JP2003046260A - Multilayer circuit board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately inhibit high-frequency noise without mounting a capacitor to a multilayer circuit board, by easily increasing capacitance in the capacitor using the interlayer insulating layer of the multilayer circuit board as a dielectric layer, and by increasing and reducing the density and thickness of a circuit, respectively. SOLUTION: In the multilayer circuit board, a polyimide film 14 is sandwiched by ground and power supply layers 13 and 15, and a lamination structure comprising a glass epoxy insulating layer 11 for covering them is included.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer circuit board which is less likely to generate high frequency noise and is suitable for increasing the density and size of a circuit, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, in a multilayer circuit board used in electronic equipment, high frequency noise is generated in a power supply due to switching of the circuit, etc. Therefore, in order to remove this high frequency noise, a capacitor should be provided in the circuit. The characteristic impedance is reduced by adding the capacitance and increasing the capacitance.

However, the required number of capacitors to be mounted must be increased as the circuit becomes higher in density and finer, and therefore, the density of the circuit and finer the circuit are impeded.

In order to increase the capacitance, the thickness of the insulating layer corresponding to the capacitor dielectric layer is reduced, the area is increased, or the dielectric constant of the insulating layer material is increased. It is necessary to take the means of.

However, if the means for increasing the area is adopted and the outer shapes of the circuit boards are the same, the number of layers used for obtaining the capacitance must be increased, which immediately increases the cost. Will be tied to.

Therefore, other means, that is, reducing the layer thickness of the interlayer insulating layer or improving the dielectric constant of the insulating layer material is adopted.

Conventionally, in a structure for obtaining capacitance by using an insulating layer in a multilayer circuit board as a capacitor dielectric layer,
As a means for increasing the capacitance, a technique of reducing the thickness of the interlayer insulating layer between the power supply layer and the ground layer has been proposed (see Japanese Patent No. 2738590).

FIG. 5 is a side sectional view showing a known multi-layer circuit board for explaining a conventional technique. In the figure,
Reference numeral 1 is an insulating layer made of a glass epoxy composite material, 2 is a signal layer, 3 is a ground layer, and 4 is a power supply layer.

In the above-mentioned known invention, the ground layer 3
Also, when a glass epoxy composite material is used for the capacitor dielectric layer sandwiched between the power supply layer 4 and an insulating layer of less than 50 [μm] is formed of this material, reliability of insulation and uniformity of layer thickness are realized. In addition, when industrially mass-produced, defects due to defects in the insulating layer increase, and there is a problem that stable production is difficult with a high production yield.

Furthermore, in order to increase the capacitance, an attempt is made to increase the dielectric constant by mixing an inorganic ferroelectric material into the material. However, in such a case, the mechanical strength of the material is lowered and the product There is a big problem that it is difficult to maintain reliability and stable industrial production.

[0011]

SUMMARY OF THE INVENTION In the present invention, a capacitor having an interlayer insulating layer of a multilayer circuit board as a dielectric layer in order to suppress high frequency noise well without mounting the capacitor on the multilayer circuit board. It is possible to easily increase the capacitance in the circuit, and to increase the density and miniaturization of the circuit.

[0012]

In the present invention, the glass epoxy composite material layer employed in the above-mentioned known invention has a layer thickness of 100 [μm] to 50 [μm], whereas
As a result of repeatedly selecting and evaluating a material having a stable insulating property with a thickness of less than 0 [μm], it was found that the polyimide film is the best.

FIG. 1 is a cutaway side view of an essential part showing a multilayer circuit board for explaining the principle of the present invention. In FIG.
Reference numeral 1 is an insulating layer made of a glass epoxy composite material, 12 is a signal layer, 13 is a ground layer, 14 is an insulating layer made of polyimide, that is, a polyimide film, and 15 is a power supply layer.

In the present invention, as described above, the ground layer 1
3 and the insulating layer sandwiched between the power supply layer 15 and the polyimide film 14 reduce the thickness to increase the capacitance and the circuit inductance.

By the way, in the illustrated multilayer circuit board,
With the polyimide film 14 acting as the dielectric layer of the capacitor, there are problems that must be resolved.

That is, since the multilayer circuit board shown in the drawing shows only a part, the ground layer 13 and the power supply layer 15, which have a larger area than the signal line, contact the entire surface of the polyimide film 14. It looks like
Since it is patterned similarly to the signal line and has a linear shape, the polyimide film 14 is directly adhered to the insulating layer 11 made of the glass epoxy composite material on the side of the linear ground layer 13 and the power supply layer 15. Must.

However, the polyimide film 14
Has weak adhesion to other materials, and of course, the same applies to the insulating layer 11 made of a glass epoxy composite material. It is very advantageous in terms of compatibility with, material cost, manufacturing cost, etc., and is indispensable at present.

In the present invention, as the polyimide film, one having thermoplastic adhesiveness on both surfaces is used, and the insulating layer made of glass epoxy composite material is formed by forming irregularities on those surfaces to make them rough. The basic idea is to improve the adhesion with.

By adopting the above means, it becomes possible to use a polyimide film for the insulating layer which acts as the dielectric layer of the capacitor, and therefore its thickness can be made thinner than the conventional one. It is possible to realize a large capacitance, reduce circuit inductance, improve insulation reliability, and eliminate the need for a capacitor that was conventionally mounted to remove high frequency noise. Can greatly contribute to realization.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a sectional side view showing the essential parts of a multi-layer circuit board in the process steps for explaining the basic embodiment of the present invention. I will explain. Incidentally, in the present invention, since the adhesion between the polyimide film and the epoxy resin of the glass epoxy composite material layer is emphasized, that portion is mainly shown.

See FIG. 2A. (1) A thermoplastic polyimide film 22 having a thickness of 25 μm, at least one surface of which is roughened, has a thickness of 18 μm.
The electrolytic copper foils 21 and 23 are laminated so that the temperature is 3
The temperature is set to 00 [° C.] and a pressure of 5 [MPa] is applied to perform thermocompression bonding to prepare a polyimide film double-sided copper clad board material.

See FIG. 2B. (2) By applying the lithography technique, the copper foil 2
Patterning 1 and 23 is performed to form a ground layer and a power supply layer.

In the drawing, the cut surface of the portion where the ground layer and the power supply layer formed by patterning the copper foils 21 and 23 does not exist is shown. Therefore, the unevenness of the copper foils 21 and 23 is transferred to the surface and the rough surface is formed. Only the thermoplastic polyimide film 22 is shown.

Referring to FIG. 2C, (3) a polyimide film 22 having a ground layer and a power supply layer is laminated so as to be sandwiched between epoxy resin layers 24, and other necessary layers such as a signal layer are laminated together to form a laminated layer. A multilayer circuit board is formed by applying pressure in a pressing process.

According to the same process as described above, 10 identical multilayer circuit boards are manufactured, and a thickness of 50 is separately prepared.
Using a glass-epoxy composite material double-sided copper clad board of [μm], 10 multi-layer circuit boards were prepared as comparative examples by the same steps as those described above, and 120 [° C.] 85 [%] RH 20 [V ] As a result of performing the insulation reliability evaluation for 100 hours, in the comparative example using the glass epoxy composite material layer between the power supply layer and the ground layer, the insulation resistance of the substrate is 10 [MΩ] or less and While there were 6 points judged to be non-defective, all of the multilayer circuit boards of the present invention maintained the insulation resistance unchanged from that before the test.

FIGS. 3 and 4 are side sectional views showing essential parts of a multilayer circuit board in process steps for explaining a specific embodiment of the present invention. While explaining.

See FIG. 3 (1) Copper wirings 31A and 31B in which copper foils attached to both front and back surfaces are processed into a required pattern by applying a lithography technique.
A polyimide film 32 having is prepared.

(2) Prepare glass epoxy composite layers 33 and 34 in a semi-cured state called prepreg.

(3) Copper wiring 35 in which copper foils attached to both front and back surfaces are processed into a required pattern by applying a lithographic technique.
Glass epoxy composite layer 36 with A and 35B and glass epoxy composite layer 38 with copper wiring 37A and 37B
To prepare.

(4) As shown in the figure, the glass epoxy composite material layer 36, the glass epoxy composite material layer 33, the polyimide film 32, the glass epoxy composite material layer 34, and the glass epoxy composite material layer 38 are stacked in the above order.

(5) A multilayer circuit board is formed by integrating the stacked layers by a collective laminating press process using a vacuum heating press. A multilayer circuit board having 6 wiring layers is formed.

The multi-layer circuit board formed by the above process has six wiring layers, and the glass epoxy composite material layers 33 and 34 in the semi-cured state are cured.

(6) Thereafter, through holes are formed by drilling, and conductive connection between wiring layers is made by plating or the like.

[0034]

In the multilayer circuit board according to the present invention,
A laminated structure including a resin insulating layer sandwiching a polyimide film between a ground layer and a power supply layer and covering them is included.

By adopting the above structure, it becomes possible to use a polyimide film for the insulating layer which acts as the dielectric layer of the capacitor, and therefore its thickness can be made thinner than the conventional one. It is possible to realize a large capacitance, reduce the circuit inductance, improve the insulation reliability, and eliminate the need for a capacitor that was conventionally mounted to remove high frequency noise. Can greatly contribute to realization.

[Brief description of drawings]

FIG. 1 is a cutaway side view showing a main part of a multilayer circuit board for explaining the principle of the present invention.

FIG. 2 is a side sectional view showing a main part of a multi-layer circuit board at a process step for explaining an embodiment of the present invention.

FIG. 3 is a side sectional view showing a main part of a multilayer circuit board at a process step for explaining a specific embodiment according to the present invention.

FIG. 4 is a side sectional view showing an essential part of a multi-layer circuit board at a process step for explaining a specific embodiment of the present invention.

FIG. 5 is a cutaway side view of a main part of a known multilayer circuit board for explaining a conventional technique.

[Explanation of symbols]

11 Insulating Layer Made of Glass Epoxy 12 Signal Layer 13 Ground Layer 14 Insulating Layer Made of Polyimide (Polyimide Film) 15 Power Supply Layer

Claims (3)

[Claims] 1. A multi-layer circuit board comprising a laminated structure including a resin film sandwiching a polyimide film between a ground layer and a power supply layer and covering them. 2. A step of thermocompression sandwiching a rough surface of a copper foil having a roughened surface with a rough surface side facing a polyimide film, followed by thermocompression bonding, and then patterning the copper foil to form a ground layer and a power supply. A polyimide layer on which the concavities and convexities of the copper foil are transferred while forming the layer.
A step of exposing a part of the film, and then a resin insulation layer covering a ground layer, a power supply layer and a part of the exposed polyimide film, and further stacking a required layer such as a signal layer and performing a collective lamination press. And a step of forming a multilayer circuit board. 3. The method for manufacturing a multilayer circuit board according to claim 2, wherein the other resin insulation layer of the polyimide film is a glass epoxy composite material layer.