JP2001230508A - Via hole of strip line structure and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board via hole structure which is suitable for high precision matching of characteristic impedance. SOLUTION: In a via hole of a printed wiring board, where a conductor pattern is connected from a surface to the back, the via hole of a strip line structure is formed where a pattern having the same width as a surface layer pattern of the printed wiring board is formed, so as to be continuous with the surface layer pattern along a wall surface of a cylindrical through-hole. The strip line is formed in a spiral shape along the wall surface of the cylindrical through-hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a via hole in a printed wiring board, and more particularly to a via hole having a strip line structure.

[0002]

2. Description of the Related Art Printed wiring boards are important basic components for electronic devices that fix electronic components and provide wiring between the electronic component terminals. Before printed wiring boards were put to practical use, electronic components were mounted on a metal chassis, and terminals were connected by soldering copper wires. Even in the early days of printed wiring boards, single-sided and double-sided boards without through-hole plating were used in the early days. At present, not only a double-sided through-hole board but also a high multilayer board having several tens of layers can be manufactured, and it has almost satisfied various electrical and mechanical requirements for printed wiring boards from electronic devices. . For example, for a high-frequency circuit or a high-speed digital circuit, it has become possible to accurately form a signal line matching a required characteristic impedance.

[0003]

However, for matching characteristic impedance, it is ideal that the line width, the line thickness, the distance between the line and the ground, and the dielectric constant of the insulator interposed between the line and the ground are all uniform. In addition, the structure of the via hole that connects the signal line between the layers by the conventional cylindrical through hole works disadvantageously in the characteristic impedance matching. The present invention has been made to solve the above problems, and has as its object to provide a printed wiring board via hole structure that is convenient for high-precision matching of characteristic impedance.

[0004]

According to the first aspect of the present invention, there is provided a via hole of a printed wiring board for connecting a conductor pattern from a front surface to a rear surface, the via hole having a strip line structure.
A pattern having the same width as the surface layer pattern of the printed wiring board is formed along the wall surface of the cylindrical through hole so as to be continuous with the surface layer pattern.

According to the strip hole structure of the first aspect, since the pattern connecting the front surface and the back surface is continuous with the same width as the surface layer pattern, the characteristic impedance of the pattern can be realized with high precision, and It is possible to meet a high demand for a signal line of a wiring board.

According to a second aspect of the present invention, in the via hole having the strip line structure, a conductor pattern is formed in a spiral shape along the cylindrical wall surface of the through hole.

According to the via hole having the strip line structure according to the second aspect, since the pattern bent portion from the surface layer pattern to the via hole pattern is gentle,
A more accurate characteristic impedance signal line can be realized.

According to a third aspect of the present invention, there is provided a method of manufacturing a via hole of a printed wiring board, wherein a conductive pattern is connected from a front surface to a rear surface.
After drilling a pilot hole at the corresponding via hole in the laminate, cut a spiral groove in the pilot hole with a tapping tool,
Electroless copper plating and electrolytic copper plating are applied to the hole walls and both surfaces of the substrate, and the through-hole is filled with a resin, dried and cured, and then the both surfaces of the substrate are polished and cleaned. Further, the plated copper in the spiral groove portion is left in the through hole by forming an enlarged hole in the through hole filled with the resin.

According to the method for manufacturing a via hole having a strip line structure according to the third aspect, a spiral strip line conductor pattern can be formed in a through hole portion of a printed wiring board. Is obtained.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a via hole of a printed wiring board for connecting a conductive pattern from a front surface to a rear surface.
After manufacturing a conventional through-hole printed wiring board, excess copper in the through-hole is removed by a laser.

According to the method for manufacturing a via hole having a strip line structure according to the fourth aspect, a conductive pattern having a band shape, not a cylindrical shape, can be formed in a through hole portion of a printed wiring board. The obtained pattern shape is obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A via hole having a strip line structure according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic overhead view of a conductor when the inside of a through-hole is viewed from the top surface of a via-hole structure according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an upper hole edge of a printed wiring board through hole, 2 denotes a lower hole edge of the through hole, 3 denotes an upper conductor pattern, 4 denotes a lower conductor pattern, and 5 denotes a conductor pattern in the through hole. The three types of conductor pattern widths are substantially the same and are formed so as to be continuous. Also,
A plurality of conductor patterns can be passed through one through hole, and FIG. 2 shows an example in which four conductor patterns are passed through one through hole.

The material of the substrate of the printed wiring board is suitably a resin containing no glass fiber in consideration of workability. The resin may be any resin as long as it is a resin used for a general printed wiring board. For example, an epoxy resin, a polyimide resin, a Teflon resin, or the like is generally used, and is selected according to a necessary dielectric constant.

Prior to the processing of the via hole, a laminated board is manufactured using the above-mentioned resin with a ground pattern having a clearance provided at a location corresponding to the location of the via hole as an inner layer. The method of manufacturing the laminated board is not different from the method of manufacturing a normal printed wiring board, and thus will not be described in detail. However, as described above, it is necessary to devise a method of increasing the finishing accuracy of the thickness of the laminated board in order to secure the finishing accuracy of the characteristic impedance more than that of a normal printed wiring board because it is a resin containing no glass fiber. As a laminating method for increasing the laminated plate thickness accuracy, a method of laminating a no-flow type prepreg between three resin-coated copper foils as shown in FIG. 3 is simple. In FIG. 3, 6 is a copper foil with resin, 7
Denotes a resin-coated copper foil having a clearance provided with a ground pattern, and 8 denotes a no-flow prepreg.

[0015] After drilling a pilot hole in the corresponding place of the via hole of the laminate prepared above, the tapping tool 9 shown in FIG. 4 and a drilling machine whose rotation angle can be controlled not shown in the figure are used to form a spiral in the pilot hole. A groove is formed. Next, the hole walls and the front and back copper foils are covered with plated copper by applying electroless copper plating and electrolytic copper plating.

After the copper plating is completed, the through holes are filled with a resin, dried and cured, and then polished and cleaned to remove excess resin adhering to the surface of the base material and increase the smoothness of both surfaces of the base material. Only the inside of the through hole is covered with a resin, and the plated copper in the through hole is protected from an etching solution in a later step. Next, a resist process is performed on the front and back surfaces of the base material by a normal printed wiring board manufacturing method to form a conductor pattern.
After the formation of the front and back conductor patterns, the via holes are enlarged and drilled with a drill having a diameter slightly larger (50 to 200 μm) than the prepared hole diameter, so that the plated copper adhered to the prepared hole portion is cut and removed. The resin in the through hole also functions to protect the copper remaining in the through hole from being peeled off by the teeth of the drill during the drilling of the enlarged hole. FIG. 5 is a schematic sectional view of a hole showing the relationship between the size of the pilot hole, the spiral groove, and the enlarged hole. Reference numeral 10 denotes a pilot hole, 11 denotes a spiral groove, 12 denotes an enlarged hole, and 13 denotes a copper plating line in a through hole. And 14 indicate copper plating patterns in the through holes.

The via hole of the strip line structure according to the present invention can be formed not only by the above-mentioned spiral groove processing method, but also by a method of processing a general through-hole cylindrical plated copper and then removing only unnecessary copper by a laser. Can be formed. Further, the conductor pattern in the through hole is not necessarily limited to the spiral shape as described above, and may be a linear shape along the through hole. In the case of processing by laser, it is easier to form a straight line than a spiral line.

[0018]

According to the present invention, a pattern can be formed from a surface layer to another surface layer via holes in a state where the distance to the inner layer ground pattern is constant and the conductor width is substantially constant. In addition, it is possible to design and manufacture a signal line that requires high-precision matching of characteristic impedance using not only one layer but also a plurality of layers.

[Brief description of the drawings]

FIG. 1 is a schematic overhead view of a conductor when a via hole structure according to an embodiment of the present invention is viewed from the upper surface into a through hole.

FIG. 2 is an embodiment of the present invention in which four conductor patterns are passed through one through hole.

FIG. 3 is a schematic view showing lamination with a no-flow type prepreg sandwiched between three resin-coated copper foils.

FIG. 4 is a schematic view showing a tapping tool.

FIG. 5 is a schematic sectional view of a hole showing a relationship among sizes of a pilot hole, a spiral groove, and an enlarged hole.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Printed wiring board through hole upper surface hole edge 2 Printed wiring board through hole lower hole edge 3 Upper surface conductor pattern 4 Lower surface conductor pattern 5 Conductor pattern in through hole 6 Copper foil with resin 7 Copper foil with resin and ground pattern formed with clearance Reference Signs List 8 No-flow prepreg 9 Tapping tool 10 Preparatory hole 11 Spiral groove 12 Enlarged hole 13 Copper plating line in through hole 14 Copper plating pattern in through hole

Claims (4)

[Claims] In a via hole of a printed wiring board for connecting a conductor pattern from the front surface to the back surface, a pattern having the same width as the surface layer pattern of the printed wiring board is connected to the surface layer pattern along the wall surface of the cylindrical through hole. A via hole having a strip line structure, characterized in that the via hole is formed. 2. A conductor pattern formed spirally along a cylindrical wall surface of a through hole.
Via hole with stripline structure as described. 3. A method of manufacturing a via hole of a printed wiring board for connecting a conductor pattern from a front surface to a back surface, wherein a drilled hole is drilled at a portion corresponding to the via hole of the laminated board, and then a spiral groove is formed in the prepared hole by a tapping tool. Cutting, applying electroless copper plating and electrolytic copper plating on the hole wall and both sides of the base material, filling and drying and curing the resin in the through holes, polishing and cleaning both sides of the base material, performing resist treatment on the front and back of the base material, and performing surface treatment. A method for manufacturing a via hole having a strip line structure, wherein a pattern is formed, and the plated copper in the spiral groove portion is left in the through hole by forming an enlarged hole in the resin filled through hole. 4. A method of manufacturing a via hole of a printed wiring board for connecting a conductive pattern from the front surface to the back surface, wherein a conventional through hole printed wiring board is manufactured, and then excess copper in the through hole is removed by a laser. A method of manufacturing via holes having a strip line structure.