JPH05167258A - Multilayer wiring board - Google Patents

Abstract

PURPOSE:To enable a signal transmission line to be set uniform in characteristic impedance and prevent delay and malfunction caused by the reflection of signal. CONSTITUTION:Recessed holes 126 and 127 whose ends are open on the rear side are made just under a terminal connection pad 121 and a surface wiring layer 122 located on the component mounting surface of a multilayer wiring board. Holes 128 and 129 are made between the base of the recessed hole 126 or 127 and the terminal connection pad 121 or the surface wiring layer 122 respectively, and rigid coaxial cables 130 and 140 and their conductors 131 ands 141 are inserted into the recessed holes 126 and 127 and the holes 128 and 129 respectively. Furthermore, the conductors 131 and 141 are connected to the terminal connection pad 121 and the surface wiring layer 122 respectively. In a multilayer wiring board 120 constituted as above, signals are inputted into the terminal 111 of an LSI 110 through the terminal connection pad 121 or transmitted to the surface wiring layer 122 through the intermediary of the conductors 131 and 141 of the rigid coaxial cables 130 and 140.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer wiring board, and more particularly to a multi-layer wiring board used in a multi-chip package having input / output pins on a surface mounting surface of a component and an opposite back surface.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional example of a multilayer wiring board used in a multi-chip package or the like. On the component mounting surface of the multi-layer wiring board 410, surface wiring composed of a surface wiring layer (or a pad for terminal connection) 411 is provided, and on the back surface thereof, input / output pins 416 are provided.
The transmission path of the input / output signal between the surface wiring layer 411 and the input / output pin 416 is a signal wiring layer 412 inside the multilayer wiring substrate 410, or a ground layer 413 and a through-hole-shaped interlayer formed between the layers. This is performed via the wiring 414.

[0003]

However, in the above-mentioned conventional multilayer wiring board, signal transmission between the surface wiring layer and the input / output pins is performed via the internal signal wiring layer and the interlayer wiring as described above. The characteristic impedance (Z0) in the signal transmission path in the thickness direction between the component mounting surface and the back surface is non-uniform, and signal reflection easily occurs. For this reason, when the substrate is multi-layered and thickened, or when the signal operation speed is increased, signal delay and malfunction occur, which makes it difficult to transmit signals accurately.

Therefore, an object of the present invention is to provide a multilayer wiring board capable of preventing signal delay and malfunction due to non-uniformity of characteristic impedance of a signal transmission path in the thickness direction and performing accurate signal transmission. To provide.

[0005]

According to the present invention, a recessed hole in which a plating film on the inner surface is connected to an inner ground layer, and a rigid coaxial cable provided between the bottom surface of the recessed hole and the surface wiring. And connecting the rigid coaxial cable inserted into the concave hole and the through hole to the surface wiring, and further connecting the plating film to the shield of the rigid coaxial cable. A multilayer wiring board having That is, in this multilayer wiring board, the plated film on the inner surface is connected to the inner ground layer, and a concave hole having a size into which the rigid coaxial cable can be inserted is provided from the back surface of the board.

According to the present invention, the plating film on the inner surface has a through hole connected to the inner ground layer, the rigid coaxial cable inserted into the through hole is connected to the surface wiring, and the plating film is further formed. Is connected to the shield of the rigid coaxial cable to obtain a multilayer wiring board. That is, this multilayer wiring board is provided with a through hole having a size such that the plating film on the inner surface is connected to the inner ground layer and the rigid coaxial cable can be inserted.

Further, according to the present invention, in the multilayer wiring board in which the front surface wiring and the input / output pins on the back surface are directly connected by the core wires, the core wires are the core wires within a range excluding the vicinity of the front and back surfaces of the multilayer wiring board. Is covered with a dielectric in a concentric cylindrical shape with the central axis as a central axis, the outside of the dielectric is covered with a shield, and the shield is connected to a ground layer of an inner layer, can get. That is, this multilayer wiring board has a core wire that connects the front surface wiring and the input / output pin on the back surface, a dielectric that is concentric in a cylindrical shape with the core wire as a central axis, and covers the core wire. It is provided with a coaxial cable consisting of shields connected to layers.

[0008]

By configuring the signal transmission path in the thickness direction between the component mounting surface and the back surface with the coaxial cable, the characteristic impedance in the signal transmission path becomes uniform and continuous, and signal reflection hardly occurs. Therefore, even if the substrate becomes multi-layered and becomes thicker or the signal operation speed becomes faster, delay or malfunction due to signal reflection is less likely to occur, and signal transmission can be performed accurately.

[0009]

EXAMPLES Examples of the present invention will be described below. 1 is an embodiment of the present invention as set forth in claim 1 and is a cross-sectional view of a multilayer wiring board when an LSI is mounted. 2 and 3 are sectional views showing embodiments of the present invention according to claims 2 and 3, respectively.

In the multilayer wiring board 120 shown in FIG. 1, recessed holes 126 and 127 opening to the back side are provided immediately below the terminal connecting pads 121 on the component mounting surface and the desired surface wiring layer 122. There is. Recessed holes 126, 12
7 is a size into which the rigid coaxial cables 130 and 140 can be inserted. The inner surfaces of the concave holes 126 and 127 are plated with metal to form plated films 124 and 125. These plated films 124 and 125 are respectively connected to the inner ground layer 123 and have a ground potential.

The length between the bottom surface of the concave hole 126 or 127 and the terminal connecting pad 121 or the surface wiring layer 122 is not destroyed even when a component is mounted on the component mounting surface, and the plating films 124 and 125 are formed. Is preferably as short as possible, as long as it does not contact the terminal connection pad 121 or the surface wiring layer 122.

Further, between the bottom surface of the concave hole 126 or 127 and the terminal connecting pad 121 or the surface wiring layer 122, the core wire 1 of the rigid coaxial cable 130, 140 is provided.
Holes 128 and 129 are formed to allow the passage of 31, 141. In these holes 128, 129, the rigid coaxial cables 130, 140 and their core wires 131, 14 are placed.
1 is inserted. The core wires 131 and 141 are further connected to the terminal connection pad 121 and the surface wiring layer 122, respectively.

In the multilayer wiring board 120 having the above structure, signals are transmitted through the core wires 13 of the rigid coaxial cables 130 and 140.
1, 141, through the terminal connection pad 121
It is input / output to / from the terminal 111 of the SI 110 or transmitted to the surface wiring layer 122. The shields 132 and 142 on the outer periphery of the rigid coaxial cable are plated films 124 and 125 on the surfaces of the concave holes 126 and 127 of the multilayer wiring board 120.
It is in contact with, and is at the ground potential.

In FIG. 2, a through hole 226 is provided near the surface wiring layer (or terminal connecting pad) 212 of the multilayer wiring board 210. The through hole 226 has a size such that the rigid coaxial cable 220 can be inserted therein. The inner surface of the through hole 226 is plated with metal to form a plated film 214. The plating film 214 is connected to the inner ground layer 213 and has a ground potential. The rigid coaxial cable 220 is inserted into the through hole 226. The core wire 221 of the rigid coaxial cable 220 is drawn out to the component mounting surface and connected to the surface wiring layer (or terminal connection pad) 212.

In the multilayer wiring board 210 having this structure, signals are transmitted from the outside to the core wire 22 of the rigid coaxial cable 220.
Surface wiring layer (or terminal connection pad) 2
Input / output to / from 12. The shield 222 on the outer periphery of the rigid coaxial cable 220 has the through hole 2 of the multilayer wiring board 210.
It contacts the plated film 213 on the surface of 26 and has a ground potential.

In FIG. 3, the surface wiring layer (or the terminal connecting pad) 312 of the multilayer wiring board 310 and the input / output pin 316 are directly connected by a core wire 311. In addition, in the range excluding the vicinity of the front and back surfaces inside the multilayer wiring board 310, the outer circumference of the core wire 311 is covered with a dielectric 315 in a concentric cylindrical shape with the core wire 311 as the central axis. Dielectric 3
The outside of 15 is covered with a shield 314 made of a metal layer. The shield 314 is connected to the ground layer 315 inside the multilayer wiring substrate 310 and has a ground potential.

The length between the front surface or the back surface of the multilayer wiring board 310 and the shield 314 is as long as possible, as long as the shield 314 does not come into contact with the front surface wiring layer (or the terminal connection pad) 312 or the back surface input / output pin 316. It is preferable to shorten it. And these core wires 311,
The dielectric 315 and the ground potential shield 314 form a coaxial cable.

[0018]

As described above, in the multilayer wiring board of the present invention, the characteristic impedance is uniform and continuous because the signal transmission path in the thickness direction between the component mounting surface and the back surface is constituted by the coaxial cable. Therefore, signal reflection is unlikely to occur. Therefore, even if the substrate becomes multi-layered and becomes thicker, or the signal operation speed becomes faster, delay and malfunction due to signal reflection are less likely to occur, and the signal can be accurately transmitted.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view of another embodiment of the present invention.

FIG. 3 is a sectional view of another embodiment of the present invention.

FIG. 4 is a sectional view of a conventional example.

[Explanation of symbols]

 110 LSI 111 LSI terminal 120, 210, 310, 410 Multi-layer wiring board 121 Terminal connection pad 122, 212, 312 Surface wiring layer 123, 213, 313, 413 Ground layer 124, 125, 214 Plating film 126, 127 Recessed hole 130 , 140, 220 Rigid coaxial cable 131, 141, 221, 311 Core wire 132, 142, 222, 314 Shield 226 Through hole 316, 416 Input / output pin

Claims (3)

[Claims] 1. A plated film on an inner surface has a concave hole connected to an inner ground layer, and a through hole for a core wire of a rigid coaxial cable provided between a bottom surface of the concave hole and surface wiring. A multi-layer wiring board characterized in that a rigid coaxial cable inserted into the recessed hole and the passage hole is connected to the surface wiring, and further the plating film is connected to a shield of the rigid coaxial cable. 2. The plated film on the inner surface has a through hole connected to the inner ground layer, the rigid coaxial cable inserted into the through hole is connected to the surface wiring, and the plated film is further connected to the rigid coaxial cable. A multilayer wiring board characterized by being connected to the shield of. 3. In a multilayer wiring board in which front surface wiring and input / output pins on the back surface are directly connected by a core wire, the core wire is concentric with the core wire as a central axis in a range excluding the vicinity of the front and back surfaces of the multilayer wiring board. A multilayer wiring board, which is covered with a dielectric in a cylindrical shape, the outside of the dielectric is covered with a shield, and the shield is connected to an inner ground layer.