JP2015162644A - Wiring board and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin wiring board which has high reliability in electrical insulation and high density wiring; and provide a manufacturing method of the wiring board.SOLUTION: A wiring board comprises a wiring conductor composed of a plated conductor which fills a through hole 5 of an insulation layer 1 and which is coated on a top surface and an undersurface of the insulation layer 1 by a semi-additive method. The plated conductor is composed of a first plated conductor 7 which only fills a central part of the through hole 5 in a vertical direction and a second plated conductor 9 which fills a part in the through hole 5 and outside the first plated conductor 7 and forms the wiring conductor 2 on the top face and the undersurface of the insulation layer 1. The first plated conductor 7 is formed by using a carbon black film 6 which covers an inner wall of the through hole 5 as a base conductor. The second plated conductor 9 is formed by using the carbon black film 6 and an electroless film 8 on the carbon black film 6 as a base conductor at the inner wall of the through hole 5 and using only the electroless plated film 8 as a base conductor at the top face and the undersurface of the insulation layer 1.

Description

  The present invention relates to a wiring board and a manufacturing method thereof.

  Conventionally, as a thin wiring board, a plurality of tapered through holes, for example, are provided in a thin insulating layer, the insides of these through holes are filled with plating conductors, and wiring conductors made of the same plating conductor are formed on the upper and lower surfaces of the insulating layer. A printed wiring board is known.

  However, in such a wiring board, the plated conductor filling the through hole and the plated conductors on the upper and lower surfaces of the insulating layer are made of the same plated conductor, so try to form a plated conductor sufficient to fill the through hole sufficiently. Then, a thick plated conductor having a thickness of, for example, about 40 μm is also formed on the upper and lower surfaces of the insulating layer. Thus, when the thickness of the plating conductor formed on the upper and lower surfaces of the insulating layer is as thick as about 40 μm, the width and interval of the wiring conductor formed by the plating conductor include the thickness of the plating conductor and the anchor depth with the insulating layer. In consideration of this, the width of the wiring conductor is about 50 μm, and the distance between the wiring conductors is limited to about 60 μm, and it is difficult to form wiring conductors with a narrower width and narrower spacing than that. Therefore, in such a conventional wiring board, it has been impossible to obtain a thin wiring board having high-density wiring with a wiring conductor width and interval of 30 μm or less, for example.

  Therefore, the applicant of the present application previously proposed a method for providing a thin wiring board having high-density wiring in Japanese Patent Application No. 2010-185803 (Japanese Patent Laid-Open No. 2012-44081). In this method, after a through hole is provided in an insulating layer, a first plated conductor is once formed in and around the through hole so as to fill the through hole, and then the first plated conductor is formed in the through hole. A second etching process is performed so as to fill and leave the central portion in the vertical direction of the first and second portions, and then fill a portion outside the first plated conductor in the through hole and form a wiring conductor on the upper and lower surfaces of the insulating layer. And a step of forming the plated conductor by a semi-additive method.

  However, in the wiring board formed by the method proposed in Japanese Patent Application No. 2010-185803, if the through-hole arrangement pitch is made narrower in response to the demand for higher density, plating that fills the inside of the through-holes is performed. There has been a problem in that the metal ions constituting the conductor cause migration between adjacent through-holes, resulting in a decrease in electrical insulation reliability. This is because when a through hole is provided, a cross section of a glass cloth that is generally contained as a reinforcing material in the central portion in the thickness direction of the insulating layer is exposed in the through hole, and the exposed glass cloth and the resin material This is because metal ions move through the interface.

JP 2002-43752 A JP 2012-44081 A

  According to the present invention, even if the pitch between adjacent through holes is narrow, migration between adjacent through holes can be effectively prevented, and thereby thin wiring having high-density wiring with high electrical insulation reliability. It is an object of the present invention to provide a substrate and a manufacturing method thereof.

  The wiring board of the present invention is made of a resin material containing glass cloth, and has an insulating layer having a through-hole penetrating vertically, and fills the inside of the through-hole and is attached to the upper and lower surfaces of the insulating layer by a semi-additive method. A wiring board comprising a plated conductor, wherein the plated conductor includes a first plated conductor that fills only a central portion in the vertical direction of the through-hole, and the above-described plated conductor. A second plating conductor that fills a portion outside the first plating conductor and forms the wiring conductors on the upper and lower surfaces, and the first plating conductor is carbon black that covers the inner wall of the through hole. The second plating conductor is formed on the inner wall of the through hole with the carbon black film and the electroless plating film thereon as a base conductor, and the insulating layer The lower surface is characterized in that it is formed only electroless plated film as a base conductor.

  The method for manufacturing a wiring board according to the present invention includes a step of forming a through hole from the upper surface to the lower surface of a double-sided copper clad laminate in which a copper foil is stretched on the upper and lower surfaces of an insulating layer made of a resin material containing glass cloth, A step of coating the inner wall of the through hole and the exposed surface of the copper foil with a carbon black film, and performing electrolytic plating on the entire surface using the carbon black film as a base conductor, thereby forming the through hole in the through hole and on the copper foil. A step of forming a first plating conductor having a thickness to be completely filled; and etching the first plating conductor and the copper foil to expose the upper and lower surfaces of the insulating layer, and the vertical center of the through hole A step of leaving the first plating conductor so as to fill a portion, and covering a portion outside the first plating conductor in the through hole and the upper and lower surfaces of the insulating layer with an electroless plating film Then, by performing electroplating by the semi-additive method using the electroless plating film as a base conductor, a portion outside the first plating conductor in the through hole is filled and the upper and lower surfaces become wiring conductors. And a step of forming a second plated conductor.

  According to the wiring board of the present invention, since the second plating conductor forming the wiring conductor on the upper and lower surfaces of the insulating layer is formed by the semi-additive method using only the electroless plating film as the base conductor, the adjacent wiring High-density wiring with excellent electrical insulation reliability between conductors is possible. Further, since the first plating conductor and the second plating conductor filling the inside of the through hole have a carbon black film covering the inner wall of the through hole as a base conductor, the carbon black film functions as a migration barrier. Therefore, even if the arrangement pitch of adjacent through holes is narrow, migration between adjacent through holes is effectively prevented, and a wiring board with high insulation reliability can be obtained.

  In addition, according to the method for manufacturing a wiring board of the present invention, the carbon black film is used as a base conductor after the inside of the through hole of the double-sided copper clad laminate having the through hole and the exposed surface of the copper foil are coated with the carbon black film By performing electrolytic plating on the entire surface, a first plated conductor having a thickness that completely fills the through hole in the through hole and on the copper foil is formed, and then the first plated conductor and the copper foil are etched to be insulated. Since the upper and lower surfaces of the layer are exposed and the first plated conductor is left so as to fill the vertical center of the through hole, only the inner wall of the through hole is covered with the carbon black film. Since the carbon black film functions as a barrier against migration between the through holes, even if the arrangement pitch of the adjacent through holes is narrow, migration between the adjacent through holes is effectively prevented.

  Furthermore, the portion outside the first plating conductor in the through hole and the upper and lower surfaces of the insulating layer are covered with an electroless plating film, and the electroless plating film is electroplated by a semi-additive method using the electroless plating film as a base conductor. Since the second plating conductor serving as the wiring conductor is formed on the upper and lower surfaces of the insulating layer while filling the portion outside the first plating conductor in the through-hole, the electroless copper is formed on the upper and lower surfaces of the insulating layer. A wiring conductor composed of the second plating conductor formed by the semi-additive method using only plating as a base conductor can be formed with high insulation reliability and high density.

FIG. 1 is a schematic cross-sectional view of an essential part for explaining an example of an embodiment of a wiring board according to the present invention. FIGS. 2A to 2E are schematic cross-sectional views of relevant parts for each step for explaining an example of an embodiment in the method for manufacturing a wiring board of the present invention. FIGS. 3F to 3J are schematic cross-sectional views of main parts for each process for explaining an example of the embodiment in the method for manufacturing a wiring board of the present invention.

  Next, an example of an embodiment of a wiring board according to the present invention will be described with reference to FIG. In FIG. 1, 1 is an insulating layer, 2 is a wiring conductor, and the wiring board 10 is mainly formed of these.

  The insulating layer 1 is made of a resin material 4 containing a glass cloth 3. The thickness of the insulating layer 1 is about 150 to 250 μm. As the resin material 4, a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin is used.

  A plurality of through holes 5 are formed from the upper surface to the lower surface of the insulating layer 1. The diameter of the through hole 5 is about 30 to 100 μm.

  The inner wall of the through hole 5 is covered with a carbon black film 6. The carbon black film 6 is formed of a continuous layer of carbon black fine particles. The particle size of the carbon black forming the carbon black film 6 is about 0.05 to 0.1 μm.

  A first plated conductor 7 is formed at the center in the thickness direction of the through hole 5 in which the carbon black film 6 is formed. The first plating conductor 7 is formed by electrolytic copper plating using the carbon black film 6 as a base conductor, and fills only the central portion of the through hole 5 in the thickness direction.

  A second plated conductor 9 is formed by a semi-additive method on the outer side of the first plated conductor 7 in the through hole 5 and on the upper and lower surfaces of the insulating layer 1 using the electroless copper plated film 8 as a base conductor. Yes. The second plating conductor 9 is made of electrolytic copper plating, fills a portion outside the first plating conductor 7 in the through hole 5, and forms the wiring conductor 2 on the upper and lower surfaces of the insulating layer 1. The thickness of the electroless copper plating film 8 is about 0.1 to 1 μm. The thickness of the second plated conductor 9 is about 10 to 20 μm on the upper and lower surfaces of the insulating layer 1.

  In this wiring board 10, since the central portion in the thickness direction of the through hole 5 is filled with the first plating conductor 7, the second plating conductor 9 only needs to fill the remaining portion of the through hole 5. . Therefore, when forming the 2nd plating conductor 9 so that it may mention later, the thickness of the 2nd plating conductor 9 in the upper and lower surfaces of the insulating layer 1 can be made thin about 10-20 micrometers. Furthermore, since the second plated conductors 9 on the upper and lower surfaces of the insulating layer 1 are formed by a semi-additive method suitable for fine processing, the width and interval of the wiring conductors 2 on the upper and lower surfaces of the insulating substrate 1 are 30 μm or less. The wiring conductor 2 can be formed with high density.

  Further, as described above, the inside of the through hole 5 is covered with the carbon black film 6. The carbon black film 6 functions as a barrier against metal ion migration. Therefore, even if the arrangement pitch P of the adjacent through holes 5 is narrow, for example, 150 μm or less, the migration of copper ions between the adjacent through holes 5 is effectively prevented by the carbon black film 6.

  Thus, according to the wiring board 10 of the present example, even if the arrangement pitch P of the adjacent through holes 5 is narrow, migration between the adjacent through holes 5 is effectively prevented, thereby improving the electrical insulation reliability. A thin wiring board 10 having high density and high density wiring can be provided.

  Next, an example of an embodiment of the method for manufacturing a wiring board according to the present invention will be described with reference to FIGS. 2 (a) to 2 (e) and FIGS. 3 (f) to 3 (j). 2 and 3, the same parts as those of the wiring board 10 described above are denoted by the same reference numerals, and detailed description thereof is omitted to avoid complexity.

  First, as shown in FIG. 2A, a double-sided copper-clad laminate 11 is prepared. The double-sided copper-clad laminate 11 is obtained by attaching copper foils 12 to the upper and lower surfaces of the insulating layer 1 made of the resin material 4 containing the glass cloth 3. The thickness of the insulating layer 1 is about 150 to 200 μm, and the thickness of the copper foil 13 is about 2 to 18 μm.

  Next, as shown in FIG. 2 (b), the through holes 5 are formed from the upper surface to the lower surface of the double-sided copper-clad plate 11. The through hole 5 is formed by, for example, laser processing. In laser processing, the opening diameter on the incident side of the laser in the through hole 5 is larger than the opening diameter on the emission side. Accordingly, the through hole 5 is tapered. When the through hole 5 is tapered as described above, it becomes easy to fill the inside of the through hole 5 with a plating conductor. The diameter of the through hole 5 in the insulating layer 1 is about 80 to 100 μm on the laser incident side and about 30 to 60 μm on the laser emission side. Further, since the copper foil 12 is harder to be laser processed than the insulating layer 1, a part of the copper foil 12 protrudes in a bowl shape at the upper and lower ends of the through hole 5. In addition, after forming the through-hole 5, it is preferable to perform a desmear process.

  Next, as shown in FIG. 2C, the inner wall of the through hole 5 and the exposed surface of the copper foil 12 are covered with a carbon black film 6. The coating with the carbon black film 6 is performed by charging the surface of the double-sided copper-clad laminate 11 having the through holes 5 to a positive charge by cleaning and conditioning, and then adsorbing the carbon black particles having a negative charge on the charged surface. Is used. In order to adsorb the carbon black fine particles, a method of immersing the double-sided copper clad laminate 11 in a carbon black dispersion in which the carbon black fine particles are dispersed or spraying the carbon black dispersion is employed. Thereby, a continuous film of carbon black fine particles is formed. If necessary, the adsorption of the carbon black particles may be repeated a plurality of times.

  Next, as shown in FIG. 2 (d), the first plated conductor 7 is formed in the through hole 5 and on the copper foil 12. The first plating conductor 7 is formed by plating electrolytic copper plating over the entire surface using the carbon black film 6 as a base conductor. At this time, plating is performed so that the first plating conductor 7 completely fills the inside of the through-hole 5 and the thickness of the first plating conductor 7 on the copper foil 12 is about 40 μm.

  Next, as shown in FIG. 2 (e), the first plated conductor 7 and the copper foil 12 are etched to expose the upper and lower surfaces of the insulating layer 1, and the central portion in the vertical direction of the through hole 5 is filled. Thus, the first plated conductor 7 is left. At this time, the first plated conductor 7 remaining in the through hole 5 is etched to a degree of being recessed by 5 to 40 μm from the upper and lower surfaces of the insulating layer 1. When the first plated conductor 7 remaining in the through-hole 5 is etched so as to be recessed from the upper and lower surfaces of the insulating layer 1 to be shallower than 5 μm, the copper foil 12 partially remains on the upper and lower surfaces of the insulating layer 1 and is fine. The risk of hindering the formation of the wiring conductor 2 increases, and conversely, if etching is performed so as to be recessed deeper than 40 μm, the top of the insulating layer 1 is formed to completely fill the recess when forming the second plated conductor 9. The thickness of the second plating conductor 9 deposited on the lower surface is thicker than 20 μm, and it is difficult to form the fine wiring conductor 2.

  Next, as shown in FIG. 3 (f), the portion outside the first plating conductor 7 in the through hole 5 and the upper and lower surfaces of the insulating layer 1 are covered with an electroless copper plating film 8. The thickness of the electroless copper plating film 8 is about 0.1 to 1 μm.

  Next, as shown in FIG. 3G, a plating resist 13 having an opening pattern corresponding to the pattern of the wiring conductor 2 is formed on the electroless copper plating film 8 on the upper and lower surfaces of the insulating layer 1. The opening pattern of the plating resist 13 includes an opening pattern having a width and an interval of 30 μm or less.

  Next, as shown in FIG. 3H, a second plated conductor 9 is deposited on the surface of the electroless copper plating film 8 exposed from the opening pattern of the plating resist 13 by an electrolytic copper plating method. The second plating conductor 9 is formed so as to fill a portion outside the first plating conductor 7 of the through hole 5 and to have a thickness of about 10 to 20 μm on the upper and lower surfaces of the insulating layer 1. In this case, since the central portion of the through hole 5 in the thickness direction is already filled with the first plated conductor 7, the second plated conductor 9 is deposited to a thickness that fills only the upper and lower end portions of the through hole 5. Therefore, the thin second plating conductor 9 having a thickness of 10 to 20 μm can be formed on the upper and lower surfaces of the insulating layer 1.

  Next, as shown in FIG. 3I, the plating resist 13 is peeled and removed. An alkaline stripping solution can be used for stripping the plating resist 13.

  Finally, as shown in FIG. 3 (j), the electroless plating film 8 exposed from the second plating conductor 9 is removed by etching. Thereby, the inside of the through hole 5 is filled with the first plating conductor 7 and the second plating conductor 9, and the wiring conductor 2 composed of the second plating conductor 9 is formed on the upper and lower surfaces of the insulating layer 1. The substrate 10 is completed. The method of forming the wiring conductor 2 composed of the second plating conductor 9 is called a semi-additive method, and a second pattern having a pattern corresponding to the wiring conductor 2 is formed on the electroless plating film 8 which is a base conductor. After the plating conductor 9 is selectively deposited, the wiring conductor 2 is formed by etching away the electroless plating film 8 exposed from the second plating conductor 9, so that the wiring conductor 2 is formed on the upper and lower surfaces of the insulating layer 1. The second plating conductor 9 that forms the film is not greatly etched. Therefore, according to the semi-additive method, for example, fine wiring conductors 2 having a width and interval of 30 μm or less can be formed at high density.

  In addition, since the inner wall of the through hole 5 is covered with the carbon black film 6, the carbon black film 6 functions as a barrier against migration between the through holes 5. For example, even if it is a narrow one of 150 μm or less, migration between adjacent through holes 6 is effectively prevented.

  Therefore, according to the manufacturing method of the wiring board of this example, even if the arrangement pitch P of the adjacent through holes 5 is narrow, the migration between the adjacent through holes 5 is effectively prevented, thereby electrically insulating. A thin wiring substrate 10 having high-reliability and high-density wiring can be provided.

DESCRIPTION OF SYMBOLS 1 Insulating layer 2 Wiring conductor 3 Glass cloth 4 Resin material 5 Through-hole 6 Carbon black film 7 1st plating conductor 8 Electroless plating film 9 2nd plating conductor 10 Wiring board 11 Double-sided copper clad laminated board 12 Copper foil

Claims (2)

  A wiring conductor made of a resin material containing glass cloth and having a through hole penetrating vertically, and a plating conductor filling the inside of the through hole and deposited on the upper and lower surfaces of the insulating layer by a semi-additive method And the plating conductor includes a first plating conductor that fills only a central portion in the vertical direction of the through-hole, and a first plating conductor in the through-hole. The first plating conductor is formed with a carbon black film covering the inner wall of the through hole as a base conductor. The second plating conductor fills an outer portion and forms the wiring conductors on the upper and lower surfaces. The second plating conductor has the carbon black film and the electroless plating film thereon as a base conductor on the inner wall of the through hole, and an electroless plating on the upper and lower surfaces of the insulating layer. Wiring board, characterized in that it is formed a film only as underlying conductor.   Forming a through hole from the upper surface to the lower surface of a double-sided copper clad laminate in which a copper foil is attached to the upper and lower surfaces of an insulating layer made of a resin material containing glass cloth, and the exposed surface of the inner wall of the through hole and the copper foil And a first plating having a thickness that completely fills the through-holes in the through-holes and on the copper foil by performing electrolytic plating on the entire surface using the carbon black film as a base conductor. Forming a conductor; etching the first plated conductor and the copper foil to expose the upper and lower surfaces of the insulating layer; and filling the vertical center of the through hole with the first A step of leaving a plating conductor; a step of covering the outer side of the first plating conductor in the through hole and the upper and lower surfaces of the insulating layer with an electroless plating film; Forming a second plating conductor serving as a wiring conductor on the upper and lower surfaces while filling a portion outside the first plating conductor in the through hole by performing electrolytic plating as a conductor by a semi-additive method; A method for manufacturing a wiring board, comprising:

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