used. Moreover, you may improve removal efficiency by irradiating an ultrasonic wave during 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 is obtained without substantially decomposing or dissolving the insulating substrate 1, the swellable resin film 2, and the plating catalyst or its precursor 5. Any liquid can be used without particular limitation as long as it can swell to such an extent that 2 can be easily peeled off. Such a swelling liquid can be appropriately selected depending on the type and thickness of the swellable resin film 2. Specifically, for example, when the swellable resin film is formed of an elastomer such as a diene elastomer, an acrylic elastomer, and a polyester elastomer, for example, sodium hydroxide having a concentration of about 1 to 10% An aqueous alkali solution such as an aqueous solution 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 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, 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.

  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.

  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. A method may be used in which an electroless plating film (plating layer) is deposited only on the portions.

  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.

  The film thickness of the electroless plating layer 6 is not particularly limited. Specifically, for example, it is preferably about 0.1 to 10 μm, more preferably about 1 to 5 μm. In particular, by increasing the depth of the circuit groove 3, it is possible to easily form a metal wiring having a large thickness and a large cross-sectional area. In this case, it is preferable because the strength of the metal wiring can be improved.

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

(Second Embodiment)
The insulating base material 1 used in the film forming step may be obtained by pressing with a smooth plate, a smooth film, a smooth sheet, or a smooth foil. That is, a smoothing step of smoothing at least the surface on which the resin coating is formed of the insulating base used in the coating forming step may be provided before the coating forming step. More specifically, in the method for manufacturing a circuit board according to the present embodiment, at least one surface roughness is Ra by pressing an insulating substrate with a smooth plate, a smooth film, a smooth sheet, or a smooth foil. A smoothing step for smoothing to 0.5 μm or less, a film forming step for forming a resin coating on the smoothed surface of the insulating substrate, and an insulating substrate from the outer surface side of the resin coating. A circuit pattern forming step of forming a circuit pattern portion by forming at least one of a circuit groove and a hole having a desired shape and depth by laser processing or machining, and a surface of the circuit pattern portion and the resin coating A catalyst deposition step for depositing a plating catalyst or a precursor thereof on the surface of the substrate, a coating stripping step for stripping the resin coating from the insulating substrate, and an electroless coating on the insulating substrate from which the resin coating has been stripped. Characterized in that it comprises a plating treatment step of performing come. The film forming process, the circuit pattern forming process, the catalyst deposition process, the film peeling process, and the plating process, which are processes other than the smoothing process, are the same as those in the first embodiment.

  In the smoothing step, the surface of the insulating substrate used in the coating forming step is formed with a surface roughness by pressing the insulating substrate with a smooth plate, a smooth film, a smooth sheet, or a smooth foil. However, there is no particular limitation as long as the surface can be smoothed by Ra of 0.5 μm or less. Specifically, the following processes are mentioned, for example. First, a PET film is laminated on the surface of the insulating substrate. And the laminated body is pressure-heat-molded. Thereafter, the PET film is peeled off. By doing so, an insulating substrate having a smooth surface with a surface roughness Ra of 0.5 μm or less is obtained. Moreover, the insulating base material before pressurizing with a smooth plate, a smooth film, a smooth sheet, or a smooth foil can be utilized regardless of the surface roughness. Specifically, if the surface roughness exceeds 0.5 μm in Ra, an insulating substrate having a smooth surface with Ra of 0.5 μm or less can be obtained. If the surface roughness is originally 0.5 μm or less in Ra, the surface roughness can be further reduced and an electric circuit can be formed with higher accuracy.

  The smooth plate, smooth film, smooth sheet, and smooth foil are not particularly limited as long as the surface roughness is 0.5 μm or less in terms of Ra. Specifically, for example, a polyethylene terephthalate (PET) film, a polytetrafluoroethylene sheet, a metal foil S surface, a low roughness metal foil M surface, and the like having a surface roughness Ra of 0.5 μm or less. Can be mentioned. In the case where the PET film or the like is peeled after the insulating base material is cured and molded, the surface of the PET film may be subjected to a mold release treatment in advance so that it can be easily peeled off.

  Examples of the conditions for the pressure heating molding include 0.1 to 4 Pa, 40 to 200 ° C., and 0.5 to 180 minutes.

  Moreover, as the smoothing step, as described above, the surface of at least the resin film of the insulating substrate formed by pressing with a smooth plate, a smooth film, a smooth sheet, or a smooth foil has a surface roughness of Ra. If it can be made into the smooth surface of 0.5 micrometer or less, it will not specifically limit. Specifically, the following processes are mentioned, for example.

  First, a smooth plate, a smooth film, a smooth sheet, or a smooth foil is laminated on the surface of the substrate, and the resulting laminate is subjected to pressure heating molding, and the resin constituting the insulating substrate is cured, and then the smooth plate And a method of removing a smooth film, a smooth sheet, or a smooth foil by peeling or etching.

  As another method, a smooth plate, a smooth film, a smooth sheet, or a smooth foil is laminated on the surface of the base material, and the obtained laminate is press-heated and cured until cured to a B stage state. , A method of peeling a smooth plate, a smooth film, a smooth sheet, or a smooth foil, and then further heating and curing.

  Furthermore, as another method, a smooth plate, a smooth film, a smooth sheet, or a smooth foil is laminated on the surface of the base material, and the obtained laminate is pressed and heated to such an extent that it does not cure as necessary. After finishing, a smooth plate, a smooth film, a smooth sheet, or a smooth foil is peeled off, and then heated and further cured.

  As still another method, a smooth plate, a smooth film, a smooth sheet, or a smooth foil is laminated on the surface of the base material, and the obtained laminate is press-heated and molded until it becomes a B-stage state. After curing, there is a method in which the pressurization is stopped and the coating is further cured by heating.

  According to the manufacturing method as described above, even if an insulating base material having a surface roughness of Ra exceeding 0.5 μm is used, an electric circuit is formed on the insulating base material with high accuracy as in the first embodiment. can do.

(Third embodiment)
In the first embodiment and the second embodiment, the circuit board obtained by forming the electric circuit on the planar insulating base material has been described, but the present invention is not particularly limited thereto. Specifically, even when a three-dimensional insulating base material having a stepped three-dimensional surface is used as the insulating base material, a circuit board (stereoscopic circuit board) having an accurate electric circuit of wiring can be obtained.

  Hereinafter, a method for manufacturing a three-dimensional circuit board according to the third embodiment will be described.

  FIG. 4 is a schematic cross-sectional view for explaining each step of manufacturing the three-dimensional circuit board according to the third embodiment.

  First, as shown in FIG. 4A, the resin coating 2 is formed on the surface of the three-dimensional insulating substrate 51 having a stepped portion. This process corresponds to a film forming process.

  As the three-dimensional insulating base 51, various resin molded bodies that can be used for manufacturing a three-dimensional circuit board known in the art 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 resin coating 2 is not particularly limited. Specifically, for example, the same formation method as in the first embodiment can be used.

  Next, as shown in FIG. 4 (B), a desired shape and depth are obtained by laser processing or machining the three-dimensional insulating substrate 51 on which the resin coating 2 is formed from the outer surface side of the resin coating 2. At least one of the circuit groove 3 and the through hole is formed. That is, if necessary, only the circuit groove 3 may be formed, only the through hole 4 may be formed, or both the circuit groove 3 and the through hole 4 may be formed. Good. The laser processing or machining for forming the circuit groove 3 is performed by cutting beyond the thickness of the resin coating 2 on the basis of the outer surface of the resin coating 2. Further, the laser processing or machining for forming the through hole is a drilling process that cuts beyond the thickness of the resin coating 2 and the insulating substrate 1. The circuit groove 3 and the through hole correspond to a circuit pattern portion, and this process corresponds to a circuit pattern forming process. FIG. 4 shows a case where the circuit groove 3 is formed as a circuit pattern portion. Hereinafter, the case where the circuit groove 3 is formed will be described, but the same applies to the case where the through hole is formed.

  The circuit groove 3 defines a portion where a plating layer is formed by electroless plating, that is, a portion where an electric circuit is formed.

  Next, as shown in FIG. 4C, a plating catalyst or its precursor 5 is deposited on the surface of the circuit groove 3 and the surface of the resin film 2 on which the circuit groove 3 is not formed. This step corresponds to a catalyst deposition step. By such a catalyst deposition treatment, the plating catalyst or its precursor 5 can be deposited on the surface of the circuit groove 3 and the surface of the resin coating 2 as shown in FIG.

  Next, as shown in FIG. 4D, the resin coating 2 is peeled from the three-dimensional insulating substrate 51. By doing so, the plating catalyst or its precursor 5 can remain only on the surface of the portion of the three-dimensional insulating base 51 where the circuit groove 3 is 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 peeling process.

  Next, as shown in FIG. 4 (E), electroless plating is applied to the three-dimensional insulating substrate 51 from which the resin film 2 has been peeled off. By doing so, the plating layer 6 is formed only in the portion where the plating catalyst or its precursor 5 remains. That is, the plating layer 6 which becomes an electric circuit is formed in the portion where the circuit groove 3 and the through hole 4 are formed. This process corresponds to a plating process.

  Through the above steps, a circuit board 60 in which the electric circuit 6 is formed on the three-dimensional solid insulating base 51 as shown in FIG. 4E is formed. The circuit board 60 formed in this way can form an electric circuit with high accuracy even if the line width and line interval of the electric circuit formed on the insulating base material are narrow. In addition, the circuit board according to the present embodiment is accurately and easily formed on the surface of the three-dimensional circuit board having the stepped portion.

  Hereinafter, the manufacturing method of the present embodiment will be described more specifically with reference to examples. The scope of the present invention is not construed as being limited in any way by the following examples.

Example 1
First, bisphenol A type epoxy resin (850S made by DIC Corporation), dicyandiamide (DICY made by Nippon Carbide Industry Co., Ltd.) as a curing agent, and 2-methyl-4-methylimidazole (made by Shikoku Kasei Kogyo Co., Ltd.) as a curing accelerator. 2E4MZ), silica (FB1SDX manufactured by Denki Kagaku Kogyo Co., Ltd.) as the inorganic filler, and the surface of the substrate made of a resin composition containing methyl ethyl ketone (MEK) and N, N-dimethylformamide (DMF) as the solvent, A PET film (TN100 manufactured by Toyobo Co., Ltd., Ra: 0.05 μm, Rz: 0.8 μm) was laminated. And the laminated body was pressure-heat-molded at 0.4 Pa and 100 degreeC for 1 minute. Thereafter, the substrate was dried by heating at 175 ° C. for 90 minutes to cure the substrate. Thereafter, the PET film was peeled off. By doing so, an insulating substrate was obtained. And the surface roughness of the obtained insulating substrate was measured with a scanning confocal laser microscope (LEXT OLS3000 manufactured by Olympus Corporation). As a result, Ra was 0.05 μm and Rz was 0.8 μm.

  Next, a 3 μm-thick styrene-butadiene copolymer (SBR) coating (resin coating) was formed on the surface of the insulating substrate. The coating was formed on the main surface (smooth surface) of the insulating base material by methyl ethyl ketone (MEK) suspension (manufactured by Nippon Zeon Co., Ltd., acid equivalent 600, particle diameter 200 nm) of styrene-butadiene copolymer (SBR). The solid content was 15%) and dried at 80 ° C. for 30 minutes. Further, the ratio of Ra of the insulating base material to the thickness of the resin coating film was 1/60, and Rz of the insulating base material was smaller than the thickness of the resin coating film.

  Then, a circuit groove having a substantially rectangular cross section having a width of 20 μm, a depth of 20 μm, and a length of 30 mm was formed on the insulating base material on which the resin coating was formed by laser processing. For laser processing, a laser beam irradiation device (MODEL 5330 manufactured by ESI) equipped with a UV-YAG laser was used.

  Next, the insulating 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 and 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, a pre-dip process was performed using PD404 (manufactured by Shipley Far East Co., Ltd., pH <1). And palladium which becomes the nucleus (plating catalyst) of electroless copper plating by immersing in the acidic Pd-Sn colloidal solution (CAT44, Shipley Far East Co., Ltd.) of pH 1 containing stannous chloride and palladium chloride. Was adsorbed on an insulating substrate in the form of a tin-palladium 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 insulating substrate was immersed for 10 minutes in a 5% aqueous sodium hydroxide solution of pH 14 while being subjected to ultrasonic treatment. As a result, the SBR coating on the surface swelled and peeled cleanly. At this time, no SBR coating fragments remained on the surface of the insulating base. Then, the insulating substrate was immersed in an electroless plating solution (CM328A, CM328L, CM328C, manufactured by Shipley Far East Co., Ltd.) to perform an electroless copper plating process.

  A plating layer having a thickness of 5 μm was formed on the circuit groove by the electroless copper plating treatment. Furthermore, electroless copper plating treatment (fill-up plating) was performed until the circuit groove was filled.

  The swelling degree of the swellable resin film was determined as follows.

  The 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 resin film having a thickness of 3 μm was formed. And the 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. The weighed sample was immersed in 10 ml of 5% aqueous sodium hydroxide solution at 20 ± 2 ° C. for 15 minutes. Similarly, another sample was immersed in 10 ml of a 5% aqueous hydrochloric acid solution (pH 1) at 20 ± 2 ° C. for 15 minutes.

  Then, centrifugation was performed at 1000 G for about 10 minutes using a centrifuge to remove moisture and the like attached to the sample. Then, the weight of the swollen sample after centrifugation was measured and set as the weight m (a) after swelling. From the obtained weight m (b) before swelling and weight m (a) after swelling, the formula “swelling degree SW = (m (a) −m (b)) / m (b) × 100 (%)” From this, the degree of swelling was calculated. 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%.

(Example 2)
Example 1 is the same as Example 1 except that the resin film is formed so as to have a thickness of 7 μm. The ratio of Ra of the insulating substrate to the thickness of the resin coating was 1/140, and Rz of the insulating substrate was smaller than the thickness of the resin coating.

(Example 3)
The same as Example 1 except that the insulating base material described later was used as the insulating base material, and the resin film was formed so as to have a thickness of 5 μm.

  The insulating base material used in Example 3 was manufactured as follows. First, bisphenol A type epoxy resin (850S made by DIC Corporation), dicyandiamide (DICY made by Nippon Carbide Industry Co., Ltd.) as a curing agent, and 2-methyl-4-methylimidazole (Shikoku Chemical Industries Co., Ltd.) as a curing accelerator 2E4MZ manufactured by company, silica (FB1SDX manufactured by Denki Kagaku Kogyo Co., Ltd.) as an inorganic filler, and a base material comprising a resin composition containing methyl ethyl ketone (MEK) and N, N-dimethylformamide (DMF) as a solvent. On the surface, the M surface of the copper foil (JTC 12 μm foil manufactured by Nikko Metal Co., Ltd.) was laminated so as to contact the substrate surface. And the laminated body was pressure-heat-molded at 0.4 Pa and 100 degreeC for 1 minute. Thereafter, the substrate was dried by heating at 175 ° C. for 90 minutes to cure the substrate. Thereafter, the copper foil was removed by etching. By doing so, an insulating substrate was obtained. And the surface roughness of the obtained insulating substrate was measured with a scanning confocal laser microscope (LEXT OLS3000 manufactured by Olympus Corporation). As a result, Ra was 0.4 μm and Rz was 5 μm.

  The ratio of Ra of the insulating base to the thickness of the resin coating was 0.4 / 5, and the thickness of the resin coating was the same as Rz of the insulating base.

(Comparative Example 1)
Example 1 is the same as Example 1 except that an insulating base described later is used as the insulating base.

  The insulating base material used in Comparative Example 1 is manufactured as follows. The copper foil of the cured CCL (R1515T manufactured by Panasonic Electric Works Co., Ltd.) was removed by etching. By doing so, an insulating substrate was obtained. The surface roughness of the obtained insulating substrate was measured with a scanning confocal laser microscope (LEXT OLS3000 manufactured by Olympus Corporation). As a result, Ra was 0.6 μm and Rz was 7.0 μm.

  The ratio of Ra of the insulating base to the thickness of the resin coating was 1/5, and Rz of the insulating base was larger than the thickness of the resin coating.

(Comparative Example 2)
It is the same as that of the comparative example 1 except having formed the resin film so that thickness may be set to 7 micrometers. The ratio of Ra of the insulating substrate to the thickness of the resin coating was 0.6 / 7, and Rz of the insulating substrate was approximately the same as the thickness of the resin coating.

  Examples 1 to 3 and Comparative Examples 1 and 2 were evaluated as follows.

(Accuracy of electrical circuit)
The periphery of the entire electric circuit (width 20 μm, length 30 mm) formed on the insulating substrate was observed using a microscope (KH-7700 manufactured by Hilox Co., Ltd.). And it evaluated on the following references | standards. If the location where the plating layer is formed other than the circuit formation portion cannot be confirmed at all, it is evaluated as “◯”, and if the number of locations where the plating layer is formed other than the circuit formation portion is 2 or less, “△” When the location where the plating layer was formed other than the circuit forming portion exceeded two locations, it was evaluated as “x”.

  As a result, the circuit boards according to Examples 1 to 3 were both evaluated as “◯”. On the other hand, the circuit board according to Comparative Example 1 was evaluated as “×”, and the circuit board according to Comparative Example 2 was evaluated as “Δ”. As can be seen from the above evaluation results, a method for producing a circuit board (Examples 1 to 1) using an insulating base material having a smooth surface with a surface roughness of Ra of 0.5 μm or less and forming a resin film on the smooth surface. The circuit board obtained by 3) was able to form an electric circuit with high accuracy. On the other hand, the circuit board obtained by the method of manufacturing a circuit board (Comparative Example 1 and Comparative Example 2) using an insulating base material having a surface roughness Ra exceeding 0.5 μm is an It was difficult to form with high accuracy. From these, it was found that according to Examples 1 to 3, a circuit board having a highly accurate electric circuit can be obtained.

  In Comparative Example 2, the resin film formed on the surface of the insulating base material is thicker than Comparative Example 1. When it did so, the location where the plating layer was formed other than the circuit formation part decreased. However, if the resin film formed on the surface of the insulating substrate is made thick, it tends to be difficult to form the formed circuit grooves and through holes with high accuracy, which is not preferable. Therefore, according to the present invention, even if the thickness of the resin coating is as thin as 2 μm, a highly accurate electric circuit can be formed in which a portion where the plating layer is formed other than the circuit forming portion is not confirmed.

DESCRIPTION OF SYMBOLS 1,21 Insulation base material 2,22 Resin film 3,23 Circuit groove 4 Through-hole 5 Plating catalyst or its precursor 6 Plating layer (electric circuit)
7 Plating Layer 10 Circuit Board 11 Filler 51 Three-Dimensional Insulating Base Material 60 Circuit Board

Claims (5)

A film forming step of forming a resin film on the surface of the insulating substrate;
A circuit pattern for forming a circuit pattern portion by forming at least one of a circuit groove and a hole having a desired shape and depth by laser processing or machining the insulating base material from the outer surface side of the resin coating. Forming process;
A catalyst deposition step of depositing a plating catalyst or a precursor thereof on the surface of the circuit pattern portion and the surface of the resin coating;
A film peeling step for peeling the resin film from the insulating substrate;
A plating process step of performing electroless plating on the insulating base material from which the resin film has been peeled off,
In the film forming step, as the insulating base material, a resin base material having a smooth surface with a surface roughness of Ra of 0.5 μm or less,
Forming the resin film on the smooth surface side ;
A method for producing a circuit board, wherein the resin coating has a thickness of 10 μm or less .   The method for manufacturing a circuit board according to claim 1, wherein the smooth surface has a surface roughness represented by Ra of 1/10 or less of the thickness of the resin coating.   The method for manufacturing a circuit board according to claim 1, wherein the smooth surface has a surface roughness represented by Rz that is equal to or less than a thickness of the resin coating.   The circuit board according to any one of claims 1 to 3, wherein the insulating base material used in the film forming step is obtained by pressing with a smooth plate, a smooth film, a smooth sheet, or a smooth foil. Production method.   The circuit board obtained by the manufacturing method of the circuit board of any one of Claims 1-4.

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