JPS6138638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new method for manufacturing printed circuit boards with apertures.

A method called the additive method has recently attracted attention as a promising printed circuit board manufacturing method and is being actively developed in various fields. This method is a method in which the conductor is attached only to the required portions on the substrate by electroless plating, and it is also easy to fabricate through-holes, and it also has favorable features since it does not cause undercuts that occur with the etching method. are doing. However, printed circuit boards to which integrated circuit chips can be directly bonded, as is increasingly required, cannot be produced using this additive method. Printed circuits to which integrated circuit chips can be directly connected are those with so-called apertures. FIG. 1 shows a cross-sectional view of a printed circuit board with a window opening. The conductor 2 on the substrate 1 is
It protrudes from the top of a hole drilled in the board, and this part is called a window. As shown in FIG. 2, the integrated circuit chip 3 is connected to the conductor 2 at the window.

Producing such a printed circuit board with apertures by the additive method was the biggest challenge of this method.

The inventors have proposed a carrier substrate on which a conductive circuit pattern made of a highly conductive metal is formed on a metal layer, or a substrate selected from a film or a laminate with windows in the required areas. After applying a thermosetting adhesive and drying it, the conductor circuit pattern of the carrier board was adhesively transferred onto the board, and then the metal layer was melted and released, thereby creating the printed circuit board with the above-mentioned apertures for the first time. This paved the way for production using additive methods.

FIG. 3 is a cross-sectional view of a carrier substrate used in the present invention. It has a structure in which a conductive circuit pattern 2 is formed on a thin metal layer 4, and the thin metal layer is formed on a base substrate 5 to provide strength reinforcement. Although this base substrate is preferably present when manufacturing the carrier substrate, this substrate may not be present as a carrier substrate. In this case, the material for the thin metal layer is
A1, Cu, Ni, Sn, etc. are preferably used. The thickness of the metal layer may be any thickness that can be removed by the removal method described below, and is preferably 1.2 to 50 μm. Further, as the material for the conductive circuit pattern, A1, Cu, Ni, Sn, Au, Ag, etc. are preferably used. The conductor material and the metal layer material may be the same or different.
When the material of the conductor and the material of the metal are the same, the thickness of the conductor needs to be at least twice the thickness of the metal. In the case of metals in which the material of the conductor and the material of the metal layer are different, this condition does not exist, but the thickness of the metal layer can be made thin as long as it has sufficient strength to withstand the transfer described below.

As the base substrate, polyester film, polyimide film, Teflon film, etc. are preferably used, but it is needless to say that the base substrate is not limited to these, and a wide variety of polymer films can be used.

The base substrate may further have a polymer coating layer on its surface, consisting of a thermoplastic adhesive or an epoxy adhesive, or may be provided with a catalyst for depositing a metal layer on the surface by electroless plating. There is also.

FIG. 4 shows another example of the carrier substrate used in the present invention, in which a conductor circuit pattern 2 is formed on the upper surface of a thin metal film 4'.

In the present invention, the metal layer in the example of FIG.
The metal layer may be plated on the base substrate, or may be formed by vapor deposition, sputtering, or the like, or may be formed by adhering a thin metal foil. The metal layer in the example in Figure 4 is thin.
Metal films such as Cu, A1, Sn, etc. are preferably used.

The conductor circuit pattern formed on the metal layer can be formed by applying a plating resist onto the metal layer by a method such as screen printing, leaving only the conductor circuit pattern, or by applying a photoresist, exposing the circuit pattern, and then developing it. Thereafter, metal is deposited to a desired thickness by electroless plating or electroplating using the metal layer as an electrode, thereby producing a carrier substrate. For example, when electrolytically plating copper to form a conductor circuit pattern, a copper pyrophosphate bath, a copper sulfate bath, and a copper cyanide bath are preferably used.

Next, a method of manufacturing a printed circuit board of the present invention using the above-mentioned carrier substrate will be described. Only the conductor circuit pattern on the carrier substrate is adhesively transferred onto the pre-perforated substrate in the steps described below to produce the perforated printed circuit board of the present invention.

The substrate provided with windows in required portions may be, for example, a film or a laminate made of polyester, polyimide, or the like. However, film materials are particularly preferred. The adhesive used to adhesively transfer the conductor circuit pattern on the carrier board onto the board with holes drilled in the required areas is a method that adhesively transfers the board and the conductor circuit in a state where the adhesive has no fluidity. Therefore, a thermosetting adhesive, particularly an epoxy adhesive, most preferably a phenol-epoxy adhesive, is preferably used.

FIG. 5 shows a carrier substrate coated with adhesive 6.

As shown in FIG. 6, a carrier substrate is bonded with adhesive 6 onto a substrate 7 with a pre-opened window. The hole shown at 8 is a window in the board. In FIG. 6, the adhesive 6 is applied to the carrier substrate for bonding, but the adhesive may also be applied to the substrate 7, or it may be applied to both the carrier substrate surface and the substrate 7. You can stay there. Furthermore, conductor 2
It is also possible to apply it only on top of the . Further, for this adhesion, compression bonding, heat compression bonding, or the like is preferably used. In particular, roll crimping is a preferred method.
In this way, after the conductor 2 is firmly bonded onto the perforated substrate, the base substrate 5 of the carrier substrate is bonded.
is removed, for example, by tearing it off.
Next, only the metal layer 4 is etched, for example.
It is removed leaving only conductor 2. It goes without saying that unnecessary adhesive on the window portion is also removed at this time. If the carrier substrate shown in FIG. 4 is used, it is only necessary to remove the metal film 4', for example by etching. Metals can also be dispersed and removed by irradiation with a powerful radiant energy electron beam.

In this way, the conductive circuit pattern 2 made of conductive metal is transfer-adhered onto the windowed substrate 7, as shown in FIG. 7, and the printed circuit of the present invention having the windowed openings is manufactured. Ru.

According to the transfer method using the carrier substrate of the present invention, it is possible to remove the thin metal layer without peeling it off, and therefore, a printed circuit board with a window can be produced extremely easily and stably. Therefore, the present invention, as a new technology in the production of printed circuits using the additive method, brings about a significant advance in this method, and also provides a low-cost, high-precision window that takes advantage of the features of the additive method. The present invention provides a method for manufacturing a printed circuit board having an opening, and its usefulness is extremely large.

Next, the present invention will be described based on examples, but the present invention is not limited to these examples and can be modified in various ways.

Example 1 10μ on a 0.2mm thick polyester film
A base substrate was prepared by applying a thermoplastic urethane adhesive to a thickness of . Therefore, in order to perform electroless plating of copper on the surface of the underlying substrate, the surface of the coated layer was sensitized by dipping it in an acidic solution of stannous chloride in hydrochloric acid, and then activating the surface of the coated layer with an acidic solution of palladium chloride in hydrochloric acid. Next, manufactured by Situpre,
Using CP-70 electroless plating solution, plating was performed at a temperature of 50°C for 2 hours to form a 10μ thick copper layer on the surface. next,
A plating resist was applied over the copper layer by screen printing leaving the desired conductor circuit pattern. Next, using a copper pyrophosphate plating bath, electrolytic copper with a thickness of 35 μm was deposited on the conductor circuit pattern portion to form a conductor. After thoroughly washing the plating solution with water and drying the surface of the carrier board, apply Bostik's phenol epoxy resin for copper plating to a thickness of 20 μm, dry for 30 minutes, allow the solution to evaporate, and pre-drill holes in the predetermined positions. The polyimide film was placed on a 75μ thick window board at 160℃ for 30 minutes.
I did heat compression bonding. After that, the polyester film was peeled off and the whole was immersed in a copper etching solution made of ferric chloride for 5 minutes to remove the metal layer formed by electroless copper plating, leaving only the copper conductor part. A printed circuit board of the present invention having a window opening in which only the conductor circuit pattern by electroplating was adhesively transferred was produced by dissolving and removing the board. This printed circuit board not only allowed direct bonding of integrated circuits (ICs), but also demonstrated the great utility of the method of the present invention.

Example 2 A resist was printed on an aluminum foil having a thickness of 30 μm by screen printing, leaving only the desired conductor pattern portions. Next, using this aluminum foil as an electrode, electrolytic plating was performed on the conductor circuit pattern portion to form a copper conductor pattern with a thickness of 35 μm. 20 µm of phenol epoxy resin manufactured by Bostik Co., Ltd. was applied as a thermosetting adhesive onto the thus prepared carrier substrate and dried for 30 minutes to evaporate the solvent.

Next, the thickness is determined by opening windows in the required areas in advance.
A carrier substrate was bonded onto a 75μ polyimide film at 160°C for 30 minutes. Next, the above-mentioned carrier board and window board are immersed in a selective etching solution for aluminum for about 10 minutes to dissolve and remove only the aluminum foil, leaving the window board with only the conductor circuit pattern adhesively transferred. The printed circuit of the present invention could be manufactured. Of course, this printed circuit board could be used for direct bonding of ICs.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a printed circuit board with an aperture. Figure 2 shows an IC using the printed circuit shown in Figure 1.
FIG. 3 is a cross-sectional view of the chip 3 in a bonded state. 3 and 4 are cross-sectional views of the carrier substrate of the present invention. FIG. 5 is a cross-sectional view of the carrier substrate of FIG. 3 with adhesive applied thereto. FIG. 6 shows a cross-sectional view of a carrier substrate bonded via an adhesive 6 onto a perforated substrate 7. As shown in FIG. FIG. 7 is a printed circuit with apertures made in accordance with the present invention.

Claims (1)

[Claims] 1 A thermosetting adhesive is applied to a carrier substrate on which a conductive circuit pattern made of a highly conductive metal is formed on a metal layer, or a substrate selected from films or laminates with windows in the required areas. A method for producing a printed circuit board with a window, which comprises applying an agent and drying it, adhesively transferring a conductor circuit pattern of a carrier board onto the board, and then dissolving and removing the metal layer.