JPH04250642A - Method for dissolving polyimide resin - 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]

0001

[Industrial Application Field] The present invention manufactures circuit wiring boards using a substrate obtained by applying a copper coating to the surface of a polyimide resin by electroless plating or subsequent electroplating, and then heat-treating the surface. Regarding how to.

0002

[Prior art] Polyimide resin has excellent heat resistance,
Since its mechanical, electrical, and chemical properties are comparable to or better than other plastic materials, it is often used as an insulating material for electrical equipment. For example, circuit wiring boards such as printed wiring boards (PWB), flexible printed circuits (FPC), and tape automatic bonding (TAB) tapes are manufactured by photo-etching a copper coating provided on the surface of this polyimide resin.

[0003] When manufacturing TAB tape, after the above steps, it is necessary to form a device hole so that the inner lead part that will be bonded to the IC chip is exposed from the polyimide resin, and the polyimide resin in this part is removed by punching or melting. Remove.

[0004] Conventionally, copper polyimide substrates, which are materials for such PWBs, FPCs, and TABs, have generally been obtained by a lamination method in which polyimide resin and copper foil are bonded together with an adhesive. However, in the substrate obtained by this method, impurities such as chlorine ions and sulfate ions are adsorbed to the adhesive layer that exists 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 eliminate these drawbacks, a method has been proposed in which a metal layer is directly formed on the surface of a polyimide resin by electroless plating without intervening an adhesive or the like. For example, after etching and activating the surface of a polyimide resin, a catalyst is applied to the surface, and then electroless plating is applied, followed by electrolytic plating if necessary to obtain a copper polyimide substrate, and the polyimide resin and copper are bonded together. In order to improve adhesion and chemical resistance at high temperatures, the substrate is heat treated at 120° C. or higher. Through this heat treatment, the heat resistance and chemical resistance at high temperatures of the substrate were improved, and the inherently excellent electrical and mechanical properties of the substrate were fully exhibited. It has become possible to obtain highly reliable products when manufacturing FPCs and the like.

However, on the other hand, when producing a TAB tape using the above-mentioned heat-treated substrate,
A new problem has arisen as shown below.

That is, when manufacturing TAB tape using an electroless plated copper polyimide substrate, a plating resist is first applied to the surface of the copper plating film of the substrate,
After exposure and development, copper electroplating is performed on the electroless plating film exposed on the surface, and then the previously applied resist film is removed, and unnecessary parts of the electroless copper plating film are removed. After that, a polyimide resin etching resist is applied to the entire surface of the substrate, a prescribed mask is placed on the resist surface on the polyimide resin side, and after exposure and development, the polyimide resin is dissolved using a solution containing hydrazine hydrate. ,
When a TAB tape is manufactured according to the above steps using a substrate that has been heat treated after electroless plating, the polyimide resin is not sufficiently dissolved in the final step of dissolving the polyimide resin, resulting in a thickness of about 0.01 to 10 μm. A phenomenon occurred in which the resin layer remained discontinuously as an organic film on the copper surface which was the back surface of the copper lead portion. In such a circuit, it is difficult to completely plate the back surface of the copper lead portion with gold or tin, and as a result, problems such as poor bonding between the copper lead and the IC chip often occur.

Furthermore, as the functionality of TAB has recently become more sophisticated, metal layers have been formed on both sides of polyimide resin to ensure conduction between both sides through via holes, thereby forming a signal layer and a ground layer for high frequency signal transmission. However, in this case, the via holes are formed by dissolving the polyimide resin, so the resin layer is not completely dissolved and even a part of it is covered with an organic coating. If it remains on the surface of the metal layer, a problem arises in that conduction is incomplete.

The present inventors have found a method to solve this problem by applying electroless plating to the polyimide resin surface, followed by electroplating if necessary to form a copper coating, and then heat-treating the surface of the polyimide resin. In the process of manufacturing a circuit wiring board by patterning a copper polyimide substrate to form lead parts, etching the electroless plating film in unnecessary parts, and then dissolving and removing the polyimide resin in desired parts of the board. After forming the lead portion, a first step of dissolving most of the polyimide resin in a desired portion of the substrate with a solution containing hydrazine hydrate, and removing an organic film that remains undissolved in the first step and containing ammonium ions. The present invention proposes a method comprising a second step of completely dissolving and removing a desired portion of polyimide by dissolving it using one or more of a solution, a solution containing halogen ions, and a solution that dissolves copper. ing.

[0010] By following this method, it has become possible to obtain a circuit wiring board with relatively high reliability.

[0011] Subsequently, as a result of further investigation, it was found that using a sodium hypochlorite solution in the second step of dissolving the polyimide resin is more effective, and the circuit wiring board thus obtained exhibits high reliability. I understand. However, when etching polyimide resin continuously, the dissolving ability of the sodium hypochlorite solution decreases as the processing amount increases, and the polyimide resin cannot be completely dissolved and removed within a certain processing time, resulting in defective products. A problem has arisen in which . Further, in some cases, a phenomenon in which the copper coating of the substrate changed color was also observed. This discoloration of the copper coating is not improved even after subsequent cleaning with acid, etc., and when gold or tin plating is applied to the copper coating, the resulting plating film will have defects in appearance such as stains, and the product will become unusable. The problem arose that it was not possible.

The present inventor has already discovered that when dissolving polyimide resin in a sodium hypochlorite solution in the second step,
It has been disclosed that the above problems can be solved by specifying the concentration, pH, and temperature of the sodium hypochlorite solution to be used. However, this method requires frequent replenishment of alkali as the pH decreases, resulting in problems in productivity and economy.

[0013]

[Problems to be Solved by the Invention] The object of the present invention is to provide a copper film obtained by applying electroless plating to the surface of a polyimide resin, followed by electroplating if necessary to form a copper coating, and then heat-treating the surface of the polyimide resin. In the process of manufacturing circuit wiring boards using polyimide substrates, even if the polyimide resin of the substrate is continuously dissolved and removed during the process, no insoluble organic film remains and the copper film does not discolor. We are trying to provide a method that will not cause this.

[0014]

[Means for Solving the Problems] As a result of various studies to solve the above problems, the present inventor has developed a solution that is used in the second step of dissolving polyimide resin and contains a certain amount of sodium hypochlorite. Ensuring sufficient dissolving capacity;
If the pH at the start of treatment is above a certain value, decomposition of sodium hypochlorite is difficult to occur even if a large amount of polyimide resin is continuously dissolved, there is no need to replenish alkali, and the surfactant is Solubility and pH by addition
It was discovered that this can be maintained for a longer period of time, leading to the present invention.

That is, the method of the present invention for solving the above problems is obtained by electroless plating a polyimide resin, followed by electroplating if necessary to form a copper coating, and then heat-treating the polyimide resin. After patterning a copper polyimide substrate to form lead parts and etching the copper plating film in unnecessary areas, most of the polyimide resin in the desired areas of the substrate is dissolved in a solution containing hydrazine hydrate (
In the method of manufacturing a circuit wiring board by dissolving the remaining organic film in a sodium hypochlorite solution (first step), the remaining organic film is dissolved in a sodium hypochlorite solution (second step).
It is characterized by containing 0 to 80% by volume of sodium hypochlorite and a surfactant, and having a pH of 12 or more at the start of treatment.

[0016]

[Operation] When dissolving polyimide resin continuously, the reason why the pH of the sodium hypochlorite solution in the second step is frequently adjusted is because the hypochlorite ions in the solution decompose.
This is considered to be because the pH decreases.

[0017] In the present invention, the pH is adjusted by using a solution containing 10 to 80% by volume of sodium hypochlorite and a surfactant and having a pH of 12 or more at the start of the treatment as the dissolving solution in the second step. This makes it possible to eliminate the work of adding alkali for.

If the concentration of the sodium hypochlorite solution used in the present invention is too low, the organic film remaining after the first step cannot be completely removed, and if it is too high, the hypochlorite ion will decompose during the second step. is intense, and the accompanying pH
The drop in the alkali becomes significant and it becomes necessary to replenish the alkali. Therefore, the sodium hypochlorite concentration is 10-8
It is necessary to set it to 0% by volume.

[0019] Furthermore, the pH at the start of treatment is set to 12 or more because if the pH is less than 12, hypochlorite ions in the solution are likely to decompose, and the pH of the solution will decrease significantly. This is because the remaining organic film cannot be removed. Furthermore, the method of adjusting the pH of the solution at the start of treatment is not particularly limited.

[0020] Furthermore, the reason why a surfactant is added to the sodium hypochlorite solution is to further enhance the above effects. In other words, when a surfactant is added, the foaming action of the surfactant can block contact between hypochlorite ions and the atmosphere, and as a result, the decomposition of hypochlorite ions can be suppressed. . Furthermore, the addition of a surfactant improves the permeability of the sodium hyposulfite solution.
Even when fine holes such as via holes are made in polyimide resin, it can sufficiently penetrate into the fine holes and dissolve the organic coating.

[0021] The surfactant to be used may be one that does not decompose under alkaline conditions and does not decompose under hypochlorous acid, and the added concentration is not particularly critical as the effect is sufficiently exerted even if the concentration is extremely small. Further explanation will be given below using examples.

[0022]

[Example] One side of a polyimide resin film with a width of 35 mm, a length of 40 mm, and a thickness of 50 μm was sealed, etched by immersing it in an aqueous solution at 25°C containing 50% by weight of hydrazine hydrate for 30 seconds, and then washed with water. It was immersed in a 5% by weight hydrochloric acid solution for 15 seconds. Wash this with water and use Okuno Pharmaceutical Co., Ltd. O.
After applying catalyst for 5 minutes at 25°C using PC-80 Catalyst M and thoroughly washing with water, OPC manufactured by Okuno Pharmaceutical Co., Ltd.
Acceleration treatment was performed with a -555 accelerator at 25°C for 7 minutes. Furthermore, after washing with water, the surface of the polyimide resin was dried at 20° C. for 2 minutes, and the seal was peeled off. After completing the above pretreatment process, electroless copper plating was performed on the polyimide resin surface under the conditions shown below. (Bath composition) CuSO4.5H2O: 10 g/
lEDTA・2Na: 30
g/l 37%HCHO:
5 m/l dipyridyl
: 10mg/l PEG#1000
: 0.5g/l (plating conditions) Temperature :
Stir at 65℃
: Air stirring time
: pH for 10 minutes
: 12
．． 5

After the obtained substrate was heat-treated for 4 hours in a heating furnace maintained in a nitrogen atmosphere at 350° C., a photoresist PMER HC manufactured by Tokyo Ohka Kogyo Co., Ltd. was applied on the copper film.
-600 was applied evenly to a thickness of 40 μm, and
It was dried at 0°C for 15 minutes. Thereafter, the resist layer was exposed to ultraviolet rays of 1000 mJ/cm2 using a TAB mask, and further developed. Copper electroplating was performed on the electroless plated film exposed thereby under the conditions shown below. (Bath composition) CuSO4・5H2O: 80
g/lH2SO4:
180 g/l (plating conditions) Temperature:
25℃ cathode current density
: 3 A/dm2 stirring
: Air stirring and cathode lock time :
1 hour

The resist layer of the substrate thus obtained was peeled off, and the exposed electroless copper plating film was treated with 20% by weight dichloride dichloride using the electrolytic copper plating film as a mask.
Peeling treatment was performed at 25° C. for 1 minute using an iron aqueous solution. Thereafter, photoresist FSR-S manufactured by Fuji Pharmaceutical Co., Ltd. was applied uniformly to a thickness of 10 μm over the entire surface of the substrate, and the temperature was increased to 70°C.
for 30 minutes, exposed using a mask for device hole opening, developed, and then exposed using hydrazine hydrate for 50 minutes.
The first step of dissolving the polyimide resin was carried out at 0° C. for 5 minutes. Thereafter, a second step of dissolving the polyimide resin was carried out under the conditions shown below. (Liquid composition 1) Sodium hypochlorite solution: 100 m
l/l Sodium oxide sulfonate: 50 mg/l p at the start of treatment
H: 12.0 (adjusted with sodium hydroxide) (dissolution conditions) Time:
Stir for 10 minutes
: none

FS after the above processing
When R was peeled off and the dissolved portion of the polyimide resin was observed, no remaining dissolved polyimide resin was observed. Next, continuous dissolution treatment of polyimide resin was performed using solutions having the liquid composition 1 and the following liquid composition, and the relationship between the amount of polyimide resin to be dissolved, the pH of each solution, and the amount of dissolved polyimide resin was investigated. The results obtained are shown in Table 1. In this test, alkali was not replenished and the liquid temperature was 20°C. The polyimide resin used has 30 device holes per meter.

(Liquid composition 2) Sodium hypochlorite solution: 300 m
l/l Sodium oxide sulfonate: 10 mg/l p at the start of treatment
H: 13.2 (adjusted with sodium hydroxide)

(Liquid composition 3) Sodium hypochlorite solution: 800 m
l/l Sodium oxide sulfonate: 100 mg/l pH at the start of treatment
: 13.5 (adjusted with sodium hydroxide)

(Liquid composition 4) Sodium hypochlorite solution: 300 m
pH at the start of l/l treatment:
13.2 (adjusted with sodium hydroxide)

(Liquid composition 5) Sodium hypochlorite solution: 90
ml/l Sodium calcium sulfonate: 50 mg/l pH at the start of treatment: 13.2 (adjusted with sodium hydroxide)

(Liquid composition 6) Sodium hypochlorite solution: 900 m
l/l Sodium oxide sulfonate: 50 mg/l p at the start of treatment
H: 13.5 (adjusted with sodium hydroxide)

(Liquid composition 7) Sodium hypochlorite solution: 100 m
l/l Sodium oxide sulfonate: 50 mg/l p at the start of treatment
H: 11.5 (adjusted with sodium hydroxide)

Table 1

Table 1 shows that the concentration of the sodium hypochlorite solution used in the second step of dissolving the polyimide resin is 10 to 80% by volume, and the p of the solution at the start of the process is
By setting H to 12 or more and adding a surfactant to the solution, it is expected that a TAB tape with excellent performance can be produced continuously and stably.

[0034]

According to the method of the present invention, an insoluble organic coating can be removed without requiring frequent pH adjustment and without discoloring the copper coating. Therefore, TAB with excellent performance
Tape can be obtained continuously and stably.

Claims (1)

[Claims] [Claim 1] Electroless plating is applied to a polyimide resin, followed by electroplating if necessary to form a copper film, and then heat treatment is performed to obtain a copper polyimide substrate, which is then patterned to form lead parts. After etching the copper plating film on unnecessary parts, most of the polyimide resin on the desired parts of the substrate is dissolved in a solution containing hydrazine hydrate (first step), and then the remaining organic film is etched with hypochlorous acid. In the method of manufacturing a circuit wiring board by dissolving in a sodium solution (second step), the hypochlorous acid solution used in the second step contains 10 to 80% by volume of sodium hypochlorite and surface activity, and the treatment is started. A method for dissolving a polyimide resin, characterized in that the pH is 12 or more.