JPS6089996A - Multilayer circuit 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 (Field of Industrial Application) The present invention relates to a multilayer circuit board that can be used in a wide variety of electronic devices ranging from industrial to general consumer use.

(Conventional configurations and their problems) In recent years, many electronic devices such as VTRs have become smaller, lighter, and more highly functional. has become an indispensable condition. Under these circumstances, various measures have been taken to increase the density of electronic circuits, and in particular, increasing the number of layers of circuit boards for configuring electronic circuits has become an important issue.

Conventionally, various types of multilayer circuit boards have been used depending on the purpose, and among them, a multilayer circuit board as shown in FIG. 1 is a typical one. This multilayer circuit board is mainly used as a module board for circuit blocks, and is configured as follows. In FIG. 1, reference numeral 1 denotes an insulating substrate made of synthetic resin such as glass epoxy or ceramics such as alumina, on the surface of which is formed a first circuit conductor layer 2 made of a thick film conductor such as copper foil or silver thread. The surface of the insulating substrate 1 on which the first circuit conductor layer 2 is formed is an interlayer formed by exposing and developing a photosensitive resin layer made of an acrylic resin formed into a dry film to provide micropores 3. It is covered with an insulating layer 4, and a second circuit conductor layer 5 is formed on this interlayer insulating layer 4 by an additive method or the like. In addition,
The second circuit conductor layer 5 is electrically connected to the first circuit conductor layer 2 through minute holes 3, so-called peer holes, in the interlayer insulating layer 4.

However, such conventional multilayer circuit boards have the following drawbacks because the interlayer insulating layer 4 is made of acrylic resin. That is, since the adhesion between the interlayer insulating layer 4 and the first circuit conductor layer 2 formed on the insulating substrate 1+ was poor, the reliability of the interlayer insulating layer 4 in the moisture resistance and temperature cycle tests was low. However, since the interlayer insulating layer 4 has a large coefficient of thermal expansion, the interlayer insulating layer 4 is likely to peel off in a thermal shock test, and the insulating substrate 1 is likely to crack or break. When using a multilayer circuit board with a built-in resistor, the resistor layer is formed on a ceramic substrate.However, in the case of a multilayer circuit board with a built-in resistor, cracks may occur in the resistor layer as well. There were times when it became impossible to perform its functions. Furthermore, since the dielectric constant of the interlayer insulating layer 4 is large, it is necessary to take stray capacitance into consideration when creating multilayer wiring, and the degree of freedom in wiring the circuit is limited.

(Object of the Invention) The present invention has been made in view of the drawbacks of the conventional example described in 1. The purpose of the present invention is to provide a multilayer circuit board with improved properties and high reliability.

(Structure of the Invention) In order to achieve the above object, the present invention provides an insulating substrate on which a first circuit conductor layer is formed. A second circuit conductor layer is formed which has a two-layer structure in which layers are sequentially laminated and has micropores, and the second circuit conductor layer is electrically connected to the first circuit conductor layer through the micropores in this interlayer insulator layer. It is designed to form a .

(Explanation of Examples) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a sectional view of a main part of an embodiment of the present invention. Second
In the figure, the insulating substrate 6 is made of synthetic resin such as glass epoxy, glass polyimide, paper phenol or composite material, and first has a first circuit conductor layer 7 made of copper foil etched on its main surface. is formed. Then, on the insulating substrate 6 on which the first circuit conductor layer 7 is formed, an interlayer insulating layer 8 having a two-layer structure in which a resin with excellent thermal shock resistance and a resin with excellent heat resistance are sequentially laminated is formed. 1, minute holes 9 are formed in the interlayer insulating layer 8. Here, the interlayer insulating layer 8 having a two-layer structure is a first layer of resin having excellent thermal shock resistance, that is, a resin that is in close contact with the insulating substrate 6 and the first circuit conductor layer 7 formed on the surface thereof. A cyclized rubber-based polybutadiene resin and an acrylic resin are used as the resin with excellent heat resistance for the second layer.

These resin materials are coated in two layers on a polyester film to form a film and are imparted with photosensitivity, and this is coated as a photosensitive resin layer on the insulating substrate 6 on which the first circuit conductor layer 7 is formed. The microscopic holes 9, so-called pier holes, are formed through seven different operations such as exposure and development. On the interlayer insulating layer 8 formed in this way, a thin film technique such as electroless plating, vapor deposition, and ion blating, or a method such as printing a conductive paste i.
6= When the second circuit conductor layer 10 is formed and the trench is formed,
The second circuit conductor layer 10 is electrically connected to the first circuit conductor layer 7 through the microholes 9 formed in the interlayer insulating layer 8 .

In the above configuration, 1 in this embodiment, the interlayer insulating layer 8 has a two-layer structure, and the first layer that is in close contact with the surface of the insulating substrate 60 on which the first circuit conductor layer 7 is formed is flexible. Since it is made of a cyclized rubber-based polybutadiene resin having a The adhesion between the layers is very good, improving the moisture resistance of the interlayer insulating layer 8, and the cyclized rubber-based polybucdiene resin in the first layer acts as a buffer against heat, so it is resistant to sudden thermal shocks. Peeling of the interlayer insulating layer 8 can be prevented.

Furthermore, by constructing the interlayer insulating layer 8 with two layers of acrylic resin and cyclized rubber-based polybutadiene resin as shown in ``-'', the dielectric constant of the interlayer insulating layer 8 can be made smaller than that of the conventional one. The dielectric constant of the conventional acrylic resin alone was 4.0, but in this example it is 30 or less. Also, the influence of stray capacitance on the second circuit conductor layer 10 can be alleviated, and the degree of freedom of the circuit film n'' is increased.

Further, as another embodiment of the present invention, a multilayer circuit board with a built-in resistor is shown in FIG. Components with the same functions as those in FIG. 2 are designated by the same reference numerals. In this embodiment, the insulating substrate 6
A ceramic substrate such as alumina is used as a substrate, and a first circuit conductor layer 7 is formed on the surface of the substrate using a thick film conductor made of a metal brace conductor material such as silver or silver-palladium. A resistor layer 11 made of a metal brace resistor material is formed. And the first
An insulating substrate 6 on which a circuit conductor layer 7 and a resistor layer 11 are formed.
-, in the same manner as in the above embodiment, an interlayer insulating layer 8 having micropores 9 and having a two-layer structure of a cyclized rubber-based polybutadiene resin and an acrylic resin is formed using photo technology, A second circuit conductor layer is formed on the surface of this interlayer insulating layer 8, that is, on the surface of the acrylic resin layer, and is electrically connected to the first circuit conductor layer 7 through micropores 9 by an additive method using electroless plating technology. 10 to form a multilayer circuit board with a built-in resistor.

In the above configuration, this embodiment uses ceramics with an extremely small coefficient of thermal expansion for the insulating substrate 6, but even when a substrate with such a small coefficient of thermal expansion is used, the interlayer insulating layer having a two-layer structure Since the layer of cyclized rubber-based polybutadiene resin 8 adheres to the surface of the insulating substrate 6 and acts as a buffer material, the interlayer insulating layer 8 is not peeled off from the insulating substrate 6 due to thermal shock during soldering or temperature cycle testing. Moreover, there is no possibility of cracking or cracking of the insulating substrate 6, and furthermore, there is no adverse effect on the resistor layer 11 formed on the insulating substrate 6.

In the above two embodiments, the first circuit conductor layer 7 is formed only on one main surface of the insulating substrate 6, and the second circuit conductor layer is formed thereon via the interlayer insulating layer 8 having a two-layer structure. Although a two-stage multilayer circuit board in which the layer 10 is formed has been described, the present invention is not limited to the structure described in ``1''. The first circuit conductor layer 7 can be formed on both main surfaces of the insulating substrate 6, and the first circuit conductor layer 7 can be formed on both main surfaces of the insulating substrate 6, and the two can be connected through holes. The first circuit conductor layers 7 on both main surfaces of the substrate 6 may be formed into multilayer wiring, and multilayering may be promoted in both the front and back directions of the insulating substrate 6.

(Effects of the Invention) As explained above, the present invention provides a double layer in which a resin with excellent thermal shock resistance and a resin with excellent heat resistance are sequentially laminated on an insulating substrate on which a first circuit conductor layer is formed. The adhesion between the interlayer insulating layer and the first circuit conductor layer is significantly improved by forming an interlayer insulating layer with a layered structure and forming a circuit body layer 20 times on top of the interlayer insulating layer to form multilayer wiring. At the same time, the first layer of the interlayer insulating layer, a resin layer with excellent thermal shock resistance, acts as a buffer against heat. It is possible to prevent cracks and breakage defects on the board, improve the reliability of multilayer circuit boards, and reduce the dielectric constant of the interlayer insulation layer to reduce the effects of stray capacitance. This has the effect of increasing the degree of freedom in circuit design.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a conventional multilayer circuit board, FIG. 2 is a sectional view of a main part of an embodiment of the present invention, and FIG. 3 is a sectional view of a main part of another embodiment of the present invention. It is. 6...Insulating substrate, 7...First circuit 2 layer, 8...Interlayer insulating layer, 9...・・Micropore, IO・・・・・・・・
Second circuit conductor layer, 11...Resistor layer. Patent applicant Matsushita Electric Industrial Co., Ltd.: -t 11- Figure 1 Figure 2 Figure 3

Claims (4)

[Claims] (1) An insulating substrate, a first circuit conductor layer formed on at least one main surface of the insulating substrate, and a resin having excellent thermal shock resistance on the insulating substrate on which the first circuit conductor layer is formed. an interlayer insulating layer with a two-layer structure in which fine pores are formed by exposing and developing a photosensitive resin layer made by sequentially laminating a resin with excellent heat resistance; A multilayer circuit board comprising a second circuit conductor layer electrically connected to the first circuit conductor layer. (2) The interlayer insulating layer of the two-layer structure uses a cyclized rubber-based polybutadiene resin as the resin with excellent thermal shock resistance, and an acrylic resin as the resin with excellent heat resistance. A multilayer circuit board as described in Range No. ( ]). (3) The multilayer circuit board according to claim (1), wherein the insulating substrate is made of synthetic resin, and the first circuit conductor layer is made of metal foil. (4) The insulating substrate is made of ceramics, and the first
The circuit conductor layer is made of old metal glaze conductor material.
The multilayer circuit board according to claim 1, further comprising a metal glaze-based resistor layer formed on the insulating substrate together with the first circuit conductor layer.