JPS6235594A - Flexible circuit board and its manufacturing method - 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] (Industrial Application Field) This invention relates to a flexible circuit board and an E133 method thereof, and more specifically to a flexible circuit board in which an electric circuit is printed on a flexible board, and a method for manufacturing the same. It is.

<Conventional technology> Conventionally, the film substrate of a flexible circuit board is a laminate film in which a polyimide or polyester resin film and copper foil are laminated with a thermosetting resin adhesive. A flexible circuit board is obtained by etching to form a conductor pattern that becomes a circuit. However, for conventional film base materials, it is important to have good lamination between copper foil and film, and the process of processing this lamination 1 is complicated, resulting in high costs. A plating catalyst application step was required, and the increase in the number of steps resulted in a problem of high costs.

(Problems to be Solved by the Invention) This invention attempts to solve the above-mentioned conventional problems, and by omitting the conventional troublesome lamination process, the number of steps J3 and the plating catalyst nucleation process are simplified. It is an object of the present invention to provide a flexible circuit board and a method for manufacturing the flexible circuit board, which can be easily manufactured and manufactured at a lower cost than before.

(Means for Solving the Problems) In order to solve the above problems, the means of the first invention, which is a flexible circuit board, is comprised of an insulating polymer film base material, metal fine particles, and a resin composition kneaded together. a paste layer in which a paste is applied to the circuit pattern forming part on the base material so that the metal fine particles are exposed on the surface; and a conductive layer provided on the circuit pattern forming part by electroless plating using the metal fine particles as plating nuclei. It has a structure consisting of a magnetic metal coating and The means of the second invention for obtaining a flexible circuit board is to apply a paste made by kneading metal fine particles and a resin composition to a circuit pattern forming portion on an insulating polymer film base material to form a paste layer. a step of polishing the paste layer and adding the metal fine particles to the base layer;
- ff1 is exposed on the surface; and a step of depositing a conductive metal film on the circuit pattern forming portion by electroless plating using the metal fine particles as plating nuclei. The above-mentioned insulating polymer film base materials include polysulfon, polyethersulfon,
A flexible and insulating polymer film such as polyetheretherketone, polyetherimide, polyimide, etc. is used. The metal particles mixed into the paste are silver and copper.

Spherical or scale-like fine particles of nickel or the like are used.

The conductive metal coating depends on the composition of the electroless plating solution and the temperature of the solution.

A predetermined thickness is achieved by controlling the processing time.

(Function of the Invention) In the first invention, the conductive metal film is deposited by electroless plating via metal fine particles on the surface of the paste layer applied to the circuit pattern forming portion, and is formed in the same pattern as the paste layer. The film base material is insulative, and the conductive metal coating is used as an electric circuit.

In the second invention, a hard paste layer is applied to the film base material in the form of a circuit pattern, and a conductive metal coating is formed on the paste layer. The conductive metal film is formed in the same pattern as the paste layer by depositing and fixing the metal component of the electroless plating solution using the metal fine particles exposed on the surface of the paste layer as plating catalyst nuclei and growing.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

A polysulfon film base material 1 with a thickness of 0.2 m is cut into a predetermined shape, and through holes 2 to 2 are formed in predetermined portions that will become the circuit patterns P for connecting the circuit patterns P on both the upper and lower surfaces.
2 is formed. On one side of the film base material 1, an undercoating paste 3A is applied by printing in the shape of a predetermined circuit pattern P so that each of the through holes 2 to 2 is in a predetermined position. The paste 3 is a paste made by kneading metal fine particles 4 and a soft resin composition, and in this example, it is made of an epoxy resin containing 72% of spherical silver particles with a diameter of about 0.2 μm and a high boiling point epoxy resin. Paste 3 mixed with alcohol solvent
△ was used. The paste 3A has good adhesion and is applied to one surface of the film base material and also to the inside of the n-holes 2 and 2.

The film base material 1 coated with the paste 3A is transferred to a heating chamber and heated at 150° C. for 20 minutes to harden the paste 3A and form a hard paste layer 3. Next, the upper surface of the paste layer 3 of the film base material 1 is subjected to chemical polishing by immersion in a chemical solution or polishing treatment by mechanical polishing to expose the metal fine particles 4 to 4 on the surface of the paste layer 3. After that, the film base material 1 having the paste layer 3 is immersed in an electroless plating solution (chemical plating solution) M to remove metal fine particles 4 on the surface of the paste layer 3.
Electroless plating (chemical plating) using ~4 as a plating catalyst nucleus
A conductive metal film 5 is formed by performing the following steps.

That is, since the surface of the layer 3 is where the metal fine particles 4 to 4 are exposed, the gold hole component of the electroless plating solution M precipitates and grows on the exposed metal fine particles 4 to 4, and the film base material 1 A conductive metal coating 5 is formed on the base material surface and the paste layer 3 of the through hole 2, and the through hole 2 on which the metal coating 5 is formed
2 are through holes 6 for connecting the conductive metal coatings 5 on both sides of the film base material 1. In this example, the film base material 1 is immersed in an electroless plating solution M having the liquid composition shown in the table below, and the paste layer 3 is coated with metal under the processing conditions of a solution temperature of 468 to 72°C, a plating speed of rcJ, and a plating rate of 2.5 to 5 μ/h. Copper was deposited to form a copper coating.

<Table> Electroless plating solution composition In addition, electroless plating solution M contains il! ia lubricant, stabilizer.

Plating properties can be improved by adding a small amount of a conductivity improver.

Thereafter, the film base material 1 was taken out from the electroless plating solution M, washed with water, and dried to obtain a circuit board 7 having a metal coating 5 having the same circuit pattern P as the paste layer 3. That is, this circuit board 7 includes an insulating film base material 1, a paste layer 3 coated and cured in a circuit pattern on the base material, and metal fine particles 4 to 4 of the paste layer 3. It has a structure consisting of a conductive metal coating 5 deposited by electroless plating as a plating catalyst core, and has a predetermined circuit pattern P with the metal coating 5 deposited only on the paste diagram 3 portion, and The film base material 1 is flexible because it uses a film body. The physical properties of the copper coating in this example were determined to have a tensile strength of 35 to 45 Kyl. Growth rate 1
It was 0 to 20%, and was sufficiently applicable to practical use.

In the circuit board 7 of the above embodiment, the circuit pattern P was formed on one side of the film base material 1, but as shown in FIG. Accordingly, a predetermined circuit pattern Q1. made of the conductive metal coating 15 is formed on both sides of the film base material 11. Q2
A flexible circuit board 17 can be obtained. Note that the circuit pattern Q1. Q2 is connected by a predetermined through hole 18.

(Effects of the Invention) Since the present invention is a means for solving the above-described problem, the desired problem can be solved by the above-mentioned action. That is, according to the first invention and the second invention, it is possible to omit the conventional laminating process and the plating catalyst nucleation process for electroless plating, and it is easy to manufacture. It is possible to reduce costs by improving

[Brief explanation of drawings]

The drawings show an example of the manufacturing process of the present invention, and FIG. 1 is an enlarged sectional view of a film base material on which a paste layer is formed,
The figure is an explanatory diagram of the action of electroless plating treatment, Figure 3 is an enlarged sectional view of the film base material on which the conductive metal coating is formed, Figure 4 is a front view showing a part of the formed circuit board, and Figure 5 The figure is an enlarged cross-sectional view of the main part showing the cutting down of the circuit board. 1.11...Film base material 3.13...Paste layer 3Δ...Paste 4.14...Metal fine particles 5.15...Conductive metal coating 7.17...Circuit board

Claims (2)

[Claims] (1) A paste layer in which a paste made by kneading an insulating polymer film base material, metal fine particles, and a resin composition is applied to the circuit pattern forming portion of the base material so that the metal fine particles are exposed on the surface. A flexible circuit board comprising: and a conductive metal coating provided on the circuit pattern forming portion by electroless plating using the metal fine particles as plating nuclei. (2) A step of applying a paste obtained by kneading metal fine particles and a resin composition to a circuit pattern forming portion on an insulating polymer film base material to form a paste layer, and polishing the paste layer. , a step of exposing the metal fine particles on the surface of the paste layer; and a step of depositing a conductive metal film on the circuit pattern forming portion by electroless plating using the metal fine particles as plating nuclei. Method of manufacturing circuit boards.