JPH04187774A - Method for etching polyimide resin - Google Patents

Abstract

PURPOSE:To improve the adhesion of the surface of a copper-polyimide substrate to a resist and to enhance etching accuracy by washing the surface of the substrate with toluene at a prescribed temp., forming an etching resist layer and carrying out etching. CONSTITUTION:The surface of polyimide resin is electroless-plated or further electroplated and a copper-polyimide substrate is formed. The surface of this substrate is washed with toluene at 30-50 deg.C to remove impurities sticking to the surface and to improve the adhesion to an etching resist layer formed on the surface. The etching resist layer is then formed on the washed surface and the part of the substrate not covered with the layer is etched.

Description

[Detailed description of the invention] [Industrial application field] The present invention forms a copper coating on the surface of a polyimide resin by electroless plating or subsequent electrolytic plating,
The present invention then relates to a method of forming a circuit using a copper polyimide substrate obtained by subjecting it to heat treatment.

[Prior Art] Polyimide resin has excellent heat resistance and mechanical, electrical, and chemical properties comparable to other plastic materials, so it is often used as an insulating material for electrical equipment. There is. For example, printed wiring boards (PWB), flexible printed circuits (FPC), tape automatic bonding (TAB) mounting, etc. are manufactured by processing copper polyimide substrates obtained by forming a copper coating on this polyimide resin. It will be done.

Conventionally, copper polyimide substrates, which are materials for such PWBs, FPCs, and TABs, have generally been manufactured using a lamination method in which polyimide resin and copper foil are bonded together using an adhesive.

However, in the substrate obtained by this lamination method, impurities such as chlorine ions and sulfate ions are adsorbed to the adhesive layer existing at the interface between the copper coating and the polyimide resin during the etching process of the copper coating and the peeling process of the photoresist. If the distance between the circuits formed on the substrate is particularly narrow, problems such as poor insulation may occur. In order to overcome these drawbacks, a method has been proposed in which a metal layer is directly formed on the surface of a polyimide resin without intervening an adhesive or the like to obtain a copper polyimide substrate. For example, a copper polyimide substrate is obtained by etching and activating the polyimide resin surface, applying a catalyst, then electroless plating and, if necessary, continuing electrolytic plating. The substrate is heat treated at 120''C or higher to improve adhesion and chemical resistance.

[Problems to be Solved by the Invention] The copper polyimide substrate obtained by the above method not only maintains high adhesion between the copper coating and the polyimide resin even in a high temperature environment, but also has excellent chemical resistance, so it is suitable for PWB.
It is suitable as a material for electronic components such as SFPC and TAB.

By the way, a general process for manufacturing a TAB, which allows for the highest density among the above-mentioned electronic components, includes a process of forming holes such as sprocket holes and device holes. This process involves forming a resist layer on the polyimide resin surface of a copper polyimide substrate, exposing it to light using a desired mask, developing and dissolving it to expose a desired part of the polyimide resin, and removing this part by etching. It is something. When the polyimide resin of the copper polyimide substrate obtained by the above method is etched using this method, unlike the conventional method, the part covered with the polyimide resin etching resist layer is etched, making it impossible to obtain holes of the desired shape. A new problem has arisen.

The purpose of the present invention is to form a copper coating by electroless plating on the surface of a polyimide resin, and if necessary, to perform subsequent electrolytic plating, and then to dissolve the polyimide resin portion of the copper polyimide substrate obtained by heat treatment. An object of the present invention is to provide a method for etching a polyimide resin that enables only desired portions of the polyimide resin to be dissolved during removal.

[Means for Solving the Problems] As a result of various studies in order to solve the above problems, the present inventors found that because the adhesion between the polyimide resin surface and the etching resist was insufficient, the solution of the polyimide resin did not interact with the polyimide resin. It was discovered that the polyimide resin penetrates into the interface of the etching resist, and the polyimide resin begins to dissolve from the interface, and as a result, part of the polyimide resin that is covered with the etching resist layer and should not be dissolved is also dissolved. This led to the present invention.

That is, the method of the present invention for solving the above problems involves forming a copper coating on the surface of a polyimide resin by electroless plating, if necessary, by subsequent electrolytic plating, and then heat-treating the surface of the polyimide resin. In etching the polyimide resin of a polyimide substrate, the surface of the polyimide resin is cleaned with toluene at 30 to 50 DEG C., and then an etching resist layer is formed and etched to dissolve and remove the polyimide resin in desired areas.

[Action] A copper film is formed by electroless plating on the surface of the copolyimide resin, if necessary, by electrolytic plating, and then heat treatment is performed to form a copper film between the polyimide resin surface and the etching resist of the copper polyimide substrate. The reason why sufficient adhesion cannot be obtained is that impurities adhere to the polyimide resin surface when the substrate is heat-treated, and these impurities cannot be completely removed by normal cleaning methods and remain on the polyimide resin surface. it is conceivable that. Although sufficient knowledge has not been obtained regarding the mechanism by which the impurities are generated, it is thought that substances generated from within the polyimide resin when the substrate was heat-treated adhered firmly to the surface of the polyimide resin.

The present invention improves the adhesion between the polyimide resin surface and the etching resist by cleaning the polyimide resin surface with toluene before applying the etching resist to the substrate. This is the knowledge obtained as a result of this, and it is considered to be the most effective cleaning method for removing the impurities.

The toluene cleaning performed in the present invention is performed using toluene at 30 to 50°C. If the temperature of toluene is 30° C. or lower, the resulting product will not have sufficient adhesion and the polyimide resin portion covered with the etching resist will be partially dissolved during etching of the polyimide resin. Furthermore, when the temperature of toluene exceeds 50°C, although the cleaning effect is satisfactory, the working environment is significantly degraded, and the risk of ignition and explosion of toluene increases.

The cleaning time in the present invention is influenced by the heat treatment conditions of the substrate and cannot be determined unconditionally. Therefore, during the treatment, it is necessary to determine appropriate conditions in advance through preliminary experiments to avoid insufficient cleaning.

Note that it is not necessary to use a special etching resist for polyimide resin, as long as it is resistant to a solution of polyimide resin, and the effects of the present invention can be sufficiently obtained under conventional conditions for formation.

[Example 1] After forming a copper plating film with a thickness of 1.5 μm on an NPI-50 type polyimide film manufactured by Kanekabuchi Kagaku Kogyo Co., Ltd. by electroless copper plating method, the substrate was left standing in a vacuum heating furnace. Temperature increase rate 10℃/win at vacuum level 10-' torr
After heating at 400° C. for 1 hour, the mixture was cooled to room temperature. The obtained substrate was added to toluene at 40℃ for 5 minutes.
The sample was immersed for a minute, washed with ethyl alcohol, thoroughly washed with water, and dried. Thereafter, a photoresist PMERHC-600 manufactured by Tokyo Ohka Kogyo Co., Ltd. was applied to a thickness of 4 mm on the copper plating film of the substrate.
It was applied uniformly to a thickness of 0 μm and dried at 70° C. for 30 minutes. Thereafter, a mixture of photoresist FSR-S manufactured by Fuji Pharmaceutical Co., Ltd. and diluent FSR-T in an equal volume ratio was uniformly applied to the polyimide resin surface of the substrate to a thickness of 10 μm, and heated at 70°C for 30 minutes.
Dry for a minute. Masking was performed on the PMER side of the obtained substrate so that leads with a lead width of 70 μm and a lead spacing of 60 μm were formed at the inner lead part, while the PS
Masking was performed on the R side so that a device hole and a sprocket hole were formed, and each photoresist layer was injected with 1000 mJ/c+i'' and 100 m
After irradiation with ultraviolet rays of "J/c+a", development was performed. After that, copper was electroplated to a thickness of 35 μm on the exposed electroless copper plating film, and after PMER was removed, the electroless copper plating film was electroplated. Dissolution and removal was performed using the copper plating film as a mask.Fuji Pharmaceutical Co., Ltd. photoresist FS was then applied to the electrolytic copper plating film and the exposed polyimide resin surface.
Apply R-S uniformly to a thickness of 15 μm and heat at 130℃ for 3
Dry for 0 minutes.

The substrate obtained by the above treatment was added to hydrazine hydrate for 50 min.
The polyimide resin was dissolved and removed by immersion at ℃ for 5 minutes. Furthermore, by peeling off the FSR from the substrate, a TAB tape having leads with a lead width of 70 μm and a lead spacing of 60 μm at the inner lead portion was obtained.

The polyimide resin opening shape in the obtained TAB tape was good, and a TAB tape having excellent electrical, mechanical, and heat resistance properties could be manufactured accurately and stably.

[Example 2] A TAB tape was manufactured in the same manner as in Example 1, except that the substrate was washed with toluene at 30° C. for 10 minutes.

The polyimide resin opening shape in the obtained TAB tape was good, and a TAB tape having excellent electrical, mechanical, and heat resistance properties could be manufactured accurately and stably.

[Comparative Example 1] In the process of Example 1, the 6 substrates were not cleaned with toluene, and the other steps were performed using TAB in the same manner as in Example 1.
manufactured the tape.

Regarding the shape of the polyimide resin openings in the obtained TAB tape, over-etching of about 1100t1 was observed in the device hole portion and the sprocket hole portion, and this TAB tape would lack reliability when used as an electronic component.

[Comparative Example 2] A TAB tape was manufactured in the same manner as in Example 1, except that the substrate was cleaned with toluene at 20''C for 1 hour.

Regarding the shape of the polyimide resin openings in the obtained TAB tape, over-etching of about 50 μm was observed in the device hole portion and the sprocket hole portion, and this TAB tape would lack reliability when used as an electronic component.

[Effects of the Invention] According to the method of the present invention, the adhesion between the polyimide resin surface and the etching resist can be easily improved.

Therefore, the etching accuracy of the polyimide resin is improved, and a TAB tape that is excellent electrically, mechanically, and thermally can be manufactured accurately and stably.

Patent applicant: Sumitomo Metal Mining Co., Ltd.

Claims (1)

[Claims] By electroless plating on the polyimide resin surface,
In etching the polyimide resin of the copper polyimide substrate obtained by forming a copper coating by subsequent electrolytic plating if necessary and then applying heat treatment, after cleaning the surface of the polyimide resin with toluene at 30 to 50 ° C. A polyimide resin etching method characterized by forming an etching resist layer and etching.