Compositions – Etching or brightening compositions
Reexamination Certificate
2001-07-26
2004-06-08
Norton, Nadine G. (Department: 1765)
Compositions
Etching or brightening compositions
C252S079200, C252S079400, C438S745000
Reexamination Certificate
active
06746621
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a micro-etching composition for copper or copper alloys useful in the manufacture of printed circuit boards and the like, and a micro-etching method using the micro-etching composition.
2. Description of the Background Art
A multilayer printed circuit board is a laminated board having a plurality of conductive layers, each separated from the others by an insulating layer. Through-holes of which the inside is plated with the copper are formed through the multilayer printed circuit board. The conductive layers in the multilayer printed circuit board are electrically connected by the through-holes.
The conductive layers are made from copper and the insulating layers are made from a resin. Both the copper and the resins exhibit poor adhesion. To improve the adhesion of the copper with the resins, the surface of the copper is treated with a strong alkaline aqueous solution at a high temperature to produce fine needle-like copper oxide on the surface of the copper. This treatment is called “oxide treatment”.
However, the needle-like copper oxide formed on the copper surface is easily dissolved in an acidic plating solution used in the plating process for the through-holes. The phenomenon of copper oxide dissolution is called “haloing”. Moreover, the oxide treatment process not only involves poor work performance, but also takes a long time. To overcome these problems, a method of reducing the needle-like copper oxide to copper while retaining the needle-like configuration, thereby rendering the surface less soluble in an acidic plating solution has been used. However, this method is not preferable because of a larger number of process steps.
As a method involving a smaller number of process steps and exhibiting better productivity, a method of improving adhesiveness of copper with a resin by roughening the copper surface using a micro-etching composition comprising sulfuric acid and hydrogen peroxide as a main ingredient has been studied.
For example, Japanese Patent No. 2740768 describes a method of roughening the copper surface using an aqueous solution containing an inorganic acid, hydrogen peroxide, a corrosion inhibitor such as benzotriazole, and a surfactant. Japanese Patent Application Laid-open No. 96088/1998 describes a method of roughening the copper surface using an aqueous solution containing an inorganic acid, a peroxide, an azole compound such as benzotriazole, and a halide compound. Japanese Patent Application Laid-open No. 21517/1999 describes a method of roughening the copper surface using an aqueous solution containing an oxidizing agent such as an acid or hydrogen peroxide, a corrosion inhibitor such as benzotriazole, and a halide ion. Japanese Patent Application Laid-open No. 29883/1999 describes a method of roughening the copper surface using an aqueous solution containing sulfuric acid, hydrogen peroxide, and a tetrazole derivative such as a phenyltetrazole. Japanese Patent Application Laid-open No. 315381/1999 describes a method of roughening the copper surface using an aqueous solution containing an inorganic acid, hydrogen peroxide, and an amine compound. Japanese Patent Application Laid-open No. 140669/1999 describes a method of roughening the copper surface using an aqueous solution containing an inorganic acid, hydrogen peroxide, and a stabilizer such as an alkane sulfonic acid.
However, the method of using these micro-etching compositions also has drawbacks such as insufficient adhesion with resins and production of a brown or black deposit during the copper treatment with these compositions. Further improvement of these micro-etching compositions has been desired.
An object of the present invention is therefore to provide a micro-etching composition for copper or copper alloys free from the above drawbacks, exhibiting improved adhesion with resins, and capable of continuously treating copper and copper alloys without producing a brown or black deposit, as well as a method of micro-etching using such a micro-etching composition.
As a result of extensive studies, the inventors of the present invention have found that the surfaces of copper and copper alloys can be sufficiently roughened without producing a brown or black deposit when such surfaces are continuously treated by using a micro-etching composition containing sulfuric acid and hydrogen peroxide and an assisting ingredient with a novel combination.
SUMMARY OF THE INVENTION
Specifically, the above object is solved in the present invention by an aqueous solution for micro-etching copper or a copper alloy comprising a main ingredient consisting of sulfuric acid and hydrogen peroxide and an assisting ingredient consisting of a phenyltetrazole and a chloride ion source (such an aqueous solution is hereinafter referred to as “micro-etching composition”).
In the above micro-etching composition, the concentration of sulfuric acid is preferably 60-220 g/l.
In the above micro-etching composition, the concentration of hydrogen peroxide is preferably 5-70 g/l.
In the above micro-etching composition, preferable examples of the phenyltetrazole are 1-phenyltetrazole or 5-phenyltetrazole.
In the above micro-etching composition, the concentration of the phenyltetrazole is preferably 0.01-0.4 g/l.
In the above micro-etching composition, the chloride ion source is one or more compounds selected from the group consisting of sodium chloride, potassium chloride, ammonium chloride, and hydrochloric acid.
In the above micro-etching composition, the concentration of the chloride ion source is preferably 1-60 ppm.
In a preferred embodiment of the present invention, the above micro-etching composition further comprises a benzene sulfonic acid.
In the above micro-etching composition, the benzene sulfonic acid is one or more compounds selected from the group consisting of benzene sulfonic acid, toluene sulfonic acid, m-xylene sulfonic acid, phenol sulfonic acid, cresol sulfonic acid, sulfosalicylic acid, m-nitro benzene sulfonic acid, and p-amino benzene sulfonic acid.
The above object is further solved according to the present invention by a method of micro-etching a surface of copper or a copper alloy comprising causing the surface of copper or a copper alloy to come into contact with the micro-etching composition, thereby roughening the surface to the etching amount of 0.5-3 &mgr;m.
The above object is further solved according to the present invention by a method of manufacturing a printed circuit board comprising: micro-etching a surface of copper or a copper alloy by causing the surface of copper or a copper alloy to come into contact with the micro-etching composition, thereby roughening the surface to the etching amount of 0.5-3 &mgr;m, and laminating insulating resin layers.
Other objects, features and advantages of the invention will hereinafter become more readily apparent from the following description.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
Although the concentration of sulfuric acid in the micro-etching composition of the present invention is suitably adjusted according to the etching rate and the solubility of copper in the etching solution, such a concentration is usually 60-220 g/l, and preferably 90-220 g/l. If the concentration is less than 60 g/l, the etching rate becomes slow. If the concentration is more than 220 g/l, not only can any increase corresponding to the increase in the concentration not be seen, but also copper sulfate crystals tend to deposit.
Although the concentration of hydrogen peroxide in the micro-etching composition of the present invention is suitably adjusted according to the etching rate and the desired surface roughening capability, such a concentration is usually 5-70 g/l, and preferably 7-56 g/l. If the concentration of hydrogen peroxide is less than 5 g/l, the etching rate is slow and the micro-etching composition cannot adequately roughen the copper surface; if more than 70 g/l, on the other hand, the etching rate becomes too fast to perform uniform etching, resultin
Kameda Etsuji
Kurii Yoshihiro
Nakamura Sachiko
Mec Co., Ltd.
Umez-Eronini Lynette T.
LandOfFree
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