JPH0353795B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a circuit board, and particularly to a circuit board suitable for high-density mounting of integrated circuits that perform high-speed switching operations, such as in high-speed computers.

(Prior Art) An example of a conventional circuit board of this type includes a first ground layer or a plurality of first ground layers and a first
A ceramic substrate having a power supply layer is provided with contact pins on the entire surface or almost the entire surface of one surface, and pads electrically connected to these contact pins are provided on the other surface, and polyimide is formed on the pad layer. At least one signal layer is formed therebetween.

(Problems to be Solved by the Invention) In such a conventional configuration, the distance between the signal layer and the ground layer or power layer is large, so the characteristic impedance of the signal line is high and crosstalk noise between the signal lines is high. The problem is that it is large.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a circuit board that reduces crosstalk noise between signal lines.

(Means for Solving the Problems) To this end, the circuit board of the first aspect of the present invention is made of one of the ceramic substrates each having one or more first ground layers and a first power layer in the inner layer. A contact pin is provided on the entire surface or substantially the entire surface of the contact pin, and a pad to which the contact pin is electrically connected is provided on the other surface, and at least one signal layer is provided on the pad via polyimide, A third ground or power supply layer is formed on the uppermost layer of the signal layer via the polyimide.

Further, the circuit board of the second aspect of the present invention has one or more first ground layers and a first
A ceramic substrate having a power supply layer is provided with a contact pin on the entire surface or almost the entire surface of one surface, and a pad electrically connected to the contact pin is provided on the other surface, and a mesh is provided on the same layer as the pad. a second ground or power layer on top of the layer, at least one signal layer via polyimide, and a third ground or power layer on the top layer of the signal layer via the polyimide, respectively. It is characterized by the fact that it has been formed.

(Example) Referring to FIG. 1 showing a sectional view of an example of the second invention, this example is a ceramic substrate having a first ground layer G1 and a first power layer P1 in the inner layer. A contact pin CP is provided on the entire bottom surface of the CB, and a pad PD is electrically connected to the contact pin CP via a through hole TH on the entire top surface, and a mesh-shaped second power supply is provided on the same layer as the pad PD. A first signal layer S1 and a second signal layer S2 each having a polyimide PI as an insulating layer are formed on the second power supply layer P2, and a first signal layer S1 and a second signal layer S2 are formed on the second signal layer S2 via the polyimide PI. Second ground layer G
2 are formed respectively. Polyimide PI is a high-quality insulator with high insulation properties and low dielectric constant, and is often used in this type of circuit board.

Although not shown, an integrated circuit chip is mounted on the second ground layer G2, and the first signal layer S
1, second signal layer S2, first power supply layer P1, second
power supply layer P2, first ground layer G1 and second
It is connected to the ground layer G2 through a through hole.

As is clear from Figure 1, the ceramic substrate
Since the second power supply layer P2 is interposed between CB and polyimide PI, both are electromagnetically shielded.
Therefore, the effective relative permittivity ε _re of the first signal layer S1 and the second signal layer S2 is approximately equal to the relative permittivity of polyimide. First signal layer S1
The propagation delay time T (ns/m) of the signal in the second signal layer S2 is generally expressed by the following equation, so T=3.335√ _re The propagation delay time T increases as the effective permittivity ε _re decreases. You can see that it becomes smaller.

Further, the first signal layer S1 and the second signal layer S
2 is covered with the second ground layer G2 and the second power supply layer P2 on its upper and lower sides, so that the first signal layer S
The distance between the first and second signal layers S2 and the ground layer or power supply layer is reduced, the characteristic impedance is reduced, and crosstalk noise between signal lines is reduced.

An embodiment of the first invention is shown in FIG.
This can be easily illustrated by a diagram in which the second power supply layer P2 is removed.

Also in this case, due to the presence of the second ground layer G2, the first signal layer S1 and the second signal layer S
2 and the ground layer becomes smaller, the characteristic impedance decreases, and crosstalk noise between signal lines decreases.

However, since there is nothing to electromagnetically shield the ceramic substrate CB and polyimide PI,
The signal propagation delay times in the first signal layer S1 and the second signal layer S2 remain almost the same as in the conventional case.

In all the embodiments described above, the first
The power supply layer P1 and the first ground layer G1 each have a single layer, but they may have multiple layers.

In addition, the second power layer P2 and the second ground layer G
2 may be exchanged with each other, and both layers may be a power supply layer or a ground layer.

(Effects of the Invention) According to the present invention, by employing the above configuration, crosstalk noise between signal lines is reduced,
It becomes possible to obtain a circuit board suitable for mounting integrated circuits that perform high-speed switching operations at high density.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the second invention. CB...ceramic substrate, PI...polyimide,
CP...Contact pin, PD...Packed, P1...
...First power layer, P2... Second power layer, G1...
...first ground layer, G2...second ground layer, S1...first signal layer, S2...second signal layer.

Claims (1)

[Claims] 1. A ceramic substrate having one or more first ground layers and a first power supply layer in its inner layers, contact pins on the entire surface or almost the entire surface of one surface, and contact pins on the entire surface or substantially the entire surface of one surface, and Each surface is provided with a pad electrically connected to the contact pin, at least one signal layer is formed on the pad through polyimide, and a third signal layer is formed on the top layer of the signal layer through polyimide. A circuit board characterized by forming a ground layer or a power layer. 2 A ceramic substrate each having one or more first ground layers and a first power supply layer in its inner layer has contact pins on the entire surface or almost the entire surface of one surface, and the contact pins and the other surface on the other surface. A mesh-shaped second ground or power layer is provided on the same layer as the pad, at least one signal layer is provided on the layer through polyimide, and a second ground or power layer is provided on the same layer as the pad. A circuit board characterized in that a third ground or power layer is formed on the uppermost layer via the polyimide.