JPH01194393A - Multilayer interconnection circuit board - Google Patents

Abstract

PURPOSE:To obtain a high-density and multilayer circuit board by using a thick-film and thin-film hybrid substrate and by making the maximum value of signal wiring length in thin film smaller than that of signal wiring length in thin-film. CONSTITUTION:When wiring becomes thinner, conductor resistance becomes higher and signal is attenuated according to exp[-R.l/2 Z0] and does not exceed the threshold. Z0 is characteristics impedance, R is resistance, and l is wiring length. Wiring length of wiring substrate is generally short. Also, generally in precision wiring made by optic processing, wiring resistance becomes relatively large as compared with thick-film resistance. For example, although resistance of a copper wiring with a width of 20mum and a thickness of 2mum is 5ohms/cm or more, resistance of W wire with a width of 100mum and a thickness of 10mum is 1ohms/cm or less and wiring can be made only as much as 1/5 the length of thick-film. W thick-film wirings 2 and 3, thin-film insulation layer 4, and a copper thin-film wiring 5 are piled up on an alumina ceramics 1, allowable amount of signal attenuation is determined, high integration by a thin-film and low-resistance wiring by a thick-film can be made to allow a high-density multi-layer substrate to be formed while retaining transmission characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Nail] The present invention relates to a thin film, thick ys mixed high-density multilayer wiring board.

[Conventional technology]

In order to increase the speed of computers, etc., it is necessary to reduce the signal delay in the semiconductor circuits that are the logic elements, and also to reduce the signal delay (propagation delay time) on the wiring board that connects them. . Due to recent advances in semiconductor technology, the delay in the former is now comparable to that in the latter. In order to reduce signal delay on a wiring board, the distance between elements *1 must be shortened, in other words, a high-density mounting board is required. Such a high-density mounting board satisfies the following requirements. There is a need.

0) High f-degree pattern < fine pattern) is possible.

(2) Good thermal conductivity.

(3) Low conductor resistance.

(4) Desired characteristic impedance Z, (generally 5
The thickness of the insulating layer can be specified relatively freely so as to obtain 0Ω).

etc.

[Problem to be solved by the invention]

However, satisfying all of these requirements at the same time is
Have difficulty. For example, with conventional thin film technology in which patterns are formed by photoetching or the like, high-density wiring is possible, but because the wiring becomes thinner, the thermal conductor resistance increases. If the conductor resistance is high, the signals d g, r7x (-R-t/2Z,
) and will not exceed the threshold level. Here, R is the wiring resistance value per unit length, and t is the wiring length. In order to lower this resistance value, there are methods of widening the wiring width and increasing the thickness of the wiring, but each method has the following drawbacks. Increasing the wiring width requires more layers to accommodate the same amount of wiring, and at the same time, it is necessary to thicken the insulation j- to obtain a constant characteristic impedance. Increasing the thickness of the film in this way is achieved through thin film technology.
This is the direction in which the yield will decrease by ft. Furthermore, increasing the thickness of the wiring itself also increases the difficulty of etching and impairs the flatness of the surface of the next insulating layer.

Next, with thick film technology, it is easy to increase the film thickness and ensure a constant characteristic impedance, but - because the wiring capacity per layer is small, it becomes extremely multi-layered, resulting in disadvantages such as a decrease in yield during firing. becomes.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and provide a high-density multilayer board that takes transmission characteristics into consideration.

[Means to solve the problem]

In order to achieve the above object, the present invention uses a thick film/thin film mixed substrate, and the maximum value of the signal wiring length in the thin film is made smaller than the maximum value of the signal wiring length in the thick film. .

[Effect]

The first factor is the distribution of wiring lengths on a certain wiring board. It can be seen from this that the wiring lengths are not uniformly distributed, and that there are very few long wirings.

Furthermore, in fine wiring formed by optical processing such as photoetching, the wiring resistance is generally much higher than that of thick film resistors. For example, in a thin film copper wiring with a width of 20JFA and a thickness of 2j1yL, the wiring resistance is 5Q.
10n or more, width 100JIFK thickness 10layers mlD
The resistance of the thick film tungsten wiring becomes 1Q/Cm or less. As already noted, the signal is −xp(−R−1/2·
Z. ], so in the above example, the thin film can only be wired as long as 115 of the thick film. In the present invention, the above-mentioned facts are effectively utilized.

[Fu example]

Hereinafter, the present invention will be specifically explained using the drawings.

FIG. 2 shows a cross-sectional view of a multilayer board according to an embodiment of the present invention. Reference numeral 1 is made of alumina ceramics with a thickness of approximately 500 μm, 2 is a power supply layer made of a tungsten conductor, and 3 is a signal wiring made of a tungsten conductor, which is usually a pair of X and Y layers. 4 is approximately 10 μm made of glass, (bolioid), etc.
The thick thin film insulating layer 5 is a signal wiring, which is made of a thin film conductor layer such as aluminum or copper, and like 3, it is usually a pair of an X layer and a y layer. The pitch of 3 is 1001" and the pitch is 4.
50 srN, wiring 4 resistance is 1 (VCm.5
The wiring has a width of 2 (1++ m and a pitch of j '177178
．． The wiring resistance is %5Q/ctyt. Now, if we allow up to 70% attenuation in the wiring, the maximum wiring length for each is
3 will be about 56:rl'L, and 5 will be about 7 cotton. Therefore, in Figure 1, 7 (rllJJ, the lower wiring is 5
With layers of.

It is sufficient to route wiring in a layer of 7 cm or less (Ii!1lt-3). ,7
7% will be wired in 5 layers.

Even if all of this were to be achieved with three layers, a total of 10 signal wiring layers would be required because the wiring density per layer is low. On the other hand, it is clear that it is impossible to realize all of this with five layers due to the condition of signal attenuation.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a high-density multilayer substrate with high integration using a thin film and low resistance wiring using a thick film while maintaining high yield and transmission characteristics.

[Brief explanation of the drawing]

1: To alumina ceramic 2.5: Tungsten conductor, 4: thin film insulating layer, 5: Thin film conductor layer.

Claims (1)

[Claims] 1. In a multilayer wiring board in which an insulating layer and a conductor wiring layer are alternately formed on a ceramic substrate having thick film conductor wiring co-fired with the substrate material on the surface or inside, the signal conductor wiring is optically The maximum length of the signal conductor wiring formed by the optical method is shorter than the maximum length of the signal thick film wiring conductor provided on or inside the ceramic substrate. Multilayer wiring board.