JPH02277286A - Multilayer printed board - Google Patents

Abstract

PURPOSE:To reduce dispersion of characteristic impedance in a signal wiring layer by forming a signal wiring layer at the first main face of insulating base material and an power source layer or an grounding layer at the second main face, and laminating plural sheets of insulating materials through insulating materials so that the first main faces may face each other. CONSTITUTION:A signal wiring layer 4 consisting of a conductor pattern for signal transmission is formed at a first main face 1a of an insulating base material 1, and a power source layer or a grounding layer 2 consisting of a conductor patter for power supply is formed at a second main face 1b which is the reverse side of this first main face 1a, and plural sheets of insulating base materials 1 are laminated through insulating base materials 3 so that the first main faces 1a may face each other. Hereby, the distance between layers 4 and 2, which influence greatly the dispersion of characteristic impedance, becomes a fixed value which is determined by the thickness of the insulating base material 1 without being influences by pressurizing treatment, etc., in manufacturing process, and dispersion of the characteristic impedance in the signal wiring layer 4 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multilayer printed wiring board, and particularly to a multilayer printed wiring board suitable for mounting high-speed semiconductor integrated circuit devices in general-purpose computers and the like.

[Conventional technology]

For example, published by Dempa Shimbunsha, May 20, 1980,
As described in the comprehensive electronic handbook JP1120 to P1123 of the Japan Electronics Machinery Industry Association, multilayer printed wiring boards are used for mounting semiconductor integrated circuit devices such as logic elements and memories in general-purpose computers, etc. is known to be used.

By the way, since these logic elements and memories operate at high speed, the frequency of the electrical signals sent and received between them becomes extremely high, and the characteristic impedance of the signal wiring layer provided on the multilayer printed wiring board that serves as the transmission path for this electrical signal increases. Variations in this result in noise and other disturbances, which greatly affect the performance of the entire electronic computer system.

Conventionally, as such a multilayer printed wiring board, one having a structure as shown in FIG. 4, for example, is known.

That is, the insulating base material 101b insulates a plurality of insulating base materials 101a on which a power supply layer or a ground layer 2 is formed on both the front and back sides, and a plurality of insulating base materials 101b on which a signal wiring layer 4 is formed on both the front and back sides. They are laminated with insulating adhesive sheets 3 interposed therebetween so as to be sandwiched between base materials 101H, and are pressed and bonded at a predetermined temperature using a press technique or the like.

This means that there are two power layers or ground layers with similar conductor pattern densities on both the front and back surfaces of the insulating base materials 101a and 101b.
By forming the signal wiring layer 4, warping and deformation can be prevented.

The characteristic impedance Zo in a multilayer printed wiring board having such a structure is generally determined by the following experimental formula.

Zo "K+ / (Er ・ln (K2 ・B
/W) )"'where, εr: Effective dielectric constant W: Signal wiring width B: Thickness of the insulating layer sandwiching the signal wiring + K2: Experimentally determined coefficient As is clear from the above equation, characteristic impedance The variation in Z0 is determined by ε1.W.

By the way, according to the research of the present inventors, when the thickness B of the insulating layer sandwiching the signal wiring is constant, the characteristic impedance Zo is determined by the distance between the signal wiring layer and the power supply layer or the ground layer shown in Fig. 4. It was found that it changes greatly depending on the value of H.

In other words, Figure 2 shows the change in characteristic impedance of 2° due to a change in B when the value of H is constant, and Figure 3 shows the change in characteristic impedance due to a change in the value of H when the value of B is constant. It shows the change in impedance Z, and as is clear from these diagrams, the thickness B of the insulating layer sandwiching the signal wiring
The distance f between the signal wiring layer and the power supply layer or ground layer
The variation in iH is the characteristic impedance Z. It can be seen that this has a large effect on the variation in

[Problem to be solved by the invention]

However, in the conventional multilayer printed wiring board with the structure shown in Fig. 4, the distance H between the signal wiring layer and the power supply layer or the ground layer has an insulating adhesive that changes due to pressure applied during the manufacturing process. Since the dimensions of the sheet are included, there is a problem in that variations in the path #H, that is, variations in characteristic impedance, tend to increase.

In other words, as stated in the above-mentioned literature,
Adhesive sheets are generally made of glass cloth impregnated with semi-hardened epoxy resin, etc., which softens due to the temperature and pressure during bonding, fills the gap between the insulating base materials in this softened state, and then hardens to form the bond. In order to act,
This is because it is difficult to control the value of H including this adhesive sheet to be constant.

Recently, in response to the demand for further miniaturization and speeding up of electronic computer systems, the density of multilayer printed wiring boards used for mounting has become higher and higher. As gaps between insulating base materials are becoming narrower, variations in characteristic impedance due to the causes mentioned above will become an increasingly important problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a multilayer printed wiring board that can reduce variations in characteristic impedance in a signal wiring layer.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, in the multilayer printed wiring board according to the present invention, a signal wiring layer consisting of a conductive pattern for signal transmission is formed on the first main surface of the insulating base material, and the signal wiring layer is formed on the front and back sides of the first main surface. A power layer or a ground layer made of a conductive pattern for power supply is formed on the second main surface, and a plurality of the insulating layers are arranged so that the first main surface on which the signal wiring layer is formed faces each other. It is constructed by laminating base materials with an insulating material in between.

[Effect]

According to the above-described multilayer printed wiring board of the present invention, the signal wiring layer and the power supply layer or the ground layer are respectively formed on the first and second main surfaces of the two insulating base materials, which are opposite to each other. The distance between the two, which has a large effect on variations in characteristic impedance, remains a constant value determined by the thickness of the insulating base material without being affected by pressure treatment during the manufacturing process, reducing variations in characteristic impedance in the signal wiring layer. can do.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a multilayer printed wiring board according to an embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a multilayer printed wiring board according to this embodiment.

Note that FIG. 1 shows an example of the arrangement of each member as described below before crimping by a press technique or the like.

For example, glass epoxy materials and polyimide materials.

A first principal surface Ia and a second principal surface of each of the plurality of insulating base materials l made of an insulating material such as a ceramic material are opposite to each other.
On the main surface 1b, there is a signal wiring layer 4 made of a conductor pattern for transmitting signals between each other and the outside, such as a semiconductor integrated circuit device (not shown) to be mounted later, and the semiconductor integrated circuit device. A power supply layer or ground layer 2 for supplying operating power to the device is formed by a combination of plating and etching techniques.

Furthermore, these plurality of insulating base materials l are arranged so that the signal wiring layer 4 is on the inside, and the first main surface 1 a s where the signal wiring layer 4 is formed and the power supply layer or ground layer 2
The second main surfaces 1b on which are formed are arranged so as to face each other with an insulating adhesive sheet 3 interposed therebetween.

The adhesive sheet 3 is manufactured by, for example, impregnating glass cloth with a semi-cured epoxy resin.

Then, by pressing the plurality of insulating base materials 1 arranged as shown in FIG. 1 in the stacking direction at a predetermined temperature using a press or the like, the adhesive sheet 3 is softened by the temperature and pressure. In this softened state, it fills the gaps between the plurality of adjacent insulating base materials 1 and then hardens, so that the plurality of adjacent insulating base materials 1 are bonded together to form a multilayer printed wiring board.

Here, as described above, the first main surface 1 of each insulating base material 1
The characteristic impedance Z0 in the signal wiring layer 4 formed in a is caused by a change in the distance H between the signal wiring layer 4 and the power supply layer or the ground layer 2, rather than by a change in the thickness B of the insulating material sandwiching the signal wiring layer 4. more affected.

However, in the case of this embodiment, the signal wiring layer 4 and the power supply layer or ground layer 2 are formed on the first and second main surfaces 1a and 1b of each insulating base material 1, which are opposite to each other. Therefore, the signal wiring layer 4 has a large influence on the variation in characteristic impedance Z0 in the signal wiring layer 4.
The distance H between the power supply layer or the ground layer 2 is the thickness dimension of each insulating base material 1 that does not change even when pressure is applied during the manufacturing process.

As a result, as shown in FIG. 2, even if the value of the thickness B of the insulating material, including the thickness dimension of the highly deformable adhesive sheet 3, changes due to pressure, etc., the signal wiring layer 4 and the power supply Since the distance H to the layer or ground layer 2 is maintained constant, the characteristic impedance Z0 in the signal wiring layer 4 does not vary greatly, and the characteristic impedance Z0 can be controlled to a desired design value.

As a result, for example, when mounting semiconductor integrated circuit devices such as high-speed logic elements and memory elements using the multilayer printed wiring board of this embodiment to configure an electronic computer system, The occurrence of disturbances such as noise in the signal wiring layer 4, which serves as a transmission path for high-frequency electrical signals between the device and the outside, is reliably reduced, and this can contribute to improving the performance of computer systems and the like.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, it goes without saying that the materials constituting the insulating base material, adhesive sheet, etc. are not limited to those exemplified in the above embodiments, but may be other materials having similar functions and performance.

〔Effect of the invention〕

Among the inventions disclosed in this application, the effects obtained by typical inventions are briefly described below.

That is, in the multilayer printed wiring board according to the present invention, a signal wiring layer consisting of a conductive pattern for signal transmission is formed on the first main surface of the insulating base material, and the signal wiring layer is formed on the front and back sides of the first main surface. A power layer or a ground layer made of a conductive pattern for power supply is formed on the second main surface, and a plurality of the insulating layers are arranged so that the first main surface on which the signal wiring layer is formed faces each other. Since the structure is made by laminating base materials with insulating materials in between, the distance between the signal wiring layer and the power supply layer or ground layer, which has a large effect on variations in characteristic impedance, is
A constant value determined by the thickness of the insulating base material is obtained without being affected by pressure treatment during the manufacturing process, and variations in characteristic impedance in the signal wiring layer can be reliably reduced.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of a multilayer printed wiring board according to the present embodiment; FIG. 2 is a diagram showing an example of the relationship between the dimensions of each part of the multilayer printed wiring board and variations in characteristic impedance; Similarly, FIG. 4 is a diagram showing an example of the relationship between the dimensions of each part of a multilayer printed wiring board and variations in characteristic impedance, and FIG. 4 is a sectional view showing an example of the structure of a conventional multilayer printed wiring board. DESCRIPTION OF SYMBOLS 1... Insulating base material, 1a... 1st main surface, 1b... 2nd main surface, 2... Power supply layer or ground layer, 3... Adhesive sheet (insulating material), 4... - Signal wiring layer, B...Thickness of the insulating material sandwiching the signal wiring layer, H...Distance between the power supply layer or ground layer and the signal wiring layer, Zo...Characteristic impedance in the signal wiring layer, 101a, 101b...Insulating base material. Figure 101a Distance between power supply layer or ground layer and signal wiring layer Figure 101a. 101b: Insulating base material

Claims (1)

[Claims] 1. A signal wiring layer consisting of a conductor pattern for signal transmission is formed on the first main surface of the insulating base material, and a signal wiring layer for power supply is formed on the second main surface, which is opposite to the first main surface. A plurality of the insulating base materials are laminated with an insulating material in between so that a power layer or a ground layer made of a conductive pattern is formed, and the first main surface on which the signal wiring layer is formed faces each other. Multilayer printed wiring board.