JPH0217946B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to metal foil used in printed wiring circuits. [Prior Art] As metal foils used for printed wiring circuits, so-called electrolytic copper foils formed by electrodeposition from copper-containing ion solutions have been used consistently for the past few decades. On the other hand, in recent years, with the advancement of film carriers or flexible printed circuits (FPC),
Electrolytic copper foil, which is extremely lacking in flexibility, is being avoided, and the need for rolled copper foil is rapidly becoming more important. However, the surface of rolled copper foil is extremely smooth, and the bonding strength between the oxide film generated on the surface and the base material is weak, so it lacks adhesion. However, it is impossible to put it into practical use. For this reason, the AC etching method, in which the rolled copper foil is introduced into an electrolytic solution and supplied with AC power to roughen the surface, or the electrodeposition method, in which the surface of the rolled copper foil is plated with coarse copper particles to roughen the surface, is used. Currently, it has been adopted and maintains adhesive strength. Furthermore, in order to maintain storage stability of rolled copper foil and prevent discoloration due to high temperatures when laminated and integrated with an insulating substrate, zinc/chrome plating is generally applied. [Problems to be solved by the invention] The roughening treatment of rolled copper foil by AC etching or electrodeposition described above has a shallower and more uniform roughening depth than electrolytic copper foil, which has been the mainstream in the industry for many years. Therefore, it has the advantage of being able to form fine circuits from the viewpoint of preventing side etching, but it has the disadvantage of being slightly inferior in adhesive strength on the opposite side. In addition, although this is not limited to copper foil with a roughened surface, zinc/chrome plating may partially peel off during storage in a hot and humid atmosphere during the summer, but due to the diffusion of copper, It often causes discoloration and becomes worthless as a product. The present invention has been made based on the above, and aims to provide a metal foil for printed wiring circuits that can improve adhesive strength to an insulating base material and can prevent discoloration during storage. [Means for Solving the Problems] The metal foil for printed wiring circuits of the present invention is a roughened or roughened rolled copper foil whose one or both sides have been roughened by etching or the like by AC power supply in an electrolytic solution. 200% by vapor phase plating method on roughened and non-roughened surfaces.
It is characterized by forming an aluminum thin film with a thickness of 1.5 Å or more. The reason why metallic copper has a significant lack of adhesive strength is that the bonding strength between the base metal and the copper oxide film that inevitably occurs on its surface is extremely low. It is expected that the adhesive will have an anchoring effect by expanding the surface area. On the other hand, the bonding strength between the oxide film and the base metal of aluminum is extremely strong, and therefore the strength of the laminated adhesive using adhesive is also extremely high.If a thin aluminum film is formed on the roughened surface of rolled copper foil, the adhesive strength can be increased. An increase is expected. In addition, the strong aluminum oxide barrier layer that occurs on the surface of aluminum prevents the penetration of corrosive gases such as moisture, so forming this on the surface of the copper foil will prevent the discoloration of the copper foil during storage. It is also expected to prevent oxidative discoloration at high temperatures. However, due to the difference in ionization tendency, it is impossible to electrochemically plate an aluminum film directly on copper foil, so the inventors developed a method for forming an aluminum thin film using vapor phase plating (ion vapor deposition). Adopted. In this case, the thickness of the aluminum thin film is 200 Å
Otherwise, sufficient adhesive effect and discoloration prevention effect cannot be obtained. If only one side of the rolled copper foil is roughened, the aluminum thin film may be formed only on the roughened side, or may be formed on both the roughened side and the non-roughened side. [Example] Figure 1 shows an example of the metal foil of the present invention, in which 1 is a rolled copper foil whose surface has been roughened, and 2 and 3 are aluminum layers formed by vapor phase plating. be. FIG. 2 schematically shows an example of an apparatus for roughening the surface of rolled copper foil by AC etching. 4 is a rolled copper foil, 5 and 6 are guide rollers,
7 is an electrode, 8 is a tank, 9 is an electrolytic solution, and 10 is an AC power source. AC power is supplied to an electrode 7 provided in an electrolytic solution 9 such as hydrochloric acid, sulfuric acid, nitric acid, etc., a rolled copper foil 4 is run between the electrodes, and then a post-treatment after pickling and drying is performed to coat the surface with numerous particles. A surface-roughened rolled copper foil 1 having micropores is obtained. FIG. 3 schematically shows an example of an apparatus for forming an aluminum layer on the surface-roughened rolled copper foil 1 by vapor phase plating. Reference numeral 11 denotes a casing, which is designed to isolate the inside from the outside. 12 is a sending part of the copper foil 1;
3 is a rolled-up portion of copper foil that has been plated. 1
4 is aluminum for vapor deposition, 15 is a crucible, 16 is a high frequency power source, and 17 is a high frequency coil. Inside the housing 11, there is about 4 times argon gas.
The copper foil 1 is sealed to maintain a pressure of 10 ^-4 Torr, and the copper foil 1 is continuously moved from the sending section 12 to the winding section 13 with a bias voltage of about -1600 V applied. There is. By supplying a high frequency output of 13.56 MHz and 400 W to the coil 17 from the power supply 16, the copper foil 1 is plated with aluminum. To apply vapor phase plating to both sides of copper foil 1,
You can do this by inverting the side. Table 1 shows the roughened surface of rolled copper foil with a thickness of 35 μm by AC etching.
Aluminum layers of 200 Å and 800 Å thick were formed by vapor phase plating, and zinc/chromium (about 500 Å thick) were formed on the roughened surface of the same rolled copper foil by conventional electrochemical plating. Comparison 3:1) The results of evaluating the adhesion strength to the paper/phenol substrate with plating formed are shown. Table 2 shows the surface of rolled copper foil with a thickness of 35 μm.
200 Å, 500 Å, 800 Å thick aluminum layers formed by vapor phase plating, and 500 Å thick zinc/chromium (3:1 ratio) plating by elastic electrochemical plating. This is a comparison of the degree of discoloration in the atmosphere at 180℃ for those that have formed.

【table】

[Table] As is clear from Tables 1 and 2, the aluminum layer is equivalent to conventional zinc/chrome plating in adhesive strength and discoloration prevention effect at 200 Å.
Much better results are shown at 500 Å and 800 Å. [Effects of the Invention] As explained above, the present invention provides a metal foil for printed wiring circuits that can improve adhesive strength with an insulating substrate and prevent discoloration during storage or lamination with an insulating substrate. Rolled copper foil can now be obtained. Moreover, since the present invention is based on vapor phase plating, there is no fear of industrial pollution, and its industrial value is extremely large.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of an example of rolled copper foil in which aluminum is vapor-phase plated on surface-roughened rolled copper foil;
The figure is a schematic explanatory diagram of an example of an apparatus for roughening the surface of rolled copper foil by AC etching, and FIG. 3 is a schematic explanatory diagram of an example of an apparatus for vapor phase plating aluminum on the surface of the surface-roughened rolled copper foil. . 1: Rolled copper foil, 2, 3: Aluminum layer.

Claims (1)

[Claims] 1. A thin aluminum film with a thickness of 200 Å or more is applied to the roughened surface or the roughened surface and the non-roughened surface of a rolled copper foil that has been roughened on one or both sides by a vapor phase plating method. A metal foil for printed wiring circuits, which is formed by forming a metal foil. 2. The metal foil for printed wiring circuits according to claim 1, wherein the roughened surface is formed by introducing the rolled copper foil into an electrolytic solution and etching it by AC power supply.