JP7409151B2 - 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.

Electronic devices such as LCD panels, notebook computers, digital cameras, and mobile phones use flexible printed wiring boards, in which wiring patterns are formed on the surface of a resin film, and chip-on films, in which semiconductor chips are mounted on flexible printed wiring boards. It will be done.

Flexible printed wiring boards are manufactured from copper-clad laminates. 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 flexible printed wiring board can be obtained by forming a wiring pattern on a copper-clad laminate using a subtractive method, a semi-additive method (see Patent Document 1), or the like. Furthermore, after tin-plating a flexible printed wiring board, a protective film is formed using a solder resist, a coverlay, etc., and a semiconductor chip is mounted on the board to obtain a chip-on-film.

JP2006-278950A

When manufacturing a copper-clad laminate, if a roll-to-roll plating device is used to form a copper plating film on one surface of a base material, the resulting copper-clad laminate may warp. If the copper-clad laminate is warped, the copper-clad laminate cannot be transported stably within an apparatus that forms wiring patterns. Further, vacuum suction of the copper-clad laminate during the exposure process becomes difficult. Therefore, it is required to manufacture copper-clad laminates that do not warp.

The warping of copper-clad laminates is caused by the transport tension applied to the base material in roll-to-roll plating equipment. In the case of a film that stretches easily under transport tension, the copper plating film is formed while the film is stretched. After plating, the film released from the transport tension tends to shrink to its original length. However, since a copper plating film is formed on the surface of the film, the copper plating film side cannot shrink. Therefore, a convex warpage occurs in the copper-clad laminate, with the copper plating film side protruding. On the other hand, in the case of a film that does not stretch easily under transport tension, the film does not shrink much after plating. However, the copper plating film tends to shrink as recrystallization progresses over time. Therefore, the copper-clad laminate has a concave warpage in which the copper plating film side is depressed.

For example, liquid crystal polymer films for high frequencies tend to stretch under transport tension. Therefore, when a copper-clad laminate is manufactured using a liquid crystal polymer film, convex warpage is likely to occur. Furthermore, polyimide films do not stretch easily under conveying tension. Therefore, when a copper-clad laminate is manufactured using a polyimide film, concave warpage is likely to occur. In this way, the tendency for warping differs depending on the type of film.

In view of the above circumstances, an object of the present invention is to provide a method for manufacturing a copper-clad laminate that can produce a copper-clad laminate with less warpage.

The method for producing a copper-clad laminate according to the first aspect includes transporting the base material by roll-to-roll, and transferring the base material to a plating tank in which electrolytic plating is performed using a copper plating solution containing a brightener component. When forming a copper plating film on one side of the substrate to obtain a copper-clad laminate, the brightener component of the copper plating solution is By increasing the concentration of the brightener component of the copper-clad laminate, the warpage of the copper-plated layer side of the copper-clad laminate is reduced, and by decreasing the concentration of the brightener component of the copper-plating solution, the It is characterized by reducing warpage of the convex shape where the copper plating film side protrudes .
The method for producing a copper-clad laminate according to the second aspect includes transporting the base material by roll-to-roll, and transferring the base material to a plating tank in which electrolytic plating is performed using a copper plating solution containing a brightener component. When forming a copper plating film on one side of the substrate to obtain a copper-clad laminate, the brightener component of the copper plating solution is A first copper -clad laminate is manufactured by setting the concentration of When the second copper-clad laminate is manufactured by increasing the concentration of the brightener component, and the first copper-clad laminate has a convex warp with the copper plating film side protruding , the concentration of the copper plating solution is increased. The method is characterized in that the second copper-clad laminate is manufactured by lowering the concentration of the brightener component.

According to the present invention, a copper-clad laminate with less warpage can be manufactured by adjusting the concentration of the brightener component in the copper plating solution.

FIG. 2 is a cross-sectional view of a copper-clad laminate. FIG. 2 is an explanatory diagram 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 formed by forming a metal layer 12 on the surface of a base film 11 having insulating properties. As the base film 11, a resin film such as a liquid crystal polymer (LCP) film or a polyimide film can be used. The metal layer 12 is formed by a dry film forming method such as 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. 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 12 μm. Note that 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, for example, a roll-to-roll type plating apparatus 3 as shown in FIG. 2 . 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.

A plurality of plating tanks 33 are provided on the transport path of the base material 10. Copper plating solution is stored in the plating tank 33. Further, an anode is arranged inside the plating tank 33. When the base material 10 passes through the plating bath 33, it is immersed in the copper plating solution. In this state, electrolytic plating is performed by passing a current between the anode and the base material 10, and a copper plating film 20 is formed on the surface of the base material 10.

A space is provided between adjacent plating tanks 33. This space is referred to as a free running section 34. Electrolytic plating is not performed in the idle running section 34. In the idle running section 34, the base material 10 is lifted out of the copper plating solution and conveyed in the air. A plurality of conveyance rollers for conveying the base material 10 are arranged in each idle running section 34. Further, a power supply roller that supplies current to the base material 10 is generally arranged in the idle running section 34 .

Copper plating solution is attached to the base material 10 immediately after coming out of the plating bath 33. The copper plating solution adhering to the base material 10 is scraped off and removed by the conveyance roller. Therefore, in the idle running section 34, the copper plating solution adhering to the base material 10 is removed. The larger the angle of embrace of the conveyance rollers, the more copper plating solution is scraped off by the conveyance rollers, so the amount of copper plating solution removed increases. Here, the embracing angle is the angle around the rotation axis of the conveying roller at the portion of the circumferential surface of the conveying roller that is in contact with the plating surface of the base material 10 (the surface on which the copper plating film 20 is formed). means range.

The base material 10 alternately passes through the plating bath 33 and the idle running section 34. During this transportation process, a copper plating film 20 is formed on the surface of the base material 10 by electrolytic plating. As a result, a long strip-shaped copper-clad laminate 1 is obtained.

Note that the number of plating tanks 33 and idle running sections 34 is not particularly limited. Generally, 4 to 19 plating tanks 33 are arranged, and 3 to 18 empty running sections 34 are arranged. A pretreatment tank may be provided between the most upstream plating tank 33 and the supply device 31. Further, a post-treatment tank may be provided between the most downstream plating tank 33 and the winding device 32.

In this embodiment, the copper plating film 20 is formed on one surface of the base material 10 by a single plating process in which the base material 10 is transported from the supply device 31 to the winding device 32. When manufacturing a single-sided copper-clad laminate in which the copper plating film 20 is formed on only one side of the base material 10, the plating process is completed in one time. When manufacturing a double-sided copper-clad laminate in which the copper plating film 20 is formed on both sides of the base material 10, the plating process is performed twice while the base material 10 is turned over. Specifically, after forming the copper plating film 20 on one surface of the base material 10 to obtain a single-sided copper-clad laminate, the base material 10 is turned over and the copper plating film 20 is deposited on the other surface. A film is formed to obtain a double-sided copper-clad laminate. In particular, when manufacturing a double-sided copper-clad laminate in which the copper plating films 20 on the front and back sides have different thicknesses, the copper-clad laminate 1 may warp depending on the conditions of film formation.

The copper plating solution stored in the plating tank 33 contains 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. The copper plating solution contains at least a brightener component. Further, the copper plating solution may contain a leveler component, a polymer component, a chlorine component, and the like.

Brightener ingredients contain sulfur. 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 33. 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.

The copper plating film 20 formed by alternately performing electrolytic plating and dry transport (transportation without electrolytic plating) has a laminated structure as shown in FIG. That is, the copper plating film 20 has a structure in which low sulfur concentration layers 21 and high sulfur concentration layers 22 are alternately laminated in the thickness direction. Here, the low sulfur concentration layer 21 is a layer with a relatively low sulfur concentration, and the high sulfur concentration layer 22 is a layer with a relatively high sulfur concentration.

The reason why the low sulfur concentration layer 21 and the high sulfur concentration layer 22 are stacked in this way is considered to be as follows.
During electrolysis, additives (brightener component, leveler component, and polymer component) are adsorbed on the surface of the copper plating film 20. Here, the leveler component and the polymer component are adsorbed onto the surface of the copper plating film 20 by electrical action caused by electrolysis. On the other hand, the brightener component is adsorbed on the surface of the copper plating film 20 regardless of electrolysis.

When idle running is performed after electrolysis, most of the copper plating solution adhering to the surface of the copper plating film 20 is removed by the conveyance roller. Along with this, most of the leveler component and polymer component adsorbed on the surface of the copper plating film 20 fall off. This is because the attraction due to electrical action is eliminated and the physical action from the conveyance rollers is activated. On the other hand, the brightener component tends to remain on the surface of the copper plating film 20 relatively easily. As a result, the surface of the copper plating film 20 has a relatively large amount of brightener component adsorbed thereon.

When the next electrolysis is performed in this state, many brightener components are taken in when new copper is deposited on the copper plating film 20 in the early stage of the electrolysis. In this case, a layer containing a relatively high brightener component is formed. Since the brightener component contains sulfur, the layer with a high concentration of the brightener component becomes the high sulfur concentration layer 22.

By the way, the copper-clad laminate 1 may have warpage. The base film 11 constituting the copper-clad laminate 1 is stretched due to the conveying tension of the plating device 3, and therefore tends to contract when released from the conveying tension after plating. Further, the copper plating film 20 tends to shrink as recrystallization progresses over time. When the base film 11 shrinks more than the copper plating film 20, a convex warpage occurs in the copper clad laminate 1 with the copper plating film 20 side protruding. On the other hand, when the copper plating film 20 shrinks more than the base film 11, a concave warpage occurs in the copper clad laminate 1 with the copper plating film 20 side depressed.

The inventor of the present application has discovered that warping of the copper-clad laminate 1 can be reduced by adjusting the concentration of the brightener component in the copper plating solution. Specifically, by increasing the concentration of the brightener component in the copper plating solution, the warpage of the concave shape of the copper-clad laminate 1 can be reduced. Further, by lowering the concentration of the brightener component of the copper plating solution, warping of the convex shape of the copper-clad laminate 1 can be reduced.

The reason why the warpage of the copper-clad laminate 1 changes depending on the concentration of the brightener component of the copper plating solution is considered to be as follows.
When the concentration of the brightener component of the copper plating solution is increased, the additive remaining on the surface of the copper plating film 20 even after the copper plating solution is removed in the free running section 34 has a ratio of the leveler component and the polymer component. The ratio of brightener ingredients is high. The total amount of impurities incorporated into the copper plating film 20 is determined by the plating conditions. Therefore, if the plating conditions are the same, the higher the proportion of the brightener component of the additive remaining on the surface of the copper plating film 20, the higher the sulfur concentration in the high sulfur concentration layer 22. As a result, the effect of suppressing recrystallization of the copper plating film 20 becomes high, and shrinkage of the copper plating film 20 is suppressed. Since the shrinkage of the copper plating film 20 is suppressed, the warpage of the copper clad laminate 1 changes to the convex tendency side.

On the other hand, when the concentration of the brightener component in the copper plating solution is lowered, even after the copper plating solution is removed in the free running section 34, the additive remaining on the surface of the copper plating film 20 is reduced to a leveler component and The proportion of polymer components is high and the proportion of brightener components is low. Therefore, the sulfur concentration in the high sulfur concentration layer 22 becomes low. As a result, the effect of suppressing recrystallization of the copper plating film 20 becomes low, and the copper plating film 20 tends to shrink. Since the copper plating film 20 tends to shrink, the warpage of the copper clad laminate 1 changes to the concave tendency side.

The ease with which the copper plating film 20 shrinks varies depending on the concentration of the brightener component in the copper plating solution. By balancing the shrinkage of the copper plating film 20 with the shrinkage of the base film 11, warping of the copper-clad laminate 1 can be reduced.

The concentration of the brightener component in the copper plating solution is adjusted by feeding back the amount of warpage of the manufactured copper-clad laminate 1. First, the first copper-clad laminate 1 is manufactured by setting the concentration of the brightener component of the copper plating solution to a predetermined value. Then, the amount of warpage of the first copper-clad laminate 1 is measured. When the first copper-clad laminate 1 has a concave warpage, the second copper-clad laminate 1 is manufactured by increasing the concentration of the brightener component in the copper plating solution. If the first copper-clad laminate 1 has a convex warp, the second copper-clad laminate 1 is manufactured by lowering the concentration of the brightener component in the copper plating solution. By repeating this process, the concentration of the brightener component at which a copper-clad laminate 1 without warping (the amount of warping is within an acceptable range) is determined. As described above, by adjusting the concentration of the brightener component of the copper plating solution, a copper-clad laminate 1 with less warpage can be manufactured.

Next, an example will be described.
(Evaluation of the relationship between brightener component concentration and amount of warpage 1)
The relationship between the brightener component concentration of the copper plating solution and the amount of warpage of the copper-clad laminate was evaluated.
A base material was prepared according to the following procedure. A 35 μm thick liquid crystal polymer film (SAR35 manufactured by KGK) 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 18 nm was formed on one side of the base film under a vacuum atmosphere, and a copper thin film layer with a thickness of 150 nm 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. Bis(3-sulfopropyl) disulfide (a reagent manufactured by RASCHIG GmbH) was used as a brightener component. Four types of copper plating solutions with brightener component concentrations of 5, 10, 15, and 20 mg/L were prepared.

A copper plating film with a thickness of 8.0 μm was formed on one side of the base material using a roll-to-roll type plating apparatus. Here, the base material was passed alternately through a plating tank in which the copper plating solution was stored and an idle running section. The temperature of the copper plating solution was 31°C. 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.

There are 7 plating tanks and 6 empty running sections. The time per electrolytic plating is 2 minutes. In the first electrolytic plating bath, the current density was 1 A/dm ² . In the second electrolytic plating bath, the current density was 2 A/dm ² . In the third to seventh electrolytic plating baths, the current density was 3 A/dm ² . Further, the embrace angle of the base material of the conveyance roller in the idle running section was set to 120°.

Four copper-clad laminates were manufactured using four types of copper plating solutions with different concentrations of brightener components. The four copper-clad laminates obtained are referred to as samples 1 to 4, respectively. The amount of warpage of the obtained samples 1 to 4 was measured according to the following procedure. First, the sample was cut into a square with one side of 10 cm. The cut sample was observed from the side and the amount of warpage was measured. Here, when the surface on which the copper plating film was formed was facing upward and there was a concave warp with raised four corners, the amount of raised four corners was defined as the amount of warp. Hereinafter, the amount of warpage of the concave shape is indicated by +. In addition, when the surface on which the copper plating film was formed was facing upward and there was a convex warp with a raised central portion, the amount of raised central portion was defined as the amount of warpage. Hereinafter, the amount of warpage of the convex shape will be expressed as -.

The results are shown in Table 1.

From Table 1, the higher the concentration of the brightener component in the copper plating solution, the more the warpage of the copper-clad laminate changes to the convex tendency side. From this, it was confirmed that warping of the copper-clad laminate can be reduced by adjusting the concentration of the brightener component.

(Evaluation of the relationship between brightener component concentration and amount of warpage 2)
A copper-clad laminate was manufactured in the same manner as in the above evaluation except that a 35 μm thick polyimide film (Upilex-35SGAV1, manufactured by Ube Industries, Ltd.) was used as the base film. Further, the embrace angle of the base material of the conveyance roller in the idle running section was set to 180°.

Four copper-clad laminates were manufactured using four types of copper plating solutions with different concentrations of brightener components. The four copper-clad laminates obtained are referred to as Samples 5 to 8, respectively.

The amount of warpage was measured for the obtained samples 5 to 8. The results are shown in Table 2.

Table 2 also shows that the higher the concentration of the brightener component in the copper plating solution, the more the warpage of the copper-clad laminate changes to the convex tendency side. Therefore, it was confirmed that warping of a copper-clad laminate can be reduced by adjusting the concentration of the brightener component, not only when a liquid crystal polymer film is used but also when a polyimide film is used.

1 Copper-clad laminate 10 Base material 20 Copper plating film 3 Plating device 33 Plating tank 34 Free running section

Claims (2)

A plating tank in which the base material is electrolytically plated using a copper plating solution containing a brightener component while the base material is conveyed by roll-to-roll, and an idle running section in which the copper plating solution adhering to the base material is removed. to form a copper plating film on one side of the base material to obtain a copper-clad laminate.
By increasing the concentration of the brightener component of the copper plating solution, the warpage of the copper-clad laminate having a concave shape in which the copper plating film side is depressed is reduced, and the concentration of the brightener component of the copper plating solution is lowered. A method for manufacturing a copper -clad laminate, characterized in that warpage in a protruding convex shape on the copper-plated film side of the copper-clad laminate is reduced. A plating tank in which the base material is electrolytically plated using a copper plating solution containing a brightener component while the base material is conveyed by roll-to-roll, and an idle running section in which the copper plating solution adhering to the base material is removed. to form a copper plating film on one side of the base material to obtain a copper-clad laminate.
manufacturing a first copper-clad laminate by setting the concentration of the brightener component of the copper plating solution to a predetermined value;
If the first copper-clad laminate has a concave warp in which the copper plating film side is depressed , a second copper-clad laminate is manufactured by increasing the concentration of the brightener component of the copper plating solution,
When the first copper-clad laminate has a convex warp with the copper plating film side protruding , a second copper-clad laminate is manufactured by lowering the concentration of the brightener component of the copper plating solution. A method for manufacturing a copper-clad laminate, characterized by: