JPH0451079B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a multilayer wiring board in which a plurality of layers of conductive patterns are provided on a board. [Background technology and its problems] With the miniaturization and thinning of various electronic devices, the space for storing wiring boards constituting a predetermined electric circuit has become extremely limited. In order to be able to mount a wiring board constituting a desired electrical circuit within a storage space, a so-called multilayer wiring board is used, which has multiple layers of conductive patterns laminated to increase the density of circuit wiring. There is. This multilayer wiring board not only provides high-density packaging circuits, but also has great practical advantages, such as being able to shorten the length of conductors connecting components and improve signal transmission speed. By the way, this type of multilayer wiring board is made by laminating a plurality of insulating substrates each having a predetermined conductive pattern formed on one or both sides through a prepreg that performs adhesion between each layer and also serves to protect the conductive pattern and provide interlayer insulation. It is manufactured by multi-layer lamination molding by pressing, and through holes are drilled at the locations where connection and continuity are required between the conductive patterns of each layer, and so-called through-hole plating is applied inside these through holes to establish continuity. It is common to aim for However, in the above manufacturing method, the plating process for through-hole plating is particularly complicated, which not only reduces productivity, but also requires large-scale plating equipment and wastewater treatment facilities, increasing manufacturing costs. It is closed. Furthermore, when attempting to establish electrical continuity between the conductive patterns in each layer by using the above-mentioned through-hole plating, there is a risk that the electrical continuity will be hindered by the occurrence of so-called smear, which will significantly reduce the reliability of the multilayer wiring board. There is. Furthermore, in the past, thick film patterns formed by printing a conductive paste such as Ag-Pd paste on an insulating substrate such as a ceramic substrate and glass insulating layers were alternately laminated to create multilayer wiring. A laminated plate has been proposed, but this fired glass laminated plate has the disadvantage of poor workability and is easily damaged by the slightest impact, and the above-mentioned thick film pattern has a high resistance value. The signal processing speed decreases, which is disadvantageous for manufacturing large substrates. Alternatively, conductive patterns formed of copper foil or the like are laminated on the substrate via a printed organic insulator or a photo-formed organic insulator so that the connecting portions partially overlap, and the connecting portions are connected between each conductive pattern. proposed a method of manufacturing a multilayer wiring board by using a conductive paste such as Cu paste, Gd alloy paste, or solder paste through a connection window provided in the organic insulator. In this manufacturing method, high precision is required for printing the conductive paste, making the work complicated and reducing the manufacturing yield. [Object of the Invention] Therefore, the present invention has been proposed in view of the above-mentioned conventional situation, and provides a multilayer wiring board that can simplify the process by eliminating the need for complicated plating processes, printing processes, etc. Another object of the present invention is to provide a method for manufacturing a multilayer wiring board that does not require large-scale equipment and can reduce manufacturing costs. A further object of the present invention is to provide a manufacturing method that can ensure electrical continuity between conductive patterns and obtain a highly reliable multilayer wiring board. [Summary of the invention] In order to achieve the above-mentioned objects, the present invention has the following features:
After forming an insulating layer having a connection window on a substrate on which a first conductive pattern has been formed in advance, and bonding a conductive metal foil having at least a portion covered with a conductive film on the insulating layer, This method is characterized in that the conductive metal foil is etched to form a second conductive pattern. [Example] Hereinafter, specific examples of the present invention will be described with reference to the drawings. 1 to 6 show a method for manufacturing a multilayer wiring board to which the present invention is applied, according to the process order. That is, in the present invention, as shown in FIG. 1, first, a laminate is formed of an insulating material such as a glass epoxy resin laminate, a paper phenol laminate, or a polytetrafluoroethylene board, or a metal material such as aluminum or iron. After preparing a base 1 and bonding a conductive metal foil such as copper foil onto the base 1, the conductive metal foil is etched to form a first conductive pattern 2.
form. In addition, when using a metal plate such as an aluminum plate or a steel plate as the base 1, an epoxy adhesive is applied to the base 1 in advance to a thickness of about 40 μm, and the above adhesive layer is coated on the base 1. 1 conductive pattern 2 is formed. Next, as shown in FIG. 2, an insulating layer 3 is laminated on the base 1 so as to cover the first conductive pattern 2. The insulating layer 3 serves to electrically insulate the first conductive pattern 2 and a second conductive pattern (described later) and also acts as an adhesive for bonding the second conductive pattern. It is necessary to provide adhesive properties by forming the adhesive using a polyamide resin, an epoxy/acrylic thermosetting resin, an epoxy/acrylate ultraviolet curable resin containing acrylic rubber, or the like. Further, it is necessary to provide a connection window 4 in a portion of the insulating layer 3 where it is necessary to establish a connection between the first conductive pattern 2 and a second conductive pattern described below. In order to form the connection window 4, the insulating layer 3 may be deposited using a screen printing method, a dry film type photography method, a liquid photoresist photography method, or the like. Therefore, the insulating layer 3 can be formed by, for example, printing epoxy/acrylic adhesive to a thickness of 40μ and drying it at 80°C for 2 minutes or 100°C for 1 minute, or using epoxy/acrylate resin. First, print it to a thickness of 30μ, cure it by UV irradiation, and then apply 10μ of epoxy/acrylic adhesive.
Examples include a method of printing and drying, and a method of photoforming using a combination of ultraviolet and heat curing photoresist made by adding 30% by weight of acrylic rubber to epoxy acrylate resin. On the other hand, apart from the base 1, a conductive metal foil 5 is prepared as shown in FIG. 3, and one surface of the conductive metal foil 5 is coated with low melting point solder or conductive adhesive over the entire surface to make it conductive. A protective film 6 is formed in advance. The conductive metal foil 5 may be made of any conductive metal material, but copper foil having a thickness of about 18 to 35 microns is usually used. The low melting point solder used to form the conductive film 6 is an alloy material whose melting point temperature is lower than that of general solder, such as the various alloys shown in the table below or the product name U Alloy (Osaka Asahi Metal company), etc.

〔Effect of the invention〕

As is clear from the description of the embodiments described above, according to the present invention, the conductive patterns of each layer are bonded and at the same time the conductive patterns are connected by the conductive film, which simplifies the manufacturing process and improves productivity. At the same time, since the plating process is no longer necessary, large-scale equipment is not required, making it possible to reduce manufacturing costs. Further, according to the present invention, conduction between the respective conductive patterns is reliably achieved by melting or adhering the conductive film, and the reliability of the obtained multilayer wiring board is high.

[Brief explanation of drawings]

1 to 6 are schematic cross-sectional views showing one embodiment of a method for manufacturing a multilayer wiring board to which the present invention is applied according to the process order, and FIG.
Figure 2 shows the insulating layer forming process, Figure 3 shows the conductive film forming process, Figure 4 shows the conductive metal foil bonding process, Figure 5 shows the conductive metal foil etching process, and Figure 6 shows the conductive pattern forming process. The process of etching the film is shown below. 7 to 9 are schematic cross-sectional views showing a part of the manufacturing process in another embodiment of the present invention, in which FIG.
The figure shows the conductive metal foil bonding process, and FIG. 9 shows the conductive metal foil etching process. 10 to 16 are schematic cross-sectional views showing still other embodiments of the present invention according to the process order, and FIG.
The figure shows the first conductive pattern forming step, FIG. 11 shows the insulating layer forming step, FIG. 12 shows the conductive film and epoxy adhesive adhesion step, FIG. 13 shows the conductive metal foil preliminary thermocompression bonding step, and The figure shows the conductive metal foil etching process, FIG. 15 shows the thermocompression bonding process, and FIG. 16 shows the conductive film etching process. DESCRIPTION OF SYMBOLS 1... Base body, 2... First conductive pattern, 3... Insulating layer, 4... Connection window, 5... Conductive metal foil, 6... Conductive film, 7... Second conductive pattern.

Claims (1)

[Claims] 1. After forming an insulating layer having a connection window on a substrate on which a first conductive pattern has been formed in advance, and bonding a conductive metal foil with a conductive film coated on at least a portion of the insulating layer, the above-mentioned A method for manufacturing a multilayer wiring board, comprising etching a conductive metal foil to form a second conductive pattern.