JPS61296799A - Multilayer printed wiring board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a multilayer printed wiring board, and more particularly to the composition of an insulating resin used in the inner layer of a multilayer printed wiring board.

[Conventional technology]

In recent years, as electronic components such as ICs and LSIs mounted on printed wiring boards have become more sophisticated and more densely packaged, it has become a problem to stably supply power to these electronic components. For this reason, the thickness of the inner conductor layer of a multilayer printed wiring board is conventionally 35 to 70 μm.
The company is trying to ensure a stable supply of electricity by designing the thickness of the existing material to be more than 100 μm. In this case, the method of forming a circuit pattern by etching the copper foil on a copper-clad laminate, which is commonly used, has a large overhang and deteriorates the accuracy of forming the circuit pattern.
As in Japanese Patent No. 03, an example has been proposed in which a single piece of copper foil is simultaneously etched on both the upper and lower surfaces and is used as the inner conductor layer. This type of multilayer printed wiring board will be explained below with reference to FIGS. 1(8) to 1).

First, metal foils 1 and 2 are prepared as shown in FIG. 1 (5) @. For the metal foils 1 and 2, copper foil with a thickness of 100 μm or more is used.

Next, as shown in FIG. .

Next, as shown in FIGS.
Form 3.14.

Next, as shown in FIG.
Etch the parts not covered in step 4.

Then, as shown in FIGS. 1(I) and 1(J), the etching resist films 11.12 and 13.14 are removed.

Next, as shown in FIG. 1N, the etched metal foil 1
, 2 are arranged above and below through the prepreg 15'li-.
As shown in Figure (G), an inner layer plate 16 can be formed by thermocompression bonding using a hot press.

Next, as shown in FIG. 1, an insulating resin layer 17 is formed on the front and back surfaces of the inner layer board 16 by a method such as screen printing or roll coating to form an insulating resin coated inner layer board 18.

Next, as shown in FIG. 1 (f), the insulating resin coated inner layer plate 18 and the outer conductor layer 20 are placed through the prepreg 19, and as shown in FIG. , a multilayer substrate 21 is formed.

Next, a through hole 22 is formed, and after forming through hole plating 23 on the inner wall surface of the through hole 22, an outer layer circuit 24 is formed by a tenting method to form a multilayer printed wiring as shown in FIG. A plate 25 is obtained.

[Problem that the invention seeks to solve]

However, in the conventional multilayer printed wiring board described above, the inner layer board 16
The clearance part is filled with resin only 9,
Because the thermal expansion coefficients of the resin and metal foil are significantly different (1.2), residual stress occurs in the resin after thermocompression bonding, and the mechanical strength of the resin is weaker than that of metal foil or glass cloth.
Since cutting stress during cutting of the through hole 22 is concentrated on the resin, cracks are generated there, and residues from the liquid treatment process remain in the cracks, causing insulation failure.

An object of the present invention is to solve the drawbacks of the conventional multilayer printed wiring board and to provide a multilayer printed wiring board that is free from insulation defects.

[Means for solving problems]

That is, according to the present invention, an etching resist film of a desired shape is formed on the front and back surfaces of a conductor layer, and chemical etching is performed at a desired position from the front and back surfaces, and the etched conductor layer is placed above and below a prepreg and heated. A step of crimping and forming an inner layer plate, a step of applying an insulating resin to the surface of the inner layer plate to form an insulating layer, and arranging one or more inner layer plates with the above insulating layer formed on the inner layer, and applying prepreg to the inner layer through prepreg. Obtained by a step of thermocompression bonding an outer conductor layer to form a multilayer substrate, a step of forming through holes at desired positions of the multilayer substrate and performing through-hole plating, and a step of forming an outer layer circuit on the outer conductor layer. In the multilayer printed wiring board, the composition of the insulating resin applied to the surface of the inner layer board is a thermosetting resin, and contains 5 to 50 parts by weight of filler per 100-i parts of the insulating resin. At the same time, a multilayer printed wiring board characterized in that the filler is made of an inorganic material such as aluminum hydroxide, silica, and antimony trioxide is obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be described in comparison with conventional examples.

Resin A in Table 1 is Conventional Example 1, which uses epoxy as a basic resin and does not contain fillers. Resin B is Conventional Example 2, in which the basic resin is modified polyimide and no filler is added. Resin C-I was prepared by appropriately adding the type of fi-2- shown in Table 1 to these conventional resins, and a multilayer printed wiring board was manufactured by the above-mentioned manufacturing method, and cracks occurred after through-hole plating. We investigated the situation. As a result, in Conventional Examples 1 and 2 to which no filler was added, cracks were observed to occur frequently. Resin E to which 3 parts by weight of aluminum hydroxide powder was added as a filler
The crack generation rate was significantly improved, and no cracks were observed in resin F to which 5 parts by weight of aluminum hydroxide powder was added. Furthermore, the amount of filler is increased,
Resin D containing 40 parts by weight of aluminum hydroxide powder
No cracks were observed in either resin H, and it can be easily inferred that even if the amount of filler is increased beyond this level, there is an effect of preventing cracks. However, it has been found that when the amount of filler added exceeds 50 parts by weight, the increase in viscosity increases significantly and kneading becomes difficult. Similarly, the effect of preventing crack generation was also observed for Resin I to which silica powder was added. In other words, by adding an inorganic filler such as aluminum hydroxide or silica to the resin, it is possible to reduce the difference in thermal expansion coefficient between the resin and the metal foil and reduce the residual stress after curing. .

Furthermore, the addition of filler improves mechanical strength, improves machinability, and prevents cracks.

〔Effect of the invention〕

As explained above, by applying an insulating resin containing an inorganic filler to the surface of the inner layer board according to the present invention, there will be no cracks that occur during the manufacturing process of multilayer printed wiring boards, that is, when forming through holes, and there will be no insulation defects. There is an effect that a printed wiring board can be obtained.

[Brief explanation of drawings]

Table 1 is a table showing the insulating resin composition of the conventional example and the first to seventh embodiments of the present invention, and Figures 1 (8) to 0 show the manufacturing method of the multilayer printed wiring board according to the conventional example and the present invention. FIG. 4 is a cross-sectional view shown in order of steps for explanation. 1.2... Metal foil, 3.4, 5.6...
・Photoresist, 7,8,9.10...Photomask, 11゜12.13.14...Etching resist film, 15.19...Prepreg, 1
6... Inner layer plate, 17... Insulating resin layer,
18... Insulating resin coat inner layer plate, 20...
...Outer conductor layer, 21...Multilayer substrate, 22.
...J (A hole, 23...Through hole plating, 24...Outer layer circuit, 25...Multilayer printed wiring board. Agent: Patent attorney El Uchihara ,. to , to , to .
To (C cry force - Kaya l Drawing procedure amendment (method) 6% formula% 1, Indication of incident 1985 Patent Application No. 1387
No. 07 No. 2, Title of the invention: Multilayer printed wiring board 3, Relationship with the amended case: Applicant: 5-33-1-4, Shiba 5-chome, Minato-ku, Tokyo, Agent: 5-37 Shiba, Minato-ku, Tokyo, 108 No. 8 Resident Mita Building ■ "Brief explanation of drawings" column of the specification subject to amendment. Contents of the amendment: ``Table 1 is a table showing the insulating resin compositions of the conventional example and the first to seventh embodiments of the present invention'' from page 8, line 19 to page 9, line 1 will be deleted. Agent: Susumu Uchihara, patent attorney, 7. ′、゛−′
ri\1den゛,''

Claims (1)

[Claims] A step of forming an etching resist film in a desired shape on the front and back surfaces of the conductor layer and chemically etching it at the desired position from the front and back surfaces, and placing the etched conductor layer above and below the prepreg and thermocompression bonding to form an inner layer plate. a step of applying an insulating resin to the surface of the inner layer plate to form an insulating layer, arranging one or more inner layer plates with the insulating layer formed thereon, and thermocompression bonding an outer conductor layer via a prepreg. In a multilayer printed wiring board obtained by forming a multilayer board, forming through holes at desired positions of the multilayer board and performing through-hole plating, and forming an outer layer circuit on the outer conductor layer, The composition of the insulating resin applied to the surface of the inner layer plate is a thermosetting resin, and contains 5 to 50 parts by weight of filler based on 100 parts by weight of solid content of the insulating resin, and the filler is hydroxylated. aluminum,
A multilayer printed wiring board characterized by being made of inorganic materials such as silica and antimony trioxide.