JP7343280B2 - Manufacturing method for copper clad laminates - Google Patents

Description

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

Flexible printed wiring boards, in which a wiring pattern is formed on the surface of a resin film, are used in liquid crystal panels, notebook computers, digital cameras, mobile phones, and the like. Flexible printed wiring boards are manufactured from copper-clad laminates, for example.

A metallizing method is known as a method for manufacturing copper-clad laminates. The manufacture of a copper-clad laminate by the metallizing method is performed, for example, by 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. The conductor layer is thickened by copper plating until it has a thickness suitable for forming a wiring pattern. By the metallizing method, a copper-clad laminate of a so-called two-layer board type in which a conductor layer is directly formed on a resin film is obtained.

A semi-additive method is known as a method for manufacturing flexible printed wiring boards using this type of copper-clad laminate. Manufacturing of a flexible printed wiring board by the semi-additive method is performed in the following steps (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 a wiring pattern will be formed. Next, electrolytic plating is performed using the copper plating film exposed through 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. Thereby, a flexible printed wiring board is obtained.

In the semi-additive method, a dry film resist is sometimes used to form a resist layer on the surface of a copper plating film. In this case, after chemically polishing the surface of the copper plating film, a dry film resist is attached. By creating fine irregularities on the surface of the copper plating film through chemical polishing, the adhesion of the dry film resist is improved due to the anchor effect. However, if the surface of the copper plating film has excessive irregularities, the adhesion of the dry film resist may deteriorate on the contrary.

JP2006-278950A

The surface roughness of the copper plating film after chemical polishing is influenced by the crystal 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 the plating process. When chemical polishing is performed on a copper plating film that is undergoing recrystallization, the surface roughness of the copper plating film after chemical polishing changes depending on the elapsed time from the plating process at the time of chemical polishing. Therefore, process control in wiring processing becomes difficult. Further, since the crystal grains of the copper plating film that has been recrystallized have become large, the surface roughness may become excessive after chemical polishing. Therefore, the copper plating film of the copper-clad laminate is sometimes required to undergo slow recrystallization.

In view of the above circumstances, an object of the present invention is to provide a method for manufacturing a copper-clad laminate having a copper plating film in which recrystallization progresses slowly.

The method for manufacturing a copper-clad laminate according to the first invention is a method for obtaining a copper-clad laminate by forming a copper plating film on the surface of a base material by electrolytic plating using a copper plating solution, The concentration of sulfur contained in the brightener component in the liquid is 5.4 to 9.1 mg/L, the brightener component is 3-mercaptopropane-1-sulfonic acid, and the recrystallization time of the copper plating film is is characterized by being for 4 days or more.
A method for manufacturing a copper-clad laminate according to a second invention is the method according to the first invention, wherein the copper plating solution has a copper concentration of 15 to 70 g/L, a sulfuric acid concentration of 20 to 250 g/L, and a chlorine concentration of 20 to 80 mg/L. It is characterized by
A method for manufacturing a copper-clad laminate according to a third aspect of the invention is characterized in that, in the first or second aspect , the current density of the electrolytic plating is 0.1 to 4.5 A/dm ² .

According to the present invention, sulfur contained in the brightener component of the copper plating solution is incorporated into the copper plating film. Since recrystallization is inhibited by sulfur incorporated into the copper plating film, the progress of recrystallization of the copper plating film can be slowed down.

FIG. 2 is a cross-sectional view of a copper-clad laminate. FIG. 2 is a perspective view of a plating apparatus.

Next, embodiments of the present invention will be described based on the drawings.
As shown in FIG. 1, a copper-clad laminate 1 manufactured by a method according to an embodiment of the present invention includes a base material 10 and a copper plating film 20 formed on the surface of the base material 10. As shown in FIG. 1, the copper plating film 20 may be formed on only one side of the base material 10, or the copper plating film 20 may be formed on both sides of the base material 10.

The copper plating film 20 is formed by electrolytic plating. Therefore, the base material 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 base material 10 is one in which a metal layer 12 is formed on the surface of a base film 11 having insulating properties. As the base film 11, a resin film such as a polyimide film can be used. The metal layer 12 is formed by, for example, a sputtering method. The metal layer 12 consists of a base metal layer 13 and a copper thin film layer 14. The base metal layer 13 and the copper thin film layer 14 are laminated in this order on the surface of the base film 11. Generally, base metal layer 13 is made of nickel, chromium, or a nickel-chromium alloy. The metal layer 12 and the copper plating film 20 constitute a conductor layer.

Electrolytic plating is performed using, for example, a plating apparatus 3 shown in FIG.
The plating apparatus 3 is an apparatus that performs electrolytic plating on the base material 10 while conveying the long strip-shaped base material 10 by roll-to-roll. The plating device 3 includes a supply device 31 that feeds out a base material 10 wound into a roll, and a winding device 32 that winds up the base material 10 (copper-clad laminate 1) after plating into a roll.

The plating apparatus 3 has a pair of upper and lower endless belts 33 (the lower endless belt 33 is not shown) that transports the base material 10. Each endless belt 33 is provided with a plurality of clamps 34 that grip the base material 10. The base material 10 fed out 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 base material 10 circulates within the plating device 3 by driving the endless belt 33, it is released from the clamp 34 and wound up by the winding device 32.

A pre-treatment tank 35, a plating tank 40, and a post-treatment tank 36 are arranged on the transport path of the base material 10. A copper plating solution is stored in the plating tank 40. The entire base material 10 being transported in the plating tank 40 is immersed in the copper plating solution. While the base material 10 is being transported within the plating bath 40, a copper plating film 20 is formed on its surface by electrolytic plating. As a result, a long strip-shaped copper-clad laminate 1 is obtained.

The copper plating solution contains a water-soluble copper salt. Any water-soluble copper salt commonly used in copper plating solutions may be used without particular limitation. Examples of water-soluble copper salts include inorganic copper salts, alkanesulfonic acid copper salts, alkanolsulfonic acid copper salts, and organic acid copper salts. Examples of inorganic copper salts include copper sulfate, copper oxide, copper chloride, and copper carbonate. Examples of the copper alkanesulfonate include copper methanesulfonate and copper propanesulfonate. Examples of copper alkanolsulfonate salts include copper isethionate and copper propanolsulfonate. Examples of organic acid copper salts include copper acetate, copper citrate, and copper tartrate.

As the water-soluble copper salt used in the copper plating solution, one type selected from inorganic copper salts, alkanesulfonic acid copper salts, alkanolsulfonic acid copper salts, organic acid copper salts, etc. may be used alone, or two or more types may be used. may be used in combination. For example, when combining copper sulfate and copper chloride, two or more different types within one category selected from inorganic copper salts, alkanesulfonic acid copper salts, alkanolsulfonic acid copper salts, organic acid copper salts, etc. 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.

Copper plating solutions generally include additives that are added to the plating solution. Examples of additives include brightener components, leveler components, polymer components, and chlorine components. As the additive, one type selected from a brightener component, a leveler component, a polymer component, a chlorine component, etc. may be used alone, or two or more types may be used in combination.

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

The content of each component in the copper plating solution can be arbitrarily selected. However, the copper plating solution preferably contains 15 to 70 g/L of copper and 20 to 250 g/L of sulfuric acid. In this way, the copper plating film 20 can be formed at a sufficient speed. The copper plating solution preferably contains a brightener component of 1 to 50 mg/L. By doing so, the precipitated crystals can be made finer and the surface of the copper plating film 20 can be made smooth. The copper plating solution preferably contains a leveler component of 1 to 300 mg/L. In this way, protrusions can be suppressed and a flat copper plating film 20 can be formed. The copper plating solution preferably contains a polymer component of 10 to 1,500 mg/L. By doing so, current concentration on the end portion of the base material 10 can be alleviated and a uniform copper plating film 20 can be formed. The copper plating solution preferably contains 20 to 80 mg/L of chlorine component. In this way, abnormal precipitation can be suppressed.

The temperature of the copper plating solution is preferably 20 to 35°C. Further, it is preferable to stir the copper plating solution in the plating tank 40. The means for stirring the copper plating solution is not particularly limited, but means using jet flow can be used. For example, the copper plating solution can be stirred by spraying the copper plating solution jetted from a nozzle onto the base material 10.

Inside the plating tank 40, a plurality of anodes are arranged along the conveyance direction of the base material 10. By passing a current between the anode and the base material 10, the copper plating film 20 can be formed on the surface of the base material 10. A rectifier is connected to each of the plurality of anodes. Therefore, it is possible to set different current densities for each anode. The current density is preferably 0.1 to 4.5 A/dm ² .

The inventor of the present application has found that in the above electrolytic plating, the recrystallization time of the copper plating film 20 can be lengthened by adjusting the concentration of the brightener component in the copper plating solution to an appropriate range. There is.

Although some of the reasons for this are unclear, it is generally thought to be as follows. When additives are added to the copper plating solution, impurities derived from the additives are incorporated into the copper plating film 20. For example, when a brightener component is added to the copper plating solution, sulfur contained in the brightener component is incorporated into the copper plating film 20. The sulfur taken into the copper plating film 20 exists at the grain boundaries of the copper plating film 20 and suppresses the bonding between the crystal grains. This inhibits the growth of crystal grains to a large size, thereby slowing down the progress of recrystallization.

Specifically, it is preferable that the concentration of sulfur contained in the brightener component in the copper plating solution (hereinafter simply referred to as "sulfur concentration") is 1.8 to 9.1 mg/L. Here, the sulfur concentration means the mass of sulfur in the brightener component per unit volume of the copper plating solution. For example, as shown in equation (1), _the sulfur concentration C _s is determined by the concentration ρ _b of the brightener component in the copper plating solution, and the atomic weight Ar ( It can be found by multiplying the ratio of the sum of S).

The amount of brightener component added to the copper plating solution is adjusted based on the sulfur concentration. What influences the progress of recrystallization is not the brightener component itself, but the sulfur derived from the brightener component incorporated into the copper plating film 20. Therefore, it is preferable to use the concentration of sulfur contained in the brightener component as the standard.

Next, an example will be explained.
(Test 1)
A base material was prepared according to the following procedure. A polyimide film (Upilex-35SGAV1, manufactured by Ube Industries, Ltd.) with 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 device. The composition of the nickel-chromium alloy target is 20% by mass of Cr and 80% by mass of Ni. A base metal layer made of a nickel chromium alloy with a thickness of 250 Å was formed on one side of the base film under a vacuum atmosphere, and a copper thin film layer with a thickness of 1,500 Å was formed thereon.

Next, a copper plating solution was prepared. The copper plating solution contains 30 g/L of copper, 70 g/L of sulfuric acid, 50 mg/L of leveler component, 1,100 mg/L of polymer component, and 50 mg/L of chlorine component. 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 a polymer component. Hydrochloric acid (35% hydrochloric acid manufactured by Wako Pure Chemical Industries, Ltd.) was used as the chlorine component.

Further, the copper plating solution contains a brightener component. As a brightener component, bis(3-sulfopropyl) disulfide (a reagent manufactured by RASCHIG GmbH, hereinafter the same) was used. Six types of copper plating solutions having different brightener component concentrations (brightener component concentrations: 1, 5, 10, 15, 25, and 35 mg/L) were prepared. These are referred to as copper plating solutions 1 to 6.

Bis(3-sulfopropyl) disulfide is represented by the following structural formula. The molecular weight is 354.4, and one molecule contains four sulfur atoms (atomic weight 32.1). When the concentration of the brightener component is 10 mg/L, the sulfur concentration is found to be 3.6 mg/L (=10 [mg/L]×128.3/354.4). Hereinafter, the sulfur concentration when bis(3-sulfopropyl) disulfide is used as the brightener component is determined using the same procedure.

A base material was supplied to a plating tank in which the copper plating solution prepared as described above was stored. A copper plating film with a thickness of 2.0 μm was formed on one side of the base material by electrolytic plating. Here, the temperature of the copper plating solution was 31°C. Further, during electrolytic plating, the copper plating solution was sprayed from a nozzle approximately perpendicularly to the surface of the base material, thereby stirring the copper plating solution.

In electrolytic plating, the current density from the start to the end of plating is 0.4 A/dm ² for 50 seconds, 0.6 A/dm ² for 50 seconds, 0.8 A/dm ² for 50 seconds, 1.0 A/dm ² 50 seconds, 1.2 A/dm ² for 50 seconds, 1.5 A/dm ² for 50 seconds, and 2.0 A/dm ² for 160 seconds. Copper-clad laminates obtained using copper plating solutions 1 to 6 are referred to as samples 1 to 6, respectively.

The recrystallization time of the copper plating film was measured for the six samples 1 to 6 obtained by the above procedure. The recrystallization time was measured by observing the change in resistivity of the copper plating film using the four-probe method. As the recrystallization of the copper plating film progresses, the crystal grains become larger and the resistivity changes. It is determined that recrystallization is complete when the resistivity becomes constant. The elapsed time from plating treatment to completion of recrystallization was defined as recrystallization time. Note that Loresta AX MCP-T370 manufactured by Mitsubishi Chemical Analytic was used as a resistivity measuring instrument.

The results are shown in Table 1.

From Table 1, it can be seen that by adjusting the sulfur concentration to 1.8 to 9.1 mg/L, the recrystallization time of the copper plating film can be increased to 4 days or more. Furthermore, it can be seen that by adjusting the sulfur concentration to 3.6 to 5.4 mg/L, the recrystallization time of the copper plating film can be reduced to 5 days.

(Test 2)
A base material was prepared in the same manner as in Test 1.
Next, a copper plating solution was prepared. A copper plating solution was prepared under the same conditions as Test 1, except that the concentration of the leveler component was 15 mg/L and Janus Green B (a reagent manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the leveler component.

Six types of copper plating solutions having different concentrations of brightener components (concentration of brightener components: 1, 5, 10, 15, 25, 35 mg/L) are referred to as copper plating solutions 7 to 12.

Next, electrolytic plating was performed using the same procedure as Test 1. Copper-clad laminates obtained using copper plating solutions 7 to 12 are referred to as samples 7 to 12, respectively. Further, for the six samples 7 to 12 obtained, the recrystallization time of the copper plating film was measured using the same procedure as Test 1.

The results are shown in Table 2.

From Table 2, it can be seen that even if the leveler component of the copper plating solution is changed, the recrystallization time of the copper plating film can be increased to 4 days or more by adjusting the sulfur concentration to 1.8 to 9.1 mg/L.

1 Copper-clad laminate 10 Base material 11 Base film 12 Metal layer 13 Base metal layer 14 Copper thin film layer

Claims (3)

A method for obtaining a copper-clad laminate by forming a copper plating film on the surface of a base material by electrolytic plating using a copper plating solution, the method comprising:
The concentration of sulfur contained in the brightener component in the copper plating solution is 5.4 to 9.1 mg/L,
The brightener component is 3-mercaptopropane-1-sulfonic acid,
A method for manufacturing a copper-clad laminate, characterized in that the recrystallization time of the copper plating film is 4 days or more. The copper-clad laminate according to claim 1 , wherein the copper plating solution has a copper concentration of 15 to 70 g/L, a sulfuric acid concentration of 20 to 250 g/L, and a chlorine concentration of 20 to 80 mg/L. Production method. The method for producing a copper-clad laminate according to claim 1 or 2, wherein the current density of the electrolytic plating is 0.1 to 4.5 A/dm ² .

Images