JP2982323B2 - Method for manufacturing polyimide substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyimide substrate having good adhesion at high temperatures.

[0002]

2. Description of the Related Art Polyimide resins have excellent heat resistance.
It also has good mechanical, electrical and chemical properties and is comparable to other plastics. For this reason, the polyimide resin is used as an insulating material for parts for electric equipment such as a printed wiring board (PWB), a flexible printed circuit (FPC), and a board for mounting a tape automatic bonding (TAB).

[0003] Such a PWB, FPC, or TAB mounting substrate is formed by processing a substrate provided with a conductive coating on the surface of a polyimide resin. Examples of a method for directly forming a conductive film on a polyimide resin include a sputtering method, an evaporation method, an ion plating method, an electroless plating method, a casting method, and a thermocompression bonding method. However, the substrates formed by these methods have a drawback that if the substrates are left in a high-temperature environment such as 200 ° C. for 10 minutes, the adhesion strength between the conductive coating and the polyimide resin is remarkably reduced, so that the substrates cannot be used. Various methods have been studied to solve this drawback. One of the most effective methods among them is a method of heat-treating the substrate at a temperature of 200 ° C. or more. According to this method, the adhesion strength in a high temperature environment is certainly improved. However, the degree of this improvement is related to the thickness of the conductive film, and as the thickness of the film increases, the degree of improvement decreases, and the film thickness becomes 10 μm.
If it exceeds m, there is a phenomenon that the degree of reduction becomes remarkable, and there is a problem that the adhesion strength varies between the obtained products.

In order to solve this problem, further studies have been made, and a method of performing heat treatment after performing electroless plating on a polyimide resin has been studied. According to this method, the adhesion strength between the electroless plating film and the polyimide resin was increased, and a stable value was obtained. However, if the electroless plating film is applied and then heat-treated, and then the surface of the electroless plating film is subjected to activation treatment such as alkali degreasing, electrolytic degreasing, and pickling, then the electroless plating film and the electrolytic plating film are applied. It was found that the film was easily peeled off from the boundary with. PWB or FPC using such a substrate
When TAB or TAB is formed, peeling, short-circuiting, or disconnection of the lead occurs, resulting in an unreliable product.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polyimide substrate having a high adhesion strength between an electroless plating film and an electrolytic plating film, which enables the production of highly reliable PWB, FPC and TAB. In the offer.

[0006]

According to the present invention, there is provided a method of manufacturing a polyimide substrate having a conductive film provided on one or both surfaces of a polyimide resin.
After a conductive thin film having a thickness of 10 μm or less, preferably 5 μm or less is provided on the surface of the polyimide resin, the conductive thin film is formed in an inert atmosphere.
Heat treatment at 0 to 500 ° C., and then washing the surface of the conductive film with a solution containing at least one ion selected from the group consisting of hypochlorite ion, chlorite ion and perchlorate ion. The conductive thin film is formed by further performing electroplating on the surface of the conductive thin film.

[0007]

Generally, when an electrolytic plating film is provided on a conductive thin film, an activation process such as alkali degreasing, electrolytic degreasing, pickling, etc. is performed to remove dirt and oxide film on the surface of the conductive thin film. . The purpose is to prevent the conductive thin film and the electrolytic plating film from peeling off. When a conductive thin film is provided on the surface of a polyimide resin and then an electrolytic plating film is provided thereon, the adhesion strength between the conductive thin film and the electrolytic plating film is obtained by performing the above-described activation treatment without performing heat treatment. Is large, and peeling occurs from the interface between the conductive thin film and the polyimide resin. After the heat treatment, the pre-treatment is performed in the same manner, and then the electrolytic plating is performed. Then, separation occurs from the interface between the conductive thin film and the electrolytic plating film. It is not clear whether the use of a solution containing at least one of perchlorate ions increases the adhesion strength between the conductive thin film and the electrolytic plating film. The present inventors volatilize substances such as an unpolymerized substance and a plasticizer from the polyimide resin during the heat treatment, and a substance such as inorganic carbon generated by thermal decomposition adheres to the surface of the conductive thin film and the activity of the surface of the thin film is reduced. It is presumed that activation is possible only by strongly oxidizing substances such as hypochlorite ion, chlorite ion and perchlorate ion.

In the present invention, the solution containing hypochlorite ion, chlorite ion and perchlorate ion is obtained by dissolving hypochlorite, chlorite and perchlorate in water, respectively. However, the type of each salt is not particularly particular. For example, in the case of hypochlorite, sodium salts and potassium salts are suitable from the viewpoint of cost and ease of handling.

The pretreatment conditions, such as the concentration of each ion, cannot be limited because they are affected by the heat treatment conditions of the electroless plating film, but are usually 0.01 to 5 mol / l, in order to prevent the decomposition of each ion. The pH is preferably adjusted to 7 or more.
Further, the processing time is preferably from 5 seconds to 30 minutes, and the liquid temperature during the processing is preferably from 10 to 60 ° C. from the viewpoint of preventing the working environment from deteriorating.

[0010] The conductive thin film and the electrolytic plating film referred to in the present invention are those obtained by using metals such as copper, gold, silver, nickel, cobalt and palladium and alloys thereof, and conductive oxides and semiconductors. . Hereinafter, the present invention will be further described using examples.

[0011]

【Example】

(Example 1) Kanegabuchi Chemical Co., Ltd. measuring 30 × 30 cm
A test sample of an Apical NPI-50 polyimide resin film was placed in a 25% hydrazine hydrate solution at 25 ° C. for 30 minutes.
After dipping for 2 seconds and making the surface hydrophilic, mask one side,
A normal activation treatment was performed, and an electroless plating treatment was performed under the following conditions.

(Bath composition) CuSO ₄ .5H ₂ O 10 g / l EDTA.2Na 30 g / l 37% HCHO 5 g / l Dipyridyl 20 mg / l PEG # 1000 0.5 g / l

(Plating conditions) Temperature 65 ° C. Stirring Air stirring time 20 minutes

The thickness of the obtained electroless plating film is 0.4
μm. This was placed in an atmosphere adjusting furnace, heated to 350 ° C. at a rate of 10 ° C./min in an argon atmosphere, heated at 350 ° C. for 10 hours, and then naturally cooled to room temperature while being kept in the furnace. Thereafter, the copper surface was heated at 25 ° C.
It was immersed in a 5 mol / l sodium hypochlorite solution for 3 minutes, and then subjected to electrolytic copper plating under the following conditions.

[0015] (bath _{composition) CuSO 4 · 5H 2 O 120} g / l H 2 SO 4 150 g / l

(Electrolysis conditions) Temperature 25 ° C. Stirring Stirring time by air blowing 90 minutes Current density 2 A / dm ² The thickness of the obtained copper film was 35 μm.

Next, a resist is applied to the copper surface, a predetermined mask is brought into close contact, exposed, developed, and etched to form a strip-shaped copper layer having a width of 10 mm and a length of 100 mm. The adhesion was examined by pulling up and peeling off the substrate at right angles. As a result, the adhesion strength is 1k
g / cm 2 or more, and peeling occurred between the copper layer and the polyimide layer, indicating that the adhesion between the electroless plating film and the electrolytic copper plating film was good. Therefore, by using the polyimide substrate of this embodiment, a highly reliable P
It turns out that it is possible to create WB, FPC and TAB.

Comparative Example 1 A substrate was obtained in the same manner as in Example 1 except that the activation treatment after the heat treatment was performed by electrolytic degreasing without using a sodium hypochlorite solution, and the adhesion of the copper layer was similarly performed. The sex was examined. As a result, the adhesion strength is 1 kg / cm
Before and after, 23% of the total number of surveys showed peeling between the electroless plating film and the electrolytic copper plating film. This means that the substrate obtained by this method has a highly reliable P
This indicates that WB, FPC, and TAB cannot be created.

(Example 2) A test material in which a copper coating having a thickness of 0.6 μm was provided on a 30 × 30 cm Kapton 200H type polyimide resin film manufactured by Dupont Toray Co., Ltd. by a sputtering method was used as an atmosphere control furnace. Then, the temperature was raised to 420 ° C. at a rate of 10 ° C./min in an argon atmosphere, and the temperature was maintained for 1 hour. Thereafter, the copper surface was immersed in a 3.1 mol / l ammonium perchlorate solution at 25 ° C. for 10 seconds, and then subjected to electrolytic copper plating in the same manner as in Example 1 to obtain a copper film having a thickness of 35 μm.

Next, the adhesion strength between the copper layer and the polyimide layer was examined in the same manner as in Example 1. As a result, it was found that the adhesion strength was 1 kg / cm 2 or more, the peeling occurred between the copper layer and the polyimide layer, and the adhesion between the electrolytic copper plating film and the copper film deposited by the sputtering method was good. . Therefore, by using the polyimide substrate of this embodiment, it is possible to produce highly reliable PWB, FPC, or TAB.

Comparative Example 2 A substrate was obtained in the same manner as in Example 2 except that the activation treatment after the heat treatment was performed by alkali degreasing without using an ammonium perchlorate solution, and the adhesion of the copper layer was similarly performed. Was examined. As a result, the adhesion strength was 1 kg /
cm 2, and 18% of the total number of samples was peeled between the copper film formed by the sputtering method and the electrolytic copper plating film. This indicates that a substrate obtained by this method cannot produce highly reliable PWB, FPC, or TAB.

(Example 3) A test sample of a polyimide resin film of Upilex-50SS type having a size of 30 × 30 cm manufactured by Ube Industries, Ltd. was immersed in a 25% hydrazine hydrate solution at 25 ° C. for 30 seconds. After making the surface hydrophilic, one surface was masked, a normal activation treatment was performed, and an electroless nickel-boron plating treatment was performed under the following conditions.

[0023] (bath _{composition) NiSO 4 · 6H 2 O 30} g / l DMAB 5 g / l glycine 18 g / l malic acid 27 g / l aqueous ammonia (28%) 30 g / l

(Plating conditions) Temperature 70 ° C. Stirring Air stirring time 2 minutes

The thickness of the obtained electroless plating film is 0.2
μm. This was placed in an atmosphere adjusting furnace, heated to 480 ° C. at a rate of 100 ° C./min in an argon atmosphere, held for 5 minutes, and then cooled to room temperature at a rate of 20 ° C./min. Thereafter, the copper surface was immersed in a 0.1 mol / l calcium hypochlorite solution at 25 ° C. for 10 minutes, and then subjected to electrolytic copper plating in the same manner as in Example 1 to a thickness of 3
A conductive film of 5 μm was obtained.

Next, the adhesion strength between the conductive film and the polyimide layer was examined in the same manner as in Example 1. As a result, it was found that the adhesion strength was 1 kg / cm 2 or more, the peeling occurred between the conductive film and the polyimide layer, and the adhesion between the electrolytic copper plating film and the electroless nickel / boron film was good. Was. Therefore, by using the polyimide substrate of this embodiment, it is possible to produce highly reliable PWB, FPC, or TAB.

[0027]

According to the method of the present invention, a substrate having good adhesion between the conductive layer and the polyimide layer can be manufactured. By using the polyimide substrate thus obtained, highly reliable PWB, FPC or TAB can be produced.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05K 3/38 H05K 3/18 B32B 15/08

Claims (5)

(57) [Claims] In a method of manufacturing a polyimide substrate having a conductive film provided on one or both sides of a polyimide resin, a conductive thin film having a thickness of 10 μm or less is provided on the surface of the polyimide resin, and then the thin film is subjected to 300 to 300 μm in an inert atmosphere. Heat treatment at 500 ° C., and then wash the surface of the conductive film with a solution containing at least one ion of hypochlorite ion, chlorite ion, and perchlorate ion; Forming a conductive film by further performing electroplating on the surface of the polyimide substrate. 2. A conductive thin film formed on one or both sides of a polyimide resin by at least one of sputtering, vapor deposition, ion plating, electroless plating, casting, thermocompression, and electrolytic plating. 2. The method for producing a polyimide substrate according to claim 1, wherein a heat treatment is performed after the step (a). 3. A hypochlorite ion, a chlorite ion,
A solution containing at least one of perchlorate ions has a temperature of 10 to 60 ° C, a concentration of 0.01 to 5 mol / l, and a pH
3. The method for producing a polyimide substrate according to claim 1, wherein the solution is 7 or more, and the cleaning time is 5 seconds to 30 minutes. 4. The conductive thin film and the conductive coating are copper,
4. The method for producing a polyimide substrate according to claim 1, comprising at least one of gold, silver, nickel, cobalt, palladium, a conductive oxide, and a semiconductor. 5. The method according to claim 1, wherein the conductive film has a thickness of 5 μm or less.