JPS6355236B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to provide a novel printed wiring board that is extremely simple and quick to mount electronic components, and is thin and compact on which high-density electronic components can be mounted. The purpose of the invention is to provide a method for manufacturing the same.

Generally, when semiconductor elements or electronic component chip elements (hereinafter simply referred to as electronic components) are mounted on or connected to a printed wiring board, conventionally the electronic components are mounted on a conductor circuit on the printed wiring board and soldered. , or wire bonding,
Methods such as applying adhesive in advance to the mounting area of electronic components and soldering after adhering and fixing the components have been adopted, but these conventional methods involve extremely frequent work, and the electronic components Since positioning of the elements is difficult, there are drawbacks such as the need for expensive equipment and extra work steps such as adhesive application.

Further, Japanese Patent Publication No. 47-3206 discloses a method in which a lead wire is formed over a through hole in an insulating film and a semiconductor is bonded to the center of the lead wire. However, with this method, not only is it necessary to support the film in some way after the semiconductors are bonded, but also it is difficult to create a through-hole substrate due to the process.

On the other hand, when storing electronic circuits in extremely limited spaces such as watches or cameras,
It is necessary to minimize the space occupied by electronic components mounted on a printed wiring board and to make it thin and compact, which requires high-density wiring such as double-sided through holes or a multilayer board.

Therefore, the present invention has been devised to solve the drawbacks and technical unresolved problems of the conventional technology, and as a result,
We have discovered a new method for manufacturing printed wiring boards that can successfully solve this problem using the following technical means.

That is, a copper foil whose one side is plated with a different metal than copper is prepared in advance, and the plated side of the copper foil with a different metal and the non-copper-plated insulating substrate with no copper foil applied or with copper foil applied on one side are prepared in advance. The adhesive layer-covered surface of the substrate, which has a through-hole of a desired shape and one side of which is coated with a thermosetting resin layer, is bonded and bonded to the adhesive layer-covered surface, and after heating and press-forming the two together, an insulating substrate without copper foil is formed. When using an insulating substrate coated with copper foil on one side, the desired pattern is formed on the copper foil surface of the molded body obtained as described above by resist printing. After drilling a hole in the hole and through-hole plating the hole, a desired pattern is formed on the copper surface by resist printing, and in either case, only the exposed copper surface is etched to remove the surface and the through hole. The above object is achieved by a method of manufacturing a printed wiring board, which is characterized in that the resist film is removed after selectively etching the dissimilar metal plating layer on the hole.

Next, in giving a detailed explanation of the method for manufacturing a printed wiring board of the present invention, embodiments of the present invention will be described in the order of manufacturing steps based on the drawings.

FIG. 1 shows an outline of a flow sheet of the method for manufacturing a printed wiring board of the present invention, and shows partially enlarged vertical cross-sectional schematic diagrams of raw materials, intermediate products, and final products in the order of the manufacturing process. It is.

In FIG. 1, the copper foil 1, for example, has a thickness of
One side of the 18 μm copper foil is plated with a metal different from copper, such as nickel, tin, solder, gold, silver, chromium, etc., which has etching selectivity with copper. . In the present invention, it is preferable to use a nickel plating layer, which has the best selective etching property with copper among these different metals and is relatively inexpensive.

In addition, there are no particular restrictions on the thickness of the copper foil, but
The thickness of the copper foil normally used for this type of insulating board,
For example, a material with a thickness of about 18 to 70 microns can be used, and one that has enough stiffness to handle and does not interfere with copper etching is selected.

Next, a thermosetting resin adhesive is applied to the copper foil-free surface of either the copper foil-free insulating substrate 2 or the single-sided copper-coated insulating substrate 3 prepared separately, and the adhesive is applied to one side. An insulating substrate 4 whose surface has been polished is obtained.

For the adhesive application surface C, select an epoxy resin having heat resistance and plating resistance, and apply it using a normal method such as a roll coater or brush coating. Leave it in a semi-dry, uncured state for about a minute. Further, a commercially available epoxy resin film-like adhesive sheet may be used for the adhesive-applied surface C, and it is sufficient to form a state in which it is coated with a thermosetting resin adhesive layer.

Note that the adhesive layer is not limited to epoxy resin, and various thermosetting resins can be appropriately selected and used depending on the usage temperature and electrical properties.

At least one through hole 5 in the shape of a desired electronic component is formed in a desired location of the thus obtained insulating substrate 4, which has one side covered with a thermosetting adhesive layer C, by die punching or a hole drill. More than 10 locations will be set up as needed.

Then, on one side of the copper foil 1, a plating layer made of a different metal than copper, for example a nickel plating layer A, and a surface covered with the adhesive layer C, for example a surface C covered with a film-like adhesive sheet layer of epoxy resin, are bonded and pasted. Then, the molded body 6 is obtained by heat-pressing molding these integral parts. The heating and pressurizing conditions vary depending on the type of adhesive for the thermosetting resin, but are approximately 120°C.
50Kg/cm ² to 150Kg/cm ² under heating from ℃ to 180℃
It is usual to heat and pressurize the material under pressure for 20 to 60 minutes.

Here, when a single-sided copper coated insulating substrate 3 is used, conductive holes 7 of a desired shape are bored at desired locations, and chemical copper is applied to the entire surface of the substrate, including the through holes 5 and the conductive holes 7. The plating is deposited, and an electrolytic copper plating layer 8 is applied to a thickness of approximately 10 to 30 μm,
A through-hole plating layer for front and back conduction is provided in the conduction hole 7.

Next, a desired pattern 9 is photographed on the copper surface of the molded body thus obtained or the molded body having through-holes on both sides, that is, on the copper surface of the substrate including at least the surface of the copper foil above the through hole 5. The exposed copper surface of the pattern is etched away using a liquid capable of selectively etching only the copper exposed surface of the pattern, such as an ammonia-based etching solution, and the surface of the substrate and the through hole are etched away. A circuit is formed on the dissimilar metal plating layer. At this time, the conductor circuit on the through hole has a dissimilar plating layer, such as a nickel plating layer, provided under the copper foil, which has the effect of blocking contact with the etching solution from below, so that the conductor circuit is removed from the etching solution. This will protect the foil layer.

Furthermore, since the nickel plating layer A supports the copper foil layer above it, even if the etching solution collides with this part, the conductor circuit on the part can be completely prevented from bending or sagging. It also has functions.

This is extremely important when the manufacturing method of the present invention is used to form the copper foil portion 10 protruding above the through hole of the board, which could not be obtained by the conventional manufacturing method of the printed wiring board. This is of great significance, and the formation of the copper foil portion 10 in this portion is possible only by providing a dissimilar metal plating layer, for example, a nickel plating layer, thereunder.

Next, using the resist film 9 and the copper pattern portion 10 as an etching resist, selective etching of nickel is performed, or rapid etching is performed using a cupric chloride solution or the like to remove nickel plating in unnecessary areas, that is, in the inside of the through hole. By removing the exposed nickel plating layer and dissolving and removing the resist film, it is possible to obtain a printed wiring board 11 having circuits on both sides of the board including the tops of the through holes.

In this way, it is possible to provide a printed wiring board 11 that is extremely simple and quick to mount electronic components, which is the object of the present invention, and is thin and compact on which high-density electronic components can be mounted. This is the manufacturing method.

The printed wiring board manufactured by the method of manufacturing the present invention has several excellent effects as listed below.

(1) After forming a circuit on the printed wiring board,
By applying arbitrary metal plating such as tin, solder, nickel, gold, etc. to the conductor circuit, when installing and mounting electronic components in the through hole or on the surface circuit,
Heat soldering or thermocompression bonding is possible.

(2) Electronic component 1 is placed in the through hole of the printed wiring board.
By embedding 2, an electrical connection can be made as shown in FIG. 2 with the connection part 13 of the electronic component and the copper foil part 10 on the through hole in contact with each other. Compared to the method of mounting electronic components three-dimensionally on top, it is possible to form a thinner and more compact electronic circuit board, and by making the thickness of the electronic components and chip elements similar, Moreover, a thin and compact flat circuit board as shown in the left part A of FIG. 3 can be manufactured.

(3) The through holes of the printed wiring board are processed into various shapes corresponding to the shapes of electronic components, which not only facilitates the mounting of electronic components;
The inserted electronic components are easily fixed in place,
Handling becomes easier, and unnecessary and frequent work such as temporarily attaching electronic components with adhesive can be omitted.

(4) By using a base material thicker than the electronic components buried in the through-holes of the printed wiring board, chip elements such as the one shown in right part B of Fig. 3, which were impossible with conventional printed wiring boards, can be created. For the first time, intersecting mounting (multi-component mounting) of electronic components becomes possible, which greatly increases the density of electronic components and the degree of freedom in circuit design.

[Brief explanation of drawings]

FIG. 1 shows an outline of a flow sheet of the method for manufacturing a printed wiring board of the present invention, and FIG. A vertical cross-sectional view showing a state in which a semiconductor (electronic component) is buried in a through-hole of a final product obtained by the wiring board manufacturing method and subjected to thermocompression bonding. Fig. 4 is a plan view showing an example of conductor formation on the through-hole of the final product, and Fig. 5 is the final product. FIG. 3 is a plan view showing an example of brazing with a conductive adhesive on the through-hole of FIG. In the above drawings, 1... copper foil, 2... insulating board without copper foil, 3... insulating board with copper foil on one side, 4
...One-sided adhesive layer coated insulating substrate, 5...Through hole, 6
...Molded body, 7...Conducting hole, 8...Electrolytic copper plating layer, 9...Resist film pattern, 10...Protruding copper foil portion, 11...Printed wiring board of the present invention, 12
...Electronic component, 13... Connection part of electronic component, 1
4... Conductive adhesive.

Claims (1)

[Scope of Claims] 1. An insulator in which one side is provided with a thermosetting resin adhesive layer comprising a dissimilar metal plating surface of a copper foil plated with a dissimilar metal different from copper on one side, and a through hole of a desired shape. After bonding and adhering the adhesive layer surface of the substrate and molding them together under heat and pressure, a desired pattern is formed on the copper surface of this molded body by resist etching, and only the exposed copper surface is etched to form the substrate surface and A method for manufacturing a printed wiring board, comprising: forming a circuit on the dissimilar metal plating layer above the through hole, selectively etching the dissimilar metal plating layer other than the circuit portion, and then removing the resist film. . 2. Adhesion of thermosetting resin to the dissimilar metal-plated side of the copper foil, which is plated with a dissimilar metal other than copper on one side, and to the non-copper-coated side of the single-sided copper-coated insulating substrate, which has a through hole of the desired shape. After bonding and adhering the layer to the adhesive coating surface on one side and molding them together under heat and pressure, holes are punched in desired portions of the molded body, through-hole plating is applied to the holes, and then the copper layer is bonded and pasted. A desired pattern is formed on the surface by resist printing, and only the exposed copper surface is etched to form a circuit on the substrate surface and the dissimilar metal plating layer on the through hole, and the dissimilar metal plating layer other than the circuit portion is selected. 1. A method of manufacturing a printed wiring board, which comprises removing the resist film after etching the resist film.