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JP-2026075283-A - Printed circuit board and method for manufacturing the same

JP2026075283AJP 2026075283 AJP2026075283 AJP 2026075283AJP-2026075283-A

Abstract

[Problem] To provide a printed circuit board that can realize thick copper circuits of 15 to 100 μm at low cost by suppressing transmission loss using FCCL material with a sputtered copper layer formed by a highly smooth sputtering method. [Solution] The invention provides a core material 2 comprising an insulating resin material 2a and a roughened copper foil 2b attached to the surface of the insulating resin material, wherein the maximum interface roughness (Rz) is 1 μm or more; an FCCL material 3 comprising a resin film 3a and a sputtered metal layer formed on one surface of the resin film, wherein the maximum interface roughness (Rz) is 0.6 μm or less, and the FCCL material is laminated to the core material such that the other surface of the resin film faces the roughened copper foil of the core material; a hole 4 formed in the FCCL material; a first plated copper layer 5 that fills the hole and connects the roughened copper foil and the sputtered copper layer; and a second plated copper layer 6 formed on the first plated copper layer and the sputtered metal layer, wherein the combined thickness with the sputtered metal layer is more than 15 μm and less than or equal to 100 μm. [Selection Diagram] Figure 1

Inventors

  • 下地 匠

Assignees

  • 株式会社伸光製作所

Dates

Publication Date
20260508
Application Date
20241022

Claims (10)

  1. A core material comprising an insulating resin material and a roughened copper foil attached to at least one surface of the insulating resin material, wherein the maximum roughness (Rz) of the interface between the insulating resin material and the roughened copper foil is 1 μm or more. An FCCL material comprising a resin film and a sputtered metal layer formed on one surface of the resin film, wherein the maximum roughness (Rz) of the interface between the resin film and the sputtered metal layer is 0.6 μm or less, and the other surface of the resin film is laminated to the core material such that it faces the roughened copper foil of the core material, The hole formed in the FCCL material, A first plated copper layer fills the aforementioned hole and connects the roughened copper foil and the sputtered metal layer, A second plated copper layer is formed on the first plated copper layer and the sputtered metal layer, and the combined thickness of the sputtered metal layer and the second plated copper layer is greater than 15 μm and less than or equal to 100 μm. A printed circuit board characterized by having the following.
  2. The printed circuit board according to claim 1, characterized in that the first plating layer is formed by electroless plating and electroplating, and the second plating layer is formed by electroplating.
  3. The printed circuit board according to claim 1, characterized in that the sputtered metal layer consists of a sputtered copper layer.
  4. The printed circuit board according to claim 1, characterized in that the sputtered metal layer comprises a sputtered copper layer and a metallized layer provided between the resin film and the sputtered copper layer.
  5. The FCCL material is laminated onto the core material via a prepreg. The printed circuit board according to claim 1, characterized in that the prepreg has holes that communicate with holes formed in the core material.
  6. The printed circuit board according to claim 4, characterized in that the metallized layer consists of nickel, chromium, or two or more alloys selected from nickel, chromium, and copper.
  7. A step of preparing a core material in which a roughened copper foil is attached to at least one surface of an insulating resin material, and the maximum roughness (Rz) of the interface between the insulating resin material and the roughened copper foil is 1 μm or more, The process involves forming a circuit pattern on the roughened copper foil attached to the core material by etching, A step of laminating an FCCL material, in which sputtered metal is formed on one surface of a resin film by sputtering, and the maximum interface roughness (Rz) between the resin film and the copper layer is 0.6 μm or less, onto the side of the core material on which the roughened copper foil is attached, with the other side of the resin film facing the core material. The process of forming holes in the FCCL material that reach the roughened copper foil by etching, A step of forming a copper film on the inner circumferential surface of the hole by electroless plating, and connecting the copper film to the roughened copper foil of the core material and the sputtered metal layer of the FCCL material, A step of forming a first plated copper layer by filling the holes surrounded by the roughened copper foil and the sputtered metal film with copper by electroplating, and growing a second plated copper layer on the FCCL material and the first plated copper layer such that the combined thickness of the sputtered metal layer and the second plated copper layer exceeds a desired thickness of more than 15 μm and 100 μm or less. A method for manufacturing a printed circuit board, characterized by having the following features.
  8. The process involves chemically polishing the second plated copper layer grown on the FCCL material to a desired thickness of more than 15 μm and 100 μm or less, when combined with the sputtered metal layer. A process of forming a circuit pattern on a surfaced conductor layer by etching, The method for manufacturing a printed circuit board according to claim 7, further comprising:
  9. The method for manufacturing a printed circuit board according to claim 7, characterized in that the sputtered metal layer consists of a sputtered copper layer.
  10. In the process of laminating the FCCL material onto the side of the core material on which the roughened copper foil is attached, such that the other side of the resin film faces the core material, the FCCL material is laminated onto the core material via a prepreg. In the process of forming the aforementioned holes, holes reaching the roughened copper foil are formed in the FCCL material and the prepreg by etching. The method for manufacturing a printed circuit board according to feature 7.

Description

This invention relates to printed circuit boards, and more particularly to high-frequency compatible printed circuit boards used in communication equipment and the like. With the increasing performance of various electronic devices in recent years, the printed circuit boards (PCBs) used in them are also required to meet these performance demands. For example, communication devices and sensors transmit signals at higher frequencies, necessitating high-frequency PCBs capable of handling these higher frequencies. A conventional high-frequency circuit board used in such electronic devices is, for example, the multilayer printed circuit board described in Patent Document 1. The multilayer printed circuit board described in Patent Document 1 has a high-frequency substrate laminated and integrated onto one side of a base substrate via an insulating adhesive layer, and the outer layer of the high-frequency substrate has a high-frequency wiring pattern formed by etching a conductor layer. Patent No. 6444651 This is an explanatory diagram schematically showing an example of a cross-sectional structure of a printed circuit board according to the first embodiment of the present invention.This is a schematic diagram illustrating an example of a method for manufacturing a printed circuit board according to the first embodiment of the present invention.This is an explanatory diagram schematically showing an example of a cross-sectional structure of a printed circuit board according to a second embodiment of the present invention. Before describing the embodiments, we will explain the circumstances that led to the invention and the effects of the invention. As mentioned above, conventional high-frequency circuit boards used in the manufacture of printed circuit boards are generally manufactured by laminating a low-dielectric resin substrate with roughened copper foil in order to obtain adhesion between the copper foil and the resin substrate. However, there is a problem that transmission loss increases if the conductor surface is rough. Even with fine copper foil, a roughness (Rz) of 1 μm or more is required, so the transmission loss problem cannot be resolved. On the other hand, FCCL material is known as a substrate that provides a smooth interface between the resin and the conductive layer. FCCL material allows for the formation of a highly adhesive conductive layer even on a smooth resin surface with a roughness (Rz) of 0.6 μm or less by sputtering, but the thickness of the conductive layer that can be formed is less than 1 μm. Furthermore, because the formation of the conductive layer on the resin film surface by sputtering is performed in a high-vacuum environment, FCCL material is generally manufactured using a roll-to-roll method that continuously processes long films. Therefore, even if electroplating is performed to increase the thickness of the conductive layer, there is a limit to the current that can be supplied to the long material through a thin sputtered layer. The maximum plating thickness that can be grown by plating is 8 μm, and at most 13-15 μm; it is not easy to grow the plating thicker than that. However, in printed circuit boards, the thickness of the conductor needs to be between 15 μm and 100 μm. Therefore, even when using FCCL material to obtain a printed circuit board with reduced transmission loss, electroplating is necessary until the plating thickness grows to 15 μm to 100 μm. However, this would result in excessively long electroplating times, poor manufacturing efficiency, and high costs. Here, the inventors of this case have considered and investigated strategies for reducing transmission loss while growing conductors to 15 μm to 100 μm by electroplating, by combining the characteristics of FCCL material (where transmission loss can be suppressed by a smooth surface with a roughness (Rz) of 0.6 μm or less, but where it is difficult to grow the conductor layer by electroplating due to the thinness of the conductor layer formed by the sputtering method) and high-frequency substrates manufactured by laminating a low-dielectric resin substrate and roughened copper foil (where conductors can be grown to 15 μm to 100 μm, but transmission loss is high due to the rough surface). As a result, we hypothesized that by constructing a printed circuit board with a high-frequency substrate made by laminating a low-dielectric resin substrate and roughened copper foil, and by electrically connecting the thick roughened copper foil in the high-frequency substrate with the thin, smooth copper layer in the FCCL material, it would be possible to facilitate the growth of the thin, smooth copper layer in the FCCL material by allowing the current flowing through the thick copper foil in the high-frequency substrate to also flow through the thin, smooth copper layer during electroplating. Furthermore, the inventors of this invention conceived a method for electrically connecting the thick roughened copper foil in a