JP7215211B2 - Method for manufacturing copper-clad laminate - Google Patents

Description

The present invention relates to a method for manufacturing a copper-clad laminate. More particularly, the present invention relates to a method of manufacturing a copper- clad laminate used for manufacturing flexible printed circuit boards (FPC) and the like.

A flexible printed wiring board having a wiring pattern formed on the surface of a resin film is used for liquid crystal panels, laptop computers, digital cameras, mobile phones, and the like. A flexible printed wiring board is manufactured, for example, from a copper-clad laminate.

A metallizing method is known as a method of manufacturing a copper-clad laminate. A copper-clad laminate is manufactured by the metallizing method, for example, in the following procedure. First, a base metal layer made of a nickel-chromium alloy is formed on the surface of a resin film. Next, a copper thin film layer is formed on the base metal layer. Next, a copper plating film is formed on the copper thin film layer. By copper plating, the conductor layer is thickened to a thickness suitable for forming a wiring pattern. A copper-clad laminate of a type called a two-layer substrate, in which a conductor layer is directly formed on a resin film, is obtained by the metallizing method.

A semi-additive method is known as a method of manufacturing a flexible printed wiring board using this kind of copper-clad laminate. A flexible printed wiring board is manufactured by the semi-additive method according to the following procedure (see Patent Document 1). First, a resist layer is formed on the surface of the copper plating film of the copper-clad laminate. Next, an opening is formed in a portion of the resist layer where the wiring pattern is to be formed. Next, electrolytic plating is performed using the copper plating film exposed from the opening of the resist layer as a cathode to form a wiring portion. Next, the resist layer is removed, and the conductor layer other than the wiring portion is removed by flash etching or the like. A flexible printed wiring board is thus obtained.

In the semi-additive method, a dry film resist is sometimes used to form a resist layer on the surface of the copper plating film. In this case, after chemically polishing the surface of the copper plating film, a dry film resist is applied. By chemically polishing the surface of the copper-plated film with fine unevenness, the anchor effect enhances the adhesion of the dry film resist. However, if the unevenness on the surface of the copper plating film is excessive, the adhesion of the dry film resist may rather deteriorate.

JP 2006-278950 A

The surface roughness of the copper plating film after chemical polishing is affected by the grain size of the copper plating film. There is a tendency that the smaller the crystal grains, the smoother the surface of the copper plating film after chemical polishing, and the larger the crystal grains, the rougher the surface of the copper plating film after chemical polishing.

The crystal grains of the copper plating film gradually become larger as recrystallization progresses after plating. When chemical polishing is performed on a copper plating film in progress of recrystallization, the surface roughness of the copper plating film after chemical polishing changes depending on the elapsed time from the plating treatment at the time of chemical polishing. Therefore, process control in wiring processing becomes difficult. In addition, since the crystal grains of the recrystallized copper plating film are large, the surface roughness after chemical polishing may be excessive. Therefore, the copper plating film of the copper-clad laminate is sometimes required to progress recrystallization slowly.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a copper- clad laminate having a copper-plated film in which recrystallization progresses slowly.

A method for producing a copper-clad laminate according to the first invention is characterized in that, in obtaining a copper-clad laminate by forming a copper plating film on the surface of a base material, a brightener containing a brightener component is formed on the surface of the base material in a non-energized state. After contact with the brightener solution, electroplating is performed using a copper plating solution to form the copper plating film, the concentration of the brightener component in the brightener solution is 5 mg / L or more, and the base material is The contact time with the brightener solution is 5 seconds or longer, and the brightener component contained in the brightener solution is bis(3-sulfopropyl)disulfide .
In the method for producing a copper clad laminate of the second invention, in obtaining a copper clad laminate by forming a copper plating film on the surface of the base material while conveying the base material by roll-to-roll, the base material is A pretreatment tank in which a brightener solution containing a brightener component is stored and a plating tank in which electroplating is performed using a copper plating solution are arranged in this order from upstream to downstream in a conveying path, and the brightener solution is disposed in this order from upstream to downstream. concentration of the brightener component is 5 mg/L or more, the contact time of the substrate with the brightener liquid is 5 seconds or more, and the brightener component contained in the brightener liquid is bis(3-sulfopropyl ) disulfide .

According to the present invention, the sulfur concentration in the vicinity of the interface with the substrate in the copper plating film is increased. Since a large amount of sulfur that suppresses the progress of recrystallization is contained in the vicinity of the interface with the substrate where recrystallization tends to progress, the progress of recrystallization of the copper plating film can be slowed down.

1 is a cross-sectional view of a copper-clad laminate according to one embodiment of the present invention; FIG. 1 is a perspective view of a plating apparatus; FIG. It is a top view of a pretreatment tank.

Next, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a copper-clad laminate 1 according to one embodiment of the present invention comprises a base material 10 and a copper plating film 20 formed on the surface of the base material 10 . The copper plating film 20 may be formed only on one side of the substrate 10 as shown in FIG.

The copper plating film 20 is deposited by electrolytic plating. Therefore, the substrate 10 may be any material as long as it has conductivity on the surface on which the copper plating film 20 is formed. For example, the substrate 10 is formed by forming a metal layer 12 on the surface of an insulating base film 11 . A resin film such as a polyimide film can be used as the base film 11 . The metal layer 12 is formed by sputtering, for example. The metal layer 12 consists of a base metal layer 13 and a copper thin film layer 14 . The underlying metal layer 13 and the copper thin film layer 14 are laminated in this order on the surface of the base film 11 . Underlying metal layer 13 is generally comprised of nickel, chromium, or a nickel-chromium alloy. Although not particularly limited, the thickness of the base metal layer 13 is generally 5 to 50 nm, and the thickness of the copper thin film layer 14 is generally 50 to 400 nm.

A copper plating film 20 is formed on the surface of the metal layer 12 . Although not particularly limited, the thickness of the copper plating film 20 is generally 1 to 3 μm. The metal layer 12 and the copper plating film 20 are collectively referred to as a "conductor layer".

The copper plating film 20 is formed by the plating apparatus 3 shown in FIG. 2, although not particularly limited.
The plating apparatus 3 is an apparatus that performs electrolytic plating on the base material 10 while conveying the base material 10 in the form of a long strip by roll-to-roll. The plating apparatus 3 has a supply device 31 that feeds out the base material 10 wound in a roll shape, and a winding device 32 that winds up the base material 10 (copper-clad laminate 1) after plating into a roll shape.

The plating apparatus 3 also has a pair of upper and lower endless belts 33 (the lower endless belt 33 is not shown) for conveying the substrate 10 . Each endless belt 33 is provided with a plurality of clamps 34 for gripping the substrate 10 . The base material 10 delivered from the supply device 31 is in a suspended position with its width direction along the vertical direction, and both edges are gripped by the upper and lower clamps 34 . After the substrate 10 is circulated inside the plating device 3 by driving the endless belt 33 , the substrate 10 is released from the clamp 34 and wound up by the winding device 32 .

A pretreatment bath 40 , a plating bath 35 , and a posttreatment bath 36 are arranged in this order from upstream to downstream along the transport path of the substrate 10 . While the base material 10 is conveyed in the plating tank 35, a copper plating film 20 is formed on its surface by electrolytic plating. Thus, a long belt-shaped copper-clad laminate 1 is obtained.

As shown in FIG. 3, the pretreatment bath 40 is a horizontally elongated bath along the conveying direction of the substrate 10 . The interior of the pretreatment tank 40 is divided into six sections 41-46. From upstream to downstream of the conveying path of the base material 10, an alkali treatment section 41, a water washing section 42, an acid treatment section 43, a water washing section 44, a brightener treatment section 45, and a water washing section 46 are arranged in this order.

A degreasing liquid using an alkali salt such as sodium hydroxide or sodium carbonate is stored in the alkali treatment section 41 . The base material 10 conveyed through the alkali treatment section 41 is entirely immersed in the degreasing liquid. This alkali treatment removes oils and fats adhering to the surface of the substrate 10 .

Water is stored in each of the washing sections 42, 44, 46. FIG. The substrate 10 conveyed through the washing sections 42, 44, 46 is entirely immersed in water and thereby washed with water.

An acid such as sulfuric acid or hydrochloric acid is stored in the acid treatment section 43 . The substrate 10 conveyed through the acid treatment section 43 is entirely immersed in acid. This acid treatment removes oxides from the surface of the substrate 10 (the surface of the copper thin film layer 14).

A brightener liquid is stored in the brightener processing section 45 . A brightener liquid is a liquid containing a brightener component. As a brightener component, one that is generally added to a plating solution can be used. Although not particularly limited, as a brightener component, one or two selected from bis(3-sulfopropyl)disulfide (abbreviated as SPS), 3-mercaptopropane-1-sulfonic acid (abbreviated as MPS), etc. It is preferable to use a combination of the above.

Preferably, the brightener solution contains sulfuric acid and copper. By doing so, it is possible to prevent algae from growing on the wall surface of the tank storing the brightener solution. Alternatively, a copper plating solution stored in the plating tank 35 may be used as the brightener solution. In this case, the copper plating solution may contain additives other than the brightener component, such as a leveler component, a polymer component, and a chlorine component. If a copper plating solution is used as the brightener solution, there is no need to prepare a brightener solution separately from the copper plating solution.

The substrate 10 conveyed through the brightener treatment section 45 is entirely immersed in the brightener liquid. By this brightener treatment, the brightener liquid comes into contact with the surface of the base material 10 (the surface of the copper thin film layer 14), and the brightener component is adsorbed.

The substrate 10 is subjected to alkali treatment, acid treatment, and brightener treatment while being transported through the pretreatment bath 40 . The alkali treatment, acid treatment and brightener treatment are preferably performed in this order. The brightener component can then be adsorbed onto a clean metal surface from which grease and oxides have been removed. However, at least a brightener treatment may be performed as a pretreatment. Other processing may be performed as necessary.

The pretreatment is performed in a non-energized state, that is, in a state in which no current is supplied to the substrate 10 . Even if the brightener treatment is performed in a non-energized state, the brightener component is adsorbed on the surface of the substrate 10 (the surface of the copper thin film layer 14).

It is preferable to provide a nozzle for ejecting a treatment liquid (alkali, acid, brightener liquid, washing water) toward the substrate 10 inside each of the sections 41 to 46 .

As shown in FIG. 2, the plating tank 35 is a horizontally long single tank along the conveying direction of the substrate 10 . A plating bath 35 stores a copper plating solution. The base material 10 conveyed in the plating tank 35 is entirely immersed in the copper plating solution.

A copper plating solution contains a water-soluble copper salt. Any water-soluble copper salt generally used in copper plating solutions can be used without particular limitation. Examples of water-soluble copper salts include inorganic copper salts, alkanesulfonate copper salts, alkanol sulfonate copper salts, and organic acid copper salts. Inorganic copper salts include copper sulfate, copper oxide, copper chloride, copper carbonate, and the like. Copper alkanesulfonates include copper methanesulfonate and copper propanesulfonate. Alkanol sulfonic acid copper salts include copper isethionate and copper propanol sulfonate. Organic acid copper salts include copper acetate, copper citrate, copper tartrate and the like.

As the water-soluble copper salt used in the copper plating solution, one kind selected from inorganic copper salts, alkanesulfonate copper salts, alkanol sulfonate copper salts, organic acid copper salts, etc. may be used alone, or two or more kinds may be used. may be used in combination. For example, two or more different types in one category selected from inorganic copper salts, alkanesulfonate copper salts, alkanol sulfonate copper salts, organic acid copper salts, etc., as in the case of combining copper sulfate and copper chloride. They may be used in combination. However, from the viewpoint of managing the copper plating solution, it is preferable to use one type of water-soluble copper salt alone.

The copper plating solution may contain sulfuric acid. By adjusting the amount of sulfuric acid added, the pH and sulfate ion concentration of the copper plating solution can be adjusted.

The copper plating solution may contain additives that are commonly added to plating solutions. Additives include brightener components, leveler components, polymer components, chlorine components, and the like. The copper plating solution may contain one selected from a brightener component, a leveler component, a polymer component, a chlorine component, etc., or may contain two or more components.

The brightener component contains sulfur. The brightener component is not particularly limited, but one or two selected from bis(3-sulfopropyl)disulfide (abbreviated as SPS), 3-mercaptopropane-1-sulfonic acid (abbreviated as MPS), etc. It is preferable to use a combination of the above. The leveler component is composed of a nitrogen-containing amine or the like. The leveler component is not particularly limited, but it is preferable to use one selected from diallyldimethylammonium chloride, Janus Green B, etc. alone or in combination of two or more. The polymer component is not particularly limited, but it is preferable to use one selected from polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol copolymer alone or in combination of two or more. The chlorine component is not particularly limited, but it is preferable to use one selected from hydrochloric acid, sodium chloride, etc. alone or in combination of two or more.

The content of each component of the copper plating solution can be selected arbitrarily. However, the copper plating solution preferably contains 15 to 70 g/L of copper and 20 to 250 g/L of sulfuric acid. Then, the copper plating film 20 can be formed at a sufficient speed. The copper plating solution preferably contains 1 to 30 mg/L of brightener component. By doing so, the precipitated crystals can be made finer and the surface of the copper plating film 20 can be smoothed. The copper plating solution preferably contains 0.5 to 50 mg/L of leveler component. By doing so, a flat copper plating film 20 can be formed by suppressing protrusions. The copper plating solution preferably contains 10 to 1,500 mg/L of polymer component. By doing so, it is possible to reduce current concentration at the edge of the substrate 10 and form a uniform copper plating film 20 . The copper plating solution preferably contains 20 to 80 mg/L of chlorine component. Then, abnormal precipitation can be suppressed.

The temperature of the copper plating solution is preferably 23-38°C. Moreover, it is preferable to stir the copper plating solution in the plating tank 35 . The means for stirring the copper plating solution is not particularly limited, but means using a jet flow can be used. For example, the copper plating solution can be agitated by spraying the copper plating solution ejected from a nozzle onto the substrate 10 .

A plurality of anodes are arranged inside the plating tank 35 along the transport direction of the substrate 10 . The material and structure of the anode are not particularly limited, but may be, for example, a mesh-like insoluble electrode in which titanium is coated with iridium oxide. An electric current is also supplied to the substrate 10 via a clamp 34 that grips it. When an electric current is passed between the substrate 10 and the anode, electrolytic plating is performed using the substrate 10 as a cathode. By performing electrolytic plating, a copper plating film 20 can be formed on the surface of the base material 10, and a copper-clad laminate 1 in the form of a long belt can be obtained.

A rectifier is connected to each of the plurality of anodes arranged inside the plating bath 35 . Therefore, it is possible to set different current densities for each anode. It is preferable to set the current density to 0.3 to 10 A/dm ² . Moreover, it is preferable to set the current density so as to increase stepwise toward the downstream side in the conveying direction of the substrate 10 .

As described above, after bringing the brightener solution into contact with the surface of the substrate 10 in a non-energized state, electroplating is performed using the copper plating solution to form the copper plating film 20 . The copper plating film 20 formed by such a method contains a large amount of sulfur as an impurity in the vicinity of the interface with the substrate 10 . That is, as shown in FIG. 1, the copper plating film 20 consists of a high sulfur concentration layer 21 near the interface with the substrate 10 and a low sulfur concentration layer 22 laminated thereon. Here, the high sulfur concentration layer 21 is a layer with a relatively high sulfur concentration, and the low sulfur concentration layer 22 is a layer with a relatively low sulfur concentration.

The reason why the high sulfur concentration layer 21 and the low sulfur concentration layer 22 are formed in this manner is considered as follows.
When the substrate 10 comes into contact with the brightener liquid in the pretreatment tank 40 , the brightener component is adsorbed on the surface of the substrate 10 , that is, the surface of the copper thin film layer 14 . When electroplating is performed on the base material 10 in this state, the copper plating film 20 is formed while the brightener component adsorbed on the surface of the copper thin film layer 14 is taken in at the initial stage of the electrolysis. Therefore, the vicinity of the interface with the substrate 10 in the copper plating film 20 contains a large amount of sulfur derived from the brightener component, and becomes a high sulfur concentration layer 21 .

When electroplating is subsequently performed, a layer having a sulfur concentration obtained by ordinary electrolysis is formed because the brightener component is only supplied from the copper plating solution. This is the low sulfur concentration layer 22 .

The copper plating film 20 having such a structure has the property of slow progress of recrystallization. Although the reason for this is unclear, it is generally believed to be as follows.
Immediately after the electroplating is completed, the copper plating film 20 tends to expand at the portion containing a large amount of impurities and shrink at the portion containing a small amount of impurities. However, since the copper plating film 20 is in close contact with the base material 10, it cannot actually expand or contract, and therefore stress is generated in the copper plating film 20. FIG. In particular, stress increases in the vicinity of the interface with the substrate 10 in the copper plating film 20 . Therefore, recrystallization of the copper plating film 20 progresses from the vicinity of the interface with the substrate 10 .

On the other hand, the copper plating film 20 has a high sulfur concentration in the vicinity of the interface with the substrate 10 . Sulfur in the copper plating film 20 has an effect of suppressing progress of recrystallization. Since a large amount of sulfur that suppresses the progress of recrystallization is contained in the vicinity of the interface with the substrate 10 where recrystallization tends to progress, the progress of recrystallization of the copper plating film 20 can be slowed down.

In order to obtain the above effect, a sufficient amount of the brightener component should be adsorbed on the surface of the substrate 10 before electroplating. Therefore, it is preferable to set the concentration of the brightener component in the brightener liquid (hereinafter referred to as "brightener concentration") to 5 mg/L or more. Further, it is preferable that the contact time of the substrate 10 with the brightener liquid (hereinafter referred to as "contact time") is 5 seconds or longer. The contact time can be adjusted by adjusting the transport speed of the substrate 10 and the length of the brightener treatment section 45 .

Since the brightener component is adsorbed on copper, it is considered that the adsorption stops when the surface of the copper thin film layer 14 is covered with the brightener component. After the adsorption amount of the brightener component reaches a saturated state, it is considered that the sulfur concentration of the high sulfur concentration layer 21 does not increase even if the brightener concentration is increased or the contact time is lengthened. From this point of view, there is no upper limit to the brightener concentration and contact time.

The copper plating film 20 may contain impurities other than sulfur, such as nitrogen, chlorine, carbon, and oxygen derived from additives of the copper plating solution.

Next, an example will be described.
(Recrystallization time measurement test)
First, a recrystallization time measurement test was conducted.
A substrate was prepared by the following procedure. A polyimide film (Upilex-35SGAV1 manufactured by Ube Industries, Ltd.) having a thickness of 35 μm was prepared as a base film. The base film was set in a magnetron sputtering device. A nickel-chromium alloy target and a copper target are installed in the magnetron sputtering apparatus. The composition of the nickel-chromium alloy target is 20% by mass of Cr and 80% by mass of Ni. In a vacuum atmosphere, a base metal layer made of a nickel-chromium alloy with a thickness of 25 nm was formed on one side of the base film, and a copper thin film layer with a thickness of 150 nm was formed thereon.

Next, a brightener solution was prepared. The brightener liquid contains a brightener component. Bis(3-sulfopropyl)disulfide (a reagent manufactured by RASCHIG GmbH, the same shall apply hereinafter) was used as a brightener component. Also, the brightener solution contains 120 g/L of copper sulfate and 70 g/L of sulfuric acid.

Next, a copper plating solution was prepared. The copper plating solution contains 120 g/L of copper sulfate, 70 g/L of sulfuric acid, 16 mg/L of brightener component, 50 mg/L of leveler component, 1,100 mg/L of polymer component, and 50 mg/L of chlorine component. Bis(3-sulfopropyl)disulfide was used as the brightener component. A diallyldimethylammonium chloride-sulfur dioxide copolymer (PAS-A-5 manufactured by Nittobo Medical Co., Ltd.) was used as a leveler component. A polyethylene glycol-polypropylene glycol copolymer (Unilube 50MB-11 manufactured by NOF Corporation) was used as the polymer component. Hydrochloric acid (35% hydrochloric acid manufactured by Wako Pure Chemical Industries, Ltd.) was used as the chlorine component.

Pretreatment and electroplating were performed on the base material to form a 2.0 μm-thick copper plating film on one side of the base material. Alkaline treatment, acid treatment and brightener treatment were carried out in this order as pretreatments. Alkaline treatment was carried out by immersing the base material in a degreasing solution (Pakuna LF-612N2, manufactured by Yuken Industry Co., Ltd., 40 g/L). The acid treatment was carried out by immersing the substrate in sulfuric acid (96% sulfuric acid manufactured by Kanto Kagaku Co., Ltd. adjusted to 100 g/L). The treatment time for the alkali treatment and the acid treatment is 20 seconds each.

Also, the temperature of the copper plating solution was set to 31°C. In electrolytic plating, the current density from the start to finish of plating was changed from 0.4 A/dm ² for 40 seconds, 1.5 A/dm ² for 40 seconds, and 3.0 A/dm ² for 175 seconds.

In the above procedure, the contact time in the brightener treatment was changed in three patterns of 5, 15, and 25 seconds. Also, the brightener concentration of the brightener solution was varied in three patterns of 5, 15 and 25 mg/L. Furthermore, a sample was also prepared without brightener treatment.

The 10 types of copper clad laminates obtained by the above treatments are referred to as samples 1 to 10, respectively. For samples 1 to 10, the recrystallization time of the copper plating film was measured. The recrystallization time was measured by observing the change in resistivity of the copper plating film by the four-probe method. As the recrystallization of the copper plating film progresses, the grain size increases and the resistivity changes. When the resistivity becomes constant, it is determined that the recrystallization is finished. The recrystallization time was defined as the elapsed time from plating to completion of recrystallization. As a resistivity measuring instrument, Loresta AX MCP-T370 manufactured by Mitsubishi Chemical Analytics was used.

Table 1 shows the results.

From Table 1, it can be seen that the progress of recrystallization of the copper plating film is delayed when the brightener treatment is performed (Samples 2 to 10) as compared to when it is not performed (Sample 1). Also, the longer the contact time, the longer the recrystallization time. If the contact time is 5 seconds or more, the recrystallization time can be made sufficiently long. At least, a contact time in the range of 5 to 25 seconds can provide a sufficiently long recrystallization time. Also, the higher the brightener concentration, the longer the recrystallization time. A brightener concentration of 5 mg/L or more can sufficiently lengthen the recrystallization time. At least, the recrystallization time can be sufficiently long when the brightener concentration is in the range of 5 to 25 mg/L.

(Gloss measurement test)
Next, samples 1 to 10 were subjected to a glossiness measurement test.
For each of Samples 1 to 10, the glossiness of the surface of the copper plating film immediately after plating was measured. In addition, chemical polishing was performed on each of samples 1 to 10 one week after the plating treatment, and the glossiness of the surface of the copper plating film after chemical polishing was measured. Furthermore, each of Samples 1 to 10 two weeks after the plating treatment was subjected to chemical polishing, and the glossiness of the surface of the copper plating film after chemical polishing was measured. As a glossiness measuring instrument, VSR400 manufactured by Nippon Denshoku Industries Co., Ltd. was used.

Table 2 shows the results.

Glossiness can be used as an index of the surface roughness of the copper plating film. The higher the gloss, the smoother, and the lower the gloss, the rougher. From Table 2, if the contact time is 5 seconds or more and the brightener concentration is 5 mg/L or more, the glossiness of 0.9 or more can be maintained even after 2 weeks from the plating treatment, and the surface of the copper plating film after chemical polishing. was confirmed to be smooth.

REFERENCE SIGNS LIST 1 copper-clad laminate 10 substrate 11 base film 12 metal layer 13 base metal layer 14 copper thin film layer 20 copper plating film 21 high sulfur concentration layer 22 low sulfur concentration layer

Claims (2)

In obtaining a copper clad laminate by forming a copper plating film on the surface of a base material,
After bringing a brightener solution containing a brightener component into contact with the surface of the base material in a non-energized state, electroplating is performed using a copper plating solution to form the copper plating film ,
The concentration of the brightener component in the brightener liquid is 5 mg/L or more,
The contact time of the base material with the brightener liquid is 5 seconds or more,
The brightener component contained in the brightener solution is bis(3-sulfopropyl)disulfide
A method for producing a copper-clad laminate, characterized by: In obtaining a copper clad laminate by forming a copper plating film on the surface of the base material while conveying the base material by roll-to-roll,
A pretreatment tank in which a brightener solution containing a brightener component is stored and a plating tank in which electroplating is performed using a copper plating solution are arranged in this order from upstream to downstream in the transport path of the base material,
The concentration of the brightener component in the brightener liquid is 5 mg/L or more,
The contact time of the base material with the brightener liquid is 5 seconds or more,
The brightener component contained in the brightener solution is bis(3-sulfopropyl)disulfide
A method for producing a copper-clad laminate, characterized by:

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