JPH07162129A - Pretreatment method for electroless plating - Google Patents

Abstract

PURPOSE:To provide a method for formation of a metal layer by electroless plating on the surface only of the circuit formed on a board using a board obtained by heat treatment after a metal layer formed on a polyimide resin surface by non-electroless plating or by, first, electroplating and, next, electroplating. CONSTITUTION:After a circuit has been formed by patterning the metal layer of a board, the board surface is treated by a treatment solution containing hypochlorous acid, and a catalyzer is given to the circuit and polyimide resin surface. Then, the catalyzer-absorbed polyimide resin is eluted, and then a metal layer is formed on the circuit surface by electroless plating. Consequently, as a metal layer can be formed only on the surface of the circuit after it is formed by an electroless plating method even when a board is used, the electronic part such as TAB, FPC and the like, having multifunction and a high reliability, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pretreatment method for subjecting a circuit surface formed on a polyimide resin surface only to an electroless plating method.

[0002]

2. Description of the Related Art Flexible printed circuit (FPC)
Electronic components such as plates and tape automatic bonding (TAB) tapes can be obtained from a copper-polyimide substrate having a copper coating formed on the surface of a polyimide resin. As one of the copper-polyimide substrates, there is electroless plating on the surface of a polyimide resin, or electroless plating followed by electroplating, followed by heat treatment at about 400 ° C. This substrate is not only excellent in heat resistance and chemical resistance, but also has various advantages.

For example, this copper-polyimide substrate has no adhesive layer at the interface between the polyimide resin and the copper coating,
There is no defect that impurities adhere to the adhesive layer exposed at the time of circuit formation and cause insulation failure between circuits. Therefore, electronic components such as FPCs and TAB tapes produced using this substrate have high thermal and electrical reliability.

By the way, the recent increase in the density and multifunction of electronic parts has required the density and the function of wiring in FPCs and TABs. For example, a circuit board has a three-layer structure of copper, nickel, and gold from the surface of an insulator.
The following methods have been studied to obtain such a substrate.

(1) A circuit is formed by patterning a metal layer of a copper polyimide substrate. (2) A catalyst is applied to the entire surface of the substrate. (3) The catalyst adsorbed on the surface of the polyimide resin is dissolved and removed together with the resin using a polyimide resin solution such as a hydrazine-containing solution. (4) Apply electroless nickel plating to the circuit surface. (5) Finally, electroless gold plating is applied to the circuit surface.

However, when this method is applied to a substrate formed by a process including the above-mentioned heat treatment, good results are not always obtained. This is because the problem that a metal layer is formed not only on the circuit surface but also on the polyimide resin surface by electroless plating occurs. And the method to solve this problem has not been established yet.

[0007]

The present invention has been made to solve the above problems. That is, electroless plating on the surface of the polyimide resin, or after electroless plating after electroplating to provide a conductor layer, using a copper polyimide substrate obtained by heat treatment, the conductor layer is patterned to form a circuit, Then, it is an object to provide a method for forming a metal layer by electroless plating only on the surface of the circuit.

[0008]

Means for Solving the Problems The present inventors have found that the above problems are caused by the fact that the polyimide resin having the catalyst adsorbed thereon is not completely removed, and have completed the present invention. That is, the method of the present invention to solve the above problems, after forming a metal layer by subjecting the polyimide resin surface to electroless plating or subsequent electroplating, using the substrate obtained by heat treatment, After patterning the metal layer of the substrate to form a circuit, apply a catalyst to the circuit and the polyimide resin surface, then elute the polyimide resin on which the catalyst is adsorbed, and then form a metal layer on the circuit surface by electroless plating In the method, the surface of the substrate is treated with a treatment solution containing hypochlorous acid after the circuit is formed and before the catalyst is applied. Further, the effective chlorine concentration in the treatment liquid is preferably 2% or more.

[0009]

[Function] The substrate (hereinafter referred to as "main substrate") obtained by subjecting the surface of the polyimide resin to electroless plating or electroplating to form a metal layer and then heat-treating the metal layer is used. When a circuit is formed by patterning the metal layer of, the catalyst is applied to the circuit and the polyimide resin surface, and the polyimide resin layer adsorbing the catalyst is removed with a solution of polyimide such as hydrazine, the polyimide exposed between the circuits is exposed. The resin, that is, the polyimide resin layer on which the catalyst is adsorbed cannot be completely removed.

This is because the polyimide resin layer in contact with the metal layer is altered by the heat treatment in the substrate manufacturing process, and the chemical resistance is improved. This is because the conventional hydrazine-containing solution, which is a polyimide resin solution, cannot sufficiently dissolve and remove the polyimide resin layer adsorbing the catalyst.

In the method of the present invention, the polyimide layer is dissolved after the circuit is formed and before the catalyst is applied. The modified layer of the substrate is dissolved and removed before the catalyst is applied, and the polyimide resin surface which is easily dissolved in the hydrazine-containing solution is removed. This is because it is exposed and the catalyst is adsorbed on this surface. As a result, it becomes possible to dissolve and remove the catalyst-added polyimide resin layer by using the conventional hydrazine-containing solution. Further, if the treatments are carried out in the order of the present invention, there is no possibility of dissolving and removing the catalyst adsorbed on the surface of the circuit coating, even if severe dissolution conditions are selected to dissolve the deteriorated layer.

It is a hypochlorous acid solution that can satisfactorily dissolve the deteriorated layer of the polyimide resin generated by the above heat treatment. When a hypochlorous acid solution is used, its ability is evaluated by the effective chlorine concentration.

If the effective chlorine concentration is low, the deteriorated layer cannot be sufficiently dissolved even if the treatment time is extended. Therefore, the effective chlorine concentration of the hypochlorous acid solution is preferably 2% or more. When the effective chlorine concentration is high, it is possible to satisfactorily dissolve and remove the deteriorated layer by appropriately adjusting the treatment time, the treatment temperature and the like. Note that these conditions cannot be unconditionally determined because they depend on the effective chlorine concentration of the hypochlorous acid solution, the cross-linking structure of the altered layer, and the like, and it is preferable to previously determine an appropriate range in actual operation. .

The method of applying a catalyst to the surface of the polyimide resin and the surface of the circuit according to the present invention is not particularly limited, and a known catalyzing / accelerating method, sensitizing / activating method or the like may be used. The solution used in the dissolution treatment of the polyimide resin after applying the catalyst in the present invention may be a known solution of polyimide. For example, hydrazine, an alkali metal hydroxide aqueous solution or the like can be used. Further, the electroless plating method used in the present invention and the metal species deposited by electroless plating are not particularly limited.

[0015]

EXAMPLES The present invention will be further described with reference to Examples and Comparative Examples. (Example 1) 35 mm wide and 1 m long polyimide resin film manufactured by Toray-Dupont (trade name: Kapton 20)
The surface of (0H) was subjected to etching treatment with a 30% by volume aqueous solution of hydrazine monohydrate at 25 ° C. for 30 seconds, then washed with water, and treated with “OPC-80 Catalyst M” manufactured by Okuno Seiyaku at 25 ° C. for 5 minutes. After that, it was washed with water and used at 7 ° C at 25 ° C using "OPC-555 Accelerator" manufactured by Okuno Seiyaku.
After treatment for minutes, it was washed with water, and electroless copper plating was performed under the following electroless copper plating conditions using an electroless copper plating solution having the composition shown below to form a copper coating having a thickness of 0.2 μm on the polyimide resin surface. .

(Composition of Electroless Copper Plating Solution) CuSO ₄ .5H ₂ O: 10 g / l EDTA.2Na: 30 g / l 37% HCHO: 5 ml / l PEG # 1000: 0.5 g / l 2 , 2'-bipyridyl: 10 mg / l

(Electroless Copper Plating Conditions) Temperature: 65 ° C. Stirring: Air stirring time: 10 minutes pH: 12.5

The obtained substrate was heat-treated at 400 ° C. for 1 hour in a vacuum atmosphere of 10 ⁻³ Torr and then cooled to room temperature to obtain a copper polyimide substrate (main substrate).

On the copper surface of the substrate, a negative photoresist (product name PMERHC-600) manufactured by Tokyo Ohka Kogyo Co., Ltd. is used.
Evenly applied to a thickness of μm, circuit width 40μ
m, set the mask so that the circuit interval is 40 μm,
It was irradiated with ultraviolet rays of 800 mJ / cm ² , developed, and dried. Subsequently, an electrolytic copper plating solution having the composition shown below was used for the copper coating exposed by the development treatment, and electrolytic copper plating was performed under the plating conditions shown below.

(Composition of Electrolytic Copper Plating Solution) CuSO4.5H20: 80 g / l H2SO4: 180 g / l

(Plating conditions) Temperature: 23 ° C. Positive electrode: Phosphorus-containing copper Cathode current density: 3 A / dm2 Stirring: Air and cathode rocker time: 1 hour

After the above treatment, the photoresist layer was peeled off, and the obtained substrate was immersed in a 200 g / l ferric chloride aqueous solution at room temperature for 30 seconds to expose the electroless copper plating layer exposed by peeling off the resist layer. Was removed. By the above treatment, the width of the polyimide resin surface is 40 μm, the interval is 40 μm, and the thickness is 3 μm.
A 5 μm copper circuit was formed.

Then, the circuit-formed substrate was immersed in a sodium hypochlorite solution having an effective chlorine concentration of 5% at 20 ° C. for 10 minutes and then washed with water. After washing with water "OPC" made by Okuno Seiyaku
“-80 Catalyst M” was treated at 25 ° C. for 5 minutes to give a catalyst, and after washing with water, “OPC-” manufactured by Okuno Seiyaku
The catalyst was activated by treatment with "555 Accelerator" at 25 ° C for 7 minutes. After that, 50
1% at 25 ° C. using a volume% hydrazine monohydrate aqueous solution
It was treated for a minute and washed with water. Then, using the electroless plating solution having the composition shown below, under the electroless plating conditions shown below,
Electroless nickel plating having a thickness of 0.5 μm was applied on the copper circuit. (Plating solution _{composition) NiSO 4 · 6H 2 O:} 0.1 mol / l _{glycine: 0.3 mol / l NaPH 2 O} 2 · H 2 O: 0.3 mol / l

(Plating Conditions) Temperature: 60 ° C. Time: 10 minutes pH: 7

When the surface of the obtained substrate was observed, the nickel layer on the circuit was uniform, nickel was not deposited on the surface of the polyimide resin, and the insulation between the circuits was good.

Example 2 A circuit surface was electroless nickel-plated in the same manner as in Example 1 except that a potassium hypochlorite solution having an effective chlorine concentration of 2% was used and treated at 20 ° C. for 30 minutes. A uniform nickel plating film having a thickness of 0.5 μm was formed on the circuit surface. At this time, no nickel deposition was observed on the surface of the polyimide resin, and the insulation between the circuits was good.

COMPARATIVE EXAMPLE 1 Electroless nickel plating was applied to the circuit surface in the same manner as in Example 1 except that the treatment with the solution containing hypochlorous acid was not carried out. 0.5 on most of the surface
A μm nickel plating film was deposited and a short circuit occurred between the circuits.

Comparative Example 2 A circuit surface was electroless nickel plated in the same manner as in Example 1 except that a sodium hypochlorite solution having an effective chlorine concentration of 1% was used and treated at 20 ° C. for 1 hour. A 0.5 μm-thick nickel plating film was deposited not only on the circuit surface but also on the polyimide resin surface, and a short circuit occurred between the circuits.

(Comparative Example 3) Electrolytic nickel was applied to the circuit surface in the same manner as in Example 1 except that the treatment with the solution containing hypochlorous acid was not performed before the catalyst application but after the catalyst application in Example 1. When plating was performed, no electroless nickel plating film was deposited.

[0030]

As described above, according to the method of the present invention, a substrate obtained by forming a metal layer by subjecting a polyimide resin surface to electroless plating or subsequent electroplating and then heat-treating it is used. Even in such a case, the metal layer can be formed only on the circuit surface by electroless plating after the circuit is formed. Therefore, by applying the method of the present invention, it is possible to obtain a multifunctional and highly reliable electronic component such as TAB or FPC.

Claims (2)

[Claims] 1. Electroless plating on a polyimide resin surface,
Alternatively, after a metal layer is formed by subsequently performing electroplating, a substrate obtained by heat-treating the metal layer is used to form a circuit by patterning the metal layer of the substrate, and then a catalyst is formed on the circuit and the polyimide resin surface. Applied, then elute the polyimide resin with the catalyst adsorbed,
Then, in the method of forming a metal layer on the circuit surface by electroless plating, after the circuit formation, before applying a catalyst, the substrate surface is treated with a treatment solution containing hypochlorous acid Pretreatment method for plating. 2. The pretreatment method for electroless plating according to claim 1, wherein the effective chlorine concentration in the solution containing hypochlorous acid is 2% or more.