JP7151758B2 - COPPER CLAD LAMINATES AND METHOD FOR MANUFACTURING COPPER CLAD LAMINATES - Google Patents

Description

TECHNICAL FIELD The present invention relates to a copper-clad laminate and a method for producing the copper-clad laminate. More particularly, the present invention relates to a copper-clad laminate used for producing flexible printed wiring boards, chip-on-films, etc., and a method for producing the copper-clad laminate.

Electronic devices such as liquid crystal panels, notebook computers, digital cameras, and mobile phones use flexible printed wiring boards (FPC), in which wiring patterns are formed on the surface of a resin film, and chip-on boards, in which semiconductor chips are mounted on flexible printed wiring boards. A film (COF) is used.

A flexible printed wiring board is obtained by forming a wiring pattern on a copper-clad laminate by a semi-additive method, a subtractive method, or the like. In particular, the semi-additive method is used when forming fine wiring or when highly accurate wiring dimensions are required (for example, Patent Document 1).

In the semi-additive method, unnecessary portions of the conductor layer of the copper-clad laminate are removed by etching. If the conductor layer is too thick, the etching time will be long, and the etching of the wiring portion will progress, making it difficult to make the cross-sectional shape of the wiring rectangular. Therefore, the conductor layer of the copper-clad laminate processed by the semi-additive method is preferably thin. Therefore, as a copper-clad laminate processed by the semi-additive method, one having a conductor layer with a thickness of 0.2 to 3.0 μm is often used.

A chip-on-film is manufactured by sequentially processing a copper clad laminate by a wiring pattern maker and an assembly maker. A wiring pattern maker forms a plurality of wiring patterns, which will later become a plurality of individual pieces, on a long belt-like copper-clad laminate, and ships the long belt-like flexible printed wiring board to an assembly maker. Here, among the plurality of wiring patterns, those having defects such as disconnection or lack of wiring are marked as defective. Assembly manufacturers mount semiconductor chips on individual wiring patterns. At this time, if the defect rate of the flexible printed wiring board (the ratio of defective wiring patterns among the plurality of wiring patterns formed on the flexible printed wiring board) is high, the productivity of mounting decreases. Therefore, flexible printed wiring boards delivered to assembly makers are often provided with a permissible defective rate of wiring patterns. Although the specifications differ depending on the assembly manufacturer, the permissible defect rate is often set at 30%.

JP 2010-108964 A

SUMMARY OF THE INVENTION It is an object of the present invention to provide a copper-clad laminate and a method for manufacturing a copper-clad laminate that can reduce the defect rate of wiring patterns formed by a semi-additive method.

The copper clad laminate of the present invention has a conductor layer containing a copper plating film formed on the surface of the base film, the conductor layer having a thickness of 0.4 to 3.0 μm and a diameter of 5 μm or more. The number of pinholes is 0.01 /cm ² or less.
In the method for producing a copper-clad laminate of the present invention, a plating apparatus is used to transport a base material by roll-to-roll, and a copper-plated film is formed on the surface of the base material by electrolytic plating to form a thickness of 0. In order to obtain a copper-clad laminate having a conductor layer of 4 to 3.0 μm, the plating apparatus should have a surface roughness (Rmax) of 0.1 μm on the conveying surface of all rollers in contact with the plating surface of the base material. It is characterized by the following.

In the copper clad laminate of the present invention, the number of pinholes having a diameter of 5 μm or more in the conductor layer is 0.01 /cm ² or less, so that the defect rate of the wiring pattern formed by the semi-additive method is 18 % or less. can be suppressed.
According to the method for producing a copper-clad laminate of the present invention, a copper-clad laminate having a conductor layer with 0.04 or less pinholes/cm ² having a diameter of 5 μm or more can be produced.

1 is a cross-sectional view of a copper-clad laminate according to one embodiment of the present invention; FIG.

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

A resin film such as a polyimide film or a liquid crystal polymer (LCP) film can be used as the base film 10 . The conductor layer 20 consists of a metal layer 21 formed by a dry film forming method such as sputtering, and a copper plating film 22 formed by electrolytic plating. The metal layer 21 and the copper plating film 22 are laminated in this order on the surface of the base film 10 .

The metal layer 21 consists of a base metal layer 21a and a copper thin film layer 21b. The base metal layer 21a and the copper thin film layer 21b are laminated on the surface of the base film 10 in this order. Typically, the underlying metal layer 21a is made of nickel, chromium, or a nickel-chromium alloy. The base metal layer 21a may be omitted. The copper thin film layer 21b may be formed on the surface of the base film 10 via the base metal layer 21a, or may be formed directly on the surface of the base film 10 without the base metal layer 21a.

Although not particularly limited, the thickness of the base film 10 is generally 10 to 100 μm. The thickness of the base metal layer 21a is generally 5 to 50 nm, and the thickness of the copper thin film layer 21b is generally 50 to 400 nm. In the case of the copper-clad laminate 1 processed by the semi-additive method, the thickness of the conductor layer 20 is generally 0.4-3.0 μm.

A flexible printed wiring board can be manufactured by processing the copper-clad laminate 1 by a semi-additive method. The production of a flexible printed wiring board by the semi-additive method is carried out by the following procedure. First, a resist layer is formed on the surface of the copper plating film 22 of the copper-clad laminate 1 . 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 22 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 20 other than the wiring portion is removed by flash etching or the like. A flexible printed wiring board is thus obtained.

Since the copper-clad laminate 1 processed by the semi-additive method has a thin copper-plated film 22, pinholes are likely to occur when the copper-plated film 22 is formed by electroplating. In the semi-additive method, the copper plating of the wiring pattern is laminated on the copper plating film 22 by electroplating. At this time, if a pinhole exists in the copper plating film 22, the growth of the laminated copper plating is inhibited, and defects such as disconnection and chipping of the wiring occur. In particular, when manufacturing a chip-on-film, it is necessary to form fine wiring with a wiring width of 15 μm or less, so wiring defects due to pinholes are likely to occur.

The smaller the number of pinholes in the conductor layer 20, the less likely the defects will occur in the wiring, and the less defective the wiring pattern will be. The conductor layer 20 of the copper-clad laminate 1 according to this embodiment has 0.04 or less pinholes/cm ² with a diameter of 5 μm or more. As described above, since the number of pinholes in the conductor layer 20 is small, the defect rate of the wiring pattern formed by the semi-additive method can be suppressed to 30% or less.

(Manufacturing method of copper-clad laminate)
Next, a method for manufacturing a copper-clad laminate according to one embodiment of the present invention will be described.
The metal layer 21 can be formed on the surface of the long belt-shaped base film 10 by using a roll-to-roll type sputtering apparatus. Hereinafter, the base film 10 having the metal layer 21 formed thereon is referred to as a substrate. If a roll-to-roll type plating apparatus is used, the copper plating film 22 can be formed on the surface of the long strip-shaped base material. Thus, a long belt-shaped copper-clad laminate 1 is obtained.

A plating apparatus is an apparatus that performs electrolytic plating on a base material while transporting the base material in the form of a long strip by roll-to-roll. The plating apparatus has a supply device for feeding out the base material wound into a roll, and a winding device for winding the base material (copper-clad laminate 1) after plating into a roll. A pre-treatment tank, a plating tank, and a post-treatment tank are arranged on the transport path between the supply device and the winding device. Electroplating is performed in the plating bath. While the base material is conveyed in the plating bath, a copper plating film 22 is formed on the surface thereof by electrolytic plating.

A copper plating solution is stored in the plating tank. A copper plating solution contains a water-soluble copper salt. Any water-soluble copper salt commonly used in copper plating solutions can be used without particular limitation. 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. As additives, one selected from brightener components, leveler components, polymer components, chlorine components, etc. may be used alone, or two or more may be used in combination.

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 22 can be formed at a sufficient speed. The copper plating solution preferably contains 1 to 50 mg/L of brightener component. By doing so, the precipitated crystals can be made finer and the surface of the copper plating film 22 can be smoothed. The copper plating solution preferably contains 1 to 300 mg/L of leveler component. Then, a flat copper plating film 22 can be formed while 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 and form a uniform copper plating film 22 . 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 20-35°C. Moreover, it is preferable to stir the copper plating solution in the plating bath. For example, the copper plating solution can be agitated by spraying the base material with the copper plating solution ejected from a nozzle.

The thickness of the copper plating film 22 can be adjusted by the current density and plating time in electrolytic plating. For example, the thickness of the copper plating film 22 is adjusted so that the thickness of the conductor layer 20 is 0.4 to 3.0 μm.

A plating apparatus has various rollers for conveying the base material. Among the rollers of the plating apparatus, all rollers in contact with the plated surface of the base material have a surface roughness (Rmax) of 0.1 μm on the conveying surface (the area of the outer peripheral surface of the roller that contacts the plated surface of the base material). The following rollers are used. By doing so, pinholes are less likely to occur when the copper plating film 22 is formed by electrolytic plating. Therefore, the copper-clad laminate 1 having the conductor layer 20 with 0.04 or less pinholes/cm ² having a diameter of 5 μm or more can be manufactured.

(common conditions)
As a base film, a long belt-shaped polyimide film (Upilex manufactured by Ube Industries, Ltd.) having a width of 570 mm and a thickness of 34 μm was prepared. 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 100 nm was formed thereon.

A copper-plated film was formed on one side of the substrate using a roll-to-roll plating apparatus to obtain a copper-clad laminate. The copper plating solution stored in the plating tank contains 120 g/L of copper sulfate, 70 g/L of sulfuric acid, 16 mg/L of brightener component, 20 mg/L of leveler component, 1,100 mg/L of polymer component, and 1,100 mg/L of chlorine component. Contains 50 mg/L. Bis(3-sulfopropyl)disulfide (reagent manufactured by RASCHIG GmbH) was used as a 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.

(Example 1)
Among the rollers of the plating apparatus, rollers having a conveying surface with a surface roughness (Rmax) of 0.068 to 0.074 μm were used as all the rollers in contact with the plated surface of the substrate. The thickness of the copper plating film was adjusted so that the thickness of the conductor layer was 0.4 μm.

(Example 2)
Among the rollers of the plating apparatus, rollers having a conveying surface with a surface roughness (Rmax) of 0.068 to 0.074 μm were used as all the rollers in contact with the plated surface of the substrate. The thickness of the copper plating film was adjusted so that the thickness of the conductor layer was 2.0 μm.

(Example 3)
Among the rollers of the plating apparatus, rollers having a conveying surface with a surface roughness (Rmax) of 0.068 to 0.074 μm were used as all the rollers in contact with the plated surface of the substrate. The thickness of the copper plating film was adjusted so that the conductor layer had a thickness of 3.0 μm.

(Comparative example 1)
Among the rollers of the plating apparatus, rollers having a conveying surface with a surface roughness (Rmax) of 4.003 to 4.218 μm were used as all the rollers in contact with the plated surface of the substrate. The thickness of the copper plating film was adjusted so that the conductor layer had a thickness of 3.0 μm.

(Comparative example 2)
Among the rollers of the plating apparatus, rollers having a conveying surface with a surface roughness (Rmax) of 7.101 to 7.129 μm were used as all the rollers in contact with the plated surface of the substrate. The thickness of the copper plating film was adjusted so that the thickness of the conductor layer was 0.5 μm.

A sample of 250×160 mm was cut out from each of the copper-clad laminates obtained in Examples 1-3 and Comparative Examples 1 and 2. Each sample was inspected under backlight illumination using a halogen lamp as a light source, and the number of pinholes with a diameter of 5 μm or more was counted. The inspection was carried out visually and compared with a pre-prepared sample of pinholes having a diameter of 5 μm. Table 1 shows the results.

In Examples 1 to 3 using rollers with a surface roughness (Rmax) of 0.068 to 0.074 μm, the number of pinholes was 0.04/cm ² or less. On the other hand, in Comparative Examples 1 and 2 using rollers with a surface roughness (Rmax) of 4.003 to 4.218 μm or 7.101 to 7.129 μm, the number of pinholes was 0.04/ ^cm2 was exceeded. From this, it was confirmed that a copper-clad laminate having a conductor layer with 0.04 or less pinholes/cm ² or less with a diameter of 5 μm or more can be produced by using a roller with a surface roughness (Rmax) of 0.1 μm or less. rice field.

Next, the copper clad laminates obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were processed to produce flexible printed wiring boards. A flexible printed wiring board was manufactured by the following procedure. A dry film resist was laminated on the surface of the copper plating film of the copper-clad laminate to form a resist mask in which a plurality of wiring patterns were arranged. Each wiring pattern has a size of approximately 70×40 mm, a minimum pitch of 20 μm, and a wiring width of 10 μm. Next, electrolytic plating was performed using the copper plating film exposed from the openings of the resist mask as a cathode, and the copper plating was laminated so that the total thickness of the conductor layer of the copper-clad laminate was 8 μm.

The laminated copper plating (wiring pattern) exposed from the opening of the resist mask was observed with a microscope. Wiring patterns with chipping or disconnection of a size of 1/3 or more of the wiring width were judged to be defective, and the defect rate of the wiring pattern was obtained. Table 1 shows the results.

In Examples 1 to 3, in which the number of pinholes in the conductor layer was 0.04/cm ² or less, the defect rate was 30% or less, which was confirmed to be within the allowable range. On the other hand, in Comparative Examples 1 and 2 in which the number of pinholes in the conductor layer was 0.07/cm ² and 0.10/cm ² , the defect rate exceeded 30%. From this, it was confirmed that if the number of pinholes in the conductor layer is 0.04/cm ² or less, the defect rate of the wiring pattern formed by the semi-additive method becomes 30% or less.

Also, from Table 1, it can be seen that the smaller the number of pinholes in the conductor layer, the lower the defect rate of the wiring pattern. If the number of pinholes is 0.04/cm ² or less, the defect rate can be 27% or less. If the number of pinholes is 0.02/cm ² or less, the defect rate can be 21% or less. If the number of pinholes is 0.01/cm ² or less, the defect rate can be 18% or less.

REFERENCE SIGNS LIST 1 copper clad laminate 10 base film 20 conductor layer 21 metal layer 21a base metal layer 21b copper thin film layer 22 copper plating film

Claims (2)

Having a conductor layer formed directly on the surface of the base film,
The conductor layer is
a metal layer formed directly on the base film by a dry film forming method;
a copper plating film formed directly on the metal layer by electrolytic plating;
A copper-clad laminate, wherein the conductor layer has a thickness of 0.4 to 3.0 μm and has 0.01 /cm ² or less of pinholes with a diameter of 5 μm or more. Using a plating apparatus, a copper plating film is formed on the surface of the base material by electrolytic plating while conveying the base material by roll-to-roll, and the thickness is 0.4 to 3.0 μm and the diameter is 5 μm. In obtaining the above copper-clad laminate having a conductor layer with pinholes of 0.04/cm ² or less,
The method for producing a copper-clad laminate, wherein the plating apparatus has a surface roughness (Rmax) of 0.1 μm or less on the conveying surfaces of all the rollers in contact with the plating surface of the base material.

Images