JPH0432298A - Multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To extensively avoid the break of a fine circuit pattern, etc., by thermal history, temperature change in use circumstance, etc., by constituting an inner layer circuit pattern and a interlayer conductor out of a conductive resin composition, which contains metallic powder, and besides constituting at least one layer of the inner circuit pattern out of a metallic foil. CONSTITUTION:A copper foil 12mum thick is stuck together to a polysulfone resin film approximately 0.05mm thick, and a required hole for connection is bored, and then a circuit pattern is formed on one side or both sides by selective etching. Next, an inner layer circuit pattern element plate is prepared, in which an interlayer connecting conductor 5 is made by charging conductive paste, containing dispersed copper powder with the polysulfone resin as a binder ingredient, in the hole for connection by screen printing method. Plural sheets of inner layer circuit pattern element plates prepared are combined with said second circuit pattern element plates, and are aligned and a put on the other. The fellow surfaces facing each other are fused together and united, and also the interlayer connecting conductors 5 corresponding to each other are filled up and united.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to multilayer printed wiring boards, and more particularly to improved multilayer printed wiring boards for packaged circuit devices.

(Prior art) For the purpose of downsizing wiring circuits or making circuit parts more compact, mounted circuit devices with a multilayer printed wiring board as a base, on which required electronic components are mounted and mounted, have been widely used. It is put into practical use.

As a type of the above-mentioned multilayer printed wiring board for mounted circuits, there is a synthetic resin multilayer printed wiring board. That is, as a first method, an inner layer circuit pattern blank is formed with a desired circuit pattern by selective etching of a metal foil pasted on the surface of a resin-impregnated insulator layer made of insulating paper or glass cloth as a base material; A prepreg hardened layer that interposes on this inner layer circuit pattern blank plate and integrates them, and an outermost layer circuit pattern blank formed by selective etching of metal foil that is also integrated via the prepreg hardened layer. For example, a multilayer printed wiring board consisting of Second
Examples of this method include a multilayer printed wiring board in which the circuit patterns of the inner and outer layers are made of a conductive composition containing a metal powder such as silver, copper, gold, or nickel, and a synthetic resin as a binder. In the multilayer printed wiring board having the above configuration, necessary electrical connections are made between inner layer circuit patterns, between inner layer circuit patterns and outer layer circuit patterns, or between outer layer circuit patterns using through holes, peer holes, or the like.

(Problems to be Solved by the Invention) However, the synthetic resin multilayer printed wiring board having the above structure has the following practical disadvantages. First, in the case of the first method, that is, in the case of a multilayer printed wiring board in which the circuit pattern of each layer is formed based on metal foil,
Because the electrical connection layer between the circuit pattern layers and the physical properties of the circuit pattern layer and the synthetic resin (insulator) forming the matrix, such as coefficient of thermal expansion, are significantly different, thermal history, stress action, or cooling/heating cycles may cause microscopic differences. There are problems with reliability, such as circuit patterns often being cut, and required circuit functions being impaired. Also, the second
In the case of the above method, that is, in the case of a multilayer printed wiring board in which the entire conductor region including the inner layer circuit pattern is formed with a so-called conductive paste, the circuit formation method is screen printing, so the pattern width and pattern spacing ( There are major restrictions on miniaturization (gap width), making it impossible to obtain high wiring density.

The present invention was made in response to the above-mentioned circumstances, and an object of the present invention is to provide a multilayer printed wiring board with high wiring density.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a multilayer circuit pattern that includes an outermost layer circuit pattern on which electronic components are mounted and soldered, an inner layer circuit pattern, and an interlayer conductor that electrically connects the circuit pattern layers. The printed wiring board is characterized in that the inner layer circuit pattern and the interlayer conductor are made of a conductive resin composition containing metal powder, and at least one layer of the inner layer circuit pattern is made of metal foil.

(Function) According to the above configuration, the physical properties of the electrical connection layer between the circuit pattern layers and some of the circuit pattern layers and the synthetic resin system (insulator) forming the matrix are similar, such as the coefficient of thermal expansion. , breakage of minute circuit patterns due to thermal history or temperature changes in the usage environment can be completely avoided. Moreover, since at least one layer of the inner layer circuit pattern (a part of the inner layer circuit pattern) is formed by etching based on metal foil, high wiring density can be achieved.

(Example) The present invention will be described in detail below with reference to FIG. FIG. 1 shows a cross-sectional view of an example of the structure of a multilayer printed wiring board according to the present invention, in which 1 is a heat-resistant thermoplastic resin layer such as polysulfone resin, and 2 is a layer of heat-resistant thermoplastic resin in the heat-resistant thermoplastic resin layer 1. This is an inner circuit pattern layer arranged in multiple layers and electrically insulated from each other. A portion (some layers) of this inner circuit pattern layer 2 is formed by selective etching using metal oil as a base. Further, 3 is an outer circuit pattern layer having pads for soldering such as mounts and leads of the necessary electronic components 4, and is made of a conductive paste containing a synthetic resin as a binder component together with a part of the inner circuit pattern layer 2. It is formed. 5 is between the inner circuit pattern layers 2 and 2-
Between outer circuit pattern layers 3 or outer circuit pattern layers 3
This is an interlayer connection conductor section made of a conductive paste containing a so-called synthetic resin as a binder component, which performs the required electrical connection by using through holes or pier holes between the layers.

Therefore, the multilayer printed wiring board according to the present invention having the above structure can be easily manufactured as follows.

For example, a copper foil with a thickness of 12 μm is bonded to a polysulfone resin film with a thickness of about 0.051 mm, the required connection holes are bored, and a circuit pattern is formed on one or both sides of the film by selective etching. Next, a conductive paste containing polysulfone resin as a binder component and copper powder dispersed therein is filled into the connection holes by a screen printing method to form an interlayer connection conductor portion 5, thereby preparing an inner circuit pattern blank. On the other hand, the thickness
o. A required connection hole is made in a polysulfone resin film of about 0.05 mm, and a conductive paste containing polysulfone resin as a binder component and 15 copper powder dispersed therein is printed using a screen printing method to form the required circuit pattern. Then, a second circuit pattern blank plate on which interlayer connection conductor portions 5 are formed is prepared.

After that, the plurality of inner layer circuit pattern blank plates prepared above are combined with the second circuit pattern blank plate, and alignment 1 is performed.
7 and overlap. In this superposition, the second circuit pattern blank plate is positioned at least on the outside, but in the inner layer, the inner layer circuit pattern blank plate and the second circuit pattern blank plate may be arranged alternately, or both circuit pattern blank plates may be arranged alternately. It is also possible to have a configuration in which they are arranged for each pattern blank.

After the above-mentioned alignment and stacking, heating and pressure molding processing is performed to weld and integrate the mutually opposing surfaces of the stacked polysulfone resin films, and the corresponding interlayer connection conductor portions 5 are filled and integrated. By this, a desired multilayer printed wiring board can be obtained.

A multilayer printed wiring board according to the present invention that can be constructed in this manner, for example, IOX lee board, thickness 0.5 mm,
A multilayer printed wiring board (embodiment) having a four-layer circuit pattern structure and having 500 interlayer connection conductor parts between the inner circuit pattern layers and between the inner circuit pattern layer and the outer circuit pattern layer, and 100 through connection conductor parts, and the conventional A thermal shock test and a bending test were conducted on a multilayer printed wiring board (comparative example) with the same structure in which the insulating layer was made of glass cloth and epoxy resin based on the first method of the example, and the following results were obtained. Met.

For example.

Thermal shock test: No abnormality in the conductor layer forming the circuit. Bending test: No abnormality in the conductor layer forming the circuit. Comparative example.

Thermal shock test: The conductor layer that forms the circuit has many opens, making measurement impossible. Bending test: After one bend, the conductor layer that forms the circuit generates an oven. Thermal shock test is conducted at -60℃ for 30 minutes and +125℃ for 30 minutes.
This is the case where 500 cycles are repeated with 0 minutes as one cycle, and the bending test is 100 cycles with a bending rate of 20%.
This is the case where it is repeated 0 times.

In the above example, the insulating layer of the multilayer printed wiring board is made of polysulfone resin, but other thermoplastic resins such as polyphenylene sulfide resin, polyether resin, polyetherimide resin, polyether ether ketone resin, etc., or insulating paper or insulating cloth may be used. It may be based on.

Further, the formation of the electrical connection conductor portion between the circuit pattern layers and the inner circuit pattern layer is not limited to the above-mentioned conductive paste, but may be formed using another conductive paste using a synthetic resin as a binder.

[Effects of the Invention] According to the present invention, the electrical connection conductor between the circuit pattern layers and the physical properties of the circuit pattern layer and the synthetic resin system (insulator) forming the matrix are similar, so thermal history and Breakage of minute circuit patterns due to temperature changes in the usage environment is completely avoided, and the required circuit functions can be maintained at all times. Moreover, since at least one layer of the inner circuit pattern (a part of the inner circuit pattern layer) is formed using metal foil as a base, high wiring density can be achieved. Thus, it can be said that the multilayer printed wiring board according to the present invention is suitable for constructing a mounted circuit device with high functionality and reliability.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of the structure of a multilayer printed wiring board according to the present invention. 1...Heat-resistant thermoplastic resin layer 2...Inner circuit pattern layer 3...Outermost circuit pattern layer 4...Electronic component 5... ...Circuit pattern interlayer connection conductor section applicant
Toshiba Corporation

Claims (1)

[Scope of Claims] A multilayer printed wiring board comprising an outermost layer circuit pattern on which electronic components are mounted and soldered, an inner layer circuit pattern, and an interlayer conductor that electrically connects the circuit pattern layers, the inner layer circuit pattern and the interlayer conductor 1. A multilayer printed wiring board, comprising: a conductive resin composition containing metal powder; and at least one layer of an inner layer circuit pattern is made of metal foil.