JP2012160559A - Method for manufacturing wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a thin, high density wiring board having a wiring conductor width of 30 μm and a wiring conductor interval of less than 40 μm.SOLUTION: An insulating layer 1 with copper foil 7 is prepared. A through hole 3 is formed through the insulating layer 1. A first plating metal layer 4 is selectively deposited in the through hole 3, vicinities thereof and positions to form wiring conductors 9 to a thickness incompletely filling the through hole 3. Second plating metal layers 5 for forming a through conductor 6 and lands 8 are deposited in the through hole 3 and on the vicinal first plating metal layer 4 to a thickness completely filling the through hole 3. The copper foil 7 exposed from the first plating metal layer 4 is removed to leave, in the through hole 3, the through conductor 6 comprising the first and second plating metal layers 4, 5 and, on both surfaces of the insulating layer 1, the lands 8 comprising the copper foil 7 and first and second plating metal layers 4, 5 and the wiring conductors 9 comprising the copper foil 7 and the first plating metal layer 4.

Description

  The present invention relates to a method for manufacturing a wiring board.

  Conventionally, as a thin wiring substrate, for example, a plurality of tapered through holes having a diameter of about 30 to 100 μm are provided in a thin insulating layer having a thickness of about 40 to 300 μm, and the inside of these through holes is filled with a plated metal layer. There is known a wiring board in which a through conductor is formed and a wiring conductor made of the same plated metal layer as the through conductor is formed on the upper and lower surfaces of an insulating layer. In such a wiring board, for example, a plurality of tapered through holes having a diameter of about 30 to 100 μm are formed by laser processing in an insulating layer having a thickness of about 40 to 300 μm, and the inner walls of the through holes and the insulating layer are formed by electroless plating. After depositing a thin electroless plating layer of about 0.1 to 1 μm on the upper and lower surfaces, a plating metal layer is deposited on the electroless plating layer until the inside of the through hole is completely filled by electrolytic plating. Finally, a method of selectively etching the plated metal layer on the insulating layer into a pattern corresponding to the wiring conductor is preferably used.

  However, in such a method, if an attempt is made to form a plated metal layer sufficient to fill the through hole sufficiently, a thick plated metal layer having a thickness of about 40 μm, for example, is also formed on the upper and lower surfaces of the insulating layer. When the thickness of the plated metal layer formed on the upper and lower surfaces of the insulating layer is as thick as about 40 μm, the width of the wiring conductor formed by selectively etching the plated metal layer into a predetermined pattern is about 50 μm. 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 manufacturing method, it has not been possible to obtain a thin wiring substrate having a high-density wiring in which, for example, the width of the wiring conductor is 30 μm or less and the distance between the wiring conductors is less than 40 μm.

JP 2002-43752 A

  The present invention fills the inside of a through hole provided in a thin insulating layer with copper foil stuck on both sides with a plated conductor, and has a wiring conductor composed of a copper foil and a plated metal layer on the upper and lower surfaces of the insulating layer. An object of the present invention is to provide a method for manufacturing a thin wiring board having high-density wirings, for example, having a wiring conductor width of 30 μm or less and a spacing between the wiring conductors of less than 40 μm.

  The manufacturing method of the present invention includes a step of preparing an insulating layer with copper foil in which copper foil is stuck on both surfaces of the insulating layer, a step of forming a through hole in the insulating layer with copper foil, and a filling of the through hole. The first plated metal layer for forming the through conductor and the land connected to the through conductor and the wiring conductor extending over the insulating layer is completely formed in and around the through hole and at the position where the wiring conductor is formed. Fully fill the through hole with a second plating metal layer to form through conductors and lands on the first plated metal layer in and around the through hole, and selectively depositing the unfilled thickness A step of selectively depositing the copper foil exposed from the first plated metal layer by etching and removing the copper foil exposed from the first plated metal layer in the through hole; and a through conductor comprising the first and second plated metal layers; Copper foil on both sides and first and second And performing a land made of come metal layer, and a step of leaving a wiring conductor made of copper foil and the first plated metal layer.

  According to the method for manufacturing a wiring board of the present invention, the first plated metal is selectively formed in a thickness that does not completely fill the through hole in and around the through hole of the insulating layer having the through hole and the position where the wiring conductor is formed. After the layer is formed, the second plated metal layer is formed on the first plated metal layer only in and around the through hole to fill the through hole, so that the wiring conductors on the upper and lower surfaces of the insulating layer The thickness of the copper foil and the first plated metal layer can be made as thin as, for example, 20 μm or less, the width of the wiring conductor is 30 μm or less, and a fine wiring conductor with a spacing between the wiring conductors of less than 40 μm is high. Therefore, a thin wiring board can be manufactured with high-density wiring.

FIG. 1 is a schematic cross-sectional view showing an example of a wiring board manufactured by the manufacturing method of the present invention. FIGS. 2A to 2H are schematic cross-sectional views of main parts for each process for explaining an example of an embodiment in the method for manufacturing a wiring board of the present invention.

  First, an example of a wiring board manufactured by the manufacturing method of the present invention will be described with reference to FIG. As shown in FIG. 1, a wiring board 20 manufactured by the manufacturing method of the present invention has a build-up insulating layer 2 laminated on the upper and lower surfaces of a core insulating layer 1, for example. A plurality of through holes 3 are formed in the insulating layer 1 for the core, and the through conductors 6 including the first plated metal layer 4 and the second plated metal layer 5 are filled in the through holes 3. Has been. Further, on the upper and lower surfaces of the insulating layer 1, the land 8 composed of the first plating metal layer 4 and the second plating metal layer 5 with the copper foil 7 as a base, and the first plating with the copper foil 7 as a base. A core wiring conductor 9 made of a metal layer 4 is attached.

A plurality of via holes 10 having lands 8 and wiring conductors 9 as bottom surfaces are formed in the insulating layer 2, and a buildup made of a third plated metal layer 11 is formed inside the via hole 10 and on the surface of the insulating layer 2. The wiring conductor 12 is attached. Thus, the core land 8 and the wiring conductor 9 are electrically connected to the build-up wiring conductor 12. Furthermore, a solder resist layer 13 having an opening 13a that exposes a part of the wiring conductor 12 as a connection pad used for connection to an electronic component or a circuit board is deposited on the surfaces of the insulating layer 2 and the wiring conductor 12. Yes.

  Next, an example of an embodiment in the production method of the present invention will be described with reference to FIGS. In FIG. 2, the same parts as those in FIG. First, as shown in FIG. 2A, an insulating layer 1 is prepared in which a copper foil 7 is stuck on the upper and lower surfaces. The insulating layer 1 is made of, for example, an electrically insulating material in which a glass cloth is impregnated with a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin. The thickness of the insulating layer 1 is about 40 to 300 μm. Such an insulating layer 1 is obtained by attaching a copper foil 7 having a thickness of about 3 to 5 μm to both surfaces of a prepreg obtained by impregnating a glass cloth with a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin. Is obtained by thermosetting.

  Next, as shown in FIG.2 (b), the through-hole 3 is formed in the insulating layer 1 to which the copper foil 7 was stuck. The through hole 3 is formed by, for example, laser processing. In laser processing, the opening diameter on the incident side of the laser in the through hole 3 is larger than the opening diameter on the emission side. The opening diameter of the through hole 3 is about 80 to 100 μm on the laser incident side and about 30 to 80 μm on the emission side. Therefore, the through hole 3 is tapered. When the through hole 3 has such a tapered shape, it becomes easy to satisfactorily fill the inside of the through hole 3 with the plated metal layer. In addition, after forming the through-hole 3, it is preferable to perform a desmear process. Thereafter, a thin electroless plating layer (not shown) having a thickness of about 0.1 to 1 μm is deposited on the inner wall of the through hole 3 and the surface of the copper foil 7. The electroless plating layer functions as a base metal for the first plating metal layer 4 to be described later. For example, an electroless copper plating layer is preferably used.

  Next, as shown in FIG. 2 (c), first plating resists 14 having openings for exposing the positions inside and around the through holes 3 and the positions where the wiring conductors 9 are formed are formed on the upper and lower surfaces of the copper foil 7. To do.

  Next, as shown in FIG. 2 (d), a first electroplating method is applied to the surface of the copper foil 7 in and around the through hole 3 exposed from the first plating resist 14 and the position where the wiring conductor 9 is to be formed. The plated metal layer 4 is deposited to a thickness that does not completely fill the through hole 3. At this time, the first plated metal layer 4 is formed at a position where the wiring conductor 9 is formed, for example, with a thickness of about 20 μm, together with the thickness of the copper foil. In addition, as the 1st metal plating layer 4, an electrolytic copper plating layer is used suitably. In this case, since the first plated metal layer 4 is deposited to a thickness that does not completely fill the through-hole 3, the thickness of the first plated metal layer 4 deposited at the position where the wiring conductor 9 is formed is set to a copper foil. For example, it can be made sufficiently thin, for example, about 20 μm.

  Next, as shown in FIG. 2 (e), the first plating resist 14 and the wiring conductor 9 are exposed so as to expose the first plating metal layer 4 only in and around the through hole 3. A second plating resist 15 is coated on the metal layer 4.

  Next, as shown in FIG. 2 (f), the second plated metal layer 5 is completely deposited in the through hole 3 by electrolytic plating on the first plated metal layer 4 exposed from the second plating resist 15. Adhere to fill. At this time, a through conductor 6 composed of the first plated metal layer 4 and the second plated metal layer 5 is formed in the through hole 3, and the copper foil 7 and the second metal are formed on and around the through conductor 6. A metal layer for the land 8 composed of one plated conductor layer 4 and the second plated conductor layer 5 is formed. In addition, since the first plated metal layer 4 at the position where the wiring conductor 9 is formed is covered with the second plating resist 15, the second plated metal layer 5 remains thin without being deposited. As the second plating metal layer 5, an electrolytic copper plating layer is preferably used. The thickness of the second plated metal layer 5 may be in a range necessary for sufficiently filling the through hole 3, but the combined thickness of the copper foil 7 and the first plated metal layer 4 is 25 to 25. It is preferably about 35 μm.

  Next, as shown in FIG. 2G, the metal layer for the land 8 is etched to a predetermined thickness by etching. At this time, the thickness of the land 8 is preferably about 20 to 30 μm. When etching is performed until the land 8 has a thickness of less than 20 μm, the insulating layer 2 covering the land 8 becomes thick when the build-up insulating layer 2 is laminated thereon, and the insulating layer 2 has a thickness in the via hole 10. When the wiring conductor 12 for buildup is formed, the connection reliability is lowered. On the contrary, if etching is performed to the extent that the thickness exceeding 30 μm remains, the step between the land 8 and the periphery thereof becomes large. Therefore, there is a risk that the insulating layer 2 becomes thin and the insulation reliability is lowered.

  Finally, as shown in FIG. 2H, both plating resists 14 and 15 are removed, and the copper foil 7 exposed from the first plating metal layer 4 is removed by etching. As a result, the through conductor 6 in which the inside of the through hole 3 is filled with the first and second plated metal layers 4 and 5, and the first and second first and second surfaces of the insulating layer 1 with the copper foil 7 as the base are provided. A land 8 made of the plated metal layers 4 and 5 and a wiring conductor 9 made of the first plated metal layer 4 with the copper foil 7 as a base are formed. Thereafter, the build-up insulating layer 2, the wiring conductor 12, and the solder resist layer 13 are formed by using a well-known build-up technique, thereby completing the wiring substrate 20 shown in FIG. In the case of this example, the wiring conductor 9 formed of the first plated metal layer 4 with the copper foils 7 on the upper and lower surfaces of the insulating layer 1 as a base is a thin one having a thickness of 20 μm or less, and the width of the wiring conductor 9 is 30 μm. In the following, fine wiring conductors 9 having a spacing of less than 40 μm between the wiring conductors 9 can be formed with high density, whereby a thin wiring board can be manufactured with high-density wiring. Furthermore, in this example, since the copper foil 7 deposited on the upper and lower surfaces of the insulating layer 1 is used as the base metal of the wiring conductor 9 made of the first plated metal layer 4, the first plated metal layer 4 is used. The wiring conductor 9 formed can be bonded to the upper and lower surfaces of the insulating layer 1 very firmly via the copper foil 7.

DESCRIPTION OF SYMBOLS 1 Insulation layer 3 Through-hole 4 1st plating conductor 5 2nd plating conductor 6 Through conductor 7 Copper foil 8 Land 9 Wiring conductor

Claims (1)

  A step of preparing an insulating layer with copper foil in which copper foil is stuck on both sides of the insulating layer, a step of forming a through hole in the insulating layer with copper foil, a through conductor filling the through hole, and the through hole The through hole is completely filled in and around the through hole and at the position where the wiring conductor is formed with a land connected to the conductor and a first plated metal layer for forming a wiring conductor extending on the insulating layer A step of selectively depositing to a thickness not to be formed, and a second plated metal layer for forming the through conductor and the land on the first plated metal layer in and around the through hole. And selectively depositing the copper foil exposed from the first plated metal layer by etching to remove the copper foil exposed from the first plated metal layer from the first and second plated metal layers. Through conductors and front Leaving a land made of the copper foil and the first and second plated metal layers and a wiring conductor made of the copper foil and the first plated metal layer on both surfaces of the insulating layer. A method of manufacturing a wiring board.

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