JPH11204902A - Manufacture of adhesive-coated flexible printed-circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a high thermal resistant adhesive-coated flexible printed-circuit board having no curl at all. SOLUTION: A polyamidic acid film 2 is formed from polyamidic acid solution of polyimide resin having a smaller linear expansion coefficient than that of copper to be annealed at a high temperature after thermocompression bonding with a copper foil 3, so that the polyamidic acid may be turned into ring-closed imide to form the copper foil 3 with polyimide enabling the adhesive-coated flexible printed-circuit board to be manufactured by fluidly coating and drying an adhesive resin solution on this polyimide layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible, heat-resistant adhesive with no curl, which is capable of bonding to another circuit board or bonding and fixing a semiconductor element or an electric or electronic component after forming a circuit. The present invention relates to a method for manufacturing a printed circuit board.

[0002]

2. Description of the Related Art Conventionally, a flexible printed circuit board has
It is manufactured by laminating a copper foil and an insulating film with an adhesive by thermocompression bonding or by applying a polyamic acid resin solution directly on the copper foil and drying to obtain a polyimide flexible printed circuit board without an adhesive layer. . Further, an adhesive resin layer is provided on an insulating layer of a flexible printed circuit board, and is bonded to another printed circuit board, or a semiconductor element or an electronic component is bonded and fixed.

[0003]

However, such a flexible printed circuit board with an adhesive has the following problems. When an insulating film with an adhesive is thermocompression-bonded to a copper foil, the adhesive of the insulating film has a low heat resistance. Therefore, an adhesive having a high heat resistance that needs to be dried at a high temperature is used as the adhesive applied on the insulating layer. I couldn't do that. In addition, in a method of obtaining a polyimide flexible printed circuit board without an adhesive layer by applying a polyamic acid resin directly on a copper foil and drying and then annealing it, since the heat resistance is good, the adhesive applied on the insulating layer is Although a high heat-resistant adhesive can be used, in general, such a polyimide flexible circuit board without an adhesive layer is designed so that no curl occurs without providing an adhesive on the polyimide resin, and the insulating material is insulated. If an adhesive layer is formed on the layer, curling will be greatly generated with the resin layer inside, which will hinder circuit processing and handling.

Accordingly, the present invention has been made as a result of intensive studies in view of the above-mentioned problems of the conventional flexible printed circuit board with an adhesive. An object of the present invention is to provide a method for producing a flexible printed board with an agent.

[0005]

In order to achieve the above object, a method for producing a flexible printed board with an adhesive according to the present invention comprises a polyamic acid solution of a polyimide resin having a linear expansion coefficient after imidization smaller than that of copper. From a polyamic acid film, thermocompression bonding with copper foil and laminating,
A step of annealing the obtained copper foil with a polyamic acid film at a high temperature to close the polyamic acid to obtain a copper foil with a polyimide, and a step of applying and drying an adhesive resin solution on the polyimide layer. And

[0006]

FIG. 1 shows an example of a method for manufacturing a flexible printed circuit board with an adhesive according to the present invention. In FIG. 1, first, a polyamic acid resin solution is cast and applied on a mold releasable substrate, and semi-dried to obtain a polyamic acid film. Next, the polyamic acid film is thermocompression-bonded to the copper foil with the polyamic acid resin surface facing the copper foil while the substrate is still attached, and then the substrate is peeled off. The obtained copper foil with a polyamic acid film is dried and annealed to close the polyamic acid to form a polyimide resin. Further, an adhesive resin solution is cast and coated on the polyimide resin layer to obtain a flexible printed circuit board with an adhesive.

A polyamic acid solution is obtained by mixing and stirring an acid anhydride and a diamine, which are raw materials for polyimide, in a solvent. It is necessary that the coefficient of linear expansion of a polyimide resin obtained by heating and imidizing a polyamic acid be smaller than the coefficient of linear expansion of a copper foil. If the coefficient of linear expansion is larger than that of the copper foil, the copper foil is removed when the adhesive is applied, and curling occurs.

In the method of preparing a polyamic acid film by applying a polyamic acid solution, a doctor blade, a knife coater, a bar coater, a curtain coater, a die coater, a roll coater, a reverse coater and the like can be used.

A metal foil or a resin film can be used as a base material on which the polyamic acid is applied. However, since the polyamic acid film obtained here is subsequently imidized by heating at a high temperature to form a polyimide insulating layer, metal foreign substances are contained. It is not preferable to use a resin film. Since the polyamic acid film is used in a semi-dried state, there is no need to apply a high temperature as in the production of a normal polyimide film, so that a resin film can be used.

As the resin film, a film made of a resin such as polyimide, polyamide imide, polyester, polypropylene and polyethylene can be used. Various release treatments may be applied to the surface of the resin film.

The drying of the polyamic acid film needs to be completed in a semi-dry state containing a solvent. The solvent content at the time of semi-drying is preferably 1% or more and less than 20%. If it is too dry and the solvent content drops below 1%,
Next, in the step of heat lamination with a copper foil, sufficient adhesive strength is not obtained, and a flexible printed board cannot be obtained.
If the drying is insufficient and the solvent remains at 20% or more, it is not preferable because foaming occurs at the time of heat lamination or the resin flows to cause uneven thickness.

For laminating the polyamic acid film and the copper foil, a roll laminator that can be heated can be suitably used. Lamination may be performed by directly laminating a polyamic acid film directly with a copper foil.However, since the polyamic acid film is deformed when peeled off from the substrate or a foreign substance adheres due to static electricity, the substrate used for preparing the polyamic acid film is used. It is better to laminate the polyamic acid film with the polyamic acid film surface facing the copper foil with the film attached to the polyamic acid film. By controlling the heating temperature, the laminating speed, and the laminating pressure, the polyamic acid film and the copper foil are laminated while maintaining a uniform thickness while obtaining a sufficient adhesive strength. The heating temperature depends on the composition of the polyamic acid-filled resin to be used.
It is performed at a temperature of 0 ° C to 200 ° C. If the heating temperature is too high, the polyamic acid softens and flows, resulting in a non-uniform thickness, or the solvent component is rapidly vaporized and foamed. If the heating temperature is too low, sufficient adhesive strength will not be obtained, and peeling will occur in the step of heat imidization. The laminating speed is usually high when the heating temperature is high, and slow when the heating temperature is low. If the lamination pressure is too low, sufficient adhesive strength will not be obtained,
If the pressure is too high, the polyamic acid film flows to cause uneven thickness.

The copper foil on which the polyamic acid film is laminated is heated at a high temperature to close the polyamic acid to form a polyimide. The maximum heating temperature at this time differs depending on the polyamic acid resin used.
It is heated at a maximum temperature of 50 ° C to 450 ° C. Heating is performed in multiple temperature steps. If the temperature is raised from the beginning, the solvent component remaining in the polyamic acid film is undesirably rapidly vaporized and foamed.

Next, an adhesive is applied to the polyimide surface of the obtained copper foil with a polyimide film. The same method as the method for producing a polyamic acid film can be used for the application.

As the adhesive resin, thermoplastic, thermosetting, or a mixture thereof can be used, but epoxy, phenol, polyimide, polyamideimide, polyetherimide and the like can be preferably used. In particular, a resin obtained by mixing an epoxy resin with a silicone-modified polyimide can be bonded at a low temperature, has a high adhesive strength, and has a low moisture absorption rate.

[0016]

EXAMPLE 1 A 15% by weight NMP solution of polyamic acid having a linear expansion coefficient of 10 ppm after imidization was applied on a 75 μm-thick polyester film by a die coater and dried at 100 ° C. for 10 minutes. Thus, a polyamic acid film having a thickness of 50 μm was obtained. The above polyamic acid film was superimposed on a rolled copper foil of 18 μm (manufactured by Nippon Mining Co., Ltd.), and heated and pressed at 140 ° C. with a roll laminator. The obtained polyamic acid film with copper foil was continuously heated at 150 ° C, 200 ° C, 250 ° C, 300 ° C, 35 ° C in a nitrogen dryer.
Each was heated at 0 ° C. for 15 minutes, and further heated at 400 ° C. for 2 hours to perform imidization. The polyimide layer after imidization had a thickness of 25 μm and was curled with a radius of curvature of 50 cm with the copper foil inside. On this polyimide layer, NM of an adhesive resin obtained by mixing a silicone-modified polyimide and an epoxy resin
The P solution was cast and applied with a bar coater,
After drying at 220 ° C. for 3 minutes, an adhesive layer having a thickness of 10 μm was formed. The obtained flexible printed board with adhesive has no curl, and the circuit surface of the semiconductor chip has a temperature of 250 ° C.
Peel strength when heat-pressed for 10 seconds at 1.5kg
/ Cm.

Example 2 A 13% by weight NMP solution of polyamic acid having a linear expansion coefficient of 12 ppm after imidization was applied on a 75 μm-thick polyester film by a die coater, and dried at 100 ° C. for 10 minutes. , Thickness is 40μm
Was obtained. The above polyamic acid film was superimposed on a rolled copper foil of 18 μm (manufactured by Nippon Mining Co., Ltd.), and heated and pressed at 140 ° C. with a roll laminator. The resulting polyamic acid film with copper foil in a nitrogen dryer,
Continuously 150 ° C, 200 ° C, 250 ° C, 300 ° C, 3
Each was heated at 50 ° C. for 15 minutes, and further heated at 400 ° C. for 2 hours to perform imidization. The polyimide layer after imidization had a thickness of 20 μm and was curled with a radius of curvature of 30 cm with the copper foil inside. An NMP solution of a silicone-modified polyimide adhesive resin was cast and applied on the polyimide layer with a bar coater, and dried at 80 ° C., 150 ° C., and 230 ° C. for 5 minutes each to form a 12 μm adhesive layer. The obtained flexible printed board with the adhesive had no curl, and had a peel strength of 1.3 kg / cm when heated and pressed at 250 ° C. for 10 seconds on the circuit surface of the semiconductor chip.

Example 3 A 15% by weight NMP solution of polyamic acid having a linear expansion coefficient of 10 ppm after imidization was applied on a 75 μm-thick polyester film by a die coater and dried at 100 ° C. for 10 minutes. 25 μm thick
Was obtained. The above polyamic acid film was superimposed on a rolled copper foil of 18 μm (manufactured by Nippon Mining Co., Ltd.) and heated and pressed at 130 ° C. with a roll laminator. The resulting polyamic acid film with copper foil in a nitrogen dryer,
Continuously 150 ° C, 200 ° C, 250 ° C, 300 ° C, 3
Each was heated at 50 ° C. for 15 minutes, and further heated at 400 ° C. for 2 hours to perform imidization. The polyimide layer after imidization had a thickness of 12 μm and was curled with a radius of curvature of 60 cm with the copper foil inside. On this polyimide layer, an N-type adhesive resin obtained by mixing a silicone-modified polyimide and an epoxy resin is used.
The MP solution was applied by casting with a bar coater,
After drying at 230C for 5 minutes each, an adhesive layer having a thickness of 10 m was formed. The obtained flexible printed board with adhesive has no curl, and the circuit surface of the semiconductor chip has a temperature of 250 ° C.
Peel strength is 1.6kg when pressed with heat for 10 seconds
/ Cm

Comparative Example 1 A 15 wt% NMP solution of polyamic acid having a linear expansion coefficient of 25 ppm after imidization was applied on a 75 μm thick polyester film by a die coater and dried at 100 ° C. for 10 minutes. , Thickness 50μm
Was obtained. The above polyamic acid film was superimposed on a rolled copper foil of 18 μm (manufactured by Nippon Mining Co., Ltd.), and was heated and pressed at 140 ° C. with a roll laminator. The resulting polyamic acid film with copper foil in a nitrogen dryer,
Continuously 150 ° C, 200 ° C, 250 ° C, 300 ° C, 3
Each was heated at 50 ° C. for 15 minutes, and further heated at 400 ° C. for 2 hours to perform imidization. The polyimide layer after imidization had a thickness of 25 μm and was curled with a radius of curvature of 60 cm with the copper foil outside. An NMP solution of a silicone-modified polyimide adhesive resin was cast and applied on this polyimide layer with a bar coater, and dried at 80 ° C., 150 ° C., and 230 ° C. for 5 minutes each to form a 10 μm adhesive layer. The obtained flexible printed board with an adhesive was curled with a radius of curvature of 10 cm outside the copper foil, and could not be used as a flexible circuit board for processing fine circuits.

[0020]

According to the method of manufacturing a flexible printed circuit board with an adhesive of the present invention, after forming a circuit, it can be bonded to another circuit board or a semiconductor element or an electric / electronic component can be bonded and fixed. And a flexible printed circuit board with an adhesive having good heat resistance can be obtained.

[Brief description of the drawings]

FIG. 1 shows an example of a method for producing a flexible circuit board with an adhesive according to the present invention.

[Explanation of symbols]

 1: Coating base material 2: Amic acid film 3: Copper foil 4: Adhesive resin layer

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H05K 3/38 H05K 3/38 E // C09J 179/08 C09J 179/08 Z (72) Inventor Hideaki Sasashima Shinagawa-ku, Tokyo Shinagawa 2-5-8 Sumitomo Bakelite Co., Ltd.

Claims (2)

[Claims] 1. A step of preparing a polyamic acid film from a polyamic acid solution of a polyimide resin having a linear expansion coefficient smaller than that of copper after imidization, thermocompression bonding with a copper foil, and attaching the obtained polyamic acid film. A method for producing a flexible printed board with an adhesive, comprising: a step of annealing a copper foil at a high temperature to close a polyamic acid to obtain a copper foil with a polyimide; and a step of applying and drying an adhesive resin solution on the polyimide layer. 2. The method for producing a flexible printed board with an adhesive according to claim 1, wherein the adhesive resin is a mixture of a silicone-modified polyimide and an epoxy resin.