JP4106592B2 - Wiring board and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wiring board suitable for incorporating a high-speed signal processing circuit and a method useful for manufacturing the wiring board.
[0002]
[Prior art]
An invention related to a wiring board that is suitable for constructing a high-speed signal processing circuit by incorporating a coaxial cable into the wiring board, so that there is no disturbance in the signal waveform due to cross-talk noise and characteristic impedance fluctuations. Is disclosed in, for example, Japanese Patent Publication No. 45-21438.
[0003]
As for various improved inventions related to the above-mentioned invention, for example, “JP-A-4-294595”, “JP-A-4-302497”, “JP-A-4-342191”, “JP-A-6-275958”. No. 7-115276, “Japanese Laid-Open Patent Publication No. 7-212455”, and “Japanese Unexamined Patent Publication No. 7-212455”.
[0004]
The basic structure and manufacturing method of the wiring board disclosed in each of the above inventions are the same, and all of them require a large number of manufacturing processes and require a precise and advanced technique.
[0005]
For example, in the invention disclosed in Japanese Patent Laid-Open No. 4-342191, a through hole is formed by plating a printed circuit board having a wiring pattern formed on the surface, and the coaxial cable incorporated in the printed circuit board is formed in the through hole. The central conductor is connected, and the outer conductor of the coaxial cable is connected to the ground layer laminated inside the printed circuit board.
[0006]
In order to realize this structure, a step of arranging a coaxial cable in a desired shape, a step of partially etching the outer conductor of the coaxial cable, a step of connecting the outer conductor to the ground layer, and the like are disclosed in the publication. It is not difficult to imagine that a lot of precise processes and workers will require a high degree of skill just by looking at the product name, in fact, a product name that seems to be a product based on the technology disclosed in the publication A “multi-wire substrate” is very expensive.
[0007]
[Problems to be solved by the invention]
The present invention intends to provide means capable of inexpensively manufacturing a wiring board suitable for incorporating a high-speed signal processing circuit.
[0008]
[Means for Solving the Problems]
In the present invention, the two end faces of the coaxial cable are exposed separately at two desired positions on the multilayer wiring board, and the coaxial cable itself basically has a structure embedded in the multilayer circuit board. It has become.
[0009]
By adopting the above-mentioned means, it is possible to realize a multilayer circuit board suitable for incorporating a high-speed signal processing circuit without any disturbance in signal waveform due to cross-talk noise and characteristic impedance fluctuations. .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cutaway side view of an essential part for explaining the basic part of a wiring board according to the present invention. In the figure, 1 is a wiring board, 2 is an embedded coaxial cable, 2A is a central conductor, 2B Denotes an outer conductor, and 2C denotes an end face.
[0011]
2 and 3 are side sectional views of the main part of the wiring board at process points for explaining the process of manufacturing the wiring board according to the present invention, and will be described below with reference to these drawings. .
[0012]
See FIGS. 2A, 2B, and 2C (1)
Holes 11 </ b> A are formed at two required locations on the lamination substrate 11. A drill or a laser can be used as the means for opening holes.
[0013]
The shape of the hole 11A is not limited to the vertical shape seen in (A), but is slanted as seen in (B), or one of the edges of the hole 11A as seen in (C). A taper portion or the like may be employed as appropriate. This is effective for alleviating the bending applied to the coaxial cable.
[0014]
Refer to FIG. 2D (2)
The coaxial cable 12 is wired on the substrate 11 for lamination, and both ends thereof can be seen through the hole 11A. Of course, the outermost outer side of the coaxial cable 12 is an external conductor, and therefore the symbol 12B is given to the external conductor in the figure.
[0015]
Refer to FIG. 2 (E) (3)
Resin 13 is filled in hole 11A, and both ends of coaxial cable 12 are fixed to substrate 11 for lamination.
[0016]
See FIGS. 3A and 3B (4)
A backside laminating substrate 15 is laminated via a prepreg 14 on the laminating substrate 11 in which the coaxial cable 12 is wired, and is integrated by heating and pressing. FIG. 3B shows the wiring board 16 that is laminated and integrated. In this case, the shape of the hole 11A described with reference to FIGS. 2B and 2C is effective. Further, an uncured thermosetting resin layer may be formed on the lamination substrate 11 or the back side lamination substrate 15 instead of the prepreg 14.
[0017]
See FIG. 3C (5)
The surface of the wiring board 16 is polished and flattened. In particular, this polishing is performed so that both ends of the coaxial cable 12 are flush with the surface of the wiring board 16.
[0018]
In the wiring board 16 manufactured as described above, various structures can be used to connect the outer conductor 12B of the coaxial cable 12 to the ground.
[0019]
4A and 4B are diagrams for explaining an example of a structure for connecting the outer conductor of the coaxial cable to the ground. FIGS. 4A and 4B are plane views, and FIG. The symbols used in FIGS. 2 and 3 represent the same parts or have the same meaning.
[0020]
In the figure, 12A is a central conductor of the coaxial cable, 12B is an outer conductor of the coaxial cable, 17 is a ground layer formed on the surface of the laminated substrate 11, and 17A is a lead drawn from the ground layer. .
[0021]
FIG. 5 is a diagram for explaining another example of a structure in which the outer conductor of the coaxial cable is connected to the ground. (A), (B), and (C) show the cut side surface of the main part, and (D ) Respectively show the enlarged side view of the main part, and the same symbols as those used in FIGS. 2 to 4 represent the same parts or have the same meanings.
[0022]
See FIG. 5A (1)
Holes 11 </ b> A are formed at two required positions on the lamination substrate 11 using a drill or a laser. The laminated substrate 11 used here is different from that in the wiring substrate 16 described with reference to FIGS. 2 and 3 in that a metal layer 18 as a ground layer is lined on the back side.
[0023]
(2)
The coaxial cable 12 is wired on the metal layer 18 side of the substrate 11 for lamination, and both ends thereof can be seen through the hole 11A.
[0024]
Refer to FIG. 5B (3)
A conductive adhesive 19 is filled between the hole 11A and the outer conductor 12B of the coaxial cable 12, and both ends of the coaxial cable 12 are fixed to the laminated substrate 11, and the conductive connection between the outer conductor 12B and the metal layer 18 is performed. Make sure.
[0025]
See FIGS. 5C and 5D (4)
A back side laminating substrate 15 is laminated via a prepreg 14 on the metal layer 18 side of the laminating substrate 11 on which the coaxial cable 12 is wired and fixed, and integrated by heating and pressurizing to produce a wiring substrate 16. 5D clearly shows that the outer conductor 12B of the coaxial cable 12 and the metal layer 18 as the ground layer are conductively connected via the conductive adhesive 19. FIG.
[0026]
(5)
The surface of the wiring board 16 is polished and flattened. In particular, this polishing is performed so that both ends of the coaxial cable 12 are flush with the surface of the wiring board 16.
[0027]
Various structures can also be employed when a semiconductor chip is mounted on the wiring board 16 manufactured as described above and conductively connected to the central conductor 12A of the coaxial cable 12.
[0028]
FIG. 6 is a cutaway side view illustrating a structure in which a semiconductor chip is mounted on a wiring board. The same symbols as those used in FIGS. 2 to 5 represent the same parts or have the same meaning. To do.
[0029]
An example of a process for realizing the structure seen in FIG. 6 will be described.
(1)
The insulating layer 20 made of a photosensitive resin is formed on the surface side of the wiring board 16, that is, the side where the end face of the coaxial cable 12 is exposed, and then the central conductor 12A is displayed by applying a photo process. An opening 20A for exiting is formed.
[0030]
(2)
By applying a vacuum deposition method, a photolithographic technique, or the like, a wiring (or pad) 21A for extracting a signal from the central conductor 12A to the surface of the insulating layer 20 and other wiring 21B are formed.
[0031]
(3)
The semiconductor chip 22 is connected and mounted on the wirings 21 </ b> A and 21 </ b> B on the surface of the wiring substrate 16 via the bumps 23.
[0032]
When a semiconductor chip having a large number of connection terminals is mounted, the wiring board can be further multilayered. In that case, the coaxial cable to be embedded may be multilayered.
[0033]
7A and 7B are cutaway side views illustrating an essential part of a wiring board having an increased number of layers, where FIG. 7A shows a case where a printed board is multilayered, and FIG. 7B shows a case where a coaxial cable to be embedded is multilayered. The same symbols as those used in FIG. 6 represent the same parts or have the same meaning.
[0034]
In the figure, 31 is a wiring board, 32 is a second layer stacking board, 33 is a wiring board, and 34A to 34C are embedded coaxial cables.
[0035]
Specific examples in the case of manufacturing a wiring board according to the present invention will be described.
Example (1)
A hole with a short diameter of 150 [μm] is formed in an oblique direction in a direction approaching a predetermined two places of a 200 [μm] single-sided copper layer-clad glass-polyimide lamination substrate.
[0036]
(2)
A coaxial cable having a diameter of 100 [μm] φ is laid out on the copper layer tension side of the lamination substrate, and both ends are inserted into the holes in the oblique direction to project the tip. The coaxial cable used here may be a commercially available product, but in the experiment, a product based on the invention disclosed in Japanese Patent Application No. 2001-324434 was used.
[0037]
(3)
Coaxially protruding from the hole after the copper layer and the outer conductor (shield layer) of the coaxial cable are conductively connected and fixed between the hole formed in the laminated substrate and the coaxial cable. Cut off the end of the cable.
[0038]
(4)
Wiring is performed by laminating the prepreg and the other single-sided copper layer-clad glass-polyimide laminated substrate with the copper layer-clad side facing the prepreg on the copper layer-clad side of the substrate for lamination, and heating and pressurizing to integrate them. A substrate is formed.
[0039]
(5)
The surface side of the wiring board, that is, the side where the tip of the coaxial cable and the conductive adhesive protrude is polished and removed to flatten it.
[0040]
(6)
Photosensitive polyimide (UR5100 manufactured by Toray) is applied to the surface of the wiring board, and exposure and development are performed to form a via hole that exposes the central conductor of the coaxial cable. In this case, the diameter of the via hole is 80 [μm] φ on the upper surface side and 50 [μm] φ on the lower surface side so that the outer conductor of the coaxial cable is not exposed.
[0041]
(7)
Heating is performed to cure the photosensitive polyimide. The cured polyimide has a layer thickness of about 20 [μm].
[0042]
(8)
By applying the sputtering method, a Cu seed layer having a thickness of 5000 [Å] is formed, and after forming a resist layer having a necessary pattern, Cu is thickened by electroplating. The plating thickness at this time is about 10 [μm].
[0043]
(9)
After the resist layer is peeled off and the Cu seed layer is etched, a wiring connected to the central conductor is formed and completed.
[0044]
In the present invention, the present invention can be implemented in many forms including the above-described embodiment, which will be exemplified below as supplementary notes.
[0045]
(Appendix 1)
A wiring board comprising: a coaxial cable embedded in a laminated board and having both ends penetrating the board and exposed while being substantially flush with the surface of the board.
[0046]
(Appendix 2)
The wiring board according to (Appendix 1), characterized in that the central conductor at the end face of the coaxial cable exposed on the surface of the board is connected to the wiring on the same board surface.
[0047]
(Appendix 3)
The wiring board according to (Appendix 1), wherein an outer conductor at an end face of the coaxial cable exposed on the surface of the board is connected to a ground layer or a power supply layer on the same board surface.
[0048]
(Appendix 4)
The wiring board according to (Appendix 1), wherein an outer conductor in a coaxial cable whose end face is exposed on the board surface is conductively connected through a ground layer or a power supply layer formed inside the board. .
[0049]
(Appendix 5)
The outer conductor is fixed to the substrate with a resin applied between the substrate and the periphery of the outer conductor in the coaxial cable whose end surface is exposed on the substrate surface (Appendix 3) The wiring board described.
[0050]
(Appendix 6)
Conductive adhesion applied between the periphery of the outer conductor and the substrate through which the outer conductor of the coaxial cable whose end face is exposed on the substrate surface passes through the ground layer or the power supply layer formed on the inner side of the substrate. The wiring board according to (Appendix 4), wherein the external conductor is fixed to the board with an agent and is electrically connected.
[0051]
(Appendix 7)
Forming a through-hole with a laser or a drill at a required position of the substrate for lamination;
Inserting a coaxial cable through the through hole and projecting the tip, and then applying resin to the through hole to fix the coaxial cable to the lamination substrate; and
A step of laminating another lamination substrate via a prepreg on the side opposite to the side from which the tip of the coaxial cable protrudes, heating and pressurizing and integrating,
A method of manufacturing a wiring board comprising the step of polishing the surface of the coaxial cable from which the tip protrudes to flatten the end face of the coaxial cable and the surface of the substrate for lamination. .
[0052]
(Appendix 8)
The wiring board according to (Appendix 7), further comprising a step of forming a metal layer that is a ground layer or a power supply layer on a side opposite to a side where the end of the coaxial cable protrudes in the laminated board. Production method.
[0053]
(Appendix 9)
A step of applying a conductive adhesive to the outer conductor of the coaxial cable passing through the lamination substrate provided with the metal layer which is a ground layer or a power supply layer to be fixed to the lamination substrate and conductively connected to the metal layer. A manufacturing method of a wiring board as set forth in (Appendix 8).
[0054]
(Appendix 10)
(Appendix 7) to (Appendix 9), including a step of forming an uncured thermosetting resin layer to be substituted for the prepreg on at least one of the laminate substrates to be laminated (Appendix 7) to (Appendix 9) A method for manufacturing a wiring board according to any one of the above.
[0055]
【The invention's effect】
In the wiring board and the method of manufacturing the same according to the present invention, the coaxial cable is embedded in a laminated board and both ends penetrate the board and are exposed while maintaining substantially the same plane as the board surface. It is fundamental to have.
[0056]
By adopting the above configuration, it is possible to realize a multilayer circuit board suitable for incorporating a high-speed signal processing circuit at low cost without any disturbance of the signal waveform due to cross talk noise and characteristic impedance fluctuations. .
[Brief description of the drawings]
FIG. 1 is a cutaway side view of an essential part for explaining a basic part of a wiring board according to the present invention.
FIG. 2 is a cutaway side view showing a main part of a wiring board at a process point for explaining a process of manufacturing a wiring board according to the present invention.
FIG. 3 is a cutaway side view showing a main part of a wiring board at a process point for explaining a process of manufacturing a wiring board according to the present invention.
FIG. 4 is a diagram for explaining an example of a structure for connecting an outer conductor of a coaxial cable to a ground.
FIG. 5 is a diagram for explaining another example of a structure for connecting an outer conductor of a coaxial cable to a ground.
FIG. 6 is a cutaway side view of a main part illustrating a structure in which a semiconductor chip is mounted on a wiring board.
FIG. 7 is a cutaway side view of a main part illustrating a wiring board having an increased number of layers.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Wiring board 2 Embedded coaxial cable 2A Center conductor 2B Outer conductor 2C End surface 11 Laminating board 11A Hole 12 Coaxial cable 12A Central conductor 12B Outer conductor 13 Resin 14 Prepreg 15 Back side laminating board 16 Wiring board 17 Ground layer

Claims (5)

A substrate laminated with a ground layer or a power supply layer on the inside; and
A coaxial cable embedded in the substrate and having both ends exposed through the substrate and maintained substantially flush with the surface of the substrate, and an external conductor is conductively connected through the ground layer or power supply layer;
Wiring board characterized in that it comprises a. 2. The wiring board according to claim 1, wherein the central conductor at the end face of the coaxial cable exposed on the surface of the board is connected to the wiring on the same board surface. 2. The wiring board according to claim 1, wherein an outer conductor on the end face of the coaxial cable exposed on the surface of the board is connected to a ground layer or a power supply layer on the same board surface. Conductive adhesion applied between the periphery of the outer conductor and the substrate through which the outer conductor of the coaxial cable whose end face is exposed on the substrate surface penetrates the ground layer or the power supply layer formed on the inner side of the substrate. 2. The wiring board according to claim 1 , wherein the outer conductor is fixed to the board and electrically conductively connected with an agent . Forming a through-hole with a laser or a drill at a required position of the substrate for lamination;
Inserting a coaxial cable through the through-hole and projecting the tip, and then applying resin to the through-hole to fix the coaxial cable to the lamination substrate; and
A step of laminating another lamination substrate via a prepreg on the side opposite to the side where the tip of the coaxial cable protrudes, and heating and pressurizing and integrating,
A method of manufacturing a wiring board, comprising: polishing a surface of the coaxial cable from which a tip protrudes to flatten the end surface of the coaxial cable and the surface of the lamination substrate. .

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