JP3166868B2 - Method for manufacturing copper 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 flexible printed wiring board (EPC) and a tape automatic bonding (TAB).
The present invention relates to a method for manufacturing a copper polyimide substrate used as a material for a printed wiring board (PWB) such as a tape.

[0002]

2. Description of the Related Art In recent years, high wiring density and high functionality have been required for printed wiring boards due to the miniaturization and high speed of electronic equipment. For this reason, a substrate material for a printed wiring board is required to have a low dielectric constant, a high insulation resistance, and a good heat resistance. Polyimide resin is attracting attention as a material that satisfies this requirement, and is frequently used as a material such as EPC or TAB tape. A copper polyimide substrate using copper as a metal layer is usually used.

[0003] As a method of forming a copper layer on a polyimide resin film, a lamination method in which a polyimide resin film and a copper foil are pasted with an adhesive has conventionally been adopted. In recent years, a method of forming copper directly on the surface of a polyimide resin film by a sputtering method, an ion plating method, a vapor deposition method, an electroless plating method, or the like has been developed because of adverse effects.

However, when a copper-polyimide substrate obtained by forming a copper layer directly on the surface of a polyimide resin film is left in a high-temperature environment for a long time, the adhesion strength at the interface between the copper layer and the polyimide resin film is reduced. Problems arise.
As a result of various studies on this problem, it was found that the decrease in adhesion strength was caused by the diffusion of copper to the polyimide side. Therefore, as a method for preventing the diffusion of copper, a study was conducted to form a different metal by electroless plating to form a barrier layer. An example of using nickel, cobalt, or an alloy thereof as this dissimilar metal has already been proposed in JP-A-63-286580, but the purpose of this proposal is to prevent a decrease in adhesion strength due to thermal shock during soldering. 0.15 μm as the required metal layer thickness
I have requested more.

[0005] By the way, a copper polyimide substrate is made of EPC or TPC.
When used for an AB tape, it is necessary to form a copper lead by a subtractive method, a semi-additive method, a full-additive method, or the like. For example, when a copper lead is formed by a subtractive method, a copper layer is provided on the surface of a polyimide resin film by electroless plating, and if necessary, electroless plating is performed after electroless plating, and a resist is applied to this surface, and After closely contacting the mask,
Develop and then etch to form the leads and strip the resist.

In this case, the above-mentioned JP-A-63-286580 is used.
When a copper polyimide substrate having a dissimilar metal layer such as nickel as a base obtained by the method disclosed in the above is used, the etching rate between copper and the dissimilar metal layer is different. If the shape of the lead portion is to be maintained well, the underlying dissimilar metal layer remains on the polyimide resin film and causes the insulation resistance between the leads to decrease.When the base is completely dissolved and removed, even the copper lead is etched. Then, the width of the wiring is reduced to about half.

For example, when copper leads are formed by the most general semi-additive method, a copper layer is provided on the surface of a polyimide resin film by electroless plating, and this is used as a base, and a resist is applied to the base surface. After a predetermined mask is brought into close contact, exposure and development are performed, and then copper is deposited on the exposed metal surface by copper electroplating, lead portions are formed, the resist is peeled off, and the base is removed by etching.

In this case, the above-mentioned JP-A-63-286580 is used.
When using a copper polyimide substrate having a dissimilar metal layer such as nickel on the underlayer obtained by the method disclosed in the above, the etching rate between copper and the dissimilar metal layer is different. If the shape of the lead portion is to be maintained well, the dissimilar metal layer serving as the base remains on the polyimide resin film, causing the insulation resistance between the leads to decrease.When the base is completely dissolved and removed, the copper lead is excessively etched. Then, the width of the wiring is reduced to about half.

In view of the above, Japanese Patent Application Laid-Open No. 63-286
In the case where a wiring board is formed using a copper polyimide substrate having a dissimilar metal layer such as nickel as a base obtained by the method disclosed in 580, a step of selectively etching only the dissimilar metal layer such as nickel is included in the manufacturing process. In addition, there is a problem that the lead formation process is complicated.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a copper-polyimide resin film without impairing the adhesion strength.
It is an object of the present invention to provide a copper-polyimide substrate capable of neglecting a decrease in adhesion strength due to long-term standing in a high-temperature environment and enabling the conventional base metal layer removal step to be adopted.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for hydrophilizing the surface of a polyimide resin film, applying a catalyst, performing electroless plating, and then performing electroless copper plating or electrolytic copper plating. In the method for producing a copper-polyimide substrate by carrying out, the hydrazine hydrate is used for 1 to 15 mol for the hydrophilization treatment of the polyimide resin film.
l / l, alkali metal hydroxide 0.5 to 5 mol / l
Using an aqueous solution of 10 to 50 ° C. containing at a ratio of, after applying the catalyst, nickel, cobalt or one of their alloys is electrolessly plated to a thickness of 0.01 to 0.1 μm.
With m, a plating layer having an impurity quality of 10% or less is formed.

In the method of the present invention, usable alkali metals include sodium, potassium, lithium and the like.
The type of impurities in the nickel, cobalt, or alloy layer thereof is not particularly limited, but is usually phosphorus or boron.

[0013]

In the present invention, the reason why the nickel or cobalt or their alloy layers are provided at the interface between the copper and the polyimide resin film is that these layers prevent oxidation of copper and diffusion of copper into the polyimide. .

An aqueous solution of hydrazine hydrate and an alkali metal hydroxide is used as an etching solution for the polyimide resin film because the imide bond is cut by hydrazine hydrate and the polyimide resin film is hydrolyzed by an alkali metal hydroxide. This is for making the surface hydrophilic and facilitating the adsorption of catalyst nuclei for electroless plating.

When the concentration of hydrazine hydrate is less than 1 mol / l, the imide bond is not cut sufficiently, and when the concentration of hydrazine hydrate is more than 15 mol / l, the adhesion strength between the electroless plating layer and the polyimide resin film. The concentration of hydrazine hydrate is 1 to 15 mol
/ L is good. In the case of an alkali metal hydroxide, when the alkali metal hydroxide concentration is less than 0.5 mol / l, hydrolysis is insufficient, and when the alkali metal hydroxide concentration is more than 5 mol / l, the adhesion strength is reduced. The oxide concentration is preferably 0.5 to 5 mol / l.

The method of hydrophilization may be the same as the ordinary etching treatment, and the required treatment time varies depending on conditions and the like.
Although it cannot be specified unconditionally, it is usually about 30 seconds to 5 minutes. Limiting the thickness of nickel or cobalt or their alloy layer to 0.01 to 0.1 μm is 0.01 to 0.1 μm.
If it is less than μm, the diffusion of copper to the polyimide resin film side cannot be sufficiently prevented, and the adhesion strength of the copper-polyimide substrate is reduced by leaving it at about 150 ° C. for a long time in an atmosphere containing oxygen such as the air. If the thickness is 0.1 μm or more, nickel or cobalt or an alloy thereof is left in an etching step of a base when a wiring board is manufactured by a subtractive method or a semi-additive method, thereby lowering insulation resistance between wirings. is there.

Further, in the present invention, the content of impurities in the nickel, cobalt or alloy layer thereof is set to 10% or less. This is to improve the solubility of copper in the etching solution. If it exceeds, the solubility of the nickel or cobalt or their alloy layer is reduced, and in the copper etching step when fabricating a wiring board by a subtractive method or a semi-additive method, the nickel or cobalt or their alloy layer is not removed. This causes a problem that the insulation resistance between the wirings is reduced.

In the present invention, other metals can be used instead of copper, and various conditions may be appropriately selected.

[0019]

The present invention will be described below with reference to examples.

Example 1 A 30 cm square Kapton 200H type polyimide resin film manufactured by Toray DuPont was placed in a 25 ° C. aqueous solution containing 5 mol / l hydrazine foam water and 3 mol / l sodium hydroxide for 60 seconds. After immersion to make the surface of the polyimide resin film hydrophilic, one side was masked, a normal catalyst activation treatment was performed, and the following electroless plating of nickel was performed.

(Bath composition) NiCl ₂ .6H ₂ O: 0.1 M NaH ₂ PO ₂ .H ₂ O: 0.1 M Sodium citrate: 0.2 M pH: 9

(Plating conditions) Temperature: 60 ° C. Time: 30 seconds

The thickness of the obtained electroless nickel plating layer was 0.05 μm. Further, the impurity was only phosphorus, and the content of phosphorus was 7%. Thereafter, the core substrate was subjected to the following electroless copper plating.

(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 Time: 10 minutes

The thickness of the obtained electroless plating layer is 0.4 μm.
m. Further, copper electroplating was performed on the electroless plating layer under the following conditions.

[0027] (bath _{composition) CuSO 4 · 5H 2 O:} 120g / l H 2 SO 4: 150g / l

(Electrolysis conditions) Temperature: 25 ° C. Cathode current density: 2 A / dm ² Stirring: Air stirring Time: 90 minutes

The thickness of the obtained copper layer was 35 μm.
Acrylic resin-based photoresist was applied on the copper layer of the copper-polyimide substrate having a nickel layer obtained here at 10 μm.
And baked at 70 ° C. for 30 minutes. Thereafter, masking was performed on the substrate so that the wiring width became 200 μm, and the photoresist layer was irradiated with ultraviolet rays of 300 mj / cm 2 and developed.

Thereafter, the exposed copper surface was dissolved with the following copper etching solution.

(Bath composition) 30% H ₂ O ₂ : 100 g / l H ₂ SO ₄ : 150 g / l

(Conditions) Temperature: 25 ° C. Time: 4 minutes Stirring: rocking stirring

Thereafter, the resist layer is peeled off at 60 ° C. for 1 minute using a 4 wt% sodium hydroxide aqueous solution.
Observation between wirings and insulation resistance were measured. As a result, no nickel layer remained between the wirings, and the insulation resistance was 1 ×
10 ¹⁰ Ω (IPC-TM-650 2.6.3.2 C
According to the method specified in 24/23/50. ), And good results were obtained. Also, when the adhesion strength between the copper and the polyimide resin film was measured, it was 1100 g /
cm and a good value.

Further, this substrate was left in the atmosphere at 150 ° C. for 1,000 hours in the air, and the adhesion strength was measured. As a result, the adhesion strength was 900 g / cm, and the adhesion strength was hardly reduced.

The result shows that the nickel alloy layer having a thickness of 0.05 μm and an impurity content of 7% of the copper polyimide substrate obtained by the method of the present invention was completely dissolved under the conventional copper etching conditions, and the metal layer and the polyimide layer were mixed. The adhesion strength with the resin film layer hardly decreased even after being left at high temperature, indicating that the wiring board obtained by using the copper polyimide substrate obtained by the method of the present invention has high reliability.

(Example 2) A 30 cm square sample substrate of a Kapton 200H type polyimide resin film manufactured by Du Pont-Toray Co., Ltd. was treated with 10 mol / l of hydrazine hydrate.
After immersing in a 25 ° C. aqueous solution containing potassium hydroxide of mol / l for 60 seconds to make the surface hydrophilic, one side is masked and a normal catalyst activation treatment is performed, and the following electroless plating of cobalt is performed. Processing was performed.

[0037] (bath _{composition) CoSO 4 · 7H 2 O:} 0.05M NaH 2 PO 2 · H 2 O: 0.2M sodium citrate: 0.2M pH: 10

(Plating Conditions) Temperature: 60 ° C. Time: 2 minutes

The thickness of the obtained electroless cobalt plating layer was 0.05 μm. The impurity was only phosphorus, and the content was 3%.

Thereafter, a copper polyimide substrate was prepared in the same manner as in Example 1, and wiring was formed. Then, the observation between wirings and the insulation resistance were measured. As a result, no cobalt layer remained between the wirings, and the insulation resistance was 1 × 10 ¹⁰ Ω (IPC-TM
-650 2.6.3.2 According to the method specified in C-24 / 23/50. )
And good results were obtained. When the adhesion strength between the copper and the polyimide resin film was measured, it was found to be 1000
g / cm, which was a good value.

Further, the substrate was left in the atmosphere at 150 ° C. for 1,000 hours in the air, and the adhesion strength was measured. As a result, the adhesion strength was 800 g / cm, and the adhesion strength was hardly reduced.

The results show that the copper alloy layer of the copper polyimide substrate obtained by the method of the present invention having a thickness of 0.05 μm and an impurity content of 3% was completely dissolved under the conventional copper etching conditions, and the metal layer and the polyimide layer were mixed. The adhesion strength with the resin film layer hardly decreased even after being left at high temperature, indicating that the wiring board obtained by using the copper polyimide substrate obtained by the method of the present invention has high reliability.

Example 3 A copper polyimide substrate was prepared and wiring was formed in the same manner as in Example 1 except that both surfaces of the polyimide resin were subjected to electroless plating of nickel. Then, the observation between wirings and the insulation resistance were measured. As a result, no nickel layer remained between the wires on both sides, and the insulation resistance was 1 × 10 ¹⁰ Ω and 2 × 10 ¹⁰ Ω (IPC-TM-650
2.6.3.2 According to the method specified in C-24 / 23/50. ), And good results were obtained. When the adhesion strength between the copper and the polyimide resin film was measured, it was found that the adhesion strength was 10
The values were 50 g / cm and 950 g / cm, which were values having no practical problems.

Further, this substrate was left in the atmosphere at 150 ° C. for 1,000 hours in the air, and the adhesion strength was measured. As a result, the adhesion strength was 850 g / cm and 750 g / cm, respectively.
cm and the adhesion strength were hardly reduced, which was a good result.

The results show that the nickel alloy layer of the copper-polyimide substrate obtained by the method of the present invention completely dissolved under the conventional copper etching conditions, and that the adhesion strength between the metal layer and the polyimide resin film layer was maintained even after being left at a high temperature. There is almost no decrease, indicating that the wiring board obtained using the copper polyimide substrate obtained by the method of the present invention has high reliability.

Example 4 After electroless plating of nickel,
The same process as in Example 1 was carried out except that direct copper electroplating was carried out to produce a copper polyimide substrate and to form wiring.
Thereafter, observation between wirings and insulation resistance were measured. As a result, no nickel layer remained between the wires, and the insulation resistance was 1 × 10 ¹⁰ Ω (IPC-TM-650 2.6.3.2 C-24 /
According to the method specified in 23/50. ), And good results were obtained. Further, when the adhesion strength between the copper and the polyimide resin film was measured, it was a good value of 1100 g / cm.

Further, the substrate was left in the atmosphere at 150 ° C. for 1,000 hours in the air, and the adhesion strength was measured. As a result, the adhesion strength was 800 g / cm, which was the same as that of Example 1 with almost no decrease in the adhesion strength.

The results show that the nickel alloy layer of the copper-polyimide substrate obtained by the method of the present invention completely dissolved under the conventional copper etching conditions, and that the adhesion strength between the metal layer and the polyimide resin film layer was maintained even after being left at a high temperature. There is almost no decrease, indicating that the wiring board obtained using the copper polyimide substrate obtained by the method of the present invention has high reliability.

Comparative Example 1 A 30 cm square Kapton 200H type polyimide resin film manufactured by Du Pont-Toray Co., Ltd. was mixed with 0.5 mol / l of hydrazine hydrate and 0.3 mol.
Immersion in a 25 ° C. aqueous solution containing 1 / l sodium hydroxide for 2 minutes to make the surface hydrophilic, then masking one side and subjecting it to normal catalyst activation treatment, the same electroless nickel electrolysis as in Example 1 A plating process was performed. As a result, nickel deposition became non-uniform, and the subsequent steps could not be performed.

The results show that when the concentrations of hydrazine hydrate and alkali hydroxide are below the range of the present invention, the formation of the electroless plating layer is insufficient.

Comparative Example 2 A 30 cm square Kapton 200H type polyimide resin film manufactured by Du Pont-Toray Co., Ltd. was placed in a 25 ° C. aqueous solution containing 5 mol / l hydrazine hydrate and 3 ml / l sodium hydroxide for 60 seconds. After immersion to make the surface hydrophilic, one side was masked, a normal catalyst activation treatment was performed, and a nickel electroless plating treatment described below was performed.

(Bath composition) NiCl ₂ .6H ₂ O: 0.1 M NaH ₂ PO ₂ .H ₂ O: 0.1 M Sodium citrate: 0.1 M pH: 5.6

(Plating conditions) Temperature: 60 ° C. Time: 1 minute

The thickness of the obtained electroless nickel plating layer was 0.05 μm. The impurity was phosphorus, and the content was 12%.

In the subsequent tests, the same processing as in Example 1 was performed.
Then, observation between wirings and insulation resistance were measured. as a result,
A nickel layer remains between the wires, and the insulation resistance is 1
× 10 4Ω (specified in IPC-TM-650 2.6.3.2 C-24 / 23/50
Depending on the method. ) And there is a significant drop in resistance
Was.

This result indicates that the nickel alloy layer of the copper polyimide substrate obtained by the method of the present invention having a thickness of 0.05 μm and an impurity content of 12% was not completely dissolved under the conventional copper etching conditions, and the insulation resistance was lowered. It indicates that the reliability is reduced.

Comparative Example 3 A 30 cm square Kapton 200H type polyimide resin film manufactured by Dupont Toray Co., Ltd. was placed in a 25 ° C. aqueous solution containing 5 mol / l hydrazine hydrate and 3 mol / l sodium hydroxide for 30 seconds. After immersion to make the surface hydrophilic, one side was masked, a normal catalyst activation treatment was performed, and a nickel electroless plating treatment described below was performed.

(Bath composition) NiCl ₂ .6H ₂ O: 0.1 M NaH ₂ PO ₂ .H ₂ O: 0.1 M sodium pyrophosphate: 0.2 M pH: 10 Temperature: 60 ° C. Time: 5 minutes

The thickness of the obtained electroless nickel plating layer was 0.15 μm. Further, the content of phosphorus as an impurity was 3.4%.

In the subsequent tests, the same processing as in Example 1 was performed.
Then, observation between wirings and insulation resistance were measured. as a result,
A nickel layer remains between the wires, and the insulation resistance is 5
× 10 6Ω (specified in IPC-TM-650 2.6.3.2 C-24 / 23/50
Depending on the method. ) And there is a significant drop in resistance
Was.

This result shows that when the thickness of the electroless nickel layer formed on the surface of the polyimide resin film is larger than 0.1 μm, even if the impurity content is 10% or less, the nickel layer can be formed under the conventional copper etching conditions. Indicates that the insulation resistance decreases and the reliability decreases.

Comparative Example 4 A 30 cm square Kapton 200H type polyimide resin film manufactured by Toray DuPont was placed in a 25 ° C. aqueous solution containing 5 mol / l hydrazine hydrate and 3 mol / l sodium hydroxide for 30 seconds. After immersion to make the surface hydrophilic, one side was masked, a normal catalyst activation treatment was performed, and a nickel electroless plating treatment described below was performed.

(Bath composition) NiCl ₂ .6H ₂ O: 0.1 M NaH ₂ PO ₂ .H ₂ O: 0.1 M sodium pyrophosphate: 0.2 M pH: 10 Temperature: 60 ° C. Time: 10 seconds

The thickness of the obtained electroless nickel plating layer was 0.005 μm. Further, the content of phosphorus as an impurity was 3.4%.

In the subsequent tests, the same treatment as in Example 1 was performed, and the observation between wirings and the insulation resistance were measured. as a result,
No residual nickel layer was observed between the wires, and the insulation resistance was 1 × 10 14 Ω (by the method specified in IPC-TM-650 2.6.3.2 C-24 / 23/50), and good results were obtained. Obtained.
However, this substrate was placed in an atmosphere at 150 ° C.
When left for 00 hours, the adhesion strength is 1100 to 100
g / cm.

This result indicates that when the thickness of the nickel layer formed on the surface of the polyimide resin film is smaller than 0.01 μm, the adhesion strength is reduced and the reliability is deteriorated by leaving it in a high-temperature environment for a long time. .

[0067]

According to the present invention, it is possible to form an electroless plating layer of nickel or cobalt or an alloy thereof without lowering the adhesion strength, and it is possible to prevent a reduction in adhesion strength in a high-temperature environment. When EPC, TAB, or the like is manufactured using this substrate, a wiring can be formed without nickel, cobalt, or an alloy thereof remaining in the copper etching step. This greatly contributes to improving the reliability of a printed wiring board such as an EPC or TAB tape under a high temperature environment.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Miki Takenaka 12-12 Hoshikoshi-cho, Niihama-shi, Ehime (56) References JP-A-63-286580 (JP, A) JP-A-2- 144987 (JP, A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H05K 3/18

Claims (1)

(57) [Claims] 1. A method for producing a copper-polyimide substrate by hydrophilizing the surface of a polyimide resin film, applying a catalyst, performing electroless plating, and then performing electroless copper plating or electrolytic copper plating. For the hydrophilization treatment of the film, 1 to 15 mol / l of hydrazine hydrate and 0.1 to 0.1 mol of alkali metal hydroxide were used.
Using an aqueous solution of 10 to 50 ° C. containing 5 to 5 mol / l, after applying the catalyst, nickel, cobalt or one of their alloys is electrolessly plated to a thickness of 0.01 to 0.1 μm. Forming a plating layer having an impurity quality of 10% or less.