JPH0555752A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To provide a method of preventing the generation of lamination voids, enhancing the accuracy of the thickness of an insulation layer and preventing copper transfer. CONSTITUTION:An insulation board 13b having a conductor pattern 13a made of a copper foil is heated and pressed so that the conductor pattern 13a is buried in the insulation board 13b. Then, after the surface of the conductor pattern 13a and the surface of the insulation board 13b are placed flash, glass cloth is impregnated with liquid resin and a prepreg 12 dry-to-the touch and a copper film 11 are overlapped, heated, pressed and laminated, which makes it possible to prevent the resin contained in the prepreg 11 from being supplied between the inner layer conductor patterns 13a and form an insulation layer portion between an outer conductor pattern of a multilayer printed wiring board and the inner layer conductor pattern 13b in a further equalized and smooth fashion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board which is widely used in various electronic devices for industrial use and consumer use.

[0002]

2. Description of the Related Art In recent years, with the spread of personal computers, word processors, video-integrated cameras, mobile phones, etc., the demand for multilayer printed wiring boards has been increasing more and more. Mainly because of reasons such as noise reduction for electronic devices becoming smaller, lighter and more multifunctional, and for increasing the frequency range used. For multilayer printed wiring boards, the wiring board thickness is reduced and the electrical characteristics are stable. In order to improve the insulating property between the high-density conductor patterns for stabilizing the dielectric constant and increasing the wiring density by improving the layer spacing for improving the insulating layer thickness accuracy, in manufacturing a multilayer printed wiring board, The lamination process of heating and pressurizing a plurality of inner layer materials that fulfills those requirements is a very important process.

A stacking method using an inner layer material, prepreg and copper foil in a conventional multilayer printed wiring board will be described below.

FIG. 2 shows a conventional method for manufacturing a multilayer printed wiring board. In FIG. 2, 1 is a copper foil, 2 is a prepreg, 3 is an inner layer material, 3a is a conductor pattern for an inner layer, 3b is an insulating substrate for an inner layer, 4 is a cavity (hereinafter, referred to as a laminated void), and 5 is an inside. It is a multi-layer copper clad laminate having a conductor pattern on.

A method of laminating the multilayer printed wiring board having the above structure will be described below.

First, as shown in FIG. 2A, a glass cloth-based epoxy resin laminated plate or the like is used as an insulating substrate, and copper foil is laminated on both sides of the insulating substrate. Forming an etching resist by using a method such as a photo method or a photographic method, etching with a solution of cupric chloride or ferric chloride, and then peeling the etching resist to form the conductor pattern 3a for the inner layer. The inner layer material 3 for a multilayer printed wiring board is obtained.

Next, as shown in FIG. 2B, the inner layer material 3
Inner layer conductor pattern 3 formed on the insulating substrate 3b of
An inner layer material 3 whose surface is a is oxidized, a prepreg 2 in which a glass cloth is impregnated with an epoxy resin to semi-harden the resin, and a copper foil 1 for forming a conductor pattern of the outermost layer are superposed. Then, it is set by sandwiching it in a heat press machine such as a stainless steel plate, heated and pressed to melt, cool and solidify the inner layer material 3, the prepreg 2 and the copper foil 1, and then to the inside as shown in FIG. 2 (c). A multilayer copper clad laminate 5 having a conductor pattern 3a is obtained.

[0008]

However, in the above-mentioned conventional method, the prepreg 2 is softened / heated during heating / pressurization.
There is a risk that the molten resin does not flow sufficiently between the conductor patterns 3a of the inner layer material 3 and the laminated voids 4 are formed between the inner layer conductor patterns 3a inside the multilayer copper clad laminate 5 after cooling and solidification. Have The laminated voids 4 inside the multilayer copper clad laminate 5 significantly affect the electrical performance such as the dielectric constant between the layers of the multilayer printed wiring board.

Further, as the resin in the prepreg 2 is filled between the conductor patterns 3a of the inner layer material 3, the conductor pattern 3a of the inner layer material 3 is sparsely and densely isolated, so that insulation between the conductor pattern 3a and the copper foil 1 is achieved. There is a problem that the layer thickness becomes non-uniform in the multilayer copper clad laminate 5. This means that when the conductor pattern for the inner layer is relatively sparse, most of the resin that constitutes the prepreg is applied to the space between the conductor pattern for the inner layer and the insulating substrate, so the absolute amount of resin is Insufficient, the glass cloth constituting the prepreg will come into contact with the conductor pattern for the inner layer without interposing the resin, leading to a decrease in the adhesive force between the prepreg and the conductor pattern of the inner layer material, After stacking
In addition to causing interlayer delamination of the insulating layer due to heating in the process or rapid heating during mounting and soldering of electronic components in the electronic device manufacturing process, depending on the voltage and operating environment during operation of the electronic device, The copper of the copper foil that constitutes the conductor pattern is ionized, and copper ions move at the interface between the glass fiber and the resin that constitutes the glass cloth, inducing insulation deterioration between the conductor patterns for the inner layer, and finally the conductor pattern. It is also a factor that promotes copper migration, which leads to short circuits.

In order to prevent these, it is necessary to properly use prepregs having different resin contents or to partially use prepregs having different resin contents in accordance with the density of the conductor pattern of the inner layer material. In the manufacture of wiring boards, it is extremely difficult to implement, which significantly reduces productivity and makes prepreg storage and management complicated.

The present invention solves the above-mentioned conventional problems, and provides a method for manufacturing a multilayer printed wiring board that prevents the occurrence of laminated voids, improves the accuracy of insulating layer thickness, and prevents copper migration. The purpose is to

[0012]

In order to achieve this object, a method of manufacturing a multilayer printed wiring board according to the present invention comprises heating and pressurizing an insulating substrate having a conductor pattern to embed the conductor pattern in the insulating substrate. After leveling the surface of the conductor pattern and the surface of the insulating substrate, the insulating substrate is laminated by heating and pressing the prepreg and the copper foil which are impregnated with the liquid resin in the glass cloth and dried by touching. Have a configuration.

[0013]

With this structure, the resin contained in the prepreg is not supplied between the conductor patterns for the inner layer, and the insulating layer portion between the conductor pattern for the outer layer and the conductor pattern for the inner layer of the multilayer printed wiring board is more effectively removed. It can be formed uniformly and flatly.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a stacking process of a multilayer printed wiring board according to an embodiment of the present invention. In FIG. 1, 11 is a copper foil, 12 is a prepreg, 13 is an inner layer material, 13a is a conductor pattern for the inner layer, 13b is an insulating substrate for the inner layer, and 15 is a multilayer copper clad laminate after lamination.

A method of manufacturing the multilayer printed wiring board having the above structure will be described with reference to FIG.

First, an etching resist is formed on a copper foil surface of a copper clad laminate using a glass cloth base epoxy resin laminate as an insulating substrate by a conventional method such as a screen printing method or a photographic method. 2 After etching with a solution of copper or ferric chloride, the etching resist is peeled off, and the inner layer conductor pattern 13a is formed on the inner layer insulating substrate 13b.
Is formed to obtain an inner layer material 13 for a multilayer printed wiring board having conductor patterns 13a for the inner layer on the upper and lower surfaces.

Next, as shown in FIG. 1A, the inner layer material 13 having the conductor patterns 13a for the inner layer on the upper and lower surfaces thereof is set in a hot press machine by sandwiching it with a stainless plate or the like, and the temperature 12
By heating at 0 to 150 ° C. to soften the resin in the insulating substrate 3b of the inner layer material 13 and applying pressure at the same time, the conductor pattern 13a is embedded in the resin of the insulating substrate 13b, and then cooled and solidified. It is taken out from the hot press machine to obtain the inner layer material 13 in which the conductor pattern 13a is embedded.

After that, as shown in FIG. 1B, the inner layer material 13 in which the conductor pattern 13a is embedded, the prepreg 12 in which the resin portion is semi-cured by impregnating glass cloth with epoxy resin, and the conductor of the outer layer. Copper foils 11 for forming a pattern are superposed, set on a heat press machine by sandwiching them with a stainless steel plate, etc., and heated and pressed to form a conductor pattern 13a.
The inner layer material 13, the prepreg 12 and the copper foil 11 embedded in are melted, cooled and solidified to obtain a multilayer copper clad laminate 16 having a conductor pattern 13a inside as shown in FIG. 1 (c).

Comparing the characteristics of the multilayer printed wiring board according to this embodiment, that is, the multilayer copper-clad laminate and the conventional multilayer copper-clad laminate, the area of the printed wiring board (100 ×
Although the number of laminated voids per 100 cm) was several, no laminated void was observed in this example.

Also, in terms of copper migration, it is 10 to 50D.
Humidity test under C voltage load condition (Temperature 85 ℃, Relative humidity 8
5%, 2000 hours or more), an excellent effect that no copper migration occurred was obtained.

As described above, according to this embodiment, by using the inner layer material in which the conductor pattern is embedded in the insulating layer of the inner layer material as the inner layer material for the multilayer printed wiring board, the occurrence of laminated voids and copper migration The risk of can be suppressed almost completely.

In the embodiment, the insulating substrate 1 for the inner layer is used.
Although 3b is a glass cloth base epoxy resin laminated plate, it goes without saying that the insulating substrate 13b may be a glass nonwoven fabric base epoxy resin laminated plate or a paper base epoxy resin laminated plate for the inner layer insulating substrate 13b.

[0023]

As described above, according to the present invention, after the conductor pattern of the inner layer material is embedded in the insulating layer of the inner layer material, the inner layer material, the prepreg, and the copper foil are superposed, and the heating / pressing, By stacking, it is possible to easily prevent the occurrence of stacking voids, and at the same time improve the accuracy of the insulating layer thickness and maintain the insulating distance between the glass fiber that constitutes the prepreg and the conductor pattern for the inner layer, and to prevent copper migration or between insulating layers. It is possible to realize an excellent multilayer printed wiring board capable of preventing a decrease in adhesive strength.

[Brief description of drawings]

1A to 1C are cross-sectional views of a stacking process of a multilayer printed wiring board according to an embodiment of the present invention.

2A to 2C are cross-sectional views of a stacking process of a conventional multilayer printed wiring board.

[Explanation of symbols]

 11 Copper foil 12 Prepreg 13 Inner layer material 13a Inner layer conductor pattern 13b Inner layer insulating substrate 15 Multilayer copper clad laminate

Claims (1)

[Claims] 1. An insulating substrate having a conductor pattern is heated and pressed so that the conductor pattern is embedded in an insulating layer of the insulating substrate, and the surface of the conductor pattern and the surface of the insulating substrate are leveled. A method for producing a multilayer printed wiring board, characterized in that glass cloth is impregnated with a liquid resin and dried by touch, and prepreg and copper foil are superposed and laminated by heating and pressing.